Critical infrastructure restored at Sand Island Wastewater Treatment Plant

Sand Island Wastewater Treatment Plant (File photo)

City crews and contract workers have successfully restored critical parts of Sand Island Wastewater Treatment Plant to pre-Hurricane Ana levels of operation.

On Sunday morning, Oct. 19, heavy rains caused by Hurricane Ana and ongoing construction prompted 5,000 gallons of partially treated wastewater to overflow into Honolulu Harbor, and 20 million gallons to flood the plant’s basement.

The flooding short circuited some of the plant’s electrical systems and knocked clarifiers 4, 6, 7 and 8 offline.

Officials say all four settling tanks were back in working order as of Monday, Oct. 27. Rotating arms on those clarifiers are now functioning and solids can now be moved out of those tanks to the gravity thickeners for processing.

The plant needs at least three clarifiers online at any given time during normal operations to process all of the incoming wastewater. With four currently in operation, there is an extra clarifier for redundancy.

The remaining clarifiers at the plant are intentionally offline for routine maintenance and previously planned reconstruction projects.

The egg-shaped digester operated by Synagro Technologies was restored to full service and resumed converting the plant’s sludge into soil amendment pellets on Tuesday night, Oct. 21.

In addition, contractor Parsons last Wednesday, Oct. 22, plugged up the two holes in an offline channel to prevent a reoccurrence of wastewater overflowing into the basement area that contains electrical paneling.

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