Overcoming limitations in photochemical UVC/H2O2 systems using a mili-photoreactor (NETmix): Oxytetracycline oxidation

Jonathan C Espíndola; Raquel O Cristóvão; Diego A Mayer; Rui A R Boaventura; Madalena M Dias; José Carlos B Lopes; Vítor J P Vilar

doi:10.1016/j.scitotenv.2019.01.012

Overcoming limitations in photochemical UVC/H₂O₂ systems using a mili-photoreactor (NETmix): Oxytetracycline oxidation

Sci Total Environ. 2019 Apr 10:660:982-992. doi: 10.1016/j.scitotenv.2019.01.012. Epub 2019 Jan 6.

Authors

Jonathan C Espíndola¹, Raquel O Cristóvão², Diego A Mayer³, Rui A R Boaventura⁴, Madalena M Dias⁴, José Carlos B Lopes⁴, Vítor J P Vilar⁵

Affiliations

¹ Laboratory of Separation and Reaction Engineering, Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal; CNPq - National Council for Scientific and Technological Development, Brazil.
² Laboratory of Separation and Reaction Engineering, Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. Electronic address: raquel.cristovao@fe.up.pt.
³ Laboratório de Transferência de Massa e Simulação Numérica de Sistemas Químicos, Federal University of Santa Catarina, PO Box 476, CEP, 88040-900 Florianópolis, SC, Brazil.
⁴ Laboratory of Separation and Reaction Engineering, Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
⁵ Laboratory of Separation and Reaction Engineering, Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. Electronic address: vilar@fe.up.pt.

PMID: 30743982
DOI: 10.1016/j.scitotenv.2019.01.012

Abstract

This study focuses on the intensification of a photochemical UVC/H₂O₂ system using a mili-photoreactor (NETmix) for a better and faster elimination of oxytetracycline (OTC) from urban wastewater. This mili-photoreactor comprises a network of small cylindrical chambers and prismatic transport channels sealed by a UVC transparent quartz slab allowing unique properties. Since light has a profound effect on the photochemical process, UVC photons distribution over the reaction medium was investigated using a multiple UVC lamp design (4, 6 or 11 W) allocated in parallel or perpendicular to the solution movement. In addition, the effect of other operating variables, such as oxidant dosage (100-900 mg L^-1), oxidant feed configuration (single entry or continuous multi-injection) and flow rate (50-100 L h^-1) was studied. A kinetic model able to describe the OTC oxidation by the UVC/H₂O₂ photochemical system in the mili-photoreactor was also developed. Moreover, matrix effect was evaluated by spiking OTC in a secondary effluent from an urban WWTP. In this case, OTC degradation was inhibited in about 2 to 3 times due to the presence of organic/inorganic substances (soluble and particulate), inherent to the real matrix, that act as scavenger of oxidant species and as UVC light filter. The NETmix mili-photoreactor presented high photochemical space time yield (PSTY) values when compared with a conventional tubular photoreactor. This highlights the NETmix capacity to enhance UVC/H₂O₂ processes through an homogeneous light distribution over the entire reaction medium.

Keywords: NETmix photoreactor; Oxytetracycline oxidation; Process intensification; UVC/H(2)O(2) photochemical process; Urban wastewater.