The usefulness of solid oxidants for biostimulation, determined by their kinetics and stoichiometry

Abstract

The increased interest in in situ bioremediation has developed a commensurate increased interest in soil chemical amendments. These amendments increase the level of one or more limiting nutrients in the natural environment. Along with the conventional constituents of interest such as nitrogen and phosphorous, oxygen (02) is an important, often limiting, compound in both flooded and subsurface soils. Chemical formulations were developed to provide oxygen to these anoxic environments. We evaluated, in distilled water, the release rates of four chemical compounds formulated for the slow release of oxygen that may be used to enhance bioremediation. The release rates were determined by polarographic measurement of the 02 concentration over time from sealed batch reactors. The acquired analog data was converted to digital and logged to computer. This research addressed the questions of release rates, oxygen to solid ratios, and probability of migration into the soil. We developed a predictive model for the release of oxygen from these solid additives. The four oxidants were: sodium-percarbonate (Na2CO3'1.5H202) encapsulated in poly(vinyhdene chloride) (PVDC); free sodium-percarbonate crystals; calcium peroxide (CaO2); and magnesium peroxide (MgO2). The highest calculated release rate was generated by the unencapsulated Na2CO3'1.5H202 (132 mgl-' hr-'), followed by CaO2 (3.2 mgr' hr-'), then the encapsulated Na2CO3'1.5H202 (1.77X 10-2 mgrl hr-'). The lowest release rate was for M902 (1.57X 10-3 mgr' hr-'). The data indicated that M902 or a niix of M902 and CaO2 hold the highest promise for use in saturated surface soil applications.