Naperville Nutrient Removal
The Springbrook Water Reclamation Center is a wastewater treatment facility serving the cities of Naperville and Warrenville, Illinois. Wastewater treatment is a collection of physical, chemical and biological processes that remove contaminants, including nutrients, from wastewater to make it safer for the environment before it is discharged back into area bodies of water. Recent environmental regulations set stricter limits on the amount of nutrients that can be discharged from wastewater treatment facilities within the Mississippi River basin. This is the story of how the City of Naperville’s Springbrook Water Reclamation Center is making strides towards complying with those stricter regulations.
What are Nutrients and Why Are We Working to Limit Them?
Phosphorus and nitrogen are naturally-occurring elements. However, when too much of these nutrients enter waterways, excessive algae growth occurs, impacting water quality, animal habitats and ecosystems.
Oftentimes, excessive nutrient introduction to waterways is due to human factors. Fertilizer run-off from farm fields, detergents, human waste and food all contain these nutrients. These excessive nutrients entering waterways have led to vast hypoxic (low dissolved oxygen) "dead zones" in the Gulf of Mexico in and around the Mississippi River delta.
In 2008, the U.S. Environmental Protection Agency released the Gulf Hypoxia Action Plan, which calls for each of the 12 states in the Mississippi River basin to develop a strategy to reduce the amount of nitrogen and phosphorus being discharged into the basin waterways.
More information can be found here:
Current Treatment Process Gives Us a Good Start
The City of Naperville’s Springbrook Water Reclamation Center currently utilizes an activated sludge treatment process. Activated sludge is a biological process that uses microorganisms to treat wastewater and remove pollutants. During the treatment process, the nutrients (phosphorus and nitrogen) present in the untreated wastewater the plant receives are absorbed by the microorganisms, which use the nutrients for growth and reproduction. Ultimately, this reduces the amount of nutrients present in the treated water that is discharged.
The Road Ahead
In 2016, the City of Naperville filed for renewal of its NPDES (National Pollutant Discharge Elimination System) permit from the Illinois Environmental Protection Agency (IEPA). This permit is the primary regulatory device for setting wastewater treatment and discharge standards for treatment facilities like Naperville’s Springbrook Water Reclamation Center.
The City expects that the IEPA will issue a new permit limiting the amount of phosphorus that can be discharged from Springbrook Water Reclamation Center at a concentration of 0.5 Mg/L to 1.0 Mg/L, to be implemented over a multi-year timeframe.
Realizing the sizeable cost of treatment facilities needed to meet the new limits, and recognizing the fact that wastewater treatment plants are only partly responsible for the nutrient loading in area waterways, the permit will grant municipalities additional time to achieve the new limits as long as they belong to watershed planning groups. The goal of these planning groups is to improve overall water quality in local waterways using a science- and evidence-based approach.
The City of Naperville belongs to two watershed planning groups: the DuPage River Salt Creek Workgroup (DRSCW) and the Lower DuPageRiver Watershed Coalition (LDRWC). Through these groups, Naperville will work with member communities to complete various stream improvement projects throughout the watershed intended to focus on improving water quality, habitat and aquatic life. These projects will take place over the course of about eight years and will provide immediate benefits to the environment, while staff uses that additional time to plan for and construct permanent phosphorus removal systems at Springbrook to meet the new stricter limits. Estimates for this work range from $40 million to $60 million, so the extended, multi-year implementation period allowed through our involvement in the watershed planning groups allows staff the opportunity to build cash reserves to limit borrowing.
Moving Forward in a Financially Responsible Way
In 2015, the Naperville City Council adopted four "ends policies" to guide the City's priorities in the coming years. One of these policies is centered around financial stability, specifically, increasing reserves and reducing debt. Staff has incorporated this commitment to financial stability into its plan for funding the permanent phosphorus removal systems at Springbrook. To provide a balance between water rate increases and a significant increase of the Water Utility’s debt burden, a monthly surcharge was adopted in 2017. City ordinance 17-167 explains:
The monthly Phosphorus surcharge shall be assessed to all customers to fund 50 percent (50%) of the improvements to the Springbrook Water Reclamation Center to remove Phosphorus nutrients. Funds collected under the surcharge shall be restricted to the Phosphorus improvements including, but not limited to, preliminary engineering, engineering, and construction of said improvements. The Phosphorus surcharge shall expire at the end of the calendar year within which it is determined that fifty percent (50%) of the estimated cost to build such improvements has been collected, as determined by Council based on staff projections reported annually.
Currently, staff estimates it will take 8-10 years to raise $25 million, which is estimated to be 50% of the cost of improvements to the Springbrook Water Reclamation Center.