A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Carrier-bound photocatalytic oxidation and ozonation within wastewater treatment$von Simon Mehling
The discharge of anthropogenic organic micro-pollutants into natural water cycles poses a substantial threat to ecological water quality and the safety of drinking water resources, with municipal wastewater representing a major discharge pathway. In the future, due to climate change (low dilution in water bodies, necessity to obtain service water from wastewater) and changes within the age structure of society (increase in average age and consumption of pharmaceuticals), a significant aggravation of this problem is predictable. Conventional wastewater treatment technology allows only a partial removal of specific substances in the wastewater treatment process. Likewise, for a large fraction of the pollutants (pharmaceuticals), no significant emission reduction can be implemented through avoidance. Thus, there is a need for a more advanced chemical wastewater treatment that retains a broad spectrum of pollutants. Large-scale implementations of this fourth treatment stage include oxidation via ozone and adsorption on activated carbon. Both processes have substance-specific affinities and therefore, even in combination, cannot enable non-specific advanced wastewater treatment. Ozone oxidation also leads to the formation of partlyunknown transformation products, whose toxicological properties are often unknown or partially known to be problematic. AOP allow, through a multitude of methods, the formation of hydroxyl radicals as oxidants. These highly unstable radicals exhibit increased oxidation strength compared to ozone and thus enable more non-specific advanced chemical wastewater treatment. The subject of this work is the research of photocatalytic oxidation and ozonation using surface fixed catalysts and UV-A LEDs. This process enables the formation of hydroxyl radicals by photo-excitation of the semiconductor material titanium dioxide. Due to technical innovations regarding UV-A LEDs and catalyst coating, there are new application and development opportunities for this long known process in the context of wastewater treatment. For the construction of photocatalytic reactors different approaches exist whose effectiveness and efficiency are unknown in the context of the currently discussed (German) 4th treatment stage. Furthermore, the question arises, which influence the constructive implementation of the reactor has on its photocatalytic cleaning performance and energetic efficiency. One development approach is the combination of photocatalysis and ozonation. Here, the acceptor reaction of ozone is capable of reducing the semiconductor recombination of photocatalysis, thus enabling a synergetic increase in efficiency. The practical combination of these technologies, as well as their purification performance in real-world applications, is insufficiently known and to be determined experimentally. The reaction with hydroxyl radicals allows mineralization (degradation to CO2 and mineral salts) of many known micro-pollutants. However, this requires a multiple of the treatment effort necessary for the degradation of the parent substance (current treatment target of the 4th treatment stage) of this pollutant. A further research question is which behavior the organic wastewater matrix shows through a photocatalytic treatment in the context of a 4th treatment stage, which statements on transformation products this enables and to what extent this correlates to the degradation of the parent substances.
Carrier-bound photocatalytic oxidation and ozonation within wastewater treatment$von Simon Mehling
The discharge of anthropogenic organic micro-pollutants into natural water cycles poses a substantial threat to ecological water quality and the safety of drinking water resources, with municipal wastewater representing a major discharge pathway. In the future, due to climate change (low dilution in water bodies, necessity to obtain service water from wastewater) and changes within the age structure of society (increase in average age and consumption of pharmaceuticals), a significant aggravation of this problem is predictable. Conventional wastewater treatment technology allows only a partial removal of specific substances in the wastewater treatment process. Likewise, for a large fraction of the pollutants (pharmaceuticals), no significant emission reduction can be implemented through avoidance. Thus, there is a need for a more advanced chemical wastewater treatment that retains a broad spectrum of pollutants. Large-scale implementations of this fourth treatment stage include oxidation via ozone and adsorption on activated carbon. Both processes have substance-specific affinities and therefore, even in combination, cannot enable non-specific advanced wastewater treatment. Ozone oxidation also leads to the formation of partlyunknown transformation products, whose toxicological properties are often unknown or partially known to be problematic. AOP allow, through a multitude of methods, the formation of hydroxyl radicals as oxidants. These highly unstable radicals exhibit increased oxidation strength compared to ozone and thus enable more non-specific advanced chemical wastewater treatment. The subject of this work is the research of photocatalytic oxidation and ozonation using surface fixed catalysts and UV-A LEDs. This process enables the formation of hydroxyl radicals by photo-excitation of the semiconductor material titanium dioxide. Due to technical innovations regarding UV-A LEDs and catalyst coating, there are new application and development opportunities for this long known process in the context of wastewater treatment. For the construction of photocatalytic reactors different approaches exist whose effectiveness and efficiency are unknown in the context of the currently discussed (German) 4th treatment stage. Furthermore, the question arises, which influence the constructive implementation of the reactor has on its photocatalytic cleaning performance and energetic efficiency. One development approach is the combination of photocatalysis and ozonation. Here, the acceptor reaction of ozone is capable of reducing the semiconductor recombination of photocatalysis, thus enabling a synergetic increase in efficiency. The practical combination of these technologies, as well as their purification performance in real-world applications, is insufficiently known and to be determined experimentally. The reaction with hydroxyl radicals allows mineralization (degradation to CO2 and mineral salts) of many known micro-pollutants. However, this requires a multiple of the treatment effort necessary for the degradation of the parent substance (current treatment target of the 4th treatment stage) of this pollutant. A further research question is which behavior the organic wastewater matrix shows through a photocatalytic treatment in the context of a 4th treatment stage, which statements on transformation products this enables and to what extent this correlates to the degradation of the parent substances.
Carrier-bound photocatalytic oxidation and ozonation within wastewater treatment$von Simon Mehling
Mehling, Simon (author) / Londong, Jörg (tutor) / Beier, Silvio (tutor) / Wintgens, Thomas (tutor) / Bauhaus-Universität Weimar (degree granting institution)
2023
1 Online-Ressource (166 Seiten)
5 Anhänge
Illustrationen, Diagramme
Theses
Electronic Resource
English
BKL:
56.35
Siedlungswasserwirtschaft, industrielle Wasserwirtschaft
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