This study aimed to evaluate the use of coagulation/flocculation and Fenton processes for the removal of the recalcitrant component, in particular humic substances, from two different leachates generated in the Gericinó and Gramacho landfills in Rio de Janeiro State (Brazil). A coagulation/flocculation process, using FeCl·6HO as the coagulant, was applied to the two leachate samples. In the case of the leachate from Gericinó landfill, the treatment removed 93% of color, 71% of TOC, 69% of COD, 76% of HS, 73% of humic acids (HA) and 82% of fulvic acids (FA). In addition, there was a 75% reduction in the absorbance at 254 nm, using 3,000 mg L of coagulant. In the case of the leachate from Gramacho landfill, the treatment removed 91% of color, 69% of TOC, 68% of COD, 77% of HS, 75% of HA and 80% of FA. In addition, there was a 70% reduction in the absorbance at 254 nm using the same concentration of coagulant (3,000 mg L). The Fenton processes, using FeSO·7HO and HO in a ratio of 1:5, were also applied to the two leachate samples. In the case of the Gericinó leachate, the Fenton treatment removed 95% of color, 75% of TOC, 68% of COD, 82% of HS, 77% of HA and 93% of FA. In addition, there was a 93% reduction in the absorbance at 254 nm. In the case of the Gramacho leachate, the Fenton treatment removed 93% of color, 73% of TOC, 71% of COD, 81% of HS, 76% of HA, 90% of FA, and there was an 84% reduction in the absorbance at 254 nm. The results of humic substances, color, organic matter and aromatic organic matter (absorbance at 254 nm) demonstrate that the coagulation/flocculation and Fenton processes were efficient in the removal of recalcitrant organic matter from landfill leachates.

RESUMOSubstâncias Húmicas (SH) são definidas como polímeros amorfos, de massa molar elevada, estruturas complexas e heterogêneas, que alteram com frequência as suas conformações em função das interações que ocorrem entre os grupos funcionais presentes na sua estrutura. A presença dessas substâncias principalmente nos lixiviados de aterros de resíduos sólidos e, em maior quantidade, em lixiviados de aterros antigos, dificulta o tratamento dos lixiviados, devido ao alto grau de recalcitrância de tal matéria orgânica. Palavras-chave: ácidos fúlvicos, ácidos húmicos, matéria orgânica recalcitrante. Analysis of quantification methodologies for humic substances in leachates from solid waste landfills ABSTRACTHumic substances (HS) are defined as amorphous polymers, with high molecular weight and complex and heterogeneous structures that frequently change their configurations depending on the interactions between the functional groups present in their structures. The presence of these substances, particularly in landfill leachates and in greater quantities in