Some 21,000 gallons of treated and “digested sewage sludge” from the Lihue Wastewater Treatment Plant spilled into an earthen drainage channel next to the facility Thursday.

A county official said the sludge did not discharge into Kalapaki Bay or other bodies of water.

In an emailed statement, acting County Engineer Lyle Tabata said: “There has not been sufficient rain during the past day for runoff from the area to carry sludge to any stream or the Kalapaki Bay.”

Shortly after midnight, sludge was in the process of being transferred to a drying bed when it lapped over the bed and flowed into the channel. About 21,000 gallons of sludge overflowed for more than 3-1/2 hours before crew members contained it at about 3:30 a.m.

A crew from the Wastewater Management Division cleaned up the spill by pumping out the sludge. The area was also disinfected with chlorine granules.

Officials said the Department of Health has been notified of the spill. Although the spill did not occur near any public access areas, signs were to be posted to inform the public to steer clear of the area.

Digested sewage sludge, also called biosolids, consists of treated solids that are removed from wastewater following separation of the solids from the liquids. “Treatment is conducted by concentrating the solids and allowing anaerobic microorganisms to digest the pathogens over time in an anaerobic digester,” Tabata said.

“In this case, the spilled sludge still contained liquid, which normally is removed by drying prior to disposal or beneficial use of the dried biosolids.”