# Novel and Emerging Technologies for

Produced Water Treatment Pei Xu, Tzahi Cath and J örg 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 RO FEED 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 : EVRAS TM • Total Separation Solutions: SPR - PYROS TM 

### 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 Permeate P 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 (+) Cl Na + Na + Anion Exchange Membrane Cation Exchange Membrane Cation Exchange Membrane 

# - - - - - - - - - - - -

Feed + + + + + + + + + + + Na + Na + Na + Cl Cl Cl Cl Na +

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 ( E DI ) 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 partial vapor 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 

### membraneProduced

water Energy Recovery Drinking Water RO Forward Osmosis 

# 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