About the Project
The Synagro In-Vessel Bioconversion Facility Upgrades at the Sand Island Wastewater Treatment Plant in Honolulu, Hawaii, supports the City and County of Honolulu’s long-term biosolids management and sustainability goals. The project replaces aging infrastructure with a modern, high-efficiency system that converts wastewater solids into beneficial reuse products and renewable energy.
Using a collaborative design‑build delivery, the scope includes two 2.35‑million‑gallon anaerobic digesters, sludge storage tanks, a new control building, advanced odor control systems and related tunnel and utility upgrades. Together, these improvements increase treatment capacity, enhance operational efficiency and reduce the environmental impact of the wastewater treatment process.
By modernizing the bioconversion facility, the project transforms organic waste into usable resources while strengthening public health, environmental stewardship and long‑term system resiliency. This investment is a critical component of Honolulu’s efforts to modernize essential infrastructure and prepare for future wastewater demands.
Scheduled for completion in December 2028, the project will deliver reliable, resilient treatment capacity to support the Honolulu community for decades to come.
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