Effect of Temperature on the Relationship Between Quorum-Sensing and Sludge Bulking

Temperature is a critical determinant in sludge swelling. Quorum sensing (QS) serves as a regulatory mechanism for bacterial self-propagation, growth, and variations in population density. It may have implications for controlling or limiting the phenomenon of sludge swelling. This study investigates the influence of temperature on system performance, population sensing, and microbial communities. Three SBRs were operated at distinct temperature settings: 30 degrees C (R1), room temperature (R2), and 15 degrees C (R3). The study findings indicate that at a temperature of 15 degrees C, the removal efficiency of NH4(+)-N and COD by the SBR was lower compared to other temperature settings. Microorganisms at this temperature secreted a higher quantity of EPS, with PN/PS levels surpassing those observed in the other reactors. R3 was stabilized to remain slightly swollen, with an SVI of 140-154 mg/L, and particle size growth was impeded. The study explored the correlation between QS and activated sludge performance. Enrichment of temperature-affected C4-HSL and C6-HSL within R3 was generally lower compared to the other reactors. Low temperature reduces the impact of the short-chain signaling molecules, while the long-chain C8-HSL becomes the dominating factor in QS. Temperature significantly determines the composition of microbial communities in systems. Thiothrix abundance was highest in R3 at 8.78 %, compared to R1 (1.49 %) and R2 (3.89 %) at the same stage. This suggests that Thiothrix is more easily enriched at low temperatures, resulting in poorer settling and sludge micro-swelling. Hydrogenophaga has potential to secrete C4-HSL and quench C8-HSL, while Novosphingobium has potential to secrete C6-HSL and C8-HSL in R3.