Use	of	High-Voltage	Plasma	Discharges		

for	the	Treatment	of	Frac/Produced	Water	

Young	Cho,	Professor	

Department	of	Mechanical	Eng.	and	Mechanics	

(Drexel	Plasma	InsFtute)	

Drexel	University,	Philadelphia,	PA	

Nov.	19,	2014	

Shale	Play	Water	Management	2014	

Dallas,	TX	

1	
Table	of	Contents	

• What	is	plasma?	

• How	to	generate	plasma	in	produced	water?	

• What	are	the	goals	of	plasma	treatment?	

• Spark	discharge	for	produced	water	treatment	

• ValidaFon	tests?	

• What	is	the	cost	of	plasma	treatment?	

• How	to	implement?	

2	 /43	
Pulsed	Corona	in	water	 Spark	Discharge	in	water	

Gliding	Arc	Discharge	

with	Water	Spray		

Spark	Discharge	in	water	

Plasma	Discharges	in	Water	at	Drexel	University	

Plasma	Arrays	in	water	

Pinhole	Discharge	in	water	

3	
Products	of	Plasma	Discharge	in	Water	

4	 /43	

Acidity	

H+	and	NOx

ReacFve	Species	

O,	OH,	HO2,	etc.	 UV	RadiaFon

High	Temp	

Over	2000K	

Shock	Waves

Electric	Field	

CavitaFon	
Book:	Plasma	Discharge	in	Liquid	

5	 /43	
Goals	of	Produced	Water	Treatment	

• DisinfecFon	

• Sobening:	prevenFon	of	mineral	fouling	

• Suspended	solid	removal	

• De-oiling:	removing	dispersed	oil	and	grease	

• Dissolved	gas	removal:	light	hydrocarbon	

• Soluble	organics	removal	

• DesalinaFon	

Ahmadun,	F.-R.,	et	al.,	Journal	of	hazardous	materials,	2009.	170(2-3):	p.	530-551.		 6	 /43	
ConvenFonal	Methods		

• Physical:	filtraFon,	ion	exchange,	RO	

• DisinfecFon:	UV,	biocides,	ozone	

• Biological	treatment	including	MBR		

• Water	sobening	with	chemicals	

• Segling	ponds		

• EvaporaFon,	steam	stripping		

• Others		

Ahmadun,	F.-R.,	et	al.,	Journal	of	hazardous	materials,	2009.	170(2-3):	p.	530-551.		 7	 /43	
ConvenFonal	Methods	

Hayes,	T.	and	D.	Arthur.	Overview	of	emerging	produced	water	treatment	technologies.	in	

The	11th	Annual	Interna:onal	Petroleum	Environmental	Conference.	2004.	.		

8	 /43	
Drexel	Plasma	Research	UFlizes	

Spark	Discharge	

• Short	pulses	of	10-20	μs

• Energy	efficient		

• Powerful	shock	waves	

9	 /43	
Spark	Discharge	in	Produced	Water	

10	 /43	
Spark	Discharges		

11	 /43	
Co-Axial	Electrode	ConfiguraFon	

Center	HV	electrode:	O.D.	=	0.625	inches		

Outer	Ground	electrode:	I.D.	=	1.05	inches

/43	
How	to	Generate	Spark	Discharge	in	Water?		

Use	Air	Spark-Gap	Switch	(low-to-mid	conducFvity)	

Ch-1: Voltage with H.V. probe (x 1000) in air spark Gap 

HV probe Tektronix P6015A High Voltage Probe 1000X 75MHz

Ch-2: Voltage with H.V. probe (x 1000) in water

Ch-3: Current with three attenuators (x 160) and probe (x 10) in Ground; 

current probe (Model: CM-10-L)

Cooling	Water	=	0.2	mS/cm	

Seawater	=	50	mS/cm	

Produced	W.=	100-200	mS/cm	

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Ch-1	:	Voltage	

Ch-3	:	Current	

Peak	Voltage	=	1.6	V	(per	

division)	x	1000	(Voltage	

probe)	=	1,600	V	

Peak	Current	=	2.5	A	x	5	(per	

division)	x	9.2	(agenuator)	x	

10	(current	probe)	=	1,150	A			

The energy in a spark pulse was calculated by the two different methods: 

(1) Energy (J per pulse) = 0.5CV2 = 0.5(8 microF)(3 kV)2 = 36 J/pulse 

(2) Energy (J per pulse) from integration method = ! ! ! ! !" =

80 !/!"#$%

The actual value of the spark energy per pulse should be between the two 

calculated values.

Spark:	Voltage	and	Current	Profiles	

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ValidaFon	Tests

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Tank	B	 Tank	A	

1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark

/43	
Tank	B	 Tank	A	

1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark

/43	
APB	result	

Day	14	

10^7	

10^6	

10^5	

10^4	

10^3	

10^2	

10^1	

Sample	

no.	

Tr

3-3	

Tr

3-2	

Tr

3-1 Con	

3-2	

Con	

2-1	 Flow	

Rate	

5	Gal/min	

Red	color	

Yellow	color	

1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark	(Produced	Water)

/43	
APB test results showed 2-log reduction after 10 

minutes of spark discharge.

1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark

/43	
SRB	result	

Day	0		 -	0	Hour	

Day	1		

Day	2		

Day	3	

Day	4		

Control	

Tr-1	

:1	min	

Tr-2	

:3	min	

Tr-3	

:5	min	

Tr-4	

:8	min	

Tr-5	

:10	min	

Tr-5:	1-log	reducFon	

1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark

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SRB	result	

Day	0		

Day	2		

Day	3	

Con		

1-1	

Con	

1-2	

Con	

2-2	

Con	

3-2	

Tr

1-1	

Tr

1-2	

Tr

1-3	

Tr

2-1	

Tr

2-2	

Tr

2-3	

Tr

3-1	

Tr

3-2	

Tr

3-3	

1	Gal/min	 3	Gal/min	 5	Gal/min	

Produced	water	without	diluFon	was	too	dark	for	SRB	test.	

1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark

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0	

1	

2	

3	

4	

5	

0	(Post	

FiltraFon)	

1	 3	 5	 10	

Log	reducFon	(cfu/mL)	

Treatment	Time	(min)	

SRB	0	hr	

SRB	24	hr	

APB	0	hr	

APB	24	hr	

0 hr means immediate incubation at the completion of plasma 

treatment, whereas 24 hr means that incubation started 24 h after 

the completion of plasma treatment.

DisinfecFon	

• 4-log	reducFon	for	SRB	@	10-min	treatment	

• 2-log	reducFon	for	APB	@	3-min	treatment	

22	 /43	

2-log	reducFon	for	SRB	

4-log	reducFon	for	SRB	

2-log	reducFon	for	APB	
0	

2	

4	

6	

8	

10	

12	

1	 3	 5	

Energy	Cost	[kJ/L	per	1-log]	

GPM	

dark,	opaque	water		

semi-transparent	water	

Energy cost (determined through APB reductions)

DisinfecFon	using	Plasma	Spark	Discharge

23	 /43	
1. Plasma	DisinfecFon:		

	 	Once-Through	Flow	with	Spark

UV	is	the	most	useful	in	disinfecFon.	

Produced	water	from	shale	gas	(Marcellus):		

Clear	water	à 0.1	kJ/L/one-log	reducFon	

Produced	water	from	shale	oil	(Eagle	Ford):	

Dark	water	à 2	kJ/L/one-log	reducFon

/43	
Energy cost = 4 kJ/L per 2-log Reduction (99%) 

@ 500 GPM (12 bbl/min) (= 33 L/s) 

 4 kJ/L * 33 L/s = 133 kW 

For 1 hour operation (720 Bbls), 

 Energy consumed = 133 kW * 1 h 

 = 133 kW.h 

 = $13.00/720 bbl 

 = $0.02/bbl

Sample Calculation:for PW from Shale Oil (Dark)

For produced water from Marcellus: 

Disinfection energy cost is 20 times less. 25	 /43	
2.	Spark-Assisted	Self-Cleaning	FiltraFon	

Co#axial(

electrodes(

Filter(

housing(

Tank(B( Flow(

meter(

Pump(

Tank(A(

26	 /43	
2.	Spark-Assisted	Self-Cleaning	FiltraFon	

RecirculaFon	flow	test	was	used	to	monitor	changes	in	

pressure	drop	across	filter	membrane	over	Fme.		

		 27	 /43	
2.	Spark-Assisted	Self-Cleaning	FiltraFon	

0 3 6 9 12 15 18 21 24 27 30 33

0

3

6

9

12

15

18

21

24

27

30

33

36

39

42

Flow Rate:5 GPM_TDS: 2600 ppm_Pore size: 5 micron

P res s ure0D rop0(ps i)

T ime0(min)

B a s eline0

00000000(No$S park$Dis c harg e)

0S pa rk0dis c ha rge

Pumping failed

28	 /43	
Control-1

-Original filter condition (clean)

Control-2 : No spark at 5 

GPM

Spark treatment at 5 GPM

2.	Spark-Assisted	Self-Cleaning	FiltraFon	

29	 /43	
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

)3

0

3

6

9

12

15

18

21

24

27

30

33

36

39

42

45

48

P res s ure1D rop1(ps i)

T ime1(min)

B a s eline1

11111111(No$S park$Dis c harg e)

1S pa rk1dis c ha rge

PRODUCED WATER_Flow Rate:2 GPM_TDS: 50,000 ppm_Pore size: 5 micron

Pumping failed

2.	Spark-Assisted	Self-Cleaning	FiltraFon:	

Produced	Water	

30	 /43	
2.	Spark-Assisted	Self-Cleaning	FiltraFon:	

Produced	Water	

31	 /43	
3.	Plasma-Assisted	Water	Sobening

Gliding	Arc	with	3	kV,	

200	W	power	supply		 32	 /43	
3.	Plasma-Assisted	Sobening:	Mechanisms

Plasma	discharge	surface	temperature:	2,000	–	4,000	K	

High	temperature	plasma	dissociates	

														bicarbonate	ions	in	water.	

Calcium	ions	in	produced	water	can	be	10,000	–	20,000	ppm.	

Bicarbonate	ions	(max)	is	4,000	ppm	(usually	<	1,000	ppm).	

Once,	bicarbonate	ions	in	PW	are	removed,	carbonate	scales	

cannot	be	formed.	ValidaFon	for	sulfate	salts	is	ongoing.	

Note:	H+	ions	produced	by	plasma	also	removes	HCO3

-

.	

( ) ( ) ( ) (Re 1) 3 2 HCO aq ⇔ OH aq + CO g action − −

33	 /43	
PrevenFon	of	CaCO3	Fouling	in	HeaFng	Elements		

With	Plasma	Discharge	(with	Ca2+	=	5,000	ppm)	

CaCO3	scale	

No	scale	

Wright-Cho DesalinaFon	2014	345	64-71

34	 /43	
3.	Plasma-Assisted	Water	Sobening:	

What	about	Sulfate	Ions?	(e.g.,	mine	water	treatment)	

Plasma	surface	temperature:	2,000	–	4,000	K	

High	temperature	plasma	dissociates	sulfate	ions	in	water.	

35	 /43	
3.	Plasma-Assisted	Water	Sobening	

Chemical	Treatment	vs.	Plasma?

Chemicals	are	used	for	water	sobening	such	as:	

• Lime,	Ca(OH)2

• Soda	ash,	Na2CO3

• CausFc	soda,	NaOH	

However,	the	addiFon	of	these	chemicals	increases	the	

volume	and	cost	of	sludge	to	be	disposed.		

Plasma	water	sobening	removes	bicarbonate	(and	sulfate)	

ions	to	prevent	mineral	fouling	problems	without	

increasing	sludge.		 36	 /43	
4.	OxidaFon	of	Hydrocarbons	with	Plasma		

Produced	Water	

Baseline Plasma Treatment

Initial Filtered 30 s 1 min 2 min 3 min 4 min 5 min 7 min 10 min

Baseline

Plasma Treatment

30 s 1 min 2 min 3 min 4 min 5 min

37	 /43	
Simultaneous	Hydrocarbon	OxidaFon	and	DisinfecFon		

with	Plasma	

 

Adenosine	triphosphate	(ATP)		Assessments	

Control Plasma Treatment Time

30 s 1 min 5 min

Bacteria 

Assesments

ATP (Microbial 

Equivalents/ mL) 107.65 107.44 107.48 105.07

SRB (CFU/mL) 104 104 104 < 100

APB (CFU/mL) 104 104 104 100

38	 /43	
ImplementaFon	of	Plasma	Treatment	

Three	key	components	to	generate	plasma	discharge:		

• Plasma	Reactor	

• Electrodes	(Cathode	and	Anode)	

• High	Voltage	Power	Supply	

Successful	plasma	treatment	at	5	GPM	and	30	GPM	

Current	ongoing	development:		

Skid	systems	for	100	GPM	(2.5	bbl)	and	500	GPM	(12	bbl)	

39	 /43	
For	2,000	GPM	(50	bbl), 		

four	12-bbl	modules	can	be	used.	

12	bbl	Skid	

12	bbl	Skid	

12	bbl	Skid	

12	bbl	Skid	

Untreated	

Produced	

Water	

Treated	

Produced	

Water	

40	 /43	
Skid		

Water	Tank		

Bagery	

Pump	

Plasma	Reactor	

HV	Power	Supply	

Plasma-treated		

water	

ImplementaFon	of	Plasma	Treatment	

Once-through	flow	mode	(on-the-fly	system)	

Frac	well		

41	 /43	
Treatment	Skid		

PW	in	Storage	Pond	

Pump	

Plasma	Reactor	

HV	Power	Supply	

Plasma-treated	water	return		

ImplementaFon	of	Plasma	Treatment	

RecirculaFng	flow	mode	

42	 /43	
Summary:		

Plasma	Treatment	can	Perform	MulFple	FuncFons	

with	Low	Energy	Cost	(~$0.02/bbl)		

1. DisinfecFon	

2. Water	sobening	

3. OxidaFon	of	dissolved	hydrocarbons	

4. Self-cleaning	filtraFon	

5. De-oiling	

6. Oxidize	and	precipitate	metal	ions	so	that	

they	can	be	removed	by	filtraFon		

Plasma-treated	produced	water	can	be	fed	to	disFllaFon	

unit	without	mineral	fouling	problem.	

43	 /43	
Acknowledgement	

Funded	by	RPSEA	(The	U.S.	Department	of	Energy,	NETL)	

Funding	 for	 this	 project	 is	 provided	 by	 RPSEA	 through	 the	 “Ultra-Deepwater	 and	

UnconvenFonal	Natural	Gas	and	Other	 Petroleum	 Resources”	 program	authorized	 by	 the	

U.S.	Energy	Policy	Act	of	2005.	 	RPSEA	 (www.rpsea.org)	is	a	nonprofit	corporaFon	whose	

mission	is	to	provide	a	stewardship	role	in	ensuring	the	focused	research,	development	and	

deployment	of	safe	and	environmentally	responsible	technology	that	can	effecFvely	deliver	

hydrocarbons	 from	 domesFc	 resources	 to	 the	 ciFzens	 of	 the	 United	 States.	 	 RPSEA,	

operaFng	 as	 a	 consorFum	 of	 premier	 U.S.	 energy	 research	 universiFes,	 industry,	 and	

independent	research	organizaFons,	manages	the	program	under	a	contract	with	the	U.S.	

Department	of	Energy’s	NaFonal	Energy	Technology	Laboratory.	

/43	
Thank	you!	

/43