Recovery of anaerobic ammonium oxidation via hydrazine following sulfate inhibition

Abstract

The presence of sulfate in sewage treatment has obvious impacts on biological nitrogen removal. We explored the influence mechanism of sulfate on anammox and the recovery via hydrazine of anammox after inhibition. The sulfate inhibited HDH activity and functional gene abundance, which had serious effects on the metabolic process of hydrazine synthesis and oxidation. The conversion rates of ammonia nitrogen and nitrite dropped from 0.49 mgN gvss⁻¹ h⁻¹ and 0.63 mgN gvss⁻¹ h⁻¹ to 0.17 mgN gvss⁻¹ h⁻¹ and 0.25 mgN gvss⁻¹ h⁻¹. The absolute abundance of hzsA, hzsB and hzo dropped greatly from 7.3 × 10⁴ to 3.7 × 10⁴, 17.5 × 10⁵ to 4.9 × 10⁴ and 1.8 × 10⁴ to 0.35 × 10⁴, respectively. After supplying 10 mg L⁻¹ of hydrazine, the normal metabolism of anammox was maintained. The addition of hydrazine helps cells resist the decaying effects and enhances the recovery capability of anammox bacteria following inhibition. These results demonstrate the promise of recovering anammox activity via hydrazine.