With Anaerobic Bioremdiation and all remediation processes come down to mass balance. How many pounds or kilograms of a contaminant exists in the subsurface, and how much of this mass can be removed by the proposed remediation system? With reductive dechlorination, the mass balance is a function of the stoichiometry of the oxidation-reduction reactions that govern the biological utilization of a particular compound. For example, oxidation-reduction reactions for the reductive dechlorination of PCE are as follows:
Oxidation Reaction: C6H12O6 + 6 H2O → 6 CO2 + 24 H+ + 24 e–
Reduction Reaction: 3 C2Cl4 + 12 H+ + 24 e– → 3 C2H4 + 12 Cl–
Overall Reaction: C6H12O6 + 3 C2Cl4 + 6 H2O → 3 C2H4 + 12 Cl– + 12 H+ + 6 CO2
The C6H12O6 requirement for this reaction is that 1 mole of C6H12O6 can degrade 3 moles of C2Cl4. Converting to the appropriate mass ratio results in the following:
1 unit C6H12O6 : 3 x (180/166) units of C2Cl4, or 1 unit C6H12O6 can degrade more than 3 units of C2Cl4.
Additional info on the science behind Anaerobic Bioremediation can be found at the ETEC web site.