Evaluating the impacts of a high concentration of powdered activated carbon in a ceramic membrane bioreactor: Mixed liquor properties, hydraulic performance and fouling mechanism

Owing to the lack of comprehensive studies on the impacts of a high concentration of powdered activated carbon (PAC) in a ceramic membrane bioreactor (MBR), its performance (at 20 g/L) in terms of mixed liquor properties, hydraulic performance and fouling mechanism was elucidated in this study. In addition to the increase in floc size by 29%, zeta potential of the mixed liquor in PAC-MBR increased (from -19 +/- 2 mV to -11 +/- 2 mV), which was due to the sorption of soluble microbial products on PAC. Importantly, even at a high dose of 20 g/L, membrane fouling was reduced by 33% in PAC-MBR and was attributed to the membrane scouring by PAC and reduced SMP and EPS concentration in the mixed liquor. The viability of the four single and five combined fouling models was assessed to explain the membrane fouling mechanisms in ceramic MBRs for the first time. The intermediate-standard and cake-intermediate models well explained the fouling mechanism in the 'control' and PAC-MBR, respectively, and the intermediate fouling was the major component of the combined models. This study clarifies that MBR could be operated at a high PAC concentration without compromising the effluent quality, mixed liquor properties and membrane hydraulic performance.