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The City and County of Honolulu’s Sand Island Wastewater Treatment Plant (WWTP) Secondary Treatment Phase 1 project represents a major investment in Hawaii’s critical water infrastructure and environmental stewardship. This large‑scale upgrade modernizes the existing Sand Island WWTP to provide secondary wastewater treatment compliant with a 2010 U.S. Environmental Protection Agency Consent Decree.
Located on a 24‑acre site between Honolulu’s downtown business district and the airport, the project involves both new construction and significant rehabilitation of existing facilities. Once complete, the upgraded plant will treat 20 million gallons per day (MGD) using advanced membrane bioreactor (MBR) technology, significantly improving effluent quality before discharge through the existing ultraviolet disinfection system and ocean outfall.
Key elements of the project include construction of a new Intermediate Pump Station and Blower Building, MBR service and processing facilities, sludge thickening and processing systems, enhanced odor control and new effluent flow routing, including tunnels and channels. The project combines new facilities with extensive renovations to the active treatment plant.
Delivered using a design‑bid‑build approach, the project requires complex sequencing and close coordination to maintain continuous plant operations throughout construction. The work includes extensive cast‑in‑place concrete, below‑grade construction, dewatering and the installation of mechanical, electrical, instrumentation and process systems critical to wastewater treatment performance.
Scheduled for completion in December 2026, the Sand Island Wastewater Treatment Plant Secondary Treatment Phase 1 project will play a vital role in protecting Hawaii’s coastal waters, supporting public health and setting the foundation for future wastewater treatment upgrades across the island.
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