The effect of alkaline-stabilized-sludge application on the microbiological quality of soil and leachate

Abstract

The influences of fly ash and fly-ash-quicklime-treated-sludge mixtures (with fly-ash doses of 40%, 80%, and 120% on dry-weight basis) on the microbial numbers in soil and leachate were investigated by using 60 cm soil columns. Heterotrophic bacteria and total coliform numbers were determined in soil and leachate samples following an artificial rainfall event. The results indicated that land application of untreated sludge and fly-ash-sludge mixtures appear to introduce large numbers of bacteria to leachates and soil. Although the numbers in leachates and soils were found to decrease with increasing ash ratios, they were still all significantly above the control levels. Application of alkaline-stabilized and pasteurized sludge did not increase bacterial numbers significantly in soil and leachate. Distribution of heterotrophic bacteria through soil profile clearly showed no increase in soils amended with alkaline-stabilized and pasteurized sludges. Additionally, no significant inhibitory effect of lignite fly ash on soil microbial population was observed.