More than 45,000 gallons of treated water that had not been disinfected was sent into Lake Wilson yesterday because of two malfunctions at the Wahiawa Wastewater Treatment Plant.

Warning signs were posted at Lake Wilson, water samples were collected and the public was warned to stay away from affected waters.

The first malfunction to the plant's ultraviolet disinfection unit occurred from 8:14 to 8:29 a.m., sending 26,555 gallons of treated, but not disinfected, wastewater into Lake Wilson.

The second discharge of about 18,775 gallons occurred from 12:15 to 12:28 p.m. when treatment plant workers noticed that the ultraviolet disinfection lights were flickering off and on, said Ross Tanimoto, monitoring and compliance branch chief with the city's Department of Environmental Services.

A switch suspected of causing the malfunctions is being repaired, city officials said.

Lake Wilson, which has a depth of about 60 feet, holds about 1 billion gallons of water. The Wahiawa Wastewater Treatment Plant discharges 2 million to 3 million gallons per day of treated and disinfected water into the lake, Tani-moto said. The city has an agreement with the state Department of Health to treat and disinfect wastewater before sending it into the lake, Tanimoto said.