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Abstract
In this study, the influence of temperature on sludge settleability and bacterial community structure was investigated in two EBPR systems for a better understanding of the seasonally variable settleability. The results indicated that settleability depended both on the filament content and on the non-soluble phosphorus (Pns) and non-volatile suspended solids (NVSS) contents at varying temperatures. When the temperature was increased, settleability was significantly improved because of the substantial reduction in the filaments. When the temperature was decreased, settleability changed slightly in the long run and was mainly determined by Pns/VSS and NVSS/VSS (p < 0.05). Canonical correspondence analysis results indicated that bacterial community structure was significantly correlated with temperature and settleability (p < 0.01). At a high temperature (25°C), 21 species mostly affiliated with Proteobacteria, followed by Bacteroidetes, were stimulated greatly. The proliferation of Bacteroidetes might have a close relation with the improvement of settleability. At a low temperature (15°C), 25 species which were different from that at a high temperature proliferated in the system. These species mostly affiliated with Proteobacteria, followed by Actinobacteria. The large population of Actinobacteria was closely correlated with poor settleability. This work provides a valuable basis for the control of seasonal sludge bulking in EBPR systems.