Optimized operational parameters of a pilot scale membrane bioreactor for high-strength organic wastewater treatment

A pilot-scale test was conducted in a submerged membrane bioreactor (SMBR) for 452 days to treat high-strength traditional Chinese medicine wastewater from two-phase anaerobic digest effluent. This study focuses on the effects of operational parameters on effluent quality of a SMBR. The parameters include shorter hydraulic retention time (HRT), higher influent COD concentration, higher COD loading rate and mixed liquor suspended solids (MLSS). The experimental results demonstrated that when HRT was 5 h and the influent COD was less than 3000 mg L−1, the effluent quality of the SMBR evaluated from its COD content (CODfilt) could meet the accepted Chinese standards for water reclamation; when HRT was 3.2 h and the influent COD was less than 3000 mg L −1, or HRT was 5 h and the influent COD fluctuated between 3000 and 6000 mg L−1, the effluent quality of the SMBR could meet the normal Chinese discharged standard. Statistical analyses showed that CODfilt correlated positively with the COD loading rate. It correlated negatively with the MLSS for MLSS values between 7543 and 13 694 mg L−1. When MLSS was >13 694 mg L−1 it correlated positively with CODfilt. Based on experimental values from SMBR and on values predicted by a simulation model generated using the back propagation neural network (BPNN) theory, the optimum operational parameters for the treatment of a high-strength TCM wastewater were as follows: HRT was 5 h, SRT was 100 day, COD loading rate was<20.5 kg m−3 d−1, the range of MLSS was 7543–13 694 mg L−1.