Abstract
This work aims to identify the best treatment condition for removal of chemical oxigen demand (COD) and increase of biodegradability in an advanced oxidative process of photocatalytic ozonation with titanium dioxide (TiO2), applied to the remediation of the leachate produced at the municipal landfill of Campo Mourão, Paraná. The experiment was carried out using a photocatalytic chamber and an ozonation system based on the corona effect. A statistical model of the central composite rotatable design (CCRD) was elaborated and three variables (pH, TiO2 dose and airflow) were analyzed, to define the optimum condition that allows the highest perfomance of the treatment. The statistical model was valid for the data. The best condition identified was: pH = 3.3 TiO2 dose = 0.012 g and flow = 9.0 L.min-1 (8.79 g, O3.min-1). The removal of filtrate COD was approximately 30% and increase in biodegradability (BOD/COD) = 0.59 in the optimum condition. Factors such as the complex composition of the leachate and treatment time were considered as possible limitants for better results. The treatment did not allow to reach the permissible limits for disposal of the effluent at the environment, in Brazil.
Highlights
With the increase of the population and the improvement of the quality of life, consumption is boosted by technological development, leading to the generation of a large amount of waste and effluents, such as the leachate
For Renou et al (2008), the biochemical oxygen demand (BOD)/chemical oxygen demand (COD) ratio decreases from 0.70 to 0.04 as time passes in the landfills, because large recalcitrant molecules are released by the residues, which renders the landfill leachate “mature” characteristic, presenting low values of BOD/COD, for example
According to Kurniawan et al (2006b), for a BOD/COD ratio of 0.3 or higher, the biological treatment is more indicated because the organic compounds in the leachate have already been transformed into more biodegradable compounds
Summary
With the increase of the population and the improvement of the quality of life, consumption is boosted by technological development, leading to the generation of a large amount of waste and effluents, such as the leachate. The leachate has a specific physicochemical composition, according to the original decomposed material, containing components such as dissolved and solubilized organic matter; nutrients; intermediate products of anaerobic digestion of the waste, as volatile organic acids; and chemicals, that include heavy metals like cadmium (Cd) and mercury (Hg), for example. This composition origins an effluent considered extremely damaging to the environment, being responsible for the contamination of soil, surface water bodies and groundwater, on site and in the whole surrounding region, due its toxic caracter. The leachate carries pathogenic microorganisms that are harmful to humans, such as Enterococcus, P. aeruginosa, heterotrophic bacteria, fungi and even thermotolerant coliforms (E. coli) (Tavares 2011, Castilhos Junior et al 2006, Peixoto 2008, Silva et al 2011, Jucá & Sobrinho 2012).
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