Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB
Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB
Bestimmung von Ozonübergang, Schaumverhalten und Behandlungskosten.
Bestimmung von Ozonübergang, Schaumverhalten und Behandlungskosten

Advanced Oxidation Processes (AOP)

The removal of pollutants in low concentrations, known as organic trace substances or micropollutants, is becoming an increasingly important priority in water treatment.

 

Removal of micropollutants in wastewater and process water with AOP

Oxidative water treatment (AOP, advanced oxidation processes) is understood as processes for chemical water treatment in which hydroxyl radicals are formed. These highly reactive radicals are available for chemical decomposition reactions and react with organic or inorganic substances that are not easy to break down biologically. They can be formed by adding oxidative substances such as ozone and hydrogen peroxide, or by introducing energy by means of UV radiation, ultrasound or electric current via inert electrodes as well as by a combination of these processes.

At present, catalytic, photochemical, and electrochemical processes as well as plasma processes for oxidative water treatment are investigated at Fraunhofer IGB. Various experimental set-ups for continuous, semi-continuous and batch trials are available for this purpose.

 

Advantages and application areas

AOP processes are always used when a biological decomposition is not feasible or cannot be carried out efficiently, for example because the contaminations contain persistent substances. Also, AOP processes are the method of choice when the process wastewater has a toxic effect on the microorganisms of a biological purification stage or occurs extremely discontinuously. The energy required for operating the system can be provided by electricity from renewable sources such as solar and wind power.

Batch-Reaktor zur UV-C/H2O2-Behandlung von Wasser.
Batch-Reaktor zur UV-C/H₂O₂-Behandlung von Wasser.
Bestimmung von Ozonübergang, Schaumverhalten und Behandlungskosten.
Bestimmung von Ozonübergang, Schaumverhalten und Behandlungskosten
Dipl.-Ing. Christiane Chaumette im Labor.
Dipl.-Ing. Christiane Chaumette im Labor.

Removal of trace organics and hard COD

The challenge: regulated monitoring of micropollutants in water

On a European level the process is more systematic. REACH regulation, EU-monitoring lists, regular reporting as part of the water framework directive and regular updates of the EU directives for drinking water and urban wastewater include risk evaluation and assess systems as a whole. The limit values of EU directives are then successively implemented into national legislation. The German Federal Center for Trace Substances at⁠ UBA, located in Leipzig, was founded in 2021. It connects interest groups with the goal to reduce critical substances emissions to water even faster.

Many German wastewater treatment plants are currently already planning or building an additional treatment step called the 4th stage to further reduce emissions – usually ozonation and filtration or active carbon adsorption. This is already obligatory in Switzerland and in wastewater treatment plants which indirectly feed into drinking water reservoirs.

However, the lists of substances to monitor are growing longer, as are the lists of individual substances of potential concern. Intensive research is currently being conducted into the avoidance, replacement and removal of per- and polyfluorinated substances (PFAS), which are man-made and have been proven to be detrimental to human health in some cases.

 

Fraunhofer IGB: partner for R&D and independent scientific consulting

Fraunhofer IGB offers independent scientific consulting on pollutants and trace pollutants removal to public and industrial customers. Our technicians regularly test degradation of biologically inert organic pollutants called hard COD by ozone and UVC-H2O2. Because accumulation of hard COD prevents closed water cycles in many production lines. Our engineers and scientists compare these treatment options to our customer’s respective alternatives, e.g. filtration and adsorption units.

 

Further development for reduced carbon footprint

Development and application of emerging technologies along with their critical assessment in view of environmental and economic benefits is our daily task in several research projects. These national and international cooperations of several partners are often partially supported by public funds.   

 

Plasmaoxidation, electrooxidation, 172-nm UV-irradiation and catalytic degradation induced by UVA or sunlight can remove water pollutants at concentrations of several hundred mg/l but also at trace levels of a few ng/l. This is however only useful in those cases in which pollution prevention and biological treatment are inefficient.  

We develop tailored solutions for your wastewater

Your challenges

  • Required water combustion is too expensive
  • Expensive fees for discharging persistent substances
  • High performance of AOP required
  • Process water contains persistent substances
  • Established processes require high use of chemicals, are toxic and dangerous

Our development

  • Cost-effective alternatives/cost reduction
  • Customized AOP performance
  • Solutions for persistent substances
  • Chemical-free, non-toxic, non-hazardous processes and systems

Your advantages

  • Design based on scientific expertise
  • Comprehensive technology portfolio
  • Industry-relevant proprietary data and test systems
  • Interdisciplinary team with extensive experience in process/system development
  • Modular, combinable technologies and exclusive technologies
  • Applied electrochemistry with industry-relevant implementation
  • One-stop shop

Services and collaboration

  • Testing the feasibility of AOP with your process water or wastewater
  • Evaluation of the best specific AOP process
  • Information basis for consulting
  • Decision support and recommendations for action
  • Parameters for designs
  • Performance data for designs
  • Technology transfer and system development

We would be happy to provide you with a customized offer.

Available processes and equipment

At Fraunhofer IGB, we offer a wide range of different methods and reactors for the elimination of micropollutants in wastewater in order to reduce pollutant concentrations from several hundred mg/l to just a few ng/l.

At our plants, we investigate the degradability of substances in real wastewater samples on behalf of industrial clients and develop optimized oxidative processes for treating their wastewater.

We also compare different methodological approaches according to your company's purification requirements.

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Technikumsanlage zur Entwicklung von Oxidationsprozessen (AOP) am Fraunhofer IGB
Pilot plant for the development of Advanced Oxidation Processes (AOP) at the Fraunhofer IGB.

AOP processes at Fraunhofer IGB

  • Plasma oxidation
  • Electrooxidation
  • 172 nm UV radiation
  • Photocatalysis with UV/visible light/sunlight
  • Ozone generator (up to 4 g ozone/h),
  • Ozone reactor
  • UV reactor (2 kW medium-pressure mercury lamp),
  • Ultrasonic units (25 kHz and 40 kHz; 1.7 kW)
  • Electrolysis cell (up to 50 A and 10 V) with separate anolyte and catholyte circuits (electrode surface 180 cm2 each)

 

Application areas

  • Investigation of wastewater samples from industrial wastewater/municipal wastewater using selected AOP processes on behalf of industry
  • Further development of oxidative water treatment processes
  • Cost-effective testing of treatment strategies on a pilot scale and development for large-scale industrial use
  • Determination of economic efficiency and specific energy input
  • Investigation of the degradability of substances (degradation tests)
  • Parameter screening

Oxidation reactor for the elimination of micro pollutants in waste water.
Oxidation reactor for the elimination of micro pollutants in waste water.

In municipal wastewater treatment plants, activated carbon adsorption and ozone treatment are currently the state of the art for the removal of trace substances. For industrial wastewater streams, process water and private households, a wide range of other technologies are being researched and are finding their market under the respective legal regulations and requirements.

 

Oxidative degradation on UV-activated TiO2

The oxidative degradation of micropollutants on a titanium dioxide catalyst, activated by UVA‑LEDs (light emitting diodes), has been investigated at Fraunhofer IGB on behalf of PMK Kunststoffverarbeitungs GmbH from Geisingen‑Gutmadingen and compared with advanced oxidation using hydrogen peroxide and mercury UVC emitters – a classical AOP process. For this purpose, the performance of the catalyst was demonstrated first followed by optimization of the operating parameters. Volume flow, irradiance and oxidizing additives were varied according to the statistical design of experiment. The degradation of drug residues was demonstrated at the optimized operating point.

The specific methods and the oxidation reactor of PMK Kunststoffverarbeitungs GmbH are now available at the IGB for degradation studies.

Combination and integration of oxidative and electrolytic processes

EpF-Reaktor

Oxidative and adsorptive processes such as electrophysical precipitation can be combined, 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 processes 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-optimized treatment.

Application examples

AOP processes are always used when a biological decomposition is not feasible or cannot be carried out efficiently, for example because the contaminations contain persistent substances. Also, AOP processes are the method of choice when the process wastewater has a toxic effect on the microorganisms of a biological purification stage or occurs extremely discontinuously. The energy required for operating the system can be provided by electricity from renewable sources such as solar and wind power.

 

Quantification of methylene blue degradation

A problem in the field of oxidative wastewater treatment is the formation of degradation by-products, some of which are hazardous or are not sufficiently evaluated toxicologically. However, the formation of toxic by-products can be avoided in almost all cases by choosing suitable process parameters. In order to quantify the reaction mechanisms and degradation products of various AOP methods in the AOP research facility, tests with the model substance methylene blue (C16H18Cl N3S) were carried out. In addition to the decoloration (measurement at 664 nm), the formation of by-products was observed using HPLC, coupled with UV and mass spectrometry. In a comparison of anodic oxidation, ozone treatment und UV treatment, the ozone treatment turned out to be the best method for this wastewater model.

 

Decoloration of organic dyes by UV / H2O2 and anodic oxidation

As models for real wastewater from the textile industry, a dissolved organic dye and a particulate organic dye were discolored by more than 90 percent – 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.

Reference projects