OUR Response To Aerobic Phosphorus Uptake In Enhanced Biological Phosphorus Removal Process

Purpose of this research is to understand the characteristics of oxygen utility inbiological P removal and investigate the potential application in state monitoring andparameter identification. PAOs were enriched in lab-scale anaerobic-aerobic SBR.Using this enriched sludge, respirometric experiments of aerobic P uptake underdifferent conditions were conducted. Forthermore, the response relationship betweenOUR （Oxygen Uptake Rate） variation and the normal state indexes, such as P uptakerate and PHA oxidation rate, were investigated qualitatively and quantificationally.Finally, OUR-based parameter identification of aerobic P uptake submodel were studiedand parameters/parameter combinations were estimated using OUR data. Through theseresearches the following results and conclusions have been obtained.①The methanogens were successfully enriched in the SBR reactor. The effluentPO₄^3--P reached below1.2mg/L after approximately2-months anaerobic-aerobic SBR’soperation by alternating carbon sources between acetate and propionate at a frequencyof one sludge ages. Using acetate acid and propionate acid as carbon source,PO₄^3--P/VFA, PHA/VFA, specific phosphorus release rate and Specific PHA synthesisrate of the enriched sludge during anaerobic stage are0.65mmol-P/mmol-C and0.4mmol-P/mmol-C,1.25mmol-C/mmol-C and1.2mmol-C/mmol-C,0.98mmol-Pg^-1vss*h^-1and0.39mmol-Pg^-1vss*h^-1,1.91mmol-Cg-1vss*h^-1and1.17mmol-Cg-1vss*h^-1, respectively. These indexes are in the ranges of reported values,demonstrating the successful enrichment of PAOs.②Respirometry of aerobic P uptake under PHA as sole carbon sourse show clearOUR response to P uptake. The end-point of P uptake corresponds with the start-pointof endogeneous respitation. Meanwhile, the variations of P uptake rate and PHAoxidation rate represent obvious consistency with OUR changes. It is concluded thatunder this condition, OUR is capable of monitoring of the process state of aerobinc Puptake.③Under the condition of PHA as sole carbon sourse, relative error between themeasured PHB,（PHV+PH2MV） and the estimated PHB,（PHV+PH2MV） based onOUR were0.35％-30.2％and2.95％-29.8％. Comparing to the complexity andaccuracy of ordinary PHA testing, soft measurement of PHA based on OUR isfeasibile. ④PHA can be aerobically oxidized without P uptake, resulting OUR response.However, the uptake of P could accelarate the degradation of PHA and change the OURcharacteristics, which showed that using OUR to control the running of wastewatertreatment process is feasible.⑤In term of the exogenous COD concentrations used in this research, the totalOUR profiles are still correspondent to the P uptake and PHA oxidation. However, withthe increase of exogenous COD concentration, profiles of OUR that measured inexperiment tends to saturation, and apart from the concentration-time curves of P andPHA. This result implicates that the enough high exogenous COD would generatedextra OUR “covering” the OUR relating to PHA oxidation and P uptake, resulting infailure in the application of OUR for the monitoring of aerobic P uptake process.⑥The influence of pH on the metabolic activity of PAOs could be indicated by themax value and the feature of OUR profile. Also, pH changes could indicate the uptakeof PO43—P, but OUR are more significant and sensitive than pH signal.⑦The parameter identification of aerobic P uptake sub-model based on OUR assole measurements was investigated. The results showed that it is impossible to estimatethe stoichiometric kinetic parameters of PAOs during aerobic phase by OUR and SPO4were measured. However, when OUR, SPO4and XPHA（0） were measured, threeparameters or parameter combinations of PAO’s aerobic growth process could beestimated. The estimated results are as follows:Y_PAO=0.75g（COD）/g（COD）,K_PHA· X_PAO=6.9351g（COD）/m³, μ_PAO·(1-Y_PAO)/Y_PAO·X_PAO=0.49918g（COD）/m min^-1,which were similar to the recommended values ASM2（20℃）.