‘Pelletized biosolids’ as waste solution in Winston-Salem
The treatment of raw sewage produces at least three things in abundance: reclaimed water, sludgy leftovers and wonky euphemisms.
Consider the case of “pelletized biosolids.” No, it isn’t what you think it is. At least not entirely. Instead, it’s the utilities commission’s latest attempt to grapple with a problem that’s persisted since the birth of modern plumbing.
What do we do with the… leftovers?
Forsyth County and the city of Winston-Salem want to turn it into pellets. The joint city-county utilities commission approved a $26 million investment in a drying facility that will turn the solids, metals and microbes extracted from sewage into nitrogen-rich pellets suitable for selling to tree farmers.
It’s the latest development in a 20-year saga, said utilities director David Saunders.
“Our goal has always been to find a beneficial reuse of this byproduct,” Saunders said.
Until recently, the city disposed of its sludge on nearby farmland. The farmers signed up to receive the free sludge, which city employees trucked to their property and slathered on fields.
“Obviously they would want it because it was a free fertilizer,” Saunders said.
Among some people living in and around land application sites, the appeal of free sewage sludge has been a little less obvious. The Blue Ridge Environmental Defense League published a handout on sewage sludge that lists several toxic substances found in the product, including dioxins, heavy metals and bacteria.
A grassroots movement called NO-BS (Neighbors Opposing Bio-Sludge) formed to fight the widespread practice of applying sewage sludge to farmland. At the same time, the farmland itself began disappearing.
“As more and more of these farms turned into subdivisions and golf courses,” Saunders said, “we found it harder and harder to meet our needs.”
The first thing the city did was turn the sludge into a cake. They extracted almost all the water, decreasing the volume of byproduct and the amount of land needed to get rid of it.
But the city still spent money transporting the cakes to farmers. And the farmers kept disappearing. So the city council voted to approve the drying facility, which will be fueled by methane produced onsite at the Archie Elledge Wastewater Treatment Plant.
On Jan. 14, the city-county utilities commission also approved a contract with Blackstone, Va.-based PineGro to sell the pellets to the company for $3 a ton. The commission expects the facility to produce 9,000 tons of pellets a year.
The contract will only generate about $30,000 a year, not enough to offset the cost of the drying plant, but the county will also save the more than $800,000 dollars it spent last year transporting sewage sludge to farms and landfills. Saunders said the city also worried about disposing of sludge in landfills, because the material would take up precious space in facilities that are already filling up.
PineGro already handles the pellets produced by the town of Cary’s sludge dryer. They market the product as a fertilizer for timber farmers. PineGro will be buying all of the county’s pellets and will be required to dispose of any they don’t sell.
Thermal drying facilities like the one under construction at the Elledge plant are one of the ways cities and counties are dealing with the problem of sludge. Greensboro incinerates its sludge and Charlotte composts it. A couple of South Carolina cities are drying their wastewater sludge, Saunders said, along with the city of Louisville, Ky.
“If you look toward the future, we’re ahead of the game,” Saunders said. “In the long run, this is going to save us money, because as the available land shrinks, our options will be limited.”
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