The WPCF is currently permitted to produce effluent with a maximum nitrogen concentration of 10 milligrams per liter (mg/L). The process currently in use is generally able to produce effluent with a concentration of approximately 6 mg/L. When this project is complete, the nitrogen concentration in the effluent should be approximately 3 mg/L.

The equipment being installed as part of this project is the latest in pollutant reduction. There are two main technologies that will be added to the treatment process currently used at the WPCF.

4-Stage Bardenpho Process

Equipment being installed as part of this project will result in a 4-stage Bardenpho Process. This process flows wastewater through four steps, each using a biological treatment (microscopic organisms) to remove pollutants such as nitrogen.

1. First Anoxic (No Oxygen) Zone
   • Due to the lack of oxygen, bacteria resort to using nitrate (NO3) from organic materials as an oxygen source, leaving behind nitrogen gas which is release into the atmosphere.
2. Aerobic (Oxygen) Zone
   • Oxygen is added back to the wastewater and remaining nitrogen is converted to nitrate. Some bacteria consume the phosphorous in the wastewater.
3. Second Anoxic Zone
   • Oxygen is again removed from the wastewater, essentially repeating the first step and producing nitrogen gas.
4. Re-Aeration
   • The final addition of oxygen ensures that any remaining organic matter contains oxygen and helps improve settling in the secondary clarifier.

At the conclusion of the four stages, wastewater is pumped into a membrane bioreactor to further treat the wastewater.

Membrane Bioreactors

Also known as MBRs, this technology utilizes a straw-like structure which combines biological treatment with membrane filtration. When wastewater enters the MBR, micro-organisms break down organic pollutants. The wastewater then gets filtered through membranes which removes the microscopic organisms that were utilized in the treatment process. These organisms can then be re-introduced to the Bardenpho process and reused. With this technology, items as small as a virus (20-300 nanometers) are removed from the wastewater.

Existing Technology

Existing systems such as screening, primary clarification, chlorination, and associated piping/conveyance structures will be upgraded as part of this project.

To accommodate the new equipment and processes, several buildings will receive modifications to their electrical and instrumentation infrastructure, including:

• Primary Pump Building
  • Electrical and Instrumentation Modifications
• Aeration Tanks
  • Modified to accomodate the Bardenpho process.
• Aeration Building
  • Mechanical, Architectural, and Electrical Modifications. This building will also receive a new roof.
• Effluent Pump Room
  • Electrical modifications and additional pumps

Several buildings/structures will be added to the WPCF to allow for additional flow and treatment. These buildings/structures include:

• Aeration Tank
• Yard Pump Station
• Transformer and Dual Generator Services
• Fine Screen Building
• Intermediate Pump Station
• MBR Tank
• Process Building
• Deoxygenation Tank
• Septage Receiving Building
• Headworks Building
• Hydrogen Peroxide Building

As we understand more about potential pollutants, it is necessary to prepare for contaminants of emerging concern, such as PFAS/PFOA. By centralizing wastewater treatment at a single site, treating these contaminants is as simple as adding equipment at the WPCF.

As identified in the Town’s Comprehensive Wastewater Management Plan (CWMP), upgrades to the WPCF are necessary to accommodate new sewer connections, which will bring an additional 2.7 million gallons per day to the WPCF for treatment.