Process water treatment by oxidative and electrolytic Processes · 2020-06-12 · 3 aoP –...
Transcript of Process water treatment by oxidative and electrolytic Processes · 2020-06-12 · 3 aoP –...
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F r a u n h o F E r I n s t I t u t E F o r I n t E r F a C I a l E n G I n E E r I n G a n d B I o t E C h n o l o G y I G B
Process water treatment by oxidative and electrolytic Processes
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the Challenge
Nowadays, the recirculation of water in industrial production
processes is recognized as a necessity. In order to re-use wa-
ter sensibly, the undesired substances that build up have to
be removed with as little expenditure of time and money as
possible. With the development of new products and materi-
als as well as the introduction of new production methods
and techniques, new issues arise for the treatment of the re-
spective process waters. Examples of this problem:
New complex dyestuffs, pesticides, tensides and
pharmaceuticals
The use of nanoparticles
Varying wastewater contamination resulting from rapid
product change
There are new challenges concerning the treatment of raw
water as well. The pollution of the past now affects natural
water sources, surface waters, and groundwater.
The build-up of pesticides and pharmaceuticals in rivers,
lakes, and groundwater is an example of this. Systematically
detecting these micropollutants and their decomposition and
reaction products has only recently become possible with im-
proved methods of analysis.
In many cases the currently established processes and systems
cannot do the job without adaptation and support from new,
selective systems. The Fraunhofer IGB has recognized this ne-
cessity and is working on the improvement of existing pro-
cesses such as adsorption, filtration, flocculation/precipitation,
electrodialysis, homogenization and disinfection as well as on
new approaches in process and unit operations. The use of
oxidative and electrolytic processes for water treatment is one
of our main fields of research. Together with industrial part-
ners, new concepts and technologies are being developed at
the Fraunhofer IGB up to industrial scale. Water treatment and
the circulation of process water can thus be carried out eco-
nomically and sustainably.
In numerous production processes water is used as a solvent or means of conveyance, as cooling water or washing water. In-
creasing costs for the purification and disposal of wastewater, regional or seasonal shortage of water, and a growing awareness
of environmental issues within companies have increased water recycling. Water is used several times and impurities have to be
removed selectively.
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aoP – advanced oxidation Processes
Oxidative water treatment (AOP, advanced oxidation process-
es) is understood as processes for chemical treatment in
which hydroxyl radicals are formed. These highly reactive radi-
cals are available for chemical decomposition reactions and
also react with organic or inorganic substances that are not
easy to break down biologically. They can be formed by add-
ing oxidative substances such as ozone (O3) and hydrogen
peroxide (H2O2), or by introducing energy by means of UV ra-
diation, ultrasound or electric current via inert electrodes as
well as by a combination of these processes.
At present, catalytic, photochemical, and electrochemical pro-
cesses as well as plasma processes for oxidative water treat-
ment are investigated at the Fraunhofer IGB. Various experi-
mental set-ups for continuous, semi-continuous and batch
trials are available for this purpose. Among other equipment,
the Fraunhofer IGB has an AOP plant, with which all the well-
established processes can be tested individually or in combina-
tion. Due to comprehensive sensing and automation, the test
parameters can be adapted and varied automatically.
oxidative and electrolytic Processes
advanced oxidation Processes and technologies: technologies: taoPs, aotsaotsaot
Photochemical processes Super critical water
oxidation (SUWOX)
Electron beamirradiation
Sonolysis
Non-thermal plasma processes
Electrochemicalprocesses
Catalytic processes
Solar processesphotocatalysis
X-ray irradiation
Gamma-Radiolysis
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1 Pilot plant for the development of Advanced Oxidation
Processes (AOP) at the Fraunhofer IGB.
2 Oxidation processes for water treatment.
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Electro-physical precipitation
Another process established at the Fraunhofer IGB is electro-
physical precipitation (EpF). Here the water to be treated is
passed through a reactor, in which an electric current flows
through sacrificial electrodes. This results in electrochemical
reactions; the sacrificial electrodes dissolve, releasing their
metal ions. Besides reactive radicals (AOP process), metal hy-
droxide flocs are produced in the process. These electrolyti-
cally generated metal hydroxide flocs have a high adsorption
capability and can thus bind to finely dispersed particles. In
addition, there are coprecipitation and occlusion precipitation
reactions, in which dissolved organic and inorganic substanc-
es are precipitated. The precipitated substances can then be
separated mechanically.
Electro-physical precipitation replaces conventional chemical
flocculation techniques with the advantage that the floccu-
lants are made available electrolytically from solid state elec-
trodes where they are required in dissolved molecular form.
Iron or aluminium can be used as electrode material; these
are inexpensive, readily available, and easy to handle. The
metal ion is specifically added only to the water to be treated;
an increase in the salt content does not occur. Using this pro-
cess there are no costs for the purchase, handling, and dis-
persal of flocculants and flocculating additives.
The Fraunhofer IGB has an extensive range of laboratory and
pilot plant equipment with plants of up to 500 l/h flow rate.
We can therefore treat greatly differing volumes of process
water – from general feasibility studies to continuous extend-
ed-time trials. Optimal infrastructure at the Fraunhofer IGB en-
ables quick analysis of water samples as well as quick process
adaptation to varying requirements.
Combination and integration of oxidative and
electrolytic processes
Oxidative and adsorptive processes such as EpF can be com-
bined, depending on the problems to be solved. By doing this,
results can be achieved that exceed the sum of the results of
the individual processes. A further advantage of these pro-
cesses is that they are suited to standby operation and can be
switched on or off at any time. Integration into existing plants
and automation including autonomous operation or remote
control are feasible without any problems. Continuous online
logging of organic carbon (TOC, total organic carbon) can be
effected, enabling requirement-based and thus energy-opti-
mized treatment.
However, not only oxidative and adsorptive processes can be
combined advantageously. The combination with aerobic
and anaerobic biological treatment stages can also be real-
ized at the Fraunhofer IGB in laboratory scale and pilot plant
demonstrations.
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In general, electrolytic and oxidative processes have the
following advantages:
Complete mineralization of pollutants possible
No increase in salinity, which enables recirculation
Less handling of hazardous chemical agents
No disinfection by-products – in particular no halogenated
compounds
Little or no sludge formed
Hygienic outflow water
Robust process – discharge criteria can be met reliably
Available quickly – standby operation possible
Suitable for varying quantities and qualities of wastewater
Staff savings and increased reliability
Electrolytic and oxidative processes offer economically attrac-Electrolytic and oxidative processes offer economically attrac-Electrolytic and oxidative processes offer economically attrac
tive and sustainable solutions for the purification of industrial,
process waters, and wastewaters. They are a good alternative
for substances that cannot be broken down conventionally or
that are only degradable at great expense.
With oxidative and electrolytic processes, it is possible to oxi-
dize dissolved contaminants or pollutants that are difficult to
break down. Pollutants are either directly oxidized or precipi-
tated by way of hydroxide flocs. Electrogenerated hydroxide
flocs are extremely well suited for removing the finest particle
contaminants. The proposed oxidative and electrolytic pro-
cesses do not increase water salinity, and the maintenance re-
quired is minimal. By process combination full treatment can
be guaranteed even for varying pollutant load.
Electrolytic and oxidative processes can be integrated advan-
tageously in a treatment chain with biological processes, for
example to remove substances that cannot be broken down
biologically. Furthermore, oxidative methods are effective in
treating toxic, carcinogenic, or mutagenic (TCM) substances,
pharmaceuticals, and hormonally active substances.
advantages
1 Electrolytically generated iron hydroxide. Removal of particle
contaminants by means of an electro-physical process.
2 Continuously operating reactor for the removal of color particles
from 5 m3/h process wastewater.
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Halving the treatment costs for paper mill wastewater
by means of electro-physical precipitation
For a paper manufacturer we optimized an existing process
water treatment plant by increasing its capacity. We replaced
conventional flocculation with a plant using the principle of
electro-physical precipitation. Savings on chemicals, floccu-
lants, polyelectrolytes, and sodium hydroxide reduced the
treatment cost by half.
Removal of finely suspended substances from paint
wastewater by electro-physical precipitation
In a feasibility study for an aircraft manufacturer we success-
fully treated paint wastewater from the painting systems by
means of electro-physical precipitation. The turbidity of the
wastewater was reduced by 95 % and the chemical oxygen
demand (COD) by 75 %. Similar studies were carried out for
paint manufacturers. Here too, we were able to show that it
is possible to reduce the turbidity, the COD, and the smell
significantly.
Decoloration of organic dyes by UV / H2O2 and anodic
oxidation using iridium oxide electrodes
As models for real wastewater from the textile industry, a dis-
solved organic dye and a particulate organic dye were discol-
ored by more than 90 % – until the liquids were transparent
to the human eye. The study also served to determine the
most energy-efficient process parameters and compared the
decomposition products produced by each method.
Reduction of the biological contamination of cooling
lubricant with ultrasound / ozone
In a publicly funded project we investigated whether the effi-
cient reduction of microbial contamination in cooling lubricant
emulsions can be achieved by means of ultrasound or ultra-
sound in combination with specific AOP processes. Depending
on the type and concentration of the microbial contamination
we were able to achieve a sustained reduction, without im-
pairing the quality of the cooling lubricant.
Electrolytic ozone production on laboratory and
pilot plant scale
We have investigated electrolytic ozone production on the
laboratory and pilot plant scale. Ozone was produced using
boron-doped diamond electrodes in divided and undivided
cells. Cell geometry, electrode materials and shapes, solid
electrolyte and connecting material, as well as the operational
parameters were optimized in cooperation with our industrial
partners. Up to 5 g ozone/h and up to 22 vol% ozone can be
produced in the gas phase.
aPPlications and references
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Further projects
In a number of publicly funded projects, we are developing
technologies, components, and systems for specific water
treatment tasks in co-operation with our European project
partners.
A good example is our development of a new type of high-
performance UV light source for the sterilization of water. It
was effected in co-operation with a European industrial part-
ner. The UV light in this application is emitted by a plasma,
which is stimulated by microwaves. Unlike conventional mer-
cury discharge lamps, the resulting UV light has a broad
range of different wavelengths. The UV-spectrum was tai-
lored to reach maximal germicidal effect.
In another project funded by the EU we are developing, to-
gether with the consortium, a new type of AOP-system to
break down complex organic pollutants in wastewater into
harmless compounds. This goal is reached by using multi-
chromatic UV light without adding any chemicals.
For the production of ozone we have developed an electro-
chemical cell, with which ozone can be generated efficiently
and inexpensively for environmentally compatible disinfection.
The Fraunhofer Institute for Interfacial Engineering and Bio-
technology IGB develops and optimizes processes and plants
for water treatment and adapts these to the requirements of
industrial practice. The services provided include:
Scientific assessment, technical advice, studies on electro-
lytic and oxidative processes for water treatment
Market and technology studies for process water treatment
Comprehensive chemical and physical analyses to charac-
terize process water
Laboratory plants for customized pre-trials relating to floc-
culation and oxidation characteristics of the process water
Pilot plants for:
Electro-physical precipitation
Ozone + / - hydrogen peroxide + / - catalysts
UV irradiation
Ultrasound
Anodic oxidation (direct / indirect), cathode reactions
Mobile prototype plants for on-site studies and trials
Development of plant technology including automation
and scaling up to industrial size in cooperation with indus-
trial partners
Process optimization for the treatment of water as well as
viscous media, such as cooling lubricants, foodstuffs, slud-
ges, and pastes
Integrated solutions by means of combination with aerobic
and anaerobic biological processes
Combination with processes for desalination or the recov-
ery of acids and bases
services Provided
Fraunhofer Institute for
Interfacial Engineering
and Biotechnology IGB
(Fraunhofer-Institut für
Grenzflächen- und
Bioverfahrenstechnik IGB)
Nobelstrasse 12
70569 Stuttgart
Germany
Phone +49 711 970-4401
Fax +49 711 970-4200
Director
Prof. Dr. Thomas Hirth
Phone +49 711 970-4400
www.igb.fraunhofer.de
Fraunhofer IGB brief profile
The Fraunhofer IGB develops and optimizes processes and products in the fields of medicine,
pharmacy, chemistry, the environment and energy. We combine the highest scientific quality
with professional expertise in our fields of competence – Interfacial Engineering and Materials
Science, Molecular Biotechnology, Physical Process Technology, Environmental Biotechnology
and Bioprocess Engineering, as well as Cell and Tissue Engineering – always with a view to eco-
nomic efficiency and sustainability. Our strength lies in offering complete solutions from labo-
ratory scale to pilot plant. Customers benefit from the constructive cooperation of the various
disciplines at our institute, which is opening up novel approaches in fields such as medical en-
gineering, nanotechnology, industrial biotechnology, and wastewater purification. The Fraun-
hofer IGB is one of more than 80 research units of the Fraunhofer-Gesellschaft, Europe’s larg-
est organization for application-oriented research.
www.igb.fraunhofer.de
Contact
Dipl.-Ing. Christiane Chaumette
Phone +49 711 970-4131
Alexander Karos, M. Sc.
Phone +49 711 970-3564
Dipl.-Ing. Siegfried Egner
Head of Department
Physical Process Technology
Phone +49 711 970-3643