THESIS
2012
xii, 100 p. : ill. ; 30 cm
Abstract
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...[
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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 cm
2 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.
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