Long-term performance of a full-scale submerged membrane bioreactor for bath wastewater reclamation

Bath wastewater is an ideal source for wastewater reclamation for its large amount, simple pollutant composition and low pollutant content. The long-term stability of reclaiming bath wastewater was investigated with a 240 m(3)/d full-scale submerged membrane bioreactor (SMBR) at an organic load of 1.04-2.80 kg-COD/(m(3). d). The operation was continued for 450 days. Quality of obtained effluent met the wastewater reclamation standard of China, with COD<35 mg/L, NH3-N <2.0 mg/L, anionic detergent <0.3 mg/L. Biological treatment removed most pollutants in the influent, degrading 46.9-93.5% of COD, 68.1-99.4% of NH3-N and 98% of anionic detergent. Membrane separation balanced the unstable biological treatment of COD and NH3-N but showed idleness to anionic detergent removal. Inorganic substances were not found to accumulate in the bioreactor. The main reason for membrane fouling was considered as sludge adhesion and gel layer formation over the outer membrane surface and microbial growth over the inner membrane surface. On line periodical chemical cleaning was effective to remove the fouling.