...program, plants that remove more nitrogen than its target earn credits that can be sold to plants that are not in compliance. Nitrogen removal upgrades or expansions are eligible for water fund grants and 2%, 20-year loans.

"The program is working for us," says Gary Johnson, Connecticut DEP senior environmental engineer. "Every year we have more capital improvements getting under way and we’re removing more nitrogen from the sound."

The credit trading approach gives municipalities flexibility in moving toward the overall goal, he says. "If we made everyone comply on a tight schedule, the capacity for consulting engineering and contractors would be maxed out very quickly, driving costs up," he says. The program is phased in over three stages of increasingly stringent levels.

So Far, So Good.

Connecticut’s records for 2003 are expected to be released this month, but Johnson says positive trends established in 2002 are continuing. The program removed 2.8 million lb of nitrogen from effluent streams at a capital and operation and maintenance cost of $4.7 million. The overall daily equalized nitrogen discharge stream was 15.8 million lb, 13% less than projected. The state computed the price of a credit at $1.65. In 2003, the price rose to $2.14. Eight facilities completed upgrades in 2002 and 2003. The program is gaining momentum. "In all, 25 facili-ties have come to us for financing," says Johnson.

Each municipality has its own plan. About 10 years ago, New Haven hired the Boston office of CH2M Hill Cos. to assess an interim nitrogen removal program. The city’s 40-mgd plant is the largest on the Connecticut shore, says Ray Smedberg, the city’s water pollution credits manager.

New Haven had expanded its wastewater treatment system to accommodate population growth that "never happened," says Smedberg. Taking advantage of the extra volume of tanks, the city spent $8 million to convert from mechanical aeration to fine bubble diffusion and add nitrate recycling pumps, he says. As a result, the plant discharges effluent "a shade under 3 mg/l," well below the program’s present limit of 7.5 mg/l, Smedberg says. In the past two years, the city has earned $1.2 million in credits.

Danbury last year spent $273,000 to buy nitrogen credits, says Mario Ricozzi, superintendent of public utilities. The city spent about $65 million in plant improvements about 10 years ago and is in the seventh year of a 20-year operations contract with Houston-based Veolia North America. "Right now, it makes better sense for us to buy the credits and try to optimize operations. We’ll wait a few years before tackling another big capital program," Ricozzi says.

Major Retrofit. Stamford plant’s $105-million upgrade is the largest capital project in the city’s history. (Photo courtesy of Warren Jagger Photography Inc.)

Stamford is 33 months into a $110-million, 40-month upgrade and expansion of its municipal treatment plant, says Jeffrey Fournier, project manager with prime contractor Carlin Contracting Co. Inc., Waterford, Conn. Its contract climbed from $86.4 million to $91 million because excavation for 20-ft-deep aeration tanks involved removing spoil that was contaminated with heavy metals from the old town landfill.

"This is the largest capital improvement program in the city’s history," says Jeanette S. Brown, plant manager. Along with a denitrification train, flows will move through an anoxic zone, an aerobic zone, followed by another anoxic zone to treat ammonia, followed by a secondary aerobic zone to treat nitrates. "So much of what we do in wastewater engineering is simply to try to mimic nature’s own processes," says Brown.

Stamford already is banking nitrogen credits and expects to have more in its pocket soon. With full treatment scheduled to come online soon, "next year will be a great credit trading year for us," Brown says.