EPA/600/A-93/005
Comparison of Ground-Water Sampling Devices Based On National GrOUndwdtcr
Equilibration of Water Quality Indicator Parameters Sampling Symposium
Comparison of
Ground-Water Sampling Devices
Based On Equilibration of Water
Quality Indicator Parameters
by
Cynthia J. Paul and Robert W. Puls
ManTech Environmental Technology, Inc. R.S. U-S' Environmental Protection Agency, R.S.
Ken- Environmental Research Laboratory Kerr Environmental Research Laboratory
P.O. Box 1198 P.O. Box 1198
Ada, OK 74872 Ada, OK 74820
Cynthia J. Paul and Robert W. Puls Page 21
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National Groundwatcr
Comparison of Ground-Water Sampling Devices Based On
Equilibration of Water Quality Indicator Parameters
. Sampling Symposium
Abstract:
The sampling device selected when obtaining ground-
watersamples can have a significant impact on the
representativeness and reproducibility of the sample. This
study evaluated several different sampling devices (low
speed submersible pump, peristaltic pump, and bladder
pump) in two monitoring wells to obtain ground-water
samples based on the equilibration of water quality indicator
parameters. The indicator parameters were continuously
monitored during purging and sampling with all devices
and include: turbidity, specific conductance, pH, oxidation-
reduction potential, dissolved oxygen, and temperature.
Contaminant (chromium, trichlorethylene (TCE))
concentration levels were also measured for all devices.
The bladder pump produced the highest equilibrium
turbidity levels, although this effect may be compensated for
by careful control of the charge discharge cycles of the
pump controller. The peristaltic pump produced the highest
levels of dissolved oxygen, specific conductance and pH,
whereas the low speed submersible pump generated the
highest temperatures. There were no significant differences
in Cr concentrations among the various sampling devices.
TCE concentration values were generally in the order: low
speed submersible > bladder > peristaltic. The submersible
pump generates excess heat which might be expected to
impact concentrations of volatile organic compounds. The
peristaltic pump resulted in sample degassing adversely
impacting the sample quality. As this is a suction lift
device, its use is limited to shallow wells. Results of this
study indicate the low speed submersible pump produced the
least negative impacts in trying to obtain representative and
reproducible ground-water samples in these wells at this
site.
Introduction:
Proper sampling methods for obtaining accurate,
representative, and reproducible ground-water samples has
been atopic of considerable debate during the past several
years. Amyriad of reports, articles, guidance documents and
handbooks have been written addressing this problem (U.S.
EPA, 1982; NCASI, 1982; Claasen, 1982; Gillham et al.
1983; Barcelona et al. 1985; EPRI, 1985; U.S. EPA, 1986;
Barcelona et al. 1987; Nielsen, 1991; U.S. EPA, 199la;
U.S. EPA, 1991b). Factors such as complex chemical,
geological, physical, and biological processes make quality
sample collection extremely difficult (Puls and Powell,
1992). Puls and Powell (1992) also note that the best
sampling approach is one which creates as little disturbance
as possible at the sampling point, with minimum change in
the chemical properties of the sample. The method of
sample collection can significantly impact the quality of the
data obtained. Many examples exist of questionable
analytical data generated by haphazard sampling methods
(Barcelona, 1983). Nielsen and Yeates (1985) point out that
ground-water samples should be representative of water
within the aquifer, and Powell and Puls (1992) state the
necessity for ground-water samples to "...truly define the
aqueous geochemistry of the subsurface system at the point
of collection". Potential sources of sample alteration
include: the method and extent of well development and
purging; the choice of sampling device; and filtration,
preservation and sample handling (Barcelona, 1983;
Barcelona et al. 1984; Nielsen and Yeates, 1985; Kent and
Payne, 1988; Barcelona et al. 1988; Puls and Barcelona,
1989; Puls and Powell, 1992). While all of these factors can
significantly impact ground-water sample integrity, perhaps
the most crucial element of ground-water sample collection
is the sampling mechanism itself (Barcelona, 1983). Also of
particular importance is how wells are purged prior to
sample collection. Puls and Powell (1992) recommend the
use of low flow rates during both purging and sampling,
with placement of the sampling device intake at the desired
sampling point and minimal disturbance of the stagnant
water column above the screened interval. Excessive
sample turbidity may indicate disturbance of the sampling
zone. Puls and Barcelona (1989) and Puls et al (1991)
advocate monitoring of water quality indicator parameters
(turbidity, temperature, specific conductance, pH, oxidation-
reduction potential, and dissolved oxygen) while purging to
establish baseline conditions to initiate sampling, thus
providing a consistent basis for sample comparison. Puls
and Powell (1992) have shown specific conductance, pH,
and temperature to be the least sensitive of these indicator
parameters while contaminant concentration, dissolved
oxygen, redox and turbidity are most sensitive. Comparably
low flow rates were used in this study in an attempt to
diminish any effects caused by this variable. The purpose of
this study was to evaluate three distinctly different sampling
devices based on the equilibration of ground-water quality
indicator parameters.
Materials and Methods:
Ground-water samples were obtained from two
monitoring wells located on the U.S. Coast Guard Air
Support Center near Elizabeth City, NC. A chrome plating
shop on the base has discharged a mixture of chrome-
plating wastes into the soils and aquifer below the shop,
which is located 197 ft. (60 m) south of the Pasquotank
River. The site geology consists of Atlantic coastal plain
sediments composed of variable sequences of surficial
sands, silts and clays. Ground-water flow near the plating
shop is complicated by wind tides but is generally to the
north. Hydraulic conductivity is estimated to average about
Page 22
Cynthia J. Paul and Robert W. Puls
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Comparison of Ground-Water Sampling Devices Based On
National Groundwater
Sampling Symposium
xiuilibration of Water Quality Indicator Parameters
;0 ft/d (IS m/d) but may be somewhat lower in the region of
he waste plume. Ground water is about seven feet (2.J m)
>elow ground surface. Both wells are completed 15 feet
4.57 m) below ground surface with PVC casing and 5 foot
>creens (0.010-inch (0.025 cm) slot size). Three different
rypes of ground-water sampling devices were evaluated: a
low speed submersible pump, a bladder pump, and a
peristaltic pump (Table 1). An open-end Teflon® bailer was
used to collect samples for comparison of contaminant
concentrations only.
Ground-water quality indicator parameters were
continuously monitored during purging and sampling with
all devices. A multi-parameter instrument with a flow-
through cell was used to monitor temperature, pH, specific
conductance, dissolved oxygen, and oxidation-reduction
potential. Turbidity values, measured in nephelometric
turbidity units (NTUs), were also measured using a flow-
through cell. A diagram of the sampling set-up is shown in
Figure 1. Alkalinity values were determined in the field
using a portable colorimetric titration kit (Hach Co.).
Flow rates were kept comparably low (< 500 ml/min)
during purging and sampling to minimize turbidity and allow
for more rapid equilibration of other parameters as
recommended by Puls and Powell (1992). It should be noted
that the flow rate for the bladder pump was measured by ml/
pump cycle and converted to ml/min. That is, flow was
measured over time at the surface which is different (lower)
than the actual flow rate during an intake cycle within the well
screen. Also, the flow rate of the submersible pump while in
MW17 was increased from 250 ml/min to 940 ml/min after 99
min to observe effects on the ground-water indicator
parameters. The volume of water removed from the wells, as
well as purge time required to achieve stabilized indicator
values, varied with each device used (Table 2).
Samples were collected unfiltered after all indicator
parameters had stabilized. Atmospheric exposure was kept
to a minimum during sample collection through the use of
thick walled tubing and in-line monitoring. Samples were
collected for volatile organic compound (VOC) analysis in
40 ml glass vials, filled to overflowing and capped with zero
headspace using Teflon® septum caps. These samples were
immediately placed on ice for transportation to the
laboratory. Samples for metals analysis were collected in
polyethylene bottles and acidified to pH <2 with
concentrated ultra-pure HNOr
Metals analyses (e.g. Cr, Fe, A], Ca, etc.) were
performed in the laboratory using inductively coupled
plasma (ICP). A Technicon® Autoanalyzer was used for
major inorganic anions (e.g. Cl~, SO4", NO3~). TCE was
analyzed by headspace-gas chromalography (GC) with a
flame ionization detector (FID).
Results and Discussion:
Ground-Water Quality Indicator Parameters
Data shown in Table 3 represents the final equilibrated
values for specific conductance, turbidity, dissolved oxygen,
pH, redox, and temperature. Sampling device appeared to
have no significant impact on redox values. While
temperature is considered a fairly insensitive parameter, it
does have some significance in this study. Figures 2 and 3
show temperature values to be highest with the submersible
pump. This increased temperature appears to be due to the
operational design of the pump. The sharp peak in MW17
was generated when the flow rate of the submersible pump
was intentionally increased from 250 ml/min to 940 ml/min
to monitor the effect on the indicator parameters. Although
the temperature increased sharply initially, it quickly re-
equilibrated to lower values and within the range of the
peristaltic pump. This pump appears to generate more heat
when operating at the lower flow rates. The effect of this
increased temperature on contaminant concentration will be
discussed later.
Variation in dissolved oxygen levels are indicative of
the degree of aeration and degassing produced by the
various sampling devices. Figures 4 and 5 reveal the
peristaltic pump produced the highest levels of dissolved
oxygen (DO) in both wells. Peristaltic pumps subject the
water sample to strong negative pressure which causes
degassing (Nielsen and Yeates, 1985; Kent and Payne,
1988). The low speed submersible pump produced fairly low
DO values in MW16; however, the bladder pump generated
the lowest values in both wells. Bladder pumps minimize
aeration and gas stripping of the sample by allowing water
flow to only contact the bladder (Nielsen and Yeates, 1985),
resulting in lower dissolved oxygen values.
Equilibrated turbidity values are compared with levels
of Fe and Al in Table 4. There is a direct association
between high turbidity (solid particles) and increased levels
of Fe and Al. X-ray diffraction analysis and scanning
electron microscopy have identified the mobilized particles
as iron oxide and iron-coated kaolinite and feldspars.
Figures 6 and 7 show turbidity equilibrating rapidly to low
levels using the low speed submersible and peristaltic pumps.
Turbidity values with the bladder pump decreased slowly and
never reached acceptably low levels (< 10 NTUs) as
determined for this particular site. The equilibrated turbidity
values for MW16 and MW17 using the bladder pump were 42
and 15 NTUs, respectively. More careful adjustment of the
charge and discharge cycles of the bladder pump can result in
lower flow rates which in turn would probably result in lower
turbidity. Flow rate at the surface was averaged over several
cycles for the bladder pump. This is somewhat misleading for
evaluating turbidity since the intake velocity of the pump
within the screen is much faster, with water drawn in during
Cynthia J. Paul and Robert W. Pub
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National Groundwatgr
Comparison ol Ground-Water Sampling Devices Based On
Equilibration of Water Quality Indicator Parameters
. Sampling Symposium
one portion of the complete cycle. As a result, actual flow rate
into the bladder pump is much faster than the time-averaged
flow at the surface and elevated turbidity compared to the other
devices can be explained.
Specific conductance and pH were higher in both wells
with the peristaltic pump (Table 5). As previously
mentioned, peristaltic pumps exert a vacuum that can cause
degassing whereby CO2 evolution causes consumption of
hydrogen ions, resulting in increased pH values (Loux et al,
1990). Figures 8 through 11 show a definite correlation
between specific conductance and pH values.
Contaminant Concentrations
Table 6 shows contaminant concentrations for both
wells. As previously discussed, the sample temperature was
significantly higher with the low speed submersible pump.
There has been some concern that the increased temperature
generated by this pump could volatilize certain organic
contaminants, resulting in artificially low sample values.
Clearly, this was not demonstrated in this study, where the
VOC of interest was TCE (Henry's law constant 0.0099
atm3 • m/mol at 20°C (Roberts and Dandliker, 1983)). The
bailer recovered the lowest TCE values while the peristaltic
and bladder pumps were slightly higher. The low speed
submersible pump obtained the highest TCE values in both
wells; however, this may not be true for more volatile
compounds which have a higher Henry's law constant.
Further evaluation of this phenomenon with more volatile
compounds is suggested.
There was very little difference in chromium
concentrations among the various sampling devices. Even
in the more turbid samples, (bladder, bailer) no significant
differences were observed. Cr (VI) adsorbs very weakly to
mineral surfaces and at this particular site has been shown
to be only slightly retarded in dynamic column tests (Rr=
1.6 — 1.8, Puls et al, 1992) using the actual aquifer
material. With such low adsorption to solid surfaces,
variations in turbidity would not be expected to significantly
impact aqueous Cr concentration differences. If strongly
adsorbing contaminants were present in the samples, the
influence of turbidity differences could be important.
Conclusions:
Monitoring of ground-water quality indicator
parameters during well purging has been shown to be an
effective guide for obtaining representative and reproducible
ground-water samples. The sampling device selected can
affect these parameter values and time required for their
equilibration, and must therefore be chosen carefully. As
demonstrated in this study, disadvantages of the peristaltic
pump are excessive degassing of the water and its limitation
to shallow wells. A disadvantage of the bladder pump is
excessive turbidity. The only disadvantage of the low speed
submersible pump determined by this study appears to be
the increased heat generated, which might affect certain
volatile organic compounds. Even with this possibility,
however, it gave the highest recoveries for TCE of any of
the tested devices.
Disclaimer
Although the research described in this article has been
funded wholly or in part by the United States Environmental
Protection Agency, it has not been subjected to the Agency's
peer and administrative review and therefore may not
necessarily reflect the views of the Agency and no official
endorsement may be inferred.
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Cynthia J. Paul and Robert W. Puls
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Comparison of Ground-Water Sampling Devices Based On
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Sampling Symposium
Equilibration of Water Quality Indicator Parameters
Acknowledgements:.
The authors would like to thank Robert M, Powell
(ManTech Environmental Technology, Inc.) for his helpful
advice and editing assistance. We wish to acknowledge the
analytical support of Don A, Clark (U.S. EPA RSKERL)
and Steve A. Vandegrift (ManTech Environmental
Technology, Inc.).
Biographical Sketches:
Cynthia J. Paul is currently employed with ManTech
Environmental Technology, Inc. at the R.S. Kerr
Environmental Research Laboratory (RSKERL) in Ada,
Oklahoma. She received her bachelor's degree from East
Central University and is currently pursuing her master's
degree in Environmental Science at the University of
Oklahoma- She was employed by RSKERL, U.S. EPA for
three years before joining ManTech two years ago. Her
research interests include ground water sampling methods
and metal sorption-desorption reactions as related to
subsurface contaaminant fate and transport.
Robert W, Puls is currently employed at the R.S. Kerr
Environmental Research Laboratory, U.S. EPA, in the
Processes and Systems Research Division. He received a
bachelor's degree in soil science from the University of
Wisconsin-Madison and a master's degree in forest
resources from the University of Washington. He received
his pH.D. in soil and water science (minor in analytical
chemistry) from the University of Arizona, Following
completion of his doctorate he worked on the High Level
Nuclear Waste Repository Research Program (DOE)
investigating the fate and transport of radionuclides in
ground water. He has been employed at RSKERL since
1987. His recent publications have covered a range of
topics including ground water sampling for inorganics,
colloidal transport ir ground water, organic-metal-mineral
interactions, aquifer remediation, and metal and metalloid
sorption-desorption reactions governing subsurface
contaminant transport.
References:
Barcelona, M.J. 1983. Chemical Problems in Ground-
Water Monitoring Programs. Proceedings of the Third
National Symposium on Aquifer Restoration and Ground-
Water Monitoring. National Water Well Association,
Worthington, OH, pp 263-271.
Barcelona, M.J., J.A. Helfrich, E.E. Garske, and J.P. Gibb,
1984. A Laboratory Evaluation of Ground Water Sampling
Mechanisms. Ground Water Monitoring Review. V.4, no.2,
pp 32-41.
Barcelona, M.J., J.P. Gibb, J.A. Helfrich, and E.E. Garske.
1985. Practical Guide for Ground Water Sampling. EPA/
600/2-/85/104, 169pp.
Barcelona, M.J., J.F. Keeley, W. A. Pettyjohn, and A.
Wehrmann. 3987. Handbook: Ground Water. EPA/626/6-
87/016,212 pp.
Barcelona, M.J., J.A. Helfrich, and E.E. Garske. 1988.
Verification of Sampling Methods and Selection of
Materials for Ground-Water Contamination Studies.
Ground-Water Contamination: Field Methods. ASTM STP
963. A. G. Collins and A.I. Johnson, Eds., American
Society for Testing and Materials, Philadelphia, pp 221-
231.
Classen, J.C. 1982. Guidelines and Techniques for
Obtaining Water Samples that Accurately Represent the
Water Chemistry of an Aquifer. U.S. Geological Survey
Open File Report 982-1024, 49 pp.
EPRI. 1985. Field Measurement Methods for
Hydrogeologic Investigations: A Critical Review of the
Literature. Electric Power Research Institute. EA 4301, 241
pp.
Gillham, R.W., M.J.L. Robin, J.F. Barker, and J.A. Cherry.
1983. American Petroleum Institute. API Publication 4367,
206 pp.
Kent, R.T., and K.E. Payne. 1988. Sampling Groundwater
Monitoring Wells — Special Quality Assurance and Quality
Control Considerations. Principles of Environmental
Sampling. L.H. Keith, Ed., American Chemical Society,
Washington, D.C., pp 231-246.
Loux, NT., A.W. Garrison, and C.R. Chafm. 1990.
Acquisition and Analysis of Groundwater/Aquifer Samples:
Current Technology and the Trade Off Between Quality
Assurance and Practical Considerations. Intern. J. Environ.
Anal Chem.. Vol 38, pp 231-253.
Cynthia J, Paul and Robert W. Puls
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National Groundwatcr
Comparison of Ground-Water Sampling Devices Based On
Sampling Symposium
Equilibration of Water Qualirylndicator Parameters
Nielsen, D.M., and G.L. Yeates. 1985. A Comparison of
Sampling Mechanisms Available for Small-Diameter
Ground Water Monitoring Wells. Ground Water
Monitoring Review, v.5, no.2, pp 83-99.
Nielsen, D.M. (ed) 1991. Practical Handbook of Ground
Water Monitoring, Lewis Publishers, Chesea, Michigan,
717pp.
NCASI. 1982. A Guide to Ground Water Sampling.
National Council of the Paper Industry for Air and Stream
Improvements. Tech. Bull. No. 362, 53 pp.
Panko, A.W., and P. Earth. 1988. Chemical Stability Prior
to Ground-Water Sampling: A Review of Current Well
Purging Methods. Ground-Water Contamination: Field
Methods. ASTM STP 963. A. G. Collins and A. I. Johnson,
Eds., American Society for Testing and Materials,
Philadelphia, pp 232-239.
Powell R.M., and R. W. Puls. 1992. Passive Sampling of
Ground Water Monitoring Wells Without Purging:
Multilevel Well Chemistry and Tracer Disappearance.
Journal of Contaminant Hydrology (in press).
Puls, R.W., and M.J. Barcelona. 1989. Ground Water
Sampling for Metals Analyses. EPA/540/4-89-001,6 pp.
Puls, R.W., R.M. Powell, D.A. Clark, and C.J. Paul. 1991.
Facilitated Transport of Inorganic Contaminants in Ground
Water: Part II. Colloidal Transport. EPA/600/M-91-040, 12
pp.
Puls, R.W., D. A. Clark, B. Bledsoe, R.M. Powell and C.J.
Paul. 1992. Metals in Ground Water: Sampling Artifacts
and Reproducibility. Hazardous Waste & Hazardous
Materials, v.9, no. 2, pp 149-162.
Puls, R.W., and R.M. Powell. 1992. Acquisition of
Representative Ground Water Quality Samples for Metals.
Ground Water Monitoring Review. Summer-92, pp 167-
176.
Roberts, P.V., and P.O. Dandliker. 1983. Mass Transfer of
Volatile Organic Contaminants from Aqueous Solution to
the Atmosphere During Surface Aeration. Environ. Sci.
Techno!., v.17, no. 8, pp 484-489.
U.S. EPA. 1982. Handbook for Sampling and Sample
Preservation of Water and Wastewater. EPA/600/4-82-029,
402 pp.
U.S. EPA. 1986. RCRA Ground-Water Monitoring
Technical Enforcement Guidance Document. OSWER
9950.1,207pp.
U.S. EPA. 1991a. Compendium of ERT Ground Water
Sampling Procedures. EPA/540/P-91-007, 63 pp.
U.S. EPA. 1991b. Handbook: Ground Water Volume II:
Methodology. EPA/625/6-90/016b, 141 pp.
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Comparison of Ground-Water Sampling Devices Based On
National Groundwater
Sampling Symposium
Equilibration ol Water Quality Indicator Parameters
TABLES
TABLE 1.
Ground-Water Sampling Devices Evaluated
Mechanism
Type
Commercial Brand
Positive Displacement Bladder inflation Geoiech® (Small
(bladder, Diameter Well Pump)
gas displacement)
Positive Displacement Submersible,
(mechanical) centrifugal
Suction-lift
Peristaltic
Grundfos® (Redi-Fto2)
Millipore® (Variable
Speed)
TABLE 2.
Purge Volume and Time To Reach Equilibration
(three successive readings ±10 %).
* One casing volume was 5.85 L
Device
MW16
Peristaltic
Bladder
Low Speed
Submersible
MW17
Peristaltic
Bladder
Low Speed
Submersible
Casing Volumes*
3.02
14.31
2.95
1.06
8.41
2.14
Time (min)
82
140
80
31
105
37
TABLE 3.
Equilibrated Ground-water Indicator Values
Cond
MW16
Peristaltic
Bladder
Submersible
MW17
Peristaltic
Bladder
Submersible
.760
.705
.706
,622
.547
.504
Turb
7.6
42
4.3
1.29
15
1.13
DO
0.13
0.02
0.03
1.90
0.02
0.30
pH
5.90
5.81
5.87
6.57
6.33
6.27
Redox
.320
.362
.331
.312
274
zn
Temp
26.28
25.68
32.14
25.73
25.25
2B.64'
Temperature for submersible in MW 17 is before pump rate was turned
up from 250 ml/min to 940 ml/mm. Final temperature was 25.94' C.
TABLE 4.
Comparison of Turbidity Values With Element
Concentrations
Turbidity (NTUs) Fe (mg/L)
MW16
Peristaltic 4.3
Bladder 42
Submersible 7.6
MW17
Peristaltic 1 .3
Bladder 15
Submersible 1.1
0.32
3,45
1.43
<0.10
1.48
0.27
Al (mg/L)
0.2?
2.23
0.55
<0.10
0.93
<0.10
Cynthia J Paul and Robert W. Puls
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Comparison of Ground-Water Sampling Devices Based On
L Sampling Symposium
Equilibration of Water Quality indicator Parameters
TABLE 5.
Comparison of Specific Conductance, pH, Alkalinity and
Calcium,
Cond pH Alk Ca
(mS/cm) (mg/L) (mg/L)
MW16
Peristaltic
Bladder
Submersible
MW17
Peristanic
Bladder
Submersible
,760 5,90 62 28.3
.705 5.81 51 25.0
.706 5,87 61 26.5
.622 6.57 137 27.5
.547 6.33 110 17.5
.504 6.27 106 16.6
TABLE 6.
Ground-Water Contaminant Concentrations (ppb).
Device
Peristaltic
Bladder
Submersible
Bailer
MW16Cr
220
200
240
220
MW16TCE
8945
9030
9445
8195
MW17Cr
1790
1780
1530
1550
MW17 TCE
212
224
378
190
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Comparison ol Ground-Water Sampling Devices Based On
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Equilibration of Water Quality Indicator Parameters
Sampling Symposium
FIGURES
Figure 1
Sampling
Device
Turbidimeter
Multiparameter
Monitoring
Device
Sample
Bottle
Figure 1: Sampling set-up for monitoring ground-water quality indicator parameters.
Cynthia J. Paul and Robert W. Puls
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Comparison of Ground-Water Sampling Devices Based On
Equilibration of Water Quality Indicator Parameters
Sampling Symposium
Figure 2
34
33
32
31
^ 30
(A
% 29
& 28
27
26
25
24
15 30
, Peristaltic
45 60
Time (min)
Bladder
75
. Submersible
90
105
Figure 2: Equilibration of temperature values during purging and sampling for MW16.
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Comparison of Ground-Water Sampling Devices Based On
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Equilibration of Water Quality Indicator Parameters
Figure 3
33
32
31
30
29
8. 28
Eb
Q
27
26
25
24
23
0 15 30 45
60 75
Time (min)
, Peristaltic t Bladder A Submersible
Note: Submersible pump rate was increased to 940 ml/min after 99 min.
Figure 3: Equilibration of temperature values during purging and sampling for MW17,
90 105 120
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Comparison of Ground-Water Sampling Devices Based On
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Figure 4
Equilibration of water Quality Indicator Parameters
0.35
0.3
0.25
0.2
0.15
0.1
0.05
15 30
, Peristaltic
45 60
Time (min)
Bladder _
75
Submersible
90
105
Figure 4: Equilibration of dissolved oxygen values during purging and sampling for MW16.
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Comparison of Ground-Water Sampling Devices Based On
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Equilibration of Water Quality Indicator Parameters
Sampling Symposium
Figure 5
0.6
0.5
0.4
0.3
0.2
0.1
0 15 30 45 60 75 90 105
Time (min)
, Peristaltic t Bladder A Submersible
Note: Submersible pump rate was increased to 940 ml/min after 99 min.
120
Figure 5: Equilibration of dissolved oxygen values during purging and sampling for MW17.
Cynthia J. Paul and Robert W. Puls
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Comparison of Ground-Water Sampling Devices Based On
Equilibration of Water Quality Indicator Parameters
Sampling Symposium
Figure 6
1500
- 1000
500
15
30
Peristaltic
45 60 75
Time (min)
_+_ Bladder (2Y)
105
. Submersible
120
Figure 6: Equilibration of turbidity levels during purging and sampling for MW16.
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Comparison of Ground-Water Sampling Devices Based On
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Sampling Symposium
Figure 7
90
80
70
60
50
40
30
20
10
0 15 30 45
60 75 90
Time (min)
m Peristaltic » Bladder (2Y) _A,_ Submersible
Note: Submersible pump rate was increased to 940 ml/min after 99 min.
300
250
200
150
100
50
105 120 135 150
Figure 7: Equilibration of turbidity levels during purging and sampling for MW17.
Cynthia J. Paul and Robert W. Puls
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Comparison of Ground-Water Sampling Devices Based On
Sampling Symposium
Figure 8
Equilibration of Water Quality Indicator Parameters
0.82
0.8
0.78
0.76
I 0.74
B
0.72
0.7
0.68
0.66
15 30
- Peristaltic
45 60
Time (min)
. Bladder _
75
Submersible
90
105
Figure 8: Equilibration of specific conductance during purging and sampling for MW16,
Page 36
Cynthia J. Paul and Robert W. Pub
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Comparison of Ground-Water Sampling Devices Based On
National Groundwater
Equilibration of Water Quality Indicator Parameters
Sampling Symposium
Figure 9
t/3
0.7
0.65
0.6
0.55
0.5
0.45
0 15 30 45 60 75 90 105 120
Time (min)
, PerisLaitic + Bladder A Submersible
Note: Submersible pump rate was increased to 9-SO ml/mm after 103 min.
Figure 9: Equilibration of specific conductance during purging and sampling for MW17.
Cynthia J, Paul and Robert W Pub
Page 37
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National Groundwater
Comparison o( Ground-Water Sampling Devices Based On
Sampling Symposium
Equilibration of Water Quality Indicator Parameters
Figure 10
6.1
6.05
5.95
5.9
5.85
5.8
5.75
15
30
Peristaltic
45 60
Time (min)
_ Bladder
75
Submersible
90
105
Figure 10: Equilibration of pH during purging and sampling for MW16.
Page 38
Cynthia J. Paul and Robert W. Puts
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Comparison ol Ground-Water Sampling Devices Based On
National Groundwater
Sampling Symposium
i
Equilibration of Water Quality Indicator Parameters
Figure 11
7
6.9
6.8
6.7
3 6.6
c
3
% 6.5
6.4
6.3
6.2
6.1
0
15
30 45
60 75
Time (min)
90 105
120
_f_ Peristaltic » Bladder _A_ Submersible
Note: Submersible pump rale was increased to 940 ml/min after 99 min.
Figure 11: Equilibration of pH during purging and sampling for MWI7.
Cynthia J. Paul and Robert W Puls
Page 39
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TECHNICAL REPORT DATA
{Please reatl Instructions on the reverte btfort complet'
EPA/600/A-93/005
4. TITLE AND SUBTITLE
Comparison of Ground-Water Sampling Devices Based on
Equilibration of Water Quality Indicator Parameters
S. REPORT OATS.
November 1992
6, PERFORMING ORGANIZATION CODE
7. AUTHORIS1
*Cynthia J. Paul - ManTech Environmental Technology, Inc.
**Robert W. Puls - RSKERL - U.S. Environmental Protection ,
8. PERFORMING ORGANIZATION REPORT NO.
ency
SJ*ERFORM1NG ORGANIZATION NAME AND ADDRESS
*ManTecn Environmental Tech., Inc.
R.S, Kerr Environmental Res.
P.O. Box 1198
Ada, OK 74820
Lab
**R.S. Kerr Env. Res
U.S.E.P.A. •
P.O. Box 1198
Ada, OK 74820,
to. PROGRAM ELEMENT NO,
Lab
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
13. TYPE OF REPORT AND PERIOD COVERED
Proceedings - Presentation
14. SPONSORING AGiNCY CODE
EPA/600/15
IS. SUPPLEMENTARY NOTES
In Proceedings: National Ground Water Sampling Symposium, Washington, DC,
November 30, 1992.
16. ABSTRACT
The sampling device selected when obtaining ground-water samples can have a
significant impact on the representativeness and reproducibility of the sample. This
study evaluated several different sampling devices (low speed submersible pump,
peristaltic pump, and bladder pump) in two monitoring wells to obtain ground-water
samples based on the equilibration of water quality indicator parameters. The indicator
parameters were continuously monitored during purging and sampling with all devices and
include: turbidity, specific conductance, pp, oxidation-reduction potential, dissolved
oxygen, and temperature. Contaminant (chromium, trichloroethylene (TCE) concentration
levels were also measured for all devices.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFlERS/OPEN ENDED TERMS
. COSATi Field, Group
Ground Water
Sampling Devices
Indicator Parameter
Water Quality
18. DISTRIBUTION STATEMENT
EP* Form 2220-1 (R«». 4-77} previous eo
19. SECURITY CLASS {ThisRtportl
21, NO. OP "AGES
18
20. SECURITY CLASS iT/iis ptigi"
22.
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