Characterization and Ecotoxicity of Raw and Treated Liquid Effluent from the Washing of Soybean Seed Treatment Machines

In agriculture, there is a constant search for increased productivity, which leads to increased use of fungicides, insecticides, and inoculants, among other products to perform seed treatment before planting. After treatment, the machines and equipment are sanitized, generating a liquid residue with potentially negative environmental impacts. This study aimed to characterize and evaluate the toxicity of the effluent generated from washing soybean seed treatment machines and suggest treatment methods for this residue. The applied treatment was a combined process of coagulation followed by heterogeneous photocatalysis and ozonization. The treatments caused a significant decrease in the concentration of sedimentable solids (95.22%), total solids (25.26%), and total dissolved solids (9.14%). The chemical oxygen demand and the active ingredient thiamethoxam were also reduced by 31.55% and 40.98%, respectively. Despite the reduction of the physical and chemical parameters of the effluent, it still presented acute toxicity to the bioindicators Artemia salina L. and Eisenia fetida since these showed mortality in the tests. The results confirm the risk that this effluent presents to the environment and highlights the importance of continuing the search for new treatment technologies to promote the reduction of the physicochemical parameters and the final toxicity.