MANAGEMENT OF RAINWATER HARVESTING SUPPLY SYSTEM

Transcription

1 MANAGEMENT OF RAINWATER HARVESTING SUPPLY SYSTEM GUIDE FOR ADEQUATE MANAGEMENT, MAINTENANCE, CLEANING AND PROTECTION OF RAINWATER HARVESTING SUPPLY SYSTEM Training Manual 2007 J E A N P I E R R E N S H I M Y I M A N A E N V I R O N M E N T A L H E A L T H C O N S U L T A N T, N J E P I E Y A H O O. FR/ N J E P I E G M A I L. C O M

2 TABLE OF CONTENTS TABLE OF CONTENTS... 1 INTRODUCTION... 1 PURPOSE OF THE TRAINING... 2 WHO WILL BE TRAINED?... 2 CHAPTER 1: RAINWATER HARVESTING SYSTEM COMPONENTS OF A RAINWATER HARVESTING SYSTEM roof Gutters Pipes Storage facilities (water tanks or reservoir) Tap water ADVANTAGES AND BENEFITS OF RAINWATER HARVESTING SYSTEM... 6 CHAPTER 2: RAINWATER QUALITY A. FACTORS AFFECTING WATER QUALITY a.1. Ph (acidity/alkalinity) a.2. Particulate matter a.3. Chemical compounds A.4. Catchment surface A.5. Tanks B. WATER TREATMENT... 8 TREATMENT TECHNIQUES... 9 CHAPTER 3: MAINTENANCE AND CLEANING MAINTENANCE CLEANNING HOW TO CLEAN YOUR WATER TANK ONGOING MAINTENANCE AND REPAIRS DISINFECTING YOUR RAINWATER TANK CHAPTER 4: RAINWATER QUALITY AND HEALTH DIAGRAMS ILLUSTRATING HOW RAINWATER AFFECTS HEALTH REFERENCES AND FURTHER READING

3 INTRODUCTION A sufficient, clean drinking water supply is essential to life. Millions of people throughout the world still do not have access to this basic necessity. After decades of work by governments and organizations to bring potable water to the poorer people of the world, the situation is still dire. The reasons are many and varied but generally speaking, the poor of the world cannot afford the capital intensive and technically complex traditional water supply systems which are widely promoted by governments and agencies throughout the world. Rainwater harvesting is an option that has been adopted in many areas of the world where conventional water supply systems have failed to meet people s needs or are not adequate due to the geology of the considered area. It is a technique that has been used since antiquity. Many individuals and groups have taken the initiative and developed a wide variety of Rainwater harvesting systems throughout the world. It is a technology that is flexible and adaptable to a very wide variety of conditions, being used in the richest and the poorest societies on our planet, and in the wettest and the driest regions of the World. The reason that Rainwater harvesting is rarely considered is often due to lack of information both technical and otherwise. In many areas where rainwater harvesting has been introduced as part of a wider drinking water supply program, it was at first unpopular, simply because little was known about the technology by the beneficiaries. This training guide is focusing on adequate management and maintenance of rainwater supply system. It is an important issue to insure in order to attend the satisfactory results from the system. Motivation, commitment, incentive and level of awareness are critical factors in the maintenance and repair of rainwater harvesting systems. In order to ensure the long-term sustainability of rainwater harvesting systems these factors need to be addressed at various levels within all of different kind of users (the household, community, public places, etc.). The step-by-step approach will be used to build this motivation for the operation and maintenance of rainwater harvesting systems. Through an examination of the links between water quality and health, participants clearly see the importance of maintenance in relation to the good health of everybody. Participants come to appreciate that 1

4 prevention is the key to good health. This encourages people to place maintenance and repair activities as a top priority. Once this high priority has been established, beneficiaries are more likely to devote the necessary level of attention to the technical aspects of maintenance and repair of their rainwater harvesting systems and the system that has been installed at Bisate Health Center, Bisate Primary School and Trackers House will be our focus during the training. PURPOSE OF THE TRAINING To raise the awareness of the controllers and users of the rainwater harvesting system in order ensure adequate maintenance, repair, cleaning and usage of the system. WHO WILL BE TRAINED? The training about rainwater harvesting system will concern all the personnel that will be regarded with the rainwater management especially the in charge of water management at Bisate Trackers house, Bisate Clinic and Bisate primary school. Bisoke and Kaguhu Cells of Kinigi sector where those infrastructures will be installed will also send their representatives. The people how will be trained will be the light of their community members who did not participate. 2

5 CHAPTER 1: RAINWATER HARVESTING SYSTEM 1.1. COMPONENTS OF A RAINWATER HARVESTING SYSTEM Rainwater harvesting system will usually comprise a collection surface (a clean roof or ground area), a storage tank, and guttering to transport the water from the roof to the storage tank. Other peripheral equipment is sometimes incorporated, for example: first flush systems to divert the dirty water which contains roof debris after prolonged dry periods; filtration equipment and settling chambers to remove debris and contaminants before water enters the storage tank or cistern; hand pumps for water extraction; water level indicators, etc ROOF The roof of the house is a surface of water collection. It is the basic of a rainwater harvesting system because without it we can not be able to get the quantity of water that is needed. Even the roof of the house play an important role in water collection, it can also be the source of contamination if it is not kept clean or if the children used to flow 3

6 dirty objects on the roof. Water quality from different roof catchments is a function of the type of roof material, climatic conditions, and the surrounding environment (Vasudevan, 2002). A. Metal roof The quantity of rainwater that can be collected from a roof is in part a function of the roof texture: the smoother the better. A commonly used roofing material for rainwater harvesting is sold under the trade name Galvalume, a 55 percent aluminum/45 percent zinc allocated sheet steel. Galvalume is also available with a baked enamel coating, or it can be painted with epoxy paint. Some caution should be exercised regarding roof components. Roofs with copper flashings can cause discoloration of porcelain fixtures. B. Clay/concrete tile Clay and concrete tiles are both porous. Easily available materials are suitable for potable or non potable systems, but may contribute to as much as a 10-percent loss due to texture, inefficient flow, or evaporation. To reduce water loss, tiles can be painted or coated with a sealant. There is some chance of toxins leaching from the tile sealant or paint, but this roof surface is safer when painted with a special sealant or paint to prevent bacterial growth on porous materials GUTTERS The gutters have the main role of putting together the amount of water collected on the roof and directing it to the pipes that will transport the water to the storage facility. They can also be the source of water contaminations if they are not kept clean PIPES The pipes have the role of water transportation from the gutters to the water storage facilities (Water tank or reservoir). They also have to be kept clean and protect from any source of breakage. They don t have to be used like relaxing object for the little kids or any other person who may have that bad behavior. 4

7 STORAGE FACILITIES (WATER TANKS OR RESERVOIR) The water storage facility has normally three many roles: The first role is storing the amount of water from the roof for further usage. The second role is that by storing the water from the roof it will favor the sedimentation of suspended material that may come in with the rainwater thus assuming the role of water treatment. The third role is that by the storing water a long time especially more that 48 hours living microorganism like pathogenic germs will die and thus assuming the role of biological treatment of rainwater. Therefore we will be sure that any pathogenic micro organisms will be dead after that storing period. Even if treatment seem to be the main role of the storing facility, that capacity doesn t remove cleaning work inside the water tanks when this is necessary especially after along period of dry season or when any undesired object which are subjected to be the source of contamination are suspected to have been entered the water storage TAP WATER The tap water has the main role of helping users to get water from the water storage facility. It has to keep safe and protected from any leakage or blockage that may occur due to inadequate maintenance. N.B: Even if we cited five rainwater components, they can differ from the above according to the collection object that has been preferred by the community to be used like ground collection facility to be used for irrigation. Above we discussed the principal components, when visiting any rainwater harvesting you should not be surprised by the small components that have not been discussed e.g. Small pipes joining the tank to the filter, etc. 5

8 1.2. ADVANTAGES AND BENEFITS OF RAINWATER HARVESTING SYSTEM Advantages and benefits of rainwater harvesting are numerous (Krishna, 2003). The water is free; the only cost is for collection and use. The end use of harvested water is located close to the source, eliminating the need for complex and costly distribution systems. Rainwater provides a water source when groundwater is unacceptable or unavailable, or it can augment limited groundwater supplies. The zero hardness of rainwater helps prevent scale on appliances, extending their use; rainwater eliminates the need for a water softener and the salts added during the softening process. Rainwater is sodium-free, important for persons on low-sodium diets. Rainwater is superior for landscape irrigation. Rainwater harvesting reduces flow to storm water drains and also reduces nonpoint source pollution. Rainwater harvesting helps utilities reduce the summer demand peak and delay expansion of existing water treatment plants. Rainwater harvesting reduces consumers utility bills. Rainwater harvesting increases water resource and thus increases the rate of water accessibility. The rainwater reduces the spread of waterborne diseases, thus playing role in the reduction of parasites diseases burden in the community. Rainwater harvesting increases the participation of women and children in the developing activities or projects. Rainwater harvesting system plays the important role in conservation because it suppresses the movement of the people entering the parks or other protected areas for fetching water. Rainwater harvesting can reduce the volume of storm water, thereby lessening the impact on erosion and decreasing the load on storm sewers. Decreasing storm water volume also helps keep potential storm water pollutants, such as pesticides, fertilizers, and petroleum products, out of rivers and groundwater. 6

9 CHAPTER 2: RAINWATER QUALITY The raindrop as it falls from the cloud is soft, and is among the cleanest water sources. Use of captured rainwater offers several advantages: Rainwater is sodium-free, a benefit for persons on restricted sodium diets; Irrigation with captured rainwater promotes healthy plant growth. Also, being soft water, rainwater extends the life of appliances as it does not form scale or mineral deposits; etc. The environment, the catchment surface, and the storage tanks affect the quality of harvested rainwater. With minimal treatment and adequate care of the system, however, rainfall can be used as potable water, as well as for irrigation. The falling raindrop acquires slight acidity as it dissolves carbon dioxide and nitrogen. Contaminants captured by the rain from the catchment surface and storage tanks are of concern for those intending to use rainwater as their potable water source. The catchment area may have dust, dirt, fecal matter from birds and small animals, and plant debris such as leaves and twigs. Rainwater intended for domestic potable use must be treated using appropriate filtration and disinfection equipment. 2. A. Factors Affecting Water Quality 2.A.1. ph (acidity/alkalinity) As a raindrop falls and comes in contact with the atmosphere, it dissolves naturally occurring carbon dioxide to form a weak acid. The resultant ph is about 5.7, whereas a ph of 7.0 is neutral. Also, a concrete storage tank will impart a slight alkalinity to the water. 2.A.2. Particulate matter Particulate matter refers to smoke, dust, and soot suspended in the air. Fine particulates can be emitted by industrial and residential combustion, vehicle exhaust, agricultural controlled burns, and sandstorms. As rainwater falls through the atmosphere, it can incorporate these contaminants. 7

10 2.A.3. Chemical compounds In agricultural areas, rainwater could have a higher concentration of nitrates due to fertilizer residue in the atmosphere (Thomas and Grenne, 1993). Pesticide residues from crop dusting in agricultural areas may also be present. Also, dust derived from calciumrich soils can add 1 mg/l to 2 mg/l of hardness to the water. Hard water has a high mineral content, usually consisting of calcium and magnesium in the form of carbonates. In industrial areas, rainwater samples can have slightly higher values of suspended solids concentration and turbidity due to the greater amount of particulate matter in the air (Thomas and Grenne, 1993). 2. A.4. Catchment surface When rainwater comes in contact with a catchment surface, it can wash bacteria, molds, algae, fecal matter, other organic matter, and/or dust into storage tanks. The longer the span of continuous number of dry days (days without rainfall), the more catchment debris is washed off the roof by a rainfall event (Thomas and Grenne, 1993; Vasudevan, 2002). 2. A.5. Tanks The more filtering of rainwater prior to the storage tanks, the less sedimentation and introduction of organic matter will occur within the tanks. Gutter screens, first-flush diverters, roof washers, and other types of pre-tank filters, etc. Sedimentation reduces the capacity of tanks, and the breakdown of plant and animal matter may affect the color and taste of water, in addition to providing nutrients for microorganisms. Most storage tanks are equipped with manholes to allow access for cleaning. Sediment and sludge can be pumped out or siphoned out using hose with an inverted funnel at one end without draining the tank annually. Multiple linked tanks allow one tank to be taken off line for cleaning by closing the valve on the linking pipe between tanks. 2. B. Water Treatment The cleanliness of the roof in a rainwater harvesting system most directly affects the quality of the captured water. The cleaner the roof, the less strain is placed on the treatment equipment. It is advisable that overhanging branches be cut away both to avoid tree litter and to deny access to the roof by rodents and lizards. For potable systems, a 8

11 plain galvanized roof or a metal roof with epoxy or latex paint is recommended. Composite or asphalt shingles are not advisable, as toxic components can be leached out by rainwater. To improve water quality, several treatment methods are can be used: boiling the water, using sand filter, house filter, etc. It is the responsibility of the individual installer or homeowner to weigh the advantages and disadvantages of each method for appropriateness for the individual situation. TREATMENT TECHNIQUES METHODS LOCATION RESULTS Treatment Screening Leaf screens and strainers gutters and downspouts prevent leaves and other debris from entering tank Settling Sedimentation within tank settles out particulate matter Activated charcoal before tap removes chlorine* Filtering Roof washer before tank eliminates suspended material In-line/multi-cartridge after pump sieves sediment Activated charcoal removes after sediment filter chlorine, improves taste Slow sand separate tank traps particulate matter Microbiological treatment /Disinfection Boiling/distilling before use kills microorganisms Chemical treatments (Chlorine or Iodine) Ultraviolet light Ozonation Nanofiltration Reverse osmosis within tank or at pump (liquid, tablet, or granular) before activated charcoal filter after activated charcoal filter, before tap after activated charcoal filter, before tap before use; polymer membrane (pores 10-3 to 10-6 inch ) before use: polymer membrane (pores 10-9 inch) kills microorganisms kills microorganisms kills microorganisms removes molecules removes ions (contaminants and microorganisms) * Should be used if chlorine has been used as a disinfectant. Adapted from Texas Guide to Rainwater Harvesting, Second Edition, Texas Water Development Board,

12 CHAPTER 3: MAINTENANCE AND CLEANING 3.1 MAINTENANCE Along with the independence of rainwater harvesting systems comes the inherent responsibility of operation and maintenance. For all systems, this responsibility includes purging the first flush system, regularly cleaning roof washers and tanks, maintaining pumps, and filtering water. For potable systems, responsibilities include all of the above, and the owner must replace cartridge filters and maintain disinfection equipment on schedule, arrange to have water tested, and monitor tank levels. Rainwater used for drinking should be tested, at a minimum, for pathogens. Maintenance of a rainwater harvesting system is also an ongoing periodic duty, to include: Monitoring tank levels, Cleaning gutters and first-flush devices, Repairing leaks, Repairing and maintaining the system, and adopting efficient water use practices. In addition, owners of potable systems must adopt a regimen of: Changing out filters regularly, Maintaining disinfection equipment, such as cleaning Regularly testing water quality. Maintenance responsibilities are for everyone who uses the rainwater harvesting system to cover her or his daily water demand especially when that is installed for the public usage. 3.2 CLEANNING Cleaning is the action done to protect the rainwater harvesting system from the dirty objects that can adversely affect the human being. It is very essential when the area has been under going a long period of dry season. The in charge of the water harvesting system has to be in control of the whole system cleaning activities that have to be curried out on the system and organize it effectively. The cleaning program interests the following points: 10

13 Roof; Gutters; pipes and water tanks. Those parts of the rainwater harvesting system have to be cleaned depending on how they are dirty. Among the factors that affects the cleanliness of the rainwater harvesting system, we can cite: Seasons especially the dry season. The situation can also be worse during the rain season due to the intensity of the winds that collect dirty objects from the soil and transport them to the roofs. If there are not removed they can affect the system. Roofs can also be unclean due to the small kids that flash some objects to the roof of the house. 3.3 HOW TO CLEAN YOUR WATER TANK Remember to Clean Your Water Tank Once a Year You will need: Liquid chlorine (such as Dash or Janola) or chlorine tablets Bucket Brush Eye and hand protection (glasses, rubber gloves) 1. Drain any water in the tank to level at tap. Transfer water to clean contaminant free storage or temporary vessel. 2. Add 1 bottle of bleach or X number of chlorine tablets to the remaining water in the tank. 3. Climb inside the tank. Using a brush thoroughly scrub the bottom and sides of the tank. 4. Remove the water and bleach solution with a bucket. 5. Refill the tank with water. 6. Leave the water to settle overnight before use. Wear proper hand and eye protection when preparing and handling chlorine solutions to avoid burning skin and damaging eyes. 11

14 3.4 ONGOING MAINTENANCE AND REPAIRS Parts Roof ONGOING MAINTENANCE AND REPAIRS -Wash off roof with water when dust/dirt accumulates diverting runoff away from tank inlet. -Trim and cut trees around tank. -Replace rusted roofing. -Fix holes for maximum runoff. HOW OFTEN? MATERIALS TOOLS Check monthly and especially after long period of dry weather and cyclone and heavy wind. Roofing iron Paint Water Hand saw Nails Hammer Brush Gutters -Paint if rust is present using lead-free paint. -Clean and washout bird droppings, leaves etc. with water. -Check and repair gutters. Check monthly and especially after a long period of dry weather and cyclone or heavy wind. Water Guttering Gutter hanger Gutter fittings Brush Screwdriver Screws Hammer Nails Level -Add more guttering to increase water collected. When possible. -Ensure guttering is slanted to ensure steady flow of water avoid pooling of water, collection of dirt, debris, etc. 12

15 Tank Clean. (See Fact Sheet 6) Repair leaks. Disinfect. Cut nearby tree roots. Once a year. (See Fact Sheets 7& 8) Water Disinfectant Cement Sand Gravel Proper lid Brush Shovel Wheelbarrow Saw Trowel Tap Down pipe Ensure lid is sturdy and secure to prevent animals and children from falling in. Fix leaking taps. If new taps are needed brass taps are stronger. Sponge out excess water to ensure it does not pool or collect under tap. Place stones or gravel on bottom of collection area to help drainage. Repairing holes and replace if screen is damaged. Ensure there are no gaps where mosquitoes can enter or exit. Tap Washer Plumbing tape Glue Rubber Stones/gravel Stainless steel wire mesh Twine PVC pipe Glue Spanner Wrench Pliers Screwdriver Pliers Tin snips Overflow Repair leaks at elbows. Securely fasten mosquito screen over the end of the overflow pipe/valve. When required Wire mesh Twine Pliers Tin snips Ensure there are no gaps where mosquitoes can enter or exit. 13

16 Fence Repair screen if damaged. Ensure fence is high and strong enough around tank and collection area to keep out pigs, dogs and small children. Repair any gaps or damage to fence. Fencing wire Poles Nails Hammer Digging hoe First Flush Devices Remove down pipe from tank inlet to divert water. Securely replace the down pipe after first flush. Before starting to collect water, and especially after a long period of dry weather, a cyclone or heavy wind. PVC pipe Pipe fittings Pipe wrench 14

17 3.5 DISINFECTING YOUR RAINWATER TANK You should disinfect your tank only when one or more of the following situations are present: People are getting sick from drinking the water with sore stomachs and diarrhea; Animal or human waste, including bird droppings has entered the tank; After tank repairs or maintenance where people have entered the tank; The water has been tested and there is a known bacterial contamination. 1. Calculate the volume of water in your tank (see Fact Sheet 7). 2. Add ½ bottle (125 ml) of plain household grade unscented and uncolored bleach (with 4% active chlorine) to every 1,000 liters of water currently in your tank. Amount of water in the tank Amount of bleach 1,000 litres 125 ml 2,000 litres 250 ml 3,000 litres 375 ml Etc 3. Wait 24 hours after putting in the chlorine to allow enough time to disinfect the water before you drink it. Any chlorine smell and taste in the water will go away after a short time. If you find the taste of chlorine unacceptable boil the water for at least 5 minutes before drinking it. Remember to wear proper hand and eye protection when preparing and handling chlorine solutions to avoid burning skin and damaging eyes. 15

18 CHAPTER 4: RAINWATER QUALITY AND HEALTH Rainwater is often used for drinking and cooking and so it is vital that the highest possible standards are met. Rainwater, unfortunately, often does not meet the World Health Organization (WHO) water quality guidelines. This does not mean that the water is unsafe to drink. Generally the chemical quality of rainwater will fall within the World Health Organization (WHO) guidelines and rarely presents problems. There are two main issues when looking at the quality and health aspects of Drinking Rainwater harvesting: 1. There is the issue of bacteriological water quality. Rainwater can become contaminated by faeces entering the tank from the catchment area. It is advised that the catchment surface always be kept clean. Rainwater tanks should be designed to protect the water from contamination by leaves, dust, insects, vermin, and other industrial or agricultural pollutants. Tanks should be sited away from trees, with good fitting lids and kept in good condition. Incoming water should be filtered or screened, or allowed to settle to take out foreign matter (as described in a previous section). Water which is relatively clean on entry to the tank will usually improve in quality if allowed to sit for some time inside the tank. Bacteria entering the tank will die off rapidly if the water is relatively clean. Algae will grow inside a tank if sufficient sunlight is available for photosynthesis. Keeping a tank dark and sited in a shady spot will prevent algae growth and also keep the water cool. As mentioned in a previous section, there are a number of ways of diverting the dirty first flush water away from the storage tank. The area surrounding a RWH should be kept in good sanitary condition, fenced off to prevent animals fouling the area or children playing around the tank. Any pools of water gathering around the tank should be drained and filled. Gould points out that in a study carried out in north-east Thailand 90 per cent of in-house storage jars were contaminated whilst only 40% of the Rainwater Harvesting jars were contaminated. This suggests secondary contamination (through poor hygiene) is a major cause of concern. 2. There is a need to prevent insect vectors from breeding inside the tank. In areas where malaria is present, providing water tanks without any care for preventing insect breeding can cause more problems than it solves. All tanks should be sealed to prevent insects from entering. Mosquito proof screens should be fitted to all openings. 16

19 DIAGRAMS ILLUSTRATING HOW RAINWATER AFFECTS HEALTH FAECAL-ORAL DISEASES Organisms from human or animal faeces can reach the mouth and make a person ill and cause diarrhea. These organisms can be spread by hands, clothes, food, as well as cups, glasses, plates and utensils used for eating and drinking. Taps on rainwater tanks and containers used to collect and store rainwater can become contaminated and spread disease. SPREAD BY INSECTS Diseases such as dengue and malaria are spread by insects. Mosquitoes can breed inside rainwater tanks or in pools of water in gutters or beneath leaking tanks or taps and then spread disease. HOW RAINWATER AFFECTS YOUR HEALTH DISEASES RELATED TO WATER SCARCITY Proper bathing is necessary to stop skin diseases like scabies. During droughts, infrequent bathing due to a lack of available water in rainwater tanks can make diseases get worse. WATER-BORNE DISEASES Disease-causing organisms can be present in drinking water and can cause diseases such as diarrhea, cholera and typhoid. Rainwater collected in the tank can become contaminated when leaves, bird or rat droppings get into the tank. 17

20 REFERENCES AND FURTHER READING 1. Dr. Hari J. Krishna, P.E., the Texas Manual on Rainwater Harvesting Third Edition 2005, Austin, Texas. 2. Harvesting the heavens, a manual for participatory training in rainwater harvesting, Compiled by the South Pacific Applied Geoscience Commission (SOPAC) for the United Nations Environment Programme (UNEP) in conjunction with the Tonga Community Development Trust (TCDT) and funded by The Swedish Development Agency (SIDA), Krishna H. 2003, An overview of rainwater harvesting systems and guidelines in the United States. Proceedings of the First American Rainwater Harvesting Conference; 2003 Aug 21-23; Austin (TX). 4. Nicolas K., Bryan K., Hunter H.; Calhoun Fields Learning Lab Rainwater Harvesting System Operating Instructions & Parts Manual, Rainwater Catchment Systems for Domestic Supply, by John Gould and Erik Nissen- Petersen, IT Publications Ltd., Rainwater harvesting in developing countries; Practical action the Schumacher Center of Technology and development. Retrieved on February,27 th, 2007 from 7. The Gulf Islands Rainwater Connection; Owners manual rainwater harvesting and water supply system, January Thomas PR, Grenne GR Rainwater quality from different roof catchments. Water Science Technology (28):