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.

透明的外聚合物颗粒（TEP）是一类透明的凝胶状多糖，已在几乎每种膜系统的进水（包括淡水，海水和废水）中被广泛检测到。尽管人们认为TEP与膜结垢有关，但目前尚无有关其影响机理以及与生物结垢发展有关的信息。因此，本研究旨在探讨TEP对超滤过程中生物污损发展的影响。在过滤之前，将TEP样品用细菌接种数小时，然后检查“ protobiofilm”（细菌预先定殖的TEP）的形成，并确定其对生物污染的影响。据观察，细菌可以轻松，快速地附着在TEP上并形成原生生物膜。超滤实验进一步表明，TEP-protobiobiofilms充当载体，促进并加速细菌向膜表面的运输，从而导致超滤膜表面生物积垢的迅速发展。此外，与包含独立细菌和TEP的给水相比，使用TEP-protobiobiofilms观察到更多的通量下降。因此，从这项研究中可以看出，TEP原生物膜在膜生物污损的发展中起着至关重要的作用，但不幸的是，这种现象在文献中经常被忽略。显然，这些发现又可能挑战当前对有机污垢和生物污垢的理解，因为由TEP-protobiobiofilm引起的膜污垢是两者的结合。