A Framework on How to Prepare and Develop Public Health Risk Management Plans for Drinking-water Supplies

Transcription

1 A Framework on How to Prepare and Develop Public Health Risk Management Plans for Drinking-water Supplies

2 Citation: Ministry of Health A Framework on How to Prepare and Develop Public Health. Wellington: Ministry of Health. Published in June 2005 by the Ministry of Health PO Box 5013, Wellington, New Zealand ISBN (Book) ISBN (Internet) HP 4141 This document is available on the Ministry of Health s website:

3 Contents Introduction 1 Preparing and Using Plans 3 Getting help 3 Glossary 9 Appendices Appendix 1: Barriers to Contamination 10 Appendix 2: Estimating Risk 11 A Framework on How to Prepare and Develop Public Health iii

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5 Introduction Making sure people have clean water to drink is an important step towards public health. In the past, public health management of supplies relied largely on monitoring the quality of the water produced by individual water suppliers to check that it complied with the Drinking-water Standards for New Zealand (DWSNZ). While monitoring is always important, public health risk management plans for drinking-water supplies provide the additional benefit of reducing the likelihood of contaminants entering supplies in the first place. By the time monitoring shows that contaminants are present, something has already gone wrong and a hazard is already present in the water. Public health risk management plans encourage the use of risk-management principles during treatment and distribution so that monitoring is not the only water quality management technique used and further reducing the risk of contamination. To help you create and operate a public health risk management plan (Plan) for your drinkingwater supply a set of model Public Health Risk Management Plan Guides (Guides) has been prepared by the Ministry of Health. Table 1 sets out the information contained in the Guides that will help you prepare a Plan. This overview document also suggests how to prepare and operate a plan. It helps you understand the information contained in the model Guides and how this information can be used. Table 1 tells you what information is contained in the Guides. You may wish to use the information given here and in the Guides, or you may prefer a different approach. You do not have to prepare your Plan using the Guides, nor do you have to follow the steps for preparing them described in this document. Your Plan needs to show how you will reduce risks to public health from drinking-water. It should identify the situations that may lead to contamination and the actions necessary to protect the public. In the Guides we have tried to identify all the events that might lead to contaminants reaching the public, but some events and their causes and preventive measures may have been overlooked. When preparing your own Plan, it is important that you identify and include possibilities not mentioned in the Guides. We intend the Guides to be living documents and to develop as experience in using them grows. If you have any comments or suggestions about this document or the Guides, please write to the: Environmental Health Team Public Health Programmes Group Ministry of Health PO Box 5013 Wellington. A Framework on How to Prepare and Develop Public Health 1

6 Table 1: Structure of the Guides Section Purpose Information Context Risk summary Risk information table Contingency plans PHRMP performance assessment To describe the water supply component covered by the Guide and how it may be affected by other parts of the system. To provide a summary of the key information contained in the risk information table. To provide detailed information to be used in managing risks linked to this supply element. To provide guidance on determining when hazards may have entered the water distribution system, and the actions to take to protect public health should this happen. To provide guidance on steps that could be taken to assess whether a Plan is operating properly. The supply stage, supply element and supply subelement the Guide refers to and Guide reference number. What information is in the Guide. A list of possible events linked to the supply element and their possible public health consequences. How this supply element is influenced by or influences other supply elements. The event linked to this supply element that creates the greatest risk to public health. The most important measures that can be taken to prevent or minimise the effects of this event. Possible events and the hazards that may be introduced into the water. A rough guide to the level of risk created by each event. Possible causes of each event. Preventive measures for each cause. Details of checks to decide whether the preventive measures are working. Corrective actions that should be taken should an event happen. Events arising from the failure of corrective actions to stop hazards entering the distribution system. Possible signs that such an event has happened. Actions to take should the event happen. What can be measured or observed to decide how well the Plan is working. How often these measurements or observations should be made. A guide to what should be done with the results of measurements and observations. 2 A Framework on How to Prepare and Develop Public Health

7 Preparing and Using Plans Your Plan will show how you will manage the public health risk that might arise from contaminated drinking-water reaching the public. Figure 1 and Figure 2 are provided to help you put together the Plan. Figure 1 shows you how to develop your Plan. On the left-hand side of the diagram are the suggested steps for preparing the Plan. To the right of each step, an arrow points to the detailed instruction for carrying out the step; further to the right is what you need to include in your Plan. Figure 2 suggests how to use the Plan once it has been developed. Again, the steps are set out at the left of the diagram, more detailed notes are on the right. You will need to know the Guides (and the supply elements they cover) that are available when you start your Plan. A flow diagram showing these is given in Figure 3. Getting help A health protection officer at your public health service provider will be able to tell you where you can get help in preparing your Plan if you need it. A Framework on How to Prepare and Develop Public Health 3

8 Figure 1: Developing your public health risk management plan Step Detailed Instruction Add to your Public Health Risk Management Plan Produce an overview of your supply and decide which Public Health Risk Management Plan Guides are needed. Draw a flow diagram of your supply, including all its elements from source to consumer. (Figure 3 in this document shows the level of detail necessary.) Go to Figure 3 and mark on it which supply elements shown there are also present in your flow diagram. Using the elements marked in Figure 3 and their reference numbers refer to the corresponding Guides. Read the Context section of each Guide you have selected to see whether other Guides may also contain useful information. Flow diagram of your supply Identify the barriers to contamination your supply has. Water quality is best protected by having several barriers to the entry of contaminants. The barriers need to: prevent contaminants entering the raw water remove particles from the water kill germs in the water maintain the quality of the water during distribution. Look at the flow diagram of your supply, and using Appendix 1 in this document, decide which barriers are present in your supply. Checklist of barriers present Use the Guides to identify events that may introduce hazards into the water. Use the Guides to identify: possible causes of each event preventive measures to avoid each event correct actions to use if preventive measures fail. Next page Each Guide contains a Risk Information Table that provides information to help prepare your Plan. Not all of the information contained in this table may apply to your supply. You may therefore find it useful to prepare a similar table to record only the information you will use for your plan. Look in the event sections of the Risk Information Table of each Guide to see what may go wrong and lead to hazards in the drinking-water. Decide which of these events are possible in your supply; some may not be. For each of your supply elements, think about other things that may go wrong that are not listed in the Guide, and add them to your own Risk Information Table. Group all events for each supply element together in the table. Look at the Risk Information Table for each element in your supply, and see which of the causes for the events you noted in the previous step might apply to your supply. Record these in your Risk Information Table with the corresponding event. From the Risk Information Tables record the preventive measures that could be used to reduce the chance of each event happening. There needs to be at least one preventive measure for each cause. Don t limit your list of preventive measures to those in the Guide. Add measures that have been useful in your experience. From the Risk Information Tables record the corrective actions that should be taken if the checks on the preventive measures show an event has occurred despite the preventive measures. Risk Information Table for your supply 4 A Framework on How to Prepare and Develop Public Health

9 Figure 1: (continued) Step Detailed Instruction Add to your Public Health Risk Management Plan Decide where improvements in your supply should be made. Compare the list of barriers present in your supply with the four types that are considered necessary (see above or Appendix 1). Place any barriers missing from your supply on a list of improvements to be considered. Compare the preventive measures, checks and corrective actions in your Risk Information Table with those in the Guides. Place any of these items not present in your supply on the list of improvements to be considered. Decide on the order in which improvements will be made. You will need to think about a number of factors when deciding on the order of importance of the improvements. These include the level of risk of each event, availability of physical and financial resources, how easy it is to make the improvement. The following suggestions may help. Give high priority to: making sure the four barriers are present, especially where disinfection is missing improvements that can be easily made at little cost. For the remaining improvements, estimate the level of risk attached to the event each improvement is linked to. The levels of risk give an order of importance for the improvements. Estimate the costs of these improvements and use these to change the order in which the improvements will be made. The Guides offer help with this in two ways. The Risk Summary in each Guide could be used for identifying which event presents the greatest risk and which preventive measures for this event are most important. This could be done if you wish to consider only the most important event. If you wish to consider more events, get the estimates of their level of risk from the Risk Information Table. The higher the level of risk of an event, the more important it is to put preventive measures, checks and corrective actions in place to deal with it. The risk levels given in the Risk Information Table are generalised estimates only, and they may change depending on the situation of the supply. Appendix 2 of this document provides a further guide to estimating risk levels for events in your supply. Improvement Schedule listing: improvements needed their levels of importance a timetable for their introduction responsibilities Draw up a timetable for making the improvements. Prepare a timetable, based on the order of importance from the previous step, giving the improvement to be made, the date when you expect it to be made, and the person who will have responsibility for making it. Note links to other quality assurance systems. Next page Note any other quality assurance systems (eg, ISO 9000/14000 series systems) you operate within your supply, and how these will link to your Plan. You may have monitoring programmes or maintenance schedules already in use as preventive measures or as checks on preventive measures. Make sure these are linked to your Plan. Note of other quality assurance systems and their links with the Plan. A Framework on How to Prepare and Develop Public Health 5

10 Figure 1: (continued) Step Detailed Instruction Add to your Public Health Risk Management Plan Look through the Contingency Plans provided in the Guide for each supply element, and decide which may be useful in your situation. Copy those that are useful into your Plan, or use them as a guide only. Whichever way you do it, your Plan should have Contingency Plans associated with each element. Use the Guide to prepare Contingency Plans. Include in the Contingency Plans advice for identifying the reason for the failure of the system should the plan have to be used. The following approach is suggested. Work through the possible causes noted in the Risk Information Table to decide what caused the event. From monitoring records, or other observations, decide which preventive measure was not in place, or which corrective action failed, or whether there is a need to consider a cause not listed. Examine the corrective action more closely to identify the reason for failure (Was it used correctly? Was it the right action to use? Could something have interfered with it?). Set of Contingency Plans for each supply element. Use the Guide to prepare instructions for checking that your Plan is working properly Performance Assessment. The PHRMP Performance Assessment section of the Guides can be used as a basis for preparing instructions for reviewing the operation of your overall Public Health Risk Management Plan. Record in the Plan what needs to be done for checking the performance of the Plan overall. This should include: how often the Plan should be reviewed for each supply element, what should be measured, or observed, to decide whether the Plan is working properly. In many instances, these will be the same as the checks noted in the Risk Information Table how often these measurements or observations need to be made, where they are to be recorded, and who has responsibility for recording them. Results may need to be recorded to meet legislative requirements or to allow the performance of the Plan to be checked. The WINZ database provides a useful tool for this purpose a record of any events that have occurred since the last review and actions taken (to allow the Plan to be changed to avoid the same problem again) changes to any of the supply elements which may make changes to the Plan necessary who has responsibility for carrying out the review. Set of instructions for review of the performance of the Plan. Decide on communication policy and needs. END Identify and record to whom reports concerning the management of public health risk for the supply need to be made, what information they are to receive and how often. Those receiving reports might be: managers councillors and consumers school board of trustees assessors acting on behalf of the Ministry of Health. Set of instructions for reporting. 6 A Framework on How to Prepare and Develop Public Health

11 Figure 2: Using your public health risk management plan Step Notes 1. Undertake any necessary capital works. 2. Obtain and put in place any necessary new plant. Refer to the Improvement Schedule prepared in your Plan. Following the timetable of the Schedule, put in place: preventive measures checks corrective actions that are needed, but not already present. 3. Put in place monitoring programmes that are required. These should state: what is being monitored when samples are to be taken where samples are to be taken who will take the samples which laboratory is to be used, or whether to make the measurement in the field what is to happen to the results. 4. Put in place maintenance programmes that are required. These should state: what is to be checked and maintained how often checks are to be made who is to make the checks what is to happen to the results of the checks. 5. Put in place staff training programmes that are required. These should state: the purpose of the training which staff are to be trained how often refresher courses are needed. Everybody has a part to play in ensuring that the water supply is protected from the entry of hazards. Review information gathered by monitoring and maintenance programmes. Monitoring programmes and maintenance schedules are often present as preventive measures, or checks on preventive measures. Staff who carry out maintenance checks, or who receive analysis reports from the laboratory, have responsibility for telling their managers of problems or possible problems they see. It is also important that someone is responsible for regularly looking through summaries of monitoring results and maintenance logs, perhaps every month. This study of information gathered over a long period may assist in spotting early signs of future problems. Each person with responsibility for checking results should know who to report to if they see something of concern. Refer to and use the Contingency Plans should this be necessary. If something goes wrong, and a Contingency Plan has to be used, the actions that need to be taken will depend on such things as the type of hazard that is in the water, its likely concentration and how far it has travelled into the distribution system. Consultation with the Medical Officer of Health may be necessary in assessing the seriousness of the event. It is important that the reasons for things going wrong are identified. This information can be used in the review of the Plan. Review how well the Plan is working and make changes where necessary. Elements within your supply may change, or events may occur that highlight weaknesses in the Plan. In both cases, there is a need to decide what has to be changed in the Plan to take account of changes or overcome the weaknesses. This is the purpose of regularly reviewing the Plan. Review of the Plan may require the Improvement Schedule to be changed, because of changes in the order of importance that become evident. A Framework on How to Prepare and Develop Public Health 7

12 Figure 3: Supply elements and public health risk management plan guides Source Treatment Distribution System S1 Raw water S1.1 Surface and groundwaters S1.2 Roof catchments P1 Source abstraction P1.1 Surface waters rivers/streams/infiltration galleries P1.2 Surface waters lakes/reservoirs P1.3 Groundwaters wells/bores P1.4 Groundwaters springs P4 Pre-treatment processes P4.1 Algicide application P4.2 Destratification P4.3 Pre-oxidation P4.4 Waste-liquor reintroduction P2 Water Transmission (also applicable to distribution system) P5 Coagulation/flocculation processes P5.1 Conventional coagulation/ flocculation/sedimentation P5.2 Dissolved air flotation P5.3 Direct filtration P3 Pre-treatment storage P6 Filtration P6.1 Rapid (gravity) sand filtration P6.2 Slow sand filtration P6.3 Cartridge filtration P6.4 Diatomaceous earth filtration P6.5 Membrane filtration D1 Post-treatment storage D2 Reticulation network D2.1 Construction materials (also applicable to treatment processes) D2.2 System pressure D2.3 Operation D2.4 Backflow prevention Water transmission (see P2) S2 Development of new supplies P7 Disinfection P7.1 Chlorination P7.2 Chlorine dioxide treatment P7.3 Ozonization P7.4 Ultra-violet irradiation P8 Aesthetic property adjustment P8.1 ph adjustment P8.2 Iron and manganese removal P8.3 Softening P8.4 Trace organics removal P9 Fluoridation Pump operation (see P10) P10 Pump operation (also applicable to distribution system) P11 Drinking-water treatment plant construction and operation Construction materials (see D2.1) General Elements (applicable to all elements) G1 Staff training G2 Monitoring 8 A Framework on How to Prepare and Develop Public Health

13 Glossary Cause Contingency plan Corrective action Determinand Event Germ Hazard Preventive measure Risk Supply element Supply stage Supply subelement The situation, action or inaction resulting in an event. A plan to be followed should corrective actions fail to stop a hazard, or hazards, entering the distribution system. In most cases, contingency plans are intended to deal with the possible breakthrough of germs into the distribution system, or situations in which acute risk to public health arises because of the presence of a chemical hazard. An action taken after an event has occurred to reduce the likelihood of the event occurring again by improving the preventive measures in place, or to minimise the risk created by the event. Compare with preventive measures. A constituent or property of the water that is determined, or estimated, in a sample (DWSNZ). An incident or situation that may introduce a hazard (or hazards) into the water. Micro-organisms that can cause disease. Included in this general term are bacteria, viruses, protozoan (eg, Giardia and Cryptosporidium), helminths (worm), cyanobacteria and toxic algae. A microbiological or chemical determinand that may cause sickness. An action taken, or process, designed to reduce the likelihood of an event happening. The chance of something happening that will have an impact upon objectives (AS/NZS 4360:1999). Risk is measured in terms of consequences and likelihood. Here, the objectives are the maintenance of water quality and therefore the protection of public health. A physical or operational component of a water supply. Supply elements act together to determine the quantity and quality of the water received by the consumer. One of the three major sections composing a supply. Supplies are regarded as being made up of raw water, treatment processes and the distribution system. A sub-component of a supply element. These components are identified separately because each may need to be treated differently for the purposes of public health risk management. An example is disinfection, which has the subelements of chlorination, chlorine dioxide treatment, ozonisation and ultra-violet irradiation. A Framework on How to Prepare and Develop Public Health 9

14 Appendix 1: Barriers to Contamination To understand whether there is a major weakness in your supply against contamination you will need to consider what barriers you have in place. For you to provide safe drinking-water, your supply needs to have barriers in place to prevent contaminants reaching the public. The barriers should: prevent contaminants entering the raw water remove particles from the water kill germs in the water maintain the quality of the water during distribution. While each of these barriers helps to reduce the risk to public health from the drinking water supply, the greatest protection is gained when all are in place. When developing your Plan, you need to decide which of the four types of barrier noted above are in your supply. The following table should help in recognising which barriers you have in place. Barriers to: Stop contamination of raw water Remove particles from the water Actions or supply elements contributing to these barriers Use of secure groundwaters Abstraction point positioned and constructed to avoid contamination Source protected from further contamination Actions to avoid contamination of roof catchments, and contaminants being washed from roofs Coagulation/flocculation/clarification Dissolved air filtration Filtration Kill germs in the water Disinfection (chlorine, chlorine dioxide, ozone, ultra-violet light) Prevention recontamination after treatment Measures to stop contamination of storage tanks Maintenance of a disinfecting residual Installation of backflow preventers where necessary Actions taken to avoid contamination during distribution system maintenance 10 A Framework on How to Prepare and Develop Public Health

15 Appendix 2: Estimating Risk The levels of risk noted in the risk information tables of the Guides are considered typical, and provide a rough guide only. It is not possible to provide an estimate of risk that will apply to all supplies, because the factors affecting the level of risk are likely to be different for each supply. This appendix offers direction on estimating qualitative risk, if you would prefer to estimate the level of risk for your supply yourself. The level of risk associated with a particular event is calculated based on the likelihood of the event occurring, and the consequences (or outcome) of it occurring. Factors affecting the consequence include the number of people that may be affected; the duration of the event, the severity of the event (this would depend on the hazard introduced into the water by the event). The AS/NZS 4360:1999 Risk Management Standard provides a matrix for estimating risk. The matrix is based on five categories of likelihood and five of consequence. You may find the following scale descriptions more helpful than those in the Standard for water supplies, or you can use your own scales. Likelihood scale Likelihood ranking Rare Unlikely Possible Likely Almost certain Description May occur only in exceptional circumstances (once in 1000 years) Could occur (once in 100 years) Might occur at some time (once in 10 years) Will probably occur (once in 1 or 2 years) Is expected to occur in most circumstances Consequence scale Consequence ranking Insignificant Minor Moderate Major Catastrophic Description Insignificant Minor impact for small population Minor impact for big population Major impact for small population Major impact for big population A Framework on How to Prepare and Develop Public Health 11

16 This gives the following estimates of risk: Likelihood Consequences Insignificant Minor Moderate Major Catastrophic Almost certain High High Extreme Extreme Extreme Likely Moderate High High Extreme Extreme Possible Low Moderate High Extreme Extreme Unlikely Low Low Moderate High Extreme Rare Low Low Moderate High High 12 A Framework on How to Prepare and Develop Public Health