Solidification/Stabilization

Guidance and Other Resources

Several documents are available to guide practitioners through the selection and application of S/S as a remedial technology. The resources listed in the links below include guidance documents that are open access, primarily government-funded initiatives published by the Federal Remediation Technologies Roundtable (FRTR), EPA, Interstate Technology and Regulatory Council (ITRC), and the U.S. Army Corps of Engineers (USACE). There are also links to journal articles and other reports grouped by primary topic area.

Community Guide to Solidification and Stabilization
EPA 542-F-21-023, 2021

Two-page fact sheet written for Superfund site communities answers questions about S/S: 1) What is it? 2) How does it work? 3) How long will it take? 4) Is it safe? 5) How might it affect me? 6) Why use it?

Technology Screening Matrix — Solidification and Stabilization
Federal Remediation Technologies Roundtable, 17 pp, 2020

Document provides an overview on S/S technology variations and discusses common processes, applicability based on contaminant, implementation considerations, and cost.

In Situ Treatment Performance Monitoring: Issues and Best Practices: Ground Water Forum Issue Paper
U.S. EPA, Superfund Technical Support Project, Ground Water Forum. EPA 542-F-18-002, 15 pp, 2018

The purpose of this issue paper is to describe how in situ treatment technologies may impact sampling and analysis results used to monitor treatment performance and provide best practices to identify and mitigate issues that may affect sampling or analysis. This paper discusses eight potential sampling or analytical issues associated with groundwater monitoring at sites where in situ treatment technologies are applied. These issues are grouped under three topic areas: issues related to monitoring wells; representativeness of monitoring wells; and post-sampling artifacts.

Development of Performance Specifications for Solidification/Stabilization
Interstate Technology & Regulatory Council Solidification/Stabilization Team. Report No: SS-1, 162 pp, 2011

Guidance document provides an overview of S/S, information on applicable contaminants, and the development of performance specifications in the design, treatability studies, implementation, and long-term stewardship phases of S/S.

Technology Performance Review: Selecting and Using Solidification/Stabilization Treatment for Site Remediation
Barnett, F., S. Lynn, and D. Reisman.
EPA 600-R-09-148, 28 pp, 2009

Report discusses the applicability of S/S and important factors to consider in selecting S/S treatment. Case studies include a brief project description, regulatory status, the selected S/S treatment approach, and a summary of the performance data. Estimated treatment costs and maintenance activities are also included where available.

Treatment Technologies for Mercury in Soil, Waste, and Water
Office of Superfund Remediation and Technology Innovation, EPA 542-R-07-003, 133 pp, 2007

Document provides information on the availability, performance, and cost of eight treatment technologies for mercury contamination: (1) soil washing; S/S vitrification, and thermal methods for soil and waste treatment; and (2) water: precipitation/coprecipitation, adsorption, membrane filtration, and biological methods for water treatment.

Solidification/Stabilization Use at Superfund Sites
Technology Innovation Office, EPA 542-R-00-010, 23 pp, 2000

EPA performed a review and analysis of S/S applications at Superfund sites highlighting trends in use, project status, types of applications, performance, and treatment cost.

Solidification/Stabilization Resource Guide
EPA 542-B-99-002, 99 pp, 1999

Guide provides abstracts of available S/S technology guidance and policy documents, overview/program documents, studies and demonstrations, and additional in situ S/S resources and guides, including a lookup table to aid in finding relevant information sources.

Innovative Site Remediation Technology Design and Application, Volume 4: Stabilization/Solidification
Kalb, P.D., J.R. Conner, J.L. Mayberry, B.R. Patel, J.M. Perez, and R.L. Treat. EPA 542-B-97-007, 234 pp, 1997

Document addresses innovative S/S technologies that were sufficiently developed at the time of compilation to be used in full-scale applications. It discusses detailed aspects of the technologies including application, design, and implementation.

Stabilization/Solidification Processes For Mixed Waste
EPA Office of Radiation and Indoor Air and DOE Office of Environmental Restoration, EPA 402-R-96-014, 91 pp, 1996

Report includes information and technical data for four S/S processes, including Grout/Portland Cement Stabilization, Sulfur Polymer Encapsulation, Polymer Encapsulation, and Phoenix Ash Technology.

Engineering and Design: Treatability Studies for Solidification/Stabilization of Contaminated Material
U.S. Army Corps of Engineers. ETL 1110-1-158, 38 pp, 1995

Technical letter furnishes information and guidance on scoping a treatability study for S/S of contaminated material.

Stabilization/Solidification of CERCLA and RCRA Wastes: Physical Tests, Chemical Testing Procedures, Technology Screening and Field Activities
EPA Office of Research and Development, Laboratory, EPA 625-6-89-022, 79 pp, 1989

Report details the physical testing methods used to characterize solid and hazardous wastes before and after S/S and contains an overview of leaching mechanisms, leach test methods and applications, factors affecting results, selection and interpretation of leach tests.

Handbook For Stabilization /Solidification Of Hazardous Waste
Cullinane, M.J., L.W. Jones, and P.G. Malone.
EPA 540-2-86-001, 172 pp, 1986

Document provides information and general guidance to determine the feasibility of S/S technology to control contaminant migration from hazardous waste disposal. The report is comprehensive and includes information on the regulatory basis for the use of S/S, physical and chemical characterization, selection of S/S processes, bench, and pilot-scale testing, in addition to sections on quality control, cleanup and closure.

In-situ Solidification/Stabilization and Cutoff Wall Design and Construction: Standards of Practice and Lessons Learned
Schultz, M., J. Jathal, and M. Passaro. 38 slides, 2021

In this webinar, CDM Smith presents an overview of in situ S/S applications, data requirements, and discuss phases of the project lifecycle, including pre-design, treatability study, pilot testing, design, implementation, and performance. In addition, long-term performance and lessons learned from case studies are discussed.

Stabilization/Solidification of Contaminated Marine Sediment
De Gisi, S., C. Labianca, F. Todaro, and M. Notarnicola.
Low Carbon Stabilization and Solidification of Hazardous Wastes Chapter 8:113-127, 2021

Chapter 8 of Low Carbon Stabilization and Solidification of Hazardous Wastes explores the main aspects of applying stabilization/solidification (S/S) to contaminated marine sediments, including characterization methods, examples of chemical-physical characterization output, main binders and additives used, and examples of S/S application to sediments with only organic and mixed inorganic/organic contamination. The chapter concludes by outlining current lines of research.

Solidification/Stabilization for Soil Remediation: An Old Technology with New Vitality
Shen, Z., J. Fei, D. O'Connor, and D. Hou.
Environmental Science & Technology 53(20):11615-11617(2019)

Article describes recent improvements to S/S technology, including the use of high-performance and more efficient materials, designed for both sustainability and long-term performance to achieve remediation goals.

Fact Sheet: Ex Situ Solidification/Stabilization
Ricciardi-Rigault, M., M. Desilets, D. Charette, and C. Kimmerly.
Public Services and Procurement Canada, Last updated 31 March 2017.

Fact sheet provides detailed design considerations for ex situ applications of S/S.

Fact Sheet: In Situ Solidification/Stabilization
Desilets, M., D. Charette, and J. McNicoll.
Public Services and Procurement Canada, Last updated 31 March 2017.

Fact sheet provides detailed design considerations for in situ applications of S/S.

Stabilization and Solidification of Contaminated Soil and Waste: A Manual of Practice
Bates, E. and C. Hills. Hygge Media, 603 pp, 2015

The Manual of Practice was designed as a practical reference for regulators, site owners, engineering firms, and others involved in selecting, designing, bidding, and providing oversight for the remediation of hazardous waste sites using S/S. Guidance on applicable contaminants, site characteristics, project planning, equipment capabilities, production rates, performance specifications, and the quality assurance of S/S treated materials is provided. It also includes an extensive reference list of completed projects where S/S was successfully applied.

Stabilization/Solidification (S/S)
Grobbel, L. and Z. Wang.
GeoEngineer: The International Information Center for Geotechnical Engineers, CEE-549: Web-Based Class Project on Geoenvironmental Remediation, University of Michigan, 2013

Webpage presents an overview of S/S technology, applicability, comparison of different methods, field setup of in situ and ex-situ processes, treatment costs, and details three case studies. Also, recommended reading and references are provided.

Development of Performance Specifications for Solidification/Stabilization
Interstate Technology & Regulatory Council, Clu-In webinar, 135 minutes, January 2012

Webinar provides information for developing, testing, and evaluating S/S performance and guidance on designing appropriate long-term stewardship programs.

Cement Stabilization and Solidification (STSO): Review of Techniques and Methods
Maijala, A., J. Forsman, P. Lahtinen, M. Leppaenen, A. Helland, A.-O.H. Roger, and M. Konieczny.
Ramboll Norge AS, Oslo, Norway. Report No. Rap001-Id01, 57 pp, 2009

Review presents different types of cement S/S techniques, mixing methods, and uses. The main techniques are column stabilization, mass stabilization, and layer stabilization. The different techniques serve different purposes, e.g., improving the strength of subsoil and/or preventing leaching of contaminants from soil. Different purposes require different stabilizers or mixtures of stabilizers and mixing technology.

Stabilisation/Solidification for the Treatment of Contaminated Soil
Guidance Bulletin. CL:AIRE (Contaminated Land: Applications in Real Environments), London, UK. GB1, 8 pp, Nov 2005

Article by the United Kingdom's Environment Agency documents standard practice guidance on S/S techniques.

State of Practice Report, UK Stabilization/Solidification Treatment and Remediation: Part 7: Good Practice Guidance Documents
A.S.R. Perera, Al-Tabbaa, A., and D. Johnson, 2005

Part 7: Good Practice Guidance Documents summarizes various guidance documents, policy, and other related publications on S/S technology. It also provides a listing of other guidance and references available on S/S practices.

Review of Scientific Literature on the Use Of Stabilisation/Solidification for the Treatment of Contaminated Soil, Solid Waste and Sludges
Bone, B.D., L.H. Barnard, D.I. Boardman, P.J. Carey, C.D. Hills, H.M. Jones, C.L. MacLeod, and M. Tyrer.
The Environment Agency Science Report SC980003/SR2, Bristol, 375 pp, 2004

Companion document and reference resource to "Guidance on the Use of Stabilisation/Solidification for the Treatment of Contaminated Soil" (Environment Agency 2004).

Enhanced In Situ Solidification and Stabilization (ISS) Blends: Impacts of Adding Sodium Persulfate, and Water Content
Smith, B. | REMTECH 2021: The Remediation Technologies Symposium, Banff, AB, Canada, 13-15 October, 25 slides, 2021

The impact of different ratios of binder and sodium persulfate to treat a soil matrix using in situ solidification and stabilization (S/S) was evaluated. Binders tested included Type I/II Portland cement (PC) and a Portland cement/blast furnace slag (BFS) blend. The blends were varied to assess the benefit of varied binder, sodium persulfate, and moisture content on key geotechnical characteristics, including compressive strength over time, hydraulic conductivity, and volume of displaced soil (bulking) during the soil mixing application. Results showed that binder content and blend ratios can have significant impacts on the key geotechnical design parameters. PC only and PC/BFS blends solidified at different rates, with PC-only reactions achieving a higher unconfined compressive strength (UCS) in early time points. The PC/BFS blend resulted in greater UCS after 28 days. Water content had a deleterious impact on UCS but minimal to no impact on hydraulic conductivity. Adding low levels of sodium persulfate to the binders resulted in higher UCS and in a lower overall volume (less bulking) to achieve the same UCS as binder-only blends.

First to Field Mass Mixing In-Situ Stabilization/Solidification Remediation in Uncharted Waters of Kendall Bay
Meric, D., C. Robb, and P. Hutson. Ç€ Remediation Technologies Symposium East, 1-3 June, Niagara Falls, Ontario, 22 slides, 2022

Sediments within Kendall Bay are impacted with PAHs, total recoverable hydrocarbons, and BTEX by former MGP operations. In-situ stabilization/solidification (ISS) was selected as the remedial approach to address impacted sediments while minimizing impacts to adjacent residential areas. A multi-stage laboratory treatability study evaluated a range of cementitious reagent dosages, grout modifiers, and enhancers to achieve performance criteria. Following the treatability study, a two-phase pilot study was implemented to assess the constructability, construction approach, and field verify remedy effectiveness. A tiered validation plan was developed using multiple lines of evidence to allow pass/fail determination within 2 to 7 days from field mixing. Additional design elements consisted of quantitatively establishing a soft sediment buffer zone to mitigate excess surface water ingress to the mixing zone and associated methods to reduce mixing energy. Full-scale ISS remediation was completed in November 2020. The project is the first field implementation of ISS remediation of subaqueous sediments using mass mixing techniques. The project also demonstrated that ISS could be successfully implemented in subaqueous sediments using innovative sediment remediation technology.

Recycling Contaminated Marine Sediments as Filling Materials By Pilot Scale Stabilization/Solidification With Lime, Organoclay and Activated Carbon
De Gisi, S., F. Todaro, E. Mesto, E. Schingaro, and M. Notarnicola.
Journal of Cleaner Production 269:122416(2020)

The technical feasibility of recycling contaminated marine sediments (CMSs) as filling materials by stabilization/solidification treatments with lime, organoclay, and activated carbon was evaluated using marine sediment contaminated with heavy metals, PCBs, and PAHs. Different mixtures were pilot tested. The absence of some pre-treatments resulted in a product that failed to comply with the 28-day leaching test for copper. CMSs cured for 56 days resulted in a product that complied with leaching tests for all investigated metals. While organic contamination slowed down the chemical stabilization process, it resulted in an environmentally compatible product. The unconfined compression strength values measured would allow potential CMSs recycling for environmental enhancement.

Bacterial-Induced Mineralization (BIM) for Soil Solidification and Heavy Metal Stabilization: A Critical Review (Abstract)
Han, L., J. Li, Q. Xue, Z. Chen, Y. Zhou, and C.S. Poon.
Science of The Total Environment 746:140967(2020)

Reviews the basic theories of BIM technology, evaluates the remediation effects and long-term stability in terms of soil solidification and heavy metal stabilization, and reviews factors in BIM-S/S application.

Contaminated Marine Sediment Stabilization/Solidification Treatment with Cement/Lime: Leaching Behaviour Investigation (Abstract)
Todaro, F., S. De Gisi, and M. Notarnicola.
Environmental Science and Pollution Research International 27(17):21407-21415(2020)

A laboratory investigation was carried out on contaminated sediments from the Mar Piccolo of Taranto in Southern Italy to assess the effectiveness of solidification/stabilization (S/S) treatment using Portland cement/lime as binders on heavy metals, PAHs, and PCBs.

Reappraisal Review on Geopolymer: A New Era of Aluminosilicate Binder for Metal Immobilization (Abstract)
Takia, K., S. Mukherjeeb, A.K. Patel, and M. Kumar.
Environmental Nanotechnology, Monitoring & Management 14:100345(2020)

Article reviews literature on the structural chemistry and environmental applications of geopolymer binders and discusses use of aluminosilicate-based binders.

Stabilization of Lead Contaminated Soil with Traditional and Alternative Binders (Abstract)
Contessi, S., L. Calgaro, M.C. Dalconi A. Bonetto, M.P. Bellotto, G. Ferrari, A. Marcomini, and G. Artioli. Journal of Hazardous Materials 382:120990(2020)

The performance of Pb stabilization was evaluated by comparing the use of calcium aluminate cement and an alkali activated metakaolin binder in place of Portland Cement.

In-Situ Solidification/Stabilization of Heavy Metals Contaminated Site Using a Dry Jet Mixing Method and New Hydroxyapatite Based Binder (Abstract)
Xia, W.-Y., Y.-J. Du, F.-S. Li, C.-P. Li, X.-L. Yan, A. Arulrajah, F. Wang, and D.-J. Song.
Journal of Hazardous Materials 369:353-361(2019)

In situ S/S treatment using a new hydroxyapatite-based binder and a dry jet mixing method was evaluated to treat soil contaminated with heavy metals.

Solidification and Stabilization of Heavy Metal — Contaminated Industrial Site Soil Using KMP Binder (Abstract)
Xia, W.-Y., Y.-S. Feng, Y.-J. Du, K. R. Reddy.
Journal of Materials in Civil Engineering 30:6(2018)

A new and innovative binder KMP consisting of acid-activated phosphate rock, monopotassium phosphate, and reactive magnesia was tested for S/S of soil contaminated with heavy metals such as Pb, Zn, and Cd.

Stabilization/Solidification Remediation Method for Contaminated Soil: A Review
Tajudin, S.A.A., M.A.M. Azmi, and A.T.A. Nabila.
IOP Conference Series: Materials Science and Engineering 136:012043(2016)

Article reviews the materials used as a binder in S/S and the ability of the binders to remediate soil contaminated with heavy metals.

A Comparative Study on the Heavy Metal Solidification/Stabilization Performance of Four Chemical Solidifying Agents in Municipal Solid Waste Incineration Fly Ash (Abstract)
Wang, F.-H., F. Zhang, Y.-J. Chen, J. Gao, and B. Zhao.
Journal of Hazardous Materials 300:451-458(2015)

The performance of four solidifying agents in fly ash are compared and their leachability were analyzed using different extraction procedures.

The Performance of Blended Conventional and Novel Binders in the In-Situ Stabilisation/Solidification of a Contaminated Site Soil (Abstract)
Wang, F., H. Wang, F. Jin, and A. Al-Tabbaa.
Journal of Hazardous Materials 285:46-52(2015)

The use of novel binders and pH values and their effectiveness on in situ S/S techniques in treating heavy metal and organic-contaminated soil was investigated.

Secondary Waste Form Down Selection Data Package: Ceramicrete
Cantrell, K.J. and J.H. Westsik, Jr.
PNNL-20681, 99 pp, 2011

Report evaluates and summarizes existing information on Ceramicrete, one of four waste forms considered for the stabilization and solidification of low-activity, secondary liquid wastes at the Hanford Site.

Solidification-Stabilization Technique for Metal Bearing Solid Waste from Zinc Industry: A Case Study
Vyas, A.K.
2011 International Conference on Environmental and Computer Science: IPCBEE 19(30):151-155(2011)

S/S was performed on Jarosite waste with different combinations of binder/waste ratio in cement concrete mixed in the ratio of 1:2:4. Sand was replaced by Jarosite at 20, 40, 60, 80, and 100% in fine aggregate. Ordinary Portland cement (OPC), sulfate-resistant Portland cement (SRPC), and their combinations were used as binders in cement concrete mixes.

Treatability Study Report for In Situ Lead Immobilization Using Phosphate-Based Binders
Bricka, R.M., A. Marwaha, and G. Fabian.
ATC-9137195, ESTCP Project ER-0111, 195 pp, 2008

Phosphate-based binders marketed by four vendors were evaluated at Camp Withycombe, OR, for immobilization performance of Pb in soil at small arms firing range soil.

State of Practice Report, UK Stabilization/Solidification Treatment and Remediation: Binders & Technologies. Part 1: Basic Principles, Part 2: Research, and Part 3: Applications
Al-Tabbaa, A. and A.S.R. Perera, 2002.

In-Situ Immobilization of Cadmium-Polluted Upland Soil: A Ten-Year Field Study (Abstract)
Wang, G., Q. Zhang, W. Du, R. Lin, J. Li, F. Ai, Y. Yin, R. Ji, X. Wang, and H. Guo.
Ecotoxicology and Environmental Safety 207:111275(2021)

A 10-year experiment evaluated the long-term stability of lime, silicon fertilizer (SF), fused calcium magnesium phosphate fertilizer (FCMP), bone charcoal, steel slag, and blast furnace slag after a one-time application in a Cd-polluted agricultural field. SF and FCMP amendments led to high Cd immobilization by increasing the soil pH and decreasing the soil acid-extractable Cd content, conditions were closely associated with Cd uptake by Artemisia selengensis.

Recycling Contaminated Marine Sediments as Filling Materials by Pilot Scale Stabilization/Solidification with Lime, Organoclay and Activated Carbon
De Gisi, S., F. Todaro, E. Mesto, E. Schingaro, and M. Notarnicola.
Journal of Cleaner Production 269:122416(2020)

Ex-Situ Remediation of Sediment from Serbia Using a Combination of Electrokinetic and Stabilization/Solidification with Accelerated Carbonation Treatments (Abstract)
Popov, N., S. Roncevic, N. Dudukovic, D. Krcmar, Z. Mihaljev, M.Z. Balos, and S. Dordievski.
Environmental Science and Pollution Research [Published 22 November 2020 prior to print]

Three ex situ remediation technologies were applied to Begej River sediments. Conventional electrokinetic treatment (EK) was implemented first to reduce the amount of contaminated sediment and enhance metals accumulation, followed by S/S to immobilize the accumulated metals. Two types of bio ash immobilizing agents were used. Following treatment, sequential extraction procedure, TCLP and DIN 3841-4 S4 leaching tests were performed.

Solidification/Stabilization of Heavy Metals and Its Efficiency in Lead-Zinc Tailings Using Different Chemical Agents (Abstract)
Luo, Z., C. Tang, Y. Hao, Z. Wang, G. Yang, Y. Wang and Y. Mu.
Environmental Technology [Published online 21 November 2020 prior to print]

Chemical stabilization of heavy metals in lead-zinc tailings investigated using four typical agents (Na₂S, NaH₂PO₄, TMT and Na₂EDTA). Based on stabilization efficiency and dosage, using TMT achieved the best results.

Implementation of Solidification/Stabilization Process to Reduce Hazardous Impurities and Stabilize Soil Matrices
Reza, A., S. Anzum, R.C. Saha, S. Chakraborty, and Md.H. Rahman.
E3S Web of Conferences: 6th International Conference on Environment Pollution and Prevention 2018 96:01003(2019)

Article presents characteristics of various reagents and additives used in S/S technology, advantages and disadvantages of in situ and ex situ S/S, and factors that affect long-term performance.

OW-5/55R Area In-Situ Geochemical Stabilization Remediation Pilot Test, Former Koppers Company Inc. Site, Nashua, New Hampshire
New Hampshire Department of Environmental Services, 96 pp, 2014

In situ geochemical stabilization technology involves injecting an enhanced permanganate-based reagent (RemOx EC) into NAPL-impacted zones to achieve containment or stabilization and solute flux reduction. Silica-based precipitates are deposited around NAPL ganglia and droplets following reagent injection, which leaves a mineral shell that reduces overall permeability in the treated area, thereby reducing the volumetric flux of upgradient groundwater into and through the impacted area.

Amending Soils with Phosphate as Means to Mitigate Soil Lead Hazard: A Critical Review of the State of the Science (Abstract)
Scheckel, G.L. Diamond, M.F. Burgess, J.M. Klotzbach, M. Maddaloni, B.W. Miller, C.R. Partridge, and S.M. Serda.
Journal of Toxicology and Environmental Health, Part B: Critical Reviews 16(6):337-380(2013)

Review describes phosphate chemistry and the goal of converting Pb into insoluble pyromorphite in soil.

Mechanical and Leaching Behaviour of Slag-Cement and Lime-Activated Slag (Abstract)
Kogbara, R.B. and A. Al-Tabbaa.
Science of the Total Environment 409(11):2325-2335(2011)

Study investigated the potential of ground granulated blast furnace slag activated by cement and lime for S/S treatment of a mixed contaminated soil.

Preparation and Characterization of Chemically Bonded Phosphate Ceramics (CBPC) for Encapsulation of Harmful Waste
Ibrahim, W.A., H.A. Sibak, and M.F. Abadir.
Journal of American Science 7(9):543-548(2011)

A chemically bonded phosphate ceramic material was developed to encapsulate lead battery waste. The optimum conditions for the preparation of magnesium potassium phosphate compacts were determined and the formation of the final product assessed using XRD.

Chemical Stabilization: Phosphate and Biosolids Treatment
Mining Waste Treatment Technology Selection. ITRC, MW-1, 2010

The ITRC Technology overview presents the applicability, advantages, performance, costs, and regulatory considerations of chemical stabilization using phosphate for treatment of solid mining wastes as a permanent remedy to reduce the mobility of divalent heavy metals both ex situ and in situ.

Leaching Behavior of Magnesium Phosphate Cements Containing High Quantities of Heavy Metals (Abstract)
Buj, I., J. Torras, M. Rovira, and J. de Pablo.
Journal of Hazardous Materials 175(1-3):789-794(2010)

Four different leaching tests were conducted on magnesium phosphate cement pastes to compare the retention of metals.

Evaluation of Quicklime Mixing for The Remediation of Petroleum Contaminated Soils (Abstract)
Schifano, V., C. MacLeod, N. Hadlow, and R. Dudeney.
Journal of Hazardous Materials 141(2):395-409(2007)

After mixing two different soils with quicklime, researchers determined temperature, pH, moisture content, Atterberg limits, and concentrations of petroleum hydrocarbon compounds in samples extracted from the treated soils.

Solidification/Stabilization of Organic and Inorganic Contaminants Using Portland Cement: A Literature Review
Paria, S. and P.K. Yuet.
Environmental Reviews 14(4):217-255(2006)

Survey focuses on (1) cement chemistry, (2) the effects of inorganic (heavy metals) and organic compounds on cement hydration, and (3) the mechanisms of immobilization of different organic and inorganic compounds.

For examples of projects that successfully utilized S/S to treat specific contaminants, visit Examples of Site-Specific Use.

Coal Tar

In-Situ Solidification of Contaminated Sediments: A Technology Demonstration Project
Electric Power Research Institute (EPRI), Palo Alto, CA. Project 3002005216, 1086 pp, 2014

As an alternative to dredging and capping sediments affected by historical MGP operations, a pilot demonstration was performed to determine if in situ solidification (ISS) and support equipment contained on a barge could solidify tar-contaminated sediments through a column of water using readily available grout components while meeting U.S. EPA performance goals. Project elements included the control of turbidity, pH, and sheen using a dual-turbidity curtain system. Results showed that rigid controls such as steel sheet piling may not be required for good performance. The primary result of the project was proof of concept that ISS of submerged sediments is achievable and is ready to be tested at a larger scale. Additional information: Connecticut River ISS update by Jansen et al. in Remediation Journal 26(2):25-49(2016)

Metals

Field Demonstration of On-Site Immobilization of Arsenic and Lead in Soil Using a Ternary Amending Agent
Tu, Y., D. Zhao, Y. Gong, Z. Li, H. Deng, and X. Liu.
Journal of Hazardous Materials 426:127791(2022)

A novel tertiary amending agent consisting of Fe₂O₃, MnO₂, and Mg(OH)₂ (molar ratio = 1.0:5.5:5.5) to immobilize As(III) and Pb(II) was tested in contaminated soil at an abandoned chemical plant site. Field monitoring data indicated that the amendment served as a pH buffer and a long-term sequester for As and Pb in the soil. At a 3 wt% dosage, the acid-leachable As and Pb decreased from 0.042-0.077 mg/L and 0.013-0.022 mg/L to 0.0062-0.0093 mg/L and 0.0030-0.0080 mg/L, respectively, after one day of amendment, and further decreased to 0.0020-0.0050 mg/L and 0.0020-0.0054 mg/L after 240 days of aging. As(III) was oxidized to As(V) and subsequently immobilized via complexation and precipitation. Pb(II) was sequestered via electrostatic attraction and chemical precipitation. Results indicate that complex contaminants in soil can be effectively immobilized using combined amending agents that can interact with the target chemicals and induce synergistic immobilization reactions.

Application of Soil Amendments to Contaminated Soils for Heavy Metal Immobilization and Improved Soil Quality — A Critical Review
Lwin, C.S., B.-H. Seo, H.-U. Kim, G. Owens, and K.-R. Kim.
Soil Science and Plant Nutrition, 64:2:156-167(2018)

Article reviews the use of immobilizing agents and the effects of soil amendments on soil quality parameters in heavy metal-contaminated agricultural and mining soil.

Low-Carbon and Low-Alkalinity Stabilization/Solidification of High-Pb Contaminated Soil (Abstract)
Wang, L., K. Yu J.-S. Li, D.C.W. Tsang, C.S. Poon, J.-C. Yoo, K. Baek, S. Ding, D. Hou, and J.-G. Dai.
Chemical Engineering Journal 351:418-427(2018)

A low-carbon approach was developed combining ground granulated blast furnace slag and ordinary Portland cement with phosphate-/sulphate-rich byproducts to produce a low-alkalinity, high compatibility, high-strength binary cement for S/S.

Remediation Techniques for Heavy-Metal-Contaminated Soils: Principles and Applicability (Abstract)
Liu, L., W. Li, W. Song, and M. Guo.
Science of The Total Environment 633:206-219(2018)

Article reviews in situ and ex situ S/S techniques to treat heavy metal-contaminated sites and emphasizes the importance of conducting a treatability study in selecting a feasible S/S application for a soil remediation project.

Extended Summary on Pre-Treatment Technologies for Metallic Mercury
European Commission, Brussels. Reference 07.0307/2009/530302, 14 pp, 2010

Review of existing literature and practical approaches provides conclusions and recommendations concerning S/S and encapsulation of elemental Hg.

PFAS

Field-Scale Demonstration of PFAS Leachability Following In Situ Soil Stabilization
McDonough, J.T., R.H. Anderson, J.R. Lang, D. Liles, K. Matteson, and T. Olechiw.
ACS Omega 7(1):419-429(2022)

A field-scale validation compared the efficacy of commercially available stabilization amendments to mitigate PFAS leaching from aqueous film-forming foam (AFFF)-impacted source zones. The work included bench-scale testing to evaluate multiple amendments and application concentrations to mitigate PFAS leachability, followed by field-scale soil mixing. FLUORO-SORB Adsorbent (FS) and RemBind (RB) were selected for field-scale evaluation. Five ~28 m³ test pits (~3m x 3m x 3m) were mixed using conventional construction equipment. One control test pit (Test Pit 1) included Portland cement (PC) only (5% dw). The other four test pits (Test Pits 2 through 5) compared 5 and 10% ratios (dw) of FS and RB (with PC). Five separate monitoring events included two to three sample cores collected from each test pit for EPA Method 1315 leaching analysis. After 1 year, a mass balance for each test pit compared the total PFAS soil mass before, during, and after leach testing. Bench-scale and field-scale data demonstrated a >99% decrease in total PFAS leachability (mass basis; >98% mole basis), confirmed by total oxidizable precursor assay results.

Evaluation of a Solidification/Stabilization Process for PFAS Contaminated Soils
Barth, E., J. McKernan, D. Bless, D. Cutt, S. Hartzell, and K. Dasu.
The Remplex Virtual Global Summit, 8-12 November, virtual, 25 slides, 2021

Granular activated carbon (GAC), an activated carbon-clay blend, modified clay, biochar, and an Fe-amended biochar were evaluated in a bench-scale study as potential sorbents for in situ stabilization/solidification of PFAS-contaminated soil. Cement was added as a binding agent to achieve physical solidification. Results indicated that GAC was slightly more effective than the other sorbents for a 3,000 µg/L solution containing a mixture of six PFAS analytes (500 µg/L concentration each of shorter- and longer-chain alkyl acids), and was the only sorbent further evaluated in the study. Immobilization effectiveness was evaluated on samples obtained from two sites using EPA Method 1312, Synthetic Precipitation Leaching Procedure. Adding GAC sorbent substantially reduced PFAS leachability from contaminated soil samples for most PFAS. Adding cement as a physical binding agent further decreased leachability for many PFAS compounds. Immobilization of PFAS detected in the leachate from two samples ranged from 87.1% to 99.9%. The lab results may apply to pilot or field-scale studies within a broader suite of PFAS contaminated site treatment options currently available to address contaminated soil.

Stabilization Remediation of Soils Contaminated With Per- and Polyfluoroalkyl Substances (PFASs)
Sorengard, M. Ph.D Thesis No. 2020:39, Uppsala University, ISBN 978-91-7760-596-6 ,ISBN 978-91-7760-597-3 , 53 pp, 2020

S/S treatment of PFAS-contaminated soil was evaluated using cost-effective cementitious-material and different additives in a pilot-scale leaching experiment.

Stabilization and Solidification Remediation of Soil Contaminated with Poly- and Perfluoroalkyl Substances (PFASs) (Abstract)
Sorengard, M., D. B. Klejab, and L. Ahrens.
Journal of Hazardous Materials 367:639-646(2019)

S/S treatment of aged PFAS-contaminated soil, artificially spiked with 14 PFAS, was assessed. To reduce leaching of PFAS and enhance remediation performance in S/S treated soil, seven different additives were tested at 2% concentration.

Stabilization of PFAS-Contaminated Soil with Sewage Sludge- and Wood-Based Biochar Sorbents
Sormo, E., C.B.M. Lade, J. Zhang, A.G. Asimakopoulos, G. Wold Asli, M. Hubert, A.I. Goranov, H.P.H. Arp, and G. Cornelissen.
Science of The Total Environment 922:170971(2024)

A study investigated the effects of waste-based biochars on PFAS leaching from sandy soil at a former fire-fighting facility with a low total organic carbon content (TOC, 0.57 ± 0.04%) impacted by PFAS from AFFF. Six different biochars (pyrolyzed at 700-900°C) made from clean wood chips (CWC), waste timber (WT), activated waste timber (aWT), two digested sewage sludges (DSS-1 and DSS-2), and de-watered raw sewage sludge (DWSS) were tested. Up-flow column percolation tests (15 days and 16 pore volume replacements) with 1% biochar indicated that PFOS was retained best by the aWT biochar (99.9% reduction) in the leachate, followed by sludge-based DWSS (98.9%) and DSS-2 (97.8%) and DSS-1 (91.6%). The non-activated wood-based biochars (CWC and WT) reduced leaching by < 42.4 %. Extrapolating this to field conditions, 90% leaching of PFOS would occur after 15 y for unamended soil, and after 1200 y and 12,000 y, respectively, for soil amended with 1% DWSS-amended and aWT biochar. The high effectiveness of aWT and the three sludge-based biochars in reducing PFAS leaching from the soil was attributed largely to high porosity in a pore size range (>1.5 nm) that can accommodate the large PFAS molecules (>1.02-2.20 nm) combined with a high affinity to the biochar matrix. Other factors, like anionic exchange capacity, could play a contributing role. Sorbent effectiveness was better for long-chain than short-chain PFAS due to weaker apolar interactions between the biochar and the latter's shorter hydrophobic CF2-tails.

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