Recovery remediation well

After a recovery-remediation well has been constructed and tested for well capacity, an appropriate submersible pump may be installed. Materials of construction must be compatible with the fluids to be pumped (water, oil, silt/sand). Most... 

Microemulsions became well known from about 1975 to 1980 because of their use ia "micellar-polymer" enhanced oil recovery (EOR) (35). This technology exploits the ultralow iaterfacial tensions that exist among top, microemulsion, and bottom phases to remove large amounts of petroleum from porous rocks, that would be unrecoverable by conventional technologies (36,37). Siace about 1990, iaterest ia the use of this property of microemulsions has shifted to the recovery of chloriaated compounds and other iadustrial solveats from shallow aquifers. The latter appHcatioa (15) is sometimes called surfactant-enhanced aquifer remediation (SEAR). 

Hot water injection via injection wells heats the soil and groundwater and enhances contaminant release. Hot water injection also displaces fluids (including LNAPL and DNAPL free product) and decreases contaminant viscosity in the subsurface to accelerate remediation through enhanced recovery. 

MPE provides several advantages when compared with the use of SVE or pump-and-treat alone. MPE provides for an increase in groundwater recovery rates, an increase in ROI in individual ground-water recovery wells, and recovery of shallow free product. By depressing the groundwater table in the vicinity of the extraction wells, MPE provides for remediation of the capillary fringe and smear zone, and remediation of volatile, residual contaminants located above and below the water table.46... 

Residual hydrocarbons will continue to serve as a source of groundwater contamination thus, remediation strategies for DNAPLs should emphasize long-term control and management (i.e., source containment, pool control, and recovery) vs. short-term fixes. Regardless of an increased level of effort (i.e., additional wells, increased pumping rates, etc.), the overall time for remediation is not expected to shorten by more than a factor of five. 

Recovery of spilled hydrocarbons has been occurring almost as long as petroleum has been refined. The earliest attempt reported was the use of pitcher pumps attached to shallow posthole depth wells along a breached pipeline. This pre-1900 effort was not driven by environmental concerns, but by its ease in recovery and the perceived economic value of the oil. Most recovery efforts were continued until the labor value exceeded the product value, and then stopped. Primitive equipment, coupled with a lack of understanding of the mechanics of product migration in the subsurface, and the relatively low value placed on the recovered product provided little incentive for the development of remedial technologies. 

A traditional approach to aquifer remediation is to remove the contaminated water by pumping, treating the water at the surface, and then either discharging it or reinjecting it back into the aquifer. When the recovery wells are properly located, this approach has the advantage of creating a capture area which contains and prevents the contamination from migrating. 

Traditionally air sparging has been used as a groundwater remediation tool. Occasionally, however, it has been successfully used to remediate the vadose zone. In this application, the compressed air is injected through a well screen that is open to the VOC-contaminated area. The injection wells may be either vertical or horizontal (Figure 10.7). In this setting, the injected air is usually captured by a corresponding set of SVE wells (Figure 10.8). Properly spaced patterns of injection and recovery wells are necessary for efficient operation. 

Laney, D. F., 1988, Hydrocarbon Recovery as Remediation of Vadose Zone Soil/Gas Contamination In Proceedings of the National Water Well Association Second National Outdoor Conference on Aquifer Restoration, Groundwater Monitoring and Geophysical Methods, Vol. Ill, Las Vegas, NV, May, pp. 1147-1171. 

Use of these equations to predict future production from a recovery project is described by the following example. An abandoned refinery property is being dismantled and the underlying aquifer remediated. Substantial LNAPL product accumulations occurred overlying the fine silty sand aquifer. Preliminary investigation indicated that a four-well system would effectively remove most of the product within a reasonable time at a modest cost. The production rate over time is illustrated in Figure 11.4. Peak production occurred on day 78 of operation, then declined. Final measurement occurred on day 141. 

Several recovery scenarios were considered for remediation. Initially, construction of a narrow, permeable trench parallel to the canal appeared to be an appropriate interception system. The construction technique considered was use of a specially designed deep trenching unit. This type of trench would have included a tile drain leading to a single two-pump recovery well. However, a review of the subsurface site plans and interviews with long-term employees determined that an unknown number of buried pipes traverse the area intended for the trench construction. Disruption of refining operations and safety considerations resulted in rejection of this option. 

The injection wells at the site have been utilized since 1982 for disposal of water generated from the hydrocarbon recovery system. The water is reinjected into the aquifer from which it was originally withdrawn so the quality of the receiving formation is not adversely affected. This type of remediation strategy also allows less strain on the wastewater handling capabilities of the facility. 

Reclaim is a passive, in situ technology that uses a hydrophobic porous polymer to attract, adsorb, and concentrate petroleum hydrocarbons and volatile organic compounds (VOCs) from soils and/or groundwater. Reclaim is considered a passive treatment technology because it requires no mechanical equipment remediation consists of placing polymer-filled canisters in recovery wells and allowing the containers to attract and adsorb organic contaminants. Reclaim canisters are then recycled and contaminants recovered for analysis and/or disposal. This polymer extracts contaminants whether they are in liquid phase, vapor phase or dissolved phase in water. 

In situ oil skimmers are commercially available for the recovery of free product [i.e., light non-aqueous-phase liquids (LNAPLs) such as oil, grease, or other hydrocarbons] floating on the water table. Oil skimmers can be used alone or in conjunction with other remediation technologies, such as (in situ) soil vapor extraction, bioventing, or bioremediation, or (ex sim) membrane filters, coalescers, or chemical processes. The technology is implemented in sim by lowering the skimmers into wells located in the zone of contamination. 

The extension of SVE techniques to low-permeability soils was based on monitoring the vapor recovery rate and using the results of mini-pilot tests to adjust SVE system operation. The periodic mini-pilot tests provided information from individual SVE wells, including air flow, well vacuum, and hydrocarbon concentration in the extracted vapors, that was used to balance the flows. Wells with low hydrocarbon concentrations were shut off to focus remedial efforts on the most contaminated locations, and during some periods, wells with high flows were shut off to allow a more balanced flow from low flow wells or to provide hydraulic control along the periphery of the perched groundwater contaminant plume. 

Micro-foam, or colloidal gas aphrons have also been reportedly used for soil flushing in contaminated-site remediation [494—498], These also have been adapted from processes developed for enhanced oil recovery (see Section 11.2.2.2). A recent review of surfactant-enhanced soil remediation [530] lists various classes of biosurfactants, some of which have been used in enhanced oil recovery, and discusses their performance on removing different type of hydrocarbons, as well as the removal of metal contaminants such as copper and zinc. In the latter area, the application of heavy metal ion complexing surfactants to remediation of landfill and mine leachate, is showing promise [541]. 

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