Thus, both wastewater treatment plants and household septic systems can be a significant source of micro-pollutants which can contain a host of harmful chemicals. The most common type of septic system used in Ontario is composed of a septic tank and a leaching bed. All wastewater from homes or cottages that are not connected to municipal water treatment systems flows into individual septic tanks strategically located to maximize functioning while protecting nearby bodies of surface water. The heavier solids settle to the bottom of the tank while fatty substances, such as soap suds and oils, float to the surface where they gradually form a thick layer of scum. Meanwhile, bacteria in the tank get to work decomposing the solids that sink to the bottom which, over time, turn into a sludge. When both the lighter layer of solids at the top and the sludge at the bottom reach a certain size and/or level, it’s time to pump out the tank, typically every 3-5 years, to ensure proper functioning and prevent back-ups. In conventional systems, approximately 30-50% of wastewater treatment is completed in the septic tank. Although some microfibers may get trapped in either the sludge or scum, their size and weight mean that they can also remain in the wastewater which flows out of the tank and, eventually, into the leaching bed. Due to the very tiny nature, it is impossible to remove all microfibers from wastewater treated in both septic tanks and municipal treatment plants. Microfibers that settle into the bottom sludge are removed when the septic tank is pumped out. From here, the sludge may be disposed of in a landfill, or transported to a municipal wastewater treatment plant where it undergoes further treatment along with the bio-solids generated by the facility. The microfibers in these bio-solids still pose a threat to the environment as they are often applied on land as fertilizer on agricultural fields. Although the organic material in the bio-solids is beneficial to the crops, plastic microfibers that remain in the mix become a source of environmental pollution that won’t biodegrade. During the next stage of septic system wastewater treatment, the remaining liquids in the tank typically flow through an effluent filter before being pumped into a series of pipes that distribute wastewater throughout a septic (or leaching) bed. A septic bed is composed of porous materials, such as gravel and sand, which act as filters between the liquid and the surrounding ground water system. The size of a septic bed and the amount of materials present will depend on the natural soil type present. For example, well drained, permeable soils don’t need as large a septic bed as do areas that are less permeable.In conventional septic systems, approximately 50-70% of wastewater treatment is completed in the septic bed where any remaining particles are removed from the water. However, because they are often too small to be filtered out by gravel and sand, microfibers can flow right through and follow the water into the surrounding environment, including into surface and groundwater. Surface water, often a source of drinking water for cottagers, may be contaminated with microfibers, making unsuspecting cottagers susceptible to this type of pollution.
So, what can be done to prevent microfibers from polluting our surface and groundwater?
One solution is to deny them entry into our septic and municipal wastewater treatment systems. This can be done by installing a filter on washing machines to trap the fibers and prevent them from being discharged into wastewater. Filtration devices are generally made with a fine mesh which enables them to capture more and even smaller fibers than septic or treatment systems. These simple filtration devices are a good investment, and much easier and cheaper to clean than septic beds, and the lint collected can be easily disposed of responsibly. With increasing focus on the extent of plastic pollution, we will only become more aware of how it is affecting our lives. In the case of microfiber pollution, it is important to consider options such as washing machine filters to protect not only the environment and the waters of Georgian Bay, but also our health.
Washing Machine Filter FAQs
Where do I get one?There are commercial options available in the marketplace that you can research. U of T Rochman lab tested 2 outside washing machine filters. The Lint Luv'r and the Wexco FIltrol 160, and found they were 87 to 89% effective at capturing fibers. Both are available in Canada if you search online (if you buy outside of Canada, you will be subject to fees if you import them). Last time we looked they cost anywhere from $180 to around $220 BEFORE installment and shipping. For the Divert and Capture project, GBF is installing the Filtrol 160 from Wexco into Parry Sound residences for our filter study. Here is GBF's Amber using it :(link)
How does it prevent flooding and damage if the filter bag is used up?GBF cannot be responsible for the functioning of products people buy or corporations make. Here is a response from Wexco who makes a filter called the FILTROL "The bypass “system” is actually built into the rim of the filter bag. If the owner forgets to clean out their filter and the bag fills up to the top of the filter bag it will simply just flow through the 4 oblong holes along the rim and down into the canister. Of course that water will not be filtered and defeats the purpose of the unit but it will prevent flooding and damage to the washing machine."
In addition to the environmental benefits, how does it help save my drainage pipes and septic?From WEXCO, makers of the FILTOL, "The Filtrol 160 is a patented, reusable filter that attaches to your washing machine discharge hose. It removes non-biodegradable fibers like polyester, hair, sand, pet fur, and nylon from your washing machine’s wastewater, keeping it from going into and clogging your drainpipes. It preserves your plumbing and septic while also protecting the environment. Fibers that stay in the tank can still find their way into the environment when tanks are cleaned and pumped. Fibers that migrate into the drain field may be trapped in the soil, but then create a premature plugging layer. So either way filtering laundry when on a septic system is a very good practice and can increase the life span of the system and keep more plastic fibers out of the environment. "
Can I get more information on microplastic pollution and GBF's efforts to mitigate it getting into the waterYES! Check out this link and learn about the project "Divert and Capture: the fight to keep microplastics out of our water". There are ways you can help us with this project.
About the author
Lindsay Cass is a Bioresource Engineering graduate from McGill University and winner of the Quebec Engineering Competition. In her final year, Cass and two other students designed a washing machine filter to prevent microfiber discharge into waste water. Their invention also earned the design team third place in the Canadian Engineering Competition and a Canadian Society of Biological Engineers (CSBE) Design Award.