Difference between revisions of "User:Jhurley/sandbox"

From Enviro Wiki
Jump to: navigation, search
(→‎Porewater and Surface Water Collection Sub-system)
 
Line 1: Line 1:
−
The persistent release of residual contaminants from low hydraulic conductivity (low ''k'') zones prevents many chlorinated solvent sites from reaching groundwater cleanup goals. Low ''k'' aquifer settings limit the effectiveness of many conventional remediation technologies that rely on extraction, recirculation, or amendment delivery and distribution to achieve contact between the residual contaminants and the reagents, contact which is necessary for subsequent contaminant transformation or destruction. Alternative methods are needed to effectively distribute remedial amendments, to control contaminants leaving low ''k'' source zones, and to enhance natural attenuation processes. Two innovative remediation technologies for the treatment of chlorinated solvents and other contaminants in low ''k'' media are introduced, along with operational and performance results from recent field demonstrations.
+
==''In Situ'' Toxicity Identification Evaluation (iTIE)==
 +
The ''in situ'' Toxicity Identification Evaluation system is a tool to incorporate into weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
  
 
'''Related Article(s):'''
 
'''Related Article(s):'''
−
* [[Bioremediation - Anaerobic | Anaerobic Bioremediation]]
 
−
* [[Chemical Oxidation (In Situ - ISCO) | In Situ Chemical Oxidation]]
 
−
* [[Chemical Reduction (In Situ - ISCR) | In Situ Chemical Reduction]]
 
  
−
'''CONTRIBUTOR(S): '''
+
*[[Contaminated Sediments - Introduction]]
−
* [[Stephen D. Richardson, Ph.D., PE]]
+
*[[Contaminated Sediment Risk Assessment]]
−
* [[Craig E. Divine, Ph.D., PG]]
 
  
−
'''Key Resource(s):'''
+
'''Contributors:''' Dr. G. Allen Burton Jr., Austin Crane
−
* The Horizontal Reactive Media Treatment Well (HRX Well<sup>&reg;</sup>) for Passive In-Situ Remediation<ref name="Divine2018a">Divine, C. E., Roth, T, Crimi, M., DiMarco, A.C., Spurlin, M., Gillow, J., and Leone, G., 2018. The Horizontal Reactive Media Treatment Well (HRX Well<sup>&reg;</sup>) for Passive In-Situ Remediation. Groundwater Monitoring & Remediation, 38(1), pp. 56–65.  [https://doi.org/10.1111/gwmr.12252 DOI: 10.1111/gwmr.12252]</ref>
 
  
−
* The Horizontal Reactive Media Treatment Well (HRX Well<sup>&reg;</sup>) for Passive In Situ Remediation: Design, Implementation, and Sustainability Considerations<ref name="Divine2018">Divine, C.E., Wright, J., Wang, J., McDonough, J., Kladias, M., Crimi, M., Nzeribe, B.N., Devlin, J.F., Lubrecht, M., Ombalski, D., Hodge, B., Voscott, H., and Gerber, K., 2018. The Horizontal Reactive Media Treatment Well (HRX Well<sup>&reg;</sup>) for Passive In Situ Remediation: Design, Implementation, and Sustainability Considerations. Remediation, 28(4), pp. 5-16. [https://doi.org/10.1002/rem.21571 DOI: 10.1002/rem.21571]&nbsp;&nbsp; Also available from: [https://www.researchgate.net/publication/327487096_The_horizontal_reactive_media_treatment_well_HRX_WellR_for_passive_in_situ_remediation_Design_implementation_and_sustainability_considerations ResearchGate]</ref>
+
'''Key Resources:'''
−
 
+
*A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites<ref name="BurtonEtAl2020">Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M., Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. [https://doi.org/10.1002/etc.4799 doi: 10.1002/etc.4799]</ref>  
−
* New Application of A Geotechnical Technology to Remediate Low-Permeability Contaminated Media – Final Technical Report<ref name="Richardson2020">Richardson, S.D., Hart, D.M., Long, J.A., and Newell, C.J., 2020. New Application of A Geotechnical Technology to Remediate Low-Permeability Contaminated Media – Final Technical Report. ER-201627, Environmental Security Technology Certification Program (ESTCP). [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Persistent-Contamination/ER-201627/ Project Overview]</ref>
+
*An in situ toxicity identification and evaluation water analysis system: Laboratory validation<ref name="SteigmeyerEtAl2017">Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. [https://doi.org/10.1002/etc.3696 doi: 10.1002/etc.3696]</ref>
 +
*Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document- <ref>United States Environmental Protection Agency, 2007. Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1003GR1.txt Free Download]&nbsp; [[Media: EPA2007.pdf | Report.pdf]]</ref>
 +
*In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- <ref>In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification [https://serdp-estcp.mil/projects/details/88a8f9ba-542b-4b98-bfa4-f693435535cd/er18-1181-project-overview Project Website]&nbsp; [[Media: ER18-1181Ph.II.pdf | Final Report.pdf]]</ref>
  
 
==Introduction==
 
==Introduction==
−
[[File:Richardson1w2Fig1.png | thumb | 400px | Figure 1. Examples of low ''k'' geology. Upper left: bay muds, Oakland, California; lower left: weathered siltstone, Denver, Colorado; right: tailings slimes, central New Mexico<ref name="Horst2019"/>.]]
+
In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)<ref>Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. [https://www.epa.gov/sites/default/files/2015-09/documents/owm0255.pdf Free Download from US EPA]&nbsp; [[Media: usepa1992.pdf | Report.pdf]]</ref>, can be confounded by sample manipulation artifacts and temporal limitations of ''ex situ'' organism exposures<ref name="BurtonEtAl2020"/>. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The ''in situ'' Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.  
−
[[File:Richardson1w2Fig2.png | thumb | 400px | Figure 2. Contaminant back diffusion (“Matrix Diffusion”) from low ''k'' zones<ref name="NRC2005">National Research Council, 2005. Contaminants in the Subsurface: Source Zone Assessment and Remediation. National Academies Press, Washington, DC, pp. 372. [https://doi.org/10.17226/11146 DOI: 10.17226/11146]&nbsp;&nbsp; [[Media: NRC2005.pdf | Book.pdf]]</ref>.]]
 
−
A critical challenge preventing many chlorinated solvent sites from achieving groundwater cleanup goals is the long term release of residual contaminants from low hydraulic conductivity (low ''k'') zones such as silts, clays, glacial till, over-bank deposits, marine deposits, tailings “slimes”, saprolite and bedrock (see Figure 1)<ref name ="Horst2019">Horst, J., Divine, C., Schnobrich, M., Oesterreich, R., and Munholland, J., 2019. Groundwater Remediation in Low-Permeability Settings: The Evolving Spectrum of Proven and Potential. Groundwater Monitoring & Remediation, 39(1), pp. 11-19. [https://doi.org/10.1111/gwmr.12316 DOI: 10.1111/gwmr.12316]</ref><ref name ="Sale2008">Sale, T., C. Newell, H. Stroo, R. Hinchee, and Johnson, P., 2008. Frequently Asked Questions Regarding Management of Chlorinated Solvents in Soils and Groundwater. Environmental Security Technology Certification Program (ESTCP) Project ER-0530, 38 pp. [[Media:2008-Sale-Frequently_Asked_Questions_Regarding_Management_of_Chlorinated_Solvent_in_Soils_and_Groundwater.pdf  | Report.pdf]]&nbsp;&nbsp; [https://serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Persistent-Contamination/ER-200530/(language)/eng-US Project overview]</ref>. Such sites may be dominated by matrix diffusion processes (see Figure 2) which can significantly prolong restoration and site management timeframes. Residual contaminants residing in low permeability zones slowly diffuse from the low ''k'' matrix back into higher permeability zones, becoming a persistent source that is very difficult to remediate. One of the side effects of matrix diffusion is concentration rebound after an ''in situ'' treatment is applied. This is commonly observed at sites treated with chemical oxidation<ref name="McGuire2006">McGuire, T.M., McDade, J.M., and Newell, C.J., 2006. Performance of DNAPL Source Depletion Technologies at 59 Chlorinated Solvent-Impacted Sites. Groundwater Monitoring & Remediation. Volume 26, Issue 1, pp. 73-84.  [https://doi.org/10.1111/j.1745-6592.2006.00054.x DOI: 10.1111/j.1745-6592.2006.00054.x]&nbsp;&nbsp; [https://www.provectusenvironmental.com/marketing/p-ox1/McGuire%20et%20al%202006.pdf Free download.pdf]</ref><ref name="Krembs2010">Krembs, F., Siegrist, R., Crimi, M., Furrer, R., and Petri, B., 2010. ISCO for Groundwater Remediation: Analysis of Field Applications and Performance. Groundwater Monitoring & Remediation, 30(4), pp. 42-53.  [https://doi.org/10.1111/j.1745-6592.2010.01312.x DOI: 10.1111/j.1745-6592.2010.01312.x]</ref> and has the potential to occur at ''in situ'' bioremediation sites after the depletion of electron donors<ref name="Adamson2011">Adamson, D., McGuire, T., Newell, C., and Stroo, H., 2011. Sustained Treatment: Implications for Treatment Timescales Associated with Source-Depletion Technologies. Remediation, 21(2), pp. 27-50.  [https://doi.org/10.1002/rem.20280 DOI: 10.1002/rem.20280]</ref>.
 
  
−
Currently, there are limited remediation options available to treat residual contamination trapped in low ''k'' zones. Low ''k'' settings limit the applicability and effectiveness of conventional remediation technologies due to the constraint on fluid introduction and recovery. As such, methods relying on extraction, recirculation, or reagent delivery and distribution are often limited in their effectiveness. For the long lived, difficult to treat sites, innovative technologies are needed that will reliably address mass flux limitations of contaminants leaving low ''k'' source zones, and also increase the actual treatment of the contaminants leaving these low ''k'' zones by enhancing natural attenuation processes. Two innovative technologies investigated by ESTCP are summarized below.
+
The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods<ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. [https://doi.org/10.1897/03-409.1 doi: 10.1897/03-409.1]</ref><ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. [https://doi.org/10.1897/03-468.1 doi: 10.1897/03-468.1]</ref><ref name="BurtonEtAl2020"/><ref name="SteigmeyerEtAl2017"/>. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, [[Metal and Metalloid Contaminants | metals]], pesticides, polychlorinated biphenyls (PCB), [[Polycyclic Aromatic Hydrocarbons (PAHs) | polycyclic aromatic hydrocarbons (PAH)]], and [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression<ref name="BurtonEtAl2020"/>.
  
−
==“Grout Bomber”==
+
==System Components and Validation==
−
===Technology Description===  
+
[[File: CraneFig1.png | thumb | 600 px | Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.]]
−
[[File:Richardson1w2Fig3.png | thumb | left | 400px | Figure 3. a) Grout Bomber equipment; b) hopper for mixing and delivery of grout to the “stitcher”; and c) grout exiting the mandrel]]
+
The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water ''in situ''. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.
−
[[File:Richardson1w2Fig4.png | thumb | left | 400px | Figure 4. Application of the Bomber technology for contaminated sites in low ''k'' materials.]]
 
−
[[File:Richardson1w2Fig5.png | thumb | left | 400px | Figure 5. Chlorinated ethene concentrations at well pair (CMT-1 and IS17MW04).]]
 
−
The geotechnical industry offers a variety of well-established techniques for quickly and efficiently accessing the subsurface for the purposes of ground stabilization, foundation rehabilitation, porewater drainage, and structural support. The speed and efficiency of these techniques can also be a major advantage for emplacement of remedial amendments into the subsurface. One promising approach is the Grout Bomber, a larger adaptation of conventional cement or compaction grouting techniques for subsurface stabilization. The technology uses an excavator equipped with specialized equipment (a “stitcher”) to quickly push a mandrel (3.5 in. diameter hollow cylindrical rod) into the subsurface and subsequently fill the hole and subsurface voids with cement grout (from bottom to top) using an in-line grout delivery system. The typical arrangement of the Grout Bomber technology includes the installation rig (excavator with the “stitcher” mast; see Figure 3a) and an on-site grout mixing and delivery unit consisting of mixing hopper, pumps, hosing, and power supply. Raw materials are loaded into the mixing hopper (see Figure 3b) where it is mixed to the appropriate consistency, then pumped to the Bomber rig at a rate of approximately 0.25 cubic feet per pump stroke. At the exit end of the Bomber mandrel (see Figure 3c), the grout flows in a continuous and uniform manner, allowing the columns to be emplaced with grout while the mandrel (which was pushed into the subsurface) is lifted to the surface. Hundreds of closely spaced vertical grout columns can be installed per day using this technology.
 
  
−
For environmental applications, the Grout Bomber approach can be “repurposed” as a means to improve delivery of remediation amendments into contaminated treatment zones in low ''k'' materials. The remedial amendment (e.g., mixture of zero-valent iron (ZVI), sand, neat oil) can replace the grout and be directly placed into the subsurface from bottom to top (not injected into the surrounding formation), creating hundreds of reaction columns. The Bomber technology offers the following benefits:
+
===Porewater and Surface Water Collection Sub-system===
−
* '''Reduces uncertainty: '''
+
[[File: CraneFig2.png | thumb | 600 px | Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver]]
−
The Bomber technology circumvents the “delivery problem” associated with conventional injection-based remediation approaches, particularly in low ''k'' zones. The closely spaced nature of the reaction columns (2-3 ft spacing) reduces the diffusion lengths out of low ''k'' zones and also the uncertainty associated with amendment delivery because contaminants are always < 1 - 1.5 ft from an active treatment zone (see Figure 4).  
+
Given&nbsp;the&nbsp;importance&nbsp;of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies<ref>Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.</ref>. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.  
  
−
* '''Rapid installation of reaction columns: '''
+
The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.
−
The Grout Bomber can install 100+ reaction columns per day to depths of 40-50 ft below ground surface (bgs) to encourage contaminant degradation in source zones. Since the Grout Bomber is a direct push technique, it is better suited to silts and clays with blow counts < 35. Consolidated materials with higher blow counts will require additional equipment to pre-drill the columns prior to amendment emplacement. In general, this technology represents a much simpler, less intensive, and easier to install version of complete soil mixing.  
 
  
−
* '''Accommodates various amendment types: '''
+
Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.
−
In one example<ref name="Richardson2020"/>, vertical reaction columns containing a mixture of ZVI, vegetable oil, sand and minor amounts of water were installed to a depth of 30 ft bgs in a low ''k'' treatment area consisting primarily of silts, sandy clays, and lean clays<ref name="Divine2018"/>. The ZVI-sand-oil mixture was designed to have a similar consistency (or viscosity) to cement grout, thus requiring no major alterations to the existing Bomber equipment for the project.  Recommended practices to ensure uninterrupted flow of amendments to the Bomber mandrel include:
 
−
** Conduct simple pumping pilot studies with amendments of varying consistencies,
 
−
** Consult with a well trained pump operator, and
 
−
** Minimize the length of hosing between mixing hopper pump and Bomber mandrel.  
 
  
−
* '''Cost effective source zone treatment: '''
+
===Oxygen Coil, Overflow Bag and Drip Chamber===
−
Estimated treatment costs associated with emplacement of amendments with the Grout Bomber are ~$35 per cubic yard of source zone treated (including contractor labor, equipment, and materials). This is generally less than the reported unit cost for ''in situ'' biodegradation ($20-$80/yd<sup>3</sup>) and significantly less than chemical oxidation ($125/yd<sup>3</sup>) and thermal remediation (median $200/yd<sup>3</sup>)<ref name="McDade2005">McDade, J.M., T.M. McGuire, and Newell, C.J., 2005. Analysis of DNAPL Source Depletion Costs at 36 Field Sites, Remediation, 15(2), pp. 9-18. [https://doi.org/10.1002/rem.20039 DOI: 10.1002/rem.20039]</ref>.
+
[[File: CraneFig3.png | thumb | left | 400 px | Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.]]
 +
Porewater&nbsp;is&nbsp;naturally&nbsp;anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.
  
−
===Operational Approach & Results===
+
Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.
−
A field demonstration was conducted at Site 17, Naval Support Facility Indian Head, Maryland. The treatment area consists primarily of silts, sandy clays, and lean clays with TCE concentrations in soil and groundwater of up to 250 mg/kg and 400 mg/L, respectively. Eight hundred reaction columns (consisting of ZVI/sand or oil/sand), were installed 2-3 ft apart, to a depth of 30 ft bgs at the site. Approximately 100 reaction columns were installed per day, with the most productive day totaling 180 columns. During operation, installation time for each reaction column was on the order of 1-2 minutes. Overall, 77,000 lbs of ZVI and 650 gallons of vegetable oil were emplaced within the source area of ~5,000 ft<sup>2</sup>.  
 
  
−
===Performance Results===
+
===iTIE Units: Fractionation and Organism Exposure Chambers===
−
Ongoing post installation monitoring of treatment area groundwater has found moderate reductions in TCE in site monitoring wells and that key degradation products that serve as indicators for both abiotic and biotic mechanisms (i.e., acetylene, ethene/ethane) are present. Samples from Continuous Multilevel Tubing (CMT) wells installed within reaction columns (anulus filled with ZVI amendment) have demonstrated 1-3 orders of magnitude reductions in TCE relative to the surrounding formation water (see Figure 5). These results provide evidence that the reaction columns are creating steep concentration gradients that could drive contaminants out of low permeability zones. Further, gaseous products (e.g., propane, propene, i-butane, n-butane, n-pentane, n-hexane) were detected in the unsaturated zone of several reaction columns further supporting abiotic TCE degradation. Results of this full scale project were very promising and, although several operational improvements were identified (e.g., improved pumpability of ZVI/sand mixture; minor equipment modifications; improved site prep practices), the Bomber technology has the potential to be an important remediation alternative for hard-to-treat chlorinated source zones, particularly ones with large, persistent matrix diffusion sources over large areas.
+
At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton ''et al.''<ref name="BurtonEtAl2020"/>, the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an in situ exposure. Currently, the iTIE system can support four independent iTIE treatment units.
  
−
==Horizontal Reactive Treatment Well (HRX Well<sup><small>&reg;</small></sup>)==
+
After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.  
−
{| class="wikitable" style="margin-left: auto; margin-right: 30px; float:left; text-align:center;"
+
−
|+ Table 1. Potential reactive media types and target groundwater contaminants for an HRX Well<sup>&reg;</sup>
+
===Pumping Sub-system===
−
|-
 
−
! Reactive Media !! Potential Target Groundwater Contaminants
 
−
|-
 
−
| Zero valent iron (ZVI)</br>Bimetallics (e.g., ZVI + Pd, Pt, or Ni) || Chlorinated solvents (CVOCs), nitrate, perchlorate, energetics, chromium, arsenic
 
−
|-
 
−
| Granulated activated carbon (GAC)</br>Organosilicates || CVOCs, Poly- and Perfluoroalkyl substances (PFASs), hydrocarbons, halomethanes
 
−
|-
 
−
| Sustained Release Oxidants || CVOCs, 1,4-dioxane, hydrocarbons,</br>polyaromatic hydrocarbons (PAHs), phenolic compounds
 
−
|-
 
−
| Biodegradable particulate organic carbon</br>(e.g., mulch) || CVOCs, nitrate, perchlorate, energetics
 
−
|-
 
−
| Ion exchange resins || PFAS, brines
 
−
|-
 
−
| Phosphates (e.g., apatite) || Lead, uranium, other metals and radionuclides
 
−
|-
 
−
| Limestone, lime, magnesium oxide || Low pH, acid rock drainage
 
−
|-
 
−
| Barium sulfate (barite) || Radium
 
−
|-
 
−
| Iron sulfide || Chromium, high pH
 
−
|-
 
−
| Zeolites || Ammonium, radionuclides, PFAS
 
−
|}
 
−
[[File:Richardson1w2Fig6.png | thumb | 400px | Figure 6.  Conceptual HRX Well design<ref name="Divine2018a"/>. Groundwater (blue flowlines) is passively focused and flows into the fully screened HRX Well where it is treated as it flows through reactive media before exiting back into the aquifer. The hot colors represent high contaminant concentrations and cool colors represent treated water.]]
 
−
[[File:Richardson1w2Fig7.png | thumb | 400px | Figure 7. HRX Well completion demonstrating the minimal surface footprint requirement.]]
 
  
  
−
The Horizontal Reactive Media Treatment Well (HRX Well<sup>&reg;</sup>)<ref name="Divine2013"> Divine, C.E., Leone, G., Gillow, J, Roth, T., Brenton, H., and Spurlin, M., 2013. Horizontal In-well Treatment System and Source Area Bypass System and Method for Groundwater Remediation. U.S. Patent US8596351 B2. U.S. Patents and Trademarks Office, Alexandria, VA.    [[Media: HRXwellPatent.pdf  Patent.pdf ]]</ref><ref name="Divine2018a"/><ref name="Divine2018"/> is a new passive flux-control technology that utilizes large diameter horizontal wells filled with solid phase reactive media to treat contaminated groundwater ''in situ''.  The HRX Well is installed parallel to the direction of groundwater flow and the design leverages natural “flow focusing” behavior induced by the engineered contrast in hydraulic conductivity between the reactive media and the ambient aquifer hydraulic conductivity to passively capture and treat proportionally large volumes of groundwater within the well. Treated groundwater then exits the horizontal well along its down-gradient sections (Figure 6). The HRX Well can quickly reduce contaminant mass flux and control migration, however it will not directly treat source mass or contamination located in low permeability zones. It requires a limited above-ground footprint (Figure 7) and can be installed under buildings or other surface infrastructure.  In involves no active groundwater management or above ground treatment systems, and minimal ongoing maintenance (except for periodic media replacement as the media becomes exhausted). As shown in Table 1, many different types of solid reactive media are already available; therefore, this concept could be used to address a wide range of contaminants.  Note that it is anticipated that solid phase media would be used in most applications, however, other media types or treatment processes could conceivably be employed. It is expected that reactive media use would be more efficient, and its eventual replacement would be simpler and less costly for an HRX Well than for a conventional [[Zerovalent Iron Permeable Reactive Barriers | Permeable Reactive Barrier (PRB)]].
+
<br clear="left"/>
  
−
For relatively thin aquifers, the vertically averaged capture and treatment zone width (''w<sub><small>ave</small></sub>'') for an individual well can be estimated through a simple manipulation of Darcy’s Law<ref name="Divine2018a"/>:
+
==Advantages==
−
::{|
+
A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by ''e<sub><small>aq</small></sub><sup><big>'''-'''</big></sup>'', low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:
−
| Equation 1.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ||'''''<big>w'''<sub><small>ave</small></sub>''' = <sup>(K<sub><small>HRX</small></sub> &pi; r<sub><small>HRX</small></sub><sup>2</sup> i<sub><small>HRX</small></sub>)</sup> &frasl; <sub>(K<sub><small>A</small></sub> b<sub><small>A</small></sub> i<sub><small>A</small></sub>)</sub></big>'''''
+
*'''High efficiency for short- and ultrashort-chain PFAS:''' While the degradation efficiency for short-chain PFAS is challenging for some treatment technologies<ref>Singh, R.K., Brown, E., Mededovic Thagard, S., Holson, T.M., 2021. Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor. Journal of Hazardous Materials, 408, Article 124452. [https://doi.org/10.1016/j.jhazmat.2020.124452 doi: 10.1016/j.jhazmat.2020.124452]</ref><ref>Singh, R.K., Multari, N., Nau-Hix, C., Woodard, S., Nickelsen, M., Mededovic Thagard, S., Holson, T.M., 2020. Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor. Environmental Science and Technology, 54(21), pp. 13973-80. [https://doi.org/10.1021/acs.est.0c02158 doi: 10.1021/acs.est.0c02158]</ref><ref>Nau-Hix, C., Multari, N., Singh, R.K., Richardson, S., Kulkarni, P., Anderson, R.H., Holsen, T.M., Mededovic Thagard S., 2021. Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater. American Chemical Society’s Environmental Science and Technology (ES&T) Water, 1(3), pp. 680-87. [https://doi.org/10.1021/acsestwater.0c00170 doi: 10.1021/acsestwater.0c00170]</ref>, the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including [[Wikipedia: Trifluoroacetic acid | trifluoroacetic acid (TFA)]] and [[Wikipedia: Perfluoropropionic acid | perfluoropropionic acid (PFPrA)]]. 
−
|-
+
*'''High defluorination ratio:''' As shown in Figure 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
−
| Where:&nbsp;&nbsp;&nbsp;&nbsp;
+
*'''No harmful byproducts:''' While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.
−
|-
+
*'''Ambient pressure and low temperature:''' The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS. 
−
| ''K<sub><small>HRX</small></sub>'' || is the hydraulic conductivity of the treatment media,
+
*'''Low energy consumption:''' The electrical energy per order values for the degradation of [[Wikipedia: Perfluoroalkyl carboxylic acids | perfluorocarboxylic acids (PFCAs)]] by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., [[Supercritical Water Oxidation (SCWO) | supercritical water oxidation]])<ref>Nzeribe, B.N., Crimi, M., Mededovic Thagard, S., Holsen, T.M., 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A Review. Critical Reviews in Environmental Science and Technology, 49(10), pp. 866-915. [https://doi.org/10.1080/10643389.2018.1542916 doi: 10.1080/10643389.2018.1542916]</ref>.
−
|-
+
*'''Co-contaminant destruction:''' The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride<ref>Jung, B., Farzaneh, H., Khodary, A., Abdel-Wahab, A., 2015. Photochemical degradation of trichloroethylene by sulfite-mediated UV irradiation. Journal of Environmental Chemical Engineering, 3(3), pp. 2194-2202. [https://doi.org/10.1016/j.jece.2015.07.026 doi: 10.1016/j.jece.2015.07.026]</ref><ref>Liu, X., Yoon, S., Batchelor, B., Abdel-Wahab, A., 2013. Photochemical degradation of vinyl chloride with an Advanced Reduction Process (ARP) – Effects of reagents and pH. Chemical Engineering Journal, 215-216, pp. 868-875. [https://doi.org/10.1016/j.cej.2012.11.086 doi: 10.1016/j.cej.2012.11.086]</ref><ref>Li, X., Ma, J., Liu, G., Fang, J., Yue, S., Guan, Y., Chen, L., Liu, X., 2012. Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process. Environmental Science and Technology, 46(13), pp. 7342-49. [https://doi.org/10.1021/es3008535 doi: 10.1021/es3008535]</ref><ref>Li, X., Fang, J., Liu, G., Zhang, S., Pan, B., Ma, J., 2014. Kinetics and efficiency of the hydrated electron-induced dehalogenation by the sulfite/UV process. Water Research, 62, pp. 220-228. [https://doi.org/10.1016/j.watres.2014.05.051 doi: 10.1016/j.watres.2014.05.051]</ref>.
−
| ''r<sub><small>HRX</small></sub>'' || is the radius of the HRX Well,
 
−
|-
 
−
| ''i<sub><small>HRX</small></sub>'' || is the hydraulic gradient along the HRX Well,
 
−
|-
 
−
| ''K<sub><small>A</small></sub>'' || is the average hydraulic conductivity of the aquifer,
 
−
|-
 
−
| ''b<sub><small>A</small></sub>'' || is the targeted aquifer zone thickness, and
 
−
|-
 
−
| ''i<sub><small>A</small></sub>'' || is the ambient aquifer hydraulic gradient.
 
−
|}
 
−
In all cases, ''i<sub><small>HRX</small></sub>'' < ''i<sub><small>A</small></sub>'', but for short wells, ''i<sub><small>HRX</small></sub>'' << ''i<sub><small>A</small></sub>'', and ''w<sub><small>ave</small></sub>'' is small. However, for long wells (several hundred feet or more), the difference between the hydraulic gradients diminishes. When used as a screening calculation, ''i<sub><small>HRX</small></sub>'' and ''i<sub><small>A</small></sub>'' can be assumed to be approximately equal in many cases. By inspection of Equation 1, it is clear that ''w<sub><small>ave</small></sub>'' increases as the permeability contrast between the aquifer and reactive media increases, and therefore this approach may be practical and cost effective for many moderate and lower permeability sites. If necessary, multiple HRX Wells can be installed side by side to achieve target treatment widths. 
 
  
−
{| style="float:left; margin-left:auto; margin-right:30px;
+
==Limitations==
−
| [[File:Richardson1w2Fig8.png | thumb | 480px | Figure 8.  Changes in groundwater flow characteristics before and after HRX Well installation showing the hydraulic effects of water discharging from the outlet screen. Posted and contoured values are groundwater elevations in feet above mean sea level.]]
+
Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.
−
| [[File:Richardson1w2Fig9.png | thumb | 400px | Figure 9. HRX Well installed at VAFB showing groundwater inflow (blue curved lines) and approximate outlet zone (shaded blue cone). Posted values represent reductions in TCE concentrations observed 436 days after HRX Well installation.]]
+
*Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
−
|}
+
*Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
−
The HRX Well concept has been evaluated with numerical models and physical sand tank experiments<ref name="Divine2018a"/><ref name="Divine2018"/>, and the first field scale installation of this technology was completed in August 2018 at Vandenberg Air Force Base (VAFB) in Central California.  This purpose of the HRX Well is to control trichloroethene (TCE) flux in a thin (7 to 12 ft) low permeability aquifer (average hydraulic conductivity is approximately 0.1 to 0.5 ft/day) impacted at concentrations up to about 30 to 50 milligrams per liter (mg/L).  The HRX Well consists of 85 ft of inlet screen and 70 ft of outlet screen separated by 165 ft of casing, with removeable treatment media cartridges (35 percent ZVI by weight, media hydraulic conductivity is approximately 100 ft/d) installed in 70 ft of the cased section. Hydraulic performance data (as shown in Figure 8) and treatment effectiveness data (Figure 9) indicate the following:
+
*The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and [[Wikipedia: Perfluorobutanesulfonic acid | perfluorobutanesulfonate (PFBS)]] exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.
−
* The capture and treatment zone for this single HRX Well exceeded 50 ft, consistent with estimates predicted by Equation 1.
 
−
* TCE concentrations were reduced by more than 99.99% based on concentrations at the HRX Well outlet.
 
−
* Initial treatment response was observed in nearby monitoring wells generally within 150 days after HRX Well installation, which is consistent with the design model.
 
−
* 436 days after HRX Well installation, the TCE concentration in treatment wells was reduced by an average of 63%.  
 
  
−
For this site, the HRX Well concept compared favorably in terms of sustainability, relative to pump and treat (P&T) and conventional trench based PRB approaches.  The system operates passively ''in situ'', therefore, the recurring and cumulative energy requirements, carbon footprint, life cycle water consumption, recurring material use, and waste generation are low, and are primarily associated with replacement of treatment media. For the VAFB site, ZVI is contained in removable cartridges that are anticipated to require replacement every five to 10 years.  However, media replacement frequency is site specific and a function of contaminant loading and treatment media volume and characteristics. Lifecycle cost estimates for full-scale 30-yr systems also compared favorably: $2.5M to $3.1M for a three well HRX Well system, $3.8M to $4.7M for a P&T system, and $3.6M to $4.5M for a PRB design.  
+
==State of the Practice==
 +
[[File: XiongFig2.png | thumb | 500 px | Figure 2. Field demonstration of EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.]]
 +
[[File: XiongFig3.png | thumb | 500 px | Figure 3. Field demonstration of a treatment train (SAFF + EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.]]  
 +
The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the [[Wikipedia: TOP Assay | total oxidizable precursor (TOP) assay]], adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.
 +
*Under the [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)] [https://serdp-estcp.mil/projects/details/4c073623-e73e-4f07-a36d-e35c7acc75b6/er21-5152-project-overview Project ER21-5152], a field demonstration of EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an ''in situ'' foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
 +
*Another field demonstration was completed at an Air Force base in California, where a treatment train combining [https://serdp-estcp.mil/projects/details/263f9b50-8665-4ecc-81bd-d96b74445ca2 Surface Active Foam Fractionation (SAFF)] and EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).
  
 
==References==
 
==References==
−
 
+
<references />
−
<references/>
 
  
 
==See Also==
 
==See Also==

Latest revision as of 18:23, 12 February 2026

In Situ Toxicity Identification Evaluation (iTIE)

The in situ Toxicity Identification Evaluation system is a tool to incorporate into weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.

Related Article(s):

Contributors: Dr. G. Allen Burton Jr., Austin Crane

Key Resources:

  • A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites[1]
  • An in situ toxicity identification and evaluation water analysis system: Laboratory validation[2]
  • Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document- [3]
  • In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- [4]

Introduction

In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)[5], can be confounded by sample manipulation artifacts and temporal limitations of ex situ organism exposures[1]. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The in situ Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.

The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods[6][7][1][2]. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, metals, pesticides, polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), and per- and polyfluoroalkyl substances (PFAS), among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression[1].

System Components and Validation

Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.

The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water in situ. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.

Porewater and Surface Water Collection Sub-system

Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver

Given the importance of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies[8]. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.

The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.

Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.

Oxygen Coil, Overflow Bag and Drip Chamber

Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.

Porewater is naturally anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.

Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.

iTIE Units: Fractionation and Organism Exposure Chambers

At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton et al.[1], the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an in situ exposure. Currently, the iTIE system can support four independent iTIE treatment units.

After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.

Pumping Sub-system


Advantages

A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by eaq-, low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:

  • High efficiency for short- and ultrashort-chain PFAS: While the degradation efficiency for short-chain PFAS is challenging for some treatment technologies[9][10][11], the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including trifluoroacetic acid (TFA) and perfluoropropionic acid (PFPrA).
  • High defluorination ratio: As shown in Figure 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
  • No harmful byproducts: While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.
  • Ambient pressure and low temperature: The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS.
  • Low energy consumption: The electrical energy per order values for the degradation of perfluorocarboxylic acids (PFCAs) by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., supercritical water oxidation)[12].
  • Co-contaminant destruction: The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride[13][14][15][16].

Limitations

Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.

  • Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
  • Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
  • The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and perfluorobutanesulfonate (PFBS) exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.

State of the Practice

Figure 2. Field demonstration of EradiFluorTM[17] for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.
Figure 3. Field demonstration of a treatment train (SAFF + EradiFluorTM[17]) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluorTM[17]; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.

The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluorTM[17] system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the total oxidizable precursor (TOP) assay, adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.

  • Under the Environmental Security Technology Certification Program (ESTCP) Project ER21-5152, a field demonstration of EradiFluorTM[17] was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an in situ foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
  • Another field demonstration was completed at an Air Force base in California, where a treatment train combining Surface Active Foam Fractionation (SAFF) and EradiFluorTM[17] was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluorTM[17] was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluorTM[17]. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).

References

  1. ^ 1.0 1.1 1.2 1.3 1.4 Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M., Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. doi: 10.1002/etc.4799
  2. ^ 2.0 2.1 Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. doi: 10.1002/etc.3696
  3. ^ United States Environmental Protection Agency, 2007. Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. Free Download  Report.pdf
  4. ^ In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification Project Website  Final Report.pdf
  5. ^ Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. Free Download from US EPA  Report.pdf
  6. ^ Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. doi: 10.1897/03-409.1
  7. ^ Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. doi: 10.1897/03-468.1
  8. ^ Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.
  9. ^ Singh, R.K., Brown, E., Mededovic Thagard, S., Holson, T.M., 2021. Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor. Journal of Hazardous Materials, 408, Article 124452. doi: 10.1016/j.jhazmat.2020.124452
  10. ^ Singh, R.K., Multari, N., Nau-Hix, C., Woodard, S., Nickelsen, M., Mededovic Thagard, S., Holson, T.M., 2020. Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor. Environmental Science and Technology, 54(21), pp. 13973-80. doi: 10.1021/acs.est.0c02158
  11. ^ Nau-Hix, C., Multari, N., Singh, R.K., Richardson, S., Kulkarni, P., Anderson, R.H., Holsen, T.M., Mededovic Thagard S., 2021. Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater. American Chemical Society’s Environmental Science and Technology (ES&T) Water, 1(3), pp. 680-87. doi: 10.1021/acsestwater.0c00170
  12. ^ Nzeribe, B.N., Crimi, M., Mededovic Thagard, S., Holsen, T.M., 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A Review. Critical Reviews in Environmental Science and Technology, 49(10), pp. 866-915. doi: 10.1080/10643389.2018.1542916
  13. ^ Jung, B., Farzaneh, H., Khodary, A., Abdel-Wahab, A., 2015. Photochemical degradation of trichloroethylene by sulfite-mediated UV irradiation. Journal of Environmental Chemical Engineering, 3(3), pp. 2194-2202. doi: 10.1016/j.jece.2015.07.026
  14. ^ Liu, X., Yoon, S., Batchelor, B., Abdel-Wahab, A., 2013. Photochemical degradation of vinyl chloride with an Advanced Reduction Process (ARP) – Effects of reagents and pH. Chemical Engineering Journal, 215-216, pp. 868-875. doi: 10.1016/j.cej.2012.11.086
  15. ^ Li, X., Ma, J., Liu, G., Fang, J., Yue, S., Guan, Y., Chen, L., Liu, X., 2012. Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process. Environmental Science and Technology, 46(13), pp. 7342-49. doi: 10.1021/es3008535
  16. ^ Li, X., Fang, J., Liu, G., Zhang, S., Pan, B., Ma, J., 2014. Kinetics and efficiency of the hydrated electron-induced dehalogenation by the sulfite/UV process. Water Research, 62, pp. 220-228. doi: 10.1016/j.watres.2014.05.051
  17. ^ 17.0 17.1 17.2 17.3 17.4 17.5 17.6 17.7 Cite error: Invalid <ref> tag; no text was provided for refs named EradiFluor

See Also

Retrieved from "https://www.enviro.wiki/index.php?title=User:Jhurley/sandbox&oldid=17978"