Frequently Asked Questions about Bioremediation and EOS Products . .
Got questions about bioremediation or EOS products?

We have compiled a list of frequently asked questions about bioremediation and EOS products. What is bioremediation? Why would a project manager choose bioremediation as a remedy? What is EOS? Will environmental regulators let me use it? Find these topics and more explained in this FAQ.

If yours is not a frequently asked question, contact our technical representatives today. They can talk with you directly and in depth about remediation technologies and solutions for complex site conditions.

What is bioremediation?

Bioremediation is a cost-effective, sustainable, natural approach to cleaning up contaminated soil and groundwater through the use of biological agents such as bacteria, microbes, fungi, and other organisms of their enzymes.

The process of bioremediation requires two key components:
1) Electron Donor: typically hydrogen which can be derived from a carbon source such as vegetable oil, lactate, or petroleum-based contaminants
2) Electron Acceptor: a respiring agent like oxygen, although many microorganisms are capable of using other agents such as nitrate, sulfate or even a chlorinated solvent (PCE or TCE).

Contaminants can fill either role of electron donor or electron acceptor. For example a petroleum based hydrocarbon could be a usable carbon source for certain bacteria, similarly a chloringated solvent such as tetrachloroethene (PCE) could be utilized by a different strain of bacteria as an electron acceptor.
A critical understanding in the success of a bioremediation project is determining the role of the contaminant at the site and what key component is required to foster bioactivity. Below are two tables illustrating some common examples of electron donors and acceptors.

If the correct components are available at a contaminated site, the process of bioremediation can occur naturally with no human intervention. This is known in the industry as monitored natural attenuation (MNA) because all the components needed for cell growth and reproduction are present and bioremediation occurs without outside stimulus.

When an electron donor or acceptor are lacking, often biostimulation is an option to provide the missing component. And when the microorganisms themselves that perform these reactions are not present, bioaugmentation can allow the reaction to continue and facilitate bioremediation.

Biostimulation: The addition of nutritional amendments to increase microbial metabolism and to encourage biodegradation (often organic compounds, e.g. EOS indigenous microbes present, but substrates and/or nutrients are limited and must be added to foster bioactivity).

Bioaugmentation: the addition of beneficial microorganisms to improve the rate or extent of biodegradation (e.g. Indigenous microbes not present or in low quantity so organisms are added).

Why choose Bioremediation?

Most project managers give two reasons to select a particular remediation technology:

Price and Performance
For most project situations, bioremediation meets or exceeds both criteria (price and performance) compared to other remediation technologies. At EOS Remediation, we also offer project support from planning to completion at no extra cost.

Price (Remediation Cost in the U.S.)

  • Enhanced Bioremediation $29/yd3
  • Thermal Treatment $88/yd3
  • Chemical Oxidation $125/yd3
  • Surfactant Co-solvent Flushing $385/yd3


McDade et al. Remediation Journal 15, 9-18, 2005.
McGuire et al. Ground Water Monitoring and Remediation 26, 73-84, 2006.

What does EAS® stand for?

EAS® stands for quality; it is the trademark of EOS Remediation, derived from “Electron Acceptor Solution” and from “Effective Anaerobic Solution.”

Will EAS® work on gross petroleum free product?

EAS® is not recommended for sites where gross, petroleum-based free product is measurable (i.e., light non-aqueous phase liquid = LNAPL).  EAS® can be used at sites with residual impact (“sheen” or high dissolved concentrations) and it can be used to polish off sites where free product has been removed. Residual soil impact in the vadose zone may need to be addressed by other techniques.

Are there any limitations with the EAS® technology?
  • The groundwater must be deeper than 1,5 m below ground surface
  • The distance to residence, surface water or private well must be greater than 30 m
  • Distance to municipal Drinking Water well (100s of gpm) > 380 m
  • The plume should be stable or decreasing
How does EOS® work?

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.

Will EOS® float on the water table?
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.
Will emulsified oils mobilize contaminants?
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.
Will EOS® clog the aquifer?
EOS® is engineered to have droplet sizes significantly smaller than most pore spaces. The slight negative charges on the droplets repel the droplets from each other, while sorbing them onto the slightly positively charged aquifer soils.
Does emulsification cause the soybean oil to biodegrade too rapidly?
The metabolic breakdown of soybean oil in the aquifer (i.e., fermentation to H2 and acetate) is the critical first step to enhancing reductive dechlorination. But without emulsification, soybean oil would degrade so slowly that it would not effectively stimulate biodegradation processes. Soybean oil blends the desired biodegradability with longevity, allowing EOS® to remain effective in the aquifer for at least three to five years.
Do contaminants sorb to oil preventing biodegradation?
EOS® treatment can result in a temporary sorption of the contaminants into the oil phase, a clearly beneficial effect. Biodegradation does not occur in the oil, but the sorption can retard migration of the contaminant, especially DNAPL. Years of laboratory and field research have shown that, over time, contaminants are eventually released from the sorbed phase to the aqueous phase as biodegradation in the aqueous phase proceeds. The overall effect is to keep the contaminants in the area that has been enhanced, lowering the potential for migration out of the treatment zone.
How long will EOS® last?

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 US 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 Remediation representative can assist you with designing sufficient substrate life for your project.

Can I use EOS® for source control?

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.

How do I determine my well spacing?

Field tests have shown that EOS® can be distributed large distances in the subsurface from just a few injection points. However, drilling costs are only one part of the total project cost. Using a larger well spacing can increase the total cost by increasing the time (i.e. labor cost) for injection.

The graph below illustrates the effect of drilling costs and injection well-flow rates on the least cost well spacing. When injection rates and drilling costs are low, it is actually less expensive to use closely spaced wells. However, as drilling costs and/or feasible injection rates increase, larger well spacings become more cost effective. For large projects, it is useful to generate cost estimates for several different well spacings to find the least cost alternative. A site-specific analysis should consider the available water supply, access restrictions, continuous versus intermittent injection, labor and drilling costs, etc.

How do I inject EOS®?

EOS®, a low-viscosity fluid, requires no specialized material handling or pumping equipment. It is designed to migrate out into the aquifer away from the injection point at ambient temperature and low pressure. The ability to emplace the material into the aquifer at a considerable distance from the injection point is a major benefit of EOS®.

EOS® is delivered to a site in 55-gallon drums, totes or in bulk as a concentrate and must be diluted with a ratio of at least four parts of water to one part of EOS® before injection. Based on your specific design, either a “water chase” or an initial dilution ratio of 10:1 can be used for injection purposes. Both methods are equally effective and each has its advantages. The key consideration is to provide the correct amount of EOS® throughout the treatment zone.

A benefit of using EOS® at your site is employing your choice of injection methods. Our experience has shown that where direct push technology can be used, installation of micro wells (¾ to 1-inch PVC wells) can be very cost effective option. However, micro wells are neither better nor worse than conventionally installed wells. If multiple technologies are appropriate, cost factors normally determine the conveyance choice.

There are a variety of injection techniques, including injecting multiple wells simultaneously, to reduce injection costs. EOS® can be diluted in a holding tank and then injected or can be injected using a Dosatron. The Dosatron eliminates tank mixing and reduces injection labor costs. Your EOS Remediation representative can help recommend suitable injection methods.

Click here for a short video to help you understand EOS injections.

Do I need to chase EOS® with water?

EOS® is designed to be easily emplaced throughout the aquifer treatment zone. We have found that using chase water reduces labor costs. Increasing the dilution rate of the concentrate has the same effect as water chase. Instead of diluting the concentrate 4:1 with water and using a water chase, you could simply increase the dilution with no follow-up water chase. By using chase water, the system can be automated to deliver potable water into the subsurface. A low-pressure feed of potable water does not require onsite supervision; an injected dilute emulsion, however, should be monitored. Either method meets the design requirement.

Can EOS® be used in a recirculation system?

There are numerous sites where recirculation has been used during the injection of EOS®. Recirculation during injection offers the advantages of using an available on-site water supply to generate groundwater flow gradients to draw EOS® through the aquifer.

Have regulators accepted EOS® ?

Yes. EOS® is a natural, food-grade substrate and can be produced with Non-GMO vegetable oil.

To date our remediation products have been used in:


Australia, Austria, Belgium, Brazil, Canada, France, Germany, Hungry, Italy, Japan, Netherlands, New Zealand, South Africa, Spain, Taiwan, UK

Have regulators disallowed the use of any EOS® products?


How do I prevent migration of EOS® outside (downgradient) of the intended remediation area?

We have found that EOS® does not migrate a significant distance away from the injection point. Once the injection process stops, the driving force ceases and EOS®, by design, sorbs to the aquifer materials and does not continue to migrate with groundwater. Downgradient monitoring using visual indicators (such as breakthrough into downgradient performance monitoring wells), or increases in total organic carbon (TOC) can be used to evaluate how far EOS® has moved through the aquifer. Recirculation is another way to provide hydraulic control during injection or to move EOS® in a particular direction or distance in the subsurface.

What groundwater parameters should I monitor after injection of EOS®?

Your monitoring program may be specified for your site by the regulatory agency with site jurisdiction. At a minimum, your monitoring program should incorporate the contaminants of concern and reduction-oxidation (REDOX) potential. Field parameters including pH, conductivity and dissolved oxygen are also recommended. Apparent turbidity, observed as a faint white tint, can sometimes be used as a visual indicator of EOS® presence.

A more detailed monitoring program could include inorganic compounds (e.g., nitrate and sulfate), metals (e.g., iron and manganese), total organic carbon, light hydrocarbon gases (methane, ethane, ethene) and possibly volatile fatty acids. Increasingly complex sites could also monitor for phospholipids fatty acids and a variety of Molecular Biology Tools that would include population counts for Dehalococcoides ssp., other dehalogenating microorganisms, and functional genes.

How do I measure the presence of EOS® in the aquifer?

There are both direct and indirect ways to measure the presence of EOS® in the aquifer.  Apparent turbidity, observed as a faint white tint in performance monitoring wells, can sometimes be used as a visual indicator of EOS® presence.  Laboratory analysis for total organic carbon (TOC) and volatile fatty acids (VFA) can also provide direct indications of the presence of substrate.  Indirectly, changes in groundwater geochemisty as a result of formation of anaerobic reducing conditions suggest that EOS® is present.

Can EOS® be used to effectively immobilize heavy metals?

Yes metals immobilization is possible. Because EOS® creates reducing conditions in the aquifer, certain redox sensitive metals (i.e. Al, Cu, Pb, Mn, and Zn) can be precipitated into non-mobile forms of various metal sulfide species. If your site doesn’t have a sufficient sulfate concentration then the addition of EAS may be required. Please contact us for more information and to discuss the details of your site.