Experimental study of domestic sewage treatment with a metal membrane bioreactor

A novel stainless steel membrane module with a 0.2 mu m nominal pore diameter was applied in an aerated submerged membrane bioreactor to treat synthetic domestic sewage. The pore size of metal membrane was more homogeneous and of tighter distribution than that of organic membrane. The steady membrane flux was more than 17 Lm(-2)h(-1). The mean COD removal efficiency achieved 97.0 %. The mean NO3--N/TN ratio was 74.6 % in effluent. There was a certain positive correlation between membrane fouling and extraceller polymeric substances of activated sludge solution. Membrane fouling could be effectively alleviated by the on-line backwash and intermittent running mode. In addition, membrane fouling could be eliminated almost entirely by off-line cleaning with 0.25 % (wt) NaClO solution with pH 12. After off-line cleaning, membrane flux could be recovered by about 93.3 %. These results implied that it was economical for using the stainless steel membrane in a membrane bioreactor for wastewater treatment.