waste water treatment technology-aop
TRANSCRIPT
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Wastewater Treatment
Technology – AOP
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Table of Contents Cinkarna Celje and green technologies ................................................................................................... 4
Ultrafine titanium dioxide as water treatment catalyst.......................................................................... 4
Magnetic photocatalyst (MP).................................................................................................................. 5
The efficiency of the MP in comparison to other photocatalysts........................................................... 5
Wastewater treatment technology using MPs ....................................................................................... 6
Wastewater treatment ....................................................................................................................... 6
Retrieving and re‐using MPs ............................................................................................................... 6
Development approach to the custom‐made solution for the user................................................... 6
MP technology advantages in comparison to other AOP technologies ............................................. 7
MP technology limitations .................................................................................................................. 8
General information concerning photocatalysis – MP energy source.................................................... 8
AOP globally – overview.......................................................................................................................... 9
Existing AOP technologies ..................................................................................................................... 10
References............................................................................................................................................. 10
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Magnetni fotokatalizator (MF) Z razvojem lastnega produkta smo združili več pozitivnih lastnosti zgoraj naštetih metod v prid čim več ji
učinkovitosti in enostavnosti čiščenja onesnaženih vod. Magnetni fotokatalizator (MF) izkorišča
fotokatalitične lastnosti titanovega dioksida za razgradnjo onesnažil ter magnetne lastnosti nosilca za
recikliranje materiala. Za pripravo magnetnega fotokatalizatorja uporabljamo lasten ultrafini titanov
dioksid, tip CCA 100 AS.
Učinkovitost MF v primerjavi z drugimi fotokatalizatorji
Za določevanje fotokatalitske učinkovitosti uporabljamo v Cinkarni Celje interno metodo razgradnje
mravljinčne kisline. Na spodnjem grafu so prikazane učinkovitosti različnih vzorcev (MF, suspenzije in
nanosi na steklu lastnih ter konkurenčnih proizvodov) kot sprememba konverzije v časovni enoti.
Graf 1: Hitrost razgradnje vzorcev TiO2 v suspenziji in na trdnih nosilcih ter MF v suspenziji.
Najnižjo aktivnost izkazujeta vzorca, ki sta nanesena na trdnih nosilcih (CCA 100 AS na ploščah in konkurenčni vzorec na ploščah). Pri teh vzorcih je aktivna površina dosti manjša, kot v primeru
suspendiranih nanodelcev. Temu primerno je aktivnost mnogo nižja, vendar je njihovo odstranjevanje po
čiščenju enostavno. Suspenzije lastnih in konkurenčnih proizvodov izkazujejo primerljivo aktivnost,
najhitrejšo razgradnjo mravljinčne kisline pa smo dosegli z magnetnim fotokatalizatorjem.
Photocatalyc HCOOH degradaon
[H]/[Ho]
Time
CCA 100 AS
1
0,8
0,6
0,4
0,2
0
0 2 4 6
CCA 200 BS
MF CC 2.4.2013
CCA 100 AS on plates
Competng sample
in a suspension
Competng sample
on plates
Magnetic
photocatalyst
(MP)
By developing our own product, we combined numerous positive features of the methods that were
listed above in order to benefit the maximum efficiency and simplicity of wastewater treatment. A
magnetic
photocatalyst
(MP)
uses
the
photocatalytic
properties
of
titanium
dioxide
to
disintegrate
pollutants
and
the
magnetic
properties
of
the
carrier
to
recycle
material.
The
ultrafine
titanium
dioxide, CCA 100 AS, which is used for preparing the magnetic photocatalyst (MP), is also Cinkarna
Celje’s
own
product.
The efficiency of the MP in comparison to other
photocatalysts
At Cinkarna Celje, we have been using our own method for decomposing formic acid in order to
determine the efficiency of the photocatalyst. The diagram below shows the efficiency of various
samples (MP, the suspension, and the deposits on the glass of our products and competing products)
as the change of the conversion in a certain time period.
Diagram
1:
degradation
speed
of
TiO2 samples in a suspension and on solid carriers as well as MP in a
suspension
The lowest activities are noticed in the samples that were applied on the solid carriers (CCA 100 AS
on
plates
and
the
competing
product
on
plates).
In
these
samples,
the
active
surface
is
much
smaller
than
in
suspended
nano
particles
and
the
activity
levels
are
corresponding.
However,
their
removal
is
simple. The activity of the suspensions of our own products and the competing products are
comparable. The fastest degradation of formic acid was achieved with a magnetic photocatalyst.
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Wastewater treatment technology using MPs The treatment technology includes two main stages:
1. Wastewater treatment,
2. Retrieving and re‐using MPs.
Wastewater treatment The catalyst, the amount of which is determined beforehand by a lab device (the concentrations tend
to range between 20 and 250 mg/L), is dispersed in the water that we wish to treat. A pump then
moves the water including the suspended MP particles through a UV reactor (see Figure 1) where the
pollutant degradation takes place. The residence time changes according to the water pollution level,
pollutant type, and required treatment level.
The residence time is determined according to the type of the water pollutant – the degradation
level is measured as the change of COD and BOD5 values. In the event of more complex pollutants,
more complex
analytical
methods
are
applied
that
help
us
precisely
determine
the
concentration
of
the selected pollutant.
Figure 1: Depiction of treatment plant operation
Retrieving and re-using MPs The catalyst is prepared in the form of a water suspension which is added to wastewater. After the
reaction is concluded, the treated water with the MP is led through a magnetic separator (MS). The
separation is
performed
on
the
basis
of
magnetism
and
does
not
require
an
additional
energy
source.
After the separation process is concluded, the catalyst remains in the separator. The treated water is
pumped out of the system (Figure 2) and replaced with new wastewater that first needs to circulate
through the separator to collect the catalyst particles. The treatment and recycling stages are then
interchanged until all of the water that is brought to the system is treated.
Development approach to the custom-made solution for the user The vision of the company is to use its own high‐tech products with the purpose of reducing harmful
substances in the environment. The development of the wastewater treatment application using a
magnetic photocatalyst requires a solution custom‐made for the buyers because the application
Treatment cycle description:
1. Polluted water is put into the mixer
reactor,
2. the catalyst is added to the polluted
water,
3. the water with the catalyst circulates
through the
UV
reactor,
4.
the treated water flows out through
the magnetic separator,
5. the catalyst is recycled.
UV
reactor
Mixer
reactor
Magnetic
separator
Polluted water inflow
Treated water
outflow
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depends
on
the
water
pollutant
type.
There
is
a
pilot
device
set
up
at
the
company
which
demonstrates
the
treatment
technology
using
various
types
of
wastewater.
Table
1:
The
level
of
the
degradation
of
industrial
wastewater
sample
with
a
magnetic
photocatalyst.
54.21
–
23
Jan
2012
BOD5
COD mg/L
O2
mg/L O2 27
165
UV 0,1 TiO2 – 24 Jan 2012 BOD
COD
mg/L O2
mg/L
O2
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- MP particles are dispersed in polluted water and thus have a significantly larger specific
surface in comparison with catalysts that are fixed on reactor or carrier surfaces,
- during the treatment reaction, no substances need to be added to enable the pollutant
degradation reaction,
- in order to function, the technology only uses UV energy and MPs,
- the catalyst is recycled following each treatment cycle,
- MPs
cause
the
degradation
of
a wide
range
of
organic
pollutants
(hormone
disruptors,
pesticides, antibiotics, carbohydrates, phenols, bacteria, algae, etc.),
- MPs degrades microorganisms and not merely deactivates their reproduction,
- the catalyst is not harmful to the environment and people.
MP
technology
limitations
- the water pH value needs to be between 3 and 9,
- the water may not include any non‐dissolved pollutants1,
- the oxygen concentration in the water needs to be as close as possible to saturated
concentration,
- water
temperature
may
not
be
higher
than
45
°C,
- this technology is more suitable for lower concentration pollution, except in the case of
specific pollutants where the highest efficiency level is achieved.
General
information
concerning
photocatalysis
–
MP
energy
source
The term photocatalysis denotes types of reactions that take place in the presence of light and a
catalyst. Ultrafine titanium dioxide needs a UV light source for its functioning. This light then induces
the process of charge separation in material a – TiO2 is a semi‐conductor that becomes charged
under the influence of UV light with specific energy.
The electrons and electron holes that are created due to the migration of electrons contribute to the
creation of active radicals. On the surface of the catalyst, the electrons and electron holes react with
oxygen and water molecules. The products of this reaction are hydroxyl and superoxide radicals that
trigger the degradation of pollutants in water [2].
Oxidant
Oxidation
Potential
(eV)
•OH
O3
H2O2
Hydroperoxyl Radicals
Permanganate
Chlorine Dioxide
Chlorine
O2
2.80
2.07
1.77
1.70
1.67
1.50
1.36
1.23
Table 2: The comparison of oxidation potential values of individual oxidants [3].
1 In the event of non‐dissolved substances, preliminary filtration is required.
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AOP globally – overview The technology of advanced oxidation methods has been known in the world for approximately 20
years. Nowadays, mainly the combination of UV light and an oxidation agent is used for wastewater
treatment, and not so much any individual methods.
Photocatalysis with titanium dioxide is an AOP wastewater treatment method that requires a UV
light source
for
its
functioning.
In
addition
to
the
strength
of
the
UV
light
source,
the
lifespan
of
UV
light bulbs is also very important from the technoeceonomic point of view. In practice, this lifespan is
12 to 18 months if used 24/7. Equipment costs are calculated on the basis of the amount of
wastewater and the desired effect of the degradation of the pollutant (power input).
The largest users of UV equipment are municipal treatment plants that need UV light for tertiary
treatment (systems with a flow rate of a few hundred m3/min). The MP technology is an upgrade of
the UV water treatment/preparation system that combines the removal of microorganisms and the
degradation of toxic substances which may not be degraded using standard methods or the removal
of which is not economically viable. The use of MP treatment technology also makes sense for users
who already have set‐up UV disinfection/wastewater treatment systems because it reduces the
residence time
(saves
energy)
or
increases
the
level
of
treatment,
even
up
to
40
percent2.
However,
the main advantage that the use of the MP technology has over other technologies is that the use of
MPs does not require the addition of chemicals or other substances in order to achieve the desired
treatment effect.
The largest AOP water treatment systems are currently in the USA (the removal of NDMA, 1,4‐
dioxane) where treatment costs are already approximately 0.01 EUR/m3 of wastewater [5].
2 The percentage of the increased treatment effect depends on the type of water.
Conduction band
Electron
excitation
Valence band
Photon
absorption
OXIDATION
REDUCTION
UV
photon
Figure 3: Depiction of the photocatalysis process on TiO2 nano particle 4.
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The application for ballast water treatment is also very interesting. In the future, this application will
be required by law. There are systems on the market that provide the removal of all microorganisms
with the help of TiO2 UV technology [6].
This application is also suitable in the field of providing drinking water. Within the projects of the
European research inititative Seventh Framework Programme, the photocatalytic removal of various
pollutants that
affect
the
end
quality
of
drinking
water
is
being
tested
[7].
Existing
AOP
technologies
AOP or advanced oxidation processes consist of a dozen pollutant removal technologies, in which
hydroxyl radicals serve as the active medium. The methods are separated according to the source of
the formation of OH* radicals [8]:
- TiO2 photocatalysis,
- ozonization,
- UV disinfection,
- UV wastewater treatment,
- the
application
of
hydrogen
peroxide
(H2O2),
- Fenton/Photo‐Fenton reaction,
- various combinations of the above methods.
References
[1] Mohajerani M, Mehrvar M., Ein‐Mozaffari F. An overview of the integration of advanced oxidation
technologies and other processes for water and wastewater treatment. International journal of
Engineering 3, 120 (2009).
[2] Chong M. N., Jin B., Chow C., Saint C. Recent developments in photocatalytic water treatment
technology: A
review.
Water
research 44,
2997
(2010).
[3] Sharma S., Ruparelia J.P., Patel M.L. A general review on advanced oxidation processes for waste
water treatment. International conference on current trends in technology , Nuicone (2011)
[4] http://projekti.gimvic.org/2009/2a/kataliza/fotokataliza_teorija.html (6 June 2013).
[5] Kaneko M., Okura E. Photocatalysis Science and Technology . Springer, Japan, 2002.
[6] Matheickal J., Raaymakers S. 2nd
International ballast water treatment R&D symposium.
Globallast monograph series 15 (2003).
[7] http://www.observatorynano.eu/project/ (6 June 2013).
[8] Kommineni, S. et. al. 3.0 Advanced Oxidation Processes. http://www.nwri‐
usa.org/pdfs/TTChapter3AOPs.pdf (11 June 2013).
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Contact:
Peter Bastl M.Sci.
Product sales manager
tel.: 00386 3/427 - 6083
gsm: 00386 41/271 - 615
e-mail: [email protected]
Aljaž Selišnik
Research and development
tel.: 00386 3/427 - 6087
fax.: 00386 3/427 - 6116
e-mail: [email protected]