An international benchmark for wastewater treatment

A internationally recognized leader in wastewater treatment and stormwater management, the MWRD treats an average of 1.3 billion gallons of wastewater each day via its seven water reclamation plants.

Digester

The MWRD is the wastewater treatment and stormwater management agency for the City of Chicago and 128 suburban communities throughout Cook County. We work every day to mitigate flooding and convert wastewater into valuable resources like clean water, phosphorus, biosolids and natural gas. If you live within our service area, the water that goes down your toilet, sinks and drains eventually comes to us to be cleaned.

We treat wastewater from homes and businesses throughout our 882.1-square-mile service area in addition to stormwater from some communities. All of this wastewater and stormwater flows through local sewers into our interceptors before flowing to our water reclamation plants where we clean the water and recover resources using a combination of physical, biological, and sometimes chemical, treatment processes. Nearly 450 billion gallons of wastewater is treated by our seven facilities every year.

The MWRD owns and operates one of the world’s largest water reclamation plants (Stickney plant, located in Cicero) in addition to six other plants and 22 pumping stations.

The MWRD's total wastewater treatment capacity is over 2.0 billion gallons per day.

Modern facilities

The MWRD’s seven water reclamation plants are modern facilities that provide excellent treatment for residential and industrial wastewater – meeting permitted discharge limits virtually at all times. The treatment process is protected by a pre-treatment program to guard against hazardous substances and toxic chemicals. These are strictly regulated pursuant to federal and state requirements. The MWRD routinely monitors all industries and non-residential sources to assure that wastes are disposed of in an environmentally responsible and lawful manner. Click here to watch a video of our O’Brien WRP.

Tour

Contact our Office of Public Affairs at Tours@mwrd.org to schedule a tour of one of our water reclamation plants (WRPs) and see where your used water goes. We offer facility tours for groups of up to 30 Tuesday - Friday. Scheduled on an as-needed basis, tours may begin between 9 a.m. and 1 p.m. and are open to adults of all ages and students in grade seven or higher. Please allow approximately two hours for your tour.

Tours are available at our following treatment facilities:

How do we know we’re doing a good job?

Wastewater treatment facilities are regulated under the Environmental Protection Agency’s National Pollutant Discharge Elimination System (NPDES) permit program. NPDES permits set rigorous standards that the water from the plant must meet. The National Association of Clean Water Agencies has given each of our water reclamation plants the association’s highest awards for compliance with these standards. We also see the benefits of our work resulting in increased recreation on the waterways, such as kayaking and canoeing, a rebounding aquatic habitat and increases in fish species. We’re reducing energy use at our facilities with a goal of reducing greenhouse gas emissions, and we’re recovering valuable resources and expanding the use of biosolids throughout the region.

Interesting things collected during the treatment process

Some of the things that have turned up in the coarse screens of our plants over the years include:

  • A 14″ diameter snapping turtle
  • Car wheels and tires
  • 2x4 studs
  • Super balls
  • Parking blocks
  • Money
  • A huge ball of rope
  • A 50 foot extension cord
  • Mop heads
  • Tree branches
  • Two opossums
  • ID card of a man from Argentina
  • A bowling ball (with no pins)
  • Fish
  • A prosthetic leg

A continued commitment to protect our water environment

In 1919, the MWRD Board of Commissioners passed an ordinance committing the agency to the construction and operation of sewage treatment plants to protect and preserve Lake Michigan, our source of drinking water for the millions of people living in Chicago, Cook County communities and neighboring counties today.

The boundaries of the MWRD include more than five million residents of Cook County. These people, plus the thousands of industries within the MWRD, generate 1.4 billion gallons of wastewater each day.

While exercising no direct control over wastewater collection systems owned and maintained by cities, villages, sewer districts and utilities, the MWRD does control municipal sewer construction by permits outside the city of Chicago. It also owns a network of intercepting sewers to convey wastewater from the local collection systems to the water reclamation plants.

The MWRD is divided into seven service areas. Each sends its wastewater to a different treatment plant through the sewer systems. These seven plants range in capacity from 1.2 billion gallons per day at the Stickney Plant, to 2.3 million gallons per day at the Lemont Plant.

Treatment Processes

Local sewers from each of the 125 municipalities within MWRD boundaries connect to the large MWRD interceptors which gather the wastewater and convey it to one of the treatment plants. Here it undergoes a number of cleaning processes:

Primary Treatment

Primary treatment consists of removing contaminants by some physical mechanism:

  1. Screens remove debris which can clog the machinery. The wastewater flows into chambers where heavy solids such as sand and grit sink to the bottom; these solids are washed before being deposited in a sanitary landfill.

  2. It then goes to a primary settling tank where a significant portion of the organic solids settle to the bottom while fats, oils and grease rise to the top.

  3. Revolving "arms" simultaneously scrape the primary (untreated) solids from the bottom and skim the grease from the top.

Secondary Treatment

Secondary treatment usually employs a biological process whereby a large population of micro-organisms help convert the remaining organic material into other forms which can be easily separated into solids and a clear liquid.

The primary affluent flows through a series of large rectangular aeration tanks which have been seeded with bacteria and other microbes (tiny organisms which exist naturally in plant and animal life). Filtered air is pumped through the liquid to enable the microbes to breathe and grow. In the constantly churning water, these microbes flourish and multiply, eating the remaining organic materials and nutrients in the wastewater.

This mixture of microbes and water flows into a secondary settling tank. The microbes, now stabilized, clump together and settle to the bottom of the tank where they become part of the organic residuals and are removed. Approximately eighty-five percent of these microbes are recycled to the start of the aeration tanks to begin the biological treatment process for the primary effluent.

The cleaned water flows out of the top of the secondary settling tank to be returned to the waterway or to the tertiary treatment process.

Tertiary Treatment

Tertiary treatment is only required when the final effluent must be so clean that 95% or more of the contaminants must be removed by wastewater treatment. Tertiary treatment may include:

  • Filtration
  • Removal of Ammonia and other specific contaminants
  • Disinfection to destroy bacteria which can cause disease in humans.

Within a few hours, the cleansing action of hundreds of miles of flowing river has been replicated within the series of tanks. The reclaimed water has more than 95% of the impurities removed and can be deposited into a river or stream without any adverse environmental impacts. This "effluent" is often cleaner than the water of the stream. The entire process from the time wastewater reaches the treatment plant to the time it is cleaned and "reclaimed" takes less than 12 hours.

Picture of Water Reclamation Plant