IWC 11-09

The Real Cost of ZLD for Shale Gas Frac 

Water in the Marcellus Shale Play

WILLIAM A. SHAW, P.E. 

HPD, LLC, a Veolia Water Solutions & Technologies company

Plainfield, Illinois
IWC 11-09

Keywords: Marcellus Shale, frac water, hydrofracking, shale gas, produced water, 

flowback water

ABSTRACT

In the Marcellus Shale play in particular, both surface and underground disposal of the 

frac water are not options, and re-use of the brine in further fracturing operations is 

limited. Zero liquid discharge is the apparent long-term solution to the problem, using 

evaporators and crystallizers to concentrate the brine, crystallize out the salts and 

recover clean distilled water for re-use or direct discharge to the environment.

By focusing on the chemistry of frac water and the physics required to transport, treat, 

evaporate, crystallize, and dispose of the solids, this paper will calculate the true costs 

of a complete ZLD solution for Marcellus Shale frac water.
IWC 11-09

INTRODUCTION

The Next Big Thing in the water 

treatment business seems to be finding 

ways to treat the millions of gallons of 

water brought to the surface in the 

fracking process used to drill for natural 

gas in deep shale formations. 

Natural gas -- especially that produced 

from so-called unconventional sources, 

such as coal seams, tight sands and 

shale formations -- is one of the fastestgrowing energy sources in the United 

States and across the world. One of the

primary considerations in developing 

this resource is the management of the 

water produced in association with the 

gas. While the volume and quality of 

flowback and produced waters vary 

considerably between plays, a common 

characteristic of almost all shale gas 

produced water is the presence of high 

concentrations of total dissolved solids

(TDS) including corrosive salts, 

hydrocarbons, silica, and naturally 

occurring radioactive elements.

After the drilling and fracturing of the 

well are completed, water is produced 

along with the natural gas. Some of this 

water is returned fracture fluid and some 

is natural formation water. Regardless of 

the source, these produced waters that 

move back through the wellhead with 

the gas represent a stream that must be 

managed. 

Disposing of shale gas produced water 

requires a range of management and 

treatment approaches and depends on 

several site-specific factors, including 

water salinity, flow rate, lease 

agreements with landowners, total cost 

of disposal including treatment and 

transportation, discharge options 

available, and a variety of other 

influences. The industry currently uses 

several different water management 

tools, such as direct discharge, 

managed irrigation, storage and 

infiltration, and deep well injection. In 

many cases, these options are not 

available or sufficient and the only 

feasible option is direct "end-of-pipe" 

treatment.

As development of shale gas resources 

increases, so too does the regulatory 

and public pressure to apply direct 

treatment in the field. Unfortunately, all 

end-of-pipe technologies currently in 

use in the oil and gas industry are 

limited by an array of technical 

challenges and a substantially higher 

cost in comparison to traditional, nontreatment alternatives. For evaporation

technologies, much of the cost is 

attributed to brine disposal. In fact, in 

some instances it has been shown that 

brine disposal accounts for more than 

50% of the cost of produced water 

treatment systems. Therefore, reducing 

the volume of brine requiring disposal 

should be a key objective of most 

produced water treatment systems.

In the Marcellus Shale play in particular, 

both surface and underground disposal 

of the frac water are limited options. 

New regulations in Pennsylvania limit 

surface discharge to brines containing 

less than 500 ppm TDS, less than 250 
IWC 11-09

ppm chloride, and less than 250 ppm 

sulfate. The nearest Class II salt water 

disposal wells are located in Ohio, with 

resulting high transportation costs. 

Zero liquid discharge (ZLD) is the 

apparent long-term solution to the 

problem, using evaporators and 

crystallizers to concentrate the brine, 

crystallize out the salts and recover 

clean distilled water for re-use or direct 

discharge to the environment.

Evaporation is a very energy-intensive 

process, but the energy consumption 

can be made less onerous by the use of 

such techniques as mechanical vapor 

compression (MVC). So the news from 

Pennsylvania is filled with stories of 

companies who have designed mobile 

evaporators to deploy at the drilling 

sites. These machines, we are told, 

can recover and recycle 50 to 75% of 

the frac water at a total cost, including 

energy, which is less than the cost of 

transportation and tipping fees to a 

POTW, an option that used to be 

available in Pennsylvania, but is no 

longer. 

What are the disposal options for the 

concentrated brine from the mobile 

evaporators, still 25 to 50% of the total 

frac water volume? The obvious answer 

is crystallizers to recover the remaining 

water and produce a solid waste for 

disposal. But crystallization is even 

more energy intensive than evaporation, 

and MVC is usually not possible. Steam 

and cooling water are usually required; 

so a boiler and cooling tower are 

required also. Extensive chemical pretreatment of the brine may be necessary 

to keep the energy consumption of a 

crystallizer and its material of 

construction reasonable. Because of 

these requirements and limitations, 

conventional crystallization is not 

practical to do at the drill site with mobile 

units. 

Let us focus on the chemistry of frac 

water and the physics required to 

transport, treat, evaporate, crystallize, 

and dispose of the solids, in order to

calculate the true costs of a complete 

ZLD solution for Marcellus Shale frac 

water.

CHEMISTRY OF FRAC WATER

The amount of water needed to drill and 

fracture a horizontal shale gas well 

generally ranges from about 2 million to 

4 million gallons, depending on the 

basin and formation characteristics. 

After a hydraulic fracture treatment, 

when the pumping pressure has been 

relieved from the well, the water-based 

fracturing fluid, mixed with any natural 

formation water present, begins to flow 

back through the well casing to the 

wellhead. This produced water may also 

contain dissolved constituents from the 

formation itself. The dissolved 

constituents are naturally occurring 

compounds and may vary from one 

shale play to the next or even by area 

within a shale play. Initial produced 

water can vary from fresh (<5,000 ppm 

Total Dissolved Solids (TDS)) to varying 

degrees of saline (5,000 ppm to 150,000 
IWC 11-09

ppm TDS or higher). The majority of 

fracturing fluid is recovered in a matter 

of several hours to a couple of weeks. In 

various basins and shale gas plays, the 

volume of produced water may account 

for less than 30% to more than 70% of 

the original fracture fluid volume. In 

some cases, flow back of fracturing fluid 

in produced water can continue for 

several months after gas production has 

begun. Natural formation water has 

been in contact with the reservoir 

formation for millions of years and thus 

contains minerals native to the reservoir 

rock. The salinity, TDS, and overall 

quality of formation water vary by 

geologic basin and specific rock strata. 

After initial production, produced water 

can vary from brackish (5,000 ppm to 

35,000 ppm TDS), to saline (35,000 

ppm to 50,000 ppm TDS), to 

supersaturated brine (50,000 ppm to

>200,000 ppm TDS).

The initial flowback water is recovered 

at a high rate and contains dissolved 

salts and low concentrations of oil and 

metals, which are primarily from the 

shale formation. Additionally the water 

may contain residual chemicals used in 

the frac process. After the well is placed 

into production, water continues to flow 

out of the well at a lower rate, but with 

higher salt concentrations. This water is

referred to as produced water.

The primary constituent in flowback and 

produced waters is chloride salts. These

salts include calcium chloride, sodium 

chloride, and magnesium chloride and 

are generally corrosive and limit the 

treatability and reuse options of the 

water. 

Table 1 below gives analyses for 

flowback and produced waters over time 

from a typical drilling site in 

southwestern Pennsylvania. These 

analyses illustrate the changing 

composition of the water recovered from 

drilling operations from initial 

hydrofracturing to producing gas well.
IWC 11-09

Table 1 – Changing Composition of Frac Water Over Time from a Marcellus Well

Day 1 Day 15 Produced

Frac Frac Water

pH 7.4 5.63 5.45

Total Solids % 2.22 18.69 21.87

Total Susp. Solids ppm 14 231 239

T.O.C. ppm 565 412 253

Sodium % 0.64 4.85 5.86

Chloride % 1.35 11.00 12.90

Calcium % 0.12 1.37 1.60

Potassium ppm 434 2820 3540

Magnesium ppm 157 1180 1470

Strontium ppm 197 3620 3960

Ammonia as NH3 ppm 50 323 345

Total Sulfur as S ppm 362 <20 <20

TIC (ppm) ppm 66 22 21

Silicon ppm 17 13 9

Lithium ppm 9 80 70

Barium ppm 1 814 678

Boron ppm 20 110 141

Iron ppm 7 80 95

Manganese ppm 0.4 <1 <1

Aluminum ppm <2 <1 <1

Antimony ppm <0.1 <1 <1

Arsenic ppm <1 <10 <10

Beryllium ppm <0.1 <1 <1

Cadmium ppm <0.1 <1 <1

Chromium ppm <0.1 <1 <1

Cobalt ppm <0.1 <1 <1

Copper ppm <0.1 <1 <1

Lead ppm <0.1 <1 <1

Molybdenum ppm <0.1 <1 <1

Nickel ppm <0.1 <1 <1

Phosphorus ppm <1 <10 <10

Selenium ppm <1 <10 <10

Silver ppm <0.1 <1 <1

Thallium ppm <0.1 <10 <10

Tin ppm <1 <10 <10

Vanadium ppm <0.1 <1 <1

Zinc ppm <0.1 <1 <1
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Table 2 below represents the 

anticipated characteristics of equalized 

flowback and produced water from a 

number of wells in a given area in 

southwestern Pennsylvania, averaged 

over time. This is the “typical” Marcellus 

shale water that we will use for the 

purposes of calculating the costs 

associated with a true ZLD solution. 

The main points to note are the high 

TDS concentration, the high 

concentration of alkaline earth Group II 

cations such as calcium, magnesium, 

barium, and strontium, the high 

concentration of chloride, and the low 

concentration of sulfate. Although 

conventional wisdom holds that a ZLD 

system consists of three unit operations 

– a Reverse Osmosis step followed by a 

Brine Concentrator and a Crystallizer --

the characteristics of the equalized frac 

water make such a system infeasible. 

While a detailed discussion of the 

effects of these constituents on the 

design of a ZLD process is outside the 

scope of this paper, the following points 

should be noted:

1. Due to the very high TDS levels, 

concentration by any means 

other than evaporation is not 

practical. The use of Reverse 

Osmosis (including HERO and 

other enhanced RO processes) 

to treat the equalized frac water 

is not feasible due to osmotic 

pressure limitations. 

2. The most efficient form of 

evaporation is Mechanical Vapor 

Compression (MVC) in a falling 

film evaporator. However, the 

practical concentration factor 

(CF) by falling film evaporation is 

limited to about 2 due to the high 

TDS. This means a recovery of 

only 50% is practical. Also, since 

the feed contains hardly any 

sulfate, a seeded slurry brine 

concentrator is not feasible. 

3. Concentration to dry solids can 

be done, however unique 

treatment steps and/or special 

crystallization equipment not 

normally used in conventional 

ZLD systems is required. 

4. Since the TDS is composed of 

primarily CaCl2 and MgCl2 salts, 

and since these salts are very 

aggressive, the choice of 

materials of construction (MOC) 

is very critical to ensuring a 

typical industrial life for the ZLD 

system.
IWC 11-09

Table 2 – Equalized Flowback and Produced Water Analysis

COSTS TO EVAPORATE AND 

DISPOSE OF FRAC WATER

As the previous section revealed, 

Reverse Osmosis of any type is not 

suitable to concentrate our “typical” 

equalized Marcellus shale frac water 

characterized in Table 2. A falling film 

MVC can concentrate the high TDS 

brine (11-13% by weight) at most two 

times. This is because the solubility 

limit of sodium chloride in the brine is

nearly reached. When the solubility limit 

of a salt is reached in an evaporator, the 

evaporator design must take into 

account the propagation and growth of 

crystals within the bulk solution. Falling 

film evaporators can handle at most a 

few percent suspended solids in the 

recirculating brine without severe fouling 

and plugging problems, so it is 

necessary to operate the evaporator 

below the solubility limit of the least 

soluble salt, in this case, sodium 

chloride. 

Based on the assumed chemistry of the 

equalized frac water given in Table 2, 

and measured boiling point rise data, a

falling film evaporator using MVC will 

have a total energy consumption of 6.5–

7.5 kWh/bbl of water evaporated. 

Assuming a wellhead price for natural 

gas of about $5/1000 ft3 and a genset 

Constituent Concentration

Total Suspended Solids <10 mg/L

Oil & Grease <1000 mg/L

Total Dissolved Solids 110,000 to 130,000 mg/L

Chloride, Cl 70,000 to 100,000 mg/L

Sulfate, SO4 <20 mg/L

Total Hardness (as CaCO3) 35,000 to 45,000 mg/L

Calcium, Ca 11,000 to 14,000 mg/L

Magnesium, Mg <4,000 mg/L

Sodium, Na 21,000 to 26,000 mg/L

Iron, Fe(II) <250 mg/L

Potassium, K <400 mg/L

Barium, Ba <200 mg/L

Strontium, Sr <3,000 mg/L

Manganese, Mn <50 mg/L

pH 5.5 – 7.0 s.u.

Temperature Ambient for SW PA
IWC 11-09

efficiency of 35%, the cost of electric 

power generated at the drilling site to 

power a mobile MVC evaporator is 

roughly $0.055/kWh. Therefore the cost 

of power to evaporate one barrel of 

water at site is roughly $0.40. 

A truly mobile evaporator is likely limited 

to a maximum evaporation rate of about 

1 bbl/min (42 gpm), or roughly 500,000 

bbl/year. We will assume that the 

drilling operator leases the mobile 

evaporator, genset, and other ancillary 

equipment, which has a capital value of 

about $6 million. Amortizing the capital 

cost of the equipment at 12% cost of 

capital plus a profit yields an annual 

lease cost to the operator of about 

$1,500,000. We can further assume 

that operating and maintenance (O&M) 

costs are roughly $125/hr, so the annual 

O&M cost for the drilling operator is 

about $1 million per year. If we add the 

annual lease cost, the cost of power, 

and the O&M costs, the cost to 

evaporate 500,000 bbl of water per year 

is about $2.7 million, or $5.40/bbl 

($0.13/gal). This cost compares 

favorably with the tipping fees for drilling 

wastewaters that were assessed by 

Pennsylvania POTW’s prior to May 

2010.

However, since a mobile MVC 

evaporator can only evaporate 1 bbl of 

water from every 2 bbl of frac water that 

is processed, the drilling operator is left 

with 500,000 bbl annually of 

concentrated brine containing 25% salt 

to dispose of. If this brine must be 

trucked to Ohio for disposal in a Class II 

injection well, the distance is roughly 

200 miles from southwestern 

Pennsylvania, and 300 miles from 

northeastern Pennsylvania. Brine waste 

haulers generally charge by the hour

including waiting and loading time at the 

drill site, round trip driving time to the 

injection well, and waiting time to unload 

at the disposal site. Reported charges 

vary from $150 to $200/hr. Including

tipping fees assessed by the injection 

well operators of about $2/bbl, the cost 

to dispose of concentrated brine 

originating at Pennsylvania drill sites in 

Ohio injection wells will easily cost 

$15/bbl ($0.36/gal). 

Using the example above, the total cost 

of a ZLD solution for 1 million bbl/year of 

frac water involving evaporation of half 

of the water at the drilling site in 

Pennsylvania using a mobile evaporator 

and disposal of the remaining 

concentrate in injection wells in Ohio will 

be roughly $10,000,000, or 

$20/bbl.($0.48/gal). Evaporation at site 

covers only about 25-30% of the total 

cost of disposal.

COSTS TO EVAPORATE AND 

CRYSTALLIZE FRAC WATER

An alternative to the scenario above is 

to evaporate the frac water at the drilling 

site and then haul the concentrate to a 

central crystallization facility to reduce 

the concentrated brine to solid salts for 

disposal or re-use. The collected 

distillate from the crystallizer can be 

returned to the drill operator as water to 

be used in additional fracking 

operations. As stated in the 
IWC 11-09

Introduction, conventional crystallization 

is not practical to do at the drill site, as a 

boiler and cooling tower are required, as 

well as storage and dosing facilities for 

chemicals for pre-treatment. Instead, 

central crystallization facilities should be 

located within a reasonable distance; 

say 50 miles, from drilling sites and 

landfills, in order to minimize truck traffic 

and transportation costs. 

In order to calculate the cost to 

crystallize out the salts in the frac water, 

we must return to the chemistry of the 

frac water in Table 2. After evaporation 

of half of the water using a mobile 

evaporator in the field, the concentration 

of the salts in the remaining brine will be 

doubled. The equalized feed to the 

crystallizer will contain about 25% 

dissolved solids. About half of the 

dissolved salt is sodium chloride, and 

the other half is mainly calcium chloride 

with lesser amounts of magnesium, 

strontium, and barium chlorides. 

Sodium chloride is easy to precipitate 

out using an evaporative crystallizer 

because it is nearly at its solubility limit 

in the brine. But the other salts all have 

very high solubility and the boiling point 

of the brine rises exponentially as these 

salts are concentrated. By the time 

these salts reach their solubility limit, the 

boiling point rise of the solution will total 

more than 150 degrees F over that of 

pure water. The chloride salts of Group 

II alkaline earth elements are also acid 

salts, meaning that the pH of the brine is 

lowered substantially as these salts 

concentrate in the crystallizer. This 

means that the crystallizer must be 

constructed of expensive highly alloyed 

corrosion-resistant metals such as 

Titanium, Inconel, Hastelloy, and the 

like. 

In order to overcome the operating 

issues and costs that the Group II 

chloride salts that predominate in frac 

water pose to a conventional 

crystallizer, it may be better to remove 

the Group II cations from the brine 

before crystallization. This can be 

accomplished by softening the brine 

using lime and soda ash. The net effect 

of treating the brine with these two 

chemicals is that the calcium,

magnesium, barium, and strontium, and 

most transition metal cations are 

precipitated from the brine as insoluble 

hydroxide and carbonate salts. These 

salts can be settled out by clarification 

and dewatered in a filter press and 

ultimately disposed in a landfill. The 

Group II and metal cations precipitated 

from the brine in the softening reactions 

are replaced by sodium ions. So after 

the softening process and separation of 

the precipitated alkaline earth and metal 

salts, the brine that is sent to the 

crystallizer still contains 25% salt by 

weight, but it is almost all sodium 

chloride. 

To calculate the total cost to process the 

brine in a central crystallizer plant to 

precipitated salts for landfill disposal, we 

need the amortized cost of capital, the 

O&M cost, the cost of chemicals, steam, 

and power, and the cost for 

transportation and landfill disposal of the 

precipitated salts, both from the softener 
IWC 11-09

and from the crystallizer. A central 

crystallization plant must be large 

enough to be economical; as an 

example we will consider a plant sized 

to handle 250,000 gallons per day 

(6,000 bbl/day) of incoming brine 

concentrate containing 25% salt by 

weight. The complete plant consists of:

• Truck unloading and impoundment of 

incoming concentrated brine

• Truck or rail unloading and storage 

silos for lime and soda ash

• Reaction tanks for softening

• Clarifier and sludge storage tanks for 

settling out precipitated salts

• Sludge dewatering and handling 

system for softener sludge

• Crystallizer system in three effects and 

condenser for minimum practical 

energy consumption

• Salt cake dewatering and handling 

system for crystallizer salt

• Recovered water impoundment

• Truck loading of recovered water for 

reuse

• Utilities and ancillary systems 

including: steam boiler, cooling tower,

chemical addition, motor control 

center, control room, and laboratory

The installed cost for such a plant is 

estimated to be about $30 million, to be 

amortized over 15 years at 12% cost of 

capital. The assumptions to be used for 

operating costs include 

• Purchased electric power at 

$0.10/kWh

• Steam at $20/ton generated from 

purchased natural gas 

• O&M costs for 6 people to operate the 

plant @ $125/hr each plus $500,000 

annual maintenance consumables

• Lime at $80/ton and soda ash at 

$300/ton delivered

• Solid waste disposal for softener 

sludge and crystallizer salt at $60/ton 

including transportation to a landfill 

less than 50 miles away.

The daily quantities of chemicals, 

steam, power, and solid waste required 

to process 250,000 gal/day of 25% TDS 

brine concentrate derived from the frac 

water analysis given in Table 2 are:

Lime: 30 t/d

Soda ash: 140 t/d

Steam: 330 t/d

Power: 3000 kWh/d

Softener sludge (40% by wt): 430 t/d

Crystallizer salt (90% by wt): 350 t/d

O&M cost: $21,000/day

Amortized capital: $13,000/day: 

Using the daily costs assumed above 

and dividing by the daily plant capacity 

of 250,000 gallons gives a total cost of 

$0.52/gal ($22/bbl). This analysis shows 

that the softening/crystallization/ landfill 

approach has a higher total cost than 
IWC 11-09

transporting the concentrated brine to 

an injection well in Ohio. It may, 

however, be a more sustainable method 

of disposal in the long term depending 

on how much deep well capacity can 

ultimately be developed in Ohio.

If the calcium, magnesium, strontium, 

and barium chloride salts could be 

crystallized directly from solution without 

softening, it would eliminate the need 

for, and save the cost of, lime, soda ash, 

and more than half of the solid waste. 

But the high solubility, and boiling point, 

and corrosivity of these salts make the 

crystallizer design required impractical 

and very expensive. 

There is a technology called cold 

crystallization that is used in the 

commercial production of Group II 

chloride salts that mitigates the negative 

effects of Group II chloride solution 

chemistry. The principle behind the cold 

crystallization technology is that the 

solubility of most salts (including all of 

the Group II chlorides) decreases as the 

temperature of the solution is lowered. 

The boiling point also decreases, as 

does the tendency of the salts to 

hydrolyze, or become more acidic as 

they are concentrated. A cold 

crystallizer is operated under a deep 

vacuum, which significantly reduces the 

boiling temperature of the solution. It is 

possible to reduce the solubility and the 

boiling temperature by half. 

With a cold crystallizer, there is no need 

for a softening step to precede the 

crystallization step. This eliminates not 

only the softening equipment – tanks, 

pumps, clarifier, and filter -- but also the 

chemicals and requisite unloading, 

storage, and handling facilities. In 

addition, as mentioned above, the 

ongoing costs of lime, soda ash, and 

softener sludge handling and disposal 

are eliminated. The capital savings 

realized by eliminating the softening 

equipment is offset by the fact that the 

crystallizer vessels must be larger 

because of the low operating pressure 

and the requirement for a vacuum 

system and chilled water system to 

reach the low pressure that the cold 

crystallizer operates at. The energy 

consumption for the cold crystallizer is 

slightly higher due to the vacuum and 

chiller systems. 

A cold crystallizer sized to process 

250,000 gal/day of 25% TDS brine 

concentrate derived from the frac water 

analysis in Table 2 has the following 

daily costs:

Lime, Soda Ash, Softener Sludge: 0 t/d

Steam: 340 t/d

Power: 10,000 kWh/d

Crystallizer salt (90% by wt): 350 t/d

O&M cost: $21,000/day

Amortized capital: $13,000/day.

These costs total $0.26/gal ($11/bbl), 

half the cost of the softener/crystallizer/ 

landfill system, and 25% less than the 

cost of deep well disposal in Ohio. 

Table 3 below summarizes the three 

approaches to ZLD discussed above.
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Table 3 – Comparison of Costs to Dispose of 250,000 GPD of Concentrated Brine

from Mobile Evaporators Located at Drilling Sites*

250,000 GPD

(6,000 bbl/day)

Injection Well 

in Ohio

Softener/Crystallizer /

Landfill Sludge &

Salt**

Cold Crystallizer /

Landfill Salt**

Lime, t/d 0 30 0

Soda Ash, t/d 0 140 0

Softener Sludge, t/d 0 430 0

Crystallizer Salt, t/d 0 350 350

Brine, bbl/d 6,000 0 0

Power, kWh/d 0 3,000 10,000

Steam, t/d 0 330 340

Annual Costs

Lime @ $80/t 0 $800,000 0

Soda Ash @ $300/t 0 $14,000,000 0

Sludge Disposal @ 

$60/t

0 $8,600,000 0

Salt Disposal @ $60/t 0 $7,000,000 $7,000,000

Brine Disposal @ 

$15/bbl

$30,000,000 0 0

Power @ $0.10/kWh 0 $100,000 $330,000

Steam @ $20/t 0 $2,200,000 $2,300,000

O&M @ $21,000/day 0 $7,600,000 $7,600,000

Capital @ 

$13,000/day

0 $4,750,000 $4,750,000

Total $30,000,000 $45,000,000 $22,000,000

Cost per barrel $15/bbl $22/bbl $11bbl

Cost per gallon $0.36/gal $0.52/gal 0.26/gal

*Cost to evaporate frac water at drill site with mobile evaporator is an additional 

$5.40/bbl ($0.13/gal)

**Located within 50 miles of drill site.
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CONCLUSION

The chemistry of Marcellus Shale 

flowback and produced waters, in 

particular, high TDS and high 

concentrations of Group II alkaline earth 

chloride salts, preclude the application 

of a conventional ZLD approach 

consisting of reverse osmosis followed 

by evaporation and crystallization. 

Mobile evaporators are only part of the 

solution for achieving zero liquid 

discharge for frac water in the Marcellus 

Shale Play, since only about 50% of the 

water can be recovered from typical 

Marcellus frac water. Crystallization of 

the highly concentrated brine that 

remains requires steam and cooling 

water, making on-site crystallization

impractical. 

One solution to dispose of the remaining 

concentrated brine is to transport it to 

disposal wells, the nearest of which are 

located in Ohio. However, an analysis of 

the costs shows that the cost of 

evaporation at the site is only 25-30% of 

the total cost of disposal.

Crystallization, while not practical to do 

at the drilling sites, is practical to do at 

centralized plants located within a 

reasonable distance, say 50 miles, of 

gas drilling sites. The chemistry of the 

frac water requires the brine be pretreated in a lime and soda ash softening 

process before crystallization in a 

conventional atmospheric crystallizer. 

When the costs of equipment, 

chemicals, energy, and transportation 

and disposal of the solid residues are 

totaled, conventional crystallization with 

chemical softening costs almost 50% 

more than the cost of deep well disposal 

in Ohio.

Cold crystallization provides the least 

expensive solution for a total ZLD 

solution for Marcellus brine. Because it 

operates under deep vacuum at low 

temperature, the cold crystallization 

process takes advantage of reduced 

solubility and boiling point of Group II 

alkaline earth chloride salts at low 

temperature. The cold crystallization 

process does not require chemical 

softening prior to crystallization, saving 

the costs for chemicals and substantially 

reducing the amount of solid residues to 

dispose of. The cost of disposal of the 

final concentrate using centrally located 

cold crystallization plants is 25% less 

than the cost of deep well disposal in 

Ohio.