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Differential impacts of conventional and biodegradable microplastics on treatment performance and bacterial community in sequencing batch reactors
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"Biodegradable" plastics are often assumed to be the eco-friendly choice, but this study found that biodegradable microplastics (PLA) actually disrupted wastewater treatment more than conventional plastics like polystyrene or polyethylene, reducing bacteria's ability to break down waste and potentially allowing harmful microbes to thrive. This matters because wastewater treatment plants help keep our water supply clean, so if biodegradable plastics interfere with that process, it could undermine efforts to protect water quality even as we try to reduce plastic pollution.
Microplastics (MPs) are emerging contaminants in wastewater treatment plants (WWTPs), yet their polymer-specific impacts on biological treatment processes remain poorly understood. This study systematically compared the effects of conventional (Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Polyethylene terephthalate (PET)) and biodegradable (Polylactic acid (PLA)) MPs under identical sequencing batch reactor (SBR) conditions (100 particles/g VSS, 30-day exposure). Conventional MPs induced moderate microbial stress, evidenced by increased reactive oxygen species (~2-fold with PS), but had minimal inhibitory effects on COD removal (83–86 %) and ammonia oxidation (86–92 %). In contrast, PLA significantly affected system performance by reducing the removal of COD and ammonia by 4.3 % and 5.9 %, respectively. PLA also caused suppression (~0.7–0.8-fold as compared to the control experiment) in the production of extracellular polymeric substance (EPS), and abundance in Proteobacteria by ~14.6 %. PLA also led to reduced microbial richness (the Chao1 index) and diversity (the Simpson index), likely due to selective biofilm formation, with potential enrichment of pathogenic taxa. These findings raise concern over the generalized perception that biodegradable MPs are inherently safer and emphasize the need for polymer-specific risk assessments for different MPs found in WWTPs. • Conventional and biodegradable microplastics had distinct impacts on treatment. • Polylactic acid inhibited COD removal (4.3 %) and ammonia oxidation (5.9 %). • Polystyrene microplastics significantly inhibited denitrification (16.7 %). • Conventional microplastics enhanced extracellular polymeric substance secretion. • Polylactic acid and polystyrene induced elevated oxidative stress in sludge.
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"Biodegradable" plastics are often marketed as eco-friendly, but this study found they still disrupt sediment ecosystems, changing the chemistry of organic matter and shifting microbial communities much like conventional plastics do. This matters because these microbial and chemical changes could affect water quality and nutrient cycling, showing that swapping to biodegradable plastics isn't automatically safer for the environment.
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Researchers compared the effects of biodegradable and non-biodegradable microplastics on nitrogen removal in wastewater treatment bioreactors over an extended period. They found that biodegradable polylactic acid particles were actually more harmful than conventional PET microplastics, significantly reducing the efficiency of ammonia removal by damaging beneficial bacteria. The study challenges the assumption that biodegradable plastics are always safer for wastewater treatment systems.
Biodegradable and conventional microplastics affect soil-plant systems through altering microbial community assembly and functions
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"Biodegradable" plastics are often marketed as the eco-friendly choice, but this study found that when they break down into microplastics in soil, they actually harm plant growth and soil health more than regular plastics like polyethylene do, by disrupting the soil bacteria that plants depend on for nutrients. This matters because these microplastics could end up in the crops we eat, and it suggests that switching to "biodegradable" plastics isn't automatically a safer bet for our food supply without more research into how they actually break down in real farm soil.
Response mechanism of non-biodegradable polyethylene terephthalate microplastics and biodegradable polylactic acid microplastics to nitrogen removal in activated sludge system
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Researchers compared how non-biodegradable PET and biodegradable PLA microplastics affect nitrogen removal in wastewater treatment systems. Surprisingly, the biodegradable PLA caused a much larger reduction in ammonia removal efficiency than the conventional PET plastic. The study suggests that even biodegradable plastics can significantly disrupt the microbial processes that wastewater treatment plants rely on to clean water.
The impacts of biodegradable and non-biodegradable microplastic on the performance and microbial community characterization of aerobic granular sludge
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Researchers compared the effects of biodegradable polylactic acid microplastics and non-biodegradable polyethylene microplastics on aerobic granular sludge used in wastewater treatment. They found that high concentrations of both types impaired the sludge's ability to remove organic pollutants, but both actually enhanced nitrogen and phosphorus removal at moderate levels. The study reveals that even biodegradable microplastics can disrupt wastewater treatment processes in unexpected ways.
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