IFAS SYSTEM DEMONSTRATION OF COLD TEMPERATURE NITROGEN REMOVAL

The secondary wastewater treatment facility in Westerly Rhode Island has a design capacity of 3.3 mgd. A new permit limit for ammonia of 5.5 mg/l required a plant upgrade. Because of site constraints, a hybrid technology was chosen to meet the new permit limit. This technology is an integrated fixed activated sludge (IFAS) process utilizing the Linpor® System. Engineered, 0.6-inch foam cubes, are suspended in the aeration tank to effectively increase the total mixed liquor suspended solids by allowing the microbes to attach and grow within the pore spaces of the cubes. The mixed liquor suspended solids concentration in the liquid phase remains at conventional levels.A demonstration pilot plant was operated from February to April of 2001. The influent wastewater temperatures during most of the testing ranged from 9 °C to 12 °C. The pilot facility demonstrated that the permit limit of 5.5 mg/l of ammonia nitrogen and a secondary goal of total nitrogen below 15 mg/l was achievable. In addition, desirable SVI were maintained with a high biomass concentration.