Methane gas at Pima County's Ina Road Wastewater Reclamation Facility soon may be converted into electricity to help power the plant, once a power generation and energy recovery facility is constructed at the site.
Eric Wieduwilt, deputy director of the planning and engineering division of the Regional Wastewater Reclamation Department, said the county has issued a "request for qualifications" from interested firms to design, construct, start up, commission and test, and to obtain permits for such a facility at the Ina Road site.
Pima County would use a "design-build-operate" delivery method, with a single firm responsible for the design, construction and operation of the power generation and energy recovery facility.
The design and construction budget is estimated to be $21 million.
Laura Fairbanks, community relations manager, said the new power generation facility would use methane gas generated at the plant from biosolids digesters to produce electricity.
The county is in the process of implementing a $500 million regional optimization master plan that will upgrade and expand the Ina Road facility and transfer all biosolids (formerly called "sludge") to Ina Road from the Roger Road treatment plant. The Roger Road facility will be closed and a new water reclamation campus will be built adjacent to the site, but it will not treat biosolids, Fairbanks said.
Wieduwilt said "part of the concept is that all of the biosolids will be transferred to Ina Road so we'll have a single location for biosolids digestion, which is the treatment process that generates methane gas. That methane gas then can be used for power generation to help power the facility with electricity and heat.
"Not only does the wastewater plant require electricity, but it also requires heat in some of its processes, so this new power generation and energy recovery facility would also generate some of that heat to facilitate the digesters," Wieduwilt said.
He estimated the power generation facility would produce between 3 and 4 kilowatts of power, which would be approximately 50 percent of the plant's electrical and thermal needs.
Wieduwilt noted the project is in the early stages of the procurement process, which is conducted under chapter 6 of Title 34 of the Arizona Revised Statutes.
"The first step is a qualifications-based submittal and evaluation where respondents submit statements of qualifications describing in detail their technical and financial qualifications to perform the contract services," he said. "After all those RFQs are reviewed, a short list is developed, usually consisting of three qualified companies, and a second phase of evaluation of proposals with a cost element is carried out."
Wieduwilt said if all goes according to plan, he expects a contract to be awarded around June 2010. At that time, two separate agreements would be signed with a single company — one for the facility's construction and the other for its operation.
The power generation and energy recovery facility would be paid for by customers through the fee structure. He said the plant could be paid for through cash, revenue bonds or obligation bonds, but he didn't expect that it would be cash.
In addition to the power generation facility, the county also is installing a 2-megawatt photovoltaic solar facility at the Ina Road plant, Wieduwilt said, "to show we're responsive to the costs of energy and the power needs of operating these facilities."
He pointed out both the power generation plant and the photovoltaic facility are being set up as net metering units, meaning they would feed the electricity they generate into the Tucson Electric Power grid, creating a credit for Pima County for the amount of energy generated, which can then be tapped in the form of electricity usage.