by Paige Jessup, Climate Change Resiliency Intern
Our septic systems are often something that are out of sight and out of mind. Some people may not even know what a septic system is, especially if you live in a city or town that has a wastewater treatment plant. No matter where you live, we should all be thinking about where our wastewater goes when we flush.
Where is Untreated Wastewater Going?
If you live in an area that is connected to a municipal sewer system, the water that is going down your drains travels through underground pipes to a wastewater plant for treatment. From there, it eventually returns to the local water system, like a river. If you live in a rural area, a small community, or have a cottage, you probably have your own septic system. Septic systems are on-site wastewater treatment units that fulfill the role of municipal sewers in rural areas. Anything that goes down the drain — every shower drip and toilet flush — flows to your septic system. A septic system is made up of a tank, a network of pipes, and billions of organisms that process your waste.
A septic system works by collecting wastewater in the septic tank, where it is separated from liquid and solid. The partially treated water then goes out of the septic tank through an outtake pipe that takes it to a distribution box, where it then gets evenly distributed through to a network of pipes that lie buried in the trenches of the drain field. The drain field allows the water to filter through the soil and by further bacterial action removes the remaining particles in the wastewater. When it finally reaches the water table, the wastewater has been treated (Regional District of Nanaimo, 2011).
Why do Septic Systems Fail?
There are a few ways a septic system can fail. The first way is by using more water than the soil can absorb, causing the water to be pushed back through the system into the house. A second way is improper design and construction, leading to a system usually failing in a few months because they are inadequately sized, installed in impermeable soils, or are not properly constructed. Thirdly, lack of maintenance; a septic tank should be pumped out every three years to prevent clogging of the soil absorption field. Maintenance includes checking the condition of your septic tank’s “T” fittings, also known as baffles, at the inlet and outlet. This is especially important because the outlet baffle prevents the floatable scum from moving out into the soil absorption field. No matter how your system may fail, it leads to the possibility of contaminated water runoff flowing into either ground water or local water bodies.
Impacts on Freshwater
Improperly treated wastewater may contain bacteria, viruses, phosphorus, and nitrogen, all of which can wreak havoc on aquatic environments. High levels of nitrogen in waterways have severe impacts on shoreline ecosystems. Nitrogen acts as a fertilizer, causing algae blooms that deplete the dissolved oxygen in the water. This leads to plant mass decomposing which uses up the oxygen, often causing mass die-offs of fish, invertebrates, and other aquatic life (Dias, 2021). Sewage discharge has also been associated with rising temperatures in water bodies, which has ecological impacts on aquatic life. Temperature also affects the solubility of the water and the available oxygen in it (Bhat et al., 2021).
Other Environmental Impacts
Along with the impact to freshwater, improperly treated wastewater can also affect biodiversity in terrestrial ecosystems by changing soil chemistry, plant and microbial community structure, prevalence of certain plant species, and susceptibility of some plant species to herbivory, disease, and cold stress.
Each aquatic plant species has specific morphological and physiological characteristics that make it thrive in particular locations or areas with very specific characteristics present (Tilman, 1988). With the addition of nutrients, the natural balance of an ecosystem is changed which can lead to ideal conditions for non-native species. This shift in aquatic plant diversity and species composition has cascading impacts throughout the entire food chain (Smith et al., 1999).
Keep up on Maintenance
It is important to keep up on the maintenance of your septic system. By inspecting it frequently, conserving water so less enters the tank, properly disposing of waste, and maintaining your drain field, we can all work together to protect the health of lakes, rivers, and shorelines. Learn some best practice do’s and don’ts in this blog post!
This blog is part of a larger education toolkit about septic systems. To access all of the resources from the toolkit, visit watersheds.ca/septics.
Your $5 donation today will ensure more landowners, municipalities, and families have access to the resources they need to protect Canada’s freshwater – donate now!
References
Dias, M. (2021, April 28). How do septic systems pollute coastal watersheds. Surfrider Foundation. Retrieved from https://www.surfrider.org/news/how-do-septic-systems-pollute-coastal-watersheds
“How Septic Systems Work.” (2011). Regional District of Nanaimo. https://www.rdn.bc.ca/dms/documents/wastewater-services/septicsmart/septicsmart_kit.pdf
Smith, V.H., Tilman, G.D., Nekola, J.C. (1999). Eutrophication: impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems. Environmental Pollution. 100(1–3), 179-196, https://doi.org/10.1016/S0269-7491(99)00091-3.
Tilman, D. (1982). Resource competition and community structure (Vol. 296). Princeton University Press.
“Why Do Septic Systems Fail?” (n.a.). Galveston County Health District. Retrieved from https://www.gchd.org/about-us/environmental-health-services/consumer-health-services/on-site-sewage-facilities/why-do-septic-systems-fail.