Tratamento de efluente de esgoto pela integração de processos de coagulação e oxidativos avançados

Abstract

The search for new sewage treatments has intensified due to water crises and contamination of water bodies by emerging contaminants, particularly endocrine disruptors. Sewage effluents contain large amounts of organic matter, turbidity, micropollutants, and coloration. Depending on their toxicity, they can cause disease and death to living organisms present in water bodies. A significant portion of Brazil lacks a Sewage Treatment Plant (STP), and wastewater is discharged directly into the nearest water bodies, thus generating negative environmental impacts. For the treatment of this type of effluent, advanced oxidative processes (AOPs) such as electrochemical, photo-Fenton, and combined electrochemical and photo-Fenton processes appear as an alternative for integration with current conventional treatments for sewage contaminated by endocrine disruptors due to their high degradation capacity for organic substances through the generation of hydroxyl radicals. Thus, the present work proposes the combined use of coagulation and AOP techniques in the treatment of sewage contaminated by 17-𝛃-Estradiol (E2). The dosage of 8 mL/L (best condition) of the chemical coagulant (FeCl3), equivalent to a concentration of 200 mg/L of FeCl3 (at pH 7.0) resulted in the total removal of turbidity from the residue, as well as the elimination of 99% of the chemical oxygen demand (COD), in addition to removing the color from the effluent. After treatment with the coagulation process, the results showed that some micropollutants remained in the sewage effluent, indicating that additional treatments should be performed to remove these compounds. Subsequently, considering the persistence of the physicochemical characteristics and hormone concentration, the conventional photo-Fenton process with artificial radiation was used, using a mercury lamp without a protective bulb. At Fe2+ concentrations of 0.025 g/L and H2O2 of 9.97 g/L, a 97.4% removal rate of 17-β-estradiol was achieved using the photo-Fenton process with artificial radiation at pH 3. Using a solar radiation source, seeking to minimize process energy consumption, the conventional solar photo-Fenton process was used, achieving 99.4% removal. With the electrochemical process and the application of current densities of 3 mA/cm² and 12 mA/cm², the E2 removal rates were 86.5% and 99.6%, respectively. In the combined electrochemical and photo-Fenton processes, E2 removal was complete. Therefore, AOPs are very promising for the treatment of sewage contaminated with the hormone E2, resulting in a significant reduction in environmental impact and health impacts.