Technology: Hunter Point Shipyard -- Two zero-valent iron (ZVI) injection studies were conducted, one in the source area and the other in the groundwater plume. -- In the first study, 16,000 lbs of micron-sized ZVI powder was mixed with tap water to produce an iron slurry (265 grams per Liter [g/L]). The iron slurry was then injected into the dense non-aqueous phase liquid (DNAPL) source zone by pneumatic fracturing, using nitrogen as the carrier gas. -- In the second study, 72,650 lbs of microscale ZVI was made into a 300 g/L slurry with tap water and was injected into a region of less contamination next to the DNAPL source using pneumatic fracturing. Naval Air Station Jacksonville -- 300 lbs of bimetallic nanoscale particles (BNP) was mixed with water drawn from an extraction well to produce an iron slurry (4.5 to 10 g/L). -- The slurry was injected into the subsurface by a combination of direct push and closed-loop recirculation wells. -- Injection was conducted first at 10 "hot spot&#; locations and the recirculation wells were used to distribute the slurry to the rest of the suspected source zone. Naval Air Engineering Station Lakehurst -- 300 lbs of BNP was mixed with water drawn from an extraction well and from a fire hydrant to produce a dilute iron slurry (2 g/L). -- The slurry was injected in to the subsurface using direct push technology. -- Injections were done at 10 &#;hot spot&#; locations in the Northern Plume and at five locations in the Southern Plume.
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Results: Hunters Point Shipyard: First study: -- TCE levels declined sharply in all monitoring wells in the treatment zone without any significant formation of cis-1,2-DCE and vinyl chloride. -- Sharp declines in oxygen-release potential (ORP) and noticeable increases in pH supported the contention that strongly reducing condition suitable for abiotic reduction of CVOCs was created. -- Pneumatic fracturing combined with liquid atomization injection of the ZVI slurry was successful in distributing ZVI through most of the target treatment zone. -- Injecting at shallow depths may lead to nitrogen and slurry seeping up to the ground surface. Second study: -- TCE and DCE were reduced rapidly in the treatment zone wells. Naval Air Station Jacksonville: -- Within five weeks after injection, concentrations of parent VOCs were reduced by 65 to 99%. -- ORP reduction was experienced in most of the source zone monitoring wells, indicating that the direct push and recirculation methods of injection worked relatively well. -- The injection did not create the strongly reducing conditions necessary to generate substantial abiotic degradation of TCE. Naval Air Engineering Station Lakehurst: -- TCE and PCE concentrations were reduced on average by 79% and 83%, respectively. -- The average decrease in total VOC concentrations was 74%. -- Monitoring data was unable to determine what caused reductions in the CVOC concentrations.
Description:
Hunters Point Shipyard:
Hunters Point is situated on a long promontory located in the southeastern portion of San Francisco County and extends eastward into the San Francisco Bay. From through , it operated as a ship repair, maintenance, and commercial facility. In , the Navy designated Hunters Point for closure under the federal Base Closure and Realignment Act. Hunters Point was divided into six separate geographic parcels (Parcels A through F) to facilitate the closure process. The first and second ZVI demonstrations were performed at Site RU-C4 in Parcel C, which is located in the eastern portion of Hunters Point. The groundwater plume at Site RU-C4 had been contaminated with chlorinated solvents, primarily TCE.
The first ZVI injection was conducted in the source area of the contamination. The treatment zone covered an area of 1,818 ft². The total cost of the first study was $289,300. The second ZVI injection was conducted in the groundwater plume. The approximate treatment area was 8,700 ft². The total cost for the second injection project was $1,390,000.
Naval Air Station Jacksonville:
Naval Air Station (NAS) Jacksonville is located in Duval County, Florida and has been used for Navy operations since . The demonstration site, H1K, was located in the interior portion of the facility and contained two USTs. The USTs previously received waste solvents and other substances from a wash rack, manhole and other operations. The tanks and associated pipelines were removed and capped in . Cleanup of H1K is managed under CERCLA, and the groundwater monitoring program is managed under RCRA.
In and , an Interim Remedial Action consisting of chemical oxidation was conducted in the source area. In March , a site characterization sampling effort was performed to redefine the extent of contamination. The horizontal extent of contamination is approximately 1,450 ft² with a thickness of 18 ft (saturated zone), resulting in a total volume of 967 cubic yards of soil.
Iron slurry was injected into the subsurface by a combination of direct push and closed-loop recirculation wells. Within five weeks after injection, concentrations of parent VOCs were reduced by 65 to 99%. The approximate total cost reported for the field demonstration was $259,000, with an additional $153,000 for administrative tasks.
Naval Air Engineering Station Lakehurst:
Naval Air Engineering Station Lakehurst is located in Jackson and Manchester Townships, Ocean County, New Jersey, 14 miles inland from the Atlantic Ocean. The facility covers 7,383 acres and is within the Pinelands National Reserve.
The demonstration project involved two areas with the highest groundwater contaminant concentrations within the northern plume and the southern plume, Areas I and J. The contamination vertically extends 70 ft below the groundwater table. The largest amount of contamination is located in the zone from 45 to 60 ft below the groundwater table.
A bench-scale treatability study in and a pilot test study in were performed at the facility to evaluate the feasibility of using BNP as an in situ remediation technology to reduce or eliminate the contaminants at Areas I and J. This preliminary testing showed that BNP had the potential to perform better than NZVI without any catalyst coating. 10 injections of BNP were conducted in the northern plume and five injections were conducted in the southern plume. The approximate total cost for the field demonstration was $255,500.
Hepure is a key wholesale supplier of Zero Valent Iron (ZVI) powders for ZVI water and soil treatment. In nearly tons of ZVI were provided to over 15 projects within the US and internationally. Hepure as a distributor has supplied a little at 1 pound for laboratory testing to over 4,000,000 pounds for a single project. Each requires a knowledge of project requirements and trucking logistics. Samples of ZVI are typically provided in 1- and 5-pound (lb.) sizes. Additional amounts in 100 lb. bags, and lb. barrels are available for pilot testing. Typical project deliveries are in lb. super sacks. Hepure can supply small projects from domestic supply and import full containers (40,000 lb.) for larger projects. Containers can be brought into any port (domestic and international) reducing the trucking cost for final delivery.
Since entering the environmental remediation market in , Hepure&#;s ZVI reactive iron powders have become the most widely used micron-scale iron powders in the market, with documented successful outcomes at more than 150 sites across North America.
Zero valent iron (ZVI) powders are inert metallic iron shavings capable of treating chlorinated solvents abiotically, avoiding the production of harmful daughter products (DCE and VC). The use of ZVI as an in situ chemical reductant has become increasingly popular with the advancement of application processes. With smaller particle sizes and increased sophistication of injection equipment, zero valent iron powder is commonly injected in source areas and hard to reach areas where a typical permeable reactive barrier (PRB) is not feasible. Hepure also offers Ferox Plus, and emulsified zero valent iron solution.
Benefits of Zero Valent Iron Remediation (ZVI):
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ZVI Case Studies
Hepure&#;s reactive iron powder lines are produced from high quality cast iron feedstock and proprietary catalytic iron powders. The product line is available in several grades and mesh sizes for various applications. Using high quality feedstock, a proprietary grinding and pulverizing method creates reactive iron powders suitable for the most demanding of remediation environments.
From the selection of raw materials through manufacturing and packaging, all processes satisfy Hepure&#;s demanding product standards. Quality assurance testing is performed at every stage of production so that product consistency is assured[/vc_column_text][/vc_column]
Figure 1. TCE Degradation First-Order Rate Constants for Various Iron Powders When Normalized to Surface Area
Detailed kinetics studies have revealed that not all iron powders are the same, and that Hepure&#;s Ferox iron powders have exceptional value. When these kinetic values are normalized to mass or surface area concentrations, Ferox Flow gave the most favorable results over for the degradation of chlorinated volatile organic compounds (cVOCs). Ferox Flow had more than twice the activity of leading competitor&#;s iron powders.
For more information, please visit Nanometer ZVI for redox reactions.
Figure 2 &#; TCE Degradation of First-Order Rate Constants Normalized to Mass Per Dollar
In a recent evaluation of ZVI iron powders performed in his laboratories, Dr. Paul Tratnyek noted that, &#;The rates of TCE degradation from the column experiments in this study are surprisingly consistent with previously published work.
&#;Ferox Flow gave the most favorable results of the ZVIs tested in this study.&#;
Dr. Paul G. Tratnyek is a Professor at Oregon Health & Science University and is a leading researcher on ZVI reactive iron powders.
Zero valent iron is capable of reducing chlorinated compounds to harmless components, as shown in the general reaction formula below:
2Fe0 + R-Cl + 3H2O &#; 2Fe2+ + R-H + 3OH&#; + H2 + Cl&#; (R = Aryl group)
The chlorinated compounds can be reduced as follows:
1. Reduction at the metal surface in the presence of a proton donor
Fe0 + R-Cl + H+ &#; Fe2+ + R-H+ Cl&#; (1)
2. Continuation of reaction 1 by the further oxidation of Fe2+ to Fe3+
2Fe2+ + R-Cl + H+&#; 2Fe3+ + R-H+ Cl&#; (2)
3. The hydrogen gas which is produced in the corrosion reaction of water with zero-valent iron can also be involved in the dechlorination of VOCs.
Fe0 + 2H2O &#; Fe2+ + H2 + 2OH&#; (3)
H2 + R-Cl &#; R-H + H+ + Cl&#; (4)
In the estimate of the amount of zero valent iron needed, the reaction of zero valent iron with dissolved oxygen (5), water (3) and other oxidized organic and inorganic components (e.g. nitrate, sulfate) must also be taken into account.
2Fe0 + 4H+ + O2 &#; 2Fe2+ + 2H2O (5)
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Zero Valent Iron For Water Remediation:
Zero-valent iron (ZVI), thanks to its reductive capabilities, is a common choice for water treatment and remediation. Here&#;s how it works:
Zero Valent Iron For Soil Remediation:
The specific effectiveness of ZVI in soil remediation will depend on a variety of factors, including the nature of the soil, the type and concentration of contaminants present, and the presence of other substances that might react with the ZVI.
Click here for Zero Valent Iron Product List &#;
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