Retrofitted Wooster waste-water facility generates renewable energy

The City of Wooster’s retrofitted waste-water facility (photo credit: biocycle.net)
Caroline Ward, S&E editor

In 2013, the City of Wooster partnered with quasar energy group, a Cleveland-based waste-to-energy company, with the goal of retrofitting its pre-existing water-waste facility into a virtual water resource recovery facility. Construction finished in 2014, transforming the waste-water plant into a fully energy-self- sufficient operation capable of generating an annual 5,256 MWh of electricity and 1,650 gasoline gallon equivalents per day in renewable fuel generation. Through this partnership, the City of Wooster was able to reduce energy-related costs by over $300,000 per year, as well as achieve Ohio EPA compliance.

Water resource recovery facilities promote sustainability in a number of ways. According to the Environmental Protection Agency, classic water pollution control facilities often account for 30% to 40% of total energy consumed in a municipal government energy budget. And for the facility itself, electricity costs alone can constitute 25% to 40% of a wastewater treatment plant’s annual operating budget. The EPA estimates that “by incorporating energy efficiency practices into their

water and waste-water plants, municipalities and utilities can save 15 to 30 percent, saving thousands of dollars with payback periods of only a few months to a few years.” In total, quasar energy estimates that treatment plants consume 3% of the total US energy demand.

However, retrofitted waste-water facilities significantly cut energy costs and general operating costs. For the City of Wooster and other municipal governments, all construction costs of the retrofit are eventually offset by the massive reduction in energy and operating costs. Beyond this, excess energy can be redirected to the local area, once again cutting total municipal energy costs.

A technique of energy recycling commonly employed when retrofitting these facilities is called anaerobic digestion. The EPA defines anaerobic digestion as the biological degradation of organic matters in the absence of oxygen, converting the chemical energy in organic carbon to biogas. In this way, wastewater functions as a renewable resource when properly processed. In Wooster, a quasar generator was installed at the municipal sewer plant, capable of producing an average of 1,100 kilowatts of electricity,

as well as natural gas. Since this is significantly more electricity than is needed to power the sewage plant, the rest of the energy was directed to the water treatment plant, enabling it to achieve energy-self-sufficient status.

The benefits of such green- energy technology are evident. quasar energy estimates that biosolids have the potential to produce 12% of the US electric demand. But a 2013 study by the National Association of Clean Water Agencies found that federal funding allocated to address these challenges has decreased 90% since the 1980’s. Although partnerships with private companies like quasar energy can be incredibly beneficial for the municipal districts they partner with, federal initiatives are necessary in ensuring large-scale national success.

The most recent and ongoing initiative was announced in 2016, when the Department of Energy launched Phase 1 of the Sustainable Wastewater Infrastructure of the Future (SWIFt) Initiative, a three- year partnership between 25 state, regional, and local agencies. During this time, partners were able to reduce their total energy consumption by almost 7%. Due to the success of Phase 1, SWIFt Phase 2 was introduced in 2020, expected to run until 2023. Phase 2 engages 100 additional facilities, as well as shifting focus to renewable energy, resource recovery, and advanced data management in 25 of those facilities. Such initiatives are key in ensuring that national sustainability efforts will be maintained long-term.

For the City of Wooster, the partnership with quasar energy proved to be a real solution for its municipal treatment plant. But unfortunately, the municipal water-waste plant is no longer energy-neutral.

“We were bringing in lots of third-party waste,” says Chad Frank, Wooster Water Utilities Master Operator. “It generated a lot of workload on a piece of equipment…and if we would lose a piece of equipment, we had no ability to keep running. The biggest reason we stopped was the engine was at its useful service life. So we needed a new engine, which is very very costly.”

But the city is hopeful to soon return to an energy- recycling model. “Currently, we are working with another group, looking into updating the digestors to move back to creating power again, or cleaning and selling gas back to the grid,” Frank says. “It’s in the works to upgrade our facility, but it’s still in the brainstorming phase. Once we get the permits, we want to move on it. We’re hoping to have the facility remodeled in the next couple of years so that we can bring in some third- party waste to start generating energy again.”

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