Enhanced biofilm solubilization by urea in reverse osmosis membrane systems

Journal article (2018)

Authors

H. Sanawar Water Desalination and Reuse Center, King Abdullah University of Science and Technology
I.S.M. Pinel OLD BT/Cell Systems Engineering , BT/Environmental Biotechnology - AS
N. M. Farhat King Abdullah University of Science and Technology
Sz S. Bucs King Abdullah University of Science and Technology
J. Zlopasa BT/Environmental Biotechnology - AS , OLD BT/Cell Systems Engineering
J. C. Kruithof Centre of Excellence for Sustainable Water Technology, Wetsus, European Centre of Excellence for Sustainable Water Technology
G.J. Witkamp King Abdullah University of Science and Technology, OLD BT/Cell Systems Engineering , BT/Environmental Biotechnology - AS
Mark M.C. van Loosdrecht BT/Environmental Biotechnology - AS , OLD BT/Cell Systems Engineering
Mark C.M. van Loosdrecht BT/Environmental Biotechnology - AS , OLD BT/Cell Systems Engineering
J.S. Vrouwenvelder BT/Environmental Biotechnology - AS , OLD BT/Cell Systems Engineering , King Abdullah University of Science and Technology
Research Group
BT/Environmental Biotechnology (AS) (TU Delft)
Copyright: © 2018 H. Sanawar, I.S.M. Pinel, N. M. Farhat, Sz S. Bucs, J. Zlopasa, J. C. Kruithof, G.J. Witkamp, Mark C.M. van Loosdrecht, J.S. Vrouwenvelder
DOI: https://doi.org/10.1016/j.wroa.2018.10.001
More Info
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Published Date

2018

Language

English

Faculty

Applied Sciences

Department

BT/Biotechnologie

Research Group

BT/Environmental Biotechnology

Abstract


Chemical cleaning is routinely performed in reverse osmosis (RO) plants for the regeneration of RO membranes that suffer from biofouling problems. The potential of urea as a chaotropic agent to enhance the solubilization of biofilm proteins has been reported briefly in the literature. In this paper the efficiency of urea cleaning for RO membrane systems has been compared to conventionally applied acid/alkali treatment. Preliminary assessment confirmed that urea did not damage the RO polyamide membranes and that the membrane cleaning efficiency increased with increasing concentrations of urea and temperature. Accelerated biofilm formation was carried out in membrane fouling simulators which were subsequently cleaned with (i) 0.01M sodium hydroxide (NaOH) and 0.1M hydrochloric acid (HCl) (typically applied in industry), (ii) urea (CO(NH
2
)
2
) and hydrochloric acid, or (iii) urea only (1340 g/L
water
). The pressure drop over the flow channel was used to evaluate the efficiency of the applied chemical cleanings. Biomass removal was evaluated by measuring chemical oxygen demand (COD), adenosine triphosphate (ATP), protein, and carbohydrate content from the membrane and spacer surfaces after cleaning. In addition to protein and carbohydrate quantification of the extracellular polymeric substances (EPS), fluorescence excitation−emission matrix (FEEM) spectroscopy was used to distinguish the difference in organic matter of the remaining biomass to assess biofilm solubilization efficacy of the different cleaning agents. Results indicated that two-stage CO(NH
2
)
2
/HCl cleaning was as effective as cleaning with NaOH/HCl in terms of restoring the feed channel pressure drop (>70% pressure drop decrease). One-stage cleaning with urea only was not as effective indicating the importance of the second-stage low pH acid cleaning in weakening the biofilm matrix. All three chemical cleaning protocols were equally effective in reducing the concentration of predominant EPS components protein and carbohydrate (>50% reduction in concentrations). However, urea-based cleaning strategies were more effective in solubilizing protein-like matter and tyrosine-containing proteins. Furthermore, ATP measurements showed that biomass inactivation was up to two-fold greater after treatment with urea-based chemical cleanings compared to the conventional acid/alkali treatment. The applicability of urea as an alternative, economical, eco-friendly and effective chemical cleaning agent for the control of biological fouling was successfully demonstrated.