Air Sparging (AS) and Soil Vapor Extraction (SVE) have been used for remediation of petroleum compounds for decades. It can be an effective remediation method if installed with adequate infrastructure and equipment in the right geology. The AS volatilizes dissolved phase contaminants that are captured by the SVE. When the dissolved phase concentrations decrease, more soil-bound contaminants partition to the water. This process is happening continuously or intermittently depending upon operation.
Many times, though, these systems operate for longer than expected, especially when attempting to achieve very low cleanup limits. An AS/SVE system is most effective at removing high concentration volatile contaminants, while it has difficulty removing low concentration and less volatile contaminants. Rebound following system shutdown is also very common causing the system to be restarted.
To overcome these shortcomings, soluble bioremediation products can be utilized to increase the efficiency of AS/SVE systems. A well designed and operating AS/SVE system will be adding an inexhaustible oxygen supply that can overcome the biggest shortcoming associated with bioremediation of petroleum, a limited supply of electron acceptors. With the AS/AVE system supplying more oxygen than the microbial community can use and the bioremediation products supplying nutrients and everything else the bacteria need, it is a fantastic combination treatment.
With the AS/SVE physically removing dissolved-phase contaminants and soil-bound bacteria working on desorbing and consuming soil-bound contaminants, remediation of the total contaminant mass is occurring. This solves the two problems with AS/SVE, achieving low cleanup goals and eliminating rebound of contaminants.
Why is bioremediation not used more in combination with AS/SVE? Convincing a site owner to use two different treatments is harder than talking them into one. Also, the lack of bioremediation products that pair well, meaning fully soluble and nutrient-rich, can also be a contributor. Whether starting a remediation project with the plan of using AS/SVE with bioremediation or attempting to reach closure by breathing life into an old operating system, ETEC has a lot of experience and the right products to make the combined treatment successful.