A New Approach to Modeling Operational Conditions for Mitigating Fouling in Membrane Bioreactor

Modeling and optimization tools play a key role in membrane fouling control in membrane bioreactor (MBR) systems by delineating the more important variables involved. In this study, the influence of sludge retention time (SRT), aeration rate and filtration mode on hollow fiber membrane fouling was investigated. Using the response surface methodology (RSM) for modeling and central composite rotatable design (CCRD) for design of experiments, mathematical models were developed for fouling rate and protein (P1, P2) and carbohydrate (C1, C2) concentrations in two layers of fouling. Results showed that sludge retention time (SRT) was the most important variable in most models followed by aeration rate. Aeration showed a more effective role on the models of the rinsed layer (P1, C1) than backwashed layer (P2, C2). Backwashed layer had more influence on total fouling rate than rinsed layer. The optimal point for MBR operation was: SRT = 30 days, aeration = 10.7 L/min, relaxation interval = 8.8 minutes, and relaxation duration = 41.8 seconds.