Study On Performance Evaluation Of A Pilot-scale Microbubble-aerated Biofilm Reactor

The microbubble aeration is a new type of aeration technology.The high efficiencies of oxygen utilization and contaminant removal could be achieved using microbubble aeration in aerobic biological wastewater treatment.Therefore,mirobubble aeration shows potential application advantages for aerobic biological wastewater treatment.In this study,the operation performance and biofilm characteristics of a microbubble aerated biofilm reactor were investigated when different aeration modes were applied.Then a pilot scale biofilm reactor using OHR(Original Hydrodynamic Reaction)mixer for microbubble aeration was operated to treat campus domestic wastewater and its performances were compared under different operating conditions.Finally,the performance of the pilot scale microbubble aerated biofilm reactor was evaluated,and compared with conventional biological treatment processes under the same influent conditions.The results indicated that both carbon and nitrogen were removed simultaneously in the microbubble aerated biofilm reactor.When continuous aeration mode was applied,the removal efficiencies of COD,NH3-N and TN were 88.5%,53.4% and 43.4%,respectively.The corresponding loading rates removed of COD,NH3-N and TN were 1.60kg·(m3·d)-1,0.089kg·(m3·d)-1and 0.092kg·(m3·d)-1.When intermittent microbubble aeration mode was applied in the reactor,the aeration energy consumption decreased along with a decrease in aeration time,but the dissolved oxygen(DO)concentration also decreased.As a result,the biofilm active biomass,the abundances of functional microbial populations and aerobic bioactivity decreased all.Therefore,the contaminant removal became inefficient in the intermittent microbubble aeration mode.The elastic fiber filler seemed more suitable for the biofilm formation in the pilot-scale microbubble-aerated biofilm reactor.When the hydraulic retention time was 1h and the air flow rate was 40L·min-1,the better performance of the pilot-scale microbubble-aerated biofilm reactor was achieved.Under these conditions,the effluent COD concentration of the pilot-scale microbubble-aerated biofilm reactor was50~80mg·L-1.The loading rates removed of COD and NH3-N were 1.53kg·(m3·d)-1 and0.32kg·(m3·d)-1.When the raw campus domestic wastewater was treated in the pilot-scale microbubble-aerated biofilm reactor,the average COD ? NH3-N and TN removal efficiencies were 57.0%?17.4% and 15.8%,and the loading rates removed of COD?NH3-N and TN were 2.68kg·(m3·d)-1?0.17kg·(m3·d)-1 and 0.21kg·(m3·d)-1.The average oxygen utilization efficiency reached to 100% in this case.When the effluent of biological contact oxidation tank with poor biodegradability was treated in the pilot system,the average COD?NH3-N and TN removal efficiencies were 46.0%?17.1% and 14.1%,and loading rates removed of COD?NH3-N and TN were 1.53kg·(m3·d)-1?0.32kg·(m3·d)-1and0.28kg·(m3·d)-1.The average oxygen utilization efficiency was higher than 50% in this case.The contaminant removal performance of the pilot system was much more efficient than conventional biological contact oxidation process and biological aeration filter process under the same influent conditions.