Ozone in water treatment: Options and limitations for micropollutant

Ozone in water treatment: Options and limitations for micropollutant

Ozone in water treatment:
Options and limitations for micropollutant mitigation
Urs von Gunten
EPFL, Ecole Polytechnique Fédérale de Lausanne
Eawag, Swiss Federal Institute of Aquatic Science and
Techology
Discovery of ozone in
Switzerland
Discoverer of ozone:
Christian Friedrich Schönbein
1799-1868
Professor at University of Basel
Ozone: 1839
Greek: όζειν (όzein): to smell
Indigo method to measure O3
Fuel cell: 1839
Fenton reaction: 1857
Basics of ozone
§  Ozone is an electrophile
§  Direct reactions primarily with electron-rich moieties (olefins,
phenols, amines, sulfur-containing compounds)
§  Reactions with OH radicals which are formed from ozone
decomposition (natural process)
§  Enhanced ozone decomposition (H2O2, UV, activated carbon)
è Advanced Oxidation Process (AOP)
§  Ozone does not undergo acid-base speciation
§  pH dependence of reactions with compounds that undergo
acid-base speciation
pH-dependence of ozone reactions:
Acid-base properties of reaction partner
Phenolic compounds
Triclosan, antimicrobial compound
present in cosmetics (e.g. soaps)
Reactivity pKa
Application of chemical oxidants in water treatment
Microorganisms
Bacteria, viruses
protozoa
Oxidation
Micropollutants
Kinetics
ms – days
Oxidation
Mechanisms
Pesticides
Fuel additives
Pharmaceuticals
Cyanotoxins
Taste and odor
….
Phys.-chem.
Properties?
Reactions with matrix
Precursor removal
Loss of efficiency
Oxidation by-products
-  Assimilable organic carbon
-  Halo-organic compounds
-  Halogenates
-  Nitrosamines, etc….
CO2, H2O
Transformation
products
Biodegradability
Δ Biological
effects
Kinetics of ozone reaction
•  Typically second order processes
d [ P]
−
= k ⋅ [ox ] ⋅ [ P]
dt
ln
[ P]
[ P] 0
= −k ⋅ [ox ] ⋅ t
•  Second-order rate constants k available in literature and webbased data bases (~€500 k-value for ozone; ~ 2000 k-values for
hydroxyl radicals)
•  Measurment of second-order rate constants k by direct or indirect
methods (competition kinetics)
•  Quantitative Structure Activity Relationships (QSARs)
•  Quantum chemical calculations
Predictions for the reactivity of aromatic compounds
with ozone: QSAR, Quantum Chemistry (ADF)
Aromatic compounds (19 benzene, 21 phenol, and 10 aniline derivatives)
log k
QSAR approach
Quantum Chemistry, HOMO
(Highest Occupied Molecular Orbital)
Lee and von Gunten, Water Res. 2012, 46(19), 6177-6195.
Lee et al, in prep.
Ozone rate constants span over > 10 order of magnitude
QSAR and quantum chemistry give similar results
Endocrine disruptors, pharmaceuticals and personal
care products in the environment
Estrogenic compounds
Antibiotics
Betablockers
Antiinflamatory compounds
Lipid regulators
Antiepileptics
Personal care products
…..
Ecotoxicology
Human toxicology
Micropollutant cycle and elimination processes in the
anthropogenic water cycle
Wastewater
treatment
Indirect reuse
Water resources
Groundwater, lakes
Rivers
Natural attenuation
dilution
Natu
proc ral
esse
s
Direct reuse
Household
Drinking water
treatment
Treatment processes:
Oxidation
NF/RO
Activated carbon
Biological processes
Swiss Strategy Micropoll
•  Swiss EPA (FOEN) recommends upgrading of wastewater treatment plants
to remove micropollutants
•  Large WWTPs (>100‘000 inhabitants) to reduce large sources (economic
and international responsability (Rhein river))
•  WWTPs at rivers with high percentage of (ecosystems protection)
•  WWTPs at rivers with important bankfiltration (protection of drinking
water resources)
•  Ozonation or Powdered Activated Carbon
•  Ca. 100 WWTP (of 700)
•  Investment costs: 1.2 billion CHF, additional yearly costs 130 Mio CHF
•  Increase of costs at WWTPs:
•  Small WWTPs (10‘000 Inh.): 7%-25%
•  Large WWTP (100‘000 Inh.): 2% - 10%
Ozonation: % Elimination of triclosan from secondary
wastewater effluents
Ozone doses: 0.25 – 1.0 g O3/g DOC
Comparable removal based on normalized ozone dose
Independent of origin of water
Works also for less reactive compounds
DEET
Lee et al. ES&T, 2013
Transformation products
Micropollutants
Phys.-chem.
Properties?
Kinetics
ms – days
Mechanisms
Reactions with
matrix
Efficiency
Oxidation by-products
CO2, H2O
Transformation
products
Biodegradability
Δ Biological
effects
Reaction products from 17α-ethinylestradiol
(EE2) attack by ozone
Postulated primary products
OH
O
Criegee
HO
HO
attack on phenol
O
OH
OH
OH
O3
HO
Singlett
oxygen
HO
HO
HO
OH
17α-ethinylestradiol (EE2)
OH
O
Superoxide
O
Huber et al., ES&T, 2004
Oxidation of 17α-ethinylestradiol (EE2) by O3:
Very fast process, small fraction reacts back to EE2
Attack on phenol
Attack on ethinyl group
!
EE2
!
Huber et al., 2004
Prediction tool for transformation products –
under construction
UMBBD-PPS (microbial transformation) and O3PPS (Ozone Pathway Prediction System)
Theoretical
investigations
16/14
Pathway preciction: Olefins
Definition of reaction rules
Prediction results
Reaction Rule 1 (otoc0001)
Tetramethylethene
Progesterone
Reaction Rule 2 (otoc0002)
Reaction Rule 3 (otoc0003)
•••
Final major products reported in literature
17/14
Transformation products – biological effects
Micropollutants
Phys.-chem.
Properties?
Kinetics
ms – days
Mechanisms
Reactions with
matrix
Efficiency
Oxidation by-products
CO2, H2O
Transformation
products
Biodegradability
Δ Biological
effects
Biological approach: Loss of estrogenicity?
Yeast estrogen screen (YES)
Estrogenic compound
Ozone
Effect
Estrogen receptor
Effect ?
Reduction of the estrogenic activity (EEEQ) and elimination of
EE2 by oxidation: Yeast Estrogen Screen (YES)
Bromine
Chlorine
0.6
r2 = 0.96
0.6
1
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1
0.4
0.2
0.0
0.0
1.0
r2 = 0.99
0.6
0.2
Relative EE2
0.4
0.6
0.8
Relative EE2
0.8
1
0.4
0.2
0.0
0.0
1.0
r2 = 0.99
0.6
0.2
0.4
0.6
0.8
Relative EE2
1.0
0.4
0
EE2
EEEQ
5
10
15
20
25
30
0
5
10
dose, µM
0.6
r2 = 0.99
0.6
1
0.4
0.2
0.0
0.0
25
30
0
5
10
0.2
0.4
0.6
0.8
15
0.8
30
Ferrate
r2 = 0.99
1
0.4
0.2
0.2
0.4
0.6
0.8
0.8
1
0.4
0.2
0.0
0.0
1.0
r2 = 0.99
0.6
0.2
Relative EE2
Relative EE2
25
1.0
0.6
0.0
0.0
1.0
20
dose, µM
1.0
Relative EEEQ
Relative EEEQ
0.8
0.8
20
Chlorine dioxide
OH radical
1.0
1.0
15
dose, µM
Relative EEEQ
0.2
0.0
Relative EE2 or EEEQ
0.8
Ozone
1.0
Relative EEEQ
0.8
0.8
1.0
Relative EEEQ
1.0
Relative EEEQ
Relative EE2 or EEEQ
1.0
0.4
0.6
0.8
1.0
Relative EE2
0.4
0.2
0.0
0
100
200
300
UV fluence, mJ/cm
400
0
5
2
Loss of estrogenicity for all
oxidants is proportional to loss
of EE2
10
15
dose, µM
20
25
30
0
10
20
30
40
dose, µM
Residual estrogenicity of
products is <<10% of EE2
Lee et al. 2008
Oxidation of the antibiotic sulfamethoxazole and its main
metabolite N-acetyl-sulfamethoxazole by ozone (OH
radicals)
106
0.1
50
105
10
50,0
1000
sec
app
10
1/2
M s
4
t
-1 -1
1
k
EC
EC50,0/EC
/EC(EC
Residual potency
/EC50)
EC 50,0
/EC 5050 50,0
Ozone oxidation kinetics
Antimicrobial activity as
a function of transformation
100
1.0
1.0
1.0
0.8
0.8
0.8
0.6
0.6
0.6
0.4
0.4
0.4
0.2
0.2
0.2
0.0
0.0
0.0
1.0
1.0
1.0
Ideal
Ideal
SMX,OH
SMX,O
Ideal 3
SMX,O3
0.8
0.8
0.8
0.6
0.6
0.6
0.4
0.4
0.4
0.2
0.2
0.2
0.0
0.0
[C]/[C]
[C]/[C]
[C]/[C]000
100
1000
Essentially 1:1 deactivation of SMX by O3
and by OH radicals
10
3
4
5
6
7
8
9
10
11
pH
Huber et al., 2003, Dodd et al., 2006, Dodd et al. 2009
Triclosan ozonation: Loss of antibacterial activity
and formation of a new activity
1.2×10 -11
1.0
c/c0
8.0×10 -12
0.6
6.0×10 -12
0.4
4.0×10 -12
0.2
0.0
2.0×10 -12
0
5.0×10 -5
1.0×10 -4
TCDD-TEQ (M)
1.0×10 -11
0.8
- Products could not be
identified so far
-  Toxicity is transient and does
not persist
0
1.5×10 -4
O3 (M)
Formation of a dioxin-like compounds also by ozonation:
Dioxins can by detected by measuring EROD activity using rainbow trout liver
cells →TCDD-TEQ
Suarez et al. 2007, Mestankova et al. 2009
E. coli bioassay
Dessert
How can strawberries affect the drinking water quality?
From a fungicide to N,N-nitrosodimethylamine (NDMA)
O
O
S
H3C
CH3
N
CH3
N
S
O
O
100 %
S
H3C
CH3
N
CH3
N
H
CCl2F
O
CH3
O
O
O3
N,NS
N
Dimethylsulfamide
H2N
CH3
50 %
DMS
(DMS) is a newly
discovered metabolite
Drinking
water
plant with
with
high
mobility
inozone
DMS in low µg/L levels ⇒ several 100 ng/L NDMA in drinking water
groundwaters
Shutdown of ozonation
Ban of tolylfluanide in many European countries
DMST
CH3
N
N
NDMA
CH3
Schmidt and Brauch, 2008
Fungicide
Tolylfluanide
NDMA formation during ozonation of DMS: Role of
bromide
1.4
Br
1.2
-
-
Br + NOM
NDMA µM
1
0.8
1:1 formation
0.6
von Gunten et al., 2010
0.4
Bromide catalysis
0.2
0
0.0
0.5
1.0
1.5
-
2.0
2.5
3.0
Br µM
Haag and Hoigné et al., 1984
An unpredictable cocktail….
Fungicide
Natural bromide
Water treatment
}
Conclusions
q  Ozonation processes are suitable for oxidative water
treatment
q  Efficiency depends on reaction kinetics
q  Typically no mineralization: Transformation products
q  Biological activity of transformation products
q  Role of bromide
-  Oxidation by-products (e.g. bromate)
-  Catalytic activity
Acknowledgements
q  Jürg Hoigné, Clemens von Sonntag
q  Marc Huber, Yunho Lee, Beate Escher
q  Michael Dodd, Sonia Suarez
q  Bill Arnold, Carsten Schmidt, Lisa Salhi
q  Hana Mestankova, Kristin Schirmer, Silvio
Canonica, Karl Linden, Austa Parker
q  EU-POSEIDON, Suez Environment, KOSEF, NSF,
Water Research Foundation, Water Reuse Foundation,
Swiss EPA, Eawag
Merçi !
New text book on ozone
chemistry and its application
IWA publisher, London, 2012