Efficiency evaluation of hydrogen sulfide-producing bacteria as an indicator in the assessment of microbial quality of water sources

 The object of this study was to assess the usefulness of the H 2 S test for detection of fecal pollution of water in comparison to fecal indicator bacteria (FIB). 

 A total of 70 raw water samples were collected from drinking water sources in Isfahan province of Iran, aseptically in sterile containers during May-October 2012.The modified H 2 S test medium of Manja et al. was used except that L-cysteine was added as an additional medium component. Total coliforms (TCs), fecal coliforms (FCs), and fecal streptococci (FS) were also estimated by multiple-tube fermentation method. Statistical analyses were carried out using SPSS 20 at the 95% confidence level (α = 0.05). 

 It was found that out of 70 water samples assessed, 48.3%, 30.0%, 34.6%, and 32.9% of the samples were positive for TCs, FCs, FS, and H 2 S, respectively. Analysis of data showed that 95.6%, 69.5%, and 76.9% of water samples, which were positive for H 2 S test were also positive for TCs, FCs, and FS, respectively. The H 2 S test was found to have the highest accuracy for the detection of FS, but it was not a suitable indicator for the prediction of FCs. 

 Our results showed that H 2 S test is not a suitable alternative approach for routine water quality monitoring. However, the H 2 S test could be used as an easy and economic test to assess the quality of drinking water in communities where manpower and sophisticated equipment are inadequate. More laboratory and field studies are required to assess the reliability of the method as an alternative method of traditional indicators.