Nitrogen management plans (NMPs) help wastewater treatment facility (WWTF) operators and managers understand the inputs of nitrogen to their facilities and the capabilities of their facilities to address those nitrogen inputs. NMPs help to evaluate pollution prevention and WWTF optimization and treatment options that can reduce the amount of nitrogen discharged to Minnesota waters. Reducing nitrogen inputs and outputs can reduce WWTF operating costs.
Nitrogen is a common pollutant in wastewater discharges and has the potential to negatively impact aquatic life in Minnesota surface waters, contaminate drinking water sources, and degrade downstream water quality.
National Pollutant Discharge Elimination System (NPDES) and State Disposal System (SDS) permits may require the preparation of NMPs. The resources listed here can help you work through the process of developing an NMP.
NPDES/SDS permitting
Beginning in 2024, NPDES/SDS permits for municipal and industrial wastewater dischargers with high concentrations of total nitrogen will require the development and implementation of NMPs.
NMPs should include an evaluation of the facility’s influent reduction measures, effluent reduction measures, and nitrogen effluent concentration as well as a plan to implement the necessary nitrogen management and reduction measures over the permit term.
The level of detail needed for facility’s NMP will depend on any factors including, but not limited to, your facility’s classification as a major municipal WWTP or high concentration municipal WWTP or industrial nitrogen discharger, downstream waterbody nitrate reduction requirements, permit requirements for new, expanding or significantly upgraded facilities and any existing or proposed NPDES/SDS permit nitrate or total nitrogen effluent limits.
NMPs for low concentration facilities may be simple reviews of influent (where available) and effluent nitrogen data to confirm that the existing facility operations ensure optimal nitrogen management. NMPs for high concentration facilities are expected to be more complex, including analysis of source reduction facility optimization opportunities.
Develop a plan
The following suggested NMP development outline is described in greater detail in the MPCA’s Nitrogen management plan guidance.
- Data review: Summarize the last 5-years of available influent and effluent flow and nitrogen series monitoring data.
- Facility performance determination (benchmarking): Your facility’s influent and effluent nitrogen levels can be compared to those from other facilities using the MPCA’s Wastewater Data Browser.
- Develop a process control monitoring plan: The goal of process control monitoring for nitrogen removal is to obtain data needed to evaluate and understand the facility’s nitrogen removal process. These data are necessary for making informed operational changes related to total nitrogen removal.
- Develop goals: Your NMP goals may be based on facility priorities or driven by permit requirements or Minnesota’s wastewater nitrogen reduction strategy.
- Develop the facility’s nitrogen management implementation plan: Provide a detailed sequence of implementation steps designed to achieve your NMP’s chosen goals.
Enhanced nitrogen management plans
Also starting in 2024, NPDES/SDS permits for all WWTFs discharging upstream of Index of Biotic Integrity (IBI) impaired waters with nitrate stressors will require the development and implementation of enhanced NMPs.
Enhanced NMP requirements include plans to achieve effluent nitrogen reductions to levels sufficient to protect sensitive downstream waters and aquatic life.