This study aimed to optimize two oxidation processes for wastewater reuse of an urban wastewater treatment plant (UWWTP) effluent intended for human consumption. Ozonation and TiO2 photocatalytic oxidation (PCO) processes were compared for their effectiveness in terms of organic matter degradation (measured as UV absorbance at 254 nm, UV254), disinfection by products formation (measured as trihalomethanes formation potential, THMFP), and ecotoxicity (evaluated by Daphnia magna and Lepidium sativum), on secondary treated wastewater collected from a UWWTP in the province of Salerno (southern Italy). Accordingly, ozonation experiments using 28 mg/L ozone dose and PCO experiments using 250W lamp (emission range: 315–400 nm; emission peak: 14.7 lW/cm2 at 340 nm) and varying TiO2 dose from 1 to 3 g/L were carried out. Ozonation (t1/2 = 71.6 min) was not found as effective as PCO for organic matter degradation at all TiO2 doses, and 3 g/L of TiO2 was found to be the most effective photocatalyst loading (t1/2 = 41.8 min). Moreover, PCO-treated samples resulted in a lower THMFP compared to ozonation process. While ozonation did not increase toxicity to D. magna severely (10% of immobilization), PCO-treated samples exhibited varying toxicity end-points possibly due to formed oxidation intermediate products. However, Cl2 disinfection of treated wastewater samples played an improving role in toxicity of PCO-treated samples. In particular, in 30 min oxidized samples, toxicity to D. magna was decreased up to 50% (from 40 to 20% of immobilization) while germination index of L. sativum, a phytotoxicity test used for irrigation quality testing purpose, improved at 30% after Cl2 disinfection in 3 g/L of TiO2 treated sample.
A comparative evaluation of ozonation and heterogeneous photocatalytic oxidation processes for reuse of secondary treated urban wastewater
RIZZO, Luigi;BELGIORNO, Vincenzo
2014-01-01
Abstract
This study aimed to optimize two oxidation processes for wastewater reuse of an urban wastewater treatment plant (UWWTP) effluent intended for human consumption. Ozonation and TiO2 photocatalytic oxidation (PCO) processes were compared for their effectiveness in terms of organic matter degradation (measured as UV absorbance at 254 nm, UV254), disinfection by products formation (measured as trihalomethanes formation potential, THMFP), and ecotoxicity (evaluated by Daphnia magna and Lepidium sativum), on secondary treated wastewater collected from a UWWTP in the province of Salerno (southern Italy). Accordingly, ozonation experiments using 28 mg/L ozone dose and PCO experiments using 250W lamp (emission range: 315–400 nm; emission peak: 14.7 lW/cm2 at 340 nm) and varying TiO2 dose from 1 to 3 g/L were carried out. Ozonation (t1/2 = 71.6 min) was not found as effective as PCO for organic matter degradation at all TiO2 doses, and 3 g/L of TiO2 was found to be the most effective photocatalyst loading (t1/2 = 41.8 min). Moreover, PCO-treated samples resulted in a lower THMFP compared to ozonation process. While ozonation did not increase toxicity to D. magna severely (10% of immobilization), PCO-treated samples exhibited varying toxicity end-points possibly due to formed oxidation intermediate products. However, Cl2 disinfection of treated wastewater samples played an improving role in toxicity of PCO-treated samples. In particular, in 30 min oxidized samples, toxicity to D. magna was decreased up to 50% (from 40 to 20% of immobilization) while germination index of L. sativum, a phytotoxicity test used for irrigation quality testing purpose, improved at 30% after Cl2 disinfection in 3 g/L of TiO2 treated sample.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
