Evaluating Modifications to the Application of ISCO Technologies to Mitigate the Impacts of Metals Mobilization
While ISCO has proven very effective in treating organic contaminants, the application of ISCO can alter the geochemical conditions (pH, Eh) in the subsurface, resulting in a transient mobilization of metals and metalloids at some sites. The intent of this research was to evaluate several potential modifications to the application of ISCO to help mitigate the mobilization of metals. This is part of the research being funded by SERDP grant ER-2132.
Potential modifications were tested with iron activated persulfate, alkaline activated persulfate, potassium permanganate, and catalyzed hydrogen peroxide. Potential modifications to the application of ISCO were first evaluated in batch reactors and then a series of column studies. The modifications included pretreatment of the soil prior to the application of ISCO, amendments added with ISCO reagents during the application of ISCO, and amendments added after the application of ISCO. The pretreatment of soils with sodium sulfide, sodium phosphate, iron oxide, and ferric sulfate was evaluated. Amendments applied during the application of ISCO included the potential biotic stimulants of whey, soybean oil, sodium lactate, sodium citrate, and sodium acetate. The amendment of the ISCO reagents with sodium phosphate and sodium sulfate was also evaluated. Post application treatment technologies evaluated included pH adjustment to near neutral, sodium lactate to stimulate biotic activity, sodium sulfide, sodium sulfate, and sodium phosphate. Only the best performing approaches were from the batch reactor experiments were tested in the column reactors.
ER-2132 is completed. The research provided important insight into the interaction of ISCO with the subsurface mineralogy, and key differences in metals mobilization potential between activated persulfate, permanganate and catalyzed hydrogen peroxide.