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Classical bacterial indicators and organic matter contents were analyzed for sediment
samples and the suspended particles collected from the sewage waste of Islamabad
city. The suspended particles were most affected by proximity of point source and
sewage overflows, which were associated with significant increases in the
concentration of faecal coliforms, faecal streptococci and Clostridium perfringens
spores. In contrast, only faecal coliform counts significantly increased in sediments
with increasing distance from the point source. Sewage overflow again resulted in
increased concentrations of faecal coliforms, faecal streptococci and Clostridium
perfringens spores in suspended particulate matter. Faecal coliforms were identified
as the most useful indicator of faecal pollution as only this indicator correlated
significantly to the organic matter contents (r = 0.88, rs = 0.93) for sediment samples.
The amount of organic matter in suspended particulate matter was not significantly
different but a gradual increase in the organic matter with an average value of 2 to
3% was detected in the sediment samples with increasing distance from the point
source. Our findings indicate a high level of faecal pollution in Nullah Leh,
particularly coliforms, in amounts several magnitudes higher than the standards
permit. It is concluded that minimization of hazards lies only in the treatment of
sewage waste prior to its discharge in open environment.