The former head of New London-based Sheffield Pharmaceuticals pleaded guilty Tuesday to a criminal charge of knowingly allowing the dumping chemical pollutants into Thames River for more than seven years.

Thomas H. Faria is due to be sentenced in October and could face a prison term of up to three years plus thousands of dollars in fines for every day his company was in violation of the federal Clean Water Act.

Federal investigators alleged that Sheffield Pharmaceuticals had been illegally discharging pollutants into the river for 25 years, long before Faria took over as president and CEO in 2003.

According to prosecutors, Faria was told by company employees of the dumping when he became president and did nothing to stop it. Sheffield Pharmaceuticals manufactures a variety of over-the-counter products sold under the Dr. Sheffield and Lee brands, including creams, anti-itch and anti-fungal ointments, toothpaste and analgesics.

"Any CEO operating a factory in Connecticut who ignores federal and state environmental laws risks not only significant fines but also a jail sentence," said U.S. Attorney for Connecticut Deirdre M. Daly.

This case was the second time in recent months that the U.S. Attorney's Office in Connecticut secured a conviction against a company in this state for major environmental violations.

In April, Unilever Home & Personal Care USA was handed a $1 million fine and sentenced to three months probation for creating an "illegal bypass" that allowed the company to discharge waste water into a storm drain that lead into Clinton's Hayden Creek. As a result of the federal action, the company also contributed $3.5 million to state and local environmental programs.

Faria resigned as head of Sheffield Pharmaceutical in March as part of the negotiations surrounding his guilty plea. His 38 percent interest in Sheffield's parent company (Faria Limited) was also converted to non-voting shares.

The pollution case against Sheffield and Faria was triggered by an inspection in 2011 by the state Department of Energy and Environmental Protection. State officials found the company had no wastewater discharge permits.

Later investigations by the U.S. Environmental Protection Agency determined Sheffield had been illegally discharging industrial pollutants that went untreated to New London's sewer plant and from there was released into the Thames.

The EPA found Faria was told about the pollution flowing out of the New London plant by consultants and various company employees. They all warned him the company needed to spend money to correct the problem, but Faria refused, federal officials said.

"He [Faria] pursued this illegal course over the objection of a manager who urged him in writing to bring the company in compliance with the law," said Daly.

"Blatant disregard for our environmental laws occurs whenever greed and poor judgment intersect," said John K. Gauthier, acting special agent in charge of the EPA's New England criminal investigations unit.

Faria's felony conviction is punishable by a maximum of three years in prison and fines of not less than $5,000 per day of violation, up to $50,000 per day for the period when the law was being violated.