Synergistic Integration of Anaerobic Enhancement and Zero Valent Iron

One example of IET's in-house technologies focuses on chlorinated solvent treatment in-situ.  Patent US 7,129,388 B2 provides the technology to achieve accelerated dechlorination of soil and water contaminated with chlorinated solvents by coordinating zero valent iron technology with a programmed stimulation of anaerobic microorganisms.  The result is accelerated dechlorination of the given solvents. This is accomplished by a treatment process consisting of a colloidal suspension of iron powder (ZVI), polylactate ester (an electron donor such as glycerol tripolylactate), and slow release hydrogen donors like xylitol pentapolylactate, and sorbitol hexapolylactate.  In addition, chemical oxygen scavengers (reducing agents) in solution are provided with essential nutrients (ortho-phosphate and nitrogen compounds), and vitamin stimulants such as B2 and B12 delivered via compressed gases like N or CO2 so as not to oxygenate an environment targeted for anaerobic processes. The treatment stimulates naturally occurring microorganisms, while oxidizing dissolved phase target compounds via the surface action of the iron particles.  The result is the breakdown of chlorinated solvents such as tetrachloroethene, trichloroethene, carbon tetrachloride, trichloroethane and their daughter products. The incorporation of the B12 acts as both an enzymatic stimulus for the anaerobic action by lowering the activation energy required for electron transfer to chlorinated intermediates, and as a surface catalyst of the iron particle. The core element of the B12, cobalt, enhances the surface oxidation of the iron. The iron particles provide for direct oxidation of dissolved phase organics, along with hydrogen ions necessary for the anaerobic dechlorination process.  The ferrous iron by-products may further act as electron donors and precipitate any biologically generated sulfides while simultaneously allowing the ferrous sulfide to remove this common toxicant.