Elizabeth City aims to upgrade 'too pretty' sludge

ELIZABETH CITY

Ava Goodwin, chief operator of the Elizabeth City water treatment plant, held in her hand a capped, clear canister of sludge that looked more like a latte to go.

This stuff is too pretty looking to be labeled sludge, she said. She prefers to call it biosolids.

"This is perfectly harmless," Goodwin said. "And it doesn't smell. I don't know why they call it sludge."

Left over from the treatment process, the sample in the can ister represented 2.7 million gallons of watered-down lime hauled annually to 6,270 acres of state-certified farm fields near Elizabeth City. In 2007, the city's cost for lime disposal was $120,000, she said.

Sludge recycling is a resource-saving effort that's been widespread for at least two decades, since long before the "green" movement.

But as clean looking as it is, Elizabeth City lime sludge gets a B rating from the state. The city is seeking an A rating so the sludge can be spread over more fields than just those certified by the state. Row-crop growing seasons can limit how many acres are available for application, and storage space is limited.

Grade A sludge must have three characteristics. It must contain no or only a minimal amount of pathogens such as fecal coliform. It must have no or only small traces of heavy metals such as arsenic or mercury. And it should not attract animals that could spread disease, a condition known by waste experts as vector attraction reduction.

Elizabeth City's sludge meets all the requirements, Goodwin said. After an arduous paperwork process, the state is expected to give an A grade to Elizabeth City's water treatment sludge early next year, she said.

Many cities in the state don't go to the trouble of getting an A grade, said Jon Risgaard, an environmental engineer with the North Carolina Division of Water Quality.

"But more are asking about it," he said.

An A grade would open up a large market around Elizabeth City for free lime sludge, said Scott Carpenter, a soil scientist with Soil Plus, the company that transports the city's water treatment and waste treatment sludges to farm fields.

Lime is used to improve acidic soils, allow ing crops to better absorb nutrients in the soil and produce higher yields. Farmers get the sludge at no cost, saving about $45 a ton from the cost of commercial lime, Carpenter said. Some soils here are acidic enough to need two to three tons of lime per acre each year, said Al Wood, Pasquotank County cooperative extension agent.

"Farmers are always looking for inexpensive alternatives for soil amendments," he said. "Just like they're looking for fuel alternatives."

Elizabeth City produces 2.4 million gallons a day of treated water to its customers. About three tons of lime a day is added to soften the water. After most of the lime solids are removed, the water is treated with other chemicals such as fluoride and chlorine.

Cities all over the country use lime to soften water and must dispose of the leftover sludge, Risgaard said. Some cities pay to have sludge spread on farm fields while others use methods such as composting, pasteurizing or drying it into pellets, he said.

Jeff Hampton, (252) 338-0159, jeff.hampton@pilotonline.com