A hybrid membrane process for simultaneous thickening and digestion of waste activated sludge

Abstract

A hybrid membrane process for simultaneous sludge thickening and digestion (MSTD) was studied. During one cycle (15 d) of operation under a hydraulic retention time of 1 d, the concentration of mixed liquor suspended solids (MLSS) continuously increased from about 4 g$L -1 to 34 g$L -1 , and the mixed liquor volatile suspended solids (MLVSS) increased from about 3 g$L -1 to over 22 g$L -1 . About 42% of the MLVSS and 39% of the MLSS reduction were achieved. The thickening and digestion effects in the MSTD were further analyzed based on a mass balance analysis. Test results showed that biopolymers and cations of biomass were gradually released to the bulk solution during the process. It was also found that the capillary suction time, colloidal chemical oxygen demand, soluble microbial products, viscosity, and MLSS had significant positive correlations with the membrane fouling rate, whereas extracellular polymeric substances, polysaccharides, and proteins extracted from biomass had negative impacts on membrane fouling.

Optimization Design and Experimental Study of Two‐Phase Integrated Sludge Thickening and Digestion Reactor

“…Although some new digesters, such as vertical tubular anaerobic sludge digester (Ai et al, 2005), UASR reactor (Zeeman et al, 1997), fixed-bed digester (Sanchez et al, 1995), and membrane digester (Wang et al, 2010), have been invented, these technologies are still at laboratory or pilot scale, and most fullscale anaerobic digesters still use CSTRs similar to those used around 50 years ago.…”