The intensified effect of nitrogen removal properties using Pseudomonas fulva K3 and MgBC for the weathered crust rare earth wastewater treatment

A new bacteria named Pseudomonas fulva K3 (P. fulva) strain was isolated from the surroundings of weathered crust rare earth tailing with efficient NH4+-N removal ability via heterotrophic nitrification and aerobic denitrification. The nitrogen removal properties could be intensified by the synergistic effect between as-prepared magnesium-modified biochar (MgBC) and P. fulva strain. The results show that P. fulva exhibited a rod-shaped morphology and $NH_4+-N$ can be completely biodegraded under the optimal conditions of pH=7.0~8.0, temperature 30 oC and initial $NH_4+-N$ concentration of 100 ~150 mg/L. The $NH_4+-N$ tolerant concentration for P. fulva was determined to be 300 mg/L. The magnesium-modified biochar (MgBC) worked as an adsorbent of $NH_4+-N$. The kinetics and isotherm model for adsorption could be described by the pseudo-secondorder kinetic and Freundlich model, respectively. The XPS results showed that $NH_4+-N$ was mainly adsorbed on the surface by chemical adsorption. Furthermore, the P. fulva could be immobilized on MgBC due to its large surface area, adjusting the concentration of $NH_4+-N$ to a proper range for the growth of P. fulva by adsorption and desorption equilibrium, and leading to the intensified effect on nitrogen removal. The total nitrogen removal efficiency of the eluted weathered crust rare earth tailing reached 84.7 % in MgBC + P. fulva system.