Study On System And Operation Optimization Of A Biofilm Reactor With Microbubble Aeration Using SPG Membrane

Aeration is the basic process for aerobic biological wastewater treatment processes.Bubble technology is the most widely used for aeration. One of the main purposes ofaeration is to provide dissolved oxygen for microbial to remove pollutants, andsimultaneously, aeration is the main power consumption. Microbubble could enhance theoxygen mass transfer process. Microbubble generation using the SPG membrane as thegas liquid dispersion medium has been developed. Continuous operation of biofilmreactors with microbubble aeration using SPG membrane has been realized. Themicrobubble generation conditions and oxygen transfer characteristics were studied inclean water. The system of biofilm reactor with microbubble aeration using SPGmembrane was optimizated, including SPG membrane types, filler type and filling mode.The operatiional conditions of microbubble aerated biofilm reactor were also optimizated,including air flux and organic loading rate.The results showed that the microbubbles could be generated stablly at air flux of20mL/min. Gas-water mixture presented milk white. A lot of microbubbles wereobserved in liquid phase with uniform distribution. To increase the surface wettability orreduce the pore size of SPG membrane were helpful to produce smaller bubbles, improvethe gas holdup and enhance oxygen mass transfer at air flux of20mL/min. Whenhydrophilic membrane with pore size of0.6μm was used under these conditions, themean diameter of generated microbubbles was31μm, the gas holdup was0.6%, the masstransfer coefficient was0.31min-1, and oxygen transfer efficiency was82.3%. In addition,to reduce surface wettability or increase the pore size of SPG membrane could reducepower consumption under the same conditions.Biofilm reactor with microbubble aeration using SPG membrane could be used for along-term operation. System optimization results showed that the removal of pollutantscould be improved when pore size of hydrophobic SPG membranes was sammler, porousfiber filler was selected and the bed layer was loosed. When SPG membrane with porediameter of0.6μm and porous fiber filler with bed porosity of81.34%were employed, theremoval efficiency of COD and ammonia could reach85.61%and82.63%. Oxygenutilization efficiency could reach close to100%. When stereo hollow fillers were used,COD removal rate could reach91.94%, but total nitrogen removal was reduced due todenitrification inhibitation. Optimization of operating parameters results showed that increasing air flux and organic loading rate were favorable for the removal of pollutants.The better air flow was50mL/min, and COD and ammonia nitrogen removal rate were91.32%and93.56%. The better organic loading rate was0.9kg (m3.d)-1, and COD andammonia nitrogen removal rate were90.18%and36.08%. Oxygen utilization efficencywas close to100%.