The Dynamic Principles Of Denitrifying Simultaneous Phosphorus Removal And Application To Improving The Performance Of MSBR Operation

The research, development and application of activated sludge models and biological metabolic model are new aspects of international water science and technology field, the integration with different models and application are recently focused on. This study proposed the mixture VFA integrated model for enhanced phosphate uptaking, through integrating ASM 2D with biological metabolic model. After evaluating the model, MSBR system was simulated and optimized. Through these researches the following conclusions have been obtained.â‘ Based on the research of biochemistry metabolic mechanism and mixture VFA anaerobic metabolic model, the mixture VFA biological phosphate uptaking model was proposed, and the theoretical stoichiometries were determined. In place of the part related with phosphate of ASM 2D by biological metabolic phosphate uptaking model, the enhanced biological phosphate uptaking integrated model was formed. In the integrated model, Stoichiometry and kinetic equation were refined, and two different sets of kinetic parameters were used to describe aerobic and anoxic phosphorus uptaking process.â‘¡With the aim of the enrichment of phosphate accumulating organisms and nitrifying bacteria, anaerobic-aerobic/anoxic and aerobic SBR were operated. MSBR system was operated inoculated activated sludge enriched by SBRs, and had stable nutrient removal efficiency. Effluent COD was less than 30mg/L, and the removal efficiency was 92%⁹3%. The PO₄^3--P removal efficiency was about 86%⁹5%, and the effluent phosphate was 0.31⁰.71mg-P/L。The average total phosphate uptake was 19.62 mg-P/L, and the uptake amount in aerobic tank and anoxic phase of SBR was about 16.42mg-P/L and 2.00mg-P/L, respectively. TN removal efficiency was just 66%⁷5%, effluent TN was 15.30²3.10mg-N/L, and mainly owe to nitrate form, about 3.9²1.1mg-N/L.â‘¢Aerobic and anoxic phosphate uptaking stoichiometric characteristic experimental results of activated sludge from MSBR showed that under aerobic condition, when acetic and propionic acid was as carbon source, the amount of Poly-P produced and glycogen regenerated per PHA oxidized during aerobic phase was 0.65 and 0.51mmol-P X_PP/mmol-C X_PHA, 0.35 and 0.26mmol-C X_GLY/mmol-C X_PHA, respectively. Under anoxic condition, the stoichiometry of Poly-P produced and glycogen regenerated was 0.61 and 0.44 mmol-P X_PP/mmol-C X_PHA , 0.39 and 0.28 mmol-C X_GLY/mmol-C X_PHA when the carbon source was acetic acid to propionic acid, respectively. The efficiency for nitrate denitrifying was more higher when actetic acid was carbon source, the amount of phosphate and glycogen per denitrifying 1 mmol-N/L NO₃^- was 1.32 mmol-P and 0.85 mmol-C。However, when propionic acid as the carbon source, these values was 1.03 mmol-P X_PP/mmol-N NO₃^- and 0.66 mmol-C X_GLY/mmol-N NO₃^-, respectively. Meanwhile the results also showed that when anoxic initial PO₄^3--P/NO₃^--N was1.05⁰.84(mmol-P/mmol-N), simultaneously denitrifying phosphate and nitrogen removal was completed.â‘£Aerobic and anoxic phosphate uptaking kinetic characteristic experimental results indicated that the maximum aerobic and anoxic specific conversion rate of Poly-P produced, PHA oxidized and glycogen regenerated was 0.035 and 0.023mmol-P X_PP/mmol-C X_PAO/h, 0.243 and 0.023mmol-C X_PHA/mmol-C X_PAO/h, 0.044 and 0.031mmol-C X_GLY/mmol-C X_PAO/h, respectively。Comparing with these, the specific Poly-P produced rate was only 65.7% of aerobic rate, 85% and 70% for PHA oxidization and glycogen regeneration.⑤Model parameter sensitivity analysis showed that Ypo4, Yxglyo2, Yxphano3, YA, and kh, bH, kpp, kgly, and kpha,μA of the integrated model had significant impact on the performance of the system and denitrifying phosphate uptaking efficiency. The estimated results are as follows: YH=0.76, bH=0.293d-1,μH=5.79d-1, YA=0.235,μA=1.00d-1, which were similar to the recommended values ASM 2D (20℃). The specific conversion rate of aerobic and anoxic PHA oxidation, Poly-P synthesis and glycogen regeneration for PAO were 5.72 and 4.73mg-COD X_PHA/mg-COD X_PAO/d, 0.52 and 0.09mg-P X_PP/mg-COD X_PAO/d, 0.68 and 0.43mg-COD X_GLY/mg-COD X_PAO/d, respectively. X_OHO, X_PAO and X_AUT accounting for VSS of activated sludge in the MSBR system, was about 25%, 15% and 5.17%, respectively.â‘¥Based on the proposed enhanced biological phosphate uptaking integrated model, MSBR mathematical model developed. MSBR was again operated after optimizing operational parameters by model orthogonal test. The data indicated that the removal efficiency of COD and PO₄^3--P was about 95% and 72%⁸4%. PO₄^3--P in effluent was about 1.02¹.23mg/L. The ratio of aerobic and anoxic phosphate uptake amount among the total uptake amount was 55.09% and 42.46%. NH4+-N and NO₃^--N in effluent was about 0.03⁰.79mg/L and 6.60⁸.06mg/L, the removal efficiency was up to 99.3% and 89.64%. TN in effluent was largely reduced to 10mg/L. After optimized, TN removal efficiency was improved, and NO₃^--N effluent was reduced. The PO43--P removal efficiency was slightly reduced. However, the ration of anoxic phosphate uptake amount was increased, and the denitrification was complete, so the denitrifying phosphate removing was enhanced, the effluent PO₄^3--P was more than 1.0mg/L. So system operating parameters must be adjusted. After adjustment, the removal efficiency of COD was not significant changed, PO₄^3--P removal efficiency was increased to 87%⁹3% and PO₄^3--P in effluent was less than 0.5mg/L. The average ratio of aerobic phosphate uptake amount was increased to 69.63%, while the ration of anoxic was reduced to 30.02%. NH4+-N in effluent was steady about 0.2mg/L, NO₃^--N in effluent was increased to 13.06mg/L and TN could be stabilized less than 15mg/L.⑦The simulation results of MSBR system with enhanced biological phosphate uptaking integrated model showed that the simulation error for COD timely distribution was less than 10%. For the simulation of anaerobic phosphate release and aerobic phosphate uptake, the error was only 1.55% and 4.92%. However the absolute simulation error of anoxic and effluent PO₄^3--P was 0.04⁰.14mg/L. The average simulation error for NH4+-N concentration on the anaerobic pond was ahout 5.21%. The relative error of aerobic tank, anoxic and effluent NO₃^--N concentrations between measured and predicted values was 2.84%, 5.00% and 0.83%, respectively.⑧Diversity of activated sludge microbial community structure analysis showed that three systems had a high diversity of bacterias, including Betaproteobacteria, Bacteroidetes, Deltaproteobacteria, Gammaproteobacteria, Alphaproteobacteria, the homology with similar species was 93% to 100%. In anaerobic/aerobic, there were Sphingobacterium, Moraxella, Comamonas testosteroni, Flavobacterium sp., Pseudomonas. Anaerobic-anoxic SBR mainly contained Pseudomonas, Uncultured Bacteroidetes, Brevundimonas. Pseudomonas, Acinetobacte, Brevundimonas, Sphingomonas, Nevskia sp. and Shigella sp., Uncultured bacterium were detected in MSBR system, and the bacterial community succession were as follows: Pseudomonas, Brevundimonas, Sphingomonas, Nevskia,.