presentación de powerpoint - home -...
TRANSCRIPT
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
1. WHY ADVANCED TREATMENT?
Aims of (waste)water treatment
To produce fit-for-purpose water quality, meaning the control of water
quality hazards to yield an acceptable level of risk, whereby
risk = frequency x probability of adverse outcome x severity of effect
Risk can refer to public health, financial, reputational, environmental,
social…
1. WHY ADVANCED TREATMENT?
Fit-for-purpose water quality
Water quality that is appropriate, and of a necessary standard, for its intended use.
“Don’t crack a nut with a sledgehammer!”
Example: Typical recycled water end-uses:
- Augmentation of Drinking Water Supplies
- Managed Aquifer Recharge
- Dual reticulation indoor (toilet, laundry)
- Dual reticulation outdoor (irrigation, car washing,…)
- Municipal irrigation (controlled / uncontrolled)
- Agriculture (different quality depending on crop)
- Fire fighting
- Commercial (dust suppression, cooling water)
- Replacement of environmental flows
Level of treatment depends on initial water quality and end-use!
1. WHY ADVANCED TREATMENT?
D. Sedlak (2014), Water 4.0: The Past,
Present, and Future of the World’s Most
Vital Resource, 352p. Yale University Press.
Pre-human development
1. WHY ADVANCED TREATMENT?
D. Sedlak (2014), Water 4.0: The Past,
Present, and Future of the World’s Most
Vital Resource, 352p. Yale University Press.
Pre-human development
Water 1.0 Supply and Drainage
1. WHY ADVANCED TREATMENT?
D. Sedlak (2014), Water 4.0: The Past,
Present, and Future of the World’s Most
Vital Resource, 352p. Yale University Press.
Pre-human development
Water 1.0 Supply and Drainage
Water 2.0 Water Treatment
1. WHY ADVANCED TREATMENT?
D. Sedlak (2014), Water 4.0: The Past,
Present, and Future of the World’s Most
Vital Resource, 352p. Yale University Press.
Pre-human development
Water 1.0 Supply and Drainage
Water 2.0 Water Treatment
Water 3.0 Wastewater Treatment
1. WHY ADVANCED TREATMENT?
Water scarcity and strife for
efficiency gains create a
diversity of source and target
water qualities.
D. Sedlak (2014), Water 4.0: The Past,
Present, and Future of the World’s Most
Vital Resource, 352p. Yale University Press.
Pre-human development
Water 1.0 Supply and Drainage
Water 2.0 Water Treatment
Water 3.0 Wastewater Treatment
Water 4.0 Diversity of Supply
1. WHY ADVANCED TREATMENT?
Opportunities and need for
alternative treatments that
MAY also be “ADVANCED”.
Water scarcity and strife for
efficiency gains create a
diversity of source and target
water qualities.
D. Sedlak (2014), Water 4.0: The Past,
Present, and Future of the World’s Most
Vital Resource, 352p. Yale University Press.
Pre-human development
Water 1.0 Supply and Drainage
Water 2.0 Water Treatment
Water 3.0 Wastewater Treatment
Water 4.0 Diversity of Supply
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
• Liquid but certain viscosity
• “heavy”, 1L = 1kg (approx.)
• Non-compressible
• Transparent
• Polar, dielectric fluid, H-bonds
• Dissolves well polar organic and many
inorganic substances
• Dissolves gases to some extent, some
polar gases are dissolved very well
• Surface tension, capillary action
• Heat capacity 4.184 J/g.K
• Enthalpy of vaporization, 2260 kJ/kg
• Vapour pressure f(T), 23mbar @ 20°C
• Abundant on earth?
Water – H2O
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
Of, relating to, or denoting compounds containing carbon (other
than simple binary compounds and salts) and chiefly or ultimately
of biological origin
Of, relating to, or denoting compounds that are not organic
(broadly, compounds not containing carbon)
Organic substances
Inorganic substances
Biological material
Any material containing genetic information and capable of
reproducing itself or being reproduced in a biological system.
Contaminant classification
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
Contaminants – only some examples…
temperature
Total organic
carbon (TOC)
Chemical oxygen
demand (COD)
Biological oxygen
demand (BOD)
Heterotrophic plate
count (HPC)
Suspended solids
Colour
turbidity
Organic
micropollutants
Humic substances
Dissolved mercury,
other toxic metals
Human adenovirus
Total phosphorus
nitrate, ammonium
salt
Cryptosporidium spp
Salmonella, E.coli
Disinfection
byproducts
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
Biological contamination: pathogens Disease causing microorganisms are called pathogens.
But there are a lot of “good microorganisms”. According to a recent National Institutes
of Health (NIH) estimate, 90% of cells in the human body are bacterial, fungal, or
otherwise non-human. http://mpkb.org/home/pathogenesis/microbiota
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
Vapour pressure: Easy to oxidize / reduce?
Electrical charge: Solubility:
Hydrophobicity/hydrophilicity: Biodegradability:
Size:
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
Vapour pressure: • Air stripping
• Distillation
Easy to oxidize / reduce?
• Ozonation, advanced oxidation
• Chlorination and chloramination
• Metal finishing
• Coagulation
• Reverse & forward osmosis
• Electrodialysis
Electrical charge: Solubility:
• Precipitation
• Adsorption
Hydrophobicity/hydrophilicity: • Adsorption
• Extraction
• Coagulation
• Secondary treatment
• Reverse & forward osmosis
Biodegradability: • Primary and secondary wastewater
treatment, MBR
• biofiltration
Size: • Filtration processes
• Adsorption
FURTHER READING
David Sedlak (2014), Water 4.0: The Past, Present, and Future
of the World’s Most Vital Resource, 352p. Yale University Press.
John C. Crittenden, R. Rhodes Trussell, David W. Hand, Kerry J.
Howe, George Tchobanoglous. (2012). MWH's Water Treatment:
Principles and Design, Third Edition.
Guidelines for drinking-water quality, fourth edition. World Health
Organization (2011).
http://www.who.int/water_sanitation_health/publications/2011/dw
q_guidelines/en/index.html
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
MEMBRANE FILTRATION
ADSORPTION
(ADVANCED) OXIDATION PROCESSES
BIOLOGICAL TREATMENT, DISTILLATION
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
MEMBRANE FILTRATION - OVERVIEW
APPLIED FULL SCALE ROUTINELY
1. Pressure driven: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF),
reverse osmosis (RO)
2. Charge separation: Electrodialysis (ED), electrodialysis reversal (EDR)
PILOT / DEMONSTRATION SCALE
3. Osmotic processes: Forward osmosis (FO), pressure retarded osmosis
(PRO), pressure assisted forward osmosis (PAO)
4. Thermal separation: Membrane distillation (MD)
PRESSURE DRIVEN MEMBRANE FILTRATION
Microfiltration Ultrafiltration Nanofiltration Reverse
osmosis
PORE SIZE (μm): 0.05 – 10 0.01 – 0.05 <0.005 <0.002
FLOW (L/m2.h)1: 40 – 150 20 – 60 10 – 30 10 – 30
PRESSURE (bar): 0-1 0-5 2-15 5-75
Rejects well2: Solids, bacteria,
protozoa
Virus,
macromolecules
Polyvalent salt,
OMP
Monovalent salt,
OMP
Materials3: PVDF, PTFE, PES, PS, ceramic, etc Fully crosslinked aromatic polyamide
in thin-film composite membrane
(PES, PE support)
Operational
aspects:
Fouling/Scaling, hydraulic
backwashing & chlorine cleaning
possible
Fouling/Scaling, need good
pretreatment, not resistant to oxidants,
no hydraulic backwash possible
1 rapid sand filter: approx 10’000 L/m2.h, river bank filtration 200-1’000 L/m2.h
2 as pore size decreases, of course also larger solutes are rejected mentioned to the left in the table
3 PVDF: polyvinidylfluoride; PTFE: polytetrafluoroethylene; PES: polyethersulfone; PS: polysulfone; PE: polyester
REJECTION MECHANISMS IN NF/RO
RO
Concentrate
Feed 1 Feed 2 Feed 3
Total Permeate Permeate 1
Permeate 2 Permeate 3
PV 2
PV 3
PV 4
PV 1
PV 2
Stage 1 Stage 2 Stage 3
1 Train
PV 1
PV 1
PV = Pressure Vessel
RO Train: 4:2:1 configuration of pressure vessels (PV)
On-line conductivity measure
REJECTION MECHANISMS IN NF/RO
RO membranes are not simply ‘molecular sieves’ but complex working filters
~ 0.1 µm
Frequently, so-called “solute-diffusion” model
used to model rejection
REJECTION BY NF/RO - pharmaceuticals
Rejection with virgin RO membrane at pilot-scale and bench-scale
Lower rejection with spiral wound membrane at pilot-scale Higher recovery & Lower cross-flow velocity towards the end of the pressure vessel
Enhanced concentration polarization
Source: Chrystelle Ayache (2013). PhD thesis. The University of Queensland.
REJECTION BY NF/RO – disinfection byproducts
Source: Doederer et al (2014). PhD thesis. The University of Queensland.
0
10
20
30
40
50
60
70
80
90
100
DB
P r
eje
ction
(%
)
RO
NF
REJECTION BY NF/RO – process parameters: T
Source: Doederer et al (2014). PhD thesis. The University of Queensland.
0,E+00
1,E-11
2,E-11
3,E-11
wa
ter
pe
rme
ab
ility
(m
) ↑ pore size
0
20
40
60
80
100
20 30 40
DB
P r
eje
ctio
n (
%)
Temperature (oC)
BDCM
BDIM
BCAN
1,1-DCP
0,0
0,5
1,0
1,5
2,0
2,5
70 80 90 100 110 120
Re
jectio
n r
atio
23
oC
/35
oC
-1
Molecular volume (Å3)
↑ solute diffusivity ↑ partitioning
REJECTION BY NF/RO: SUMMARY
• Rejection mechanisms: 1) size exclusion; 2) charge
interaction; 3) hydrophobic interaction
• % Rejection can be very high, often 90-99.5% (RO > NF)
• Small hydrophilic compounds not well rejected, e.g. boric acid,
nitrosodimethylamine (NDMA) sometimes 0-50%
• Hydrophobic compounds can also be problematic, particularly
when “cake-enhanced concentration polarization” occurs.
• Flow, temperature, fouling influence rejection %
• Many other water quality benefits: salinity, solids, pathogens
• Concentrate management can be a problem
MEMBRANE FILTRATION - OVERVIEW
APPLIED FULL SCALE ROUTINELY
1. Pressure driven: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF),
reverse osmosis (RO)
2. Charge separation: Electrodialysis (ED), electrodialysis reversal (EDR)
PILOT / DEMONSTRATION SCALE
3. Osmotic processes: Forward osmosis (FO), pressure retarded osmosis
(PRO), pressure assisted forward osmosis (PAO)
4. Thermal separation: Membrane distillation (MD)
ELIMINATION OF OMP BY ELECTRODIALYSIS
https://youtu.be/wvS7jsIhGBQ
https://www.gewater.com/products/electrodialysis-reversal-water-treatment
How does ED(R) work?
Nice video from General Electric on youtube:
ELIMINATION OF OMP BY ELECTRODIALYSIS
Drinking water treatment – pilot plant EDR process
Llobregat river: 50 organic micropollutants detected
Removal up to 60% of the EDR process for charged compounds
no effect was observed for neutral compounds
For comparison: approximately 70-85% of inorganic ions are removed
Source: Gabarrón et al. J. Hazard. Mater. 309 (2016) 192-201.
ELIMINATION OF OMP BY FORWARD OSMOSIS
High
concentration (osmotic agent,
draw solution)
Low
concentration (feed solution)
McCutcheon et al. JMS, 278 (2006) 114.
Because of internal concentration polarization new, thinner membranes needed
with open support structure.
ELIMINATION OF OMP BY FORWARD OSMOSIS
Example of integration of FO or PRO with seawater desalination for direct potable reuse:
Kim et al. Desalination, 322 (2013) 121-130.
• In application, potentially a doublé barrier against micropollutants
compared to traditional MF-RO approach in potable reuse applications.
• Because of membrane characteristics (thin, high permeability) rejection
is somewhat lower than for RO membranes.
• Similar to NF big differences among membranes on the market.
FURTHER READING
Bellona et al., Factors affecting the rejection of organic solutes
during NF/RO treatment—a literature review. Water Res. 38 (2004) 2795-2809.
Arne Verliefde (2008). Rejection of organic micropollutants by high pressure membranes
(NF/RO). PhD Thesis, TU Delft.
http://www.citg.tudelft.nl/fileadmin/Faculteit/CiTG/Over_de_faculteit/Afdelingen/Afdeling_
watermanagement/Secties/gezondheidstechniek/leerstoelen/Drinkwater/Research/Compl
eted_PhD_projects/doc/PhD-Thesis_ARD_Verliefde.pdf
Doederer et al., Rejection of disinfection byproducts by RO and NF membranes:
Influence of solute properties and operational parameters. J. Memb. Sci. 467 (2014) 195-
205.
Vanoppen M. et al, Properties governing the transport of trace organic contaminants
through ion-exchange membranes. Environ. Sci. Technol. 49(1) (2015) 489-497.
Gabarrón S. et al, Evaluation of Emerging Contaminants in a Drinking Water Treatment
Plant using Electrodialysis Reversal Technology. J. Hazard. Mater. 309 (2016) 192-201.
Coday B.D. et al, Rejection of trace organic compounds by forward osmosis membranes:
A literature review. Environ. Sci. Technol. 48(7) (2014) 3612-3624.
Other manuscripts cited on previous slides
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
MEMBRANE FILTRATION
ADSORPTION
(ADVANCED) OXIDATION PROCESSES
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
ADSORPTION
Adsorbent Technology Application
Granular Activated
Carbon (GAC)
Fixed bed, e.g. filter Organics removal (bulk and
micropollutant)
Biological Activated
Carbon (BAC)
Fixed bed, e.g. filter Organics removal (bulk and
micropollutant), often after
oxidation process to remove
biodegradable matter
Powdered Activated
Carbon (PAC)
Dosed in suspensión,
needs removal, often
applied temporarily as
emergency response to
contamination
Organics removal (bulk and
micropollutant), often to combat
seasonal taste & odour problems
in WTP
Zeolites Both, suspended and
fixed bed
Ion exchange, softening, heavy
metals
Ion exchange resins Suspended, need
regeneration
Ion Exchange, softening, natural
organic matter removal
Novel materials:
carbón nanotubes,
graphene oxide, etc
Diversity of tailored surfaces, adsorbents, applications,
ADSORPTION – example: 3 full scale BAC
Source: Reungoat et al. Water Res. 46 (2012) 863-872.
BAC bed age:
Caboolture: 2.5 y, 68’000 beds
Landsborough: 8 y, 350’000 beds
Gerringong: 50% of media: 8y,
95’000 beds, 50% 1y, 13’000 beds
ADSORPTION – summary
• Removal can be high, >90%, particularly on fresh GAC
• Adsorption depends on molecule charge / hydrophobicity – i.e. negative
or hydrophilic compounds break through earlier or are hardly adsorbed
on carbon (e.g. iodinated constrast agents)
• Adsorption is an equilibrium process with desorption – high spikes can
be well mitigated, during times of low influent concentration desorption
may occur.
• Re-activation / renewal of carbón and civil works are major cost factors,
otherwise low direct energy consumption compared to oxidation and
membrane filtration processes
FURTHER READING
Gabarrón S. et al, Evaluation of Emerging Contaminants in a Drinking Water Treatment
Plant using Electrodialysis Reversal Technology. J. Hazard. Mater. 309 (2016) 192-201.
Reungoat J. et al, Ozonation and biological activated carbon filtration of wastewater
treatment plant effluents. Water Res. 46 (2012) 863-872.
Rattier M., Reungoat J., Gernjak W., and Keller J. (2012), Organic Micropollutant
Removal by Biological Activated Carbon Filtration: A Review. Urban Water Security
Research Alliance Technical Report No. 53.
http://www.urbanwateralliance.org.au/publications/UWSRA-tr53.pdf
Jingyi Hu (2016). Micro-pollutant removal from wastewater treatment plant effluent by
activated carbon. PhD thesis, Delft University of Technology.
http://www.citg.tudelft.nl/fileadmin/Faculteit/CiTG/Gezondheidstechniek/doc/Proefschrifte
n/Jingyi_Hu_-_Micro-
pollutant_removal_from_wastewater_treatment_plant_effluent_by_activated_carbon.pdf
David de Ridder (2012). Adsorption of organic micropollutants onto activated carbon and
zeolites. PhD thesis. Delft University of Technology.
http://repository.tudelft.nl/islandora/object/uuid%3A36768caf-ba11-45b8-9d71-
b6ebbf5cc9e8?collection=research
John C. Crittenden, R. Rhodes Trussell, David W. Hand, Kerry J. Howe, George
Tchobanoglous. (2012). MWH's Water Treatment: Principles and Design, Third Edition.
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
MEMBRANE FILTRATION
ADSORPTION
(ADVANCED) OXIDATION PROCESSES
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
OXIDATION – Theory and Processes
Reduction - augment number of electrons in molecule
Oxidation - reduce number of electrons in molecule
Source: Braun et al. Chem. Rev. 93(2) (1993) 671-698.
Wid
ely
ap
plied
in
wate
r in
du
str
y
OXIDATION – Theory and Processes
A number of other oxidants, e.g. electron holes in valence band of semiconductors.
Also reductants can be interesting:
• electrons in conduction band of semiconductors or solvated
• Hydrogen atoms, nascent hydrogen
Advanced oxidation processes defined as those generating hydroxyl radicals,
but often not the only mechanism. They have sparked particular attention in
research, although not so many applications other than ozone and UV/H2O2 in
relatively clean water, some Fenton applications in industrial wastewater.
Many good and exhaustive reviews, e.g.:
Braun et al, Chem. Rev. 93(2) (1993) 671-698.
Gogate and Pandit, Adv. Environ. Res. 8 (2004) 501-551.
Gogate and Pandit, Adv. Environ. Res. 8 (2004) 553-597.
Pignatello et al, Crit. Rev. Env. Sci. Technol. 36 (2006) 1-84.
Malato et al, Catal. Today 147(1) (2009) 1-60.
OXIDATION – Theory and Processes
Conventional and industrially applied oxidation processes:
HOCl: chiefly employed as disinfectant, inconvenience of generating halogenated
disinfection byproducts (DBPs)
NH2Cl: disinfectant for distribution, fewer DBPs, but e.g. NDMA formation.
ClO2: disinfectant or pre-oxidation before HOCl to reduce DBP formation, but
forms chlorite.
O3: cheap, energy efficient, good removal for many electron rich contaminants,
generates bromate in bromide rich waters
UV/H2O2: more expensive, higher cost/energy compared to O3, no byproduct/
bromate formation
All oxidation processes generally only transform molecules but don´t
mineralize! Even if a process is capable of mineralizing, doing so would be
uneconomical in most situations.
OXIDATION – Theory and Processes
Advanced oxidation processes
UV-C/H2O2: mostly •OH reaction pathways
O3: mix of ozone and •OH reaction pathways, addition of H2O2 and/or UV-C and/or
raising pH can promote • OH generation.
Fenton & photo-Fenton (with UV or solar): wide variety of conditions, typically
pH=3, sludge generation. Mix of reactions, e.g. also photolysis of iron-
organic complexes
Semiconductor photocatalysis (UV-A or solar): suspension or immobilised – both
with respective trade-offs. A lot of materials research on photocatalyst
development, TiO2 remains the standard. Inherently low quantum
efficiency due to prevalent electron – hole recombination. Much
research (>40’000 papers) – Little application.
Electrochemical oxidation: Existing applications rely on mediated oxidation (e.g.
generate HOCl from Cl- in situ), sulfate as mediator “hot topic”,
electrode and reactor development required. Also direct oxidation.
Sonolysis & Hydrodynamic cavitation: generate bubbles that collapse generating
high temperature & pressure in minute space. Complex chemistry
(e.g. water splitting). Energy intensive.
OXIDATION – Theory and Processes
More (advanced) oxidation processes
Non-thermal equilibrium plasma: energy intensive, complex chemistry, little understood
Vacuum UV: direct water splitting, complex chemistry
Electron beam treatment: often used as reference AOP – only • OH generated.
Wet oxidation
Supercritical oxidation
Persulfate/UV or Persulfate/UV/Fe
Photo-electro Fenton, photoelectrocatalysis
etc.
OXIDATION – Theory and Processes
Some general considerations:
1) Pollutants occur usually homogeneously distributed
• Hence a process acting across entire volume often more efficient, especially
important for disinfection where 99-99.99% inactivation is typically desired.
• Local generation of reactive species creates important challenges for reactor
design to overcome mass transfer limitations.
• In light-driven processes, increase in wavelength will increase penetration
depth.
• Competition among pollutants, scavenging capacity, and radical
recombination, e.g. how many of my photons trigger the “right” reaction? How
many of the reactive species react with pollutants?
• Hence, deeper light penetration and longer wavelength are only then
favourable, if the ratio of desired/undesired reactions increases.
OXIDATION – Theory and Processes
2) Reactive species will have different lifetimes from ns to days. Consider the
importance for mass transfer.
• E.g. typically velocities in strongly mixed reactor are in the range of m/s. If
lifetime is 10 ns and speed is 10 m/s, lifetime “distance” is 0.0001mm. Often
the strongest oxidant will not be the best, particularly if generated
heterogeneously across the solution.
3) Energy efficiency in oxidation processes is in the end about minimizing
undesired losses.
• UV/H2O2: Conversion of electricity into light – typical efficiencies are between
15% (medium pressure Hg lamps) and 40% (low pressure Hg lamps). Then
conversion of light to chemically useful species/energy. Yield% of useful
reactions.
• Sonolysis: Conversion of electrical energy into mechanical energy,
mechanical energy into chemical energy. Yield% of useful reactions.
• O3 or HOCl: Synthesis of oxidant. Yield% of useful reactions.
To compare processes: “Electrical energy per order of contaminant decrease”
Source: Bolton et al. Pure Appl. Chem. 73(4) (2001) 627-637.
OXIDATION – Theory and Processes
• A lot of (advanced) oxidation processes, but only few are really applied broadly.
Others only applied in research or niche applications.
• Many processes generate a mix of reactive species.
• Water chemistry (matrix) and treatment objective will define the fit-for-purpose
application.
• Homogeneous versus heterogeneous reaction systems taking into account
oxidant lifetime and mass transfer.
• (Electrical) energy per order of contaminant transformation typical figure-of-
merit.
• Oxidation rather transforms organic contaminants instead of mineralizing them.
• Most organic contaminants can be treated by AOPs (fewer by conventional
oxidation) – the questions is which is the process least costly, energy intensive,
does not generate undesired secondary contamination, by-products, most
safe, resilient etc.
• Some exceptions exist, e.g. polyfluorinated compounds, but most react simply
more or less rapidly, i.e. treatment becomes more or less effective.
Summary:
OXIDATION – Some applications
Source: Reungoat et al. Water Res. 46 (2012) 863-872.
Tertiary treatment with O3/BAC for
subsequent water reuse.
OXIDATION – Some applications
Source: Reungoat et al. Water Res. 46 (2012) 863-872.
Generally good removal % - these treatment plants employ actually
a low to médium O3 dose.
OXIDATION – Some applications
Source: Lee et al. Env. Sci. Technol. 50 (2016) 3809-3819.
Comparison of several processes, including energy and byproducts
OXIDATION – Issue of transformation products
Toxicity is a general term applied to different non-specific and specific
biologically adverse effects.
Specific effects (e.g. estrogenicity) almost always decrease after a target
molecule has been transformed.
Non-specific effects (e.g. baseline toxicity, mutagenicity, oxidative stress) may
increase after transformation of target molecule.
In most cases, despite a possible initial increase of a biologically adverse effect
upon oxidation, further transformation decreases again toxicity need to
understand a specific application (water to be treated + technology applied).
Often, oxygen inserting oxidation technologies generate reactive aldehydes or
quinones that increase toxicity.
These transformation byproducts are however often quite biodegradable, i.e.
not an issue in a properly designed treatment train. See e.g.
de Vera et al. Water Res. 106 (2016) 550-561.
Escher et al. J. Environ. Monitor. 11(10) (2009) 1836-1846.
Macova et al, Water Res. 44(2) (2010) 477-492.
OXIDATION – Issue of transformation products
Nevertheless, transformation products can be an issue.
Examples of known toxic transformation products:
Triclosan photolysis (also in the environment) can generate dioxins.
Latch et al. J. Photochem. Photobiol. A: Chem. 158(1) (2003) 63-66.
Generation of halogenated byproducts with HOCl and related toxicity.
De Vera et al. Water Res. 87 (2015) 49-58.
Farré et al. Water Res. 47(14) (2013) 5409-5421.
Generation of other byproducts NDMA (monochloramine), bromate (ozone),
chlorite (chlorine dioxide)…
Certainly some more could be cited…
Although only few examples with a clear issue are known, it is
hard to deal with known unknowns from a risk based approach
(which is how water managers take their decisions).
OXIDATION – Issue of transformation products
Studying transformation pathways can help to understand a
specific problem, but is not a generally applicable solution
(too many compounds, too many processes).
Radjenovic et al.
Environ. Sci. Technol. 46
(2012) 8356-8364.
FURTHER READING
International ozone association
http://www.ioa-pag.org/
International UV association
http://www.iuva.org/
Von Sonntag C. and von Gunten U. (2012). Chemistry of Ozone in Water and
Wastewater Treatment. 320p. IWA Publishing. ISBN: 9781843393139.
Bas Wols (2010). CFD in in drinking water treatment. PhD Thesis. TU Delft.
http://repository.tudelft.nl/islandora/object/uuid%3Ab1d4405e-a364-4105-ab03-
21800b46df5b?collection=research
B. Escher and F. Leusch (2011). Bioanalytical Tools in Water Quality Assessment. 272p.
IWA Publishing. ISBN: 9781843393689.
Review manuscripts on AOPs:
Braun et al, Chem. Rev. 93(2) (1993) 671-698.
Gogate and Pandit, Adv. Environ. Res. 8 (2004) 501-551.
Gogate and Pandit, Adv. Environ. Res. 8 (2004) 553-597.
Pignatello et al, Crit. Rev. Env. Sci. Technol. 36 (2006) 1-84.
Malato et al, Catal. Today 147(1) (2009) 1-60.
Other manuscripts cited on previous slides
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
MEMBRANE FILTRATION
ADSORPTION
(ADVANCED) OXIDATION PROCESSES
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
DESIGNING A TREATMENT SOLUTION
1. Description of project need & opportunity
2. Source water characterization & definition of target water quality
3. Definition of treatment objectives (inorganic, chemical, biological) & constraints
(e.g. financial, energy consumption, mínimum water recovery)
4. Sketch out options for treatment trains
5. Cost-benefit analysis (multidimensional analysis, economic-
environmental-social)
6. Design & Operation guidelines
7. Performance validation & verification
3. Sketch out options for treatment trains – consider redundancy &
multi-barrier approaches
Example:
• Scheme A: 1 treatment process with 4-log removal
• Scheme B: 2 independent, sequential treatment processes with 2-log removal,
total max 4-log removal
• Assume that each process has 99% reliability and fails completely 1% of time
Scheme A Scheme B
4-log removal 99% 98.01%
2-log removal - 1.98%
0-log removal 1% 0.01%
DESIGNING A TREATMENT SOLUTION
3. Sketch out options for treatment trains – consider redundancy
All risks and contaminants must be adequately addressed, some examples of
treatment trains for potable reuse can be found here:
Gerrity et al (2013), J. Wat. Supply: Res. Technol. – AQUA, 62(6) (2013) 321-338.
Some tricky questions:
• How to deal with residual water quality risk or other uncertainties?
• Multi-criteria optimization always needed, weighting in decision process may not solely
based on human health or technical criteria
• Stakeholder engagement – when and how much?
DESIGNING A TREATMENT SOLUTION
LEARNING OBJECTIVES
1. WHY ADVANCED TREATMENT?
2. CONTAMINANT PROPERTIES AND CHOICE OF TREATMENT
3. OPTIONS FOR ADVANCED TREATMENT – FATE OF MICROPOLLUTANTS
MEMBRANE FILTRATION
ADSORPTION
(ADVANCED) OXIDATION PROCESSES
4. ASSESSING AND EMBEDDING A TECHNOLOGY IN A TREATMENT TRAIN
SOME KEY PHRASES
• Opportunities for advanced treatment arise from water supply source
diversification and new internal recycle loops.
• Treatment is defined by source and required final water quality.
• Water and contaminant properties will clearly influence the choice of a treatment
train and its performance.
• Many technologies are researched, only few applied – there may be a reason
behind this ;-).
• RO/NF membranes are not simple filters – other properties than size do matter
as well.
• Adsorption is relatively energy efficient and can mitigate contamination spikes.
Contaminant hydrophobicity and charge are important.
• In oxidation consider trade-offs between oxidant strength and life-time.
• Oxidation transforms contaminants rather than removing them. This may be a
problem. Also, other byproducts may be formed (e.g. bromate).
• Consider that each treatment step is always part of a train.
• Implementation may require tricky non-technical questions to be solved.
INSTITUT CATALÀ DE RECERCA DE L’AIGUA (ICRA)
Wolfgang Gernjak ICREA Research Professor ICRA - Institut Català de Recerca de l'Aigua / Catalan Institute for Water Research Carrer Emili Grahit,101 Edifici H2O E- 17003 Girona (Spain) Tel: (+34) 972 18 33 80 Fax: (+34) 972 18 32 48 [email protected], www.icra.cat, www.icrea.cat http://orcid.org/0000-0003-3317-7710