soil remediation methods

8/3/2019 Soil Remediation Methods

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ented at the:Twenty-Fifth DoD Explosives Safety SeminarAnaheim, California

SOIL REMEDIATION METHODS

C. James Dahn&Bernadette N. Reyes

Safety Consulting Engineers, Inc.Schaumburg, Illinois 60173

ABSTRACT

Remediationmethods, problems and optimization techniquesfor removal of propellants, explosives and pyrotechnics insoils are discussed. Process flow sheets to select best soilremediation methods plus an example of optimization arepresented. Many parameters which effect remediation arediscussed.

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1. REPORT DATE

AUG 19922. REPORT TYPE

3. DATES COVERED

00-00-1992 to 00-00-1992

4. TITLE AND SUBTITLE

Soil Remediation Methods

5a. CONTRACT NUMBER

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5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) 5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Safety Consulting Engineers, Inc,2131 Hammond

Dr,Schaumburg,IL,60173

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See also ADA260984, Volume I. Minutes of the Twenty-Fifth Explosives Safety Seminar Held in Anaheim,

CA on 18-20 August 1992.

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Standard Form 298 (Rev. 8-98)Prescribed by ANSI Std Z39-18


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INTRODUCTIONIn the past, waste propellants, explosives and pyrotechnics(PEP) would be burned in open pits or recovered if economicallyfeasible. In many manufacturing, loading and end use applications,residual and scrap was landfilled, placed in leaching ponds orseparation from water and other chemicals, or accidentally spilled

or deposited onto adjacent land. Within the last fifteen years,great emphasis was placed on removal of the hazardous PEP from thesoils and ground for safety (potential fires or explosions) andenvironmental protection (chemicals in water system). Eachpropellant, explosive or pyrotechnic in the soil presenteddifferent issues regarding soil remediation. Much emphasis todayis on incineration to destroy the PEPS at significant cost andeffort. In this paper, we review the issues related to soilremediation and present optimization methods.PROBTiEM DEFINITIONS

When it is known that propellants, explosives or pyrotechnicsare in the ground, various ways to remediate the situation arepossible as fol.lows:- Leave it and treat it- neutralize- decompose- Dig it out and- burn it- decompose it- recover it- Wash it out and- burn it- decompose it- recover it- Add dil.uent to soil to reduce hazardous concentrationsBefore any remediation is attempted, study is necessary toidentify the seriousness of hazard -and ways to remedy thesituation. A flow chart showing the remediation optimizationprocess is illustrated in Figure 1. Basically, the process steps

are as follows:1. Characterize and locate hazardous material and soil.2 . Remediation method study.3. Selection of best method.4 . Follow through.

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C l% lR A C TER I ZE HAZARDOUS MATERIALS(PROPELLANT, EXPLOSIVE AND/OR PYROTECHNICS)CHARACTERIZE SOIL, SURROUNDINGS AN DHAZARDOUS MATERIAL LOCATIONS1REMEDIATION STUDY

I 1IRECOVERY5GROUND REMOVALMETHODSSOIL SEPARATION IMETHODS 1IRECOVER PEP

NEUTRALIZATION

IN SITUDECOMPOSITIONOR DETONATION1.GROUNDREMOVAL

1SOILSEPARATIONi METHODS.1

.1I

c

DESTRUCTION O RNEUTRALIZATIONL METHODS

RESIDUEDISPOSALMETHODS ,I 1

Figure 1. Soil remediation optimization process.45


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The PEP characterization consists of identifying its physical,chemical, thermal, electrical and ignition sensitivity properties(see Figure 2). Since the hazardous material may be mixed withother explosives, propellants, or pyrotechnics and/or otherchemicals, PEP compatibility analysis is necessary to identify theeffects on sensitivity to initiation, &ability and quality.Soil sampling is usually necessary to determine location andcondition of the PEP in the ground. Core samplers can sometimesgive erroneous results especially if used in sandy soils, i.e., thecorexan plug up with sample sufficiently to permit soil to flow bythe core as it descends into the ground. If large pieces of PEPare present, soil coring may be very dangerous causing impact orfriction initiation of the PEP which may propagate into a fire orexplosion. Sometimes, if PEP distribution in the soil is very non-uniform, mapping from soil sampling can be very deceiving.Seismic analysis techniques can be used to identify PEPlocations provided that the seismic signals are not great enough to

initiate the PEP. If large areas &re contaminated with PEP,seismic methods may be more cost effective and will produce betterdefinitions of PEP locations. Some core sampling will still benecessary to identify PEP physical and chemical conditions. A l s o ,initiation sensitivity testing will be necessary to identifyeffects of changes of state, conditions and contamination ofignition sensitivity and quality. See Figure 3 .Soil remediation can be accomplished by destroying ordecomposing PEP in situ or by removing PEP from the soil andrecovering or destroying/decomposing it.In situ destruction or decomposition can be accomplished bydetonation, bulk decomposition or separation of components (e.g.,pyrotechnics). See Figure 4 . Methods to verify completion ofdestruction (e.g., soil borings and lab tests) may be costly, timeconsuming and dangerous. This in situ destruction approach may beineffective and too costly.Removing the PEP and soil from the ground by earth-movingequipment and/or water washout techniques will depend on itsconcentration and ignition sensitivity. Water washout techniques(like river dredging) could facilitate water separation of PEP fromsoil via hydroclones. A l so , the PEP may be much safer to handle if

in water-wet conditions rather than in dry conditions.Earth removal by earth-moving equipment may be very hazardousespecially if the PEP or mixture is very impact, friction orelectrostatic discharge ignition sensitive. Water washdown can beused during excavating to render the PEP-8Oil mixture safe tohandle. If high concentrations of PEP in soil (enough to causesoil to be detonable) are found, special ways to dilute or inertthe PEP may be necessary. If the PEP concentration is low enough,or is brought low enough by adding more soil, (concentration below

10% of detonable limits), the soil mixture can be destroyed by

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IDENTIFY NORMAL MATERIAL PROPERTIES__ I I I

1 J

I1 3

I ,THERMALI3. s ISENSITIVITY TO INITIATION AND PROPAGATIONIMPACT THERMAL ESD THERMAL -.___1 EFFECTS OF SOILS, CONTAMINANTS AND AGEON SENSITIVITY, STABILITY AND QUALITY OF PEPDENSITY,COATINGS,

.t.INITIATION SENSITIVITY,REACTIVITY ANDSTABILITY TESTING

4CHEMICAL ANDTHERMAL TESTINGACTIVATION ENERGYPH, ETC.

1 1ICHANGESN STATE 1AND CONDITION OF PEP1PEP DATA BANK

Figure 2. Characterization of prcpellants, explosives and pyrotechnics,(PEP) in soil. 47


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' ILOCATEPEP IN

I1 'trIDENTIFY IDENTIFY PEPCONDITION SOIL CONCENTRATIONOF PEP CONDITIONS PROFILES

-MICROSCOPIC AND T H E W T ANALYSIS

CONTAMINATI(AND WATERCONTENT I1SOIL

Figure 3. PEP-soil c h a r a c t e r i z a t i o n .48


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1 DESTRUCTION OR NEUTRALIZATION METHODS I

JN SITUOR DETONATIONDECOMPOSITION1 11t $.I VERIFICATION METHODS 7

I I1ERIODIC INSPECTIONSI

i EARTH-

I OR WASHINGOUT OF SOIL

REMOVAL

t -8METHOD FORSEPARATIONFROM SOIL

1CHEMICAL PHYSICAL 1 THERMAI, 1I MELT

SCREENINGSEPARATION

v J1 LEACH [COAGULENT;

JMETHOD FOR DESTRUCTION OR DECOMPOSIINCINEmTION, REACTOR 'ION1

RESIDUALS DISPOSITIONLANDFILL, ETC.

Figure 4 . Remediation study- destruction.49


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incineration (popular today) or decomposition (or neutralization)by chemical reaction.In either case, residual material must be disposed of properly(landfill if safe or mixing in other safe processes). For directincineration of the recovered PEP-soil, a massive amount ofresidual dirt must be disposed of somewhere and extensive tests maybe necessary to verify soil environmental safety.During stockpiling of removed PEP-soil, migration can occur ifthe PEP particle size and density is greatly different from thesoil, or the PEP is water soluble when rains occur.Once removed from the ground, the PEP-soil mix can beseparated prior to destruction by chemical, physical and thermalmeans. See Figure 4 .For PEP recovery process, the PEP also can be separated out bythe same means as listed above. See Figure 5.Some PEP can be separated from the soil using water solublesolvents (e.g., acetone, etc.) In this case, the solvent added tothe PEP-soil mixture causes the PEP to coagulate and clingtogether. Later, water separation via hydroclone or screening willseparate the soil from the PEP. Sobvent separation from watercould be accomplished by distillation at a later time.Dry screening can separate PEP from soil, as long as it is ofdifferent particle size from the soil. If PEP is dusty, dryscreening may not be safe and hydraulic (water) separation may bemore appropriate.Some PEPS can be heated to melting point and the soil can thenbe screened out from the liquid (e.g., TNT). Caution is necessaryto characterize PEP thermal stability as encountered in the soil sothat at large scale, runaway reaction can be prevented.Once separated, the PEP will need to be in a safe conditionfor handling. Diluents, solvents or inerting agents may be addedto assure safety and maintain quality or recovery.A purification process may be necessary to bring the PEP

quality up to standard levels. Recrystalization, solventpurification and chemical treatment may be necessary here.

Packaging and storage of purified PEP should be such that noadverse effect on safety, quality or storage aging will occur.TRADE-OFF STUDY

The next step in identifying the best remediation method is toconduct a trade-off analysis of important selection parameters.Some typical parameters to be considered (see Figure 6 ) are asfollows

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r

I S O I L SEPARATION PROCESS STUDY II

TU RE

1IiYDRAULICWATERSEPARATION,

THERMAL

SOLUBILITYIN WATE R

SHAPE OFPARTICLE

SEPARATION FROCESSINGI

11 RESIDUAL DISPOSITION METHOD S

Figu re 5. Remediat ion study - recov 'efy.51


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COST ANALYSIS-FUNCTIONALITY~

1 EFFECTIVENESS I1HUMAN FACTORS

.5.S A F ~ c14

REGULATION EFFECTS]-I TIMELINESS 1I+

LABOR LOAD EFFECTS

I DISPOSAL AND PEP DISPOSITION EFFORTS

METHODS

Figure 6. Trade-off study.52


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costFunctionality and simplicityCleanup effectivenessSafetyTime to completeProcess equipment availabilityEnvironmental impact and regulationsLabor availabilityDisposal or recovery ease

For each remediation method considered, estimates on cost,safety and availability of equipment and labor should be made.Preliminary hazards analysis should be conducted for each viablemethod to identify major safety restrictions prior to completion ofthe trade-off analysis. Thus, remediation methods which are toohazardous can be removed from consideration.The relative importance of each remediation method selectionparameter should be agreed upon early in the study. See Figure 7.A typical ranking multiplier for explosives in soil is shown in thefollowing table:

TYPICAL RANKING MULTIPLIERS

Next, each parameter is assigned a relative ranking scale toassist in evaluating its level for each remediation method. Someexamples are as follows:

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S ET U P S E L E C T I O N C R I T E R I A

~~ ~~

RANKING O F TRADE-OFF S T U D Y PARAblETERS

1! I D E N T I F Y SYSTEM INTERFACES~t

I DEVELOP MANAGEMENT AND SAFETY PLAN I

F i g u r e - 7 . S e l e c t i o n of b e s t m e t ho d.54


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ICOST

543

12

RANKING

< l o 31 41 51 61 7

IIDOLLARS

21

I

5 1 1 3 it1 61 7

4 I 1 4 ~ -11

rCLEANUP EFFECTIVENESSRANKING PERCENT

5 1004 92

3 902 701 20

3 I 1 5 II

54

32

EasyRelativelyComplexComplex

Very Complex

FUNCTIONALITYRANKING LEVEL

RANKING53

1

TIMEReadily

RelativelyAvailableNot Available

1

I6 Months1 2 Years

ExtremelyI Difficult

TIME TO COMPLETERANKING

3 I 1 Month 11

ISAFETY

RANKING DOLLARS LOSTPER YEAR

r LABOR AVAILABILITYRANKING LEVEL

3 I ReadilyRelativelyAvailable

ENVIRONMENTAL IMPACTRANKING I LEVEL

MinorMajor

5 5


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The next step is assigning ranking values of parameters foreach remediation method. An example far optimization is shown inTable 1 f o r nitrocellulose in soil which has slightly decomposed.The process options are shown in Figure 8 . This is an example andeach situation 'may require different parameter values and ranking.By multiplying each parameter ranking by the relative importancevalue and adding up all numerical values, an overall ranking foreach method is made. The method is selected based on the highestnumerical ranki.ng value.IMPLEHENTATION

Once the method of remediation has been chosen, managementplans for various options as shown in Figure 9, should beundertaken. Contingency plans should also be formulated, sinceexcavation could yield major changes in composition, concentration,contaminants and soil conditions which may require changedremediation methods.CONCLUSZONS AND RECOMMENDATIONS

Various soil remediation methods have been reviewed andselection criteria and methods were given for PEPs. An example oftrade-off analysis and optimization was given.Soil remediation is very complex and can be very dangerous

concentrations are high in the soil, potential detonations of PEPscould occur. Chemical, physical, thermal and hydraulic methods canbe used to separate PEPs from the soil once excavated. Excavationcan be done by mechanical o r water washout methods. Depending onthe type of PEP, destruction, decomposition or recovery ispossible.

especially with mixtures of PEPs end other chemicals. If

It is recommended that thorough study and trade-off analysesbe conducted on contaminated soils before remediation is attempted.A l s o , soil sampling is essential to be sure what is in thesoil and what its condition is.Detailed ignition sensitivity testing is essential to evaluatethe hazards presented by of PEP-soil remediation. A l s o , detailedhazard analyses must be done on the processes and theircontingencies prior to startup to assure safety. For recoverymethods, great care must be exercised to be sure that the PEP ispure, free from contaminants and has not aged sufficiently to losestability.


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TABLE 1

METHODIn situdestruction

Dig out andincinerateDig out anddecompose

Dig out separateand incinerateDig out andrecover

(10) (10) (7) (5) (2) (4) (5) (3)ENVIRON-EFFECTIVE- AVAILABILITY TIME TO MENTAL RANKINGCOST SAFETY FUNC TION NESS OF EQUIPMENT PEOPLE COMPLETE IMPACT TOTA LS

(3) (3) (1) (2) (3) (2) (3) (1) 10930 30 7 10 6 8 15 3(1) (4) (4) (4) (1) (2) (2) (2) 1 2 410 40 28 20 2 8 10 6(3) (2) (4) (2 ) (3) (2) (2 ) (2) 11830 20 28 10 6 8 10 6(1) (4) (2) (5) (1) (2) (1) (2) 11810 40 14 25 2 8 5 6(2) (2) (2) (4) (1) (2 ) (2) (3) 10320 20 14 20 2 8 10 9

Select # 2 , D i g Out and Incinerate


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S i t u a t i o i i : N i t r o c e l l u l o s e a n d c e l& l o s e~~ p r o d u c t s b u r n e d i n s o i

O P T I O N

\SOIL SAMPLING!I

*[ W A T E R WASH A N D ]REMOVE FROM S O I LBY M ECH AN I CAL Ml3ANSI R E C L A : M M E T H O D \1

L A R G E C H U N K SI N C I N E R A T O R - +S M A L L PIECES I N S O I L

WATER WASHED

W AT ER SO L U B L E S C n V E N TI N T O W A T E R

f C O N C E N T R A T E I O P T I O N

S O L U B L ES O L V E N T

*A N D U S E I N 1PROCESS

W ET S E P A R A T I O N ,IN I T R O C E L Z U L O S E 1I N C I N E R A T E D

I 11[ A S H TO 1 t1 LANDFILL^ .t-1 RE-DEPOSIT I N GROUND^

Figure 8 . T y p i c a l s o i l r e m e d i a k i o n process.58


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S O I L S N I P L I N G5-MAP OUT PEP LOCATIONS, DEPTHS, CONCENTRATIONS AND CONDITIONS

SELECT I3EST GROUND I?EMOVAL TECEiNIQUESA N D IMPLEMENT MATERIALS REMOVAL AND STORAGE

I -HAZARD ANALYSIS+-

I SEPARATE PEP FROM S O I L 11IECOVERYIr'

CHARACTER1ZE

P U R I F I C A T I O N

REMOVALFROM S I T E

Y

+,RESIDUE

soil remediation methods

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