The aim of environmental remediation is to remove contaminants from the soil, groundwater, surface water and sediments.
From a regulatory perspective, the concept of ‘remediation of contaminated sites’ was introduced by Legislative Decree No. 22 of 5 February 1997 and by Decree No. 471 of 1999.
Today, environmental remediation is governed entirely by the Consolidated Environmental Act (namely Legislative Decree No. 152/2006) in Title V of Part IV, which implements European Directive 2004/35/EC (Prevention and Remediation of Environmental Damage).
The regulation sets out in great detail all the procedures, criteria and methods of action required to reduce or completely eliminate pollutants or sources of pollution.
To protect the environment, BEA has developed a range of products based on mixtures of enzymes, naturally derived polymers and selected microorganisms.
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What are the main techniques for remediating land contaminated with hydrocarbons?
The aim of contaminated land remediation works is to reduce the levels of pollutants present to below the limit values set by the Risk Threshold Concentrations (RTC) and Contamination Threshold Concentrations (CTC).
Remediation techniques are classified as chemical-physical and biological; in both cases, a distinction is made between in situ and ex situ methods.
The following are included amongst in-situ biological remediation measures:
- Biosparging and bioventing, used when the contaminants to be removed are not particularly biodegradable;
- Bioventing: the subsoil is remediated of contaminants by means of air, which acts as a ‘carrier’ of oxygen for the microorganisms.
The following fall within the scope of ex situ biological remediation measures:
- Biobattery: this technique is used for the biodegradation of both volatile and non-volatile hydrocarbons, as well as polycyclic aromatic hydrocarbons;
- Bioremediation: this is the best solution when, in addition to removing the contaminant, there is a need to introduce bacterial flora, reducing agents and oxidising agents into the subsoil.
The following fall within the scope of in-situ chemical and physical remediation measures:
- Chemical Oxidation: chemical oxidants such as potassium permanganate or hydrogen peroxide are injected into the soil;
- Air sparging: contaminants are ‘stripped’ from the soil being remediated using pressurised air;
- Soil Vapour Extraction: this process is carried out when volatile organic compounds are extracted in vapour form and treated on the surface;
- Pump and Treat: this technique is used when the operation involves the remediation of contaminated groundwater. Specifically, the water is pumped to the surface and treated to remove LNAPLs (mineral oils, benzene, alkanes, kerosene, diesel and BITEX), miscible contaminants and DNAPLs (chlorinated solvents, halogenated hydrocarbons).
The following fall within the scope of ex situ chemical and physical remediation measures:
- Vitrification;
- Thermal destruction;
- Thermal desorption;
- Soilwashing: ideal for use on soils with a medium grain size;
- Inertisation: a technique suitable for treating soil and sludge containing PCBs and heavy metals;
- Soil extraction: a technique used to remediate soil contaminated with volatile organic compounds.
A brief overview of the biobattery for the remediation of soil contaminated with hydrocarbons
The remediation of land contaminated with hydrocarbons using the bio-pile technique involves the restoration of the subsoil by utilising the microorganisms present and their ability to degrade certain types of contaminants when specific environmental conditions are met.
One example is the remediation of land contaminated with oil.
As required by the biological windrow technique, a separate piping system is used to introduce air, nutrients (namely phosphates and nitrates) and water.
This allows the bacterial flora necessary to initiate the aerobic – that is, oxygen-dependent – degradation of the pollutants to develop.
When the pollutants to be removed are of a petroleum nature, we have:
- the removal of lighter compounds through volatilisation during soil aeration;
- the removal of the heaviest compounds through biodegradation.
