In-situ Remediation – Five Reasons to Use Electrokinetic Oxidation

There are 340.000 contaminated sites estimated in Europe alone. Cleaning them up is a vast global undertaking. Despite many in-situ remediation techniques are available, it can be hard to determine, which one to use. This article explains you Five reasons to use Electrokinetic Oxidation in in-situ soil and groundwater remediation projects!

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What is In-situ Remediation?

In-situ remediation method means that the contaminated soil, groundwater, and sediment is treated on-site. The medium is not excavated and transported to another location for treatment. Within in-situ bioremediation, the organic contaminants such as aliphatic hydrocarbons (gasoline, petrol, diesel, heavy oil, crude oil), BTEX compounds (benzene, toluene, ethylbenzene, xylenes), PAH (Polyaromatic Hydrocarbons), MTBE, ETBE and TBA as well as chlorinated compounds (PCB-PCDF-PCDD) and solvents (PCD,TCE,DCE and VC) can be treated and neutralized in the original location.

In contrary, ex-situ remediation means that the polluted soil is excavated and transported to a specific treatment place or container to remove or neutralize the contaminants.

The flexible Electrokinetic Oxidation remediation technique can be used in both, in-situ and ex-situ remediation. It is an advanced oxidation remediation technique providing a fast, cost-efficient and environmentally friendly contamination neutralization process.

This article provides a detailed overview and run-down of Five key advantages!

In-situ Remediation based on Electrokinetic Oxidation

Electrokinetic Oxidation is an advanced in-situ remediation technique. It utilizes electrochemical phenomena to generate chemical radicals on soil particle surfaces and electrokinetic and electro-osmotic phenomena to increase availability of organic contaminants for bioremediation, chemical degradation or mechanical removal.

Effects are deployed through steel electrodes inserted into the contaminated soil, sediment or groundwater medium. The electrodes of the Electrokinetic Oxidation system are laid out in a grid formation into rows of anodes and cathodes. The electrodes should be installed over the depth and width of the polluted medium.

The electrode rows will then have low voltage electric pulses driven through the grid controlled by an above-the-ground control unit.

Electrokinetic remediation solution layout - EKOGRID

In-situ Soil Remediation

The Electrokinetic Oxidation technique is optimal for capillary soil conditions, in which the effective oxidizing and reducing agents such as hydroxyl radicals and oxygen are formed at the surface of each grain of soil. Because of this, the remediation effect is evenly spread in the polluted soil. The finer the soil grain size is, the more effectively the Electrokinetic Oxidation system operates.

The Electrokinetic Oxidation technique can also be used underwater to treat bottom sediments. It also works in fractured porous bedrock. The system utilizes the soil matrix and reactions that occur at the surface of each grain, precisely where the pollution is.

In conclusion, Electrokinetic Oxidation is an in-situ remediation method that provides enhanced bioremediation; microbiological activity is boosted with oxygen formed in the reactions and the constant changes in polarity of the electric field enhance the bio-availability of the contaminants in the soil.

The electro-kinetic oxidation method has proven to be a fast, ecological, sustainable and cost-efficient way for remediating soil and groundwater affected by various organic contaminants.

  

In-Situ Groundwater Remediation

Electrokinetic Oxidation technique is used for in-situ groundwater remediation. It is conducted within the contaminated site to treat and remove contaminants in the saturated zone. With Electrokinetic Oxidation and Reduction remediation, the groundwater layer can be treated simultaneously and with the same equipment as the remediation of the unsaturated zone.

In-situ Remediation of Vadose Zone

In combination with the in-situ groundwater remediation, the vadose zone can be remediated using Electrokinetic Oxidation. The treatment is conducted at the site and most of the soil excavations can be avoided. With Electrokinetic Oxidation remediation of the vadose zone, or unsaturated soil can be done simultaneously and with the same equipment as the remediation of the groundwater layer.

What’s the Remediation Effect of In-situ Electrokinetic Oxidation?

The EKOGRID patented pulsed voltage output creates redox reactions such as the electrolysis of water on the soil particle surfaces and the electro-osmotic forces move the charged contents of the pore water quickly backward and forwards in the medium.

Freshly formed oxygen and hydroxyl radicals oxidize and split hydrocarbon chains to lighter fractions, and eventually form carbon dioxide and water, which are the end products of the remediation process. Reducing effect is mediated through soil iron and manganese which will donate the electrons further to the use of microbes while the mixing effect releases the organic compounds and soil nutrients stocks. These effects promote the growth of microbes and enable faster degradation of various types of organic contaminants.

In conclusion, Electrokinetic Oxidation technique is not only a method to crack hydrocarbons. It is also an efficient method to enhance bioremediation or mechanical remediation methods such as Pump and Treat or Soil Vapor Extraction.

Five Advantages of Electrokinetic Oxidation

Although the reactions and advantages described in this article can be achieved through many in-situ bioremediation methods based on oxidation and advanced oxidation processes, the Electrokinetic Oxidation method provides several additional advantages. Here is a run-down of the main benefits!

1. In-situ Electrokinetic Oxidation Saves Time

Electrokinetic Oxidation technique can speed up an in-situ remediation project in several ways.

Firstly, depending on the site and the pollutant mix, Electrokinetic Oxidation technique could be the only remediation technique needed in a remediation project.

Electrokinetic Oxidation is provenly capable of degrading many organic contaminants such as aliphatic hydrocarbons (gasoline, petrol, diesel, heavy oil, crude oil), BTEX compunds (benzene, toluene, ethylbenzene, xylenes), PAHs, MTBE, ETBE, TBA, chlorinated compounds and solvents, and creosote.

When additional remediation techniques such as chemical surfactants can be avoided, the time and costs of the in-situ remediation project can be reduced significantly.

Secondly, in optimal conditions, the Electrokinetic Oxidation process has proven to provide much faster remediation than conventional methods alone. Several examples exist, such as the fast in-situ remediation of a contaminated railway yard project in Sao Paolo in Brazil, where the soil contaminated by PAH compounds was cleaned up in three months.

2. Electrokinetic Oxidation Saves Energy in In-situ Remediation

The Electrokinetic Oxidation techniques are based on optimized low voltage pulse, which makes the technique extremely energy efficient compared to e.g. thermal in-situ remediation techniques. The low amount of energy consumption also enables the use of alternative energy sources, such as solar panels or wind turbines, to power the entire remediation process.

3. In-situ Remediation Costs Reduced through Electrokinetic Oxidation

One single treatment is sufficient to obtain the decontamination of both groundwater and soil. Since this can take place in-situ, the expenses due to excavation, storage, final processing or removal of polluted soil, or acquisition of clean replacements will be greatly reduced or become not necessary at all.

4. Improves Microbial Degradation

In addition to time and cost savings, Electrokinetic Oxidation also improves microbial degradation. This is done via hybrid solutions combining other technologies such as pump and treat and optimizing the bioremediation process.

  • Electrokinetic Oxidation increases the availability of nutrients and pollutants to soil microbes by movement and mixing of soil pore contents
  • Electrokinetic Oxidation repetitively polarizes the natural soil particle – surface cation -structure and produces oxidants from soil water on soil particles and reductants at the soil cations
  • The technique can be used for efficient and accurate transport of bioremediation enhancing agents to low permeable soils

Water, nutrients, biosurfactants, absorbents, enzymes, microbes can be transported to source areas or e.g. spill plumes under buildings or other infrastructure by using Electrokinetic Oxidation technique.

5. In-situ Remediation with Electrokinetic Oxidation is Environmentally Friendly

Several aspects make Electrokinetic Oxidation and Reduction an environmentally friendly in-situ remediation technique.

Firstly, the remediation effects are achieved through a low voltage pulse emitted in the contaminated medium. Harmful chemicals are not needed, which means that secondary pollution is not generated.

In contrary, some in-situ chemical oxidation compounds can react aggressively with organic contaminants and can generate unwanted or toxic oxidation products.

Because of the extremely low operation voltage and very low current densities applied, Electrokinetic Oxidation causes no hazard or danger to humans, flora, or wildlife. In fact, after installation, normal daily activities can continue, allowing remediation to be carried out simultaneously with construction or daily operation activities on site.

In-situ Remediation Case Studies

There are several polluted soil and groundwater sites that have been successfully cleaned and remediated using in-situ remediation based on Electrokinetic Oxidation. Here are links to a few case studies.

In Conclusion

Eko Harden Technologies is a global in-situ remediation technology and service provider. Our patented EKOGRID solution for Electro-Kinetic Oxidation has been proven in several successful in-situ remediation projects in five continents.

Contact us to learn more!