Carbon source affects the resource recovery in aerobic granular sludge systems treating wastewater

This study evaluated the influence of carbon sources on alginate-like exopolymers (ALE) and tryptophan (Trp) biosynthesis in the aerobic granular sludge (AGS). With acetate, the highest biopolymers levels, per gram of volatile suspended solids (VSS) (418.7 mgALE.g(-1) and 4.1 mgTrp.VSS-1), were found likely due to biomass loss throughout the operation, which resulted in lower sludge age (4-7 days) and shorter famine period. During granulation, encouraging results on ALE production were obtained with propionate (> 250 mgALE.VSS-1), significantly higher than those found with glycerol, glucose, and sucrose. Regarding tryptophan production, propionate and glycerol proved to be good substrates, although the content was still lower than acetate (1.6 mgTrp.gVSS(-1)). Granules fed with glucose showed the worst results compared to the other substrates (38.5 mgALE.VSS-1 and 0.6 mgTrp.gVSS(-1)) due to the filamentous microorganisms' abundance found. Therefore, this study provides insights to value the production of compounds of industrial interest in AGS systems.