Investigation of In-situ Immobilization of Contaminated Sediments using Alginate Gels for the Reduction of Ecological Risk

Remediation methods for contaminated sediments include dredging, treatment and disposal and sediment isolation through capping. These methods are costly and adversely impact local ecosystems, in some cases causing major disturbances to the sediment bed and water column. A new remediation technique is proposed for slowly biodegradable contaminants using alginate hydrogels as a binding agent of sediment. The rational is that sediment particles bound in alginate hydrogel are less likely to be resuspended and the treatment is less disruptive than capping. Here we show addition of alginate increased the shear strength of sediment comprised of defined particle sizes. The increase in strength becomes more pronounced as the normal stress is increased. Alginate's ability to trap contaminates in its structure was found to be pH-dependent, with more effective contaminant sequestration at lower pH. . Lab scale tests on contaminant tranpsort from alginate bound sediment showed Naphthalene diffusion from sediment was reduced.