Performance of an activated sludge followed by membrane process (AS-MP) treating simulated industrial wastewaters: effects of operating factors and feed characteristics

Abstract

Abstract The main aim of the present study is to determine the optimum operating conditions for different feed compositions with less irreversible membrane fouling in an activated sludge followed by membrane process (AS-MP). In this regard, three different wastewaters with different BOD5/COD ratios (0.83 for soft drink, 0.63 for pineapple fruit juice and 0.36 for amoxicillin) as an index of biodegradability were selected. The AS-MP system was operated with biomass concentration of 7000–8000 mg/l and different hydraulic retention times (HRTs) in the range of 4–20 h. The optimal HRT was decreased as BOD5/COD ratio was increased. In order to investigate fouling behavior of membranes in the AS-MP, a commercial polyvinylidene fluoride (PVDF) microfiltration (MF) membrane and high-performance synthetic ZnFe2O4/SiO2 embedded polyether sulfone (PES) ultrafiltration (UF) membrane were applied. As a result, the UF membrane indicated the highest flux recovery ratio (FRR) for pineapple fruit juice wastewater relative to the other wastewaters. Soft drink wastewater had the maximum permeability and FRR for MF membrane due to low turbidity of the feed and low interaction with MF membrane composition, whereas this wastewater showed a lower permeability and FRR in the UF membrane, implying an effective interaction between the residual soluble microbial products and the UF membrane composition. Both membranes showed almost the same performance for amoxicillin wastewater.