The importance of laboratory water quality for studying initial bacterial adhesion during NF filtration processes

Title: The importance of laboratory water quality for studying initial bacterial adhesion during NF filtration processes
Authors: Correia-Semião, Andrea Joana C.
Habimana, Olivier
Cao, Huayu
Heffernan, Rory
Safari, Ashkan
Casey, Eoin
Permanent link: http://hdl.handle.net/10197/4309
Date: 15-May-2013
Abstract: Biofouling of nanofiltration (NF) and reverse osmosis (RO) membranes for water treatment has been the subject of increased research effort in recent years. A prerequisite for undertaking fundamental experimental investigation on NF and RO processes is a procedure called compaction. This involves an initial phase of clean water permeation at high pressures until a stable permeate flux is reached. However water quality used during the compaction process may vary from one laboratory to another. The aim of this study was to investigate the impact of laboratory water quality during compaction of NF membranes. A second objective was to investigate if the water quality used during compaction influences initial bacterial adhesion. Experiments were undertaken with NF270 membranes at 15 bar for permeate volumes of 0.5L, 2L, and 5L using MilliQ, deionized or tap water. Membrane autopsies were performed at each permeation point for membrane surface characterisation by contact angle measurements, profilometry, and scanning electron microscopy. The biological content of compacted membranes was assessed by direct epi-fluorescence observation following nucleic acid staining. The compacted membranes were also employed as substrata for monitoring the initial adhesion of Ps. fluorescens under dynamic flow conditions for 30 minutes at 5 minutes intervals. Compared to MilliQ water, membrane compaction using deionized and tap water led to decreases in permeate flux, increase in surface hydrophobicity and led to significant buildup of a homogenous fouling layer composed of both living and dead organisms (>10⁶cells.cm−2). Subsequent measurements of bacterial adhesion resulted in cell loadings of 0.2×10⁵, 1.0×10⁵cells×cm−2 and 2.6×10⁵ cells.cm−2 for deionized, tap water and MilliQ water, respectively. These differences in initial cell adhesion rates demonstrate that choice of laboratory water can significantly impact the results of bacterial adhesion on NF membranes. Standardized protocols are therefore needed for the fundamental studies of bacterial adhesion and biofouling formation on NF and RO membrane. This can be implemented by first employing pure water during all membrane compaction proceduresand for the modelled feed solutions used in the experiment.
Funding Details: Science Foundation Ireland
European Research Council
Type of material: Journal Article
Publisher: Elsevier
Copyright (published version): 2013 Elsevier Ltd.
Keywords: CompactionWater qualityCell adhesionNanofiltration
DOI: 10.1016/j.watres.2013.03.020
Language: en
Status of Item: Peer reviewed
Appears in Collections:Chemical and Bioprocess Engineering Research Collection

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