Anacortes weighs biosolids alternatives as aging incinerator nears $8.4 million regulatory threshold

Anacortes weighs biosolids alternatives as aging incinerator nears $8.4 million regulatory thresholdThe Washington municipality is partnering with Brown and Caldwell to map out a long-term biosolids strategy, evaluating options ranging from anaerobic digestion to a major air pollution control upgrade to meet stringent EPA limits.

The city's 1992-vintage sewage sludge incinerator requires replacement or significant upgrades within three to five years.

Anacortes can spend an estimated $4.6 million on near-term repairs before triggering EPA Subpart LLLL regulations, which would mandate an $8.4 million air pollution control upgrade.

Consultant Brown and Caldwell is leading a multi-criteria decision analysis to screen technologies including anaerobic digestion, thermal hydrolysis, and pyrolysis.

Future PFAS regulations, including Washington's SB 5033 requiring biosolids sampling by 2028, are factoring into the technology screening process.

The City of Anacortes, Washington, has launched a comprehensive alternatives analysis for its wastewater treatment plant's solids handling system, driven by an aging sewage sludge incinerator and looming federal air quality regulations. Built in 1992, the incinerator has processed approximately 28,000 dry tons of biosolids over 34 years, reducing the city's waste to sterile mineral ash without the need for off-site trucking. However, escalating maintenance costs and the end of the equipment's service life mean the city must make a long-term decision on its biosolids management within the next three to five years. A major driver of the planning process is a strict regulatory threshold under EPA 40 CFR Part 62 Subpart LLLL, also known as Quad L. According to Greg Makos, solids and energy practice leader at Brown and Caldwell, if cumulative modifications to the incinerator exceed 50 percent of the original build cost, the facility will be subject to more stringent emission limits. Makos estimated the city can spend up to $4.6 million on maintenance before triggering this rule. Upgrading the facility to meet Quad L standards would require a completely new air pollution control treatment train and a building extension, carrying a planning-level cost estimate of $8.4 million. To map out a durable and cost-effective roadmap, Anacortes is evaluating a wide universe of stabilization technologies. The city's mandatory goals require that any new technology fit within the existing physical space, possess at least one commercial installation of equivalent size in the U.S., avoid proprietary consumables, and operate without 24-hour staffing. The screening process has narrowed the field to options such as mesophilic anaerobic digestion, thermal hydrolysis, fluidized bed incineration, pyrolysis, and gasification. Brown and Caldwell will develop six end-to-end alternatives for a multi-criteria decision analysis workshop slated for later this year. The technology selection will also weigh the impact of emerging per- and polyfluoroalkyl substances (PFAS) regulations. Under Washington State's SB 5033, the city will be required to sample its biosolids for PFAS between 2027 and 2028. While initial voluntary testing showed Anacortes' PFAS levels are in line with or below comparable utilities, the potential for future limits on land application remains a risk factor in the decision-making process. City council members and public works staff will provide input on evaluation criteria through an upcoming survey to weigh the environmental, financial, and regulatory tradeoffs of each technology. A preferred alternative for the city's biosolids roadmap is expected to be identified by next March.