ZVI 101: What is ZVI Emplacement and How Does It Work?
Nov 19, 2019 -
Zero valent iron (ZVI) technology has been around for nearly 30 years, and is a preferred remediation tool for many regulators and experts. As such, it’s important for every environmental consultant to understand what it is and how it works.
If you’d like to dive in deeper and learn about the most suitable geology or site constraints that could affect a ZVI remedy, register for tomorrow’s webinar, 2019 Has Been a Good Year for ZVI Emplacement. All attendees will receive a certificate of completion and have the opportunity to ask questions.
First, let’s cover the most basic question: What is zero valent iron emplacement?
ZVI emplacement is an in situ amendment for the treatment of chlorinated solvents. It was the first in trenched barrier application nearly 30 years ago, and now is also injected and blended with contaminated substances.
Not all ZVI are the same. They differ by size, iron content, porosity, hydraulic conductivity, surface area, reactivity, and longevity. Based on site characteristics, chlorinated solvent contaminant concentrations, and remediation objectives, the ZVI can be optimized for a particular site. In many applications, a combined ZVI (abiotic) and carbon substrate/bioaugmentation culture (biotic) mixture is used as a very aggressive in situ approach to achieve remediation expectations faster and limit the production of vinyl chloride break down products.
How does ZVI emplacement work?
ZVI is a catalyst that, in the 1970s and 1980s, was found to encourage the breakdown of chlorinated compounds in aqueous solutions. This is what makes it an excellent technology for the remediation of contaminated groundwater.
Pneumatic emplacement of ZVI begins when fractures are created using high pressure nitrogen. Then, using hydraulic injection, ZVI amendments can be added to the fractured zone. Typically, this is done using straddle packers in open boreholes, through sonic casing, or direct push technology (DPT).
A typical process flow for hydraulic emplacement of ZVI.
ZVIs can also be emplaced using other methods, such as trenchless permeable reactive barriers (PRB), which use casing dilation. Multiple injections of ZVI—which is carried in food-grade cross-linked guar—are utilized to ensure the barrier wall is thick enough.
Another method for using ZVI is soil mixing. Soil mixing is performed either with augers for deep applications, or with custom-made rotary mixers for shallow applications that are generally less than 25 feet. It is best applied where injection approaches can’t achieve the contact necessary for contaminant treatment or stabilization. Ideal sites include fine grained soils, and high concentrations of contaminants.
How do you choose the best ZVI emplacement method for your project site?
Every site is different, and choosing the right ZVI emplacement method can make a huge difference in achieving project goals. When selecting, one must consider the lithology, the contaminant(s), and source v. plume. The charts below highlights when a ZVI delivery is recommended, as well as what delivery approach would be most suitable.
ZVI is an effective and cost-efficient technology for groundwater remediation, but it requires careful planning and expert application to ensure success.
If you’d like to learn more about ZVI emplacement, see some case studies, and speak to renowned fracturing experts, register for tomorrow’s webinar, 2019 Has Been a Good Year for ZVI Emplacement.
If you can’t make it, register anyway and a link to the recording will be emailed to you.
Ready to use ZVI for an upcoming project? Request a quote.
ABOUT THE AUTHORS
DebORAH Shaffer Schnell, PE
Vice President, GeoSierra
Deborah Shaffer Schnell is the Vice President at GeoSierra Environmental, a Cascade Company. She has spent 20+ years working in the remediation industry. An innovative technology implementer and fracturing expert, she has specialized in emplacement of remedial amendments by injection and fracturing technologies.
As founder and former President of Pneumatic Fracturing, Inc., Deborah’s experience includes the design and implementation of in situ permeable barriers, source area grid injection systems, directional injection for targeted delivery, and formation enhancement using fracturing techniques under structures and active facilities. She has also worked as a consultant practicing soil and groundwater investigation and remediation, including in situ chemical oxidation and reduction systems, and soil vapor extraction and air sparging. Deborah has extensive environmental management experience in Superfund work, RCRA RI, SPCC plans, risk-based investigative and remedial strategies for complex sites. She provides value-added engineering and is instrumental in client problem solving.
SR. PROJECT MANAGER
Eric Moskal is a Senior Project Manager at Cascade Environmental. He is our national expert on pneumatic and hydraulic emplacement of ZVI and combined ZVI-bioremediation remedies for complex chlorinated solvent sites He also provides pneumatic permeability enhancement of finer grained soils to optimize SVE systems for both hydrocarbons and chlorinated solvents removal.
Eric has worked in the environmental services industry for 15 years and has led some of the largest in situ remediation projects at Cascade. He has extensive hands-on field experience overcoming site-specific challenges that become evident once field applications commence and is an excellent resource for clients needing delivery of in situ solutions at sites where traditional injection is not viable.