The process of using flat-sheet membrane for thickening and digestion of waste activated sludge.

The mechanisms of sludge digestion and membrane fouling in the process of using flat-sheet membrane for simultaneous thickening and digestion of waste activated sludge(MSTD) were investigated in a pilot-scale reactor.In the MSTD process,the mixed liquor suspended solids(MLSS) reached approximate 34.2g/L from 3.6g/L,and the destruction efficiencies of MLSS and mixed liquor volatile suspended solids(MLVSS) were about 47% and 52%,respectively.The MSTD process successfully realized simultaneous thickening and digestion of waste activated sludge after the operation of 15d.According to the variations of dissolved oxygen(DO),the digestion mechanisms of the MSTD process could be divided into two stages,similarly aerobic and anaerobic digestion,which degraded the biopolymers linked by divalent and iron cations,respectively.The membrane permeability of the MSTD process intensively declined due to the violent variations of sludge properties caused by the filtration of membrane and sludge digestion,and the MLSS,extracellular polymeric substances(EPS) and soluble microbial products(SMP) had significant impacts on membrane fouling.