Enhanced Acetogenesis of Waste Activated Sludge by Conditioning with Processed Organic Wastes in Co-Fermentation: Kinetics, Performance and Microbial Response

Aimed at the low ratio of carbon and nitrogen (C/N, approximately 7/1) of waste activated sludge (WAS), which would inhibit the acetogenesis process during anaerobic fermentation, this study
introduced three brewing wastes, including vinegar (VR), stillage (SR) and soy sauce (SSR) residues, to promote acetogenesis by co-fermenting with WAS. Results showed that different brewing wastes
contributed differently to the volatile fatty acids (VFAs) yield. The best performance was observed with SSR (4517 ± 367 mg COD/L), particularly rich in C2–C3 VFAs, corresponding to 40% and 52% higher
concentrations than with SR and VR, respectively. Meanwhile, the hydrolysis rate constant peaked at 0.0059 h−1 in the SSR test, compared to the sole WAS test (0.0018 h−1). Furthermore, canonical correlation analysis reflected that the functional consortia, known to ferment saccharides/amino acids into C2–C3 VFAs (i.e., Proteiniclasticum, Petrimonas, Cloacibacillus and Gemmobacter), was related to the characteristics of the feedstock.