Transparent exopolymer particles (TEPs)-associated protobiofilm: A neglected contributor to biofouling during membrane filtration

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 TEP-protobiofilms. 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 an effective mitigation strategy. (c) Higher Education Press 2020

Automated summary

This study found that transparent exopolymer particles (TEPs) in combination with bacteria-formed protobiofilms play a vital role in the development of membrane biofouling, accelerating the transport of bacteria and leading to rapid biofouling on membrane surfaces. This phenomenon, often overlooked, challenges current understanding of organic and biofouling as the TEP-protobiofilm combination causes membrane fouling. It is suggested that further research is needed to develop effective mitigation strategies for membrane fouling.