ProAct has over 20 years’ experience remediating soils contaminated with volatile organic compounds (VOCs) and semi- volatile organic compounds (SVOCs), using air sparging (AS) and vapor extraction. Both technologies reduce the concentrations of VOCs and SVOCs that are adsorbed to soils and dissolved in groundwater. The processes are usually used in tandem.
An AS blower or compressor discharges compressed air into an air sparge manifold which distributes the compressed air outside the trailer. The contaminant-free air is then injected into the subsurface through well points. The fresh air forms bubbles that help VOCs and SVOCs which are dissolved in the soil water undergo a phase transfer. The dissolved gases come out of solution as a vapor. The bubbles carry the VOC and SVOC vapors up through the soil.
Contaminants with higher vapor pressure, such as benzene, ethylbenzene, toluene, and xylene are easier to transfer into a vapor. That is why AS works best on these types of contaminants. Likewise, SVE does not remove heavy oils. However, since AS and sol vapor extraction (SVE) increase the oxygen in the soil, they may give moil microbes a boost in the biodegradation of low-volatility organic compounds.
The SVE vacuum pulls vapor (“wet gases”) out of the soil through wells and into the treatment trailer. Well intakes transmit the vapors into a knock-out (KO) tank. The contaminated water and vapor are separated in the KO tank. They leave the KO tank and follow separate paths as they pass through the rest of the treatment system.
The contaminated vapor leaving the KO tank passes through one or more flow meters, particulate filters, and silencers. The exact component sequence may vary from one of ProAct’s treatment trailers to another. The air leaving the trailer may be vented to the atmosphere through a stack. Alternatively, the filtered air may need further treatment, such as vapor carbon adsorption, catalytic oxidation, or another process.
Project parameters such as well depth, injection pressure, vacuum pressure, and expected treatment duration depends on many factors, such as contaminant depth and concentration, soil chemical and physical characteristics, and regulatory requirements. For example, depending on soil texture, a regenerative blower, positive displacement blower, rotary claw blowers, or liquid ring pump might be used.
Extraction wells are usually 5 feet or deeper. Sometimes the contaminated air surface is covered with an impermeable barrier to prevent pulling atmospheric vapors into the system and to prevent soil vapors from escaping directly to the air.
Not only do AS and SVE treat soil contamination, it can prevent the spread of VOCs and SVOCs. AS and SVE systems create a negative pressure in the unsaturated zone. This helps reduce vapor plume migration.
ProAct builds soil vapor extraction systems (SVE) and can bring them to your site on short notice either for rent, or for operation by our experienced field staff. ProAct is standing by to meet your project needs. Contact us today and let's get started!