Abstract:To investigate the effects of direct continuous recycling of waste streams generated from drinking water treatment plant on effluent water quality, polite-scale experimental models was constructed and the changing rule of water quality was studied for 14 days both in summer and winter in the northeast China. The optimal recycle ratios of sedimentation sludge and filter backwash water were found to be 4% and 6% in summer, respectively, and was 2% and 6% in winter. Under the optimal recycle ratios, the continuous direct recycling waste streams could reduced the coagulant dosage by 33.3% in summer and 18.2% in winter compared to control trials based on reaching the sedimentation effluent standard (< 2.5 NTU). Water quality parameters such as turbidity, color, UV254, TOC in settled and filtrated water were monitored periodically. Results indicated that contaminants could be removed more effectively in the recycling process compared to the control trials. Moreover, relative higher temperature could improve removal efficiencies. Over the entire operation period, there was no significant contaminants accumulation. Recycling waste steams was a feasible approach for enhancing coagulation process.