Tratamento combinado de lixiviado de aterro sanitário e esgoto sanitário com lodos ativados e monitoramento de emissão de óxido nitroso

Abstract

The combined treatment of landfill leachate with sanitary sewage by biological processes used in treatment plants is an economical and efficient alternative. However, the leachate can present toxic substances capable of compromising the efficiency of the process, and it is necessary to evaluate previously the leachate / sewage relation to be adopted. The activated sludge process is widely used in large cities and can promote the biological removal of nitrogen through operational modifications. This is a relevant characteristic in combined treatment, since the addition of leachate represents a contribution of nitrogenous material. However, during the removal of nitrogen the emission of nitrous oxide (N2O), a greenhouse gas, occurs. Thus, this work had the objective of evaluating the cotreatment of landfill leachate and sanitary sewage using a sequential batch reactor (SBR), in addition to monitoring N2O emissions. A reactor with a useful volume of approximately 35 L was used and it operated with cycles of 6 hours. The experiment was conducted in two stages: STAGE 1 using only sanitary sewage and STAGE 2 with the addition of sanitary landfill leachate (0.5% v/v). The experimente evaluated the efficiency of removal of organic matter and nitrogen before and after the addition of leachate besides the emission of N2O during the process. The addition of leachate caused a decrease in biomass and affected some operational parameters observed (SVI, DO and OUR). In STAGE 2 the process was able to reduce the concentration of parameters true color (48%) and apparent color (80%), as well as ABS 254 (43%). Such efficiency values are high when compared to other types of processes such as activated carbon. However, the addition of leachate led to the reduction of COD, DOC and NTK removal efficiencies. In STAGE 1, COD and DOC removal efficiencies were 90% and 83%, respectively, while in STAGE 2, these average removals were 67% and 72%, respectively. Regarding TKN, in STAGE 1 a removal of 85% was obtained and in STAGE 2 of 67%. Despite the reduction in process efficiency, the addition of leachate (0.5% v/v) did not compromise the quality of the treated effluent. With regard to N2O emissions, the emission fluxes of this gas were slightly lower when the process operated with the addition of leachate. This behavior was contrary to that reported in the literature, probably due to the low concentrations of organic matter affluent observed only along STAGE 2, and to the suspension of the sludge discard that may have favored the establishment of nitrifying microorganisms. The masses of N-N2O emitted by the RBS were 82 mg/cycle without leachate and 61 mg/cycle with leachate, and the analysis of variance with a significance level of 95% did not indicate statistical difference, so the presence of the leachate did not impact the emission of this gas.