Diurnal and Seasonal Variations of Pathogenic Bacteria in Dandora Sewage Treatment Plant Wastewater, Nairobi, Kenya

Abstract

Diurnal and seasonal variation of pathogenic bacteria diversity and loads at Dandora Sewage Treatment Plant (DSTP), and compliance of effluent with local and international statutory requirements was assessed. Standard bacteriological techniques were used to describe bacteria content from wastewater samples collected from influent and effluent sources. Diurnal variation of bacterial loads occurred only in the effluent (F ꞊ 22.788, p ꞊ 0.000) with lower counts in the afternoon. Seasonal variation was observed in both influent (F ꞊ 14.795, p ꞊ 0.001) and the effluent (F ꞊ 23.574, p = 0.000), with more pollution during the dry season. The effluent microbiological quality, irrespective of diurnal and seasonal changes, did not adhere to local and international statutory requirements for discharge into natural environment. The effluents were polluted with pathogens including; Escherichia coli, Enterococcus faecalis, Staphylococcus typhi, Pseudomonas aeruginosa, and Klebsiella aerogenes. The health risk posed to downstream users of DSTP effluent occurs notwithstanding the time of the day or season. The findings in this study suggest need for appropriate measures to monitor and control the microbiological quality of DSTP effluent