Enzymatic activities in a moving bed membrane bioreactor for real urban wastewater treatment: Effect of operational conditions

The microbial hydrolytic enzymatic activities (acid phosphatase, alkaline phosphatase and glucosidase) in a moving bed membrane bioreactor (MBMBR system) for real urban wastewater treatment were investigated. This study was conducted in both suspended biomass and attached biofilm present in a MBMBR system. For this, four experimental phases with 20% and 35% (v/v) carrier filling ratios (CFRs) were conducted, which combined two mixed liquor total suspended solid (MLTSS) concentrations (c.a. 2500 and 4500 mg/L) and two hydraulic retention times (HRTs) (10 and 24 h). Hydrolytic activities of acid phosphatase, alkaline phosphatase and α-glucosidase in the mixed liquor (suspended biomass) were higher than in the biofilm (independent of the carrier concentration), during the four experiments, possibly due to better substrate diffusion in the mixed liquor. A redundancy analysis (RDA) was performed to evaluate the relationship between enzymatic activities and chemical oxygen demand (COD), biological oxygen demand at 5 days (BOD5), mixed liquor volatile suspended solid concentration (MLVSS), biofilm total solids (BTS), HRT, pH, CFR and temperature. According to the results obtained with the Monte Carlo permutation test, CFR, MLVSS, BTS, COD, temperature and HRT significantly contributed to the variation of enzymatic activities in the MBMBR.