Enhancement of sustainable flux by optimizing filtration mode of a high-solid anaerobic membrane bioreactor during long-term continuous treatment of food waste

Abstract

Membrane fouling or flux limitation is the major bottleneck that hinders anaerobic membrane bioreactor (AnMBR) application. An AnMBR with a working volume of 15 L was operated for 180 days to investigate the maximum sustainable flux at different high solid concentrations during the anaerobic treatment of food waste. A total of eight filtration-to-relaxation (F/R) ratios were incorporated, with a fixed filtration time of 3 min and varied relaxation times (decreased from 12 to 1 min). Besides, a total of five instantaneous fluxes were applied: 12, 14, 16, 18 and 20 L/m2/h (LMH). Results showed that sustainable flux was greatly enhanced by filtration mode optimization. The optimal F/R ratios were 3:1, 3:1, 3:1 and 3:6 at mixed liquor total solid (MLTS) concentrations of 10, 15, 20 and 25 g/L, respectively. The corresponding sustainable flux values were 13.2 ± 0.3, 10.1 ± 0.4, 9.3 ± 0.2 and 4.0 ± 0.3 LMH, respectively. These values were 29%, 35%, 52% and 21% higher than the critical flux determined by the flux-stepping technique. The results of this study were used to perform a mathematical simulation. The obtained regression equation between the maximum sustainable flux and MLTS concentration can be used to predict the sustainable flux at other MLTS concentrations. This work provides valuable insight into the design and operation of high-solid AnMBRs, and is expected to contribute to further advances in the application of AnMBRs in industry.