Comparison Of Characteristics Between MBR And CAS And A Preliminary Study Of The MBR-CAS

MBR(Membrane Bioreactor) is synthesized by the function of highly effective solid fluid separation from the membrane module and the function of the microorganism biodegradation from the biological reactor. And its membrane module substitutes secondary sedimentation tank and the post treatment system in CAS(Conventional Activated Sludge process). Compared with other biological treatment processes, MBR has much obvious superiority. However, it also exists expensive membrane construction and membrane pollution and so on. CAS is used in bio-chemical process firstly and it has been applied widely since last 90's. Because of some insufficient itself, it developed and innovated unceasingly in the practice and made several transformed processes, such as oxidation ditch, A-B process, SBR process, A-O process and so on.The study focused on the research of comparation between MBR and CAS under the same operation condition, its goal was to understand MBR process theoretically and to provide scientific base for the MBR development and the research of the membrane pollution. Additionally, the study discussed the feasibility research of MBR-CAS process and analyzed the rule of system and characteristics of techniques. And seeked for an economical and effective method for the wastewater reuse and provided theory knowledge for further engineering practice.Experiment results showed that during the sludge acclimation period MBR's average removal rate of CODcr was 82%, and NH3-N was 52%, their values were bigger than CAS respectively. SMP was partly accumulated in these two reactors, and had different affect to the effluent quality. The characteristic of sludge changed a lot, mostly about biological appearance, sludge concentration, sludge sedimentation performance, sludge grain diameter and so on.Compared the ability of dephosphorization and eliminating organic material with others, MBR was better. The average removal of CODcr was 92.3%, and TP was 61.9%. SMP was accumulated in MBR, also changed a lot. From membrane transferring resistance, membrane pollution was bad and needed more care. Inspecting from the sludge characteristic, difference was big. CAS sludge floc was hard, and it's arrangement was regular, the protozoon and the metazoa's type was various and active. MBR sludge microscopic examination results showed that sludge floc was loose, the edge of zoogloea was muddy, the protozoon and the metazoan also performed languishment and their types were thin. Two reactors sludge concentration gradually grew correspondingly along with the running time. Sludge concentration in MBR was about 16000 mg/L and grew quicker in the latter term. In these two systems, process had no sludge expand and the sludge kept good activity.In the MBR-CAS process, the membrane effluent quality is better than sedimentation tank. The average of effluent CODcr was 23.2mg/L. Sedimentation tank kept natural effluent, and had no sludge expand. Sludge concentration and sludge sedimentation performed relatively steady. The features of this process were that we optimized the ratio of the effluent and changed operation conditions appropriately according to the water quality criteria for non-potable household to become one of the best economy and feasible treatment ways.