Moringa oleifera e sulfato de alumínio aplicados como coagulantes ao esgoto sanitário: Análise do efluente tratado e do lodo residual

Abstract

Sanitary sewage is formed by water from domestic and industrial sewage and river networks. Its composition contains less than 1% solids, which influences the physical, chemical, and biological aspects of the effluent, consequently reflecting on the composition of the process's residual sludge, composed of organic matter and heavy metals. The coagulants used during treatment also influence the composition of the sewage sludge. When using inorganic coagulants or sludge, it tends to have remaining metals, making reuse difficult, while organic coagulants produce a greater volume of organic matter, enhancing biodegradability processes. Aiming to compare the application of the organic coagulant Moringa oleifera and the inorganic coagulant Aluminum Sulfate to sanitary sewage effluent, the treatment was carried out using the jar test, where the coagulation, flocculation, and sedimentation processes were simulated. The treated effluent samples, the following parameters were evaluated: pH, electrical conductivity, turbidity, apparent color, and chemical oxygen demand (COD). The pH showed little variation when compared to the raw value. Electrical conductivity was influenced by the use of Moringa oleifera coagulant. For the removal of turbidity, the best result was obtained with the organic coagulant, which obtained rates above 70%, while the treatment with Aluminum Sulfate ended the treatment with 44.75%. Likewise, the treatment with Moringa oleifera achieved the best removal for apparent color, with a removal rate close to 91% at the end of the test, while the treatment with Aluminum Sulfate achieved removal close to 70%. As for COD removal, both treatments presented values close to 90%. The results obtained were compared with the relevant legislation and examined using ANOVA statistical analysis. The sludge generated during the jar test was dried in an oven, subjected to acid digestion, and then analyzed using atomic absorption spectrometry with flame atomization, to determine the heavy metals Cadmium, Chromium, Lead, Zinc, and Nickel. Compared to raw sludge, the chromium concentration was the only one that showed a reduction both for treatment with organic and inorganic coagulants. Therefore, the declared organic coagulant is viable for the treatment of sanitary sewage effluent, whereas, about the presence of heavy metals in the sludge, it was not possible to analyze the efficiency in reducing the concentration.