Sand Island Wastewater Treatment Plant Upgrade - Planning and Design

Sand Island Wastewater Treatment Plant is the largest treatment facility in Hawaii and serves Honolulu and Waikiki, from East Oahu to Pearl Harbor. The City and County of Honolulu is currently responding to a consent decree to upgrade the facility to secondary treatment standards.

The plant treats an average flow of 65 million gallons per day (MGD)—246 megalitres per day (MLD)—a maximum monthly flow of 90 MGD (341 MLD), and a wet weather peak flow of 240 MGD (909 MLD), through chemically-enhanced primary treatment and UV disinfection prior to ocean discharge. The plant is undergoing construction of a 20 MGD (76 MLD) membrane bioreactor (MBR) process as Phase 1 of the secondary expansion. Along with our joint venture partner, RM Towill Corporation, we’re completing the planning phase and entering the design phase of the Phase 2 expansion to achieve complete secondary treatment, employing aerobic granular sludge (AGS) in a dual system with the MBR process.

Phase 2 will include peak flow equalization, upgrades to preliminary and primary treatment, and expanded solids treatment to manage the additional waste-activated solids generated by the new dual secondary process train. Additionally, Phase 2 includes an organic waste sustainability plan (OWSP) that focuses on sustainable approaches to use feedstocks, such as fats, oils, grease, and commercially-available food waste to supplement anaerobic digestion—creating opportunities for reducing greenhouse gas emissions and producing green power through cogeneration.