SLUDGE VICTIMS

Hanscom has listened to neighbors' concerns. In tile beginning, she concedes, there were things that didn't smell that good,.

Such as the windrows. Those were the 12 piles, each 8 feet tall and 10 feet wide, of the leftover solids mixed with wood chips -- to ease the scent -- and laid out to dry.

"It was one of the few odors I ever smelled," she said. "It was musty, like a ceflar, or when you kick a dead tree. It didn't smell that good. But it was one the first things we stopped doing."

Instead, starting in 1987, that sludge was sent to the city landfill. Now, at $69 per ton, the city ships 4,200 wet tons of the sludge to northern New Hampshire for disposal each year.

Neighbors still complained about the smells.

In response, the city updated the plant's technology.

The key is oxygen, Hanscom explained. Oxygen keeps sewage from going septic."

In 1991, the city installed oxygen-injection equipment at a major sewage pumping station at Martell Court. In the late 1980s, the plant had stopped adding chlorine to the treated water before it emptied into the Ashuelot River,

At the time, chlorine was standard treatment to kill naturally occurring bacteria that, essentially, eat sludge. These little guys live for 12 to 30 minutes, just enough time to chow down and reproduce.

Today, the plant instead uses ultraviolet fights, which sterilizes the bacteria before they go into the river.

Also, a few years ago, the plant switched a major part of the cleaning process -- from mechanical mixing to diffused aeration. That reduced splashing and increased oxygen in the massive cleaning vat.

"We switched to aeration for energy and efficiency reasons," said Kurt Blomquist, director of Keene public works. "A side benefit was the reduction of odor.