| Denitrifying phosphorus removal granular sludge is a kind of new process for biological phosphorus and nitrogen removal which has the both advantages of denitrifying phosphorus removal and aerobic granular sludge. This study investigates two different cultivation modes of denitrifying phosphorus removal granular sludge: A/O→A/O/A (anaerobic/oxic→anaerobic/oxic/anoxic) mode and A/O/A (anaerobic/oxic/anoxic) mode, researches the possibilities of enriching DPAOs after the granulation process and enriching DPAOs with the granulation process, studies the physical characteristics of granules cultivated under different modes and nutrients removal efficiencies, and analyzes the denitrifying phosphorus removal performances of granules. In addition, this study uses the SBARs (sequencing batch airlifting reactors) which have low H/D (height/diameter) ratio, and cultivates granules without temperature control, which could provide theoretical basis and technical support for practical application of aerobic granular sludge. Conclusions are mainly following as,1. It takes 49 d and 58 d for mature granules formation under A/O→A/O/A mode and A/O/A mode, respectively. SEM observation shows that the surface of granules cultivated under A/O→A/O/A mode consists of bacillus and a little amount of filamentous, while cocci plays a dominating role in granules cultivated under A/O/A mode.2. Settling velocity and specific gravity of granules cultivated under A/O/A mode (35.9 m/h and 1.061 g/cm3) are higher than that of granules cultivated under A/O→A/O/A mode (30.4 m/h and 1.022 g/cm3), and the mean size of the former is also larger than that of the latter, but the granular relative intensity has not been influenced by that.3. Under both cultivation modes, the variation trends of EPS are increase-decrease-increase. PN/PS ratio is positively correlated with the relative hydrophobicity. The coefficients of A/O→A/O/A mode and A/O/A mode are 0.949 and 0.988, respectively.4. In this study, the C, N and P loading of influent are 0.48 - 0.74 kg/m3·d, 0.063 -0.076 kg/m3d and 0.011 - 0.018 kg/m3·d. The average effluent concentrations of COD, NH4+-N and TP in A/O→A/O/A reactor are 57.18 mg/L, below 1 mg/L and 4.55 mg/L. Their corresponding removal efficiencies are 86.48%,99.17% and 65.56%. After the addition of anoxic phase, removal effciencies of TN and TP are improved. The maximum TN removal effciency is 74.3%. The average effluent concentrations of COD, NH4+-N and TP in A/O/A reactor are 59.72 mg/L, below 1 mg/L and 1.74 mg/L. Their corresponding removal effciencies are 85.9%,98.46% and 91.13%. The maximum TN removal effciency is 81.8%. The 33 d of sludge refrigation has unfavourable influence on the TP removal in A/O→A/O/A reactor.5. Under the two modes, variation trends of P content of sludge and PHB content are both accorded with the metabolic characteristics of PAOs, especially under A/O/A mode. It is shown from batch experiments that the DPAOs fractions in A/O→A/O/A reactor and A/O/A reactor are 20.9% and 44.7%, respectively. Therefore, in terms of DPAOs enrichment, A/O/A mode has superiority.
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