Why Does Wastewater Need to be Treated?

Above, untreated wastewater pollutes a waterway in India.

If you’ve been following along, you’ll know we’ve been doing a series of posts explaining how wastewater is treated. In our last one, we talked about how solids are removed from wastewater, then sent to the primary settling tanks for stabilization and treatment.

What we haven’t covered yet is why wastewater needs to be treated – after all, the ecosystem takes care of animal waste, right?

The U.S. Geological Survey sums it up nicely: “Nature has an amazing ability to cope with small amounts of water wastes and pollution, but it would be overwhelmed if we didn’t treat the billions of gallons of wastewater and sewage produced every day before releasing it back to the environment. Treatment plants reduce pollutants in wastewater to a level nature can handle.”

Raw sewage contains a host of harmful substances, including bacteria, viruses, parasitic organisms, intestinal worms, and even molds and fungi. All of these microorganisms are shed by the body and expelled along with human waste. Although even healthy humans shed pathogens, those who are sick add even more to the waste stream.

The diseases caused by these microorganisms may range in severity from mild gastroenteritis (stomach cramps and diarrhea) to life-threatening ailments such as cholera, dysentery, infectious hepatitis, severe gastroenteritis, and more. There are chemicals and medications in wastewater, too — ranging from cleaning solutions used in bathrooms to things that should never have gone down the drain in the first place.

Additionally, wastewater sludge is an excellent food source for bacteria and fungi that grow on decaying organic matter. These microorganisms generally use oxygen when they break down organic waste.

If the Kline’s Island treatment plant did not exist and the wastewater was discharged directly into the Lehigh River, the dissolved oxygen required to support aquatic life in the river would be used up — the same thing that happens during algal blooms.

Fish and other organisms would die off, and the river would be transformed into a toxic flowing cesspool. Disease would run rampant. The water would be undrinkable, the river would be unsuitable for recreational use, and our quality of life would rapidly decline. The contaminated water would start a domino effect — ecosystems that rely on the river would collapse, and the polluted water would contaminate other water supplies, too.

Furthermore, the banks of the river would be strewn with 54 cubic feet per day of things that should never have been flushed in the first place: feminine hygiene products, condoms, disposable wipes, toilet paper, rags, paper towels and more!

Treatment mitigates these consequences and protects the environment. Treated water, called effluent, can be safely discharged into our waterways. Treated solids, called sludge, are returned back to the environment in the form of soil amendments used in the agricultural industry.

Wastewater treatment plants play a crucial role in safeguarding our ecosystem and our health. We’ve come to take them for granted, but without them, our daily lives would look a lot different!


For the rest in our Behind the Scenes series, please see:

Wastewater Treatment Starts with Screening Out Items That Don’t Belong

Pump it Up: The Role of LCA’s Giant Wastewater Movers

Clean and Green: How Waste is Turned into Energy at Kline’s Island

Sludge 101: How Solids Are Removed From Wastewater

The Sludge Report: What Happens After Treatment?

How Is Liquid Waste Treated? It’s All About Biology

Tertiary Nitrification: How Ammonia Is Removed From Wastewater

Disinfection and Testing — the Final Steps in Wastewater Treatment