Groundwater Extraction And Treatment For Source Control And Containment
Three Case Studies
Groundwater Treatment and Recovery
The two most common objectives of groundwater pumping include removal of dissolved and/or phase-separated contaminants from the subsurface and containment of contaminated groundwater to prevent migration.
Precision Environmental Services, Inc.'s technical staff determine the applicability of groundwater pumping during the process of performing a thorough site characterization. Site characteristics, such as hydraulic conductivity, are used to determine the range of remedial options possible. Chemical properties of the site and plume are established to characterize the transport of the contaminant and evaluate the feasibility of groundwater pumping. To determine if groundwater pumping is appropriate for a site, one needs to know the history of the contamination event, the properties of the subsurface, and the biological and chemical contaminant characteristics. PES project members identify the chemical and physical site characteristics; define the groundwater contaminant plume in three dimensions, and determining aquifer and soil properties necessary in designing an effective groundwater pumping strategy.
Once the decision to implement groundwater extraction methods is made based on site-specific data, the following decision process is performed by PES project management to map a pathway to site closure.
The first step of any remediation project consists of defining the remedial action objectives to be accomplished at the site. This involves gathering enough background site information and field data to make assessments of remedial requirements and possible cleanup levels. The first determination is whether cleanup or containment will be the most appropriate remedial action. If cleanup is chosen, the level of cleanup must be determined. If containment is chosen, groundwater pumping is used as a hydraulic barrier to prevent off-site migration of contaminant plumes.
The next component consists of the design and implementation of the groundwater pumping system based on data evaluated in setting the goals and objectives. The criteria for well design, pumping system, and treatment are dependent on the physical site characteristics and contaminant type. The actual treatment may include the design of a train of processes such as gravity segregation, air strippers, carbon systems tailored to remove specific contaminants.
The third essential component of any groundwater extraction system is a groundwater monitoring program to verify its effectiveness. Monitoring the remedial process with wells and piezometers allows the operator to make iterative adjustments to the system in response to changes in subsurface conditions caused by the remediation.
The final component is determining the termination requirements. Termination requirements are based on the cleanup objectives defined in the initial stage of the remedial process. The termination criteria are also dependent on the specific site aspects revealed during remedial operations.
Our experience includes the design, installation, operation, and optimization of:
Conventional Groundwater Extraction using down well pneumatic and/or electric pumps
Vacuum-assisted Groundwater extraction
Total Fluid (Multi-Phase) Extraction
Air stripper tray and packed Towers
Granular Activated Carbon Treatment
Free product Recovery
Total Fluid Extraction – Process Overview
Total Fluid Extraction (TFE), also known as multi-phase extraction, vacuum-enhanced extraction, or sometimes bioslurping, is a technology that uses a high vacuum system to remove various combinations of contaminated groundwater, separate-phase petroleum product, and hydrocarbon vapor from the subsurface. Extracted liquids and vapor are treated and collected for disposal, or re-injected to the subsurface (where permissible under applicable state laws).
In DPE systems for liquid/vapor treatment, a high vacuum system is utilized to remove liquid and gas from low permeability or heterogeneous formations. The vacuum extraction well includes a screened section in the zone of contaminated soils and groundwater. It removes contaminants from above and below the water table. The system lowers the water table around the well, exposing more of the formation. Contaminants in the newly exposed vadose zone are then accessible to vapor extraction. Once above ground, the extracted vapors or liquid-phase organics and groundwater are separated and treated. TFE for liquid/vapor treatment is generally combined with bioremediation, air sparging, or bioventing when the target contaminants include long-chained hydrocarbons. The use of dual-phase extraction with these technologies can shorten the cleanup time at a site. It also can be used with pump-and-treat technologies to recover groundwater in higher-yielding aquifers.