Zero Discharge Water Management for 

Horizontal Shale Gas Well Development

Final Report

Start Date: October 1, 2009

End Date: March 31, 2012

Authors: Paul Ziemkiewicz, PhD

Jennifer Hause

Raymond Lovett, PhD

David Locke

Harry Johnson

Doug Patchen, PG

Report Date Issued: June 2012

DOE Award #: DE-FE0001466

Submitting Organization: West Virginia Water Research Institute

West Virginia University

PO Box 6064

Morgantown, WV 26506-6064

FilterSure, Inc.

PO Box 1277

McLean, VA 22101

ShipShaper, LLP

PO Box 2

Morgantown, WV 26507
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Acknowledgment

"This material is based upon work supported by the Department of Energy under Award Number 

DE-FE0001466." 

Disclaimer

"This report was prepared as an account of work sponsored by an agency of the United States 

Government. Neither the United States Government nor any agency thereof, nor any of their 

employees, makes any warranty, express or implied, or assumes any legal liability or 

responsibility for the accuracy, completeness, or usefulness of any information, apparatus, 

product, or process disclosed, or represents that its use would not infringe privately owned rights. 

Reference herein to any specific commercial product, process, or service by trade name, 

trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, 

recommendation, or favoring by the United States Government or any agency thereof. The 

views and opinions of authors expressed herein do not necessarily state or reflect those of the 

United States Government or any agency thereof." 

Abstract

Hydraulic fracturing technology (fracking), coupled with horizontal drilling, has facilitated 

exploitation of huge natural gas (gas) reserves in the Devonian-age Marcellus Shale Formation 

(Marcellus) of the Appalachian Basin. The most-efficient technique for stimulating Marcellus 

gas production involves hydraulic fracturing (injection of a water-based fluid and sand mixture) 

along a horizontal well bore to create a series of hydraulic fractures in the Marcellus. The 

hydraulic fractures free the shale-trapped gas, allowing it to flow to the well bore where it is 

conveyed to pipelines for transport and distribution.

The hydraulic fracturing process has two significant effects on the local environment. First, 

water withdrawals from local sources compete with the water requirements of ecosystems, 

domestic and recreational users, and/or agricultural and industrial uses. Second, when the 

injection phase is over, 10 to 30% of the injected water returns to the surface. This water 

consists of flowback, which occurs between the completion of fracturing and gas production, and 

produced water, which occurs during gas production. Collectively referred to as returned frac 

water (RFW), it is highly saline with varying amounts of organic contamination. It can be 

disposed of, either by injection into an approved underground injection well, or treated to remove 

contaminants so that the water meets the requirements of either surface release or recycle use. 

Depending on the characteristics of the RFW and the availability of satisfactory disposal 

alternatives, disposal can impose serious costs to the operator. In any case, large quantities of 

water must be transported to and from well locations, contributing to wear and tear on local 

roadways that were not designed to handle the heavy loads and increased traffic. The search for a 

way to mitigate the situation and improve the overall efficiency of shale gas production 

suggested a treatment method that would allow RFW to be used as make-up water for successive 
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fracs. RFW, however, contains dissolved salts, suspended sediment and oils that may interfere 

with fracking fluids and/or clog fractures. This would lead to impaired well productivity. The 

major technical constraints to recycling RFW involves: identification of its composition, 

determination of industry standards for make-up water, and development of techniques to treat 

RFW to acceptable levels. If large scale RFW recycling becomes feasible, the industry will 

realize lower transportation and disposal costs, environmental conflicts, and risks of interruption 

in well development schedules. 
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Table of Contents

Acknowledgment ............................................................................................................................ 2

Disclaimer....................................................................................................................................... 2

Abstract........................................................................................................................................... 2

Overview......................................................................................................................................... 6

Project Structure.............................................................................................................................. 7

Phase I......................................................................................................................................... 7

Recommendations of the Industry Contact Group.................................................................. 7

Table 1: Industry Contact Group Chemical Criteria for Frac Water Make-up ............... 8

Phase II........................................................................................................................................ 9

Phase I:............................................................................................................................................ 9

Filtration with Pretreatment ............................................................................................................ 9

Dissolved Solids Removal .......................................................................................................... 9

Table 2: Costs of Various Treatment Methods.............................................................. 10

Figure 1: Comparison of Cost and Efficiency for Nanofiltration and RO...................... 11

Figure 2: Comparison of Cost and Flow of Nanofiltration and RO................................ 11

Figure 3: Comparison of Cost and Electricity Cost of Nanofiltration and RO............... 12

Table 3: Chemical Results of Raw Samples of RFW ................................................... 13

Salts Removal Research............................................................................................................ 13

Table 4: Frac Water Treatment Using 44% 2-propanol ................................................ 14

Table 5: Frac Water Evaluated w/ Ammonia (Bottle Method, mean of 3 trials).......... 15

Table 6: Frac Water Evaluated w/ 2-propanol (Bottle Method, mean of 3 trials)......... 16

Table 7: Frac Water Evaluated w/ 2-propanol (Beaker Method, mean of 3 trials)....... 17

Laboratory Verification of PDU ............................................................................................... 17

Figure 4: Media Testing of PDU for Treating Marcellus RFW...................................... 18

Table 8: Summary of PDU and Laboratory Test Data .................................................. 19

Figure 5: PSD Before and After FilterSure Filtration of a RFW Sample ....................... 20

Figure 6: Particle Size in Raw and EC-Treated Marcellus RFW.................................... 21

Filtration without Pretreatment..................................................................................................... 22

Figure 7: Predicting Stabilized Frac Water TDS when Recycling RFW.............. 24

Table 9: RFW Dilution Model ...................................................................................... 25

Phase II: ........................................................................................................................................ 25

Mobile Treatment Unit Design, Construction and Operations..................................................... 25

Figure 8: MTU General Arrangement............................................................................. 26
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Figure 9: Mobile Treatment Unit Piping Schematic Diagram........................................ 27

Figure 10: Finished Exterior View of MTU ..................................................................... 27

Figure 11: Completed Interior View of MTU................................................................... 28

Figure 12: Particle Size Distribution Results.................................................................... 29

Table 10: Filtration Results of Filtered RFW Samples.................................................... 30

Field Trials.................................................................................................................................... 30

Site 1: Utica Shale Site .......................................................................................................... 30

Figure 13: On Location at Utica Shale Site in Ohio ......................................................... 31

Figure 14: Oil/Polymer Mixture Treated by MTU ........................................................... 32

Figure 15: MTU Control Panel ......................................................................................... 33

Figure 16: Control Panel Close-Up View ......................................................................... 33

Figure 17: Pressure Drop Measurements of MTU in Operation....................................... 34

Figure 18: Day 1 through Day 6 Filtration Rates and Pressures....................................... 35

Figure 19: Filtration Rate and Pressure, Days 1 through 9 ............................................... 36

Lessons Learned from Site 1..................................................................................................... 37

Site 2: Marcellus Shale Site ................................................................................................... 37

Figure 20: Marcellus Shale Site, West Virginia................................................................ 38

Figure 21: Water Treated for Fracturing Stages ............................................................... 39

Figure 22: Rate and Pressure Data during Water Treatment ............................................ 40

Figure 23: Influent and Effluent PSD from West Virginia RFW ..................................... 41

Table 11: Marcellus Shale Site Water Chemistry............................................................ 42

Lessons Learned........................................................................................................................ 42

Project Summary........................................................................................................................... 42

Table 12: RFW Chemical Analyses................................................................................. 43

Acronyms, Abbreviations and Units of Measurement.................................................................. 45
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Overview

Shale gas production depends on the creation of permeability within an otherwise nearly 

impermeable rock formation. Two technologies have been applied to produce natural gas from 

tight shale formations: directional/horizontal drilling and hydraulic fracturing. Hydraulic 

fracturing (fracking) uses large volumes of water to create numerous channels within the shale 

formation. Sand, pumped with the water, props open the hydraulic fractures, thus providing 

multiple, permeable flow paths for the natural gas. 

Terminology used throughout this report to describe various types of water used in the fracking

process includes:

1. Frac water – fluid prepared to carry sand (proppant) down-hole under high pressure to 

create fracs (fissures) in the shale formation;

2. Flowback water – water that returns to the well head in advance of gas production;

3. Produced water – water that returns to the well head with gas during production; and

4. Return frac water (RFW) – flowback and produced water.

RFW is highly variable, changing from well to well and also as a function of time. Besides 

water and sand, frac water contains a number of chemical additives with the end purpose to 

enhanced gas production. Unless saline RFW is used to make up the frac water, the frac water 

will have a low salinity. Flowback water contains a high proportion of the frac water. The 

salinity of produced water is substantially higher than flowback water, probably due to the longer 

formation residence time in which the water comes into contact with the formation salts. The 

Marcellus is known to be desiccated. Otherwise, it would undergo plastic deformation rather 

than fracture under pressure. Exceptions might occur where the well bore encounters a nontarget formation; but, most of the water that returns from the well is the original injected water, 

or frac water. Our use of the term RFW recognizes in actual operations, flowback and produced 

waters are often mixed or otherwise managed as a single commodity.

The hydraulic fracturing process has two significant effects on the local environment. First, 

water withdrawals from local sources compete with the water requirements of ecosystems, 

domestic and recreational users, and/or agricultural and industrial uses. Second, when the 

injection phase is over, 10 to 30% of the injected water returns to the surface. This water 

consists of flowback, which occurs between the completion of fracturing and gas production, and 

produced water, which occurs during gas production. Collectively referred to as returned frac 

water (RFW), it is highly saline with varying amounts of organic contamination. It can be 

disposed of, either by injection into an approved underground injection well, or treated to remove 

contaminants so that the water meets the requirements of either surface release or recycle use. 

Depending on the characteristics of the RFW and the availability of satisfactory disposal 

alternatives, disposal can impose serious costs to the operator. In any case, large quantities of 

water must be transported to and from well locations, contributing to wear and tear on local 
7 | P a g e

roadways that were not designed to handle the heavy loads and increased traffic. The search for a 

way to mitigate the situation and improve the overall efficiency of shale gas production 

suggested a treatment method that would allow RFW to be used as make-up water for successive 

fracs. RFW, however, contains dissolved salts, suspended sediment and oils that may interfere 

with fracking fluids and/or clog fractures. This would lead to impaired well productivity. The 

major technical constraints to recycling RFW involves: identification of its composition, 

determination of industry standards for make-up water, and development of techniques to treat 

RFW to acceptable levels. If large scale RFW recycling becomes feasible, the industry will 

realize lower transportation and disposal costs, environmental conflicts, and risks of interruption 

in well development schedules. 

On October 1, 2009, the United States Department of Energy’s (DOE) National Energy 

Technology Laboratory (NETL) awarded West Virginia University (WVU) a cost-sharing 

contract to evaluate techniques to be used or adapted to treat RFW. The project resulted from a 

DOE Funding Opportunity Announcement (FOA) to encourage research of methods to managing 

hydraulic fracturing water withdrawals and RFW from gas development in the Marcellus. 

Filtration was considered a critical step in treating RFW for recycle. In developing the project 

for DOE, WVU partnered with FilterSure, Inc. a developer of a multi-media filter. The project 

was designed to characterize RFW, identify industry standards for make-up water, evaluate 

treatment methods, and determine if pairing a technology with filtration was necessary and 

economically feasible to treat RFW prior to recycling for subsequent fracking operations.

Project Structure

Phase I

Phase I objectives included the determination of water quality requirements for frac water makeup by compiling information on hydraulic fracturing practices, shale gas production practices, 

and associated problems in the Appalachian shale formations. This led to the development and 

adaptation of advanced water treatment and filtration technologies that would convert the RFW 

into a usable substitute of fresh water for hydraulic fracturing. A Technology Status Report was 

compiled and provided an overview of current industry practices and associated costs to 

treat and/or dispose of RFW. The analysis indicated treatment and reuse of RFW for 

another drilling operation was a promising water management option and focused the 

project on treatment toward that goal.

Recommendations of the Industry Contact Group

An Industry Contact Group was identified and a detailed questionnaire was sent to the members. 

Responses yielded valuable information regarding RFW volumes and criteria necessary for 

recycling. The Industry Contact Group provided access to well development sites, water 

samples for testing by the FilterSure process demonstration unit (PDU) and invaluable advice 
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regarding configuration of our field-deployable technology to match the contingencies of field 

operations. Some key results from discussions with the Industry Contact Group included:

 slickwater hydraulic fracturing was confirmed as the dominant type of stimulation 

treatment;

 water demand for most horizontal wells range from about 4 to 6 million gallons, with up 

to 10 stages, and as much as 250 tons of sand per stage;

 vertical well hydraulic fracturings are similar in size to a single horizontal well stage, 

500,000+ gallons, usually in a single stage, with a total of 250 to 500 tons of sand;

 RFW is approximately 10-30% of the amount injected. Flow is greatest during the first 

few days of water flow back and greatly reduced after the first week to 10 days, with

initial flow back rates averaging 3,000 to 5,000 barrels per day (90 to 150 gallons per 

minute (gpm)) and declining to less than a barrel per day after 60 days; and

 horizontal and vertical fracs are both successful but horizontal wells appear to provide 

better economics.

Industry standards for acceptable recycle water quality standards continued to evolve. The 

consensus from the Industry Contact Group concerning acceptable water quality for recycled 

RFW indicated total suspended solids (TSS) below 20 microns along with a range of other 

parameters presented in Table 1. The TSS criteria reflects concerns with sediment accumulating 

in pores and the well bore while the chemical water quality parameters are thought to play a role 

in interfering with the performance of the frac water or with scale formation. 

Table 1: Industry Contact Group Chemical Criteria for Frac Water Make-up

Chemical Parameter Maximum Value (mg/L)*

TDS 50,000

Hardness 26,000

HCO3 300

SO4 50

Cl 45,000

Na 36,000

Ca 8,000

Mg 1,200

K 1,000

Fe 10

Ba 10

Sr 10

Mn 10

*Requirements of Industry Contact Group Members
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Industry also required a treatment system with minimal operational and maintenance needs and a

small footprint with minimal mobilization and de-mobilization requirements. Upon review of 

the laboratory tests results and multiple discussion sessions with Industry representatives, the 

project team determined that the multi-media filtration system was a necessary step in any 

treatment scheme. Removal of dissolved solids was considered important but not critical since 

most of the criteria in Table 1 could be achieved through dilution with fresh water make-up. 

Nonetheless, the project proceeded with two salt removal approaches: electro-coagulation and a 

novel process in the conceptual stage of development.

Industry Contact Group recommendations were critical in refining project objectives. The 

testing and review of various water treatment technologies during Phase I of the project allowed 

the WVU project team to identify two options with potential for on-site treatment and recycling 

of RFW:

1. Filtration to reduce suspended solids, and

2. Electro-coagulation (EC) to determine whether or not it could significantly reduce 

dissolved salts.

Phase II

Phase II of this project consisted of the design, fabrication and field deployment of a mobile 

treatment unit (MTU). The objective was to demonstrate a practical technology for TSS removal 

under actual field operating conditions. A project goal was for the treatment system design to 

meet the needs of industry while providing a level of environmental protection and adaptability 

for future water quality and quantity criteria. The successful development of a technology to treat 

and recycle RFW will advance shale gas development through improved economics and 

environmental impacts. Improved economics will be achieved by reducing the amount of 

trucking and disposal of RFW and costs associated with these activities. By reusing the RFW for 

subsequent hydraulic fractures, the need for fresh water will be reduced. The better you treat the 

RFW, the higher the blend ratio with fresh water, the less dependence and strain on local water 

resources, and the less impact on local infrastructure and the surrounding environment.

Phase I:

Filtration with Pretreatment

Early in the project, it was decided to test if filtration, which removes suspended solids but few 

dissolved solids, would benefit by coupling with a process for removing salts. Various processes 

were examined that included reverse osmosis (RO), nanofiltration, and electro-coagulation (EC).

Dissolved Solids Removal

A WVU-developed computer program that calculates the unit costs of various treatment methods 

was revised with the addition of new treatment methods (such as nanofiltration and EC) and 
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updated costs. Table 2 shows costs per 1000 gallons for a number of treatment options utilized 

to manage RFW, including EC. The EC method appeared to be competitively priced among the 

various options.

Table 2: Costs of Various Treatment Methods

Treatment Method $ per1000 gallons

Surface disposal $0.07

Deep injection well - existing $0.66

Evaporation/infiltration pond w/ spray $0.99

Spray Irrigation $1.08

Microfiltration $1.36

Evaporative pond - Lined-Spray $1.97

Electro-coagulation $2.00

Shallow injection/aquifer renewal $2.85

Evaporative pond/infiltration $2.98

Water hauling $4.82

Deep injection well - new $5.64

Nanofiltration $6.15

Reverse Osmosis $6.94

Evaporative pond - Lined $27.56

Figures 1 through 3 detail some of the initial investigations comparing reverse osmosis and 

nanofiltration, the former removing all ions while the latter only removed multi-valent ions. 

These are two proposed technologies for total dissolved solids (TDS) reduction or removal. The 

graphs compare cost versus process efficiency, cost versus flow, and cost versus electricity cost. 

In all instances, nanofiltration was cheaper because of its lower pressure requirements. The rise 

in cost at low efficiency for the first plot is due to increasing reject disposal costs. Low flow also 

increases the cost due to the fixed costs associated with the system. The increase in cost due to 

electricity rates is almost linear.
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Figure 1: Comparison of Cost and Efficiency for Nanofiltration and RO

Figure 2: Comparison of Cost and Flow of Nanofiltration and RO
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Figure 3: Comparison of Cost and Electricity Cost of Nanofiltration and RO

To accurately characterize RFW, the project team analyzed a number of samples provided by the 

Industry Contact Group. The samples represented RFW from operating sites in New York, 

Pennsylvania and West Virginia. The samples were drawn from storage tanks or pits and 

represented a mixture of flowback and produced water. Five samples from the Marcellus and 

one sample from the Utica shale were tested. Table 3 provides a summary of the chemistry of 

six raw RFW samples used in this study.
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Table 3: Chemical Results of Raw Samples of RFW 

RFW 

#1

RFW

#2

RFW

#3

RFW

#4

RFW

#5

RFW

#6

pH 7.46 6.1 7.4 6.3 6.3 6.7

Conductivity 23655 16807 66300 190100 183000 13900

SO4 99 71 28 nd 414 19

Fe 37 27 37 59 30 27

Ca 319 1749 1640 19487 12800 698

Mg 31 122 193 1257 1470 60

Na 3550 2863 8560 35500 33700 2060

K nd 57 243 479 444 43

Sr 0.011 0.011 301 3559 1440 51

Ba 27 0 175 1641 176 14

Cl 6575 7172 17100 112457 65000 4600

TSS 44 220 99 74 570 25

TDS 16559 11765 46410 133070 128100 9730

Hardness 923 4870 4890 53836 38000 1990

Oil & Grease 5 49 5 33 nd nd

nd = not detected

Salts Removal Research

Removal of highly soluble ions is difficult. As mentioned, reverse osmosis and nano-filtration 

are able to remove the ions at a high cost. Electro-coagulation was found to be ineffective. 

Preliminary research to determine the technical feasibility of using methods of dielectric 

lowering to remove salts was conducted. Ideally, this method would be coupled with the 

FilterSure filtration system for solids removal.

Preliminary research on methods for removal of salts using dielectric reduction with solvents and 

mixed solvent systems was conducted. The aqueous solubility for potassium chloride (KCl) was 

determined to be 34.5 gm/100 gm of water. Investigations of mixed solids beginning with the 

use of 2-propanol followed to evaluate solubility and conductivity. The solubility of KCl in 2-

propanol/water mixtures showed that the initial 26% KCl by weight dropped to nearly 1% when 

the solvent was 80% 2-propanol by weight. The concentration, referenced to the original water, 

decreased from 345,000 mg/L to approximately 40,000 mg/L. Removal of the precipitated salt 

followed by removal of the 2-propanol resulted in an 88% reduction of salt. 

Experiments with potassium sulfate (K2SO4) showed 90% less solubility with 20% (w/w) 2-

propanol than pure water. Although the analyses were conducted at 22oC, and not at 50oC, 

K2SO4 would be more soluble at the higher temperature. 
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Potassium sulfate was found to have a solubility of 11.17 gm K2SO4/100 gm of water using the 

method developed earlier. The literature solubility is 12 gm/100 gm. The solubility of K2SO4 in 

a 20:80 w/w 2-propanol:water mixture was found to be 0.98 gm/100 gm solvent. 

One hundred milliliters (mL) of hydraulic fracturing water was also treated with 2-propanol, 

resulting in a lowering of the conductivity by about half. The behavior was tracked using 

conductivity. Lower conductivity is a complex function of solution dielectric changes and salt 

loss. The solution was recovered through filtering after addition of 80 gm of 2-propanol. The 2-

propanol was evaporated, regenerating an aqueous solution that had a conductivity of 97 microsiemens per centimeter (μS/cm), 50.5% of the original value. Comparison of salt content of the 

original and final solutions showed 24% of the original sodium (55,000 mg/L) and 37% of the 

original chloride (100,000 mg/L) were removed, yielding 41,800 mg/L sodium and 63,000 mg/L

chloride. The final added 2-propanol, 80 gm, corresponded to a solution that was 44% 2-

propanol. When converted to molar concentration, 0.57M of sodium is removed and 1M of 

chloride. Other ions must be involved in chloride removal, 1:1 molar removal is expected for 

sodium chloride (NaCl). The resultant solution was analyzed for the major ions, Table 4,

showing significant reductions in the divalent cations calcium, strontium and barium. 

Table 4: Frac Water Treatment Using 44% 2-propanol

Ion Original water, mg/L Treated water, mg/L Percent reduction

Ca 21200 423 98

Sr 2970 <0.011 ~100

Ba 1280 <0.012 ~100

Ammonia was chosen to be the eventual agent due to its ease of removal from solution. Initial 

studies used a 25% (w/w) aqueous ammonia solution. A new method was developed to avoid 

dilution of the ammonia. The solubility was determined by evaporating the water from the 

sample then reconstituting it in the 25% ammonia. The method was tested using K2SO4 and 

water. The solubility found using the new method was 11.88 gm K2SO4/100 gm water, which is 

in better agreement with the literature value than the original method. The solubility of K2SO4 in 

the 25% ammonia solution was determined to be 0.43 gm/100 gm solvent. A literature value is 

0.22 gm/100 gm solvent with 25.2% ammonia at 20oC. 

The analytical results (measurements of solution concentrations of the recovered water) for 

K2SO4 solubility in ammonia showed sulfate concentrations near 1200 mg/L. This value 

corresponds to about 0.22 gm/100g m solvent (although the volume has changed due to ammonia 

evaporation). The analytical results are disquieting for potassium. The potassium concentration 

should be near 1000 mg/L, but are reported to be around 1 mg/L. The lack of accuracy 

implicates all analyses. The solutions for K2SO4 solubility, for example, should have sulfate 
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concentrations near 65,000 mg/L and 61,000 mg/L was found. However, very little potassium 

was found. 

The method was applied to mine water and applied to a second hydraulic fracturing water 

sample. The mine water had a reduction of calcium from 800 mg/L to roughly 25 mg/L. 

Sulfate, however, remained roughly the same as in the original sample. This is inconsistent, 

since gypsum is the least soluble solid for calcium in the system. An analytical error is 

suspected, probably for calcium. Mine water has a lower TDS content than hydraulic fracturing

water and the method will be less effective. 

Using what is called the Bottle Method, where the water of concern is evaporated, reconstituted 

in the solvent of interest and filtered, hydraulic fracturing water was tested with 25% ammonia 

and 2-propanol. In addition, the original method, the Beaker Method, where 2-propanol is added 

to the solution, then evaporated, was used. 

The hydraulic fracturing water had an initial pH of 6.6. After re-dissolving the salt in ammonia 

solution, then driving off much of the ammonia, the pH was 8.2. The solution contained 680 

mg/L ammonia nitrogen, 826 mg/L ammonia, which indicates over 96% removal of ammonia. 

The conductivity increased from 13.9 μS/cm2to 15 μS/cm2, an increase of 7.9%. The increase 

can be attributed to ammonia.

Ion concentrations shown in Table 5 decreased substantially for the alkaline earth elements 

magnesium, calcium, strontium and barium (Mg, Ca, Sr, and Ba), by one third for sulfate (SO4) 

and marginally for potassium (K) and chloride (Cl). The total dissolved solids for the original 

hydraulic fracturing water was 9760 mg/L, which is rather low to expect substantial removal by 

solubility decrease. The solubility of pure K2SO4 in 25% ammonia is 0.22 gm/100 gm solvent, 

roughly 2.2 gm/L, far in excess of the 43 mg/L seen here. 

Table 5: Frac Water Evaluated w/ Ammonia (Bottle Method, mean of 3 trials)

Ion Original water, mg/L Treated water, mg/L Percent reduction

Ca 698 10.3 98.5

Sr 51 7.5 86

Ba 14 0.063 99.5

Mg 60 <0.5 >99

SO4 19 11.9 37

K 43 37.3 13

Cl 4600 4160 10
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The removal of alkaline earth ions is largely through precipitation of their hydroxides at the high 

pH of the initial ammonia solution. That solution was filtered, then the ammonia driven off for 

the final pH of 8.2. The hydroxide solubilities are Ba>Sr>Ca>Mg. The sulfate solubilities are 

Mg>Ca>Sr>Ba. The removal order in ammonia is Ba>Mg>Ca>Sr, with barium out of order. 

The very low barium value is likely due to some barium sulfate precipitation, making it less 

concentrated than the strontium. 

The Bottle Method using 2-propanol, results tabulated in Table 6, is more indicative of dielectric 

constant lowering. Barium and strontium, the least soluble sulfates, are decreased, while 

magnesium and calcium are barely removed. The sulfate decrease indicates removal by barium 

and strontium, although a mass balance does not provide enough sulfates to account for all the 

strontium. The chloride decrease cannot be balanced by the measured cations. Sodium may be 

the cation associated with chloride. The hydraulic fracturing water contained 2060 mg/L

sodium, but its removal was not measured in the treated samples. The conductivity decreased to 

0.67 μS/cm2, a 95% decrease. Roughly half the salt isolated from the hydraulic fracturing water 

dissolved in the 2-propanol, whereas 84% dissolved in the 25% ammonia solvent. 

Table 6: Frac Water Evaluated w/ 2-propanol (Bottle Method, mean of 3 trials)

Ion Original water, mg/L Treated water, mg/L Percent reduction

Ca 698 629 0.9

Sr 51 14.8 71

Ba 14 0.27 98

Mg 60 56 6.8

SO4 19 5.54 71

K 43 4.9 89

Cl 4600 1117 76

The more practical Beaker Method was conducted using 2-propanol. Two hundred grams of 2-

propanol were added to 100 grams of the hydraulic fracturing water. The 2-propanol was 

evaporated and water recovered. Very little solid was generated and with the exception of 

barium, very little change in concentration for the ions were seen, as presented in Table 7. The 

conductivity of the resultant solutions averaged 14 μS/cm2.
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Table 7: Frac Water Evaluated w/ 2-propanol (Beaker Method, mean of 3 trials)

Ion Original water, mg/L Treated water, mg/L Percent reduction

Ca 698 801 -15

Sr 51 54.5 -7

Ba 14 1.0 93

Mg 60 69 -14

SO4 19 16.5 13

K 43 41.5 3

Cl 4600 4240 8

The Beaker Method has been shown to successfully remove salts from higher dissolved solids 

hydraulic fracturing waters, but this water was too dilute. The intent was to lower TDS to 50,000 

mg/L. This water started at 10,000 mg/L TDS. Barium removal was consistent in all cases. The 

change in solvent polarity lowered the solubility, which is small even in water, and removed 

barium as the sulfate. Other ions were not removed. Some ions showed a negative removal. 

The final volume in all three treatments was less than the starting volume, hence some ions 

showed higher concentrations. 

Laboratory Verification of PDU

Laboratory studies consisted of multiple filtration runs, with and without EC pretreatment, with 

the objectives to determine an acceptable combination of filter media and evaluate the impact of 

EC pretreatment on the filtrate. Actual Marcellus RFW samples were used for all tests. 

The PDU consisted of the 2-gpm FilterSure multiple module, multi-media filtration unit as 

shown in Figure 4. The unit consisted of five sequential modules containing selected filter 

media. As configured here, the five modules are made up of two stacks, three in one stack and 

two in the other, all five operating sequentially. If the media are selected correctly, all five 

modules will load up with solids at the same rate, minimizing offline time for backwashing the 

modules. A rented laboratory-scale EC unit was used to pretreat water samples.
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Figure 4: Media Testing of PDU for Treating Marcellus RFW

Once analyses were conducted on the raw RFW samples, each sample was divided into three 

sub-samples, one to be treated with EC only, one to be treated with the FilterSure filtration 

system, and one to be treated by the combination of EC plus FilterSure filtration. All samples 

were analyzed for natural salt constituents, TDS, TSS, hardness, pH, and particle size 

distribution, both before and after each test. Results of tests were summarized in Table 8.

Results indicated significant reductions in divalent ion concentrations and TSS were reduced by 

up to 76% with retention of nearly 100% of particles larger than three microns. Therefore, the 

process design system proposed by the WVU project team and verified through analyses, 

consisting of the EC technology followed by the FilterSure filtration system, showed the 

capability to lower water hardness, reduce heavy metals to environmentally safe concentrations, 

and lower TDS values of RFW to be ready-for-use for the next hydraulic fracturing operation. 
19 | P a g e

Table 8: Summary of PDU and Laboratory Test Data

A: 

Raw

A:

FS

A: 

EC*

A: 

EC+FS

B:

Raw

B:

FS

B:

EC*

B: 

EC+FS

C:

Raw

C:

FS

C:

EC*

C: 

EC+FS

pH 7.4 7.7 7.4 7.9 5.3 6.3 5.7 6.0 5.5 5.0 5.9 5.5

Cond 66300 51000 61500 48800 183000 148000 182000 182000 194000 195000 326000 200000

SO4 28 11 21 13 414 101 131 88 73 - - -

Fe 32 15 0 0 6 8 - - 40 45 - -

Ca 1610 1540 1870 1040 10600 7830 9160 8820 21000 19300 20400 14600

Mg 188 175 196 121 1200 786 978 933 2220 2270 2050 1120

Na 8530 7260 9050 4960 32800 19500 21800 22600 45400 34400 42500 31100

K 243 297 213 207 444 996 434 347 701 601 535 595

Sr 280 249 334 214 1340 1090 1110 1250 2980 3120 3110 3090

Ba 172 165 128 71 201 93 142 120 1440 1520 1390 741

Cl 17100 13000 14800 12600 65000 51000 61800 62400 80400 95400 64400 89600

TSS 99 81 5010 66 570 187 1050 138 882 681 112 302

TDS 38700 28200 35000 26800 112000 81400 95600 96500 188000 187000 210000 166000

Hardness

4890 4650 5620 3960 38000 22000 28900 25200 63400 74100 66000 42200

O&G nd nd nd nd nd nd nd nd 13 nd nd nd

FS = FilterSure; EC = electro-coagulation; Cond = Conductivity

*EC technology provider considers the EC values to be misleading since lab tests can yield values for dissolved solids that 

include suspended solids. Provider filters their water with a 10-micron absolute filter to remove suspended solids before 

analyzing for solutes.

Based on the laboratory studies and the preliminary analysis of various treatment options, taking 

into account costs and their capabilities to potentially treat RFW, the WVU project team 

determined to further evaluate the use of filtration coupled with EC. A conceptual process train 

was developed to include the EC unit preceding the multiple module, multi-media filtration unit

provided by FilterSure. The upstream component, the EC unit, would pretreat the RFW to 

enhance the filtration efficiency of the FilterSure system. The EC converts some of the dissolved 

solids to suspended solids, by chemical or electro-chemical means. Early testing demonstrated 

the capability to remove up to 99% suspended solids and reduced certain important dissolved 

solids; therefore, the need for subsequent processing to reduce TDS did not appear to be 

necessary based on industry experience with recycling of RFW at that time. 

The FilterSure filtration system had proved itself under a number of water treatment scenarios; 

however, performance treating RFW and its unique water chemistry was unknown. Three

samples of RFW obtained had TDS values ranging from 10,000 to upwards of 188,000 mg/L. 

Radioactivity was determined to be at or below background levels and total hardness ranged 

from 5,000 to nearly 64,000 mg/L. Particle Size Distribution (PSD) analyses were performed on 

the RFW samples prior to and after filtration, and before and after EC. Figure 5 shows PSD

results of a RFW sample. A second RFW sample was treated by the EC unit followed by the 

FilterSure filtration system. As shown in Figure 6, this non-optimized EC test verified that EC 

was effective in coagulating many small particles to create much larger, easily filtered particles. 

All small particles, less than approximately 8-microns, were converted to larger particles ranging 
20 | P a g e

from about 10- to 200-microns, making them relatively easy targets for removal by the FilterSure 

filtration system. 

Figure 5: PSD Before and After FilterSure Filtration of a RFW Sample

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 Relative PSD, Pct

Particle Size, microns

Particle Size Distribution Comparison, Sample #2, Marcellus Shale 

Before & After FilterSureTM

BEFORE

Over 40% particulate AFTER

removal from 

1.5 to 3 microns

Complete particulate 

removal above 3 microns
21 | P a g e

Figure 6: Particle Size in Raw and EC-Treated Marcellus RFW

0

1

2

3

4

5

6

7

8

0.01 0.1 1 1 0 100 1000

Particle Size Distributions, pct

Particle Size, microns (logarithmic Scale)

Particle Size Distribution, Sample #3 & 3EC, Marcellus Shale

Before and After Electrical Coagulation

PSD of Raw Water, before EC treatment

PSD of Water after EC Treatment
22 | P a g e

Filtration without Pretreatment

Members of the WVU project team met with members of the Industry Contact Group 

and toured active well development sites in Pennsylvania and West Virginia. The 

purpose of these meetings and site visits was to confirm current water management 

practices being implemented in the field and determine how this project might impact 

industry practices. 

From the information obtained during these meetings and site visits, it was clear that 

large Marcellus Shale operators were not chemically treating their RFW prior to 

recycling. If they were treating the RFW, the treatment choice was 20-micron sized bag 

filters. Water treatment options were expected to have minimal operation and 

maintenance requirements and consist of a small, modular footprint. The operators 

indicated a desire for further dissolved metallic solids reduction and sulfates reduction; 

however, the removal of barium and strontium was no longer considered critical. Some of 

the producers injected untreated RFW, ignoring ideal design criteria established by the hydraulic 

fracturing support companies.

As a result of this industry input, it became clear to the WVU project team, major producers did 

not want or need the addition of EC or chemical flocculation prior to filtration as part of their

RFW treatment system for recycling purposes. Although the companies indicated a desire for 

heavy metals removal, they were not interested in anything that might slow down or complicate 

fracking operations, including large equipment on their “always too small” well sites. Industry 

demonstrated their primary needs were high-rate filtration operations, a minimum of 100 gpm

and preferably much higher, while achieving suspended solids removal down to 20 microns. A 

reduction in sulfates was also considered important because of its capacity to form scaling 

compounds when the RFW would be recycled for new fracking operations. Additionally, the 

treatment system would need minimal operator support and maintenance, occupy a small 

footprint, and be easily mobilized and de-mobilized from site to site.

At the same time these activities were ongoing, the WVU project team was investigating the 

requirements for a full-scale EC unit to pair with the FilterSure system. It was becoming 

apparent that the EC unit would be more cumbersome than originally envisioned, require its own 

mobile trailer unit and large source of power, and would cost more to obtain and operate; not 

entirely insurmountable problems but worth further investigation. 

The use of the multi-media FilterSure filtration system without EC pretreatment would provide

better mobility requiring only one mobile trailer unit, lower capital and operating costs, and

flexibility to meet throughput needs while meeting industry water treatment requirements for 

recycling RFW. Therefore, the WVU project team concluded:
23 | P a g e

 FilterSure’s multiple module, multi-media filtration unit met industry needs and offered a 

desirable level of environmental protection, and 

 EC treatment was not a viable industry option for mobile treatment of Marcellus RFW, 

with on-site recycling as the end objective. Rather, EC was more suited for use at a 

stationary treatment facility where water would be brought to the facility for treatment. 

An EC unit that would be able to adequately handle the throughput needs of industry 

would require a much larger footprint and source of power, two characteristics that are 

not conducive or available to a Marcellus well site environment. 

The WVU project team briefed DOE on the two viable options to move the project forward into 

the design, construction and field deployment phase:

1. Construct the EC and FilterSure mobile unit having a combined rated capacity of 30-gpm 

with a provision for by-passing the EC unit. This configuration would require two 

mobile trailer units, one for the EC unit and its separate power generator and one for all 

other components. The 30-gpm size was determined to be the largest-sized EC unit to

keep the footprint and power requirements manageable for on-site applications. 

However, industry throughput requirements would not be met, or 

2. Construct a mobile unit using only the FilterSure multiple module, multi-media filtration 

technology providing a throughput capacity of 120-gpm with the possibility to approach 

150-gpm, while meeting minimum RFW treatment requirements. This configuration 

would require one mobile trailer unit for all components and power supply would be 

provided by a generator packaged with the mobile unit. 

After further evaluation, along with input from the DOE, option two was subsequently 

approved. The design of the prototype Mobile Treatment Unit (MTU) would consist of two 

FilterSure multiple module, multi-media filtration units to provide the throughput capacity and 

minimum treatment requirements needed by industry for on-site treatment of RFW. 

Opting for filtration without EC or other chemical pretreatment was expected to result in little or 

no reduction in dissolved solids. Because RFW typically consist of high concentrations of 

various natural salts, the question arose among some Marcellus operators if salt concentrations 

could reach a level that would deem the continued use of recycled RFW as part of the make-up 

of hydraulic fracturing water detrimental to well production. Analysis showed recycled RFW

could be reused indefinitely. The process of combining fresh water with the saltier RFW 

resulted in a predictable but quickly-stabilized build-up of salt concentrations in the hydraulic 

fracturing water with successive blending cycles of RFW and fresh water. 

For a given development region, the saltiness of water mixtures used for any subsequent 

hydraulic fracturing operation should quickly reach a maximum. This maximum value is a 
24 | P a g e

function of the amount of RFW available for blending and its initial salt concentrations. This 

stabilization, or maximum salt concentration, occurs by the 3rd repeat cycle as shown in Figure 7

and Table 9. The salt concentration is approximately the same for the 4th hydraulic fracturing

cycle as for the 3rd cycle, and will remain constant for all subsequent hydraulic fracturing

operations, assuming no effective changes in significant variables from well to well. 

Figure 7: Predicting Stabilized Frac Water TDS when Recycling RFW

Table 9 provides a snapshot of the spreadsheet developed to calculate major ions and TDS 

concentrations of RFW recycled for subsequent fracturing operations. These values are based on 

the percent RFW recycled and blended with make-up water and initial water quality 

characteristics of both the make-up water and RFW. The user of Table 9 inputs the percent 

recycle rate along with initial water quality characteristics for the make-up water and RFW. 

Results of chemical analyses of the make-up water source and the RFW being used are entered 

into the spreadsheet. Values for TDS and the various ions listed are then calculated for each 

repeat cycle. For example, if the typical amount of RFW is 20% of the total amount of frac

water injected, and the TDS of the RFW is 108,665 mg/L, the stabilized salt concentration, TDS, 

for future hydraulic fracturing jobs will be approximately 27,366 mg/L. Levels of the ions 

barium (Ba), strontium (Sr) and sulfate (SO4) found in the RFW, may be limiting factors for how 

much RFW can be blended with fresh make-up water for subsequent fracturing operations. 
25 | P a g e

Table 9: RFW Dilution Model

Insert date in yellow cells only

*From BJ Services FR and SI (Scaltrol 720)

Phase II:

Mobile Treatment Unit Design, Construction and Operations

With approval to move to the design and construction phase, two 60-gpm FilterSure commercial 

filters were selected for installation in a standard shipping container 40 feet long by 8 feet wide

by 8 feet in height, mounted on a mobile chassis. Dual filter system controls provide automatic 

operation, maintenance operation, and monitoring of both filtration units. The system functions 

are controlled by a programmable logic controller (PLC) located in the control panel shown in 

Figure 8. The PLC interfaces with an operator interface Touchscreen (also referred to as an 

HMI – human machine interface), remote sensors and system devices. The HMI monitors and 

controls normal operation; system set-up such as timing, backwash settings and alarm settings; 

status and alarm conditions; and manual maintenance control. An operations manual along with 

instructions, drawings and schematics were placed inside the MTU for operator reference.

Designed to process up to 5,000 barrels/day, the mobile treatment unit (MTU), Figure 8, was

customized for well-site applications providing a small footprint with an external generator for 

power (50 kVA), easy movement between well pads, and quick set up for subsequent hydraulic 

fracturing activities. Once set up at a well pad site, the MTU will operate automatically 

requiring routine maintenance between fracturing treatments.

recycle 

rate RFW

20% RFW makeup Maximum* 1 2 3 4 5 6 7 8 9 10

TDS 108,665 200 50,000 26,272 27,147 27,322 27,357 27,364 27,366 27,366 27,366 27,366 27,366

Hardness 28,200 50 26,000 6,816 7,043 7,089 7,098 7,100 7,100 7,100 7,100 7,100 7,100

HCO3 100 20 300 43 45 45 45 45 45 45 45 45 45

SO4 50 60 50 70 72 72 72 72 72 72 72 72 72

C l 45,000 10 45,000 10,810 11,170 11,242 11,256 11,259 11,260 11,260 11,260 11,260 11,260

N a 50,000 10 36,000 12,010 12,410 12,490 12,506 12,509 12,510 12,510 12,510 12,510 12,510

C a 8,000 20 8,000 1,939 2,004 2,017 2,019 2,020 2,020 2,020 2,020 2,020 2,020

Mg 2,000 10 1,200 490 506 509 510 510 510 510 510 510 510

K 500 15 1,000 134 139 140 140 140 140 140 140 140 140

Fe 5 1 10 2 2 2 2 2 2 2 2 2 2

Ba 800 - 10 192 198 200 200 200 200 200 200 200 200

Sr 2,200 - 10 528 546 549 550 550 550 550 550 550 550

Mn 10 1 10 3 3 3 3 3 3 3 3 3 3

initial cycle

RFW dilution model: all ions
26 | P a g e

Figure 8: MTU General Arrangement

The flow of RFW through the mobile treatment unit is straightforward as detailed by the piping 

schematic in Figure 9. An in-line strainer is used to remove sticks and other large items that 

may be present in the RFW. The strained RFW then flows through two non-metallic centrifugal 

pumps. Flow meters are present prior to each filtration unit and sampling ports have been built 

into the treatment process prior to and after filtration. Each pump feeds one filter at a pressure of

80 pounds per square inch (psi) or less. The filters are designed with a media configuration 

capable of removing particles larger than three microns, making the filtered water suitable for 

recycling purposes. The filtered water exits the MTU and is ready for blending with fresh water

for the next hydraulic fracturing operation.

Backwashing of a filter is determined by monitoring the pressure across each of the media 

modules and will occur on an as-needed basis, typically no more than twice each day, taking 

approximately 10 minutes for each backwash cycle per filtration unit (all five modules). 

Backwashing of the filtration units is staggered to maintain one filtration unit in operation at all 

times. Each filter unit is constructed to allow for one or all media modules to be taken off-line 

and backwashed. Captured solids are flushed using water stored in the backwash water tank (see 

Figures 8 and 9). These solids exit the MTU and are managed for disposal by the operator. The 

backwashed filter is returned to operation and the second filter is then taken off-line to be 

backwashed. Backwash water is returned to the beginning of the treatment process and mixed 

with incoming RFW for treatment. However, the piping configuration for entering and exiting 

the MTU allows for flexibility in managing the backwash water.
27 | P a g e

Figure 9: Mobile Treatment Unit Piping Schematic Diagram

Construction of the MTU began in the spring of 2011 and proceeded without major issues. 

Figures 10 and Figure 11, exterior and interior photographs respectively, show progress near 

the end of the construction phase. 

Figure 10: Finished Exterior View of MTU
28 | P a g e

Figure 11: Completed Interior View of MTU

Selection of the final filter media to be used in the MTU was determined by additional laboratory 

testing using the FilterSure 2-gpm PDU. Nearly 100 barrels of Marcellus shale RFW were 

provided by a local operator for the additional laboratory tests. The RFW contained solids 

ranging in size from less than 3 microns to over 100 microns. Under high rate conditions, the 

PDU operating at rates up to 6-gpm, the media selected for the PDU removed particles larger 

than 3 microns as shown in Figure 12.
29 | P a g e

Figure 12: Particle Size Distribution Results

Over the course of the laboratory testing phase, the 2-gpm FilterSure PDU consistently removed 

solids and reduced various ions such as chlorides, sulfates, sodium and barium as summarized in 

Table 10. Chemically, the filtered RFW met the current industry standards for continued use as 

frac water when blended with fresh water. Therefore, the media and sequence tested in the 2-

gpm PDU was duplicated for both FilterSure filtration units installed in the MTU. Designed to 

process 5,000 barrels/day, the MTU was prepared for field deployment and real-time testing.
30 | P a g e

Table 10: Filtration Results of Filtered RFW Samples

A:

Raw

A:

FS

B:

Raw

B:

FS

C:

Raw

C:

FS

D:

Raw

D:

FS

Average 

Change, 

%

Cl 17100 13000 65000 51000 80400 95400 150000 106667 -14

SO4 28 11 414 101 73 - 0 0 -69

Fe 32 15 6 8 40 45 64 66 0

Ca 1610 1540 10600 7830 21000 19300 21000 22183 -8

Mg 188 175 1200 786 2220 2270 2120 2187 -9

Na 8530 7260 32800 19500 45400 34400 42780 42780 20

K 243 297 444 996 701 601 1810 1875 34

Sr 280 249 1340 1090 2980 3120 5060 5267 -5

Ba 172 165 201 93 1440 1520 2290 2397 -12

pH 7.4 7.7 5.3 6.3 5.5 5.0 - - 4

Cond 66300 51000 183000 148000 194000 195000 197000 197167 -10

TSS 99 81 570 187 882 681 484 313 -36

TDS 38700 28200 11200 81400 188000 187000 187000 168667 -16

Hardness 4890 4650 38000 22000 63400 74100 65900 69300 -6

O&G nd nd nd nd 13 nd nd nd

Charge 

Balance, 

%diff

0 14 13 6 38 3 25 11 14

nd = not detected

Field Trials

Two field trials were completed, both under a lease agreement with Chesapeake Energy

(Chesapeake). The first location was a Utica Shale site in Carrollton, Ohio. The second was a 

Marcellus Shale site located near Wheeling, West Virginia. 

Site 1: Utica Shale Site

FilterSure moved the MTU from the manufacturing location to the first drilling site located in 

Carroll County, Ohio. Storage containers were available on site to hold water prior to filtration 

and to provide storage after treatment prior to blending with fresh water for the next fracturing 

operation. At this particular site, storage containers were the preferred method of water storage 
31 | P a g e

instead of impoundments. Chesapeake positioned the MTU where untreated water from the 

yellow tanks shown in Figure 13 could be easily connected to the MTU. The filtered water was 

transferred to empty storage tanks located to the right of the MTU (not shown in this 

photograph). Filtered RFW was blended with fresh water and used in subsequent hydraulic 

fracturing operations. 

Figure 13: On Location at Utica Shale Site in Ohio

The MTU was on site in Carrollton, Ohio for eleven days, of which the unit was in “operational 

mode” nine days. Once the MTU was positioned by Chesapeake on the well pad, it was 

connected to the generator for power and connections were made to the water storage tanks 

supplying water to be treated and collecting water after treatment. Commands for the PLC were 

updated and initial testing of the system was conducted prior to start-up to ensure the alarm 

system and automatic shutdown mode executed properly. Emergency and safety systems were in 

place and worked according to the operations manual.

The Ohio site consisted of one well with 15 fracking stages. The company on site overseeing the 

fracturing operations performed two fracking stages per day. Water was collected from various 

Chesapeake development wells and trucked to the Ohio site to be treated by the MTU prior to 

blending with fresh water. These liquids ranged in quality from rain water to highly saline water. 

Some of the liquids also contained oils and polymers collected from recently fracked oil wells. 

In addition, as a part of its water management plan, Chesapeake routinely removed rain water 

trapped behind an extensive dyke system constructed for secondary containment of water that 

may leak from storage operations. This water was pumped into the “raw” water storage tanks to 

be treated by the MTU for recycling as well (yellow tanks shown in Figure 13). The quality of 
32 | P a g e

the water being processed through the MTU was unpredictable, it was a highly variable liquid 

that sometimes contained a significant quantity of oil and/or polymer, as seen in Figure 14. 

Although the oil and polymer mixture was processed (removed) by the MTU, it was at a cost of 

higher pressure and a reduced throughput rate.

Figure 14: Oil/Polymer Mixture Treated by MTU

At the Carrollton, Ohio site, the MTU processed water for fracking at a rate of 122 gallons/min 

(about 4,000 barrels/day). Pressure across the filter modules remained relatively low, averaging 

around 30 psi. Water leaving the MTU was clear in appearance and influent and effluent 

samples were collected and processed for laboratory analysis. However, these samples were not

considered to adequately represent the entire 200,000 gallons of water treated at the Ohio site 

because of the variation in water brought in to the site. The water chemistry was fairly consistent 

with other hydraulic fracturing water samples taken during this project for analysis. Also, 

filtration did not significantly change the water chemistry of the major ionic species. 

The MTU is designed for automatic or manual operations. However, to meet Chesapeake’s site 

safety guidelines, an MTU operator was on site while the unit was in operation. The panel 

mounted on the wall shown in the background of Figure 15, controls the MTU operations and 

records all operational conditions. Figure 16 is a photograph of the Touchscreen or HMI 

showing Filter 1 operating at 41 gpm and Filter 2 operating at 43 gpm; thus, the total flow 

through the MTU at the time of the photograph was 84 gpm, or 2,880 barrels/day (bpd).
33 | P a g e

Figure 15: MTU Control Panel

Figure 16: Control Panel Close-Up View

A pressure gauge records the pressure drop from the inlet to the outlet of each filter, Figure 17. 

At the time of this photograph, Figure 17, the pressure drop across Filter 1 was 64 psig and

across Filter 2 was 68 psig. The pressure drop across each module monitors the performance of 

the media contained in each filtration cell (build-up of solids removed from the water), is used to 

adjust backwash cycles as needed and to modify selection of media for future applications based 

on the quality of water being treated by the MTU.
34 | P a g e

Figure 17: Pressure Drop Measurements of MTU in Operation

Initial operations showed a gradual decline in the throughput (filtration) rate and a gradual 

increase in pressure as the media collected solids and the system stabilized. Figure 18 plots the 

throughput rates and inlet pressures for the first six days of operation. On day one, the MTU 

began processing water at a throughput rate of 122 gpm (4,183 bpd) and stabilized at a 

throughput rate of 104 gpm (3,566 bpd) by day five. Over this period, the pressure increased 

from an initial pressure of 30 psig to 53 psig.
35 | P a g e

Figure 18: Day 1 through Day 6 Filtration Rates and Pressures

During day six of operations, processed water containing a high concentration of an oil and 

polymer mixture, as shown previously in Figure 14, was received and processed through the 

MTU. The impact of the heavy solids and oil/polymer loading on pressure and filtration rate is 

reflected in Figure 19. Pressure increased 32%, from 53 psig to 70 psig. At the same time, the 

rate decreased 25%, from 104 gpm to 78 gpm. Most of the oil and polymer mixture was 

captured during the normal programmed backwash cycles; however, some of this mixture was 

retained on the filter media. By day eight, the backwash cycles had successfully removed the 

remaining mixture of oil and polymer with trapped solids on the filter media, increasing 

throughput from 78 gpm to 84 gpm while simultaneously lowering the pressure from 70 psig to 

66 psig. The backwash cleaning process returned operating conditions to a 100 gpm throughput 

rate at an inlet pressure of approximately 45 psig by the end of day nine.
36 | P a g e

Figure 19: Filtration Rate and Pressure, Days 1 through 9

Backwash cycles were originally programmed to occur once every twelve hours of operation. 

Each module is backwashed individually for a period of two minutes, with a total backwash time 

lapse of ten minutes per filtration unit. Backwash cycles were set manually at the Carrollton, 

Ohio site until the MTU operators learned to manage the sporadic availability of RFW to process 

for recycling and system upsets caused by the unpredictable introduction of the oil and polymer

mixture in the influent stream. Visual observation of the backwash water verified solids were 

being removed by the media. This initial field operation validated the extensive laboratory 

testing of the 2-gpm PDU conducted at West Virginia University (WVU). Media selected for 

the 2-gpm PDU were subjected to extended-run tests, leading to the selection of the media that 

were subsequently loaded into the MTU. No technical issues were encountered scaling from the 

2-gpm PDU used in the WVU tests to the 120-gpm MTU.

At the Carrollton, Ohio site, trucks delivered water around the clock in preparation for the 

hydraulic fracturing operations. In addition to the MTU treating the water being received on site, 

a 10-micron bag filtration system was also on site as a second treatment option. The flow of 

water was split and sent to the MTU or bag filters for treatment. However, within minutes of 

receiving the water containing the oil and polymer mixture, the bag filters plugged and had to be 

taken off-line in order for the filters to be replaced. Processing of the water was slowed, reduced 

throughput, but the MTU operations continued without interruption, removing the oil/polymer 

mixture from the water and recapturing it through the backwash cycles.

0

2 0

4 0

6 0

8 0

100

120

140

1 2 3 4 5 6 7 8 9 Throughput Rate, GPM Inlet Pressure, psig

Operating Time, days

Throughput, GPM

Inlet Press., psig
37 | P a g e

The MTU utilizing the FilterSure technology proved to be highly versatile responding to “upset”

conditions. This response capability will continue to improve with future plans to introduce an 

additional media module that will capture oil-based solutions before passing through to the other 

media modules of the filtration unit.

Lessons Learned from Site 1

Laboratory tests using a consistent quality of produced water cannot match the variable quality 

and quantity of the water delivered to a site by hundreds of trucks supplying water from a wide 

variety of sources. Even so, laboratory tests conducted at WVU utilizing the 2-gpm PDU for 

processing various RFW samples resulted in the selection of five media types that treated the 

water for recycling purposes. 

Media for the MTU needs to be more robust in its capability to capture oil and/or polymers 

before this mixture enters the lower modules of the filter. In the future, an oil-loving media will 

be used to process the influent before it enters the MTU or placed in the first of the five filtration 

modules used in the FilterSure technology. This approach will protect the lower modules from 

fouling, and greatly reduce the time to backwash the unit to restore overall throughput at a 

reasonable inlet pressure.

Site 2: Marcellus Shale Site

Upon completion of water treatment operations at the Carrollton, Ohio site, Chesapeake 

relocated the MTU to a location near Wheeling, West Virginia. Figure 20 shows the 

arrangement of water storage tanks and the MTU, the MTU is located in the left top corner of the 

photograph, on the well pad. RFW for filtration was trucked onto the site and stored in the tanks 

in the foreground as shown in Figure 20. From the storage tanks, the water was processed 

through the MTU. The filtered water was stored in the yellow tanks positioned to the right of the 

FilterSure unit and ready for blending with fresh water supplies prior to the hydraulic fracturing 

operations.
38 | P a g e

Figure 20: Marcellus Shale Site, West Virginia

Upon arrival at the new site, the Dytko Site, in West Virginia, a series of system checks were 

performed and the MTU was prepared to begin operations. The MTU supported a nine-stage 

fracking operation, operating at an average filtration rate of 104 gpm and at a pressure of 52 psig

to treat RFW prior to blending with fresh water supplies. Within four days, all stored RFW, 

approximately 147,000 gallons, was filtered and consumed the storage capacity provided for 

processed (treated) water ready for recycling. Once fracturing operations began, the MTU was 

taken off-line during the actual fracture operations while water was withdrawn from the filtered 

water tanks and blended with fresh water for use in fracturing. Filtration resumed after each 

fracture stage.

Figure 21 details the fracturing stages and the amount of RFW processed by the MTU. MTU 

operations were able to keep up with the ongoing demands to support the eight hydraulic 

fracturing stages. One additional fracture was supported but not shown in Figure 21 before 

fracture operations were completed. Nearly 288,000 gallons of water was processed by the MTU 

at the Dytko Site.
39 | P a g e

Figure 21: Water Treated for Fracturing Stages

Frequent rate and pressure data were taken during the fracking operations. Figure 22

summarizes this data showing stable throughput (filtration) rates and pressures. Filtration rates

averaged 104 gpm at an average filter inlet pressure of 52 psig. There were no major deviations 

in the rate and pressure data, reflecting relatively clean water was being processed for recycle

purposes. 
40 | P a g e

Figure 22: Rate and Pressure Data during Water Treatment

As mentioned previously, during active fracturing, the MTU was off-line. While off-line, 

captured solids were removed by backwashing each filter individually. Ten backwash cycles 

were completed using an average volume of 400 gallons per cycle. Backwash volume totaled 

4,000 gallons. RFW processed for recycle totaled 288,000 gallons for blending with fresh water. 

Of the total volume of water sent through the MTU unit, 98.6% was recycled with 1.4% returned 

for disposal.

MTU operators learned from the Ohio site operations that water collected for physical and 

chemical analyses need to reflect a broad range of water influent and effluent. Accordingly, 

MTU operators collected composite samples over a period of time while at the Dytko Site. 

These composite samples were submitted for particle size distribution (PSD) to the Civil 

Engineering Department at WVU and for chemical analysis by REIC Laboratories located in 

Beaver, West Virginia. 

Concentration of particles in the collected water was unexpected. All prior testing of Marcellus 

Shale RFW had particle size distributions ranging from near-zero to over 100 microns in size. 

However, both the influent and effluent water collected from the West Virginia site had particles 

that ranged from near-zero to less than three microns. Concentration of the influent and effluent 

particles is shown in Figure 23. 
41 | P a g e

Figure 23: Influent and Effluent PSD from West Virginia RFW

It is clear from Figure 23, particle size data the MTU did indeed remove particles that were as 

small as 0.5 microns in diameter. This is remarkable removal efficiency and is shown 

graphically as the difference between the blue (influent) and the red (effluent) curves of Figure 

23. This reduction in volume shows up as a reduction in Total Suspended Solids (TSS) in the 

water chemistry analysis prepared by REIC laboratories.

Water chemistry analysis results are presented in Table 11. These results independently verify 

the MTU removed 32% of the suspended solids. Specifically, the TSS fell from 360 mg/L to 

244 mg/L, a reduction of 116 mg/L. Previous controlled laboratory testing using Marcellus 

Shale RFW samples had an average TSS influent of 517 mg/L and an average effluent of 316 

mg/L; a reduction of 39%. The laboratory and the current TSS reductions from the West 

Virginia site were therefore similar. 

TDS readings were very low, with the influent and effluent water at about 22,000 mg/L. Prior 

Marcellus Shale RFW tested at WVU averaged 113,000 mg/L. Looking at the water chemistry 

of the RFW water received at the Dytko Site may have consisted mostly of early flowback water 
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(water returning back up hole in advance of gas production) and previously blended with fresh 

water. Comparing water quality parameters of the MTU influent and effluent to the values 

determined to be critical by the Industry Contact Group detailed in Table 1, both met the criteria 

with the exception of iron, barium and strontium.

Table 11: Marcellus Shale Site Water Chemistry

Avg Influent

mg/L

Avg Effluent

mg/L

Avg Change

mg/L

Avg Change,

%

Cl 15400 12300 -3100 -20

SO4 24 24 0 0

TDS 21300 22600 1300 6

TSS 360 244 -116 -32

Ba 35 37 2 8

Ca 2660 2740 80 3

Fe 17 18 1 2

Mg 293 308 15 5

K 117 127 10 9

Na 5620 5830 210 4

Sr 360 364 4 1

Lessons Learned

Water collected for testing from the West Virginia site had very fine particles (less than 3 

microns) and low TDS values (average of 21,300 mg/L). Marcellus Shale water samples tested 

at the WVU laboratory during Phase I of the project as well as additional testing conducted at the 

beginning of Phase II to finalize filter media selections had significantly larger particles (over 

100 microns) and a much higher TDS (average of 113,000 mg/L). Although RFW treatment 

results met industry requirements for recycling, additional analyses of the influent and effluent 

water stream may have been able to clarify the initial water quality results of the raw RFW

received at the Dytko Site.

Project Summary

Shale gas production depends on the creation of permeability within an otherwise nearly 

impermeable rock formation. Horizontal drilling and hydraulic fracturing have been applied to 

produce natural gas from tight shale formations previously thought to be non-obtainable.
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Hydraulic fracturing (fracking) uses large volumes of water to create numerous channels within 

the shale formation. Sand, pumped with the water, props open the hydraulic fractures, thus 

providing multiple, permeable flow paths for the natural gas. However, the withdrawal of local 

water resources for fracking and the returned frac water (RFW) create two significant

environmental issues that must be dealt with. The search for a way to mitigate the situation and 

improve the overall efficiency of shale gas production suggested treatment of the RFW that 

would allow for the water to be recycled and reused for successive fracking operations. This 

would reduce the demand on local water resources and provide an economical and 

environmentally friendly way to manage the RFW. Project objectives were to identify the 

composition of RFW, define industry standards for the quality of make-up water used for 

fracking, and develop a technique to treat RFW for blending recycling.

Several samples of Marcellus Shale RFW were obtained and analyzed throughout the course of 

this project. Table 12 provides an overview of various chemical parameters acknowledging 

RFW is best characterized by providing a range of values for each. Differences in parameter 

values from sample to sample may be the result of 1) when the sample was taken during flow 

back, 2) the water quality characteristics of the original frac water because sources of make-up 

water vary, 3) chemical additives blended with the frac water since each company has their own 

mixture which is often proprietary, and/or 4) differences throughout the formation itself.

Table 12: RFW Chemical Analyses

Raw RFW Samples Industry Guidelines

TDS 9730 – 188000 50000

Hardness 923 – 63400 26000

SO4 nd – 414 50

Cl 4600 – 80400 45000

Na 2060 – 45400 36000

Ca 319 – 21000 8000

Mg 31 – 2200 1200

K nd – 701 1000

Fe 6 – 59 10

Ba 0 – 1640 10

Sr <1 – 3559 10

*Treated by FilterSure multiple module multi-media filtration system

Industry standard for acceptable RFW water quality standards continue to evolve. When 

contacted, the consensus from the Industry Contact Group concerning acceptable water quality 

for recycled RFW indicated TSS values below 20 microns along with a range of other 

parameters also provided in Table 12 above. Concerns with sediment accumulations in the 

pores and well bore were reflected by industry’s TSS requirements. The other chemical 
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parameters were thought to interfere with the performance of the frac water and/or potentially 

increase scale formation. Dissolved solids removal was important but not critical because most 

of the industry criteria could be achieved with blending of the treated RFW and fresh water.

Based on industry input and preliminary analyses of RFW samples, the WVU project team 

proceeded to determine an efficient and effective method to treat RFW for recycling purposes. 

Filtration was determined to be a necessary treatment step, possibly coupled with a process for 

removing salts. Various processes were examined such as reverse osmosis (RO), nanofiltration 

and electro-coagulation (EC). Upon review of costs and operational requirements of the various 

processes, further evaluation of EC was recommended. 

Several RFW samples were obtained from various Industry Contact Group members. Samples 

were treated by a small-scale EC unit and a 2-gpm process demonstration unit (PDU) of the 

FilterSure multiple module, multi-media filtration system. Laboratory analyses showed that 

pretreatment of the water by EC prior to the FilterSure PDU filtration system was not required to 

meet the water quality criteria of industry at that time for recycling RFW. These results led to 

the design and construction of a mobile treatment unit (MTU) utilizing the FilterSure multiple 

module, muti-media technology to field test.

A fully-automated MTU was designed, constructed and delivered to a Utica Shale site in 

Carrollton, Ohio during September 2011. The MTU consisted of two FilterSure filtration units 

each capable of operating between 60 and 70 gpm. Operations at the Utica Shale site were 

followed by operations at a Marcellus Shale site location near Wheeling, West Virginia. 

Capacity of the MTU was adequate to support field operations at both sites. The mobile unit was 

able to keep up with on-going fracking operations and produce a quality effluent for blending 

with fresh water and used for subsequent fracturing operations thus reducing the overall quantity 

of fresh water needed for fracking operations and providing a cost-effective, environmentallysound alternative for managing RFW. Over 600,000 gallons of water were treated at the two

locations with 98.6% of the water being recycled. The remaining 1.4% was used to backwash 

the filtration units and then disposed of properly. Suspended solids were reduced by one-third, 

particles as small as 0.5 microns were removed, and reduction in some divalent ion 

concentrations were observed during field testing. The MTU was able to handle water 

containing a highly-viscous oil and polymer mixture that was part of the RFW to be treated at the 

Utica Shale site in Ohio. Overall, the MTU proved to be highly capable of responding to “upset”

conditions and treating RFW with widely variable concentrations of various chemical water 

quality parameters. 
45 | P a g e

Acronyms, Abbreviations and Units of Measurement

avg average

Ba Barium

bpd barrels per day, barrels/day

Ca Calcium

Cl Chloride

cndctvty conductivity

DOE Department of Energy

EC Electro-coagulation

ECFS Electro-coagulation and FilterSure

Fe Iron

FOA Funding Opportunity Announcement

gm gram

gpm gallons per minute

HMI Human Interface Machine, Touchscreen

K Potassium

KCl Potassium Chloride

K2SO4 Potassium Sulfate

kVA kilovolt ampere

Mg Magnesium

mg/L milligrams per liter

mL milliliters

MTU Mobile Treatment Unit

Na Sodium

NaCl Sodium Chloride

NETL National Energy Technology Laboratory 

O&G Oil and Grease
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Pct Rtn percent (%) return

PDU Process Demonstration Unit

PSD Particle Size Distribution

psi pounds per square inch

psig pounds per square inch gauge

RFW Return Frac Water

RO Reverse Osmosis 

SO4

-2

Sulfate

Sr Strontium

TDS Total Dissolved Solids

TSS Total Suspended Solids

WVU West Virginia University

w/ with

w/w wet weight

μM micro-meter

μS/cm micro-siemens per centimeter

μS/cm2 micro-siemens per square centimeter