Organic colloids and their influence on low-pressure membrane filtration.
Wastewater treatment by low-pressure membrane filtration (MF and UF) is affected to a large extent by macromolecules and colloids. In order to investigate the influence of organic colloids on the membrane filtration process, colloids were isolated from a wastewater treatment plant effluent using a rotary-evaporation pre-concentration step followed by dialysis. Stirred cell tests were carried out using redissolved colloids, with and without additional glass fiber filtration. After constant pressure membrane filtration of 190 L/m2, the initial flux had declined by 50% for colloids > 6-8 kD (glass fiber filtered) with a hydrophilic MF membrane and for colloids > 12-14 kD (glass fiber filtered) with a hydrophobic MF membrane. For the non-filtered colloidal solutions, the flux decline was even steeper with the flux being below 10% of the initial flux after 190 L/m2 were passed through the membranes. As with larger particles, colloids form a filtration cake layer on top of the membrane surface when used as isolates without prior filtration. This filtration cake is easily removed during backwashing. However, polysaccharides as a macromolecular component of the colloid isolate cause severe fouling by the formation of a gel layer on the membrane surface that is difficult to remove completely.
Laabs
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Technical University Berlin, Department of Water Quality Control, 10623 Berlin, Germany. Claudia.Laabs@tu-berlin.de
Amy
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Jekel
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D003102:Colloids / Q000737:chemistry*; D005374:Filtration / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D008970:Molecular Weight; D009930:Organic Chemicals / Q000737:chemistry* / Q000302:isolation & purification; D010539:Permeability; D011134:Polysaccharides / Q000737:chemistry / Q000302:isolation & purification; D011312:Pressure; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
D003102:Colloids; D008567:Membranes, Artificial; D009930:Organic Chemicals; D011134:Polysaccharides