Treatment of ammonium nitrogen wastewater using MC-FeCo catalyzed ozonation combined with biological denitrification

Abstract

The conventional biological methods for removing ammonium nitrogen (NH4+-N) involve nitrification to convert NH4+-N into nitrate nitrogen (NO3−-N), followed by denitrification to transform NO3−-N into gaseous nitrogen. However, the process has low efficiency and a long reaction cycle. In this study, a microbial carbon-loaded iron (Fe)/cobalt (Co) catalyst (MC-FeCo) was first prepared. The MC-FeCo efficiently catalyzed ozone (O3) to convert NH4+-N into partially gaseous nitrogen and primarily NO3−-N, with the remaining NO3−-N further reduced to gaseous nitrogen through denitrification. The results showed that the removal efficiency and gaseous nitrogen yield of NH4+-N (50 mg/L) by MC-FeCo catalytic O3 oxidation were 72.54 % and 16.28 %, respectively. In addition, the NO3−-N (270 mg/L) removal efficiency reached 100 %, with a lack of NO2−-N accumulation in the denitrification system, at C/N ratio and solution pH values of 10.0 and 8.0, respectively. The actual rare earth-derived wastewater containing NH4+-N (100.85 mg/L) was treated by the catalytic ozonation-combined biological denitrification system, resulting in a final NH4+-N concentration of 7.06 mg/L, meeting the discharge criterion (NH4+-N < 8 mg/L) of the emission standard of pollutants for rare earth industry in China (GB 26451–2011).