Geosyntec Consultants in collaboration with Carus Chemical Corporation and Clarkson University has developed a novel chemical oxidation method utilizing permanganate to generate mixed manganese and iron oxides and low molecular-weight organics that activate sodium persulfate (MnAP) for the treatment of recalcitrant organics. This innovative method was developed based on the hypothesis that mixed manganese- and iron-oxides can activate persulfate as demonstrated in recent academic literature (Mushtaque et al (2010) and Sedlak et al (2014)). However, the main objective of this academic literature was to determine the impact of naturally occurring organic and inorganic components, including iron and manganese oxides, on the activation of persulfate. In addition, permanganate oxidation of soil organic matter and other reduced carbon in sediments can produce low molecular weight aldehydes and ketones (Siegrist et al (2011)) that also activate persulfate decomposition (Ocampo (2009)) that can sustain treatment of recalcitrant organics.
The modes of action of MnAP will be discussed based on related water treatment literature and the findings of our research and development. Freshly precipitated manganese and iron oxides nano-particles are formed from permanganate consumption under controlled geochemical conditions that then act as activators for persulfate that propagate the persulfate radical-based oxidative chemistry. Fortuitous production of organic persulfate activators can sustain oxidative conditions as permanganate is consumed and continuing persulfate decomposition.
Compared to the more well-known activation methods of persulfate (pH, iron, heat, peroxide), persulfate activation by reactions at mineral surfaces is not as well understood. Recent studies have shown that aquifer materials such as iron and manganese oxides can also activate persulfate. The recent lab-based academic studies Mushtaque et al (2010) determined that the greatest potential for persulfate activation was through an increased concentration of the mineral manganese dioxide (MnO2) (Mushtaque et al (2010)) and more recently, Sedlak et al (2014) determined that the rate of persulfate activation would increase in zones ‘rich’ in iron- or manganese-oxides.
A series of several laboratory treatability studies of MnAP have treated between 300 and 500 mg/L of trichloroethene (TCE) over 99.9% in both the aqueous and solid phases, as well as, benzene, ethylbenzene, toluene and dichloroethane. The treatability data also showed that MnAP can achieve high levels of treatment using less of each of the two oxidants (lower dosage) as compared to single oxidant approaches using typical permanganate and persulfate formulations. This circum-neutral pH process produces fewer by-products than the single oxidant approaches or classical persulfate activation methods evaluated (matrix, iron, base and hydrogen peroxide activation).
Carus Chemical has conducted laboratory studies of treatment of contaminant mixtures using sustained released technologies (oxidant within an inert matrix). These results suggest synergistic treatment of recalcitrant contaminant mixtures with a permanganate-persulfate treatment chemistry.
Geosyntec designed and conducted large-scale applications of MnAP at the Middlefield-Ellis-Whisman Superfund Site in California, USA. The target zone is a heterogeneous mix of dense clays and sands. The site-specific design involved injecting 80,000 liters of oxidant solution (1,800 Kg of sodium permanganate and 5,500 Kg of sodium persulfate). Oxidant residual was present for greater than 3-months after each of four injection events over five years. The treatment removed more mass than 25 years of groundwater extraction and treatment. This combined oxidative approach is a lower cost than traditional permanganate or persulfate chemistries or groundwater extraction and treatment. Geosyntec has completed a TCE and ¼-Dioxane source area ISCO process to support enhanced in-situ biological treatment of a groundwater plume as a replacement to groundwater extraction and treatment. Treatability studies are used to screen candidate sites and optimize a site-specific ISCO formulation.
Mr. Bruce Marvin, Geosyntec
Bruce Marvin is a Senior Principal Environmental Engineer based in California with more than 15 years of consulting experience focused on remediation strategy development, technology selection, engineering process design, and quality assurance procedures. His clients include private and governmental entities in the United States, Japan, Canada, and Australia. Bruce is internationally recognized for his in situ remediation expertise, establishing industry best practices for ISCO and performed numerous pioneering projects involving ozone, permanganate, and persulfate. Bruce received his B.S. in Civil Engineering from Northeastern University and his M.S. in Environmental Engineering and Science from Stanford University. He holds certificates in Safety Management through the American Society of Safety Engineers.