Autotrophic denitrification supported by sphalerite and oyster shells: Chemical and microbiome analysis

This research evaluated the metal-sulfide mineral, sphalerite, as an electron donor for autotrophic denitrification, with and without oyster shells (OS). Batch reactors containing sphalerite simultaneously removed NO3- and PO43- from groundwater. OS addition minimized NO2- accumulation and removed 100% PO43- in approximately half the time compared with sphalerite alone. Further investigation using domestic wastewater revealed that sphalerite and OS removed NO3- at a rate of 0.76 ± 0.36 mg NO3--N/(L · d), while maintaining consistent PO43- removal (∼97%) over 140 days. Increasing the sphalerite and OS dose did not improve the denitrification rate. 16S rRNA amplicon sequencing indicated that sulfur-oxidizing species of Chromatiales, Burkholderiales, and Thiobacillus played a role in N removal during sphalerite autotrophic denitrification. This study provides a comprehensive understanding of N removal during sphalerite autotrophic denitrification, which was previously unknown. Knowledge from this work could be used to develop novel technologies for addressing nutrient pollution.