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Impact of Polylactic Acid Microplastics on Performance and Microbial Dynamics in Activated Sludge System
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This study found that polylactic acid microplastics at higher concentrations impaired nitrification and phosphorus removal in activated sludge wastewater treatment systems. Even biodegradable microplastics can disrupt the microbial communities essential for wastewater treatment, potentially reducing the quality of treated water discharged to the environment.
A large number of microplastics (MPs) have been found in various stages of wastewater treatment plants, which may affect the functional microbial activity in activated sludge and lead to unstable pollutant removal performance. In this study, the effects of different concentrations of polylactic acid microplastics (PLA MPs) on system performance, nitrification and phosphorus (P) removal activities, and extracellular polymeric substances (EPS) were evaluated. The results showed that under the same influent conditions, low concentrations (50 particles/(g TS)) of PLA MPs had no significant effect on effluent quality. The average removal efficiencies of chemical oxygen demand, phosphate and ammonia were all above 80%, and the average removal efficiencies of total nitrogen remained above 70%. High concentrations (200 particles/(g TS)) of PLA MPs inhibited the activities of polyphosphate accumulating organisms (PAOs) and nitrifying bacteria. The specific anaerobic P release rate decreased from 37.7 to 23.1 mg P/(g VSS·h), and the specific aerobic P uptake rate also decreased significantly. The specific ammonia oxidation rate decreased from 0.67 to 0.34 mg N/(g VSS·h), while the change in specific nitrite oxidation rate was not significant. The dosing of PLA MPs decreased the total EPS and humic acid content. As the concentration of PLA MPs increased, microbial community diversity increased. The relative abundance of potential PAOs (i.e., Acinetobacter) increased from 0.08% to 12.57%, while the relative abundance of glycogen accumulating organisms (i.e., Competibacter and Defluviicoccus) showed no significant changes, which would lead to improved P removal performance. The relative abundance of denitrifying bacteria (i.e., Pseudomonas) decreased from 95.43% to 58.98%, potentially contributing to the decline in denitrification performance.
More Papers Like This
Impacts of Polylactic Acid Microplastics on Performance and Microbial Dynamics in Activated Sludge System
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Researchers examined the effects of polylactic acid (PLA) microplastics at different concentrations on activated sludge system performance, including nitrification, phosphorus removal, and extracellular polymeric substances (EPS). The study found that PLA microplastics disrupted microbial activity and pollutant removal performance in wastewater treatment under comparable conditions.
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.
The microbial response to biodegradable polylactic acid microplastics during anaerobic fermentation of waste activated sludge
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Polylactic acid (PLA) microplastics — often assumed to be benign because they are 'biodegradable' — were found to inhibit the breakdown of organic matter in wastewater sludge by 5–18%, disrupting microbial communities and key enzymes. The result challenges the assumption that biodegradable plastics are environmentally safe once they enter wastewater treatment systems.
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.
Laboratory-scale study of a biodegradable microplastic polylactic acid stabilizing aerobic granular sludge system
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Researchers found that adding biodegradable polylactic acid microplastics to aerobic granular sludge systems at low-to-moderate concentrations actually stabilized granule formation and improved pollutant removal by stimulating extracellular polymer secretion.
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