While it is good news that a Millinocket mill plans to no longer use phosphoric acid, the cause of a massive algae bloom on the Penobscot River this summer, the Department of Environmental Protection is wisely not just taking the company’s word this time and will limit phosphorus discharges from the mill. Closer monitoring of mill discharges and a thorough review and public explanation of how this situation developed will help the department restore public confidence.

After a large algae bloom on the Penobscot in 2004, Katahdin Paper, which operates the former Great Northern Paper Co. mills in Millinocket and East Millinocket, agreed to reduce or eliminate phosphoric acid as a bleaching agent at the Millinocket facility. No limits on phosphorus discharges were set because DEP believed the company had stopped using the chemical. Phosphorus can trigger large blooms of the potentially toxic blue-green algae during the warm summer months when water levels are low. The algae can take up much of a river’s oxygen, choking off fish and other species.

This spring, the company increased its use of phosphoric acid at its Millinocket facility due to concerns about the brightness of the paper made there. Inexplicably, the company did not notify DEP of the change, according to Andrew Fisk, director of the department’s Bureau of Land and Water Quality.

In July, as part of routine monitoring, officials from the Penobscot Nation, DEP and Katahdin Paper collected samples along the Penobscot River. That is when the bloom was discovered. DEP sent out a violation notice to the paper company last month. Whether the company will face financial penalties for reducing oxygen levels in the river will be determined later.

This week, Katahdin Paper said it has found alternatives to phosphoric acid and that it has removed the chemical from the mill. This is an important step, but DEP is rightly, if belatedly, going further and setting limits on phosphorus discharges from the mill. A consent agreement, which is being drafted by the department and must be agreed to by the company, will set a phosphorus limit of 0.5 milligrams per liter of water discharged, a standard the department believes will protect the water quality of the Penobscot. The limit will be in place until a discharge license is issued for the mill, likely next year.

The license will be the first issued by the state under the federal Clean Water Act. The state in 1999 applied for the authority to issue federal permits, triggering a decade of legal wrangling with the state’s Indian tribes, which wanted the federal government to retain permitting authority in tribal areas. The state’s licensing authority was upheld by a federal court last month, although it warned that the state must use that authority wisely or risk breaching its responsibility to the tribes. The Office of Program Oversight and Government Accountability was asked Thursday to consider reviewing whether DEP is fulfilling the court’s charge. It took a first step in this direction and will seek more information from the agency.

Such a review and public explanation of how Katahdin Paper came to discharge so much phosphorus into the river will help determine whether DEP is up to the job of protecting the water of the tribes and the state in general.