Production Test Of Physicochemical/Biochemical Synergistic Phosphorus In Modified Oxidation Ditch

Currently, Modified oxidation ditch process is more used for biological nutrientremoval process, and has better removal effect. But it is difficult to meet the effluentstandards of TP and TN, when the influent C/N of urban sewage is low, the processstandards. In this paper, in the premise of ensuring biological nutrient removal throughthe priority process regulation, used the Physicochemical/Biochemical synergisticphosphorus removal processes to improved phosphorus removal capacity of oxidationditch.In the Production test studied the effect of the improved oxidation ditchPhysicochemical/Biochemical synergistic phosphorus removal system, the effect ofdosing polyphosphate ferric sulfate （PPFS） for the activated sludge system. Examinedthe mechanism and strengthen measures of anaerobic phosphorus release and aerobicphosphorus uptake in the Physicochemical/Biochemical synergistic phosphorus removalsystem, determined the control parameters of stable operation, analyzed the matchingmod of this new system with the original biological processing system. The mainconclusions through the experiments are the following:①When dosing15mg/L polyphosphate ferric sulfate （PPFS） in oxidation ditchoutlet, the effluent TP is less than1.0mg/L, the average removal rate is60%⁷5%. TheCOD, TN and NH₄⁺-N removal effect have little change, and basically stable at88%,75%and94%. Dosing flocculant had no apparent negative impact for biochemicalsludge activity, and improved the sludge settling properties. Also the increased physicaland chemical sludge accounted for the amount of the sludge growth rarely, so need notchange the original sludge disposal system.②The main control condition of anaerobic phosphorus release in the improvedoxidation ditch physicochemical/biochemical system are: the reflux ratio R is75%¹00%, the MLSS is3000³500mg/L, the DO in anaerobic tank is0.2mg/L or less.At the same time, in order to ensure fully release of the phosphorus, should keep theORP lower. Then maintaining good conditions of denitrification, reduced the effect ofnitrate for the anaerobic phosphorus release.③According to the result of test and process operation control, the controlparameter of the system are: the MLSS is3000³500mg/L, the DO in oxidation ditch is1.2².0mg/L, DO in the anoxic zone is0.2⁰.5mg/L, DO in anaerobic tank is0.2mg/L or less, the ORP is-100⁵0mV, the R is75%¹00%, the SRT is6¹0days. The effluentwater quality reaches the first Grade B standard of《the standard of pollution emissionsin Urban sewage treatment plant》（GB18918-2002）.④The Physicochemical/Biochemical synergistic phosphorus removal system havea good match with the oxidation ditch SND process, and increased sludge have noimpact on the original process system, so no need to strictly control the refluxconditions, and need not change the original sludge treatment system. The amount ofdischarge sludge can increase every5days, the increase amount is about three times thecumulative dosage.