EOS® (Emulsified Oil Substrate) is an engineered organic substrate specifically designed for soil and groundwater bioremediation. Its formula and production have been meticulously designed for effective distribution in the subsurface to provide a long-lasting source of hydrogen used by microorganisms to reductively degrade certain contaminating compounds (i.e. tetrachloroethylene aka PCE and its daughter products). Generic products that mimic our technology are referred to as emulsified vegetable oils or EVO.
Unlike generic EVO products, our patented EOS®technology is formulated to have small oil droplets (~1 micron) and a slight negative charge to prevent them from coalescing, simultaneously enhancing sorption onto slightly positively charged aquifer materials. Our emulsion is designed to transport through the pore spaces and adhere to the sediment, providing a hydrogen source that will last for years.
Very simply, anaerobic bacteria required for reductive dechlorination (the biotic process of converting PCE to non-toxic ethene) requires a food source. EOS® provides both quickly available carbon (soluble substrate) and slow-release carbon (soybean oil) with nutrients required for biotic stimulation. In the presence of the available food and nutrients, the anaerobic bacteria “breathe” the chlorinated solvents resulting in harmless waste products and energy for growth. Due to its effective transport EOS® substrates can be deployed across a wide variety of site conditions.
Extensive laboratory and field studies have shown that EOS® will support anaerobic biodegradation for three to five years depending on the amount of substrate injected and site conditions. In a laboratory column study, Long and Borden (2005) showed that a single injection of emulsified soybean oil can support complete reductive de-chlorination of 10,000 µg/L to PCE to ethene for up to seven years. Field tests of the emulsified oil technology by the Air Force Center for Environmental Excellence (AFCEE) have shown that emulsified edible oils have lasted over three and one-half years at Dover Air Force Base (AFB), over three years at Edwards AFB, and over two and one-half years at Altus AFB. A recent biobarrier project supported by the Environmental Security Technology Certification Program demonstrated that a single EOS® injection lasted over one and one-half years while reducing influent perchlorate concentrations to below detection (over 99.9% reduction) with concurrent reduction of 1,1,1-TCA to non-toxic end-products (Zawtocki et al., 2004). Monitoring is continuing to evaluate the effective life of this barrier.
Based on bench scale and field studies, proper application of EOS® should last at least three to five years in the aquifer. As part of the engineering design criteria, you control the life expectancy of the remediation. Your EOS ASIA Remediation representative can assist you with designing sufficient substrate life for your project.
Absolutely. For source control applications, EOS® is usually injected on a grid spacing or in a series of closely spaced barriers. Depending on the proximity of property boundaries, a recirculation system may be considered.
Unlike field-prepared emulsions and neat soybean oil, EOS® will not float on the water table. EOS® is engineered to prevent agglomeration or flocculation of the small oil droplets. This facilitates spreading the emulsion during injection to the designed distance in the subsurface while sorbing substrate to sediment surfaces along the way.
After the injection process is finished, EOS® adheres to the aquifer sediments very quickly, so contaminants are not mobilized. In fact, some chlorinated solvents can sorb to the substrate, further reducing potential for mobilization.