Treating wastewater is typically a highly energy-intensive process, and a significant expense for municipalities. Conservation measures can alleviate these costs to an extent, but some utilities are going a step further and exploring strategies for recovering energy from the treatment process. Co-digestion is one example where treatment plant operators have been able to recover energy for beneficial and, in some cases, revenue-generating reuse. Facilities that use anaerobic digesters to extract energy from wastewater—and have excess capacity—can accept additional organic waste like fats, oil, and grease and food scraps to increase the generation of biogas. This methane-based fuel can be used onsite for heat and electricity or can be processed and sold as a new revenue stream.

EPA’s Office of Research and Development studied a small (i.e., 1 million gallons per day) facility in southwestern New York that was considering adding this capability. Like many communities across the country, the facility in Bath was facing stricter nutrient limits to protect the quality of local receiving waters. Co-digestion was identified as a possible strategy to offset the increased energy requirements for nutrient removal. “Environmental Life Cycle Assessment and Cost Analysis of Bath, NY Wastewater Treatment Plant: Potential Upgrade Implications” seeks to quantify the environmental and economic tradeoffs between operating the legacy plant using conventional activated sludge versus investing in upgraded capabilities, including chemically enhanced primary settling, secondary treatment, and anaerobic digestion.

The study suggests some scenarios in which a resource recovery model like the one Bath was exploring can result in positive environmental and economic outcomes. To further the understanding of the subject, EPA has begun analyzing a larger wastewater utility in order to determine the economies of scale for integrated resource recovery. For more information about the Agency’s research on co-digestion and other innovative wastewater treatment technologies, contact Jason Turgeon (turgeon.jason@epa.gov), Energy and Water Specialist, EPA Region 1, 617-918-1637.