Exploring the potential of urban sewage sludge for liquid humus production

Abstract

Worldwide, scientists have long been researching municipal sewage sludge management options in the context of the circular economy. In Chile, in particular, there have been a lot of misgivings about the disposal of sewage sludge. Liquid humus is a solution of humic and fulvic acids that can be used to add organic matter to soil via irrigation. The objective of this study was to evaluate the industrial potential of sewage sludge as a source material for the production of liquid humus. The sludges analyzed in the study produced liquid humus with high concentrations of humic and fulvic acids (7.3–7.9 g L^-1). In one sludge under study, humic acids constituted the principal ingredient, while in another sludge, humic and fulvic acids were found in similar proportions. Since the results point to the occurrence of sewage sludge humification, such sludge from wastewater treatment plants may potentially be used as a source for the production of liquid humus. However, future studies are needed to evaluate agronomical performance of liquid humus sourced from urban sewage sludge.