Performance of sulfur-based autotrophic denitrification and denitrifiers for wastewater treatment under acidic conditions

Autotrophic denitrification under acidic conditions using sulfide (S2-), elemental sulfur (S-0), and thiosulfate (S2O32-) as electron donors are evaluated. Results from batch and column experiments show that when different S species were supplied, different pH conditions and denitrifier communities were required for denitrification to occur. Nitrate and nitrite were removed via autotrophic denitrification at pH ranging from 4 to 8, when S2- or S2O32- was the electron donor, while with S-0 denitrification was only observed at pH > 6. When S2- was used as electron donor, it was converted to S-0, and S-0 was not used while S2- was available. When addition of S2- was discontinued, or S2- depleted, S-0 that had accumulated was used as electron donor for denitrification. These findings demonstrate that sulfur-based autotrophic denitrification can proceed under acidic conditions, but that the addition of appropriate S species and the presence of an effective denitrifier community are required.