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Aerobic In-situ Bioremediation

A number of methods are available for the in-situ bioremediation of contaminants that are susceptible to aerobic biodegradation.

th1Churngold Remediation have successfully applied a number of methodsĀ for the in-situ bioremediation of contaminants that are susceptible to aerobic biodegradation. In a similar way to ex-situ soil treatment it is necessary to uniformly distribute oxygen and nutrients within the treatment zone. A number of methods are available to do this including but not limited to:
  • biosparging (the controlled injection of air)
  • oxygen infusion (using pure oxygen injected through a high surface area membrane)
  • electrolytic oxygenation (using electrolysis to split oxygen molecules from water)
  • oxygen release chemicals (peroxides)

Churngold has applied each of these techniques. The selection of the most appropriate type of in-situ oxygenation will be dependent on site-specific conditions. Biosparging has the advantage of introducing a greater mass of oxygen, but its performance can be limited in low permeability soil and care needs to be taken to avoid mobilising VOC in the vadose zone. Oxygen infusion and electrolytic oxygenation both introduce much higher concentrations of dissolved oxygen, enabling greater diffusion into impermeable zones. However the masses of oxygen introduced are low compared to biosparging and therefore they may be better applied in a biobarrier application. Similarly consideration needs to given to the mass of oxygen being introduced by oxygen release chemicals.

One of the issues with these techniques are the time it will take to complete the treatment. Often UK groundwater temperatures are less than 12oC, which will slow the rate that bacteria metabolise the contamination. Additionally desorption/dissolution of contamination locked within soil or NAPL will be rate limited and therefore needs to be carefully considered. As the performance of In-situ bioremediation is limited it is probably best applied as a polishing tool following a more aggressive technique such as Steam Enhanced Remediation or Chemical Oxidation.