Bacteriological quality of drinking water in Punjab: evaluation of H2S strip test.

OBJECTIVE To assess bacteriological quality of drinking water in Punjab and to evaluate usefulness of H2S strip test in comparison with multiple tube test. METHOD Samples of water were tested using H2S strips and multiple tube test. RESULTS Maximum bacterial contamination was observed in water from domestic pumps (95.83%). Followed by tap water in rural areas of Punjab (91.30%) and tap water in Lahore (42.85%). Bacterial contamination was significantly higher (p < 0.001) in rural areas as compared to urban areas. Comparison of results of testing water samples by H2S strip test and multiple tube test revealed that H2S strip is 87.24% sensitive and 100% specific for detection of bacterial contamination with a positive predictive value of 100%. It was also observed that 100% water samples negative for total coliforms were also negative by H2S strip method. Moreover, with increase in number of total coliforms in the water samples, positivity by H2S strip method also increased (samples with more than 10 total coliforms/100 ml were 100% positive by H2S strip method). Therefore, H2S strip test can be used as alternative to multiple tube test for detection of bacterial contamination of water supplies. CONCLUSION It is concluded that bacterial contamination of water is a significant problem in Punjab. It can be improved by regular monitoring of water supplies. For this purpose use of H2S strip test is advocated at house hold level.