Domestic Wastewater Treatment Using M-CASS Switched Technics

With the development of industry and our city,the absence of water resource has become a serious problem we have to face. The amount of water that we have used and discharged is increasing everyday.Cyclic Activated Sludge System is a kind of improvement on SBR. It has the merits of simple process,small area,easy control,flexible operation,easy to adapt the water quantitative and water quality,removal of nitrogen and phosphorus simultaneous etc.By replacing a secondary clarifier by a membrane separation unit in an activated sludge process,Membrane Bioreactor(MBR) technologies have emerged as one of the innovative and promising solutions for the complete retention of sludge.The experiment which is in the foundation of formerly studied combines CASS and MBR together. It can exert the advantage of each other by the greatest extent according to different effluent standard and make the effluent quality assurable. When the effluent has no request of reclamation and reuse,it runs as CASS,the effluent reach the demand quality of integrated wastewater discharge standard(GB18918-2002,grade 1)and some low water quality standard for miscellaneous water consumption. When the effluent has the request of reclamation and reuse,it runs as MBR,the effluent reach the demand quality of wastewater reclamation and reuse(GB/T18920-2002,GB/T18921-2002).This experiment is divided into three stages to carry on: the first stage runs according to the CASS,the average removal percent for turbidity,COD,NH3-N and TN is 97.47%,87.57%,98.78%,86.68% respectively;the second stage runs according to the MBR,the average removal percent for turbidity,COD,NH3-N and TN is 98.08%,92.76%,96.97%,69.95% respectively;the third stage runs according to the CASS again,the average removal percent for turbidity,COD,NH3-N and TN is 96.87%,97.67%,98.8%,88.64% respectively.It has been found that the CASS and MBR process can remain satisfactory effluent and have a good adaptability to several shock loading during the running period.This experiment realizes the switch of the CASS and MBR freely and the effluent reach the demand of integrated wastewater discharge standard (GB18918- 2002,grade 1) and the standard of wastewater reclamation and reuse (GB/T18920-2002 , GB/T18921-2002), it offers another feasible way for the engineering practice.It also has some shortage such as the relative worse sedimentation performance of activated sludge,the oxygen utilization efficiency of perforated tube is comparatively lower and membrane fouling need further research.