The operation of the Bay Park Sewage Treatment Plant has improved under the management of a private company, including a reduction in odor and noise complaints and a decline in nitrogen pollution, according to a report card by a coalition of Nassau County environmental watchdogs.

The Western Bays Coalition found that Suez Environment, which took over operations of Nassau’s sprawling sewer system in 2015, addressed many of the concerns identified by the group three years ago when Nassau was running the plant.

“The management of the plant is better, the effluent is cleaner, the odor complaints are down and the community transparency is up,” said Adrienne Esposito, executive director of Citizens Campaign for the Environment, at a news conference in Freeport.

Between 2010 and 2014, the state Department of Environmental Conservational hit the county with 127 violations, including excess amounts of ammonium, heavy metals, nitrogen and chlorine in the water. Nassau was also criticized for odor and noise emanating from the plant and for a lack of public meetings with the community.

At the time, the coalition identified 10 key objectives for improvement, giving the county a grade of “F.”

Since Suez took over 20 months ago, there have been no DEC violations, odor complaints have gone down and the firm hosts monthly meetings with neighbors, Esposito said.

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The coalition now gives Suez a grade of “B+.”

For example, nitrogen in the effluent from Bay Park, which serves 532,000 people on Nassau’s South Shore, has caused severe environmental damage to Reynolds Channel in the Western Bays, a series of waterways that are part of the South Shore Estuary Reserve. New technology being installed by Suez will cut nitrogen levels in half, Esposito said.

Scott Bochner of Long Beach, co-founder of Sludge Stoppers Task Force, said Suez installed odor controls throughout the plant and stopped using outside generators, which had prompted noise complaints.

“We are really happy with what we requested and what Suez has done,” Bochner said.

The coalition now wants Suez to begin an educational program to discourage residents and businesses from flushing pharmaceuticals down the toilet, which allows toxins to enter the county waterways.

“We know that a lot of work needs to be done,” said Suez spokesman Mike Martino. “We have 1.5 million residents to answer to and the scrutiny will always remain.”