How safe is your water?July 13, 2010
How safe is your water?
|It is easy to train people in handling the testing equipment|
Time to act: Simple tests to check the presence of harmful bacteria in water are needed
Water-borne disease is one of the primary causes of morbidity and mortality, especially among children. In simple language, diarrhoea, dysentery, cholera and typhoid are all diseases caused by bacteria in water. Simple tests to determine the safety of water from a micro-biological point of view are crucial to take preventive measures.
One of the simplest is the H2S (hydrogen sulphide) strip test which is a basic indicator test of the presence of e-coli bacteria in water. The test also has the capacity to detect enteric and harmful bacteria such as salmonella and citrobacter. The presence of e-coli, an indicator bacteria, can be seen as showing the presence of cholera and typhoid.
How it works
The H2S strip test was developed by K.S. Manja and team. It is a simple pre-sterilised coated paper in a small, sealed bottle. The sealed cap of the bottle is opened with clean hands. The sample of water to be tested is filled to an appropriately marked line on the bottle. The cap is then put back and closed. The water sample is usually observed for 24 to 48 hours when kept in room temperature of between 25 to 37 degrees C.
If the sample of water and the coated paper turns black it indicates the presence of coliform bacteria or faecal contamination of water, making further treatment of the water necessary before consumption. Even if a certain amount of chlorine is present in water it can also be instantly removed by the medium present in the bottle.
All types of drinking water — whether from pipelines, wells, borewells, rainwater, ponds, rivers springs and even bottled water — can be tested, sometimes with surprising results.
The H2S test is a basic field level indicator test. If necessary, detailed investigations can begin after the establishment of the presence of unwanted bacteria. The test is low cost and easy to conduct unlike laboratory-based tests which tend to be complex and costly. The system is rugged and has a high shelf life and therefore can be used for years if kept safely.
It is easy to train people in the use of the method. Even school children can do the test and learn about water quality as part of developing general water literacy. In a recent endeavour it was used to check the quality of rooftop rainwater in the tanks constructed for the purpose of providing drinking water to school children all across Karnataka.
In another instance, drinking water stored in secondary storages/kitchen containers was checked to see the contamination that could occur when water is stored or handled in an unhygienic manner. In both cases suitable measures could be suggested to ensure that water was made potable before being consumed.
The H2S strip test is a one-time test in the sense the bottle can be used for one test only. The bottles are not easily available all over India. It may at times give a false positive result i.e. identifying the presence of harmful bacteria when perhaps there are none. It also gives a yes/no result without giving the number or amount of such bacteria in a given volume. It does not identify chemical or physical contaminants in water but only microbiological contaminants. The bottle itself is breakable, as it is made of glass. It also requires to be safely disposed of once the test is over.
Much more needs to be done to raise general awareness of this simple and easy method available and developed in India. As there are increasing reports of bacterial contamination of groundwater and pipeline water the H2S strip test can give consumers and providers a quick check on the prevention methods necessary to take control of this contamination.
Bottles should become cheaper and available in all villages and towns. In addition, people should be armed with affordable techniques to take care of the contamination either through chlorination or sterilisation of the drinking water.
No-cost or low-cost methods such as SODIS ( Solar disinfection) — which use PET bottles or glass bottles to sterilise water by keeping it in the sun for five hours or more — need to be propagated.
The H2S bottles are usually available at shops selling chemicals and allied equipment.
The local UNICEF office or the Total Sanitation Campaign office may also be of help.
In general, water wisdom lies in understanding and using simple tests to check the presence of harmful bacteria in water and taking action to avoid the harm they can cause.