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Dual-Phase Extraction FAQs

Dual-Phase Extraction FAQs
  1. What is a Dual-Phase Extraction?

Dual-phase extraction (DPE) is one of the most effective remediation methods, extracting pollutants from soil and groundwater on-site (in situ). DPE (also known as multi-phase extraction and bioslurping) system treats and collects removed liquids for disposal or injects them back into the subsurface. There are two general categories of DPE technologies: single and dual-pump DPE systems.

  1. Where Can DPE Be Applied?

DPE removes various combinations of contaminated groundwater from the surface, including separate-phase petroleum products and hydrocarbons. The system treats gasoline, diesel fuel from underground storage, and other light nonaqueous phase liquids (LNAPL). Furthermore, DPE works with volatile organic compounds (VOCs), gasoline components, diesel fuel components, and other dissolved contaminants. In addition, it can extract raw crude oil.

  1. Who Invented DPE?

Vincent A. Capitanio invented DPE in 1995. Since then, DPE has become a standard method for the in-situ remediation of petroleum sites, removing up to 95% hydrocarbon contamination.

  1. How Does the Process Work?

The DPE process consists of several phases. First, a high vacuum system extracts contaminated groundwater and hydrocarbon vapor from the subsurface and sends them into containment vessels. The next step is separating and treating contaminants. The system can then dispose of them. Following the separation and treatment phase, DPE proceeds with the vapor phase, using condensers and other equipment to reinject or burn pollutants for fuel. Finally, the liquid phase produces clean water suitable for washing down systems on-site. DPE system enables disposing of hydrocarbon-free soil without any special precautions.

  1. What Are the Components of the DPE System?

DPE system consists of multiple components, such as extraction wells, manifold piping, vapor pretreatment, vapor treatment, blowers, instrumentation, and controls. In addition to standard units, there are optional DPE components such as land surface seals and injection wells.

  1. How To Evaluate DPE Effectiveness?

Evaluating DPE effectiveness means determining whether the method will be the appropriate remedy for a particular site. The first step in DPE effectiveness evaluation is initial screening which includes assessing the permeability of the petroleum-contaminated soils and the volatility of the petroleum constituents. Detailed examination of DPE effectiveness involves checking key site characteristics and chemical properties.

  1. What Are Key Site Characteristics for a Successful DPE?

An effective DPE requires appropriate intrinsic permeability, soil structure and stratification, moisture content, and other site characteristics.

  1. What Are Chemical Properties That Affect the DPE Process?

The crucial chemical parameters affecting DPE effectiveness are volatility and chemical sorptive capacity.

  1. What Are the Advantages of the DPE System?

Unlike traditional methods, DPE requires less time to generate positive outcomes (short-term treatments – 6 months to 2 years). DPE can remove various pollutants simultaneously while using less energy and creating fewer greenhouse gas emissions. DPE offers high performance in low-permeability soils, so no downhole pumps are necessary. The disturbance to site operations is minimal (suitable for use under buildings and other locations that do not allow excavation). Finally, DPE increases groundwater extraction rates. At the same time, it reduces the cost of treatment using air stripping within the vacuum extraction tube.

  1. What Are the Disadvantages of Using DPE?

The implementation of DPE is expensive at sites with medium to high-permeability soils. Furthermore, the system requires special equipment, and monitoring during operation is complex. DPE can extract a large volume of groundwater – but that requires treatment, which can be expensive and time-consuming. Finally, DPE is not effective on sites with large water table fluctuations.