CEE Seminar: Cell Entrapment for Mitigating Fouling in Membrane Bioreactors Treating Domestic Wastewater

Abstract: Membrane bioreactors (MBRs) have been a process of choice for wastewater treatment and reuse because of several advantages over the 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. Three versions of entrapped cell-based MBR processes, aerobic MBR, anaerobic MBR and anaerobic forward osmosis (FO) MBR, have been developed by using polyvinyl alcohol as a cell-entrapment matrix. Their domestic wastewater treatment performances and fouling characteristics were tested and compared with their traditional and novel suspended cell-based MBR counterparts. For aerobic and anaerobic MBRs, entrapped cell-based processes provided similar organic removal but experienced delayed fouling compared to suspended cell-based processes. The entrapment diminished bound extracellular polymeric substances (bEPS) and soluble microbial products (SMP), which are a main cause of irreversible fouling through pore blocking. Entrapped cell-based aerobic and anaerobic processes had 5 and 8 times, respectively, lower pore-blocking resistance than corresponding suspended cell-based processes. For anaerobic FO MBR, the entrapment protected cells from reverse salt flux leading to slightly higher organic removal. Lower bEPS and SMP in entrapped cell-based FO MBR led to higher permeate flux compared to suspended cell-based FO MBR. The delayed membrane fouling in entrapped cell-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 FO MBR, an emerging wastewater treatment process.

Bio: Eakalak Khan is a professor in the civil and environmental engineering department, and the director of the environmental and conservation sciences program at North Dakota State University. He received his Ph.D. in civil engineering from UCLA in 1997. His main research interests are in the areas of process development for water and wastewater treatment and remediation, and water and wastewater quality, especially on the biodegradability level. He has published 82 refereed journal articles. His research has been supported by various federal and state agencies including the National Science Foundation, United States Geological Survey, United States Department of Agriculture, New York State and the District of Columbia. He was awarded a prestigious NSF CAREER grant in 2005. His honors include the NDSU Odney Award for Excellence in Teaching in 2008 and Researcher of the Year, College of Engineering and Architecture, NDSU, 2005.