Pressurized air is injected into the soil through filters that are installed below the groundwater table. Volatile compounds are ‘stripped’ and the air bubbles transport the compounds into the unsaturated zone: In Situ Air Sparging. Because the aerobic degradation is also stimulated, degradable contaminants can be exposed to a low air supply causing an increase of the oxygen concentration in groundwater (biosparging).
Air Injection is, as Air Sparging / Stripping applied for volatile compounds such as oil compounds with a chain length shorter than C12, aromatics and chloroethene or, by means of biosparging, aerobically degradable organic compounds. Air injection is applicable in both saturated and unsaturated zone. The permeability of the soil (above 0.5 m / day), soil structure (small range in heterogeneous soils), soil matrix (e.g. because of iron oxidation with clogs filters) and the organic matter content (slow desorption, oxidation of peat) are of great importance. The technique is applicable for both the source and the plume. Air injection is often combined with groundwater and soil vapor extraction. With Air Sparging or Stripping soil vapor extraction is always necessary.
Depending on the type of contamination, size and soil properties, this method can take months to decades. The disturbance of the site is generally low. However, the extraction of air requires an air treatment installation on site.
Related cases and HIP-pilots
Related cases: Aerobic bioremediation of oil and BTEX (The Hague)***, Beek: Mineral oil Kerosine *, Bergen op Zoom (busstation): Mineral oil, BTEX en PAH’s***, Boekelo (Texoprint): CVOC ***, Kampen (IJsseldijk): Mineral oil, BTEX, naphthalene**, Leidschendam (Neherpark): CVOC and BTEX***, Lochem: mineral oil,BTEX,PAH,naphthalene,creosote ***, Nijverdal (Smidsweg 100a):BTEX, PAH’s, naphthalene and mineral oil**, Petrol station: combined techniques for BTEXN and oil (Putten)***, Putten (Garage Koster): Mineral oil, BTEX, Naphthalene***, Rotterdam Europoort: mineral oil and BTEX, Veere (Neeltje Jans): Mineral oil***