Photocatalytic ozonation of urban wastewater and surface water using immobilized TiO2 with LEDs: Micropollutants, antibiotic resistance genes and estrogenic activity

Abstract

Photocatalytic ozonation was employed for the first time in continuous mode with TiO2-coated glass Raschig rings and light emitting diodes (LEDs) to treat urban wastewater as well as surface water collected from the supply area of a drinking water treatment plant (DWTP). Different levels of contamination and types of contaminants were considered in this work, including chemical priority substances (PSs) and contaminants of emerging concern (CECs), as well as potential human opportunistic antibiotic resistant bacteria and their genes (ARB&ARG). Photocatalytic ozonation was more effective than single ozonation (or even than TiO2 catalytic ozonation) in the degradation of typical reaction by-products (such as oxalic acid), and more effective than photocatalysis to remove the parent micropollutants determined in urban wastewater. In fact, only fluoxetine, clarithromycin, erythromycin and 17-alpha-ethinylestradiol (EE2) were detected after photocatalytic ozonation, by using solid-phase extraction (SPE) pre-concentration and LC-MS/MS analysis. In surface water, this treatment allowed the removal of all determined micropollutants to levels below the limit of detection (0.01-0.20 ng L(-1)). The efficiency of this process was then assessed based on the capacity to remove different groups of cultivable microorganisms and housekeeping (16S rRNA) and antibiotic resistance or related genes (intI1, blaTEM, qnrS, sul1). Photocatalytic ozonation was observed to efficiently remove microorganisms and ARGs. Although after storage total heterotrophic and ARB (to ciprofloxacin, gentamicin, meropenem), fungi, and the genes 16S rRNA and intI1, increased to values close to the pre-treatment levels, the ARGs (blaTEM, qnrS and sul1) were reduced to levels below/close to the quantification limit even after 3-days storage of treated surface water or wastewater. Yeast estrogen screen (YES), thiazolyl blue tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) assays were also performed before and after photocatalytic ozonation to evaluate the potential estrogenic activity, the cellular metabolic activity and the cell viability. Compounds with estrogenic effects and significant differences concerning cell viability were not observed in any case. A slight cytotoxicity was only detected for Caco-2 and hCMEC/D3 cell lines after treatment of the urban wastewater, but not for L929 fibroblasts.

Mined pyrite and chalcopyrite as catalysts for spontaneous acidic pH adjustment in Fenton and LED photo‐Fenton‐like processes

“…The amount of H 2 O 2 formed spontaneously seems to be more appropriate for the degradation of organic micropollutants appearing in effluents at much lower concentrations, for instance at ng L ‐1 level in effluents from conventional urban wastewater treatment plants (WWTPs) . In the case of OMW treatment, H 2 O 2 should be supplied in significantly larger amounts due to the much higher organic content in these effluents typically (up to 200 g L ‐1 ), in comparison with effluents from urban WWTPs (10–25 mg L ‐1 ) …”

“…TY is one of the main compounds (0.5–25 g L ‐1 ) present in the polyphenolic fraction of OMW . LEDs offer advantages over conventional lamps, such as long life and low energy consumption . The influence of typical operating variables, such as initial H 2 O 2 and TY concentrations, were examined considering the total organic carbon (TOC) abatement, the H 2 O 2 conversion () and the iron leached to the solution.…”

Effect of Noble Metals (Ag, Pd, Pt) Loading over the Efficiency of TiO2 during Photocatalytic Ozonation on the Toxicity of Parabens

“…The photocatalytic ozonation using TiO 2 under LED irradiation was used for removal micropollutants from urban wastewater with high efficiency [9]. The band gap is 3.2 eV for anatase TiO 2 (λ < 387 nm), therefore, for exciting an electron from the valence band to the conduction band, UV-light is required [10].…”

Ozonation inactivation of Escherichia coli in aqueous solution over MgO nanocrystals: modelling and mechanism

“…Despite the use of HCOP for the degradation of organic pollutants being common practice, their use in water disinfection is rare. Up to now, only TiO 2 and Ag‐TiO 2 mediated catalytic ozonation processes have been reported for the inactivation of microorganisms, and only used as a control experiment to compare with photocatalytic ozonation . It is noted that without light irradiation, TiO 2 and Ag‐TiO 2 show poor catalytic activities towards the inactivation of microorganisms.…”