Related video above: In September, four million gallons of raw sewage leaked into a Pinellas County neighborhood.

BRADENTON, Fla. (WFLA) — An operator error led to a chlorine disinfection violation in Bradenton last week, according to the Florida Department of Environmental Protection.

On Nov. 21, officials said there was a period of high chlorine demand due to a backwash from 6:28 p.m. to 9:38 p.m.

One of the operators “reacted incorrectly,” which caused the residual chlorine to fall below the limit in one of the chambers. As a result, the wastewater was not fully disinfected during that timeframe.

An incoming operator immediately recognized the mistake and corrected the issue, by pouring bleach back into auto, the FDEP said.

Within the three hours, it’s estimated that roughly 525,000 gallons of partially treated wastewater filtered through.

According to the FDEP, the City of Bradenton is ensuring additional on-the-job training to ensure all operators have the base knowledge.