Nitrogen pollution from Maryland sewage plants and industries increased in 2012, a new report says, partially undermining gains the state has made in prior years in cleaning up the Chesapeake Bay.

While nitrogen discharges from treatment plants and factories declined overall across the six-state bay watershed from 2011 to 2012, they grew in Maryland, Delaware and New York, according to the Environmental Integrity Project, a Washington-based watchdog group.

Analyzing publicly available data from state agencies and the Environmental Protection Agency, the group found that nitrogen discharges from plants in Maryland were more than 400,000 pounds higher in 2012 than the year before.  In Virginia, by comparison, nitrogen pollution from sewage plants and factories dropped by more than 1 million pounds the same year.

Tarah Heinzen, a lawyer with the environmental group, said it's not entirely clear why nitrogen pollution may have increased in Maryland.  But she noted that collectively the state's sewage plants and industries violated their permit limits on nitrogen discharges in 2012 by more than 300,000 pounds.

"Maryland was making very good progress between 2010 and 2011,'' Heinzen said, "and that progress seems to have essentially stoped between 2011 and 2012."

Jay Apperson, spokesman for the Maryland Department of the Environment, said state officials are unable to verify the group's data, and that figures they have on wastewater treatment plants indicate there have been decreases in nutrient pollution both years.

According to the group's report, three wastewater treatment plants - in Salisbury, Frederick and on Ballenger Creek in Frederick County - collectively accounted for more than two-thirds of the nitrogen discharge violations in Maryland.  Sewage overflows also flushed nearly 34,000 pounds of nitrogen into streams and the bay that year.

While the six bay states and the District of Columbia have made progress overall in reducing discharges of nitrogen, phosphorus and sediments - the pollutants blamed for algae blooms and dead zones in the Chesapeake - none has cut enough yet to meet limits set under the bay "pollution diet" imposed by the EPA more than three years ago.

"Unfortunately, violations of permit limits for nitrogen, phosphorus, and sediment remain common throughout the Bay states, even for significant dischargers," the report says. The group called for regulators to crack down on chronic violators and tighten discharge permits.

“As significant pollution reductions become more difficult and expensive to achieve, addressing illegal discharges and poor data reporting at these plants will become increasingly critical,” Heinzen said in a statement released with the report. 

But Apperson disputed the group's contention that there's been any letup in Maryland's efforts to reduce pollution. More than 30 sewage treatment plants have been upgraded to remove more nitrogen and phosphorus, he said, and upgrades are in the works for a similar number of plants. State officials are enforcing facilities' discharge permits, he added, and where there are problems have legal agreements in place "to ensure that improvements are made in a timely manner."

"Any suggestion that the level of enforcement of permits for municipal and industrial sewage treatment plants jeopardizes Maryland's efforts to clean up the Bay is off base," he said.