Treatment of municipal wastewater with the sequence batch reactor under uncoupling metabolic conditions

The activated sludge process generates large quantities of excess sludge as by-product, which is one of the most serious challenges in biological wastewater treatment. In this study, the feasibility of 2,4,6-trichlorophenol (TCP) as metabolic uncoupler to reduce sludge generation in the Sequence Batch Reactor (SBR) for the long-term treatment of municipal wastewater was evaluated. The results of 90 days continuous treatment showed that 2 mg/L TCP reduced sludge generation by about 47%, while COD removal efficiency and sludge ability to settle were only slightly decreased. The specific substrate removal rate of sludge in the reactor with TCP exceeded the removal rate of sludge in the control reactor, indicating that the catabolism and anabolism of sludge in the reactor with TCP was uncoupled. Microscopic and 16s DNA analyses showed that the microbial population of sludge varied when TCP was fed into the SBR. The occurrence of filaments and the disappearance of some protozoa in the sludge system might be reasons for the slight variation of sludge ability to settle under uncoupled metabolic conditions.