Study Session 10  Household Water Collection, Treatment, Storage and Handling

Introduction

Water utilities are responsible for putting fully treated water into the distribution system, but it can become contaminated after it has left the treatment works if not handled with care. The contamination can originate from several different sources, but it is obviously important to eliminate any introduction of faecal material for health reasons. Research in Sodo woreda, Guraghe Zone, in the Southern Nations, Nationalities and Peoples’ Region (SNNPR) showed that 61% of the water in households was faecally contaminated and for five woredas in Amhara Region the figure was 74% (Kinfegabriel, 2015). These findings demonstrate that safe water collection, treatment and handling at household level are key considerations for potable water availability in the home.

This study session will discuss safe water collection methods and the ways in which water can be treated at household level. It also presents the basic principles of safe water storage and handling in the home.

Learning Outcomes for Study Session 10

When you have studied this session, you should be able to:

10.1 Define and use correctly the key words printed in bold. (SAQ 10.1)

10.2 List the methods by which households can safely collect water for use. (SAQ 10.2)

10.3 Describe the methods by which water can be treated at household level. (SAQ 10.1)

10.4 Describe the options for safe storage of water. (SAQ 10.3)

10.5 Summarise the methods for safe handling of water in the home. (SAQ 10.3)

10.1  Methods of safe household water collection

Households in urban areas that do not have a tap connection in their house or yard will probably collect water from a water point or kiosk. Even where there is a household connection, residents may sometimes need to use other sources, for example if there is a break in supply. In longer-term emergency situations, safe water may be delivered by tanker to residential areas for distribution to householders. In both of these instances, collection vessels such as those shown in Figure 10.1 will be used to carry water to the home.

Figure 10.1  Commonly used water collection vessels.

A water container has to be clean, and must not previously have been used to contain any toxic material (such as pesticides). Ideally, the mouth of the vessel should be narrow and it should have a lid. It should have handles so that it can be carried easily.

An alternative to the containers shown in Figure 10.1 is the Hippo Water Roller (Figure 10.2), which enables water to be transported more easily and efficiently. It is a 90-litre drum made from UV-stabilised, low-density polyethylene that can be rolled along the ground using a steel clip-on handle. The device is designed to cope with rough surfaces and is very stable in the upright position. The roller is rounded at the shoulders and has hand grips at the top and bottom to make it easier to tilt a full roller when pouring.

Figure 10.2  Hippo Water Rollers in use.

10.2  Methods of household treatment of water

Just as in the water treatment works, if the water is turbid (muddy), then giving it time to settle (become calm) helps in sedimentation. This process can be assisted by adding a coagulant that encourages the formation of larger, heavier particles (flocculation) that then settle easily to the bottom of the container and make the water clear. At the household level, natural coagulants can be used such as the crushed, dry seeds of the Moringa fruit, shown in Figure 10.3 (Davis and Lambert, 1995). Moringa fruit comes from Moringa trees, which grow in tropical countries

Figure 10.3  Fruits of Moringa oleifera.

After the suspended particles have settled, the clear water at the top can be carefully poured into another container for further processing. The three-pot method is one method of sedimentation.

The three-pot method

The three-pot method (Figure 10.4) is a means of reducing dirt and micro-organisms in water, by storing the water in a container, allowing the dirt to settle, and moving the cleaner water to different containers over time. Water in a container should be allowed to settle for a day before it is decanted into the next container. Only water from Pot 3 should be consumed. The three-pot system is low-cost, easy to use and is something people can do themselves. However, it does not totally remove disease-causing micro-organisms, so some method of disinfection is still needed to remove the risk of disease completely.

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Figure 10.4  The three-pot water treatment system (IFRCRC, 2008).

10.2.2  Filtration

Filtration is another method of removing suspended particles and is also relatively easy. There are several different methods of filtration that can be used in the home.

Cloth filtration

Cloth filtration (Figure 10.5) is cheap, easy to carry out and a common water treatment technique. Pouring turbid water through a piece of fine, clean cotton cloth will remove larger contaminants and a certain amount of suspended solids. It is better to use a used, rather than new, piece of cloth.

Figure 10.5  Cloth filtration.

The steps in cloth filtration are as follows:

1. Use a large cloth, preferably made of finely-woven cotton. Fold the cloth at least four times so that there are multiple layers of fabric, and place this over the opening of the storage vessel.
2. The cloth, once folded, must be big enough to easily cover the opening of the receiving water container.
3. Place the cloth over the mouth of the container.
4. Fasten the cloth securely around the rim of the opening, using string. If reusing the cloth, always use the same side up each time.
5. Pour the water through the cloth, into the container.
6. Wash the filter cloth after each use, with a final rinse using cloth-filtered water, and then leave the cloth in the sun until it is dry.
7. Clean the cloth regularly using detergent, and use a new piece of cloth as soon as there are any visible tears or holes.
8. Always keep filtered water separate from non-filtered water.

Household sand filtration

A household sand filter can usually be made from locally available and inexpensive materials like clay pots or barrels. They are simple and easy to use. One such system consists of a pot and a storage vessel (Figure 10.6).

Figure 10.6  A household sand filter system, comprising a pot and a storage vessel.

The details of the system are as follows:

1. The bottom of the pot is perforated (has tiny holes in it).
2. The pot contains layers of gravel (about 5 cm deep), coarse sand (about 5 cm deep) and fine sand (about 10 cm deep).
3. Water is poured in at the top and, as it passes through the layers, any particles within it are filtered out.
4. Clean water drips into the storage container.
5. The storage container should have a tap to enable the clean water to be drawn out easily and safely.
6. The sand and gravel should be changed when the rate of filtration starts to slow; at a minimum it should be changed every two to three months.

Ceramic filtration

For ceramic filtration, a water filter in the form of a ceramic pot can be made using clay, sawdust or rice husks, and a plastic bucket. The pot is made by mixing clay with the sawdust or rice husks, forming it into a flowerpot shape and then firing it in a kiln. The sawdust or rice husks burn away, leaving tiny pores in the ceramic through which water can be filtered. The small pore size of the ceramic material traps the particles and most micro-organisms.

To use the filter, the pot is inserted into a container so that its lip prevents it from slipping into the container (Figure 10.7). The raw water is then poured into the ceramic pot. Cleaned water percolates out of the pot and is collected in the container below. A tap on the container allows water to be drawn out.

The filter is cleaned by gently scrubbing the surface, and it is recommended that the filter be replaced every 1–2 years, as fine cracks not visible to the naked eye may have developed.

Figure 10.7  Ceramic pot method of water filtration.

10.2.3  Disinfection

Disinfection is the final stage of water treatment in the home. All water treated using one or more of the previous steps will need to be disinfected to ensure that all pathogens are killed. The three common methods of disinfection are described below.

Boiling

Boiling drinking water is a simple way of killing pathogens and is suitable for use at household level. Boiling destroys pathogens such as bacteria and viruses, and any parasite ova (eggs) present in water. The water should be heated until large bubbles come continuously to the surface of the water (referred to as a ‘rolling boil’), for at least 5 minutes. This has been shown to inactivate cholera and Shigella organisms (Luff and Clarke, 2006). If the location of the site is at a high elevation (as in Addis Ababa) the water should be boiled for longer. Boiling will make the water taste flat but this can be remedied by shaking the water in a clean bottle, or by adding a pinch of salt to one litre of water. If the water is turbid with particles, it should be filtered before boiling. Water should be boiled, cooled and stored, all in the one container and consumed within 24 hours to prevent re-contamination.

Solar disinfection (SODIS)

Solar disinfection, known as SODIS, is a water treatment method that uses ultraviolet (UV) radiation and high temperature from the sun to destroy micro-organisms in water. The technique requires only some clear plastic bottles (without labels) and sunlight (Figure 10.8).

Figure 10.8  Plastic bottles full of water being laid out in the sun for disinfection.

The steps to take for SODIS are shown in Figure 10.9. In Step 5, the bottles are placed on a corrugated iron sheet (often used as roofing material) which is painted black so that it retains heat from the sun, speeding up the rate of heating of the water.

Figure 10.9  The procedure for solar disinfection of water (SODIS).

Chemical disinfection using chlorine

Chlorine solution, also known as sodium hypochlorite or bleach, is the most affordable and widely available chemical for household water treatment. Typically the procedure is to add a capful of chlorine solution to water in a 20–25 litre storage container, then stir and wait for 30 minutes. As you learned in Study Session 5, this period of time is referred to as the contact time. After this, the water can be used.

Chlorination is effective if the water is not turbid. If the water is turbid, micro-organisms can shelter within the particles and escape the effect of the chlorine. Solids should therefore first be removed by sedimentation or filtration. It is important that some residual chlorine remains in the water at the time it is used, so that it stays safe to drink. A minimum concentration of 0.5 mg l^–1 is recommended; this will kill any organism that enters the water later.

10.3  Household water treatment using commercial products

One example you may be familiar with is Wuha Agar, a commercial product available in Ethiopia for household water treatment. It is a chlorine-based solution used for disinfection, as described above. There are several others.

10.3.1  Bishan Gari Water Purifier

The Bishan Gari Water Purifier (Figure 10.10) is a combined coagulant–flocculant–disinfectant powder mixture produced in Ethiopia for water treatment. Bishan Gari comes in a 2.5-g sachet, which is used to treat 20 litres of water. The sachet contains aluminium sulphate as coagulant and a flocculant for reducing turbidity, and calcium hypochlorite as a disinfectant to kill bacteria and viruses.

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Figure 10.10  A Bishan Gari sachet.

The directions for using Bishan Gari powder are as follows:

1. Put 20 litres of raw water into a clean bucket.
2. Open the Bishan Gari sachet and add the contents to the bucket.
3. Stir rapidly with a stick for 2 minutes (to disperse the chemicals) and then stir slowly for an additional 3–4 minutes (to help the solid particles come together to form larger particles or flocs).
4. Wait for at least 20 minutes for the flocs to settle and the micro-organism to die. The longer you wait, the clearer the treated water will be.
5. Strain the water through a thick cotton cloth into a safe water storage container, from which it can be consumed.
6. Dispose of the material that settles at the bottom of the bucket by burying it.

10.3.2  Aquatabs

Aquatabs is the brand name of a solid form of sodium dichloroisocyanurate (NaDCC), a disinfectant. The tablets (Figure 10.11), which have to be imported, are easier than bleach to store, handle and transport. One tablet contains 67 mg of NaDCC and can treat 20 litres of clear water. The tablet has to be dissolved in the water by vigorous mixing, and a contact time of 30 minutes is necessary. If the water is turbid, two tablets will be needed.

Figure 10.11  Aquatabs tablets for household water treatment.

10.3.3  P&G Purifier of water

P&G Purifier of Water is the brand name of a combined coagulant, flocculant and disinfectant product produced by Procter & Gamble (Figure 10.12), which is imported into Ethiopia. The coagulant/flocculant is ferrous sulphate and the disinfectant is calcium hypochlorite. It can be used to treat raw source waters with a wide range of turbidity and pathogen load. This water treatment chemical allows flocculation to take place and helps to remove Giardia and Cryptosporidium cysts that are resistant to chlorine disinfection. (A cyst is a dormant stage in the life cycle of some protozoa and bacteria that is resistant to adverse environmental conditions and therefore difficult to destroy.) P&G Purifier of Water comes in sachets and one sachet is needed to treat 10 litres of water.

Figure 10.12  P&G Purifier of Water.

The procedure for using P&G Purifier of Water is illustrated in Figure 10.13.

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Figure 10.13  How to use P&G Purifier of Water.

10.4  Safe storage and handling of water in the home

The most desirable specification for a water storage vessel for households is that it:

• has a capacity of between 10 and 25 litres, is rectangular or cylindrical with a flat base and has one or more handles, for portability, stability and ease of storage
• is made oflightweight, oxidation-resistant plastic (so that it does not deteriorate with time), such as high-density polyethylene or polypropylene, for durability and shock resistance
• is opaque to prevent the growth of algae
• is fitted with a screw-cap opening that is wide enough to facilitate cleaning but small enough to discourage or prevent the introduction of hands or dipping utensils
• is fitted with a durable tap for dispensing water so that human contact with the stored water is impossible (Figure 10.14).

Figure 10.14  Containers for poor handling (left) and safe handling (right) of water.

Having collected, transported, treated and stored the water, households have to handle the water carefully so that it does not become contaminated. It is essential that hands are not put into the treated water. The best option is to use a tap. If the container does not have a tap, and the container has a narrow neck, the water can be poured out carefully. If the container has a wide neck, a long-handled ladle (Figure 10.15) should be used to take the water out of the container. This is preferable to using a mug or jug, because hands can inadvertently contaminate the water.

Figure 10.15  A long-handled ladle for taking water from a container.

Summary of Study Session 10

In Study Session 10 you have learned that:

1. Households may have to collect their own water if there is no water distribution system to take water to individual houses. They may also have to do this if there is a water emergency and water is distributed by tankers.
2. A container used to collect the water must be clean and must not have previously held any toxic compounds. It should have a narrow mouth, a lid, and handles for portability. An easy option is to use the Hippo Water Roller.
3. Household water treatment is needed if the safety of the water for human consumption is in any doubt.
4. Removal of suspended particles is the first step in household water treatment. This can be done by sedimentation, for example by using the three-pot method.
5. The crushed seeds of the Moringa fruit can be used as a natural coagulant, to aid sedimentation of solids.
6. Filtration (for example, by using cloth, a household sand filter, or a ceramic filter) is also a way to remove suspended particles.
7. Disinfection (for example, by boiling or using solar energy) eliminates pathogenic (disease-causing) micro-organisms from the water.
8. Water treatment chemicals such as Wuha Agar, Bishan Gari, Aquatabs and P&G Purifier of Water can also be used for household water treatment.
9. The ideal household storage container for treated water is made of lightweight, oxidation-resistant, opaque plastic, with a screw-cap opening for ease of cleaning, handles for portability and a tap to eliminate human contact with the water inside the container. When handling treated water, a tap or a long-handled ladle should be used.

Self-Assessment Questions for Study Session 10

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.