Waste water treatment plant nearly back to normal operation

The screening and settling steps of the treatment process, which remove solid material such as sludge, continued running during the partial shutdown. But the ozone disinfection and bacteria treatments of the waste water were shut down, allowing 5.6 million gallons of largely untreated waste water to flow daily from the plant into Antietam Creek.

The plant began using a chlorine disinfection process on Feb. 12, which killed most bacteria and essentially ended the flow of contaminated waste water into the creek, Maryland Department of the Environment spokesman Richard McIntire has said.

New bacteria used to break down complex bacteria and other chemicals is growing at the plant. Barton said that as the bacteria reproduces it will do a better and better job of treating the sewage.

At about 12:30 p.m. Monday, the plant switched back to using ozone to disinfect the waste water, Barton said.

The ozone will do a better and more consistent job of killing bacteria because the plant is designed to use ozone, he said.

Barton said the plant's biological nutrient removal process, which removes phosphorous and nitrogen from the waste water, was still down, but tests of the waste water taken last week showed that nitrogen and phosphorous levels were within state limits.

The public was still being advised not to come into contact with the creek.

Hagerstown and state officials have said the millions of gallons of untreated or partially treated waste water that has flowed from the city sewer plant over the past week hasn't harmed people or wildlife along the creek.