| Aerobic granular sludge is a kind of compact microbial self mmobilized aggregates.Extensive attention has been paid to the aerobic sludge granulation in the fields of wastewater treament technology due to its imparable advantages such as maintenance of high biomass, high setting velocity,withstanding to high organc load,etc.Previous studies indicated that almost aerobic granules were cultivated in either continuously operated reactors,such as aerobic upflow sludge blanket(UASB)or sequencing batch reactors(SBR).Alought there have already been a few reports on the cultivation of aerobic granular sludge under continuous-flow operation, but the results did not provide any information about mechanism of the reactors' design and aerobic granulation process.Bacsed on the previous aerobic granulation reactors designed by other reseachers,this article took the factor influencing the formation of aerobic granulation and the characteristics of aerobic granulation into consideration,designing an innovative continuous-flow reactor,which have the advantages of the collections of ABR reactor, anaerobic/oxic sludge process and the swimming—bed technology.In order to illuminate the effects of the pore plate,a same reactor without the pore plate was set up and carried out at similar conditions for comparative experiments.Suspended flocculent sludge was inoculated for the starup of the two rectors,and the system was fed with domestic wastewater.Under the same operating conditions,the aerobic granules was observed on the 10 th day and became mature on the 30 th day.The mean diameter of the mature aerobic granules in R1 is about 3mm after the system reached the steady state.However, aerobic granules appeared on the 15 th dayt in the reactor without the pore plate and it took 44 days to become mature granules.And its average diameter is about 1.0—3.0mm.The aerobic granules in R1 has a higher setting velocity and better stability than that in R2.Then,the R1 kept stable operation until 100 th day,while the aerobic granules in R2 was disintegrated on 63 th day and R2 was collapsed on 65 th day.In the formation of the aerobic granules,R1 has a higher pollutant removal rate than R2. The maximum removel rate to CODcr was 94%, TN85%, NH3—N93%,TP81% after the system stablized in R1.While R2 has a comparative lower removel rate: to CODcr was84%, TN 72%, NH3—N 84%,TP 73%.There are two reasons behind this difference:(1)R1 has a higher biomass concentration and richer microbial population due to the retention of microorganisms and the biofilm on the pore plate.(2)The aerobic granules in R1 has a better biological activity than that in R2.In order to obtain a further understanding of the pore plate in the formation of the aerobic granules,this article analyzed the microbial and hydrodynamic effects of the pore plate,eventually drew the following conclusions:(1)The biofilm detached from the pore plat with the action of hydrodynamic shear force would become a intial granular nucleus,which reduced the time for granulation.While the the microbe in R2 must experienced continuous collisions to join the particles together to form sludge aggregates.(2)The results of simulation software showed that the flow pattern in R2 was optimized in the presence of the pore plate,which created the conditions for the deached biofilm and made the deached biofilm trun into a regular granule,hence promoted the granulation process. |
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