Relationships Between Operational Conditions and Nitrogen Removal and Media Biofilm Accumulation in an IFAS Process Demonstration Study

Abstract

Recent changes in discharge regulations limiting the six James River (VA) Basin treatment plants operated by the Hampton Roads Sanitation District (HRSD) to an aggregate mass discharge of total nitrogen (TN) to 6,000,000 lbs/year by January 1, 2011 has prompted implementation of a strategy to reduce discharges from each of the six treatment plants. At the 16.7 MGD James River Wastewater Treatment Plant (JRTP) modification of the existing conventional activated sludge process to an integrated fixed-film activated sludge (IFAS) process is being considered to achieve a target effluent TN at this facility of approximately 8 mg/L (annual average). To better understand the capabilities of the process and to better design the IFAS system, an IFAS demonstration study at JRTP was conducted to evaluate nutrient removal, temporal and spatial accumulation of biomass on the media, media distribution in the aeration basin, and overall operational conditions and the effect on performance. To accomplish these objectives, one of the nine existing fully-aerobic conventional aeration basins with dedicated secondary clarification was converted to a 1.86 MGD (2.22 MGD max month) IFAS train in a modified Ludzack-Ettinger (MLE) configuration with a 50% fill plastic biofilm carriers in the aerobic zone. During the study, biomass concentrations on the biofilm carriers were monitored as well as nitrogen species concentrations in the IFAS reactor to quantify the nitrogen transformations occurring within the demonstration tank. It was observed that continuous monitoring of the biomass on the IFAS media is necessary for successful operation of IFAS system. The performance of the nitrogen removal process was identified through nitrogen species measurements across the demonstration tank and conducting nitrogen mass balances.