title: Impact of biofilm accumulation on transmembrane and feed channel pressure drop: effects of crossflow velocity, feed spacer and biodegradable nutrient.
abstract: Biofilm formation causes performance loss in spiral-wound membrane systems. In this study a microfiltration membrane was used in experiments to simulate fouling in spiral-wound reverse osmosis (RO) and nanofiltration (NF) membrane modules without the influence of concentration polarization. The resistance of a microfiltration membrane is much lower than the intrinsic biofilm resistance, enabling the detection of biofilm accumulation in an early stage. The impact of biofilm accumulation on the transmembrane (biofilm) resistance and feed channel pressure drop as a function of the crossflow velocity (0.05 and 0.20 m s(-1)) and feed spacer presence was studied in transparent membrane biofouling monitors operated at a permeate flux of 20 L m(-2) h(-1). As biodegradable nutrient, acetate was dosed to the feed water (1.0 and 0.25 mg L(-1) carbon) to enhance biofilm accumulation in the monitors. The studies showed that biofilm formation caused an increased transmembrane resistance and feed channel pressure drop. The effect was strongest at the highest crossflow velocity (0.2 m s(-1)) and in the presence of a feed spacer. Simulating conditions as currently applied in nanofiltration and reverse osmosis installations (crossflow velocity 0.2 m s(-1) and standard feed spacer) showed that the impact of biofilm formation on performance, in terms of transmembrane and feed channel pressure drop, was strong. This emphasized the importance of hydrodynamics and feed spacer design. Biomass accumulation was related to the nutrient load (nutrient concentration and linear flow velocity). Reducing the nutrient concentration of the feed water enabled the application of higher crossflow velocities. Pretreatment to remove biodegradable nutrient and removal of biomass from the membrane elements played an important part to prevent or restrict biofouling.
authors.affiliation: Wetsus, Centre of Excellence for Sustainable Water Technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden, The Netherlands; Biofilm Centre, University Duisburg-Essen, Universitätsstrasse 5, 45141 Essen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Dreszer
authors.affiliation: Biofilm Centre, University Duisburg-Essen, Universitätsstrasse 5, 45141 Essen, Germany.
authors.forename: H-C
authors.initials: HC
authors.lastname: Flemming
authors.affiliation: Wetsus, Centre of Excellence for Sustainable Water Technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Zwijnenburg
authors.affiliation: Wetsus, Centre of Excellence for Sustainable Water Technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden, The Netherlands.
authors.forename: J C
authors.initials: JC
authors.lastname: Kruithof
authors.affiliation: Wetsus, Centre of Excellence for Sustainable Water Technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden, The Netherlands; Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands; King Abdullah University of Science and Technology, Water Desalination and Reuse Center, Thuwal, Saudi Arabia. Electronic address: j.s.vrouwenvelder@tudelft.nl.
authors.forename: J S
authors.initials: JS
authors.lastname: Vrouwenvelder
mesh_terms: D000085:Acetates / Q000737:chemistry*; D001673:Biodegradation, Environmental; D018441:Biofilms; D057219:Biofouling; D002244:Carbon / Q000032:analysis; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D011312:Pressure; D012212:Rheology
chemical_list: D000085:Acetates; D008567:Membranes, Artificial; D002244:Carbon
keywords: Biofouling; Linear flow velocity; MF; Spacer channel pressure drop; Substrate load; Trans membrane pressure drop