Tratamento de efluente da piscicultura utilizando os processos fenton e eletroquímico: eficiência e toxicidade

Abstract

Fish farming is an important process of food production that seeks to meet the population growth, however is a source of pollution generating large volumes of contaminated water, causing environmental pollution. In order to minimize this impact, this study aimed to evaluate the efficiency of two advanced oxidative techniques to treat real effluent from fish farming, the Fenton reaction and electrochemistry. Treatments were carry out on a pilot scale (60L) and laboratory scale (250 mL). The efficiency of the reactions was assessed by the reduction of turbidity and COD of the effluent, as well as the toxicity of the effluent after treatment in germination lettuce (Lactura sativa) and mortality and sensory performance of the Nile tilapia (Oreochromis niloticus). For the Fenton reaction, it assessed the influence of the concentration of Fenton reagent (Fe2+ and H2O2), and the electrochemical process evaluated the applied current density and the supporting electrolyte (Na2SO4, H2SO4 and NaCl). According to the results of the physicochemical analyzes, both technologies were also effective in the treatment of this effluent, with reductions of 99% and 95% of the turbidity and COD respectively, for the Fenton reaction followed by flocculation; and 95% to 89% in turbidity and COD respectively, for the electrochemical process. In the electrochemical process the efficiency was associated with direct and indirect oxidation of pollutants and flotation of the particulate material through electrogenerated gas. In toxicological test of Fenton reagent with lettuce seeds, the Fe2+ concentrations showed no toxicity, since the H2O2 concentrations indicated high toxicity. Tests with Nile tilapia corroborate the results of lettuce seeds. After the treatment with Fenton's reaction effluent treated with 10 mmol of H2O2 L-1 and 0.5 mmol Fe2+ had the same germination and root growth rates of the raw wastewater, as in the tests with Nile tilapia effluent showed considerable toxicity, possibly due to residual peroxide. In the electrochemical process the best results were obtained when employed the H2SO4 as supporting electrolyte and the lowest current density (10 mA cm-2). The toxicology tests with lettuce and Nile tilapia indicated that the treated effluent has low toxicity with germination rate and lettuce radicle growth equal to control, and Nile tilapia the mortality rate was zero, even after 96 hours of fish contact with the treated effluent. The techniques applied in this study showed high efficiency in the treatment of real effluent from fish farming, making it adequate for disposal or reutilization.