Hydrophilic and hydrophobic fractions of water-soluble organic matter in digestates obtained from different organic wastes

Up to now, it is unknown how anaerobic digestion of biowastes affects the chemical composition of water-soluble organic matter (WSOM) in the digestate and, thus, the potential distribution and mobility of hydrophobic organic contaminants. The aim of the present work was to estimate the proportions of hydrophilic (HI) and hydrophobic (HO) fractions of WSOM in anaerobic digestates obtained from different mixtures of biomass. The overall goal was correlating proportions of HI and HO fractions to the different chemical characteristics of the biowastes subjected to anaerobic digestion. More than 70% of WSOM was with the HI fractions of digestates derived from 1:1 mixtures of the organic part of municipal solid wastes and sewage sludge. Larger HO fractions were observed for digestates derived from energy crop plus smaller contributions of poultry manure, stomach residue, and apple residues, likely due to the concentration of fibers during the digestion. Ratios between HO fractions in digestates and in their corresponding ingestates were used as indicators of the transformation of WSOM during the process.