Research on enhancement of zero-valent iron on dissimilatory nitrate/nitrite reduction to ammonium of Desulfovibrio sp. CMX

The process of nitrate dissimilation to ammonium (DNRA) is an important way for storing nitrogen in nature and DNRA is a key step in efficient recovery of nitrogen in wastewater. However, in view of the low conversion efficiency of DNRA, zero-valent iron (ZVI) was used to enhance the DNRA process of Desulfovibrio sp. CMX. ZVI can obviously promote the nitrate/nitrite reduction. The experiment indicated that 5 g/L 300 mesh ZVI could convert 5 mmol/L nitrate or nitrite to ammonium in 48 h or 36 h respectively, and the conversion ratio of NO₂^- to NH₄⁺ could reach more than 90%. The ZVI provided a suitable growth environment for the Desulfovibrio sp. CMX through chemical reduction of nitrite, production of divalent iron (Fe²⁺), reduction of oxidation-reduction potential (ORP) and adjustment of pH, which strengthened the DNRA performance. This experiment is advantageous for increasing efficiency of DNRA and provides a new idea for efficient recovery of nitrogen resources.