GROUNDWATER AND LEACHATE: IN-SITU BIOLOGICAL TREATMENT
Enhanced Bioremediation for Contaminated Ground water (air sparging)
Oxygen-Enhanced Bioremediation System by Air Sparging
Enhancement options: (below the WT)
1) Oxygen-Enhanced Bioremediation with Air Sparging - Aerobic
2) Oxygen-Enhanced H2O2 Bioremediation - Aerobic
3) Nitrate-Enhanced Bioremediation - Anaerobic
During each process indigenous or inoculated micro-organisms (e.g. fungi, bacteria) biologically degrade organic contaminants found in soil and/or ground water.
These processes attempt to accelerate the natural bio-degradation process by increasing the concentration of nutrients, electron acceptors (e.g. Oxygen if aerobic, Nitrate is anaerobic), and competent degrading microorganisms.
1) Oxygen Enhancement with Air Sparging
Uses:
Limitations:
Cost:
- Highly variable - dependent on the nature and depth of the contaminants, groundwater pumping rates & electron acceptor used.
- e.g. For oxygen enhancement with air sparging, typical costs are $10-$20 per 1,000 litres of ground water treated (much more expensive for H2O2 or Nitrate).
1) Oxygen-Enhanced Bioremediation with Air Sparging - Aerobic
2) Oxygen-Enhanced H2O2 Bioremediation - Aerobic
3) Nitrate-Enhanced Bioremediation - Anaerobic
During each process indigenous or inoculated micro-organisms (e.g. fungi, bacteria) biologically degrade organic contaminants found in soil and/or ground water.
These processes attempt to accelerate the natural bio-degradation process by increasing the concentration of nutrients, electron acceptors (e.g. Oxygen if aerobic, Nitrate is anaerobic), and competent degrading microorganisms.
1) Oxygen Enhancement with Air Sparging
- Air sparging below the WT (saturated zone) increases the oxygen content in the water and increases the 'mixing' (greater contact between MOs & contaminant), enhancing the rate of contaminant degradation.
- The small-diameter air injection points are simple & low cost to install allowing more flexibile designs.
- Can be further enhanced with SVE or bioventing - increasing rates and area of treatment.
- A dilute solution of H2O2 is circulated through the contaminated ground water zone - again increases oxygen content to enhance the rate of (aerobic) bio-degradation.
- Solubilised nitrate is circulated throughout ground water contamination zones to enhance the rate of degradation (of organic contaminants).
Uses:
- Treats fuels, non-halogenated VOCs & SVOCs.
- Less effective for Pesticides
- Nitrate enhancement allows bioremediation of BTEX, toluene, ethylbenzene, and xylenes.
Limitations:
- Very difficult to evenly deliver Nitrate or H2O2 in heterogeneous ground - here less permeable zones would require much longer treatment time.
- H2O2 injection requires additional safety precautions - high concentrations may in fact inhibit the growth of micro-organisms.
- A ground water re-circulation system must be created so contaminants do not escape from bio-degradation zones.
- Nitrate injection has the potential to contaminate drinking water.
- Further surface treatment (e.g. air stripping/carbon adsorption) may be required.
- The effectiveness is highly dependent upon soil properties and biodegradability of the contaminants.
- As it is a relatively new technology used, there is limited knowledge of the rates achieved and costs.
- Typically long-term technology (several years).
Cost:
- Highly variable - dependent on the nature and depth of the contaminants, groundwater pumping rates & electron acceptor used.
- e.g. For oxygen enhancement with air sparging, typical costs are $10-$20 per 1,000 litres of ground water treated (much more expensive for H2O2 or Nitrate).