Experimental study of domestic sewage treatment with a metal membrane bioreactor

A novel stainless steel membrane module with a 0.2 µm 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.

A novel stainless steel membrane module, with a 0.2 µm nominal pore size, was used in an experimental submerged MBR to treat synthetic domestic sewage. The performance of a metal membrane was investigated. The results showed that: 1. the stainless steel membrane had a greater homogeneous pore size and narrower pore size distribution than organic membrane; 2. organic substance removal was quite effective, COD removal efficiency achieved 97%. The metal membrane promoted development of nitrobacteria in the bioreactor and enhanced nitration ! efficiency. NO3 -N/TN ratio in permeate was 74.6%; 3. EPS was positively correlated with membrane fouling, which was presumed to be the primary parameter affecting membrane fouling; 4. on-line backwash could greatly alleviate membrane fouling and prolong membrane running time. It was easier to clean the metal membrane than the organic one. A better cleaning procedure was to flush the membrane surface with tap water after scraping floc on it, then immersing it in 0.25 wt% NaClO solution at pH 12 for 2 h. The study shows that it is possible a for stainless steel membrane to be used in a MBR for wastewater treatment.