Danbury, Connecticut

The challenge

Pioneering public-private partnership features a 20-year agreement that includes an operations, maintenance and management (O&M) contract and capital improvements to the city's wastewater treatment plant, all of which benefit the City of Danbury and ratepayers with a strong wastewater treatment infrastructure.

The project challenges are:

  • In 1997 Veolia North America signed a 20-year contract with the City of Danbury — one of the first of its kind under IRS 97-13 regulations.

  • Under the contract, Veolia is responsible for the O&M of Danbury's 15.5-MGD advanced trickling filter/activated sludge wastewater treatment plant and 20 pump stations, serving a population of 71,000.

  • The plant uses selector zones to treat wastewater and provide biological nutrient removal. Phosphorous is removed using chemical precipitation with ferric chloride in the primary clarifiers.

  • In addition, Veolia manages a revenue-generating a septage receiving program and disposal of more than 1.5 tons of biosolids per year.

  • The company also has worked with EDS Millipore on a process to reclaim and refine methanol for industrial purposes, using denitrification as the preferred beneficial reuse application.

The solution

Innovative solutions:

  • Danbury maintains control over its rate-setting and inter-municipal agreements.

  • Guarantee employment of existing wastewater plant personnel, a successful transition that represented a cooperative effort between the city, Veolia, and the employees' union.

  • Employees received comparable wages and benefits, plus additional training and advancement opportunities within Veolia.

  • Guarantee effluent quality to meet or exceed Danbury's historical performance.

  • Allow the city to realize additional revenues through Veolia's development and management of an expanded septage receiving program.

  • After a two-year testing process, obtained approval for the City of Danbury to buy recycled methanol rather than purchase virgin methanol, which is the food source for the microorganisms that reduce the nitrates to nitrogen gas in the denitrification process.

Benefits for our clients


  • 20-year contract that included a $10 million concession fee from Veolia which the city used to close an existing landfill.

  • In the first year of operation with Veolia, the city's wastewater treatment plant won the prestigious William D. Hatfield Award from the New England Water Environment Association and an O&M Excellence Award from the U.S. Environmental Protection Agency.

  • Received the U.S. Conference of Mayor's Best Practices Recognition Award.

  • Ratepayers benefit from guaranteed performance and new infrastructure while enjoying stable user fees over the 20-year partnership.

  • Achieved nitrogen discharge reductions through O&M strategies and improvements to the plant's original design, resulting in significant recurring savings to the city.

  • Partnered with a sister Veolia company to develop sustainable use of reclaimed methanol for the facility's BNR system, delivering $60,000 in recurring annual savings for the city.

  • As part of the denitrification process, sustainability has increased across the board, costs have come down and the City of Danbury saves 15 percent to 33 percent each year on the cost of methanol.

  • ​Win-win solution that leverages Veolia's strength in managing the city's wastewater facility and protecting the environment to the fullest extent possible.