Evaluation of L-Cystine-amended H2S test for the detection of faecal pollution in potable water: comparison with standard multiple tube fermentation method

L-Cystine-amended H₂S strip test was compared with conventional multiple tube fermentation tests for detecting faecal pollution in 200 drinking water samples drawn from different water sources. Of these, 134 samples were positive for total coliforms (TC), whereas the cystine-amended H₂S test was positive with 116 samples. Faecal coliforms were present in 99 samples. Seventy-seven samples were also tested with presence–absence (P–A) strip test. By taking only the colour change (acid production) as positive indication for the presence of coliforms, 12 (47%) out of 26 water samples were graded as polluted in the absence of detectable coliforms. This indicated the critical importance of observing P–A bottle for gas production along with the colour. This aspect is important when commercially available P–A bottles are used in rural areas by unskilled personnel. Among different unpiped water sources tested, 94% samples drawn from India Mark II hand-pumps had TC counts within WHO guidelines. This revised version was published online in July 2006 with corrections to the Cover Date.