Bioaugmentation of intertidal sludge enhancing the development of salt-tolerant aerobic granular sludge.

Three parallel bioreactors were operated with different inoculation of activated sludge (R1), intertidal sludge (ItS) (R2), and ItS-added AS (R3), respectively, to explore the effects of ItS bioaugmentation on the formation of salt-tolerant aerobic granular sludge (SAGS) and the enhancement of COD removal performance. The results showed that compared to the control (R1-2), R3 promoted a more rapid development of SAGS with a cultivation time of 25 d. Following 110-day cultivation, R3 exhibited a higher granular diameter of 1.3 mm and a higher hydrophobic aromatic protein content than that in control. Compared to the control, the salt-tolerant performance in R3 was also enhanced with the COD removal efficiency of 96.4% due to the higher sludge specific activity of 14.4 g·gVSS−1·d−1 and the salinity inhibition constant of 49.3 gL−1. Read- and genome-resolved metagenomics together indicated that a higher level of tryptophan/tyrosine synthase gene (trpBD , tyrBC) and enrichment of the key gene hosts Rhodobacteraceae , Marinicella in R3, which was about 5.4-fold and 1.4-fold of that in control, could be the driving factors of rapid development of SAGS. Furthermore, the augmented salt-tolerant potential in R3 could result from that R1 was dominated by Rhodospirillaceae , Bacteroidales , which carried more trehalose synthase gene (otsB , treS), while the dominant members Rhodobacteraceae , Marinicella in R3 were main contributors to the glycine betaine synthase gene (ectC , betB , gbsA). This study could provide deeper insights into the rapid development and improved salt-tolerant potential of SAGS via bioaugmentation of intertidal sludge, which could promote the application of hypersaline wastewater treatment. [Display omitted] • Intertidal sludge-added activated sludge was more favorable for granulation process. • The intertidal sludge enhanced the salt-tolerant potential of SAGS. • The possible tryptophan/tyrosine protein contributor Rhodobacteraceae, Marinicella were dominated. • The metagenomic portrait of communities responsible for salt-tolerant physiology were identified. [ABSTRACT FROM AUTHOR]