Washing machine filters proving effective in reducing microfibre pollution, study shows

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Wastewater treatment plants are not designed to catch and dispose of microfibre pollution, but a new collaboration is exploring the use of washing machine filters to capture lint that presents a risk for aquatic ecosystems in lakes and oceans.

The collaboration between Georgian Bay Forever (GBF) and the Rochman Laboratory at the University of Toronto became a pilot project that engaged 97 households in Parry Sound, Ontario, to test the laundry machine filters outside of a lab environment, where they had already proved effective.

The community-scale pilot project households captured 6.4 grams of lint per week per filter, preventing an estimated 179,000 to 2,707,200 microfibres per week from going down the drain. These tiny strands of less than 5 mm can be as high as 700,000 per wash load, depending on the amount and the type of materials in the wash.

The project collaborators say they’re inspired by results that could be a practical solution for laundry machines in Canada and the U.S, which can release upwards of 878 tonnes of microfibre pollution to the aquatic environment each year, according to a 2019 study by the Ocean Wise Plastics Lab in Vancouver.

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“We’re excited because this is the first time a lab-proven filter solution has demonstrated positive results in a real-life application,” said Brooke Harrison, co-ordinator of GBF’s Divert and Capture project, in a statement about the findings.

The researchers also found that there was a 41% reduction in the total microfibres found in the final effluent of the Parry Sound wastewater treatment plant during the project, despite the filters representing just 10% of the properties connected to the WWTP.

Researchers noted that they were surprised by the large decrease in effluent microfibres since filters were only installed in 10% of homes. They said a possible explanation for this could be related to “behavioural changes” due to the project’s recruiting efforts and public awareness campaigns. These changes may have included such things as, washing less, washing with cold cycles, or using a washing bag.

The final effluent of the Parry Sound WWTP was collected in four sample periods, researchers noted, and added that the project resulted in less microfibre pollution entering Lake Huron via treated effluent.

In the pilot project study, there were a total of 38 front-loader and 44 top-loader washing machines, with the latter proving more effective at reducing microfibres. The top-loader washing machines captured 1.5x more lint per week.

The study team had set a target of recruiting 100 households, but fell just short. Many households were turned away due to limitations of the filter, including lack of space to mount the filter, inaccessible effluent drains, such as plumbing behind drywall, and accessibility issues where participants could not reach behind their washing machine to empty the filter.

The effectiveness of laundry machine filters recently caught the attention of NDP MPPs Ian Arthur and Jessica Bell, who introduced Ontario Private Member’s Bill 279 in the spring to prohibit the sale of washing machines not equipped with a specified microplastics [microfibre] filter.

According to the GBP collaborative study, washing machine filters are commercially available in Canada at a cost of about $180 to $200. The devices, typically about 38 cm tall, connect to the machine’s discharge hose. The lid can be easily removed to clean the filter.

The device tested in the study was the Filtrol 160, which contains a 100 μm polyester mesh and has a capture rate of 89% of microfibres shed from laundry into wash water by weight. The filter also contains a bypass, meaning that if the filter is full, the water will bypass the filter and prevent flooding.

Participants in the pilot project emptied the filter’s content every one to two weeks using a metal spoon, then stored the material in a pre-labeled sealable plastic bag. Samples from each household were stored in home freezers, then were collected and sent to the laboratory every three to six months for further analysis, the study states.

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