RPSEA

Final Report

08122-36.Final

Produced Water Pretreatment for 

Water Recovery and Salt Production

08122-36

January 26, 2012

Principal Investigator: James M. Silva

Senior Chemical Engineer

General Electric Global Research Center

1 Research Circle

Niskayuna, NY 12309
ii

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iii

Produced Water Pretreatment for Water Recovery

and Salt Production

James M. Silva, Hope Matis, William L. Kostedt IV, and Vicki Watkins

Abstract:

Horizontal drilling and slickwater hydrofracturing have enabled shale gas to become a 

significant contributor to the United States’ energy supply. Hydrofracturing typically requires 

2MM – 6.5MM gallons of water per shale gas well. About 15-25% of this water returns to the 

surface as “flowback” within 30 days after hydrofracturing. “Produced water” continues to 

flow at a much reduced rate, e.g. 2-10 bbl/day, for the life of the well. In addition to high 

salinity and hardness levels (Mg, Ca, Sr, Ba), much Marcellus produced water also contains 

significant levels of naturally occurring radioactive materials (NORM), particularly radium. The 

near absence of disposal wells in Pennsylvania initially forced much of the produced water to 

be trucked into Ohio for disposal by deep-well injection (UIC). Currently up to 95% of the 

flowback and produced water is reused in subsequent hydrofracturing operations. However, 

eventually the supply of flowback and produced water is expected to exceed the reuse capacity. 

At this point, a growing volume of high-TDS produced water must either be deep-well injected, 

or water and salt recovery is required. The objective of this study is to identify cost-effective 

softening technologies, primarily for barium and radium removal, that enable thermal recovery 

of distilled water and a salable salt product from produced water. 

Current technology utilizes evaporation to recover about 56% of the produced water as distilled 

water and a salt concentrate, which is disposed of by UIC (design case). To achieve 80-95% 

water recovery, it is necessary to generate a solid salt (NaCl) product. For use as road salt, the 

salt product TCLP extract must contain no more than 100 mg/L barium. It is also assumed that 

the salt product must also meet 226Ra specifications for disposal of solids as nonhazardous solid 

waste, which is 25 pCi/gm in Pennsylvania. Based on a pilot study by GE Water and Process 

Technologies (GEWPT) of Marcellus produced water evaporation and salt crystallization, we 

defined a map of pretreatment needs as a function of the produced water barium and radium 

concentrations. We concluded that produced waters containing less than a specific barium 

concentration ([Ba]max, about 1,000-2,000 mg Ba/L) and essentially arbitrary radium activities 

do not require barium removal prior to NaCl crystallization (“Type I” produced water). 

Produced water with a barium concentration greater than [Ba]max and very low radium activity 

(<200-1,000 pCi 226Ra/L; upper limit depends on the produced water barium concentration) 

may be economically treated for barium removal by sulfate precipitation (“Type II” produced 

water) prior to NaCl crystallization. Produced water with a barium concentration greater than 

[Ba]max and higher radium activity (>200-1,000 pCi 226Ra/L; lower limit depends on the produced 

water barium concentration) requires barium removal by a method other than direct sulfate 

precipitation prior to NaCl crystallization (“Type III” produced water). We focused on defining 

economical pretreatment processes for Type III produced water.
iv

Selective removal of radium from Type III produced water in order to enable barium removal by 

sulfate precipitation is not practical. We found that the radium capacity of DOWEXTM RSC, a 

commercially available ion exchange resin for radium removal from aqueous streams, is too low 

to be economical. 

We defined two pretreatment processes to remove both barium and radium from Type III 

produced water. Each process generates a barium and radium concentrate waste stream that 

may be disposed of by UIC. The first process utilizes a modified lime-soda softening process to 

completely soften produced water. Magnesium, calcium, and strontium are first selectively 

precipitated to yield a solid sludge that may be disposed of as nonhazardous waste in a RCRA-D 

facility. This is followed by precipitation of barium and radium as carbonates. The carbonates 

from the second precipitation step are redissolved with HCl to yield a liquid concentrate that 

can be disposed of by UIC. For the design case, about 0.05 bbl of concentrate for UIC disposal 

and about 25 lb. RCRA-D solid waste are generated per bbl raw produced water. For this case, 

the materials and disposal cost is estimated to be $3.5/bbl produced water. Further 

development work is needed to maximize the selectivity of the first precipitation step for 

calcium and strontium over barium and radium and to reduce the materials cost.

The second process utilizes high surface area, HCl-regenerable MnO2 as an adsorbent for 

barium and radium. The estimated materials and disposal costs for this process are in the 

range of $1.7-$2.3 per bbl produced water for the design case produced water (10, 5 cycles of 

adsorbent life, respectively). Because this process utilizes micron or submicron MnO2 particles, 

further work is required to define cost-effective particle-water separation processes for both 

produced water treatment and MnO2 regeneration. In addition, MnO2 regeneration requires 

dilute HCl (ca. 0.1N), but the regeneration product for UIC disposal is a BaCl2-RaCl2 concentrate. 

MnO2 regeneration with a solution of dilute HCl and concentrated BaCl2-RaCl2 needs to be 

demonstrated in the laboratory.

Both processes have undergone preliminary laboratory scoping studies with field produced 

waters. It is recommended that the modified lime-soda process be further developed in the 

laboratory in preparation for pilot-scale testing. It is also recommended that the further 

laboratory development of the MnO2 adsorption process be conducted. This process has 

potential for lower treatment and disposal costs than the modified lime-soda process. It is also 

recommended that additional laboratory and pilot evaporation and crystallization studies be 

conducted with field produced waters to better define [Ba]max.

Signature and Date Stamp
v

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vi

Table of Contents

Abstract ................................................................................................................................... iii

I. Introduction ........................................................................................................................1

II. Produced Water Composition .............................................................................................4

A. Literature Data .................................................................................................................4

B. Produced Water Samples .................................................................................................5

III. Current Processes for Produced Water Recovery ................................................................6

A. GEWPT Pilot-Scale Evaporator/Crystallizer Trials with Marcellus Produced Water............7

B. Produced Water Pretreatment Map .................................................................................9

IV. Type III Produced Water Pretreatment Process Options....................................................11

A. Ion Exchange ..................................................................................................................11

B. Nanofiltration.................................................................................................................12

C. Sulfate Coprecipitation of Barium and Radium ...............................................................12

D. Lime-Soda Precipitation ..............................................................................................15

E. Modified Lime-Soda Process...........................................................................................16

1. Introduction ............................................................................................................16

2. Aspen Plus/OLI Simulations...................................................................................17

3. Modified Lime-Soda Pretreatment Process Cost Calculations..................................18

4. Laboratory Tests of Modified Lime-Soda Process.....................................................19

F. MnO2 Barium and Radium Adsorption Process...............................................................22

1. MnO2 Characterization and Capacity Screening .......................................................22

2. MnO2 Regeneration Process....................................................................................23

3. PNNL-C Adsorbent Capacity and Regenerability ......................................................25

4. MnO2 Barium and Radium Adsorption-Regeneration Process..................................26
vii

V. Conclusions.......................................................................................................................29

VI. Recommendations ............................................................................................................31

VII. Acknowledgements...........................................................................................................31

VIII. References ........................................................................................................................32

Appendix I. Selective Radium Removal from Produced Water............................................. AI-1

Appendix II. Produced Water Softening by Ion Exchange .................................................... AII-1

Appendix III. Produced Water Softening by Nanofiltration .................................................. AIII-1

Appendix IV. Modified Lime-Soda Process Analysis and Experimental Results..................... AIV-1
1

Produced Water Pretreatment for Water Recovery

and Salt Production

James M. Silva, Hope Matis, William L. Kostedt IV, and Vicki Watkins

I. Introduction

Horizontal drilling and slickwater hydrofracturing have enabled shale gas to become a 

significant contributor to the United States’ energy supply. Developed largely in the Barnett 

shale, these technologies have more recently been applied to the Marcellus shale, which has 

the potential to become the second largest natural gas field in the world1. Hydrofracturing a 

shale gas well typically requires 2MM – 6.5MM gallons of water. About 15-25% of this water 

returns to the surface as “flowback” within 30 days after hydrofracturing. “Produced water” 

continues to flow at a much reduced rate, e.g., 2-10 bbl/day, for the life of the well. It is 

estimated that in Pennsylvania, in 2011, about 25 MM bbl of flowback and produced water will 

be generated2. A potential limitation to developing the Marcellus is the disposal cost of

hydrofracturing flowback and produced water, which are collectively referred to as “frac” water 

in this report. In addition to high salinity and hardness levels (Mg, Ca, Sr, Ba), much Marcellus 

produced water also contains significant levels of naturally occurring radioactive materials 

(NORM), particularly radium. The near absence of disposal wells in Pennsylvania initially forced 

much of the produced water to be trucked into Ohio for disposal by deep-well injection (UIC3). 

The cost of trucking from eastern Pennsylvania to Ohio and disposal by UIC is in the range of 

$10-12/bbl4. 

Since 2009, there has been a significant increase in frac water reuse for subsequent

hydrofracturing jobs. Current estimates of Pennsylvania Marcellus frac water reuse (after 

various forms of pretreatment) range from about two-thirds5to about 95%2. Because flowback

water has much lower TDS6than produced water, flowback water is more likely to be reused in 

subsequent hydrofracturing operations than produced water. Recovered frac water is often 

reused with significant dilution by fresh water. Even assuming 95% reuse, there is still an 

average of approximately 0.15-0.3 MM gallons per day of produced water in the Pennsylvania 

Marcellus shale gas play that must be disposed of by UIC7. As the number of shale gas wells 

within a given geographic region (e.g. a county) grows, the supply of produced water with high 

TDS levels (viz. TDS levels at or above about 125,000 ppm) also grows. This increase is due to 

the lengthy production lifetime of the shale gas wells, each of which continually yields 

produced water. Reuse also increases the TDS level of the produced water. Based on an 

analysis by Hayes8, for a given geographic area, sometime after the rate of hydrofracturing and 

refrac operations peaks, the supply of produced water is expected to exceed the reuse capacity. 

At this point, a growing volume of high-TDS produced water must either be deep-well injected, 

or water and salt recovery is required.
2

There has been much recent regulatory activity with respect to frac water disposal, particularly 

in Pennsylvania. For example, since May 19, 2011, in Pennsylvania, shale gas drillers have been 

directed by PADEP to cease delivering wastewater to the 15 wastewater treatment plants that 

had been accepting it and had been granted “grandfather” status with respect to PADEP’s 2010 

Total Dissolved Solids regulations. These wastewater treatment plants include Publicly Owned 

Treatment Works (POTW) and Centralized Wastewater Treatment (CWT) facilities

9

. 

The purpose of this study is to identify pretreatment technologies that enable economic 

recovery of distilled water and a salable salt product from high-TDS Marcellus shale gas 

produced water. The high TDS levels in the produced water require thermal processes 

(evaporation and crystallization) for economic water and salt recovery. Pretreatment 

technologies include both softening (primarily barium removal) and NORM removal. Softened 

produced water enables a higher recovery of both distilled water and salt product, compared 

with non-softened water. Consistent with these higher recoveries, the crystallizer purge stream, 

which must be disposed of by UIC, is smaller with softened water than with non-softened water.

In produced water, soluble NORM species comprise 226Ra and 228Ra, which are daughter 

products of naturally occurring 238U and 232Th, respectively. 226Ra is of principal interest 

because of its long half-life (1600 years), its water solubility as a divalent cation, and its status 

as a known carcinogen10,11. 

226Ra is an alpha emitter (4.781 MeV) and a gamma emitter (186.2 

keV). The 228Ra activity12 was typically less than 10% of the 226Ra activity for the water samples 

analyzed from the Marcellus Shale formation13. For removal processes, it is expected that 226Ra 

and 228Ra will behave similarly. Therefore, with respect to NORM, this study is focused on 226Ra.

We defined a “design case” produced water composition based on data from the literature as 

well as seven produced water samples that we obtained (six from the Pennsylvania Marcellus 

and one from the Barnett). For the design case, current water recovery technology comprises 

evaporation to recover about 56% of the produced water as distilled water. This process also 

yields a salt concentrate, which is disposed of by UIC. 

To achieve 80-95% water recovery, it is necessary to generate a solid salt product. For use as 

road salt, the solid salt (NaCl) product must pass TCLP14, which includes the requirement that

the TCLP extract of the salt product contain less than 100 mg barium/L. Although there is 

currently no radium specification for road salt in either New York or Pennsylvania15, it is 

assumed that road salt must meet 226Ra specifications for disposal of solids as nonhazardous 

solid waste, which is 25 pCi/gm in Pennsylvania. 

Based on a GEWPT pilot study of Marcellus produced water evaporation and salt crystallization, 

we defined three types of produced water based on their barium and radium concentrations. 

Each type of produced water requires a different pretreatment process to enable recovery of a 

salt product. “Type I” produced waters contain less than a specific barium concentration, 

[Ba]max, (~1,000-2,000 mg Ba/L) and are not restricted with respect to 226Ra activity. Type I 

produced waters require neither barium nor radium removal prior to NaCl crystallization. 
3

“Type II” produced waters contain a higher barium concentration than [Ba]max and very low 

radium activities (<200-1,000 pCi 226Ra/L; upper limit depends on the produced water barium 

concentration). Type II produced waters may be economically treated for barium and radium 

removal by conventional sulfate precipitation prior to NaCl crystallization.

“Type III” produced waters contain a higher barium concentration than [Ba]max and higher 

radium activities (>200-1,000 pCi 226Ra/L; lower limit depends on the produced water barium 

concentration). Type III produced waters require barium removal using a method other than 

direct sulfate precipitation prior to NaCl crystallization. In this project, we focused on defining 

economical barium and radium removal pretreatment processes for Type III produced waters.

We explored several classes of adsorbents to selectively remove radium from produced water, 

which would enable barium to be subsequently removed by sulfate precipitation. DOWEXTM

RSC (radium-specific complexer) has been utilized to remove radium in municipal water 

systems16. However, we found that the 226Ra capacity for RSC (and all other adsorbents 

screened) was too low to economically remove radium from produced water.

We considered ion exchange and nanofiltration as potential methods of softening Type III 

produced water. Based on the design case produced water composition, we found that neither 

process was economically attractive. For ion exchange, the cost of regeneration chemicals and 

waste disposal was over $6/bbl produced water. In addition, the ion exchange regeneration 

waste volume would be comparable to the volume of produced water being treated. For 

softening by nanofiltration, simulations showed that the water recovery fraction would be too 

low to be economical. 

We identified two processes to remove barium and radium from Type III produced water17. The 

byproduct from each process is a concentrated solution of barium and radium that may be 

disposed of by UIC. In the first process, the produced water is completely softened by a 

modified lime-soda process. After magnesium is precipitated as a hydroxide, calcium and 

strontium are precipitated as carbonates and disposed of as nonhazardous waste in a RCRA-D

18

landfill. A second step precipitates barium and radium as carbonates. After these carbonate 

salt solids are removed from the produced water, they are redissolved by addition of HCl to 

form an aqueous solution of BaCl2 and RaCl2, which is disposed of by UIC. For the design case 

produced water, the cost of materials and disposal for this process is $3.5/bbl produced water.

In the second process, barium and radium are removed from produced water by adsorption 

onto a MnO2 adsorbent. This adsorbent is regenerated by dilute HCl treatment, which yields a 

BaCl2-RaCl2 concentrate for disposal by UIC. For the design case produced water, the cost of 

chemicals and disposal for this process is $1.7-$2.3/bbl produced water (based on 10 and 5 

adsorption-regeneration cycles, respectively). This report shows laboratory experimental 

results and costs for both processes.
4

II. Produced Water Composition

A. Literature Data

Figure 1 shows volume and TDS flowback profiles for a characteristic hydrofractured well in the 

Marcellus. This figure was constructed from flow and composition data presented by Vidic19. 

The flowrate is relatively high through Day 6 and then drops to a relatively constant rate 

through Day 22. The instantaneous TDS increases essentially monotonically throughout the 

first 17 days and then plateaus at about 150,000 mg/L. About 27% of the water used to 

hydrofracture the well returned within 22 days. 

0

5

10

15

20

25

30

35

40

0

20000

40000

60000

80000

100000

120000

140000

160000

0 5 10 15 20 25

 Cumulative Water Recovery (%)

mg/L TDS

Time (Days Since Start Flowback)

Instantaneous

TDS

Cumulative TDS

(time zero start: days 0-n)

% Recovery

Cumulative TDS 

(late start: days n-22)

Figure 1. Marcellus Shale Flowback and Produced Water Profiles

Two cumulative TDS levels are also plotted. Each point on the line labeled “Cumulative TDS 

(time zero start: Days 0-n)” represents the volume average TDS of the flowback and produced

water between the beginning of flowback (Day 0) and Day “n”. The value of this cumulative 

TDS measurement for Day 15 is about 60,000 mg/L. Currently, in the Marcellus, much of the 

early flowback water is reused with minimal treatment (e.g. removal of suspended solids and 

bacteria, with optional softening). In this example, the cumulative TDS for the first five days is 

about 50,000 mg/L and represents about 80% of the water returned during the first 22 days. 

This water could be minimally treated and reused in subsequent hydrofracturing jobs. 

Each point on the line labeled “Cumulative TDS (late start: Days n-22” represents the volume 

average TDS for the time interval from Day “n” through Day 22. The value of this cumulative 
5

TDS measurement for Day 6 is about 130,000 mg/L. This value represents the volume average 

TDS for flowback and produced water collected from Day 6 through Day 22. Flowback and 

produced water from this interval may be pretreated and thermally recovered as distilled water 

and salt.

Keister20 reported frac water compositions, giving values for low-, medium-, and high-TDS frac 

water, as well as a “typical” frac water. Table 1 shows the values reported by Keister.

A private report of Marcellus frac water composition was prepared for the Marcellus Shale 

Coalition21. This report surveyed frac waters from 19 locations during both the early flowback 

period (1-5 days) and later periods (14, 90 days). The range and median values of TDS and 

specific ion concentrations reported are consistent with values shown in Table 1 and in the 

samples that we obtained (discussed in Section II-B below).

Table 1. Marcellus Frac Water Compositions

(all concentrations in mg/L)

Component Low-TDS Medium-TDS High-TDS “Typical”

TDS 69,640 175,300 248,000 195,000

Mg 438 938 1,630 1,300

Ca 5,140 14,100 31,300 18,000

Sr 1,390 6,830 2,000 4,000

Ba 2,300 3,310 4,300 6,500

Fe 11.2 52.5 134 60

Mn 1.9 5.17 7 5.0

B. Produced Water Samples

We obtained Marcellus shale gas produced water from horizontal wells in four Pennsylvania 

counties. Samples were obtained from either portable frac tanks adjacent to a recently 

hydrofractured well or from a permanent tank at a well site. In addition, one sample was taken 

from a salt water disposal facility in the Barnett Shale (Texas).

Table 2 shows the measured composition for these samples. All ionic species were measured 

by inductively coupled plasma (ICP). Only one sample (Well-4) had a measurable level of 

sulfates; the same sample had a very low barium level. The appearance of the frac water 

samples when received ranged from clear to orange-brown.

The level of 226Ra in each sample was measured using gamma spectrometry. Several of the 

226Ra gamma spectrometry measurements were conducted both at GEGR and at the New York 

State Department of Health, with excellent agreement between the two sites. The GEGR 

results are reported in Table 2.
6

Based on the measured composition of the Marcellus produced water samples shown in Table 

2, we identified a design case produced water composition (“Design Case”). For the design case, 

each species concentration approximates the median of the measured concentrations.

Table 2. Produced Water Compositions from Pennsylvania Marcellus Shale Gas Wells.

(all quantities mg/L except where noted)

Well-1 Well-2 Well-3 Well-4 Well-5 Well-6 Well-7

a Design

Case

County Bradford Bradford Bradford Butler Tioga Washington

pHb7.3 6.3 5.4 5.8 5.9 6.2 6.6 7.0

TDS 98,294 155,705 199,242 68,439 149,188 122,562 124,421 132,460

Na+26,500 38,200 51,800 19,200 39,000 32,300 33,900 35,000

Mg++ 460 840 1290 570 1,000 800 1,170 800

Ca++ 5,560 10,280 13,120 5,360 13,000 8,700 10,880 9,500

Sr++ 2,030 3,670 4,580 1,290 2,600 2,340 1,750 2,500

Ba++ 6,580 13,200 11,600 32 3,500 5,800 147 6,200

Fe++ 26 74 123 55 32 75 47 50

Mn++ 1.5 2.5 3.4 1.7 2.7 4.3 1.2 3

Cl-e57,120 89,429 116,713 41,845 90,014 72,525 76,493 78,407

SO4

=

<10 <10 <10 57 <5 <50 <100 0

SiO2 16.7 11 13 29 39 18 33 0

Hardness 

as Ca++ 9,167 17,196 20,727 6,899 16,860 12,782 13,653 13,772

226Rac

5,400 7,600 4,200 4,600 5,600 820 2300 5,000

TSS 202 282 500 62 520 210 898 0

Turbidityd78 399 1160 17.4 192 45 164 0

TOC <10 11.8 11.8 72 151 160 88 0

PW TypefIII III III I III III I III

a

Produced water from Barnett Shale (TX)

b

dimensionless

c

pCi/Liter

d

Turbidity units: NTU

e

adjusted to force ion balance (prior analyses found other anions were <1% of the chloride on a 

molar basis)

f

Produced Water Type (see Figure 4 below for map of produced water types)

III. Current Processes for Produced Water Recovery

Figure 2 shows a schematic diagram of GEWPT’s current mobile evaporation process for 

recovery of distilled water and a brine concentrate from produced water. In this figure, all 

quantities are based on the design case produced water composition. This is a very direct

option for frac water recovery, including high-TDS produced waters that contain significant 

levels of 226Ra and/or barium. This results in limited water recovery, but avoids generating 

solids with high 226Ra or barium levels. Current methods for produced water pretreatment 
7

prior to thermal evaporation include oxidation and lime treatment, which precipitates iron and 

manganese and removes suspended solids22,23. Pretreatment for barium and radium is not 

required; barium and radium are carried along with the concentrate. Assuming that the 

concentrate leaving the evaporator has 300,000 mg/L TDS, 0.56 bbl of distilled water is 

recovered per bbl feed produced water for the design case. Table 3 shows the concentration 

factor and the cost of transportation and disposal of the concentrate, assuming transport from 

north-central Pennsylvania to Ohio and disposal by UIC in Ohio. The estimated cost for 

concentrate transportation from central Pennsylvania to Ohio and disposal by UIC is $11/bbl.

In lab experiments with Marcellus produced waters, the 226Ra activity measured by gamma 

spectrometry in the pretreated produced water was identical to that of the untreated produced 

water, within the accuracy of the measurement. From this, we infer that the pretreatment 

sludge contains negligible 226Ra activity.

The GEWPT mobile evaporator is currently undergoing field trials with produced water.

Figure 2. Current Produced Water Recovery Process

(Design Case Produced Water Composition)

A. GEWPT Pilot-Scale Evaporator/Crystallizer Trials with Marcellus Produced

Water

GEWPT conducted pilot-scale trials of Marcellus produced water evaporation in a vertical falling 

film evaporator and crystallization of the evaporator blowdown to generate a solid NaCl salt 

product and distilled water. Table 4 shows the composition of the evaporator feed (pretreated 

produced water) and the crystallizer feed. The crystallizer product passed TCLP and met ASTM 

D-635 standards for use as road deicing salt. Figure 3 contrasts the appearance of the original 

produced water, the distilled water product, and the recovered salt product. 
8

Table 3. Produced Water Evaporation: Water Recovery

Well Number 1 2 3 4 5 6 7

Design 

Case

Feed TDS, mg/L 98,294 155,705 199,242 68,439 149,188 122,562 124,421 132,460

max water recovery:

(wt H2O)/(wt feed)

b 0.902 0.844 0.801 0.932 0.851 0.877 0.876 0.868

Max water recovery:

(vol H2O)/(vol feed) 0.970 0.947 0.930 0.981 0.950 0.960 0.959 0.956

Evaporation only: 

fraction of maximum 

water recoveryc

0.705 0.522 0.376 0.796 0.543 0.628 0.623 0.597

concentration factor, 

(Vol feed)/(Vol conc)

3.05 1.93 1.51 4.38 2.01 2.45 2.41 2.26

bbl distilled water/

bbl feed 0.700 0.513 0.365 0.793 0.535 0.622 0.616 0.590

Concentrate disposal 

costa, $/bbl feed $3.93 $6.23 $7.97 $2.74 $5.97 $4.90 $4.98 $5.30

a

Cost for transportation from north-central Pennsylvania to Ohio and UIC disposal in Ohio

b

100% dry salt product

c

Concentrate: 300,000 mg/L TDS

Based on the measured barium concentration in the salt product and in the produced water, 

we estimated the produced water barium concentration for which the resulting barium 

concentration in a TCLP extract would equal 100 mg/L, the maximum value permissible under 

TCLP. The estimated value, [Ba]max, is in the range of 1,000-2,000 mg Ba/L produced water. 

Assuming that barium and radium behave identically in the NaCl crystallization process, we 

estimated the radium content in the solid salt product for a specified radium activity in the 

produced water. This assumption is based on the fact that the ionic radii of Ba+2 (1.49 Å) and 

Ra+2 (1.62 Å) are very similar, and that barium and radium behave essentially identically in all 

crystallization processes24.

The design case produced water contains 5,000 pCi 226Ra/liter. For this case, the estimated 

226Ra activity in the salt product is well below 10 pCi/gm.
9

Untreated

Frac

Water

Recovered

Distilled

Water

Recovered

NaCl

Figure 3. GEWPT Pilot Trial Results for Thermal Recovery of 

Water and Salt from Produced Water

This pilot test of produced water evaporation and crystallization demonstrates the feasibility of 

recovering distilled water and a salable salt product from produced water by thermal 

evaporation and NaCl crystallization. This pilot test also provides a basis for estimating [Ba]max. 

These pilot results support the assertion that for the design case produced water (5,000 pCi 

226Ra/L) as well as produced waters with significantly higher radium activities, the estimated 

radium activity in the product salt is well below the permissible level for disposal as 

nonhazardous waste in a RCRA-D landfill (<25 pCi 226Ra/gm in PA) and is therefore negligible.

Table 4. Produced Water Composition for Pilot Evaporator and Crystallizer Test

(all quantities mg/L except where noted)

Evaporator 

Feed

Crystallizer 

Feed

pH 6.0 5.9

TDS 122,000 271,000

Na+30,800 68,100

Fe++ <0.5 <0.5

Mn++ <0.2 <0.2

Cl70,200 155,000

SO4

=

<10 15

SiO2 <10 42

TSS None None

Turbidity, NTU <0.1 0.4

B. Produced Water Pretreatment Map

We developed the pretreatment map shown in Figure 4 based on the results of the produced 

water evaporation and crystallization pilot study conducted by GEWPT described above and 

sulfate precipitation material balance calculations (Section IV.C, below). This map identifies 

three “types” of produced water based on their barium concentrations and radium activities. 

The produced water compositions analyzed in this study are superimposed on this map. Each 
10

type of produced water requires a different pretreatment for barium removal prior to NaCl 

crystallization.

Type I: The produced water barium concentration is below [Ba]max (a value in 

the range 1,000-2,000 mg/L) and is not restricted with respect to 226Ra activity. 

Type I produced waters require neither barium nor radium removal prior to NaCl 

crystallization. Produced waters from Well-4 and Well-6 are of Type I. 

Type II: The produced water barium concentration is higher than [Ba]max. 

Barium removal is needed prior to NaCl crystallization. Pretreatment of Type II 

produced water by sulfate precipitation yields a sulfate sludge that is safe for 

disposal in a RCRA-D landfill because the 226Ra activity in the sludge is below the 

limit established by the state (25 pCi 226Ra/gm sludge in PA). The location of the 

red line in Figure 4 depends on the RCRA-D limit for 226Ra activity in a particular 

state. It is assumed that the sulfate sludge is 45 wt% solids.

Type III: The produced water barium concentration is above [Ba]max. Therefore, 

barium removal is needed prior to NaCl crystallization. Because the 226Ra activity 

is above the red line in Figure 4, a pretreatment process other than direct sulfate 

precipitation must be used. 

0

1000

2000

3000

4000

5000

6000

7000

8000

0 5000 10000 15000

pCi 226Ra/L Frac Water

mg Ba/L Frac Water

Type III: Ba Removal Needed

Direct Sulfate ppt Not OK

(>25 pCi 226Ra/gm wet ppt)

Type I: No Ba, Ra Removal Needed

Type II: Ba Removal Needed

Sulfate Precipitation OK

(<25 pCi 226Ra/gm wet ppt)

Design

Case

[Ba]

max

Figure 4. Map of Produced Water Types and Barium Removal Pretreatment Requirements

(symbols represent produced water compositions analyzed in this study)
11

IV. Type III Produced Water Pretreatment Process Options

To recover distilled water and a salable salt from Type III produced waters, it is necessary to 

remove barium by a method other than direct sulfate precipitation. Sulfate precipitation for 

Type III produced waters would be acceptable if the radium is first removed from the produced 

water. We sought methods to selectively remove radium from produced water, including 

DOWEXTM RSC (radium specific complexer) resin. In Appendix I, we review the literature on RSC 

resins and show the results of laboratory screening of a variety of adsorbents for selective 

removal of radium from produced water. As described in Appendix I, of the 60 adsorbents that 

we screened, none was economically feasible. Therefore, we abandoned the effort to 

selectively remove radium from produced water.

As shown in Figure 5, we analyzed six processes for removal of barium, radium, and other 

multivalent cations from high-TDS brines. These include ion exchange, nanofiltration, sulfate 

precipitation, carbonate precipitation, the modified lime-soda process, and MnO2 adsorption. 

Each process is reviewed in the following sections.

Figure 5. Schematic Diagram of Type III Produced Water Recovery Process

and Pretreatment Options

A. Ion Exchange

As shown in Appendix II for the design case produced water, approximately one bed volume of 

chelating ion exchange resin is required to soften one bed volume of produced water. Thus, 

the ion exchange resin will be exhausted after it has processed one bed volume of produced

water. The cost for regeneration chemicals and disposal of waste streams by UIC is calculated 

to be over $6/bbl produced water. This cost is quite high, and it does not include the cost of 

sourcing or disposing of rinse water, which is needed after acid treatment and after caustic 
12

treatment. The regeneration rinse waters could most likely be combined, neutralized, and sent 

to an industrial wastewater treatment plant. Because of the high cost and need to handle 

significant volumes of rinse water, chelating ion exchange is not recommended for softening

Marcellus produced water.

B. Nanofiltration

Appendix III shows simulation results for NF softening of produced water using WINFLOWS 

software from GEWPT. Produced waters from both the design case and Well-5 were 

considered. Maximum softened water (permeate) recovery calculations were based on a feed 

pressure upper limit of 600 psia. Table 5 shows the maximum permeate recovery calculated 

from the simulations for both cases. 

Table 5. Nanofiltration: Simulation Results

Well-1 Well-2 Well-3 Well-4 Well-5 Well-6 Well-7

Design

Case

Maximum permeate 

recovery based on 

Winflows Simulation (%)

15 30

As noted above, the estimated cost for concentrate transportation from central Pennsylvania to

Ohio and disposal by UIC is $11/bbl. For the design case produced water, the maximum 

permeate water recovery was 30%. At this recovery level, the transportation and disposal cost 

for the concentrate is $7.70 per bbl feed produced water. Based on the low recovery and the 

resulting high disposal cost of the concentrate, it is recommended that NF technology not be 

pursued for produced water softening.

C. Sulfate Coprecipitation of Barium and Radium

This section describes produced water pretreatment by sulfate precipitation and shows 

(through material balance calculations) that direct sulfate precipitation should not be utilized to 

pretreat Type III produced waters. 

Sulfate precipitation is currently practiced for treating produced water. ProChemTech 

International, Inc. describes a chemical treatment process that pretreats produced water using 

three sequential precipitation steps25. The first step removes barium by precipitation as barium 

sulfate26, which is non-leaching by TCLP. The subsequent precipitation steps remove the 

remaining scale formers. ProChemTech also describes a process in which produced water is 

treated with sulfuric acid to precipitate a barium sulfate sludge followed by lime/soda softening 

to generate a calcium carbonate sludge27.

Veil28 describes four commercial wastewater disposal facilities in Pennsylvania that, as of May, 

2010, treated frac water and disposed of the treated water to either a POTW or a river under 

NPDES29 permits. At these facilities, frac water is typically treated with sodium sulfate in order 
13

to precipitate barium, followed by lime treatment to precipitate magnesium and other 

hardness species. Precipitate from these steps is settled in a thickener and dewatered in a filter 

press. The sludge is sent to a local landfill.

Reserved Environmental Services30 operates a 1.2 MGD produced water treatment facility in 

southwest Pennsylvania. TerrAqua31 operates a 0.4 MGD facility in Williamsport, Pennsylvania. 

Both facilities remove barium, strontium, iron, and suspended solids from produced water and 

return the treated water to the customer for use in subsequent drilling and hydrofracturing 

operations. Because the sludge generated must pass TCLP, it is assumed that sulfate is used to 

precipitate barium and strontium as BaSO4 and SrSO4, respectively. Precipitation of barium and 

strontium with sulfate is attractive because sodium sulfate is relatively inexpensive ($130-

160/short ton, anhydrous)32, and BaSO4 and SrSO4 are nonhazardous. These plants may be 

expanded to include thermal evaporation and crystallization to yield a saleable salt product and 

distilled water. Additional frac water treatment plants are in operation in Pennsylvania. 

Dozens of additional treatment plants are in the planning stages and many have received 

permits28.

a) Radium Solubility in Sulfate Environments

For radium-containing produced waters, sulfate treatment yields a coprecipitate of barium 

sulfate and radium sulfate (radio barite, Ba(Ra)SO4), which is a solid solution of RaSO4 and 

BaSO4. Radio barite is well-known in the oil and gas industry. The EPA estimates that one-third 

of all domestic oil and gas wells produce some radium-contaminated scale33. Radium sulfate is 

one of the least water-soluble salts. The solubility of RaSO4 alone in water is 4.8x10-8 M (11

ppb/w Ra, or 11x106pCi Ra/L)

34, which is about three orders of magnitude higher than the 

highest 226Ra activity found in Marcellus produced water (10,000 pCi/L). However, the 

presence of barium reduces the radium sulfate solubility significantly. Doener and Hoskins35, in 

1925, confirmed that in the presence of sulfate ion, a solution of RaCl2 and BaCl2 coprecipitates 

as RaSO4 and BaSO4 even when the concentrations of Ra++ and SO4=are far below the solubility 

of RaSO4 in water. They concluded that barium and radium coprecipitate to form a solid 

solution of RaSO4 and BaSO4. Under ideal solid solution conditions, the calculated solubility36 of 

RaSO4 in equilibrium with a solid solution of (Ra,Ba,Ca,Sr)SO4 is 7 x 10-13 M, or 2 x 10-7ppm/w37

Ra. This calculated solubility of Ra is equivalent to 200 pCi/L of 226Ra. In GEGR laboratory 

experiments with Well-3 produced water, the radium activity in solution after addition of an 

excess of sodium sulfate (vs. barium) was non-detectable by high purity germanium (HPGe) 

gamma spectrometry. The detection limit for 226Ra was 17 pCi/liter.

b) Material Balance for Barium and Radium Sulfate Precipitation

As noted above, sulfate sludge may be safely and economically disposed of as nonhazardous 

solid waste in a RCRA-D landfill if the 226Ra activity in the sludge is below 5-50 pCi/gm. The limit 

varies by state and is 25 pCi/gm for Pennsylvania. The cost for sludge disposal as nonhazardous 

waste in a RCRA-D landfill is typically about $50/ton. Sludge that exceeds this value must be 

disposed of as Low Level Radioactive Waste (LLRW). Energy Solutions, Inc. (Utah) charges 

about $200/ft3(excluding transportation) for disposal of Class A LLRW, which can contain up to 

10 nCi/gm 226Ra.
14

We conducted a simple material balance to estimate the radium activity in the (Ba,Ra)SO4

sludge. We assumed that on addition of a stoichiometric amount of Na2SO4 to produced water,

all the barium and radium in the raw produced water precipitate as (Ba,Ra)SO4 sludge, and that 

no other components precipitate. We also assumed that the sludge would be dried to 45% 

solids before being transported to a landfill. Figure 6 shows the calculated radium activity in 

the wet sludge as a function of the radium activity in the produced water feed for six levels of 

barium in the produced water 38. Design case produced water contains 6,200 mg barium/L. For 

this barium concentration, the produced water 226Ra activity must be below about 600 pCi/L for 

the resulting sulfate sludge to meet Pennsylvania’s RCRA-D disposal criteria. For all produced

waters analyzed in this study, the calculated 226Ra activity in a hypothetical (Ba,Ra)SO4 sludge is

above 25 pCi/gm, as shown in Table 6. Therefore, the sulfate sludge would need to be either 

blended with sufficient non-radioactive solid waste to meet the RCRA-D specification for 226Ra 

activity or treated as LLRW.

Table 6 also shows the amount of wet sulfate sludge generated per barrel of produced water, 

as well as the cost of disposing of this sludge as LLRW. The cost of sludge disposal as LLRW is 

prohibitive. Because Well-4 and Well-7 are Type I produced waters, they do not need 

pretreatment for barium removal prior to NaCl crystallization.

Table 6. Material Balance for BaSO4-RaSO4 Sludge (45 wt% solids)

Well Number 1 2 3 4

a

5 6 7

a Design 

Case

226Ra Activity in wet 

Sludge, pCi/gm 217 152 95.9 - 424 37.4 - 213

Wet Sludge quantity

lb/bbl Produced Water 8.71 17.5 15.4 - 4.63 7.68 - 8.21

LLRW Disposal Cost 

$/bbl Produced Water

$18 $36 $32 - $10 $16 - $17

a

Type I produced water
15

0

10

20

30

40

50

60

70

80

0 200 400 600 800 1000 1200

1,000

3,500

5,000

6,200

10,000

13,000

226Ra Activity in Wet (Ba,Ra)SO4 Sludge (pCi/gm)

226Ra Activity in Produced Water Feed (pCi/L)

Feed Produced Water Ba (mg/L)

PA RCRA-D Limit

Figure 6. Calculated Sludge 226Ra Activity for (Ra,Ba)SO4 Coprecipitation 

D. Lime-Soda Precipitation

Treating produced water with lime and sodium carbonate precipitates magnesium as Mg(OH)2

and calcium, strontium, barium, and radium39 as their corresponding carbonates. Table 7

shows, for each produced water, the calculated 226Ra activity for the wet carbonate sludge 

resulting from complete softening by lime-soda treatment (sludge: 45 wt% solids). Each of 

these activities is higher than the maximum level permitted for RCRA-D disposal in Pennsylvania. 

These sludges would have to be disposed of as LLRW, and the cost for disposal would be 

prohibitive.

Table 7. Calculated Barium Concentration and 226Ra Activity in Wet Carbonate Sludge 

for Lime-Soda Treated Produced Waters (45% solids)

Well Number 1 2 3 4 5 6 7

Design 

Case

pCi 226Ra/gm wet sludge 87.2 64.7 31.4 143.2 56.9 10.3 31.2 58.0

Ba in wet sludge, ppm/w 106K 112K 86.6K 848 35.5K 72.6K 2.00K 80.0K

LLRW Disposal cost, $/bbl $45 $86 $98 $28 $72 $59 $54 $63

Produced Water Type III III III I III III I III

In addition, barium carbonate is easily leached with acid, and sludge that yields above 100 mg 

barium/L in a TCLP extract will not pass TCLP. Table 7 shows that for all Type III produced 

waters, the barium concentration in the precipitate is far too high to be suitable for disposal in 
16

a RCRA-D landfill. Thus, lime-soda softening and sludge disposal of Type III produced water is 

not practical.

E. Modified Lime-Soda Process

1. Introduction

Table 8 shows the costs of disposal and restrictions on 226Ra activity for three disposal options

for pretreatment process byproducts. The low disposal cost by UIC for waste that contains 

226Ra is a strong motivation to develop a process that yields an aqueous 226Ra (and barium) 

concentrate. According to the Ohio Department of Natural Resources, which manages the 

underground injection control (UIC) program, there is currently no official limitation on the 

226Ra activity or barium concentration in liquids disposed of by UIC. In addition, disposal by UIC 

is regarded as a safe method to avoid groundwater or aquifer contamination.

Table 8. Disposal Costs (excluding transportation)

RCRA-D Nonhazardous 

Landfill

UIC (Deep-well 

Injection)

Low-Level Radioactive 

Waste (LLRW)

Locations 50 sites in PA Ohio, WV Utah

Maximum 226Ra pCi/gm 25 (in PA) - 10,000

Disposal cost: $/short ton 50 11.5 6,400

Figure 7 shows a schematic diagram of the modified lime-soda process to pretreat Type III 

produced water. Produced water is first oxidized and contacted with lime to precipitate 

magnesium as Mg(OH)2, iron as Fe(OH)3, and manganese as MnO2. Just over 1 mole Ca(OH)2

per mole Mg results in essentially complete precipitation of Mg as Mg(OH)2. The pH in 

Precipitation Stage 1A is about 10.6-10.8. Sodium carbonate is then added to selectively 

precipitate calcium and strontium. The pH in Precipitation Stage 1B is about 11-11.3. 

Precipitation Stages 1A and 1B may be conducted in a single vessel. The precipitates from 

Stages 1A and 1B are nonhazardous and may be disposed of in a RCRA-D nonhazardous landfill. 

In Precipitation Stage 2, the produced water is treated with additional sodium carbonate to 

precipitate both barium and radium as carbonates. The Stage 2 precipitate is removed from 

the produced water and treated with concentrated HCl to convert BaCO3 and RaCO3 to CO2, 

BaCl2, and RaCl2. Carbon dioxide is vented to the atmosphere, optionally though a carbon 

adsorbent to trap radon gas. The HCl addition is adjusted to achieve a pH low enough to strip 

essentially all of the carbonates from the aqueous concentrate stream (e.g. pH 2-4). This 

concentrate stream may be neutralized if desired prior to disposal by UIC. 

After Precipitation Stage 2, the softened produced water still contains a significant 

concentration of dissolved carbonates (about 450 ppm/w CO3

=

for design case produced water). 

HCl is added to this stream to drive off CO2. The softened, decarbonated produced water may 

then be thermally treated to recover distilled water and a solid salt product. 
17

Figure 7. Schematic Diagram of Modified Lime-Soda Process

This process exploits the relative solubilities of the Group II metal carbonates. Table 9 shows 

that calcium and strontium carbonate are less soluble than either barium or radium carbonate 

and are thus expected to precipitate preferentially over barium and radium carbonate as 

sodium carbonate is added to the system.

The produced water pretreated by this process is essentially completely softened. This enables 

very high water and NaCl recoveries. Further, the relatively pure salt product may be usable for 

higher value applications than road deicing. For example, the salt product may be used as 

feedstock for caustic and chlorine production or for industrial water softening.

Table 9. Water Solubility of Group II Metal Carbonates40

Species Solubility, gm/100 gm H2O Temperature, C

MgCO3.5H2O 0.176 7

MgCO3 0.0106 ~20

CaCO3 (calcite) 0.0014 25

CaCO3 (aragonite) 0.00153 25

SrCO3 0.0011 18

BaCO3-alpha 0.002 20

BaCO3-beta 0.022 18

BaCO3-gamma 0.0022 18

RaCO3 more soluble than barium carbonate24

2. Aspen Plus/OLI Simulations

We conducted Aspen Plus/OLI simulations of the modified lime-soda process. Figure 8 shows 

simulation results for the design case. Prior to Na2CO3 addition, the magnesium has been 

essentially completely precipitated by lime addition. This figure shows that as Na2CO3 is added 

to the system, CaCO3 precipitates first, followed by coprecipitation of both CaCO3 and SrCO3. 
18

Barium carbonate does not begin to precipitate until the calcium and strontium have been 

nearly completely precipitated. At about 1.15 times the stoichiometric amount of Na2CO3, the 

barium precipitation is essentially complete. At this point, the solution contains about 50 

ppm/w Ba (compared with over 5600 ppm/w in the feed solution). The target barium 

concentration in Precipitation Stage 2 may be defined through additional laboratory and pilot 

testing. Appendix IV shows precipitation plots for each of the produced waters characterized in 

this study.

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm/w Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Design Case

Figure 8. Simulation Results for Modified Lime-Soda Process: Design Case

3. Modified Lime-Soda Pretreatment Process Cost Calculations

Table 10 shows the calculated chemical and disposal costs for the produced waters considered 

in this study. Table 10 reports both a minimum and maximum cost estimate for each produced 

water considered in this study. The minimum cost assumes that in both Precipitation Stages 

1A-1B, and Precipitation Stage 2, equilibrium conditions prevail. Under equilibrium conditions, 

negligible amounts of barium and radium precipitate in Stages 1A-1B along with the magnesium, 

calcium, and strontium. Similarly, negligible amounts of magnesium, calcium, and strontium 

precipitate in Stage 2. For the design case produced water, the minimum cost for chemicals 

and disposal is $3.5/bbl produced water feed. 

The maximum cost is based on no selectivity in the carbonate precipitation process. Thus, 

Precipitation Stages 1B and 2 are combined. Calcium, strontium, barium, and radium 

precipitate together as a single mixture. In this case, no carbonates are disposed of as RCRA-D 

waste. All carbonates are treated by HCl to generate a chloride concentrate for UIC disposal. 
19

For the design case produced water, the maximum cost for chemicals and disposal is $5.8/bbl 

produced water feed. 

Table 10. Chemical and Disposal Costs for Modified Lime-Soda Process

Well Number 1 2 3 4 5 6 7 Design

Feed TDS, mg/L 98,294 155,705 199,242 68,439 149,188 122,562 124,421 132,460

Hardness as Ca++, mg/L 9,167 17,196 20,727 6,899 16,860 12,782 13,653 13,772

Feed Ba, mg/L 6,580 13,200 11,600 32 3,500 5,800 147 6,200

lb dry Ca(OH)2/bbl PrWa0.489 0.918 1.45 0.589 1.01 0.870 1.24 0.876

lb dry Na2CO3/bbl PrW 8.56 16.8 21.0 6.71 14.9 14.6 13.1 13.2

Case 1: 100% Carbonate Precipitation Selectivity (Minimum Cost)

lb dry HCl/bbl PrW 1.44 2.95 2.91 0.288 1.25 2.50 0.285 1.51

Chemicals & Disposal 

$/bbl Produced Water $2.45 $4.87 $5.78 $1.54 $3.77 $3.89 $2.98 $3.50

bbl UIC disposal/bbl PrW 0.0307 0.0633 0.0606 3.3x10-50.0251 0.0301 5.2x10-40.0305

lb wet solids to RCRA-D/

bbl Produced Water 15.0 28.8 38.6 14.3 29.8 23.1 29.0 25.2

Case 2: 0% Carbonate Precipitation Selectivity (Maximum Cost)

lb dry HCl/bbl PrW 5.68 11.1 13.78 4.19 9.94 8.07 8.60 8.74

Chemicals & Disposal

$/bbl Produced Water $3.84 $7.53 $9.37 $2.93 $6.67 $6.09 $5.84 $5.91

bbl UIC disposal/bbl PrW 0.0944 0.185 0.227 0.0664 0.161 0.132 0.133 0.143

lb wet solids to RCRA-D/

bbl Produced Water 0.83 1.59 2.51 1.01 1.74 1.47 2.14 1.49

a

PrW: Produced water

4. Laboratory Tests of Modified Lime-Soda Process

We conducted two exploratory laboratory experiments to test the modified lime-soda process

and one experiment in which NaOH was substituted for Na2CO3 during Precipitation Stages 1A 

and 1B. Appendix IV shows the details of these experiments. In each of the first two 

experiments, a sample of produced water was added to a beaker and first treated with lime, 

followed by addition of Na2CO3, either portionwise or continuously. Samples of the 

supernatant were filtered and analyzed for residual radium by Liquid Scintillation Counting 

(LSC). For a given sample, the radium activity is proportional to the measured counts per 

minute (CPM). Results are reported as the fraction of the produced water CPM remaining in 

solution after a specific amount of Na2CO3 has been added. Since barium and radium

coprecipitate as carbonates, it is assumed that the fraction barium remaining in solution is 

approximately equal to the fraction radium remaining in solution24.

Ideally, the fraction radium activity remaining in solution is unity until the number of moles of 

Na2CO3 added equals the number of moles of Ca++ + Sr++ in the feed solution, followed by a 

decrease to zero as the number of moles to Na2CO3 increases to about 1.15 times the number 

of moles of Ca++ + Sr++ + Ba++ initially in the produced water. The 15% molar excess carbonate 

value is based on the simulation results for Well-5 produced water. According to the simulation, 
20

with 15% molar excess Na2CO3 addition, the residual barium concentration in solution is 59 

ppm/w, which corresponds to a reduction of about 99% vs. feed concentration. 

a) Experiment 20110826 with Well-5 Produced Water

We added one liter of Well-5 produced water and a magnetic stir bar to a beaker. After 

Ca(OH)2 addition, Na2CO3 was added to the agitated mixture in ten equal portions. Enough 

Na2CO3 was added to precipitate all of the calcium, strontium, and barium. Each portion was 

added essentially instantaneously. Approximately two minutes elapsed between Na2CO3

additions.

Instead of the ideal behavior, Figure 9 shows that the fraction feed CPM decreased

monotonically with increasing Na2CO3 addition. This suggests that barium and radium

precipitated in proportion to the amount of Na2CO3 addition. Thus, under these conditions, the 

process showed no selectivity for the less soluble carbonates (Ca, Sr) over barium and radium. 

It is hypothesized that the Na2CO3 addition rate was too high (for the mixing intensity afforded 

by the magnetic stir bar) for near-equilibrium conditions to apply.

Figure 9. LSC Results for Experiment 20110826

b) Experiment 20110901 with Well-5 Produced Water

Experiment 20110826 was repeated with addition of a solution of Na2CO3 to an agitated 

mixture of Well-5 produced water at a constant rate over the course of 316 minutes. Figure 10

shows the results of this experiment. Although the ideal behavior was not achieved, this 

experiment shows that steady, slower Na2CO3 addition resulted in much better selectivity than 

observed in experiment 20110826. Additional tests are planned with improved agitation and 

other techniques to more closely approach ideal behavior.
21

Figure 10. LSC Results for Expt 20110901

c) Experiment 20110708 with Well-5 Produced Water

This test utilized NaOH to precipitate Mg, Ca, and Sr as the corresponding hydroxides, followed 

by Na2CO3 to precipitate Ba and Ra as the carbonates. This approach is based on the relatively 

high solubility of Ba(OH)2 (5.6 gm Ba(OH).8H2O per 100 gm H2O at 15C

40), which serves to keep 

barium and radium in solution while magnesium, calcium, and strontium precipitate as 

hydroxides. 

NaOH was added portionwise to a beaker of Well-5 produced water and the supernatant was 

sampled after each aliquot for LSC analysis. After the last NaOH addition, the slurry was filtered 

through a 1 glass filter. The filtrate was placed back into the beaker and the agitation was 

restarted. Then a series of six portions of Na2CO3 was added in the same manner, with 

sampling after each portion.

Figure 11 shows the results of this experiment. Here, the barium and radium remain in solution 

throughout the course of the NaOH addition. The total amount of NaOH was sufficient to 

precipitate all of the magnesium, calcium, and strontium. Although excess Na2CO3 was added, 

more Na2CO3 may be necessary to completely precipitate the barium and radium as carbonates. 

This can be determined with further experimental and simulation studies. Although this 

process shows better selectivity toward Group II metals other than barium and radium in the 

first step, the cost of NaOH per equivalent is about 30% higher than the cost of Na2CO3 per 

equivalent. Further, the precipitate obtained from the NaOH addition was very difficult to filter. 
22

Figure 11. LSC Results for Experiment 20110708

F. MnO2 Barium and Radium Adsorption Process

We identified MnO2 as an effective adsorbent for barium and radium removal from produced

water. We tested MnO2 adsorbents that were made at Pacific Northwest National Laboratory 

(PNNL) and obtained from commercial sources.

We also demonstrated that barium and radium can be stripped from these adsorbents using 

dilute HCl. This concentrate of RaCl2 and BaCl2 can be disposed of by UIC. We showed that 

regenerated MnO2 adsorbent is effective for reuse. Alternatively, HCl-treated adsorbent can be 

rinsed and disposed of as nonhazardous solid waste as long as it meets RCRA-D disposal criteria. 

On the basis of the materials and disposal costs, this process is less expensive than the modified 

lime-soda process. However, for adsorbents that have commercially practical barium and 

radium capacity in produced water applications, the particle size is in the micron or submicron 

range. Additional development is required to define cost-effective methods of particle handling. 

Suitable methods must be developed for contacting the particles with produced water, filtering 

the particles from the treated produced water, and recovering the particles for HCl treatment 

and disposal. This process is currently under development at GEGR.

1. MnO2 Characterization and Capacity Screening

For adsorbent capacity screening studies, we measured the radium capacity of each adsorbent 

by LSC. Adsorption experiments were also conducted in which both barium and radium

capacities were measured. These experiments, in substantial agreement with an earlier study 

by Moon et al41, showed that MnO2 adsorbs comparable percentages of both barium and 

radium from solution.

We measured the 226Ra adsorption capacity of both commercially available MnO2 powder 

(Fluka Activated MnO2) and 14 proprietary MnO2 adsorbents obtained from PNNL. All materials 

in this study were powders. The Fluka activated MnO2 was pure MnO2 powder. Each PNNL 
23

material was characterized by BET for surface area and by Energy Dispersive Spectroscopy (EDS) 

for bulk composition. As shown in Table 11, the materials from PNNL comprise various forms of 

MnO2 supported on silica. These materials are referred to as “resins”.

We first screened the PNNL materials for their 226Ra capacity using Well-4 produced water. 

Even though Well-4 produced water is Type I, it was useful for these studies because it afforded 

significant 226Ra capacity to each adsorbent, which enabled the use of LSC for capacity 

measurements. Table 11 shows that PNNL samples C, D, F, G, I, K, and L have the highest 226Ra

capacities. 

We also evaluated the adsorption and regeneration performance of material “C” for both 226Ra 

and barium. For these studies, we measured 226Ra activity by LSC and barium concentration by 

ICP.

2. MnO2 Regeneration Process

We conducted nine adsorption-regeneration tests with Fluka activated MnO2, using Well-4 

produced water and HCl for regeneration. These tests focused on defining regeneration 

process conditions. The performance of a given regeneration condition was measured by both 

the amount of 226Ra removed from the adsorbent and the amount of 226Ra capacity in the next 

adsorption cycle, as measured by LSC.

Table 11. Characterization of PNNL Adsorbents

Resin: 

PNNLBET 

Area, 

m

2

/gm

Principal Components 

(EDS)

226Ra Capacity,

pCi/gm resin with 

Well-4 produced

water

Morphology

A 32.1 Mn 69 ~100 , multi-faceted 

particles; very little fine 

structure

B

<30

Mn 13

C 203 Mn, Si support, K 2350

Aggregates of ~100 nM 

particles; high surface 

area

D 75.7 Mn, Si support, K 2165

E 74.9 Fe 102

F 54 Mn, Fe 2015

G 280 Mn, Si support 2620

H 69.7 Fe 5

I 96.0 Mn, Fe 2120

J 82.6 Fe 619

K 149.2 Mn, Fe 2130

L 95.2 Mn, Fe 2220

M 107.7 Mn, Fe 253

N 65.82 Mn, Fe 419
24

Each MnO2 sample went through four complete adsorption-regeneration cycles, followed by a 

fifth adsorption capacity test. The regeneration experiments utilized either 0.01N, 0.1N, or 

1.0N HCl. These tests covered a factor of 400 in the amount of regeneration HCl per gram 

MnO2 (0.2-80 mmol HCl per gm MnO2).

Figure 12 shows the performance of Fluka activated MnO2 with respect to 226Ra adsorption and 

regeneration. The adsorption behavior was essentially unchanged from cycle-to-cycle, but 

surprisingly, the regeneration effectiveness increases in each subsequent cycle. 

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5

Adsorption

Regeneration

pCi 226Ra Adsorbed (Desorbed)

Cycle Number

Adsorption: 40 mL Well-4 Produced Water

Regeneration: 40 mL 0.01N HCl

Figure 12. Adsorption and Regeneration Study for Fluka Activated MnO2

Figure 13 shows the effect of regeneration HCl usage on the effectiveness of the regeneration 

for each of the four regeneration cycles. The amount of 226Ra regenerated (desorbed) from 

MnO2 is roughly proportional to the log of the regeneration HCl usage, and is essentially 

independent of the HCl concentration. The results of Figure 13 suggest that 2-4 mmol HCl per 

gm MnO2 is effective for regenerating the MnO2 used in these tests. 

The regeneration effectiveness may also be measured by the amount of 226Ra that is adsorbed 

by the resin on Cycle 5. Figure 13 shows this value plotted against the regeneration HCl usage 

(mmol HCl/gm MnO2). These results suggest that 0.8 mmol HCl per gram MnO2 is sufficient to 

fully regenerate MnO2, even though at this loading the amount of 226Ra desorbed (96 pCi in 

Cycle 5) is only about 60% of the amount adsorbed. Additional testing will be needed to define 

an HCl treatment that enables tens or hundreds of adsorption-regeneration cycles.
25

0

50

100

150

200

0.1 1 10 100

4

3

2

1 Radium Removed from MnO2 by HCl Treatment (pCi)

mmol HCl in Regeneration/gm MnO2

Cycle

Test 1

2

3

4

5

6

7

8

9

Figure 13. Effect of Regeneration HCl on Radium Removal Effectiveness

3. PNNL-C Adsorbent Capacity and Regenerability

We conducted a series of experiments to test the adsorption capacity and regenerability of 

PNNL-C adsorbent. Table 12 shows the overall performance of PNNL-C adsorbent for both 

barium and 226Ra adsorption and regeneration by HCl. We used Well-4 produced water in each 

loading cycle and 0.1N HCl as a regenerant. For a regeneration control, we used DI H2O. 

Experiments 10-12 utilized one batch of PNNL-C adsorbent; Experiment 13 utilized a second, 

larger, batch of PNNL-C adsorbent.

Table 12 shows that in these tests, the PNNL-C adsorbent removed about 70-80% of the 226Ra

and about 34-72% of the barium from the Well-4 produced water. These results show that the 

PNNL-C adsorbent is only slightly selective toward radium over barium. The same behavior was 

observed for Fluka MnO2. Moon et al41 found no difference in selectivity between radium and 

barium for adsorption onto MnO2.

Regeneration with 0.1N HCl removed about 37-55% of the 226Ra and about 81-96% of the 

barium that was adsorbed during the adsorption cycle. In contrast, DI H2O removed only 5% of 

the adsorbed 226Ra and 9% of the barium that was adsorbed. Based on these experiments, 

MnO2 is effective for both barium and radium adsorption from Well-4 produced water; 0.1N 

HCl is effective for regenerating both barium and radium from MnO2.
26

Table 12. Summary of Adsorption-Regeneration Tests with PNNL-C MnO2 Adsorbent

Test Regenerant

226Ra 

capacity, 

pCi/gm

adsorbent

Fraction 

226Ra 

adsorbed 

by MnO2

Fraction 

adsorbed 

226Ra removed 

by regen

Ba 

capacity, 

mg/gm

adsorbent

Fraction 

Ba 

adsorbed 

by MnO2

Fraction 

adsorbed Ba 

removed by 

regeneration

10 0.1N HCl 3,240

3,490a

0.76

0.82 0.55 15 0.500.72 0.96

11 DI H2O

3,300

2,880a

0.77

0.68 0.05 15 0.500.34 0.093

12 0.1N HCl 3,150 0.74 0.37 15 0.50 0.81

13 0.1N HCl 3,460 0.81 0.40 16 0.52 0.83

a

Tests 10 and 11 utilized two adsorption cycles, with a regeneration step between the two cycles. The first value 

is for the first cycle; the second value is for the second cycle.

4. MnO2 Barium and Radium Adsorption-Regeneration Process

Figure 14 shows a schematic diagram of a hypothetical process for adsorbing barium and 

radium from produced water onto MnO2, regenerating the MnO2 with HCl to generate a BaCl2-

RaCl2 concentrate, and disposing of the BaCl2-RaCl2 concentrate solution by UIC. It is 

anticipated that a fraction of the MnO2 inventory would be continuously or periodically 

removed from the separation step following adsorption and regeneration. This regenerated, 

“spent MnO2”, may be disposed of as nonhazardous solid waste in a RCRA-D landfill, assuming 

that the barium concentration and 226Ra activity meet RCRA-D disposal criteria.

Figure 14. Schematic Diagram of MnO2 Barium and Radium Adsorption-Regeneration Process

Figure 15 shows a schematic diagram of a hypothetical regeneration process for MnO2

adsorbent. A concentrated solution of BaCl2 and RaCl2 in dilute HCl is recirculated over the 

loaded MnO2 to desorb RaCl2 and BaCl2. Concentrated HCl is added to the loop to maintain an 

HCl concentration of about 0.1M. The stripped MnO2 is rinsed with water, and returned to the 

adsorption process. The rinse water and a purge stream from the BaCl2-RaCl2-acid loop are 

combined and neutralized with NaOH for disposal by UIC.
27

Based on the results shown in Table 12, approximately equal percentages of barium and 226Ra

adsorb from Well-4 produced water onto MnO2 and desorb via HCl displacement from MnO2. 

For the design case produced water composition, the concentration of 226Ra is 5,000 pCi/liter 

(5x10-6 mg/L). The concentration of barium is 6,200 mg/L. Thus, the concentration of barium is 

nine orders of magnitude greater than the concentration of radium. Therefore, the materials 

and disposal costs are estimated based only on the barium concentration in the produced 

water.

We estimated the materials and disposal costs for this process for the design case produced 

water. The materials cost for MnO2 synthesis is based on a standard preparation for 

manganese oxide shown in equation (1). Manganese sulfate can be used in place of manganese 

chloride, as shown in equation (2). 

2 3 4 5 6 2 KMnO + MnCl + KOH MnO + KCl + H O 4 2 2 2 

(1)

4 2 4 2 3 4 5 3 2 KMnO + MnSO + KOH MnO + K SO + H O 4 2 2 

(2)

In addition, we made the following assumptions. 

 2.5 moles of HCl are required per mole of barium to remove barium during 

regeneration. 

 Stripped MnO2 is rinsed with twice its volume of clean water. 

 The purge from the regeneration loop and the rinse stream are combined and 

neutralized with 2.5 moles of NaOH per mole barium. 

 The neutralized mixture is disposed of by UIC. 

Figure 15. Schematic Diagram of MnO2 Regeneration Process
28

Table 13 shows the estimated costs for synthesis and regeneration of an MnO2-based 

adsorbent for barium and radium adsorption from produced water for the design case. The 

MnO2 is assumed to be usable for 5 adsorption-regeneration cycles. The estimated barium 

capacity is based on the distribution coefficient of 2,800 reported by Moon41 for both radium 

and barium adsorption on MnO2 resin. Based on equation (3), below, and a final barium 

concentration in the treated produced water of 500 mg/L, the calculated barium capacity is 

approximately 1,400 mg/gm MnO2. To be conservative, we assumed a barium capacity of 1,000 

mg/gm MnO2.

2

2

d

mg Ba on MnO

gm MnO

K = = 2800

mg Ba in solution

gm solution

     

     

(3)

Figure 16 shows the estimated cost for chemicals and disposal for the MnO2 adsorptionregeneration process as a function of the number of cycles for which the adsorbent is effective. 

In this figure, the final barium concentration refers to the barium concentration of the treated 

produced water leaving the MnO2 adsorption step. For an adsorbent lifetime of 10 cycles, and 

a treated produced water barium concentration of 500 mg/L, the materials and disposal cost 

for barium and radium removal and disposal is $1.7/bbl produced water. For this case, the 

waste volume for UIC disposal is 0.05 bbl/bbl produced water. 

Table 13. Cost of Materials and Disposal: 

MnO2 Barium and Radium Adsorption-Regeneration Process

(Design Case Produced Water; 5 Adsorption-Regeneration Cycles)

Cost item Usage/bbl produced water $/bbl produced water

MnO2 adsorbent consumption 180 gm $1.19

Disposal of spent adsorbent (MSW) 0.89 lb wet MnO2 (45% solids) $0.02

HCl to regenerate adsorbent 1.33 lb 100% HCl $0.32

NaOH for neutralization 0.91 lb 100% NaOH $0.25

BaCl2, NaCl for UIC disposal 4.6 lb

H2O in mixture for UIC disposal 17.2 lb

Total UIC disposal 0.052 bbl $0.57

Total Materials and Disposal $2.35
29

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 2 4 6 8 10

Final [Ba]: 500 mg/L

Final [Ba]: 1,000 mg/L

$/bbl produced water (chemicals and disposal)

MnO2 Lifetime (number of cycles)

Figure 16. MnO2 Adsorption-Regeneration Process Materials and Disposal Cost

V. Conclusions

For the Pennsylvania Marcellus in 2011, even with 95% produced water reuse, approximately 

0.15-0.3MM gal/day of produced water must be disposed of by UIC. This volume will increase 

significantly as the supply of produced water exceeds the demand for water in subsequent 

hydrofracturing operations. The objective of this study was to identify cost-effective 

pretreatment technologies that enable thermal recovery of distilled water and a salable salt 

product from Type III produced waters that would otherwise need to be disposed of by UIC. 

For the design case produced water composition, current technology enables water 

evaporation in either a mobile or stationary evaporator to recover about 56% of the produced

water as distilled water and about 44% as a salt concentrate. The salt concentrate is disposed 

of by UIC. In 2011, GEWPT began testing its new mobile produced water evaporator that 

utilizes mechanical vapor recompression and treats about 60 gpm produced water.

To achieve 80-95% water recovery, it is necessary to generate a solid salt product in a thermal 

crystallizer. For use as road salt, the salt product must be greater than 95 wt% NaCl and must 

pass TCLP. Thus, the barium concentration in the TCLP extract must be less than 100 mg/L. In 

the absence of a specification, it is assumed that the 226Ra activity in the salt product must be 

no greater than the level permitted for disposal as nonhazardous solid waste, which is 25 

pCi/gm in Pennsylvania. 
30

Based on a GEWPT pilot study of Marcellus produced water evaporation and salt crystallization, 

we developed a map of the produced water composition (barium concentration and 226Ra

activity) and the corresponding types of pretreatment required to obtain an acceptable salt 

product. We identified three types of produced waters. Type I produced waters contain 

barium concentrations less than [Ba]max (about 1,000-2,000 mg Ba/L) and are essentially 

unrestricted with respect to 226Ra activity. Type I produced waters do not require barium or 

226Ra removal prior to NaCl crystallization. 

Type II produced waters contain barium concentrations greater than [Ba]max and very low 

radium activities (<200-1,000 pCi 226Ra/L; upper limit depends on the produced water barium 

concentration). These produced waters may be economically treated by sulfate precipitation 

prior to NaCl crystallization. 

Type III produced waters have barium concentrations greater than [Ba]max and higher radium 

activities (>200-1,000 pCi 226Ra/L; lower limit depends on the produced water barium 

concentration). Type III produced waters should not be treated by direct sulfate precipitation 

prior to NaCl crystallization because the resulting sulfate sludge 226Ra activity would exceed 

state limits for disposal in RCRA-D landfills, and disposal as LLRW would be cost-prohibitive. 

This study focused on defining economical pretreatment processes for Type III produced waters.

The key to cost-effective barium and radium removal from Type III produced water is to 

generate a barium and radium concentrate that may be disposed of by UIC. We identified two 

such processes and conducted laboratory testing and cost analyses for each process. 

The first pretreatment process is a modified lime-soda process that completely softens the 

produced water. Magnesium, calcium, and strontium are first precipitated to yield a solid 

sludge that can be disposed of as nonhazardous waste in a RCRA-D facility. This is followed by 

precipitation of barium and radium as carbonates. These carbonates are redissolved with HCl 

to yield a concentrate that can be disposed of by UIC. For the design case, about 0.05 bbl of 

concentrate for UIC disposal and about 25 lb. RCRA-D solid waste are generated per bbl raw 

produced water. For this case, the materials and disposal cost is estimated to be $3.5/bbl 

produced water.

The second process utilizes high surface area MnO2 as an adsorbent for barium and radium. 

The MnO2 may be supported on mesoporous silica (as is the case for proprietary materials 

made by PNNL) or other supports. Alternatively, the MnO2 may be in the form of activated 

MnO2, which may be obtained commercially, or the MnO2 may be prepared in-situ. MnO2 is 

regenerated by treatment with dilute HCl. The regeneration process yields a concentrated 

solution of barium and radium, which may be disposed of by UIC. In laboratory studies, we 

demonstrated adsorption of barium and 226Ra onto MnO2. We also demonstrated regeneration 

of MnO2 by HCl treatment to yield a reusable sorbent. For the design case produced water, we 

estimated the materials and disposal cost for a regenerable MnO2 adsorbent to be in the range 

of $1.7 to $2.3 (adsorbent life 10 and 5 cycles, respectively) per bbl produced water. The 
31

volume of BaCl2-RaCl2 concentrate for disposal by UIC for the design case is estimated to be 

about 0.05 bbl per bbl produced water. Assuming that the spent MnO2 adsorbent can be 

stripped of barium and radium sufficiently to be considered nonhazardous, the spent MnO2

adsorbent may be disposed of in a RCRA-D landfill.

This modified lime-soda process is relatively simple and should be straightforward to scale up 

for commercial operation. This process results in essentially complete softening of the 

produced water, which increases water recovery and yields a higher grade salt product. This 

process appears to be in the best position for near-term implementation.

VI. Recommendations

Based on this investigation, the following recommendations are made.

For the modified lime-soda process, a series of laboratory tests should be 

conducted to define both an effective agitation intensity (power per unit volume) 

and a range of reagent addition rates that give sufficient selectivity in the first 

carbonate precipitation process (Stage 1B in Figure 7).

The MnO2 adsorption process should be further developed in the laboratory to 

establish the feasibility of this process. Identification of an effective means of 

separation of MnO2 particles from produced water and from regeneration 

streams is needed. Secondly, the regeneration purge stream to be disposed of 

must be concentrated (e.g. 20-30 wt% solids) for UIC, although the regeneration 

requires dilute HCl. The feasibility of using slightly acidic, concentrated BaCl2-

RaCl2 solutions for desorption of BaCl2 and RaCl2 from MnO2 must be established.

Additional laboratory and pilot evaporation and crystallization studies should be 

conducted with produced waters that contain higher barium concentrations (e.g. 

1,000, 2,000, and 5,000 mg Ba/L). This will enable a more robust estimate of the 

produced water barium concentration above which barium removal is needed.

A 226Ra specification for road deicing salt should be established.

VII. Acknowledgements

This work was performed under Subcontract 01822-36 to Research Partnership to Secure 

Energy for America (RPSEA), a contractor to the United States Department of Energy under 

prime contract DEAC2607NT42677.
32

VIII. References

 

1

Considine, T.J., Watson, R., and Blumsack, S., The Economic Impacts of the Pennsylvania Marcellus Shale Natural 

Gas Play: An Update, May 24, 2010.

2 Wendel, K., Shale Gas Wastewater Landscape in Pennsylvania, submitted to Oil and Gas Journal, 2011.

3

UIC: underground injection control (used interchangeably with deep-well injection)

4

Gaudlip, A., Paugh, L., and Hayes, T., Marcellus Shale Water Management Challenges in Pennsylvania, Society of 

Petroleum Engineers Paper 119898, SPE Shale Gas Production Conference, November, 2008.

5

Rassenfoss, S., From Flowback to Fracturing: Water Recycling Grows in the Marcellus Shale, Journal of Petroleum 

Technology, July, 2011, p. 48-51.

6

TDS: total dissolved solids

7

0.3MM gal/day is based on 2,000 new wells/year with 1MM gal flowback and produced water per well and 95% 

reuse. This number does not include the volume of long-term produced water from active wells drilled in earlier 

years. 0.15 MM gal/day is based on 5% of 25MM bbl frac water in 2011.

8

Hayes, Thomas, Techno-economic Assessment of Water Management Solutions, Marcellus Shale Gas Water Management 

Initiative, Canonsburg, PA, 2011.

9

Garvin, S., EPA Regional Administrator, in a letter to Michael Krancer, Pennsylvania Department of Environmental 

Protection, May 12, 2011.

10 Argonne National Laboratory, EVS, Human Health Fact Sheet, 2005.

11 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (1982): Ionizing Radiation: 

Sources and Biological Effects. http://www.unscear.org/unscear/en/publications/1982.html.

12 One picocurie (pCi) of radium is equal to 10-12 gm radium.

13 The ratio of 226Ra to 228Ra will vary by location and it is not appropriate to assume that all waters within or 

between different formations will have a ratio of 226Ra to 228Ra in the range of 10/1.

14 TCLP: Toxicity Characteristic Leaching Procedure (or Protocol)

15 Rice, T., NY State Department of Environmental Conservation; Allard, D., Pennsylvania Department of 

Environmental Protection, Dec., 2011, personal communication.

16 Mangelson, K.A. and Lauch, R.P., Removing and Disposing of Radium from Well Water, Journal of the American 

Water Works Association, 82 (6), 72-76 (1990).

17 Water Treatment Process for NORM Removal, US Patent Application Serial No. 13/307656, filed 30 November,

2011.

18 RCRA-D: Resource Conservation and Recovery Act, subtitle D, which addresses nonhazardous solid waste (EPA)

19 Vidic, R. D., Sustainable Water Management for Marcellus Shale Development, Presented at Marcellus Shale 

Natural Gas Stewardship: Understanding the Environmental Impact, Marcellus Shale Summit, Temple University, 

Philadelphia, PA, 2010.

http://www.temple.edu/environment/NRDP_pics/shale/presentations_TUsummit/Vidic-Temple-2010.pdf

20 Keister, T., Marcellus Hydrofracture Flowback and Production Wastewater Treatment, Recycle, and Disposal 

Technologies, Presented at The Science of the Marcellus Shale, Lycoming College, January 29, 2010.

21 Hayes, T.L, Sampling and Analysis of Water Streams Associated with the Development of Marcellus Shale Gas, 

Final Report, December 31, 2009, cited by Dempsey, B., Pennsylvania’s Marcellus Shale Gas: Water Supply and 

Water Quality Issues, 2010 http://www.research.psu.edu/events/2010/penn-state-energy-daydocuments/Dempsey.pdf.

22 Tinto, J. and Solomon, R., Water Recovery via Thermal Evaporative Processes for High Saline Frac Water 

Flowback, International Water Conference paper IWC-10-66, San Antonio, October, 2011.

23 Kimball, R., Key Considerations for Frac Flowback/Produced Water Reuse and Treatment, NJWEA Annual 

Conference, May, 2011, Atlantic City, NJ.

24 Kirby, H.W. and Salutsky, M., The Radiochemistry of Radium, National Academy of Sciences, 1964.

25 Keister, T., Marcellus Gas Well Supply and Wastewater Disposal, Treatment, and Recycle Technology, 

ProChemTech TAB 1208, 2008.

26 McGinty, J., McHugh, T.E., Higgins, E.A., Barium Sulfate: A Protocol for Determining Higher Site-Specific Barium 

Cleanup Levels, SPE E&P Environmental and Safety Conference held in Galveston, Texas, U.S.A., 5–7 March 2007.
33

 

27 Letter from ProChemTech in PADEP Regulatory Analysis Form, 

http://www.irrc.state.pa.us/Documents/SRCDocuments/Regulations/2806/AGENCY/Document-18068.pdf, pp. 

353-355, Jan, 2010.

28 Veil, J., Final Report: Water Management Technologies Used by Marcellus Shale Gas Producers, NETL, July, 2010. 

29 NPDES: National Pollutant Discharge Elimination System

30 R.E.S. June 11, 2010 http://www.prnewswire.com/news-releases/pennsylvania-dep-secretary-new-treatmentplant-showcases-technology-to-meet-stronger-greatly-needed-water-quality-standards-96159224.html.

31 TerrAqua Resource Management http://www.tarmsolutions.com/ (2010).

32 SRI Consulting, Chemical Economics Handbook, Sodium Sulfate, 2009.

33 Rood A.S., White G.J., Kendrick D.T., Measurement of 222Rn Flux, 222Rn Emanation, and 226;228Ra

Concentration from Injection Well Pipe Scale, Health Physics 75:187–192 (1998).

34 Lind, S.C, Underwood, J.E., and Whittemore, C.F., The Solubility of Pure RaSO4, JACS 40, No. 3, pp. 465-472 

(1918).

35 Doener, H.A. and Hoskins, W.M., Co-precipitation of Radium and Barium Sulfates, JACS 47, pp. 662-675 (1925).

36 Bruno, J. et al, Chemical Thermodynamics of Solid Solutions of Interest in Nuclear Waste Management, A Stateof-the-Art Report, OECD, p. 26, (2007).

37 ppm/w: microgram per gram (gm/gm).

38 Silva, J.M., Matis, H., Tinto, J.V., NORM Removal from Frac Water in a Central Treatment Facility, International 

Water Conference paper IWC-10-65, San Antonio, TX, October, 2010.

39 Kirby, H.W. and Salutsky, M.L, The Radiochemistry of Radium, National Academy of Sciences, National Research 

Council, p. 8 (1964).

40 CRC Handbook of Chemistry and Physics, 57th Edition, R.C. Weast, ed., 1976.

41 Moon, D.S., Burnett, W.C., Nour, S., Horwitz, E.P., and Bond A., Preconcentration of Radium Isotopes from 

Natural Waters using MnO2 Resin, Applied Radiation and Isotopes, 59 (2003) 255-262.
AI-1

Appendix I. Selective Radium Removal from Produced Water

A. Literature Background

The National Drinking Water Clearinghouse has reported ion exchange, lime softening, 

and reverse osmosis as the best available technologies for removing radium from 

groundwater

1

. In addition, Deng2cites groundwater treatment for radium removal by 

low-pressure membrane filtration, manganese greensand filtration, MnO2-impregnated 

resins, acid-washed sand filtration, and radium specific complexer (RSC) resins. Several 

chemical techniques for radium removal have been reported. These include sulfate 

treatment to coprecipitate radium and barium as RaSO4 with BaSO4, as discussed by 

Doener and Hoskins3. Bader4describes a pressurized sulfate precipitation method to 

remove radium, barium, and strontium from produced water. This method yields a solid 

sulfate product.

In an earlier study5, we suggested the possibility of using a commercial RSC resin (e.g. 

DOWEX RSC) to selectively remove radium from produced water. Snoeyink et al6

measured the radium capacity of RSC under a wide range of TDS levels. For example, at 

2,500 mg/L TDS and with a feed radium concentration of 180 pCi/L, the measured 

radium capacity was 32,000 pCi/gm. However, at 40,000 mg/L TDS and a feed radium 

concentration of 250 pCi/L, the radium capacity was only 300 pCi/gm. In contrast, 

Mangelson et al7 measured 3,500 pCi 226Ra/gm for RSC resin for treating water softener 

regeneration brine, which had 40,600 mg/L TDS and 1,181 pCi 226Ra/L. The barium level 

was not reported for the brines in the Mangelson study. These highly disparate results 

led us to conduct our own experimental study of the performance of RSC resin for 

radium removal from high-TDS brines. The results of our study are given below.

Several types of organic resins and inorganic materials have been used to remove 

radium from brines and ground waters. Since radium is a Group II metal, it is easily 

removed from dilute aqueous solutions such as well water with strong acid cation 

exchange resins. Wang8showed the effectiveness of 18 different inorganic ion 

exchangers for removing radium from simulated wastewater containing about 2100 

 

1

National Drinking Water Clearinghouse, Radionuclides, Tech Brief 13, March, 2000.

2

Deng, S., Polymeric Adsorbent for Radium Removal from Groundwater, Adsorption 11: 805-809 (2005).

3

Doener, H.A. and Hoskins, W.M., Co-precipitation of Radium and Barium Sulfates, JACS 47, pp. 662-675 

(1925).

4

Bader, M.S., Methods to Treat Produced Water, US Patent 7,963,338, June 21, 2011.

5

Silva, J.M., Matis, H., Kostedt, W.K. IV, and Watkins, V., Hydrofracturing Water Pretreatment for Water 

and Salt Recovery, International Water Conference Paper IWC-11-7, November, 2011, Orlando, FL.

6

Snoeyink, V.L., Chambers, C.C., Schmidt, C.K., Manner, R.F., Myers, A.G., Pfeffer, J.L., Richter, S.K., and 

Snyder, D.W., Removal of Barium and Radium from Groundwater, EPA Environmental Research Brief, 

Feb., 1987.

7 Mangelson, K.A. and Lauch, R.P., Removing and Disposing of Radium from Well Water, Journal of the 

American Water Works Association, 82 (6), 72-76 (1990).

8 Wang, R.S., Chen, J.X., and Liu, Z. W., The Adsorption Behavior of Microamounts of Radium on Inorganic 

Ion Exchangers, Journal of Radioanalytical and Nuclear Chemistry, Articles, Vol 111, No. 2 (1987) 289-295.
AI-2

mg/L TDS, primarily CaSO4, and 5037 pCi/L 226Ra. Although most produced waters have 

significant levels of barium, the simulated wastewater in the Wang study did not contain 

barium. BaSO4 as -100/+120 mesh granules (barite) and powdered BaSO4 both showed 

distribution coefficients9for radium of the order of 3000-4000. This is equivalent to a 

radium capacity of 3000-4000 pCi/gm for a solution containing 1000 pCi/L radium. 

Wang describes the mechanism for radium removal from solution as a chemical 

exchange between the radium ions in solution and barium ions at the BaSO4 crystalsolution interface. Based on this mechanism, it is expected that barium in the aqueous 

solution will decrease the effectiveness of a given material for radium removal.

Several metal oxides have been tested for removing radium from aqueous solutions. 

Nirdosh et al10 measured equilibrium isotherms for aqueous 226Ra solutions on oxides of 

Fe, Mn, Zr, and Ti. Among these oxides, only MnO2 had significant adsorption capacity

for 226Ra.

Patel and Clifford11 reported several adsorbents, for example hydrous manganese 

oxides, manganese-impregnated acrylic fibers, BaSO4-impregnated alumina, untreated 

alumina, and iron and manganese precipitates for removing radium from groundwater. 

They found that water treatment by hydrous manganese oxide followed by 

diatomaceous earth filtration was both economical and effective for radium removal 

from radium-spiked Houston groundwater. 

Moon et al12 describe “MnO2 Resin” from PG Research Foundation that adsorbs radium 

and barium from aqueous solutions. This material was prepared by a proprietary 

method utilizing reductive precipitation to generate MnO2 on a macroporous resin 

substrate. This material has been utilized to concentrate radium from ground water and 

sea water at the laboratory scale. Moon found that with MnO2 resin, the distribution 

coefficient for both radium and barium was 2.8 x 104for adsorption from waters of a 

significant range of salinity (DI water, and waters containing 200, 3,500, and 35,000 

mg/L TDS). Thus, MnO2 showed no selectivity for radium over barium. 

In addition, carbonaceous materials have been used to remove radium from saline 

solutions. For example, Rachkova et al13 demonstrated adsorption of radium from 

 

9    

   

/

/

Ra activityon solid gmsolid

Kd Ra activityin solution gmsolution

10 Nirdosh, I., Trembley, W.B., and Johnson, C.R., Adsorption-Desorption Studies on the 226Ra-Hydrated 

Metal Oxide System, Hydrometallurgy, 24 (1990) 237-248.

11 Patel, R. and Clifford, D., Radium Removal from Water by Manganese Dioxide Adsorption and 

Diatomaceous Earth Filtration, EPA Project Summary EPA/600/S2-91/063 (March, 1992).

12 Moon, D.S., Burnett, W.C., Nour, S., Horwitz, E.P., and Bond A., Preconcentration of Radium Isotopes 

from Natural Waters using MnO2 Resin, Applied Radiation and Isotopes, 59 (2003) 255-262.

13 Rachkova, N.G., Shuktomova, I.I., and Taskaev, A.I., Sorption of Uranium, Radium, and Thorium from 

Saline Solutions on Hydrolyzed Wood Lignin, Russian Journal of Applied Chemistry, 2006, Vol 79, No. 5, 

pp. 715-721.
AI-3

saline solutions onto hydrolyzed wood lignin. Tsezos et al14 investigated 226Ra 

adsorption on granular activated carbon for uranium mine tailings. 

3M Corporation supplies EmporeTM disks to concentrate radium from water samples15. 

The active material is a crown ether covalently bound to inert substrate particles. This 

proprietary material has affinity for both radium and barium, and can be regenerated 

with 0.25M EDTA, which would generate a concentrate of radium and barium for UIC. 

This material is proprietary, and is designed for laboratory analytical procedures.

B. Adsorbent Screening

As shown above, most of the radium adsorption literature is focused on removing 

radium from groundwater or well water. To complement this information, we screened 

about 60 materials for their ability to remove radium from produced water. We utilized 

liquid scintillation counting (LSC) to measure the performance of each material. Both 

the analytical techniques for NORM measurement and laboratory safety for handling 

NORM-containing produced water have been discussed previously16 and are included in 

Appendix IV. For this screening study, we utilized produced water from Well-4. This

produced water sample has significantly lower TDS and barium levels than the other 

samples and may be considered a “best case scenario” for adsorbent screening. The 

screened materials included carbons, molecular sieves, clays such as montmorillonite, 

strong acid cation exchange resins, insoluble salts such as barium sulfate, and inorganic 

oxides, including MnO2. For each test, 20 mL of Well-4 produced water and 

approximately 115 mg of an adsorbent were placed in a vessel and agitated overnight. 

The feed and each filtered liquid were subsequently measured for residual radioactivity 

by LSC. The reduction in counts per minute (vs. feed) is plotted for each adsorbent in

Figure AI-1. This shows that among the materials screened, manganese oxide and 

barium sulfate are the most effective adsorbents for radium removal from field 

produced water that has modest TDS and a low barium level.

 

14 Tsezos, M and Keller, D.M., Adsorption of Radium-226 by Biological Origin Adsorbents, Biotechnology 

and Bioengineering, Vol. 25, No. 1, January 1983, pp. 201-215.

15 Scarpitta, S.C., Evaluation of 3M Empore Rad Disks for Radium Determination in Water, 42nd Annual 

Conference of BioAssay, Analytical, and Environmental Radiochemistry, San Francisco, CA (1996).

16 Silva, J.M., Matis, H., Kostedt, W.K. IV, and Watkins, V., Hydrofracturing Water Pretreatment for Water 

and Salt Recovery, International Water Conference Paper IWC-11-7, November, 2011, Orlando, FL. 
AI-4

0

20

40

60

80

0 10 20 30 40 50 60

% CPM Reduction

Adsorbent Number

Barium

Sulfate

Amberlyst 15

Montmorillonite

MnO2

RSC

Resin

Figure AI-1. Radium Removal Performance for Screened Adsorbents

C. DOWEX RSC Resin for Radium Removal from Produced Water

We tested DOWEX RSC resin for selectively removing radium from produced water. 

Figure AI-2 shows a scanning electron micrograph of a resin bead that was fractured by 

immersion in liquid nitrogen followed by a light tap with a hammer. The white spots 

represent BaSO4 microcrystallites. The characteristic dimension of the microcrystallites 

is typically 20-40 nm17.

These bound BaSO4 crystallites ion exchange with radium as shown in equation (1).

RaCl + BaSO RaSO + BaCl 2(aq) 4(resin) 4(resin) 2(aq ) 

(1)

Attempts have been made to regenerate RSC resin18. However, these attempts have 

been unsuccessful, primarily because RaSO4 is so stable. Therefore, it is assumed that 

RSC resin is a single-use ion exchange resin for radium removal. Spent RSC resin is 

typically disposed of as LLRW. RSC resin is often utilized to remove radium from brine 

that is used to regenerate water softening ion exchange resins in municipal water 

systems. In a demonstration study19, hardness (Mg++, Ca++, Sr++, Ba++) and radium were 

removed from drinking water using a conventional gelular sulfonic acid ion exchange 

resin (sodium form). The softening ion exchange resin was regenerated with NaCl brine 

(average 40,600 mg/L TDS) to remove hardness and radium. The regeneration brine 

 

17 Silva, J.M., Matis, H., Tinto, J.V., NORM Removal from Frac Water in a Central Treatment Facility, 

International Water Conference paper IWC-10-65, San Antonio, TX, October, 2010.

18 Arnold, W.D., and Crouse, D.J., Radium Removal from Uranium Mill Effluents with Inorganic Ion 

Exchangers, I&EC Process Design and Development, Vol. 4, No. 3, July, 1965.

19 Mangelson, K.A. and Lauch, R.P., Removing and Disposing of Radium from Well Water, Journal of the 

American Water Works Association, 82 (6), 72-76 (1990).
AI-5

leaving the ion exchange resin contained an average of 1180 pCi radium/liter (the 

barium level in this stream was not reported). Prior to disposal, this regeneration brine 

was treated with RSC resin. The RSC resin removed an average of 99.2% of the radium 

from the softener regeneration brine. After one year of operation, the resin loading was 

3,000 pCi/cc resin.

100 nm

Figure AI-2. SEM of DOWEX RSC Resin

(50K magnification)

1. DOWEX RSC Resin Economics

The cost of DOWEX RSC resin is approximately $500/ft3. Waste containing up to 10,000 

pCi/gm can be disposed of as LLRW, which costs about $200/ft3for disposal. Figure AI-3

shows the cost of both resin and LLRW disposal for two levels of feed 226Ra activity as 

functions of the adsorbent capacity16. This figure shows that by loading a resin at 

10,000 pCi 226Ra/gm, the resin plus disposal cost adds $1.25-$2.50/bbl to the cost of 

recovering water and salt from produced water, depending on the raw produced water 

226Ra activity. Thus, for a non-regenerable material such as RSC resin, the target loading 

level is 10,000 pCi 226Ra/gm resin.

2. RSC Resin Performance

We selected DOWEX RSC resin for further testing because it showed promising results in 

the screening tests and it is commercially available. Much Marcellus produced water 

has barium and TDS levels higher than those of Well-4. Therefore, we conducted two

series of batch equilibrium capacity tests with produced waters that had been spiked 

with various barium levels. The details of both the capacity measurements and the 

equations for estimating 226Ra capacity from LSC measurements are given in Appendix 

IV. Produced waters from Well-4 (low TDS) and Well-7 (high TDS) were each spiked with 

barium to measure the effects of TDS and barium concentration on the radium capacity 
AI-6

of DOWEX RSC resin. Barium was added to the produced water as BaCl2, which was 

obtained from Sigma-Aldrich.

0

2

4

6

8

10

0 2000 4000 6000 8000 10000

5000

2500

Resin+Disposal Cost, $/bbl Frac Water Treated

Adsorbent Ra Capacity, pCi/gm

Feed Ra activity, pCi/L

Resin: $500/ft3

Disposal: $200/ft3

Figure AI-3. Resin and Disposal Cost Sensitivity to Adsorbent Capacity 

and Produced Water Feed 226Ra Activity

Figure AI-4 shows the effects of both TDS and Ba concentration on the apparent 

capacity of DOWEX RSC resin for 226Ra. The capacity was calculated based on the 

measured reduction in LSC counts per minute above background due to resin treatment 

and the measured feed 226Ra levels. This figure shows that the resin 226Ra capacity with 

unspiked Well-4 brine is comparable to that reported by Snoeyink6. This measured 226Ra 

capacity is far too low to be commercially practical, even for Well-4 produced water. 

The radium capacity decreases significantly with increasing barium levels. For the 

higher TDS brine of Well-7, the capacity is virtually negligible at all barium levels. These 

results led us to seek alternate sorbents, as well as alternate processes for removing 

radium from produced water.
AI-7

0

50

100

150

200

250

300

350

400

0 200 400 600 800 1000 1200

Well-4

Well-7

226Ra Capacity (pCi/gm)

ppm Ba in Produced Water

Figure AI-4. Effects of TDS and Barium Concentration on RSC 226Ra Capacity
AII-1

Appendix II. Produced Water Softening by Ion Exchange

A. Background

In the chlor-alkali industry, ion exchange (IEX) is used extensively for secondary sodium 

chloride brine purification prior to electrolysis in membrane electrolyzers. Chelating IEX

resins such as aminomethylphosphonic acid (AMP)- and iminodiacetic acid (IDA)-

functionalized polystyrene are used to soften concentrated NaCl brine solutions. Figure 

AII-1 shows a possible structure for the complex between a divalent cation and AMPfunctionalized polystyrene1

. The ion exchange capacity of commercially available AMP 

resins is typically 14 gm Ca per liter resin under chlor-alkali purification conditions (60C, 

300 gm/liter NaCl, 15 mg/L Ca, pH 9.5, 10 bed volumes/hr)2. Prior to ion exchange resin 

treatment, the brine must be treated to remove suspended solids to below 10 microns3. 

In this application, the feed hardness level (calcium plus magnesium) is typically 1-10 

mg/L; the treated product hardness level is below 20 μg/L. 

Produced water for use in once-through steam generators (OTSG) has been 

demineralized using ion exchange technology4. For the OTSG application, the produced 

water TDS was in the range of 4,000-7,100 mg/L and the hardness level was 447 mg/L as 

CaCO3. Both the TDS and hardness are about a factor of 20 lower than the 

corresponding frac water values. 

Produced water from coal bed methane (CBM) extraction has also been purified using 

ion exchange technology. Marathon has awarded Eco-Tec a service contract to utilize a 

Recoflo system to demineralize produced water from CBM in the Powder River Basin in 

Wyoming5. The system is designed to treat 1.5 MGD (36,000 bpd) produced water. The 

TDS range of the produced water to be treated was not specified, but a DOE survey of 

the Powder River Basin CBM produced waters utilized 1,500 mg/L TDS as a working 

value to compare the cost of Powder River Basin CBM produced water demineralization 

by ion exchange and reverse osmosis6. The TDS level for CBM demineralization is two 

orders of magnitude lower than the design case frac water TDS and an order of 

magnitude lower than the design case hardness level.

 

1

Kiefer, R. and Hoell, W., Sorption of Heavy Metals onto Selective Ion-Exchange Resins with 

Aminophosphonate Functional Groups, Ind. Eng. Chem. Res. 2001, 40, 4570-4576.

2 Wolff, J.J. and Anderson, R.E., Ion-Exchange of Feed Brine for Chlor-Alkali Electrolysis Cells: The Role of 

Duolite ES-467, Presentation at AIChE Meeting, Orlando, Fl, Spring, 1982.

3

Cocurek, D. and Woodside, G., Waste Treatment, Hazardous Waste, Kirk-Othmer Encyclopedia of 

Chemical Technology, p. 8, (Dec. 4, 2000).

4

Krause, L., Sheedy, M., and Jones, K., Produced Water Recovery at Seneca Resources Using Short Bed Ion 

Exchange, International Water Conference Paper IWC-10-21, San Antonio, TX, 2010.

5

PRNEWSWIRE, May 8, 2008. http://www.prnewswire.com/news-releases/eco-tec-awarded-cbngproduced-water-treatment-system-contract-by-marathon-oil-corporation-57216457.html

6 Bank, G. and Kuuskraa, V., The Economics of Powder River Basin Coalbed Methane Development, 

Report prepared for DOE, 2008.
AII-2

A continuous IEX system, the Higgins Loop, has been utilized commercially since 1955 

for a variety of water softening and demineralization applications. Based on 

countercurrent contact between IEX resin and the feedwater, this process generates 

lower regeneration and rinse volumes than traditional co-current flow systems7,8. No 

reference was found in which the Higgins Loop was applied to softening brines 

comparable to the design case.

Figure AII-1. AMP-Functionalized Polystyrene Resin

Chelating ion exchange resins (also referred to as weak acid cation exchange resins, or 

WAC) are regenerated by a multiple step process. First, strong acid (2-4 M or 5-15 wt% 

HCl) is used to displace hardness from the resin with protons. Following a deionized (DI) 

water rinse, 2-4 M NaOH (5-15 wt%) is used to displace protons with sodium ions. The 

resin is rinsed again with DI water and placed back into service. The regeneration 

solutions, comprising an acidic solution of concentrated alkaline earth metal chlorides 

(MgCl2, CaCl2, SrCl2, BaCl2), and a basic solution of NaCl are typically mixed, neutralized, 

and disposed of as wastewater.

The design case produced water contains the equivalent of 13,772 mg/liter of Ca++

cations, which equals 0.687 gm-equivalents of hardness per liter of frac water (109.3 

gm-equivalents per bbl frac water). The resin capacity for removing hardness from frac 

water is assumed to be 14 gm Ca++ (0.70 gm-equivalents of hardness) per liter resin9. 

Based on this assumed capacity, 0.98 volumes of IEX resin are required per volume of 

frac water to soften frac water for the design case. Thus, the ion exchange resin bed will 

become exhausted after the first bed volume of frac water passes through. Chemical 

costs and waste volumes for regeneration will therefore dominate the cost of using ion 

exchange to soften frac water. The calculations given here represent a best case 

scenario; finite mass-transfer zones for ion exchange unit operations will cause actual 

 

7

Higgins, I.R., Treating Brackish Water for High Pressure Boiler Makeup For Thermal Flooding by 

Continuous Ion Exchange: A Case History At Coronado Oil Company, Fall Meeting of the Society of 

Petroleum Engineers of AIME, 1-4 October 1967, New Orleans, Louisiana, 1967.

8

Higgins, I.R., Continuous Ion Exchange Equipment, Industrial and Engineering Chemistry, vol. 53, No. 8, 

August, 1961.

9 McKetta, J.J., Encyclopedia of Chemical Processing and Design: vol 51, Slurry Systems, Instrumentation 

to Solid-Liquid Separation, 1995, CRC Press.
AII-3

regeneration chemical usage and waste stream generation to be higher than those 

reported here. 

B. Acid Treatment

The first step in regeneration of a chelating ion exchange resin is an HCl treatment to 

strip divalent cations from the resin as their chlorides, as shown in equation (1). 

Resin - Ca+2HCl 2Resin - H+CaCl 2 2 

(1)

Equation (2) shows the HCl usage for regeneration for this case.

0.687 mole HCl 169 liter 36.5 gm HCl lb HCl 8.78 lb Regen HCl (dry)

=

liter frac water bbl mole HCl 454 gm HCl bbl frac water

                    

(2)

Equation (3) shows the volume of concentrated (35.2 wt%) HCl required per bbl frac 

water.

8.78 lb dryHCl gallon HCl soln 2.54 gallon HCl soln

=

bbl frac water 1.175× 8.33 lb HCl soln bbl frac water

lb HCl soln

0.352 lb dry HCl

     

           

(3)

The cost of HCl (2009) is about $525/metric ton for 35.2 wt% HCl (100% basis)10. 

Assuming complete reaction of HCl for regeneration11, the cost of HCl for IEX 

regeneration is shown in equation (4). For IEX regeneration, a 5-15 wt% HCl stream 

would be recirculated between a tank and the IEX resin bed. The HCl concentration is 

maintained in the tank by addition of concentrated (e.g. 35.2 wt%) HCl to the HCl 

regeneration tank. 

8.78 lb dry HCl $525 $2.09 Regen HCl

=

bbl frac water 2200 lb dry HCl bbl frac water

        

(4)

The HCl treatment generates an acidic chloride solution of the hardness cations. Based 

on a target final CaCl2 concentration of 30 wt% (as CaCl2), the initial HCl concentration 

needs to be 22.2 wt% HCl. The amount of DI water required to make up this solution 

from 35.2 wt% HCl feed is calculated below.

The amount of CaCl2 generated per barrel frac water is given by equation (5).

 

10 SRI Consulting, Chemical Economics Handbook (HCl: 2009; NaOH: 2008).

11 i.e. 100% of HCl added to system is used to displace hardness from IEX resin.
AII-4

2 2 109.3 gm - equivalent lb 111 gmCaCl 13.37lbCaCl

=

bbl frac water 2 gm - equiv 454 gm bbl frac water

           

(5)

For a 30 wt% solution of CaCl2, the amount of H2O in the regeneration solution per 

barrel frac water is given by equation (6).

2 2 2

2

13.37lbCaCl 1- 0.3lb H O 31.19lb H O in regen soln

=

bbl frac water 0.3lbCaCl bbl frac water

  

     

(6)

The amount of water in the concentrated (35.2 wt%) HCl used for regeneration (per bbl 

frac water treated) is calculated in equation (7).

2 2 2.54 gal conc HCl 8.33* 1.175 lb conc HCl 1- 0.352 lb H O 16.1lb H O

=

bbl frac water gal conc HCl lb conc HCl soln bbl frac water

           

(7)

The amount of DI water (or possibly filtered frac water or softened frac water) needed 

per barrel frac water is given by equation (8).

2 2 2

2

31.19 - 16.14 lb H O 1 gal H O 1.81 gal H O added

=

bbl frac water 8.33 lb H O bbl frac water

  

     

(8)

The CaCl2 (equivalent) concentrate will be disposed of by UIC. It is assumed that this 

concentrate is generated in North-Central Pennsylvania and transported and disposed 

of in Ohio, at a cost of $11/bbl (transportation plus UIC cost). The volume of 

concentrate from the HCl regeneration step and the cost of disposal are calculated in 

equations (9) and (10), respectively.

 

2 2

2 2

2

2

13.37 lbCaCl 1lb CaCl solution

bbl frac water 0.3 lb CaCl 4.18 gal CaCl solution

=

8.33 lb H O bbl frac water 1.2816 spgr CaCl solution

gallon

        

     

(9)

2

4.18 gal CaCl soln bbl soln $11 disposal cost $1.09 disposal cost

=

bbl frac water 42 gal soln bbl soln bbl frac water

           

(10)

C. Rinse

After the HCl treatment, the resin must be rinsed with at least one bed volume of a 

neutral water stream. The purpose of the rinse step is to displace acid solution (which 

contains divalent cations such as Mg++, from the resin so that they do not precipitate 

during the subsequent NaOH treatment. In the chlor-alkali industry, DI water is used for 
AII-5

this rinse. In this application, a softened brine stream could be used. The volume of 

rinse is calculated in equation (11).

++

++

1 bbl rinse

0.687 equiv Ca liter IEX resin 1 liter rinse 0.98 159 liter rinse bbl rinse

=

liter frac water 0.70 equiv Ca liter IEX resin bb 1 bbl frac water l frac water

159 liter frac water

                         

(11)

For the design case, the rinse stream is essentially the same volume as the frac water 

being treated. Since the purpose of the rinse stream is to remove residual divalent 

cations from the resin, the rinse source stream must be substantially free of divalent 

cations. Therefore, to conduct this rinse step, a clean source water stream is required. 

Further, this rinse stream cannot be discharged to surface water because it may have 

excess TDS and barium levels. The cost of disposal of this rinse stream by UIC is 

comparable to the cost of disposal of the original frac water.

D. NaOH Treatment

The second step in regeneration of chelating ion exchange resin is to treat the resin with 

NaOH, as shown in equation (12).

Resin - H+NaOH Resin - Na+H O  2

(12)

The NaOH usage is calculated in equation (13). 

0.687 mole NaOH 159 liter 40 gm NaOH lb NaOH 9.63 lbNaOH

=

liter frac water bbl mole NaOH 454 gm NaOH bbl frac water

                    

(13)

For IEX regeneration, a 5-15 wt% NaOH stream is recirculated between a tank and the 

IEX resin bed. The NaOH concentration in the tank is maintained by adding 

concentrated (e.g. 50 wt%) NaOH to the tank. Equation (14) shows the volume of 

makeup 50 wt% NaOH required per bbl frac water.

9.63 lb dry NaOH gallon NaOH soln 1.52 galNaOH soln

=

bbl frac water 1.52× 8.33 lb NaOH soln bbl frac water

lb NaOH soln

0.50 lb dry NaOH

     

           

(14)

The cost of NaOH is highly variable over time and geography. The most recent price 

reported by SRI (2008) is $610/dry metric ton for 50 wt% NaOH10. Assuming complete 

reaction of NaOH for IEX regeneration, the cost of NaOH for IEX regeneration is shown 

in equation (15).

9.63 lb dry NaOH $610 $2.67 Regen NaOH

=

bbl frac water 2200 lb dry NaOH bbl frac water

        

(15)
AII-6

The NaOH regeneration brine stream is typically combined with the spent HCl 

regeneration stream and disposed of by UIC. The NaOH regeneration brine stream 

comprises water from the original 50 wt% solution plus the water resulting from 

equation (12), as well as residual NaOH. Conceivable, some or all of this water may be 

used to dilute the CaCl2 stream generated by HCl treatment (equation (8)). 

2 2 9.63 lb NaOH 13.96 lb regen brine 0.5 lb H O 18 lb H O

+ =

bbl frac water 0.5 lb NaOH 40 lb NaOH bbl frac water

        

(16)

The cost for disposal of this brine stream is calculated in equation (17).

13.96 lb brine gal bbl $11 disposal $0.44 disposal

=

bbl frac water 8.33 lb 42 gal bbl brine bbl frac water

              

(17)

E. Rinse

After NaOH treatment, the resin bed must be rinsed with at least one bed volume of 

deionized or softened water rinse. This is to avoid precipitation of species such as 

Mg(OH)2 on the resin bed after placing the ion exchange system back into service after 

NaOH treatment. Again, the volume of this rinse will be comparable to the volume of 

frac water being treated. 

F. Summary

Table AII-1 shows the calculated chemical and disposal costs for both the acid and base 

treatment steps. The cost of disposing the rinse water, while not included in this table, 

would be approximately double the cost of disposing all of the frac water by UIC. For 

brines with such high hardness levels as the design case, the use of chelating ion 

exchange resin is neither economical nor practical.

Table AII-1. Regeneration Chemical Usages and Costs

Chemical Usage: 

lb 100% chemical/

bbl frac water

Usage: 

gal solution/

bbl frac water

Cost:

$/dry metric 

ton

Cost:

$/bbl frac water

HCl 8.78 2.54 $525 $2.09

HCl brine 

disposal

$1.09

NaOH 9.63 1.52 $610 $2.67

NaOH brine 

disposal

$0.44

Total $6.29
AIII-1

Appendix III. Produced Water Softening by Nanofiltration

A. Background

Nanofiltration (NF), shown schematically in Figure AIII-1, was originally developed as a 

method to achieve higher water fluxes at lower differential pressures and therefore 

lower energy costs than those associated with reverse osmosis (RO) membranes. NF 

provides an alternative to RO for applications where an extremely high-quality 

permeate product is not required. NF rejects substances by two mechanisms: neutral 

species are rejected by size (molecules larger than 200-300 gm/mole are rejected) and 

inorganic ions are rejected due to electrostatic interactions with the membrane1. 

Although the size range for rejection associated with NF overlaps those of ultrafiltration 

and reverse osmosis, the defining feature of NF is high rejection of multivalent ions 

combined with relatively low rejection of monovalent ions. This property makes NF 

attractive for water softening applications where desalination is not a key goal and it is 

desirable to achieve high removal of divalent ions such as calcium and magnesium while 

retaining high water flux.

Because the permeability of monovalent ions through NF membranes is so much greater 

than with RO, the feed pressure to an NF system is much lower than the feed pressure 

to an RO system. The maximum operating pressures of NF membranes also tend to be 

lower than those of RO. 

The use of NF membranes in drinking water applications has been reviewed by Thorsen 

et al2. NF competes with traditional softening processes such as ion exchange and lime 

softening, especially at larger facilities. The product quality is better than that of lime 

softening due to the removal of color and turbidity, while process flexibility, lower 

footprint, and zero sludge production also make NF attractive. Also, recent advances in 

reducing operating pressure requirements continue to improve the cost-effectiveness of 

NF3. Potential issues include treatment and/or disposal requirements for the 

concentrate stream, as well as membrane fouling and subsequent cleaning 

requirements. In addition, NF membranes are sensitive to both suspended solids and 

dissolved oxidizers such as chlorine. Membrane fouling may occur both by scaling of 

inorganic compounds such as CaCO3 or CaSO4 as well as by deposition of organic 

compounds or biofouling.

Unlike ion exchange and lime softening, NF requires no regeneration chemicals and only 

minimal additives (e.g. antiscalants). The concentrate stream from NF processes is brine 

 

1

Linde, K., Jonsson, A., Nanofiltration of Salt Solutions and Landfill Leachate, Desalination, 103 (1995) 

223-232.

2

Thorsen, T. and Flgstad, H., Nanofiltration in Drinking Water Treatment: Literature Review, Techneau, 

D5.3.4B, December, 2006.

3

Li, N.N. et al., Advanced Membrane Technology and Applications, John Wiley & Sons, 2008.
AIII-2

with a high concentration of multivalent species; this concentrate requires disposal by 

UIC. 

In a lab study with 1M brines (58,000 mg/L NaCl) comprising primarily monovalent 

anions, the retention of multivalent cations was higher than 70%, while the retention of 

sodium ions was less than 10%. The flux was 50 L/m2-hr for a transmembrane pressure 

of only 435 psi4. The permeate recovery was not reported in this study.

NF has been used to selectively remove multivalent ions from aqueous feed streams in 

water softening applications5. NF has been used, for example, to soften feedwater to 

seawater multistage flash units6and to remove divalent cations from concentrated 

landfill leachate solutions1.

Figure AIII-1. Schematic Diagram of NF Separation Process

B. WINFLOWS Calculations

We utilized WINFLOWS 3.0 from GE Water and Process Technologies to simulate a NF 

application7. The NF membrane tested was GEWPT membrane HR8040. The maximum 

allowable pressure was set to 600 psi. The objective of these calculations was to 

estimate the maximum permeate water recovery. Flux rates in each element were 

allowed to be outside of design guidelines.

 

4

Linde, K., Jonsson, A., op. cit.

5

Nanda, D., et. al., op. cit.

6

Awerbuch, L., ‘‘Nanofiltration: the Great Potential in Reducing Cost of Desalination’’ Proceedings of IDA 

World Congress Singapore, September 2005.

7 WINFLOWS 3.0 is available for download from: http://www.gewater.com/winflows.jsp.
AIII-3

1. Case I: Design Case Produced Water Softening

The design case produced water was fed at 50 gpm to a two-stage configuration. Four

NF modules in parallel comprise the first stage, and 8 modules in parallel comprise the 

second stage. The feed pressure to the first stage was 514.9 psia, and the feed to the 

second stage was 599.6 psia. 

The selectivity for divalent cation rejection was significant (e.g. the Mg++ concentration 

in the permeate was a factor of 10.8 lower than in the feed). There was essentially no 

rejection of monovalent cations. The calculated water recovery is 30.0 percent. Table 

AIII-1 shows the results for this simulation.

Table AIII-1. NF Simulation Results for Design Case Produced Water

(units mg/L except as indicated)

Component Feed Concentrate Permeate

TDS 132,460 149,886 96,986

Na+35,000 34,948 35,085

Mg++ 800 1,157 74.1

Ca++ 9,500 13,305 1,767

Ba++ 6,200 8,683 1,152

Sr++ 2,500 3,500 467

Fe 50 70.0 9.37

Mn 3 4.20 0.56

Cl58,008 88,218 58,431

pH 7.00 6.99 7.03

Rate (gpm) 50.00 35.01 14.99

2. Case II: Well-5 Produced Water Softening

The process configuration for Case I was also used in this case. Both the hardness and 

TDS for Well-5 produced water are higher than the design case. According to the 

simulation, the maximum water recovery for this feed was 15.2%. For water recoveries 

above 15.2%, the required feed pressure exceeds the 600 psia limitation on the 

membrane modules. Table AIII-2 shows the results for this simulation. As in Case I, 

there is essentially no rejection of monovalent cations. The Mg++ concentration in the 

permeate was a factor of 7 lower than the corresponding concentration in the feed.
AIII-4

Table AIII-2. NF Simulation Results for Well-5 Produced Water

(units mg/L except as indicated)

Component Feed Concentrate Permeate

TDS 149,149 156,545 11,972

Na+39,000 38,927 39,339

Mg++ 1,000 1,176 141

Ca++ 13,000 14,944 3,502

Ba++ 3,500 4,024 942

Sr++ 2,600 2,989 701

Fe 32.0 36.78 8.65

Mn 2.70 3.10 0.73

Cl90,014 94,446 68,337

pH 5.90 5.85 6.13

Rate (gpm) 50.00 41.50 7.61

3. Operating Costs

Table AIII-3 shows the cost of electricity to operate a NF system for the two produced

waters considered here. The electricity cost is assumed to be $0.10/kWh. 

Table AIII-3. Key NF Softening Operating Costs

Produced

Water

Electricity

Usage

(kWh/bbl)

Electricity

Cost

($/bbl)

Maximum

Permeate

Recovery, 

%

Concentrate

Transportation and 

Disposal Cost,

$/bbl feed

Design Case 0.19 0.02 30 7.70

Well-5 0.19 0.02 15 9.35

The dominant cost for produced water softening by NF arises from the low water 

recoveries predicted by the simulations. The NF concentrate stream would need to be 

disposed of by deep-well injection (UIC). The estimated cost for concentrate 

transportation from central Pennsylvania to Ohio and disposal by UIC is $11/bbl. This 

cost and the large amount of transportation required makes the use of NF for produced

water softening impractical. 
AIV-1

Appendix IV. Modified Lime-Soda Process Analysis and Experimental Results

A. Equilibrium Material Balance Calculations with Aspen Plus/OLI

We utilized Aspen Plus with an electrolyte property package from OLI Systems for all material 

balance calculations described in this appendix. Figure AIV-1 shows the process flow diagram 

for these calculations. Produced water is first treated with Ca(OH)2 to precipitate magnesium 

as Mg(OH)2. The lime slurry (LIM-SLRY) is filtered in FILTER-1 and the filtrate is sent to an 

optional NaOH precipitation step. No NaOH was added in any of the simulations reported here. 

Thus, the stream labeled OVERFLOW is the same as the stream labeled OH-FLTRT. Sodium 

carbonate is added in the block labeled CO3-PPT to generate a carbonate slurry. This slurry is 

filtered in the block labeled CO3-FLTR to yield the softened produced water product, CO3FLTRT 

and the precipitate, CO3-PPT. For all the disposal calculations, it is assumed that the 

precipitates are 45 wt% solids (balance water).

Figure AIV-1. Process Flow Diagram for Aspen Plus/OLI Simulations

Table AIV-1 shows the flow rates of each feed component used in these calculations. The total 

flow rate was about 1 MGD (million gallons/day) for each produced water simulation. We 

conducted sensitivity studies in the lime precipitation step to define the amount of lime 

required to precipitate essentially all of the magnesium in the raw produced water. We fixed 

the lime usage at the lowest multiple of 25 lb/hr Ca(OH)2 for which essentially all the 

magnesium precipitated as Mg(OH)2. For all cases, addition of 1.005-1.03 moles of Ca(OH)2 per 

mole magnesium in the feed produced water was sufficient to precipitate essentially all of the 

magnesium in the feed produced water. 

With the Ca(OH)2 addition rate fixed, we conducted sensitivity studies in which we varied the 

rate of Na2CO3 addition to the lime-treated produced water. Figure AIV-2 through Figure AIV-9

show the calculated equilibrium composition of the produced water as a function of the 

amount of Na2CO3 added. For each case, as Na2CO3 is added, essentially all of the calcium and 

strontium precipitate as carbonates prior to any barium (and therefore radium) carbonate 

precipitation. This selectivity is the basis for the modified lime-soda process.
AIV-2

Table AIV-1. Produced water Component Feed Rates for Aspen Plus/OLI Simulations 

(all units lb/hr except where noted)

Well-1 Well-2 Well-3 Well-4 Well-5 Well-6 Well-7 Design

H2O 347622 327658 312522 358011 329934 339184 338543 335737

NaCl 23422 33764 45784 16970 34471 28549 29963 30935

MgCl2 627 1144 1757 776 1362 1090 1594 1090

CaCl2 5353 9898 12632 5161 12517 8377 10475 9147

SrCl2 1277 2309 2881 811 1636 1472 1101 1573

BaCl2 3469 6959 6116 17 1845 3058 78 3269

FeCl2 21 58 97 43 25 59 37 39

MnCl2 1 2 3 1 2 3 1 2

Total 381792 381792 381792 381792 381792 381792 381792 381792

MGDa1.03 1.00 0.97 1.05 1.00 1.02 1.02 1.01

a MGD: million gallons/day

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-1

Figure AIV-2. Simulation Results for Well-1 Produced Water
AIV-3

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-2

Figure AIV- 3. Simulation Results for Well-2 Produced Water

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-3

Figure AIV-4. Simulation Results for Well-3 Produced Water
AIV-4

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-4

Figure AIV-5. Simulation Results for Well-4 Produced Water

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-5

Figure AIV-6. Simulation Results for Well-5 Produced Water
AIV-5

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-6

Figure AIV-7. Simulation Results for Well-6 Produced Water

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Well-7

Figure AIV-8. Simulation Results for Well-7 Produced Water
AIV-6

0

5000

10000

15000

0 0.5 1 1.5

Ca

Sr

Ba

pH

10.50

11.00

11.50

12.00

ppm Hardness Cation

Supernatant pH

Fraction Stoichiometric Na2CO3 (vs. Ca+Sr+Ba)

Design Case

Figure AIV-9. Simulation Results for the Design Case Produced Water

B. Experimental Results for Modified Lime-Soda Process

This section gives details of the experiments that were conducted to demonstrate the modified 

lime-soda process for softening produced water. We conducted all experiments under ambient 

conditions, using a magnetic stir bar for agitation. We utilized reagent grade Na2CO3, Ca(OH)2, 

and NaOH for these experiments. The pH was measured with a Thermo-Scientific Orion FiveStar pH meter and an Accumet 13-620-631 pH electrode. All experiments were conducted 

using Well-5 produced water.

1. Experiment 20110816 with Well-5 Produced water

We added one liter of Well-5 produced water to a 2-liter beaker and placed the beaker on a stir 

plate. The initial pH of the solution was 5.68. To this solution, 43.29 gm 10 wt% Ca(OH)2

solution was added, which increased the pH to 10.92 and precipitated the magnesium as 

Mg(OH)2. Then, 212.92 gm of 20 wt% Na2CO3 solution was added to the agitated mixture in ten 

10 mL increments. This is enough Na2CO3 to precipitate all of the calcium, strontium, and 

barium. Each increment was added essentially instantaneously. Approximately two minutes 

elapsed between Na2CO3 additions. A sample was withdrawn from the beaker after every other 

Na2CO3 addition for LSC analysis. Table AIV-2 and Figure AIV-10 show the LSC results for the 

filtrate for each amount of Na2CO3 added.
AIV-7

Table AIV-2. Results for Experiment 20110826 with Well-5 Produced water

grams 

Na2CO3

(dry) 

added

mole Na2CO3

per mole 

Ca+Sr+Ba

mole Na2CO3

per mole 

Ca+Sr

Counts/min

Above

background

Fraction feed 

counts/min 

remaining

0 0 0 13.95 1

4.26 0.11 0.113 12.95 0.93

8.52 0.21 0.227 10.58 0.76

12.78 0.32 0.340 9.08 0.65

17.03 0.42 0.454 8.75 0.63

21.29 0.53 0.567 5.35 0.38

25.55 0.64 0.681 5.25 0.38

29.81 0.74 0.794 5.92 0.42

34.07 0.85 0.908 3.55 0.25

38.33 0.95 1.021 3.38 0.24

42.58 1.06 1.135 2.48 0.18

Figure AIV-10. LSC Results for Experiment 20110826

2. Experiment 20110901 with Well-5 Produced water

We added one liter of Well-5 produced water to a 2-liter beaker and placed the beaker on a stir 

plate. The initial pH of the solution was 5.9. To this solution, 37.35 gm 10 wt% Ca(OH)2

solution was added, which increased the pH to 10.62 and precipitated the magnesium as 
AIV-8

Mg(OH)2. Then, 424.9 gm of 10 wt% Na2CO3 solution was added to the agitated mixture at a 

constant rate over the course of 316 minutes. This is enough Na2CO3 to precipitate all of the 

calcium, strontium, and barium. Samples of the supernatant were removed periodically and 

filtered through 0.45 filters. The residual radium activity of each sample was measured using 

LSC. 

Table AIV-3. Results for Experiment 20110901 with Well-5 Produced water

grams Na2CO3

solution 

added

mole 

Na2CO3

per mole 

Ca+Sr+Ba

mole 

Na2CO3 per 

mole Ca+Sr

Counts/min

Above

background

Fraction 

feed 

counts/min 

remaining

0 0.000 0.000 14.73 1.00

20 0.054 0.060 13.28 0.90

45.46 0.122 0.137 11.8 0.80

89.67 0.241 0.270 12.68 0.86

120.52 0.324 0.363 11.7 0.79

201.01 0.541 0.605 11.73 0.80

300.58 0.809 0.905 9.38 0.64

322.08 0.867 0.970 11.22 0.76

335.55 0.903 1.011 8.73 0.59

348.97 0.940 1.051 9.78 0.66

389.34 1.048 1.173 9.27 0.63

403.63 1.087 1.216 8.33 0.57

424.9 1.144 1.280 5.42 0.37

Table AIV-3 and Figure AIV-11 show the results of this experiment. Ideally, the fraction radium 

activity remaining in solution, as measured by the fraction of the feed counts/minute above 

background (column 5) remaining in solution, would be unity until the number of moles of 

Na2CO3 added equals the number of moles of Ca++ + Sr++ in the feed solution, followed by a 

decrease to zero as the number of moles to Na2CO3 increases to about 14% above the number 

of moles of Ca++ + Sr++ + Ba++ in the feed solution. The 14% molar excess carbonate value is 

based on the Aspen/OLI simulation results for Well-5 produced water (Figure AIV-6). According 

to the simulation, with 14% molar excess Na2CO3 addition, the residual barium concentration in 

solution is 59 ppm/w, which corresponds to a reduction of about 99% vs. feed concentration. 

Although the data show that this ideal behavior was not achieved, it is asserted that with 

improved agitation and other methods such as seeding and the judicial use of antiscalants, the 

ideal behavior may be approached closely enough to warrant further development. In this 

experiment, since it is known that radium and barium coprecipitate as carbonates, the fraction 

barium precipitation behavior may be inferred from the fraction radium precipitation1.
AIV-9

Figure AIV-11. LSC Results for Experiment 20110901

3. Experiment 20110708 with Well-5 Produced water

This experiment utilized NaOH to precipitate Mg, Ca, and Sr as the corresponding hydroxides, 

followed by Na2CO3 to precipitate Ba and Ra as the carbonates. One liter of Well-5 produced 

water was added to a 2-liter beaker and agitated with a magnetic stirrer. Six aliquots of 50 wt% 

NaOH (7 mL per aliquot) were sequentially added to the beaker. After each addition, the 

mixture was allowed to agitate for 2-3 minutes. Then a sample was withdrawn, filtered, and 

prepared for LSC analysis. The LSC analyses were conducted on the day of the experiment and 

two weeks later (reported here). After the last NaOH addition, the slurry was filtered through a 

1 glass filter to remove the precipitate. The filtrate was added to the 2-liter beaker and 

agitation was restarted. Then a series of six aliquots of 20 wt% Na2CO3 solution were added in 

the same manner, with sampling after each increment.

Table AIV-4 and Figure AIV-12 show the results of this experiment. Here, the radium activity 

stays in solution throughout the course of the NaOH addition.
AIV-10

Table AIV-4. LSC Results from Experiment 20110708

Mole NaOH/

per mole 

Mg+Ca+Sr

mole Na2CO3

per mole 

Mg+Ca+Sr

mole 

NaOH/2+Na2CO3

per mole 

Mg+Ca+Sr

Counts/min

Above

background

Fraction feed 

counts/min 

remaining

0 0 0 54.3 1

0.166 0 0.166 52.43 0.966

0.332 0 0.332 50.48 0.930

0.498 0 0.498 51.4 0.947

0.664 0 0.664 51.35 0.946

0.830 0 0.830 49.1 0.904

0.996 0 0.996 50.25 0.925

0.996 0.023 1.019 45.15 0.831

0.996 0.046 1.042 42.06 0.775

0.996 0.069 1.065 36.7 0.676

0.996 0.092 1.088 33 0.608

0.996 0.115 1.111 31.25 0.576

0.996 0.138 1.134 23.81 0.438

Figure AIV-12. LSC Results for Experiment 20110708

 

1

Kirby, H.W. and Salutsky, M., The Radiochemistry of Radium, National Academy of Sciences, 1964.