Tsukasa YAMAGUCHI

The Effect of Online Chemical Washing in a Single-Reactor Membrane-Separation
Activated Sludge Process

Toshiya KOMATSU Shoichi FUJITA Shuji HIMENO

Nitrogen, a cause substance of the eutrophication problem, can be efficiently removed in a single-reactor membrane-separation activated sludge process by operating the reactor with intermittent aeration. However, in membrane-separation system, permeate flux drops with long term operation by membrane fouling.
Chemical washing of membrane is necessary for preventing permeate flux drop by the fouling. This study was conducted to investigate the effect of online chemical washing on permeate flux recovery and on activity of microorganisms. Reactors were operated for 90 days under different MLSS concentrations (5000 and 20000 mg/L).
As the results, permeate flux recovered efficiently by online chemical washing and no inhibitory effect on microbial activity was observed both in short term (24 hours from online washing) and long operation. Moreover, Extra Cellular Polymer (ECP) content of suspended microorganisms, which plays a significant role in membrane fouling, decreased by online washing. It was revealed that high MLSS conditions had more advantages in recovering permeate flux. Thus, the effectiveness of online chemical washing was demonstrated.