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In late 2017, disaster struck when a stretch of the Keystone Pipeline spilled an estimated 210,000 gallons of oil near Amherst, a small town north of Sioux Falls in South Dakota. This recent oil spill incident once again highlights the need for remediation techniques to clean up contaminants found in the surrounding soils and groundwater.

The contamination of soils and groundwater due to the Keystone Pipeline oil spill poses risks of ill health effects for the local populace within and around Amherst, SD. As the main objective of environmental remediation is to address the nature and extent of contamination, ensuring threatened resources and human and environmental exposure are minimized and limited, total water management solutions must employ strategies that acknowledge these elemental factors.

The remediation techniques highlighted below play an integral role in reducing potential health and ecological risks. These techniques are frequently used to reduce or eliminate hazardous contaminants from soil or groundwater.

1. Pump-and-treat

A primary remediation technique, pump-and-treat employs one or more pumping wells to pump the groundwater to the surface so that it may be treated with contaminants. Several treatment methods are present to separate contaminants from the groundwater in question. These treatment methods include activated carbon, ultraviolet, ozone treatment, air-stripping, or precipitation, and biodegradation.

While pump-and-treat can be seen as a primary remediation technique, this method is typically reserved for contaminants that have already dissolved within groundwater. The pump-and-treat technique employs the rapid mass removal of contaminants, particularly in groundwater with heavy concentrations of contaminants.

Low permeable soils such as clay or silt limit the effectiveness of the pump-and-treat method. The effluent disposal costs and the high rate of energy required to employ this method make pump-and-treat an often expensive form of remediation treatment, especially when lengthy operations are concerned.

2. Vertical integration

While not necessarily a remediation technique, the expertise found in vertically integrated remediation solutions makes it an essential remediation solution to address the unique challenges in groundwater and soil remediation.

From site preparation, drainage grading, project roadway and lay down area installations, and the development of erosion control measures, vertical integration can serve to seamlessly integrate total project solutions for the treatment of contaminated soils and groundwater.

Their ability to provide a one-stop shop approach ensures that even the most complex, multidisciplinary remediation projects operate flawlessly.

3. Soil vapor extraction

Soil vapor extraction or SVE remove volatile and semi-volatile contaminants such as trichloroethane, trichloroethylene, benzene by inducing airflow through the soil for treatment.

A typical SVE process requires one or more extraction wells to address the contaminated soil within the soil matrix. The extraction wells used in the process are typically prepared in-situ, at a minimum of three feet or more below ground surface.

This ensures maximum efficiency when air and vapors are pulled through the soil matrix. The extracted air and contaminants that are brought to the ground surface are treated with containers of activated carbon to remove any harmful levels of volatile and semi-volatile contaminants. Another way to treat harmful levels of contaminants is by destroying the vapors through heat management.

Several determinant factors play a role in how long the SVE process will take. Factors include the concentration levels of contaminants, the depth and surface area of the contaminated area, and the density level of the soil matrix as this affects the movement of vapors.

4. In-situ well stripping process

The in-situ system employs a combination of remediation processes to address contaminated aquifers contaminated with hydrocarbons or heavy metals. These volatile and semi-volatile contaminants are addressed through three main remediation processes:

  1. Biological
  2. Chemical
  3. Physical.

The in-situ well stripping process works by integrating a combination of the three highlighted processes above, stripping volatile and semi-volatile contaminants out of groundwater through a multi-stage stripper.

This equipment typically employs several filters such as activated carbon to strip contaminants from the groundwater. Once stripped from the groundwater, these volatile and semi-volatile contaminants are converted into vapor and treated.

Once treated of contaminants, the groundwater is discharged back into aquifers.

5. Bioremediation

The bioremediation process stimulates the growth of specific microbes that are capable of sourcing their food and energy from contaminants. A cost-effective, natural and sustainable process of removing contaminants from petroleum products such as oil, solvents, and pesticides, bioremediation transforms these contaminants into harmless gases such as carbon dioxide or into small amounts of water.

While bioremediation is capable of addressing a versatile variety of chemicals of concern (COCs) and reduces environmental impact, its effectiveness is determined by several key factors. Specific temperatures, nutrients, and food must be present for bioremediation to be effective as a remediation solution. If conditions are less than ideal, the microbes deployed to eliminate COCs may be ineffective, resulting in microbes dying or growing too slowly.

In situations such as these, the addition of “amendments” improves working conditions for microbes. These amendments, such as ordinary household items like vegetable oil, enhance the growth and stimulation of microbes, allowing them to grow and multiply, thereby consuming more contaminants along the way.

Conclusion

The Keystone incident in South Dakota is far from an isolated case. The increasing demand for environmental protection coupled with continuing pollution concerns among industries such as oil and gas, automotive, mining and forestry, etc., highlight the need for effective remediation solutions.

The techniques and processes highlighted above showcase the importance of promoting and developing further innovative remediation technologies employed in remediation management solutions.

About The Author: 

Patrick Randall is the Vice President of National Sales at Hepure Technologies. He holds a BS in Mechanical and Chemical engineering from Cal Poly San Luis Obispo and an M.S. in Civil Engineering from CSUS. He has been working in the environmental and bioremediation space since graduating in 1986.

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