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For most of southeastern Connecticut, every flush of the toilet, drain of the shower and final rinse of the laundry is destined for the Thames River.
Between its beginnings in Norwich and its mouth in New London, the 16-mile estuary serves as the bottomless sink at the end of the plumbing systems for all or part of 13 communities. The five sewage treatment plants that serve these communities empty about 21 million gallons a day of wastewater into the river.
That might seem like reason to pause for anyone considering a dip in one of the riverfront beaches along Pequot Avenue in New London. But a tour of the treatment plant that serves the town of Groton and the Naval Submarine Base, considered by state environmental regulators to be a good example of the kinds of operations found along the river, would likely allay many of those reservations.
For starters, visit the plant's laboratory. On the counter are two beakers, one filled with cloudy, grayish water and the other with water as clear as any coming out of the tap. The first contains a sample of wastewater when it enters the plant, and the other is a sample of the water that pours into the river after treatment.
Marked by an orange and white buoy, the submerged discharge pipe empties in the river off Thames Street in Groton, between an Electric Boat parking lot and the Hess fuel tank farm. The outfall is tested daily, and most days, said plant manager Carl Almquist, it exceeds the quality standards set by the state.
"Everybody's trying their best to help the river," he said.
The effluent isn't drinking-water quality, he said, but it would be clean enough to be used to water golf courses, for example, or injected into the earth to recharge aquifers.
With the exception of the Norwich plant, which is in the process of a major overhaul, the plants that empty into the Thames are releasing water that's "cleaner than the river water it's going into," said Dennis J. Greci, supervising sanitary engineer for the state Department of Environmental Protection.
"The people who work in these plants take tremendous pride in their work, that they're helping to clean up the environment," he said. "For a river the size of the Thames, we're nowhere near what it can handle" in treatment plant discharges.
For the next part of the Groton tour, take a look around the plant. This is a place that handles 3 million gallons a day of some pretty nasty stuff, yet it looks remarkably clean, and odors are for the most part contained to the area immediately around the primary treatment tanks. Twice a day the plant sends truckloads of sludge strained, settled and skimmed out of the wastewater to an out-of-town incinerator.
"There's some areas where we have to get down to the nitty gritty, but for the most part, we keep it pretty clean," Almquist said.
He began his career at the plant in 1973 at age 22, a year after the enactment of the federal Clean Water Act. Over the years, the act and its enforcement by the state Department of Environmental Protection has been the engine driving the gradual improvements to treatment plants nationwide, although implementation has varied widely.
When Almquist began, much of the town was not yet sewered and the plant, by today's standards, was fairly basic, rated one step above the simplest type. Now it is a class 4 plant, one notch below the most advanced, and serves two-thirds of the town.
"It used to be that the margin of error was pretty wide," Almquist said, "but now, everybody's watching you."
Microorganisms do the work
Over the years, Almquist has watched the plant expand, modernize and become more sophisticated and complex, with many of its operations automated as it meets ever-increasing state requirements for the cleanliness of its discharge. The plant's most recent upgrade enables it to remove excess nitrogen from the wastewater, part of an effort to improve the health of Long Island Sound, where the Thames and other major state rivers flow.
Just 18 employees keep the aeration tanks flowing, the solids settling in the clarifiers, the underground labyrinth of pipes and sludge pumps working, the bacteria busy breaking down the wastes around the clock.
"The microorganisms are our workers," said Almquist, pausing over a tank crammed with little black plastic discs where the bacteria cluster. Nearby were tanks that drip chlorine at the final treatment stage, and huge bubbling cauldrons where oxygen levels of the wastewater are adjusted.
Greci said that even the best of treatment plants are still facing future upgrades so that pollutants not even considered a few years ago will be removed. Phosphorous is one target, along with the residues of all the medicines, other pharmacy products and even some foods people consume every day that end up getting passed through the human excretory system or dumped down the sink or toilet. Even caffeine is showing up in wastewater.
Some of these residues are being shown to be endocrine disrupters that can have harmful effects on developing marine life.
"We're just starting to study this," Greci said. "We've gotten all the really gross pollutants out, and now we're finding this other stuff. But we don't understand yet how much is too much. We don't really know yet which ones to worry about, or which ones are settling out in the sludge or being broken down."
Sewage treatment plants that empty into the Thames River:
New London plant:
Communities served: New London, Waterford, East Lyme, and portions of Old Lyme
Flow: 8.28 million gallons per day
Upgrades needed: $8.2 million to improve sewer system
Communities served: Montville and Mohegan
Flow: 4.5 million gallons per day
Upgrades needed: $2 million in sewer extensions
Communities served: Norwich and portions of Franklin, Sprague, Lisbon and Preston
Flow: 5.34 million gallons per day
Upgrades needed: $89.89 million in projects, the largest to improve the treatment process and create separate wastewater and stormwater systems
Groton City plant:
Community served: Groton City
Flow: 2.11 million gallons per day
Upgrades needed: no current identified needs
Groton Town plant:
Communities served: Town of Groton and Naval Submarine Base
Flow: 2.99 million gallons per day
Upgrades needed: $3.92 million to improve pump stations
Source: Connecticut Department of Environmental Protection. Flows from 2009.