About the Project
The Honouliuli Wastewater Treatment Plant (WWTP) Phase 1C – Headworks, HRBC, Solids Process and Miscellaneous Improvements project is part of a long‑term, multi‑phase initiative led by the City and County of Honolulu Department of Environmental Services. The program delivers major upgrades to both liquid and solids treatment processes, supporting wastewater treatment and environmental protection for Central and West Oahu.
Liquid stream improvements include modifications to the existing Influent Screening Facility, including the addition of two new screening channels and five new screens; construction of a new cast‑in‑place concrete grit removal facility; and conversion of the existing grit removal and aeration tank structure into a High‑Rate Biological Contactor (HRBC) process facility. The biologically enhanced primary treatment system includes five contactor tanks and ten dissolved air flotation (DAF) tanks, improving treatment performance and increasing sludge quality prior to solids processing.
Upgrades to the solids stream introduce a thermal hydrolysis process (THP) ahead of anaerobic digestion. This improvement increases biogas production while reducing digester residence time. Biogas generated through digestion will be used to power two 2.0‑MW cogeneration generators at the combined heat and power (CHP) faciltiy, supplying renewable energy back to the plant and reducing overall energy demand. Supporting these process improvements are significant electrical and controls upgrades, including new low‑voltage switchgear, motor control centers, programmable logic controllers (PLC) and enhancements to the SCADA system—supporting increased biogas generation and cogeneration at a combined heat and power facility.
The project is constructed through a sequenced, three‑phase program to support efficient commissioning: Phase 1, Liquid Stream Improvements; Phase 2, Solids Stream Improvements; and Phase 3, Perimeter and Site Facilities. Scheduled for completion in November 2029, the project will be part of a roadmap to address long‑term growth, resiliency, energy efficiency and environmental stewardship for the City and County of Honolulu.
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