Moving sludge raises big stink near plant
In recent days, workers and customers at businesses near the Westerly Sewer Treatment Plant have noticed a periodic stench.
“Nauseating,” said Appliance Outlet General Manager Duane Sipe, who grew up in a farming area and is OK with the smell of manure from time to time in rural areas. “But when you think about what THIS is. …”
Fortunately, it won’t last long – although it will return in milder form in the fall, according to authority officials, who have been fielding complaints.
The smell is coming from workers loading sludge – the semi-solid residue of sewage treatment – from stockpiles in a roofed pavilion-like storage building onto trucks for transport to area farm fields for fertilization, according to Jim Balliet of Gwin Dobson & Foreman, the authority’s consulting engineer.
Workers are doing it as fast as they can and should finish this week, he said.
Kevin Gatto of Altoona, who works near the plant, said the smell has been coming in waves, “sometimes on an hourly basis.”
“It’s just augh – bad,” he said. “Really, really bad.”
The authority “dewaters” solids every day in a centrifuge, 10,000 tons a year, according to Balliet.
But the state Department of Environmental Protection only allows the sludge to be spread on fields in the spring and fall.
In the spring, the authority needs to get rid of about seven months’ worth, he said. In the fall, the sludge has accumulated for a shorter period.
After drying, the sludge is still 78 percent water, Balliet said. “It looks like wet soil.”
It continues to decompose in storage, he said.
However, a crust forms on the surface, preventing the smell from getting into the air.
The smell gets into the air, however, when a front-end loader digs in and flips it into the beds of dump trucks for transport, he said.
The smell is worse when it’s warm and humid and if the wind is trending in your direction, he said.
Authority officials have asked Balliet to find a way to minimize the problem.
“You can spray the solids with different chemicals,” including an oxidant, he said. “But you have to be careful – you don’t want to jeopardize our land application permits.”
Environmental Services Manager George Boliski thinks the centrifuge – installed recently as part of the authority’s renovation of Westerly – contributes to the problem because it heats the sludge.
That residual heat leads to generation of additional ammonia in the stockpiles, he said.
Boliski is not alone in believing that centrifuge-dried sludge is more odoriferous, despite being about 7 percent dryer than sludge processed by the old belt press method, according to Balliet, who disagrees.
The authority could buy dryers that would take all but about 30 percent of the water away – leaving virtual powder and no odor, Boliski said.
But that would cost $500,000 for each of the authority’s two sewer plants.
“The authority wants to be a good neighbor,” Balliet said. “At the same time – it’s a wastewater treatment plant.”