Modeling The Partial Nitrification Process In SBR By Extended ASM1-2N Model Within C/N Ratio

Ammonium in wastewater can be removed through the conventional nitrification-denitrification process, during which ammonium is biologically oxidized to nitrate and then reduced to N2. Significant energy is consumed during this process due to aeration, but 25% of the energy can theoretically be saved through shortcut biological nitrogen removal (SBNR):ammonium is oxidized to nitrite and then reduced to N2.Many factors have been proved that have effects on the process of shortcut biological nitrogen removal such as temperature, pH, NH4+-N, COD in the influent et.al, while the effect of C/N ratio still needs to be furture studied. Based on the purpouse of finding out the effect of C/N on the process of partial nitrification, this study firstly took the experiment of four different effluents with different C/N ratio in SBR, then constructed the mathematical model of partial nitrification with the control item of C/N ratio and finally used this new model to fit the experiment data in SBR. Through the experiment results and modeling analysis, the main conclusion is as follows:(1) This study constructed three new models based on the ASM1-2N model. Different from the ASM1-2N, the new models transformed the nitrification process and the new C/N ratio control items were brought in. This new models extended the ASM1-2N to a new partial nitrification model with C/N ratio and the three new models ASM1-2N-standard, ASM1-2N-Monod, ASM1-2N-Logistic became the basic framework of the following modelling.(2) Under 30℃, pH=7, through changing the C/N ration in the influent of SBR, the experimental data of different forms in the water were tested in the 11h reaction period. Through these data, it was found out that the lower C/N ratio was benefit for the processs of partioal nitrification which could be a guide for how to make this process come true. In the meantime, through the analysis of the ralationships between the C/N ratio and nitrification, it was found out that when the C/N ratio was below 7.6, the reaction in the SBR was partial nitrification; when the C/N ratio was in the rank of 7.6～14, it was traditional nitrification in SBR; when C/N ratio was above 14, it was inhibition zone for the nitrification in SBR.(3) Based on the charactor of SBR reaction and the three new models, a model about SBR was constructed and was used to model three different scenarios with different C/N ratio.Through the comparing of modelling results and model evaluation, it can be seen that the performances of two models ASM1-2N-Logistic and ASM1-2N-Monod with new C/N ratio are better than the ASM1-2N-standard model.(4) Comparing the performances of three different models, the best is the ASM1-2N-Logistic model, and the sensitivity analysis of modelling parameters also finds out that the new parameters have a great effect on the effluent of N.In the meantime, the application of this new model to the highest C/N ratio influent scenario and the better performance also proves that this new model has pratical application and the control item about C/N ratio also has an important role in the modelling which constructed a better basic for the following extension and application.