Long term operation performance and membrane fouling mechanisms of anaerobic membrane bioreactor treating waste activated sludge at high solid concentration and high flux.

High solid anaerobic membrane bioreactor (HSAnMBR) is widely applied in biomass treatment and energy regeneration, while membrane operation performance and membrane fouling control remain critical issues. In this study, a HSAnMBR was utilized for waste activated sludge (WAS) treatment at organic loading rates of 3.69-3.72 gCOD/L·d and biogas yield was ranged in 0.38-0.39 L/gVSfed with the COD conversion efficiency of 40 %. The membrane operated stably when the average flux was 9.6, 4.5 and 1.2 L/m2/h at mixed liquor total solid of 25, 30 and 40 g/L with a filtration: relaxation of 4:1, 1:1 and 1:2, respectively. The distinctive characteristics of membrane fouling at high solid condition were that the polysaccharides and proteins had high fouling propensity and were the main composition of the foulant layer. Furthermore, phosphorus and magnesium were the predominant causes of inorganic fouling. The minerals precipitated on the membrane and were embedded into membrane pores, contributing to cake layer formation and pore blocking. This research provided a comprehensive analysis of the membrane operation characterization and fouling mechanisms of HSAnMBR, which was expected to push forward HSAnMBR applications to WAS treatment.