Transparent exopolymer particles (TEPs)-associated protobiofilm: A neglected contributor to biofouling during membrane f
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RESEARCH ARTICLE
Transparent exopolymer particles (TEPs)-associated protobiofilm: A neglected contributor to biofouling during membrane filtration Shujuan Meng1, Rui Wang1, Kaijing Zhang1, Xianghao Meng1, Wenchao Xue2, Hongju Liu1, Dawei Liang (✉)1, Qian Zhao3, Yu Liu4 1 School of Space and Environment, Beihang University, Beijing 100191, China 2 Department of Energy, Environment and Climate Change, School of Environment, Resources and Development, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand 3 School of Municipal and Environmental Engineering, Shandong Jianzhu University, Jinan 250101, China 4 School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore
HIGHLIGHTS
GRAPHIC ABSTRACT
• Bacteria could easily and quickly attached onto TEP to form protobiofilms. • TEP-protobiofilm facilitates the transport of bacteria to membrane surface. • More significant flux decline was observed in the presence of TEP-protobiofilms. • Membrane fouling shows higher sensitivity to protobiofilm not to bacteria level.
ARTICLE INFO Article history:
Received 20 May 2020 Revised 31 August 2020 Accepted 21 September 2020 Available online 10 November 2020 Keywords: Transparent exopolymer particles (TEPs) TEP-protobiofilm Bacteria attachment Biofouling of membrane
ABSTRACT Transparent exopolymer particles (TEPs) are a class of transparent gel-like polysaccharides, which have been widely detected in almost every kind of feed water to membrane systems, including freshwater, seawater and wastewater. Although TEP have been thought to be related to the membrane fouling, little information is currently available for their influential mechanisms and the pertinence to biofouling development. The present study, thus, aims to explore the impact of TEPs on biofouling development during ultrafiltration. TEP samples were inoculated with bacteria for several hours before filtration and the formation of “protobiofilm” (pre-colonized TEP by bacteria) was examined and its influence on biofouling was determined. It was observed that the bacteria can easily and quickly attach onto TEPs and form protobiofilms. Ultrafiltration experiments further revealed that TEP-protobiofilms served as carriers which facilitated and accelerated transport of bacteria to membrane surface, leading to rapid development of biofouling on the ultrafiltration membrane surfaces. Moreover, compared to the feed water containing independent bacteria and TEPs, more flux decline was observed with TEPprotobiofilms. Consequently, it appeared from this study that TEP-protobiofilms play a vital role in the development of membrane biofouling, but unfortunately, this phenomenon has been often overlooked in the literature. Obviously, these findings in turn may also challenge the current understanding of organic fouling and biofouling as membrane fouling caused by TEP-protobiofilm is a combination of both. It is expected that this study might promote further research in general membrane fouling mechanisms and the development of a
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