Characterization of wastewater from landfills - amount and type of humic substances extracted from leachate

Abstract

This study aimed to characterize the humic substances (HS) extracted from landfills wastewater – leachates, with different ages of exploration. To reach the objective it was applied spectroscopy techniques, UV-Vis and FTIR spectra, as well as the ratio between the absorbance analysed. First, the HS were extracted, then fractionated in fulvic acids (FA) and humic acids (HA) and it was evaluated the phytotoxicity. HS content in the leachates were higher than the typical values found in the natural aquatic humic sources. It has been identified that the leachate HS, HA and FA aromatic fractions increased with the increase of the landfilling age, suggesting that the degree of humification increased with the landfilling age. All the HS showed a high aromaticity and humification degree. The HS extracts irrespective of their source presents similar structural composition. The functional groups found are in agreement with the literature: phenols, alcohols, carboxylic groups, aliphatic structures, among others. It was found that HA are mainly organic matter with a higher aromatic degree than FA. The HS and HA showed absence of phytotoxicity, testing by germination index, suggesting that may be used to produce liquid organic fertilizers.

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

“…The HA fraction is soluble in an alkaline medium and insoluble in an acidic medium (pH , 2). The FA fraction is that which, after solubilization in alkali, remains soluble at any pH value and, lastly, the HU fraction is insoluble in any condition of pH (Lima et al 2017;Silva et al 2019).…”