Performance of up-flow anaerobic sludge blanket-membrane bioreactor (UASB-MBR) for treating rice vermicelli and flour wastewater

A laboratory-scale UASB-MBR experiment using cross-flow microfiltration was conducted to treat rice vermicelli and flour wastewater to determine the optimum operating condition and identify the fouling pattern. The chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) removal were about 99 % under 0.18 g COD/g MLVSS/d of the F/M ratio. The critical pressure condition was observed in the 0.25-0.75 bars range for sludge granule concentration between 1-7 g/L, with no significant change in permeate flux when TMP was over 0.75 bars. The relaxation during filtration time allowed the minimum cake deposit on the membrane surface while soluble organic and a small fraction of UASB effluent induced internal fouling resistance. The soluble microbial product (SMP) and the extra polymeric substance (EPS) concentrations from permeate were about 7-10 times lower than those from UASB effluent. These conditions showed that the cross-flow microfiltration could successfully remove the SS from UASB effluent while allowing all sludge granules to be retained in the system.