United States
EnvironmerfUWPHitection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research
EPA/600/S2-89/012 Aug. 1989
Project Summary
Uranium Removal from Drinking
Water Using a Small Full-Scale
System
Robert T. Jelinek, Ronald L. Clemmer, and Frank J. Johns
Sometime during 1989, the U.S.
Environmental Protection Agency
(USEPA) will propose new drinking
water regulations for radionuclides.
The Agency has indicated that the
new proposed regulations will
contain a maximum contaminant level
(MCL) for uranium, and that the MCL
will probably fall somewhere between
10 and 60 picocuries per liter (pCi/L).
Of the approximately 60,000
community water systems in the
United States, between 100 and 200
will probably require treatment to
reduce uranium levels to a
concentration within this proposed
range.
The study summarized here
presents the background and history
of water quality, the basis for design,
and 9 months of actual operating
data for a small, full-scale, strong-
base ion exchange system that is
used to reduce levels of uranium to
less than the probable MCL range.
The system was efficient in removing
over 99 percent of the uranium
present in the raw water. The
presence of radon and radium, ion
exchange regeneration results, re-
generant wastewater disposal, and
gamma radiation profiling of the
system are discussed, together with
capital costs and operation and
maintenance (O&M) costs.
This Project Summary was
developed by EPA's Risk Reduction
Engineering Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully doc-
umented in a separate report of the
same title (See Project Report
ordering information at back).
Introduction
Uranium is a naturally occurring
radionuclide that can be found in both
groundwater and surface water. The
USEPA, Office of Drinking Water, is
proposing to establish an MCL for
uranium as required by the 1986
Amendments to the Safe Drinking Water
Act. Until now, there has not been an
MCL for uranium.
Groundwaters generally contain higher
concentrations of uranium than do
surface waters. The highest average
uranium concentrations in public ground-
water supplies are found in the Rocky
Mountain area. Studies have concluded
that 300,000 people in the contiguous 48
states are served by groundwater
drinking water supplies with uranium
concentration exceeding 10 pCi/L
uranium. As many as 2,000 of the 60,000
community drinking water supplies in the
United States will exceed this 10 pCi/L,
with between 25 and 650 community
drinking water supplies exceeding 20
pCi/L concentration. Most of these
supplies are groundwater sources serving
small populations in rural areas. In May
Valley, Colorado, an average of 64 pCi/L
uranium was found in the public ground-
water system, and concentrations greater
than 100 ng/L have been reported.
To provide the supporting treatment
technology information for the removal of
uranium from water, the USEPA Drinking
Water Research Division has conducted
several laboratory and pilot-plant studies
on the application of ion exchange
treatment. In one field survey, several
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small ion exchange systems were used
to remove uranium from 12 different
water sources in Colorado and New
Mexico. The data from this survey and
the other USEPA inhouse laboratory
studies have shown that anion exchange
resins have a large capacity for uranium
and that the technology is a viable
method for uranium removal.
One participant in the field survey, the
Jefferson County School District (Dis-
trict), operates numerous educational and
maintenance facilities in the foothills west
of Denver, Colorado. Many of these
facilities are served by groundwater, and
analyses of water samples from several
of their wells have indicated gross alpha
levels in the 30 to 150 pCi/L range. These
gross alpha levels come almost entirely
from uranium-234 (1)234) and uranium-
238 (U238).
The four full-scale ion exchange
systems the District has installed to
remove uranium from groundwater
sources are considered to be among the
first full-scale facilities used primarily for
the removal of uranium from drinking
water. The report summarized here
concerns the 9-month study of the full-
scale system at the Coal Creek Elemen-
tary School - a study to determine the
operating characteristics, removal
efficiencies, regeneration efficiency, and
costs.
The mining industry has used ion
exchange in the uranium recovery
process since the 1950's. The result of
studies to determine the feasibility of
removing uranium from drinking water by
ion exchange, along with historical
information regarding ion exchange use
in uranium processing, decisively indicate
that ion exchange is suitable for uranium
removal from drinking ^ater. The Coal
Creek Elementary School system study
results agree with thjs accepted thesis
and provide information on the practical
aspects of implementing ion exchange
for uranium treatment. One of the most
difficult questions concerning the
treatment scheme is, however, disposal
of the uranium-laden brine generated
during regeneration of the ion exchange
media. Possible options for disposal of
the concentrated waste uranium brine
and the disposal method implemented at
the Coal Creek Elementary School facility
are also discussed in the report.
System Design
Over the previous 10 years, analyses
of samples from several wells operated
by the District and other private wells in
the foothills west of Denver, Colorado,
have indicated levels of gross alpha
particle activity ranging from 30 to 150
pCi/L range. More recently, taking into
account the ratio of U234 to U23g being
greater than the normally assumed 1:1,
essentially all of the gross alpha activity
in the wells operated by the District was
found to be attributed by the uranium
isotopes. Data from two wells are
presented in Table 1.
Although none of the wells in the study
serve a community water system, the
District decided in 1981 to participate in a
2-year investigation conducted by
USEPA to remove uranium from one of
the wells (raw water uranium = 28 ng/L)
by the selective ion exchange process.
Based on the results of the USEPA
field investigation at one of the District
wells, the findings of other researchers,
and the results from a 3-week pilot-scale
column study, the District constructed a
full-scale ion exchange treatment facility
for removal of uranium in May 1986. Nine
months later, a second system was
installed at another well site within the
District, then, in the summer of 1987,
systems were constructed at two
additional locations. Since well yields of
19 to 38 LVmrn (5 to 10 gpm) are similar
at all four locations, the four treatment
systems are essentially equal in capacity.
Design criteria for the Coal Creek well
system are summarized in Table 2.
The treatment system consists of two,
spiral-wound cartridge prefilters in
parallel, a two-tank commercial water
softener system arranged in series, a
brine tank to batch regenerant, and
facilities to store and transfer spent
regenerant. The water softener tank
diameter and resin volume were based
on typical loading rates and media
depths for ion exchange systems. The
second ion exchange tank was provided
for redundancy. Also, because the time
for laboratory analysis of uranium is 2
weeks, the second tank provides an
added measure of safety with respect to
uranium breakthrough.
When uranium is present in a ground-
water supply, the radon and radium that
may be present are of greater concern,
from a health effects perspective, than is
the uranium. Before the design of the
treatment system was made final, the
extent of radon and radium present was
determined. Only small levels of radon
gas and insignificant amounts of radium
were detected in the District's well water.
At all of the District locations, however,
vented, treated-water storage tanks
provide sufficient detention time and
water-air interface to release the relatively
insoluble radon gas before the treated
water reaches the point-of-use. At the
Coal Creek location, testing indicated
radon gas was being removed in
storage tank. Thus, radon remc
processes were not originally provii
with uranium removal facilities. As par
another contract, however, a gram
activated carbon (GAC) column v
added to the uranium removal treatm
scheme in August 1987, downstream
the ion exchange columns.
Results
Uranium and Gross Alpha
Removal Efficiency
Uranium and gross alpha removal 6<
for the Coal Creek system are su
marized in Tables 3 and 4, respective
Review of the uranium concentrati
results indicates that greater than
percent of the uranium present in the r;
water was removed by the resin except
two cases when the uranium in tl
effluent of column No. 1 was slighl
elevated immediately after regeneration
Although gross alpha analysis is n
as accurate an analysis for alpha-emittir
radionuclides as is determining activi
concentration of individual contributors,
is an inexpensive screening technique
determine relative occurrence of alph,
emitting species. For the first 5 months <
the Coal Creek treatment evaluatioi
gross alpha analysis was used t
compare uranium concentration data, ft
indicated in Table 4, more than 8
percent of gross alpha was removed i
column No. 1.
Regeneration Efficiency
During the study period, the systen
was regenerated twice. A typica
regeneration sequence includes one be<
volume of backwash water, approximately
five bed volumes of saturated NaC
regenerated solution, and approximately
five bed volumes of slow rinse. Thus, the
total volume of wastewater generatec
during a regeneration for the Coal Greet
system is between 200 and 300 gallons
Characteristics of the mixed regeneratior
wastewater are shown in Table 5
Comparison of the mass of uranium
loaded on the first column over the
loading cycle before regeneration with
the mass of uranium in the regeneration
wastewater indicates that 97 and 66
percent of the uranium loaded was
removed during the first and second
regenerations, respectively. Other
research has shown that 100 percent
regeneration does not occur with a NaOl
regenerant solution.
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1/234/^238
A concern about compliance with
future uranium drinking water standards
expressed in units of activity (i.e., pCi/L)
occurs when samples are analyzed for
uranium by the fluoroscopic method and
U234 and Uass exist in a ratio other than
in equilibrium (1:1). The concentration of
uranium obtained from the fluoroscope
analysis (ug/L) is typically converted to
pCi/L by using the conversion factor of
0.677 pCi/ng, assuming U234 and U238
occur in a ratio of 1:1. For example, in
West Jefferson County, Colorado, it is
difficult to account for all of the gross
alpha activity present if this conversion
factor is used since no radium is present
in the sample.
Because of this concern, several
samples from the Coal Creek system
were analyzed using alpha spectroscopy
to determine the activity of each of the
uranium species. The average U234/U238
ratio ranged from approximately 2:3 to
3:7. When U234/U238 activity ratio and
uranium concentration in pg/L are known,
converting the mass results to activity
involves multiplying the concentration (in
ng/L) times the ratio and then times the
conversion factor of 0.677 pCi/pg.
Brine Disposal
Regeneration wastewater collected in
the holding tank at the Coal Creek
location is eventually hauled by truck to a
13,000-gallons-per-day (gpd) secondary
domestic wastewater treatment facility
operated by the District at another
location. The regeneration wastewater is
introduced to an equalization basin at the
headworks of the facility. Limited data
indicate that uranium is present in the
wastewater treatment plant effluent and
may concentrate in the sludge of the
wastewater treatment plant.
Gamma Radiation Profile
A health consideration for operators of
these ion exchange facilities is that of
potential elevated exposure to gamma
radiation. A gamma radiation profile was
developed for various locations in and
around the building that contains the Coal
Creek uranium removal system and for
individual unit treatment processes within
the building. The levels for September 2,
1987, ranged from a background reading
of 18 micro Roentgens per hour (nR/hr)
to a maximum of 44 pR/hr at the 2-ft level
on ion exchange column No. 1
A gamma radiation measurement in
R/hr can conservatively be assumed to
be equivalent to the radiation dose
equivalent in rems per hour (rem/hr).
With the use of conversion and based on
the results from the September 2, 1987,
profile, the exposure of an operator at the
Coal Creek uranium removal system
could be estimated to be 44 nR/hr (26
pR/hr above natural background) for 40
hours per week, 50 weeks per year, and
yet only have received a dose of 52
mrem/yr This dose level is minor, even
when compared to the recommended
maximum dose equivalent of 100 mrem/
year for the general public. 'Further, in a
small facility such as the Coal Creek
system, an operator is only in the build-
ing for short exposure times performing
routine inspection, sampling, or regen-
eration duties.
The objective of a second gamma
survey was to measure the gamma fields
produced by the uranium-loaded resin in
column No. 1 before regeneration.
Unfortunately, between the initial gamma
survey (September 2, 1987) and the
second survey (November 18, 1987), an
unshielded GAC column was installed to
remove the radon. The gamma radiation
from the radon decay products that
accumulated in the carbon system was
sufficiently strong to produce levels
higher than the uranium-loaded resins at
all points throughout the building where
the Coal Creek system is housed.
Costs
Capital costs, including equipment,
labor, and engineering, for the Coal
Creek uranium removal system were
approximately $8,900 in 1986. Although
these costs do not include the well, well
pump, pump controls, or the building
where the treatment facilities are housed,
they are indicative of costs that may be
incurred for a system of similar capacity.
O&M costs for the uranium removal
system 'only (including labor for
operation, regeneration, and sample
collection; sample analyses; pre-filter
replacement; resin replacement; regener-
ant salt; and electrical requirements) are
estimated to be $4.30 per 1,000 gallons
of water treated. Regenerant wastewater
disposal costs (including transportation
by tanker truck to the wastewater
treatment plant for disposal and analysis
of plant effluent and sludge for uranium)
are estimated to be $2.40 per 1,000
gallons of water treated. Thus, total O&M
costs are approximately $6.70 per 1,000
gallons. Because of the costs associated
with regenerant disposal and sophis-
ticated analyses, O&M costs for similar
uranium removal systems will be
significantly higher than costs for
conventional treatment.
Conclusions
Laboratory studies and pilot-plant tests
have shown that conventional anion
exchange resins in the chloride form are
capable of removing uranium from as
high as 23.8 mg/L in drinking water to 1
ng/L. Based on the initial 6 months of
operating history for a full-scale uranium
removal system, the following
conclusions have been identified:
1. Anion exchange treatment can
consistently remove uranium in well
water at a reasonable cost for small
systems.
2. Following both regenerations, it
appears that concentrated brine
remained in column No. 1 and was
displaced into the finishes water
during the subsequent loading cycle.
This resulted m elevated levels of
uranium in the treated water from the
ion exchange columns for a very short
period of time following regeneration.
3. Disposal of uranium-laden ion
exchange regenerant wastewater is
the most complex task involved in a
project for removal of uranium from
water.
4. Gamma radiation buildup in the
individual components of the uranium
removal system does not appear to be
a health concern. If treatment is
provided for radon removal, gamma
radiation may be a concern.
Recommendations
1. If uranium is found in a drinking water
supply, the water should also be
analyzed for radon and radium.
2. Following regeneration of an iron
exchange system, the length of the
subsequent rinse cycle should be
sufficient to remove all concentrated
regenerant brine from the system.
3. Federal and/or state regulatory
agencies should establish guidelines
for both treatment (regeneration
frequency) and disposal of wastes
generated from systems removing
radionuclides from drinking water.
4. Further research is needed about the
fate of the uranium-laden ion
exchange regenerant wastewater
discharged to a wastewater treatment
facility.
The full report was submitted in
fulfillment of Contract No. 7C7639 by
Richard P. Arber Associates, Inc., under
the sponsorship of the U.S.
Environmental Protection Agency.
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Table 1.
Radiochemical Water Quality Summary
Table 2.
Design Criteria
Parameter
Coal
Creek
We'.l
Marshdale
Well
Gross alpha activity (pd/L) 50 -60 80-170
Uranium concentration (mg/L) 0.024 0.047 - 0.09
U234/U238 activity ratio 3.6 2.4
Radium 226 activity (pCHL) 1.9 06-13
Radium 228 activity (pCi/L) - 1.0-1.8
Well Pump Capacity
Prefilters
Ion exchange vessels
Resin
Length of loading cycle
before regeneration
Brine tank
38 Limm (10 gpm)
2, operated in parallel, spiral wound. 1 micron
pore opening
2, operated in series, 0.4 m dia x 1.3 m high (16-m.
x 52-in. high)
Sybron tonac A642" (potable water grade), 85 L
(3-ft3; per vessel, 0.60-m (24-m.) depth
60,000 BV
0 60-m dia x 1.04-m high (24-in. dia x 41-in. high)
255 kg (560 Ib) NaCI storage capacity
Regenerant wastewater tank 19m3 (500 gal) volume
Table 3.
Uranium Concentration Removal Coal Creek Elementary School
Uranium Concentration (\ig,L)
Sample Volumes Gallons Bed Volumes After flaw After Column After Column
Date Treated Regeneration Water No. 1 No. 2
7-2-87*
7-2-87
9-2-87
1 0-6-87
11-18-87
2-3-88'
2-3-88
66,000
67,200
116,740
165,220
218,620
284,790
284,960
2940
0
2260
4420
6800
9750
0
56.6
92.2
45.2
39.7
47.0
110.0
75.0
<0.1
0.9
0.1
0 1
<0 1
0.3
320.0
0.6
9.2
0.1
0.1
0.1
0.2
0.4
Across Carbon
Column
-
-
-
0.1
0.0
0.0
5.0
% Removal Across
Column No 1
>99
>99
>99
>99
>99
>99
0
"The first ion exchange column was regenerated on these dates.
Table 4. Gross Alpha Removal Coal Creek Elementary School
Gross Alpha (pCi!L)
Sample
Date
4-15-87
4-15-87
7-2-87+
9-2-87
2-3-88T
Raw
Gallons Treated Water
DNA"
DNA
66,000
116,740
284,785
68.9
46.8
34.5
475
575
After
Column
No. 1
10+4
3+3
2+1
3 + 1
9+2
After % Removal
Column Across
No. 2 Column No 1
DNA
DNA
2±1
3 + 1
8+2
85
93
94
93
'DNA = Data not available
fThe first ion exchange column was regenerated on this date
Tables. Characterization of Mixed Regeneration
Wastewater
Date Characteristic Amount
July 2, 1987
February 3, 1988
Calcium as (CaCOy)
Uranium
Gross alpha
Chloride
Sulfate
pH
TDS
Volume
Uranium
Gross alpha
Volume
463 mg/L
16.502 jig.L
6.754 + 580 pCi'L
18.480 mg.L
3. 100 mg L
875 units
39.600 mg,L
833 L (220 gal)
30,500 ng/L
41.000+914 pCi.L
1079 L (285 gal)
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Robert T. Jelinek, Ronald L Clemmer, and Frank J. Johns are with Richard P.
Arber Associates, Inc., Denver, CO 80206.
Thomas J. Sorg ;s the EPA Project Officer (see below).
The complete report, entitled "Uranium Removal From Drinking Water Using a
Small Full-Scale System," (Order No. PB 89-169 890/AS; Cost: $13.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-89/012
000085833 PS
US EM¥|B PfiOfECfJOB AGIMCI
REGION 5 LIBfiARY
230 S DEARBORN STREET
CHICAGO IL 60604
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