摘要：Conventional activated sludge as a biological treatment process is applied for treatment of a large number of sewage. In this paper, the effects of temperature and pH on sludge reduction in activated sludge process have been studied. The purpose of this study was evaluation of the effect of thermal-alkaline treatment in minimization of excess biological sludge production in wastewater treatment, using activated sludge. In this study, an activated sludge pilot with an aeration tank effective volume of 8 ml and a deposit tank of 3 ml were used. Activated returned sludge was changed in the temperature range 30 to 70°C, pH=11-9 and at retention times of 30, 60 and 90 minutes. After establishing a stable condition in the system, sampling and testing parameters such as COD, MLVSS, SVI, BOD5 and determination of the yield coefficient were done. Also, at 60°C, which had the lowest yield coefficient, pH was changed in the alkaline range and effects of the sewage sludge reduction were investigated. The results showed that when the temperature increases from 23 to 60°C, yield coefficient increases initially but then began to decrease to reach 0.33 per 60°C and the COD level reaches from 89mg/l to 195mg/l. The finding of this study showed that the temperature 60°C, pH=9 and retention time of 60 minutes had the best performance, because in addition to the sludge reduction rate of 44%, COD removal rate of the effluent was 80%.
