Polluted groundwater is one the most prevalent environmental liabilities rendering water and even soil located on-site unfit for use. Many contaminants gradually rise up through the soil from highly concentrated areas deep in the ground to areas of much lower or zero concentration closer to surface. This upward diffusion is particularly harmful when it manages to contaminate buildings on the surface. Another harmful and costly danger is the tendency of contaminant to migrate off-site where they contaminate neighboring properties and groundwater.

Industry’s conventional approach to contaminated groundwater remediation has been to pump the contaminated water located deep below the surfaces to above ground treatment facilities. This procedure, referred to as “pump and treat,” requires years, and sometimes even decades or centuries depending on the level of contamination and the volume of contaminated groundwater.

Sorption, the tendency of contaminants to stick to particles in the soil, retards the remediation process. Pumps do not extricate contaminants that have stuck to or “sorbed” to the soil. The pumps are only able to remove contaminants that the groundwater has dissolved. Once treated in above ground facility, the clean groundwater returns to the soil and dissolves some of the sorbed contaminants, but not all of them. The pump then brings the re-contaminated water to the surface, treats it, and sends it back to dissolve more contaminants. The cycle then repeats itself. For this reason, the pump and treat process is long, expensive, and inefficient.

In recent years, the groundwater remediation industry has begun to employ ozone as an oxidizing agent with substantial success. Instead of pumping the contaminants to the above ground treatment facility, pumps send the ozone to the contaminated groundwater and sub-surface soil, where it oxidizes organics by direct oxidation or the generation of free radicals. Sending the ozone to the contaminated soil allows for the oxidation of dissolved contaminants as well as those contaminants that have sorbed to the soil, and is, hence, much more effective and fast. The oxidation of organic contaminants yields carbon dioxide and water, or other less toxic organics, which are later oxidized again, yielding carbon dioxide and water. Other advantages include:

• Ozone’s ability to move through soil.
• Ozone will not discriminate between sorbed and dissolved contaminants – it oxidizes them both.
• Ozone is over ten times more soluble in water than oxygen.
• Oxygenation of the soil
• Ozone is generated on site.

Ozone has successfully treated the following common groundwater contaminants:

• MTBE
• BTEX
• Aliphatic Hydrocarbons
• Diesel Fuels
• Chlorinated Solvents
• Pesticides
• VOC’s
• And many more
  

Useful Links

In Situ Chemical Oxidation: An Innovative Groundwater Remediation Technology

National Small Flows Clearinghouse: Ozone Fact Sheet (PDF)