Remedies timing

It is obvious from the above calculations that realistic remediation times can be obtained using either pure oxygen or H202. The final selection will be based on the overall environmental and... 

The major disadvantage to recovery of LNAPL by vapor extraction is the large quantity of energy required to maintain rapid volatilization of the product and airflow to transport the diluted vapors to the surface. The remediation time for this type of system tends to be quite long, often in terms of years. 

Treatment systems should be demonstrated to be effective, and expandable (or reducible), in a stepwise modular fashion to ensure efficient design and operation. At many sites, it is cost-effective to install several temporary treatment systems in parallel configuration, and remove them as the need is diminished until the stable rate is achieved where a single unit can handle the load. After careful analysis, it may be determined that the best procedure is to install and operate the system at the projected long-term rate from the onset. Although this plan may extend the longterm remediation time, cost savings on equipment purchase (or lease) or initial operation labor may be justified. 

For the site of the trickling pond, a site-specific strategy for the remediation was established. Flighly contaminated hot spots were excavated to protect the groundwater. The applied biological treatment technology was tested in pilot scale on site. A feasibility study was done for the estimation of remediation time and TNT reduction which can be achieved by biological transformation. 

Can enhance bioremediation, thereby decreasing the remediation time. 

Significantly increases reaction rates and decreases remediation time. 

Mercury (Hg) It was shown by Thoming, Kliem, and Ottosen (2000) that the acidic front resulted in an increased oxidation rate of elemental Hg, but the oxidation process was slow and no Hg was removed from the soil in total. Nickel (Ni) General low removal efficiency without any enhancement even for 2 months processing. Only Clarke, Lageman, and Smedley (1997) showed that a high removal efficiency could be achieved but remediation time and conditions were not mentioned, so it could not be evaluated if the remediation was enhanced or not. 

Lead (Pb) Some really low remediation percentages (0%-10%) were obtained in studies of calcareous soil (Maini et al, 2000) and tailing soil (Kim and Kim, 2001), whereas around 50% removal was obtained in studies of different sludges (Khan and Alam, 1994 Kim et al, 2005). Highly successful removals (92%-98%) were obtained in full scale, as well as in a study of noncalcareous soil (Clarke et al, 1996 Ottosen et al, 2005). Apart from confirming the fact that acidification, and thus buffer capacity, is a determinant of remediation success, it is difficult to deduct any conclusions from the results since Clarke et al (1996) give no detailed information about remediation conditions. However, it seems that long remediation times are necessary for successful removal (Ottosen et al, 2005). 

Another group of enhancement methods aims at shortening the transport distance for the heavy metals, and thereby shortening the treatment time. The transport rate for heavy metals in soil in an applied electric field is most often significantly less than 1 cm/day (Ottosen et al., 2008), which means that in order to avoid a long remediation time, the electrodes should be placed relatively close or concentration compartments could be placed between the electrodes where the heavy metals are trapped, as suggested by Ottosen et al. (1999). Another tested solution to overcome long treatment time is to treat the soil as a suspension (Jensen, Ottosen, and Ferreira, 2007). 

Lead (Pb) Most effort has been given to enhance remediation of Pb from recalcitrant calcareous soils. The results listed in Table 4.2 suggest that EDTA, acetic acid, and treatment of soil fines in suspension successfully reduce remediation times, while treatment with ammonium citrate at pH 10 was less successful. 

Figure 14.6. The removal of heavy metals from the three sediments at 70 mA and L/S 8, with a remediation time of 14 days and air-dried sediment (Nystroem, Ottosen, and Villumsen, 2005).

Remediation time is dependent on the nature, concentration, and extent of the pollution and the capacity of the remediation equipment. More extensive polluted sites are cleaned up in sections. Cleanup duration varies from a few months to several years. 

Standard Test In the standard test, all soil material is treated in one laboratory setup. This setup is used when the client has supplied ample data on the origin of the sample and its contaminants. This kind of test gives accurate data on energy requirements and remediation time. The most reliable results are obtained when the two tests are combined a turbo test followed by a standard test run using the electrolyte solutions that came out best during the turbo test. 

Stadskanaal agrillaceous sand (also Pb, Zn, CN) to reduce Cd to <10ppm. Total remediation time 2 years (1990-1992)... 

Hausman, S. S., and H. S. Rifai, Modehng remediation time using natural attenuation at a dry-cleaner site, Remediation, 5-31, 2005. 

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