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Particle size matters: Unraveling the impact of microplastic heteroaggregates on algal–bacterial consortium in wastewater treatment
Summary
Scientists found that tiny plastic particles in wastewater can mess with the natural cleanup crew (algae and bacteria) that treats our water, and smaller plastic bits actually cause more damage than bigger ones, harming the microbes and leaving more waste behind. This matters because it suggests wastewater treatment plants may struggle to fully filter out microplastics, meaning more of these tiny particles could end up back in our environment and water supply than we'd like.
Microplastics are prevalent in municipal wastewater, posing risks to health and the environment. When treated by an algal–bacterial consortium, microplastics interact with organic matter and microorganisms to form heteroaggregates, impacting treatment efficacy. In our study, particle size significantly influenced microplastic behavior within the consortium. Smaller microplastics (25PS) caused oxidative cell damage, formed compact heteroaggregates with strong shading effects, inhibited microbial proliferation, and increased effluent organic content due to the release of intracellular substances. In contrast, larger microplastics (100PS) formed weaker heteroaggregates and primarily affected organic matter adsorption, reducing effluent organic content. Notably, 100PS upregulated K01915 expression in Chlorella , enhancing nitrogenous organic matter degradation, while 25PS suppressed K01915 and key carbon metabolism genes (K00626, K00382, K00627, K00058, K00873, K00615), impairing organic carbon hydrolysis. During sludge separation, microplastic heteroaggregates improved sludge settling efficiency, with smaller particles settling faster. However, microplastics, irrespective of size, increased solids in sludge or supernatant, complicating sludge treatment and elevating ecological risks associated with effluent.