Fixed Media IFAS in Contact Stabilization Zone

The City of Coeur d'Alene wastewater treatment plant is operating at its capacity, yet continue to increase and lower ammonia limits are looming for 2009 or 2010. The planned facility expansion won't be online until 2014.During spring of 2008, five 30,000 ft2of IFAS media were installed to test the potential of integrated fixed film activated sludge (IFAS) to improve nitrification. Because this facility is a trickling filter/contact stabilization (TF/CS) plant, the success of an IFAS upgrade was not certain due to the short hydraulic retention time and a low achievable suspended growth SRT.The results from the first season were encouraging. Once the process stabilized, the monthly average effluent ammonia concentration was lower than during any month in recent years. Taking into account the change in plant loading and the additional ammonia reduction, the estimated nitrification capacity of the installed IFAS media was between 80 lb/d and 120 lb/d in September 2008. Additional media was installed in May 2009.