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

Maria Elisabete Silva,Marlene Santos,Isabel Brás,W Cui

doi:10.1051/e3sconf/20198003002

Maria Elisabete Silva, Marlene Santos + Show 2 more

Open Access

https://doi.org/10.1051/e3sconf/20198003002

Copy DOI

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.

Highlights

The disposal of solid wastes in sanitary landfills represents nowadays the most common method of waste management
The humic substances (HS) content in the leachates was higher than the typical values found in the natural aquatic humic sources
It was identified that the leachate HS, humic acids (HA) and fulvic acids (FA) aromatic components increased with increasing landfilling age

Summary

Introduction

The disposal of solid wastes in sanitary landfills represents nowadays the most common method of waste management. Leachates or wastewater produced in landfills are generated mainly due to rainwater percolation through wastes and their decomposition products [1], leading to a complex mixture of high strength organic and inorganic contaminants [2]. The refractory HS include humic acids (HA), fulvic acids (FA) and humin that are produced during the decomposition of the biodegradable fraction of organic compounds in leachates. These compounds have a major role as fertilizers and land correctives, which may contribute to the essential functions of global soil fertility. HS, mainly HA and humin, are extremely resistant to biodegradation Given their low decomposition, HS belong to the group of stable natural organic compounds [7]. HS are composed of a very large variety of aromatic rings (phenolic and quinonic) bound by acid functional groups or by peripheral aliphatic chains (polysaccharides, peptides, etc) and grouped into the different molecular arrangements that make up the HS structure [9]

Objectives

Methods

Results

Conclusion