Influence of humic substances on the landfill leachate biodegradability with a focus on temporal seasonality

Abstract

The high resilience to biological treatments from the landfill leachate is generally associated with the presence of humic substances (HS). The brown color characteristic of this effluent is also related to these substances. Landfill leachate with low biodegradability can make biological treatments unfeasible, which can drive up the cost for the treatment of large leachate volumes. In this context, this research aimed to characterize the leachate in different seasonal periods, and verify the influence of HS species on the biodegradability of the effluent to assist in the selection of adequate treatment techniques. The HS quantification was performed using the modified Lowry method and speciation through fractionation according to the molar masses of the HS species. The tropical regions can be the precursor for the rapid stabilization of biodegradable organic matter. The warmer climate contributed to a reduced BOD/COD ratio (0.03) and the predominance of compounds of lower mass (e.g.: fulvic acids). The tests showed an HS concentration of 26.9% of the total COD in the raw leachate in the rainy season, which increased to 37.3% in the dry season. Approximately 70% of HS species refer to fulvic acids, a fraction identified as having the highest biologic treatment resilience. HIGHLIGHTS A method for HS determination in the presence of proteins was assessed.; Leachate is diluted during hydric surplus.; FA are the main compounds in stabilized leachate among the HS.; Leachate resilience to biodegradation is mainly derived from FA.; Hydraulic retention times longer than 20 days are not recommended due to cell lysis.;

Keywords

• biodegradability
• humic substances
• inert cod
• landfill leachate
• molar mass distribution