Valorization of extracted organic matter from municipal solid waste leachate: Application to soils from France and Togo

Hydrophobic like (HPO*) and transphilic like (TPH*) fractions of organic matter (OM) were extracted from municipal solid waste leachate (MSWL) to assess their opportunity of valorization as organic amendments. Two soils with different carbon organic (C_org) content were studied: a soil from Togo (C_org = 0.3% in top horizon) and a soil from France (C_org = 4.2% in top horizon). HPO* and TPH* fractions were characterized by combining elemental analysis, determination of specific ultra-violet absorbance (SUVA) index and distribution of apparent molecular weight (AMW). Comparison to natural organic matter (NOM) fractions from surface water confirmed high similarities in composition except a lower oxygen percentage explained by the different genesis processes. HPO* and TPH* adsorption tests were conducted under batch experiments on each horizon of both soils to evaluate the impact of OM fractions on the physico-chemical characteristics of soils, to determine the carbon adsorption and to calculate their adsorption capacity. Whatever the soil, C_org adsorption did not correlate with clay content but rather with initial C_org content in the horizon. HPO* fraction was better adsorbed than TPH* fraction. Besides, while C_org adsorption percentages on each horizon of soils were higher for French soil, the adsorption capacities, explained as the ratio of organic carbon mass adsorbed on soils on its initial carbon mass, were 2 to 10 times higher for soil from Togo.