A pilot study on a submerged membrane bioreactor for domestic wastewater treatment

A pilot-scale membrane bioreactor was tested for its long-term performance in domestic wastewater treatment. The treatment capacity was 5.5 m(3)/d. Over 300 days were maintained. The results demonstrated that a high-quality affluent with COD<30 mg/L and NH3-N<1 mg/L can be obtained. The bioreactor degraded 70% of the influent GOD, while the membrane separation insured 90% of the total COD would be removed. The biomass morphology and the molecular weight distribution of the organic substances were also investigated. It was observed under a scanning electronic microscope (SEM) that sludge deposition, gel-layer formation and microbial growth caused the membrane fouling. The membrane fouling can be under control through clear-water washing, intensified aeration and NaClO solution in-line cleaning.