Pump and treat

Air. Biofilters are an effective way of dealing with air from industrial processes that use halogenated solvents such chloromethane, dichioromethane, chloroethane, 1,2-dichloroethane and vinyl chloride, that support aerobic growth (26). Both compost-based dry systems and trickling filter wet systems are in use. Similar filters could be incorporated into pump-and-treat operations. 

Methane has also been used in aerobic bioreactors that are part of a pump-and-treat operation, and toluene and phenol have also been used as co-substrates at the pilot scale (29). Anaerobic reactors have also been developed for treating trichloroethylene. Eor example, Wu and co-workers (30) have developed a successful upflow anaerobic methanogenic bioreactor that converts trichloroethylene and several other halogenated compounds to ethylene. 

Pentachlorophenol is readily degraded in biofHm reactors (53), so bioremediation is a promising option for the treatment of contaminated groundwater brought to the surface as part of a pump-and-treat operation. 

If more active treatment is required, such as pump-and-treat, it is possible that biological reactors will be a cost-effective replacement for activated carbon filters (63). 

Bioremediation. Bioremediation has great appeal. It is a natural process that degrades hazardous organic chemicals into innocuous carbon dioxide and water or nonhazardous byproducts and it is often less expensive and more effective than pump and treat methods. Articles on bioremediation appear regularly in environmental journals and the U.S. EPA has its own regular series of reports on current activities called "Bioremediation in the Pield."... 

Nevertheless, an anaerobic system may be the method of choice under certain conditions (/) contamination with compounds that degrade only or better under anaerobic conditions, (2) low yield aquifers that make pump and treat methods or oxygen and nutrient distribution impractical, (J) mixed waste contamination where oxidizable compounds drive reductive dehalogenation of chlorinated compounds, or (4) deep aquifers that make oxygen and nutrient distribution mote difficult and cosdy. 

In Situ Air Stripping. An innovation to conventional pump and treat air stripping is in situ air stripping. Two horizontal wells are installed, one below the water table and one in the vadose zone. Air is injected in the lower well while contaminated soil vapor is extracted by vacuum through the upper well. 

In the early years of ground water and soil remediation, pump and treat was the conventional technology. Contaminated ground water is pumped to the surface where it is treated and reinjected or discharged to surface waters or wastewater treatment plants. Reinjection maybe used to stimulate in situ... 

Pump and treat technology is inherently slow because it depends on ground water for transport of the contaminant to the extraction well. This characteristic is particularly troublesome when the contaminant is only slightly water soluble, adheres to the soil, or collects ia pools within the aquifer. 

There are many cases of contamination by dense nonaqueous phase Hquids (DNAPLs) that have fmstrated pump and treat efforts. The general consensus is that pump and treat can reduce contamination or keep it from spreading, but it has failed ia many cases to remediate aquifers to stringent cleanup goals. 

Delineation/Verification of Gross Contamination Sampling and Analysis Interceptor Trench/Sump/Subsurface Drain Pump and Treat In-situ Treatment Temporary Cap/Cover... 

The most commonly used remediation technique for the recovery of organic contaminants from ground water has been pump- and-treat, which recovers contaminants dissolved in the aqueous phase. In this regard, the application of carbon adsorption has found extensive, but not exclusive use. Vacuum extraction (also called soil venting) has also become popular for removal of volatile organic contaminants from the unsaturated zone in the gaseous phase. Both of these techniques can, in the initial remediation phase, rapidly recover contaminants at concentrations approximately equal to the solubility limit (pump-and-treat), or the maximum gas phase concentration of the contaminant (vacuum extraction). The... 

Following the implementation of the remedy, the state or the potentially responsible party (PRP) assumes responsibility for the operation and maintenance (O M) of the site, which may include activities such as groundwater pump and treat, and cap maintenance. Once U.S. EPA has determined that all appropriate response actions have been taken and cleanup goals have been achieved, the site is deleted from the NPL through a formal rulemaking process. 

Gatliff, E.G., Vegetative remediation processes offers advantages over traditional pump-and-treat technologies, Remediation, 4, 343-352, 1994. 

In situ groundwater treatment is an alternative to the conventional pump-and-treat methods. In situ treatment uses biological or chemical agents or physical manipulations that degrade, remove, or immobilize contaminants. In situ treatment technologies can usually treat both contaminated groundwater and soil. In many instances a combination of in situ and aboveground treatment will achieve the most cost-effective treatment at an uncontrolled waste site. 

The pump-and-treat methodology is effective for groundwater remediation. It is also an effective way to prevent the further extension of a contaminated area. The cleanup involves two steps ... 

The pump-and-treat method is comparable to soil flushing. In fact, the pump-and-treat method can treat both groundwater and aquifer soil at the same time, and can also be directly applied to unsaturated soil zones. The soil flushing method is mainly considered as a treatment in unsaturated zones. 

Blast-enhanced fracturing uses explosives, such as dynamite, to fracture rock. The explosives are placed in holes and detonated. The main purpose is to create more pathways for polluted groundwater to reach wells drilled for pump-and-treat cleanup. 

Alternative 4 In Situ SVE/Soil Fixation, Cap, and Groundwater Pump-and-Treat... 

For the site remediation case shown in Figure 16.21, this alternative consists of in situ SVE of TCE-contaminated soil (Area 2), in situ soil fixation of lead-contaminated soil (Area 1), cap (Area 1), and the groundwater pump-and-treat components of Alternative 3. 

This alternative includes components of Alternatives 3 and 4 and introduces a thermal destruction component to address the TCE-contaminated soil. For the site remediation case shown in Figure 16.21, the lead-contaminated soil in Area 1 would be fixed and covered with a soil/clay cap, as described in Alternative 4. The groundwater would be addressed through pumping and treating, via an air stripper, as described in Alternatives 3 and 4. The TCE-contaminated soil in Area 2 would be excavated and treated on site by a thermal destruction unit comprisng a mobilized rotary kiln. 

Reduces risk to less than 1 X 10-6 by pump-and-treat... 

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