Effects Of Sludge Age And Internal Return Ratio On Denitrifying Phosphorus Removal In A~2/O-MBBR Process

As traditional A2/O is not as stable and efficient in simultaneous biological nitrogenand phosphorus removal as it should be, A2/O-MBBR was proposed to solve this problem.DPAOs is highly desirable as it allows simultaneous P uptake and nitrate removal, savingin both COD (chemical oxygen demand) and aeration energy demand and with low sludgeproduction.it has been a research fouse. A2/O-MBBR process requires alternatinganaerobic/anoxic/aerobic environment to enrich DNPAOs.This study change SRT（20d、16d、12d、8d、4d respectively）and change internal return ratio(50%、100%、150%、200%、250%respectively) to reach the best condition of denitrifying phosphorus removal.A2/O-MBBR can realize the efficient operation of denitrifying phosphorusremoval.The phemonen of denitrifying phosphorus removal was found since the18d,intakeof phosphorus was high than that in aerobic zones since the24d.The removal rate of COD is found to be stable,range form82%to86%at differentSRTs.So as the removal rate of TN,range from82%-84%.However,both the two seem toreduce at SRT4d. With MBBR, removal rate of NH4-N has been found to be stable,rangeform95%to100%. The removal rate of SOP was found to rise fisrt and then decline withSRT shortened.It reaches the maximum92.43%at SRT12d.the amount of phosphate releasing and uptaking for unit sludge was concidered to risefisrt and then decline with SRT shortened.It reaches the maximum13.36mg/g at SRT12d.the intake of phosphorus in anoxic zone reaches the maximum789g/d·m3,too.the useof per unit PHB to intake phophorus by DNPAOs was found to rise first then decline.itreaches the maximum at SRT12d,so as the effiency of denitrifying Phosphorus removal.The percent of Rhodocyclus and related bacteria to bacteria reaches the maximum28.5%(±2%) by FISH. the copy of DNPAOs reaches the maximum3.699（×109Copy g-1）at SRT12d.SRT12d is the best SRT for enrichment of DNPAOs.The removal rate of COD is found to be stable,range form79.3%to85.95%atdifferent SRTs.So as the removal rate of TN,range from82.5%-84.51%. removal rate ofNH4-N has been found to be stable,range form94.75%to100%. The removal rate of SOPwas found to rise with improvement of internal return ratio.It reaches the maximum90atr=200%.At the moment,intake of phophorus and ultilization of PHB reaches themaximum,and the efficiency of denitrifying phosphorus removal reaches at r=200%.