title: Presence of biofilms on ultrafiltration membrane surfaces increases the quality of permeate produced during ultra-low pressure gravity-driven membrane filtration.
abstract: This study evaluates the effect of the presence of biofilms on membrane surfaces on the quality of permeate produced during Gravity-driven membrane ultrafiltration. GDM ultrafiltration is applied to the decentralized production of drinking water. A second objective was to evaluate to what extent permeate quality is enhanced by pre-treating feed-water (using a packed bed biofilm reactor or a slow sand filter). The influence of the ageing of the biofilm on the permeate quality was evaluated and compared to the effect of virgin membranes. Permeate quality was evaluated in terms of Assimilable Organic Carbon (AOC) content and dissolved organic carbon fractions (e.g. biopolymers). Our results indicate that virgin ultrafiltration membrane remove a small fraction of the AOC and biopolymers (rejection <10%). The presence of a young and thin biofilm on the surface of the ultrafiltration membranes increases the permeate quality due to the degradation of AOC (>80%). However, over long-term the hydrolysis of the organic matter that accumulated on membrane surfaces increases the AOC content of the permeate, thus deteriorating the permeate quality. Pre-treatment of the feed-water help to control the biofilm accumulation and thus to limit the deterioration of the permeate quality. Permeate flux stabilised at average values of 7.5-8.9 L m(-2) h(-1). But the presence of pre-treatment helped to increase permeate flux (+12 and 19%, with the packed bed biofilm reactor and with the slow sand filter, respectively). Overall our study demonstrates that tolerating the presence of biofilm on membrane surface has a beneficial effect on the quality of permeate even if its quantity is decreased.
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland. Electronic address: nicolas.derlon@eawag.ch.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Derlon
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: Joao
authors.initials: J
authors.lastname: Mimoso
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: Theresa
authors.initials: T
authors.lastname: Klein
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Koetzsch
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland; Institute of Environmental Engineering, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Morgenroth
mesh_terms: D018407:Bacterial Physiological Phenomena; D018441:Biofilms; D002244:Carbon / Q000378:metabolism; D009930:Organic Chemicals / Q000378:metabolism*; D011312:Pressure; D013997:Time Factors; D014462:Ultrafiltration; D014874:Water Pollutants, Chemical / Q000378:metabolism; D018508:Water Purification
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D002244:Carbon
keywords: AOC; Biofilm; Biopolymers; Permeate quality; Slow sand filtration; Ultrafiltration