In addition to lowering the plant's energy consumption by 30%, the system will provide renewable-energy credits that can be sold on the open market. Photo: S E A Consultants Inc.

Name:: Cogeneration System Study and Design

Client: City of Pittsfield, Mass.

AEC firm: S E A Consultants Inc.

Cost: $2.5 million

Project delivery method: Design-bid-build

Completed: Late 2010

Once cost-effective only for large facilities, combined heat and power is viable for wastewater treatment plants with anaerobic facilities as small as 2 mgd.

As a result, the Pittsfield, Mass., Department of Public Works & Utilities' 50-year-old, 12-mgd facility will be the first in the state to convert the gas from its anaerobic digester into an onsite energy source that's expected to save $200,000 annually on electricity. But first, some new equipment — three 65-kW microturbines; a gas-conditioning system to remove moisture, hydrogen sulfide, and siloxanes; new digested-sludge transfer pumps; and more sludge heat exchangers — must be installed.

Construction is scheduled to begin in spring 2010. A $400,000 Large Onsite Renewables Initiative grant from the Massachusetts Technology Collaborative is helping finance the final design and construction phase.