The Science of Marcellus Shale 

January 29, 2010 

Hosted by Lycoming College in Williamsport, PA 

Sponsors: Susquehanna River Heartland Coalition for Environmental Studies and 

Foundation for Pennsylvania’s Water Sheds and Rivers. 

Marcellus Hydrofracture Flowback and Production Wastewater 

Treatment, Recycle, and Disposal Technologies 

Timothy Keister, CWT 

ProChemTech International, Inc. 

Brockway, PA 
2

Introduction: Development of the Marcellus gas play in the Northeast; primarily 

Pennsylvania, New York, and West Virginia, will generate an estimated 7,000 million 

gallons per year (mgy) of hydrofracture flowback and production wastewater that will 

have to be managed. This wastewater, as shown by the following “typical” analysis, 

contains substantial amounts of toxic barium as well as large amounts of many other 

elements and compounds. 

 

Parameter “Typical” Analysis – NE PA 

pH 6.0 

aluminum, mg/l 3.0 

barium, mg/l 6,500 

calcium, mg/l 18,000 

chloride, mg/l 116,900 

iron, mg/l 60 

lithium, mg/l 150 

magnesium, mg/l 1,300 

manganese, mg/l 5.0 

sodium, mg/l 48,000 

strontium, mg/l 4,000 

sulfate, mg/l SO4 130 

dissolved solids, mg/l 195,000 

total hardness, mg/l CaCO3 54,500 

total suspended solids, mg/l 1,200 

Three methods for management of this wastewater are considered viable today, 

pretreatment prior to additional treatment and discharge to stream via publicly owned 

treatment works (POTW), evaporationi (with and without subsequent water recovery), 

and various chemical precipitation processesii with either recycle of the treated water or 

subsequent evaporation. 

Pretreat and Discharge Via POTW 

The Brockway Area Sewer Authority (BASA) operates a new extended aeration, 

oxidation ditch activated sludge POTW treating a mix of industrial and domestic 

wastewater from Brockway and two nearby townships. BASA was approached by a gas 

well service company in 2006 as to accepting brine wastewaters for treatment and 

discharge. A treatment contract was agreed upon; following which BASA obtained an 

NPDES permit amendment from the PADEP on April 17, 2007, for treatment of up to 

14,000 gpd (9.7 gpm) through the BASA plant. The service company then constructed a 

pretreatment system consisting of an oil/solids separator and aerated equalization tank at 

the BASA plant, with the first wastewater accepted in early November, 2008. 

Several effects have been noted on treatment plant operation due to introduction of the 

brine water. 
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Development of a floating sludge layer on the final clarifiers has limited the brine flow 

rate to no more than 8 gpm of brine water at an average POTW flow of 0.5 mgd. This 

floating material is believed to result from combination of calcium in the brine water 

with soaps and fats in the plant influent. 

A substantial increase in sludge generation has also been noted. On analysis, the sludge 

was found to have a barium content of 1,490 mg/kg, which was of some concern as 

barium is a USEPA toxic (hazardous) metal. Fortunately, a subsequent hazardous waste 

determination (TCLIP) on the sludge gave a barium extract value of just 1.56 mg/l, well 

below the 100 mg/l level for classification as a hazardous waste. It has been calculated 

that at our average brine treatment rate, an extra 780 lb/day of barium sludge is being 

produced. 

Mass balance calculations on the plant effluent and input from the brine water also 

demonstrated that a substantial amount of calcium was being removed by the plant 

processes. Typically, about 240 lb/day of additional calcium sludge is being produced by 

treatment of the brine water. 

The dissolved solids in the plant effluent, less than 400 mg/l prior to acceptance of brine, 

typically are in the area of 2500 to 3000 mg/l when brine water is being treated. The 

following table compares some typical brine and BASA effluent results. 

Parameter – mg/l Composite Brine BASA Effluent 

barium 690 8.0 

calcium 23,200 240 

iron 160 0.06 

magnesium 2,240 27.6 

manganese 10.1 0.41 

strontium 732 8.1 

dissolved solids 224,300 3,005 

 

From these results, it is evident that the plant process also removes significant amounts of 

iron, magnesium, manganese, and strontium from the brine water. The amount of brine 

water that can be treated via a POTW is restricted by plant operational problems caused 

by various brine constituents and water quality criteria limits for the receiving stream. 

Evaporation 

While evaporation is a viable method to dispose of this wastewater, its use presents 

several problems that have not been addressed by the various process promoters. 

Evaporation of untreated wastewater will produce a substantial amount of residual 

soluble salt solids that will be considered a hazardous waste on testing with the required 

USEPA TCLP method. For example, using our typical wastewater above, evaporation 

would produce a mixture of soluble chloride salts containing 3.33% barium by weight. 

Running the TCLP test on this mixture would result in a leachate containing 1,665 mg/l 

of barium, the USEPA limit for being considered a hazardous waste is 100 mg/l barium. 
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Accordingly, the residual salt mixture produced by evaporation of the untreated 

wastewater would be considered to be a hazardous waste and have to be disposed of as 

such, a costly proposition. 

This problem has been recognized and is addressed by treating the wastewater prior to 

evaporation by chemical precipitation of the barium. Removal of the toxic barium as an 

insoluble, non-hazardous sludge results in a treated wastewater that can be evaporated 

without producing a hazardous waste. 

Another, generally unrecognized, problem with evaporation is the amount and chemical 

composition of the residual salts produced and how they can be managed. Using our 

typical wastewater, treated for barium removal, evaporation of 250,000 gpd will produce 

397,823 lb/day (approximately 200 tons/day) of a mixture of residual salts. Some of these 

salts, such as calcium chloride, are deliquescent (absorbing moisture from the air); all are 

very soluble in water as shown in the following tableiii

: 

Chemical Solubility Chemical Solubility 

barium chloride 37.5 g/100 ml calcium chloride 74.5 g/100 ml 

lithium chloride 63.7 g/100 ml magnesium chloride 54.25 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 treated 

wastewater evaporation in a landfill of any kind would appear to be impractical due to 

their ready formation of liquid salt solutions on contact with any water or moisture. 

Use of the residual salts, in either solid form or as a brine solution, for roadway deicing 

has been proposed. This would appear to be ruled out by the recent PADEP proposaliv to 

regulate strontium in aqueous effluent at 10 mg/l. 

Due to the deliquescent properties of calcium chloride, and its presence in large amounts 

(26% in our typical treated wastewater residual salt), use of the residual salt in any solid 

form would in practice be impossible due it its tendency to rapidly form a liquid solution 

in higher humidity conditions and cake the rest of the time. 

To address these concerns with disposal of the solids produced by evaporation, the 

process will have to be proceeded by chemical precipitation to remove the calcium, 

magnesium, and strontium from the brine water, effectively converting the brine to 

sodium chloride brine. Sodium chloride brine can then be concentrated for use as a 

deicing solution or evaporated to make salt for industrial use. 

Chemical Precipitation Processes 

Current practice for treatment of brine waters is to adjust the pH using calcium 

hydroxide, clarify the water to remove any heavy metal precipitates, and then discharge 

the treated water to stream. This process is used to treat and discharge an estimated 550 

mgy by the several brine water treatment plants currently operating in the state. 
5

New facilities will not be able to use this treat and discharge process due to the new 

dissolved solids, barium, and strontium effluent requirements in pending state 

regulations. 

Treatment of high barium and strontium content brine waters, most Marcellus 

wastewaters, will not be possible due to the high solubilities, 31,165 mg/l as barium, and 

6,123 mg/l as strontium, of the barium and strontium hydroxides produced by calcium 

hydroxide pH adjustment given the 10 mg/l effluent limits for barium and strontium in 

the pending state regulations. 

Considering recycle of the brine water following treatment, the calcium hydroxide 

precipitation process can be modified to remove both barium and strontium as insoluble 

precipitates by adding sulfate ion prior to the calcium hydroxide addition. A number of 

sourcesv

 have been utilized to determine the following parameters for successful recycle 

of treated brine water as hydrofracture makeup water. 

Recycle Water Specifications 

maximum scale formers – 2,500 mg/l as calcium carbonate 

maximum dissolved solids – 50,000 mg/l maximum iron – 3.5 mg/l 

maximum calcium – 250 mg/l pH range – 6.5 to 7.5 

 

Unfortunately, use of calcium hydroxide as the treatment reagent, even with addition of 

sulfate ion to remove barium and strontium, will result in finished water that far exceeds 

the calcium and total hardness values for successful recycle. Even with addition of 

sufficient sulfate ion to react with all the calcium present in our typical brine water to 

produce a calcium sulfate precipitate, the calcium level in the finished water would be in 

the area of 2,100 mg/l with the scale former level exceeding 5,000 mg/l. We note that one 

proposed treatment and recycle facilityvi does not give a specification for calcium in their 

finished water, likely due to the use of a sulfate/calcium hydroxide treatment process. 

Sequential Precipitation Process (SPP) 

The SPP was developed to address the problems presented by treatment of Marcellus 

wastewater for recycle or final disposal by evaporation. The process first removes barium 

from the wastewater as barium sulfate sludge via precipitation under controlled pH and 

ORP conditions. 

Following barium removal, the remaining scale formers; calcium, iron, magnesium, 

manganese, and strontium are precipitated as carbonates and hydroxides in two separate 

precipitation steps using sodium carbonate and sodium hydroxide additions. After 

clarification, the pH of the finished water is adjusted to meet recycle specifications by 

addition of carbon dioxide. As the chemical composition of Marcellus flowback and 

production wastewaters varies dependent upon the well location and elapsed time since 

the fracture was completed, we have undertaken an extensive series of treatability tests on 

a wide range of wastewaters to determine the widespread applicability of the SPP. The 

following test results are typical: 
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Marcellus flowback water sample – low dissolved solids, Hydrofracture 2 

Parameter untreated treated 

barium mg/l 2,300 <0.1 

calcium mg/l 5,140 6.0 

iron mg/l 11.2 0.04 

magnesium mg/l 438 1.09 

manganese mg/l 1.9 <0.04 

strontium mg/l 1,390 45.8 

total hardness mg/l as CaCO3 17,941 71.8 

total dissolved solids mg/l 69,640 57,660 

 Marcellus flowback water sample – moderate dissolved solids, Hydrofracture 1 

Parameter untreated treated 

barium mg/l 3,310 <0.1 

calcium mg/l 14,100 7.25 

iron mg/l 52.5 1.7 

magnesium mg/l 938 1.6 

manganese mg/l 5.17 <0.04 

strontium mg/l 6,830 10.4 

total hardness mg/l as CaCO3 49,416 39.6 

total dissolved solids mg/l 175,268 59,850 

Marcellus flowback water sample – high dissolved solids, Hydrofracture 4 

Parameter untreated treated 

barium mg/l 4,300 < 0.1 

calcium mg/l 31,300 2.15 

iron mg/l 134.1 1.60 

magnesium mg/l 1,630 1.10 

manganese mg/l 7.0 0.14 

strontium mg/l 2,000 1.60 

total hardness mg/l as CaCO3 90,633 14.9 

total dissolved solids mg/l 248,428 150,520 

The amounts of sludge produced by any precipitation process used to treat a Marcellus 

wastewater will be large. Using our typical brine water concentration of 6,500 mg/l 

barium, treatment of 100,000 gallons/day of this water would produce about 9,200 lb/day 

of dry barium sulfate sludge. We believe that this material can be further processed and 

reused as a weighting agent for drilling mud. The amounts estimated to be produced by 

treatment of Marcellus wastewaters when the play is fully developed, 250,000 tons/yr, 

would approximate 10% of the annual use of barium sulfate used in drilling mud in the 

United States. Of interest, the majority of the barium sulfate used is imported and acid 

mine drainage, common in some areas of the Marcellus gas play, can be used as a low 

cost sulfate ion source in the SPP. 
7

The second mixed sludge produced by the SPP is almost insoluble as shown in the 

following tablevii: 

Chemical compound solubility as compound, mg/l solubility as element, mg/l 

calcium carbonate 140 56 

iron hydroxide 7.2 3.75 

magnesium hydroxide 11.7 4.9 

manganese hydroxide 0.35 0.22 

strontium carbonate 10.9 6.3 

Using our typical brine water concentrations of 18,000 mg/l calcium, 1,300 mg/l 

magnesium, and 4,000 mg/l strontium; treatment of 100,000 gallons of this water would 

produce about 45,700 lb/day of dry mixed carbonate/hydroxide sludge. 

Reuse of this sludge as a raw material for production of cement has been proposed. Other 

potential uses would be as an acid soil neutralization reagent, a phosphate removal 

reagent in POTW, or as a replacement for limestone in fluidized bed boilers. 

In the event that reuse of either, or both, of the sludges produced by the SPP cannot be 

accomplished, they can be disposed of in an approved landfill as they have been TCLIP 

tested and found to be non-hazardous. 

For recycle, the SPP treated wastewater will normally have to be blended with a low 

dissolved solids water, treated acid mine drainage is ideal, to reduce the dissolved solids 

value to below the maximum value. Recycle will be a viable option for management of 

hydrofracture flowback and production wastewaters as long as the need for hydrofracture 

makeup water is substantially greater, a factor of four, than the amounts of wastewater 

produced. This will likely hold true in the Marcellus gas play for a period of 5 to 10 years 

from 2010. 

At that point in time when wastewater production exceeds demand for hydrofracture 

makedown water, evaporation of SPP treated wastewater will be required. Unlike the 

current proposed evaporation methods, evaporation of SPP treated wastewater will 

produce an almost pure sodium chloride residual salt, which has several potential uses 

such as softener regeneration, road deicing, and raw material for chemical manufacture. 

In addition to the high temperature thermal evaporation processes currently marketed, the 

SPP patent application discloses a low temperature method which utilizes low grade heat, 

such as condenser water at a power plant, for evaporation of SPP treated wastewater. As 

an example, a low temperature evaporator designed to evaporate 3,750 gpd of treated 

wastewater would require a condenser water flow of 150 gpm at 105 F, returning to the 

power plant cooling system at 85 F and using 7 hp of electrical power for unit operation. 

With reuse of produced barium sulfate, insoluble mixed sludge, short term recycle of the 

treated wastewater, and reuse of the residual salt produced by evaporation, the SPP 

appears to be the best method for management of Marcellus gas play wastewaters. 
8

 

i

 STW Resources, Inc., “GE Thermal Evaporation Technology”; Heartland Technology Partners 

LLC, LM_HT Wastewater Concentrator”, and several others. 

ii USPTO Application 61/199,588, “Treatment of Gas Well Hydrofracture Wastewaters”, filed 

11/19/2008, ProChemTech International, Inc. 

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

Compounds 

iv PAEQB, proposed rulemaking, 25 PA code, Chapter 95, PA Bulletin, Volume 39. v

 personnel communications, L. Case, Halliburton to T. Keister, ProChemTech and Proceedings 

and Minutes of the Hydraulic Fracturing Expert Panel, XTO Facilities, Fort Worth, TX, 09/26/07 

vi TerrAqua Resource Management, WEB page memo dated 01/11/10 

vii American Chemical Society “Solubilities of Inorganic and Metal Organic compounds”, Fourth 

edition, 1958 

Speaker Biography 

Timothy Keister, CWT, holds a B.Sc. in Ceramic Science from Penn State and is the 

Chief Chemist/President at ProChemTech International, Inc. He is an Association of 

Water Technologists Certified Water Technologist, Fellow of the American Institute of 

Chemists, Senior Member of the American Institute of Chemical Engineers, and member 

of the American Society of Heating, Refrigeration, and Air Conditioning Engineers, 

American Chemical Society, and the Water Environment Federation. His career in the 

environmental/technical water field began at Brockway Glass Company in 1973, where 

he was responsible for management of water and wastewater activities at 38 

manufacturing plants across the country. In 1987 he founded ProChemTech, which 

specializes in innovative water and wastewater management technology with emphasis 

on treatment/recycle and zero discharge projects. Some spare time is also devoted to 

activities as Chairman of the Brockway Area Sewerage Authority and Technical Director 

of the Toby Creek Watershed Association. 

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