Ten years ago, the wastewater treatment plant in Gresham, Oregon was the city’s biggest energy-consumer,. But a lot has changed since then.
The plant is now making the same amount of electricity as it consumes in a year, using biosolids from wastewater treatment and fats, oils and grease as well as solar energy to produce power while also reducing energy costs. As a result, the plant now exports excess energy back to the local utility.
The secret to the plant’s success is the biogas, which is naturally produced by wastewater in the form of methane. By simultaneously generating energy and heat from that methane – a process known as cogeneration – the Gresham plant can produce its own energy without having to purchase it. In addition to its cogeneration units, the city installed one of the largest land-based solar arrays in the Pacific Northwest, producing approximately 8% of the plant’s total power each year.
The city looked for a private-sector partner who could help reduce energy usage while ensuring maximum output from the cogeneration program. Veolia North America was chosen based on the company’s experience serving more than 500 North American communities, along with access to experts and a company promise to ensure more than 90% “uptime” of the cogeneration unit.
Under the contract with Gresham, Veolia manages all operations and maintenance of the city’s secondary activated sludge wastewater treatment plant, a beneficial use biosolids management program, industrial pretreatment program analyses, cogeneration operation, laboratory services and nine lift stations.