Point Source Practices

Domestic sewage can have significant concentrations of nutrients.

A point source is any site of discharge into a waterway, such as a pipe. Point sources are often associated with publicly owned treatment works and industrial wastewater treatment plants. Domestic sewage and industrial wastewater require treatment to reduce the concentration of certain pollutants, such as nitrogen and phosphorus, deposited into receiving rivers, streams, and lakes. The point source sector is implementing strategies — such as optimizing operations of existing equipment, upgrades to wastewater treatment facilities, and watershed-based approaches — to reduce these nutrient loads.

Illinois Point Sources nutrient losses to the Mississippi River

The following statistics summarize baseline measurement information from 1980 to 1996. More information can be found in the 2015 Illinois Nutrient Loss Reduction Strategy Science Assessment Findings.

  • Point sources contribute 16% of the nitrate-nitrogen losses from Illinois to the Mississippi River.
  • The total nitrate-nitrogen losses are estimated to be 87.3 million pounds.

Phosphorus losses 

  • Point sources contribute 48% of the total phosphorus losses from Illinois to the Mississippi River.
  • The total phosphorus losses are estimated to be 18.1 million pounds.

Total nutrient losses 

  • 86% of Illinois total point source nutrient losses to the Mississippi River occur via the Illinois River Basin.
  • The highest losses of total phosphorus and nitrate-nitrogen from point sources occur in these watersheds: Chicago River, Des Plaines River, Upper Fox, Upper Sangamon River, and Lower Rock River. 

A summary of baseline information (1980-1996) from the 2015 Illinois Nutrient Loss Reduction Strategy Science Assessment Findings

Extension’s impact on point-source solutions

Extension staff share up-to-date information among Illinois NLRS working groups and assist with showcasing point source efforts and successes in a biennial report. Extension watershed outreach staff provide statewide education about the Nutrient Loss Reduction Strategy and provide targeted services to watershed-based planning groups that include point source sector stakeholders.  

Illinois Nutrient Loss Reduction Strategy impact

The point source sector works to reduce nutrient losses largely through the regulated system administered by Illinois Environmental Protection Agency. The National Pollutant Discharge Elimination System permits contain requirements for publicly owned treatment plants and industrial plants to reduce nutrient loss in their wastewater discharges. 

The point source sector has directed substantial resources to capital improvements and nutrient reduction studies that identify capital needs. The Illinois EPA provides low-interest loans through the Water Pollution Control Loan Program, which funds wastewater treatment plant upgrades to improve nutrient removal, green infrastructure, urban stormwater treatment, and control of combined and sanitary sewer overflows. This program invests in projects to reduce nutrient loss through treatment plant improvements. 

NLRS recommends implementation goals and best management practices for point source dischargers:

  • Total Phosphorus limits for major (> 1 MGD) wastewater treatment facilities
  • Feasibility and Optimization studies for nutrient removal
  • Nutrient Assessment Reduction Plans
  • 1.0 mg/L total phosphorus 
  • 0.5 mg/L total phosphorus
  • Encourage Urban Watershed Planning Groups

Overall impact

  • In 2022, the point source sector reduced its phosphorus discharge by 34%, or a total of 6.2 million pounds, compared to the 2011 baseline levels. This surpasses the interim goal of 25% by 2025. These reductions were largely due to improvements by National Pollutant Discharge Elimination, NPDES, permit holders.
  • Significant total phosphorus load reductions are still anticipated in the long-term due to large wastewater treatment facilities that are scheduled to become compliant with permit requirements over the next several years. 
  • Illinois EPA incentivizes point sources to adopt biological phosphorus removal. This is because the low dissolved-oxygen environment used with biological phosphorus removal would have the additional advantage of reducing a significant fraction of the nitrogen as well. 
  • The 2022 total nitrogen load from all point sources was estimated at 77.2 million pounds, which is an 11.6% decrease form the 2011 baseline load.


National Pollutant Discharge Elimination System permit requirements 

Some major municipal wastewater facility National Pollutant Discharge Elimination System, NPDES, permits are issued with nutrient criteria and require studies to meet nutrient criteria. These nutrient criteria may include: 

  • Requirements to meet a total phosphorus concentration limit of 1 mg/L
  • Requirements to monitor for total phosphorus and total nitrogen
  • A goal of total nitrogen removal
  • A goal of total nitrogen limits

Reductions in total phosphorus loads in Illinois have been achieved by installing new technologies and optimizing operations at wastewater treatment facilities, in compliance with NPDES permit requirements. Major municipal dischargers are required to submit and implement phosphorus discharge optimization plans for existing equipment and operations as well as develop feasibility studies to meet total phosphorus concentrations of 0.5 mg/L and 0.1 mg/L. 

Nutrient Assessment Reduction Plans

The requirement to develop a Nutrient Assessment Reduction Plan, NARP, is being incorporated into many Illinois National Pollutant Discharge Elimination System, NPDES, permits for major municipal facilities that discharge into a receiving waterbody that is impaired by or at risk of eutrophication — an over-enrichment of nutrients — leading to a lack of dissolved oxygen. Eutrophication can cause excess algae, plant growth, and other offensive aquatic conditions. These plans identify phosphorus input reductions, measures to ensure waterbodies contain adequate amounts of dissolved oxygen, and measures to reduce offensive conditions from algae and aquatic plant growth. The Illinois EPA has mapped the locations of facilities required to develop a NARP.  


Operations and Technology Improvements

Improvements in the development and successful operation of technology that enhances nutrient removal are also key to achieving nutrient loss reduction goals. 


Illinois EPA Funding Resources

The point source sector has directed substantial resources to capital improvements and nutrient reduction studies that identify capital needs. The Illinois EPA offers low-interest loans through the Water Pollution Control Loan Program, which funds wastewater treatment plant upgrades to improve nutrient removal.

Illinois EPA invests in projects that reduce nutrient loss, such as: 

  • Green infrastructure
  • Urban stormwater treatment
  • Control of combined and sanitary sewer overflows
  • Treatment plant improvements