Comparison of membrane fouling in dead-end microfiltration of denitrifying granular sludge suspension and its supernatant

Nowadays, membrane biofouling remains a big challenge in application of membrane bioreactor (MBR) for wastewater reclamation. This study investigated an alternative for alleviating the membrane fouling by a combination of denitrifying granular sludge and microfiltration. The dead-end microfiltration performances of denitrifying granular sludge suspension and its supernatant were evaluated. Results showed that the permeate flux of denitrifying granular sludge was 2.35–9.4 times higher than that of suspended denitrifying sludge. It was further revealed that the superior filtration performance of denitrifying granular sludge was due to its big size, reduced surface charge and soluble polysaccharides (sPS). Microfiltration of the supernatant obtained from the suspension showed that the substances in the supernatant was mainly responsible for the membrane pore blocking in the microfiltration of denitrifying granular sludge, while the cake layer helped to remove the pore blocking-causing substances. It appears from this study that the combination of denitrifying granular sludge with membrane filtration would be an attractive alternative for high-efficiency nitrogen removal as well as for control of membrane biofouling.