The effect of metal ions on the microbial attachment ability of flocculent activate sludge

As a kind of biofilm structure, microbial attachment was believed to play an important role in the aggregation and stability of flocculent activated sludge (FAS), and also its translation to aerobic granular activated sludge (AGAS). The aim of this study was to investigate the effect of Ca2+, Mg2+, Cu2+, Fe2+, Zn2+, K+, and Na+, which were frequently found in the biological wastewater-treatment systems on the microbial attachment of FAS, in order to provide a new strategy for the cultivation of FAS and AGAS. The results showed that different metal ions had different effects on the process of microbial attachment of FAS; in particular, Cu2+, Fe2+, and Zn2+ could increase the microbial attachment ability of FAS at appropriate concentrations, and disrupted the process at higher concentrations. Mg2+ would greatly enhance the microbial attachment of FAS at lower concentrations but then the biomass of attachment was fallen down to a level close to that of the control. However, Ca2+), K+, and Na+ always exhibited a positive impact on the microbial attachment of FAS. Besides, the concentration of FAS suspension and the culture time both had an effect on the microbial attachment of FAS. Moreover, the acyl-homoserine-lactones-based quorum-sensing system, the content of EPS, and the relative hydrophobicity of FAS had been greatly influenced by metal ions. As all these parameters had close relationships with microbial attachment process, changes in these parameters may affect the microbial attachment of FAS.