Surfactants facilitate microbial growth on the surface of microplastics in biological wastewater treatment

Microplastics are prevalent in wastewater treatment plants and offer a substrate for microbial colonization. With the aging of microplastics, the community of colonized microorganisms can be restructured. Furthermore, substantial surfactants in wastewater can modulate this community by altering the surface properties of microplastics. This study examined the influence of polypropylene and polylactic acid microplastic particles, along with rhamnolipids and primary alcohol ethoxylate surfactants, on microbial colonization and the aging processes of microplastics. The microbial biomass and abundance were significantly higher on the surface of polylactic acid compared to polypropylene. Rhamnolipids reduced the nitrifying and denitrifying bacteria on polypropylene by 21.26 %, while primary alcohol ethoxylate decreased microbes capable of degrading complex organic compounds on polylactic acid by 25.90 %. The proportion of microorganisms capable of degrading complex organic pollutants in the suspended microbial community decreased by 19.40 % with polylactic acid present and 17.64 % with polypropylene. Microbial colonization accelerated microplastic aging, particularly for PLA, thereby increasing the leaching of components and elevating environmental risks. These findings highlight the interaction between microplastics and surfactants in shaping microbial community structures and affecting biological wastewater treatment.