Desenvolvimento de sistemas modulares compostos por processos oxidativos avançados e avaliação ecotoxicológica de efluente gerado pela indústria de coco

Abstract

The food industry is now one of the fastest growing activities on the planet, due to the great demand for food, which ends up generating a large amount of waste that can contaminate water and the environment. In order to minimize the possible environmental impact, it is necessary to use some effluent treatment techniques that are efficient and economically viable. In many cases, there is a need to use more than one associated technique to obtain the desired effluent quality. Among these techniques currently studied, Advanced Oxidative Processes (AOPs) have received considerable attention, due to their high efficiency and low operating cost. During the development of this study, different combinations of advanced oxidative processes were evaluated for the decontamination of effluents from the coconut processing industry, with the objective of developing a modular system with the possibility of scaling up for application in future studies. The techniques used in this study were: Fenton, electro-oxidation, photo-Fenton, electro-Fenton, associated or not. Among the techniques studied, the results with the highest percentage of COD reduction and turbidity were the results of the electro-Fenton and photoelectro-Fenton hybrid processes (95%), the latter being the best result in the ecotoxicity tests. In general, all combinations evaluated had positive results: H2O2/UV treatment was less effective in removing COD (45%), followed by photo-Fenton and electrochemical + photoFenton treatments with intermediate results (between 76-78%); in the photo-electroFenton, photo-electro-Fenton + electrochemical, electro-Fenton, electrochemical + Fenton and Fenton + electrochemical treatments, showed higher COD removal (84%-95.53%). For the photo-electro-Fenton and the electro-Fenton treatments, where higher percentages of removal for COD (95%+) were obtained, ecotoxicological tests were carried out. The ecotoxicological results obtained for the electroFenton treatment did not show relevant toxicity for the tested species, however, a slight inhibition of root growth was observed in tomato and onion seeds. The influence of the H2O2 concentration as a possible cause of the light toxicity of the photoelectro-Fenton treatment effluent was evaluated. Additionally, the economic feasibility of scaling the process to the industrial level was discussed, suggesting the use of solar panels and/or other renewable energy techniques; as well as exploring other processes (physical or biological) to improve the process.