Remediation Methods for Contaminated Sites

Risk assessment procedures undertaken on any contaminated site will establish a range of contaminants (hazards), pathways and receptors, will identify possible linkages of concern and will determine a set of remediation objectives. Any remediation subsequently proposed for the site must then be capable of fulfilling these objectives. In general terms the primary aims of any remediation is to break the linkage between contaminant source and the receptor to achieve a reduction of actual or potential risk so that unacceptable risks are reduced to acceptable levels. 

The need for, and extent of, any remediation will depend on the magnitude of the risk, which itself is a measure of the probability of an unwanted effect coming about and the consequence of it. A high probability risk with a severe consequence will raise considerably more concern than a low probability risk with a minor consequence. 

Remediation Methods for Contaminated Sites, in Contaminated Land and its Reclamation, eds. R. E. Hester and R. M. Harrison, Issues in Environmental Science and Technology No. 7, Royal Society of Chemistry, Cambridge, UK, 1997, pp. 47-71. 

Issues in Environmental Science and Technology No. 16 Assessment and Reclamation of Contaminated Land The Royal Society of Chemistry, 2001 

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Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

Whereas there are numerous remediation technologies available,1,4 6 the selected remediation method for any particular site would be dependent on site specific requirements. Any contamination can impact ... 

Phytoextraction has the potential to remediate many metal and radionuclide contaminated sites using a less invasive form of treatment than traditional methods such as escavation and disposal. There are four factors that influence or determine the ability of phytoextraction to effectively remediate a metal contaminated site 1). Site arability and plant biomass yields 2) metal solubility and availability for uptake 3) the ability of the plant to accumulate metals in the harvestable plant tissues and 4) regulatory criteria. 

With the recent Increase In activity at hazardous waste sites where cleanup and remedial action are underway, there has emerged a need for rapid analytical methods for assessing contamination in water, sediment, and soil. Of special Interest, because of widespread use and disposal. Is the group of materials known as PCB s (polychlorinated biphenyls). 

Limitations need to be carefully considered before selecting this method for site remediation. These include the depth of contamination, the total length of time required for cleanup to below accepted limits, potential contamination of vegetation and the food chain, and difficulty in establishing and maintaining vegetation at some polluted sites.8... 

Currently, many regulatory agencies recommend the common methods (EPA 418.1, EPA 801.5 Modified) or similar methods for analysis dming remediation of contaminated sites. In reality, there is no standard for the measurement of total petroleum hydrocarbons since each method may need to be chosen or adapted on the basis of site specificity. 

Pollution of soils and waters by human activities is an important and widespread problem. This pollution by, organic and inorganic substances can affect individual organisms, human populations, and ecosystems, each in its own unique way. In particular former military installations, often used for weapons production and nuclear power plants represent a ongoing and substantial threat to environment and human health because of the specific pollutants that can be released Solvents, explosives, fuels, radionuclides, heavy metals, and metalloids all have been identified in the environment around these installations. Remediation technologies for these contaminated sites have been developed based on conventional systems utilising physical and chemical treatments, such as excavation and incineration, pump-and-treat methods, ultraviolet oxidation, soil washing, etc. 

Environmental Remediation Consultants, Inc. (ERC) offers the BIO-INTEGRATION method for in sitn and ex situ destruction of organic compounds in soil, sediment, sludge, groundwater, snrface water, and wastewater. The BIO-INTEGRATION approach combines biotic and abiotic treatment methods to remediate subsurface contamination. On-site bioreactors are used to grow substrate- and contaminant-specific microbes. The microbes are combined with abiotic amendments and injected into the subsurface. 

Based on a cost analysis performed at the U.S. Department of Energy s Hanford site, in Richland, Washington, PSVE was found to be a cost-effective method for remediation of soils containing lower concentrations of volatile contaminants. PSVE used on wells that average 10 standard cubic feet per minute (scfm) airflow rates was found to be more cost-effective than active soil vapor extraction for concentrations below 500 parts per million (ppm) by volume of carbon tetrachloride. For wells that average 5 scfm, PSVE is more cost effective below 100 ppm (D14489S, p. iii). For further details of this analysis, refer to Table 1. 

In addition to the exemptions established in regulations, NRC issued guidance on concentration limits for disposal of residual thorium or uranium from past operations with no restrictions on burial method (NRC, 1981). There wouldbe no restrictions on burial method if the concentrations were less than (1) 0.4 Bq g 1 for natural thorium or uranium with its decay products present and in activity equilibrium, (2) 1.3 Bq g 1 for depleted uranium, and (3) 1 Bq g 1 for enriched uranium. These concentration limits were intended to provide criteria for remediation of contaminated sites to permit unrestricted use by the public, but they could be applied to waste disposal as well. 

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