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- Ozone membrane contactor for tertiary treatment of urban wastewater: Chemical, microbial and toxicological assessmentPublication . Presumido, Pedro Henrique; Ribeirinho-Soares, Sara; Montes, Rosa; Quintana, Jose B.; Rodil, Rosario; Ribeiro, Marta; Neuparth, Teresa; Santos, Miguel M.; Feliciano, Manuel; Nunes, Olga C.; Gomes, Ana I.; Vilar, Vítor J.P.A membrane ozone contactor, operated under continuous mode, was applied to promote the tertiary treatment of urban wastewater (UWW), targeting the removal of contaminants of emerging concern (CECs), bacterial disinfection, and toxicity reduction. This system relies on the homogeneous radial distribution of ozone (O3) in the reaction zone by "titration" through a microfiltration borosilicate tubular membrane, while the UWW swirls around the membrane and drags the O3 microbubbles generated in the membrane shell-side. The membrane is coated with titanium dioxide (TiO2-P25) and radiation can be externally supplied via four UV lamps. The ozonation tests were carried out with secondary-treated UWW collected in different seasons (winter and summer) and spiked with a mix of 19 CECs (10 & mu;g L-1 each). For an O3 dose of 18 g m-3, the best performance was obtained by increasing the O3 concentration (maximum [O3]G,inlet of 200 g Nm-3) and decreasing the gas flow rate (minimum QG of 0.15 Ndm3 min-1), providing the highest ozone transfer yield (88 %) and, thus higher specific ozone dose (g O3 per g dissolved organic carbon). Under these conditions, removals >80 % or concentrations below the limit of quantification were obtained for up to 13 of the 19 CECs and reductions up to 5 log units for total heterotrophs and below the limit of detection for enterobacteria and enterococci. Tests including a UVC dose of 0.10 kJ L-1 enhanced disinfection ability but had no impact on CECs oxidation. After ozonation, the abundance of antibiotic resistant bacteria was reduced but not elimi-nated , microbial regrowth after 3-day storage was observed. No toxic effect was detected on zebrafish embryos using a dilution factor of 4 for the ozonized UWW , when granular activated carbon adsorption was subsequently applied the dilution factor decreased to 2.
- Ozone membrane contactor to intensify gas/liquid mass transfer and contaminants of emerging concern oxidationPublication . Presumido, Pedro Henrique; Montes, Rosa; Quintana, Jose B.; Rodil, Rosario; Feliciano, Manuel; Li Puma, Gianluca; Gomes, Ana I.; Vilar, Vítor J.P.A tubular porous borosilicate membrane contactor was investigated for ozone gas/water mass transfer and the removal of contaminants of emerging concern (CECs) in water. Ozone gas/water contact occurs on the mem-brane shell-side, which is coated with a photocatalyst (TiO2-P25), as the ozone gas stream is fed from the lumen side and permeates through the pores generating micro-sized ozone bubbles uniformly delivered to the annular reaction zone where the contaminated water to be treated flows. Under continuous flow, water pH at 3.0 and temperature at 20 oC, the volumetric mass transfer coefficient (KLa) ranged from 3.5 to 9.0 min- 1 and improved with the increase of gas flow rate (QG, 1.5-fold from 0.15 to 1.0 Ndm3 min-1) and liquid flow rate (QL, 2.0-fold from 20 to 50 L h-1), due to enhanced turbulence on the membrane shell-side and annular zone. The mass transfer efficiency was more pronounced as the QG decreased and the QL increased, which is advantageous for large-scale applications. The main resistances to ozone transfer were in the water phase boundary layer (53-76%) and in the membrane (24-47%; kM = (1.14 +/- 0.01) x 10-4 m s-1). For an ozone dose of 12 g m- 3 and residence time of 3.9 s, removals >= 80% were achieved for 13 of 19 CECs spiked in demineralized water (each 10 mu g L-1), demonstrating the applicability of this membrane contactor for ozonation treatment. Photocatalytic ozonation (O3/UVC/TiO2) did not significantly improve the treatment performance due to the low residence time inside the contactor.