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Microplastics and nanoplastics in water: Improving removal in wastewater treatment plants with alternative coagulants

The Canadian Journal of Chemical Engineering 2026 Score: 40 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.

Mathieu Lapointe, Sinan Abi Farraj, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Sinan Abi Farraj, Sinan Abi Farraj, Mathieu Lapointe, Sinan Abi Farraj, Nathalie Tufenkji Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Rafael S. Kurusu, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Mathieu Lapointe, Nathalie Tufenkji Nathalie Tufenkji Mathieu Lapointe, Mathieu Lapointe, Rafael S. Kurusu, Rafael S. Kurusu, Rafael S. Kurusu, Rafael S. Kurusu, Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Rafael S. Kurusu, Mathieu Lapointe, Mathieu Lapointe, Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Mathieu Lapointe, Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji Nathalie Tufenkji

Summary

Laboratory tests showed that conventional aluminum sulfate (alum) coagulant becomes much less effective at removing micro- and nanoplastics from water at pH above 7.8—a common condition in municipal wastewater—but switching to aluminum chlorohydrate largely restores removal efficiency. This matters because wastewater treatment plants are a critical barrier preventing microplastics from entering rivers and oceans, and many currently use alum. The study gives water utilities a practical, drop-in solution to significantly improve microplastic capture under challenging water chemistry.

Study Type Environmental

Abstract Coagulation, flocculation, and settling have been shown to be important processes to remove micro‐ and nano‐sized plastic contaminants. However, limited research has been conducted to assess how challenging water chemistry characteristics (including water pH and presence of wastewater colloids) and treatment conditions (such as settling time, coagulant type, flocculant type) impact the removal of these contaminants. Our results show that plastic removal declines at higher pH values using conventional alum as a coagulant. Removal of pristine and aged nanoplastics dropped from 64% and 76%, respectively, at pH 7 to below 20% at pH >7.8. Similarly, polyester microfibre removal decreased from 97% at pH 7 to 85% at pH 8.6. Replacing alum with alternative coagulants resulted in improved plastic contaminant removal at pH >7.8 with an average microfibre removal of 94% (aluminium chlorohydrate) and an average nanoplastic removal of 66% (aluminium chlorohydrate + pDADMAC). Quartz crystal microbalance with dissipation monitoring measurements revealed that aluminium chlorohydrate coagulant species yield a thicker deposition layer on negatively charged surfaces compared to alum. Experiments with alternative flocculants revealed that anionic flocculants result in rapid nanoplastic removal, while cationic flocculants can achieve similar removal given sufficient settling times. Results from our study reveal how coagulant and flocculant selection and environmental conditions, including pH and interactions with wastewater colloids, can affect plastic contaminant removal during primary treatment. Our study also revealed that municipalities can enhance nanoplastic and microfibre removal using alternative aluminium‐based coagulants under challenging pH conditions.

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