Kinetic implication of moving warm side-stream Anaerobic ammonium oxidizing bacteria to cold mainstream wastewater

Decreased activity of Anaerobic ammonia oxidation (Anammox) at low temperatures is widely reported and one of the key challenges to applying Anammox to mainstream wastewater treatment. In this work, we systematically measured Anammox across a range of temperatures for biomass taken from a side-stream (25-30 °C) Anammox system. Using the Cardinal temperature model with inflection (CTMI) and parameters T_min = 10 °C, T_opt = 31 °C, T_max = 40 °C, and µ_max = 0.29 d^-1, the data was accurately represented. Alternatively, the popularly used Arrhenius equation was not able to consistently capture the trend we observed. The CTMI was further used to compute the relative increase in retention time and/or biomass concentration to treat the same quantity of nitrogen at sub-optimal temperatures, requiring a two-fold increase at 21 °C and three-fold increase at 19 °C. We conclude that cold adapted cultures are necessary to evaluate the possibility of cold Anammox wastewater treatment.