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Honouliuli WWTP in Hawaii undergoes comprehensive $536 million upgrade

  • Honouliuli WWTP in Hawaii undergoes comprehensive $536 million upgrade
    Credit: City and County of Honolulu
  • The upgraded facility incorporates efficient technology to provide full secondary treatment capacity.

  • The project is the second phase of a consent decree filed in federal court in 2010, which ended years of legal disputes.

The Honouliuli Wastewater Treatment Plant (WWTP) in Honolulu has completed a comprehensive $536 million upgrade, marking a significant advancement in the city's wastewater management capabilities. The project involved the installation of aeration basins, a blower building with turbo blowers, a mixed liquor distribution box, secondary clarifiers, and a secondary process pump station, as detailed in a recent news release.

In addition, the upgrade also involved various aspects of the primary treatment process, civil infrastructure, electrical systems, and SCADA technology.

Originally commissioned in 1978 as a primary treatment facility, the Honouliuli WWTP is located in southwestern Oahu, the most populated and third-largest of the Hawaiian Islands. A deep ocean outfall 1.76 miles offshore was completed a year later. It was upgraded to partial secondary treatment in 1996. The latest enhancements have now elevated it to full secondary treatment capacity, incorporating modern and efficient technology.

The upgraded facility was handed over to the operations staff of the Department of Environmental Services ahead of a consent decree deadline of June 1, 2024. This milestone is crucial for the City and County of Honolulu in meeting federal Clean Water Act regulatory requirements.

The upgrade follows a consent decree filed in federal court in 2010, which ended years of legal disputes, including lawsuits by the Sierra Club and the 2007 Beachwalk lawsuit. The decree resolved litigation over secondary treatment waivers and compliance orders from the U.S. Environmental Protection Agency and the Hawaii Department of Health.

The consent decree outlined a three-phase, 25-year implementation schedule. Phase 1 focused on upgrading the sewer collection system, while Phase 2 encompassed the secondary upgrade of the Honouliuli WWTP. Phase 3 will involve the secondary upgrade of the Sand Island WWTP. From 2010 through the fiscal year 2020, the city invested approximately $1.3 billion in Phase 1 upgrades, which included nearly 2,100 miles of pipes, 72 wastewater pump stations, and associated force mains. Currently, around 100 million gallons of wastewater are treated daily.

The secondary upgrade of Sand Island WWTP is being implemented in two phases. The first phase, which is 50% complete, is scheduled to finish by 2026. The second phase will begin in 2029 and is expected to be completed by the consent decree deadline of December 31, 2035. The Sand Island facility is an enhanced primary plant incorporating ultraviolet disinfection of effluent before it is discharged into the ocean.

The city acknowledges that the burden of funding the projects mandated by the consent decree falls on Honolulu ratepayers and uses optimum funding opportunities to save money and resources as well as modern, efficient technologies.

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