Hawai’i County NOTIFICATION OF WASTEWATER TREATMENT INCIDENT
NOTIFICATION OF WASTEWATER TREATMENT INCIDENT
Reporting Agency: County of Hawai‘i
Wastewater Division
108 Railroad Avenue
Hilo, Hawai‘i 96720
Phone No.:
Fax No.:
808 961-8338
808 961-8644
Location: Hilo WWTP, 150 Kekuanaoa Place, Hilo, HI 96720
Date of Incident: 10/18/2021-10/19/2021
Time of Incident: 4:45 p.m. on 10/18/2021 to 8:25 a.m. on 10/19/2021
Amount Of Wastewater: 2,096,068 gallons (estimated volume)
Incident Description: Loss of final effluent disinfection. About 2 million gallons of fully
treated wastewater was discharged without final chemical
disinfection.
Cause of Incident:
Chemical feed pumps supplying sodium hypochlorite for effluent disinfection stopped pumping due to loss of
signal from the effluent flow meter. Effluent flow meter signal was lost due to an electrical disruption.
Remedial Actions Taken:
On 10/19/2021 at 8:25 a.m., calcium hypochlorite tablets were deposited into the effluent channel.
At 8:37 a.m. the chemical feed pumps were put back online in manual mode.
At 9:07 am testing indicated that chloride residual at the effluent channel was 0.46 milligrams per liter,
indicating proper disinfection was restored.
At 10:50 am, power to the effluent flow meter was rerouted to a different circuit, and it was restored to normal
operation. Chemical feed pumps were then restored to normal operation. A new battery back-up power source
for the effluent flow meter was installed. Routine checks and tests of the battery back-up power source will be
implemented. Twelve signs posted around the Puhi Bay discharge area
