Site cleanup technologies reduce the contaminant levels or the levels of risks on used sites to levels pre-specified, by regional standards or site specific studies, as protective of humans and ecology. Below is a list and brief descriptions of some remediation technologies. Additional technologies and details will be added:

Excavation and Disposal ("Dig and Dump")

Earlier practices of excavation and disposal involved digging out contaminated soil from the location of contamination and dumping it off in a landfill or other locations (e.g. a depression) where the contaminated soil is not considered a hazard to human and ecological health. No treatment might have been carried out on the contaminated soil prior to dumping at the target site; hence the approach is nick-named "Dig and Dump". Regulatory restrictions on land disposals have brought some changes to this practice. In North America and most countries in Europe, it is now illegal to co-dispose hazardous and non-hazardous wastes in landfills. There are only designated or licenced landfill sites that accept PHC contaminated soils. Furthermore, disposal in landfill sites without pre-treatment is now outlawed in several jurisdictions. Wastes for disposal in landfills should be characterized and the parameters must meet certain pre-specified waste acceptance criteria. Dig and Dump approach is very simple to implement. However, it's main disadvantages are cost of transporting the contaminated soil to its final destination and the contamination (if soil is dumped untreated) of the final destination (in case of future re-use).

Soil Vapour Extraction (SVE)

Soil Vapour Extraction (SVE) is an in-situ remediation approach used for reducing the concentration of contaminants, particularly the volatile Organic Compound (VOC) and the semi volatile organic compound (SVOC) constituents of petroleum hydrocarbons to levels pre-specified as safe for human health and the environment. The VOC and the SVOC constituents usually resulting from lighter petroleum products such as, gasoline are removed mainly through vapourization. Extraction wells are constructed all over the contaminated site following a design considered effective to produce desired reduction of the contaminants. A vacuum is applied, by blowers, through the wells, creating a negative pressure that pulls the vapours from the contaminant out of the ground through the wells. The extracted vapours are then treated and discharged to the atmosphere or re-injected into the subsurface if permitted. This approach is effective for use in the upper soil layer or the unsaturated/vadoze soil zone.

Bioventing

Bioventing (BV) is an in-situ remediation technology that removes PHC constituents through biodegradation of the constituents by microorganisms. Similar to SVE, BV involves the use of extraction wells or injection wells to introduce air into the subsurface aiding the mirobial activities responsible for the breakdown of the PHC constituents. Though some volatilization occur in BV, the predominant process for contaminant reduction is biodegradation. To minimize volatilization, extraction or injection wells are operated at lower air flow rates. Some nutrients can be added to aid the microbial activities and accelerate biodegradation. BV, similar to SVE, is also applicable for soils within the topmost soil layer or the unsaturated/vadoze zone of the soil. BV has been used successfully to reduce concentrations of mid-range PHC constituents from petroleum products such as diesel and jet fuels.

Air Sparging (AS)

Air Sparging (AS) is an in situ remedial method that is used to reduce lighter molecule PHC constituents such as benzene, ethylbenzene, toluene, and xylene (BTEX), from petroleum products like gasoline from the saturated soil zone. Both the PHC constituents adsorbed to the soil and in the groundwater turns to vapours and are removed during AS. Main clean up process is volatilization using extraction wells. AS is often combined with SVE for effectiveness.

Bio-Sparging (BS)

BS is similar to bioventing. It is used to reduce middle range PHC constituents from the saturated zone through biodegradation. volatilization is minimized by ensuring lower rate of air flows. Nutrients may be added to speed up biodegradation.

SVE/AS and BV/BS combinations are commonly adopted for effective clean up. AS and BS can also be used to remove heavy PHC molecules from petroleum products such as lubricating oils.

Land Farming (or Land Treatment)

Land Farming (LF) is a remediation strategy that reduces PHC constituents in soils by biodegradation. The process is aided by aeration (tilling) and addition of nutrients and/or moisture (as required). LF can be carried out in-situ (no soil excavation required), when contamination is limited to the top 1 m. For contaminations to depth 1.5m and more, soils should be excavated and transported into Land Farm Cells or Land Treatment Units (LTU) for LF treatment, where they are spread thinly, tilled regularly to encourage microbial activities.

Biopiles

Similar to LF, Biopiles also treat contaminated soils through biodegradation using microorganisms to break down PHC constituents with or without the addition of nutrients. Contaminated soils are excavated and heaped into piles. The piles are aerated, to aid biodegradation, through a system of extraction/injection wells connected to horizontal perforated pipes running through the piles. Biopiles has proved successful in biodegrading all categories of PHC constituents (lighter to heavy molecules).

Thermal Desorption

Thermal Desorption uses HEAT to separate contaminants (e.g. PHC) from contaminated soils. Contaminated soil is excavated and transported to a Thermal Desorber where it is heated to temperatures high enough to volatize and desorb or physically separate the contaminant's constituents from the the soil. Larger particles (of diameters > 50 mm) are first screened out before introducing the soil into the desorber. The larger particles are introduced after been shredded into smaller pieces.

Partial decomposition do take place inside the desorbers, although desorbers are not made to break down contaminant's constituents. The vapour escaping from the desorbers are treated inside the Afterburner/Oxidizer. Condensers and carbon adsorption units trap organic compounds.

Treated soils are heaped into piles. Confirmatory sampling will be carried out on them to ensure that the contaminants have been reduced to the required standards. The soil can be returned to the original location they were taken from (if permitted).

Chemical Oxidation

Involves the use of chemicals for the destruction of organic contamiant constituents. The Chemical oxidants most commonly employed to date include peroxide, ozone, and permanganate.

Phytoremediation

Phytoremediation is the use of plants to remove contaminants from soil. This process can take several forms (source: Wikipedia):

• Phytoextraction - uptake and concentration of substances from the environment into the plant biomass.
• Phytostabilization - reducing the mobility of substances in the environment, for example by limiting the leaching of substances from the soil.
• Phytotransformation - chemical modification of environmental substances as a direct result of plant metabolism, often resulting in their inactivation, degradation (phytodegradation) or immobilization (phytostabilization).
• Phytostimulation - enhancement of soil microbial activity for the degradation of contaminants, typically by organisms that associate with roots. This process is also known as rhizosphere degradation.
• Phytovolatilization - removal of substances from soil or water with release into the air, sometimes as a result of phytotransformation to more volatile and / or less polluting substances.
• Rhizofiltration - filtering water through a mass of roots to remove toxic substances or excess nutrients. The pollutants remain absorbed in or adsorbed to the roots.