What Goes Down Your Sewer?
< HABIT: Not being careful about what I put into the sewer >
When I do the wash, the laundry detergent, and plus a little bit of the fabric, ends up in the sewer. When I wash the floor and pour the dirty water into the sink, the floor cleaning liquid ends up in the sewer. If I put unused medicine into the toilette, it ends up in the sewer. The material that I put into the sewer goes to a sewage treatment plant, which may or may not fully remove what I put into the sewer before it is deposited into a river or the ocean. What exactly does the sewer I am connected with remove?
Why does this matter?
Sewers take the material we put down the drain, process it, and discharge the water back into a river or into the ocean. They are not 100% effective of removing all undesirable contamination form the discharged water. Waste water treatment plants are sophisticated systems that improve on the operation of the basic home sceptic system.
If you live in a suburban or rural location, you might have a sceptic system. In this system your toilet, sink drains, dishwasher and clothes washing machine are connected to the sceptic system. The first step in the system is a tank in which bacteria digest the solids at the bottom of the tank turning them into liquid. This liquid is then sent out into a drainage field where it enters the soil. Microbes in the soil then continue to break down organic matter in the liquid. Owners of sceptic systems are advised to only use cleaners that are sceptic system safe and only put things into the sceptic system that are bio degradable. Some chemicals harm the bacteria that digest the biodegradable solids, requiring the periodic addition of septic system bacteria. Items that are not biodegradable stay in the tank until the tank is pumped out.
The waste we put into a municipal sewer is transported to a waste treatment facility that uses microbes to digest the waste material. Any solids that remain should be transported to a landfill and the water that is separated placed back into a river which ultimately flows to the ocean. Usually this water is disinfected before being discharged so as not to put harmful bacteria into our rivers which can endanger both people and marine life. Many systems are not designed to remove all potential pollutants. (See References 1,2, 3)
Waste treatment facilities remove many of the pharmaceuticals and the larger pieces of plastic and other solid matter. However, the contaminants that make it through the system can have negative effects on the river ecosystem and downstream users of the water (4). The next town down the river might take that water, process it, and use it as the town’s water source. People might swim boat or fish in the water. Studies are starting to see traces of pharmaceuticals in the water supply. There is evidence that some chemicals (endocrine disrupters) in the water that are affecting fish (5) but so far little evidence of health effects on humans (6,7).
Your washing machine is also connected to the sewer. We are familiar with the lint that is captured in the dryer, but some of the fabric is also removed in the washer and enters into the waste water of the washing machine. If the fabric contains plastic (like acrylic, nylon, rayon, . spandex and polyester) small microfibers can be liberated during washing . (8, 9). Some of these small pieces of fiber are eliminated by waste treatment, but not all. Recent studies are finding microfibers not only near the waste treatment plants discharge, but throughout the ocean.
Plastic can take a long time to decompose in the ocean (11), but I do not have a good estimate for the lifetime of microfibers as opposed to other plastics. Being small, microfibers are easily ingested by filter feeders, which include animals as large as whales and as small as shrimp. (10) These filter feeders are then eaten by other animals farther up the food chain, including humans. Microfibers have already been found in deep ocean animals (10). In addition microfibers absorb some organic pollutants, which could deliver these toxins to the animals that ingest them. This is an active area of research and much work still remains to be done, but enough research has been done to warrant lifestyle changes to protect the environment. (8)
Patagonia is one company that seems to be taking the situation seriously and have issued a report on their efforts that is worth reading.
> New Habits <
- Give unused pharmaceuticals back to the pharmacist who can dispose of them correctly.
- Use cleaners and detergent that are septic system safe or even better, are known to be bio decomposable, even if you are connected to a sewer.
- Avoid clothing with plastic fibers. Cotton and wool also create microfibers, which may have dyes and additives that are undesirable, but the fibers themselves will decompose much faster than plastic microfibers.
- Wash your clothing with plastic microfibers only when they are dirty. Consider using one of the new devices designed to capture the microfibers (see the Patagonia reference for links to some microfiber catching devices).
Written by David Larrabee
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References on Sewer Systems
References on Pharmaceuticals in the Water
References on Microfibers
9. U. Pirc et. al. “Emissions of microplastic fibers from microfiber fleece during domestic washing” Environ Sci Pollut Res (2016) 23:22206–22211
10. Taylor, M. L. et al. "Plastic Microfibre Ingestion by Deep-sea Organisms." Sci. Rep. 6, 33997; doi: 10.1038/srep33997 (2016).
11. Beginner's Guide to the Plastic Problem in the Ocean