Tratamento biológico conjugado de resíduos líquidos com ênfase na remoção de material orgânico e nitrogenado

Abstract

Landfill leachate is a liquid waste that exhibits a diversity of chemical compounds. Ammoniacal nitrogen and organic matter with difficult biodegradation are considered the most important constituents of leachate. The high concentrations of these constituents make it difficult to establish an adequate treatment process, and if launched without previous treatment, cause great environmental problems. In view of the above, the objective of this work was to study the conjugated biological treatment of leachate from the sanitary landfill of the city of João Pessoa - Paraíba plus domestic sewage in a UASB reactor followed by a percolating biological filter plus an anoxic reactor, focusing on the removal of organic and nitrogenous matter. The reactors were fed with substrate consisting of landfill leachate and domestic sewage in proportions that allowed the formation of the substrate with a mean ammoniacal nitrogen concentration of 150 mg.L^-1. The UASB reactor was operated with 6 hr TDH and volumetric organic load of 3.0 kg COD / m^3.day. The percolating biological filter (FBP) was fed in intermittent flow and the duration time of each cycle was 06 hours. The anoxic reactor had a total volume of 17.5 L and TDH of 24 h. The system showed removals of total COD of 69% and filtered COD of 57%. Low ammonia nitrogen removal efficiencies were observed during the nitrification step in the FBP, producing effluent with a mean concentration of 139 mg.L^-1 of ammoniacal nitrogen and, consequently, low concentrations of nitrite and nitrate. A nitrate reduction was observed during the denitrification step in the anoxic reactor, producing effluent with a concentration of 0.88 mg.L^-1 nitrate.