Bioremediation of Contaminated SoilsAn Evaluation of In Situ and Ex Situ TechniquesEx Situ Remediation TechniquesThermal TechniquesPhysical/Chemical TechniquesBioremediation Techniques¾Landfarming¾Biopiling¾BioreactorsThermal Ex Situ Remediation¾ Best to remove: petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), benzene, toluene, ethylbenzene, xylenes (BTEX),phenolic compounds, cyanides, and chlorinated compounds like polychlorinated biphenyls (PCB), pentchlorphenol (PCP), chlorinated hydrocarbons, chlorinated pesticides, polychlorinated dibenzodioxins(PCDD), and polychlorinated dibenzofurans (PCDF).Physical/Chemical Ex Situ Remediation¾ Wash water and vapors from this treatment must also be properly disposed of which adds to the costs. ¾ This method is most effective at removing BTEX, TPH, PAH, PCB, heavy metals, and dioxins.Ex Situ BioremediationLandfarming¾Most effective at removing PAH and PCPEx Situ BioremediationBiopiling¾Biopiling is most effective in treating pollutants such as BTEX, phenols, PAHs with up to 4 aromatic rings, and explosives such as TNT and RDX.Ex Situ BioremediationBioreactors¾Bioreactors are most successful at removing PAHs and PCBs.In Situ Remediation TechniquesThermal TechniquesChemical/Physical Techniques¾Pump and Treat¾Soil Vapor ExtractionBioremediation Techniques¾Bioventing¾Biosparging¾Bioslurping¾Phytoremediation¾Passive TreatmentsThermal In Situ Remediation¾ Only effective at removing pollutants that can be removed at low temperatures such as BTEX¾ Soil must be homogenous, permeable, and have a low organic contentChemical/Physical In Situ RemediationPump and Treat Technique¾ Most effective at removing PAHs and TCEs¾ Limited by soil permeabilityChemical/Physical In Situ RemediationSoil Vapor Extraction¾A high percentage of fine soil or a high degree of saturation can also hinder the effectiveness of soil vapor extraction.¾ This technique rarely achieves complete contaminant removal, but is very useful when combined with other techniques.In Situ BioremediationBioventing¾ The only technique that works in unsaturated soils¾ Effective in removing petroleum hydrocarbons, aromatic hydrocarbons, and non-volatile hydraulic oils.In Situ BioremediationBiosparging¾Sparge points must be installed below the contaminated zone.¾The contaminated layer must be homogenous.¾Pilot studies must be completed to determine optimum pH, moisture content, temperature, nutrient content, and carbon sources.In Situ BioremediationBioslurping¾ Bioslurping is a unique in situ treatment technique in that it also treats free product phases floating on top of the groundwater. This technique applies a vacuum to extract soil vapor, water, and free product from the subsurface. Each of those substances is then separated and properly disposed of.In Situ BioremediationPhytoremediation¾ Successfully removes TPH, BTEX, PAH, 2,4,6-trinitrotoluene (TNT), and hexahyro-1,3,5-trinitro-1,3,5 triazine (RDX).¾ Limited by the depth the plants roots can reach.In Situ BioremediationPassive Techniques:¾Activated Zones¾Bioscreens¾Reactive Walls¾Reactive Trenches These techniques can be used when removing contaminants from non-homogenous soils. These techniques are attractive because they have high longevity, no significant maintenance, and no nutrient replenishment.Summary of Removable Compounds and Soil ConstraintsSummary of Remediation Costs¾Must determine what is more important, costs or cleanup efficiency. ¾Each site is different. Pilot studies and/or lab studies must be done for each one.¾More research is need in the area bioremediation, but funding is a major