A Remediation Study of Contaminated Marine Sediment through Application of Naturally Developed Oxygen Releasing Compound

Abstract

Blocking the influx of nutrients from contaminated sediment and reducing terrigenous loads are essential to control eutrophication in coastal water areas. In this study, the use of an oyster-shell-based ORC (oxygen-releasing compound) was investigated with respect to nutrients such as nitrogen, phosphorous, and sulfur compounds in the sediment environment. The ORC, which was produced by pyrolyzing oyster shell powder, was found to be overoxidized and consisted of calcium peroxide. A series of experiments simulating a typical overlying water-sediment system were carried out in open-lid cylindrical columns over the fifteen-day experimental period. The elution and distribution of crucial contaminating species within that system are discussed. T-N, NH4 +-N, T-P, and Pi propagated with time toward the overlying water from the sediment through diffusive migration, showing a constrained increase over distance at the sediment-water interface. The nitrate levels decreased with time, possibly due to local denitrification. Partial oxidation in a homogenized mixture of sediment and oxidized oyster shell powder resulted in an increased DO level within the experimental time frame, which in turn caused T-N, NH4 +-N, T-P, and Pi to propagate at a lower rate than sediment without any ORC. Analyses for sulfates and sulfides in the sediment mixed with ORC confirmed that the chemical environment changed into a more oxidized state in fifteen days. Diffusive migration, along with chemical reactions and/or adsorption, successfully explained the propagation and distribution of the concerned nutrient species resulting from the use of oyster shell powders.