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 has received the new IEPA 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.