Wastewater Discharged into Puhi Bay

October 20, 2021, 6:04 AM HST
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About 2 million gallons of fully treated wastewater was discharged in Puhi Bay without final chemical disinfection, county officials reported Tuesday, Oct. 19.

Twelve signs were posted around the area.

The incident occurred at the county’s Waste Water Treatment Plant, located at 150 Kekuanaoa Place in Hilo, on Monday afternoon. According to county officials, chemical feed pumps supplying sodium hypochlorite for effluent disinfection stopped pumping due to loss of signal from the effluent flow meter.

“The effluent flow meter signal was lost due to an electrical disruption,” officials stated in a press release Tuesday.

On Tuesday morning, 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 a.m., testing indicated that chloride residual at the effluent channel was 0.46 milligrams per liter, indicating proper disinfection was restored. At 10:50 a.m., 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 backup power source for the effluent flow meter was installed. Routine checks and tests of the battery backup power source will be implemented.

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