| Aerobic granular sludge technology, which has the advantages of excellentsludge settleability, high MLSS, abundant microbial populations, nitrogen andphosphorus simultaneously removal ability, is one of the hotspot in the biologicalwastewater treatment field. However, the cultivation condition of aerobic granularsludge is rigorous, resulting its application limited. The previous studies of ourresearch group found that granules could form naturally in the enhanced biologicalphosphorus removal system fed with synthetic wastewater. This study attempts toachieve the application of this phosphorus removal granules to domestic sewagetreatment.Three identical sequencing batch reactors operated in A/O mode were used inthis study. R1, R2reactor were inoculated with floc sludge and R3reactorinoculated with artificial cultured biological phosphorus removal granules. InfluentPO3-4-P concentration of R1, R2and R3reactor were8.45mg/L,3.45mg/L and3.50mg/L, respectively. The influence of different inoculation sludge on thegranules system stability and the pollutants removal efficiency was investigated. Atthe same time, the effect of influentPO3-4-P concentration on the formation ofbiological phosphorus removal granular sludge was also studied.On the sixth day after inoculation, tiny white granules appeared both in the R1and R2reactor. With the granules grew up and matured, the average sludge size inthe R1and R2reactor were250.3μm and165.9μm, respectively. Most of thegranules in both reactors were white. It was found that PAOs dominated in thegranuels formed in both the R1and R2reactor using the FISH technology. Atmature period of the granular sludge system, the average effluent COD,PO3-4-P,NH4-N, TN concentration of two reactor were36.17mg/L and38.39mg/L,0.14mg/Land0.09mg/L,0.41mg/L and0.42mg/L,20.33mg/L and19.66mg/L, respective ly.Because of the breakup of granules resulted from the running problem of blender inR1reactor, the nitrogen removal efficiency in R1was lower than that of the R2reactor.In the early inoculation stage of R3, part of granules disintegrated. Withoperation, the inoculated granules adapted to the domestic sewage and the granulesgradually recovered. At stable operation period, the average particle diameter was357μm and most of the granules were yellow-brown and a small part of granules were white. The quantitative PCR resuluts showed that the proportions of PAOs tothe total bacteria in the white, yellow-brown granules and sludge flocs were92.83%,21.91%and2.22%, respectively.The average effluent concentrations ofCOD,PO3-4-P,NH4-N and TN were38.63mg/L,0.10mg/L,0.41mg/L,15.47mg/L,respectively. About31.30%of the nitrogen was removed by the simultaneousnitrification, denitrification and phosphorus removal effect. The proportion ofDPAOs was29.33%of PAOs. The granular sludge had excellent resistance to shockloading of phosphorus and COD. The A/O/A/O and step-feed process could improvethe nitrogen removal performance.The EPS properties of granules and flocs were studied. Theprotein/polysaccharides ratio of EPS in granules was3.36, which is higher than thatof the flocculent sludge (2.78). Three dimensional fluorescence spectrum analysis ofthe EPS solutions showed that there were4fluorescence peaks in the EPS ofgranules and flocs in the three reactors, which were a humic-like acid fluorescencepeak, a fulvic-like acid fluorescence peak and two protein-like fluorescence peaks.Compared with the EPS of the sludge flocs, the peaks intensity of protein-like in thethe EPS of granular sludge was higher. The FTIR analysis result showed that theprotein spectrums of the granular sludge EPS was different from that of theflocculent sludge EPS. Thus, protein play an important role in the biologicalphosphorus removal granular sludge. |
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