| As a new sewage treatment technology,aerobic granular sludge(AGS)technology has good sedimentation performance,high nitrogen and phosphorus removal efficiency,and can simplify the process,reduce the floor space and improve economic benefits during operation,so it has attracted the attention of researchers.However,the formation of AGS is a complex process,affected by a variety of factors,resulting in a long sludge granulation cycle,the required reactor H/D ratio is relatively large.Also,it is difficult to carry out pilot studies in the actual production site,which greatly limits the industrial application of this technology.This paper combines numerical simulation and experiments,studies the influence of superficial gas velocity(SGV)and reactor H/D ratios on the formation of AGS,and then quickly cultivate AGS in the laboratory by adding activated carbon,and finally carries out pilot studies in the actual production site,the main research content and conclusions are as follows.The 3-D hydrodynamic model of the Sequencing Batch Reactor(SBR)was established,and the gas-liquid two-phase flow field characteristics in the reactor with a SGV of 0.5cm/s and 1.2cm/s and a H/D ratio of 3:1 and 5:1 were simulated by using FLUENT,and the radial distribution of gas holdup,axial liquid velocity and shear rate were compared.The results showed that the liquid flow was more complete in the reactor with larger SGV,and the gas holdup,axial liquid velocity and shear rate were larger.The circulation path within the reactor with a higher H/D ratio was longer,and the number of liquid vortices formed is greater,which was more conducive to the formation of AGS.AGS was successfully cultivated using reactors with H/D ratios of 3:1 and 5:1 in the laboratory.The morphological changes of sludge during granulation were recorded,the effects of reactor H/D ratios on sludge concentration(MLSS),sludge volume index(SVI)and sludge pollutant(COD and ammonia nitrogen)removal rate were analyzed,and the influence mechanism of reactor H/D ratio on sludge granulation was discussed in combination with the flow field simulation.Th e results showed that the reactor with a large H/D ratio can quickly cultivate AGS and strengthen the particle performance.In the early stage of sludge granulation,the pollutant removal efficiency is higher,but it does not affect the removal performance of mature AGS.The influence of activated carbon on the rapid cultivation of AGS was studied in the laboratory.The sludge micromorphology,MLSS,SVI and sludge removal performance of COD and ammonia nitrogen during sludge granulation were recorded and analyzed.The results showed that activated carbon can provide a"crystal nuclei" for AGS,allowing sludge to attach to it,thereby shortening the incubation time of AGS.In the early stage of the reaction,activated carbon accelerated the sedimentation rate of the surrounding sludge and avoided the loss of sludge.However,the pollutant removal performance of mature AGS is consistent.The pilot experimental platform was built in the domestic sewage treatment plant to carry out pilot research.The start-up of the pilot system using low-carbon domestic sewage as the influent was studied,and the COD concentration of the influent water was increased in the later stage of the reaction.The results showed that some particles can be observed at day 28 under low-carbon source influent conditions,but the granular growth was slow and the granulation rate was relatively low.After increasing the COD concentration of the influent water at day 90,the rapid growth of granular sludge was realized and the granular performance was enhanced,the granulation rate of the final sludge reached 60～70%.Finally,the problems existing in the current pilot system were pointed out,which has guiding significance for promoting the industrial application of AGS technology. |
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