Numerical modelling on sorption kinetics of nitrogen species in wastewater-applied agricultural field

Abstract A one-dimensional numerical model is developed to simulate the nitrogen species in wastewater-applied agricultural field to investigate the effect of various isotherms of ammonium nitrogen and nitrate nitrogen. Results suggest that the ammonium nitrogen concentration reaches up to the depth of 40, 25 and 16 cm due to the linear, Freundlich and Langmuir isotherms of ammonium nitrogen, which is corresponding to the reduction in migration depth up to 37% by Freundlich isotherm and 55% by Langmuir isotherm as compared with linear isotherm. Similarly, the peak concentration of 25, 15 and 12 mg/l of nitrate nitrogen is observed during linear, Freundlich and Langmuir isotherms of NH4–N, respectively. Further, the results show that 4% peak concentration reduction is experienced for NO3–N due to the linear NH4–N sorption alone, 7% peak reduction is observed for NO3–N concentration by Freundlich NH4–N sorption alone, and 12.5% peak reduction is monitored for NO3–N concentration due to Langmuir NH4–N sorption alone compared with the combination of Freundlich NO3–N sorption. The numerical results suggest that the combination of Langmuir isotherm of NH4–N and Freundlich isotherm of NO3–N is identified as a best combination of isotherm scenario, which mitigates the NO3–N contamination in groundwater resources.