Hydrogel-coated feed spacers in two-phase flow cleaning in spiral wound membrane elements: A novel platform for eco-friendly biofouling mitigation

Abstract

Biofouling is still a major challenge in the application of nanofiltration and reverse osmosis membranes. Here we present a platform approach for environmentally friendly biofouling control using a combination of a hydrogel-coated feed spacer and two-phase flow cleaning.Neutral (polyHEMA-co-PEG10MA), cationic (polyDMAEMA) and anionic (polySPMA) hydrogels have been successfully grafted onto polypropylene (PP) feed spacers via plasmamediated UV-polymerization. These coatings maintained their chemical stability after 7 days incubation in neutral (pH 7), acidic (pH 5) and basic (pH 9) environments. Anti-biofouling properties of these coatings were evaluated by E. coli attachment assay and nanofiltration experiments at a TMP of 600 kPag using tap water with additional nutrients as feed and by using optical coherence tomography. Especially the anionic polySPMA-coated PP feed spacer shows reduced attachment of E. coli and biofouling in the spacer-filled narrow channels resulting in delayed biofilm growth. Employing this highly hydrophilic coating during removal of biofouling by two-phase flow cleaning also showed enhanced cleaning efficiency, feed channel pressure drop and flux recoveries. The strong hydrophilic nature and the presence of negative charge on polySPMA are most probably responsible for the improved antifouling behavior. A combination of polySPMA-coated PP feed spacers and two-phase flow cleaning therefore is promising and an environmentally friendly approach to control biofouling in NF/RO systems employing spiral-wound membrane modules.3

Tunable conjugated polymers for bacterial differentiation

“…Changing the parameters which mainly influence bacterial attachment, such as charge, hydrophobicity and roughness [61,62], can increase or decrease bacterial attachment and have found various specific applications (for example biomedical implants should inhibit bacterial attachment while, in some cases in biotechnology, the attachment of bacteria to a surface is desirable). The extensive literature in these areas reveals that changing surface parameters has different effects depending on the kind of bacteria [57].…”

Charged hydrophilic polymer brushes and their relevance for understanding marine biofouling

“…In comparison to cationic polymers, there are far fewer studies on the effects of anionic polymers on biofouling and these are typically oriented toward biomedical materials (Lei et al 2014, Lord et al 2006). However, a recent study on the influence of charge of hydrogels immobilized onto polypropylene (PP) feed spacers for use in nanofiltration membrane systems has shown significant reduction in the attachment of Escherichia coli and delayed growth of biofilms on anionic hydrogel-coated PP, relative to that on neutral and zwitterionic coatings, after seven days of filtration (Wibisono et al 2015). It was hypothesized that the lower biofouling on anionic surfaces resulted from higher surface wettability and repulsive electrostatic interactions between the anionic polymer and the negatively charged bacterial cell wall.…”

“…This polymer has antimicrobial properties against both Gram-positive and Gram-negative bacteria (Lee et al 2004, Liu et al 2007, Rawlinson et al 2010. The anionic PSPMA has also been reported to reduce bacterial adhesion and to inhibit the growth of bacteria due to high surface hydration resulting from solvation of the sulfonate groups (Guo et al 2013, Ramstedt et al 2007, and also result in lower attachment of E. coli and delayed growth of biofilm in membrane filtration tests (Wibisono et al 2015).…”

Marine microalgae Nannochloropsis oculata biomass harvesting using ultrafiltration in cross-flow mode

“…Although chemical approach such as modification of surface properties promotes low fouling [6], yet the physical cleaning is still effective [7]. In this work therefore, a utilization of ultrafiltration (UF) membrane accompanied by backwash treatment as physical cleaning method have been conducted in marine microalgae harvesting process.…”