Description
Improved methane capture and utilization of wastewater biogas resources is the greatest opportunity to reduce greenhouse gas emissions in King County wastewater facilities, with the opportunity to market revenue generating commodities. The County will advance a comprehensive and transparent approach to GHG measurement techniques related to wastewater conveyance, distribution, nutrient removal, and treatment. Use GHG data as part of decision making about wastewater treatment systems and processes and to identify other opportunities to reduce GHG emissions from wastewater treatment.
King County will improve the operational performance of the existing biogas processing equipment at the three regional treatment plant such that a combined 75 percent or more of available biogas is sent to a productive use by 2030. Finalize and implement biogas optimization strategies for the Brightwater, South Plant, and West Point wastewater treatment plants. The strategies identify timelines and designate staff to facilitate implementation. By 2030, ensure that DNRP — WTD has capital projects in place that will provide for the capacity to capture 100 percent of the biogas created during the wastewater treatment process at its regional wastewater treatment plants for beneficial use by 2035. Near term actions include, but are not limited to:
West Point:
- Improve reliability and regular operation of the cogeneration system at West Point Treatment Plant, with focused efforts and actions beginning in 2024, with a target of improving annual uptime by 15 percent in 2025 (2023 baseline). Prepare for the replacement of the West Point Treatment Plant cogeneration system in 2033.
South Plant:
- Conduct comprehensive evaluation of the South Treatment Plant biogas scrubbing system to evaluate the system components’ risk of failure and means of replacement or refurbishment by end of 2025.
- Implement biogas system improvements by end of 2027: Replace gas dryers, control valves, and scrubber water pump system to ensure mid-term reliability of South Treatment Plant biogas scrubbing system.
- Install flash tank and thermal oxidizer to reduce fugitive GHG (methane) emissions. Flash tank will reduce WTD’s fugitive emissions by 14,500 MTCO2e/year, or approximately 28 percent (2023 baseline).
- Upgrade waste gas burners to meet projected 2040 capacity requirements.
Brightwater:
- Replace failing boiler at Brightwater Treatment Plant to foster more reliable use of the plant’s biogas. Formulation project to be completed in 2026. Replaced boiler expected to increase Brightwater’s use of biogas by approximately 35 percent (2023 baseline).
- Determine selected alternative to optimize use of biogas at Brightwater Treatment Plant and implement.