Strengthening of aerobic sludge granulation by the endogenous acylated homoserine lactones-secreting strain Aeromonas sp. A-L3

Abstract

Increasing the quorum sensing effect has become an effective means of strengthening the sludge granulation process in recent years, but most of the current methods for achieving this effect involve the direct addition of signal molecules. To identify a more environmentally friendly biological method for accelerating the formation of aerobic granular sludge (AGS) and further reducing the operating cost, an Aeromonas sp. strain (A-L3) screened from AGS seed sludge was added to strengthen the granulation of aerobic sludge in a sequencing batch reactor (SBR). The results showed that strain A-L3 could secrete N-butyryl homoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL) and that these secretions were related to the OD600. The formation time of AGS could be shortened, and the aerobic granules could develop a larger size and denser structure. Furthermore, the addition of the endogenous strain A-L3 promoted the secretion of extracellular polymeric substances (EPS), and the efficiencies of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal were improved. In addition, the contents of C4-HSL and C6-HSL were 27.77% and 20.46% higher, respectively, than those in the control on day 42. In summary, the addition of the AHLs-secreting strain A-L3 may be a novel economically and environmentally favorable strategy for strengthening the formation of AGS.