United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/076 Dec. 1987
&ER& Project Summary
Removal of Uranium from
Drinking Water by Ion
Exchange and Chemical
Clarification
Steven W. Hanson, Donald B. Wilson, Naren N. Gunaji, and
Steven W. Hathaway
A pilot demonstration was con-
ducted of ion exchange and chemical
clarification equipment for removing
uranium from drinking water. Four
commercial-type ion exchange col-
umns and a prefiltering and regenera-
tion solution system were constructed
along with a pilot-scale chemical
clarification unit. These units were
assembled and installed in a van trailer
for location at a well site containing
uranium-contaminated water. Uranium
concentrations in the well varied during
the study period from 190 to 400 fjg/L.
The four ion exchange columns each
contained 2 ft3 of resin. Three different
ion exchange resins were used. The 1 -
gal/min chemical clarification unit
consisted of a rapid-mix tank and
precoat rotary vacuum filter. The unit
was operated continuously for 3
months at pH values of 6 to 10 and
ferric chloride concentrations of 15 to
40 mg/L. Greater than 99% removal
of uranium was achieved when oper-
ating at 30 mg/L ferric chloride and
pH 10. The diatomaceous earth precoat
filter achieved complete solid-liquid
separation.
In addition to the pilot study, the
report analyzes several currently oper-
ating water treatment systems whose
feed supplies contain uranium. Cost
analysis data for capital equipment is
also included in the report along with
a discussion of ultimate disposal
methods for uranium-containing water
treatment wastes.
This Project Summary was devel-
oped by EPA's Water Engineering
Research Laboratory, Cincinnati. OH,
to announce key findings of the
research project that is fully docu-
mented in a sepatate report of the same
title (see Project Report ordering
information at back).
Introduction
Background
Most drinking water supplies come
from groundwater. The quality of these
supplies depends on the mineral and
biological content, which vary widely
from source to source. Nearly all supplies
contain some small quantity of uranium.
In most drinking water supplies, the
average uranium concentration is 3 /t/g/L
(equivalent to 2.0 pCi/L Uranium), but a
large number of community supplies
have uranium concentrations in the 10-
to 50-//g/L uranium range. Though no
federal regulations currently exist setting
a maximum contaminant level (MCL) for
uranium in drinking water, the U.S.
Environmental Protection Agency (EPA)
is evaluating a limit of 15 ug/L (approx-
imately 10 pCi/L). That evaluation
involves the assessment of available
control (removal) technology for uranium
and the economic impact of such an MCL.
Aqueous solutions of uranium salts
have an acid reaction as a result of
hydrolysis, which increases in the order
U3+ < U0l+ < U4+. The uranyl, U02+, and
U4+ solutions are well studied. The main
hydrolyzed species of U0|+ at 25°C are
U02OH+, (UOz)a(OH)i+, and (UCMafOHJs;
but the system is a complex one, and the
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species present depend on the medium.
In addition to these hydrolytic products,
uranium ions can undergo complexing
reactions with all ions other than C10i.
Figure 1 shows the pH dependency of
the uranyl ion in aqueous solution in the
presence of carbonate, a constituent in
most drinking water supplies. '
Previous work at EPA's Oak Ridge
National Laboratory at Los Alamos
National Laboratory had shown that ion
exchange and chemical clarification
were effective treatment methods of
removing uranium species from aqueous
solutions.
Scope of Work
This report presents the results of a
demonstration of pilot-plant ion
exchange and chemical clarification
equipment for the removal of uranium
from drinking water. The test units were
housed in a 40-ft van trailer (Figure 2}
and located at a uranium-contaminated
groundwater welt on the New Mexico
State University campus. The well had
not been used for a long period and was
returned to service for this project. The
uranium concentration in the water
varied over the project, begining with 190
fjg/L, rising to 350 to 400 pg/L during
the project, and falling back to 200/ug/L
at the end. These levels greatly exceeded
the tentative study level of 15 0g/L(~10
pCi/L).
Four ion exchange columns were
constructed, each containing 2 ft3 of
resin. Three different ion exchange
resins were used: DOWEX SBRP,
DOWEX 21 K, and IONAC A641.* Three
columns were operated in the conven-
tional down-flow mode, and the fourth
column was operated with upward flow
of the feed water. Pretreatment con-
sisted of paniculate filtering only. Regen-
eration was by chloride ion (10% NACL).
Four bed-volumes of chloride solution
were used at one-third the normal flow
rate followed by two bed-volumes of
rinse (product water). Resin capacity was
represented by 12,000 to 20,000 bed
volumes. Four cycles of operation were
completed for each column, processing
a total of approximately 4 million gal of
feed containing an average uranium
concentration of 300 //g/L.
The chemical clarification unit con-
sisted of a Joy Manufacturing Co. Model
0-12 Laboratory Sub-A Flotation Cell as
a rapid-mix vessel and a continuous
•Mention of trade names or commercial products
does not constitute endorsement or recommendation
for use.
100
in
*
I
Figure 1. Uranium species in aqueous solution at various pH levels.
t. Water Supply
2. Feed Pump
3. Pro-Filter
4. Chemical Clarification System
5. Four Unit Ion Exchange
Columns
6. Ion exchange Control System
7. Product Pump
8. Product Tank
9. Product Discharge
1O. Regenreation Solution
11. Regeneration
12. Waste Discharge
13. PHot-Scale Up Flow Unit
Figure 2. Organization of van system.
precoat rotary vacuum filter, The system
flow rate was 1 gal/min. This system was
operated continuously over a period of
3 months using pH values of 6 to 10.0
and ferric chloride concentrations of 15
to 40 mg/L. Greater than 99% removal
of uranium was achieved when operating
at 30 mg/L ferric chloride and pH 10.0.
The diatomaceous earth precoat filter
achieved complete solid-liquid
separation.
The full report also analyzes several
currently operating water treatment
systems whose feed supplies contain
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uranium. In addition, cost analysis data
for capital equipment is included along
with a discussion of ultimate disposal
methods for uranium-containing water
treatment wastes.
Demonstration Test Program
Table 1 outlines the quality of the well
water used in this project. The major
constituent of interest was the uranium.
At the start of the project, the uranium
concentration was 190A»g/L. During the
project, the uranium concentration rose
to 450/jg/L but returned to around 200
jjg/L at the end of the project period. Both
the ion exchange units and the chemical
clarification units were operated on a
continuous basis. Initially, sampling for
uranium was performed daily. Later, it
was done weekly until breakthrough was
anticipated, and then daily samples were
taken. The chemical clarification effluent
was sampled on a daily basis until steady
state was reached (after a change in
operating conditions); then it was
sampled every other day.
Ion Exchange
Water treatment using ion exchange
technology is a well established opera-
tion. Table 2 summarizes the operation
of the four ion exchange units. Though
the feed to each unit was adjusted
individually and a uniform flow through
all columns was attempted, it was not
achieved. Each column effluent was
sampled individually, but when one
column reached breakthrough, all four
were regenerated. Thus throughout the
four cycles, some units had not been
processed to exhaustion.
All four systems operated well once the
problems of mechanical equipment had
been corrected.
Several physical and chemical charac-
teristics of the resins need to be con-
sidered in the selection of ion exchange
as a water treatment technology. Phys-
ical bead breakage may occur in some
applications. For downflow systems, this
breakage results in increased pressure
drop and reduced efficiency. The three
downflow units exhibited no resin break-
age. In an upflow unit, breakage could
result in entrainment of broken resin in
the effluent and subsequent down-
stream problems in addition to the loss
of exchange capacity through loss of
resin. The upflow unit exhibited no resin
breakage. These determinations were
based on operating pressure drop and
visual inspection of the resin at the end
of the project.
Thermal stability of the resins is a
second consideration in selecting ion
exchange. Weak-base resins are usable
up to 212 °F, followed by Type I strong
bases to 122°F (the resins of this
demonstration). Temperatures in the van
housing the units ranged from a winter
low of 35°F to a summer high of 115°F.
The average inlet (well temperature) was
65°F. No noticeable change in operation
occurred as a result of thermal effects.
Although chemical degradation is not
normally a problem in most water
treatment applications, strong oxidizing
agents can rapidly degrade the polymer
matrix and should be avoided. Slower
degradation with oxygen may be cata-
lytically induced, so ionic iron, manga-
nese, and copper should be minimized.
In the present operations, the raw water
had high iron and manganese contents
(4 mg/L and 1.1 mg/L, respectively).
Resin degradation was not observed.
The capacity of the ion exchange resin
is the measure of ionic attraction per
volume, and it is expressed in a number
of ways. Total capacity is the theoretical
measure of the total number of exchange
Table 1. Chemical Composition of Well Water* Used in Demonstration (mg/L, except as
otherwise noted)
Component
U
/Va+
/r
Ca2*
M/+
cr
COa2"
HCOi
sof
TDS
AS*
BA*
Concentration
(mg/L)
0.30±O.10*
17.9
18.4
375.2
69.0
555.2
0
96,4
400.0
2152
0.005
0.12
Component
Cd*
Cr3*
Pb"
Hg*
SE*-
Ag-
NOi
F'
Fe"
MN*
Hardness
(as CaCOJ
Alkalinity
pH
Electrical
conductivity
mmhos/cm
Concentration
(mg/L)
<0.005
<0.01
<0.005
0.0004
0.005
<0.05
0.01
0.54
1.69
0.95
1220
79
7.62
2.36
Notes:
"Uranium concentration in the well water varied and ranged from 200 to 450 ftg/L; pH of
well water was 7.62: electrical conductivity of well water was 2.36 mmhos/cm.
Table 2. Operation Summary for the Demonstration Ion Exchange Units*
Resin
Type
DOWEX21K
DOWEXSBR-P
ION AC A -641
IONACA-641
Flow
Condition
Down
Down
Down
Up
Total
Gallons
Processed
797,540
890,600
853,870
903,450
Number
of
Cycles
4
4
4
4
Average
Bed- Volumes
Treated/Cycle
12920
14925
16040
15370
Maximum
Removal
Efficiency
(%)
99
99
99
99
'Inlet water concentration ranged between 200 and 400 ug/L uranyl complex (as uranium).
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sites available and is normally calculated
in three different ways: Dry weight
capacity (meq/dry g), wet volume capac-
ity (meq/wet g) and wet volume capacity
(meq/mL). Table 3 gives the average
capacities for the resins used in this
operation.
Regardless of how it is expressed,
operating capacity is the most realistic
performance measure for ion exchange
resins, and in water treatment, it is
usually expressed as kilograins/ft3 of
resin. Here the resin is measured in a
column for actual operation under pres-
cribed conditions.
A final consideration in the selection
of an ion exchange resin is the cost of
regeneration. Small differences in effi-
ciency will be magnified over the life of
the system. Perhaps of equal importance
are the potential environmental prob-
lems encountered in disposing of waste
regenerant.
This demonstration showed that chlo-
ride ion (NaCI) successfully regenerated
all resins used.
Chemical Clarification
. The flotation cell was used as the rapid
mixer and adsorption vessel. Entrained
air only was used—that is, no forced-air
mixing was used, and no surfactants
were used to enhance bubble stability of
flocculation. This vessel had a 1-min
residence time at a 1 -gpm feed rate. The
effluent was channeled by gravity flow
to the filter vessel, where a continuous
rotary vacuum filter separated the ferric
hydroxide precipitate.
The filter membrane was 0.45-micron
polymer mesh, which allowed precipitate
to bleed through into the filtrate when
operated without precoating. A 0.25-in.
precoat of diatomaceous earth was used
and gave a complete solid-liquid sepa-
ration as measured by our analytical
procedures. Additional diatomaceous
Table 3. Ion Exchange Resin Capacity
earth (12% by weight) was added to the
filter feed and mixed by a mechanical
agitator with the feed slurry. A stationary
knife removed the cake buildup. Visual
inspection of residual precoat showed no
binding by the ferric hydroxide precipi-
tate. Sampling of the precoat material
after a run for uranium showed that all
uranium removed was adsorbed on the
ferric hydroxide and not on the diato-
maceous earth.
Table 4 summarizes the effect of pH
on removal of uranium from the well
water at a constant ferric chloride
addition of 30 mg/L
Table 5 shows how varying the ferric
chloride concentration affects uranium
removal efficiencies at pH 6 and 10.
Experimental data for the effect of the
ferric chloride dosage and the equilibra-
tion pH of the solution show that pH is
a major controlling factor in the removal
of uranium from drinking water by means
of the coagulation/filtration process.
Proper choice of pH is a requirement for
effective chemical coagulant treatment.
The results of the pH dependence for
uranium removal with iron salt can be
interpreted by the stability and charge
characteristics of uranyl species and
metal hydroxide precipitates at the
adjusted pH of the solution. No data are
shown for similar experiments examin-
ing the pH dependencies for other
dosages of ferric chloride. However,
similar results can be expected from the
physiochemical properties of the metal
hydroxide formed during the coagulation
process at a given pH and the dominant
uranyl species in the solution. The role
of ferric hydroxide as a coagulant formed
from ferric chloride in aqueous solution
is well known. The stability, solubility,
and reactivity (adsorption) of the hydrox-
ide are pH-dependent. The pH depend-
ence of the distribution of uranyl species
in natural water is also known. Dominant
Resin
DOWEX21K
DOWEXSBRP
IONACA641
IONACA641
(up flow)
Uranium
Capacity"
(kilograins/ft3)
2.95
3.15
3.67
3.54
Uranium
Wet Volume
Capacity +
(meq/mL)
0.03
0.032
0.038
0.037
Total
Wet Volume
Capacity?
(meq/L)
1.20
1.20
1.16
1.16
"As UO2(CO3)l'.
•*Average over three cycles of operation (i.e.. cycles 1,2, and4).
^Manufacturer's value: 1.2 meq/mL is 26 kilograins/ft3 as CaCOa.
uranyl species and charge characteris-
tics of iron hydroxide floe at pH 4, 6, 8,
and 10 are shown in Figure 1. At a low
pH (say pH < 5), ferric hydroxide had a
positive charge. Fe(OH)3-wandthe uranyl
carbonate complex also dissociated to a
positively charged uranyl ion (UO|+,
UOzOH*). Thus at pH 4, less adsorption
can occur because of the strong repul-
sion between ferric hydroxide and uranyl
ion or ion-complex. As the pH was
increased to 6, the dominant uranyl
complex would be U02CO3, with a small
positive charge of uranyl ions, and the
mixed charge of negative and neutral
hydrolyzed ferric iron would be overall
negative. Statistically, the possibility
exists for adsorption, since at least there
is no repulsion between the two charged
particles, UO2CO3 and Fe(OH)i. At pH 8,
the same phenomenon was observed as
at pH 4, except that both interacting
species would have negative charges.
Thus a lower removal efficiency was
obtained in both conditions (pH 4 and 8).
When the pH exceeds 9.5, the U02(CO3)4~
species are known to be stable; but
(U02)3(OH)5 would be the dominant
species in carbonate-depleted water. The
carbonate in water could be depleted by
CaCO3 precipitation during the coagulant
treatment process. The reaction is shown
as follows:
3 UO2(C03>r + 15 Ca2+ +
2 FeCI3 + 15 OH' - (U02)3(OH)J +
12 CaCO3(s) + 2 Fe(OH)f (s) + CaCI2
Since the charge of the ferric hydroxide
is pH-dependent, it should adsorb on its
active surface sites the stable uranyl
complex through electrostatic attraction.
Minimum uranium removal was there-
fore observed when the charge of the
uranyl species was the same as the
charge of the floes, and maximum
removal occurred when the charges
were opposite or neutral.
Monitoring Program
As part of this study, an analysis was
conducted of several currently operating
conventional water treatment facilities
with uranium in their feed supplies. A
detailed search was conducted to locate
such facilities. For this search, a min-
imum uranium level of 15 fjg/L was
arbitrarily selected, and conventional
water treatment facilities were defined
as any type of treatment facility more
complex than sand separation and
chlorination.
The wide variety of state and U.S.
Goverment agencies responsible for the
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Table 4. Summary of Uranium Removal Using 30 mg/L of Ferric Chloride Solution on
Samples with Various pH levels
Adjusted
pH
4.0
4.9
5.3
5.8
8.2
9.4
10.0
Uranium Remaining in
the Tested Water (ug/L)
309
251
180
86
369
6
<2
Uranium
Removed
(%)
31.3
44.2
60.0
80.9
18.0
98.7
99.0
Table 5. E ffect of Ferric Chloride Concentration on Uranium Removal Efficiency in Solutions
of pH6 and 10
FECI3
pH6
pHIO
Dosage (mg/L)
30
60
90
30
60
90
Uranium Remaining in
the Tested Water (ug/L)
86
60
59
<2
<2
<2
Uranium
Removed
(%)
80.9
86.6
86.9
98+
98+
98+
radiological monitoring of water supplies
made the search very time-consuming.
A total of 34 municipal systems and an
additional 21 municipal wells were
located in a 6-state area. Of these 55
possible study sites, only four provide
treatment above and beyond sand sep-
aration and chlorination. Three of these
cities are located in Colorado—Arvada,
Denver, and North Table Mountain—and
they all draw their water from the
uranium-contaminated Ralston Reser-
voir. The fourth city is a small city in
South Dakota (Harrisburg).
The City of Arvada treats their water
using a microfloc system. The system
employs alum and Separan (a polyelec-
trolyte) to create the microfloc. The water
is then passed through mixed-media
filters. A 125-cc water sample is col-
lected daily from the raw water and
treated water to form monthly composite
samples. For the past couple of years,
these monthly samples have been tested
for uranium. The raw water from Ralston
Reservoir contains a range of less than
1 fjg/L to 36 ug/L, with an average of
14.7 ± 9.6 (South Dakota) ug/L of
uranium. The Arvada facility removed
18% to 90% of this incoming uranium
with a mean efficiency of 60% ± 15%.
The meticulous nature of these records
and the time span of the monitoring
clearly indicate that conventional water
treatment facilities can greatly reduce
the uranium content of natural waters.
The Moffat Treatment Facility (Denver)
also draws water from Ralston Reservoir
and has been keeping uranium records
for about 2 years. Unfortunately,
Denver's monthly samples are grab
samples, and correlation between raw
and treated waters are less meaningful.
Using their records, uranium removal
efficiency varies widely: 78% ± 190%.
North Table Mountain declined to
participate.
Harrisburg, South Dakota, treats about
100,000 gal/day using aeration, KMnCu
greensand filters, chlorination, and
f luoridation. No previous data exist on the
uranium removal efficiency of this
facility. Duplicate sampling over two
different periods of operation showed no
uranium removal by the current treat-
ment system.
Ultimate Waste Disposal
As previously described, uranium-
contaminated drinking water is a com-
mon problem, particularly in the western
United States. If regulations are accepted
and enforced, many communities will be
required to remove the uranium from
their drinking water supplies. Removal
of this radioactive element produces a
new problem of radioactive waste dis-
posal. The physical form of this waste
and the longevity of uranium cause
difficulties in formulating a waste dispo-
sal plan.
Three disposal alternatives were con-
sidered in this study: Dilution and
release, reuse or resale, and burial. The
choice of method must be based on
environmental acceptability. Each partic-
ipating community will have unique
drinking water and waste characteristics,
so it is impossible to prescribe a single
solution to the problem. Each community
must consider its situation and choose
the optimum plan. The full report ana-
lyzes two cases: (1) a community using
150,000 gal water/day with 30 ug/L
uranium, and (2) a community using
150,000 gal water/day with 200 ug/L
uranium. Table 6 summarizes the quan-
tity and form of uranium to be disposed
of for each case. The first alternative of
dilution and release is by far the most
economical; however, there are usually
restrictions on the quantity of uranium
that can be returned to surface waters
(e.g., in New Mexico, such flows must
be less than 5 mg/L). Table 6 shows that
for both Cases 1 and 2, the ion exchange
regeneration solutions could be dis-
charged to surface flows. However, the
value given for Case 2 is an average
value, and during operation of this
project, we observed solutions exceeding
25 mg/L at the start of regeneration. This
discharge would be the usual disposal
solution for ion exchange systems.
Total environmental consideration
suggests that there be alternative means
of disposing of the uranium, and the filter
cake resulting from chemical clarification
is the first step in such disposal. In Case
1, the cake would contain 0.057 nano-
curies of uranium/g, and in Case 2,0.38
nanocuriesof uranium/g. Both cases are
well below the 100-nanocurie/g defini-
tion of waste requiring special packaging
and disposal in a permanent repository.
The filter cake could be drummed and
sent to an approved site for shallow
surface burial. The alternative is to send
it to a uranium mill for processing as part
of the mill feed.
Design Analaysis
Though complete cost analysis has
been covered by several recent publica-
tions, two specific designs are summar-
ized in Tables 7 an 8. They include capital
costs for equipment only, since operating
costs are site dependent.
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Table 6. Ultimate Disposal Values for Uranium in a Community Using 150,000 gal water/
day
Uranium Source
Amount and Form of
Uranium
to be Disposed of
Case } (30-iug/L uranium content):
Ion exchange treatment regenerant solution
Chemical clarification filter cake
Total uranium
Case 2 (200-ug/L uranium content):
Ion exchange treatment regenerant solution
Chemical clarification filter cake
Total uranium
0.3mg/L, 1500 gal/day
17.03 kg/day
1.7 g/day
2.0 mg/L. 1500 gal/day
17.04 kg/day
11.35 g/day
Table 7. Ion Exchange System Design*
Item
Design Data
Average influent concentration ofUO
Feed needed (1 -day basis)
based on average capacity of 3.3 kilograins/ft3
Resin needed for 1 day of operation
Size of tank based on fOgpm/ft* flow rate
Diameter of tank 9 ft
Bed depth 3 ft
Use 10O% freeboard for B/W and/or expansion
tank size
Approximate running time between regeneration
Time of operation
Salt needed for regeneration
Estimated capital equipment cost"
84 fjg/L or si 50 fjg/L as uranium
600 gal x .084 ppm x .0547
min
grains/gal , M ltr,mmins
ppm hr
3960 grains
3.96 kilograins = j 20 ft3
3.3 kilograins/ft3
600 gpm ,
10 gpm/ft2
Area = 63.6 ft1
Resin quantity = 63.6 ff
x 3 ft =191 ft3
9 ft dia. xSft side shell
191 ft3
= 160 days
1.20 ft3/day
15 Ib/ft3 x 191 ft3 = 2.86 fb
$125,000
"Cost analysis for chemical composition is given in Table 1.
The cost curves for the two unit
operations considered were updated to
1985 costs using the Civil Engineering
plant cost index data published in
Chemical Engineering. The index used
was 375.2 (July 1985) based on 1957-
59 as 100. These cost curves were scaled
for the specific processing of uranium.
Conclusions
Four commercial-type ion exchange
columns and prefiltering and regenera-
tion solution systems were tested to
remove uranium concentrations in the
water supply well in which concentra-
tions varied from 190 to 400//g/L during
the study period.
Greater than 99% removal of uranium
was achieved when operating at 30 mg/
L ferric chloride and pH 10. The diato-
maceous earth precoat filter achieved
complete solid-liquid separation. No
thermal degradation of resins were
observed in the temperature range of
35°F to 115°F. Chemical degradation
also was not experienced in this study.
Minimum uranium removal was
observed when the charge of the uranyl
species was the same as the charge of
the floes, and maximum removal was
experienced when the charges were
opposite or neutral.
Review and analysis of records of
currently operating water treatment
systems whose feed supplies contain
uranium indicated that conventional
water treatment facilities can greatly
reduce the uranium contents of natural
waters.
Ultimate waste disposal plans for
radioactive waste from drinking water
supplies are difficult to formulate
because of the longevity of uranium and
the physical form of the waste. Methods
considered in this study are dilution and
release, reuse or resale, and burial. If the
uranium content of the waste is below
that required by the permanent repos-
itory guidelines to have special packaging
and disposal, then the waste can be
drummed and sent to an approved site
for shallow surface burial or to a uranium
mill for processing as part of the mill feed.
The full report was submitted in
fulfillment of Cooperative Agreement CR
810453 by New Mexico State University,
under the sponsorship of the U.S.
Environmental Protection Agency.
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Table 8. Chemical Clarification System Design
Item Design Data
Average influent concentration 0.5 mg/L as U
Feed rate 60 gpm
Joy Manufacturing flotation cell 16 ft3
Residence time 2 min
Ferric chloride addition 25 mg/L, 35.7 Ib/day
pH adjustment (assuming feed at pH 7 to 10) 2L cone. (37%) HCI/day*
Continuous rotary vacuum (precoat) filter 6 ft2 total surface area
Filter-aid addition 2x weight of ferric chloride
(diatomaceous earth) 70 Ib/day
Total filter production/day (dry weight and wet
weight. 8% moisture) 106 to/dry weight, 115 Ib/wet weight
Total estimated capital equipment costs $44,000
*NaOH could also be used if pH needs to be increased.
Steven W. Hanson, Donald B. Wilson, and N. N. Gunaji are with New Mexico
State University, Las Cruces, NM 88003.
Richard P. Laucfi is the EPA Project Officer (see below).
The complete report, entitled "Removal of Uranium from Drinking Water by
Ion Exchange and Chemical Clarification," (Order No. PB 88-102 90O/AS;
Cost: $13.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
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