Influence of operating regime on resource recovery in aerobic granulation systems under osmotic stress

Abstract

Aerobic granular sludge (AGS) systems have great potential for biopolymers recovery, especially when subjected to adverse conditions. This work aimed to study the production of alginate-like exopolymers (ALE) and tryptophan (TRY) under osmotic pressure in conventional and staggered feeding regimes. The results revealed that systems operated with conventional feed accelerated the granulation, although less resistant to saline pressures. The staggered feeding systems favored better denitrification conditions and long-term stability. Salt addition gradient increase influenced biopolymers’ production. However, staggered feeding, despite decreasing the famine period, did not influence the production of resources and extracellular polymeric substances (EPS). Sludge retention time (SRT), which was not controlled, proved to be an important operational parameter with negative influences on biopolymers’ production in values greater than 20 days. Thus, the principal component analysis confirmed that the production of ALE at low SRT is related to better-formed granules with good sedimentation characteristics and good AGS performances.