The effect of powdered activated carbon and two-compartment configuration on membrane bioreactor performance

Abstract

The objective of this study was to investigate alternative membrane bioreactor (MER) designs in an attempt to reduce membrane fouling in the MBR system. Several approaches were investigated including (i) modifying the mixed liquor suspended solids (MLSS) using powdered activated carbon (PAC) to form biologically activated carbon (BAC), (ii) limiting the biomass formation from contacting with the membranes using a two-compartment reactor design and (iii) using relatively large polymer beads (~ 600 f.lm) to scour the membrane surface to prevent pollutant attachment and to detach fine foulants on the membrane surface. The effect of PAC addition up to 5 gIL to the activated sludge (AS) in the MBR has been investigated in detail. The benefit of PAC addition to the MBR (AS) was confirmed in a series of tests operated at sludge retention times (SRTs) of 10 and 30 days which involved the addition of 10% and 3.3% by PAC weight addition per day respectively to compensate for sludge wastage. Better performance in terms of fouling mitigation was observed for MBR (BAC) atSRT 10 days compared to 30 days. At these SRTs the MBR (BAC) experienced less fouling than the MBR (AS). However when the MBR (BAC) were operated without wastage, its performance was worse than the MBR (AS). Thus the improved performance achieved by the MBR (BAC) requires regular replenishment of aged BAC with fresh PAC.