Tiny chips let treatment plant grow by acres
By Phil Primack Globe Correspondent / November 29, 2010
The little discs look like wafers from a waffle iron. But when town officials in Hooksett, N.H., needed to increase the capacity of the waste-water treatment system, they dumped nearly 46 million of them —Biofilm M plastic chips —into waste-water holding tanks.
“The old technology would have been to just build more tanks,’’ said the Hooksett Sewer Department’s superintendent, Bruce Kudrick. “But that’s very expensive, and we don’t really have the land to expand.’’
The town’s longtime consulting firm, Graves Engineering of Worcester, suggested using Biofilm chips, made in Germany by a North Carolina subsidiary of Veolia Water, a company with operations in 66 countries.
The technology is simple. The maze of squares on the discs adds significantly to the surface area available for growing oxygen-producing microorganisms, which are essential in the process that decomposes sewage.
Initially, Kudrick was skeptical. “I said, ‘You have to prove to me that this will work,’ ’’ he said.
But after visiting treatment plants around the country that use older but similar plastic chips, he was convinced. Screens keep the discs, which he said require no maintenance, from getting out of the tanks.
The chips were added to Hooksett’s aeration tanks three months ago, creating the equivalent of 81 extra acres of surface area for microorganisms to grow.
Early results are promising, Kudrick said.
“All my bacteria are living right there in all those chips, where before, they were suspended throughout the tank,’’ he said.
Hooksett is the first US waste-water treatment plant to use the Biofilm media, though the technology is well established.
An earlier version, K3 media, also adds surface area for bacteria. Biofilm, though, has 2.4 times more surface area than its rigatoni-shaped K3 predecessor, said a Graves Engineering project manager, Steven Sylven.
“If we had used the K3 media,’’ he said, “we would not have been able to double the Hooksett plant’s capacity without building additional aeration tanks.’’
John Vetere, director of the Massachusetts Water Resources Authority’s Deer Island waste-water treatment plant, said the chips are especially effective in reducing nitrogen levels in aeration tanks. Were the MWRA to face new regulatory requirements regarding nitrogen, “we would certainly look at this technology to use in our aerators,’’ he said, because it would cost less than new construction.
Sylven said the chips and other equipment and infrastructure cost Hooksett about $2 million, saving the town more than $1 million. Federal stimulus funds helped finance the project.
Hooksett’s initial results are promising, but a much bigger test of Biofilm will play out in Rhode Island, where the Narragansett Bay Commission plans to utilize the same system to upgrade the efficiency of its Field’s Point waste-water treatment plant.
The plant discharges an average of 50 million gallons of treated water a day, compared to Hooksett’s 2.2 million gallons.
“If the technology pans out — and it worked very well in our pilot test — our experience will be helpful for other facilities as they face ever-stricter [federal] requirements’’ that take effect in 2014, said Jamie Samons, the commission’s spokeswoman.
Graves Engineering’s president, Donald Graves, says the technology has a bright future. “Engineers tend to be conservative,’’ he said, and slow to adopt new methods. “But other technologies are out there to process waste water. We just have to be open to them.’’
© Copyright 2010 Globe Newspaper Company.
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