Addressing Reverse Osmosis Fouling Within Water Reclamation — A Side-By-Side Comparison of Low-Pressure Membrane Pretreatments
Abstract:A tertiary membrane filtration (TMF) pilot operating on secondary effluent and a membrane bioreactor (MBR) were setup in a side-by-side study as pretreatments for two identical RO pilot systems. The water quality of the permeate from both low-pressure membrane pretreatment systems, as well as the fouling rate of the RO systems was compared to assess the capabilities of the two low-pressure membrane pretreatments to prevent organic fouling of the RO systems. A consistent difference in water quality and RO performance was demonstrated during the 12-month study. The MBR permeate had significantly lower TOC, COD and polysaccharides concentrations, but higher colour and specific UV absorbance compared with the permeate from the TMF pretreatment. The differences in dissolved organics concentrations were found to be associated mainly with differences in the bioreactor process conditions. The pretreatment with the MBR gave an average RO fouling rate over the entire study (0.27 Lmh/bar/month) that was less than half the value found for the RO with TMF pretreatment (0.60 Lmh/bar/month). A correlation of RO feed TOC concentration with average RO fouling rate was also established, independent of the pretreatment method used. Results from a cleaning analysis, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and fourier transformed infrared reflectometry (FT-IR) confirmed that the foulants were primarily organic in nature. It is concluded that, for this type of application and setup, MBR systems present an advantage over tertiary membrane polishing of secondary effluent for RO pretreatment.
Document Type: Research Article
Publication date: 2010-01-01
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