Airport Parkway Wastewater Treatment Facility Upgrade

South Burlington, Vermont

Client: City of South Burlington, Vermont


  • Construction Administration
  • Construction Observation
  • Grant Assistance
  • Preliminary & Final Designs
  • Rate Study Analysis & Financing

Project Summary

Hoyle, Tanner completed comprehensive facilities planning work for the Airport Parkway Wastewater Treatment Facility and service area. Facility planning work included the review and identification of upgrade needs of the City’s collection system, 24 pumping stations and treatment facility. Moving forward from planning, Hoyle, Tanner is now currently in the final stages of the design phase for the upgrade and expansion of the Airport Parkway WWTF to an advanced secondary treatment facility to meet the City’s anticipated wastewater treatment needs for design flows of 3.3 million gallons per day (MGD).

The treatment process upgrade is to implement an enhanced biological nutrient removal (BNR) treatment process for phosphorus and nitrogen removal to meet a phosphorus discharge limitation of 0.42 mg/L. The BNR process design includes implementing anaerobic and anoxic selectors with hyperbolic mixers, internal recycle pumping systems, aeration tank improvements, blowers, and energy efficiency control measures. The new BNR process will be followed by improved secondary clarification and effluent polishing with cloth disk filtration. Other upgrades to the facility include new septage receiving facilities, new headworks facilities with screening and grit removal, primary clarification upgrades, and ultraviolet disinfection.

New sludge management facilities include the conversion of the existing conventional mesophilic anaerobic digestion facilities into an advanced two-phased (thermophilic-mesophilic) anaerobic digestion process for higher volatile solids destruction, increased gas production, and pathogen destruction. This process has the potential for Class A biosolids certification by the EPA. Along with the implementation of two-phased anaerobic digestion process, a co-generation facility will be implemented to produce power and heat from the digester gas. Other solids handling facilities include the conversion of an existing 1.0 million gallon sludge storage tank into a dewatering building to house a rotary drum thickener, centrifuge dewatering equipment, and other related sludge handling equipment.

Our work with the City included completion of a detailed rate study analysis and financing recommendations to fund the $25M project. Working with the City we developed a financing approach that limited the project’s impact to user fees to only a 3% rate increase. The project is eligible for the funding through the State’s sludge and septage, and phosphorus grant programs. In addition, on behalf of the City, we applied for and received approval for a grant of $250,000 from the VT Clean Energy Development Fund for construction of the biogas co-generation facilities.

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