Usefulness of the hydrogen sulfide test for assessment of water quality in Bangladesh

Aim:  To evaluate the usefulness of the hydrogen sulfide (H2S) test for assessing water quality in Bangladesh. Methods and Results:  We tested 382 water samples from a variety of sources using locally produced H2S test kits and laboratory-based membrane filtration for the detection of Escherichia coli. Compared with membrane filtration, H2S tests, when incubated for 24 h, had both a sensitivity and positive predictive value (PPV) of <40% when analysis was restricted to water samples with E. coli levels below 100 colony forming units (CFU) per 100 ml. In contrast, for E. coli levels from 1000 to 9999 CFU per 100 ml, sensitivity was 94% and PPV 88%; specificity was 97% and negative predictive value was 99%. Conclusions:  The hydrogen sulfide test, when incubated at 24 h, is a promising alternative for assessing water quality where E. coli levels may be high. An improved understanding of the incremental impact of contamination level on health is needed to better determine its usefulness. Significance and Impact of the Study:  The hydrogen sulfide test is inexpensive, easy to use and portable. Its use may allow rapid assessment of water quality in situations where cost or logistics prevent use of other testing methods, such as in remote areas or during floods and other natural disasters.