steel bladder pump, with a PTFE bladder and
quarters. The length of the section varied, depend-
PTFE-lined sample tubing, after it had been used
ing upon the thickness of the casing wall, so that
to sample VOCs. The pump was cleaned by
the final surface area of all the sections would be
steam cleaning the outside of the pump and tub-
constant.
ing, and then circulating (15 gal.) a warm (120F
In addition, three polymeric materials (tub-
or 49C) aqueous detergent (1%) solution
ings)--polyvinylidene fluoride (PVDF), low-
through the system followed by (5 gal.) ambient
density polyethylene (LDPE), and a copolymer of
temperature rinse water. In each test, the pump
vinylidene fluoride and hexafluoropropylene
was contaminated by pumping at least five sam-
[P(VDF-HFP)]--were used in the pesticide stud-
pling pump/tubing assembly volumes of con-
ies. The internal diameter of the tubings was 0.64
taminated water. Detectable levels of TCE (12
cm and the lengths were ~2 cm. Because the wall
g/L) were found in the final rinse water when
thickness varied slightly among the tubings, the
the pump had been used to sample the two wells
actual lengths varied slightly so the total surface
with the highest TCE concentrations (1600 g/L
area would be constant for all three tubing materi-
and 2215 g/L, respectively), but not when the
als.
pump had been used to sample wells with lower
Special care was taken to eliminate contamina-
concentrations.
tion from grease or oil in the cutting process. The
Parker (1995) concluded that decontamination
cut pieces were washed in a 2% solution of Liqui-
studies that evaluate the various decontamina-
Nox detergent for 30 minutes with intermittent
tion procedures need to be conducted, and that
stirring, rinsed with several volumes of deionized
these studies should consider the type of contam-
water, and then air dried on paper towels.
inants, concentration of contaminants, materials
The test pieces were exposed to aqueous test
being decontaminated, and contact times.
solutions containing either a mixture of volatile
organic compounds (VOCs) plus one nitroaromat-
ic compound (called the VOC studies), or a mix-
PURPOSE OF THIS STUDY
ture of pesticides (called the pesticide studies).
In these studies we will evaluate the ability of
Three sorption/desorption protocols were used
various decontamination methods to remove two
in most of these experiments: 10 minutes/10 min-
types of organic contaminants: volatile organic
utes, 24 hours/10 minutes, and 24 hours/24
contaminants (VOCs), which are relatively hy-
hours. The 10-minute/10-minute time was select-
drophilic, and pesticides, which are relatively hy-
ed to represent the contact time a bailer and water
drophobic. We will use one nonpermeable sur-
sample might have in a deep well (i.e., a longer
face (stainless steel) and several polymers. We
contact time). The 24-hour contact time was
will evaluate the efficacy of several aqueous
selected to represent the time that a pump left in
cleaning methods, solvent rinsing, and the use of
the well overnight would have to sorb analytes.
air drying with and without heat. Contact (sorp-
The 10-minute desorption time (i.e., 24 hours/10
tion) time and desorption time will be considered
minutes) was selected to simulate the time that
in these studies.
materials in a cleaned pump might contact a sam-
ple while it is pumped to the surface, using slow-
flow pumping. The 24-hour desorption time (i.e.,
MATERIALS AND METHODS
24 hours/24 hours) was selected to simulate the
For these studies, the decontamination effi-
time that a cleaned pump would have to contami-
ciency was determined by measuring the amount
nate a well if it was left in the well overnight.
that was desorbed from contaminated test pieces
For all our experiments, there were three repli-
into fresh deionized (DI) water following the
cate samples for each material, time, and treat-
cleaning treatment. We considered a decontami-
ment. New materials were used throughout these
nation method effective if we were unable to de-
experiments, and stainless steel forceps were used
tect any residual analytes following treatment
to handle the test pieces.
(i.e., concentrations were below the Method De-
tection Limit [MDL]).
VOC STUDIES
Three types of 5-cm- (2-in.-) diameter well cas-
ings were used in these studies: schedule 40 PVC,
General information
PTFE, and 304 stainless steel. Sections were cut to
The VOC test solutions contained approximately
varying lengths (1.1 to 1.4 cm) and then cut into
2 mg/L of three volatile organic compounds
4
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