Sulfide odor emitted from box culvert sediments is a nuisance in coastal cities where the box culvert environment promotes biological sulfide production, due to the ample supplies of organics from misconnected sewers and sulfate from tidal seawater. Existing measures use soluble chemical oxidants to suppress the odor but their effects are temporary and unsustainable. A long-lasting, sustainable process that utilizes granular ferric hydroxide (GFH) and the natural iron-sulfur redox cycle is being developed for this specific problem. Sulfide removal in the aqueous phase by GFH under various conditions was investigated in batch tests to study the effects of iron dosages, pH, water matrices, and pre-adsorption of sulfate on the removal kinetics. The sulfide can be removed by GFH with good f...[ Read more ]

Sulfide odor emitted from box culvert sediments is a nuisance in coastal cities where the box culvert environment promotes biological sulfide production, due to the ample supplies of organics from misconnected sewers and sulfate from tidal seawater. Existing measures use soluble chemical oxidants to suppress the odor but their effects are temporary and unsustainable. A long-lasting, sustainable process that utilizes granular ferric hydroxide (GFH) and the natural iron-sulfur redox cycle is being developed for this specific problem. Sulfide removal in the aqueous phase by GFH under various conditions was investigated in batch tests to study the effects of iron dosages, pH, water matrices, and pre-adsorption of sulfate on the removal kinetics. The sulfide can be removed by GFH with good fit to pseudo-first-order kinetic expressions and the removal rate is found to be affected by the parameters studied. The regeneration and reuse of GFH for sulfide removal in seawater were also examined. The surface condition of GFH would affect the sulfide removal, the regeneration and the reuse of GFH.

Sulfide removal by GFH in the sediment phase was investigated in batch tests as well. The feasibility of utilizing GFH for sulfide control in the sediment phase was verified by batch test results. However, the longevity of the technology depends on the quantity of GFH embedded in sediments. The feasibility of using regenerated GFH to remove sulfide was also demonstrated. The 2-hour oxygenation regenerated GFH could control sulfide odor for around 20 days.

Spectroscopy results verified that oxygenation of exhausted GFH could oxidize Fe(II) to Fe(III), but it could not completely oxidize sulfide to sulfate. Therefore, some active surface sites might not be released after oxygenation.