General filtration bed design for water
contaminated with radioactive cesium
Purpose
This technical brief provides decision makers with practical information
that could be useful for managing and treating decontamination wash
water generated during remediation activities following a radioactive
cesium contamination incident. Research results related to designing
filtration beds and processing the contaminated water are summarized.
Background
The timely decontamination of high-density urban areas is critical in the
face of a terror event involving radioactive cesium (Cs), which has a 30-
year half-life with an energetic 662 keV gamma ray released during
decay. This technical brief is intended for local, state and federal agents
along with emergency management and environmental response
personnel to aid in clean-up after the detonation of a dirty bomb. It
describes how to design a filtration bed to remove radioactive Cs from
collected decontamination wash waters.1
Approach
Decontamination of urban surfaces - including roadways, external
building surfaces, and vehicle exteriors - can utilize different types of
methods [1], Some types rely on washing with water, and their efficacy
when used on certain surfaces is dependent on additives to the water.
Some additives increase physical removal, whereas others aid in
chemical removal of cesium, which inherently tends to bind to common urban surfaces, such as concrete,
asphalt, and brick. For wide area decontamination, large water volumes will be required, presenting challenges
in supplying decontamination water while simultaneously ensuring sufficient water for community use. Entry of
radiologically contaminated water, both from decontamination operations and from natural precipitation, into
urban wastewater collection systems may not be desirable, leading to its on-site containment and treatment.
The presence of additives to facilitate decontamination introduces further complexity. IWATERS (Integrated
Wash Aid Treatment and Reuse System) integrates the practice of water washing with immediate containment
and on-site recycling of contaminated wash waters (Fig. 1).
1 The model described here assumes all incoming radioactive cesium is in the dissolved ionic form (Cs+). Caution must be
exercised if small, radioactive particulates (<20-40 micrometers mean diameter) are present as these might pass through
the filtration bed and require additional clarification to completely remove the radioactivity from the recycled water.
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1
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Primary Building
Containment Berm
Sequential®
Radiation ^
Removal Basins
Recycled Water
Vehicle Wash
.Containment
Mobile Water L
Clarifying Trailer
Figure 1. Artist's rendition of potential deployment of /WATERS for large (building) and smaller-scale (vehicle)
nuclear contaminations. Early responders clean buildings with ionic wash solution (Step 1: red dashes) and treat
contaminated wash solution in one — or more — sand/clay beds (Step 2: yellow dashes), suitable for recycle (Step
3). See Reference 1 for details on a pilot-scale demonstration of I WATERS.
Critical to I WATERS, contaminated wash water is contained and treated by filtering it through a bed containing
reactive porous media such as sand and clay (Fig. 2) designed to filter radioactive Cs [3-7]. Then, the treated
water can be pumped to a storage vessel for reuse in the washing procedure or additional processing. In
practice, depending on the application, it would be necessary to utilize a variety of bed sizes, volumes, and ratios
of sand to clay. In addition, an incident will release different
amounts and types of radionuclides, and different
decontamination approaches will be needed depending on
the types of surfaces contaminated. For instance,
radionuclides penetrate different materials to differing
degrees, and may require additives, like salts, to increase
decontamination efficacy via reducing penetration into the
materials [5].
clay flakes (right, retained by 0.15 mm sieve).
Figure 2: Common play sand (left) and vermiculite
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Fig. 3 shows a general bed design, along with critical parameters that impact the removal of radionuclides. These
are the cross sectional area Ab, the head height of the contaminated water hh, and the depth of the bed
Appropriate design of the beds will depend on site-specific conditions that consider the variables of the
radioactivity level in the water, whether salt was used to improve decontamination efficacy, and the footprint
area available to place the bed.
Cross sectional area, Ah
Inflow
Head height, hh,
of contaminated —
waste water
Sand/ vermiculite
— clay mixture
bed depth, bi
Flow rate V
Perforated drain pipe is applied
across the filter bed base
Figure 3: General filtration bed design with sand/clay reactive infill and drain tile configuration (not to scale).
Infill material should be at least 1 foot (30 cm) in bed depth b, to permit sufficient reaction time between the
contaminated water and reactive clay material. It is good practice to perform a pretreatment of the water to
settle larger material and provide grossly clarified water to the filter beds.
Design of ad hoc Filter Beds via Look-up Tables
Some potential applications of differing filtration beds are shown in Fig. 4. Design of beds for a particular
application can begin by applying one of two baseline cases, using data from Tables 1 and 2, respectively. These
baseline cases consider whether fresh or salt water is to be used during decontamination. The baseline cases
assume an incoming concentration of contaminated water of 20 nCi/L to calculate the total radioactivity
captured in the bed and effluent concentration that meets the drinking water standard (200 pCi/L). Note that in
Fig. 3, vermiculite clay is mixed with sand as bed fill materials. Vermiculite has very high selectivity for cesium
ions, meaning it preferentially removes cesium from water containing a host of other salt ions [3], Other clays
and sorbents with different selectivities can also be used, but the baseline cases will need to be adjusted
accordingly. How to account for other clay or in-fill material is discussed in a separate technical brief [8],
After the baseline design is in place, look-up tables (Tables 3 and 4) provide a generic means of designing beds
to treat any amount of water or total activity of radioactive Cs. Tables 3 and 4 also enable estimation of the
bed's operation time, meaning the amount of time it can be in service before it has to be replaced because
radioactivity is beginning to exit the bed (known as breakthrough).
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Figure 4. Potential application of filter beds in IWATERS.
A (top, left) Rain gutter filtration bed for Cs-contaminated waters [55-gallon drum, 2.75 ft2 x 2 ft depth
(0.26 m2 x 0.61 m depth), 70:30 sandxlay by volume] capable of processing >7,000 gallons (26,500 L) of
contaminated tap water, or >400 gallons (1,500 L) of contaminated salt water (0.1 M KCI or 0.68%) at a
rate of up to 44 gal/hr.
B (top, right) Vehicle wash filtration bed [600ft2 x 1 ft depth (55.7 m2 x 0.30 m), 70:30 sandxlay by volume]
where a tarp was fastened to the fagade to direct runoff into the bed. This design was capable of
processing >500,000 gallons (1.89 million L) of contaminated tap water, or >31,000 gallons (117,000 L) of
contaminated salt water (0.1 M KCI or 0.68%) at a rate of 13,000 gal/hr.
C. (bottom photos) Building fagade wash filtration bed [540ft2 x 2 ft depth (50.1 m2 x 0.61 m), 70:30
sandxlay by volume] capable of processing >1.4 million gallons (5.30 million L) of contaminated tap water,
or >80,000 gallons (303,000 L) of contaminated salt water (0.1 M KCI or 0.68%) at a rate of 8,700 gal/hr.
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Baseline Case 1-When Fresh Water is Used During Decontamination
Table 1 presents the case for incoming fresh water (e.g., from a fire hydrant, river, or stream). Using a
sand:vermiculite clay ratio of 70:30 to fill a 100 ft2 bed to a depth of 1 ft, approximately 93,000 gallons of fresh
water can be processed over approximately 42 hours (h) to remove 7,100 milliCuries (mCi) of radioactive Cs (1 ft
of water maintained above the bed to promote gravity flow), after which the bed is exhausted and must be
replaced.
Table 1. Baseline technical look-up table for constructing ad-hoc filtration beds (Ab = 100 ft2, hh = 1 ft, bt =
1 ft) for processing cesium contaminated fresh (tap) water.
Wash Water: Tap
100 ft2 x 1 ft deep bed
Sand:Clay Ratio
Operation Time
(hours until
breakthrough)
Radioactivity
captured (mCi)
Volume of water
processed
(gallons)
Flow rate (gallons
per minute)
70:30
42
7,100
93,000
36
80:20
26
4,900
65,000
41
90:10
12
2,600
34,000
47
Baseline Case 2 - When Salt Water is Used During Decontamination
Table 2 presents the case for incoming water containing salt additive (0.1 M KCI), which can greatly improve
decontamination efficiency for some types of materials but can significantly reduce the capacity of the bed to
remove radioactive Cs. The result of having salt in the wash water is that the same bed from the prior example
(70:30 sand:clay in a Ab = 100 ft2 bed to a depth of /?, = 1 ft with hh = 1 ft of water head) can process 5,300 gallons
of contaminated water in 2.4 h to remove 400 mCi of radioactive Cs.
Table 2. Baseline technical look-up table for constructing ad-hoc filtration beds (Ab = 100 ft2, hh = 1 ft, hi =
1 ft) for processing cesium contaminated salt waters (0.1 molarity potassium chloride KCI or 7.4 g potassium
chloride per kg of water).
Wash Water: 0.1 M KCI
100 ft2 x 1 ft deep bed
Sand:Clay Ratio
Operation Time
(hours until
breakthrough)
Radioactivity
captured (mCi)
Volume of water
processed
(gallons)
Flow rate (gallons
per minute)
70:30
2.4
400
5,300
36
80:20
1.5
280
3,760
41
90:10
0.7
140
2,080
47
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Using Look-up Tables to Design Beds for Any Amount of Radioactivity or Volume of Water
As an example of the use of look-up tables for designing beds, Table 4 estimates the bed size needed for any
amount of radioactivity or volume of water by applying the multiplicative factors from Table 3 to the baseline
case in Table 2 (for salt water—0.1 M KCI). The main attributes that can be changed are the footprint size of the
beds and their depth. These changes are performed using Table 3. Row 1 in Table 3 represents the multiplicative
factors that must be applied for changes to the baseline value surface area of 100 ft2. Row 2 represents the
multiplicative factors that must be applied for increases in bed depth from the baseline value of 1 ft.2
Table 3. Look-up tables of variable correlation factors calculated by changes in surface area and column depth
from the baseline case (Ab = 100 ft2, hh = 1 ft, hi = 1 ft).
Operation Time
(hours until
breakthrough)
Radioactivity
captured (mCi)
Volume of water
processed
(gallons)
Flow rate (gallons per
minute)
Surface Area Ab
Increase
No Effect
x (Total Area in
ft2/100)
x (Total Area in
ft2/100)
x (Total Area in ft2/100)
Bed Depth h,
Increase
x 4 (Depth-1)
x 2.8 (Depth-1)
x 2.8 (Depth-1)
x 0.5[1+(1/Depth)]
Table 4 reflects example calculations for a bed with a surface area of 400 ft2 and a depth of 3 feet to process
contaminated water containing salt (0.1M KCI) instead of fresh water. In this example, the bed has a four times
larger surface area than the base case and can retain four times the quantity of 137Cs, process four times the
total gallons of water, and process the contaminated water at four times the rate based on this adjustment to
the base case. Moreover, the depth is increased from one to three feet, so the hours the bed can be used
increases by 4 x (3-1) = 8. The activity of 137Cs that it can retain increases by another factor of 2.8 x (3-1) = 5.6.
The total gallons it can process in that time increases by another factor of 2.8 x (3-1) = 5.6, and the flow rate
increases by another factor 0.5[l+(l/3)] = 0.833. Overall, the time before breakthrough increases by a factor of
8, the activity of 137Cs that can be retained in the bed and total volume by a factor of 22.4, and the flow rate by a
factor of 3.33.
Table 4. Look-up table for constructing ad-hoc filtration beds (Ab = 400 ft2, hh = 1 ft, ht = 3 ft) for processing
different volumes of total quantities of cesium in contaminated salt (0.1 M KCI) waters.
Wash Waters: 0.1 M KCI
400 ft2 x 3 ft deep bed
Sand:Clay Ratio
Operation Time
(hours until
breakthrough)
Radioactivity
captured (mCi)
Volume of water
processed
(gallons)
Flow rate (gallons
per minute)
70:30
19
8,960
119,000
120
80:20
12
6,272
84,000
136
90:10
5.6
3,136
46,000
156
2The look-up tables require a minimum depth of 1 ft.
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Additional Considerations
The design of the filtration beds described above is an important technical aspect of the implementation of
IWATERS. The overall logistics of IWATERS implementation are described in a study that develops a framework
to simulate deployment, estimating the timeline for decontamination operations across a range of scenarios.
The study also presents how the simulation approach can be used to characterize alternatives to reduce the
impact of limited resources on operational progress [9],
Additional considerations will be necessary during decontamination wash water treatment and disposal. The
data reported in this Technical Brief was generated based on the assumptions outlined in the text and is
specifically designed for cesium contamination present in dissolved form (as opposed to being bound onto dust
or debris particles). Replacing vermiculite clay with another clay material or active sorbent will modify the
properties of the filtration bed (the subject of another Tech Brief [8]). This Technical Brief does not consider the
manner in which the contaminated water is collected, details of filtration bed construction, or how to manage
the filtered water. Other concerns include the presence of contaminated colloidal material3 or radionuclides
other than cesium that may require additional filtration methods, clogging of the filtration bed, methods of
disposing the spent filtration beds, radioactive exposure rates from the contaminated water or the
contaminated filtration bed (see References 10 and 11), and personal protective equipment requirements.
Contact Information
Technical Contacts
Matthew Magnuson, magnuson.matthew@epa.gov
Michael Kaminski, kaminski@anl.gov
Katherine Hepler, khepler@anl.gov
General Feedback/Questions Contact
CESER@epa.gov
Disclaimer
This technical brief is for informational purposes only. It was subject to administrative review but does not
necessarily reflect the view of the U.S. Environmental Protection Agency (EPA). No official endorsement should
be inferred, as the EPA does not endorse the purchase or sale of any commercial products or services. The
submitted technical brief has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory
("Argonne"). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No.
DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up
nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute
copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
3 Colloidal material are microscopic particles that do not settle from solution due to their small size.
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Office of Research and Development
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References
1) Michael D. Kaminski, Sang Don Lee, and Matthew Magnuson. Wide-area decontamination in an urban
environment after radiological dispersion: A review and perspectives. J. Haz.Mat., Vol. 305, pp. 67-86, 2015.
https://doi.orq/10.1016/i.ihazmat.2015.11.014
2) Technical Report for the Demonstration of Wide Area Radiological Decontamination and Mitigation
Technologies for Building Structures and Vehicles, EPA/600/R-16/019, Office of Research and Development,
National Homeland Security Research Center, March 2016.
https://cfpub.epa.gov/si/si public file download.cfm?p download id=529008&Lab=NHSRC.
3) William C. Jolin and Michael Kaminski. Sorbent materials for rapid remediation of wash water during
radiological event relief. Chemosphere, Volume 162, pp. 165-171, 2016.
https://doi.Org/10.1016/i.chemosphere.2016.07.077.
4) Katherine Hepler. Characterization of pressurized wash for decontamination of porous building materials and
a Goldsim model for recycling contaminated wash. (Master of Science thesis, University of Illinois, Urbana, USA,
2017). https://hdl.handle.net/2142/98301.
5) Michael Kaminski, Christopher Oster, Nadia Kivenas, Susan Lopykinski, and Matthew Magnuson. Penetration
of Fission Products Ions into Complex Solids and the Effect of Ionic Wash. Environ Sci. Pollut. Res., Vol. 28, pp.
10114-10124, 2021. https://doi.org/10.1007/sll356-02Q-11392-w.
6) Michael Kaminski, Matthew Magnuson, Katherine Hepler, Christopher Oster, and William C. Jolin. Design of
Ad Hoc Filtration Beds for Treating Contaminated Waste Waters - 18385. Paper 18385, WM2018 Conference,
March 18 - 27, 2018, Phoenix, Arizona, USA. https://www.wmsvm.org/archivedproceedings/.
7) Katherine Hepler, Michael D. Kaminski, William Jolin, and Matthew Magnuson. Decontamination of Urban
Surfaces Contaminated with Radioactive Materials and Consequent Onsite Recycling of the Waste Water.
Environ. Technol. Innov., p. 101177, 2021. https://doi.Org/10.1016/i.eti.2020.101177
8) Katherine Hepler, Michael Kaminski, and Matthew Magnuson. Tech Brief: Generalized Design of Ad Hoc
Radioactive Filtration Beds, in preparation, see https://cfpub.epa.gov/si/.
9) Katherine Hepler, Michael D. Kaminski, Evan VanderZee, Charles VanGroningen, and Matthew Magnuson.
Logistics Simulation of a Remediation Effort for a Hypothetical Radiological Contamination Scenario, in
preparation, see https://cfpub.epa.gov/si/.
10) Keith A. Sanders. Radiological Decontamination in the Urban Environment Utilizing an Irreversible Wash-Aid
Recovery System. (Master of Science in Industrial Hygiene thesis, Air Force Institute of Technology, Wright-
Patterson Air Force Base, USA, 2018). https://scholar.afit.edu/etd/1761/.
11) Michael D. Kaminski, Keith Sanders, Katherine Hepler, Matthew Magnuson, and Jeremy Slagley. External
Dose To Recovery Teams Following A Wide-Area Nuclear Or Radiological Release Event. Health Phys., 2021.
https://doi.org/10.1097/hp.00000000000Q1381.
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