Assessing the occurrence of waterborne pathogens in Lake Ziway and drinking water system of Batu (Ziway) Town, Ethiopia
Abstract
Abstract
Background: Surface and drinking water is routinely analyzed for physicochemical parameters and indicator bacteria. However, the presence of indicator bacteria may not necessarily be equally indicative of the presence of pathogens.
Objective: In this study, the physicochemical and bacterial indicator of water quality parameters were compared with the occurrences of waterborne bacterial pathogens from water and sediment samples of Lake Ziway, Meki and Qatar Rivers and drinking water system of Batu (Ziway) Town.
Methods: Seventy eight water and sediment samples were collected from April through November 2013 and analyzed for physicochemical parameters, indicator bacteria and pathogenic bacteria (Salmonella, Shigella, Vibrio cholera, Vibrio spp., E. coli O157:H7) using standard methods.
Results: The study showed that 97 to 100% of samples of sediment and surface water, 38% of the reservoir and 63% of tap water samples were contaminated with indicator bacteria. The highest proportion of pathogenic bacteria was detected from the lake sediment (52.7%), followed by Meki and Qatar Rivers sediment (50.0%), lake water (40.4%), Qatar (33.3%) and Meki (26.7%) River water, tap water (4.8%) and none from reservoir water samples. Vibrio cholera, Vibrio spp, Salmonella and Shigella were commonly detected from surface water and sediment samples (48.9%), whereas, E. coli O157:H7 was limited to a few sources (3.3%). With respect to the microbial loads, the highest count of 4.20 log CFU/100 g of indicator bacteria was detected from river sediments and the lowest count of 0.42 log CFU/100 ml from reservoir water. Differences in concentration of indicator bacteria were statistically significant (P<0.0001) between sample sources. Spearman rank correlations show some indicators and physicochemical parameters were significantly correlated with the presence of bacterial pathogens.
Conclusion: The present study showed that surface and sediment samples have high load of indicator bacteria and harbored different pathogenic bacteria. The detection of indicator bacteria in 38% of the reservoir and 63% of the tap water samples was indicative of the inadequacy of the treatment and post contamination of water in the distribution system. Fecal coliforms were significantly correlated with Salmonella and Shigella; E. coli with Shigella, and Enterococci with Vibrio spp. of surface and sediment samples. [Ethiop. J. Health Dev. 2014;28(2):116-125]