Remediation Technologies Flashcards

Dual-phase extraction (DPE) simultaneously removes which two phases from the subsurface?

Answer: Soil vapor and groundwater (or NAPL)

DPE uses a high-vacuum system to extract both soil vapor from the vadose zone and contaminated groundwater (or free-phase NAPL) from the saturated zone through a single extraction well.

The primary distinction between LNAPL and DNAPL behavior in the subsurface is that DNAPLs:

Answer: Sink below the water table because their density exceeds that of water

DNAPLs (dense non-aqueous phase liquids) have specific gravity greater than 1.0, causing them to penetrate the water table and migrate downward until reaching an impermeable layer or residual saturation.

Which amendment is most commonly injected to stimulate enhanced reductive dechlorination (ERD) of chlorinated ethenes?

Answer: Emulsified vegetable oil (EVO) as an electron donor

EVO provides a slow-release carbon substrate that sustains anaerobic conditions and electron donor supply, enabling dehalorespiring bacteria (like Dehalococcoides) to reductively dechlorinate PCE and TCE to ethene.

Solidification/stabilization (S/S) technology treats contaminated material by:

Answer: Immobilizing contaminants within a solid matrix to reduce leachability and mobility

S/S uses binders (cement, lime, pozzolans) to physically encapsulate or chemically fix contaminants, reducing their solubility and preventing leaching rather than destroying them.

A Treatability Study is conducted during CERCLA remediation to:

Answer: Evaluate the performance and cost-effectiveness of candidate remedial technologies before full-scale implementation

Treatability studies (bench-scale or pilot-scale) test how well specific technologies work for site-specific conditions, providing data to support technology selection in the Feasibility Study.

In the context of vapor intrusion (VI) mitigation, sub-slab depressurization (SSD) works by:

Answer: Creating negative pressure beneath the slab to prevent soil vapors from entering the building

SSD installs suction points through the foundation slab and draws air from the sub-slab environment, maintaining negative pressure that prevents soil vapors from migrating into the building interior.

Which performance metric best indicates that in situ chemical oxidation (ISCO) is actively destroying organic contaminants in the target treatment zone?

Answer: Temporary increase in contaminant concentrations followed by rapid decline (oxidant push-pull)

A push-pull test showing initial concentration increase (as the oxidant mobilizes sorbed mass) followed by sharp decline confirms that ISCO is actively oxidizing the target contaminants in the treatment zone.