The world's largest wastewater treatment plant is in Stickney, Ill.

STICKNEY, Ill. -- The Metropolitan Water Reclamation District's wastewater treatment plant in near Stickney, Ill. has many names, both formal and informal.

The formal name is the Stickney Water Reclamation Plant. Gizmodo Magazine has a more appropriate name for the 413-acre facility: "The Crappiest Place On Earth."

But is it best known as the world's largest wastewater treatment plant, serving over 2.4 million people in Chicago and 46 suburban communities.

"What wastewater is essentially is any of the water that you use in your home, industry or wherever that goes down the drain, and we essentially treat it here," said Adam Gronksi, plant manager. "We treat it to a standard where basically it's good and safe for the fish and the aquatic species of the waterway that we discharge to."

The massive facility has been the world's largest wastewater facility since it opened in 1930, cleaning an average of 700 million gallons of water per day. In months like January and February, however, when melted snow and rain can add to the wastewater component, or in other rainy months during the summer, the facility can treat up to 1.44 billion gallons per day.

"For almost 100 years, this has been a tried and true method of wastewater treatment," said Joe Cummings, operations manager.

Nearly 100 years after its inception, the Stickney plant remains the world's largest for treating wastewater, according to the U.S. Water Alliance. But it now has rivals; in North America, treatment facilities in Boston, Detroit and Montreal all have the ability to treat over 1 billion gallons.

And globally, the Bahr El-Baqar wastewater treatment plant in northwest Egypt, which opened in 2021, is expected to surpass the Stickney plant. The Guinness Book of World Records already lists it as the world's largest wastewater treatment plant.

But for now, there is nothing like Stickney, especially in terms of efficiency in dealing with wastewater.

"It keeps our cities and towns in our region livable because this is a point source where lots of flow is coming in, lots of flow going out," Cummings said. "It's all done in one small step, highly efficient."

The story of Chicago's wastewater starts at your home or office. The facility is split into two plants: the western side, which opened in 1930, and a southwest side, which opened in 1939. As you flush the toilet, wash dishes, or shower, the used water begins its journey towards the plant, which takes up more than 40 percent of the land in Stickney, and overlaps into neighboring Cicero (it actually has a Cicero address).

Once there, the wastewater is subjected to the intake and pre-treatment process. This includes what is known as the "coarse screening," where the wastewater entering the plant passes through large screens that filter out debris like rags, plastics, and other large objects.

After that, the wastewater enters large primary settling tanks. Here, it sits still for about two hours, allowing heavier organic solids and fats, oils, and grease to float to the surface or sink to the bottom. These materials are skimmed off or scraped and sent for further processing. This primary treatment removes around 70-80 percent of the solids.

The wastewater then goes through the pumping and grit removal process. The wastewater is then pumped up from sewer level to flow by gravity throughout the treatment process. During this ascent, air is injected into the water in aerated grit tanks, causing heavy materials like sand and gravel to settle and be removed.

Millions of microorganisms feast on the remaining organic matter in the water. To thrive, these microbes need oxygen, so air is constantly pumped into the tanks, creating a bubbly, frothy environment.

"We're using naturally occurring bacteria to actually do the work to purify the sewage that's coming in," Cummings said. "We're actually using oxygen, air that we compress in order to give the bacteria the oxygen that it needs to survive.

After the microbes have done their job, the water flows into secondary settling tanks. These tanks allow the microorganisms to clump together and settle to the bottom, leaving the cleaner water on top. To ensure the safety of the treated water, it is disinfected with ultraviolet light or chlorine to kill any remaining harmful bacteria.

Finally, the clean, treated water meets its final destination: the Chicago Sanitary and Ship Canal.

"Under the right conditions, you can see that there's actually goldfish living down there in the tank (that feeds into the canal)," Cummings said. "That's how clean it is. It's not drinkable, we dont produce drinking water here, but its clean enough for living species in the waterways that we feed to."

After the treated water in the plant is discharged into the Sanitary and Ship Canal, it flows into the Des Plaines River, which in turn flows into the Mississippi River.

The entire wastewater treatment process at the Stickney WRP takes approximately 12 hours, a remarkable feat considering the transformation it achieves.

But the Stickney plant goes beyond simply cleaning wastewater. It also recovers valuable resources from the wastewater process.

Most notably, the organic solids removed during treatment are transformed into biosolids, a nutrient-rich soil amendment used for landscaping and agriculture. Phosphorus is also extracted from the wastewater and converted into a slow-release fertilizer, "Crystal Green," reducing reliance on mined phosphorus.

"This technology is not new; it's been going on for a long time," Cummings said. "It's a tried and true method of treatment."