C. Remediation of groundwater contaminants

1. C. Remediation of groundwater contaminants Physical, chemical, and biological remediation methods

2. Objectives: Define remediation and distinguish among physical, chemical, and biological remediation techniques (bioremediation). List, describe, and give examples of contaminated water remediation techniques.

3. Remediation of contaminants: Definition Remediation is the return of an area or component to as natural a condition as possible (e.g., contaminated water).

4. Types of remediation: Physical treatment may include air striping, filtering of water, etc. Chemical treatments include addition of chemicals that facilitate physical or biological treatments, or oxidize contaminants, etc. Biological treatment (bioremediation) utilizes complex biochemical pathways of various organisms to degrade or detoxify contaminants.

5. Techniques for remediation: The method of remediation depends on the chemical nature of the contaminant: Pure-compound recovery is possible when groundwater is contaminated with a compound that is not water soluble. Pump and Treat methods typically involves pumping contaminated groundwater out and treating with appropriate types of treatment Air striping Chemical oxidation (using ozone, chlorine, etc) In-situ Remediation doesn�t involve removal of the soil and groundwater

6. Pure-compound recovery: Organic contaminants like oil and gasoline are less soluble in water and can often be pumped off the surface of aquifers. The specific gravity of the compound may require pumping from the bottom of a confined aquifer (if > 1.0). Sometimes, the product recovered is still usable for its original function.

7. Pump and Treat/In-Situ Remediation Soil vapor extraction (SVE) removes organic contaminants (primarily from the unsaturated zone) by flushing with air on site. Air sparging (in-situ aeration) uses circulated air to remove volatile contaminants (primarily from the unsaturated zone) on site Bioventing also introduces air, but only to speed up natural aerobic microbial processess.

8. Bioremediation techniques: Bioremediation is the use of living organisms like bacteria, plants, animals, or fungi to speed up the remediation process. A tremendous variety of microbes have been used for remediation of contaminants. In-situ bioremediation introduces microbes directly into the water which then degrade contaminants through biochemical processes.

9. Examples of bioremediation: Microbes have been used for centuries to remediate wastewater (biol. treatment). Microbes can also degrade and detoxify a wide variety of synthetic organic compounds, metals, toxic elements, etc. Microbes used to degrade contaminants include bacteria, and fungi. Plants, animals, and mixed populations of different organisms can also be used .

10. Advanced treatment techniques: More advanced treatment techniques may utilize combinations of remediation techniques. Examples include injecting surfactants or chemicals underground to augment conventional pump-and-treat techniques. These are efforts to integrate in-situ bio-remediation with pump-and-treat techniques.

11. Genetically-engineered microbes: Attempts have been made to genetically engineer microbes so that they degrade contaminants more efficiently and quickly. Microbes have been patented for this purpose (�superbug� to degrade oil spills). There is concern that these �unnatural� microbes may become pests in the environment.

12. Summary: Remediation of water (or return to �natural� conditions by removal of contaminants) may use physical, chemical, or biological techniques. Remediation techniques include pure-compound recovery, air stripping, pump-and-treat techniques, bioremediation, and combinations of these.