The process of bioremediation can be monitored indirectly by measuring the Oxidation Reduction Potential or redox in soil and groundwater, together with pH, temperature, oxygen content, electron acceptor/donor concentrations, and concentration of breakdown products (e.g. carbon dioxide). This table shows the (decreasing) biological breakdown rate as function of the redox potential.
| Process | Reaction | Redox potential (Eh in mV) |
|---|---|---|
| aerobic: | O2 + 4e− + 4H+ → 2H2O | 600 ~ 400 |
| anaerobic: |
| |
| denitrification | 2NO3− + 10e− + 12H+ → N2 + 6H2O | 500 ~ 200 |
| manganese IV reduction | MnO2 + 2e− + 4H+ → Mn2+ + 2H2O | 400 ~ 200 |
| iron III reduction | Fe(OH)3 + e− + 3H+ → Fe2+ + 3H2O | 300 ~ 100 |
| sulfate reduction | SO42− + 8e− +10 H+ → H2S + 4H2O | 0 ~ −150 |
| fermentation | 2CH2O → CO2 + CH4 | −150 ~ −220 |
This, by itself and at a single site, gives little information about the process of remediation.
- It is necessary to sample enough points on and around the contaminated site to be able to determine contours of equal redox potential. Contouring is usually done using specialised software, e.g. using Kriging interpolation.
- If all the measurements of redox potential show that electron acceptors have been used up, it is in effect an indicator for total microbial activity. Chemical analysis is also required to determine when the levels of contaminants and their breakdown products have been reduced to below regulatory limits.
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