A microbiological investigation of the activated sludge of a sewage treatment plant

Abstract

The types of microfauna inhabiting the activated sludge of the Sant'Antnin sewage treatment plant were identified and their effects on effluent quality and efficiency of plant operation were investigated. Five groups of microfauna were identified and these included ciliates, rotifers and rhizopods. The dominant species were the crawling ciliates and sessile ciliates. Five physico-chemical parameters measuring effluent were investigated and these were turbidity, pH, chemical oxygen demand, ammoniacal nitrogen, electrical conductivity and permanganate value. Microfauna population densities were correlated with the results obtained to investigate if any relationship exists between the two. Several statistically significant correlations were obtained. For example flagellates correlated negatively with permanganate value. Using regression analysis four regression equations were worked out to predict effluent quality (as measured by four physico-chemical parameters) from the population density of major microfauna present. The use of microfauna as bio-indicators of plant efficiency is viable and useful, especially in the absence of qualified staff and appropriate instrumentation.