CES CES Remediation Technologies & Site Cleanup 1 — Questions and Answers
Question 1: What is 'pump-and-treat' remediation and what is its primary limitation?
- Extracting contaminated groundwater for surface treatment; limited by slow contaminant desorption and NAPL source persistence (Correct answer)
- Injecting treatment oxidants and pumping out reaction products; limited by high chemical reagent costs
- Pumping clean water into an aquifer to dilute contamination; limited by available fresh water supply
- Excavating and thermally treating saturated soil; limited by deep excavation equipment costs
Correct answer: Extracting contaminated groundwater for surface treatment; limited by slow contaminant desorption and NAPL source persistence
Pump-and-treat extracts contaminated groundwater for above-ground treatment but is limited by slow desorption of contaminants from soil and persistence of NAPL source zones that cause concentration rebound.
Question 2: What is 'in-situ chemical oxidation' (ISCO) used for in site remediation?
- Injecting chemical oxidants into the subsurface to destroy organic contaminants in place (Correct answer)
- Excavating and chemically treating contaminated soil at the surface
- Adding reducing agents to convert metals to less soluble oxidation states
- Using biological organisms to aerobically break down petroleum compounds
Correct answer: Injecting chemical oxidants into the subsurface to destroy organic contaminants in place
ISCO involves injecting chemical oxidants such as permanganate, persulfate, or catalyzed hydrogen peroxide into contaminated media to chemically destroy organic contaminants without excavation.
Question 3: Which remediation technology uses microorganisms to break down organic contaminants in soil and groundwater?
- Bioremediation (Correct answer)
- Thermal desorption
- Solidification/stabilization
- Air sparging
Correct answer: Bioremediation
Bioremediation harnesses naturally occurring or introduced microorganisms to metabolize and degrade organic contaminants under aerobic or anaerobic conditions.
Question 4: What is 'soil vapor extraction' (SVE) and what contaminants is it most effective for?
- A vacuum-based system that removes volatile organic compounds from unsaturated zone soil (Correct answer)
- A steam injection method that mobilizes semi-volatile contaminants for recovery
- An electrokinetic technique that drives contaminants toward collection wells via electrical current
- A chemical process that permanently binds volatile contaminants to soil particles
Correct answer: A vacuum-based system that removes volatile organic compounds from unsaturated zone soil
SVE applies vacuum to extraction wells to draw VOCs from vadose zone soil into the vapor phase for above-ground treatment, and is most effective for high-vapor-pressure compounds like gasoline and chlorinated solvents.
Question 5: What is 'monitored natural attenuation' (MNA) as a remediation strategy?
- Relying on natural processes like biodegradation and dilution to reduce contamination to acceptable levels while monitoring confirms progress (Correct answer)
- Excavating contaminated soil incrementally and monitoring backfill quality after placement
- Allowing a dissolved plume to discharge to surface water while collecting discharge monitoring data
- Conducting periodic soil sampling without implementing any active remediation measures
Correct answer: Relying on natural processes like biodegradation and dilution to reduce contamination to acceptable levels while monitoring confirms progress
MNA relies on naturally occurring physical, chemical, and biological processes to reduce contaminant concentrations over time, supported by monitoring to demonstrate protectiveness and progress toward cleanup goals.
Question 6: What is a 'permeable reactive barrier' (PRB) and how does it treat contaminated groundwater?
- A subsurface wall of reactive material that passively treats contaminated groundwater as it naturally flows through (Correct answer)
- A surface barrier system that prevents precipitation from infiltrating into contaminated soil
- A pump system that creates a hydraulic gradient barrier preventing plume migration downgradient
- A reactive geomembrane liner installed beneath a landfill to capture and treat leachate
Correct answer: A subsurface wall of reactive material that passively treats contaminated groundwater as it naturally flows through
A PRB is a passive in-situ treatment system consisting of reactive material (commonly zero-valent iron) installed across the path of a contaminant plume to treat groundwater as it flows through by natural hydraulic gradient.
CES CES Remediation Technologies & Site Cleanup 1
What is 'pump-and-treat' remediation and what is its primary limitation?