膜-生物反应器和传统活性污泥工艺的比较

在运行条件一致的情况下把膜-生物反应器(MBR)和传统活性污泥工艺(CAS)进行了比较研究.试验结果表明,MBR具有比CAS更为稳定良好的出水水质,其平均出水COD浓度为55.5mg/L,低于CAS工艺(79.7mg/L).MBR系统中由于膜对大分子物质的截留作用,运行前120d出现溶解性微生物产物的积累,但随着微生物的驯化,这些积累的微生物产物最后得到降解.CAS中未发生微生物产物的积累.CAS出水、MBR上清液以及MBR出水中的物质组成差别很大.CAS出水和MBR上清液中分子量大于60000的高分子物质与小于3000的小分子物质都占有相当大的比例,其中高分子物质在MBR上清液中的含量高于CAS系统;MBR出水中则主要是分子量小于3000的小分子物质.MBR污泥粒径较小,使得氧扩散速率得到提高.

A Comparison between a Submerged Membrane Bioreactor and a Conventional Activated Sludge Process

A comparison between a submerged membrane bioreactor (MBR) and a conventional activated sludge process (CAS) was carried out under similar operational conditions. MBR demonstrated a more stable and excellent effluent quality than CAS.Its effluent COD concentration was 55.5mg/L on average, much lower than that of CAS (79.7mg/L). Soluble microbial products accumulated in the MBR during the first 120 days in operation due to membrane interception of macromolecules, but these accumulated substances were degraded at last with microbial acclimation. No similar phenomenon was observed in the CAS system. Compositions of the CAS effluent, MBR supernatant and membrane permeate were found quite different. In the CAS effluent and MBR supernatant, both macromolecules with MW>60 000 and small molecules with MW<3 000 were dominant and macromolecules had a much larger occupation in the MBR supernatant. In the membrane permeate, however, small molecules with MW<3 000 were the major component. The relatively small floc size in the MBR was proved favorable to improve oxygen transfer rate.