United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-90/036 Nov. 1990
Project Summary
Radon Removal Techniques for
Small Community Public
Water Supplies
Nancy E. Kinner, James P. Malley, Jr., Jonathan A. Clement,
Peter A. Quern, and Gretchen S. Schell
The report summarized here
presents the results of an evaluation
of radon removal in small community
water supplies with the use of full-
scale granular activated carbon ad-
sorption, diffused bubble aeration,
and packed tower aeration. Various
low technology alternatives, such as
loss in a distribution system and
addition of coarse bubble aeration to
a pilot-scale atmospheric storage
tank, were also evaluated.* The full
report discusses each of the treat-
ment alternatives with respect to
their radon removal efficiency, poten-
tial problems (i.e., waste disposal,
radiation exposure, and intermedia
pollution), and economics in small
community applications. In addition,
several sampling methods, storage
times, scintillation cocktails, and ex-
traction procedures currently used in
the liquid scintillation technique for
analysis of radon in water were
compared.
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
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
As part of the 1986 amendments to
Ihe Safe Drinking Water Act, the U.S.
* Environmental Research Brief EPA/600/M-
87/031 also outlines the results of the low
technology study
Environmental Protection Agency (EPA)
is to propose a rule for Maximum
Contaminant Level Goals (MCLGs) and
National Primary Drinking Water Regula-
tions (NPDWR) including Maximum Con-
taminant Levels (MCLs) for radionuclides
in drinking water. One of the radio-
nuclides that will be regulated under the
rule is radon-222 (radon). EPA is
considering setting the MCL for radon in
the range of 200 to 2,000 pCi/L. Data on
the distribution of radon in groundwater
supplies in the United States indicate that
a large number of individual and public
water supplies will be affected by an
MCL in that range. In addition, many of
these public water supplies will be ones
serving small communities (<76 m3/day).
The rule will also contain rec-
ommendations with respect to Best Avail-
able Technologies (BATs) and analytical
methods. Three conventional water treat-
ment technologies (granular activated
carbon (GAG), diffused bubble aeration,
and packed tower aeration) have been
used to remove radon from drinking
water. The GAG process, which has been
used to treat point-of-entry and small
community water supplies, relies on the
ability of radon to adsorb to the carbon.
One unique aspect of this process is that
the breakthrough/exhaustion profile typ-
ically seen when GAC is treating con-
servative (nondecaying) contaminants is
not exhibited during radon removal.
The aeration methods are used
because radon is a highly volatile gas
with a relatively large Henry's constant
(2.80 atm m3H2O/m3 air at 100°C) that
can be easily transferred from water to
air. Aeration methods have been used in
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individual, small community, and other
public water supplies.
The primary purpose of this study was
to evaluate the performance of full-scale
GAG and diffused bubble and packed
tower aeration systems when treating
small community water supplies contain-
ing radon. In addition, several low
technology alternatives and various mod-
ifications of the liquid scintillation
counting technique used for analysis of
radon in water were evaluated.
The specific objectives of the study
were to:
Evaluate full-scale GAC systems
operating at two small communities in
New Hampshire, by monitoring them
for changes in radon removal,
radiation emissions, and general water
quality parameters (e.g., pH, iron,
turbidity, microbial numbers);
Conduct several specific monitoring
events of the GAC systems to assess
the effect on GAC performance of
diurnal variations in water flowrate and
raw water quality, high water flowrate,
and backwashing;
Core the GAC after several months of
operation to determine if iron,
manganese, microorganisms, radio-
nuclides, or all of them were
accumulating in the units;
Evaluate full-scale diffused bubble and
packed tower aeration systems
operating in small communities in New
Hampshire by monitoring them for
radon removal, general water quality
parameters, and off-gas emissions of
radon;
Operate the aeration systems over a
range of volumetric air to water (A:W)
ratios at two water flowrates to
determine the effect of these param-
eters on radon removal;
Evaluate three randomly packed
plastic media in the tower aeration
system with respect to radon removal
efficiency;
Evaluate the radon removal efficiency
of several low technology modifica-
tions (e.g., free fall vs. bottom entry,
spray nozzle entry, venturi entry,
coarse bubble aeration) retrofitted to
an existing small community atmos-
pheric storage tank;
Assess the effect of sampling
techniques (e.g., free fall, hose
connector, direct syringe collection,
volatile organic analysis (VGA) bottle
collection), storage time, scintillation
cocktail, and extraction via shaking on
the liquid scintillation analytical tech-
nique for analysis of radon in water.
Analytical Methods
Standard Methods and EPA methods
were used to determine radon; gamma/
beta emissions; the activity of total
uranium, radium-226, and lead-210;
microbial counts; pH; temperature;
dissolved oxygen; turbidity; total iron; and
manganese. The University of New
Hampshire and the State of New
Hampshire conducted the analyses; when
commercial equipment was used, it was
calibrated according to the manu-
facturer's directions.
Granular Activated Carbon
Downflow GAC systems were installed
at two mobile home parks located in
Amherst and Mont Vernon, NH. The
Amherst water system serves 56 homes
at an average daily flow of 59 ±4
m3/day. The water is obtained from one
well containing an average radon activity
of 49,500 ±11,200 pCi/L. The Mont
Vernon system supplies 40 homes at an
average flow of 31 ±11 m3/day. Water is
obtained from two wells with an average
radon activity of 222,000 ± 52,000 pCi/L.
The well water in both systems was
pumped to unpressurized (atmospheric)
storage tanks and, subsequently,
pumped through the GAC systems upon
demand from the community.
The systems were evaluated accord-
ing to the study objectives. Radon and
several genera! water quality parameters
(alkalinity, turbidity, dissolved oxygen,
temperature, pH, iron, manganese, and
bacterial numbers) were monitored at
each site Uranium and radium were also
monitored in the water supply. The GAC
was cored and analyzed for accumulation
of uranium-238, uranium-235, radium-
226, lead-210, iron, manganese, and
microbial numbers. Gamma radiation
measurements were taken at the surface
of the units and at locations inside and
outside of the pumphouses to determine
whether exposure presented significant
health ant! safety problems. The effects
of diurnal variation in loading and
backwashing were also evaluated.
The GAC used in both systems was
Barneby Cheney Type 1002.* At
Amherst, the system consisted of one
91.4-cm-diameter fiberglass tank contain-
ing 0.85 m3 of GAC At Mont Vernon, the
system consisted of two contactors in
series: a 76.2-cm-diameter contactor
* Mention of trade names or commercial products
does nol constitute endorsement or recom-
mendation tor use
(GAC #1) containing 0.57 m.3 of GAC
followed by a 91.4-cm-diameter contactor
(GAC #2) containing 0.76 m.3 of GAC.
The system at Mont Vernon was
designed with two units because of the
high influent radon activity. Taps for
collecting water samples were installed
on the influent and effluent lines and at
10 intervals in each GAC system.
The GAC systems were monitored
daily for 3 to 4 days and then every 2 to
5 days for approximately 1 month during
initial operation (Phase I). Thereafter,
during Phase II, they were monitored
weekly, biweekly, and then monthly. The
system at Amherst was monitored for 122
days, and the system at Mont Vernon
was monitored for 478 days.
During the first few days of operation
at Mont Vernon, all of the radon present
in the water was removed in GAC #1. The
radon removal front moved through the
units over time, eventually breaking
through into the effluent by Day 25. A
similar pattern was observed with the
Amherst system.
The average influent radon activity
(210,491 ± 41,384 pCi/L) at Mont Vernon
remained higher than the design influent
activity of 155,000 pCi/L. The effluent
quality during this period varied from
4,750 to 68,400 pCi/L (Figure 1). In
addition, the GAC system at Mont Vernon
had a higher average water flowrate
x"=36 ± 12 m3/day) than it was designed
to handle (25 m3/day). As a result, the
overall radon loading applied to the
system was usually higher than
anticipated, which may have accounted
for some of the increase in effluent radon
activity. Radon removal followed an
exponential pattern as a function of bed
volume (Figure 2). Similar results were
obtained at the Amherst site. During the
final 3.5 months of the study at Mont
Vernon, when a new well was operating
(influent radon activity = 68,900 ± 1,400
pCi/L), the data showed a steep (almost
straight) pattern and an overall decrease
in removal efficiency (e.g., Day 477).
Although this decrease in removal
efficiency corresponded to changes in
other water quality parameters, the
effects of raw water quality on radon
adsorption by GAC are poorly
understood, and predictions about
removal are difficult to make.
The gamrna/beta emissions data
obtained at both sites were in the 10° to
101 mR/hr range at the units' surfaces.
This range is considerably greater than
the background values of 0.03 to 0.06
mR/hr and the National Council on
Radiation Protection guidelines of an 8-hr
maximum exposure in residences of
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350.0
50 700 750 200 250 300 350
Time (days)
a. GAC #1 Contactor
400 450 500
O
d.
725.0
700.0
75.0--
50.0- -
25.0--
0 50 700 150 200 250 300 350 400 450 500
Time (days)
b. GAC #2 Contactor
Figure 1. Phase II GAC System - Mont Vernon, NH. Radon activity through GAC #7(a) and #2(b) through
477 days operation. Note scale difference between a and b. (* New well began operating.)
0.058 mR/hr. Though exposures are
highly dependent on distance from the
source, they would need to be minimised
to meet accepted occupational safety and
health standards, perhaps by using
shielding.
Several potential problems were
observed with the GAC, including
accumulation of iron, uranium-238 and
-235, radium-226, and lead-210, and
release of bacteria. The GAC provides a
good surface for bacterial attachment and
concentrates the nutrients needed by
microorganisms. At Mont Vernon, the
effluent contained as many 104 CFU/mL,
probably, in part, because of high influent
numbers; at Amherst the effluent ranged
from 200 to 400 CFU/mL. Coring data
indicated that iron precipitates were
retained in the GAC units. This occurred
even when there was little change in the
influent iron concentration as compared
with that of the effluent because of the
large volume of water passing through
the units over time.
Uranium profiles obtained from Mont
Vernon during Phase II and from core
samples indicated that uranium was
removed exponentially through the GAC
system. This contrasted with the lack of
uranium removal observed at Amherst.
The discrepancies may be explained by
the difference in pH of the raw waters at
the two sites (Amherst = 8.03 ± 0.14;
Mont Vernon = 6.5 ± 0.2). The predom-
inant uranium species between pH 7 and
8 are soluble anionic carbonate com-
plexes in natural waters, whereas at pH
<6.8, the neutral U02CO3 species
predominates. It is hypothesized that the
poorly adsorbed anionic species predom-
inated at Amherst, whereas the favorably
adsorbed neutral species predominated
at Mont Vernon.
At both sites, radium-226 was accu-
mulated, as determined by coring. Since
radium adsorption to GAC is considered
unfavorable, it is hypothesized that
radium was removed by adsorption or ion
exchange reactions occurring with either
solid phases (e.g., Fe(OH3), Mg(CO3)) or
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Day 71
A A Day 99
A A Day 119
O O Day 154
D D Day 245
~ ~ Day 477
50.0
100.0
150.0
200.0
250.0
Radon Activity (x 10J pCi/L)
Figure 2. Phase II GAC System - Mont Vernon, NH. Representative profiles of radon
activity through the GAC system (" New well began operating.)
organic matter deposited in the GAC. A
comparison of the theoretical lead-210
adsorbed (as a function of radon removal)
and the lead-210 coring results indicated
that most, if not all, of the radon progeny
were retained by the GAC. Lead-210
accumulations on the GAC at the sites
ranged from 105 to 106 pCi/kg, with the
total beds containing between 107 to 108
pCi. The GAC used at Mont Vernon and
Amherst exceeded the State of New
Hampshire Radiological Health Program
de minimus regulations for uranium-238
(58,410 pCi/kg; 2.5 x 10-5 Ci/rn3) and
radium-226 (44.39 pCi/kg; 1.4 x 108
Ci/m3). There are no regulations in New
Hampshire for lead-210. As a result, all of
the GAC used in this study was classified
as a low level radioactive waste. It should
be noted that the State of New
Hampshire has stringent de minimus
standards with respect to uranium and
radium, and that in many other slates the
material would not be considered a low
level radioactive waste. However, other
states may regulate lead-210, which was
present at much higher activities.
A detailed economic evaluation,
including only costs related to installation
and operation of the GAC systems, was
performed. Direct capital cosls were
determined from expenditures made
during the project, and indirect capital
costs were calculated based on fixed
percentages developed by the EPA
Office of Drinking Water. Annual costs
were developed by adding the amortized
(9% interest over 20 yr) total capital cost
to the annual operation and maintenance
cost. Production costs were calculated by
dividing the annual cost by the annual
design flow. All cost figures were updated
to second quarter 1989 dollars (ENR =
426). Costs are presented for com-
parative purposes only, since actual sys-
tem costs will vary and be site specific.
The production costs for the GAC
systems, including pretreatment for iron
and manganese and disposal of the spent
GAC as a regulated low-level radioactive
waste, were estimated to be $2.15/1,000
gal for Amherst and $2.64/1,000 gal for
Mont Vernon.
Diffused Bubble Aeration
A diffused bubble aeration system,
consisting of three polyethylene tanks
aligned in series (holding capacity of
each = 1022L), was installed in a small
community public water supply in Derry,
NH. An air blower with a 2.66 m3/min
capacity that forced outdoor air into
diffusers provided aeration. The diffusers
consisted of 1 90-cm-diameter coiled
plastic tubes with 0.038-cm holes drilled
in their underside (spacing between holes
= 0.5 to 1.6 cnrv). The diffusers were
located 79 cm below the water's surface
and 36 cm above the bottom of each
tank. The radon stripped from the water
was vented outside the building housing
the units.
The system allowed removal
efficiencies to be compared over a wide
range of influent radon activities (Tank 1:
60,843 to 86,355 pCi/L radon; Tank 2:
10,096 to 80,271 pCi/L; and Tank 3:
1,767 to 74,112 pCi/L). Two flow ranges
were obtained by manually operating one
(low flow = 0.047 ± 0.00053 m3 H2O/
min) or two wells (high flow = 0.10 ±
0.0019 m3/min). Radon activities aver-
aged 65,487 ± 5,657 pCi/L during high
water flow and 78,385 ± 6,120 pCi/L
during low water flow. The two water
flowrates and the two radon activities
resulted in applied radon loading rates
averaging 6,819 ± 548 nCi (103 pCi) per
minute (nCi/min) for high water flow and
3,639 ± 295 nCi/min for low water flow.
A:W ratios of 2:1, 3:1, 5:1, 7:1, 10.5:1,
15:1, and 20:1 were tested for both water
flowrates. The tanks were drained at the
end of each run and refilled with raw
water immediately before the start of a
new run.
Figure 3 shows the overall percent
removals of radon loading versus A:W
ratios for the high and low water
flowrates. These data were obtained after
steady state conditions were achieved in
the diffused bubble system. As the A:W
ratio increased from 2:1 to 5:1 for each
flowrate, there was a sharp increase in
radon removal. Above 5:1, however, there
was much less improvement in efficiency
with large increases in A:W ratio.
When operating at A:W ratios of 5:1
and greater (at both high and low water
flowrates), the overall radon removal
efficiency ranged from 90.0% to
>99.6%; the greatest efficiency was
obtained at A:W ratios of 15:1 and 20:1.
At A:W ratios of 10.5:1 and greater for the
low flowrate and 15:1 and greater for the
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700
90--
80-.-
70--
60--
50--
40
- Low Water Flowrate
A High Water Flowrate
> W 15
AirWater (X:1)
Removal as Function of A:W Ratio
20
Removec
c:
§
03
o:
a5
p
Q.
90-
80-
70-
60-
50-
40-
0.
rx^~
/ / Low Water Flowrate
. I r A A High Water Flowrate
/ A
- /
/
*
00 0.50 1.00 1.50 2.00 2.1
Air Flowrate (m /mm)
Removal as Function of Air Flowrate
Figure 3. Diffused bubble aeration - Derry, NH. Percent radon removal as a function of
(a) A:W ratios and (b) air flowrate for the low and high water flowrate.
high flowrate, there was no significant
difference in removal efficiency (a = 0.05
and 0.01, Analysis of Variance (ANOVA)).
Hence, for the diffused bubble system
tested at the given conditions of radon
loading, the lowest A:W ratios to yield
(statistically significant) maximum radon
removal for low and high water flowrates
were in the range 7:1 to 10.5:1 and 10.5:1
to 15:1, respectively. From the practical
viewpoint of designing a diffused bubble
system, the A:W ratio should also be
based on the most cost effective blower
size and mode of operation.
An evaluation of individual tank
performance indicated that radon removal
in the diffused bubble system was a
function of mass transfer. As the radon
activity became progressively lower
through the series of tanks, the driving
force (Radon Activitywater - Radon
ActivityAjr) decreased, limiting removal.
Though mass transfer may make it more
difficult to achieve low effluent activities,
the diffused bubble system tested
produced water with radon activities of
1,849 to 280 pCi/L for A:W ratios
> 10.5:1. These data suggest that it may
be possible to meet an MCL of 200 pCi/L,
if air flowrate is high, or there is a long
contact time, or both.
Stack emissions were monitored to
determine if the off-gas radon activities
from the diffused bubble system could
affect the air quality in the surrounding
environment. For the system tested, the
off-gas activities (3,361 to 18,356 pCi/L)
would need to be diluted 104 to 105 times
to be similar to radon activities found in
the ambient air at the site (0.1 to 0.15
pCi/L).
An economic evaluation, similar to that
done for the GAG systems, was per-
formed for the diffused bubble system.
The total production cost, including pre-
treatment for iron and manganese and
assuming no required treatment of the
off-gas, was estimated to be $2.14/1000
gal.
Packed Tower Aeration
The packed tower aeration system
was installed at the same mobile home
-------
park in Mont Vernon, NH, used in the
GAG study. The system consisted of a
5.49-m-tall. 0.30-m-diameter stainless
steel tower containing randomly packed
plastic media. Raw water was pumped to
the top of the tower and distributed by a
nozzle located 15.2 cm above the top of
the media. Air entered the tower 0.15 m
below the media.
The major focus of the study was a
series of separate 3-hr runs designed to
determine the tower's radon removal
efficiency for a variety of operating con-
ditions. Parameters varied included pack-
in9 type, packing height, liquid loading
rate, and volumetric A:W flow ratios.
Though fluctuations in water flowrate and
radon activity at the site during the study
prevented comparisons of the effects of
A:W ratio and packing types, there was
relatively little difference in the overall
percent radon removal observed (92.7%
to 99.8%) among the conditions tested.
This was surprising considering the
variation in water flowrate (0.18 to 2.6
m3/hr), influent radon activity (115,225 to
278,488 pCi/L), and packing type. The
resilience of the tower system is
encouraging, considering that many small
communities may experience variations
in water flowrate and radon activity
similar to those observed at the Mont
Vernon site. It is hypothesized that the
consistently higher removals occurred
because radon is a highly volatile gas
and because the packing height used
(~3.7 m) was great enough to com-
pensate for large variations in loading.
Most of the radon removal (Frigure 4)
occurred in the top 0.3 m of the tower,
probably because of end effects of free
fall, liquid distribution, and turbulence.
The data indicate that mass transfer
limitations may be a major factor in
designing towers to achieve very low
radon activities. Therefore, to meet an
MCL of 200 pCi/L with water supplies
containing moderate to high radon
activities, towers may be impractical
because of the extremely large packing
heights required.
As observed with the diffused bubble
system, radon activities in the stack
emissions from the tower were extremely
high and required dilutions of 104 to 105
to approach the ambient air activities (0 1
to 0.15 pCi/L) at the site.
An economic evaluation, similar to that
done for the GAG systems, was
performed for the packed tower. The total
production cost, including pretreatment
for iron and manganese and assuming no
required off-gas treatment, is estimated
to be $2.10/1,000 gal.
Liquid Scintillation Technique
The effects of sampling technique
(direct collection using a syringe versus
filling a VGA bottle), storage (up to 21
days), and choice of scintillation cocktail
(toluene- and mineral-oil-based cocktails
and Opti-Fluor 0) on the liquid scintillation
(LSC) analytical technique for radon in
water were evaluated. Other experiments
were conducted to determine the sources
of variability in the method (field,
preparation, instrument) and the validity
of the extraction via shaking procedure
currently defined by EPA.
Numerically, the direct syringe
sampling technique always yielded the
highest radon activities, whereas the VGA
bottle filled with free falling water yielded
the lowest. This is not surprising because
less sample handling before injection into
the scintillation vial and less agitation
during sampling should result in less loss
of radon. Though the VGA collection
techniques involve extra handling of the
sample, they can, however, produce
results statistically similar to the syringe
method, especially if a universal hose
connector is used.
The data from the storage experiment
indicated that loss of radon from VGA
bottles could be a factor in some
situations, but the loss resulting from
radioactive decay has the greatest
potential effect on storage time. Within 4
days, 50% of the radon originally present
in a sample will be lost because of
decay. For samples containing high
levels of radon, permissible storage times
could be substantial provided that the
amount remaining at the time of analysis
is above the practical quantification level.
(For example, a sample containing
approximately 7,670 pCi/L could be held
up to 10 days, even with a 20% loss due
to leakage, and still contain 1,000 pCi/L).
However, the amount of radon in a
sample is often not known, so the
maximum storage time sufficient to
obtain a valid measurement must be
based on the MCL.
A hierarchical experiment was
conducted using the direct syringe
sampling technique and collection in VGA
bottles with subsequent laboratory
analysis. The total variability associated
with the two methods was not
significantly different (a < 0.10, F test).
The total variation of 4% to 6% as a
result of sample handling and instrument
variation was not high considering the
volatile nature of radon. Most of the
variability in the direct syringe technique
(92.1% of total variance) was due to a
combination of sample handling and
instrumentation, whereas the variations
due to sample handling and instrumenta-
tion for the VGA bottle technique were
55.5% and 44.5%, respectively.
An ANOVA showed that the mean
count rates for the mineral oil-based and
Opti-Fluor 0 cocktails were not signifi-
cantly different (a < 0.10); however, the
mean count rate of the toluene-based
cocktail was significantly less than both
of these (a < 0.05). In addition, the
percent relative standard deviation (%
RSD) associated with the toluene-based
cocktail (3.22%) was greater than those
of mineral oil-based (0.90%) and Opti-
Fluor 0 (1.34%) cocktails. The choice of a
scintillation cocktail may also be
influenced by other factors such as cost,
disposal, and mailing restrictions.
The EPA procedure for analyzing
radon in water requires that the vial
containing the sample be shaken to
speed the extraction of radon from the
water into the cocktail while other
radionuclides remain in the aqueous
phase. Both shaken and nonshaken
radium-226 standards were analyzed in a
series of experiments. The data indicated
that transfer of the radon to the cocktail is
continuous and does not require the
extraction via shaking procedure, with the
possible exception of samples containing
very low radon activities. Use of
efficiency factors, which account for time
between extraction and counting, could
lead to an underestimation of actual
radon activities, especially for samples at
or near the MCL.
Conclusions and
Recommendations
When designing a treatment system to
remove radon from a small community
water supply, good data on water
flowrates and influent radon activities at
the site are essential. These data are
major inputs into the design models for
the aeration and GAG systems. As
observed in this study, for small
community supplies, variations in flowrate
and influent activity may be substantial
and will, if underestimated, lead to
inadequate system design and effluent
radon activities that exceed the design
goal. Variations in water quality at each
site may require that pilot-scale testing
be performed to determine the appro-
priate design and pre- or post-treatment
requirements.
For GAG systems, the steady state
adsorption-decay constant, a critical
component of the design model, varied
over time and was site specific. The GAG
systems tested in this study had average
effluent radon activities of 12,000 to
-------
10
20
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i.
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a:
c
o 50--
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^jjj§ 0-0.3 m
ESS 0.3-7.8 m
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-* .^i 1
0.0
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30.0 40.0
Air Flowrate (m3/hr)
50.0
60.0
Figure 4. Packed tower aeration - Mont Vernon, NH. Percent radon removal as a
function of air flowrate within the tower for one packing type (mini rings).
24,000 pC\/L. The GAG units accumu-
lated iron, manganese and particulates
(turbidity), and there were significant
numbers of bacteria growing on the
carbon. As a result, GAG systems may
require periodic backwashing to prevent
significant headless development. In
some cases, pretreatment is recom-
mended to decrease the backwashing
frequency. Gamma/beta emissions meas-
ured at the surface of the GAG units were
substantially greater than background
measurements possibly requiring shield-
ing to lower them to acceptable levels.
The data indicated that retention of
uranium-238 and -235, radium-226, and
lead-210, which appear to be related to
water quality (e.g., pH and alkalinity),
may cause the GAG to be classified as a
low level radioactive waste.
The diffused bubble aeration system
tested at A:W ratios > 5:1 yielded overall
radon removal efficiencies from 90.0% to
>99.6%. The radon removal efficiencies
for the packed tower aeration system
ranged from 92.5% to 99.8%, in spite of
variations in water flowrate, influent radon
activity, and packing type. Extrapolations
of performance data obtained at one site
with either aeration system should not,
however, be made to systems with other
configurations, process equipment, or low
influent activities, or to those required to
meet a more stringent MCL. Both
aeration systems had off-gas radon
activities that were 104 to 105 times
higher than those of the ambient air, and
their effect on the environment would
need to be considered. As with all
aeration systems, precipitation of iron
and manganese can occur and result in
operational problems. Therefore, raw
water quality should be monitored to
determine whether pretreatment is
required.
Several recommendations can be
made concerning the liquid scintillation
analytical iechnique for radon in water,
During sample collection, the universal
hose connector should be used to fill
VGA bottles. Maximum storage times for
samples collected in VOA bottles should
be established based on the MCL,
practical quantification lever, radioactive
decay, and leakage. Opti-Fluor 0 yielded
the best results of the scintillation
cocktails tested with respect to count
rates, variability, and cost and is,
therefore, lecommended. The extraction
procedure should not be used to
calculate the efficiency factor; however,
samples should be shaken, especially
those with low activities, to ensure rapid
transfer ot radon to the scintillation
cocktail.
The full report was submitted in
fulfillment of Cooperative Agreement CR-
812602 by the University of New
Hampshire Environmental Research
Group under the sponsorship of the U.S.
Environmental Protection Agency.
-------
A/. £ Kinner, J.P. Matey, Jr., J. A. Clement. P. A. Quern and G S
.
K/m R Fox /s Me EPX\ Pro/ecf Officer (see below)
The comP'^e report, entitled "Radon Removal Techniques for Small Community
Pubhc Water Suppl.es," (Order No. PB 90-257 809/AS; Cost: $3100
sub/ect to change) will be available only from: w-w,
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
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
Official Business
Penalty for Private Use $300
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S2-90/036
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