title: Impact of organic nutrient load on biomass accumulation, feed channel pressure drop increase and permeate flux decline in membrane systems.
abstract: The influence of organic nutrient load on biomass accumulation (biofouling) and pressure drop development in membrane filtration systems was investigated. Nutrient load is the product of nutrient concentration and linear flow velocity. Biofouling - excessive growth of microbial biomass in membrane systems - hampers membrane performance. The influence of biodegradable organic nutrient load on biofouling was investigated at varying (i) crossflow velocity, (ii) nutrient concentration, (iii) shear, and (iv) feed spacer thickness. Experimental studies were performed with membrane fouling simulators (MFSs) containing a reverse osmosis (RO) membrane and a 31 mil thick feed spacer, commonly applied in practice in RO and nanofiltration (NF) spiral-wound membrane modules. Numerical modeling studies were done with identical feed spacer geometry differing in thickness (28, 31 and 34 mil). Additionally, experiments were done applying a forward osmosis (FO) membrane with varying spacer thickness (28, 31 and 34 mil), addressing the permeate flux decline and biofilm development. Assessed were the development of feed channel pressure drop (MFS studies), permeate flux (FO studies) and accumulated biomass amount measured by adenosine triphosphate (ATP) and total organic carbon (TOC). Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer thickness. The impact of the same amount of accumulated biomass on feed channel pressure drop and permeate flux was influenced by membrane process design and operational conditions. Reducing the nutrient load by pretreatment slowed-down the biofilm formation. The impact of accumulated biomass on membrane performance was reduced by applying a lower crossflow velocity and/or a thicker and/or a modified geometry feed spacer. The results indicate that cleanings can be delayed but are unavoidable.
authors.affiliation: King Abdullah University of Science and Technology, Water Desalination and Reuse Center, Thuwal, Saudi Arabia; Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Sz S
authors.initials: SS
authors.lastname: Bucs
authors.affiliation: King Abdullah University of Science and Technology, Water Desalination and Reuse Center, Thuwal, Saudi Arabia; Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Valladares Linares
authors.affiliation: Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: M C M
authors.initials: MC
authors.lastname: van Loosdrecht
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: King Abdullah University of Science and Technology, Water Desalination and Reuse Center, Thuwal, Saudi Arabia; Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands; Wetsus, Centre of Excellence for Sustainable Water Technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden, The Netherlands. Electronic address: j.s.vrouwenvelder@tudelft.nl.
authors.forename: J S
authors.initials: JS
authors.lastname: Vrouwenvelder
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D057219:Biofouling; D018533:Biomass; D005374:Filtration / Q000295:instrumentation* / Q000379:methods; D008567:Membranes, Artificial; D008962:Models, Theoretical; D009995:Osmosis; D011312:Pressure; D054712:Salinity; D018508:Water Purification / Q000295:instrumentation* / Q000379:methods
chemical_list: D008567:Membranes, Artificial
keywords: Biodegradable organic substrate loading rate; Biofilm growth; Desalination; Feed channel pressure drop; Mathematical model; Permeate flux