Pump-and-treat method

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 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 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. 

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. 

According to the vendor, the two-zone plume interception treatment technology is more cost effective than the pump-and-treat method because the contaminants are destroyed on-site and the costs associated with removal, transport, recovery, or incineration are avoided (D10002D, p. 2). 

UVB is a full-scale, commercially available technology that provides an alternative to pump-and-treat methods. The vendor states that the technology has been applied at over 143 sites in Europe and 42 sites in the United States. 

Normalized costs include capital and operation and maintenance over a 2-year period for NoVOCs, air sparging, and biodegradation, and a 5-year period for pump-and-treat methods. 

Increased short-term capital costs for constrnction and installation when compared with pump-and-treat methods. 

Table 1 presents a cost comparison between phytodegradation and pump-and-treat methods. Tables 2, 3, and 4 compare cost estimates for phytoremediation with estimates for other treatment technologies. Because these values are often based on bench- or pilot-scale data, the information should be viewed with caution. 

TABLE 1 Cost Comparison between Phytodegradation Using Hybrid Poplar Trees and a Conventional Pump-and-Treat Method (3 Wells and Reverse Osmosis System)... 

Cost effective compared to current remediation technologies such as steam injection, bioventing, soil vapor extraction (SVE), and pump-and-treat methods. 

The process offers potential advantages over conventional pump-and-treat methods ... 

Advantages over conventional pump-and-treat methods include reduced volumes of contaminated fluid to be treated, shorter times for remediation, applicability to contaminants above and below the water table, and potential for reuse of recovered contaminants. 

According to the vendor. Microbial Fence has been used to treat groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs) benzene, toluene, ethylbenzene, and xylenes (BTEX) and volatile organic hydrocarbons (VOCs) at petroleum, chemical, and wood treating facilities and manufactured gas plants. Microbial Fence was used alone or in conjunction with soil venting/bioventing, aquifer aeration, pump-and-treat methods, and/or recovery of non-aqueous-phase liquids (NAPLs). 

Contamination in low-permeability soil is a problem of major importance in environmental remediation. Traditional treatments of contaminated soils include bioremediation methods, vapor extraction, and what are known as pump-and-treat methods. However, poor accessibility to the contaminants and difficulties in delivering reagents used for treatment make these current in situ methods very ineffective. Electroosmosis (combined possibly with one or more of the traditional techniques) can potentially serve as an alternative in situ treatment process, as shown in Figure 12.14. 

Extraction. In this process, sometimes referred to as the pump and treat method, polluted water is pumped to the surface, after which it is heated to remove toxic materials. Then the heated water is returned to the aquifer. Depending upon the extent of pollution, a large watertreating facility may he required adjacent the cleanup site, even though the facility may be required only for a comparatively short time of a few to several months. 

Bioreactor systems, used in pump and treat methods, can experience limitations in oxygen transfer which can slow the rate of degradation of pollutants. Hydrogen peroxide or sodium percarbonate can be applied as a supplemental oxygen source for bioreactor systems, improving the bioreactor efficiency when dealing with situations of limited oxygen supply. 

More generally for Cr -contaminated groundwater, which may also arise from other industrial activities such as tanning and electroplating, both in situ and pump and treat methods could employ biological as... 

The hydrauhc conductivity of soils varies over several orders of magnitude ranging from 1 x 10 m/s for coarse sand to 1 x 10 m/s for fine-grained dense clays. In fine-grained soils, very high hydraulic gradients need to be generated to cause even a small flux. Therefore, the pump and treat method of cleanup or bioremediation is not effective in clayey soils. 

Figure 26.5. Electrode arrangement for the pump and treat method (Narasimhan and Sri Ranjan, 1999).

The model was then used to simulate two field application scenarios, that is, soil vapor extraction and the pump and treat method. The model predictions seem to be reasonable based on what is expected under the conditions applied in the field. 

The EPA has long ago concluded that the enviromnental pump-and-treat remediation technology that has been used for removing NAPL hydrocarbon contaminants from aquifers is not working [2]. Indeed, field demonstrations of soil flushing have illustrated potential problems [13], and aquifers contaminated with DNAPLs were shown to be extremely difficult to remediate with the standard pump-and-treat methods. 

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