Living for the Long Haul: Should we be concerned about what we put down our drains? Part 1 of 3

What goes down our drains may come back to bite us


PINE RIVER — In previous columns we discussed the challenges of environmental contamination associated with the trash that ends up in landfills. Now, what about what we put down our drains every day?

Depending on where we live, this sewage either goes to a city sewage treatment plant or is deposited in a homeowner’s septic tank.

In septic tanks, solids settle to the bottom and slowly decompose. The liquid portion, which contains some smaller particles, is pumped into a drain field where it further decomposes. The water either evaporates or percolates into the ground water beneath.

The solid portion, termed sludge, is typically pumped out of septic tanks every three to four years, and is most frequently spread on farm fields as a fertilizer.

Sewage treatment plants process sewage through primary and secondary treatment processes that reduce the majority of the environmentally harmful chemicals in sewage. The liquid portion (i.e. effluent) is then discharged into bodies of water and the solid portion (i.e. sludge) is either placed in landfills or sold as fertilizer.


Whether we use a septic tank or a sewage treatment plant, anything we put down our drains or flush stays right here with us in our local community. Since 99.9% of our sewage is water, toxic products we put down our drains frequently end up in our streams and lakes and, if not, ends up in the fields where our food, or the food for the animals we eat, is raised.

But should we be concerned?

The Minnesota Pollution Control Agency monitors water quality every two years. At present, 25% of Minnesota’s lakes and streams are considered contaminated. This year, 305 more lakes and streams were added to the list of polluted water.

Most are due to an increase in phosphorus that causes algae blooms and may lead to fish kills. And recently, increases in other toxins, like nitrates, mercury, microplastics, the “forever chemicals” PFAS-PFOS, sulfates and bacteria are evident.

So what is in our sewage to be concerned about?

This is a big topic. There are about 30,000 different chemicals that are commonly used in household products. Some of these are nontoxic, some decompose or are removed during sewage treatment, some are diluted once they reach our lakes/streams/aquifers, and some degrade quickly in the environment and thus do not accumulate.

Alternatively, some chemicals remain in the environment for a long time, accumulate in plants and aquatic animals (i.e. termed bioaccumulation), and eventually work their way back up the food chain to us.

In 2018, the Environmental Protection Agency identified more than 350 pollutants in sewage sludge of which 61 are classified as “acutely hazardous.”


Let’s look at some of these hazardous chemicals and see what household products contain them.

First, household cleaning products, including laundry detergents, fabric softeners, bar soap, dish soap and specialty cleaners for the kitchen and bathroom, tend to contain a high concentration of nitrogen and phosphorus and some contain ammonia.

Nitrogen and phosphorus in sewage effluent that is discharged into rivers and lakes can stimulate rapid growth of algae. This reduces water quality and depletes oxygen levels in the water.

When severe, aquatic plants, fish and other aquatic animals suffocate and die, creating a “dead zone." In Minnesota, 25% of our lakes have high phosphorus levels.

Many specialty bathroom and kitchen cleaning products contain bleach or ammonia. Bleach, in sewage, can be converted to organochlorines that are toxic to aquatic life and take hundreds of years to decompose.

Ammonia is converted to nitrates and thus stimulates plant growth, reduces water quality and results in oxygen depletion. Ammonia is also directly toxic to fish causing high death rates, and decreased growth and reproduction levels.

There’s much more to share and we will continue this discussion in part 2.

(References to all factual information quoted provided on request and comments and questions are encouraged:


Douglas J. Weiss and Barb Mann are caretakers/directors of the nonprofit Balsam Moon Preserve in Pine River, a spiritual place of peace, sustainability and renewal.

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