Sludge to be studied for health concerns

CHAPEL HILL -- It happens.

Tons of it, accumulating with every toilet flush.

But agreement on wastewater residuals -- what's left of sewage after treated water is discharged back into rivers and streams -- pretty much stops there.

There isn't even agreement on what to call it. Environmentalists and some researchers call it sewage sludge. The industry term is "biosolids."

Some farmers swear by it, saying the free nutrients keep them in business as the costs of oil-dependent fertilizer continue to rise.

But some people living near the farms where it's spread say the heavy metals, chemicals and pharmaceuticals found in some sludge make them sick.

The Environmental Protection Agency says the practice is safe if standards are followed.

Researchers say there isn't enough science to know for sure, but two studies have been launched recently, including one that will track the health woes of people living near sludge-spreading sites in North Carolina and Virginia.

Environmentalists are asking for greater oversight and more science. This year they successfully requested the state's first public hearing on an application permit, the city of Burlington's request for renewed permission to spread sludge in Orange, Chatham and other counties.

Cheap fertilizer

Wastewater treatment plants around the country face the same challenge of disposing of residuals, mixtures of human waste, industrial discharges and whatever else goes down drains.

They typically have three options: Burn it, bury it or spread it on land.

Much of the nutrient-rich material goes to farmers as free fertilizer. Raleigh, Durham and the Orange Water and Sewer Authority all spread sludge on farmland.

Biosolids are a cheap, effective fertilizer -- less expensive than chemical fertilizers, said Karen McAdams, a farm agent for the cooperative extension service.

Chatham County farmer Gary Moon has had biosolids applied to his pastures since 1995.

"I think it's just as safe, if not safer than chemical fertilizer," he said. "Also, it makes the grass grow better than anything we've ever tried."

Moon said he and his family live on the farm and that they've never had any health problems. Nor have the beef cattle he grazes on the fields, he said. Moon said opponents' claims are unproven and that he's satisfied with the federal oversight of the practice.

Lower fertilizer costs mean lower food costs, Moon said. Without sludge, he added, "There'd be a whole lot of farmers going out of business."

Unknown contents

Humans have put their waste and animal manure on fields probably as long as there have been farms.

But industrial society -- and its waste -- is different, says Steve Wing, an epidemiologist at UNC-Chapel Hill.

"A lot of waste, the human waste, is mixed with chemical waste," said Wing. "There are metals. There are bacteria and viruses and parasites. There are other types of chemicals that are used in industrial processes."

But sludge contents can vary widely from city to city and, potentially, from truckload to truckload.

"We like not to talk about sludge, but sludges ... because you can't make these generalizations," said Murray McBride, director of the Waste Management Institute at Cornell University.

"You can't really say for sure what's going to be there," said McBride, a soil chemist.

Rules apply

The EPA sets standards for sludge contents and application and how soon fields can be grazed or harvested after spreading.

The agency regulates levels of metals and other toxins such as arsenic, lead and mercury. It sets standards for reducing pathogens such as viruses, bacteria and parasites during sewage treatment.