Dr. Michael Lee, Ph.D.

Combining Sulfidated Zero Valent Iron With Emulsified Vegetable Oil 

Dr. Michael Lee, Ph.D., Vice-President Research and Development, Terra Systems

Laboratory batch and column studies were conducted to compare the ability of several sulfidated zero valent iron (ZVI) particles to react with halogenated solvents at different loadings, incubation times, and bioaugmentation culture. The impact of several iron and sulfur containing compounds including ferrous gluconate, ferrous lactate, ferrous sulfate, and ferrous sulfide (mackinawite) alone and in combination with emulsified vegetable oil (EVO) were evaluated. Sulfate additions can promote sulfidation of ZVI to increase abiotic reactions. Laboratory batch studies were completed across a diverse range of conditions – ZVI particle sizes, ZVI loadings of 1 to 11 g/L, with and without sulfidation, with and without soluble sulfate and organic substrate electron donors. Contaminants included chlorinated ethenes (CEs) such as tetrachlorethene (PCE), trichloroethene (TCE); chlorinated methanes (CMs) such as carbon tetrachloride (CT), chloroform (CF); chlorinated ethanes (CAs) such as 1,2-dichloroethane (2DCA), 1,1,1-trichloroethane (1,1,1-TCA); bromoform (BF), and ethylene dibromide (EDB). Column tests were conducted with four ZVI particles at 4% loadings in sand and a sulfidated ZVI particle or combinations of 10 g/kg of a small ZVI particle, EVO, and a ferrous sulfide solution (FSS).     The addition of sulfide to the ZVIs generally increased the extent and rate of dechlorination for PCE, 1TCA, and EDB over the corresponding untreated ZVIs. CT or BF generally were degraded almost to completion using ZVI with and without sulfide. In the column studies, 4% by weight ZVI loading resulted in average CE removals from the influent of 79% (with 130 m ZVI) to a maximum of 98% (smaller ZVI). With the 130 m ZVI particle, the addition of sulfide increased the average CE removal from 79% to 93%. Another column study showed greater removals of the parent and daughter products with the combinations of ZVI and FSS than ZVI alone. ZVI loadings > 4 g/L and in combination with sulfidation and organic substrates, was shown to be very effective in degrading many solvents. In another lab study, chlorinated ethene degradation was 69% with the EVO, ZVI, and Dehalococcoides and increased to 98% with addition of soluble sulfate and nutrients.     The combination of small and large droplet EVO, ZVI, ferrous sulfide, nutrient, and sulfate blend and bioaugmentation culture was effective in treating overburden and bedrock zones of a redevelopment project. Reductions of chlorinated ethenes of 98 to 99% were observed in the overburden and between 92 to 99% reductions in the bedrock treated with large droplet EVO, two sulfidated ZVI particles, bioaugmentation, and nutrient and sulfate blend. At a dry cleaner site, EVO, EVO + sulfidated ZVI, sulfate, and bioaugmentation culture were applied in a dense silt with sand and gravel aquifer. Within 13 months, between 95 to >99% of the CVOCs were reduced. in a pilot at a site with interbedded sand, silt, and clay layers, up to 160 mg/L TCE was reduced by >99.9% with EVO, ZVI, pH buffer, nutrients, sulfate, and bioaugmentation. At a sandy site in Central Florida, EVO was detected up to 25 from the injection point. EVO with ZVI was distributed in thinner zones.   

Dr. Michael D. Lee is Vice-President of Research and Development at Terra Systems. (TS) of Claymont, DE, USA, a consulting and service firm specializing in the development and application of technologies for the bioremediation of surface and subsurface contaminants. He has a Doctor of Philosophy (1986) and Master of Science (1983) degrees in Environmental Science and Engineering from Rice University and a Bachelor of Science degree in Biology from University of Louisiana at Monroe (1980). Dr. Lee has over 40 years of experience in the field of bioremediation with expertise in applying in situ anaerobic bioremediation of chlorinated solvents and metals, implementing in situ aerobic bioremediation of hydrocarbons and other contaminants in groundwater and waste impoundments, conducting biodegradation and chemical oxidation treatability studies, and assessing natural attenuation of organic contaminants. He develops new emulsified vegetable oil (EVO), EVO and zero valent iron, and other bioremediation products for TS.