Metal Binding, Acid Neutralization and Minimization of Sulfide Oxidation in Dredge Spoil Material Using Virosoil Technology
Type:
Presented during:
WODCON XVIII - 2007 Orlando, Florida, USA
Authors:
Rouse, et al
Abstract: Material removed during dredging at ports typically is characterized by high sulfide concentrations, high metal loadings from upstream industrial activities, or both. Sulfide oxidation associated with sub-aerial disposal commonly produces acidic pore water; the acidity mobilizes metals that may have serious ecological impacts. When this water leaves dredge spoil disposal areas, it is hazardous to fish and other aquatic organisms. The acid conditions also adversely affect plant growth during disposal site restoration and damage engineered containment structures. ViroSoil™ Technology can be used to alter the geochemistry of dredged material to reduce sulfide oxidation rates, neutralize acidity, and precipitate heavy metals, resulting in a soil capable of sustaining plant growth and runoff that is not toxic to aquatic biota.
ViroSoil™ Technology incorporates ViroBind™ reagent, which has a high metal binding and acid neutralizing capacity and good phosphate retention for plant growth; the reagent also promotes healthy populations of soil micro-organisms. The reagent is extremely fine grained (>90% is < 10 μm) and has a very high reactive surface area but is largely insoluble and non-dispersive. This makes it ideal for blending with suction dredge discharge, or during transfer from clamshell dredging. ViroBind™ reagent is ideal for treating sulfidic dredge spoil because it not only neutralizes acidity, but also greatly reduces sulfide oxidation rates. The reagent can also be formed into granules or pellets, for use in permeable reactive barriers, or enclosed in gabions, constructed around dredge spoil disposal sites. Analysis of ViroBind™ treated material shows that metals are bound into non-leachable crystalline forms. The metal-binding strength increases with time and plants growing on treated material and earthworms living in it do not exhibit increased metal uptake.
This paper presents dredged material treatment case histories, and suggests alternative methods for non-toxic upland disposal, or beneficial use of the material.
Keywords: Contaminated sediments, beneficial uses, pollution prevention, heavy metals, sulfide oxidation