Occurrence of Waterborne Pathogens in Lake Zwai and Drinking Water System of Batu (Zwai) Town, Ethiopia: In Relation to Indicator Bacteria and Physicochemical Parameters
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Date
2014-06
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Addis Ababa Universty
Abstract
Surface and drinking waters are routinely analyzed for physicochemical parameters and indicator
bacteria. However, the presence/absence of indicator bacteria may not necessarily be equally
indicative of the presence of pathogens. 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 Zwai, Meki and Qatar Rivers and drinking
water system of Batu (Zwai) Town. Seventy eight water and sediment samples were collected
from April through November 2013 and analyzed for the physicochemical parameters (pH,
temperature, electrical conductivity, dissolved oxygen, nitrate, nitrite, ammonia and phosphate),
indicator bacteria (Escherichia coli, Enterococci, Clostridium perfringens, total and fecal
coliforms) and pathogenic bacteria (Salmonella, Shigella, Vibrio cholera, Vibrio spp., E. coli
O157:H7) using standard methods. All except temperature, the physicochemical parameters in
reservoir and tap water samples met the maximum permissible value for drinking water. The
highest proportion of pathogenic bacteria was detected from 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 in a few sources with low percentage (3.3%).
With respect to the microbial load of the tested organisms, the highest count of 4.20 log
CFU/100 g of indicator bacteria was detected from river sediment and the lowest count of 0.42
log CFU/100 ml recorded 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. Shigella was better significantly correlated with both indicator
and pathogenic bacteria. Since surface and drinking water distribution system were contaminated
with bacteria, the need to develop more effective monitoring and efficient treatment mechanism
of the drinking water source with respect to microbial contamination is necessary.
Keywords/phrases
Enterococci, fecal coliforms, Salmonella, Shigella, waterborne diseases
Description
Keywords
Enterococci, Fecal coliforms, Salmonella, Shigella, Waterborne diseases