Suitability of the H2S method for testing untreated and chlorinated water supplies

Rainwater, borewater and catchment water are used for domestic water supply purposes with or without treatment in remote areas around the world. These places seldom have any facilities for routine testing of their drinking wa ter. A simple on-site testing method is highly required in such areas. The H2S method has been tested for treated drinking water and was found to have a good correlation with the standard methods. The present study was aimed at assessing the suitability of the H2S method for testing different source s of drinking water. Since these types of water may contain H2S producing b acteria not of faecal origin the occurrence of false results in this method cannot be overruled. Therefore it was worthwhile to study whether the posi tive results are true positive results and what percentage of false positiv e and false negative results could be expected while using this test for ro utine analysis of water samples. Results were compared with the results usi ng standard procedures for testing total coliforms, Escherichia coli and Sa lmonella spp. The present experiment analysed 121 rainwater samples, 17 bor ewater samples, 41. catchment water samples and 74 remote Aboriginal commun ity water samples. Rainwater, borewater and catchment water samples gave tr ue results of 78.5%, 82.3% and 80.5% respectively while the treated and unt reated community samples gave true results of 93.7 and 84.6% respectively. It was concluded that in the developing countries where the acceptable leve l of total coliform is < 10 MPN, the H2S method would be a good test to ide ntify microbial contamination. In other regions, the H2S method could be us ed as a screening test for drinking water supplies.