Floating immobilized TiO2 catalyst for the solar photocatalytic treatment of micro-pollutants within the secondary effluent of wastewater treatment plants

Floating immobilized spherical titanium dioxide catalysts were used to degrade micro-pollutants by solar photocatalysis. The degradation of the micro-pollutants was performed in the secondary effluent of a wastewater treatment plant. During the experimental period, the continuous measurement of the solar UV radiation intensity was performed. The micro-pollutants were degraded to an average of 55% after 9 h of irradiation. A substance-specific degradation affinity was found, whereby degradation rates varied by a factor of up to 3.5. The substance specific adsorption behavior was identified as a major limitation of the reaction performance. With an increasing influence of adsorption limitation, the degradation kinetics changed from the pseudo -first order to pseudo-zero order. A correlation between degradation rate and solar irradiance could only be found for substances with high degradation/adsorption affinity. For diclofenac, a 95% degradation rate could be achieved at a radiation dose of approximately 190 mWh/m2. The investigated technology represents a promising possibility for a minimally invasive extension of wastewater treatment plants. Possibilities of implication were estimated and discussed within this work, whereby possibilities arise for large-scale as well as decentral treatment plants.