Spectroscopic analysis of dissolved organic matter in industrial sludge composting process

Dissolved organic matter (DOM) not only reflects the biochemical transformation of organic matter during the composting process, but also evaluates the humification degree of composting. However, most research focuses on laboratory composting of DOM. In this study, the stability and maturity of DOM in large-scale industrial sludge compost were studied by basic physical, chemical parameters and spectral technology. The results showed that the initial temperature of compost increased rapidly, the high temperature period was longer, and the pH value first increased and then stabilized. The increase in the UV–Vis characteristic values SUVA 280 and SUVA 254 and the decrease in E 250 /E 365 and S R indicated an increased humus content. Fourier transform infrared spectroscopy (FTIR) analysis showed that easily degradable substances such as polysaccharides and carbohydrates were decomposed into humic substances. The absorption rate of 1645 cm −1 /1103 cm −1 , 1645 cm −1 /1400 cm −1 , and 1645 cm −1 /2930 cm −1 confirmed that humic substances increased with the decomposition of polysaccharide compounds and alcohols. Fluorescence excitation-emission matrix spectroscopy (EEM) combined with parallel factor analysis (PFA) showed a gradual decrease in the C3 fraction representing the protein, with decomposition and conversion to humic and xanthate fractions, which was also confirmed by the four-component model (Fmax), the fluorescence region integral (FRI), and the humification index (HIX). This study uses a variety of spectral techniques combined with basic physicochemical parameters to assess the humification of industrial sludge composting, which provides a reference for guiding large-scale composting.