RESUMEN
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 mgALEâg-1 and 4.1 mgTrpâgVSS-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 mgALEâgVSS-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 mgTrpâgVSS-1). Granules fed with glucose showed the worst results compared to the other substrates (38.5 mgALEâVSS-1 and 0.6 mgTrpâgVSS-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.
Asunto(s)
Aguas del Alcantarillado , Aguas Residuales , Aerobiosis , Alginatos , Reactores Biológicos , Carbono , Glucosa , Glicerol , Propionatos , Aguas del Alcantarillado/química , Triptófano , Eliminación de Residuos Líquidos/métodosRESUMEN
Lately, wastewater treatment plants are much often being designed as wastewater-resource factories inserted in circular cities. Among biological treatment technologies, aerobic granular sludge (AGS), considered an evolution of activated sludge (AS), has received great attention regarding its resource recovery potential. This review presents the state-of-the-art concerning the influence of operational parameters on the recovery of alginate-like exopolysaccharides (ALE), tryptophan, phosphorus, and polyhydroxyalkanoates (PHA) from AGS systems. The carbon to nitrogen ratio was identified as a parameter that plays an important role for the optimal production of ALE, tryptophan, and PHA. The sludge retention time effect is more pronounced for the production of ALE and tryptophan. Additionally, salinity levels in the bioreactors can potentially be manipulated to increase ALE and phosphorus yields simultaneously. Some existing knowledge gaps in the scientific literature concerning the recovery of these resources from AGS were also identified. Regarding industrial applications, tryptophan has the longest way to go. On the other hand, ALE production/recovery could be considered the most mature process if we take into account that existing alternatives for phosphorus and PHA production/recovery are optimized for activated sludge rather than granular sludge. Consequently, to maintain the same effectiveness, these processes likely could not be applied to AGS without undergoing some modification. Therefore, investigating to what extent these adaptations are necessary and designing alternatives is essential.