Optimized Operation Control On M-CASS Process For Domestic Wastewater Treatment

Recently, with the development of auto-control and membrane production technology, Cyclic Activated Sludge System(CASS) and Membrane Bioreactor(MBR) are given more and more attention because of their particular advantages. The experiment which is in the foundation of formerly studied combines CASS and MBR together. It can exert the advantages of each other in the greatest extent according to different effluent standard and make the effluent quality assurable.In this paper, the artificial prepared domestic wastewater was treated by the combination process of CASS and MBR.Experiment was carried out to investigate the operation efficiency, optimize the operation condition. It mostly investigated the system's removal of COD,NH₃-N and TN from three aspects of aeration mode,Hydraulic Retention Time(HRT) and reaction period.The results as follows: (1)The effect of aeration mode on the COD,NH₃-N of effluent from CASS and MBR was less,the average removal efficiency exceeded 90% all the time.But it had great effect on the removal efficiency of TN, especially when the aeration mode was intermittent aeration, the TN of effluent from CASS and MBR was the best, the average removal efficiency reached 83.3% and 89.7%.The effluent of MBR was better than CASS, and the average effluent concentration was only 3.55mg/L. (2)The removal efficiency of COD,NH₃-N and TN will rise with Hydraulic Retention Time is lengthened, but the extent of COD is little, NH₃-N and TN is just opposite.When Hydraulic Retention Time rose from 8.3h to 11h,the removal efficiency of NH₃-N and TN increased by about 30%⁴0%.But it will require high investment and operation cost with Hydraulic Retention Time is lengthened. (3) When Hydraulic Retention Time was 11h, the effect of reaction period on the COD was little.The average removal especially of COD was 91.5% and 90.5% in reaction period of 3h and 4h.Therefore, the removal of COD,NH₃-N and TN showed better effect under the conditions of 11h's HRT and intermittent aeration by the combination process of CASS and MBR.It achieved the optimized operation.Furthermore, at this aspects of sludge loading,dissolved oxygen,temperature et al,the experiment analyzed the removal effect of nitrogen and membrane fouling in the combination process of CASS and MBR, and discussed the effect of each other.That can cause the system to achieve the best optimized operation.