Avaliação dos processos UV-C/H2O2, UV-C/S2O82 e UV-C/HSO5 e, dos custos para a degradação do herbicida tebuthiuron em efluente de estação de tratamento de esgoto

Abstract

Conventional sewage treatment technologies are not efficient to remove or degrade contaminants of emerging concern from effluents. These compounds have been detected in surface and drinking water, being harmful to humans and animals. In order to circumvent this problem, the advanced oxidation processes were studied as a complementary technology to conventional treatments, aiming the degradation of the herbicide tebuthiuron (TBH), a recalcitrant and highly water-soluble compound used in the Mining Triangle. In this work, a degradation of 100 µg L1 of TBH in sewage treatment plant effluent was evaluated by the UV-C radiation process combined with three different oxidants: hydrogen peroxide (HP), persulfate (PS) and monopersulfate (MPS). Initially, the degradation of TBH was monitored only with UV-C radiation and later, combined with the different oxidants to verify synergism. Different concentrations of HP, PS and MPS (735, 1470, 2206 and 2941 µmol L-1) were evaluated aiming at achieving the highest efficiency of TBH degradation. Among the three oxidants used, the PS that was slightly more efficient in all the applied concentrations. According to the kinetic parameters provided, PS presented the lowest values of t1/2 and electric power by order (EEO), confirming its better efficiency compared to PH and MPS. Despite a slightly higher total cost of the process (R$ 8.5 – PH, R$ 34 - PS and R$ 176 - MPS in 2206 µmol L1), at low concentrations (1470 µmol L1 of PS) and after 30 minutes of irradiation, the detection limit (LD) of the method (4 µg L–1) was reached, resulting in 96% of TBH degradation.