Development and testing of a low sludge discharge membrane bioreactor for greywater reclamation

A low sludge discharge membrane bioreactor (LSDMBR) for greywater reclamation was developed and tested in this study. LSDMBR was designed by combining an aerobic activated sludge process with an immersed membrane filtration process. LSDMBR offers the following advantages over conventional activated sludge processes. Firstly, LSDMBR has a high biomass concentration attributed to membrane filtration of the effluent and low sludge wasting, which results in reduced disposal costs. Secondly, LSDMBR provides for a favorable environment for nitrifying bacteria and the promotion of their growth. Finally, LSDMBR provides for higher treatment efficiencies and produces higher-quality effluent for reuse over conventional processes. It was found from laboratory testing that the contaminant removal efficiencies achieved by LSDMBR within 2.5 h of hydraulic retention time (HRT) were as follows: 95% removal of anionic surfactants and 90% removal of 5-day biochemical oxygen demand (BOD₅), respectively. It was also found that the effluent ammonia and total Kjeldahl nitrogen (TKN) concentrations were reduced to less than 1 mg/L and 6 mg/L, respectively. Results of the study suggested that LSDMBR is a small-scale and self-sustaining greywater reclamation system that requires low installation space and low sludge discharge.