Study on Sludge Return Technology with Powdered Activated Carbon and Polyaluminum Chloride

Dongjiang micro-polluted raw water was treated by the combined process of sludge return with powdered activated carbon(PAC) and polyaluminum chloride(PACl) and GAC-sand filtration.The removal efficiency of turbidity,UV254 and ammonia nitrogen was investigated,and the removal of these pollutants under different return ratios was compared.The results show that when the mixed sludge with PAC and PACl is returned,the removal rates of ammonia nitrogen and UV254 after sedimentation are up to 57.7% and 65.5% respectively,being 56.6% and 20% more than the conventional process.For turbidity removal,the turbidity of sedimentation effluent is above 3 NTU when the return ratio is more than 10%.For ammonia nitrogen removal,the removal rate of ammonia nitrogen after sedimentation is about 50% when the return ratio is between 7% and 10%.For UV254 removal,the removal rate of UV254 after sedimentation is about 60% when the return ratio is between 4% and 10%.