180 Second Street Chelsea, Massachusetts 02150 Tel: 617-887-2300 Fax: 617-887-0399

Technical Report # 31

Characterization of Foundry Sand Waste

October 2000

CHARACTERIZATION OF FOUNDRY SAND WASTE

Eric S. Winkler, Ph.D. - Principal InvestigatorAlexander A. Bol'shakov, Ph.D. - Project Engineer

Center for Energy Efficiency and Renewable EnergyUniversity of Massachusetts at Amherst

CHELSEA CENTER FOR RECYCLING AND ECONOMIC DEVELOPMENTTECHNICAL RESEARCH PROGRAM

October 2000

This report has been reviewed by the Chelsea Center for Recycling and Economic Development and approved for publication.Approval does not signify that the contents necessarily reflect the views and policies of the Chelsea Center, nor does themention of trade names or commercial products constitute endorsement or recommendation for use.

All rights to this report belong to the Chelsea Center for Recycling and Economic Development. The material may be duplicatedwith permission by contacting the Chelsea Center. This project was funded by EOEA through the Clean Environment Fund,which is comprised of unredeemed bottle deposits.

The Chelsea Center for Recycling and Economic Development, a part of the University of Massachusetts’ Center forEnvironmentally Appropriate Materials, was created by the Commonwealth of Massachusetts in 1995 to create jobs, supportrecycling efforts, and help the economy and the environment by increasing the use of recyclables by manufacturers. Themission of the Chelsea Center is to develop an infrastructure for a sustainable materials economy in Massachusetts, wherebusinesses will thrive that rely on locally discarded goods as their feedstock and that minimize pressure on the environment byreducing waste, pollution, dependence on virgin materials, and dependence on disposal facilities. Further information can beobtained by writing the Chelsea Center for Recycling and Economic Development, 180 Second Street, Chelsea, MA 02150.

© Chelsea Center for Recycling and Economic Development, University of Massachusetts Lowell

Center for Energy Efficiency and Renewable Energy (CEERE)

The Center for Energy Efficiency and Renewable Energy (CEERE) is located at the Universityof Massachusetts at Amherst campus and administered within the Department of Mechanical andIndustrial Engineering. The center works with issues of energy and its use, production,economics and environmental impact. CEERE's primary mission is to promote energy efficienttechnologies, practices and the use of renewable energy resources while minimizing negativeimpacts on the environment. CEERE's activities are designed to support state, federal and privatestakeholders that deal with issues of energy and its environmental impact.

Acknowledgements

The authors wish to thank all the reviewers of this report, including: the MassachusettsDepartment of Environmental Protection; representatives from the foundry industry inMassachusetts, New Hampshire, Michigan and other states; the FIRST Consortium for MarketDevelopment of Beneficial Use of Foundry By-Products; and the Chelsea Center for Recyclingand Economic Development.

i

TABLE OF CONTENTSList of Tables................................................................................................................................. ii

List of Figures .............................................................................................................................. iii

EXECUTIVE SUMMARY............................................................................................................... iviv

INTRODUCTION............................................................................................................................... 1Recycling, reclamation, reuse ........................................................................................... 2Sand characterization and the BUD process..................................................................... 4Residual sand applications ................................................................................................ 7Objectives of the study...................................................................................................... 8

REGULATED AND RECOMMENDED STANDARDS ............................................................................ 9Drinking water standards .................................................................................................. 9Non-hazardous waste characteristics .............................................................................. 10

ANALYTICAL TECHNIQUES........................................................................................................... 13Leaching procedures (TCLP and SPLP) ......................................................................... 14Methods for determination of metals .............................................................................. 16Methods for organic compound analysis ........................................................................ 17Statistical treatment ........................................................................................................ 18

CHARACTERIZATION OF VIRGIN AND SPENT FOUNDRY SAND ..................................................... 20Physical characteristics of spent sand ............................................................................. 20Characteristics of foundry binders and resins ................................................................. 22 Chemical composition of foundry sand binders....................................................... 23

CONTAMINANTS IN SPENT FOUNDRY SAND ................................................................................. 31Metallic contaminant s ..................................................................................................... 31Leaching of organics ....................................................................................................... 34Emissions of hazardous air pollutants............................................................................. 36

IMPLICATIONS AND CONCLUSIONS ............................................................................................... 38Future work ..................................................................................................................... 40

TABLES....... ................................................................................................................................. 41

REFERENCES ................................................................................................................................ 69

ii

LIST OF TABLES

Table 1. Regulated and Recommended Maximum Contaminant Levels, mg/l......................... 41

Table 2. Regulatory Limits and Guidelines for Organic Chemicals, µg/l................................. 42

Table 3. Allowable Contaminant Levels for Reuse and Disposal of Contaminated Soil atMassachusetts Landfills .............................................................................................. 44

Table 4. Proposed Illinois tier system for ranking waste .......................................................... 45

Table 5. Indiana tier system for ranking waste ......................................................................... 46

Table 6. Analysis of Semi-Volatile Organic Compounds by TCLP.......................................... 47

Table 7. Analysis of Volatile Organic Compounds by TCLP ................................................... 48

Table 8. Metallic Contaminants Analytical Methods................................................................. 49

Table 9. Detection Limits for Metallic Contaminants (30 CMR 22.06).................................... 50

Table 10. EPA Analytical Methods (SW-846) for Organic Contaminants................................ 51

Table 11. Physical Properties of Foundry Sands........................................................................ 54

Table 12. Geotechnical Characteristics of Foundry Sand Wastes ............................................. 54

Table 13. Chemical Analysis of Typical Foundry Sands............................................................ 55

Table 14. Spent Foundry Sand Chemical Oxide Composition................................................... 55

Table 15. Conventional Sand Binder Systems and Processes..................................................... 56

Table 16. Leachability of Metals from Foundry Sand Waste ..................................................... 57

Table 17. Bulk Content of Metals in Foundry Sand Waste, Reference Sands and Soils............ 58

Table 18. Typical TCLP and SPLP Results from Smelting Operation Sludge ........................... 59

Table 19. Lead Leachability versus Total Element Analysis of Red Brass Foundry Sand Samples and Synthesized Mixtures............................................................................. 59

Table 20. Binders and Sources for Organic Analysis ................................................................. 60

Table 21. Leach Test Variability (Leachate Concentrations) ..................................................... 61

Table 22. Core Oil Binder System Sample: Volatile Analyte Concentrations from GC-FIDAnalysis....................................................................................................................... 62

Table 23. Core Oil Binder System Sample: Volatile Analyte Concentrations from GC-MSAnalysis....................................................................................................................... 63

Table 24. Summary of Concentrations of Organic Compounds in Laboratory Extracts ........... 63

Table 25. Comparison of Binder System Waste Streams .......................................................... 65

Table 26. Data for Organic Compounds from Two New England Foundries ........................... 66

Table 27. Variability of Organic Content in Sand from a New England Foundry.................... 67

Table 28. Major Volatile Components Emitted from Novolac Resin at 980°C ........................ 68

iii

LIST OF FIGURES

Fig. 1. Distribution of metalcasting facilities in the United States, 1998 ..................................... 2

Fig. 2. Locations of Massachusetts foundries (after Winkler et al. [1]) ...................................... 3

Fig. 3. Massachusetts classification of industrial waste................................................................ 5

Fig. 4. Beneficial Use Determination in Massachusetts (MA DEP, 1999)................................... 6

Fig. 5. Illinois tier grading classification system …… ............................................................... 11

Fig. 6. Grain size distribution of foundry sands.......................................................................... 20

Fig. 7. Thermal degradation products of Novolac resins versus temperature............................. 38

iv

EXECUTIVE SUMMARY

INTRODUCTION

Metal casting foundries in the U.S. dispose of about 9 million tons of spent sand in landfills peryear. A typical foundry can generate from 8 to 40 individual waste products. These wastes canhave significant regulatory implications. Environmental constraints on the foundries’ operationsand handling of waste products are becoming increasingly more costly to the industry. Aprevious study on the use of spent foundry sand in Massachusetts identified several issueslimiting beneficial use of waste sand. Some of those include: a lack of understanding in chemicalcharacteristics of sands, life cycle issues, waste management practices, and a lack of clearregulatory guidance, in particular the Beneficial Use Determination (BUD) process. Issuesrelative to risk analysis and appropriate methodology for characterizing sands were alsoidentified.

Molding sand is mixed with binder and additives. The two basic binder systems are clay-bondedsand (“green sand”) and chemically-bonded sand. Chemical binders include phenolic, furan(furfuryl alcohol), and other systems. Additives include a catalyst to promote the bindingprocess. Foundry waste sand is physically suitable for many applications, although long-termenvironmental effects are not well documented. The BUD application process requires specificphysical and chemical characterization of the waste material. Results of waste characterizationshould identify hazardous wastes, determine disposal needs, and other issues. Currently, BUDapplied to spent foundry sand includes wide use as intermediate cover in landfills and a limiteduse in construction practices. Other uses for spent sand are documented across the literature. Adetailed characterization of the foundry waste materials is needed to facilitate these uses. Riskassessment, including fate of metal and organic contaminants, is also needed to characterize thespent sand.

This study focuses on chemical-specific hazards as it relates to the BUD process and reusepractices. This information will potentially make the process of permitting more cost effectiveand timely. The primary objective of this study is to characterize foundry sand waste streams,process sands and to qualify its impact on human health and the environment.

REGULATED STANDARDS AND ANALYTICAL TECHNIQUES

Regulations concerning the disposal requirements and environmental effects of utilization of thespent foundry sand are currently being developed in Massachusetts. Waste classification is usedto specify the handling and storage procedures that minimize impact to the environment. Theanalysis of wastes for the BUD applications is performed using approved EPA methods for solidwaste analysis. Most regulated metals are measured using inductively coupled plasma atomicemission - mass spectrometry (ICP-AES, ICP-MS) and regulated organic compounds aremeasured using gas chromatography interfaced with a mass spectrometer (GC-MS). The toxicitycharacteristic of solid waste leachates is determined using the Toxicity Characteristic LeachingProcedure (TCLP, Method 1311). Alternative methods for measuring leaching potential include:Synthetic Precipitation Leaching Procedure (SPLP) and Extraction Procedure (EP) Toxicity test.

v

Currently, EP has been replaced by TCLP. TCLP is now the most commonly used method toevaluate leachability of wastes and estimate likely risks to ground water. TCLP requiresdetermination of 25 organic chemicals in addition to eight metals and six pesticides regulatedunder the Resource Conservation and Recovery Act (RCRA). The TCLP is designed to modelthe leaching behavior of a materials codisposed in a decomposing municipal solid waste landfill.Based on results of this study, the various methods for analysis offer different scenarios of fateand risk estimate. For the purpose of evaluating the impact or reuse practices, the method ofextraction may be important in accurately evaluating risk potential.

Massachusetts’s foundries have not found it economical to provide waste information that wouldadequately fulfill the requirements of the BUD process, beyond the current use as daily cover inlined landfills. Several institutional barriers to broader acceptance of foundry waste sand as abeneficially usable material still exist.

CHARACTERIZATION OF VIRGIN AND SPENT FOUNDRY SAND

The major components in foundry sand are quartz sand (70-80%), clay (5-15%), additives (2-5%), and water (up to 4%). Clean, uniformly sized silica sand is bonded via binder(s) to formmolds for ferrous (iron and steel) and non-ferrous (aluminum, copper, zinc, etc.) metal castings.The largest volumes of foundry sand are used as ‘green sand’ (clay-bonded). Green sand consistsof high-quality silica sand, approximately 10% bentonite clay, 2 to 5% water and approximately5% sea-coal (a carbonaceous ingredient used to improve casting finish). Chemically bonded sandcast systems use one or more organic binders mixed with catalysts and hardeners. Chemicallybonded sand is typically 97% silica sand by weight.

Numerous authorities have investigated suitability of foundry sands for beneficial use practices.Some of these practices include: asphalt, brick, utility trench backfill, flowable fill, landfill linersand covers, Portland cement road sub-base and soil amendments. Physical characteristics ofspent foundry sand are similar to that of fine silica sand. Nearly all types of spent casting sandsfall in the particle range between 0.1 and 0.6 mm. The uniformity of these byproducts suggeststheir utility in manufacturing. Precise quantification of physical properties of the residual sand isimportant for the marketability of the spent foundry sand. Fineness and compactability (grainsize distribution) is considered in construction applications. For most applications, strengthproperties and low hydraulic conductivity are essential. The American Society for Testing andMaterials (ASTM) has developed a 1997 national specification for use of by-products instructural fills, E1861-97. Additional research is being conducted to support specification ofspent sands in construction materials.

Binders are used to bond sand grains in mold castings. Chemically bonded systems fall into twobroad categories: organic and inorganic systems. The majority of them are self–setting binders.The most common types of binders include various phenolic urethane resins, “furan” (furfurylalcohol) resin, alkyd urethane, sodium silicate, phosphate. Composition and relative proportionsof materials used in binder systems are often proprietary. Foundry cores and molds are subjectedto intense heat from the molten metal. The temperature of the mold-metal interface approaches1000°C. As a result, all organic materials (binders, additives, coatings) undergo thermaldegradation and oxidation (burning). The nature and distribution of combustion and degradation

vi

products are complex and not entirely predictable. Residual organic compounds in spent foundrysands are found only in small quantities. Therefore, spent sand, after casting, typically does notcontain organic contaminants above regulatory threshold levels.

CONTAMINANTS IN SPENT FOUNDRY SAND

The environmental stability of spent foundry sand is reported in several investigations. Variousprocedures for evaluation of leachability of chemicals to ground water exist. In these studies themethods of determining is variable and include: TCLP (EPA Method 1311), SPLP (EPA Method1312), a multiple extraction procedure (EPA Method 1320), or a "total" analysis. While samplesfrom the same type of foundry often demonstrate a large scatter in chemical parameters, adefinite similarity of characteristics exists across the foundries regardless of the metals cast.Studies suggest that spent sand disposed of in a monofill or used in highway construction leachesmetallic and organic constituents below the toxicity characteristic levels. This may be due toinsoluble forms or contaminants or materials not exposed to leaching processes. These studiessuggest that while the presence of the constituents in a bulk waste stream exists, it may not beleachable.

Metallic Contaminants

Several studies have been conducted on metal contaminants in foundry sands. Foundry sandwastes, in monofills, leach metals one to two orders of magnitude less than typical municipalmixed-waste municipal landfills. Spent foundry sand segregated from the other waste streams,disposed of in monofills or used in construction fills leaches regulated metals well below thetoxicity characteristic levels. TCLP and EP Toxicity laboratory tests usually yield significantlyhigher leachability results than what may occur under all conditions. This is because the toxicitytests are designed to simulate the worst-case conditions in a municipal landfill in the presence ofcarboxylic acids as the leachate. The Synthetic Precipitation Leaching Procedure (SPLP) may bemore appropriate to simulate conditions other than those observed in a municipal waste landfill.Under the SPLP test, leachability of lead from smelting sludge was reported to be two orders ofmagnitude lower than that under TCLP.

Even under the TCLP test, extracts from spent foundry sand contained metal concentrationsbelow the regulatory toxicity characteristic levels, provided the sand was not mixed with otherwaste streams (e.g., dust, slag, sludge). Only iron and manganese, which are not regulated underRCRA, were recorded at increased leaching potentials in a number of occasions. Several reportssuggest that mixed foundry wastes leach below the regulatory levels. However, lead, chromium,copper and zinc are reported to be of a concern for mixed foundry wastes. There is no directcorrelation between the total metal content and the leachability under TCLP. Quantities of totalmetal content in spent and virgin sands and in sandy soils are typically of the same order ofmagnitude.

Leaching of Organics

Few peer-reviewed studies have been conducted to determine organic residues in spent foundrysand and leachates from disposal sites. Laboratory studies indicate that several organic

vii

compounds are present in the spent foundry sand but leachable at low concentrations. Studies ongreen sands have demonstrated lower organic compound leaching potential compared tochemically bonded systems.

In several studies on chemically bonded sands, samples typically had concentrations below theregulated toxicity characteristic limits. However, benzoic acid, naphthalene, methylnaphthalenes,phenol, methylenebisphenol, diethylphenol, and 3-methylbutanoic acids, were reported at levelsover 300 µg/l in one or more samples. Phenolic urethane and core oil binder systems were morelikely to be of environmental concern than other binder systems. The furan hotbox, alkydisocyanate, and furan warm box sample leachates contained few compounds and atconcentrations below 100 µg/l. Xylenes were among the most common organic compoundsreported using TCLP, although at concentrations 2 to 4 orders of magnitude lower than thenational drinking water limits. Additional compounds present included benzenesulfonate,benzo(a)anthracene, bi-n-octyl phthalate, crysene, di-n-butylphthalate, fluoranthrene, pyrene,toluene-2,4-disulfonate, and 3 isomeric forms of toluenesulfonate.

Organic compounds detected in many spent chemically bonded sands, included: acetone,diethylbenzenes, p-ethyltoluene, isopropylbenzene, 1,2,4-trimethylbenzene, both 1- and 2-methylnaphthalene, dimethylnaphthalene isomers, naphthalene, and all three isomeric forms ofxylene. Benzene, tetrachloroethene, cresols, acetone, 1,1,1-trichloroethane, and toluene weredetected in the foundry waste leachates at concentrations well below the toxicity characteristiclimits and below the drinking water standards. However, benzene and trichloroethane weremeasured at concentrations around the drinking water limits.

Efforts to reduce the organic compound content should likely focus on the phenolic urethane andthe phenolic isocyanate binder systems, since they contribute more organic content than otherbinder systems. Unreacted resins and solvents in freshly mixed sand-binder systems not exposedto the catalyzing agent or high temperature are also likely sources of leachable organics.Therefore, fresh casting mixtures and core sand that have not been in contact with hot metalshould be separated from the other waste streams.

Emission of Hazardous Air Pollutants

Thermal decomposition of additives in process sand generates permanent gases in the areasproximal to the mold-metal interface. The principal evolving gases were found to be hydrogen,carbon monoxide, carbon dioxide, methane, nitrogen, oxygen, and water vapor. Volatilehydrocarbons, including: ethane, ethylene, propane, propylene, acetylene, furfuryl alcohol,methanol, and ethanol, constitute up to 5% of the gas volume. Pyrolysis is likely to be nearlycomplete at the mold to metal boundary. Inside the mold body farther from the mold/metalinterface, partial decomposition can be expected. At lower temperature and in an oxygen-leanatmosphere, more complex organic compounds are formed. Benzene, toluene, nitrous oxide, andhydrogen cyanide were identified in the atmosphere near a pouring line in a foundry using alkydisocyanate resin bonded molds. Concentrations detected in the foundry atmosphere weregenerally low.

viii

IMPLICATIONS AND CONCLUSIONS

Utilization of foundry waste products in Massachusetts is subject to Beneficial UseDeterminations by the Department of Environmental Protection under current regulations.Detailed physical and chemical characterization of the foundry waste materials is necessary inorder to obtain permits. Quantities of twelve metals and regulated organic compounds extractedfrom foundry sand waste with the Toxicity Characteristic Leaching Procedure suggest that spentfoundry sand can be beneficially used posing no or limited environmental or human health risk.Limited data on separate waste streams, suggests that spent sand be segregated from other,potentially hazardous waste streams (unprocessed molding mix, bag house dust, or sludge), untilsuch time as detailed characterization can be performed. Some of these wastes have highlyvariable levels of the toxicity characteristic constituents. Therefore, mixed foundry wastes areessentially complex and must be evaluated independently. Non-ferrous foundries may producespent sands with contaminants such as, lead, chromium, copper and zinc. Inherent variability ofchemicals in wastes ceases to be a cause for concern when their concentrations are significantlybelow the regulated standards. No direct correlation between leaching concentrations and bulkelement content was generally found.

The physical and chemical properties of foundry sands make them well suited for several reuseapplications. Detailed information about leaching potential, methods for measuring risk, andwaste management practices are still subject, which require further study. In some cases,leaching of chemicals from spent foundry sands does not appear to be a limitation for utilizationof foundry sand wastes in Massachusetts. Additional work in support of developing riskassessment should include more detailed analysis of different waste streams and use of moreappropriate analytical methods. Further work in the market acceptance of spent foundry sandswill also support this process, specifically, product specification and risk reduction measures.Regulatory practices in other states also suggest that BUD permit issues may allow for sandutilization under numerous applications and limit potential risks to health and the environment.

1

INTRODUCTION

The purpose of this work is to evaluate spent foundry sand chemical characteristics. It follows aprevious study [1], which surveyed the possibilities for various uses of the spent foundry sand inMassachusetts. The report [1] identified several issues, including a lack of understanding inchemical characteristics of spent foundry sands, temporal variations, life cycle analysis, andmethodology for characterizing sands. This study is designed as a foundation to the BeneficialUse Determinations (BUD) process with the potential to map out practices which have the leastprobability to cause environmental consequences. The BUD process is mandated statewide bythe Massachusetts Department of Environmental Protection (MA DEP). Limitations in the BUDprocess stem from a lack of understand ing of waste characteristics and evaluation of wasteminimization and beneficial use opportunities based on those characteristics.

Metalcasting foundries in the U.S. and Canada dispose of millions of tons of spent sand inlandfills. A typical foundry can generate from 8 to 40 individual waste products, including: spentmolding sand, core sand waste, cupola slag, scrubber sludge, baghouse dusts, shotblast fines,buffing wastes, and others. Identification of each generation point is important to avoidoverlooking wastes generated infrequently or in small quantities. Small-quantity wastes may nothave a major impact on disposal expenses or handling requirements. But these wastes can havesignificant regulatory implications. Environmental constraints on the foundries’ operations andhandling of pollution control and waste products are increasingly more costly to the industry. Ina 1997 survey of North American foundries, 66% had planned to change one or more processesin the next three years to ensure environmental compliance [2].

Economic and environmental concerns dominate the issue of recycling foundry sand. Thepresently accepted practice of spent sand disposal in landfills is becoming an economic burdenfor foundries as landfills close and regulations grow stricter. This economic burden may in turnencourage foundries to move into states with regulations more favorable to beneficial use orcheaper costs to dispose of spent sand. There is also concern over the environmentalramifications of using process wastes that may contain contaminants in applications where itmay be exposed to people or the environment. Furthermore, technical and economic feasibilityissues are raised for foundries that want to beneficially use their spent sands. Institutionalbarriers, such as market, business, and regulatory realities and perceptions hinder the transition tobeneficial use of foundry sand.

The significance of beneficial use barriers should be discussed in order to clarify the real andperceived problems associated with the utilization of foundry residuals and to promote furtherdiscussion among members involved in beneficial use. This process may help eliminate artificialbarriers. Beneficial use practices in other states have demonstrated that spent foundry sand canbe used in manufacturing processes with varying degrees of success in terms of physical,environmental, and economic feasibility. These projects are reported to illustrate research effortsin support of advancing foundry sand utilization practices in Massachusetts.

2

Figure 1. Distribution of metalcasting facilities in the United States, 1998

Most of U.S. metalcasting facilities are concentrated in the Midwest, Southwest, and California,with the majority of capacity (77%) located in ten states: Alabama, Illinois, Indiana, Michigan,Ohio, Pennsylvania, Tennessee, Texas, Virginia, and Wisconsin. Illinois and Ohio are home tomore than 200 foundries. Foundry locations have traditionally been sited close to raw materials,energy supplier, water and transportation. More recently, new foundries have been built nearinexpensive supplies of scrap metal and electricity as well as local markets for the cast products.Figure 1 illustrates the present distribution of foundries in the United States. Figure 2 indicatesthe geographic locations of foundries in Massachusetts [1].

RECYCLING, RECLAMATION, REUSE

Currently, there are no universally accepted definitions for the terms related to wastemanagement such as recycling, reclamation, and reuse. The federal and states regulations definethese terms in a number of somewhat different ways depending on purpose of a specificdocument. In this report recycling is defined as a cyclic process of collection of materials fromwaste or materials that would otherwise become waste, and their subsequent reprocessing orremanufacturing to produce useful products and return them to the previous stage of use.Recycling of materials implies that there exists a commercially demonstrated processing or

3

manufacturing technology which uses the material as a raw material. A common example isrecycling of scrap metals. With this definition, repeated use of spent sand (after reclamation)within the same foundry is on-site recycling, which is not currently affected by any regulatoryrequirement of a recycling plan approval, nor by a BUD application procedure. Reclamationrequires specialized machinery that recovers a quality portion of spent sand applicable to furtheruse in mold or core making.

Figure 2. Locations of Massachusetts foundries (after Winkler et al. [1])

The term reuse is controversial. In legislative language on solid waste, ‘reuse’ is reserved for thehighest level in the hierarchy of pollution prevention [3]. An EPA guide “Reuse Resources ofNew England” [4] specifies reuse as ‘the use of a product or material again in its originalunmodified form or with little enhancement or change to be utilized again for the same purpose.’An example is the reuse of soda bottles (reuse = refill). Spent foundry molds and cores can notbe reused in this sense, i.e. without crushing them down to a raw material (sand) and itsreclamation. On the other hand, within the foundry technical terminology, reuse of by-products isunderstood as their various uses outside the foundry for non-casting purposes (as opposite toreclamation for internal use). The industry meaning of ‘reuse’ sharply contradicts with theEnvironmental Protection Agency (EPA) definitions.

In this report, spent sand processing is referred to either reclamation or beneficial use. Bothterms have distinct meaning. ‘Reclamation’ is a process of restoring the durable condition of aspent material to be used in its original function (it may be considered as one cycle in the on-siterecycling process). ‘Beneficial use’ is any further use, other than the original use, of a discardedmaterial or by-product that would otherwise become waste. Presumably, a material is discardedonce it is fully used up and can not be reclaimed again for the original process, e.g., because it is

4

worn out. A certain portion of spent foundry sand is discarded during the reclamation processbecause of the reduction in sand grain sizes that precludes any further use of spent sand fines inmold or core making.

SAND CHARACTERIZATION AND THE BUD PROCESS

Molding sand is typically mixed in a specific weight proportion with binder and additives. Theamount of binder required is primarily determined by the process and quality of the sand beingused. Foundries using high quality sand typically require less binder to achieve desired shapingabilities in the mold. Although the production variables of each particular plant result in the useof many different types of binders, there are two basic binder systems: clay-bonded sand (“greensand”) and chemically bonded sand [5]. Green sand is most frequently used in iron foundrieswhereas chemically bonded sand is used primarily in non-ferrous casting. Chemically bondedsands are also used by many “green sand” foundries in their core making operations. Chemicalbinders include phenolic, furfuryl alcohol, and other inorganic binders. Other additives include acatalyst to promote the binding process. Other casting processes such as die casting and lostfoam process are used in the industry but are beyond the scope of this report.

Often the chemical characteristics of sand used in the casting process are not fully known.Additionally, the molding sand mixtures may be proprietary information, especially whenchemically bonded sands are bought pre-mixed. The casting process causes pyrolization andother decomposition reactions that change the chemical form of the binders and additives in thesand.

Spent sand must receive its own Material Safety Data Sheets (MSDS) if it is to be considered araw material for a new market [6]. The BUD application requires specific physical and chemicalcharacterization of the waste material in order to identify potentially usable waste streams andseparate potentially hazardous those. Results of a full waste characterization study (not requiredfor the BUD process) should also include biological (microbial) characterization of waste,estimation of future waste treatment, determination of disposal needs, risk assessment, and wasteminimization opportunities, such as recycling, beneficial use, or altering the production process.Other important issues are life cycle analysis and cost effectiveness.

Foundry waste sand is physically suitable for many applications, although long termenvironmental effects are not as well known or documented. Federal and state waste regulationsare designed to determine how wastes should be handled and disposed of or recycled. Wherebeneficial use is allowed, human exposure and environmental quality are important to thedecision making process. The EPA drinking water standards [7] stipulate threshold levels fornumerous metals and organic substances that are common residuals in the waste sand. Therefore,understanding the characteristics of waste is fundamental to selecting, designing andimplementing waste management solutions in the foundry industry. A clear understanding of thewaste materials will result in defensible engineering and regulatory decisions regardingbeneficial use of spent molding sand while minimizing environmental impact and maximizingeconomics.

Environmental concerns, expressed by MA DEP, include a lack of quantitative data supportingenvironmental health risk assessment of beneficial use practices for spent sand.

5

The classification of industrial by MA DEP is shown in Fig. 3. Foundry sand classified as non-hazardous conventional waste is eligible for BUD. Whether wastes are classified as hazardous ornon-hazardous is subject to tests under the Resource Conservation and Recovery Act (RCRA)for ignitability, corrosivity, reactivity, and toxicity. The Toxicity Characteristic LeachingProcedure (TCLP) test is used to characterize leachability of solid waste disposed of in anenvironment where organic acidic conditions are present, such as in a municipal landfill. Theimportance and limitations of this test are discussed in following chapters.

Figure 3. Massachusetts classification of industrial waste

States use different means of classifying a waste's degree of hazard. In general, states with multi-tiered classification systems, or systems with several "grades" of hazard level, have set standardsby which waste materials can qualify as an acceptable beneficial use material.

While many states have set beneficial use standards [8], Massachusetts, New York, and Georgiain particular do not stipulate specific test parameters for either metals or organics. InMassachusetts, the TCLP and total metal content are used to differentiate hazardous from non-hazardous industrial solid wastes. If total metal content is under a threshold, then there is no needfor the TCLP test. Spent foundry sand generally falls into a conventional waste category, since itis not defined as special (special wastes such as asbestos are specifically identified because theyrequire special handling). Specific metal and organic compound test data and other criteria areused to qualify a material for beneficial use. The distinctive parameters for spent foundry sandare not yet determined. Measurement of eight TCLP metals specified by RCRA, and EPAmethod 8270 for organic analysis may be suitable for input into various risk assessmentscenarios, although risk assessments are not required currently for the BUD applications.

Special waste(requires special controlof handling and disposal)

Industrial Waste

Hazardous Non hazardous

Conventional waste

6

The current BUD process in Massachusetts allows producers of conventional solid waste, withcertain exceptions, to apply for a permit to beneficially use their waste. Following application,MA DEP reviews the case and determines whether the waste is suitable for beneficial use. Ageneral scheme of steps in this process is depicted in Fig. 4. The specific parameters to bedetermined in "typical foundry sand" include at least eight RCRA metals: Arsenic, Barium,Cadmium, Chromium, Lead, Mercury, Selenium, Silver, and a suite of polyaromatichydrocarbons and chlorinated compounds.

Figure 4. Beneficial Use Determination in Massachusetts (MA DEP, 1999)

Health and environmental risks are a function of both the degree of exposure and the nature andconcentration of the regulated chemicals. This report is focused on the first step of riskassessment, namely substance-specific hazard identification. Once completed, the informationcan be used in many assessments of various exposure scenarios (e.g., landfill – ground water orbeneficial use – new product – ground water pathways). Since the regulatory toxicity thresholdsare based on upper estimates of exposures, the conclusions from this report will likelyoverestimate risks, until real-life frequency and duration of exposures are determined. On theother hand, the results of spent sand characterization compiled in this report will help toeliminate the need for evaluation of those chemical parameters that clearly do not present anyrisk because of their minimal leaching potentials. Questions regarding the exposure and riskassessments, other physical hazards, nuisance conditions, life cycle analysis, and possible risk

Beneficial UseRecycling

7

management proposals are still unanswered and are in need of further exploration. These aresubjects for further study.

RESIDUAL SAND APPLICATIONS

In typical foundry processes, sand from collapsed molds or cores is reclaimed and reused in thecasting process. Some new sand and binders are usually added to maintain the quality of thecasting and to make up for sand lost during normal operations. However, there is a net loss to thesand system through a sand fraction that is not reclaimable. This spent fraction can be available(when properly processed and characterized) for beneficial use outside the foundry, in most casesreplacing other conventional construction sands or granular materials. The national averagepercentage of foundry sand being disposed of is about 10-15%, roughly estimated from acumulative number of total replacement sand sold per annum. However, some foundries withgood internal reclamation and sand capture systems, that not only reclaim sand but also reduceits loss through the baghouse dust collection systems, dispose at a ratio of only 1-2%.

Spent foundry sand beneficially used in the U.S.A., notably in Wisconsin, Michigan, Illinois,Iowa, Indiana, Minnesota, Pennsylvania, Ohio, California, Texas, and Louisiana. Other countriessuch as Canada, Spain, Japan, and New Zealand also beneficially use spent foundry sand.Numerous application projects on foundry by-product utilization grouped by state (country) orby material type are documented at the Foundry Industry Recycling Starts Today (FIRST) website [9]. The FIRST on-line database contains abstracts for each article, and a number ofcomplete publications held in the FIRST beneficial use library. Some of the current beneficialuse practices are listed below:

� Asphalt and Other Pavers – Pipe Bedding� Brick Manufacturing – Portland Cement� Cemetery Vaults – Potting and Specialty Soils� Concrete Backfill – Precast Concrete Products� Construction Fill – Road Sub-Base� Drainage Layers – Rock Wool Fibers� Flowable Fill – Smelting Flux� Grouts and Mortars – Soil Amendments� Highway Barriers – Utility Trench Backfill� Landfill Liners and Covers

The by-product mixture of sand and binder has hydraulic properties similar to those of sand-bentonite mixtures that are used as barrier layers throughout the USA. Flowable fill (also knownas a controlled low strength material – CLSM) is an ideal application for beneficial use offoundry sand waste because its physical characteristics are similar to those of fine aggregate usedin high quality CLSM. The spent chemically-bonded casting sand is excellent replacement forportions of the fine aggregate in CLSM. Roadway structural fill applications provide anopportunity for high volume utilization of excess system sand. Foundry sand can effectivelyreplace conventional materials in hot mix asphalt mixtures by providing at least the same quality.These and a few other typical examples of efficient utilization of the spent foundry sand can befound in Ref. [1,5,6,9-14].

8

One of the most comprehensive listing of beneficial use applications of spent molding sand andother foundry byproducts has been summarized in a database assembled at the University ofWisconsin [10]. This database identifies materials and markets where methods and specificationswith acceptable performance exist as well as areas in need of further research. Overall, 90projects involving beneficial use of foundry by-products were evaluated or referenced, andtechnical reviews of most significant projects in the U.S. and Canada were performed. Thedatabase portrays a common problem in beneficial use practices: a lack of field performance dataand documentation for all materials. Furthermore, these reports are focused on physicalproperties and not fate of chemical constituents. Hence their applicability to the BUD process isanecdotal.

Spent foundry sand must possess several qualities to be beneficially used. It must beenvironmentally benign, i.e., it should not leach metals, alkalis, or organics in amounts thatwould pose a hazard to human health or the environment under its service condition. It must beeconomically favorable. And finally, it should be technically equivalent to the material it isreplacing in the application. These three factors require a set of definitions acceptable to theindustry, regulatory and policy stakeholders.

Beneficially used foundry sand is often diluted with other materials in its final use, although“dilution” is not always the best approach. In actual end-use scenarios, spent foundry sand maybe coated or embedded in another material (such as asphalt or concrete) making it unavailable toinfiltrating water – hence it would not leach. Furthermore, the chemical form of the metal (e.g.,oxide or silicate) may have limited solubility.

The TCLP test simulates the worst case scenario and is limited to a codisposal situation. TCLPtesting of the end-use compositions would be very helpful. However, the leachability of spentfoundry sand in its end-use structures has not been fully investigated.

OBJECTIVES OF THE STUDY

The main objective of this study is to characterize the chemical contaminants of spent foundrysand. Detailed characterization of the foundry waste materials is needed to support the BUDregulatory protocols and to specify the beneficial practices with the least probable environmentalconsequences and minimum waste. Chemical characterization must be performed in accordancewith the EPA-recommended procedures using the approved standard methods. Such provisionsnecessitate an overview of regulated standards and analytical techniques.

A second objective is to understand the complete extent of regulated elements and compoundspresent in spent foundry sand and to qualify their potential or actual impact on human health andthe environment. Furthermore, the detailed BUD regulations are expected to provide wastegenerators with a mechanism to divert safely and beneficially as much of their wastes fromlandfills as possible. This would provide numerous benefits to the environment, includingconservation of natural resources and less land needed for disposal.

9

REGULATED AND RECOMMENDED STANDARDS

Policies and regulations concerning the disposal requirements and environmental effects ofutilization of the spent foundry sand are currently being developed in Massachusetts. Wasteclassifications are used in order to specify the procedures by which wastes should be handled andstored so as to minimize impact to human health and environmental quality. Development ofbeneficial use policies ensures that materials are used in ways that do not cause harm to humanhealth or degrade environmental quality. Materials are considered to be solid wastes if they areused in a manner constituting disposal. Once a BUD is granted, the waste material ceases to beconsidered a solid waste.

DRINKING WATER STANDARDS

The potential adverse effect of land disposal of solid waste materials is on surface and groundwater quality. Drinking water standards [7] are set by EPA to control the level of contaminants inthe nation's drinking water. These standards are part of the "multiple barrier" approach todrinking water protection under the Safe Drinking Water Act (SDWA), which includes assessingand protecting drinking water sources; making sure water is treated by qualified operators; andensuring the integrity of distribution systems. In most cases EPA delegates responsibility forimplementing drinking water standards to states. The SDWA, passed in 1974 and amended in1986 and 1996, gives the EPA the authority to set drinking water standards. There are twocategories of drinking water standards: National Primary Drinking Water Regulation (or primarystandard) and National Secondary Drinking Water Regulation (or secondary standard).

National Primary Standards are legally enforceable standards that apply to public water systems.They protect drinking water quality by limiting the levels of specific contaminants (in form ofMaximum Contaminant Levels or Treatment Techniques) that can adversely affect public healthand are anticipated to occur in water.

Secondary standards are non-enforceable guidelines regarding contaminants that may causecosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, orcolor) in drinking water. EPA recommends secondary standards to water systems but does notrequire systems to comply. States may establish higher or lower levels which may be appropriatedependant upon local conditions. MA DEP encourages the suppliers of water to meet thesecondary drinking water standards. Additionally, MA DEP mandates that all detection ofsodium (Na) be reported. The agency defines 20 mg/l of Na and 0.1 mg/l of nickel (Ni) as theconcentrations in drinking water at or below which adverse, non-cancer health effects areunlikely to occur after chronic (lifetime) exposure [15]. MA DEP does not regulate levels ofsodium and nickel but only indicates a potential need for further legislative action to be decidedby its Office of Research and Standards.

Drinking water standards apply to public water systems that provide water for humanconsumption. The 1996 Amendments to SDWA require EPA to go through several steps todetermine via technological evaluation (analytical methods of detection; technical feasibility;impacts of regulation on water systems, the economy and public health) whether setting a certainstandard is appropriate for a particular contaminant.

10

In most cases, the enforceable standard is a maximum contaminant level (MCL), the maximumpermissible level of a contaminant in water which is delivered to any user of a public watersystem. The SDWA defines MCL as the level that may be achieved with the use of the bestavailable technology and other means which EPA finds available. When there is no reliablemethod that is economically and technically feasible to measure a contaminant at particularlylow concentrations, an action level for a treatment technique is set rather than MCL. A treatmenttechnique is an enforceable procedure or level of technological performance which public watersystems must follow to ensure control of a contaminant. An example of treatment technique rulesis the lead and copper rule for the optimized corrosion control and prohibition on lead use.

The EPA drinking water standards divides all regulated contaminants that can adversely affectpublic health into four groups: inorganic chemicals, organic chemicals, radionuclides, andmicroorganisms. The two latter groups of contaminants have little relevance to the foundry sandwaste, but the metals and organics are of a predominate concern. Maximum contaminant levelsof metals that are mandatory for monitoring under primary and secondary drinking waterregulations [7] are listed in the first column of Table 1. Regulatory limits for organic chemicalsare summarized in Table 2.

The drinking water regulations are closely related to the ground water monitoring requirementsas well as to the monitoring, analysis, inspection, quality assurance in implementing thehazardous waste management and land disposal restrictions. Under the existing regulations anowner or operator must sample ground water and analyze those samples for the presence andconcentration of constituents that are routinely analyzed for in the Superfund program(Comprehensive Environmental Response, Compensation, and Liability Act, 1980). Based onthis information, Regional Administrator sets the ground water protection standards, or levels forthe constituents in ground water [16]. If these levels are exceeded in the ground water, correctiveaction must be implemented.

NON-HAZARDOUS WASTE CHARACTERISTICS

The hazardous waste characteristics promulgated by EPA designate broad classes of wastes withinherent properties which would result in harm to health or the environment if mismanaged. Testmethods and regulatory levels for each characteristic property are then established. The EPAmethod 1311 (TCLP) is designed to measure the potential for toxic constituents in the waste toleach out of the solid phase [17] and contaminate ground water. The Toxicity Characteristic ismet when sample leachate exceeds the maximum concentration of any of the specified [16]contaminants. The maximum metal concentrations for TCLP toxicity and ground water are listedin Table 1. In Massachusetts, the total metals content and the TCLP test among other criteria areused to regulate reuse and disposal of contaminated soil at landfills [18]. The allowablecontaminant levels for reuse of soil at Massachusetts landfills are listed in Table 3.

Appropriate sampling procedures are needed to meet state and federal reporting requirements.Sampling protocols required by MA DEP establish the number and frequency of samples andshould include procedures for sample collection, sample preservation, chemical analysis, qualitycontrol, chain-of-custody, and data management.

11

Often, the characterization reports of spent sand from foundries have been inadequate fordetermining the risk of beneficially used materials on public health or the environment. A riskassessment, including metal and organic contaminants and life cycle effects, is needed tocharacterize the material. Changes in use of a building or road structure, for example, may resultin exposures not specified in the original use determination. While leachable metals or organicsmay be locked into a solid substance such as concrete, reducing the risk of environmentalcontact, a structure that is demolished has a renewed risk potential that may not be expected.Though long-term behavior of asphalt, brick, concrete and other materials in the environment iswell known, more specific research is necessary on the stability of those materials that have beenmade with addition of foundry waste. Generally, long-term behavior evaluation is needed for allthe applications going through the BUD process.

In states, where the foundry industry is large, they have developed multi-tiered schemes forclassifying a degree of hazard for solid wastes. Winkler et al. [1] reviewed the BUD practices inthose cases. In Illinois, a score is given to each constituent of the waste based on TCLP, pH, andwaste stream size. Values are compared to a toxicological database compiled from the Registryof Toxic Effects of Chemical Substances and other sources to give an equivalent toxicity score.These scores are then added to give a final ranking, as illustrated in Fig. 5. Materials that score alow or negligible rank may be considered for beneficial use, after issues of liability and specialwaste are addressed.

Figure 5. Illinois tier grading classification system

Constituents measured in the TCLP are often present in various chemical forms in foundrywastes. Some of these include benzene, phenols, metal oxides and silicates. These species wereconsidered in the Illinois tests for determining the level of hazard for foundry waste material [5].The Illinois four-tier grading classification system is similar to Indiana's, with the maximumallowed concentrations for both systems shown in Tables 4 and 5. Under the Indianaclassification system, wastes qualifying as type III or IV may be approved for certain beneficialuses. Wisconsin also uses a four tier classification for foundry wastes based on a detailedcharacterization of foundry by-products. The Wisconsin preventive action limit standard (PALS)determines a benchmark, typically 10% or 20% of the drinking water standard, as the "not-to-exceed" target in ground water [5].

Among the North-East states, New York regulations specify sixteen items with pre-determinedBUDs [19] allowing beneficial use of specific materials for specific purposes without projectreview. These include specific application of such materials as compost, wood chips,

Hazard level:

Score:

High Negligible

High Moderate Low Negligible

12

newspaper/newsprint, glass, tire chips, concrete, asphalt, brick, various soils and ashes. Insituations where a particular proposed beneficial use is not specifically identified, generators andpotential users shall petition for a case-specific BUD. Particularly, the New York StateDepartment of Environmental Conservation has granted a number of BUD permits for the use ofspent foundry sand as an aggregate in the production of concrete, cement, asphalt, and flowablefill. Foundry slag has been granted BUDs for the use as road base/sub-base, railroad ballast,backfill and structural fill within building foundations. Both foundry sand and slag may be usedas daily covers and barriers at New York landfills.

New Jersey DEP has also approved several BUD projects for the beneficial uses of variousfoundry waste streams: spent foundry sand as a component in cement, asphalt and concreteproducts; baghouse dust as an additive in asphalt products and roadbed aggregate; slag as anaggregate component in asphalt products or as additive in concrete products; and mixed foundrywaste in roadbed fill and asphalt aggregate.

MA DEP has received an application for a BUD proposing the foundry waste use as a base in theconstruction of a paved parking lot at a recreational facility in Middleboro. However, a BUDpermit has not been granted because of high concentration of benzo-anthracenes and benzo (a)pyrene found in a composite foundry waste sample.

In Massachusetts, general policies have not yet been developed for foundry sand as a reusablematerial. Moreover, Massachusetts foundries have not found it economical to provide wasteinformation that would adequately fulfill the requirements of the BUD process. The latter isbecause the Massachusetts foundry industry is dominated by small foundries with smallquantities of residual material that are difficult to market, but cost of necessary testing is ratherprohibitive. Several institutional barriers to broader acceptance of foundry waste sand as abeneficially usable material are cited and explained [1] in terms of Massachusetts goals in thefollowing:

1) The wide variety of regulatory and test systems employed by states to manage industrialwastes present many inconsistencies.

a) Threshold levels of leachable metals and organic compounds in industrial wastes canvary by a factor of 30 or more.

b) Environmental differences between states such as soil type and climate often are reflectedin policy differences. However, similar broad policy goals -- namely, protection ofhuman health and short- and long-term environmental quality, should promote efforts tobring some level of uniformity.

2) No universally accepted practice exists to evaluate the hazard posed by beneficially usedfoundry waste. Decision science tools, such as total life cycle or risk analysis method, wouldmake the beneficial use approval process more comprehensive and capable of assessingoverall risks and benefits.

3) State agencies do not have coordinated regulations that achieve both short and long-termobjectives. A good example of a potentially beneficial coordinated policy would be between

13

the MA DEP and Massachusetts Highway Department to address utilization of foundry sandfor transportation material related applications.

4) In some cases the criteria used to determine the health and safety of recycled materials maybe more stringent (or may not exist) than for virgin materials or natural environmentalconditions.

5) Environmental regulations and policies are complex and difficult for the business communityto understand. This deters foundries from seeking beneficial use permits, especially amongsmall foundries with limited personnel.

Recently, the Commonwealth of Massachusetts has taken several actions to assist parties seekingregulatory acceptance of innovative technologies. Particularly, MA DEP has re-organized itsmanagement structure. One of the goals of the re-organization is to bring together programs thatwork on the same problems or sites into consolidated offices, breaking up the older structure oforganizing by the environmental medium regulated, or by enabling legislation. This might helpbeneficial use technologies gain regulatory acceptance more efficiently.

14

ANALYTICAL TECHNIQUES

The chemical analysis for the BUD application procedures is normally performed using the EPAapproved methods for analysis of solid wastes (SW 846). However, the equivalent standardmethods developed and approved by other consensus organizations, such as American Societyfor Testing and Materials (ASTM) or American Water Works Association (AWWA), may beapplied in some cases. EPA accepts the performance-based measurement system as a set ofprocesses wherein the data needs, mandates, or limitations are specified, and serve as criteria forselecting appropriate methods to meet those needs in a cost-effective manner.

Several analytical techniques and methods may be used to separate, identify and quantifycontaminant species contained in both virgin and spent foundry sands and binders used in thecasting process. Most of metallic components can be quantitatively detected by inductivelycoupled plasma (ICP) atomic emission and mass spectrometry. The EPA methods for organiccompound analysis typically involve routine analytical instrumentation which include gaschromatography (GC) interfaced with either mass spectrometer (MS) or flame ionizationdetector (FID). Another common method is pyrolysis interfaced with gas chromatography andmass spectrometry (Py-GC-MS).

Toxicity characteristic of solid waste leachates is determined by Toxicity CharacteristicLeaching Procedure (TCLP, Method 1311). Leaching potential of spent foundry sand can also betested by Synthetic Precipitation Leaching Procedure (SPLP, Method 1312), Multiple ExtractionProcedure (Method 1320), Column Leaching Lysimeter Tests and other sequential tests. Someolder data were accumulated using the Extraction Procedure (EP) Toxicity test (Method 1310A)that was then replaced by the TCLP (both latter tests are similar but direct comparison of resultsfrom them is not always possible). A few modifications included in TCLP relative to the EPToxicity test are the use of 0.7 �m filter, the extraction fluid determination step, and the choiceof two fluids depending on pH of the sample. The EP Toxicity and TCLP tests were designed toapproximate one set of disposal conditions that might occur when a material was codisposedwith municipal solid waste.

Currently, TCLP is most commonly used to evaluate the leaching potential of wastes, and toestimate likely risks to ground water. TCLP requires determination of the 25 organic chemicalsin addition to the eight metals and six pesticides on the existing list of constituents regulatedunder RCRA. The TCLP is meant to model the leaching behavior of a material disposed in anactively decomposing municipal solid waste landfill in which carboxylic acids are formed frommicrobial processes. It is not meant to model the leaching behavior of materials disposed in otherscenarios. If disposal conditions are different from the municipal landfill conditions, another testmay better predict the actual leaching of a waste and provide better numerical estimates ofleaching.

Alternative analytical leaching methods, such as the SPLP are becoming increasingly popularwith regulatory agencies. The SPLP, Method 1312, was developed to simulate leaching underacid rain condition, similar to an industrial waste monofill. The procedure is similar to the TCLP,however the amount of acidity used in the test is significantly less. Furthermore, an aqueoussolution of nitric/sulfuric acid mixture is used in the SPLP as an extraction fluid, unlike a morerigorous buffered acetic acid in the TCLP. States have begun to allow the use of the SPLP for

15

characterization of waste in BUD applications. This procedure may soon become the preferredapproach, since it simulates more closely the field conditions for beneficial use.

Besides the acidic toxicity tests, the ASTM D3987-85 shake water leach test is a useful indicatorin considering the potential environmental impact of foundry sand waste and its beneficial usepractices. Moreover, a total analysis may precede the leach/extraction testing. If a total analysisof the waste demonstrates that individual analytes are present at such low concentrations that theappropriate toxicity levels could not be exceeded, the leaching tests need not be run. Routinetotal analysis at the first instance is the most common current practice in Massachusetts.

LEACHING PROCEDURES (TCLP AND SPLP)

The TCLP is the test required to determine whether a solid or multiphasic waste is a toxicitycharacteristic hazardous waste under RCRA regulations. TCLP estimates the leachability ofmetals, volatile and semi-volatile organic compounds, and pesticides under a defined set oflaboratory conditions. TCLP was developed to simulate the leaching of constituents into groundwater under conditions found in municipal solid waste (MSW) landfills. The TCLP does notsimulate the release of contaminants to non-ground water pathways or conditions which are notcharacteristic of MSW disposal sites.

In the TCLP, solid samples are extracted with an acetate buffer solution. The extraction fluidemployed is a function of the alkalinity of the solid phase of the waste. A liquid-to-solid ratio of20:1 by weight is used for an extraction period of 18 ± 2 hours. After extraction, the solids arefiltered through a 0.6 to 0.8 µm filter from the liquid extract, and analyses are conducted on theleachate to determine the constituent concentrations. If the extract contains any of the specifiedconstituents at a concentration equal to or greater than the respective regulatory limit (see Tables1 and 2, Toxicity Limits), then the waste is considered hazardous under the toxicitycharacteristic.

Method performance studies have been performed to determine the effect of variousperturbations on specific elements in the TCLP protocol. Ruggedness testing determines thesensitivity of small procedural variations which might be expected to occur during routinelaboratory application. None of the parameters had a significant effect on the results of theruggedness test.

Many TCLP precision (reproducibility) studies have been performed, and have shown that ingeneral the precision of the TCLP is comparable to or exceeds that of the EP Toxicity test, andthat method precision is adequate. One of the more significant contributions to poor precisionappears to be related to sample homogeneity, inter-laboratory variation (due to the nature ofwaste materials), and the inability of the laboratory to obtain a representative subsample of 100grams.

The results of a study of semi-volatile organic compounds, in Table 6 [17], showed excellentprecision, with greater than 90 percent of the results exhibiting relative standard deviations(RSD) less than 25%. Over 85% of all individual compounds in the multi-laboratory study fell inthe RSD range of 20-120%. It was determined that the high acetate content of the extraction fluiddid not present problems (i.e., column degradation of the gas chromatograph) for the analytical

16

conditions used. However, in some instances, the acetate matrix causes the lab to report elevatedresults.

A special extractor vessel, the zero-headspace extractor (ZHE) is used when testing for volatileanalytes. The ZHE allows for liquid/solid separation, extraction, and final extract filtrationwithin the device without opening the vessel and effectively precludes headspace.

Eleven laboratories participated in a collaborative study of the use of the ZHE with two wastetypes which were fortified with a mixture of volatile organic compounds (VOC). The results ofthe study are shown in Table 7 [17]. Precision results for VOC tend to occur over a considerablerange. However, the range and mean RSD compared very closely to the same collaborative studydone for metals. Blackburn and Show [20] concluded that at the 95% level of significance: 1)recoveries among laboratories were statistically similar, 2) recoveries did not vary significantlybetween the two sample types, and 3) each laboratory showed the same pattern of recovery foreach of the two samples.

EPA Method 1312, the SPLP is an agitated extraction method used to evaluate the potential forleaching metals into ground and surface waters. This method provides a more realisticassessment of metal mobility under actual field conditions, and therefore, may be oftenpreferable in waste characterization for BUD applications. However, the SPLP test may not beused for discriminating hazardous from non-hazardous waste under RCRA regulations. For thelatter purpose, the TCLP is the only approved method.

The SPLP extraction fluid is intended to simulate precipitation. For the eastern part of the USA(east of the Mississippi River), the fluid is slightly more acidic at pH 4.20 reflecting the airpollution impacts of heavy industrialization and coal utilization. A pH of 5.00 is used west of theMississippi. When the leachability of VOC or cyanide is being evaluated, reagent water is usedas the extraction fluid. The procedure requires particle size reduction to less than 9.5 mm, and aswith the TCLP, extraction for volatile constituents is performed in a zero-headspace extractor.

The SPLP is a method of choice when evaluating fate and transport of metals in a properlyengineered waste land disposal facility from which municipal solid waste is excluded. Othersituations may dictate the selection of a different leaching procedure.

METHODS FOR DETERMINATION OF METALS

EPA standard methods specify procedures for sample preparation techniques, samplingapproaches, and accurate quantitative analysis within specified concentration ranges. Theseprocedures are significantly different for organic and inorganic constituents. Table 8 lists theanalytical methods approved by EPA for sample preparation and determination of metalliccontaminants. Included are methods for the analysis of environmental samples (such as drinkingor ground water samples): both the EPA methods [21] and ASTM methods [22], and for theanalysis of solid waste leachate samples [17].

Determining concentrations of most of the metals can be achieved by inductively coupled plasmaatomic emission (EPA 200.7, EPA 6010, ASTM C1111-98 methods) or mass spectrometry (EPA200.8, EPA 6020, ASTM D5673-96 methods). Also, highly suitable for most of metals but less

17

expensive technique is atomic absorption spectrometry (EPA 200.9, EPA 7000 series, ASTM3919-99, ASTM4691-96 methods). Table 9 represents the analytical techniques used for theanalysis of metallic contaminants in drinking water and their detection limits as specified by MADEP [15].

Inductively coupled plasma – atomic emission spectrometry (ICP-AES) determines traceelements, including metals, in solution. All matrices, including ground water, TCLP and EPToxicity extracts, and solid wastes, require digestion prior to analysis. Samples must besolubilized or totally digested using appropriate sample preparation methods (e.g., EPA 3005-3060 methods). The ICP-AES is characterized by simultaneous, or rapid sequential,multielemental determination of elements. Detection limits, sensitivity, and optimum ranges ofthe metals vary with the matrices and model of analyzer. Use of this technique should berestricted to spectroscopists who are knowledgeable in the correction of spectral, chemical, andphysical interferences.

Inductively coupled plasma – mass spectrometry (ICP-MS) is applicable to the determination ofsub-µg/l concentrations of a large number (over 60) of elements in water samples and in wasteextracts or digests. Acid digestion prior to analysis is required for ground water and solid wastesas with the ICP-AES technique. Detection limits in simple matrices are generally below 0.1 µg/l,except for the less sensitive elements (e.g., Se and As) that may be 1.0 µg/l or higher. Thegreatest disadvantage of ICP-MS is isobaric elemental interferences. Mathematical correction forinterfering isotopic ions can minimize these interferences. An appropriate internal standard isrequired for each analyte determined by ICP-MS. In general ICP-MS exhibits superior sensitivitythan other techniques for most elements.

Flame atomic absorption spectrometry (Fl-AAS) direct aspiration determinations are normallycompleted as single element analyses and are relatively free of interelement spectralinterferences. Either a nitrous-oxide/acetylene or air/acetylene flame is used as an energy sourcefor dissociating the aspirated sample. In the analysis of some elements, the temperature or typeof flame used is critical. If the proper flame and analytical conditions are not used, chemical andionization interferences can occur. Fl-AAS and ICP-AES have comparable detection limits(within a factor of 4), except that ICP-AES exhibits greater sensitivity for refractories (Al, Ba,etc.).

Graphite furnace atomic absorption spectrometry (GF-AAS) uses an electrically heated graphitefurnace for sample atomization. In a furnace, the processes of dissolution, drying, decompositionof sample, and formation of atoms may be allowed to occur over a much longer time period thanin a flame or ICP, and at controlled temperatures. This allows an experienced analyst to removeunwanted matrix components by using temperature programming and/or matrix modifiers. Themajor advantage of this technique is that it affords very low detection limits, in general, lowerthan those in ICP-AES or Fl-AAS. Because this technique is so sensitive, interferences can be aproblem for complex matrices.

For arsenic and selenium, the hydride generation atomic absorption technique may be utilized toreduce and separate these two elements selectively from a sample digestate. Selective reductionof mercury is used in cold-vapor atomic absorption technique. These procedures are sensitive butsubjected to interferences from oxidizing agents and volatile compounds.

18

METHODS FOR ORGANIC COMPOUND ANALYSIS

The most commonly used technique for determination of organic constituents is the capillary gaschromatography with mass spectrometric detection (GC-MS). With this technique, EPAestablished two different methods for detection of volatile organic compounds (Method 8260)and for detection of semi- volatile organic compounds (Method 8270). These methods appear tohave the scope of analytes which may be present in residues of spent foundry sand. For somespecific compounds, other methods could be also useful. Method 8151, capillary gaschromatography with an electron capture detector may be applied for determining certainchlorinated acidic compounds and pentachlorphenols in aqueous, soil and waste matrices.Method 8082, capillary gas chromatography with electron capture detectors or electrolyticconductivity detectors is used to determine the concentrations of polychlorinated biphenyls(PCB) in extracts from solid and aqueous matrices. All relevant analytical methods for organiccompound detection are summarized in Table 10.

Method 8270 is used to determine the concentration of semi-volatile organic compounds inextracts prepared from various types of matrices such as solid waste, soils and ground water.This method can be used to quantitate most neutral, acidic and basic organic compounds that aresoluble in methylene chloride and capable of being eluted without derivatization. The estimatedquantitation limit of the method for determining an individual semi-volatile compound isapproximately 10 µg/l for ground water samples. Some of these organic compounds may befound in spent foundry sand.

Method 8260 is used to determine volatile organic compounds in a variety of solid wastematrices. This method is applicable to nearly all types of samples, including ground and surfacewater, waste solvents, soils, and sediments. Method 8260 can be used to quantitate most volatileorganic compounds that have boiling points below 200°C (low molecular weight halogenatedhydrocarbons, aromatics, ketones, nitriles, acetates, acrylates, ethers, and sulfides). Thequantitation limits of Method 8260 for individual compounds are instrument dependent anddependent on the choice of sample preparation/introduction method. Using standard quadrapoleinstrumentation and the purge-and-trap technique, limits should be approximately 0.5 mg/kg(wet weight) for wastes, and 5 µg/l for ground water. Lower limits may be achieved using an iontrap mass spectrometer or other instrumentation of improved design.

Method 8250 (the packed column version of Method 8270) was tested by 15 laboratories usingorganic-free reagent water, drinking water, surface water, and industrial waste water spiked at sixconcentrations over the range 5-1300 µg/l. Single operator accuracy and precision, and methodaccuracy were found to be directly related to the concentration of the analyte and essentiallyindependent of the sample matrix.

Chromatograms from calibration standards analyzed with Day 0 and Day 7 samples werecompared to detect possible deterioration of GC performance. These recoveries (using Method3510 extraction) range from 70 to 108%. The method is applicable to concentration techniquesfor preparing the extract for the appropriate determinative methods (see Table 10).

Several EPA methods were designed exclusively for analysis of drinking water [23]. Theseinclude Method 524.2 for detection of volatile organics, Method 525 for detection of extractable

19

semi-volatile organics, and Methods 508 and 508A for detection of polychlorinated biphenyls(PCB). EPA Methods 624, 625, and 608 were correspondingly allocated for determination ofvolatile, semi-volatile organic contaminants, and PCBs in surface water and wastewater.

STATISTICAL TREATMENT

To establish and analyze chemical characteristics for a wide spectrum of foundry sand wastesthat shows a high degree of random variation, statistical protocols must be used. The statisticalanalysis play a critical role in the interpretation of results and in regulatory determinations madewith regard to beneficial use applications. Statistical inference obtained from an array of datarequires systematic techniques that provide unbiased, accurate, and reproducible results. Theseresults require interpretation in accordance with the objective for which the raw data wasobtained. Different interpretations may be reached from the same data set if different parametersare used for evaluation. Consistent techniques of categorizing and testing data can be establishedonly on the statistical basis. In deciding which statistical test is appropriate, one needs toconsider the theoretical properties of the test and the characteristics of the data.

Statistical tests are used as a means of examining and comparing highly variable values of thespent sand leaching potential. It is important to be able to determine whether or not there is astatistically significant difference from an average level for each parameter and constituent. Inmaking this comparison, the analyst must apply a statistical procedure to make a determinationwhether there is statistically significant change. Such a variation can be a result of samplingerror, analysis error, or natural variation. The total expected error is usually considered in thepropagation of errors treatment. It is usually done by determining the summation of the variancesof all the measurements made in the process.

Almost all statistical procedures are based on the assumption that samples are independent andselected at random, and therefore reflect the true range of natural variability. Replicate samplesare not considered to be statistically independent measurements. Several statistical parameterssuch as simple maxima, means, medians, and relative standard deviations can be used to providean overview of the randomly scattered data. However in chemical analysis of spent foundry sand,the data scatter is so large that the relative standard deviations are often greater than therespective mean values, and therefore, the normality of data sets is violated.

The factors more appropriate for large multivariate data sets are measures of the central tendencyand the variance. These measures include the mean, median and mode; the upper confidencelevel for normally distributed data and the use of non-parametric statistics for data that is notnormally distributed (i.e., the Wilcoxon test), and the use of quartiles. For the purpose ofevaluating solid wastes, the confidence interval of 80% on normally-distributed data sets hasbeen selected. For non-normal data sets, a variety of transformations (e.g., square root,logarithmic, arcsine square root, and etc.) can be performed to stabilize the variances, improvethe normality of data distribution, and obtain the confidence intervals. If either trans formation isapplied, all subsequent statistical evaluations are performed at the transformed scale. The 80%upper confidence limit is then compared with the appropriate regulatory threshold. If the upperlimit is less than the regulatory value the chemical contaminant is not considered to be present inthe waste at a hazardous level; otherwise the opposite conclusion is drawn.

20

CHARACTERIZATION OF VIRGIN AND SPENT FOUNDRY SAND

PHYSICAL CHARACTERISTICS OF SPENT SAND

Spent foundry sands have been found suitable for various beneficial use applications. For sanduse in construction applications, its fineness and compactability (grain size distribution) must beconsidered. Its physical characteristics have been characterized as having good strengthproperties and a relatively low hydraulic conductivity. The latter quality assures that the materialis not freely draining after compaction into highway embankments [11]. Bulk specific gravity,moisture content, and grain size distribution are the most useful characteristics of beneficiallyused sand. Large foreign objects (metallic entrapments, etc.) are typically screened out beforeutilizing foundry sand waste.

The grain size distribution of spent casting sands is usually uniform, with all of the particlespassing the 600 µm sieve; more than 50 percent of the particles passing the 300 µm sieve; andnearly all of the particles retained at the 150 µm sieve. The finest content passing the 200 µmsieve constitutes up to 20% of waste foundry sand. The uniform size of spent casting sandprovides good flowability. The material properties of five samples of foundry sands and areference sample of siliceous river-run sand are given in Table 11 and the particle sizedistribution is shown in Fig. 6 [12]. Distribution of the grain sizes influences many properties ofthe material. Most notable are the effects upon permeability and surface fineness, both associatedwith the strength properties.

Figure 6. Grain size distribution of foundry sands

A – Siliceous river-run sandB – Thermally reclaimed sandC – Mechanically reclaimed sandD – Spent clay-bonded sandE – Spent clay-bonded sand

21

The material characteristics of spent foundry sand are similar to that of fine silica sand, but differin a few aspects. Nearly all types of spent casting sands fall in the particle range between 0.1 and0.6 mm. Because of a very thin band in grain sizes, waste foundry sands are blended with acoarse crushed limestone for flowable fill applications. Sand B in Fig. 6 was thermally reclaimedafter casting to burn off the excess polymer bonding agents [12]. Sand C is the same material asB, except the bonding agents were not removed, but sand was screened to separate any cores.Sands D and E are spent bentonite-bonded sands with different absorption percent, both screenedof excess residuals. The bentonite was more fully fused in the sample D, and it was coarser thansand E. The uniformity of these byproducts suggests their utility in manufactured productsprocesses.

Green (clay-bonded) sand, commonly used in metalcasting, is composed of uniform high-qualityquartz sand (85-95%), cohesive bentonite clay (4-10%) as the binder, a volatile carbonaceoussea-coal additive (2-10%) to improve casting surface finish, iron oxide (0.5-5%) for strength, andwater (2-5%). Spent chemically bonded casting sand has a very low moisture absorption. Clay-bonded sands have higher absorption with 5 to 10 percent clay minerals. The clay remaining inspent sand after the casting cycle is partially sintered and not present as raw bentonite. For greensand processes, reclaiming the sand may be as simple as capturing it once the metal casting isremoved and returning it directly to the beginning of the process. Other green sand processesmay require mechanical lump reduction to separate the sand into reusable grains.

Precise quantification of physical properties of the residual sand material is important for themarketability of the spent foundry sand. The sand wastes from the green sand systems aretypically characterized by specific gravity (2.39-2.69 g/cm3), permeability (10-3 - 10-6 cm/sec),and moisture content (0.1-10 %). Molding sands are refractory to temperatures approaching1700°C, although phase transformations involving volume changes may occur at lowertemperatures.

The American Society for Testing and Materials (ASTM) has developed a 1997 nationalspecification for use of by-products in structural fills (E1861-97). A successful use of wastefoundry sand in flowable fill was reported by Tikalsky et al. [12] and Stern [13]. Naik et al. [14]reported on utilization of used foundry sand in concrete. When foundry sands are used as apartial replacement for fine aggregates in the production of concrete the combined fineaggregates should have the gradation recommended by the ASTM C33 standard. Partridge et al.[11] conducted geotechnical investigations to determine the engineering properties of spentfoundry sand for highway embankment construction. Results from the latter study arerepresented in Table 12.

Asphalt production may benefit from the sub-angular shape of foundry waste sand if used as amix ingredient. Current regulations in many states are discouraging the use of rounded riverbottom aggregate and are instead using more angular, manufactured aggregates. Foundry sandcould potentially meet the needs of this market. A successful decade-long project using wastesand in asphalt production has been demonstrated in Canada [6]. Some concern of a possiblenegative impact on air emissions resulting from the processing of waste sand containing organicshas been addressed. It has been proven that these materials add very little to the air emission ofan asphalt plant and that these additions may be adequately captured by the facilities’ existing airpollution control equipment.

22

In order to establish technical specifications and performance standards for various engineeredbeneficial uses of spent foundry sands and slags, an industry-sponsored consortium for marketdevelopment, the Foundry Industry Recycling Starts Today (FIRST) has been recently founded.The FIRST web site [9] compiles a comprehensive list of foundry by-product utilization projects.The FIR