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

Autotrophic denitrification under acidic conditions using sulfide (S), elemental sulfur (S), and thiosulfate (SO) 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 S or SO was the electron donor, while with S denitrification was only observed at pH > 6. When S was used as electron donor, it was converted to S, and S was not used while S was available. When addition of S was discontinued, or S depleted, S 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.