Septics systems: A preventable source for microfiber pollution

By Lindsay Cass (more on the author at the end), edited By Jennifer Ferguson

Many rural homes and cottages rely on individual treatment systems known as septic systems to treat household wastewater. Much like large scale, municipal wastewater treatment facilities, household septic systems are designed to clean and purify wastewater before it is discharged back into the environment. And, like larger municipal systems, most individual septic systems are not designed to capture pollutants such as microplastics, including fine microplastic particles called microfibers.

While most people would never dream of flushing plastics down the drain, most of us unwittingly do this every time we wash our clothes and other household items. During the wash cycle, items made from synthetic materials such as polyester, fleece or nylon, shed very tiny bits of plastic less than 5 mm in size (microfibers) that are then discharged into our septic systems along with the rest of our wastewater and, eventually, make their way into the environment.

Septic filter

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.
In the case of groundwater, a recent study by researchers at the University of Illinois sampled well water in both metropolitan areas (surrounding St. Louis) and rural areas (in northwest Illinois), looking for microplastic, specifically microfiber, pollution. Of the 17 water samples drawn from these wells, 16 were found to contain microplastics. The maximum concentration observed in the study was 15.2 plastic particles per litre of water. This is concerning not only because of the environmental effects, but because these are wells people use for their drinking water. As one of the first studies of its kind, the results led researchers to question how microplastics made their way into the groundwater. One conclusion stands out from the rest: septic systems.

Examining other pollutants found also in the wells, the researchers identified many household contaminants consistent with those that flow through septic systems (septic systems are not designed to remove nutrients or chemicals from wastewater, just solids). This suggests that microfibers can flow through septic beds and follow wastewater into the surrounding groundwater. Further research is required to determine the extent and risk of microfiber pollution in groundwater.

Even if septic beds are successful in trapping microfibers, this is not a complete solution because microfibers are detrimental to the overall health of the system. Fibers that are removed during the filtration stage, remain in the septic bed which, in time, will become clogged and will have to be dug up and disposed of. Septic bed waste often ends up in a landfill and, if not done properly, the disturbance of the sand and gravel can lead to further microfiber pollution.

So, what can be done to prevent microfibers from polluting our surface and groundwater?

Filter

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. The filter that GBF is using in the Parry Sound study is the Filtrol 160 from Wexco. GBF has learned that due to additional charges of duty and fees with the product coming from the US, the Filtrol 160 will cost approximately $280-$300 Canadian dollars. We are currently working with the company in trying to reduce the additional fees, if possible, to ensure the product can be readily accessible for Ontarians and other Canadians who want to do their part in protecting our precious freshwater resources! If you are interested in helping, but want to want to wait to see if a solution can be found, please e-mail us your contact info and we will connect with you soon. info@gbf.org 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 water
YES! 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 picture

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.