Simultaneous removal of nitrate and hydrogen sulfide by autotrophic denitrification in nitrate-contaminated water...

Nitrate contamination is a risk to human health and may cause eutrophication, whereas H₂S is an undesirable constituent in biogas. In order to better understand denitrification using gaseous H₂S as electron donor, this study investigated denitrification at different molar ratios of sulfur and nitrogen (S/N ratios) and H₂S dosages. Although nitrate continued to decrease, a lag in sulfate generation was observed, implying the generation of sulfide oxidizing intermediates, which accumulated even though nitrate was in excess at lower S/N ratios of 0.19 and 0.38. More addition of H₂S could result in a longer lag of sulfate generation. Before depletion of dissolved sulfide, denitrification could proceed with little nitrite accumulation. High throughout sequencing analysis identified two major genera, Thiobacillus and Sulfurimonas, that were responsible for autotrophic denitrification. The simultaneous removal of nitrate and H₂S using a wide range of concentrations could be achieved.