Protecting Our Waterways: How Enhanced Nutrient Control at Wastewater Treatment Facilities Is Helping Communities Meet New Challenges

As communities across the Northeast and Mid-Atlantic are presented with more stringent wastewater discharge limits and grow more mindful of their environmental footprint, one critical area gaining attention is how we treat our wastewater. Gone are the days when basic drainage and treatment systems were enough. Today, municipalities are facing more stringent regulations to protect waterways from nutrient pollution and enhanced nutrient control techniques are being implemented to accomplish this mission.

Why Nutrients Like Nitrogen and Phosphorus Matter

At first glance, nutrients such as nitrogen and phosphorus don’t seem like troublemakers. They’re vital for plant growth and play key roles in ecosystems. But in excess, these same nutrients can become serious environmental threats.

When discharged into lakes, rivers, or coastal bays, high levels of nitrogen and phosphorus fuel eutrophication, the explosive growth of algae and aquatic plants. This process chokes off oxygen, kills fish, and degrades water quality. In response, many wastewater treatment facilities are being asked to go beyond traditional methods and adopt more advanced strategies like biological nutrient removal (BNR), and in some cases enhanced chemical nutrient removal.

What Are Biological Nutrient Removal and Enhanced Chemical Nutrient Removal?

BNR isn’t a single process, but rather a biological system that uses beneficial bacteria to remove nitrogen and phosphorus from wastewater before it’s discharged into the environment. These bacteria work in different zones (some with oxygen and some without) to break down and transform nutrients into harmless or easily removable forms.

Enhanced chemical nutrient removal uses chemical processes to remove or transform nutrients. Examples include adding a compound to the wastewater that reacts with phosphorous, making it a solid that can be filtered out of water; or adding an strong oxidant to wastewater to transform nitrite to nitrate.

For municipalities, biological and/or chemical nutrient removal helps meet stricter discharge permits while supporting larger goals like waterway protection and ecosystem restoration. It’s a science-based solution with environmental and regulatory benefits.

Regional Drivers Pushing Nutrient Removal Forward

Across the Mid-Atlantic and Northeastern United States, new policies and regional action plans are accelerating the adoption of BNR systems in municipal treatment plants.

The U.S. Environmental Protection Agency (EPA) is encouraging states to adopt numeric criteria for nitrogen and phosphorus in their water quality standards. These thresholds are becoming the foundation for stricter permit limits.

New York’s SPDES and LINAP

New York has tightened its regulations through the State Pollutant Discharge Elimination System (SPDES). New facilities are required to meet phosphorus limits as low as 0.2 mg/L, while existing plants face limits between 0.5 and 1.0 mg/L. The Long Island Nitrogen Action Plan (LINAP) adds another layer, targeting groundwater nitrate levels to protect sensitive aquifers and estuaries.

Maryland’s Chesapeake Bay Initiatives

Maryland is a key player in the Chesapeake Bay cleanup. The 2010 Chesapeake Bay Total Maximum Daily Load (TMDL) established nutrient and sediment limits, and the Chesapeake Bay Legacy Act, passed in 2025, ramps up the pressure. It promotes regenerative agriculture, improves monitoring systems, and supports sustainable aquaculture, all while keeping nutrient pollution in check.

Connecticut’s Market-Based Approach

In Connecticut, the Nitrogen Credit Exchange allows municipalities to buy and sell nitrogen reduction credits. This flexible, market-based model has significantly cut nitrogen discharges into Long Island Sound since its launch in 2002.

Maine’s Coastal Water Protection

Maine takes a more targeted approach, incorporating nitrogen reduction goals into permit renewals for estuary communities. BNR is becoming a key tool in protecting valuable coastal resources like Casco Bay.

Adapting to New Limits: The Village of Richfield Springs’ Path to Compliance

Let’s look at how one small village tackled a big regulatory hurdle and came out stronger for it.

Richfield Springs, located in Otsego County, New York, serves just over 1,000 residents. The village’s aging wastewater treatment plant discharges into Ocquionis Creek, a trout stream feeding into Canadarago Lake. Both waterways are prized for recreation and aquatic life, making nutrient management especially important. Richfield Springs is the northernmost WWTP that discharges into the Chesapeake Bay watershed.

The Permit Challenge

During the plant’s permit renewal, the New York State Department of Environmental Conservation (NYSDEC) introduced a new, incredibly strict limit for nitrite—0.03 mg/L. That’s over 30 times lower than the national drinking water standard, reflecting the increased focus on protecting aquatic ecosystems.

Two challenges quickly emerged:

• Detection limits: Standard testing couldn’t detect such low concentrations, so the Village partnered with its lab to adopt new testing methods capable of detecting down to 0.0037 mg/L.
• Biological complexity: In BNR systems, nitrite is an intermediate step. It forms when bacteria convert ammonia to nitrite and then nitrite to nitrate. However, one type of bacteria, Ammonia Oxidizing Bacteria (AOB), grows faster than the other, Nitrite Oxidizing Bacteria (NOB), meaning nitrite levels can spike even when everything seems to be working. Seasonal changes, ammonia surges, or chemical shocks can all disrupt this delicate balance.

The Solution: Smart Chemistry Meets Smart Engineering

Faced with these complexities, Richfield Springs is turning to a chemical solution, chlorination–dechlorination, for its low capital cost, ease of integration with existing systems, and operational reliability. By carefully dosing chlorine, the plant will be able to oxidize any remaining nitrite into nitrate, which is far less harmful and has a much higher permit threshold.

Best of all, the upgrade will require minimal additional chlorine. Dose required to oxidize nitrite to nitrate increased to 3.3 gallons per day, compared to 3.0 gallons/day already used for disinfection. The plan also includes automated analyzers to streamline dosing and improve consistency.

This solution is part of a $23.5 million WWTP upgrade, funded equally by a $9.1 million BIL grant and a $9.1 million WIIA grant. A WQIP grant application was submitted in 2025 to request the remaining $5.3 million.

In addition to nitrite control, the project will install new sequencing batch reactors; chemical precipitation and filtration of phosphorous, and improved disinfection systems to prepare for future limits on nitrogen, phosphorus, and ammonia, all essential for Chesapeake Bay watershed protection.

How Communities Can Prepare

Richfield Springs offers a valuable model for small and mid-sized communities navigating tightening water quality regulations. Here’s what other municipalities can do now to prepare:

• Read Your Permit Renewal Notices Thoroughly
  New nutrient or pollutant limits can be introduced during renewal. Stay informed so you can plan ahead.
• Upgrade Your Monitoring Tools
  Make sure your lab can detect trace levels of nutrients. This often requires newer, more sensitive testing methods.
  
• Combine Biological and Chemical Strategies
  BNR is powerful, but it isn’t foolproof. Consider backup systems like chemical polishing to meet tough permit limits.
  
• Think About Long-Term Operations
  Choose solutions that fit your plant’s size, staffing levels, and budget. Automation can help reduce strain on operators.
  

Looking Ahead

As more states revise their nutrient policies and pressure builds to restore regional waters like the Chesapeake Bay and Long Island Sound, BNR is poised to become the standard, not the exception. Communities that plan early, invest wisely, and choose practical, scalable solutions will be best positioned to meet the future with confidence.

For guidance on proactive strategies, technical solutions, and lessons learned, please contact Rich Straut, P.E., to discuss how your community can stay ahead of tightening requirements.