Unveiling the bioprocess kinetics of leachate treatment at elevated temperatures: plant-wide dynamic simulation and experimental validation

Treatment of landfill leachate (LL) poses a significant environmental challenge and requires a comprehensive evaluation. This study presents the impact of high temperature on bioprocess kinetics of a landfill leachate treatment plant (LLTP) via experimental investigation and plant-wide dynamic model simulation. The growth kinetics for nitrifiers were differentiated in terms of growth rates (1.4 and 1.8 day⁻¹ for AOB, 0.8 and 0.9 day⁻¹ for NOB) and decay rates (0.2 and 0.3 day⁻¹ for AOB, 0.17 and 0.4 day⁻¹ for NOB) for 25 °C and 35 °C, respectively. Heterotrophic growth kinetics were observed to be similar at both temperatures, with only minor variations in the maximum specific growth rates (2.2 and 2.5 day⁻¹). Dynamic model simulations indicated that Dissolved Oxygen (DO) and temperature were the two major factors governing dynamics of AOB and NOB, consequently the nitrite/nitrate route for denitrification. The phenomenon of free ammonia (FA) or free nitrous acid (FNA) inhibition on nitrifiers estimated to be limited considering the very low level of ammonia and nitrite concentrations in the reactor. Dynamic simulations also showed that glycogen accumulating organisms (GAO) can easily grow when dissolved oxygen (DO) is limited and outcompete phosphorus accumulating organisms (PAO) at high temperature.