The foul odor smell of poisonous hydrogen sulfide generated in box culverts under anaerobic conditions has raised the public concern. However there is no clue which sections in the box culverts produce more sulfide and whether the seawater intrusion at high tides will enhance the sulfate reduction process. It is crucial to identify this phenomenon so that the mitigation work can be established at low cost. The sediments collected from an odorous site were laid at a thickness of 6 cm in a reactor of 13 cm x 15.5 cm x 45 cm to stimulate sulfide generation under various seawater intrusion conditions. Results reveal that long term exposure of seawater did not inhibit sulfide generation. During high tide, the dissolved oxygen content in the water increased to 7 mg/L. Sulfide generati...[ Read more ]

The foul odor smell of poisonous hydrogen sulfide generated in box culverts under anaerobic conditions has raised the public concern. However there is no clue which sections in the box culverts produce more sulfide and whether the seawater intrusion at high tides will enhance the sulfate reduction process. It is crucial to identify this phenomenon so that the mitigation work can be established at low cost. The sediments collected from an odorous site were laid at a thickness of 6 cm in a reactor of 13 cm x 15.5 cm x 45 cm to stimulate sulfide generation under various seawater intrusion conditions. Results reveal that long term exposure of seawater did not inhibit sulfide generation. During high tide, the dissolved oxygen content in the water increased to 7 mg/L. Sulfide generation was reduced because there was insufficient organic carbon being produced though the fermentation process. During low tides, organic carbon was produced, which was accompanies with a decline in the dissolve oxygen content. These conditions enhanced the sulfate reduction process. 0.7 mg-S sulfide that accumulated in the headspace was generated from 200 cm² of the sediment during high tides and low tides. The most probable number technique was used to quantify the concentration of sulfate reducing bacteria (SRB) in the sediment. The results indicated that there were more SRB within the sediment and in the water phase during low tide, compared to the values obtained during high tide. These findings show that the downstream of box culverts that was submerged mostly with seawater produces less sulfide.