Removal of Imazethapyr and Imazapic from the Effluent of Aero-Agricultural Operations: Efficiency of a Treatment System Using Ozone

Imazethapyr and imazapic are widely used in South Brazil to control weeds in rice fields, mainly through agricultural aviation. The environmental legislation requires that agricultural aviation companies have environmental licensing, which implies that the effluent treatment system must be compliant with the regulations of the Brazilian Ministry of Agriculture, which advises the use of an ozone-based system. An evaluation of the efficiency of this system through the analysis of the content of imazethapyr and imazapic (from the herbicide Only®) in the treatment of effluent with two distinct rates of ozone (1.0 and 2.0 g O₃/h) was performed. It was found that for each tank wash is generated an average volume of 132 L of effluent (112 L of water plus 20 L of surplus diluted spray solution). After the treatment with 1.0 and 2.0 g O₃/h, imazethapyr concentration decreased − 92.4 and − 95.2%, respectively. For imazapic, the concentration in the washing effluent decreased − 69.1 and − 80.1%, respectively. The results indicate that the system was effective in the treatment of the effluent containing residues of the herbicide Only®.