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Wastewater Treatment Plant:  Kahuku WWTP


Kahuku Service Area

Kahuku Wastewater Treatment Plant (1980)
  • Secondary level of treatment with sand filtration
  • Processed 198,700 gallons per day (FY13)
  • Injection well disposal (100 foot depth)
  • Estimated 20-year CIP funding: $20 million

The Kahuku Wastewater Treatment Plant (WWTP), originally built in 1980, provides secondary treatment utilizing the activated sludge process and disposal through injection wells.  The plant was expanded in the early 1990s, doubling its capacity from 200,000 to 400,000 gpd.


This facility serves the town of Kahuku, located in the Koolauloa District of Northeastern Oahu and processes approximately 198,700 gallons of wastewater daily.  In addition to the residential areas, the plant receives flows from schools, hospital, churches and a small commercial area.  The rest of the area handles its wastewater through cesspools and septic tanks.


The facility is designed for an average daily flow of 400,000 gpd.  Secondary treated wastewater is sent through a final sand filtering process and a sodium Hypochlorite (liquid bleach) chlorination system, which disinfects the effluent.  Treated effluent is discharged into six wells at a depth of approximately 100 feet underground. The sludge produced is hauled in tanker trucks to the Kailua Regional WWTP for final processing and disposal. The Plant also uses sludge drying beds to produce treated and dried sludge that is sent to the Waimanalo Gulch Sanitary Landfill.

The Kahuku WWTP consistently produces very clean effluent.  In 1998, EPA awarded the plant a national first place award for Outstanding Wastewater Treatment Facility Operation and Maintenance.

The Kahuku WWTP operates under an Underground Injection Control (UIC) Permit (Permit No. UO-1257) effective July 29, 2011, and expiring July 28, 2016.  The UIC permit authorizes the City and County of Honolulu to discharge secondary treated wastewater effluent from the facility to the receiving subsurface environment through its injection well system in accordance with effluent limitations, monitoring requirements and other permit conditions.

Last Reviewed: Monday, September 23, 2013