Monitoramento de lixiviado em lagoa de estabilização e estudo da aplicabilidade do reagente Fenton e do coagulante vegetal tanino como formas de tratamento

Abstract

The objective of this work was to characterize the leachate generated in Paranavaí Municipal sanitary landfill, and as well as to study the physico-chemical treatment process by coagulation-flocculation with Tanfloc SGR tannin as coagulant, and the oxidation process by Fenton reagent. The leachate monitoring was performed in four different places in the stabilization pond, from September 2006 to August 2007, and the applicability study of Fenton reagent and tannin on leachate treatment was performed from September 2007 to October 2008, with in natura leachate. The qualitative parameters determined in leachates from Paranavai Municipal sanitary landfill allowed to characterize them as alkaline effluents, with intense color, high concentration of ammoniacal nitrogen and low of biodegradable organic material, indicated by the average relation DBO5//DQO lower than 0.30, demonstrating the evidence of high recalcitrance of the material. The biological treatment has proven to be efficient in pH control, turbidity, dissolved oxygen, and thermotolerant coliforms and also in controlling the major metallic effluent analyzed, such as, Ba, Cd, Cu, Fe, Ni, and Zn, however, it hasn't presented satisfactory efficiency in organic material degradation, even though approximately 70% of DBO5 removal has been observed at the releasing point. The influence of [DQO]:[ H2O2]; [H2O2]:[Fe+2] ratio, its pH, the time of DQO removal, and the volume of sludge generation were assessed in the advanced oxidative process with Fenton reagent through factorial 24 planning. It was verified that the studied variables (DQO removal and the volume of generated sludge) presented optimal values in 5.0 pH, and [DQO]:[ H2O2] = 1:8,5 e [H2O2]:[Fe+2] = 5.10:1 ratio. The treatment process optimization with Tanfloc SGR coagulant was done through a factorial 22 planning, where the pH and the concentration of Tanfloc SGR coagulant were evaluated in DQO removal and sludge generation, verifying the optimal points in pH 7,4 and [Tanfloc SGR] = 2700 mg/L. Removal of metals from oxidized effluents was observed in the process studied, however, concentration level of elements such as, As, Fe, and Se remained above standard levels established by Resolution 397/2008 (CONAMA). It was verified that the sludge resulting from Fenton reagent treatment is constituted by 50% of residual fraction, 24% of crystalline oxide, 18% of amorphous oxide, and 8% of changeable fraction. The sludge derived from treatment with Tanfloc SGR is composed of 29% of amorphous oxide, 28% of final residue, 22% of crystalline oxide, and 21% of changeable fraction. The lixiviation and solubilization tests showed that these residues are classified as dangerous - Class 1.