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

Abstract

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 PO₄^3- from groundwater. OS addition minimized NO₂^- accumulation and removed 100% PO₄^3- 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 PO₄^3- 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.

Keywords: 5-Stage Bardenpho microbiome; Autotrophic denitrification; Oyster shells; Phosphorus removal; Sphalerite.