EFFECT OF AN ARTIFICIAL SOIL MIX FROM COAL FLY-ASH AND SEWAGE-SLUDGE ON SOIL MICROBIAL ACTIVITY

An artificial soil mix was prepared from coal fly ash and sewage sludg e and an experiment was performed to evaluate their effects on soil mi crobial respiration. Coal fly ash at 0%, 5%, 10%, 35% and 50% w/w was mixed with dewatered sewage sludge and then each ash-sludge mixture wa s incubated with a sandy soil at 1:1 v/v at 28 degrees C for 42 days. All treatments showed the same carbon dioxide production pattern with a peak production at day 7 to day 14. Addition of ash-sludge mixtures to soil resulted in an increase in carbon dioxide production but the p roduction rate decreased according to the ash amendment rate. The high pH of coal fly ash and the dilution effect of the sludge were the maj or reasons for the decrease. However, the ecological dose 50% values s harply increased from 26% at day 3 to 39% ash at day 14. This indicate s the rapid acclimatization of microorganisms to the fly ash-sludge mi xtures. Therefore, a brief stabilization period may be required for th e establishment of soil microbial populations in soil amended with ash -sludge mixtures.