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 0.20ms-1) and feed spacer presence was studied in transparent membrane biofouling monitors operated at a permeate flux of 20Lm-2h-1. As biodegradable nutrient, acetate was dosed to the feed water (1.0 and 0.25mgL-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 (0.2ms-1) and in the presence of a feed spacer. Simulating conditions as currently applied in nanofiltration and reverse osmosis installations (crossflow velocity 0.2ms-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. © 2013 Elsevier Ltd.

Citation
Dreszer C, Flemming H-C, Zwijnenburg A, Kruithof JC, Vrouwenvelder JS (2014) Impact of biofilm accumulation on transmembrane and feed channel pressure drop: Effects of crossflow velocity, feed spacer and biodegradable nutrient. Water Research 50: 200–211. Available: http://dx.doi.org/10.1016/j.watres.2013.11.024.

Acknowledgements
This work was performed at Wetsus, Centre of Excellence for Sustainable Water Technology (www.wetsus.nl). Wetsus is funded by the Dutch Ministry of Economic Affairs, the European Union European Regional Development Fund, the Province of Fryslan, the city of Leeuwarden and by the EZ-KOMPAS Program of the "Samenwerkingsverband Noord-Nederland" and the King Abdullah University of Science and Technology (KAUST). The authors like to thank the participants of the research theme "Biofouling", KAUST and Evides waterbedrijf for the fruitful discussions and their financial support. In addition, the authors would especially like to thank the students Malgorzata Nowak and Stanislaw Wojciechowski for their contribution to the experimental work.

Publisher
Elsevier BV

Journal
Water Research

DOI
10.1016/j.watres.2013.11.024

PubMed ID
24374131

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