Ozonização convencional e catalítica como pré e pós tratamento de lixiviado de aterro

Abstract

The landfill leachate has a complex composition, containing dissolved organic matter, inorganic compounds, xenobiotics and heavy metals, and its treatment is fundamental for the protection of the environment and prevention of environmental impacts. Leachates from mature landfills have recalcitrant compounds in their composition, making biological treatment of effluent inefficient. Therefore, Advanced Oxidation Processes (POA) have been highlighted for their high oxidizing power and efficiency in the degradation of persistent pollutants, being used in a complementary way in the treatment line, as pre-treatment or as a tertiary treatment, or even in the treatment of specific pollutants. Among these processes, ozonation is considered as one of the most effective treatments for landfill leachate. Thus, the objective of this study was to evaluate the effect of conventional and catalytic ozonation treatment on the toxicity of landfill leachate, before and after biological treatment. The leachate samples were collected at the Pelotas landfill, which ended its operations in 2012. Two leachate samples were collected: the first in the collection box, before treatment at the landfill wastewater treatment plant (pre-leachate), and the second after the treatment carried out in the landfill (post-leachate). The experiments were conducted at the Water and Wastewater Analysis Laboratory at the Federal University of Pelotas. Tests were carried out using conventional ozonation and heterogeneous catalytic ozonation using 2g/L of rice husk ash activated with KOH as a catalyst, applying six doses of ozone to the leachate samples: 0, 183, 366, 549, 732 and 915mg O3/L. The physical-chemical characterization of the samples was carried out before and after laboratory treatment, in the parameters: pH, True color, Chemical Oxygen Demand (COD) and phosphorus (P). The heavy metals zinc (Zn), cadmium (Cd), chromium (Cr) and lead (Pb) were also analyzed, in addition to phytotoxicity tests with lettuce and cucumber seeds. Ozonation treatments provided an increase in the effluent pH, reaching pH values of up to 9.2. It was possible to remove up to 94.4% of the color of the post-leachate through catalytic ozonation, 89.7% of the COD in the treatment of pre-leachate by catalytic ozonation, and 100% of phosphorus in the treatment of post-leachate by conventional ozonation. As for heavy metals, through conventional ozonation of the post-leachate it was possible to remove up to 40.68% of zinc, 52.42% of chromium, and 100% of lead values, with the absence of cadmium in all samples analyzed. It was possible to reduce the phytotoxicity of the effluent, increasing the Germination Index from 39.4% to 42.2% in the catalytic ozonation of the post-leachate.