Wastewater Treatment Combined Heat and Power Project (2014 LGAA)

City of Schenectady (Winner)
County: Schenectady County
Population: 50,000+
City Hall: (518) 382-5000

For over 50 years, the City of Schenectady Water Pollution Control Plant (WPCP) utilized anaerobic digesters in managing biosolids. When it came time to invest in an upgrade to the WPCP's treatment system, a solution was developed that not only met the current wastewater handling needs of the City, but also improved efficiency at the WPCP that was in line with the City's multi-faceted Energy Conservation Strategy.

One of the key goals of the City's comprehensive Energy Conservation Strategy was to promote energy efficiency in all municipal operations. With this goal in mind, the design team, working in close collaboration with the City, performed a detailed study of the WPCP funded in part by the New York State Energy Research and Development Authority (NYSERDA). The study identified a number of key upgrades to the facility that would improve operating efficiency and reduce energy costs. At that time, the City's WPCP did not provide optimal sludge thickening, sludge digestion, digester gas production and collection. Many buildings, along with the anaerobic digester tanks and covers, were installed in the 1950s and most of the facilities were past their useful life.

The project had the following goals:

• Reduce operating costs for sludge thickening,
• Improve digestion (mass reduction) and lower sludge processing costs,
• Increase biogas production, produce power and utilize waste heat,
• Green-up existing infrastructure and support community revitalization,
• Reduce greenhouse gases and improve air quality, and
• State of the art data collection through NYSERDA cogeneration demonstration.

The WPCP sits along the Mohawk River and is sited in a residential area. The project has reduced odors at the plant and has set the groundwork for a large restoration of the adjacent former Alco industrial plant site. This project site is scheduled to be turned into shops, condos and town houses. The project also borders the Mohawk River and will improve tourism and water quality. Pursuant to the City's 2020 Comprehensive Plan, the City intends to develop a comprehensive system of multi-use trails and bikeways which link neighborhoods and connect to the regional trail network and the waterfront. This project will complement that initiative very well.

There are no other WWTPs in New York State that co-thicken primary and waste-activated sludge in one process, and utilize the digester gas for producing electricity and waste heat. The improvements have resulted in the production of approximately 30% of the WPCP's power demand by combusting treated digester gas in the new gas engine generator. Digester sludge and heating of two buildings have been met with the waste heat recovered from the engine exhaust and jacket water. In addition, through improved digestion, the volume of sludge to be processed has been reduced by approximately 25%. This project has saved almost $200,000 a year in operation and maintenance costs, mainly in sludge disposal costs and power production.

Finally, the City is able to efficiently treat the wastewater from Scotia, Glenville, Alplaus and portions of Niskayuna and Rotterdam, and produce methane gas for power generation and waste heat utilization. The improvements will help in stabilizing sewer rates and debt service in future years.