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*) Surface Changes in Well Casing PipeExposed to High Concentrations ofOrganics in Aqueous SolutionSusan Taylor and Louise Parker March 1990

IDTICELECTEJUN 0 5 1990

IO NTI~ A

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F'c!:-I ~oe ~ P~ i ees

Special Report 90-7 1

U.S. Army Corpsof EngineersCold Regions Research &Engineering Laboratory

Surface Changes in Well Casing PipeExposed to High Concentrations ofOrganics in Aqueous SolutionSusan Taylor and Louise Parker March 1990

CDTIC

Accesion For

NTIS CRA&IDTIC TAB1

UnlannoricLd

Justificat4 (

Sy

DistributionAvaeiabi!ty t-cde-s

Prepared forU.S. ARMY TOXIC AND HAZARDOUS MATERIALS AGENCYCETHA-TE-CR-89115

Approved for public release; distribution is unlimited. 90 06 04 159

PREFACE

This report was prepared by Susan Taylor, Research Scientist, Geological Sciences Branch,Resarch Division, and Louise Parker, Research Scientist, Applied Research Branch, ExperimentalEngineering Division, U.S. Army Cold Regions Research and Engineering Laboratory. This projectwas funded by the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA), AberdeenProving Ground, Maryland (R-90 Multi-Analytical Services), Martin H. Stutz, Project Manager.

The authors thank Bob Forest and Dennis Lambert for cutting the casing materials. Thanks also goto Marianne Walsh who made many helpful comments on the draft manuscript and Dr. ThomasJenkins and Alan Hewitt for reviewing the final draft.

The contents of this report are not to be used for advertising or for commercial purposes. Citationof brand names does not constitute an official endorsement or approval of such commercial products.

CONTENTS

Preface .................................................................................................................................... iiiIntroduction ............................................................................................................................ IM aterials and methods ............................................................................................................ IResults and discussion ........................................................................................................... 3

Visual observations ......................................................................................................... 3SEM observations ........................................................................................................... 3

Conclusions ............................................................................................................................ 4Literature cited ........................................................................................................................ 4Abstract ................................................................................................................................... 15

ILLUSTRATIONS

FigureI. Low m agnification photographs of the four casing surfaces (8x) ................................. 52. SEM m icrograph of untreated PVC (2000x) .................................................................. 63. M icrographs of PVC soaked in the test solution (2000x) ............................................... 64. M icrographs of PVC soaked in well water (2000x) ....................................................... 75. M icrograph of untreated PTFE (200x) ........................................................................... 76. M icrographs of PTFE soaked in the test solution (200x) .............................................. 87. M icrographs of PTFE soaked in well water (200x) ........................................................ 98. M icrograph of untreated SS316 (200x) .......................................................................... 109. M icrographs of SS316 soaked in the test solution (200x) ............................................ 10

10. M icrographs of SS3 16 soaked in well water (200x) ...................................................... I II1. M icrograph of untreated SS304 (200x) .......................................................................... II12. M icrographs of SS304 soaked in the test solution (200x) ............................................ 1213. M icrographs of SS304 soaked in well water (200x) ...................................................... 1314. M icrographs of SS304 (2000x) ..................................................................................... 14

iii

Surface Changes in Well Casing Pipe Exposed to

High Concentrations of Organics in Aqueous Solution

SUSAN TAYLOR AND LOUISE PARKER

INTRODUCTION recommended for approximately half of the predomi-nantly organic substances listed, whereas fluorinated

Prior to 1985 polyvinyl chloride (PVC)was the most resins (FEP, TFE and PFA) are listed as unaffected bycommonly used well casing material for ground water 99% of the compounds. Some of the tests were conduct-monitoring. In 1985 the EPA published the initial draft ed using thin-walled bottles, and the results may notof the Resource Conservation andRecoverv Act(RCRA) apply to the rigid pipe used for ground water monitor-Ground-Water Monitoring Technical Enforcement ing. It is therefore difficult to use this table withoutGuidance Document. This document stated that "steel knowledge of how the tests were conducted, and this iscasings deteriorated in corrosive environments; PVC proprietary information.deteriorated in contact with ketones, esters and aro- Our study was undertaken to assess how the surfacematic hydrocarbons..." and recommended that either structural characteristics of four common well casingTeflon or stainless steel 316 be used for constructing materials-PVC, Teflon (polytetrafluoroethylene,wells. The EPA's concerns were that PVC and the cas- PTFE), stainless steel 304 (SS304) and stainless steeling materials commonly used for ground water moni- 316 (SS3i6)-are affected by exposure to high concen-toring either altered the ground water samples or did not trations of organic chemicals in ground water. To checkmeet the long-term structural characteristics required of for surface structural changes, pieces of casing were ex-RCRA monitoring wells. amined with an SEM after being immersed for I week,

While we have found many studies that have ex- I month and 6 months in an aqueous solution contain-amined the effects of well casing materials on ground ingtetrachloroethylene, toluene,p-dichlorobenzene andwater samples (Miller 1982, Curran and Tomson 1983, o-dichlorobenzene. These substances are EPA priorityHoughton and Berger 1984, Reynolds and Gillham pollutants because they often occur in ground water.1985. Barcelona and Helfrich 1986, Parker and Jenkins1986, Sykes et al. 1986, Jones and Miller 1988, Hewitt1989, Parker and Jenkins, in press), little information MATERIALS AND METHODSexists on the long-term stability of casing materialsexposed to extreme environmental conditions such as The PVCand stainlesssteel pipe were obtained fromhigh salinity or pH, or to either pure or high concentra- Johnson Well Screen and the PTFE pipe from MIP Inc.tions of organic solvents. The casings are manufactured to meet certain specifica-

Schmidt (1987) studied the long-term stability of tions (PVC: ASTM F480-8 1, SS304 and SS316: ASTMPVC in contact with gasoline. Sections of rigid, 2-inch- A3 121; Teflon is not made to an ASTM specification,diameter, Type I PVC screen (0.006 slot size) were but themanufacturerscheck its density, tensile strengthplaced directly in several different grades of gasoline and elongation*). Only casings manufactured specifi-and allowed to sit for 6 months. After these pieces of cally for ground water monitoring were tested in thisscreen were removed from the gasoline, they were pho- study. Small sections, approximately 1.0 cm by 1.0 cm.tographed usingascanningelectronmicroscope(SEM) were cut from each type of casing. The exact dimen-to document any changes in the size of the slot opening sions varied with the thickness of the well casing so thator any other changes. Schmidt did not find any changes the surface areas for the four casing materials would beand concluded that Schedule 40, rigid, Type I PVC can the same. The dimensions of the sample pieces werebe used when monitoring for the occurrence of gaso- limited by the size of the SEM's sample port.lines in the watertable, a conclusion that agreed with his To remove any contamination derived from thefield experience.

The Nalge Company lists the chemical resistance, * Personal communication with the Nalge Company.compiled from in-house tests, of a number of plastics 'I Personal communication with Johnson Well Screen.including PVC and fluorinated resins.* PVC is not ** Personal communication with MIP Inc.

cutting, all the samples were placed in a solution of de- tative elemental analyses to be made of points or areasionized water and detergent and sonicated for 10 min- of the surface. However, only those elements heavierutes. They were then rinsed with deionized water until than sodium can bedetected, so the plastics could not bethere were no suds and sonicated again in fresh deion- analyzed using this technique.ized water for 20 minutes. After being rinsed with fresh For each of the four well casing materials, samplesdeionized water, the samples were drained and allowed that had been exposed to the test solution for I week, Ito air dry on paper towels. This cleaning procedure month and 6 months were examined with the SEM andworked well; no dirt or soap was seen on the samples compared with the control samples. Pieces of casingwhen examined with the SEM. that had not been placed in any aqueous solution were

The aqueous test solution was prepared by dissolv- also examined and are assumed to be representative ofingp-dichlorobenzene, o-dichlorobenzene, toluene and the initial structure of the casing's surface. Only the in-tetrachloroethylene in a sample of ground water ob- side wall of the casing was examined.tained from a local deep well. The concentrations were SS316 and PTFE were photographed at 35x and17.3, 33.5, 138 and 35.0 mg/L, respectively, approxi- 200x magnification, and PVC and SS304 at 200x andmately one fourth the solubility of each compound in 2000xmagnification.Thesemagnificationshighlightedwater. The high concentrations of the organics in a sin- the surface structure of each sample, and since all sam-gle aqueous solution provide a "worst case" scenario, pies were photographed at 200x magnification. it al-short of chemical attack by a pool of undiluted organic lowed all the samples to be compared.solvent, a situation rarely encountered in ground water Originally only two of the six samples of each typemonitoring, of well casing were examined with the SEM. However.

Aside from being EPA priority pollutants, the or- becauseanumberofchangeswereobservedinthePVCganics were selected because, according to the Nalge and SS304 samples and we could not tell whether theTable, all these solvents degrade PVC in their pure changes were caused by the organic solution or by inter-form. Tetrachlorethylene was selected because of its sample variation, all six of the test, control and un-apparent preferential rate of sorption (Miller 1982). Its treated SS304 and PVC samples were examined. As ithighly planarstructure might allow tetrachloroethylene was still unclear whether changes seen on the SS304to more easily penetrate the pores of a polymer (Parker surface were due to the organics, two untreated SS304and Jenkins 1986). The two isomers ofdichlorobenzene samples were photographed and then placed in a testand toluene were selected to cover a range in polarity solution to be reexamined and rephotographed after 6and molecular structure. months in the test solution. This method was not used

For each casing material, six pieces were placed into initially because the plastics need to be coated prior toeach oftwo4O-mL vials and filled with the aqueous test SEM examination and could not have been treated thesolution. No head space was left, and the vials were same way as the stainless steel samples.capped with a Teflon-lined plastic cap. Control sampleswere identical except that they were filled with the wellwater. The samples were stored at room temperature in RESULTS AND DISCUSSIONthe dark. Although no biocide was added to prevent bio-degradation of the test solution, bacteria were not ob- Visual observationsserved on any of the samples examined by SEM, and the Visual inspection of PVC casings showed them to besolutions remained clear, quite smooth except for fine grooves running parallel to

A Hitachi S500 scanning electron microscope was the casing's length. These linear features are the resultused toexaminethesamples.TheSEM waschosen over of the extrusion method used to manufacture the wellother microscopic techniques because of its wide range casing. The PTFE samples, like the PVC, have little sur-of magnifications and its good depth of field. A thin face relief, but unlike the PVC, the PTFE samples havelayer of gold and palladium was evaporated onto the apattemed surface (rough areas altemating with smoothPVC and PTFE casing surface to make the samples con- areas). Both stainless steel samples are characterized byductive. This thin film is needed to prevent thermal and a matt surface texture, but SS3 16 has more surface reliefradiation damage of the sample's surface and does not than the SS304 (Fig. i).significantly change the surface structure of the sample Since some of the stainless steel samples had rust(Goldstein et al. 1981). The two stainless steel samples, spots (1 of 12 SS316 samples and 2 of 12SS304 samplesbeing good conductors, did not need to be coated. An had one ormore spots), only samples that appeared to beacceleration voltage of 20 keV was used. free of defects, rusting, gouges or scratches were se-

In addition to images of the sample's surface, a lected to be studied with the SEM. However, despiteKevex energy dispersive spectrometer allowed quali- this preliminary screening, a dark, smooth, patchy coat-

2

ing was observed on some of the SS304 samples studied or units separated by troughs (Fig. 11) and this structurewith the SEM. Energy dispersive X-ray analysis showed is less distinct on samples exposed to the test solutionthecoatingtobealuminum.Thiscoatingprobablycame (Fig. 12) as compared to those exposed to well waterfrom the aluminum plug placed inside the well casing (Fig. 13). However, micrographs taken at random placeswhen the samples were cut on the lathe. Casing pieces on each of the six duplicate samples of the untreated, 6-having aluminum coatings were replaced by other sam- month test and 6-month control samples show that thepies for study. patterned surface is not unique to untreated or control

samples and occurs on two of the six test samples. Sim-SEM observations ilarly the less-structured features can be seen on one of

PVC the untreated samples and on one of the control samples.

Examination of the untreated PVC casings with the To resolve what effect the test solution has on SS304,we began an additional experiment. In this test, twoSEM shows them to have smooth, slightly lined sur- samples were examined and photographed prior to ex-

faces marred by an even distribution of irregularly plesere examinedprioths

shaped holes (Fig. 2). These holes are approximately 5reexamined after6 monthsrn along their longest dimension. The surface between of contact with the test solution using a magnification oflama~ngheir~ngstdmens~n'hesrfacbeteen 35x, 200x and 2000x. Neither sample showed any

the holes had dimples that appeared to have the same

geometry as the larger holes. No change in surface change (Fig. 14).The observations presented above indicate that the

structure was observed between the I week, I month, 6 s hrfaceratispcsfnte andatthmonth test samples (Fig. 3), the untreated samples (Fig. surface characteristics ofPVC, PTFE, SS316 and SS304moanthe ontest samples (Fig. ) T ntrea t ales do not change when exposed to a concentrated organic2) and the control samples (Fig. 4). The bright particles aqueous solution. Because of the lack of distinguishingin the holes and on the surface in Figure 4 are particu- features at high magnification, PTFE and SS316 were

examined at a lower magnification; consequently, small

PTFE changes that might have occurred may not have been

Untreated PTFE casings have smooth areas inter- seen. It was particularly difficult to assess whether oruteyates of pulled-out fibrous strands par- not changes had occurred on PTFE. However, no obvi-rupted by patches of pue Fibrous surace par- ous changes (swelling, pitting etc.) were seen.

alleling the length ot'the tube (Fig. 5). The surface char- Our work is preliminary, as the variability, both cas-acteristics of the PTFE varied from sample to sample, ingtocasingandmanufacturer tomanufacturer, wasnot

with large changes in both the size and the number of fi-

brous patches. Test samples (Fig. 6) could not be dis- addressed. This potential variability needs to be taken

tinguished from control samples (Fig. 7); however, the into account when using our results for predictive

lack of regular features makes it difficult to identify any purposes.

alterations which might have been caused by immersionin the test solution. CONCLUSIONS

SS316 Small sections of well casing were examined with anSS316 casings have a rough surface, with finger-like SEM to determine how they were affected by exposure

protrusions sticking out from the surface (Fig. 8). The to an aqueous solution containing high concentrationssurface area of these samples should be greaterthan that of organics thought to degrade PVC and chlorinatedof the SS304, and Hewitt (1989) found that it rusted compounds known to be sorbed by both PVC andmore rapidly than SS304. Magnifications higher than Tefloncasings.ThesurfacestructureofthePVC, SS304200x showed no detail in the areas between the protru- and SS316 was apparently unaffected by the test solu-sions, so lower magnifications were used to character- tion. PTFE showed no obvious changes, like pitting orize the surface. At a magnifications of 35x and 200x, no swelling, but its surface variability and the lack of dis-changes were seen between the I week, I month and 6 tinguishing features at high magnification make it dif-month test samples (Fig. 9) and the control samples ficult to tell if the surface has changed. Our study, al-(Fig. 10). though preliminary, suggests that the surface structure

of all these casing materials is not changed when ex-SS304 posed to high concentrations of organics in aqueous so-

SS304 showed some change among the untreated, lution. In this respect PVC, Teflon, SS304 and SS316test and control samples. Specific surface changes ap- were found to be suitable materials for monitoring evenpeared to be related to long-term residence in the test high concentrations of aqueous organics. Clearly expo-solution, since the untreated (unwetted) samples gener- sure to pure organic solvents is another issue.ally had a patterned surface composed of discrete cells

3

LITERATURE CITEDMiller, G.D. (1982) Uptake and release of lead.

Barcelona, M.J. and J. A. Helfrich (1986) Well con- chromium, and trace level volatile organics exposed tostruction and purging effects on ground-watersamples. synthetic well casings. Proceedings of the SecondEnvironumlental Science and Teclniohnl,, 20:1179-1184. National Sywnpositunm on Aquifei" Restoration and

Curran, C.M. and M.B. Tomson (1983) Leaching of Ground Water Monitoring, May 26-28. p. 236-245.trace organics into water from five common plastics. Parker, L.V. and T.F. Jenkins (in prep.) EvaluationofGroundwater Monitoring Review, 3: 68-71 four well casing materials for monitoring selected trace-Goldstein, J.I., D.E. Newbury, P. Echlin, D.C. Joy, level organics in ground water. USA Cold Regions Re-C. Fiori and E. Lifshin (1981) Scanning Electron Mi- setirch and Engineering Labc itory. Special Report.croscolpy and X-Ray Microanalysis. New York: Pie- Parker, L.V. and T.F. Jen.Ans (1986) Suitability ofnum Press. polyvinyl chloride well casings for monitoring muni-Hewitt, A.D. (1989) Influence of well casing composi- tions in ground water. Grond WaterMottitoring Review.tion on trace metals in ground water. USA Cold Regions 6(3): 92-98.Research and Engineering Laboratory, Special Report Reynolds, G.W. and R.W. Gillham (1985) Absorp-89-9. tion of halogenated organic compounds by polymerHoughton, R.L. and M.E. Berger (1984) Effects of materials commonly used in ground water monitors.well-casing composition and sampling method on ap- Proceedings qf the Second Canadian/American Con-parent quality of ground water. Proceedings of the ference on Hychogeology. p. 125-132.Fourth National Synipositin on Aquifer Restoration Schmidt, G.W. (1987) Tile use of PVC casing andand Ground Water Monitoring. p. 203-213. screen in the presence of gasolines on the ground waterJones, J.N. and G.D. Miller (1988) Adsorption of se- table. Gromund Water Monitoring Review, 7: 94-95.lected organic contaminants onto possible well casing Sykes, A.L., R.A. McAllister, and J.B. Homolyamaterials. InGrottnd-watercontamination:Fieldmeti- (1986) Sorption of organics by monitoring well con-ods (A.G. Collins and A.I. Johnson, Ed.), American structionnmaterials.GroittndWaterMitoringReiew,.Society for Testing and Materials, ASTM STP 963, p. 6(4): 44-47.185-198.

4

a. Teflon. h. PVC.

er Vc.SS36. d.S30i

Fi~~~~vire~~ 1.Lwmgiiato htgah o hfu aig iiae 8)

5 -

Fi~iei-e 2.SEM inicrogqrapli of untreated PVC (2000X). a. Soakelfrr I week.

Figure 3. Micrographs of PVC soakedI ini the test solt)ionI~l(2000x).

h. SoakedIfor Imonth. c. Soaked for 6 mnth~s.

Figure 3 (cont'd). Micro graphs of PVC soaked in the test solutlo,, (2000X).

6

Ira

u,~ %ItI

AA

. tokdfn I ek .Suefn inh

,17

4 0, 4

. Soaked frr I moteekqr5.IMcoraho unittII. E(20)

FFigure 4 (otd. Micrographs of P C soaked in well Itvar 200X)

(200)

S7

* 14

a. ~ ~ ~ ~ ~ c Soakedfo 6a Imeeonths. Jr onh

Fig'ure 6. Micrograp~hs of PTFE soaked in the test s~olution (200x).

8

4- A

a. Soaked )rn I week. h. Soakrdfmin imonth.

c. Soaked for 6 nioithis.

Figur e 7. Micro graphs of PTFE soaked int ire/i iracter (200x).

9

Fi-ie 8. Micrograph f nttreated SS316 (200x), a. Soaked for I week.

Figttre 9. Micrographs qtf SS316 soaked in the test solution(200x).

41:

1). Soaked fio" month. c. Soaked fir 6 nilonths.

Figure 9 (cont'd). Micrographs of SS316 soaked int the test solution (200X).

10

'IIO

I I I-.I.I

a. Soaked for I week. b. Soaked for I month.

Figure 10. Micrographs of SS316 soaked in well water (200x).

c. Soaked for 6 months. Figure Hi. Micrograph of untreated SS304 (200x).

Figure /0 (cont'd). Micrographs ofSS3J6 soaked in well water(200x).

a. Soaked for I week. b. Soaked for 1 month.

c. Soaked for 6 months.

Figure 12. MicrograPhs of SS304 soaked in the test solution (200~x).

12

a. Soaked for I week. b. Soaked for I monthi.

c. Soaked for 6 months.Figure 13. Micrographs of SS304 soaked in well water (200x).

13

a. Untreated SS304. b. Same sample after being sealed in (lie test solution for 6months,.

Figure 14. Micrographs of SS304 (2000x)

'4

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Surface Changes in Well Casing Pipe Exposed to High Concentrations ofOrganics in Aqueous Solution

6. AUTHORS

Susan Taylor and Louise Parker

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

U.S. Army Cold Regions Research and Engineering Laboratory72 Lyme Road Special Report 90-7Hanover, New Hampshire 03755-1290

9. SPONSORINGMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORINGAGENCY REPORT NUMBER

U.S. Army Toxic and Hazardous Materials AgencyAberdeen Proving Ground, Maryland CETHA-TE-CR-89115

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13. ABSTRACT (Maximum 200 words)

This preliminary study was undertaken to assess how the surface structural characteristics of four common well casingmaterials--polyvinyl chloride (PVC), Teflon (polytetrafluoroethylene, PTFE), stainless steel 304 (SS304) and stainlesssteel 316 (SS3 16)--are affected by exposure to an aqueous solution containing tetrachloroethylene, toluene, p-dichloro-benzene and o-dichlorobenzene in concentrations near their solubility. Casing samples that had been exposed to a testsolution for 1 week, I month and 6 months were examined with a scanning electron microscope (SEM) and comparedwith control samples placed in well water for an equivalent time period. Pieces of casing that had not been placed in anyaqueous solution were also examined and are assumed to be representative of the initial structure of the casing's surface.These organics are of concern at hazardous waste sites, where they often occur in ground water. The observations indicatethat the surface characteristics of PVC, SS316 and SS304 did not change when exposed to the organic aqueous solution.The surface variability and lack of distinguishing features at high magnification made it difficult to tell if the i TFE surfacehad changed. However, no obvious changes (swelling, pitting etc.) were seen,

14. SUBJECT TERMS 15. NUMBER OF PAGES19

Groundwatermonitoringi Organic chemicals 16. PRICE CODEHazardous waste Well casings

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