Rls 15-11 ... On Monday morning, Aug. 24, Naval Facilities Engineering Command, Hawaii’s Wastewater Treatment Plant experienced a partial bypass at the final tertiary sand filtration system. This is a controlled bypass within the facility and not a wastewater spill. The event began at approximately 7:45 a.m. and is currently ongoing. From the start of the bypass to approximately 10:45 a.m. the plant discharged approximately 100,000 gallons of fully treated and disinfected secondary effluent through its deep multiport outfall without polishing effluent sand filtration.
The bypass was caused by higher than normal amounts of rain water due to storm and flooding conditions throughout the island of Oahu that passed through the secondary treatment process which caused clogging of the sand filtration polishing system. The sand filtration is one of the final advanced processes after full secondary treatment just prior to ultraviolet disinfection. It is an enhancement to improve the effluent quality and remove residual material following the fully functional secondary treatment system.
The bypass is continuing due to current weather conditions. It is unknown at this time when it will be concluded.
Effluent quality is expected to remain within permit limitations. Treated effluent was disinfected through the ultraviolet disinfection system prior to being discharged into Mamala Bay through the plant’s 12,500 foot long outfall that extends 1.5 miles from shore and into a 150 foot deep, multi-port diffuser where it was assimilated into the receiving waters with the assistance of ocean currents.
The Navy made all necessary notifications to the State Department of Health as required by the wastewater treatment plant’s operating permit. It is expected that the bypassed secondary treated and disinfected effluent would be naturally dispersed with minimal human health and environmental impacts.
The Naval Facilities Engineering Command, Hawaii’s Wastewater Treatment Plant provides advanced secondary treatment of both domestic and non-domestic wastewater. Advanced secondary treatment uses clarifiers, an activated sludge process, aeration/anoxic tanks, effluent sand filtration and UV disinfection.