Overview of Advanced Oxidation Processes (AOPs...

John C. Crittenden, Ke Li,

Daisuke Minakata, Paul Westerhoff

Department of Civil and Environmental Engineering, Arizona State University

Potable Reuse for Water Supply Sustainability Critical Today – Essential Tomorrow, Nov 16-19, 2008. Long Beach, CA

Overview of Advanced Oxidation Processes (AOPs)

-Understanding and Improving Process Performance-

1

Outline 1.Introduction to Advanced Oxidation

Processes (AOPs)2.Various AOPs Technologies3. Factors affecting performance of AOPs4. Simplified steady-state model for AOPs5. By-products of AOPs6.Case study 1:

RO retentate by various AOPs7.Case study 2:

Removal of MtBE and tBA by UV/H2O2

8.Summary 2

Advanced Oxidation Processes (AOPs) that produce hydroxyl radicals (HO•radicals) at ambient temperature and atmospheric pressure are promising water treatment technology.

HO• radicals are highly reactive electrophiles, that react rapidly and non-selectively with the electron-rich sites of compounds.

HO• radicals are capable of mineralizingorganic compounds into carbon dioxide CO2

and water.

Introduction - what are AOPs? -

3

The most significant observed by-products are the carboxylic acids, due to the fact that the second order rate constants for these compounds are much lower than those for most organics.

If adequate reaction time is provided, all by-products (>99% as measured by a TOC mass balance) are destroyed.

General reaction rules in AOPs:

Introduction – Reaction rules in AOPs -

4

H-atom abstraction by HO•or HO• addition

O2 addition

Uni/Bi molecular decay

HydrolysisHO• reactions

Β-scission, 1,2-H shift

Peroxyl radical mechanisms

Parent compound

Carbon centered radical

Peroxyl Radical

Oxy radical

Intermediates (aldehydes, alcohols etc.)

Carbon centered radical

Carboxyl acid

CO2/Minerals

5

Various AOPs Technologies 1/2 Proved AOPs

Advantages Disadvantages

H2O2/UV

• Long stability and can be preserved prior to use of H2O2.• H2O2+UV → 2HO•+3O2

• Poor UV absorption of H2O2

• Interface of UV with the water matrix• Special reactors required for UV illumination• Residuals of H2O2

H2O2/O3

• Suitability for waters with poor UV light transmission• Special reactors requirement for UV illumination2• 2O3+H2O2 → 2HO•+3O2

• Stripped volatile organics• Expensive and inefficient to produce O3

• Residues of gaseous O3

• Difficulty of maintenance (O3/H2O2

dosages)• Low pH is detrimental

TiO2/UV

• Activated with near-UV light• Greater light transmission• TiO2+UV → h++ecb

h++H2O → H++HO•

• Occurrence of fouling of catalyst • Recovery of TiO2 required upon the use as a slurry

6

Various AOPs Technologies 2/2

HiPOx (O3/H2O2)Applied Process Technologies, Inc

Purifics (UV/TiO2) 0.5 MGDPhoto-Cat Purification

Low PressureUV system (UV/H2O2)

7

Factors Affecting AOP Performance 1/4• Destruction rate of targeted compound R by HO•

• Rate raw for HO• that reacts with an organic compound

R R HO R

HO +R byproducts

r k C C

HOR R Rr k C C Typical kR: 10

7-109 M-1s-1, CR: μM or nM, CHO•: 10

-11 ~ 10-9 M

• Half-life of an organic compoundfor CMBR

R

R HO

ln(2)t

k C

Compoundk HO•

M-1

s-1 [HO•]=10

-9 M [HO•]=10

-10 M [HO•]=10

-11 M

MtBE 1.6×109 0.01 0.1 1

Oxalic acid 1.4×106 8 83 825

Acetate ion 7×107 0.2 2 17

Trichloromethane 5.0×106 2 23 231

1,1,2-Trichloroethane 1.1×108 0.11 1 11

Chloroform 5×106 2 23 231

Chloroacetic cid 4.3×107 0.3 2.7 27

Glycolic acid 6×108 0.02 0.2 2

1,1,1-Trichloroethane 4×107 0.3 3 29

Benzene 7.8×109 0.001 0.01 0.1

Phenol 6.6×109 0.002 0.02 0.2

Halflife, min

8

Q TCE, % pHCT, CO3,

mM

HCO3-,

mM

CO32-,

mM

10.9 7.0 1 0.997 0.003

5.78 7.0 2 1.994 0.006

2.98 7.0 4 3.988 0.012

2 7.0 6 5.982 0.018

5.55 8.0 2 1.99 0.01

3.04 9.0 2 1.904 0.096

0.754 10.0 2 1.333 0.667

* TCE = 0.100 mg/L

**source Glaze and Kang 1988

• Impact of carbonate species

2 23 3 3 3

R RR

R R HCO HCO CO CO

k CQ

k C k C k C

kHCO3- = 8.5×106 M-1s-1

kCO3-- = 3.9×108 M-1s-1

H2CO3* ↔ H+ + HCO3-

(pKa=6.3)HCO3- ↔ H+ + CO3

2-

(pKa=10.3)At high pH, alkalinity

is detrimental

Factors Affecting AOP Performance 2/4

9

Factors Affecting AOP Performance 3/4• Impact of pH: O3/H2O2,

Overall: 2O3 + H2O2 → 2HO• + 3O2

H2O2 ↔ HO2- + O2- (pKa = 11.6)

Rate limiting-step: O3 + HO2- → O3•- + HO2• (k=2.8×106)

Scavenges by H2O2: HO• + HO2- → HO2• + OH- (k=7.5×109)

HO• + H2O2 → HO2• + H2O (k=2.7×107)Inefficient at low pH(<5.0) and high pH(11)

H2O2 ↔ HO2- + O2

- (pKa = 11.6)Scavenges by H2O2: HO• + HO2

- → HO2• + OH- (k=7.5×109)HO• + H2O2 → HO2• + H2O (k=2.7×107)

Higher pH is effective because HO2- has 10 times UV molar

absorptivity at 254 nm (228 L/mole•cm) than does H2O2. Higher pH is effective especially if the background water matrix absorbs a lot of UV light.

UV/H2O2,

10

Factors Affecting AOP Performance 4/4• Impact of NOM

R RR

R R NOM DOC

k CQ

k C k C

0.00.10.20.30.40.50.60.70.80.91.0

200 220 240 260 280 300

Ab

sorb

ance

(cm

-1)

wavelength (nm)

Raw water

NO3-

H2O2 10mg/L

Fe(II)

• Impact of light transmission

Typical UV absorbance spectra * H2O2 absorbs photons efficiently in the range

of 200-300 nm

Compounds k HO• (10-8 M-1s-1)

1.39 ± 0.16

1.87 ± 0.07

1.55 ± 0.04

Saguaro Lake Hydrophobic Acid 1.73 ± 0.04

Saguaro Lake Transphilic Acid 1.45 ± 0.02

Saguaro Lake Hydrophobic Neutral 2.18 ± 0.13

Nogales WWTP Hydrophobic Neutral 1.72 ± 0.13

Nogales WWTP Transphilic Neutral 4.53 ± 0.54

Nogales WWTP Transphilic Acid 3.63 ± 0.31

acetate 0.73

propionate 12

formate 0.32

pyruvate 0.31

oxalate 0.077

* Westerhoff et al., 2008

NOM

isolates

Reference

organic

compounds

Suwannee River Fulvic Acid

H2O2/O3 simplified model and example

If H2O2 is Added to a Water Containing O3, i.e. [O3]0 is known.

3O 1 2 3 9 2 10 2 2r 2k [HO ][O ] k [HO ][HO ] k [HO ][H O ]g g

H O2 2

ss,0

(pH pK )

1 2 2 0 3 res

11 3 0 12 0 13 0

[HO ]2k [H O ] 10 [O ]

k [HCO ] k [R] k [NOM]g

ss,0R 12[HO ]k k= gR Rr k [R]

H O H O2 2 2 2

2 2

pH pk pH pk

H O 1 3 0 9 ss,0 10 ss,0k k [O ] 10 k [HO ] 10 k [HO ]g g

2 2 2 2H O H O 2 2r k [H O ]

Model Assumption: 1)pseudo-steady-state; 2)ozone transfer is the limiting factor of the reaction

rate; 3)constant pH;

The city of Anytown, USA recently discovered that one of its wells was contaminated with 200 g/L (1.52 mole/L) TCE. In order to continue using the well as drinking water resource, the TCE needs to be destroyed and the effluent concentration must less than 5 g/L. During normal pumping operations, the well produces water about 0.025 m3/s (400 gal/min). The pH, alkalinity and DOC concentrations are 7.5, 400 mg/L as CaCO3, and 0.7 mg/L, respectively. The following table presents physico-chemical properties of TCE and NOM.

Compound MW

(g/mole)

OH radical rate constant,

kOH,

TCE 131.389 4.20x109 (L/mole•s)

NOM NA 3.90x108 (L/mole NOM Carbon-s)


For simplicity, a proprietary reactor will be used. It has been determined by conducting dye studies on the reactor that four completely mixed flow reactors in series could describe the reactor. Given: The H2O2 dosage is 0.8 mg/L. O3 is generated onsite and the ozone flow rate is 1mg/L•min. The partial pressure of ozone in the inlet gas is 0.07 atm, respectively. The Henry's Law coefficient for O3 at 23C is 83.9 atm•L/mole. The overall mass transfer coefficient for O3, kLa, was measured to be 710-4 s-1. The reactor volume is 5500 L (5.5 m3). Determine the expected effluent concentration for TCE.

– Example 3

1. Calculate the hydraulic detention time ():

3

3

Total Reactor Volume 5.5 m 3.7 min

Q 0.025 m /s 60 s /min

2. Calculate initial steady-state concentration of hydroxyl radical

3

3

ss,0

O

L

O

9 2 0 10 2 2 0 11 3 0 12 0 13 0

[HO ]

Pk a

H

k [HO ] k [H O ] k [HCO ] k [R] k [NOM]g

a. Obtain the reaction rate constants and acid dissociation constants.b. Calculate the concentration of each component

5

2 2 0

0.8 mg/LH O 2.35 10 mole /L

34 g/mole 1000 mg/ g

H O2 2pH pK 5 7.5 11.75

2 2 2 00

9

HO H O 10 2.35 10 mole /L 10

1.32 10 mole /L


3 0

400 mg/LHCO 0.008 mole /L


6

0 0 6

1.52 mole /LR TCE 1.52 10 mole /L

10 mole /mole

0

5

0.7 mg/LNOM

12 g carbon/mole NOM carbon 1000 mg/ g

5.83 10 mole NOM carbon/L

c. Calculate the value of rate constant times concentration of each component

9 9

9 2 0k [HO ] 7.5 10 L/mole s 1.32 10 mole /L 9.9 1/ sg

7 5

10 2 2 0k [H O ] 2.7 10 L/mole s 2.35 10 mole /L 634.5 1/ sg

6

11 3 0k [HCO ] 8.5 10 L /mole s 0.008 mole /L 68000 1/ sg


– Example 3

9 6

12 0 12 0k [R] k [TCE] 4.2 10 L /mole s 1.52 10 mole /L 6384 1/ sg

8 5

13 0k [NOM] 3.9 10 L /mole NOM C s 5.83 10 mole NOM C/L

22737 1/ s

g

d. Calculate initial steady-state concentration of hydroxyl radical

ss,0

4

12

[HO ]7 10 1/ s 0.07 atm / 83.9 L /atm mole

9.9 634.5 68000 6384 22737 1/ s

5.97 10 mole /L

gg


3. Calculate the TCE effluent concentration:a. Determine kTCE using the pseudo first order rate law

( ) ( )ss,0

9 12

R TCE 12[HO ]k k k 4.2 10 L /mole s 5.97 10 mole /L

0.025 1/ s

g g -= = = ´ ´ ´

=

b. Determine effluent TCE concentration using the tanks in series model

0

n 4

TCE

R 200 μg/LTCE R

k 0.025 1/ s 3.7 min 60 s /min1 1

n 4

6.2 μg/L


The city of Anytown, USA recently discovered that one of its wells was contaminated with 200 g/L (1.52 mole/L) TCE. Calculate the effluent concentration of TCE for H2O2 dosage is 2.5 mM (85 mg/L) and estimate the residual of H2O2 in the effluent. The treatment objective for TCE is 5.00 g/L. During normal pumping of the well field, the flow rate is 0.20 m3/s (3,200 gpm). The pH, alkalinity and DOC concentrations are 6.8, 400 mg/L as CaCO3, and 0.7 mg/L, respectively. The following table shows some important physico-chemical properties of H2O2, TCE and NOM.

Compound MW

(g/mole)

OH Radical rate constant,

kOH, (L/mole•s)

Extinction coefficient, , (L/mole•cm)

Quantum yield,

Trichloroethylene 131.389 4.20x109 Ignored 0

NOM** NA 3.90x108 0.0196 0

H2O2 34.015 - 19.6 0.5

**For NOM, the units of kOH and is L/mg s and L/mg cm, respectively

UV/H2O2 simplified model and example

For simplicity, a proprietary reactor will be used. A dye study on the reactor has shown that four completely mixed flow reactors in-series describes mixing that occurs in the reactor. The reactor size is 1 m in diameter by 3 m in height and the volume is approximately 2300 L with 12x15 kW medium-pressure lamp, as shown on the figure. To simplify the calculations, it can be assumed that the UV-light is monochromatic at 254 nm and the intensity is 3.3x10-5 einsteins/L-s. Assume that all the light is absorbed and [HO2

-] and [CO32-] can be

neglected at pH 6.8.

Solution

1. Calculate the hydraulic detention time ():

3 3

Total reactor volume 2,300 L

Q 0.20 m / s 1000 L /m 60 s /min

0.19 min


2. Calculate the fraction of light absorbed by H2O2.

To simplify the calculation, it will be assumed that all the light is absorbed by the water matrix and the walls of the vessel absorb no light when that is reflected off the walls.

2 2 2 2

2 2

2 2 2 2

3

H O H O

H O 3H O H O NOM NOM

19.6 2.5 10ε Cf

C C 19.6 2.5 10 0.0196 0.7

0.78

3. Calculate the effluent concentration of TCE:a. Convert the concentration of each component from mg/L to mole/L:

3 0

400 mg/LHCO 0.008 mole /L


5

0

0.7 mg/LNOM 5.83 10 mole NOM C/L

12 g C/mole NOM C 1000 mg/ g


b Determine values of rate constant times concentration:

7 3

10 2 2 0k [H O ] 2.7 10 L/mole s 2.5 10 mole /L 67500 1/ sg

6

11 3 0k [HCO ] 8.5 10 L /mole s 0.008 mole /L 68000 1/ sg

9 6

12 0 12 0k [R] k [TCE] 4.2 10 L /mole s 1.52 10 mole /L 6384 1/ sg

8 5

13 0k [NOM] 3.9 10 L /mole NOM C s 5.83 10 mole NOM C/L

22737 1/ s

g

Calculate [HO•]ss

2 2 2 2

A

H O 0 H O

ss,0

10 2 2 0 11 3 12 0 13 0

5

10

2 I f (1 e )[HO ]

k [H O ] k [HCO ] k [TCE] k [NOM]

2 0.5 mole/einstein 3.3 10 einstein /L s 0.78

67,500 68,000 6384 22737 1/ s

1.58 10 mole /L

g

g


d Calculate pseudo-first order rate constant for TCE:

e Calculate TCE effluent concentration using the tanks in series model

' 9 10

12 12 ss,0k k [HO ] 4.2 10 L /mole s 1.58 10 mole /L 0.66 1/ sg g

0

n 4

'

12

TCE 200 g/LTCE

0.66 1/ s 0.19 min 60 s /min1 k 1

n 4

2.9 μg/L

4. Calculate the residual hydrogen peroxide concentration

a Estimate pseudo-first order rate constant for H2O2

2 2

2 2

0 H O'

10 10 ss,0

H O 2 2 0 NOM 0

0.5Ik k [HO ]

[H O ] [NOM]


2 2

5

0 H O

4 2

0.5I 0.5 mole / einstein 19.6 L /mole s 3.3 10 einstein /L s

3.23 10 1/ s

2 2

3

H O 2 2 0[H O ] 19.6 L /mole s 2.5 10 mole /L 0.049 1/ s

NOM 0[NOM] 0.7 mg/L 0.0196 L /mg s 0.01372 1/ s

7 10

10 ss,0k [HO ] 2.7 10 L/mole s 1.58 10 mole /L 0.004266 1/ s

4 2

' 3

10

3.23 10 1/ sk 0.004266 1/ s 9.42 10 1/ s

0.049 0.01372 1/ s

b. Estimate H2O2 residual using the tanks in series model:

3

2 2 02 2 n 4

3'

10

3

2.5 10 mole /LH OH O

9.42 10 1/ s 0.19 min 60 s /min1 k 1n 4

2.25 10 mole /L 76.5 mg/L


23

By-products of AOPsParent compound

Major byproducts

(yield 10-30 mole%)

Minor byproducts

(yield 2-5 mole%)

Acetone

*Stefan and Bolton, 1999

acetic, pyruvic, and oxalic acids

pyruvaldehyde

formic and glyoxylic acids

hydroxyacetone, formaldehyde

MtBE

* Stefan et al., 2000

acetone, acetic acid, formaldehyde,

tert-butyl formate (TBF), pyruvic acid,

tert-butyl alcohol (TBA), 2-methoxy-2-

methyl propionaldehyde (MMP), formic,

methyl acetate

hydroxy-iso-butylaldehyde,

hydroxyacetone, pyruvaldehyde

and hydroxy-iso-butyric, oxalic

acid

Dioxane

*Stefan and Bolton, 1998

1,2-ethanediol diformate, formic acid,

oxalic acid, glycolic acid, formaldehyde,

1,2-ethanediol monoformate

methoxyacetic acid glyoxal

TCE

* Stefan and Bolton, 2002formic acid, oxalic acid

dichloroacetic acid,

mono-chloroacetic acid

Production of brominated byproducts and bromate (BrO3

-) in waters containing bromide ion (Br-) during O3/H2O2

Case study 1 – RO retentate by AOPs Screen DisinfectionFiltrationAeration

Reverse Osmosis

Microfiltration Aquifer Storage and

Recovery

Stabilization

Primary Clarification

Secondary Clarification

UseDisinfection

DOC: 40 ~ 50 mg/LBDOC (biologically degradable DOC5): 4.5 mg/L pH = 7.5-7.8

RO retentate

24

EE/O (electrical efficiency per order of contaminant destruction)

P = lamp power output, kWQ = water flow rate, gal/hCi = influent conc. of MtBE or tBA, µg/LCf = effuluent conc. of MtBE or tBA, µg/L

, kWh-kgal/order

Parameters for evaluations

25

27

Energy consumption v.s. DOC % reduction among AOPs

0

20

40

60

80

100

0 10 20 30 40 50 60

DO

C r

ed

uct

ion

(%

)

Energy consumption (kWh/kgal)

UV/TiO2/H2O2

(Bench)210 J/cm2

2 g/L10 mMpH = 5.0

UV/TiO2/H2O2

(Bench)960 J/cm2

2 g/L10 mMpH = 5.0

UV/TiO2/H2O2

(Bench)600 J/cm2

2 g/L10 mMpH = 5.0

UV/TiO2

(Purifics)15 W/m3

2 g/LpH = 5.0

UV/TiO2 (Bench)960 J/cm2

2 g/LpH = 4.0

O3 /H2O2 (HiPOx)730/380 mg/L 1100/550 mg/L

UV/H2O2

960 J/cm2

10 mMpH = 4.0

Source: Westerhoff. 2008

• 10 kWh/lb O3, 4.9 kWh/lb H2O2, 13.6 kWh/lb TiO2

• Fenton’s was excluded due to the limited DOC removal (49%)

DOC removal 75%

at about 70 kWh/m3

Source: Westerhoff. 2008. based on the bench scale experiments.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0 2 4 6 8 10

illumination time (hrs)

DO

C (

mg

/L)

UV/TiO2

UV/TiO2 + BDOC

Lower power can be used when combined with downstreambiodegradation (i.e., sand filter).

Essentially incorporating bio can reduce power requirements by 20% to 50% depending upon what final DOC concentration you are targeting

Removal of RO retentate DOC

28

Summary of Case Study 1

UV/TiO2 was most energy efficient for the removal of RO retentate DOC as compared to O3/H2O2, UV/H2O2 and UV/TiO2/H2O2.

UV/TiO2 required no addition of chemicals and hence is easy to operate.

UV/TiO2 treatment followed by biological treatment achieved more than 90% of RO retentate DOC removal.

29

Background

• MtBE was used as gasoline additive to enhance octane number. • Despite the ban in 1992, MtBE is still found nationwide as ground water contaminants.• Difficult to remove using adsorption or air stripping• Exposure to large dose causes significant non-cancer-related-health risk (WHO). • Ruin taste of water at 5-15 µg/L • Established treatment target at MtBE ≤ 2.5 µg/L and tBA ≤ 6 µg/L, respectively, by California Department of Public Health (CDPH)

30

Case Study 2 – Removal of MtBE and tBA by UV/H2O2 -

Initial Conditions + Major Raw Water Quality • 7000 gpm (=10.1MGD)• MtBE: 300 µg/L• tBA: 30 ug/L • TDS: 940 mg/L • Alkalinity: 318 mg/L as CaCO3

• Chloride: 138 mg/L • Nitrate: 0.9 mg/L • Iron: 0.44 mg/L • pH: 7.6 • TOC: 1.4 mg/L

Objective

MtBE ≤ 2.5 µg/L and tBA ≤ 6 µg/L

Site of water source:Charnock Wellfield,

City of Santa Monica, CA, 1995

31

Raw water + Pretreatment options

• Raw water • NAIX: Ion exchange with sea water + Dealkalization*• RO: lime softening + Reverse osmosis + Dealkalization* * Acid addition to lower pH and remove alkalinity

Estimated major water quality of raw and after pretreatment

32

AlternativeTOC

(mg/L)

Alkalinity

(mg/L as CaCO3)pH

Ferrous Iron

(mg/L)

Raw water 1.4 318 7.6 0.44

NalX + Dealkalization 1.4 0 4.65 0

RO + Dealkalization 0.07 0 4.5 0

Impact to UV/H2O2 process by compound i

k HO•/Ri = second-order reaction rate constants of HO• with compound iCi = concentration of compound i

*H2O2 conc. is assumed 10 mg/L.** Fe2+ is included only for raw water. 33

MtBE35.6%

tBA1.6%

TOC11.0%

H2O251.8%

RO + Dealk

Fe2+15.1%

HCO3-42.6%

CO3--2.9%

MtBE4.5%

tBA0.2%

TOC27.9%

H2O26.6%

HO2-0.2%

Raw water

RO + Dealkalization

NaIX + Dealkalization

Raw Water

Tool utilized for simulations

• Solved with AdoxTM (AOP Simulation Software)• no pseudo-steady-state assumption•pH is not constant• Gear algorithms utilized to solve stiff ODEs • completely mixed flow reactors with tank-in-series

Assumptions

• MtBE and tBA are the only target compounds.• Direct photolysis of MtBE and tBA is negligible. • 15 mole% of tBA is formed from MtBE oxidation. • NO3

-, Fe2+ and NOM are the only interference with UV.• Fe2+, NOM and HCO3

-/CO32- are the only HO• scavenger.

• Decrease of UV irradiation due to scaling and bulb aging is 70%. • All UV irradiation is absorbed by the water matrix.

Approach

34

Approach (cont’d)

Configuration of reactors and Modeling approach (LPUV/H2O2)

• Consist of four parallel train (each Q= 1750 gpm). Each train includes the required number of LPUV reactors in series. • Dye study data suggests 8 tanks-in-series (TIS) described reactor mixing conditions. • If both MtBE and tBA do not meet treatment objectives, the model run up to 9 maximum reactors (72 TIS).• If proved impossible to meet the criteria above, H2O2 dose is increased.

Q = 7000 gpmEach Q = 1750 gpm

Target effluent conc.MtBE ≤ 2.5 µg/L

tBA ≤ 6 µg/L 35

Simulation results (LPUV/H2O2)

• 10 mg/L of H2O2 dosage would be the better choice although the optimum dosage of H2O2 is over 20 mg/L because the cost required for over 20 mg/L of H2O2 dose overweigh the energy cost.

36

Pretreatment process

H2O2

(mg/L)

EE/O

(kwh-kgal/order)

Effluent

concentration

(μg/L)

Number of

reactors

per train

Number

of trains

in out MtBE tBA MtBE tBA

Raw Water 25 13 1.1 4.4 0.5 5.7 9 4

NalX + Dealk 10 6.9 0.77 3.0 0.6 5.8 6 4

RO + Dealk 4.0 2.9 0.11 0.29 0.2 1.8 1 4

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

5 10 15 20

EE

O (

kW

h/k

ga

l-o

rd

er)

H2O

2resi

du

al

co

nc.

(mg

/L)

H2O2 Dosage (mg/L)

Residual of H2O2 MtBE tBA

H2O2 residuals and EEO as a function of H2O2 dose (NaIX+Dealk)

Cost comparison

# of

reactors

Total power

per day

(kWh)

Cost of

energy

($/day)

H2O2

dose

(mg/L)

Total amount

per day

(lb)

Cost of

chemical

($/day)

LPUV/H2O2 24 21,300 $2,130 10 600 $899

MPUV/H2O2 10 108,000 $10,800 10 600 $899

Table 11.

Cost comparison for the desing comparing of the LPUV reactor and the

MPUV reactor

NaIX + Dealkalization pretreatment

* Unit prices for H2O2 and electrical energy are $ 1.5/lb and $0.10 kWh, respectively.

• Cost of energy for MPUV system is 5 times higher than for LPUV system.• In the design process, a comparison of EE/O versus the H2O2 dosage provides valuable insight into the tradeoffs and support determination an appropriate H2O2 dosage.

37

Summary

• Kinetic Models can be used to simulate the complex interaction of UV/H2O2 chemical physical reactions with water matrixes (e.g. TOC, carbonate species).

• Removal of carbonate species using pretreatment processes can reduce the energy cost by much as 1/3 and reduce the number of reactors from 36 to 24 which would translate into a capital cost savings by 1/3.

• For the LPUV system, the cost of chemicals can be as high as the energy cost.

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Acknowledgement

• Water Reuse Foundation (WRF): WRF-05-010

• National Science Foundation (NSF): 0607332

• Richard Snell Chair at Arizona State University

• Center for Clean Industrial and Treatment Technologies (CenCITT) by U.S. EPA at Michigan Technological University

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References 1/2• Glaze and Kang, 1988. Advanced oxidation processes for treating

groundwater contaminated with TCE and PCE: Laboratory studies. J. AWWA., 81, 5, 57-63.

• Stefan and Bolton, 1999. Reinvestigation for the acetone degradation mechanism in dilute aqueous solution by the UV/H2O2 process. Environ. Sci. Technol., 33, 870-873.

• Stefan, M. I.; Mack, J.; Bolton, J. R. Degradation pathways during the treatment of methyl tert-butyl ether by the UV/H2O2 process. Environ. Sci. Technol. 2000, 34, 650-658.

• Stefan, M. I.; Bolton, J. R. Mechanism of the degradation of 1, 4-Dioxane in dilute aqueous solution using the UV/hydrogen peroxide process. Environ. Sci. Technol. 1998, 32, 1588-1595.

• Stefan and Bolton, 2002.

• Westerhoff, P.; Mezyk, S.P.; Cooper, W.J.; Minakata, D. Electron pulse radiolysis determination of hydroxyl radical rate constants with Suwannee river fulvic acid and other dissolved organic matter isolates. Environ. Sci. & Technol. 2007, 41, 4610-4646.

• Li, K.; Hokanson, D.R.; Crittenden, J.C.; Trussell, R.R.; Minakata, D. Evaluating UV/H2O2 processes for methyl tert-butyl ether and tertiary butyl alcohol removal: Effect of pretreatment options and light sources. Wat. Res. 2008, In Press.

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References 2/2• Crittenden, J. C.; Trussell, R. R.; Hand, D. W.; Howe, K. J.; Tchobanoglous,

G., Eds. Water Treatment: Principals and Design, 2nd ed.; John Wiley: New York, 2005.

• Crittenden, J.C.; Hu, S.; Hand, W. D.; Green, A. S. A kinetic model for H2O2/UV process in a completely mixed match reactor. Wat. Res. 1999, 33(10), 2315-2328.

• Westerhoff, P.; Crittenden, J.C.; Moon, H.; Minakata, D. Oxidative treatment of organics in membrane concentrates. Final project report, Water Reuse Foundation, Alexandria, VA, 2008.

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