Investigation of Hydrogen Sulfide Production in a Polluted Estuary by Using a Vertical Column Simulator

Abstract

The emission of hydrogen sulfide (H₂S) near the estuary of a regional river (Tokyo, Japan), which is thought to be caused by biological reduction of sulfate in seawater mixing with overflow wastewater, poses a severe environmental problem. In order to investigate vertically the biochemical alteration of the river under the long-time treatment for the sulfide problem, we set up a vertical column simulator composed of artificial sewage-filled columns and packed-bed columns. During operation, we carried out chemical and biological analyses to elucidate vertical distributions of sulfide concentration, dissolved oxygen concentration, oxidation/reduction potential and microbial consortia. H₂S was not detected in the top section, which was supplied with continuous aerated artificial wastewater, whereas H₂S was formed at high concentrations under anaerobic conditions. After 1 year, we changed the supply position for aerated sewage from the top to the middle of the simulator; subsequently, the sulfide concentrations in all sections, especially in the sediment region, dropped to negligible levels. Furthermore, under each of these 2 conditions, pyrosequencing revealed that the microbial consortia differed significantly following the change of the aerated sewage supply position. On the basic of these results, purging oxygen at the border of the water column and the sediment could help to solve the sulfide problem more effectively and might enhance the growth of bacteria involved in the sulfide oxidation process.