Excess Sludge Minimization in Conventional Activated Sludge Pilot Plant by Three Chemical Matters

Document Type: Original Research Paper


1 Department of Environmental Engineering, Graduate School of the Environment and Energy, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 Department of Environmental Engineering, Graduate Faculty of the Environment, University of Tehran, Tehran, Iran


The excess sludge treatment and sludge disposal are major factors to the over-all economy of
wastewater treatment plants (WWTP). The ideal solution to the problem of sludge disposal is to combine sludge minimization with contamination removal at the source. In this study, the effect of ozonation, chlorination and 3,3,4,5–tetrachlorosalicylanilide (TCS) to treat part of the return activated sludge flow with the intention of reducing the overall plant yield in a conventional activated sludge pilot, were investigated in a side-stream pilot reactor. It was found that in the case of ozonation 8% g O3/g MLSS, and in the case of chlorination 2% g Cl2/g MLSS produce the best results. In the utilization of TCS method, the excess sludge production was reduced by 80% per day at a TCS dose of 1% g TCS/g MLSS. In all the above experiments a reduction in the
volume of the excess sludge was achieved, while the efficiency of removal chemical oxygen demand (COD) from the reactor without the use of those methods was not significantly different.