Performance evaluation of catalytic ozonation using iron shavings and iron shavings\activated carbon mixture for removal of sulfamethoxazole from aqueous solutions

Abstract

Background: Antibiotics are among resistant organic compounds and commonly, cannot be eliminated by conventional wastewater treatment processes. Then, concentrations are often found at nano to micro grams per liter in water resources. In recent years, use of advanced oxidation processes for decomposition and mineralization of resistant organic compounds have attracted the attention of many researchers. One of them is the catalytic ozonation process. The use of catalysts eliminates the major problems of the single ozonation process, such as low solubility and stability of ozone in water and slow reaction with some organic compounds. In addition, catalysts such as iron shavings and activated carbon have advantages such as availability, high stability and reusability. Therefore, the main objective of this study was to investigate the performance of catalytic ozonation using iron shavings and activated carbon/iron shavings as catalyst in removal of sulfamethoxazole from effluent of biological treatment system. Material and Methods: In order to conduct this research municipal wastewater treatment plant effluent of Gharamalek, Tabriz was used as the reaction environment. After passing the effluent samples through a 0.45 μm filter, a specific concentration of SMX (1, 3, 5 and 20 mg/l) was spiked to the samples. The effect of pH (3, 7 and 10) was also evaluated at reaction times of one to 60 minutes. Process efficiencies, effects of tert-butanol, COD and the amount of sediment formed by the catalytic ozonation process were investigated for all pHs, in the range of one to 60 minutes. The effects of matrix, TOC, LC-MS/MS, soluble ozone and off-gas were measured at neutral pH for one to 60 minutes. Finally, the experimental data were analyzed using SPSS software (IBM SPSS Statistics 19, SPSS Inc., USA). Results: The results showed that the efficiency of ozonation process in removal of SMX at any pH was higher than that of the catalytic ozonation by iron shavings.151 The TOC removal efficiency was also not significantly different between the two processes after 60 minutes of reaction (p>0.05). However, the rate of COD removal in the catalytic process was higher than that of ozonation and the concentration of COD reached from 122 to 11 mg/l at the end of the reaction. The amount of iron precipitation mud in catalytic ozonation by iron shavings was also lower in alkaline (3.1 mg) than in acidic (5.3 mg) and neutral pH (10.3 mg). The overall comparison of the three processes studied also showed that the catalytic ozonation process by iron shavings/activated carbon had the highest efficiency in the removal of SMX (99.84% at 10 min), COD (96% at 60 min) and TOC (85% at 60 min). Conclusion: The results showed that the mixture of iron shavings/ activated carbon as a catalyst had better efficiency in SMX removal and mineralization. In addition, although the efficiency of the catalytic ozonation by iron shavings in SMX removal was lower than that of the single ozonation, nonetheless, using of iron shavings as a low cost catalyst with increasing COD removal rate has environmental and economic value in ozonation of wastewater containing organic resistant compounds.