Insights into characteristics of organic matter during co-biodrying of sewage sludge and kitchen waste under different aeration intensities

This study deciphered the dynamics of organic substances during co-biodrying of sewage sludge and kitchen waste under different aeration intensities. Cornstalks were mixed with these two organic wastes as the bulking agent to amend the co-biodrying performance. Results show that increasing aeration intensity from 0.45 to 0.65 L min⁻¹ kg⁻¹ DM could enhance water removal, but reduce the biodegradation of organic substances during co-biodrying. Further enhancement in aeration intensity up to 0.85 L min⁻¹ kg⁻¹ DM insignificantly affect the co-biodrying performance. Regardless of aeration intensity, the organic reduction was mainly contributed by the biodegradation of celluloses and hemicelluloses, though soluble carbohydrates and amylums were intensively biodegraded. Detailed characterization of organic composition by fluorescence excitation–emission matrix with regional integration analysis indicates the gradual disappearance of tyrosine and tryptophan-like proteins as well as soluble microbial by-products, while the production of humic acid-like substances during co-biodrying. Low aeration intensity could facilitate matrix humification, resulting in continuous accumulation of humic acid-like substances. By contrast, these labile substrates were gradually consumed from day 9 onward of co-biodrying at aeration intensity of 0.65 L min⁻¹ kg⁻¹ DM or above. Nevertheless, the organic constitutes were insignificantly changed during co-biodrying as indicated by their stable functional groups.