Uso de ozônio no tratamento de lixiviado de aterro sanitário

Abstract

Landfill leachate can have high concentrations of nitrogen, chlorides, organic matter, organic compounds that are difficult to break down, such as humic substances and possibly metals, their treatment is one of the greatest challenges due to the high heterogeneity and variability of its characteristics over time and the presence of recalcitrant compounds. Biological and physical-chemical treatments are the most used, but they have not shown efficiency in removing pollutants, thus not reaching the legal parameters for effluent release into water bodies. Therefore, the use of Advanced Oxidative Processes (POA) has been used to treat leachate, to chemically degrade recalcitrant organic matter and increase the leachate's biodegradability. Among the types of POAs, ozonation is a promising treatment process due to its unique characteristics such as the non-generation of sludge, the high potential for removing color and organic matter in a single step and the easy decomposition of residual ozone. In this context, the objective of this work is to evaluate the effect of ozonation in the treatment of landfill effluent. The leachate samples were collected at the Candiota landfill. The experiments were conducted at the Water and Wastewater Analysis Laboratory of the Federal University of Pelotas. Tests were carried out by applying six doses of ozone to the leachate samples: 21.9, 43.7, 65.5, 131.1, 145.7 and 182.1 mg O3. The physical-chemical characterization of the samples was carried out before and after laboratory tests, in the parameters: pH, True color, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (DBO), DBO / COD Ratio, Phosphorus (P) and Total Suspended Solids (SST). Phytotoxicity tests were also carried out with lettuce and cucumber seeds. Ozonation treatments maintained the basic pH of the effluent providing a small increase, reaching pH values of up to 9.25. The true color was able to remove up to 93.36%, the BOD concentration reduced initially by 27.11%, however in the other doses there was an increase in the concentration of the parameter showing values higher than the raw effluent, with respect to COD the largest removal was 45 %, the BOD5 / COD ratio of the raw effluent was 0.08 after ozonation the ratio increased to 0.20, consequently increasing the biodegradability of the effluent, ozonation reduced the concentration of phosphorus by up to 95.87%, the SST also had a significant removal efficiency of up to 90.04%. As for phytotoxicity, the ozone doses applied were not sufficient to reduce the toxicity of the leachate.