In Situ Chemical Oxidation of Chlorobenzene, Nitrobenzene and Aniline

摘要

In-situ chemical oxidation (ISCO) has been proven to be an effective technology for the remediation of chlorinated ethenes, aromatic hydrocarbons, and other common contaminants. This paper will present the results from an ISCO pilot study that was conducted at a site in preparation for a full-scale remedial design. Historical operations at the Site have significantly impacted the soil and groundwater. Previous investigations indicated that the impacts identified in both soil and groundwater exist as generally site-wide and/or area-wide issues, rather than being discrete Areas of Concern (AOCs). Primary contaminants of concern (COCs) for both soil and groundwater are chlorobenzene, nitrobenzene, and aniline; benzene, trichloroethene (TCE) and 1,2- Dichlorobenzene are secondary COCs. Hydrogen peroxide and sodium persulfate were selected as the most appropriate oxidants for ISCO treatment of the COCs. A bench-scale treatability study was conducted to evaluate the effectiveness of both hydrogen peroxide and iron-activated sodium persulfate. The results from the treatability study indicated that hydrogen peroxide was more effective at reducing concentrations of COCs. Activated sodium persulfate was also effective, but to a lesser extent in comparison to peroxide. Given the results of the treatability study, a pilot study was proposed to evaluate each oxidant in the actual field setting. The pilot study consisted of three separate demonstrations using the following oxidant solutions: a 15 percent solution of sodium persulfate activated by iron III ethylenediaminetetraacetic acid (Fe-EDTA); an 8 percent solution of hydrogen peroxide stabilized by sodium citrate; and, a 9 percent solution of sodium persulfate activated by hydrogen peroxide. The oxidant solutions were injected under pressure into the subsurface via fixed injection points consisting of dual nested screens. This paper will discuss observations regarding the effectiveness of each oxidant solution, as well as challenges to delivery and design of an evaluation protocol.