In-situ remediation can treat contaminated soil and groundwater without having to excavate the soil
On-site treatment eliminates off site transportation and disposal of contaminated soil and strongly reduces the CO2 footprint.
On-site treatment is more cost effective as ex-situ treatment, as the treatment itself is cheaper, no transportation is needed and now new backfill needs to be brought on site.
On-site treatment reduces financial, environmental and health & safety risks.
In-situ remediation refers to the treatment of contaminated soil or groundwater at the location where the contamination has occurred. In-situ bioremediation is a technique used to treat environmental contamination by using natural processes and microorganisms to degrade or transform pollutants directly in their source area, without the need for excavation or removal of contaminated materials.
The basic concept of in-situ bioremediation involves stimulating the growth of indigenous microorganisms or introducing specific microbial cultures that can break down or transform contaminants into less harmful substances. The microorganisms involved in bioremediation can metabolize various pollutants, such as hydrocarbons, heavy metals, and certain chemicals.
Its success depends on various factors, including the type of contaminants, site conditions, microbial activity, and the ability to maintain optimal environmental conditions (e.g. aerobic anaerobic) for microbial growth and activity.
Aerobic bioremediation is a process in which natural occurring microorganisms are used to break down and remove pollutants from contaminated soil or water under aerobic (oxygen-rich) conditions.
This process can be used to treat a variety of contaminants such as petroleum hydrocarbons, solvents, pesticides, and other organic compounds. This process is typically enhanced by adding nutrients such as nitrogen and phosphorus to the contaminated area to stimulate the growth of microorganisms by means of a groundwater circulation system or injection system.
A biosparging system is often used to supply oxygen to stimulate natural biodegradation of the contaminants.Overall, aerobic bioremediation is a promising and cost-effective technique for cleaning up contaminated sites and restoring them to a more natural state.
Anaerobic bioremediation is a type of bioremediation process that uses microorganisms that do not require oxygen to break down and remove pollutants from contaminated soil and groundwater. This process is commonly used to treat sites contaminated with chlorinated solvents, and other organic contaminants.
During anaerobic bioremediation, the microorganisms use contaminants as a source of energy and convert them into less harmful compounds such as carbon dioxide, water, and harmless gases like methane. This process can occur naturally, but it can also be stimulated by adding nutrients and an electron donor to the contaminated site to enhance the breakdown process by means of a groundwater circulation system or direct push injections.
GreenSoil utilizes an in-house electron donor known as Dehalo-GS, which has been developed by the company and proven effective in similar remediation projects. This nutrient source and electron donor is rich and already fermented, containing fewer sugars compared to sugar-rich donors like Molasses. In contrast, Dehalo-GS has the advantage of not causing a pH drop and can even slightly increase the pH, making it more conducive for anaerobic biodegradation.
An in-situ biobarrier is a bioremediation technique employed to halt the spread of contaminant plumes. This method involves creating a biologically active zone through vertical wells, which treats the contaminated plume as it passes through.The design of biobarriers is dependent on the site conditions and the type of contamination, and can incorporate an aerobic, anaerobic, or hybrid approach.
Figure 1: Aerobic biobarrier
Figure 2: Anaerobic biobarrier
Soil vapor extraction is a technique employed to withdraw vapors from the soil located above the water table by applying a vacuum force to extract the vapors. The process includes the installation of one or more extraction wells into the targeted polluted soil layer. Connected to these wells is equipment, such as a blower or vacuum pump, which generates a vacuum. This vacuum facilitates the movement of air and vapors through the soil, drawing them up the well to the ground surface for subsequent treatment. This approach is particularly effective for substances that readily evaporate, such as those commonly found in solvents and gasoline, categorized as (chlorinated) Volatile Organic Compounds or "cVOC".
Multiphase Extraction (MPE) is a comprehensive term encompassing technologies designed to extract both soil vapor and groundwater in multiple 'phases' (liquid or gaseous). It represents an advancement beyond conventional Soil Vapor Extraction (SVE) systems by simultaneously extracting groundwater and soil vapor. The technique involves lowering the groundwater table to de-water the saturated zone, enabling the application of the SVE process to the newly uncovered soil. This facilitates the stripping of volatile compounds sorbed on the previously saturated soil by the induced vapor flow, allowing for their extraction. High concentrations of (chlorinated) Volatile Organic Compounds (cVOCs) can be effectively removed with the correctly dimensioned setup.
Smart pump and treat represents a refined version of conventional groundwater extraction methods. The pollutants in the source are removed by extracting groundwater. This process incorporates the use of multiple compact filters and intermittent pumping, which means periods of standstill are introduced instead of continuous pumping. This innovative approach enhances pollutant removal efficiency, allowing for a higher purification level with the same volume of pumped water.
In the process of in-situ chemical oxidation (ISCO), a potent oxidizing agent is introduced into the soil either in solid form, diluted with water, or in conjunction with air. Upon contact with the contaminant in the soil, the polluant undergoes chemical breakdown (oxidation), transforming into harmless compounds such as water, carbon dioxide, chloride, and sulfate. The effectiveness of this technique relies on ensuring that the oxidizing agent comes into contact with the contaminant in a concentration substantial enough and for a duration sufficient to facilitate its oxidation.
Chemical reduction is commonly employed by introducing reducing agents like zero-valent iron (Feo), or other granular or powdered zero-valent metal/alloy that chemically reduce or precipitate pollutants. Alternatively, the reducing agent may be incorporated in the form of a reactive zone or wall, where pollution undergoes chemical reduction or precipitation upon passing through it. Another instance involves treating a landfill contaminated with Cr(VI) using gaseous H2S. The highly mobile and toxic Cr(VI) is reduced by the sulfide to the less mobile and less toxic Cr(III).
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