Ochrobactrum anthropi used to control ammonium for nitrate removal by starch-stabilized nanoscale zero valent iron

In this study, the hydrogenotrophic denitrifying bacterium Ochrobactrum anthropi was added in to the process of nitrate removal by starch-stabilized nanoscale zero valent iron (nZVI) to minimize undesirable ammonium. The ammonium control performance and cooperative mechanism of this combined process were investigated, and batch experiments were conducted to discuss the effects of starch-stabilized nZVI dose, biomass, and pH on nitrate reduction and ammonium control of this system. The combined system achieved satisfactory performance because the anaerobic iron corrosion process generates H₂, which is used as an electron donor for the autohydrogenotrophic bacterium Ochrobactrum anthropi to achieve the autohydrogenotrophic denitrification process converting nitrate to N₂. When starch-stabilized nZVI dose was increased from 0.5 to 2.0 g/L, nitrate reduction rate gradually increased, and ammonium yield also increased from 9.40 to 60.51 mg/L. Nitrate removal rate gradually decreased and ammonium yield decreased from 14.93 to 2.61 mg/L with initial OD₆₀₀ increasing from 0.015 to 0.080. The abiotic Fe⁰ reduction process played a key role in nitrate removal in an acidic environment and generated large amounts of ammonium. Meanwhile, the nitrate removal rate decreased and ammonium yield also reduced in an alkaline environment.