Unexpected alleviation of transparent exopolymer particles-associated membrane fouling through interaction with typical organic foulants

Membrane-based treatment of municipal wastewater plays a crucial role in wastewater recycling. Recently, transparent exopolymer particles (TEP) are reported to cause severe membrane fouling, but their fate in municipal wastewater remains largely unknown. Moreover, considering the inevitable interactions between TEP and other components in wastewater, how such interactions affect TEP-associated fouling also deserves in-depth studies. In this work the distribution of TEP in three different municipal wastewater treatment plants was investigated, and TEP were found to commonly exist in the influents (4.8–10.8 mg/L) and could not be completely removed by activated sludge process. Compared to typical organic foulants (e.g., proteins, polysaccharides (TEP-free), and humic acids), TEP at even a low concentration of 0.2 mg/L could cause significant fouling by depressing the flux by 54%. However, an unexpected alleviation of fouling was observed by mixing TEP with these foulants. The interactions between TEP and typical foulants were found to reduce the adhesion energy of TEP, leading to a lower specific filtration resistance of the mixed foulants. This work underscores that the coexistence of multiple foulants does not necessarily induce more severe fouling, and a better understanding of interactions among foulants will facilitate the development of efficient anti-fouling strategies.