The Environmental Protection Agency has released its final nitrogen discharge permit for the town’s waste-water treatment plant. The permit calls for a limit of 3 milligrams per liter, the same amount as a draft permit previously released. Exeter’s treatment plant discharges into the Squamscott River, which empties into Great Bay. The town now has to decide if it wants to remain in the Great Bay Municipal Coalition with Portsmouth, Dover, and Rochester and possibly fight the permit, or build a new waste-water treatment plant. It has been estimated that it would cost $36 million to build a new plant to meet the 3-milligram limit.