Effects Of Bioparticle Circulation On The Performance Of Circulating Fluidized Bed Biofilm Reactor

A lot of biological technologies have been used in wastewater treatment.With increasingly stringent emission standards and space constraints,the traditional bioreactors have been unable to meet the demand.So more and more new reactors are used in wastewater treatment.Circulating fluidized bed bioreactor(CFBBR)is an efficient equipment.Recently It is used to treat wastewater due to the good efficiency,small footprint,low sludge production,uniform mixing in the bed and so on.And the biofilm can be effectively controlled so as to improve the performance of CFBBR by the operation of the bioparticle circulation in the CFBBR.In this paper,the CFBBR was operated in three bioparticle circulation rate of 50 g bare particles/d(Stage ?),100 g bare particles/d(Stage I)and 200 g bare particles/d(Stage III).During the 380 days of whole experiment,the performance of the synthetic wastewater treatment in CFBBR and Special Nitrification Rate and Special Denitrification Rate of the attached biomass and the detached biomass were tested.The effects of bioparticle circulation rate on nitrification and denitrification,biofilm thickness,sludge yield and the pseudo-steady state of the system were investigated.The results showed that the three bioparticle circulation rate had no effect on COD removal and ammonia nitrogen removal of the CFBBR in all stages and the removal rates were stable at 95% and 98% respectively.with the increased in bioparticle circulation rate,the overall average total nitrogen removal of the CFBBR increased slightly from 85.1% to 90%.The bioparticle circulation rate had little effect on the nitrification,and the aerobic bed was basically close to the complete nitrification in all the stages.But it had a great influence on the denitrification reaction.The lower bioparticle circulation rate(50 g bare particles/d)would lead to bad denitrification in the anoxic bed and the system could not acquire pseudo-steady state.It was also found that the high bioparticle circulation rate would not only promote and stabilize Simultaneous nitrification and denitrification(SND)occurred in the aerobic fluidized bed,but also increase the biofilm thickness of the aerobic fluidization bed.The higher bioparticle circulation rate,the faster pseudo-steady state of CFBBR system could be entered.Despite the sludge production was not affected by the bioparticle circulation rate in the experiment,the sludge residence time would increase with bioparticle circulation rate.