Microfibers originating from clothing have been found in considerable quantities in laundry wastewater. However, our understanding of which microfiber types are more susceptible to release into the environment after wastewater treatment is limited. In the first part of this study, we investigated the fate of microfibers in a conventional wastewater treatment process. The removal rate of microfibers during wastewater treatment (coagulation and flocculation) as would be the case after laundering was found to be between 95 – 99 %. We found that acrylic fibers have a higher removal efficiency compared to polyester. We also evaluate the use of an optimized treatment protocol and alternative coagulants on microfiber removal. While a considerable fraction of clothing microfibers are expected to be removed during wastewater treatment, some microfibers will be released into the environment with treated waters. These microfibers released to surface waters will experience natural weathering conditions (e.g., UV photooxidation and varying temperatures) that may impact their properties and fate (e.g., settling) in the environment. Thus, in the second part of this study, we examined the settling velocity of microfibers exposed to UV radiation in filtered and unfiltered surface waters. The settling behaviour of the UV-weathered fibers was also monitored under cold temperature conditions representative of Northern climates. UV weathering facilitated the attachment of suspended solids on polyester microfibers which significantly increased their settling rate. The observed impact on microfiber settling behavior could potentially limit microfiber transport in surface waters. The results of this research motivate the need for further studies to understand the impact of environmental conditions on microfiber properties and behavior that are needed to build robust microplastic fate and transport models.

Microfiber fate in simulated wastewater treatment and upon release with treated wastewaters

ACS Fall 2021

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