Sewer plant blue barrels: What chemical did they once hold?

The blue barrels stored behind the town's sewage treatment plant off South Street caught the eye of Planning and Zoning Commission members when they walked the site before a public hearing on plans to renovate the plant.
The blue barrels stored behind the town's sewage treatment plant off South Street caught the eye of Planning and Zoning Commission members when they walked the site before a public hearing on plans to renovate the plant.

The slightly mysterious blue barrels stored behind the town sewer plant never contained any hazardous chemicals, according to Amy Siebert, chairwoman of the Water Pollution Control Authority.
“It’s my understanding that the barrels are being removed, and the most important thing is that they did not and do not and never did have anything hazardous in them,” Siebert said in an email response to The Press.
Although the phrase “hazardous materials” was used in connection with the barrels during a back and forth discussion at a May 14 public hearing on plans to renovate the sewer plant, Siebert said later that what the barrels had contained was a “food grade polymer” commonly used as a thickening agent at wastewater plants.
The WPCA oversees the plant.
“It is my understanding the barrels in question contained polymer in their day. Polymers used in wastewater treatment are not a hazardous chemical,” she told The Press.
“Polymers are used to help particles stick together better — so you can use them to help make your sludge dewater better or to get solids to settle out of a waste stream better,” said Siebert, whose day job is as commissioner of public works — including a wastewater plant — for the town of Greenwich.
Siebert’s explanation was seconded by Mike Burke, New England operations manager for Suez, the firm that operates the plant under contract with the town: “...the barrels do not contain hazardous waste, but rather are empty barrels of polymer (coagulant food grade) used in the conditioning or thickening of wastewater sludge,” Burke wrote, following up on one of Siebert’s emails to The Press.
Curious commission
The barrels — about 40 of them, stored, apparently empty, behind the sewer plant building — attracted the interest of members of the Planning and Zoning Commission and Inland Wetlands Board when they walked the sewer plant property in anticipation of the May 14 public hearing on renovation plans for the plant.
“When we were on the walk, it caught our attention,” said Rebecca Mucchetti, commission chairwoman. “We were told it was part of what they use in the treatment at the sewer treatment facility, that all the barrels were empty, they were going to be removed…”
Mucchetti’s understanding was that the storage of the barrels on the plant site had initially been viewed as temporary.
“Somebody was supposed to come and pick them up,” she said, “ …But they didn’t.”
No one seemed to have a firm idea of how long the barrels had been quietly collecting behind the sewer plant.
The commission decided it best to list the removal of the barrels among its conditions of approval for the sewer plant expansion.
Storage building
Under the renovation plan presented at the hearing, there will be a separate building created for storage of chemicals used at the plant.
“The renovations to the treatment plant will have a building where all the chemicals will be stored,” Mucchetti said. “...All the chemicals are going to be kept in a fully enclosed building that does not have a floor drain — that is one of the conditions,”
Resolutions of approval requested by the commission for both zoning and wetlands permits are expected to come up for a final vote at the May 28 meeting.
Both Siebert, the WPCA chair, and Burke, from the contractor Suez, referred to the chemical formerly contained in the barrels as “food grade” polymer.
The chemical giant DuPont describes some of its products as “food grade polymers for food contact applications” and says that these products meet a variety of regulations, including those of the U.S. Food and Drug Administration.
Referring to the chemicals from the blue barrels, Siebert said: “The fact that it is a food grade polymer is the main thing, and then that they are typically used to help coagulate/flocculate solids — i.e., bring particles together to help settling, for example, to help remove solids from a waste stream. That can help create treatment processes run more effectively and create a better effluent quality.”
Richard Baldelli, who heads the town land use office as director of planning and zoning, said what he’d been told about the contents of the blue barrels was similar: “... they contained a plant-based (non-hazardous) natural polymer, which is a product used in the sewer treatment process,” Baldelli recalled.
Siebert said she didn’t have a chemical name or the trade name of the polymer that the barrels had contained.
“I don’t know the official name of the polymer,” she said. “...There can be many chemical formulations specific to the given vendor.”
She added, “When determining what polymer to choose, you do testing to figure out which one has the best qualities that get you the results you want, and also look at the cost associated with that performance.”
The sort of barrels that attracted the Planning and Zoning Commission’s attention are often recycled for a variety of uses by sewage treatment operators, according to Siebert.
“Many plants rinse out the barrels and use them for storage or other uses, as they are usually pretty robust,” she said.
And the use of polymers is commonplace in wastewater treatment, Siebert said.
”Some plants will use polymers all the time, some use them based on conditions that may arise, whether seasonal, flow related, or other such factors,” she said. “There is nothing to fear from the use of polymers in wastewater treatment.”