IWC 12-72 

Sequential Precipitation - Fractional 

Crystallization Treatment of Marcellus Shale 

Flowback and Production Wastewaters 

Timothy Keister 

ProChemTech International, Inc. 

Brockway, PA 
IWC 12-72 

Keywords: Marcellus, shale, flowback, production wastewater, treatment, resource recovery, 

sequential, precipitation, fractional, crystallization 

ABSTRACT 

By 2016 development of the Marcellus shale gas play in the Northeast will generate an estimated 

60 million gallons per day of hydrofracture flowback and production wastewater. This 

wastewater is close to saturation with sodium, calcium, magnesium, strontium, and barium 

chlorides as major constituents. Discharge of such wastewater has been outlawed in 

Pennsylvania, leaving deep well injection and treatment for recycle/reuse as current disposal 

options. Resource recovery by sequential precipitation and fractional crystallization, which 

produces salable products from the wastewater, has been developed as an economic disposal 

method for Marcellus wastewaters. 
IWC 12-72 

BACKGROUND 

The Marcellus gas shale deposit, which 

underlies most of northern Appalachia, is 

estimated to contain 168+ trillion cubic feet of 

natural gas. Due to the depth and compact 

nature of this formation, horizontal drilling 

with follow-up hydrofracture of the formation 

using a mixture of high pressure water and 

sand is required to obtain economic gas 

production. 

From 2 to 8 million gallons of water, mixed 

with sand and various additives, is required to 

completion fracture each horizontal deep 

well. Following hydrofracture, free water 

must be removed from the well, generally 10 

to 20% is recovered, and is commonly 

referred to as “flowback” wastewater. Recent 

developments permit recycle of flowback, 

with minimal treatment, as hydrofracture 

makeup water. 

Once a Marcellus gas well has been drilled 

and hydrofractured, “production” wastewater 

is produced for the 15 to 20 year life of the 

well at rates from 400 to 4,000 gpd. By 2016, 

with 30,000 wells expected to be in 

production, it is estimated that 60 million 

gallons per day of production wastewater will 

be generated and require proper management. 

Production wastewater is “dispersed”; the 

wells producing it are geographically spread 

over wide areas with low daily flows. 

Management of this wastewater will require 

well site tankage and tank truck based 

collection to convey it to either transshipping 

locations for transport to injection wells, out 

of state treatment; or to central resource 

recovery facilities. 

In contrast to production wastewaters from 

other gas shale plays, Marcellus production 

wastewater has a very high level of dissolved 

solids with large amounts of barium, calcium, 

magnesium, sodium, and strontium chlorides; 

with many other constituents, such as 

bromine and lithium, present in lesser 

quantities. Table 1 is a typical analysis of a 

Marcellus Production Wastewater. 

Table 1, Marcellus Production Wastewater 

Parameter as mg/l Result 

aluminum 3.0 

barium 6,500 

bromide 6,500 

calcium 18,000 

chemical oxygen 

demand 

8,000 

chloride 116,900 

iron 60 

lithium 150 

magnesium 1,300 

sodium 48,00 

strontium 4,000 

Note that chemical analysis of Marcellus 

production wastewaters presents a challenge 

to analytical laboratories due to the high 

dissolved solids content. 

PAST AND CURRENT TECHNOLOGY 

Past and current practice for disposal of 

flowback and production wastewaters has 

included use as a roadway deicer in winter 

and dust control agent in the summer, 

discharge to surface waters via publicly 

owned treatment works (POTW), treatment 

with direct discharge to stream, and 

treatment with recycle as hydrofracture 

makeup water. 
IWC 12-72 

ROADWAY DEICER/ DUST CONTROLGas well production wastewaters have been 

generated and disposed of in Pennsylvania 

for over 100 years. In the past, the majority 

of these wastewaters were either dumped 

around the producing well or used for 

roadway deicing and dust control. The 

advent of environmental regulation has 

correctly eliminated these disposal practices. 

DISCHARGE VIA POTW (Publicly Owned 

Treatment Plants)- Prior to the Marcellus 

shale development, a substantial amount of 

gas well production wastewater was 

disposed of via POTW with subsequent 

discharge to surface waters. This did not 

result in any major problems as nonMarcellus gas well production wastewaters 

are low volume and contain much lower 

amounts of barium and strontium than 

Marcellus wastewaters. In 2008, the rapid 

increase in Marcellus wastewater production 

and disposal via POTW that the 

Monongahela River was severely impacted, 

dissolved solids levels increasing by a factor 

of more than two. This prompted the PA 

Department of Environmental Protection 

(PADEP) to ban disposal of Marcellus 

wastewaters by almost all POTW. Currently 

less than ten (10) POTW are permitted for 

gas well wastewater disposal and continue to 

accept limited amounts of gas well 

wastewaters. Some specific problems noted 

by POTW accepting Marcellus gas well 

wastewaters include increased sludge 

generation, increased barium content in 

produced sludge leading to concerns as to a 

potential hazardous waste designation, and 

flotation of sludge in final clarifiers. 

TREATMENT WITH DISCHARGE- Prior 

to development of the Marcellus shale, 

several facilities existed for chemical 

treatment of gas well wastewaters with 

direct discharge to stream. These facilities 

use chemical precipitation with calcium 

hydroxide to remove suspended solids and 

some dissolved metals. 

The PADEP has prohibited discharge of 

additional, or new, high dissolved solids (over 

500 mg/l) wastewaters into waters of the 

Commonwealth. This prohibition has 

restricted these facilities to treat no more than 

historical flows, estimated at 1.5 mgd, and 

dissolved solids loading, which existed prior 

to the regulation change. 

These facilities face an additional challenge if 

Marcellus wastewaters are to be treated in that 

as their discharge permits are renewed, or 

modified, they must comply with an effluent 

limitation of 10 mg/l maximum for both 

barium and strontium. 

TREATMENT WITH RECYCLE AS 

HYDROFRACTURE MAKEUP WATERSince start of Marcellus development, several 

facilities have been constructed which treat 

gas well wastewaters by precipitation using 

sulfate to lock up barium and strontium 

followed by calcium hydroxide for general 

metals removal. 

The resulting clear brine is then returned to 

gas well drillers for use as hydrofracture 

makeup water. There is a substantial debate as 

to what standards are needed for reuse of 

treated water as hydrofracture makeup water. 

The following Table 2, Recycle Criteria, 

summaries some generally accepted recycle 

criteria. 
IWC 12-72 

Table 2, Recycle Criteria 

Parameter Criteria 

pH 6.0 to 8.0 

maximum total 

hardness 

2,5000 mg/l as 

CaCO3

maximum calcium 

hardness 

350 mg/l as CaCO3

maximum total iron 2 to 20 mg/l 

maximum sulfate 100 mg/l 

maximum dissolved 

solids 

40,000 to 150,000 

mg/l 

Note that these criteria are usually achieved 

by precipitation treatment of the Marcellus 

wastewater followed by a high rate of dilution 

with fresh water. 

Major problems with this approach include a 

large volume of mixed sludge to be landfilled 

and the potential to become water logged as 

Marcellus hydrofracture activity is replaced 

by production operations. 

TOTAL EVAPORATION- Various 

promoters have advanced use of total 

evaporation with production of a condensate 

as a viable means to dispose of Marcellus 

wastewater. Evaporation has two major 

problems. 

Evaporation of Marcellus wastewaters 

produces a solid material for disposal which, 

if the barium content is not removed or 

chemically rendered insoluble, will often test 

out as a USEPA Toxic Characteristic Leach 

Procedure (TCLP) test hazardous waste due 

to soluble barium content. This specific 

problem has been demonstrated by operation 

of a total evaporation pilot facility where the 

produced solids were determined to be a 

TCLP hazardous waste due to soluble barium 

content. 

The other problem with total evaporation is 

the amount and chemical composition of the 

solid material produced and how to manage it. 

Based on the typical Marcellus wastewater, 

pretreated for barium removal, evaporation of 

250,000 gallons would produce 397,823 

pounds (approximately 200 tons) of a mixture 

of residual salts. Some of these salts, such as 

calcium chloride, are deliquescent; all are 

very soluble in water as shown in the 

following Table 3, Residual Salts Solubility. 

Table 3, Residual Salts Solubility 

Residual Salt Solubility 

barium chloride 37.5 g/100 ml 

calcium chloride 74.5 g/100 ml 

lithium chloride 63.7 g/100 ml 

magnesium chloride 54.3 g/100 ml 

sodium chloride 35.7 g/100 ml 

strontium chloride 53.8 g/100 ml 

Based on the solubility of these salts, disposal 

of the residual salt mixture from total 

evaporation treatment in a landfill of any kind 

would appear to be impractical due to their 

ready formation of liquid salt solutions on 

contact with water or moisture. While use of 

the residual salts for roadway deicing has 

been proposed, this appears to be ruled out by 

the regulation of strontium in aqueous 

effluent at a maximum of 10 mg/l and would 

also present substantial logistics problems. 

CHEMICAL PRECIPITATION TO SALT 

BRINE- Chemical precipitation of barium, 

calcium, magnesium, and strontium from 

Marcellus wastewater results in production of 

a sodium chloride brine, which could be 

utilized for roadway deicing if other toxic 

constituents were at suitable levels. This brine 

could also be evaporated to produce a solid 

sodium chloride that may be suitable for other 
IWC 12-72 

uses. Drawbacks include generation of very 

large amounts of mixed sludge requiring 

landfill disposal and a substantial logistics 

problem. 

DEEP WELL INJECTION- Currently, a 

substantial amount of Marcellus wastewater is 

disposed of by deep well injection, most of 

the injection wells being located in Ohio. This 

disposal method has two problems, the first 

being simply that the wastewater has to be 

transported considerable distances by tank 

truck or rail tank car to the injection well site. 

Transportation costs on the order of $0.05 to 

$0.25/gallon have been reported. 

A second problem has been recently noted 

around Youngstown, OH, with several deep 

well injection sites being linked to 

earthquakes. The Ohio EPA has responded by 

shutting several injection wells down and 

restricting both the amount of wastewater that 

can be injected and development of additional 

wells. 

SEQENTIAL PRECIPITATION 

FRACTIONAL CRYSTALLIZATION 

We have developed the Sequential 

Precipitation Fractional Crystallization 

Process (SPFCP) to address economic 

disposal of Marcellus wastewater by resource 

recovery. This patent pending technology 

disposes of the wastewater by processing it 

into salable commodity chemical products 

with no landfill disposal of residual material 

or discharge of liquids. Cost of process 

operation is generally less than the revenue 

produced by product sales. 

The SPFCP must first address the high 

content of barium found in Marcellus 

wastewater. As barium is a USEPA hazardous 

heavy metal, it is desired to remove it to low 

levels from the wastewater as a salable 

product. 

BARIUM RECOVERY- The first 

precipitation step in the SPFCP is to 

chemically remove the barium as insoluble 

barium sulfate under closely defined 

conditions where precipitation of calcium, 

magnesium, and strontium are minimized. 

The concentration of barium and strontium in 

the wastewater is first determined, then 

sulfate ion (as sulfuric acid) is added in an 

amount of 40% over the calculated 

stoichiometric amount to remove the barium 

as the sulfate to low levels. In this first mix 

tank, potassium permanganate is also added 

in an amount to obtain a faint pink color, 

indicating excess permanganate, which 

oxidizes the majority of the organics present 

in the wastewater and to oxidize any ferrous 

iron present. Sodium hydroxide is also added 

to this mix tank to maintain the pH in the 

range of 2.5 to 3.5. 

In a second mix tank, the wastewater pH is 

adjusted to 3.5 to 4.0 by addition of sodium 

hydroxide to complete the barium sulfate 

precipitation. Under these process conditions, 

a fine barium sulfate precipitate is formed 

which is then flocculated in a third mix tank, 

equipped with a VFD slow speed mixer, by 

addition of a low anionic charge, high 

molecular weight polyacrylamide polymer . 

The flocculated barium sulfate is removed 

from the wastewater using an inclined plate 

clarifier, dewatered and washed with distilled 

water for retained soluble salt removal in a 

plate and frame filter press, discharged, and 

dried. The recovered barium sulfate at this 

point is a commercial product, “barite” with 

barium stripped brine remaining. 
IWC 12-72 

 STRONTIUM RECOVERY- Dependent 

upon its concentration and economics 

involved, strontium can be removed from the 

barium stripped wastewater as the sulfate in a 

process similar to that for barium and 

recovered for sale. 

SODIUM CHLORIDE RECOVERY- We 

have discovered that sodium chloride can be 

removed from the barium stripped wastewater 

by fractional crystallization to produce a very 

high purity sodium chloride crystal and a 

commercial grade solution of calcium 

chloride. 

Evaporation of the stripped wastewater results 

in concentration of the various salts present. 

As shown in the following Table 4, Three 

Phase Solubility, as the concentration of 

calcium and magnesium salts increase, the 

solubility of sodium chloride decreases, 

resulting in fractional crystallization of 

sodium chloride from the concentrating 

wastewater. 

Table 4, Three Phase Solubility 

Calcium 

Chloride 

Magnesium 

chloride 

Sodium 

chloride 

33.8 8.4 2.3 

52.9 8.2 0.9 

60.1 0 0.98 

60.2 0 0 

as grams/100 ml 

We have also discovered that sodium chloride 

crystal size and potential scaling of the 

evaporator are controlled by equipping the 

evaporator with a high energy mechanical 

mixer. 

Sodium chloride crystals are removed by 

sidestream filtration of the condensed 

wastewater from the evaporator on a 

continuous basis using a linear vacuum belt 

filter. Filtered crystals are washed with 

saturated sodium chloride brine, to remove 

the more soluble salts, and dried. The sodium 

chloride crystal at this point is a commercial 

product. 

 

CALCIUM CHLORIDE RECOVERY- By 

controlling the concentration of calcium 

chloride in the evaporator to remove sodium 

chloride to below 2.5%, the resulting calcium 

chloride solution is a salable commercial 

product. 

After removal of the sodium chloride crystals 

by sidestream filtration, the filtered calcium 

chloride solution passes through a specific 

gravity measurement device and if the 

specific gravity is above 1.44, routed to the 

calcium chloride solution storage tank. 

Calcium chloride solution below this specific 

gravity is returned to the evaporator for 

further concentration. 

Calcium chloride solution at a specific gravity 

of 1.44 will have to be diluted with distilled 

water to a specific gravity between 1.275 and 

1.310 to make a commercial grade product at 

28 to 31% calcium chloride content. 

 

DISTILLED WATER- Evaporator water 

vapor will be condensed to recover energy by 

preheating incoming barium stripped 

wastewater in a heat exchanger. This distilled 

water will provide the facility with barite 

rinse water, water for sodium chloride brine 

preparation, calcium chloride solution 

concentration adjustment, and cooling tower 

and boiler makeup. 

Any excess water could be sold for use as 

hydrofracture makeup water or even 

discharged to stream with an appropriate 

permit. 
IWC 12-72 

LABORATORY RESULTS 

The SPFCP has been tested in laboratory 

scale experiments to ascertain process 

operating parameters on a variety of actual 

Marcellus flowback and production 

wastewaters. 

The following Table 5, FRAC 15 Test 

Results, shows typical results obtained on 

one test of a Marcellus production wastewater 

from Tioga County, PA, where first the 

barium is precipitated (Ba ↓) followed by 

fractional crystallization removal of sodium 

(Na ↓). 

Table 5, FRAC 15 Test Results - as mg/l 

Parameter untreated Ba ↓ Na ↓

barium 6,000 43 50 

bromide 812 1,020 9,632 

calcium 17,500 19,300 182,000 

lithium 189 220 2,050 

magnesium 1,800 1,540 14,750 

sodium 80,000 55,500 2,600 

strontium 3,600 1,280 10,100 

The sodium chloride crystal recovered from 

this test run was analyzed with the following 

results obtained, Table 6, Sodium Chloride 

Results. 

Table 6, Sodium Chloride Results 

Parameter Result - mg/kg 

sodium 410,000 

calcium 1,535 

magnesium 107 

barium 60 

A sample of produced barite was tested using 

the USEPA TCLP to determine if the product 

could be classified as USEPA hazardous 

waste. As shown in the following Table 7, 

Barite TCLP Results, the product is not a 

hazardous waste. 

Table 7, Barite TCLP Results 

Parameter Result - mg/l 

arsenic 0.016 

barium 0.465 

cadmium <0.005 

chromium 0.0236 

lead <0.02 

mercury <0.0002 

selenium 0.402 

silver <0.01 

To date, a total of fourteen (14) Marcellus 

flowback and thirteen (13) production 

wastewaters from across Pennsylvania have 

been tested to determine if the SPFCP was 

applicable to that specific wastewater. This 

testing has confirmed that the SPFCP can be 

used to treat all of the tested Marcellus 

wastewaters. 

ECONOMICS 

BARITE- An average value for barium in 

production water is 5,000 mg/l, so a 500,000 

gpd SPFCP facility would produce 17.7 dry 

tons of barite per day or 6,469 tons per year. 

Annual world use of barite was estimated at 

7,000,000 tons in 2010 with the product 

found in drilling mud, glass, brake linings, 

paints, and mold release compounds. Annul 

US use of barite is estimated at 2,700,000 

tons with about 80% imported. Good quality 

barite sells for up to $1.00/lb, with wholesale 

prices in the $0.15 to $0.25/lb range. 

From this information it is evident that the 

barite product by resource recovery of 

Marcellus gas shale wastewaters can be easily 

absorbed into the existing market and that 
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significant revenue can be generated by barite 

sales. 

SODIUM CHLORIDE- An operating SPFCP 

facility will produce large amounts of sodium 

chloride. With a typical production water 

sodium level of 58,500 mg/l, a 500,000 gpd 

SPP facility will produce about 122 tons/day, 

annual output of 44,530 tons, of sodium 

chloride crystal. 

Annual production of sodium chloride in the 

US is estimated at 45,000,000 tons with a 

bulk wholesale price of $30/ton. Bagged, 

good quality material can be sold at up to 

$160/ton. 

As with the barite, the sodium chloride output 

of several SPFCP facilities can be readily 

absorbed into the existing market with 

significant revenue generated by salt sales. 

CALCIUM CHLORIDE- Assuming typical 

production water content of 15,000 mg/l 

calcium, a 500,000 gpd SPFCP facility will 

produce 96.5 dry tons per day, 241 tons of 

40% liquid calcium chloride product. This 

product is used in de-icing fluids and freeze 

proofing coal, coke, stone, and ore; 

production paper, fungicides, starch paste, 

concrete additive, fabric sizing, and 

electrolytic cells. Current wholesale price for 

40% calcium chloride solution is $160/ton. 

When the annual output of one SPFCP 

facility of 35,223 dry tons is compared to 

2002 annual worldwide use of 1,687,000 tons, 

it is evident that the output from several 

SPFCP facilities can be readily absorbed in 

the market. As with the barite and sodium 

chloride, significant revenue can be generated 

by sale of calcium chloride solution. 

OPERATING ECONOMICS- Based on the 

chemical and energy use of a 250,000 gpd 

capacity SPFCP facility, market pricing of the 

various inputs, and labor costs; a daily 

operating cost of $22,000 has been calculated. 

Sale of produced commodities, at wholesale 

prices as noted, will return approximately 

$35,500/day, resulting in $13,500/day income 

to pay for construction of the facility. 

FACILITY COST- Our Engineered Services 

Division recently estimated the cost to build a 

250,000 gpd capacity SPFCP facility at 

$11,316,000, exclusive of site acquisition and 

development costs. With this cost and the 

$13,500/day operating cost credit, there is a 

simple payback of 2.3 years on a SPFCP 

facility of this capacity. 

FUTURE RESEARCH 

Both bromine and lithium are concentrated in 

the calcium chloride solution to levels which 

may be economical to consider recovery of 

one, or both, materials. Future research will 

be directed towards examination of methods 

for recovery of both materials. 

CONCLUSION 

Based on extensive laboratory research, the 

SPFCP has been determined to be an 

economical method for disposal of Marcellus 

wastewaters. Production of salable 

commodities from the wastewater provides a 

positive cash flow which will pay for 

construction of a facility in a reasonable 

amount of time. 
IWC 12-72 

References 

Case, L., Halliburton Inc., personal communications 

CRC Handbook of Chemistry and Physics, 57 th Edition, Physical Constants of Inorganic 

Compounds 

Keister, T. 2010. Marcellus Hydrofracture Flowback and Production Wastewater Treatment, 

Recycle, and Disposal Technologies”, The Science of Marcellus Shale Conference, Lycoming 

College, Williamsport, PA. 

Proceedings and Minutes of the Hydraulic Fracturing Expert Panel, XTO Facilities, Fort Worth, 

TX, 09/26/07 

USPTO application #13,222,481, “Treatment of Gas Well Production Wastewaters”, filed 

08/31/2011 

USPTO application #61,199,588, “Process for treatment of gas well completion, fracture, and 

production wastewaters for recycle, discharge, and resource recovery” filed 11/19/2008