MANUAL How to reduce society s vulnerability to waterborne viral infections despite climate change

Transcription

1 MANUAL How to reduce society s vulnerability to waterborne viral infections despite climate change

2 Foreword Viruses are the most common cause of outbreaks of waterborne disease in the world, something that hits billions of people every year. VISK, the Swedish acronym that translates as The Scandinavian Knowledge Bank for Viruses in Water, has created a partnership between Denmark, Norway and Sweden that aims to investigate how to achieve a safe drinking water supply despite climate change. Within VISK, 18 organisations from the three countries have been collaborating, and the project is co-funded by the EU programme Interreg IV A. The main purpose of the project is to reduce society s vulnerability to waterborne viral infection. VISK aims to use this manual to provide information and guidance on how drinking water systems should be designed and dimensioned in order to be prepared for the possible consequences of climate change. The target group is the technical sector within municipalities and operational staff at water treatment plants, managers and administrative staff as well as decision-makers and politicians in municipalities who would like to have knowledge-based database when making decisions. We would like to extend particular thanks to the Interreg IVA Secretariat and the Swedish Water & Wastewater Association (Svenskt Vatten) for their funding of the project. We would also like to thank all contributing partners who have been involved and made this collaboration possible. Everyone has contributed to achieving positive synergies, which have developed the project. It has been extremely positive to work together on the project within this network, as expertise in the field of viruses is found all over the Nordic region. Gothenburg, March 2013 Kjetil Furuberg Norwegian Water BA Lena Blom City of Gothenburg 2

3 Table of Contents Foreword... 2 How to use this manual Background... 5 Three-year EU project...5 Microbiological risks in drinking water production...6 Climate change Water quality Where viruses come from and in what amounts...10 Analysis of viruses in water Water treatment how to control viruses in a water treatment plant Groundwater aquifers as a hygienic barrier against viruses...22 Chemical precipitation...24 Carbon filter...25 Disinfection using chlorine...27 Disinfection using ozone...28 Ultraviolet radiation...29 Ultrafilter UF Risk assessment and checking quality Contaminants in raw water...32 Sources of contamination...36 Barrier effect...39 Protecting the supply network...39 My estimate of the risk Risk reduction through preventive work Risk-reducing measures...46 Economic and administrative tools for decision-making based on risk assessment...48 Risk management and water and sewage planning Trust and confidence The value of good communication

4 How to use this manual Target group Main purpose Three language versions Main areas Plenty of 5s References and lack of references The in-depth knowledge behind it all You, the reader of this manual, presumably work within or close to one of the stages in the process that provides us with good, healthy drinking water. Or maybe you are a decisionmaker, a politician for example, who wants more knowledge before making decisions on initiatives to safeguard the quality of water. Whatever your role, the intention is that this manual will provide you with a general, factual picture of measures to prevent outbreaks of waterborne infection with a focus on an increased risk of waterborne infections from viruses as a consequence of climate change. This manual is available in Swedish, Norwegian and English, and only in digital format. The following five chapters form the core: Background The importance of raw water Measures in water treatment plants Risk assessment and checking quality Risk reduction through preventive work Trust and confidence The body text is interspersed with fact boxes, illustrations, charts and checklists. In many places, checklists have been integrated into the body text, where measures or information that are of such a nature that you may want to tick them off have a box (5) next to them. There is no absolutely stringent methodology behind the placement of these boxes in the text, which means that it is entirely up to the reader to decide whether they need to be acted upon. In some places there are references cited, often with links, while in other places references have been omitted. The intention here is not to provide a full scientific background, but for the content to be kept at a general, factual level. The research and experience on which this manual is based may be found, for example, in reports and articles published in the VISK project, but also at other bodies that work with water-related issues. The following links contain much of the base data for this manual as well as a great deal more information for anyone wishing to study these issues in more detail: og vannhygiene Vannforsyningens ABC

5 1. Background There are many sources of pathogenic microorganisms in raw water, and the field is a very complex one, but the primary source is untreated waste water. The risk that untreated waste water will reach raw water is increasing as the climate changes, as more intensive precipitation can increase the overflow of waste water to those watercourses and lakes that are used as raw water sources. Pathogenic microorganisms include viruses, bacteria and parasites. Viruses are the smallest of all and also those that are most difficult to measure and separate in water treatment plants. Three-year EU project VISK is a Swedish acronym for the Scandinavian Knowledge Bank for Viruses in Water, and is a three-year project that aims to reduce society s vulnerability to waterborne viral infection in a changed climate, and also to provide an opportunity for an early warning in the event of a suspected outbreak. The project was run within the framework of the EU programme Interreg IV A Öresund-Kattegat-Skagerrak, and was completed in March research institutions, authorities and municipalities in Sweden, Norway and Denmark were involved. VISK came into being following the performance of various risk analyses, including one in Gothenburg on the production of drinking water, where a significant microbiological risk was identified. There was an outbreak of norovirus in Lilla Edet in 2008, and in many ways this event served as an inspiration for VISK. Of all microbiological risks, the project chose to focus on viruses, partly because of the event in Lilla Edet, but also because viruses are difficult to identify in and separate from water, while at the same time only a small number of particles can cause infection. The project attempted to find cohesive solutions for how this problem should be dealt with both now and in a future when climate change will probably change the conditions for drinking water production. One of the objectives was to raise levels of awareness in, among others, decision-makers of the risks of waterborne viral infection and to create a knowledge network that can live on even after the end of the project. Hopes exist that the results of this project will have positive socio-economic effects in the long term, in the form of the preservation of good health in the general public as a consequence of less spreading of infection, and if an outbreak were to occur, that it can be resolved in a faster, safer way. The hope is that the results will be generally valid and applicable in similar conditions, especially in the Nordic region, in the same way as in the areas investigated. VISK was broken down into the following sub-projects: Epidemiology, where the correlation between the municipal water supply and gastroenteritis caused by viruses was investigated in a number of activities. Mapping of waterborne viruses in the watercourses of Glomma in Norway and the Göta älv river in Sweden. The mapping process indicated how many viruses there are, what kinds, where they occur and provided a basis for risk models. The sub-project also included the development of methods for analysing viruses. On the basis of this analysis, models were developed describing how viruses are transported, transmitted and survive in watercourses. Virus reduction, where investigations were conducted into how good different barriers at water treatment plants are at reducing viruses that can cause disease in humans. This sub-project provided base data for risk analyses and increased knowledge of which kinds of stages in the treatment process are most effective. Risk communication, which is all about analysing, evaluating and communicating the risks of waterborne viruses to all bodies involved when drinking water is produced and distributed to consumers. The results included an updated MRA tool to facilitate practical application in the water sector to assess the risk of viruses. Communication strategy, which concerns the strategy for external communication and consumers trust and confidence in their drinking water and in their drinking water producers. This manual is one of the results of this sub-project. Alongside this manual, a number of results from VISK have been published, for example research reports and articles. More information is available on the website visk.nu. 5

6 Microbiological risks in drinking water production When infectious agents and other substances harmful to health reach water sources, there is a risk that drinking water will also be contaminated. Microbiological infection is often characterised by a short incubation period and acute symptoms such as nausea, fever and gastroenteritis. Microbiological infection can also result in chronic disease and may even cause death. The World Health Organisation (WHO) has identified waterborne infection as the most important health risk associated with drinking water supplies. Waterborne infection Pathogenic microorganisms that are transmitted via drinking water include a large number of viruses, bacteria and parasites. Several parameters are important when assessing the risk of waterborne infection, for example the ability to survive in water, infectious dose, resistance to disinfection and occurrence in humans. It is unfortunately expensive and complicated to analyse and assess risks in this area, which makes preventive safety work difficult. During the first decade of the 21st century, the Nordic countries suffered a number of outbreaks of waterborne infection, which resulted in thousands of cases of disease. Among the more widely reported are the giardiasis outbreak in Bergen in 2004, the outbreak of norovirus in Lilla Edet in 2008 and the outbreaks of the cryptosporidium parasite in Östersund and Skellefteå in 2010 and It used to be difficult to determine which infectious agents were the cause of a large number of the waterborne outbreaks of disease that were reported in Sweden. But in the 2000s it was confirmed that norovirus was the primary cause of these outbreaks. Waterborne viruses, such as those that cause the winter vomiting bug, have low infectious doses and are at the same time difficult to detect and quantify in low contents. Examples of viral diseases, waterborne and/or airborne: Winter vomiting bug (norovirus) Cold Influenza Chicken pox Hepatitis HIV/AIDS Dengue fever Pathogenic viruses that are transmitted via water: Stomach and intestinal viruses: Norovirus Sapovirus Rotavirus Astrovirus Adenovirus Symptoms in several organs: Enterovirus Hepatitis with jaundice: Hepatitis A and E virus These viruses, with the exception of Hepatitis E, come from other people. Different viruses produce different symptoms, have different occurrences and are identified in different ways. 6

7 Viruses Viruses exist in various sizes, but all are smaller than bacteria. Only the biggest virus particles can be seen with a light microscope (e.g. pox virus), otherwise an electron microscope is required. This is true, for example, of common intestinal viruses such as norovirus, rotavirus and adenovirus. Viruses are not considered to be living organisms, as they do not have their own metabolism and cannot propagate on their own. A virus consists of genetic material, RNA or DNA, protected by a shell of protein. Viruses cannot move on their own, but use other media and are therefore transmitted via body fluids, air, water, physical contact or faeces. They are also very resistant and difficult to inactivate. Viruses that are transmitted by the faecal-oral route (e.g. through water) are usually naked viruses, i.e. they have a protein shell on the outside, while some viruses that are transmitted via the air (e.g. the influenza virus) have a lipid envelope on the outside. This envelope makes the virus particle more vulnerable, as the envelope can be destroyed, rendering the virus unable to cause an infection. Naked viruses can thus withstand environmental conditions better than viruses with a lipid envelope. Among other things, they can pass through the stomach, which has a very low ph, and still retain their ability to cause an infection. Naked viruses can also endure long waiting times, especially in cool conditions. They are, however, sensitive to UV rays (sunlight), which break down the DNA. In order to propagate, the virus invades a living cell and makes the cell do its job for it. To check whether a person has been infected, it is often necessary to produce a cell culture. This means that it can be more difficult to identify viruses that cause infections than bacteria (of the kind that infect via water). Once success has been achieved, the host organism often displays symptoms. What kind of symptoms these are depends on what kind of virus has infected the organism. The number of virus particles needed to create an infection (i.e. the infectious dose) varies from one virus to another and from one person to another, but as a general rule a small number is enough (approximately ten particles). Viruses that cause gastroenteritis often have a low infectious dose, which means that for some of these viruses it only takes a single virus particle to make the infected person ill and exhibit symptoms. Bacteria In contrast to viruses, bacteria are living, single-cell organisms with their own nutrient turnover, and they propagate by means of division. Most food-borne bacteria do not infect via water, as they have a high infectious dose and thus often need to propagate in a nutrient before they can cause infection. Examples of waterborne bacteria include campylobacter and single pathogenic E. coli. Parasites Parasites are living, single-cell or multi-cellular organisms that use other organisms in order to live. In this respect, parasites are similar to viruses. In contrast to bacteria, parasites have a nucleus. The host organism can often continue to live as normal, but may sometimes exhibit symptoms. Examples of pathogenic parasites that are waterborne include giardiasis and cryptosporidium, which are so-called protozoan parasites. VIRUSES BACTERIA PARASITES Size µm 1 10 µm approx. 10 µm or more Biology Have genetic material No nucleus No nutrient turnover Have genetic material No nucleus Own nutrient turnover Propagation through division Infectious dose 1 Low Low high Low Survival in raw Long Short long Medium long water 2 Have nucleus with genetic material Own nutrient turnover Different kinds of microorganisms. 1 The infectious doses of the different microorganisms are not absolute values and can vary significantly due to several factors, such as the genotype of the specific microorganism as well as the immune status and the age of the person exposed. An infectious dose defined as low requires microorganisms to cause infection in 50 per cent of healthy adults, while a medium infectious dose requires ,000 and a high dose more than 10,000 microorganisms. 2 The detection period for infectious microorganisms at 20 C where short means up to one week, medium between one week and one month and long more than one month. Source: Swedish National Food Agency (SLV) report

8 Overflow Inadequate water quality Heavy precipitation Discharge from sewage treatment plant Expansion of supply network Epidemics of disease Sabotage Drinking water-borne infection Grazing on the beach Cross-connection Manure Spring flood Flooding Leaking pipes Individual drains Treatment failure Interruption in flow Contamination of water reservoirs Pipeline breach Insufficient preparation capacity Surface water penetration in well Factors that may result in the microbiological contamination of drinking water, many of which are associated and interdependent. (From the Swedish National Food Agency s report number , Mikrobiologiska dricksvattenrisker ur ett kretsloppsperspektiv [ Microbiological drinking water risks from a cycle perspective ].) Sources of contamination A number of factors affect the extent to which pathogenic microorganisms reach drinking water and the consumer. An analysis is required for every source of raw water, describing where there are sources of contamination, what kind of pathogenic microorganisms these sources of contamination are releasing and how much. Examples of sources of contamination are treatment plants and individual drains, run-off from agricultural land and pasture, bathing sites, surface water and process water from industries. Climate and weather factors affect the quality of raw water by means of, for example, floods, spring tides and heavy rain, resulting in contaminants reaching raw water sources. The illustration shows other examples of risk factors. Knowledge is needed in several stages To be able to choose and dimension suitable barriers, knowledge is needed of where and when pathogenic microorganisms are present in raw water. Frequent analyses and investigations are required of both pathogens and so-called indicator organisms, where it is important to be able to assess the worst conditions. Another factor that affects the quality of drinking water is the ability of the preparation process to reduce various microorganisms. Disruption during distribution can also cause drinking water-born outbreaks of disease. Once an outbreak of disease is under way, prompt identification and reporting can spare the suffering of many people and save society significant resources. 8

9 The increase in the number of days with significant precipitation (more than 10 mm over an area of 50 x 50 km) as an average during Dec Feb compared with the average from , according to the IPCC s A2 and B2 climate scenarios respectively. Increase in the number of days with significant precipitation in the period compared with the average for (RCA3/Rossby Center SMHI with Echam4/OPYC3 (E) as driver). Climate change Regional climate scenarios in Sweden have been produced by the Rossby Center at the Swedish Meteorological and Hydrological Institute (SMHI), and these are available on the SMHI website. Assessments of climate change are complex and are being reworked and updated on an ongoing basis, although the general conditions for the Nordic countries have not changed. We will be having a warmer climate, where the increase in temperature will be greatest in the winter, and increased precipitation with a bigger increase in the winter than the summer. Extreme weather conditions will also be more common, with significant precipitation for several days. More run-off and more frequent overflows In Dricksvattenförsörjning i förändrat klimat, Underlag till Klimat- och sårbarbarhetsutredningen [ Drinking water supplies in connection with climate change base data for the climate and vulnerability investigation ] (Swedish Water & Wastewater Association 2007), it is shown that in particular increased precipitation in the form of rain during the winter and more extreme weather may result in increased health risks for drinking water consumers. The main source of infectious agents in drinking water is via raw water. In connection with cloudbursts and flooding, raw water is affected when it becomes necessary to allow waste water to overflow because the sewage system is overloaded. More precipitation also results in increased run-off, and thus to more pathogenic parasites and bacteria being added to raw water from pastures and agricultural land. Increased run-off also means more humic substances, particles and nutrient salts are added, which contributes to both cloudier water and greater potential for algal bloom. An increase in water temperature also enhances the potential for growth, further worsening the quality of the raw water. Increased content of humic acids also reduces the ability to detect pathogenic microorganisms by means of molecular biology. This is significant above all for virus analyses. A worsening of the quality of raw water places higher demands on water treatment and results in a greater need for separating and disinfecting barriers. At the same time, the effectiveness of the barriers is counteracted by the increasing volumes of organic material, as filter beds become saturated more quickly, ultrafilters are blocked more frequently, UV light has less effect and there is poorer disinfection capacity in chlorine treatment. Water discharge Time after start of rain The horizontal line denotes when overflowing takes place. The figure illustrates that a small increase in the intensity of rain can create a large increase in the volume of untreated waste water being released. The effect on groundwater In groundwater sources, the size of the unsaturated ground zone between groundwater level and ground level is decisive when it comes to separating microorganisms. But an increase in precipitation risks raising groundwater levels, which in turn increases the risk of contamination. But the biggest microbiological threat to groundwater sources in a future climate is perhaps above all an increase in the frequency of extreme precipitation, which eliminates the unsaturated zone and creates flooding, which in turn results in the possibility that contaminated surface water may make its way into wells. 9

10 2. Water quality The various viruses that can be transmitted by water are already in the population and being transmitted from person to person, but they can also be transferred via food such as watered vegetables and berries. Mussels and oysters can also gather large amounts of viruses in sea water affected by sewage and become sources of infection. It is at present difficult to detect low concentrations of virus particles in water, and even if the levels are higher and detectable it is difficult to quantify the amount of viruses. There is not yet a standardised method of analysing viruses in water. There are, however, a number of different methods in use at research laboratories. Where viruses come from and in what amounts Waterborne viruses come from sewage treatment plants, individual drains and from surface water and drainage water. Viruses are always present in waste water, usually even after treatment. Sewage treatment plants that discharge treated waste water into a raw water source introduce viruses into the raw water to varying degrees. A significant increase in the amounts of viruses can also be expected when waste water overflows in connection with heavy rain. When drinking water is produced in water treatment plants there is some separation of viruses; to what degree depends on which methods are used. Separation should be adapted so that the reduction in viruses is sufficient even in connection with peaks that can occur when there are overflows or outbreaks of, for example, norovirus. Presence in the population/epidemiology Pathogenic microorganisms that are transmitted via drinking water will primarily cause gastroenteritis. This is because waste water that contaminates raw water mainly contains microorganisms from the stomach and the intestine. There are also a number of viruses that are secreted with faeces, and that do not cause gastroenteritis but primarily respiratory tract infections. Human adenovirus types 40 and 41 are typical causes of gastroenteritis, while most other adenovirus types instead cause respiratory tract infections, and they too are secreted with faeces. It is not considered that viruses that cause respiratory tract infections and are secreted with faeces can give rise to infections when consumed, since they must reach the respiratory tracts by means of airborne infection. Norovirus is the virus that has usually been registered in waterborne outbreaks in Scandinavia. In other parts of the 10

11 world there have been many other kinds of viruses involved in waterborne outbreaks. It may be suspected that other viruses such as adenovirus, rotavirus and astrovirus are transmitted through drinking water but do not cause a sufficient degree of disease to have been registered as outbreaks in Scandinavia. These other viruses mainly affect children. Outbreaks that only affect a limited part of the population are difficult to identify. It usually takes per cent of the population exposed to be affected before we discover an outbreak. Enterovirus is a large, varied family of viruses that occurs commonly in waste water. These viruses can produce serious symptoms such as meningitis and paralysis, although of around 100 infected individuals (varies between different enteroviruses) only one person will normally exhibit symptoms. In such a situation it is also difficult to discover outbreaks caused by a specific source, for example drinking water. The sporadic transmission of pathogens, for example via drinking water, in a defined area that does not result in a registered outbreak but takes place primarily from person to person is what we usually call endemic infection. Calculating the scope of such infection is very difficult, and only a few surveys in the world have addressed this issue. Applying filters that remove microorganisms from household taps has obtained very widely varying results, depending on where and how the studies were conducted. Anything from virtually no effect to 34 per cent of cases of gastroenteritis being due to the consumption of drinking water. If you take an average of these kinds of studies and apply it to the Swedish population, the result is that between 100,000 and 1.3 million people contract gastroenteritis from drinking water every year. The same calculation for Norway would produce between 50,000 and 700,000 people. There is therefore a great deal of uncertainty, and the truth is that at present we have no idea where the Nordic countries are on this scale. Both Norway and Sweden have conditions similar to those in the surveys described above, while Denmark is a special case as virtually all of its drinking water comes from good quality groundwater. There is thus a high level of uncertainty about how many people contract gastroenteritis from drinking water, and surveys in the Scandinavian countries are based primarily on statistics from outbreaks. Traditional microbiological risk assessment is based above all on estimates of the amount of pathogens in, for example, drinking water and how much disease this amount should cause. This is based on an assumption that we know what proportion of the population will fall ill from a given dose of, for example, a virus. It is difficult to quantify viruses in raw water, and at present it is virtually impossible under normal conditions to analyse the amount of viruses in drinking water. There is also major uncertainty about how many viruses a water treatment plant actually removes in its preparation process. This means that calculations are associated with major uncertainties. Worth checking when it comes to water quality, in order to check the amount of viruses in a water treatment plant 55Sources that exist upstream of the water treatment plant (quantity and their location). 55Sewage treatment plant(s) which treatment stages/barriers it/they has/have and the number of people involved. 55Individual drains. 55Surface water and drainage water. 55Overflow drains number and whether there are alarms. 55How viruses are transmitted from the courses. 55Outflow ratio. 55Flow. 55Temperature (affects circulation and stratification). 55Wind. 55Sedimentation rate. 55Dilution ratio. 55Is a sampling programme needed? 55Should sampling be carried out? 55Contact with a research laboratory to discuss sampling program? (This is necessary when analyzing viruses.) 55Measurement of viruses and/or indicators? 55When and how often should samples be taken? (Event-based sampling is conducted as a supplement to a normal sampling programme. Samples are then taken regularly for at least one year in connection with worst case events.) 55See also the discussion of sampling on page

12 Ale H 2 O a survey of tap water and gastroenteritis As it is so difficult to analyse the amount of viruses in drinking water, a study was launched within VISK involving direct measurements in the population. In Ale Municipality, which draws its municipal water from Alelyckan in Gothenburg and Dösebacka in Kungälv, individual persons reported how much cold tap water they drink and how often they suffer from gastroenteritis. The intention is to attempt to determine what proportion of cases of gastroenteritis is actually caused by the consumption of drinking water. The project is called Ale H 2 O, and it has not been completed at the time of writing. The final findings will be published in an SVU report and eventually in the form of scientific publications. Telephone interviews followed by questions at regular intervals about water consumption and gastroenteritis over one year in Ale Municipality should provide base data for assessing the effect of drinking water on our health. As Ale residents draw their drinking water from two different water treatment plants and a large group of people draw their water from their own well, we can assess whether different kinds of drinking water generate different levels of gastroenteritis. There is currently a slight trend to indicate that this is the case. The study reveals so far that the average consumption of cold tap water is approximately one litre per person per day, but that 25 per cent drink more than 1.3 litres per day and 25 per cent drink less than 0.6 litres per day. Surprisingly, the group that drinks a lot of water has fewer cases of gastroenteritis than the group that drinks little water. This does not mean that pathogenic microorganisms are not being transmitted through drinking water, but that something else associated with high consumption of drinking water results in fewer cases of gastroenteritis. The conclusion is that these kinds of epidemiological investigations find it difficult to prove how drinking water contributes to the transmission of gastroenteritis. On the basis that there are such large differences in water consumption between different groups, it can nevertheless be said with a high level of certainty that the contribution of drinking water to cases of gastroenteritis is not alarming, at least not in the area investigated. Number of cases of gastroenteritis in the population After the Ale H 2 O study had been running for eight months, it was determined that every person experiences gastroenteritis an average of 0.64 times a year (annual incidence). Acute gastroenteritis (AGE) is a stricter definition of this disease, which requires diarrhoea at least three times in 24 hours or that the patient vomits during the period of disease. Using this definition, the annual incidence of AGE is Depending on how we define gastroenteritis, this corresponds to between 2.5 and 6 million cases of gastroenteritis in Sweden every year. The proportion of these that are caused by viruses will be further investigated on the basis of a profile of the symptoms and how long the symptoms persist. The contribution of drinking water to the number of cases of gastroenteritis is, however, very unclear, although ongoing and future studies will probably provide us with better information about this. So far, it may be assumed that the water produced from the two water treatment plants included in the Ale H 2 O study are satisfactory under the normal operating conditions that have prevailed during the period of the study. The Swedish National Food Agency will be conducting similar studies in some other Swedish municipalities between 2013 and Once these studies have been completed, drinking water producers and decision-makers on drinking water-related issues will hopefully have better base data for use in assessing the contribution of drinking water to the number of cases of gastroenteritis. 12

13 Sources of emissions of microorganisms 55Municipal drains Municipal waste water always contains pathogens. Molecular biology-based methods have been used to measure up to around 10 7 norovirus particles per litre of untreated water. While treatment does take place, it is rarely designed to remove microorganisms. Measurements before and after treatment in sewage treatment plants with secondary treatment (chemical precipitation and active sludge or biofilter processing) indicate a per cent (0.4 2 log) reduction in viruses, while bacteria and parasites are separated somewhat more effectively. After treatment, it can be assumed that at least a thousand infectious microorganisms per litre are released into the aquatic environment. Which ones and how many depends on the state of the community s health, but as a rule campylobacter, salmonella, norovirus, adenovirus, rotavirus, enterovirus, giardiasis and cryptosporidium are found in most waste water following treatment. Even if there is a risk associated with municipal waste water, the advantage is that this risk is fairly constant and can be taken into consideration, even if the risk varies with the state of infection in the population and the process efficiency of the treatment plant. There can, however, be peaks in emissions, for example after overflows caused by heavy rain, when some of the waste water passes the process untreated and straight into the raw water source. In the sedimentation stage and during the biological treatment of waste water, particle-bound pathogens are concentrated, and these can be found in high levels in the sewage sludge. There is some deactivation of pathogens during the composting and/or storage of the sludge, but even this treated sludge contains infectious microorganisms. 55On-site sanitation There are many small treatment facilities on the single household level in the Nordic region that can affect the quality of raw water. In contrast to municipal sewage treatment plants, an individual drain is less likely to contain pathogens, as people in a household are only infected for a small number of brief periods. If there is disease in the property, however, there is no dilution, which means that outgoing levels at these times will be higher than levels in municipal drains. The effect of on-site sanitation can vary significantly. Many individual drains are, for example, caissons or septic tanks that are unsupervised. Effective individual drains can be just as good at capturing microorganisms as municipal treatment plants as the holding time can be up to one week, although most are not. The effect also tends to become poorer with time, and there is a need to be able to provide information about/regulate the care and maintenance of individual installations. Drain installations in areas with a high protection level must manage a 90 per cent reduction in organic material and phosphorus, and a 70 per cent reduction in nitrogen, which means that a certain degree of virus separation can be expected if a water source is located in such an area. 55Storm and drainage water As a rule, storm water and drainage water has a low faecal impact from primarily birds, rodents and pets, which generates some risk of the presence of, in particular, campylobacter and giardiasis. The most important risk is that surface water is not treated, and at the same time discharges can occur close to raw water intakes, because this is not viewed as a particularly large risk. If waste water from incorrectly connected or broken pipes comes into this system, there can be serious consequences. 5 5 Faecal contamination from animals Raw water affected by faecal contamination from manure can contain various pathogenic microorganisms, primarily bacteria and parasites, depending on the kinds of animals, the health of the stocks in question and farms procedures for handling manure. Most diseases that can be transmitted from agricultural animals to humans may be found in cattle, i.e. EHEC, campylobacter, salmonella, giardiasis and cryptosporidium parvum. It is primarily young animals that are associated with the highest risk, as they are usually the ones that excrete both EHEC and cryptosporidium parvum. While dairy cattle remain in their stalls during this period, where their manure can be handled in a controlled way, calves are put out to pasture. The impact from other animals, including wild fauna, is more limited. The risk of waterborne viral infection is probably highest in the spreading of pig manure, as it has been shown that piglets excrete hepatitis E virus of the same kind that causes disease among humans. 13

14 An infected person can excrete up to virus particles per gram of vomit or faeces. These are in turn transmitted via the sewage system to the sea, lakes and through leaks into private wells. If there are mussels close to outlets from sewage treatment plants, these can enrich the virus particles and in turn infect humans via their food. Lakes and wells that are used for drinking water production, to water vegetable crops and to freeze berries are also sources that can contain microorganisms that may infect humans. 14

15 Amounts of viruses in various kinds of raw water Country Type of water Virus Content/litre Detection method Year Comments Netherlands River water Norovirus 4 4,900 PCR Random samples Rotavirus 57 5,400 PCR Reovirus 2 10 Cell culture Enterovirus Cell culture Netherlands River water Norovirus 0 1,700 PCR 2001 (and winter ) Time series Rotavirus 0 32 PCR Enterovirus 0 32 Cell culture Finland River water Norovirus Detected, no figures reported Spain River water Norovirus 0 10,000 PCR Netherlands River water Rotavirus Infectious PCR Rotavirus PCR Enterovirus Cell culture Sweden River water, lake water Norovirus 0 10,000 PCR NORVID Sweden River water Norovirus 0 9,080 PCR VISK Norway River water Adenovirus 0 9,200 PCR VISK Norovirus 0 1.5x10 5 PCR VISK Transmission of viruses in water The amounts of pathogenic viruses that may be present in raw water depend on transmission and dilution in the water source. There are several factors that affect how transmission and dilution take place, including water flow, temperature, precipitation, degradation and sedimentation. The transmission of faecal contaminants in a water source can be simulated using computer models that describe the hydrodynamic situation in the water source, as well as the deactivation and sedimentation of microorganisms. Hydrodynamic modelling has proven to be a usable tool to define the contribution from different sources of contamination to the overall contamination at the raw water intake. Modelling is used primarily to deal with the limitations associated with analysing pathogens in raw water, as concentrations are often below the detection limit. Modelling can be used to provide a continuous description of pathogens at raw water intakes, despite low concentrations, and to simulate various scenarios in order to predict the effect of various events under different conditions. Presence of viruses in waste water Field measurements of norovirus from faecal emission sources in the Göta älv river were studied during the period June 2011 June Daily proportional flow tests of incoming and outgoing waste water have been analysed from three large sewage treatment plants. As expected, the results indicate a significant seasonal variation of norovirus in both untreated and treated waste water during the year, with the highest levels during the winter season, October March. During the winter season, norovirus levels are around Norovirus/L, while during the rest of the year levels are about one log lower, at around Norovirus/L. Analyses of treated waste water indicate that the sewage treatment plants reduce the amount of viruses by 1 2 log. As a general rule, norovirus can only be detected in the Göta älv raw water source during the winter season. The results from the waste water analyses reveal that norovirus genotype G2 is over ten times more common than G1, which is interesting as it is G2 that causes the annual winter vomiting bug epidemics, while the effects of a G1 infection are much milder. It is important to point out that the levels of norovirus measured in both waste water and, in particular, raw water are expressed as the number of genome copies per litre, which does not tell us anything about the amount of infectious norovirus present in the water. Read more about microbiological risk assessments (e.g. MRA) in Chapter 4 of this manual, in other reports from VISK and in SVU reports from the Swedish Water & Wastewater Association. 15

16 Analysis of viruses in water 55As a general rule it can be said that the more samples, the better. What is important is that samples are taken both at randomly selected times (to identify values under normal circumstances) and after events that it is believed will affect the amount of viruses (e.g. overflows at sewage treatment plants). 55To gain a perception of the amount of viruses that may be present at the intake of a water treatment plant, you can analyse the source water directly and also analyse the water (treated and untreated waste water) that is added to the water source. 55It is a good idea to contact the laboratory that will be performing the analyses before you plan the sampling process. This will also provide you with good information about how the actual analysis is performed. At the time of writing (August 2014), the Department of Food Safety & Infection Biology at the Norwegian School of Veterinary Science ( is performing such analyses in Norway. In Sweden, the samples are being analysed by Laboratoriemedicin, Ryhov County Hospital, Jönköping County Council. The Public Health Agency of Sweden can, upon request, perform analyses of the presence of norovirus in water. Information about this is available on their website, In Denmark, the National Food Institute at the Technical University of Denmark can be contacted for analyses of viruses (www. food.dtu.dk). 55Modern methods of detecting viruses, especially in raw water sources, are not ideal, even though developments are ongoing. A filter is often used when pre-concentrating viruses from raw water. This filter is affected by how much organic material there is in the water, and it is usually only possible to separate a very small proportion (less than one per cent) of the virus particles in the water. Such a low extraction rate produces high variations. In order to improve the reliability of analysis results, more samples should be taken in parallel. Waste water 55Treatment plants with a water source as a recipient constitute the most important source of viruses that infect humans via drinking water. 55It can be a good idea to take samples of both untreated and treated waste water, as both kinds may be discharged. Such sampling can provide information about the plant s treatment effect and the amount of viruses discharged into the recipient. 55If possible, samples should be collected to represent a 24-hour period. You can also use individual samples, but these will vary to a greater extent. 55One set of samples per month is a good starting point. 55To obtain a more detailed analysis of the amount of viruses (especially with regard to norovirus), more frequent samples should be taken during the winter months (November April), as it is during this period that there is the highest level of norovirus circulating in the population. 55The volume collected should be in the range 500 1,000 ml. 55The samples must be kept cold (fridge) during collection and also during transport to the laboratory. 55The samples can be frozen and collected over a longer period for analysis at a later date. If so, they should be sent to the laboratory in a frozen state. Raw water 55Raw water and water from inflowing tributaries should be collected in bigger volumes (usually up to 10 litres) because of the lower concentration of viruses usually found here. 55Raw water samples must be couriered/sent to the laboratory as quickly as possible after collection, and in a chilled state. 55It is important to agree the delivery with the laboratory in advance, as the samples must be analysed as soon as possible after arrival. 55Event-based sampling should be carried out in order to obtain a general picture of virus volumes, or the presence of indicator organisms, during periods when it is likely that they will be unusually high. These data are necessary for it to be possible to perform a risk assessment for extreme events. Event-based sampling is conducted as a supplement to water treatment plants normal sampling programmes. 55Event-based sampling should be carried out over a period of at least one year. It is important to point out that the analysis of pathogens (including viruses) is normally only used in the mapping phase. In an operational situation an analysis of indicator organisms is used (read more about this in the chapter entitled Risk assessment and checking quality ). 55Event-based sampling should be carried out at regular intervals in order to check that the situation has not changed, for example every four years or if there is any suspicion of new or changed sources of contamination. 55When mapping and conducting specific investigations, it is recommended that analyses be performed for coliforms, E. coli, enterococci and clostridium spores. Data on their internal relationships (E. coli 1 log more than enterococci as well as 2 log more than clostridium spores) can provide useful information, especially if there is a risk of leaking sewage pipes and reasonably fresh faecal contamination, as the relationship between them has not yet managed to change because of different separation rates in the sewage works, die-off rates or dispersal patterns. The relationship between them is more even after sewage treatment. Please note that the GDP guidelines use an analysis of parasites (giardiasis and cryptosporidium) in risk-based sampling programmes for the worst water qualities (see Norwegian Water report 170, chapter 3). 5 5 Viruses can be present even if you fail to detect them from sampling. 16

17 Suggestion for event-based sampling programme When inland lakes, groundwater affected by surface water or groundwater from surface water infiltrated artificially are the source: 55Spring circulation (< 1/6 of the total number of samples). 55Autumn circulation (< 1/6 of the total number of samples). 55With normal daily precipitation during the summer and/or winter months (< 1/6 of the total number of samples). 55Day with heavy precipitation during the autumn and when snow is melting during spring and autumn ( > 3/6 of the total number of samples). When rivers and streams are the source: 55Here you have to use your judgement, but in these cases too a higher level of contamination is expected in connection with precipitation. Size of water treatment plant (pers.) < 1,000 > 6 1,000 10,000 > 12 > 10,000 > 24 Number of samples (per annum) It is recommended that the number of samples collected in the risk-based sampling program be at least as many as stated in the table; for most situations twice as many samples are recommended. The risk will vary from location to location. The owner of the individual water treatment plant is best placed to find out when the risk of contamination is greatest, and the risk-based sampling programme should be adapted according to this. Remember to take parallel samples close to the source(s) of contamination and by the raw water intake. Source: GDP guidelines (Norwegian Water report 170, Chapter 3.3.3) 17

18 Mussels as an indicator of virus contamination in raw water Obtaining reliable data from microbiological monitoring of surface water can represent a challenge because of short-term changes in environmental factors or random variations in data. This means that it can be difficult to interpret data from direct measurements of enteric viruses in the raw water intake for a water treatment plant that produces drinking water. Mussels that grow in contaminated water can enrich large amounts of enteric bacteria and virus particles, which collect in the mussel s flesh. One single mussel can filter two to three litres of water per hour. Filtered viruses can remain and survive in the mussel s flesh for several weeks longer than in the water column. This makes it possible to use blue mussels as biomonitors, to investigate the overall microbiological quality of the raw water that is used in drinking water production, and to evaluate the effect of measures taken to reduce the amount of viruses in discharges from sewage treatment plants. This method was used in Sweden, Denmark and Norway during the VISK project. For example, monthly monitoring took place over two years (December 2010 until November 2012), in which enteric viruses and faecal indicators were analysed in blue mussels growing in the mouth of the Göta älv river. The objective was to map out how the amount of viruses in discharges from sewage treatment plants varied over time, and to compare this pattern with measurements in the river, in sewage treatment plants, with air and water temperatures and with norovirus activity in the general public. A seasonal variation was observed in the level of norovirus. This variation appeared to correlate with both water and air temperature and with norovirus activity in the population, according to reports from the Swedish Institute for Infectious Disease Control. In contrast to this, it was found that although E. coli could be detected in all mussel samples, there was no clear seasonal variation and no significant correlation with norovirus levels measured. Direct measurements of norovirus in the Göta älv also indicate higher levels during the winter period, although it is unusual possible to detect any norovirus during other seasons, which is in contrast to the results from this study, which indicates a constant risk of enteric virus contamination in the Göta älv and thus a general risk that there is norovirus in the water intake to the drinking water plants located here NoV GU/g DT E. coli MPN/100g Temp (Average 30 days before sampling) Measured levels of norovirus (genotype groups I and II) and E. coli (used as an indicator of faecal contamination) in blue mussels, as well as air and water temperature according to monthly measurements at the mouth of the Göta älv over a period of two years. d- 10 j- 11 f- 11 m- 11 a- 11 m- 11 j- 11 j- 11 a- 11 s- 11 o- 11 n- 11 d- 11 j- 12 f- 12 m- 12 a- 12 m- 12 j- 12 j- 12 a- 12 s- 12 o- 12 n- 12 NoV Temp water Temp air E. coli 18

19 3. Water treatment how to control viruses in a water treatment plant In modern production of drinking water, viruses are removed to varying degrees depending on which methods are used. To achieve the best possible purification and disinfection of drinking water, a combination of methods and barriers is required. Climate change is expected to bring bigger and faster changes in the quality of raw water (especially as regards surface water) as well as temporary increases in the presence of microorganisms. It is therefore important to maintain continuous monitoring of the quality of raw water and the effect of purification/disinfection in the water treatment plant, so that these changes can be dealt with while still preserving the quality of the drinking water. As virus levels in treated water are generally very low, it will not be suitable for practical reasons to analyse the presence of viruses in drinking water (the results will be unreliable and may provide a false sense of security). Steps must therefore be taken to ensure good control over the stages of treatment and disinfection in order to make sure that virus separation/deactivation is as effective as possible. A combination of different water treatment methods is required to make it possible to achieve a satisfactory treatment effect for different kinds of pathogenic organisms. The tables provide an overview of how effective the most common Worth bearing in mind in connection with water treatment 55As the presence of viruses in treated water is generally very low, for practical reasons it is not appropriate to analyse viruses in drinking water. The results would be too uncertain or result in a false sense of security. 55Even if no viruses were found in the analysis, this represents no guarantee at all that there are no viruses in the water. It is therefore important to ensure good control over the stages of treatment and disinfection in order to make sure that virus separation/deactivation is as effective as possible. 55The best effect to counteract viruses is achieved when the treatment process is managed in the best possible way. To achieve the best possible treatment effect for viruses, you can therefore use the same guidelines as for the general optimisation of the treatment process. 55The separation/removal of viruses is more difficult than is the case for bacteria and parasites. This means that even small operational disruptions can result in a reduced treatment effect for viruses, even if, for example, the colour value remains low. Operating staff must therefore have good knowledge of their treatment process and work continuously to optimise it, even if the water quality is generally good. 55Vulnerability and risk analysis: 55Has an analysis been conducted of vulnerability and risk in respect of deficiencies in the hygienic barriers and contamination of the raw water? 55Is active work being carried out to prevent contamination of the raw water? 55Are there enough hygienic barriers and are they sufficiently strong in relation to the risk? 55Technical optimisation: 55Is there online monitoring of the treatment processes? 55Are the results used actively to manage the treatment process and to trigger warning systems? 55Preparedness and competence: 55Does operating staff have sufficient competence to be able to optimise the treatment process in respect of hygienic barriers and to make it possible to make necessary adjustments in the event of faults? 55Is there a sufficient level of preparedness to be able to correct and faults in the functionality of the barrier or to deal with contamination of the water source? 19

20 treatment methods are. When assessing water treatment, consideration must be given to this whole picture as a complement to an evaluation of the raw water. Various tools have been developed for this purpose: Good disinfection practice (Norwegian Water report 170/2009. Veiledning til bestemmelse av god desinfeksjonspraksis [Guidelines on the determination of good disinfection practice]). MRA Microbiological Risk Analysis (Swedish Water & Wastewater Association). WSP Water Safety Plans (WHO). HACCP Hazard Analysis and Critical Control Points (Swedish Water & Wastewater Association, Manual for HACCP internal control programme). Various trials have been conducted in VISK to determine the barrier effect for viruses in water treatment and for natural virus reduction in groundwater sources. Note that all trials involving the separation of viruses, just like the trials in the VISK project, involve a great deal of uncertainty, which must be taken into consideration when using these data. The purification effect can also vary significantly between various water treatment plants, depending on differences in operation and design. Separation method Bacteria Virus Parasites Quick filtration Poor Very poor Quite poor Precipitation + quick-filtration Very good Good Very good Membrane filtration Reverse osmosis and nanofiltration Very good Very good Very good Ultrafilter Good Quite good Very good Microfiltration Quite good Less good Very good Ultrafilter or microfiltration, with precipitation Very good Very good Very good Effectiveness of the most common separation treatment methods (source: Swedish GDP guidelines, 2012) Disinfection method Bacteria Virus Parasites Chlorination Very good Quite good Poor Ozonation Very good Very good Partly good 1 UV radiation Very good Good 2 Very good Effectiveness of the most common disinfection methods. 1 Good against giardiasis, less good against cryptosporidium. 2 Better for certain viruses than others; among others, adenovirus can withstand UV. Treatment stage Log reduction virus Comments Coagulation + filter or sedimentation 1 3 Filter or sedimentation without 0 1 precipitation Carbon filter 0 1 Slow filter 2 3 Artificial infiltration 1 4 Depends on ground s properties and dwell time. Ultrafiltration >4 For UF dimensioned for virus separation. Chlorine 4 6 Should not be counted as a barrier against parasites. Chlorine dioxide 4 6 As a rule slightly more effective than chlorine, but still not a significant barrier against parasites. Chloramine 0 1 UV 3 4 Poorer effect for adenovirus (0 1 log at doses of mj/cm 2 ). Ozone 3 4 No barrier against cryptosporidium; parasites are more resistant than viruses. Plants adapted for colour removal can be run with high doses of ozone, which produces a high log reduction for viruses. Examples of the barrier effect for viruses, based on results from VISK and studies of literature, indicate the most probable log reduction for viruses under normal operating conditions, i.e with no disruption in the disinfection or previous process stage. Unless otherwise stated in the Comments column, the reduction is more effective for bacteria and parasites. For all treatment stages, checks must be conducted on an ongoing basis to make sure they are working, in order to be able to calculate using the log reduction quoted. 20

21 Log reduction as a measure of the barrier effect One way of describing how many microorganisms have been separated from water during treatment (barrier effect) is to express this as a percentage (%). The percentage figure states either what proportion of what was there initially has been removed or how much is left. If a large proportion is removed, for example 99.99%, ultimately the figures become difficult to process and mistakes can easily be made. In this context the concept of log, which essentially tells us the same thing, can be easier to use. 90% separation corresponds to 1 log (1 power of ten, i.e. 10% left), 99% is 2 log (2 powers of ten, i.e. 1% left), 99.9% is 3 log, 99.99% is 4 log, % is 5 log, and so on. (As a rule of thumb you can say that the number of log is the same as the number of 9s in the percentage figure, which denotes how much has been reduced.) Virus levels from sewage to safe drinking water How many pathogenic viruses are there in water and how much should be separated? The main purpose of the VISK project is to attempt to answer this question. Guidance is provided further on in the manual, but to create a perception of what amounts are involved, we have created an illustration based on data from VISK. The concentration of viruses in untreated waste water is normally 10 6 per litre. To meet the WHO s target that only 1/10,000 people shall be infected per annum, a reduction of approximately 12 log is needed. This reduction is distributed across sewage treatment 1 2 log, dilution, sedimentation and deactivation in the recipient 3 5 log. It is then a matter of removing approximately 6 log in the water treatment process. Sewage Surface water Raw water intake Virus at consumer 1,000,000/l = ,000/l 1 10/L 1/10,000,00l = 10-6 /l Sewage treatment Dilution, deactivation, sedimentation Chemical precipitation/quick-filtration Chlorination 21

22 Groundwater aquifers as a hygienic barrier against viruses Most groundwater supplies in Norway and Sweden are based on the extraction of groundwater via extraction wells in sand and gravel deposits, often close to watercourses. New formation of groundwater in such deposits can take place either naturally or artificially: Naturally by means of infiltration of precipitation. Naturally by means of infiltration from a river or inland lake. Artificially by means of pumping surface water to a recharge basin or injection wells. The water in the pump well that is used to extract water from the groundwater source consists of, in both natural and artificial infiltration, a mixture of water from a surface water source with a shorter dwell time and precipitation-infiltrated groundwater with a longer dwell time. When the water passes through the ground, it is subjected to a number of different physical, chemical and biological processes, all of which contribute to purifying the water. The infiltration water corresponds to the raw water and the filtration/transport process through the sedimentary layers is water treatment. For more detailed information about groundwater extraction, see or Natural recharge 55Deactivation increases with rising temperatures and a low degree of saturation. 55Separation (filtration or sorption) increases with a smaller pore size, large contact area between the grain in the layer of soil and the virus, different charges in the virus and the grains of soil, a low degree of saturation, small grain size and long contact time. The contact time is controlled by parameters such as flow rate and transport distance. Barrier effects 55The size of the barrier effect against viruses and other contaminants depends on conditions that vary between different groundwater plants and geological media. To reduce uncertainty when determining the barrier effects in a groundwater extraction, it is therefore necessary to conduct thorough, full-scale hydrogeological investigations for each individual plant. When calculating the log reduction, for example, you must take the following into consideration: 55The properties of the aquifer. 55Protective measures in the aquifer s catchment area. 55Monitoring of the water quality and water levels in the groundwater source and the watercourse. 55The extraction rate (which affects the flow rate and contact time). 55The barrier effect is often higher in the unsaturated zone (the unsaturated zone above the groundwater table) than in the groundwater zone (the saturated zone) because of differences in factors such as temperature, degree of saturation, presence of organic materials and flow rate. 55In the groundwater zone, where the pores are partly filled with air, deactivation can make a significant contribution to virus reduction. Water Table Rainfall 55In the saturated zone, where the pores are 100 per cent filled with water and the temperature is normally lower, deactivation can be slower, but on the other hand the dwell time is often longer. Water Table Unconfined Aquifer Saturated Aquifer Recharge Basin Extraction Well Natural new groundwater formation from precipitation and watercourses or artificial new groundwater formation in recharge basin (reg: Deactivation and separation Viral threats in drinking water are eliminated through separation from the water and/or through deactivation of substances that can infect a host cell. Soil 55The physical separation from the water (with filtration/ sorption) is affected by the contact area and contact time between the grains in the layer of soil and the virus, and controls the passage of the viruses through the saturated zone in the layers of soil. 55Placing a filter deep in the production well creates an extra safety factor by providing a longer flow section and increased contact time. 55In rougher deposits with a small contact area between the virus and the layers of soil, a longer dwell time (contact time) is required in order to achieve the same barrier effect as quoted in the tables below. 55The barrier effects in unsaturated and saturated zones constitute the water treatment plant in the groundwater source. To maintain the effect of this natural water treatment process, the source s extraction area must be protected. You can read more about this in the guidelines for Beskyttelse av grunnvannsanlegg [ Protection of groundwater plants ] (Geological Survey of Norway, 2011). 22

23 Thickness, unsaturated zone Contact time, unsaturated zone Maximum log reduction virus 20 metres > 8 days 4 log 15 metres > 6 days 3 log 10 metres > 4 days 2 log 5 metres > 2 days 1 log Examples of barrier effects for virus reduction when flowing through the unsaturated zone. The examples apply on the condition that the infiltration material consists of 80% sand and that 20% of the layers of soil have a grain size of < 1 mm. The infiltration water s flow rate should be < 3 m/day. Distance between watercourse and well area Contact time in the saturated zone Maximum log reduction virus 80 metres > 20 days 4 log 60 metres > 15 days 3 log 40 metres > 10 days 2 log 20 metres > 5 days 1 log Examples of barrier effects for virus reduction when flowing through the saturated zone. The examples apply when using vertical production wells and require that the aquifer consists of 80% sand and that 10% of the layers of soil have a grain size of < 1 mm. The deposit must also be free of channels with coarser material that may cause blockages in the transport route. The groundwater s flow rate should be < 5 m/day. Basin Well Flood water level Normal water level At the normal water level, the infiltration surface against a watercourse is often clogged and has a good treatment effect on the surface water being infiltrated into the groundwater. The filtration efficiency in river beds can, however, vary during the year. There are special risks associated with periods of flooding and high water levels in rivers and inland lakes. A powerful water flow can scrape away the sludge layer on the river bed, reducing the treatment effect. If water levels are unusually high, the water can be filtered through coarser layers higher up along the riverbank (channel drainage). This produces an increased infiltration rate and reduced treatment effect (Gaut 2011, following Eckholdt & Snilsberg 1992). 23

24 Checklist for protection against microorganisms in groundwater from soils 55Choice of source vulnerability and activity rules: 55Is the aquifer an open aquifer? 55Are there any layers in the aquifer with low permeability? 55Is the aquifer in hydraulic contact with a watercourse? 55Has the thickness of the unsaturated zone been mapped out? 55Has the production well s area of influence been mapped out? 55Have sources of contaminants within the well s area of influence been identified? 55Has the groundwater s dwell time from watercourse to production wells been mapped out? 55Has the groundwater s dwell time from potential sources of contaminants to production wells been mapped out? 55Has the interaction between watercourses and the aquifer been sufficiently well mapped out? 55Is there a risk of blockages in the flow from watercourse to well in the event of flooding? 55Have protection zones been set up around the groundwater plant? 55Are there registered landowner agreements in the protection area (zones 1 and 2)? 55Have protection zones been included in the detailed plan for the area? 55Have the production wells been registered in the national groundwater database? 55Wells and water intakes safety measures 55Is the top of the well higher than the ground level? 55Is the direction of fall on the ground away from the well? 55Is the top of the well secured with a sealed lid or well housing? 55Is the area around the well housing/well lid enclosed within a fence? 55Is there any risk that surface water can make its way in around the top of the well or the pipe? 55Need for water treatment natural microbiological safety barriers: 55Has trial pumping been carried out for at least one year? 55Has the quality of the raw water in the production well been mapped out during the trial pumping period? 55Has the quality of the raw water in any filtering watercourses been mapped out during the trial pumping period? 55Is the quality of the water in production wells being monitored continuously? 55Is the quality of the water in filtering watercourses being monitored continuously? 55Have two or more hygienic barriers been set up in the water supply system? 55Is the dwell time in the saturated zone 14 days? 55Is there a risk of occasional penetration by water with a shorter dwell time? Chemical precipitation Chemical precipitation can be set up in various ways (direct filtration, sedimentation, flotation, etc. and combinations of these). What they share in common is that in principle they consist of two stages: 1. Chemical pre-treatment (coagulation and possibly flocculation). 2. Separation (sedimentation, filtration, flotation or a combination of these). The treatment effect for viruses is dependent upon both stages working effectively. Barrier effect 55For chemical precipitation, a barrier effect of 1 3 log can be assumed. Typical values for an effective precipitation system are log. This appears to hold true regardless of whether you only use filters or filters combined with pre-separation (sedimentation/flotation). 5 5 The barrier effect is specific for each water treatment plant and also depends on the level of operational optimisation, see below. 24

25 Operational optimisation 55A prerequisite for achieving the log effect described above is an effective treatment with a low level of turbidity in the outlet (< 0.1 NTU). It can be expected that to some extent the treatment effect will coincide with the outlet turbidity and that in this way, in the same way as for parasites, for example, you must make sure that you have good, stable operations, with low filter speed and a chemical dose and a precipitation ph that are as close to ideal as possible with regard to the raw water quality. In practice it may be appropriate to have a slightly higher dose, to be sure of being able to deal with variations in the water quality. 55The trials at VISK have shown that flocculation (which depends on dose and ph) is most significant for this treatment stage, just as for separation (sedimentation, flotation and/or filtration). This is assumed to be associated with the fact that viruses are extremely small particles (down to approx. 20 nm, pathogenic waterborne viruses down to approx. 30 nm) and that separation depends entirely on good chemical pre-treatment. 55An inaccurate chemical dose or an incorrect precipitation ph can easily result in a halving of the treatment effect for viruses, even if the outlet turbidity remains low. 55Major changes in the filter speed produce a more modest loss of effect, as long as the chemical pre-treatment is good. The filter speed should also be kept as constant and as low as possible. 55Read more in the VISK report from work package 4 and Norwegian Water report no. 188, Veiledning for drift av koaguleringsanlegg [Guidelines on operating a coagulation plant]. same plant (direct filtration) even though the outlet turbidity is at all times below 0.1 NTU. This means that turbidity is not a satisfactory indicator of good virus separation. 55More suitable methods might be the measurement of coagulant residues (e.g. aluminium residue) and/or particle counting. Variations have been observed in log separation that do not correlate with or cannot be explained by other water quality parameters (e.g. turbidity). Other instruments/meters that can be valuable are charge gauges, zeta potential, dosing control systems (such as DOSCON). 55Each individual water treatment plant must identify its own most sensitive parameter and set up a good follow-up process for this. See reports from Norwegian Water and the Swedish Water & Wastewater Association on optimal disinfection practice for more detailed information. Carbon filter When treating drinking water, carbon filters (filter beds with granulated active carbon) are used primarily to remove loose organic material through adsorption. Barrier effect 55No adsorption of viruses can be expected from active carbon. A carbon filter that consists of granulated active carbon, however, will act as a quick filter. 5 5 The treatment effect for filters without coagulation has not been mapped particularly well, but is assumed to be between 0 and 0.5 log. Choice of control parameters 55Climate change is expected to produce greater variation in both colour values and particle content in raw water. These variations will affect the precipitation stage and pose bigger challenges when it comes to achieving sufficient separation of viruses in water treatment plants. It will therefore be important to maintain continuous follow-up on chemical doses and precipitation ph. 55Water treatment plants should make active use of online measuring of turbidity or particles so that they can correct the chemical dose/ph as required, and they should also pay particular attention to changes in the quality of raw water. If the process is not working effectively, it is important to determine whether it is flocculation, flock separation or both that are not optimal. 55As a general rule, it can be assumed that low outlet turbidity is a sign of a good treatment effect, but although online particle measurements during/after the process are considered very important, trials indicate that the treatment effect for viruses can vary between 1 and 2 log at the 25

26 CT value (concentration time) and disinfection A virus that is to be deactivated ( killed ) with the aid of disinfectants (chlorine and ozone) must come into contact with a sufficiently large amount of disinfectant over a sufficiently long time. This combination of concentration and time is known as the CT value. The following factors affect the CT value: The water s chemical composition (ph and content of organic material) and temperature. Concentration and type of disinfectant (varying effectiveness). The contact time between the disinfectant and the organisms to be deactivated. The flow through the disinfection equipment, which determines the concentration and contact time. When chlorine or ozone are added, there is a fast reaction with the organic material in the water (initial reduction). There is then a slower reaction with the remaining disinfectant. This is illustrated in the figure. The CT value is the sum of time and concentration, corresponding to the area below the line and is expressed as mg*min/l. Pathogenic microorganisms have different levels of tolerance against disinfection, and thereby different CT values to achieve the desired log separation. For example, it is difficult to deactivate the parasite cryptosporidium to a sufficient degree with either chlorine or ozone because of its high tolerance (high CT value) to these agents. Chlorine concentration (mg/l) 0,5 Initial chlorine dose 0,4 0,3 Initial chlorine demand 0,2 0,1 Outgoing chlorine concentration Time (min) Disinfection process, chlorine. The CT value corresponds to the area below the line. 26

27 Disinfection using chlorine Disinfection using chloride compounds is a common method of deactivating bacteria and viruses. Chlorine cannot be used against parasites. Free chlorine affects both the virus s DNA and the ability of the virus to inject its DNA into the host cell, while chlorine dioxide acts primarily by ensuring that exposed virus particles cannot link to their host cells. 55The disinfection effect from the use of chlorine depends primarily on concentration and contact time, but is also affected by ph, the presence of organic material, the type of chlorine compound used and temperature. See also the fact box about CT values. 55Free chlorine is more effective at lower ph values, as the equilibrium is driven towards the more virucidal hypochlorous acid. 55As the biochemical activity increases with the temperature, the higher the temperature, the faster the deactivation of viruses takes place. Barrier effect 55The barrier effect differs from one water treatment plant to another, but it can generally be expected to be good if chlorine is used: 2 6 log for chlorine under normal conditions, i.e. without any disruption in either the disinfection process or previous processes. This is on the condition that sufficient CT values are achieved. 55Trials within VISK were conducted with one adenovirus, one reovirus (same group as rotavirus), one norovirus and one enterovirus. The initial reduction in viruses was between 2 and 5 log, with an average of over 3 log for all viruses tested. A poorer function at higher colour values could be determined in trials with bacteriophages. See the specialist report for further details. 55The measure of effectiveness used was chlorine contact time for 1 log reduction (mg*min/l). This can be easily multiplied for the desired barrier effect (x 3 for 3 log reduction, x 4 for 4 log, etc.). CT for 1 log reduction was below 1.0 mg*min/l in all trials. The highest value, 0.90, was for adenovirus in untreated raw water from the Rådasjön lake. In most cases CT for 1 log reduction was below 0.5 mg*min/l, which means that for a 4 log reduction (without initial reduction), CT > 2 mg*min/l should be achieved. See also the VISK report from work package 4. 55Trials in VISK indicate that, for example, a concentration of free chlorine of 0.2 mg/l, which after 20 min is 0.1 mg/l, would produce a CT value corresponding to 3 mg*min/l and a probable reduction of approximately 6 log, initial reduction not included. Operational optimisation 55When using chloride compounds, disinfection is most effective at low ph values, and chlorine should therefore be added before any ph adjustment. 55Chlorine added will be consumed by organic material and particles in the water, so good pre-treatment enhances the disinfection effect. It is therefore recommended that a close eye be kept on changes in the water quality and the chlorine dose adjusted accordingly. This will be needed, for example, in connection with heavy precipitation, melting snow, changes in the raw water source or deficiencies in pre-treatment. Control parameters and control 55The best way of monitoring the effectiveness of disinfection using chlorine is the online measurement of free chlorine. 55Note that the analysis uncertainty for free chlorine is very high at a detection limit of 0.05 mg/l. There must be more than 0.05 mg/l in order to detect residual chlorine, and values below 0.1 mg/l must be used with caution. 5 5 The effectiveness of chlorine is normally determined by means of calculations or concentration requirements. It is also possible to obtain an idea of the effect with the aid of other methods, such as living cells, for example. Further reading i the scientific report from VISK work package 4. 27

28 Disinfection using ozone Ozone is a stronger oxidant than chlorine (equivalent reduction at lower CT value). This disinfecting effect includes the deactivation of nucleic acids (DNA and RNA) as well as the destruction of the cell walls in bacteria or the protein envelope in viruses. The oxidation process can (put somewhat simply) be divided into two phases, in the first of which there is a rapid reduction (<1 min) as the ozone reacts with oxidisable substances, and then a slower process that is more significant for the disinfection process. 55A water treatment plant must not discharge any ozone residues, and ozonation therefore has no residual disinfection effect in the mains. 55Apart from the disinfecting effect, there is also a colour reduction, an improvement in the water s sensory quality and a breakdown of various environmental toxins where there are any. 55The colour reduction also produces an increase in the water s UV transmission, which is important when dimensioning the subsequent UV installation, which is often used in Norway as a hygienic supplementary barrier together with ozonation. Barrier effect 55To achieve a reduction in viruses and bacteria of 3 log and a reduction in parasites of 2 log at 4 C, it requires a CT value of 0.5 for bacteria, a CT value of 1.0 for viruses and a CT value of 1.5 for giardiasis. This is normally achieved with a dosage of mg ozone/l. 55When ozone is used to remove humus, the dose is often nearly 5 mg ozone/l. At such high doses, ozonation has a very good disinfection effect. 55Ozone does not provide a satisfactory barrier against cryptosporidium. Cryptosporidium is far more resistant, requiring a CT value of 30. This makes it necessary to use higher doses of ozone and not least a longer contact time. A risk assessment should be used to assess the extent to which ozonation can act as a partial barrier (for example 1 log reduction) in respect of cryptosporidium. Operational optimisation 55Ozonation, especially of surface water, requires subsequent biological filtration in order to reduce light, biodegradable organic material that is created by the oxidation of water containing humus. 55For raw water with a colour value of more than mg Pt/l, methods other than ozonation are usually recommended to remove humus. 55When new plants are constructed, it is important to prepare for sufficient flow in the contact chamber and to set up testing points to document that the required CT values are achieved. 55Important control parameters in daily operations are online measurement of the ozone concentration in gas flows from the ozone system and 2 3 testing points in the contact chamber for online measurement of the ozone concentration in the water phase. 5 5 Experiences from modern ozonation plants indicate that they are robust and reliable in operation. 28

29 Ultraviolet radiation Ultraviolet radiation (UV) is a method of disinfection that is becoming increasingly common because of its greater effectiveness when it comes to the deactivation of parasites compared with chlorine. 55The effect will vary with the presence of particles and colour values in the treated water and differs for different kinds of microorganisms. 55For detailed information about UV radiation, see Veiledning for UV-desinfeksjon av drikkevann [ Guidelines on UV disinfection of drinking water ], Norwegian Water report 164 (2009). Barrier effect 55Viruses have different levels of resistance to UV radiation. A UV dose of mj/cm 2 deactivates most viruses to the order of 3 4 log or higher. But this does not apply, for example, for certain kinds of adenovirus. Operational optimisation and control parameters 55The effectiveness of UV disinfection depends on the water s transmission and how much water passes through the system. 55The water s UV transmission (UVT) depends in particular on the content of organic material (humus, etc.), and there is often a good correlation between increased colour and reduced UVT. It is therefore important that the UV system is set up for the lowest UVT that can occur. If the water treatment plant uses decolourisation (e.g. coagulation and filtration), a decision must be made on whether the UV system is to be dimensioned to also be able to purify untreated water (raw water) in an emergency situation. 55In order to achieve the best possible transmission, pretreatment should focus on reducing the presence of particles and organic material (colour). Particles in the water can also protect pathogens from the radiation, so it is important for turbidity to be as low as possible in the system. 55If chemical precipitation and sedimentation or filtration are used before the UV system, you should be aware that disruptions in these processes may result in increased turbidity, which reduces the barrier effect significantly. 55To achieve a sufficiently large dose (30 or 40 mj/cm 2 ), it is important to check the flow of water to each unit as well as the quality of the water (measured in transmission or intensity). 2 log 3 log 4 log Calicivirus Adenovirus Enterovirus Rotavirus Hepatitis A virus UV dose (mj/cm 2 ) required to achieve 2, 3 and 4 log reduction respectively for various viruses. (Ref: Eikebrokk, Ræstad, Hem, & Gjerstad, 2008) 29

30 Ultrafilters are available in various designs, for example modules with hollow fibres that are fitted in large racks with pressurised pipes. The demonstration module in the photo is opened so that it is possible to see and feel the fibres. 30

31 Ultrafilter UF An ultrafilter used for drinking water preparation is a membrane of polymer or cellulose with pores invisible to the naked eye but well-defined in size. The water is forced through the membrane, and this effectively separates microorganisms, residual flocks and particles. 55Ultrafilters alone cannot reduce the water s colour, odour or loose environmental contaminants, this often requires a combination with chemical precipitation. 55The microorganisms that are separated are channelled to drains via a regular backwash. 55Energy consumption and water loss are very low compared with nanofiltration and reverse osmosis. 55As the membrane also separates residual flocks, they are also resistant to disruptions in the existing precipitation, which is an advantage compared with UV. Ultrafilters are available in various designs, for example modules with hollow fibres that are fitted in large racks with pressurised pipes. The photo shows membrane from Pentair X-flow. Barrier effect 55The microbiological barrier effect of ultrafilters with a pore size of approximately 25 nm is 4 log for viruses and 5 6 log for bacteria and parasites. 55One advantage of ultrafilters is the fact that the water s physical and chemical properties are not changed. An ultrafilter is a separation stage and not a killing process, so remnants of organisms in the water are minimised. 55Ultrafilters are resistant to any disruptions in previous processes, i.e. they represent an independent barrier. Direct capture with ultrafilters is also a possibility. Operational optimisation 55Optimal operation requires an intact membrane, so it is important to be able to check that this is the case. This can be done purely physically by pressurising damp membranes with air and measuring any pressure drop (Air Integrity Test) or by using a laboratory analysis that is sufficiently sensitive to detect the reduction. that it is not sufficient to use the particle counters that are used traditionally in the water and sewage industry; you need particle counters designed for this kind of clean water. Depending on the turbidity of the feed water, a suspended solids meter can be used. 55When taking samples and performing checks it is important to use parameters that provide sufficiently high levels before the membrane in order to be able to see what reduction has been achieved afterwards. Virus-like particles (VLPs), fluorescent particles (micro-algae) and living cells can be used for separation and microorganisms 3d and 7d (plate count) to check subsequent growth. The parameters are described in VISK report work package 4. 55Quality control of new membranes can take place with additive trials on mini-modules of representative fibres, or by taking samples of VLPs through the new module itself. 55Important quality control points are: 55Using an alarm to monitor the pressure difference over the membrane to avoid it being damaged. 55Regular integrity check in accordance with the membrane manufacturer s instructions. 55In connection with operating control, you should measure a parameter before and after the membrane that can indicate good reduction, for example VLPs or living cells. 55Have online instruments that can indicate leakage, for example particle counters for very small particles. 55Conductivity measurement of permeate in order to check that no washing chemicals remain in the water delivered. 55By means of trial and error, find out how the membrane needs to be washed for the water treatment plant in question. 5 5 See also SVU report on the procurement of ultrafilters for examples of specifications of requirements and production control. 55The membrane s permeability and the pressure to which it is subjected determine which intervals and chemicals are to be used for backwash and washing the membrane. Traditional water treatment plant chemicals such as lye, acid and chlorine are used for purifying, and backwashing takes place with filtered water (permeate) too. 55Online monitoring can take place with particle counters in order to trace major fibre fractures or other leaks. Note 31

32 4. Risk assessment and checking quality To be able to answer the question: Is my water supply good enough? you should start by answering the following questions: 1. How contaminated is the raw water (and how does it vary)? 2. Where does the contamination come from? 3. How effectively can the water treatment plant remove the contaminants? 4. How great a risk is there that contaminants will enter the supply network? Contaminants in raw water There are different ways of finding out how much raw water is affected, each of them with their own benefits and drawbacks. 55One way is to measure the content of pathogenic microorganisms (pathogens) in the water. The benefit is that this confirms how much is there without having to consider survival, dilution and the number of cases of disease in the population. This is currently done using methods based on the detection of DNA such as PCR. 55It is important to be aware that the absence of an indicator does not automatically mean that there is no risk, as certain pathogens can survive better in the environment, for example viruses and parasites. 55The most commonly used indicators are E. coli and enterococci. Concentration Indicator Parasites Viruses Discharges Bathing water Detection limit, indicator analysis 55As there are many different pathogenic microorganisms that can be transmitted by water and it is a complicated, expensive process to determine whether each of these is present in water samples, indicators of faecal contamination are often used instead as a measure of contamination. 55The detection of an indicator means that the water has been affected by faeces and that there is therefore an increased probability that the water contains pathogens. The presence of an indicator does not always have to mean that there actually are pathogens in the water, as the indicators may come from individuals who are not infected and in some cases also from sources other than warm-blooded animals. Time, distance from discharge The relative levels of an indicator (e.g. E. coli), parasites (such as giardiasis and cryptosporidium) as well as intestinal viruses (such as norovirus) in untreated waste water, after primary and secondary purification as well as dispersal in the aquatic environment. The further you come from the discharge, the greater the increase in the relative content of parasites and, above all, viruses in relation to the indicator. This is because they survive better in the environment. For example, sedimentation processes are an important element of separation in a water source. While indicator bacteria do not survive, clogged sediment can still contain infectious viruses and parasites. Nor do viruses settle as well as the indicator bacteria during transport. The limit for when the indicator bacteria are at a lower level than viruses and parasites varies, depending on the type of sewage treatment and conditions in the reservoir, but it is estimated to be somewhere between one and two weeks. 32

33 A summary of the chapter Risk assessment and checking quality 55It is difficult to protect against viruses in the water supply 55There is no analysis method sensitive enough to make it possible to measure the virus content directly in drinking water. You cannot therefore focus on detecting viruses in drinking water or use this as a way of checking the purification effect in a water treatment plant. 55There is very little information about concentrations and variations of viruses in raw water. The VISK project has produced some data for a small number of watercourses, but there is still very little information about how virus concentrations vary over the year or in connection with precipitation. There is also limited information about what kinds of viruses are present. 55It is difficult to remove viruses. The purification effect varies with operating conditions, and there is not as yet any detailed knowledge of how best to control the purification effect at water treatment plants. 55Viruses can cause disease, even at very low concentrations. 55When performing a risk assessment, it should be assumed that there are viruses in the raw water all cases where it is affected by human activity, especially drains. It is also not possible to rely on analyses of viruses or other microbiological indicators guaranteeing safety, even if no presence can be detected. 55Two strategies for water treatment plants 1. Select purification processes in such a way that they protect against infection from viruses. 55This can mean that you have to increase the purification efficiency over and above what is defined in current regulations, for example by assuming that chemical precipitation and ultrafiltration are not satisfactory barriers. 55This can mean that water treatment plants must consider the introduction of additional measures against viruses, for example using both UV and chlorine as supplements to other purification processes. 2. Map out viruses in the raw water source. 55A long-term analysis programme should be initiated to obtain an overview of the scope and variation of faecal contamination in the raw water, as well as the most important sources of this. 55These base data can be used over time to improve the risk assessment in the water supply process, for example by improving knowledge of which conditions are most critical in terms of viral infection. 55A mapping process can also be used as a basis for decisions on the extent to which action must be taken in the water supply process or whether other kinds of action are needed. (Disinfection of drains? Moving intakes? Moving discharges?) 55Practical recommendations 55Start to analyse the raw water. Set up an analysis programme that both takes regular samples and that identifies special conditions such as high precipitation intensity, water with high particle levels, unusually cold, etc. Feel free to collaborate with sewage treatment plans in order to get data on virus concentrations from waste water and from overflows. 55Optimise the current purification process in accordance with professional guidelines, e.g. from ODP/GDP, experts, EPA s guidelines, etc. 55Conduct investigations to identify which operating parameters are most sensitive at your water treatment plant. Possible candidates can include analysing residual coagulants, particle counting or virus-like particles. 55Conduct a risk assessment that is not based on averages, but analyse the risk based on known variations in chlorine doses, purification effect and the presence of viruses. 55Assess whether there is a need for further measures, for example using chlorine even though you already have two other barriers, or possible measures in the sewage treatment plant. 33

34 Indicator organisms Indicator organisms are used in water analyses to signal the presence of faecal contamination and thereby a risk that the water might contain microorganisms that can cause disease. This is a simpler method than analysing directly for all possible waterborne pathogenic bacteria, parasites and viruses. Indicator organisms can also be used to evaluate the effect of water treatment. The common criteria for indicator organisms are the following: Are not pathogenic. Are present in high numbers in faeces from all (warm blooded) animals and humans. Are present in higher levels in faeces than pathogenic microorganisms. Survive in water in the same way as pathogenic microorganisms. Do not form or multiply in natural water sources. Are deactivated or separated to the same degree as pathogenic microorganisms in water treatment. Can be detected by means of simple, cheap methods. There are different indicator organisms with different properties, and the choice of indicator organism depends on what is to be studied. The most commonly used indicators are coliform bacteria and E. coli. Others that may be used (as a complement) are enterococci (Ent. faecalis and Ent. faecium), spores from anaerobic sulphitereducing bacteria (Clostridium perfringens) and coliphages, which are viruses that infect certain strains of E. coli. Indicator organism Content in waste Indicates Comments water [CFU/100 ml] Coliform bacteria Surface water affected groundwater, poss. faecal contamination and contamination of supply network and/or suboptimal purification (disinfection). E. coli (Fresh) faecal contamination. Faecal enterococci Faecal contamination. Somatic coliphages Faecal contamination, risk of viruses. Limited analysis availability. Clostridium spores Remote faecal contamination. The spores are highly resistant. Total number of bacteria Total number of slow-growing bacteria A change with unusually high values can indicate surface water contamination and/or suboptimal purification (disinfection). Ditto. Should be included in analysis of groundwater. Be aware of changes. Should be included in analysis of groundwater. Be aware of changes. 34

35 55E. coli E. coli is present in high volumes in faeces from animals and humans, and is often used as an indicator of fresh faecal contamination of a water source (WHO Guidelines). However, the current method of detecting E. coli is unable to differentiate between contamination from humans and animals. E. coli is also used as a process indicator to evaluate the effect of water treatment. Intestinal viruses do, however, have a better ability to survive in a water source and in some treatment processes than E. coli. Free virus particles also settle more slowly than E. coli. E. coli is therefore not a suitable indicator for the detection and deactivation/separation of human pathogenic (i.e. pathogenic in humans) intestinal viruses in a water source, without taking the above into consideration. 55Intestinal enterococci Intestinal enterococci are gram-positive, round to egg-shaped bacteria that have the same sources as E. coli. The membrane and the shape, which mean that they have less surface in relation to volume compared with bacterial rods, make them more resistant in the environment than E. coli. They are also included in the Bathing Water Directive because of the fact that they are tolerant to high salt concentrations. In contrast to clostridium perfringens, they are excreted in high levels by many animals, and we recommend that the analysis of raw water be extended to include analyses of enterococci, as there is a complete analysis package for bathing water that can be used. 55Clostridium perfringens Clostridium perfringens produces spores that are extremely resistant to UV radiation, temperature and disinfection processes. Clostridium perfringens is not formed in the environment and is a specific indicator of faecal contamination. Because of the good ability of the spores to survive, they can be used as an indicator of older faecal contamination. 55Somatic coliphages Bacteriophages (coliphages) are viruses that are formed in bacteria (E. coli) and can be released in the intestine (in both humans and animals) and the environment when the host bacterium is destroyed. Bacteriophages therefore accompany faeces and can be used as an indicator of faecal contamination in a water source. Bacteriophages can be detected using relatively simple methods (plaque method in Petri dishes) and one advantage is that you are detecting living viruses. One drawback is that bacteriophages that are detected can come from animals and thus indicate intestinal viruses that cannot infect humans. As bacteriophages survive/settle more like pathogenic viruses than E. coli do, these can actually be a useful complement to E. coli if you want to map faecal contamination in a water source. Somatic coliphages are a large group of viruses that exist in high concentrations in waste water. They have different compositions, although some have the ability to form in the environment. The latter factor makes somatic bacteriophages less suitable as an indicator of faecal contamination. 55F-specific RNA coliphages F-RNA bacteriophages can only form at temperatures over 30 C, i.e. in the intestine of warm-blooded animals. The F-RNA bacteriophage also has a structure that is very similar to the one in an intestinal virus, which is why it is used as an indicator of these when analysing the ability to survive in water sources and sensitivity to treatment and purification processes. One drawback with F-specific bacteriophages is that they occur in lower amounts in waste water than somatic coliphages. The presence of F-RNA bacteriophages in a water source does, however, indicate faecal contamination and the possibility that it also contains intestinal viruses. 55Total number of bacteria The total number of bacteria is no indicator of faecal contamination, but it can provide information about changes in the water quality and is significant for groundwater treatment plants where you do not need to be able to detect any of the above. 5 5 Choice of analysis An analysis to determine coliform bacteria, E. coli, enterococci and clostridium spores is offered by most laboratories, and we recommend that analyses be performed for all of these parameters at least in connection with mapping and specific investigations. Taken as a whole, their internal relationships (E. coli 1 log more than enterococci as well as 2 log more than clostridium spores) can provide good information, especially if there is a risk of leaking sewage pipes and reasonably fresh faecal contamination, as the relationship between them has not managed to change because of different separation rates in the sewage works, die-off rates or dispersal patterns. The relationship between them is more evenly distributed after sewage treatment. 35

36 Sources of contamination Campylobacter, cryptosporidium and EHEC are examples of pathogens that can be transmitted from both waste water and from animals to humans. Diseases that can be transmitted from animals to humans are called zoonoses. By contrast, intestinal viruses such as norovirus have a narrower host spectrum and are as a rule only transmitted between people, for example via water contaminated with sewage. 55Sewage discharges generally represent a greater risk to health than contamination from animal droppings. 55As regards the risk of viral infection, discharges from drains are the main source. 55As PCR detects both harmless and infectious virus particles, it is impossible to find out the exact number of infectious viruses in a water source (or in waste water). The laboratory results are defined as the number of genome copies per unit of volume. How many infectious virus particles this represents is not known when it comes to norovirus, but you do have an indication of the number and can note any changes in levels. PCR (polymerase chain reaction) PCR is a molecular method used to detect RNA or DNA. RNA and DNA consist of building blocks (nucleotides) that are joined in a certain order (sequence). This sequence is different for animals and humans, viruses and bacteria, but is relatively stable for a certain species, bacterium or virus, for example norovirus. If you know the sequence of a virus, you can design a PCR to detect that virus. You select a specific part of the sequence and then use PCR to multiply it into a large number, which can be detected visually or with PCR machines (real-time PCR). Real-time PCR also makes it possible to determine the number of virus particles. In theory it would be possible to detect one (1) single particle, and this high sensitivity has made PCR the most widely used method for detecting viruses in environmental samples such as water. As a PCR reaction can only analyse a small volume, the water must contain approximately 50 particles per ml for it to be analysed directly. Water that contains fewer viruses than this must therefore be concentrated before analysis. Because PCR only detects parts of a virus particle, the method cannot tell us anything about whether or not the viruses detected can cause disease. 36

37 Organism Virus Description Calicivirus (norovirus and sapovirus) Adenovirus (40/41) Rotavirus Astrovirus Enterovirus Hepatitis A virus Hepatitis E virus Present in the population all year round. Most major outbreaks occur during the winter season (norovirus). The symptoms are violent vomiting and diarrhoea. Norovirus is the infectious agent that causes the disease usually referred to as the winter vomiting bug. Adenovirus primarily causes upper respiratory tract infections, although types 40 and 41 can cause gastroenteritis. Individuals suffering from gastroenteritis caused by adenovirus excrete virus particles in their faeces for several months. Rotavirus is the most common cause of diarrhoea in children. Adults very rarely fall ill, as most have complete immune response since childhood. A vaccine is available. Suspected of being an under-diagnosed cause of gastroenteritis. It is mainly children who fall ill, as adults usually have good immune protection. A large group of viruses with many different strains, which cause anything from minor colds to serious consequences such as meningitis. Liver inflammation that gradually causes a yellowing of the skin. Many people are protected by vaccination. Low occurrence rate, about 100 cases in Sweden and about 50 cases in Norway reported each year. Presence of zoonotic genotype among piglets and wild boar. Similar symptoms to hepatitis A virus. Few reported cases in Sweden and Norway. Bacteria Campylobacter jejuni Poultry are an important sauce of human infection, although cattle and wild fauna are also important sources. Present all year round, but most common in both poultry and humans during the summer. EHEC/VTEC These are two different kinds of E. coli bacteria that produce toxins. Cattle are an important source, with high levels during the late summer. Parasites Salmonella (not typhoid) Cryptosporidium (C. hominis, C. parvum) Giardiasis High infectious dose, probably few cases via water at present. Can also be excreted by many animals. Chlorine-resistant. C. hominis is human-specific, while C. parvum can be excreted by a number of animals, e.g. young calves, sheep and wild fauna. Chlorine-resistant. Zoonotic potential not clarified. Until further notice, assumed that it can be transmitted from animals. The same type that infects humans has been detected in sheep and many wild animals. Important waterborne organisms with a focus on viruses. In addition to what applies for the hepatitis E virus, the main source of viruses in raw water is drains, while as far as bacteria and parasites are concerned there may also be animal sources of greater or lesser significance. For links and further information, go to the Swedish Institute for Infectious Disease Control s information on diseases. 37

38 Effects of climate change Future climate changes with increased intensity of precipitation mean that today s sewage systems will have to cope with more surface water, which means that there will be more widespread overflows of untreated waste water. This means that infectious agents such as norovirus, which normally exists in large amounts in waste water, especially during the winter months, will be introduced into raw water sources to a far greater extent. Increased amounts of infectious agents will probably become more common in our raw water in future, which will mean that more drinking water consumers risk being infected by the water, unless action is taken in raw water sources or water treatment plants. Many of Scandinavia s surface water treatment plants are designed with chemical precipitation and chlorination as their only microbiological barriers, which is not sufficient to deliver safe drinking water when pathogen levels in the raw water increase in future. Microbiological risk assessment (MRA) can be used to calculate risks of infection for drinking water consumers in a supply system. If we assume we have a small city of around 500,000 drinking water consumers and water preparation consisting of chemical precipitation, slow filtration and chlorination, while at the same time drawing the raw water from a surface water source (e.g. a river) with a large, effective sewage treatment plant that discharges purified waste water some 10 km or so upstream, together with a couple of overflow points in the sewage pipeline system, an MRA analysis produces the following results: if we have no overflows, but simply treated waste water discharged into the water source, infection calculations indicate that 50 people risk becoming infected by drinking water every year. If we assume that a normal year also includes 30 overflows with around 500 m 3 untreated waste water per event over one year, 52 people will become infected every year. If we assume a future climate scenario with double, treble or seven times the amount of overflowing, untreated waste water on twice as many occasions, then 57, 61 and 74 people respectively will be infected, corresponding to a percentage increase in infections among drinking water consumers of 11%, 17% and 43% respectively. The effect of climate change in this example has a significant effect on the risk of infection for drinking water consumers. The volume of overflowing waste water does not increase on a linear basis with increases in precipitation, but takes place more exponentially and can result in significant increases as in this example. It is therefore very important to take action to reduce overflows of untreated waste water into our surface water sources. 38

39 Barrier effect In a water treatment plant there is the facility to control and assess separation and deactivation (where disinfection is applied). Investigations into the effectiveness of various purification techniques have revealed everything from no reduction to extremely high reduction. The level of reduction that is desirable depends on the quality of the raw water and what levels are accepted in the drinking water (see also Acceptable risk below). 55With the exception of disinfection using chlorine and ozone, where parasites are most resistant, viruses are the group of pathogenic organisms that are separated and deactivated least effectively. 55Process disruption in the preparation of drinking water has been identified as a risk with relatively high frequency in a study conducted within the framework of the Urban Water programme. The fact box entitled Case study: Glomma describes the effect of a couple of possible disruptions, such as the breaching of one or more filters and suboptimal coagulation. 55See the chapter entitled Measures in water treatment plants for more information about operational optimisation and monitoring. Protecting the supply network In contrast to bacteria, viruses cannot grow in the supply network, but levels at the consumer are as a rule lower than in outgoing water. However, microbial contamination of the supply network has resulted in a number of outbreaks of gastroenteritis, some caused by viruses. 55Contamination in the supply network can occur unintentionally in connection with repair works, new installations and cross-connections. 55Another problem is if there is underpressure in the supply network, as dirty water around the pipe trench can be drawn in. The frequency of this has been estimated at times per kilometre of mains pipeline per annum (Urban Water). 55Faultily constructed wells can cause problems because of surface water penetration. My estimate of the risk In order to be able to estimate the risk, first of all you perform an assessment of how many pathogens there are in the water, in order to see whether existing barriers are able to remove these to acceptable levels (see Acceptable risk on next page). 55The MRA and GDP tools are available to provide support in facilitating the risk assessment process. 55GDP is slightly more user-friendly than the MRA tool, as you only need information that is normally already available at water treatment plants, such as levels of indicator organisms. The structure, in the form of an Excel worksheet, has inbuilt safety margins and the end result consists of a recommended disinfection method and dose. Instructions are available from the Swedish Water & Wastewater Association and Norwegian Water. 55The MRA tool is better adapted for specific investigations in which you can study deviations from the normal situation in more detail. Furthermore, in the MRA tool you can take into account variations in both input data (raw water quality) and the water treatment plant s function. On the Swedish Water & Wastewater Association website you can download the MRA tool and the report that describes how the process works. 55Using GDP will often produce the same results as with the MRA tool. They can also work to complement one another. One good suggestion is first to use GDP to obtain general recommendations for the necessary barrier effect, and then use MRA to test specific scenarios and events, and how they affect drinking water safety. This result can then be used as a basis for identifying critical control points. The MRA tool can also be used to assess the effect of various supplements in upstream work that cause lower levels in raw water, and of an increase in the number of barriers. 55The lack of reliable information means that you should not use the mean value from the MRA tool to assess whether a water supply is sufficiently safe. You must use distributions in which the mean value varies with a deviation, and look at the value of the 95th percentile obtained. There are guidelines in the beforementioned SVU report and in the VISK report from work package The MRA tool is suitable for use when analysing the relative difference between different systems and is ideal for use at an early stage of the planning process in order to compare possible water and sewage solutions from an infection protection perspective (see also below). One of the objectives of the VISK project has been to obtain more reliable data on virus levels and reduction, in order to improve the MRA tool. 39

40 Statistics/data and their use in risk assessment (MRA) 55Microbiological levels in the environment have proven to be log-normal distributed, which means that if you take the logarithms of all analysis results, these will be more suitable for a normal distribution than the (original) values. One advantage for the following statistical processing is that you avoid negative values and can calculate as low as you wish (organisms per billion litres). It is also logical to use the values based on logarithms when counting log reductions over barriers (see chapter entitled Measures in water treatment plants ). 55Another distribution used to describe data is triangular distribution, in which you can enter minimum, maximum the most probable values, which produces a distribution function that looks like a triangle. A uniform distribution gives all values between minimum and maximum the same possibility of being chosen as input values in the risk assessment, but no values outside this range can be chosen. This distribution may be suitable where on-site sanitation facilities are the main source of contamination, as the uniform distribution may be better able to correspond to an intermittent effect on the raw water source than the other ones. 55One alternative is to divide your series of samples into two distributions: 1) based on samples in normal situations and 2) data from event-based samples, or on those occasions when levels are abnormally high. Another alternative is to use the mean value as the opening of a risk assessment for normal occasions and the maximum value as a measure of the level in connection with an event. 55There are also major variations in the effectiveness of different barriers. In the same way as you use distributions to describe presence in water, you also do it for the barrier effect. Normal or triangular distribution is used in particular to describe the log reduction over a barrier. Acceptable risk? Risk is the product of the probability that something undesired will occur multiplied by the consequence of what has occurred. A waterborne outbreak has major consequences for the community affected, and potentially for the individual person as well. Furthermore, infections from water in many cases lead, especially for viruses, to secondary infections. This means that a person who was infected via the water can pass it on to others in their vicinity. We also have an ageing population in the whole of our region, and they are as a rule more vulnerable to infections, which is why there are strict demands on safety in municipal drinking water. 40

41 55One expressed target of the WHO for drinking water safety is that municipal drinking water shall not cause more than one infection per ten thousand consumers per annum. 55Another measure of risk that takes account of the consequences is Disability Adjusted Life-Years (DALYs). The target that the WHO has set for drinking water is one microdaly, which corresponds quite well with the infection target, i.e. one per ten thousand consumers per annum. 55To achieve this ambitious target, the purified water should contain no more than one infectious cell (pathogenic virus, bacterium or parasite) per 100,000 1,000,000 litres of drinking water produced, i.e per litre, with the stricter requirement applying for viruses. 55In water contaminated to a moderate level by sewage (corresponding to bathing water quality, ~100 E. coli/100 ml) this corresponds to a 6, 6 and 4 log reduction in viruses, bacteria and parasites respectively. 55In cleaner raw water, with E. coli rarely or never detected, all water treatment plants should have barriers that achieve the normal level and a minimum reduction (corresponding to a 4, 4 and 2 log reduction of viruses, bacteria and parasites respectively). Without this minimum protection, water purification should definitely be extended to include additional barriers. Alternatively, it must be possible to guarantee that this minimum reduction is achieved by means of optimisation, combined with monitoring, of existing barriers. 55Contamination in certain water sources is better described as two separate distributions, normal (mean value) and in connection with an event (maximum value). The extent to which you have to cope with the event-based level depends on how often the events occur, how long they last and what their consequences are. 55Another factor to consider is what the water source might look like in future - will occasional events become more frequent and should you take preventive action? 5 5 The MRA tool can be used to try out various scenarios and to assess the health effects of various events, for example increased precipitation with a significant effect on the raw water source, filter breaches or problems in the chlorination process. Two case studies have been conducted in VISK. There is information about these in the report from VISK work package 5. The fact box describes the results of one of these case studies and how they can be used. 41

42 Experiences of waterborne infection in the supply network Finland On Wednesday 28 November 2007 there was a problem with the drinking water in Nokia in Finland, and residents complained about murky water coming out of their taps. Work was carried out throughout the whole of the following weekend to rinse out the mains, but instead of reducing the problem, the contaminants spread in the supply system. By 7 December they had determined the extent of the contaminants, after which a more systematic rinsing process could be carried out. There were not enough in-house personnel, so additional personnel were hired and people worked to clean the pipes. The main supply network was chlorinated with up to 4 mg chlorine and flushed. Once the distribution pipes had been flushed clean, quality problems remained in the service pipes to the properties. Emergency chlorination of up to 10 mg chlorine/l was employed to rectify this. Messages were distributed to subscribers concerned by means of notes being left, doors knocked on and phone calls. One element of work to chlorinate the supply network was the construction of chlorination points in the network. When samples were taken on 22 January, norovirus was still found in the properties. The chlorine dose was then increased to 10 mg/l for 24 hours and the ph value was lowered to 7.0, and every household was issued with instructions on how flushing would take place at every tap. Mandatory boiling was discontinued area by area, with the final area continuing with mandatory boiling until 28 February 2008, three months after the problem first arose. The biggest challenges were communication with consumers and deactivating or killing off remaining viruses and any giardiasis. Facilities to analyse the capacity and quality were of major significance for making it possible to confirm the usability of the water. Denmark Norovirus detected in drinking water is suspected of being the cause of an outbreak of what was known as Roskilde disease. Following reports of residents of Denmark falling ill, and with the discovery of E. coli in the local drinking water, 600 customers and a number of institutions and companies had restrictions imposed on their use of drinking water by a Danish drinking water supplier. The restrictions applied for five weeks over Christmas and the New Year, in December 2012 and January 2013, and during the first few days involved a ban on all use of water (including flushing toilets). The municipality s residents instead had to use drinking water tanks and bathing facilities provided. Between the day before Christmas Eve and the end of the period, the ban was limited to the mandatory boiling (recommended 100 C for 1 minute) of all water to be drunk or used in cooking. The State Serum Institute issued questionnaires, and during the initial phase of the contamination period took samples from clusters of ill residents with symptoms of Roskilde disease, and also of drinking water from various places in the supply system. Of 374 people questioned, 290 people had fallen ill with symptoms similar to norovirus, and nine out of ten faecal samples were found to contain norovirus genotype group II. The National Food Institute at the Technical University of Denmark found that five out of five water samples were positive for the same virus group, in concentrations of virus particles per 200 ml drinking water. Ongoing epidemiological investigations and additional characterisation of the viruses found in patients and in the drinking water will confirm or exclude the fact that the contaminated drinking water was the source of this outbreak. Cases of disease associated with virus contamination of drinking water are rarely registered in Denmark. When this has happened, the cause has been the penetration of waste water into drinking water pipes in connection with repairs to the pipe system. This happened in 2007, as a consequence of a manual connection of pipes for waste water and clean water in combination with a defective check valve, while the most recent case of water contamination in 2012 was caused by simultaneous breaches in both the drinking water pipe and the overlying waste water pipe. 42

43 Checklist for cleaning the supply network 55Make sure that contaminants are no longer being added. 55Evaluate which harmful substances including infectious agents may be present in the distribution system. 55Determine a target level for decontamination, for example by defining a proportion of the limit for unfit drinking water and follow up on the decontamination measures by taking samples. 55For infectious agents such as viruses, it can be impossible to follow up by taking samples (for infectious agents with a low infectious dose the requirement that the level must be so low that people s health cannot be damaged may mean that tens of thousands of litres need to be analysed without detection). 55If it is not possible to follow up on the decontamination results by taking samples, you can perform an assessment of how many times the water needs to be recycled. Flushing three times may suffice, but if a hazardous contaminant is involved and a situation in which a setback might damage the restoration of consumers confidence, you may decide to implement several rounds of flushing. 55Flush one part of the network at a time systematically so that the contaminant is flushed out instead of being spread. 55Strive to achieve water speeds of more than 1 m/s so that at least lighter sediment is included. 55Clean reservoirs in the area concerned. 55For limited parts of the distribution network you may, having first issued clear information to all concerned, implement chlorination at significantly higher doses than permitted for drinking water. If you allow the chlorine to act overnight, sufficiently high CT values may also be achieved to deal with chlorine-resistant infectious agents. The disinfection effect may be further enhanced by lowering the ph value. 55Flushing and chlorination may be ineffective against congealed masses, and it may be necessary to replace installations in properties. More information is available in the VAKA group s observation report. 43

44 FJELLFOTEN SEWAGE PLANT RÅNÅSFOSS SEWAGE PLANT RÅNÅSFOSS POWER STATION BINGFOSS POWER STATION RAW WATER INTAKE (NEDRE ROMERIKE WATERWORKS) Fetsund Rømua bäck Sarumsand Vorma Älv Glomma Älv Rånåsfoss Blaker Section 2 Ua bäck Årnes Section 1 Section 3 Case study: Glomma Øyeren The Glomma älv river in Norway provides raw water for 230,000 people, although its potential is far greater than that. The Nedre Romerike water treatment plant supplies 143,000 of these people with drinking water. The intake of raw water is affected by, among other things, two sewage treatment plants upstream: Rånåfoss and Fjellfoten. To assess the quality of the water at the raw water intake, all three approaches in VISK were used, i.e. indicator analyses, direct detection of viruses and hydrodynamic modelling. Measurement data, modelling Glomma älv river in Norway and indicators all result in approximately the same loading levels. However, if you adjust the measurement data for the outcome of the process control used, the load is 10,000 times greater. This higher value was used in one of the two risk characterisation exercises so far carried out, presented in brief below. The purification effect through the treatment plant was based partly on published information and partly on measurements conducted within the framework of the VISK project. Method Norovirus mean (per litre raw water) Norovirus 95th percentile (per litre) Indicators Measurement data Measurement data (corrected for the 112,000 3,500,000 method s outcome) Modelling 4 7 The opening values of norovirus from Glomma, raw water, expressed as virus particles per litre, based on an analysis of E. coli and dilution by the waste water, measured virus levels (corrected for the method s outcome) and hydrodynamic modelling from the dilution of the waste water and transport in the river. The modelling process is based on 100,000 virus particles in treated waste water. Process stage Expected reduction (log) Suboptimal operation over one day (log deterioration) Coagulation, flocculation and quick-filtration Published information: Filter breach: VISK data: Coagulation: Granular active carbon filter 0 Chlorination 4.5 Incorrect ph: Expected log reduction for norovirus through the Nedre Romerike water treatment plant and deteriorated effect of suboptimal operation over one day. 44

45 Case study: Glomma risk characterisation In an initial phase, a risk assessment was conducted based on indicators and published information, in which some possible events were tested: problems with coagulation and problems with chlorination. The results indicated that the Nedre Romerike water treatment plant can produce safe water, but that the process depends on the chlorination of water not failing. Precondition Risk mean (DALYs) Risk 95th percentile (DALYs) Normal process 1.4 x x 10-7 Fault in coagulation 1.4 x x 10-5 Fault in coagulation, increased chlorine dosage 3.8 x x 10-6 Filter breach (1 filter) 1.3 x x 10-7 Filter breach (3 filters) 3.5 x x 10-6 Fault in chlorination (absent 1 day) 7.2 x x 10-4 Disability Adjusted Life Years (DALYs) for norovirus via drinking water (acceptable risk 1.0 x 10-6 ) for Nedre Romerike water treatment plant s consumers. In the second phase, the risk assessment was based on data from VISK, for both purification and for direct measurement analyses of the raw water quality, the latter with reference to the yield for the detection method. At these significantly higher levels in the raw water, the limit for acceptable risk was exceeded. At these high levels in incoming water, safety also becomes more sensitive to events during the process and the daily risk exceeds the acceptable annual risk. The installation of UV or ultrafilters (UF) should provide a sufficient barrier effect to cope with even these events in respect of norovirus. Precondition Risk mean (Pinf) (DALYs) (DALYs) Risk 95th percentile (Pinf) (DALYs) Normal operation, published information Normal operation, VISK data With UV installed (40 mj/cm 2 ) With UF installed (pore size nm) Filter breach (1 filter)* Filter breach (3 filters)* Fault in coagulation* *Daily probability of infection (Pinf daily, acceptable level 2.7 x 10-7 ) Annual probability of infection (Pinf, acceptable level ) and for certain scenarios Disability Adjusted Life Years (DALYs) for norovirus via drinking water (acceptable risk 1.0 x 10-6 ) for the Nedre Romerike water treatment plant s consumers. Based on the size of the population and the fact that an infection results in an average of 0.25 cases of disease, a filter breach in one of eight parallel filters should potentially result in seventeen infectious and four cases of disease. A breach of three filters should result in more than forty infections and ten cases of disease. The incorrect dosage of coagulant and/or chlorine can have even more serious consequences. Drinking water safety in respect of viruses (as well as bacteria) in many surface water treatment plants is based on an effective disinfection process, in which the greatest barrier effect in the form of log reduction is achieved. This stage also depends on the previous barrier functioning reliably. It is therefore important that there is continuous monitoring of the whole process. Despite the fact that the VISK project has found chlorine to be effective also in water with higher colour values, there are indications of a poorer effect in the initial reduction in connection with substances with a higher chlorine demand in the water. 45

46 5. Risk reduction through preventive work Risk-reducing measures Raw water control/working upstream Reducing the effect on raw water can in many cases be a costefficient measure, especially if a significant proportion of the faecal effect originates from a specific source such as a waste water outlet, an overflow point or surface run-off manure from a nearby field. Below is a list of risk-reducing measures that can be implemented either separately or, if required, in combination. 55Improvement of sewage treatment and sewage system: 55Improved separation, for example by means of longer recidence times or extra treatment stages. 55Reduced risk of overflow by means of enhanced dimensioning. 55Inventory of specific overflow points. 55Improved treatment of sewage sludge (e.g. deactivation at temperatures > 50 C) with the aim of deactivating pathogens in the sludge. 55Review of individual drains and action plan for substandard drains: 55A task that should take place in the municipalities, but that will take time. The municipalities should therefore set priorities in respect of the workload (all-year-round accommodation ahead of summer accommodation), drains (toilets ahead of bathing/washing drains) and geographic location (risk of exposure to discharged water). 55Review of surface water and overflow points: 55Start closest to the raw water intake, the extraction well. 55Are there any cross-connections? 55Are their sewage pipes close to the surface water, drainage water well? 55Bathing sites: 55Infected but symptom-free bathers (especially children) can excrete pathogens in the water. The risk that other bathers will be infected is, however, greater than via drinking water. 55Boat latrines: 55Adequate emptying facilities combined with a ban on emptying latrines in the water source. 55Inspection of manure pits and manure handling 55Storage creates a dilution effect and a reduction corresponding to 99 per cent (2 log). Despite this, pathogens can be found in manure and this should therefore be spread with common sense (see below). 55Manure pits in water catchment protection areas (where leaks can affect the raw water) should be inspected at least every five years in order to avoid any risk that an accident results in a significant effect on the raw water. 55The location of the manure pit in relation to the risk of run-off in connection with a possible event should be 46

47 considered when considering granting permits for new sites. 55In connection with large-scale handling of manure, for example joint anearobic digestion from several farms, as for sludge, a sanitising treatment is recommended. 55Counteract rapid run-off from spreading manure and sludge: 55The rapid surface run-off that can happen in connection with heavy rain following manure spreading should be avoided. This is achieved by manure being worked in quickly and not spread on land that is saturated, flooded, covered in snow or frozen. 55Furthermore, a so-called buffer zone can be introduced, meaning that manure is spread a sufficient distance from the edge of fields that border watercourses or lakes. Find out more on the Swedish Board of Agriculture s website. 55If the land slopes by more than ten per cent towards the watercourse, no manure should be spread at all. 55Beach pastures: 55Beach pastures do not have the same impact as the spreading of manure. There is, however, no barrier as is the case with storage, which means that droppings/ faece may go straight into the water. As young animals are those most likely to excrete zoonotic infectious agents, one effective measure can be to limit the access of young calves (< 6 weeks) to watercourses close to raw water intakes. 55Drains more important than livestock 55Measures that limit faecal contamination from livestock as described above affect the risk of viruses being transmitted via water to a lesser extent. If the risk assessment indicates an increased risk of viruses, discharges from waste water must be limited in order to achieve an effect. Purification control/extended purification A surface water treatment plant should always have effective barriers against parasites, bacteria and viruses, no matter how clean the water source is believed to be. This is because the indicators do not necessarily correlate with contaminants from afar, re-suspended sediment or some other effect that may make its way through the separation process and where disinfection is not enough. 55Use the tools described earlier (ODP/GDP, MRA) and the chapters entitled Measures in water treatment plants and Risk assessment and checking quality in this manual in order to evaluate the water treatment plant s barriers and any possible need for additional barriers. 55Note that the effect of a barrier may be used as base data for cost-benefit analyses (described in further detail below). Early warning systems 55Information from the healthcare information service: 55As the level of pathogens in water depends on the state of health in the municipality and upstream Preventive work 55Check the risk (using MRA, ODP/GDP): 55Start with the normal values. Is the risk acceptable? If not, if there is a low level of contamination you should plan to extend to achieve a better barrier effect. If the effect is stronger, it may be more cost-efficient to reduce the effect on the raw water. Where this limit should be set is different in each individual case, but a suitable starting point may be somewhere around a mean presence of E. coli of >100 CFU/100 ml. 55Repeat the same procedure with the maximum values. Is the risk still acceptable? If not, you should review historical data in order to estimate how often the raw water can be expected to be more affected and what this means in terms of increased risk in relation to the normal values. 55The procedure with the maximum values should also be carried out on the basis of the expected values in connection with future climate change and expected increased precipitation. 55If possible, you should track the source of the contamination, so that in the next stage you can decide what is most effective: stopping it at source, improving the water treatment plant or managing peaks as they arise. A plan should be drawn up. 55Low faecal contamination, rarely detected E. coli, enterococci or Clostridium: 55Review possible surface water discharges and whether they can cause contamination at intakes/wells when an event occurs. 55Poorer raw water quality following heavy rain: 55Find out where the contaminant comes from. Review what is most effective, stopping it at source, improving the water treatment plant or managing peaks as they arise. A plan should be designed up. 55Poorer raw water quality following manure spreading: 55Perform a risk assessment. Is the risk acceptable? If not, make a plan together with the polluter, for example based on the Swedish Board of Agriculture s guidelines for spreading in nitrate-sensitive areas, in order to avoid rapid surface run-off of manure. 47

48 municipalities, the rapid reporting of intestinal diseases can form a basis for risk management. 55The system for registering calls to the healthcare information service in Sweden (1177) can provide an indication of increased disease frequency and thus an increased likelihood of higher levels of pathogens in the raw water. The parasite outbreaks in Östersund in 2010 and Skellefteå in 2011 could have been predicted at an early stage using this method. Rapidly spreading outbreaks such as the norovirus outbreak in Lilla Edet in 2008 could still not be predicted at an early stage, but it would be possible to quickly confirm an increase in cases of gastroenteritis in the municipality. 55Data from calls to the healthcare information service can easily be broken down at municipal level, and daily updates of gastroenteritis symptoms within the distribution areas of water treatment plants can be made available to the plants. This system is being developed by the Swedish Institute for Infectious Disease Control in collaboration with the Swedish National Food Agency and the Healthcare Information Service Taking samples upstream: 55There are at present analysis methods that can measure levels of coliform bacteria and E. coli in a water sample in less than six hours. This makes it possible for certain water treatment plants to deal with contamination peaks in the raw water before they have passed through the plant and reached consumers, on the condition that the samples are taken sufficiently far upstream. 55For water treatment plants with two sources, the source with the best water quality can be used. 55Sensors that detect contaminants and instantly transmit a signal if anything is wrong is one area where there is currently a great deal of development. Sensors are not currently sufficiently sensitive for specific microorganisms. There are, however, sensors that can measure a change in the water quality that have sufficiently high sensitivity to be useful and to offer a faster system than an analysis of coliform bacteria and E. coli. The supply network 55Procedures for pipeline works must be in place and be observed. Procedures can, for example, describe how to avoid contamination in the supply network via cross-connections, by dirty tools being used, by flushing with poor water or by other contaminants that can enter an exposed pipe. 55Avoid pressure drops as far as possible. 55The way to clean a contaminated supply network is described in the chapter entitled Risk assessment and checking quality. 55Read more about supply networks in Norwegian Water report 161 (2008) Helsemessig sikker drift av vannledningsnettet [Safe operation of the water supply network]. Economic and administrative tools for decision-making based on risk assessment Risk assessment allows you to assess the effects of measures such as extended wastewater treatment, improved water purification or raw water protection and what this would mean for the reduction of risk. Microbiological risk assessment is therefore a good tool in various decision-making processes. 55A barrier corresponding to a one (1) log reduction in a sewage treatment plant is, if the waste water is the only source of faecal contamination, worth just as much as a corresponding reduction in a water treatment plant. There is, however, not likely to be only one source of faecal contamination, and the effect for the consumer will therefore never be as great as in the discharge from the sewage treatment plant. But a measure upstream also reduces the risk of other transmission routes to humans via water, for example through watering, bathing and recreation. 55The cost of a case of disease (intestinal/bowel disease) is approximately SEK 10,000 (2013), distributed quite evenly between direct costs (visit to doctor, hospitalisation and medication) and indirect costs (loss of work/lost production). If every other infection results in disease, this means that the average cost per infection is SEK 5,000. The MRA tool can be used to calculate the number of infections before and after every planned measure on an annual basis, and an assessment can then be made of how many years it will take to recoup the money invested. An investment in safer water can in many cases be socio-economically profitable even in the relatively short term, especially for a large municipality with one central water treatment plant. 48

49 55The value of a DALY (disability-adjusted life year) is often quoted at approximately SEK 1 million (2013), which means about one Swedish krona per microdaly. If we look at the repayment period in a case study in Gothenburg, which is presented in a fact box, it is long when it comes to norovirus. However, it must be borne in mind that ultrafilters also create an effective barrier against more agents, for example chlorine-resistant parasites. At the same time, you also create a margin for avoiding waterborne outbreaks in connection with events in the water treatment plant or significant contamination of the raw water. The problem: Which pathogens and other risks of infection are present? 2. Assessment of exposure: Model pathogens from run-off area to tap. Land usage in run-off area, faecal sources and faecal effect. i. Well Untreated river water (C) ii. Barrier reduction and re-contamination Conventional treatment Disinfection Distribution (d) iii. Exposure volume and frequency Daily consumption of unboiled water (V) EXPOSURE Socio-economic analysis as a basis for investment in an ultrafilter installation in Gothenburg As socio-economic analysis was carried out in Gothenburg as a basis for a decision on whether to install ultrafilters at the Lackarebäck and Alelyckan water treatment plants. This analysis includes calculations of what a possible waterborne microbiological outbreak could cost society, and this was set against the risk reduction that an installation of ultrafilters would represent in financial terms. The results of the analysis show clearly that it is more economically advantageous to install ultrafilters than not to do so. Read more about the analysis in the report entitled Samhällsekonomisk analys av installation av ultrafilter vid Lackarebäcks och Alelyckans vattenverk [ Socio-economic analysis of the installation of ultrafilters at the Lackarebäck and Alelyckan water treatment plants ]. 3. Assessment of effects on health: Assess effects on health and vulnerability of target group i. Probability of infection The calculation is based on a dose response model ii. Probability of disease Based on epidemiological data iii. Probability of consequent diseases Based on epidemiological data Calculated effect on burden of disease (DALYs) 4. Risk assessment: Perform risk assessments, interpret and communicate consequences for the management of water safety Flowchart for risk assessment. Risk assessment can be used as a basis for a socio-economic cost-benefit analysis for investments made to improve water quality. 49

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51 Risk management and water and sewage planning Water and sewage planning in the municipality is the key to a safe drinking water supply even in the future with climate change. The biggest source of viruses in raw water and drinking water production is waste water, both treated from sewage treatment plants and untreated from overflows. Within a municipality, discharges of treated waste water always take place downstream of the raw water intake and therefore have no effect on their own raw water quality. But discharges of treated waste water do affect those municipalities located downstream. It is therefore important to reach agreement at a regional level on how to manage the shared resource that water constitutes. 55Regional cooperation is a key to success when it comes to securing good access to safe raw water in the future. According to the Baltic Sea Action Plan (BSAP), investments should be made by those able to do so in order to promote the common interest. It has been confirmed within the VISK project that viruses are common in Nordic raw water sources. It is also evident that the number of virus particles in the raw water has a direct effect on the risk of waterborne infection, a fact that is not currently considered when political decisions are made. Hygiene is not one of the decision-making criteria. One example of this is that evaluations of discharges from a waste water treatment plant usually take place on the basis of an economic and environmental perspective and do not consider the hygiene effect of the discharges. This is a major deficiency that results in the absence of a holistic view when decisions are made. 55It is recommended that hygiene be included as a significant decision-making criterion when public authorities perform evaluations relating to discharges from treatment plants, and that these decisions be made in consultation with water supply plants and with due consideration of other areas of application (e.g. leisure activities and bathing). 55It is also important to learn more about what our own raw water is like and what the most important sources of viruses are, which viruses are present in the water, how this varies over the year, and so on. Armed with more knowledge, it is easier to make the right, most effective decisions. 55Within a municipality it is important that this issue is included in the urban planning process at an early stage, when decisions are made on where new areas are to be built and how water and sewage are to be managed there. In the region there are many so-called transition areas, i.e. cohesive areas of summer cottages where more and more people are living permanently, which places tougher demands on water and sewage than existing solutions. There can be a number of possible water and sewage solutions, depending on the conditions. Risk assessment is one tool that can be used to draw up base data for decisions on which system is best from an infection protection perspective. Using early warning systems in water and sewage planning 55The early warning systems discussed above can be used to prevent outbreaks of disease caused by waterborne viruses. 55The local authority must choose what kind of system is to be used and then establish clear procedures for its use. 55Procedures can, for example, describe how water treatment plants located upstream raise the alarm in connection with accidents or incidents, and state that the water treatment plant s authority is involved in decisions on measures that can affect water hygiene. What investments may be needed? The nature and scale of investments needed to reduce the risk of infections being transmitted via drinking water vary from one municipality to another. Contributory factors include what risks are present in the municipality, what the raw water source is and which purification stages the drinking water passes through. 55Fundamental measures: 55Optimise the current purification process in accordance with professional guidelines. 55Get to know the raw water by analysing it in respect of viruses. 55Draw up an inventory of sources of contamination by the water source. 55Work with water catchment protection areas. 55Perform a risk assessment. 55Evaluate whether any additional measures are required to reduce the risk. 51

52 55Major investments may be required if there is a need for additional purification stages in the drinking water process, such as UV light or chemical precipitation. 55Another issue that should be considered is whether the waste water from sewage treatment plants has to be further treated before being discharged into recipients that act as raw water sources, as it has been shown that the processes most commonly used (chemical precipitation and activated sludge treatment) do not between them reduce viruses to any significant extent. Other forms of collaboration The water supply is the most significant and important of the activities relating to the use of water sources. Consideration of the water supply should thus be the most important factor when working with the Water Directive and other measures relating to contamination of water sources. Regional collaboration is one of the overarching purposes of the Water Framework Directive (2000/60/EC). The directive does not, however, include any requirement for good microbiological status. Although requirements for the good chemical and ecological status of water constitute a good tool that has had a positive impact on the microbiological quality, it would be desirable if pressure were applied from the Nordic region to also include a microbiological parameter. 55By way of suggestion, the Bathing Water Directive (2006/7/EC) could serve as a guideline. This defines levels for excellent, good, satisfactory and poor bathing water quality (see also Swedish publication Havs- och vattenmyndighetens föreskrifter och allmänna råd [ Regulations and general advice issued by the Swedish Agency for Marine and Water Management ], HVMFS 2012:14). If the water quality is poor, there should thus be tools for measures upstream, while if the quality is satisfactory it can be recommended that risk assessment be used as a tool to decide whether measures are needed to improve the quality of raw water and drinking water. One advantage of this approach is that it would mean an increase in the number of raw water samples being taken in the water source, and thus better base data for the risk assessment process. Preparedness to deal with outbreaks of waterborne disease One important element of risk management work is to be prepared for those risk events that cannot be prevented. 55If there is any indication of a worsening in the quality of drinking water, an action plan with suitable measures should be followed in order to check the quality of drinking water, stop the transmission from reaching the consumer and investigate the source of contamination. 55On the basis of the risk assessment already conducted, both a contingency plan and a crisis management plan should be drawn up for drinking water-related events. The contingency plan should contain, for example, updated information about access to water tanks and current lists of contact information both within and outside the municipality. The crisis management plan should contain procedures to effectively manage and resolve a crisis event. 55Examples of procedures for waterborne infection should include at least the following: 55A clear allocation of responsibility, contact/key persons and important phone numbers. 55Which information channels can be used and how to keep them up to date. 55A prepared media strategy to deal with questions from the press. 55When a recommendation to boil water must be produced. 55Which workgroups need to be formed and how to maintain staffing. 55How internal documentation is managed and how the event is documented. 55How to arrange emergency water supplies. 55Special measures for vulnerable users. 52

53 Example of early warning system in Gothenburg Gothenburg has for a long time had a number of measurement stations along the Göta älv river to check the raw water quality. There are also procedures describing how municipalities upstream should raise the alarm when there are overflows and if they discover a major discharge of waste water or other contaminants. Manuals for the safe handling of drinking water Beredskapsplanering för dricksvatten [Contingency planning for drinking water] (2008), Swedish National Food Agency. Krishantering för dricksvatten [Crisis management for drinking water] (2008), Swedish National Food Agency. Suggested checklists for situations requiring emergency water supplies, Økt sikkerhet og beredskap i vannforsyningen [Enhanced safety and preparedness in the water supply], Report 2006, Norwegian Food Safety Authority. Support for municipalities suffering problems with the drinking water supply is provided by VAKA, the National Water Emergency Group. Instructions about how VAKA can help are available at 53

54 Experiences from outbreaks Lilla Edet 2008 In September 2008 there was an outbreak of the winter vomiting bug in Lilla Edet Municipality, which is between Gothenburg and Trollhättan and has the Göta älv river as its drinking water source. At least 2,400 of 13,000 inhabitants fell ill, and the most likely cause was waterborne infection. An epidemic management group was set up, with representatives from the municipality, the healthcare centre and the Infection Control Division in Region Västra Götaland. VAKA, SMI, the Swedish National Food Agency and the County Veterinary Surgeon were also contacted. Measures such as recommendations to boil water, flushing out of the supply network, extra chlorination and extensive sampling were all carried out from the first day. On the basis of the results of laboratory tests and measures taken, it was possible to withdraw the recommendation to boil water after 16 days, and the epidemic management group was disbanded three days later. But subsequent work on how the infectious agent reached the Göta älv, how similar events can be managed even better in future and how future risks can be minimised continued for many years after the outbreak. One example of a new procedure introduced in Lilla Edet is that when message are received about gastroenteritis that is suspected of being caused by water quality, schools and pre-schools in the relevant area are contacted immediately in order to work with the Infection Control Division to evaluate reported absences. More lessons learnt from the events in Lilla Edet are described in SVU report no , Utbrott av calicivirus i Lilla Edet händelseförlopp och lärdomar [ Outbreak of calcivirus in Lilla Edet - sequence of events and lessons ]. Östersund 2010 In November 2010 there was an outbreak of waterborne cryptosporidium in Östersund. More than 20,000 people were infected, making this the biggest-ever waterborne outbreak in Sweden. The probable cause of the outbreak was that waste water had penetrated the water source, partly because of faulty connections of drains, which caused waste water to be channelled directly into the water source, and partly because of heavy rainfall that caused widespread overflows of waste water. The water treatment plant did not have sufficient barriers to remove and kill the parasites in the raw water. Mandatory boiling of water was announced as soon as the drinking water could not be excluded as the source of infection, and to guarantee safe water a UV system was installed in the Minnesgärdet water treatment plant and the entire distribution system in Östersund was flushed out. Mandatory boiling was stopped after twelve weeks, following extensive work to produce criteria for the all-clear from Östersund Municipality. The Municipality received excellent assistance from VAKA, the County Council s Infection Control Division and SMI. The socioeconomic cost of the outbreak is estimated at approximately SEK 220 million. Further information about the events in Östersund is described in the report entitled Vattenburet utbrott av Cryptosporidium i Östersund november-december 2010 [ Waterborne outbreak of cryptosporidium in Östersund, November-December 2010 ], which is on Östersund Municipality s website, and in SMI s report entitled Cryptosporidium i Östersund [ Cryptosporidium in Östersund ]. 54

55 6. Trust and confidence During the first decade of the 21st century, the Nordic countries suffered a number of outbreaks of waterborne infection, which resulted in thousands of cases of disease. Among the more widely reported are the giardiasis outbreak in Bergen in 2004, the Nokia incident in 2008 and the outbreaks of cryptosporidium in Östersund and Skellefteå in 2010 and Each outbreak of waterborne infection very probably results in an increase in the perceived risk of drinking water and a reduced level of acceptance among consumers. It is also probable that confidence in the water supplier is undermined. After an outbreak, organisations and units affected by the crisis must therefore work to restore acceptance and confidence, and at the same time reduce the perceived risk. Trust and confidence are extremely significant if you want to create good partnerships, both between people and between the general public and decision-makers. Trust and confidence in decision-makers affect how the general public assesses and perceives the risk associated with a potential danger. People who trust a decision-maker are more likely to believe that the risk assessments carried out by the decisionmaker are credible. These people also have a higher level of acceptance of changes and risk measures. There is a specific difference between trust and confidence: Trust is based on a degree of harmony in terms of values and opinions, in which qualities such as openness, honesty and integrity are important. Confidence is based on previous experiences that events occur as expected. Having confidence that something will happen does not necessarily mean that you trust the intentions or have the same values and people, authorities or decision-makers concerned. Trust involves risk and vulnerability, while confidence is not based on these aspects. Trust is based on social relations, while confidence is based on familiarity, knowledge and previous experiences. The subjects of trust are people, or entities that can be perceived as people, while you can have confidence in anything at all, for example that water will run out of the tap when you turn it. You can increase trust while at the same time reducing confidence. For example, if a water treatment plant says that tomorrow there will be no water coming out of the tap, confidence in the water treatment plant delivering water is reduced, but trust increases as the consumer is given advance warning and a good explanation: the water treatment plant shows that they accept responsibility when there is a problem. If the reverse were true, when the consumer has tremendous confidence that water will come, but it fails to do so, trust in the party responsible is reduced. 55

56 Outbreak Year Infection Comments on trust and confidence Bergen 2004 Giardiasis May have contributed to reducing the confidence of Norwegians in the perceived competence of governmental bodies in the short term. Consumers are now equally satisfied with the water distributors as they were before the outbreak. Nokia 2007 Viruses and parasites Speculation about possible deaths caused by the parasite outbreak and the fact that water and sewage personnel were aware of the inflow of technical water over a longer period that was stated. How the outbreak affected consumers confidence in drinking water has not been investigated. Lilla Edet 2008 Norovirus In 2005, Lilla Edet won the prize for the Best Water in Sweden. Although the authorities acted quickly and information to residents during the outbreak was high, the competence of the municipal bodies concerned came into question. The reason for this was that within the municipality there were different perceptions of the true cause of the outbreak. Municipal residents did not feel reassured that the source of the problem had been found or that relevant action had been taken to avoid similar events in future. Östersund 2010 Cryptosporidium News of the outbreak had a very widespread impact, both locally and nationally, with very intensive coverage during the first two weeks of the outbreak. The various roles in the municipality were handled excellently, knowledge was quickly obtained and action taken, and clear, regular communication was maintained. Skellefteå 2011 Cryptosporidium The reason for the limited negative publicity is believed to be because of the intensive information campaign conducted by the municipality and its partner organisations. From Day One, there was a clear message that the level of preparedness is high, that drinking water is suspected and that action is already being taken. Examples from various outbreaks in the Nordic region. 56

57 Increase trust 55Be honest: 55Assuming responsibility for a mistake for which you are responsible indicates honesty and morals. 55If it emerges later that information has been intentionally withheld, public confidence can be severely shaken. 55Display sincerity: 55Tell the whole truth, even if you yourself and others close to you are not seen in the best light. 55Do not answer questions to which you do not know the answer or that are outside your work area. Admit that you do not know the answer, but that you or others are working on it. 55Show compassion: 55Show compassion for problems experienced by the public. 55Be prepared to listen to other people s problems and show sympathy, even though it may be time-consuming. 55Assume responsibility: 55Avoid blaming others. Even if it actually is someone Increase confidence 55Keep to the facts: 55Keep to the correct facts and only provide information about them when you are certain that they are true. 55Having to refute a piece of information subsequently can have serious consequences for the organisation s credibility. 55Highlight good examples: 55Highlight actual successful initiatives (e.g. we managed to have water tanks in place within 24 hours ). 55Work preventively and talk about it: 55Plan in advance and let people know what contingency plans are in place to manage incidents. 55Do not claim that contingency plans are 100% guaranteed. No such contingency plan exists, and if you fail to live up to expectations there is a risk that you will be considered incompetent. else s fault, apportioning blame shows that you are avoiding responsibility. 55Be accessible and clear: 55Be accessible and open to questions and to being questioned by the public and media at times that suit them. 55Use one single, visible spokesperson. People are more inclined to trust a known individual rather than a faceless institution. 55Provide support: 55Help others to help themselves. Offering useful, practical advice is a sign of good intentions and a certain degree of competence. 55Carry out preventive work: 55Build up good relations with customers over a long period of time so that people understand your motives before incidents and crises occur. 55Build up relations with the media so that they know that your intentions are good. 55Be accessible: 55Have sufficient resources available to enable the public to contact you. 55Cooperate with others and be consistent: 55Maintain contact with other bodies responsible in order to avoid presenting conflicting messages. Different messages from different parties involved can appear confusing and affect public confidence, and thus also their inclination to follow any instructions relating to the crisis situation. 55Cooperate openly with other trusted sources of information. If several credible organisations can support the same message, this is a confirmation that the information being communicated is reasonable and it is less likely that the public will not trust the other groups involved. 57

58 Model I CONFIDENCE PERCEIVED RISK ACCEPTANCE Model II CONFIDENCE ACCEPTANCE PERCEIVED RISK By studying the Lilla Edet outbreak in 2008 the conclusion was reached that the consumer acts on the basis of confidence rather than emotion. This figure shows two models of interaction between confidence, perceived risk and acceptance. Consumers who are informed that their drinking water is manufactured directly from waste water (as happens in Singapore, for example) react according to model II, which means that they have a reaction influenced by emotion based on the fact that waste water is perceived as a risk and confidence is therefore less important. As regards drinking water in Lilla Edet, confidence is the most important factor, and this gives those responsible an opportunity to explain the risks and thus gain acceptance for the mandatory boiling of water, for example (model I). This means that good communication is important before, during and after a waterborne outbreak. The value of good communication Being able to communicate effectively and clearly about risks is crucial if people are to be able to act in a way that benefits their own and other people s health and safety. The quality of information communicated is also crucial for the trust and confidence of consumers. In the consumer survey from the Lilla Edet outbreak in 2008, it emerged that those who criticised the quality of information about the outbreak also tended to feel less sure about the water quality after the incident. Communication is often more effective when it is well planned, has a clear purpose and a clear recipient. If you also have a well prepared plan or method, it is more likely that the communication process will include all relevant stages and strategies before, during and after a crisis, and that nothing of importance will be left to chance. 55You should, in advance, identify possible risks and crisis situations, plan communication strategies in the event of an incident, and inform and prepare the general public for risks. 55After a crisis it can be important to communicate what has been learnt from the crisis and to rebuilt trust and confidence between the public and decision-makers. Trust and confidence in Ale The Ale H20 study (which is described in the fact box on page 12) also looked at the trust and confidence of residents when it comes to drinking water. Read more about the results at visk.nu. 58

59 Authors of the Manual: Bergstedt, Olof City of Gothenburg, Circulation and Water Blom, Lena City of Gothenburg, Circulation and Water Friberg, Joanna Municipal Association of the Gothenburg Region Furuberg, Kjetil Norwegian Water BA Gjerstad, Karl Olav IVAR IKS Grönvall, Pontus Stormen kommunikation Håkonsen, Tor VA-Support AS Kjellberg, Inger City of Gothenburg, Circulation and Water Lindgren, Per-Eric Ryhov County Hospital L. Kvitsand, Hanne Norwegian University of Science and Technology, Asplan Viak AS Malmroth, Sara City of Gothenburg, Circulation and Water Morrison, Greg Chalmers University of Technology Myrmel, Mette Norwegian School of Veterinary Science Nyström, Fredrik Linköping University Ottoson, Jakob National Veterinary Institute Petterson, Susan Norwegian University of Life Sciences Pettersson, Thomas Chalmers University of Technology Rosado, Ricardo Norwegian School of Veterinary Science Sal, Lena Solli Nedre Romerike vannverk IKS Schultz, Anna Charlotte National Food Institute, Technical University of Denmark Simonsson, Magnus Swedish National Food Agency Sokolova, Ekaterina Chalmers University of Technology Reference group for the Manual: Hem, Lars City of Oslo, Water and Sewerage Nygård, Karin Norwegian Institute of Public Health Nyström, Per-Erik Swedish National Food Agency Pott, Britt-Marie Sydvatten AB Title: Manual How to work to reduce society s vulnerability to waterborne viral infections despite climate change. Date published: Production and graphic form: Stormen kommunikation, ISBN