Cell Entrapment for Mitigating Fouling in Membrane Bioreactors Treating Domestic Wastewater
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Cell Entrapment for Mitigating Fouling in Membrane Bioreactors Treating Domestic Wastewater.pdf (4.718Mb)
Membrane bioreactors (MBRs) have been a process of choice for wastewater treatment and reuse because of several advantages over conventional process (activated sludge) including superior quality effluent, less biomass yields and more compact design. However, membrane fouling is a major drawback that hampers widespread and full-scale applications of MBRs. Cell entrapment is a relatively new wastewater treatment process. It involves cells artificially entrapped in a porous polymer matrix. In this dissertation research, three versions of entrapped cells-based MBR processes, aerobic MBR, anaerobic MBR and anaerobic forward osmosis (FO) MBR, were developed by using polyvinyl alcohol as a cell entrapment matrix. Their domestic wastewater treatment performances and fouling characteristics were tested and compared with their suspended cells-based MBR counterparts. For aerobic and anaerobic MBRs, entrapped cells-based processes provided similar organic removal but experienced delayed fouling compared to suspended cells-based processes. The entrapment diminished bound extracellular polymeric substances (bEPS) and soluble microbial products (SMP), which are a main culprit of irreversible fouling through pore blocking. Entrapped cells-based aerobic and anaerobic processes had 5 and 8 times lower pore blocking resistance than corresponding suspended cells-based processes. For anaerobic FOMBR, the entrapment protected cells from reverse salt flux leading to slightly higher organic removal. Lower bEPS and SMP in entrapped cells-based FOMBR led to higher permeate flux compared to suspended cells-based FOMBR. The delayed membrane fouling in entrapped cells-based MBRs means lower costs associated with membrane cleaning processes and longer membrane lifespan. Another contribution of this study is novel knowledge on fouling conditions and mitigation for FOMBR, an emerging wastewater treatment process.