Evaluation of the production of alginate-like exopolysaccharides (ALE) and tryptophan in aerobic granular sludge systems

Abstract

The engineering and microbiological aspects involved in the production of alginate-like exopolysaccharides (ALE) and tryp-tophan (TRY) in aerobic granular sludge systems were evaluated. The inclusion of short anoxic phase (A/O/A cycle–anaero-bic, oxic, and anoxic phase) and the control of sludge retention time (SRT ≈ 10 days) proved to be an important strategy to increase the content of these bioproducts in granules. The substrate concentration also has a relevant impact on the production of ALE and TRY. The results of the microbiological analysis showed that slow-growing heterotrophic microbial groups (i.e., PAOs and GAOs) might be associated with the production of ALE, and the EPS-producing fermentative bacteria might be associated with the TRY production. The preliminary economic evaluation indicated the potential of ALE recovery in AGS systems in decreasing the OPEX (operational expenditure) of the treatment, especially for larger sewage treatment plants or industrial wastewaters with a high organic load.