A decade ago, Pima County's Regional Wastewater Reclamation Dept., or RWRD, was facing a problem: The Arizona Dept. of Environmental Quality had ruled that the levels of nitrogen coming from RWRD's network of 10 wastewater-stripping and treatment plants were too high. At that point, the 41- million-gallons-a-day Roger Road plant was releasing wastewater with nitrogen levels between 30 milligrams and 57 mg per liter, well above the 10 mg/l requirement, say county officials.