Monitoring the toxicity of effluents from an industrial waste treatment plant using seed germination and early development plant-based bioassays: a case study

Industrial effluents may contain a wide range of contaminants capable of producing adverse environmental effects even after conventional treatment. This study aimed to assess the phytotoxic potential of effluents derived from a waste treatment company located in a rural area of Minas Gerais, Brazil, by integrating physicochemical analyses and terrestrial plant bioassays. Samples were collected from raw and treated effluents, as well as nearby surface waters, and tested using four plant species: <i>Lactuca sativa</i>, <i>Phaseolus vulgaris</i>, <i>Cenchrus americanus</i>, and <i>Zea mays</i>. Biological endpoints included germination percentage (%G), germination speed index (GSI), fresh biomass, and seedling growth parameters. The treated effluent exhibited elevated levels of biochemical oxygen demand (BOD), nickel, and surfactants, which exceeded environmental regulatory limits. Among the tested species, <i>L. sativa</i> demonstrated the highest sensitivity across all endpoints, displaying an average inhibition of 31.59% and the highest Integrated Biological Response (IBR) value. The combination of sensitivity indices and IBR confirmed the toxic potential of treated effluent, emphasizing the relevance of bioassays as complementary tools to traditional physicochemical assessments. These findings indicate the limitations of current treatment processes and reinforce the need for ecotoxicological monitoring using multiple plant models to detect sublethal and potentially genotoxic effects of effluent discharge on terrestrial and aquatic ecosystems.