In 2009, EOS Remediation commercialized EAS, a sulfate-enhanced technology for in situ remediation of contaminated groundwater. The conventional wisdom for remediation of aquifers contaminated with petroleum hydrocarbons (PHCs) is to add oxygen. EAS stimulates biodegradation by providing a soluble, readily available electron acceptor. In the presence of elevated sulfate, anaerobic groundwater bacteria use the PHCs for carbon and energy while mineralizing the hydrocarbons to carbon dioxide and water. EAS is a “Green Technology” that accelerates site cleanup. EAS enhances natural conditions and reduces carbon foot print when compared to conventional remediation – a socially responsible approach to remediation.

It was once thought that aromatic hydrocarbons do not biodegrade under anaerobic conditions. However, the importance of naturally occurring anaerobic oxidation processes in the biodegradation of petroleum hydrocarbons (PHCs) is now firmly established and is considered to be the dominant driving force in natural attenuation of PHCs in the subsurface. Sulfate reduction and methanogenesis appear to be the dominant natural degradation processes at most sites (Wiedemeier et al., 1999). A recent British Petroleum/EPA study has concluded that most hydrocarbon plumes are anaerobic and depleted of sulfate. Other studies have drawn comparable conclusions. This process occurs when terminal electron acceptor compounds such as nitrate, sulfate and iron react to reduce PHC concentrations. This process occurs through the oxidation of the PHC with the reduction of inorganic terminal electron acceptor compounds such as nitrate, sulfate and iron (Van Stempvoort et al., 2007).

Based on a solid body of published scientific evidence, adding electron acceptors such as EAS (U.S. Patent # 7,138,060) to groundwater will aid in increased degradation. EAS addition will stimulate biodegradation by providing a soluble, readily available electron acceptor. In the presence of elevated SO4-2, anaerobic groundwater bacteria use the PHCs for carbon and energy while mineralizing the hydrocarbons to CO2 and H2O. In addition, SO4-2 reduction consumes protons increasing the pH and enhancing methanogenesis. The following equation illustrates this concept using toluene as the PHC and “B” representing bacterial metabolism.

The reaction results in complete degradation of the BTEX components.

• EAS is a 'Green Technology' that accelerates site cleanup.  EAS enhances natural conditions and reduces carbon foot print when compared to conventional remediation - a socially responsible approach to remediation.
• EAS is an in situ remedial technique with minimal disruption to the site and surroundings.  Injection can be accomplished via infiltration trenches, vertical wells, surficial spreading, former recovery wells, former SVE wells or temporary Geoprobe points.
• EAS is cost effective in achieving client remediation goals. Most projects can be completed within 3-4 injections.
• EAS is safe to the environment and people.
• EAS is proven by case study results on nearly 200 sites

• Not a solution for every site, but a likely candidate for many.
• Applicable where the existing plume demonstrates a lack of electron acceptors relative to background.
• Not applicable for significant thickness of liquid phase hydrocarbons, but potentially useful for sheens.
• Effective within water saturated zone. Residual soil impact in vadose zone may need to be addressed by other techniques.
• Effective for biodegradable chemicals of concern.
• Threatened receptors may warrant additional response actions.

1.  Biodegradation requires aerobic conditions
Anaerobic degradation is the predominant mechanism for natural attenuation at most sites.

2.  This is in situ oxidation (Persulfate Radical)
EAS process is bio-enhancement.

3.  Anaerobic Biodegradation is too slow
Significant contaminant reduction occurs in as little as 3 months.

4.  Hydrogen Sulfide gas will be generated
Our clients report that they have never detected this, but they continue to monitor.

5.  Addition of sulfate solution will result in increased plume migration
The volume of sulfate solution is minimal in comparison to the volume of the aquifer being treated.

6.  This technology will result in a lingering sulfate contaminant plume
Sulfates are rapidly utilized after application

• Applied at approximately 200 sites
• Applications have been made in Michigan, Indiana, Illinois, West Virginia, North Carolina, Virginia, Iowa, Georgia, New York and California
• Applications via infiltration trenches, vertical wells, surficial spreading, former recovery wells and former SVE wells
• Variety of geological and hydrogeological settings
• Success is highly dependant upon adequate site characterization
• Not appropriate for significant thicknesses of LPH, but may be useful for sheens
• Design of application plan needs to account for the proximity of sensitive receptors
• Toluene, Ethylbenzene, Xylene degrade more rapidly then Benzene and TMB’s, but all are effectively remediated