Vermont’s wastewater treatment facilities, along with facilities in New Hampshire and Massachusetts, will be participating in a study beginning this fall to determine how to reduce nitrogen discharge into the Connecticut River. Nitrogen discharges from wastewater treatment plants contribute to an area in Long Island Sound, called a hypoxic zone, that is devoid of oxygen during parts of the year.
When there is an influx of nitrogen into the ocean, it feeds a blossoming of microscopic organisms, such as algae. This population boom is followed by a bust: The organisms decompose, a process that consumes oxygen and thereby produces a dead zone in which oxygen-dependent organisms, like fish and shellfish, cannot live. A similar process occurs with phosphorus in freshwater ecosystems.
The study will inform these states on what their current contribution to the hypoxic zone is, whether it would be feasible to reduce it, what it would cost, and how much those reductions would contribute to reaching water quality goals in Long Island Sound.
The New England Interstate Water Pollution Control Commission, a nonprofit interstate agency that supports state efforts to protect water quality, is coordinating with Massachusetts, New Hampshire and Vermont to study how to retrofit treatment plants to cheaply and effectively remove nitrogen from wastewater. The study will inform these states on what their current contribution to the hypoxic zone is, whether it would be feasible to reduce it, what it would cost, and how much those reductions would contribute to reaching water quality goals in Long Island Sound.
According to the 2009-2010 biennial report by the Long Island Sound Study, a partnership of federal, state, and non-governmental organizations to restore and protect Long Island Sound, wastewater treatment plants, particularly those in New York and Connecticut, are the single greatest contributor of nitrogen to the Long Island Sound.
Nitrogen ends up in wastewater in part because humans eat food relatively high in nutrients, and our bodies don’t extract those nutrients very well, said Don Ross, a professor of plant biology at the University of Vermont.
In addition to the low-cost retrofit study, Vermont is taking two other actions to assess its contribution to the hypoxic zone. This summer, Vermont began testing nitrogen levels going in to and out of 12 wastewater treatment plants that feed into the Connecticut River. The Vermont Agency of Natural Resources (ANR) has also asked wastewater treatment facilities to voluntarily monitor their nitrogen inputs and outputs to determine the proportion of nitrogen they remove from wastewater.
According to Tim Clear, an environmental scientist with ANR, Vermont will compile the data from the voluntary monitoring, its own monitoring, and the low-cost retrofit study to determine a reasonable TMDL to recommend to the federal Environmental Protection Agency (EPA). A TMDL, or total maximum daily load, is a limit that the state and the EPA agree upon.
The Agency of Natural Resources will divide Vermont’s TMDL among all of the facilities that feed into the Connecticut River to determine a TMDL per facility. Although the state TMDL determination is still “a few years down the road,” the facility allocation will likely occur in early 2013, said Clear.
Although Vermont is cooperating in efforts to restore the water quality of Long Island Sound, Clear said that Vermont’s contribution to the problem is “almost non-existent.”
If retrofits are necessary, the municipal wastewater treatment facilities will be responsible for the cost, though loans or grants may be available.
Although Vermont is cooperating in efforts to restore the water quality of Long Island Sound, Clear said that Vermont’s contribution to the problem is “almost non-existent.” The EPA roughly estimates that Vermont exports 1,727 pounds of nitrogen per day into the Connecticut River. By comparison, the Long Island Sound Study’s 2009-2010 biennial reports states that roughly 212,000 pounds of nitrogen enters the sound every day from wastewater treatment plants in New York and Connecticut.
“What [the EPA has] asked from us is that we essentially hold the nitrogen loading from our wastewater treatment facilities at current levels,” said Clear. No one expects Vermont to spend a lot of money to retrofit treatment plants, but that the state is hoping to pick the “low-hanging fruit” using “relatively low-cost methods.”
Susy King, the director of Water Quality Programs at the New England Interstate Water Pollution Control Commission, said that New York and Connecticut have “certainly been successful in reducing the nitrogen loads to the sound. We do know that there’s still a hypoxia problem, even though it’s getting smaller.”
King said that New York has been upgrading wastewater treatment plants with nitrogen-extracting technology, while Connecticut has implemented a nitrogen trading program that allows plants to decide whether to upgrade their equipment or buy credits from other plants.
Upgrades to wastewater treatment plants have reduced nitrogen discharges into Long Island Sound from treatment plants by 24 percent to date. Although these actions have helped — the hypoxic zone has gotten smaller and lasts for less time during the year — further action is needed to achieve the goal set in 1998 by the EPA, in cooperation with New York and Connecticut, to reduce discharges from treatment plants by 58.5 percent by 2014.
Tom Groves, director of Wastewater and Onsite Programs for New England Interstate Water Pollution Control Commission, said that the process of removing nitrogen from wastewater is to first aerate the wastewater, then limit oxygen, which allows some nitrogen to be converted and released as gas. According to a fact sheet available on the website of the Long Island Sound Study, one facility in Connecticut removed 65 to 75 percent of the total nitrogen from wastewater after installing a low-cost retrofit.
The cost of retrofitting depends on the present layout of the treatment facility, said Groves. “They need to still be able to provide the proper level of treatment. It’s kind of a case by case situation, unfortunately.” This means each facility must be evaluated separately.
The cost also depends on how much nitrogen needs to be removed. “There’s different types of treatment processes or ways that you can tweak the existing treatment process to remove nitrogen,” said Groves. “You can alter the treatment process or design a new plant upgrade with a higher degree of treatment that spends more time and money to remove nitrogen.”
And, Groves added, “Unfortunately there’s not a lot of money going around for construction and upgrade of treatment plants.”
Mark Tedesco, the director of the EPA’s Long Island Sound Office, said that so far, Connecticut wastewater treatment plants have not had difficulty funding plant upgrades because they’ve been integrated with ongoing upgrades over a 14-year period and because the state has provided support.
“There are things we can do to plan ahead and minimize the costs,” Tedesco said.
Tedesco is hopeful that treatment plant upgrades, along with efforts to reduce other sources of nitrogen, will make a difference.
“We can solve these problems. … We went through 400 years or so of increasing nutrient inputs into Long Island Sound, and we’ve now gotten about 10 to 15 years of decreasing it. So we’ve turned a corner.”