Water Recovery via Thermal Evaporative
Processes For High Saline Frac Water Flowback
JOSEPH TINTO, ROBERT SOLOMON,
GE Water & Process Technologies, Bellevue, WA
IWC
10-66
(IWC-10-XXXX)
KEYWORDS: Frac Water Treatment, Thermal Evaporative Treatment, Frac Water Recovery
To avoid the water related limitations and further the development of the nation’s shale gas
resources an economical process to recover and reuse water from hydrofracturing operations is
required. Currently, most frac water is trucked off-site for disposal by deep-well injection. This
water returns as flowback and produced water having a high TDS level (>100,000 ppm). A study
examining thermal processes for water recovery and beneficial use of salt waste was conducted.
The contribution to the U.S. energy supply
from unconventional natural gas sources
such as tight shale formations is increasing
dramatically. To release natural gas from a
shale deposit, 1-5 million gallons of water
plus hydrofracturing chemicals are pumped
under high pressure down a shale gas well.
This water (12-60%) returns as flowback
water (TDS ranging from 40,000 mg/l to
150,000 mg/l) and produced water having a
TDS level (>100,000 ppm) and high hardness
(>10,000 ppm as CaCO3), including significant
levels of barium. Currently, most frac water
is either trucked off-site for disposal by deepwell injection or is processed for reuse in
further frac operations by means of metals
removal and suspended solids removal
treatments.
The handling and processing of both the
flowback produced waters is a major cost
issue for Gas Producers. The disposition of
these waters are a major focal point of many
environmental groups across the nation as
well as a point of regulatory focus for many
state environmental protection agencies. In
some shale gas plays the availability of
source water for frac operations is at times
limited adding to the focus of recovery on
these waters.
To avoid the water related limitations and
further the development of the nation’s shale
gas resources an economical process to
recover and reuse water from
hydrofracturing operations is required. An indepth study of water recovery involving
thermal processes of evaporation combined
with salt production by crystallization was
undertaken. Studies of the reuse of the
distillate and the beneficial use of salt
products, meeting TCLP & ASTM standards as
well as State regulations were conducted.
The results of the simulations and pilot
testing are discussed in this paper.
1
Full treatment systems ranging in capacity
from a 50-gpm mobile treatment system to
fixed plants of 200,000 GPD to 1.0 MGD have
been developed and are presented.
the flowback and produced waters from the
Southwestern area of Pennsylvania, however
the results can be applied across most shale
plays upon evaluation of the specific water
characteristics.
Introduction
The frac water, as presented from wells
sampled in the Marcellus Shale in
Southwestern Pennsylvania, can be treated
to recover approximately 82% of the water in
a Pretreatment, Evaporation & Crystallization
plant. The residual salts from crystallization
can be used as feedstock for saleable salt
products such as road deicing salt or for
industrial softener processes.
The pretreatment process was developed by
GE Water & Process Technologies in our
Thermal Products lab utilizing our in depth
database of Marcellus Shale frac water
samples. The results of the pre-treatment
were applied across the samples with
consistent results.
GE Water & Process Technologies’ Bellevue,
Washington office has been conducting
analyses and performing tests on “frac
flowback water” and “produced waters” from
several natural gas wells in the Marcellus
Shale zone in SW Pennsylvania to determine
the most effective method of treating the
water via a thermal evaporative process. The
results of this effort has lead to the
development of a thermal Zero Liquid
Discharge (ZLD) discharge system for treating
natural gas drilling wastewater, known as
both frac and produced water. The project’s
primary objective is to treat the frac water,
produce dried solids suitable for recycle or
disposal, and recover water for reuse in the
gas well frac business.
The frac water samples show various high
TDS levels, ranging from 110,000 mg/l to
150,000 mg/l. The GE Water & Process
Technologies treatability study did create a
134,000 mg/l TDS blended solution for the
test as a reference flow equalized feed from
a wide gas well feedwater source. The flow
equalized feed will result from the flowback
and produced waters of many wells across a
given geography having various elapsed time
periods from the date of the well fracture.
Because this is the “first of its kind” ZLD
treatment system for frac water, an extensive
laboratory test program was developed to
generate the required process design data.
The laboratory test program consisted of
bench scale evaporator & crystallizer testing.
All shale plays are different in terms of the
water characteristics of the flowback and
produced waters returned from the gas well
fracturing and production operations. In fact,
the characteristics of these waters has been
observed to vary considerably within a
specific shale play. The study presented here
is focused on the results of an evaluation of
The specific objectives of the laboratory test
program include the following:
2
Develop process design basis
Evaluate feed pretreatment
requirements
 Identify optimum evaporator design
parameters
o Maximum concentration factor
(CF)
o Boiling point rise (BPR)
o Foaming, fouling, and scaling
tendencies
o Distillate composition
 Evaluate Crystallizer Designs &
Performance
o Boiling point rise (BPR)
o Foaming, fouling and purge
stream potential
o Salt purification / separation
TABLE 1:

Baseline Feed Chemistry

ANALYTE
Raw
Water
mg/L
pH, standard units @ 20°C
Conductivity, µmhos/cm
Turbidity, NTU
Total Suspended Solids
Total Dissolved Solids (105°C)
Total Dissolved Solids (180°C)
Fixed Solids (550°C)
Density, g/mL
Total Solids (105°C), % w/w
Acid Insoluble Matter, % w/w
Loss-On-Ignition (550°C), % w/w
Sodium
Calcium
Magnesium
Potassium
Silica by colorimetry
Silica by ICP
Total Sulfur
Sulfate
Sulfide
Chloride
Fluoride
p-Alkalinity (as CaCO3)
t-Alkalinity (as CaCO3)
Total Inorganic Carbon
Ammonia Nitrogen
Total Organic Carbon
Oil & Grease (HEM)
Total Phosphorus
A baseline feed chemistry for the ZLD system
was established. Several frac water samples
were collected, blended, and analyzed.
Based on these analyses the frac water
composition range listed in Table 1 was
established for the ZLD system process
design basis.
Frac water contains a high concentration of
total dissolved solids (TDS). The TDS is mainly
sodium chloride and calcium chloride. High
barium and strontium levels were identified
in the wastewater. High amounts of iron,
magnesium, and potassium were detected.
Overall, the frac water chemical composition
depends on the contributing frac wells and
their associated age – post frac.
Barium
Iron
Manganese
Strontium
1
6.3
115,000
8
13
134,000
130,000
31,800
8,790
770
130
25
< 20
75,560
<2
0
59.6
89
<3
3,060
71
4.2
2,430
Results are given in mg/L on a filtrate basis.
Three primary options are available for
pretreatment – either a combination of
aeration and filtration, the use of chemical
oxidizers or the use of precipitation agents.
The method of pretreatment was established
by testing the methods on sample frac water.
The frac water feed contains very high total
suspended solids (TSS); therefore, the feed will
most likely require pretreatment prior to
entering the ZLD system. A Baseline Test of
the Raw Water Feed to the Heat Exchanger &
Evaporator glassware simulators was
conducted to evaluate pretreatment
requirements.
3
Objectives
Based on our experience with fracture water
and produced waters from various shale
plays we developed a series of analysis and
tests to gather information to answer six key
questions:
1.1
What is the composition of the
water and how does if vary with
age of the well (post-frac) ?
Develop Frac Water Blends using
flow based well data.
1.2
What types of pretreatment are
appropriate to deal with the high
mineral content, suspended solids,
and total organic carbon?
1.3
What is the chemical consumption
for the process?
1.4
What is the scaling potential and
how will it be dealt with for the:
 Heat exchanger
 Evaporator
1.5
What is the recovery rate and the
chemistry of the concentrated
brine?
1.6
What is the analysis of the waste
brine and the recovered salt
properties?
Question
1. What is the
composition of
the water and
what is a
representative
sample?
Test Method
Water chemistry
analysis for daily
samples + well
production logs
2. What type of
pretreatment is
appropriate?
Simulation of:
 Aeration
 Filtration
 Precipitation
Simulation of:
 Heat exchanger
 Evaporator
3. Will scaling be a
problem with
the brine and
are scale
inhibitors a
solution?
4. What dosages
and total amounts
of chemicals will
be used?
5. What are the
water recovery
factors?
6. What is the
composition of the
Waste Brine and
recovered salt?
Test Methods
To address each of the questions, the
following methods were employed:
4
Record results of
chemical usage for:
 Pretreatment
 Scale inhibitor
usage
 Evaporator
simulation
Record results of:
 Distillate
recovery (from
evaporator
simulation)
 Saturation
indices
 Compound salts
and scaling
Chemistry analysis of
evaporator simulator
sump and crystallizer
solids.
Water Chemistry Analysis – Table 2.1
ANALYTE
pH, standard units @ 20°C
Conductivity, µmhos/cm
Turbidity, NTU
Total Suspended Solids
Total Dissolved Solids (105°C)
Total Dissolved Solids (180°C)
Fixed Solids (550°C)
Density, g/mL
Total Solids (105°C), % w/w
Acid Insoluble Matter, % w/w
Loss-On-Ignition (550°C), % w/w
Sodium
Calcium
Magnesium
Potassium
Silica by colorimetry
Silica by ICP
Total Sulfur
Sulfate
Sulfide
Chloride
Fluoride
p-Alkalinity (as CaCO3)
t-Alkalinity (as CaCO3)
Total Inorganic Carbon
Ammonia Nitrogen
Nitrite Nitrogen
Nitrate Nitrogen
Cyanide
Thiocyanate
Total Organic Carbon
Oil & Grease (HEM)
Total Phosphorus
Aluminum
Arsenic
Barium
Boron
Cadmium
Chromium
Copper
Iron
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
Silver
Sample
SX-23
Sample
SX-13
4-Feb
mg/L
4-Feb
mg/L
5.3
121,000
5.2
135,000
340
147,000
146,000
120
189,000
186,000
36,400
11,300
1,460
144
42,700
14,600
1,590
301
18
30
x
20
< 10
84,500
<2
104,000
<2
0
< 10
21
0
< 10
110
x
<5
<5
8.9
3,780
58
219
21.9
8.4
5
Water Chemistry Analysis – Table 2.2
ANALYTE
pH, standard units @ 20°C
Conductivity, µmhos/cm
Turbidity, NTU
Total Suspended Solids
Total Dissolved Solids (105°C)
Total Dissolved Solids (180°C)
Fixed Solids (550°C)
Density, g/mL
Total Solids (105°C), % w/w
Acid Insoluble Matter, % w/w
Loss-On-Ignition (550°C), % w/w
Sodium
Calcium
Magnesium
Potassium
Silica by colorimetry
Silica by ICP
Total Sulfur
Sulfate
Sulfide
Chloride
Fluoride
p-Alkalinity (as CaCO3)
t-Alkalinity (as CaCO3)
Total Inorganic Carbon
Ammonia Nitrogen
Nitrite Nitrogen
Nitrate Nitrogen
Cyanide
Thiocyanate
Total Organic Carbon
Oil & Grease (HEM)
Total Phosphorus
Aluminum
Arsenic
Barium
Boron
Cadmium
Chromium
Copper
Iron
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
Silver
Strontium
Zinc
1
Sample
M-9
Sample
PW-A
Sample
RH-1
Sample
K-3
4-Feb
mg/L
4-Feb
mg/L
4-Feb
mg/L
4-Feb
mg/L
5.9
129,000
6.4
73,000
6.9
40,000
5.5
153,000
200
162,000
158,000
95
67,400
66,000
16
32,400
31,200
160
241,000
232,000
40,200
9,940
942
1,700
17,400
4,040
408
746
8,330
2,070
220
103
57,700
17,100
1,420
2,160
21
< 10
x
34
166
27
101
19
< 20
89,900
2.3
37,600
1.7
17,900
1.6
133,000
2.5
0
47
213
0
175
102
0
266
49
0
15
314
<5
<5
<5
<5
118
5.6
6.8
1,060
15
31
10
78
1.2
0.8
1.4
1.9
2,510
860
270
4,630
x
Results are given in mg/L on a filtrate basis.
6
Baseline Testing & Evaluation
It was shown that chemical pre-treatment is
more effective in the Marcellus region while
aeration/filtration is more effective in other
shale plays.
The frac water composite blend (134,000
mg/l TDS) will be run through the Heat
Exchanger & Evaporator Simulations with
and without the use of scale inhibitors and
prior to any other pre-treatment methods.
This procedure will develop a baseline for the
thermal evaporative system performance.
Precipitation
Aeration
Chemically assisted precipitation methods
were used to evaluate alternatives to
aeration and filtration, as well as chemically
assisted oxidation. Chelating agents used in
the well frac operations can bind the
dissolved iron resisting oxidation attempts.
This test determines how quickly oxidation
occurs to exhaust the soluble iron and
magnesium. The speed and effectiveness of
oxidation was used to determine the
residence time for the influent during pretreatment (if applicable).
It was shown that chemically assisted
precipitation may overcome the chelating
agents and allow the removal of dissolved
iron. Simulation of Equipment with Scale
Building Tendency and Effectiveness of Scale
Inhibitors
Filtration
Laboratory glassware apparatus was used to
simulate equipment with scaling potential the heat exchanger and the evaporator. Two
types of solution were evaluated – a high
salinity composite (blend) of the frac water
samples - with and without the use of a scale
inhibitor.
Pre-Treatment Methods and Analysis
The aerated water was then filtered to
simulate media filtration. Filtration will
remove the suspended particles such as
insoluble iron and magnesium. The efficacy
of filtration will be determined by the time
required to filter the samples.
Heat Exchanger
Chemical Oxidation
To simulate the heat exchanger a threemouth flask was utilized with a titanium
coupon suspended via a glass rod, as shown
in figures 1 and 2 below. The titanium
coupon was submerged in the brine solution.
Distillate vapor was returned to the closed
system via a cold-water condenser. The
sample was refluxed at 206F for 20 hours (to
ensure that chemical equilibrium was
reached) and then the coupon and solution
was examined to determine if scaling
occurred on the coupon or whether there
was any turbidity in the solution.
This test determines how quickly oxidation
occurs to exhaust the soluble iron and
magnesium. The speed and effectiveness of
oxidation was used to determine the
residence time for the influent during pretreatment (if applicable). Chemically assisted
oxidation methods were used to evaluate
alternatives to aeration and filtration. Strong
oxidizers followed by filtration have been
found to successfully treat the high iron and
TSS content feed where aeration has not
been successful.
7
Figure 1 - Heat Exchanger Simulation
Figure 3
Figure 2 – Close-up of Heat Exchanger
Simulation
Bench Scale Evaporator Test Apparatus
8
Evaporator
To simulate the evaporator a three-mouth
flask was utilized with a titanium coupon
suspended via a glass rod. The titanium
coupon was submerged in the brine solution.
A pump was used to replace brine lost in the
distillation process to maintain a constant
level in the ‘sump’. The distillate was cooled
via a cold-water condenser and captured for
analysis. The procedure was carried out until
a terminal TDS value of ~300,000 mg/L is
achieved (approximately a concentration
factor of 2.1 to 2.35). After reaching the
desired concentration factor, the coupon,
condenser, and solution were examined to
determine if scaling occurred on the coupon
or condenser and whether there was any
brine foaming potential in the solution (and
how it was treated).
Figure 5 – Iron (Fe) buildup on operating
evaporation simulator wall
Figure 4 – Evaporator simulation glassware test
Careful monitoring of the sump and
condenser surfaces provides an indication of
fouling potential. Visual observations
regarding brine foaming potential was
reported, and if necessary, treated using
commercial antifoams widely with the
approaches studied for pretreatment.
Figure 6 – Iron (Fe) scale shown on
evaporation simulator wall
9
Chemical Dosage and Consumption
Estimates
and settled for retention times ranging
between 30 and 60 minutes. The results
provided virtual complete removal of the
dissolved iron. It was observed that a
majority of the TSS and TOC along with the
magnesium precipitated as well.
The chemical dosage/consumption varied
Pre-Treatment
Any chemicals used as part of the pretreatment simulation were documented to
provide a basis for a scaled up process.
Scale Inhibitor
Due to the very high iron content there were
concerns whether pre-treatment via aeration
and filtration would be sufficient. Therefore,
a scale inhibitor was analyzed to determine if
chemical treatment alone would be sufficient
and negate the need for aeration and
filtration. The use of scale inhibitors
appeared to be negligible in affecting system
performance. This could be explained by the
presence of residual inhibitors from the well
frac operation.
Chemical Oxidizing Agents
Figure 8 - Iron (Fe) sludge precipitation in
sedimentation vessel
Due to the very high iron content and the
scaling tendencies demonstrated in the
baseline testing, Chemical Oxidizing agents
(Sodium Hypochlorite and Hydrogen
Peroxide) were tested.
Below is a brief summary of the centrifuge
studies for the high Salinity Composite Frac
Water Blend, and the sludge settling
characteristics are shown in the
attachment. Centrifugations were done at
2,500 rpm (corresponding to about 1,400G)
with 100 mL samples and varying spin
duration (see below):
Sodium Hypochlorite at dosages ranging
from 20 – 500 ppm was attempted with
minimal effect on dissolved iron reduction.
Hydrogen Peroxide at dosages ranging from
20 – 500 ppm was attempted with minimal
effect on dissolved iron reduction. In both
cases aeration was attempted in conjunction
with the chemical oxidation agent however
severe foaming was observed.
Precipitation Agents
Agent was added to the frac water
composite blend raising the pH of the fluid
10
High Salinity
Agent treated
slurry pH
Total wet solids
from 1.0 L (from
filtration study)
Centrifugation at
2,500 rpm
(1,400G):
10 min pellet
2 min pellet
1 min pellet
0.5 min pellet
10.4
10.86 g
2.7% V/V
5.0% V/V
6.0% V/V
7.0% V/V
Figure 9 - Iron (Fe) sludge centrifuge test
The resulting supernatants were all visibly
crystal clear, with turbidity measurements
indicating only small amounts of fines
(especially after 0.5 minute spin time).
Turbidities were as follows: 0.5 min - 2.6
NTU, 1 min - 0.5 NTU, 2 min - < 0.2 NTU, 10
min - < 0.2 NTU.
Heat Exchanger Operation
The pre-treated frac water composite blend
was run for 24 hours through the heat
exchanger simulator operating at 205
degrees F.
The pellets were light orange, and the liquidsolid boundary was very sharp. Despite this,
no pellet was firm enough to support the
weight of a small stirring rod. On the other
hand, the supernatant brines could be
decanted without disturbing the pellets in all
cases, except for the 0.5 min spin time.
Based on the visual observations, it is
estimated that the centrifuge solids would
pass the "Paint Filter Test," possibly with the
exception of the shortest spin duration.
Figure 12 – Heat Exchanger Simulation on Frac
Water Composite Blend with Iron, TSS & TOC
removed
11
boiling point. Small retention samples of
distillate and sump concentrate were taken
at the designated concentrations, and these
were used to determine the TDS.
Figure 13 – Close up of Heat Exchanger simulation
on Frac Water composite blend with Iron, TSS &
TOC removed
Data points were taken at designated time
intervals. The volume, pH, and conductivity,
were recorded for the heated composite
blend along with the temperature. Visual
observations regarding the heated frac water
composite blend turbidity and/or
precipitation were made at each datum
point. The analytical results for precipitate
and scaling tendencies were recorded.
Figure 14 – Evaporator Simulation on
Pretreated Frac Water Composite Blend at
CF of 2.1
Evaporator Operation
On reaching the final concentration
(2.1 – 2.35 CF), the sump was refluxed to
ensure that chemical equilibrium between
dissolved and precipitated species is
reached. The final brine was analyzed.
Data points were taken at designated
concentration. The volume, pH, and
conductivity, were recorded for the distillate
along with the sump concentrate pH and
Figure 15 – Close up of Evaporator Simulation
12
Visual observations regarding sump turbidity
and/or precipitation were made at each
datum point. The analytical results for
chloride were also used to assess and verify
concentration factors.
Water Recovery, Concentrated Brine Analysis
of the Modeled System
Phase 1: Pretreatment
The pretreatment involves the removal of
iron, manganese, TSS, TOC, and a reduction
in magnesium. The iron sludge solids
removed in this process comprise roughly 5
% of the initial volume with 65 % moisture
content. The flow out of the pretreatment
process is projected as 631 gpm.
Individual Well Sample Analysis
For a modeled total system feed of 665 gpm,
the total water recovery, from the
evaporation and crystallization process is
predicted at 92% equal to 612 gpm.
The individual well samples, supplied from
wells throughout Southwestern PA, were
Tested as separate sole feed streams to
detect any potential effects on the pretreatment method. The results of the
individual well samples were consistent with
the High Salinity Frac Water Composite Blend
that was tested.
Phase 2: Evaporation
The water recovery in phase 1 – the
evaporation system, has been demonstrated
to be 60% of the evaporator feed equal to
379 gpm.
The results of the individual sample
pretreatment settling results are shown
below
Phase 3: Crystallization
The water recovery in phase 2 – the
crystallization system, has been predicted to
be 92 % of the crystallizer feed equal to 233
gpm. The salt solids account for the
remaining flow to the crystallizer.
Concentrated Brine Analysis
The concentrated brine generated from the
evaporation process (Phase 2) is envisioned
being sent to the crystallization process
(Phase 3) for the production of beneficial use
salt products.
Figure 16 – Pre-treated samples from
Individual wells
Alternatively, the concentrated brine,
projected at 252 gpm, could be hauled via
tanker truck or rail tanker to approved &
contracted disposal wells. This disposal
13
option could be employed if investment in the
crystallization plant (Phase 3) was not
desired, however the amount of trucks
required and the cost of the transportation
and ultimate deep well disposal would seem
to make this approach prohibitively
expensive.
Solids Production and Disposal Options
Pretreatment
Specific pretreatment of the concentrated
brine, prior to introduction to the
crystallization plant, is not anticipated at this
time
Initial treatability study of the concentrated
brine taken to crystallization shows the
potential production of feeder material
suitable for refinement into saleable salts for
uses such as road de-icing or industrial
softener salt.
The production of acceptable feeder material
for either road grade de-icing salts or
industrial softener salts does not guarantee
the availability of purchase contracts for the
salt. Weather and seasonal conditions may
require large storage facilities for the
salt products while awaiting contracts and
shipments.
The salt production of primary feeder
material, from the modeled facility, for road
salt production is anticipated to be over 300
tons per day.
A system for treating 1.0 MGD of frac water
flowback and produced waters, illustrated
above, can provide a treatment cost to the
producers of less than $5.00/bbl of water
brought to the facility. The facility operator is
envisioned to be independent of the natural
gas producers, though the operator would
contract with the producers for specific
treatment volumes.
Full Treatment Systems
Based upon the results of the study on
evaporative treatment of frac water flowback
and produced waters, several full scale plant
applications were developed.
14
The treatment costs for various size
operations with daily plant throughput
ranging from 1.0 MGD down to 0.25 MGD
would be affected by the ratio of the CAPEX
and OPEX costs against the plant’s
throughput.
Mobile Evaporator Systems
Trailerized, “truly mobile” evaporator systems
can handle up to 50 gpm of frac water
flowback and produced waters for volume
reduction at remote well sites. The disposal of
the reduced volumes of concentrated brine is
still required.
The projected costs for full evaporation &
crystallization treatment based upon the
previously noted plant throughputs range
from $5.00/bbl to $6.80/bbl.
Treatment cost for mobile evaporator only
operations are projected at less than
$6.50/bbl of water brought to the system.
Fixed facilities can be placed on sites of 2–4
acres, dependent upon truck access and site
water storage requirements.
Originally presented at the International Water Conference® Nov 2012.
Please visit www.eswp.com/water for more information about the conference or how to purchase the
paper or proceedings.
15