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# The R eal C ost of ZLD for S hale G as F rac W ater in the Marcellus Shale P lay

WILLIAM A. SHAW, P.E. HPD, LLC, a Veolia Water Solutions & Technologies company Plainfield, IllinoisIWC 1 1

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Keywords: Marcellus Shale, frac water, hydrofrackin g, 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 di scharge 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 chemi stry 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 1 1

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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 fastest

growing energy sources in the United
States and across the world. One of the primary consideration s 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 water s vary considerably between plays , a common characteristic of almost all shale gas
p roduced water is the presence of high
concentrations of total dissol ved s olids (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 fractu re 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 an d 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
i nfluences. The i ndustry 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
feas ible 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, non

treatment alternatives. For evaporation technologies, much of the cost is attributed to brine disposal. In fact, in
some inst ances 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 M arcellus 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 250IWC 1 1

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ppm chloride , and less than 2 50 ppm
sulfate . The nearest Class II salt water disposal wells are located in Ohio

, with resulting high transporta t ion costs

. Zero liquid discharge (ZLD) is the apparent long

- term solution to the problem, using evaporators and crystallizers to concentra te 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 a s mechanical vapor compression (MV C ). 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 wate r 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 mo bile 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 MV C is us ually not possible. Steam and cooling water are usually required; so a boiler and cooling tower are required also. Extensive chemical pre

treatment of the brine may be necessary to keep the energy consumption of a crystallizer and its material of

construc tion 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 f rom 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
forma tion 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 1 5 0,000IWC 1 1

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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 pr oduced 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 ove rall 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

t he 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

an alyses illustrate the changing composition of the water recovered from drilling operations from initial hydrofracturing to producing gas well.IWC 1 1

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Table 1

– Changing Composition of Frac Wa ter 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 Zi nc ppm <0.1 <1 <1IWC 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 tha t 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 strontiu m, 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 charact eristics 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 mos t efficient form of evaporation is Mechanical Vapor
C ompression (MVC) in a f alling
f ilm 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% i s practical. Also, s ince
the feed contains hardly any sulfate, a seeded slurry brine
concentrator is not feasible.

3. C oncentration to dry solids can be done, however unique treatment steps and/or special crystallization equipment no t normally used in con ventional
ZLD systems is required.

4. Since the TDS is composed of primarily CaCl 2 and MgCl 2 salts, and since these salts are very aggressive, the choice of materials of construction (MOC) is very critical to en suring a typical industrial life for the ZLD

sy stem.IWC 1 1

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Table 2

– Equalized Flowback and Produced Water Analysi s

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 sh ale 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 s evere 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 measur ed bo i ling point rise data, a falling film evaporator using MVC will
have a total energy consumption of 6 .5

– 7 .5 kWh/bbl o f water evaporated

. Assuming a wellhead price for natural gas of about $ 5 /1000 ft 3 and a genset Constituent Concentration
T otal 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 Manganes e, Mn <50 mg/L pH 5.5

– 7.0 s.u. Temperature Ambient for SW PAIWC 1 1

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efficiency of 35%, the cost of elect ric power generated at the drilling site to power a mobile MVC evaporator is roughly $0.05 5 /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. W e 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 t he 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 o perating and maintenance (O&M)

costs are roughly $125/hr, so the annual O&M cost for the drilling operator is
ab out $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 dril ling wastewaters that were assessed by
Pen n sylvania POTW’s prior to May

2010

.
However, since a mobile MVC evaporator can only evaporate 1 bbl of
water f rom every 2 bbl of frac water that is processed , the drilling operator is left with 500,000 bbl annuall y 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. B rine w aste 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 $ 1 5 0 to $ 200 /hr

. I ncluding
ti pping fees assessed by the injection well operators of about $2/bbl , the cost to dispose of concentrated brin e originating at Pennsylvania drill sites in Ohio injection wells will easily cost $ 1 5 /bbl ($0.36/gal)

. Using the example above , t he 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 $10,000,00 0, or $20/bbl. ($0. 48 /gal). Evaporation at site covers only about 25

- 30 % of the total cost of disposal.

COS TS 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

oper ations. As stated in theIWC 1 1

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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 crystalliz ation 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 wil l 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 chloride s

. 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 sa lts all have very high solubilit y 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 1 5 0 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 substantial ly as these salts concentrate in the crystallizer. This means that the crystallizer mu st 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 lim e 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
salt s 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 crystall izer 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 softenerIWC 1 1

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an d 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 25 0,000 gallons per day ( 6 ,000 bb l /day) of incoming brine concentrate containing 25% salt by weight. T he 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 precipit ated 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 impound ment

• 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 $ 3 0 million , to be amortized over 15 years at 12% cost of capital

. The assumptions to be used for operating costs include • P urchased electric power at $0.10/kWh

• S team at $20/ton generated from

purchased natural gas

• O&M costs for 6 people to opera te 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: 3 0 t/d

Soda ash: 1 40 t/d

Steam: 330 t/d

Power: 3000 kWh/d

Softener sludge (40% by wt): 4 30 t/d

Crystallizer salt (90% by wt) : 3 50 t/d

O&M cost: $ 2 1 ,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 to tal cost of $0. 5 2 /gal ( $ 22 /bbl)

. This analysis shows that the softening/crystallization/ landfill approach has a higher total cost thanIWC 1 1

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transporting the concentrated brine to an injection well in Ohio. It may, however, be a more sustainable method of dispo sal 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
f or, and save the cost of, lime, soda ash,
and more than half of the solid wa ste. 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 calle d 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 mos t 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 crystalliz er 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 prec ede 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 o f 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 th e 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: 3 40 t/d

Power: 10,000 kWh/d

Crystallizer salt (90% by wt): 3 50 t/ d

O&M cost: $ 21,000 /day

Amortized capital: $ 13,000 /day

.

The se costs total $0. 2 6 /gal ($ 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

ap proaches to ZLD discussed above.IWC 1 1

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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 $ 11 bbl Cost per gallon $0. 36 /gal $0. 52 /gal 0. 26 /gal

* Cost to evaporate fra c water at drill site with mobile evaporator is an additional $5. 40 /bbl ($0.13/gal)

** Located within 50 miles of drill site.IWC 1 1

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CONCLUSION

The chemistry of Marcellus Shale flowback and produced waters, in particular, high TDS and high
concentrations of G roup 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 c rystallization impractical.

One solution to dispose of the remaining

c oncentrated 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

t he 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 b rine be pre

treated 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 l ow 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 crystalliz ation, 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.