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dc.contributor.authorSanawar, Huma
dc.contributor.authorKim, L.H.
dc.contributor.authorFarhat, Nadia
dc.contributor.authorvan Loosdrecht, Mark C.M.
dc.contributor.authorVrouwenvelder, Johannes S.
dc.identifier.citationSanawar, H., Kim, L. H., Farhat, N. M., van Loosdrecht, M. C. M., & Vrouwenvelder, J. S. (2021). Periodic chemical cleaning with urea: disintegration of biofilms and reduction of key biofilm-forming bacteria from reverse osmosis membranes. Water Research X, 100117. doi:10.1016/j.wroa.2021.100117
dc.description.abstractBiofouling is one of the major factors causing decline in membrane performance in reverse osmosis (RO) plants, and perhaps the biggest hurdle of membrane technology. Chemical cleaning is periodically carried out at RO membrane installations aiming to restore membrane performance. Typical cleaning agents used in the water treatment industry include sodium hydroxide (NaOH) and hydrochloric acid (HCl) in sequence. Rapid biofilm regrowth and related membrane performance decline after conventional chemical cleaning is a routinely observed phenomenon due to the inefficient removal of biomass from membrane modules. Since extracellular polymeric substances (EPS) make up the strongest and predominant structural framework of biofilms, disintegration of the EPS matrix should be the main target for enhanced biomass removal. Previously, we demonstrated at lab-scale the use of concentrated urea as a chemical cleaning agent for RO membrane systems. The protein denaturation property of urea was exploited to solubilize the proteinaceous foulants, weakening the EPS layer, resulting in enhanced biomass solubilization and removal from RO membrane systems. In this work, we investigated the impact of repeated chemical cleaning cycles with urea/HCl as well as NaOH/HCl on biomass removal and the potential adaptation of the biofilm microbial community. Chemical cleaning with urea/HCl was consistently more effective than NaOH/HCl cleaning over 6 cleaning and regrowth cycles. At the end of the 6 cleaning cycles, the percent reduction was 35% and 41% in feed channel pressure drop, 50% and 70% in total organic carbon, 30% and 40% in EPS proteins, and 40% and 66% in the peak intensities of protein-like matter, after NaOH/HCl cleaning and Urea/HCl cleaning respectively. 16S ribosomal RNA (rRNA) gene sequencing of the biofilm microbial community revealed that urea cleaning does not select for key biofouling families such as Sphingomonadaceae and Xanthomonadaceae that are known to survive conventional chemical cleaning and produce adhesive EPS. This study reaffirmed that urea possesses all the desirable properties of a chemical cleaning agent, i.e., it dissolves the existing fouling layer, delays fresh fouling accumulation by inhibiting the production of a more viscous EPS, does not cause damage to the membranes, is chemically stable, and environmentally friendly as it can be recycled for cleaning.
dc.description.sponsorshipThe authors thank King Abdullah University of Science and Technology (KAUST) for funding this research project. The graphical abstract was produced by Xavier Pita, Scientific Illustrator at KAUST.
dc.publisherElsevier BV
dc.rightsThis is an open access article under the CC BY-NC-ND license.
dc.titlePeriodic chemical cleaning with urea: disintegration of biofilms and reduction of key biofilm-forming bacteria from reverse osmosis membranes
dc.contributor.departmentEnvironmental Science and Engineering Program
dc.contributor.departmentBiological and Environmental Science and Engineering (BESE) Division
dc.contributor.departmentKing Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Division of Biological and Environmental Science and Engineering (BESE), Thuwal, 23955-6900, Saudi Arabia.
dc.contributor.departmentWater Desalination and Reuse Research Center (WDRC)
dc.identifier.journalWater Research X
dc.eprint.versionPublisher's Version/PDF
dc.contributor.institutionDepartment of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
kaust.personSanawar, Huma
kaust.personKim, L.H.
kaust.personFarhat, Nadia M.
kaust.personVrouwenvelder, Johannes S.

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