Effect of oxygen on sulfur products from H2S removal by Thiobacillus in a biotrickling filter column

This study investigated a H2S removal process using Thiobacillus in a biotrickling filter column and the effect of dissolved oxygen on the sulfur products. Thiobacillus cultures were isolated from UASB mixed liquor of a fruit processing factory using Thiobacillus medium (for Thiobacillus thioparus) and Thiobacillus denitrificans medium (for Thiobacillus denitrificans). The two cultures were separately inoculated into two lab scale biotrickling filters with H2S fed at the bottom of the column and culture media trickled from the top. Due to its high solubility, 30-40% of the H2S was removed in abiotic (control) columns by dissolving into the liquid phase. More H2S and dissolved sulfide were removed in biotic columns. With H2S at 2000 ppmv, 89-93% removal was achieved by T. thioparus and 74-78% by T. denitrificans. The product from H2S removal by both cultures contained more sulfur in elemental form than in sulfate form. However, element sulfur production was affected by dissolved oxygen (DO). Production of element sulfur was highest at 1- 2 mgO/L. It decreased as DO increased. To determine the species involved in the removal process, molecular identification was conducted. It revealed that four species were common in the two columns. T. thioparus and T. denitrificans were found in both columns but each predominated in the column containing their respective culture medium