Pilot Study of Submerged Structured Sheet Media for Tertiary Nitrification

This study evaluated the nitrification performance of a combined high surface area density vertical flow and distribution media (VF-DM) system in a tertiary fixed-bed biofilm reactor (FBBR) at the City of Reading WWTP in Pennsylvania. A low HRT of 2 hrs was selected to represent the HRT of the existing tertiary nitrification basins at the design flow. The effluent ammonia nitrogen NH3-N concentration from the pilot FBBR was consistently lower than the plant's final permit effluent limits.An average of 95% NH3-N removal was achieved in the FBBR system for an ammonia loading up to 1.3 g/m2-day at wastewater temperatures of 10-23°C. The highest NH3-N surface removal rate observed was 1.6 g/m2-day at the loading rate of 2.2 g/m2-day and wastewater temperature of 14.9°C.The NH3-N removal capacity of the pilot system was significantly higher (2-4 times) than that of the existing treatment plant's tertiary nitrification system. The increased capacity of the pilot system was primarily attributed to the application of proprietary distribution media (DM), which not only maximized the air and wastewater distribution over the entire surface area of the media, but also optimized the airlift pumping through the VF media for sufficient mixing and effective biomass control. In addition, the media used in the pilot system had a much higher surface area (80 ft2/ft3 or 262 m2/m3) compared to the media in the existing plant (30 ft2/ft3 or 98 m2/m3), which allowed more biomass attachment and therefore increased the overall system capacity.