Avaliação do desempenho dos processos metabólicos de grupos bacterianos em sistemas de tratamento conjugado de resíduos líquidos

Abstract

The biodecomposition of solid waste in open dumps or in landfills, produces leachate, a highly polluting liquid residue. Due to the high concentration of ammoniacal nitrogen present in the landfill leachate, the combined treatment of this effluent with domestic sewage, presents itself as an efficient technological alternative to obtain a passive biological treatment effluent. In this context, biological processes are used to remove nitrogenous compounds present in effluents of anthropic origin, which, if released into the environment, cause the eutrophication of natural waters, which hinders their use for human consumption. The biological treatment of the leachate conjugate with domestic sewage can be carried out in series reactors where the necessary conditions for the occurrence of the natural stages of the nitrogen cycle of ammonification, nitrification (in two stages: nitritation and nitration) and denitrification. The present work aimed to carry out the qualitative and quantitative characterization of the bacterial groups responsible for the oxidation (nitrification) and reduction (denitrification) process, applying the Most Probable Number (MPN) technique in an experimental system consisting of a UASB reactor followed by a Percolating Biological Filter (PBF) and an anoxic reactor. The reactors were installed and monitored sequentially throughout the process of treating the conjugate of the landfill leachate with domestic sewage. The efficiency of the ammonification step in the UASB reactor evaluated during the transformation from organic to inorganic nitrogen was 6.4%, which represents an increase of 9.8 mg/L of ammoniacal nitrogen in the effluent of the reactor. The Most Probable Number (MPN) of the nitrifying bacteria was estimated in those collected in the FBP effluent. The MPN of ammonia oxidizing bacteria (AOB) varied from 0,8x10^2 a 1,4x10^5 MPN/100ml. The MPN of nitrite oxidizers (NOB), varied from 0,8x10^2 a 2,2x10^4 MPN/100ml. The denitrifying bacteria were quantified in the samples collected in the effluent of the anoxic reactor. The MPN of denitrifying bacteria varied from 7,0x10^3 a 2,6x10^4 MPN/100ml. he efficiency of biological nitrogen removal in the FBP showed an average efficiency of 16.42%, generating an effluent with an average concentration of 136.4mg N-NH4^+.L^-1 in the FBP. The results obtained during the monitoring of the experimental system, proved its capacity to carry out the global processes of transformation of nitrogen. However, the need for strict control of operational parameters is highlighted, in order to achieve greater nitrogen removal efficiencies in treatment systems.