High-Rate Nitrification Using Submerged Aerated Filter at Different Temperatures

It is well-known that temperature influences biological nitrification process, and that biofilm reactors can tolerate lower temperatures better than suspended-growth systems. Numerous works have studied the effect of temperature (majorly 8°C-30°C) on nitrification in moving bed biofilm reactor (MBBR) and biological aerated filter (BAF). Fixed-bed biofilm rectors-including BAF and submerged aerated filter (SAF)-can offer 3-5 times higher volumetric nitrification rates than MBBRs. Due to lower vulnerability to clogging and backwashing requirements, SAF is attractive over BAF. However, the effect of temperature on nitrification in SAF has not been studied. In this work, a lab-scale nitrifying SAF was operated at volumetric ammonia loading rate (vALR) of about 1500 g N·m^-3·d^-1 (surface-specific ammonia loading rate, sALR ≈1.6 g N·m^-2·d^-1) over 9°C-30°C. Surface-specific ammonia and nitrite oxidation rates (sAOR ≈1.57 and sNOR ≈1.47 g N·m^-2·d^-1) did not vary significantly for temperatures from 15°C to 30°C. At 10°C, sAOR and sNOR had declined to about 1.19 and 0.92 g N·m^-2·d^-1, respectively. The developed sigmoid function could closely predict the temperature effect on sAOR (also reported in other studies on BAF and fixed-film reactor). The surface-specific nitrification rates achieved in this work are on par with the highest rates reported with BAFs and at least 2.5 times of MBBRs. This study shows that SAF could offer robust, efficient, and high-rate nitrification in tropical, subtropical, and temperate climates.