Novel and Emerging Technologies for 

Produced Water Treatment

Pei Xu, Tzahi Cath and Jörg E. Drewes

Colorado School of Mines

US EPA Technical Workshops for the Hydraulic Fracturing

Wednesday, March 30, 2011, Arlington, VA
Selection of Treatment Technologies

► Water Chemistry

► Pressure

● Some producers inject produced water at high pressure

► Thermal resources

● Low-grade heat can be utilized for thermal desalination
Produced Water Treatment Technologies

► Requirements 

● High recovery: minimize waste volume and disposal

● High rejection of contaminants: meet stringent discharge 

requirements

● Robustness and low-maintenance: reduce labor and 

supervision requirement

● Flexibility: able to handle high variation in water quality and 

quantity

● Modular:

■ small footprint

■ minimal environmental disturbance
Treatment Technology Assessment

► Review identified 34 fundamental treatment 

technologies and 21 integrated systems/processes

● Commercial status of technology

● Feed and product water quality

● Removal efficiencies

● Recovery 

● Infrastructure considerations

● Energy consumption

● Chemical demand

● Life cycle and costs

● O&M considerations

http://aqwatec.mines.edu/produced_water/treat/docs/Tech_Assessment_PW_Treatment_Tech.pdf
Fundamental Treatment Technologies

Basic Separation

• Settling

• Electrocoagulation

• Flotation

• Hydrocyclone

Adsorption

• Activated carbon

• Zeolite

• Ion exchange

Advanced

• Chemical 

oxidation

• Microfiltration

• Ultrafiltration

Pretreatment
Desalination Treatment Technologies

High Pressure 

Membrane

• Reverse osmosis

• Nanofiltration

• VSEP

Electrically Driven 

Processes

• Electrodialysis

• Electrodionization

• CDI

Novel Membrane 

Processes

• Membrane 

distillation

• Forward osmosis MD

HOT

FEED

COLD

DISTILLATE

CONCENTRATE

DISTILLATE

FEED RO PERMEATE

CONCENTRATE

Membrane Separations
Desalination Treatment Technologies

High Pressure 

Membrane

• Reverse osmosis

• Nanofiltration

• VSEP

Electrically Driven 

Processes

• Electrodialysis

• Electrodionization

• CDI

Novel Membrane 

Processes

• Membrane 

distillation

• Forward osmosis

• Vapor compression

• Multi-effect distillation

• Multi-stage flash

• Dewvaporation

• Freeze-thaw

Membrane Separations

Thermal Technologies

• Evaporation

• Crystallizer

• Wind aided intensified evap.

Zero-liquid Discharge
Integrated Systems

Two Stage RO Hybrids

• Dual RO: chemical precip.

• Dual RO: high pH operation

• Dual RO: slurry precipitation

• Forward osmosis / RO

Commercial Solutions

• Veolia: OpusTM

• Eco-Sphere: OzonixTM

• CDM produced water sys.

• Sal-ProcTM

Pressure Driven

• Mechanical vapor compression

Aquatech and GE

• Mechanical vapor recompression

Aqua-Pure and 212 Resources 

• Intevras: EVRASTM

• Total Separation Solutions: SPR-PYROSTM

Enhanced Distillation 
http://aqwatec.mines.edu/produced_water/
More About Novel and Emerging 

Treatment Technologies 
► Pros

Cost competitive to low salinity and sodium 

bicarbonate type water

Robust

High water recovery (~ 97-99%)

► Cons

Waste disposal

Use of chemicals for regeneration (desalination)

Might not be cost-effective for other types of water

Ion Exchange Process
Pressure-Driven Membrane Separation

Particles/

solute 

molecules

Water

Feed P Permeate

Membrane
Pressure-Driven Membrane Separation

► Pros

Cost competitive to low and high 

salinity water (<40,000 mg/L TDS)

Flexible 

Robust

► Cons

Membrane fouling and scaling

Limited recovery

Extensive pretreatment for complex 

water chemistry

Waste disposal

Source: Xu & Drewes, 2006
Ceramic Ultrafiltration and Nanofiltration

► Typical materials oxides, nitrides, or carbides of 

metals (alumina, zirconia, titania)

► Benefits

● High mechanical strength

● High chemical compatibility

● High flux (up to 150 gfd)

● Long operational life

● Thermal stability

● Potentially lower life-cycle cost

► Potential limitations

● High capital cost

● Large footprint (low packing density)
Cathode (-)

Anode (+)

ClNa+

Na+

Anion Exchange 

Membrane

Cation Exchange 

Membrane

Cation Exchange 

Membrane

- - - - - - - - - - - -

Feed

+ + + + + + + + + + + 

Na+

Na+

Na+

ClClClClNa+

Na+

Na+

Diluate

Concentrate

Electro-Driven Membrane Separation
► Mature and robust technology for brackish water 

desalination

► Have been tested for produced water treatment at 

laboratory-scale

► Relatively lower fouling propensity and higher 

recovery as compared to RO systems

Electrodialysis (ED) and 

Electrodialysis Reversal (EDR)
Electrodeionization (EDI )

Field test EDI vs. Ion-Exchange Col. (IEC)

 Decreased chemical usage, waste stream 

volume

 Smaller footprint (~50 % for same resin 

capacity)

 Reduced operating/capital costs

 Used standard ED cell stack components
Capacitive Deionization

+ + + + + + + + +

- - - - - - - - -

Positive electrode

Negative electrode

Feed 

water

Treated 

water DC 

power

Neutral electrode

Neutral electrode

Regeneration 

water

Concentrate
Capacitive Deionization

► Low fouling/scaling potential

► Minimum pretreatment

► As a novel and emerging desalination technology, 

the system design and operation need further 

optimization:

● Low adsorption capacity of electrode materials

● Energy loss during regeneration

● Minimization of carry-over of ions after regeneration

● Not competitive to treat high TDS water (>1500 mg/L) 

● Long-term field testing and operation experiences
Direct Contact Membrane Distillation 

(DCMD)

► Heated feed stream in contact with the 

active side of the membrane

► Penetration of aqueous solution into the 

membrane pores is prevented by the 

hydrophobic nature of the membrane

► Cold, fresh water stream in contact with 

the support side induces partial-vapor 

pressure gradient

► Direct condensation of vapor upon 

contact with the cold stream

Transport of water vapor through microporous, 

hydrophobic membrane driven by difference in partialvapor pressure across the membrane 

adapted from: http://www.water-technology.net/
DCMD of Extreme Brines

0

50

100

150

200

250

300

350

0

2

4

6

8

10

12

0 20 40 60 80

Feed Concentration, g/L TDS

Water flux, LMH

Time, hr

Feed temperature: 40 °C

Distillate temperature: 20 °C
Osmotically-driven Membrane Processes

► Forward osmosis (wastewater treatment, 

pretreatment, desalination)

Osmosis

Feed

Solution

Forward Osmosis

(“engineered osmosis”)

Draw 

Solution

membrane

Feed

Brine /

Draw 

Solution

membrane
Produced

water

Energy

Recovery

Drinking

Water RO

ForwardOsmosis

Forward Osmosis for Produced Water
Forward Osmosis of Shale Gas Drilling 

Mud and Return Flow
Forward Osmosis of Shale Gas Drilling 

Mud and Return Flow

► Pros

● High rejection of all contaminants

● Reversible membrane fouling

● Can achieve high water flux

● High salinity produced water can be used as draw 

solution

► Cons

● Draw solution needs reconcentration

● Periodic membrane cleaning
Summary

► Many novel and improved processes are emerging

► Site specific conditions will dictate the type of 

technologies most suitable for implementation

► Both lab and field-scale testing need to be 

conducted to investigate the feasibility of the novel 

and emerging technologies for shale gas flowback 

and produced water treatment