BAUER - In-Situ Remediation Technologies
In-situ techniques are used alone or in addition to pump-and-treat and soil-vapour methods in order to sustainably reduce the remediation time. With thermal techniques, such as thermo-stripping, steam injection and hot-water-flushing long lasting remediation success was achieved in several projects within a few weeks and months.
The in-situ techniques are used when:
- continued use of a property is required even during the remediation process
- due to the local conditions, excavation of the material is technically impossible or extremely difficult
- the solution presents a cost-efficient alternative to conventional methods.
BAUER Umwelt offers its clients state-of-the-art technology. We utilise catalytic oxidation units, solvent recovery plants or air-activated carbon for purification of exhaust air.
By using Chemical methods the toxic substances are destroyed or converted into harmless compounds.
In-situ chemical oxidation (ISCO)
Various oxidising agents have the ability to react with contaminants (e.g. VOC's) and destroy them. Ozone (O3), Hydrogen peroxide (H2O2), Potassium-/Sodium - Permanganate (K/Na MnO4), Persulphate (S2O8) and Calcium-/ Magnesium - Peroxide (Ca/MgO2) belong to this group. Oxidising agents are injected into the soil by an injection technique which enables a targeted and even distribution in the soil.
Use of nano-iron
Nano-iron is composed of particles of elementary iron with a diameter of approx. 70 nm. Due to its high specific surface (30 m²/g), nano-iron reacts very quickly and effectively with VOC's.
Biological methods are based on the ability of microorganisms to convert contaminants into harmless substances like CO2 and Water. In addition to direct biological degradation, there are co-metabolisms, where the toxic substances can be removed using other metabolic pathways. Biological methods are characterised by a particularly high environmental compatibility and cost effectiveness. On the other hand, they are relatively slow.
Characteristics of aerobic methods are that the biological activity is dependent on the presence of oxygen, i.e., sufficient oxygen supply is necessary for the process. Groups of toxic substances which degrade well under aerobic conditions are: TPH's, aromatic hydrocarbons/PAH, phenols and certain VOCs (Cis-DCE, VC).
Anaerobic biological processes take place in the absence of oxygen. Anaerobic conditions are created by adding carbon sources such as molasses, lactate and ethanol. Anaerobic methods are primarily used for degradation of CVOC's.
This method is a variation of the soil vapour extraction method. The soil is heated with special probes first, this increases the volatility of the substances and a higher removal efficiency is achieved in a shorter space of time. Steam-air injection is a variation of this method.
Immobilisation Methods do not eliminate the toxic substances , the substances e fixed in the soil matrix instead. The soil is converted into a rock-like body and the substances lose their mobility and thus pose no threat to the groundwater anymore.
Mechanical mixing techniques
Most of the soil mixing techniques are on-site techniques whose goal is conditioning. For the in-situ treatment, BAUER Umwelt has developed several techniques for sludge and soil, in which additives are mixed to the soil matrix with an auger mixing tool, resulting in the toxic substances being completely immobilised with additives/fines.
The term “mixed-in-place” describes the process of mixing soil with binding agents in-situ with a triple auger system rotating in opposite directions. By this process, patented by Bauer Spezialtiefbau, the existing pores in the soil structure are filled, resulting in a solidified soil due to the geometry of the triple auger.
The Cutter Soil Mixing (CSM method) consists of an in-situ mixing self-curing suspension with natural soil by a modified milling technique.
Use of injection techniques
Various injection methods used in specialist foundation e can present the only possibility to secure a site like, e.g. Hot Spots underneath buildings. Low and high pressure injection can be used in aeras with low ceiling height. While low-pressure methods use 1-20 bar pressure, high pressure injections use approximately 500 bar.