Simple water treatment in the kitchen

Transcription

1 Simple water treatment in the kitchen Using tiny amounts of chlorine to purify water held in 20li plastic containers called chigubu s Peter Morgan

2 The current situation Currently very large numbers of people living in towns and cities in Zimbabwe are forced (due to lack of potable piped water) to find their water elsewhere. Very often this vital supply for survival comes from hand dug wells and water holes that are poorly protected and may well be contaminated by sewerage. Piped water does arrive intermittently, but there is widespread fear that it is also contaminated. The water borne sewage system is also nonfunctional in many areas, also due to a lack of water. This very serious situation can lead to outbreaks of serious disease such as cholera and typhoid. Restoring both the water supply, and the sewerage systems to their former states of functioning is urgent. But this will be a hugely difficult and costly exercise and cannot be envisaged in the short term. Hand pumps are also being fitted to boreholes to alleviate a part of the pressing problem in the cities. Whilst this may help to increase access to water supply to certain extent, the risk of drinking polluted water from contaminated ground water sources, such as unprotected wells and even boreholes remains imminent for countless people in the city and town populations. As in so many other situations people turn to their own resources to overcome these problems. One such recent development has been the increase in the number of shallow wells dug and the boom in water vending from these wells and existing boreholes. Solutions in the household There are several ways in which this risk can be reduced within the household itself. This brief manual suggests one method amongst several that might be brought to trial. The method involves, in this case, the use of chlorine to treat contaminated water. It is assumed that this solution may find a place in the towns and cities where people live close to hardware and other stores, where chlorine granules are sold mainly to treat swimming pools. The use of chlorine is largely used in emergency and development settings and its effectiveness has been proven time and again. Its simple administration is also attractive enough to try it at a household level. If applied properly it is an effective means to destroy disease-causing organisms in water such as typhoid and cholera, which is a compulsory step in delivering safe drinking water and protecting public health. 2

3 The mini dispenser for measuring small amounts of chlorine granules to water containers. The technique depends on the economical use of granular chlorine to treat small volumes of water. A novel miniature dispenser has been designed to convey very small amounts of the chlorine granules in to the litre plastic containers, known as chigubu s which are now commonly used to carry and contain water in Zimbabwe. The chlorine is available at hardware stores and supermarkets (at around $11.00 per 1.5kg) and chigubu s cost less than $5. The mini dispenser for chlorine granule transfer can, with care, be made from a ball point pen top. The contents of the larger 1.5kg chlorine container can be subdivided into smaller plastic containers with screw top to contain 100gms of granular chlorine. Making the parts of the mini chlorine dispenser At the present time this is not made commercially but can be made with care from the cap of a cheap ballpoint pen available at stores. The clip is sawn off and a short section (6.5mm) also cut off as shown in the photos. The parts are cut and then welded together on a gas stove flame. 3

4 Measurements of chlorine and containers Each mini dispenser contains 0.125gms of granular chlorine, which according to preliminary bacteriological tests, is able to purify 20 litres of contaminated water (see later). 10 grams of chlorine granules was measured out on a delicate scale. This volume was contained in 80 dispenser-fulls of the granules. This means that each 1 gram of granules is enough to fill 8 mini dispenser - fulls (MDFs) of granules (that will treat 8 X 20 litres of water = 160li water). 100gms of granules is enough to treat 800 MDFs, which will treat litres of water. 500gms of granules is enough to great 4000MDFs, which is enough to treat litres of water. Let us consider two scenarios 1. A family of 5 2. An extended family of 10 If each person drinks 2 litres of treated water a day, a family of 5 will consume about 10 litres of treated water a day. Thus 20 li will last 2 days and uses one MDF of granules every 2 days. Thus 100gms will last for at least a year (theoretically 1600 days). 4

5 If each person drinks 2 litres of treated water a day, an extended family of 10 will consume 20 litres of treated water a day, which will use one MDF of granules per day. Thus 100gms will last for at least a year (theoretically 800 days). Since the granular chlorine loses its potency over the course of a year, it would be wiser for the product to be sold or used in 100gm screw cap containers (with dispenser). Even if the dose was doubled per 20 litre container, 100gms granular chlorine could still provide protection for an extended family of 10 for a year and costs less than 1 USD. With the 100gm container and dispenser, perhaps 2 USD! In this first trial 100gms of the 1.5kg of pool chlorine granules (left photo) was moved into smaller containers which could be sealed. This smaller amount in a smaller container could be marketed together with instructions with the dispenser inside. 5

6 Using the mini dispenser Water is taken from the water source which is suspected as being contaminated. This will usually be a poorly protected well, waterhole or poorly sited borehole. Water is transfered from the well bucket into the 20li plastic container The mini dispenser is dipped into the container of chlorine granules The dispenser filled with chlorine granules is then tipped into the20 litre container. The cap is screwed back and the container shaken. It is left for at least one hour for the chlorine to kill off the bacteria. The container should be stored in the family kitchen. If the water is a bit cloudy 2 dispenser fulls should be used per 20li container. 6

7 Preliminary bacteriological tests In order to test the effectiveness of this simple treatment method, a small quantity of raw excreta was diluted with water and added to treated and untreated 20 litre containers. 1gm of raw excreta was added to a sterilised 2 litre bottle filled with borehole water (tested zero for coliforms and E. coli). Two new 20 litre chigubu s were filled with borehole water and one cup full (200mls) of the excreta laced water were added to each container. One mini dispenser of granular chlorine (0.125gms) was added to one of the containers and shaken. A 500ml sample from each chikubu was taken in a sterilised 500ml bottle after an hour and taken to the water testing laboratory where a simple 3M petrifilm test was undertaken for total coliforms and E. coli. Results (expressed as coliform forming units Cfu s) Coliforms E. coli Borehole water (s1) nil nil Borehole water (s2) nil nil Chigubu water no treatment (s1) Chigubu water no treatment (s2) Chigubu water treated (s1) nil nil Chigubu water treated (s2) nil nil Note: samples above 3 Cfu s per ml are considered unfit for drinking. These results, although very preliminary, suggest that this simple method may be of value in protecting families from enteric disease derived from contaminated water sources. The cost is low, but requires care and discipline to put into practice. 7

8 Conclusions First and formost, this method requires to be performed carefully with further trials in the field. Various sources of water should be analysed before and after treatment. Turbid water requires higher levels of chlorine treatment. If future trials prove successful, the methods and benefits need to be taught, particularly in health campaigns and at schools. The water does have a slight taste of chlorine. This must come as part of the deal if chlorination is used as the method of treating water. A carrier for 2 x 20 litre containers 20 litres of water is heavy to carry. Carriers for these water containers have been designed and built before, using the wheel barrow principle. These carriers should be promoted further to carry two x 20 litre containers (for balance) using a simple wheel (caste iron) and steel frame with handles for low cost. These simple devices offer an effective method of carrying the 20 litre containers from source to household. Priorities Whilst sources of water remain suspect, either delivered from private, communal or municipal supplies, the family itself is placed in a position where it must protect itself from the effects of pollution. Water purification tablets, known as Aquatabs are made commercially and are imported into Zimbabwe and available at chemists shops and perform the same function. Like the present method they are successful if used carefully and at all times. The use of good functional sanitation, personal hygiene and hand washing and the safe preparation and purchase of food are also important in preventing the transmission of disease. 8