Stonington has chosen a Massachusetts company with a proprietary process for enhancing wastewater cleansing as it prepares for an approximately $15 million, three-year upgrade of its treatment plant that discharges into Long Island Sound.
Harold Storrs, director of the town’s water pollution control facility, said Cambridge Water Technology’s proprietary process uses magnetite, an ion ingredient, that speeds the rate at which waste solids, nitrogen and other nutrients settle out of wastewater. This makes the treatment process more efficient and requires less equipment, Storrs said.
A four-month trial of Cambridge’s “BioMag” ingredient lowered the amount of concentrated nitrogen discharged into the Mystic River to below state requirements, officials said. The Mystic River empties into Long Island Sound.
State environmental regulators mandate that Stonington cut its average nitrogen discharge to less than 5 milligrams per liter. The BioMag trial cut the Stonington plant’s discharge to less than 4 milligrams per liter, or 12 pounds daily, from 7.5 milligrams per liter, or 30 pounds a day.
Storrs said that after Labor Day, Stonington will seek appropriations for the plant upgrade. If officials approve, teh town will do out to bid for design proposals for the plant upgrade that so far is about 10 percent complete, he said.
Design and approval will take about a year, and another 18 months to install the upgrades, the pollution control director said.
