Waste Water Treatment Technology-AOP

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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]

Waste Water Treatment Technology-AOP

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