METHOD FOR COLLABORATIVE CONTROL OF ORGANIC NITROGEN AND INORGANIC NITROGEN IN DENITRIFICATION PROCESS

Abstract

A method for collaborative optimization control method for organic nitrogen and inorganic nitrogen in a denitrification process is provided. The method includes: establishing ASM-mDON-DIN models for simultaneous simulation of microbial dissolved organic nitrogen (mDON) and inorganic nitrogen (DIN) in denitrification processes; and selecting a corresponding ASM-mDON-DIN model according to a set carbon/nitrogen ratio to collaboratively optimize the concentration values of mDON and DIN in the effluent in the denitrification process, to obtain best process operation parameter values.

Claims

1. A method, comprising: S1: establishing ASM-mDON-DIN models for simultaneous simulation of microbial dissolved organic nitrogen (mDON) and inorganic nitrogen (DIN) in denitrification processes; and S2: selecting a corresponding ASM-mDON-DIN model according to a set carbon/nitrogen ratio to collaboratively optimize concentration values of mDON and DIN in an effluent of a denitrification process, to obtain best process operation parameter values.

2. The method of claim 1, wherein in S1, operations for establishing the ASM-mDON-DIN models comprise: S1-1: data collection: measuring chemical oxygen demand (COD), total nitrogen (TN), inorganic nitrogen (iDIN), dissolved organic nitrogen (rDON) and pH in an influent of a target sewage plant in the denitrification process, inorganic nitrogen (eDIN) and dissolved organic nitrogen (eDON) in the effluent, dissolved oxygen (DO), a hydraulic retention time (t) of a denitrification stage, and a mixed liquor suspended solid (MLSS) of activated sludge; S1-2: model construction: according to a kinetic process of production, transformation and consumption of mDON during a complete denitrification process, adding mDON as a new component and a carbon/nitrogen ratio as a new parameter into the ASM-mDON-DIN models, and constructing ASM-mDON-DIN models 1 and 2 at different carbon/nitrogen ratios by using mDON and DIN as objects; S1-3: model initialization: initializing the ASM-mDON-DIN models based on data collected in S1-1, measured values of model parameters and the ASM-mDON-DIN models constructed in S1-2; S1-4: model calibration: calibrating a parameter estimation function based on simulated mDON and DIN kinetics and a result of sensitivity analysis; and S1-5: model establishment: replacing initial parameter values in the ASM-mDON-DIN models with parameter calibration values to obtain calibrated ASM-mDON-DIN models 1 and 2.

3. The method of claim 1, wherein in S3, operations for selecting collaborative optimization parameters comprise: S2-1: setting process parameter values: determining set values of carbon/nitrogen ratio, pH and dissolved oxygen; S2-2: model selection: selecting the ASM-mDON-DIN model 1 or 2 according to a numerical value of the carbon/nitrogen ratio in S2-1; S2-3: collaborative optimization: based on the model selected in S2-2, obtaining a minimum value of a sum of a concentration of organic nitrogen and a concentration of inorganic nitrogen in the effluent and corresponding process operation parameters by using the process parameter values set in S2-1 as a design factor of a response surface methodology and the sum of the concentration of organic nitrogen and the concentration of inorganic nitrogen in the effluent as a response value; and S2-4: outputting best parameter values: outputting the minimum value of the sum of the concentration of inorganic nitrogen and the concentration of organic nitrogen in the effluent and the corresponding process operation parameters comprising the carbon/nitrogen ratio, pH and dissolved oxygen, obtained in S2-3.

4. The method of claim 2, wherein the measured values of model parameters comprise initial values of a yield coefficient (Y.sub.H) of anoxic growth of heterotrophic bacteria measured based on the data collected in S1-1, a proportion (f.sub.H,DON) of mDON formed by heterotrophic bacteria based on organism growth, an ammoniated mDON half-saturation constant (K.sub.H,DON) of heterotrophic bacteria, a maximum specific growth rate (μ.sub.H) of heterotrophic bacteria and a nitrate half-saturation constant (K.sub.NO.sub.3) of heterotrophic bacteria.

5. The method of claim 2, wherein inorganic nitrogen component S.sub.DIN comprises ammonia nitrogen, nitrate nitrogen and nitrite nitrogen.

6. The method of claim 2, wherein the ASM-mDON-DIN model 1 comprises 10 components, 8 processes, 22 parameters and a kinetic parameter of an inhibition constant (K.sub.I4S.sub.s) of the anoxic substrate of heterotrophic bacteria; and, the ASM-mDON-DIN model 2 comprises 10 components, 8 processes and 22 parameters: 10 components: heterotrophic bacteria X.sub.H, particulate inert substance X.sub.I, dissolved biodegradable organic matter S.sub.S, microbial organic nitrogen S.sub.mDON, ammonia nitrogen S.sub.NH, nitrate nitrogen S.sub.NO3, nitrite nitrogen S.sub.NO2, nitric oxide S.sub.NO, nitrous oxide S.sub.N2O and alkalinity S.sub.ALK; 8 processes: four-step anoxic growth of heterotrophic bacteria based on the dissolved biodegradable organic matter, comprising conversion of nitrate nitrogen into nitrite nitrogen, conversion of nitrite nitrogen into nitric oxide, conversion of nitric oxide into nitrous oxide and conversion of nitrous oxide into nitrogen, and decay of heterotrophic bacteria, ammonification of microbial dissolved organic nitrogen, assimilative reduction of nitrate nitrogen into nitrite nitrogen and assimilative reduction of nitrite nitrogen into ammonia nitrogen; and 22 parameters: a yield coefficient Y.sub.H of anoxic Ss-based growth of heterotrophic bacteria, an oxygen containing proportion i.sub.XB of organism, a proportion f.sub.H,DON of mDON formed by heterotrophic bacteria based on organism growth, a proportion f.sub.I of inert substances produced by organism, a maximum specific growth rate μ.sub.H of anoxic growth of heterotrophic bacteria, a half-saturation utilization constant K.sub.s of a substrate of heterotrophic bacteria, an ammonia half-saturation constant K.sub.H,NH of heterotrophic bacteria, an anoxic growth factor η.sub.2 of heterotrophic bacteria in a process 2, the anoxic growth factor η.sub.3 of heterotrophic bacteria in a process 3, the anoxic growth factor η.sub.4 of heterotrophic bacteria in a process 4, the nitrate nitrogen half-saturation constant K.sub.NO.sub.3, a nitrite nitrogen half-saturation constant K.sub.NO.sub.2, a nitric oxide half-saturation constant K.sub.NO, a nitrous oxide half-saturation constant K.sub.N.sub.2.sub.O, a decay coefficient b.sub.H of heterotrophic bacteria, an ammoniated mDON half-saturation constant K.sub.H,DON of heterotrophic bacteria, an ammonification rate κ.sub.α of microbial dissolved organic nitrogen, a NO.sub.3.sup.−—N half-saturation constant K.sub.7,NO3, of ANRA, an inhibition constant K.sub.I7NH of ammonia nitrogen in the ANRA process, an inhibition constant K.sub.I8NO2 of nitrite nitrogen in the ANRA process, a half-saturation constant K.sub.8,NO2 of nitrite nitrogen in the ANRA process and an oxygen half-saturation constant K.sub.H,O of heterotrophic bacteria.

7. The method of claim 2, wherein the ASMN-mDON-DIN models 1 and 2 are divided according to the carbon/nitrogen ratio in the influent: (1) when the carbon/nitrogen ratio is less than or equal to 4, the model 1 is selected, and the kinetic equations for the model 1 are as follows: $\mathrm{DIN}\left(S_{\mathrm{DIN}}\right):\frac{{\mathrm{dS}}_{\mathrm{DIN}}}{\mathrm{dt}}=\left(-i_{\mathrm{XB}}-\frac{f_{H,\mathrm{DON}}}{Y_H}\right)\left(V_1+V_2+V_3+V_4\right)+V_6+(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+$ $\frac{1}{0.571})V_2;$ $\mathrm{mDON}\left(S_{\mathrm{mDON}}\right):\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=\frac{f_{H,\mathrm{DON}}}{Y_H}\left(V_1+V_2+V_3+V_4\right)-V_6;$ $\mathrm{heterotrophic}\mathrm{bacteria}\left(X_H\right):\frac{{\mathrm{dX}}_H}{\mathrm{dt}}=V_1+V_2+V_3+V_4-V_5;$ $\mathrm{particulate}\mathrm{inert}\mathrm{substance}\left(X_I\right):\frac{{\mathrm{dX}}_I}{\mathrm{dt}}=f_I{V}_5;$ $\mathrm{dissolved}\mathrm{biodegradable}\mathrm{organic}\mathrm{matter}\left(S_S\right):\frac{{\mathrm{dS}}_s}{\mathrm{dt}}=-\frac{1}{Y_H}(V_1+V_2+V_3+$ $V_4)-1.14V_7-3.43V_8;$ $\mathrm{nitric}\mathrm{oxide}\left(S_{\mathrm{NO}}\right):\frac{{\mathrm{dS}}_{\mathrm{NO}}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_2+\left(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+\frac{1}{0.571}\right)V_3;$ $\mathrm{nitrous}\mathrm{oxide}\left(S_{N2O}\right):\frac{{\mathrm{dS}}_{N2O}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_3+\left(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+\frac{1}{0.571}\right)V_4;$ $\mathrm{alkalinity}\left(S_{\mathrm{ALK}}\right):\frac{{\mathrm{dS}}_{\mathrm{ALK}}}{\mathrm{dt}}=\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_1-(\frac{i_{\mathrm{XB}}}{14}+\frac{f_{H,\mathrm{DON}}}{14Y_H}-$ $\frac{1+2.86f_{H,\mathrm{DON}}-Y_H}{14.Math.\left(0.571Y_H\right)})V_2+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_3+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_4+\frac{1}{14}{V}_6+\frac{1}{7}{V}_8;$ (2) when the carbon/nitrogen ratio is greater than 4, the model 2 is selected, and the kinetic equations for the model 2 are as follows: $\mathrm{DIN}\left(S_{\mathrm{DIN}}\right):\frac{{\mathrm{dS}}_{\mathrm{DIN}}}{\mathrm{dt}}=\left(-i_{\mathrm{XB}}-\frac{f_{H,\mathrm{DON}}}{Y_H}\right)\left(V_1+V_2^{\prime }+V_3+V_4^{\prime }\right)+V_6+(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+$ $\frac{1}{0.571})V_2^{\prime };$ $\mathrm{mDON}\left(S_{\mathrm{mDON}}\right):\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=\frac{f_{H,\mathrm{DON}}}{Y_H}\left(V_1+V_2^{\prime }+V_3+V_4^{\prime }\right)-V_6;$ $\mathrm{heterotrophic}\mathrm{bacteria}\left(X_H\right):\frac{{\mathrm{dX}}_H}{\mathrm{dt}}=V_1+V_2^{\prime }+V_3+V_4^{\prime }-V_5;$ $\mathrm{particulate}\mathrm{inert}\mathrm{substance}\left(X_I\right):\frac{{\mathrm{dX}}_I}{\mathrm{dt}}=f_I{V}_5;$ $\mathrm{dissolved}\mathrm{biodegradable}\mathrm{organic}\mathrm{matter}\left(S_S\right):\frac{{\mathrm{dS}}_s}{\mathrm{dt}}=-\frac{1}{Y_H}(V_1+V_2^{\prime }+V_3+$ $V_4^{\prime })-1.14V_7-3.43V_8;$ $\mathrm{nitric}\mathrm{oxide}\left(S_{\mathrm{NO}}\right):\frac{{\mathrm{dS}}_{\mathrm{NO}}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_2^{\prime }+\left(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+\frac{1}{0.571}\right)V_3;$ $\mathrm{nitrous}\mathrm{oxide}\left(S_{N2O}\right):\frac{{\mathrm{dS}}_{N2O}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_3+(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+$ $\frac{1}{0.571})V_4^{\prime };$ $\mathrm{alkalinity}\left(S_{\mathrm{ALK}}\right):\frac{{\mathrm{dS}}_{\mathrm{ALK}}}{\mathrm{dt}}=\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_1-(\frac{i_{\mathrm{XB}}}{14}+\frac{f_{H,\mathrm{DON}}}{14Y_H}-$ $\frac{1+2.86f_{H,\mathrm{DON}}-Y_H}{14.Math.\left(0.571Y_H\right)})V_2^{\prime }+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_3+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_4^{\prime }+\frac{1}{14}{V}_6+\frac{1}{7}{V}_8.$

8. The method of claim 7, wherein the ASMN-mDON-DIN models 1 and 2 comprise 8 process rate expressions respectively, which are V.sub.1-V.sub.8 and V.sub.1′-V.sub.8′: (1) anoxic growths (V.sub.1 and V.sub.1′) of heterotrophic bacteria based on dissolved biodegradable organic matters (Ss) are:
V.sub.1=μ.sub.H.Math.X.sub.H(t).Math.M.sub.H,S.sub.s(t).Math.M.sub.H,NH(t).Math.M.sub.H,NO.sub.3(t).Math.M.sub.H,O(t);
V.sub.1′=V.sub.1; (2) anoxic growths (V.sub.2 and V.sub.2′) of heterotrophic bacteria based on dissolved biodegradable organic matters are:
V.sub.2=μ.sub.H.Math.η.sub.2.Math.X.sub.H(t).Math.M.sub.H,S.sub.s(t).Math.M.sub.H,NH(t).Math.M.sub.H,NO.sub.2(t).Math.M.sub.H,O(t);
V.sub.2′=α.Math.μ.sub.H.Math.η.sub.2.Math.X.sub.H(t).Math.M.sub.H,S.sub.s(t).Math.M.sub.H,NH(t).Math.M.sub.H,NO.sub.2(t).Math.M.sub.H,O(t); (3) anoxic growths (V.sub.3 and V.sub.3′) of heterotrophic bacteria based on dissolved biodegradable organic matters are:
V.sub.3=μ.sub.H.Math.η.sub.3.Math.X.sub.H(t).Math.M.sub.H,S.sub.s(t).Math.M.sub.H,NH(t).Math.M.sub.H,NO(t).Math.M.sub.H,O(t);
V.sub.3′=V.sub.3; (4) anoxic growths (V.sub.4 and V.sub.4′) of heterotrophic bacteria based on dissolved biodegradable organic matters are:
V.sub.4=μ.sub.H.Math.η.sub.4.Math.X.sub.H(t).Math.M.sub.H,I,S.sub.s(t).Math.M.sub.H,NH(t).Math.M.sub.H,N.sub.2.sub.O(t).Math.M.sub.H,O(t);
V.sub.4′=α.Math.μ.sub.H.Math.η.sub.4.Math.X.sub.H(t).Math.M.sub.H,S.sub.s(t).Math.M.sub.H,NH(t).Math.M.sub.H,N.sub.2.sub.O(t).Math.M.sub.H,O(t); (5) decays (V.sub.5 and V.sub.s′) of heterotrophic bacteria are:
V.sub.5=b.sub.H.Math.M.sub.H,NO.sub.3(t).Math.X.sub.H(t);
V.sub.5′=V.sub.5; (6) ammonification (V.sub.6 and V.sub.6′) of microbial dissolved organic nitrogen is:
V.sub.6=κ.sub.α.Math.X.sub.H(t).Math.M.sub.H,mDON(t);
V.sub.6′=V.sub.6; (7) assimilative reduction (V.sub.7 and V.sub.7′) of nitrate into nitrite is:
V.sub.7=1.2.Math.i.sub.XB.Math.M.sub.ANRA,NO.sub.3(t).Math.M.sub.I,NH(t).Math.M.sub.I7,NO.sub.2(t)(V.sub.1+V.sub.2+V.sub.3+V.sub.4−V.sub.6);
V.sub.7′=V.sub.7; (8) assimilative reduction (V.sub.8 and V.sub.8′) of nitrate into ammonia nitrogen is:
V.sub.8=1.2.Math.i.sub.XB.Math.M.sub.ANRA,NO.sub.2(t).Math.M.sub.I,NH(t)(V.sub.1+V.sub.2+V.sub.3+V.sub.4−V.sub.6);
V.sub.8′=V.sub.8; where M.sub.H,S.sub.s(t) is a Monod item of the substrate limit using the dissolved biodegradable organic matters of heterotrophic bacteria; M.sub.H,I,S.sub.s(t) is an inhibition Monod item of the dissolved biodegradable organic matters of heterotrophic bacteria; M.sub.H,NH(t) is a Monod item of the substrate limit using ammonia nitrogen; M.sub.H,O(t) is a Monod item of the oxygen limit of heterotrophic bacteria; M.sub.H,NO.sub.3(t) is a Monod item of the nitrate nitrogen limit; M.sub.H,NO.sub.2(t) is a Monod item of the nitrite nitrogen limit; M.sub.H,NO(t) is a Monod item of the nitric oxide limit; M.sub.H,N.sub.2.sub.O(t) is a Monod item of the nitrous oxide limit; M.sub.ANRA,NO.sub.3(t) is a Monod item of the nitrate nitrogen limit during the assimilative reduction of nitrate into nitrite nitrogen; M.sub.I,NH(t) is an inhibition Monod item of ammonia nitrogen during the assimilative reduction of nitrate into nitrite nitrogen; M.sub.I7,NO.sub.2(t) is an inhibition Monod item of nitrite during the assimilative reduction of nitrate into nitrite nitrogen; M.sub.ANRA,NO.sub.2(t) is a Monod item of the nitrite limit during the assimilative reduction of nitrite nitrogen into ammonia nitrogen; and, M.sub.H,mDON(t) is a Monod item of the mDON limit produced by heterotrophic bacteria.

9. The method of claim 2, wherein the sensitivity analysis uses an absolute-relative sensitivity equation to calculate the influences of parameter changes on mDON and DIN.

10. The method of claim 2, wherein the influent of the denitrification process in the target sewage plant satisfies the following conditions: 15° C.<environmental temperature<25° C., 2000 mg/L<sludge concentration<5000 mg/L, 10 d<sludge age<30 d, 0<carbon/nitrogen ratio≤6.5, 6.5<pH≤8.5, and 0≤dissolved oxygen≤0.5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1A is a graph of the sum of the concentration of mDON and the concentration of DIN and the carbon/nitrogen ratio (C/N);

[0047] FIG. 1B is a graph of the sum of the concentration of mDON and the concentration of DIN and the pH; and

[0048] FIG. 1C is a graph of the sum of the concentration of mDON and the concentration of DIN and the dissolved oxygen (DO).

DETAILED DESCRIPTION

[0049] The post denitrification process stage of a certain municipal sewage treatment plant was selected for collaborative optimization control of organic nitrogen and inorganic nitrogen, where the chemical oxygen demand (COD), total nitrogen (TN), inorganic nitrogen (dDIN), organic nitrogen (rDON) and pH of the influent were 46.33 mg/L, 18.465 mg/L, 16.98 mg/L, 1.48 mg/L and 6.53, respectively; the organic nitrogen (eDIN) and organic nitrogen (eDON) of the effluent were 11.97 mg/L and 2.26 mg/L, respectively; and, in the process operation parameters, the dissolved oxygen (DO) was 0.1 mg/L, the hydraulic retention time (t) of denitrification was 140 min, and the mixed liquor suspended solid (MLSS) of the activated sludge was 2600 mg/L. The specific evaluation steps were described below.

[0050] S1: ASM-mDON-DIN models for simultaneous prediction of microbial dissolved organic nitrogen (mDON) and inorganic nitrogen (DIN) in denitrification processes were established.

[0051] S1-1: The measurement results of model parameters were calculated according to the collected data: Y.sub.H=0.58, f.sub.H,DON=0.068, μ.sub.H=0.35, K.sub.NO.sub.3=0.12, K.sub.H,mDON=1.55. The initial values of the remaining kinetic and chemometric parameters were shown in Table 1.

[0052] S1-2: According to the dynamic process of production, transformation and consumption of mDON during the complete denitrification process, mDON as a new component and the carbon/nitrogen ratio as a new condition were added into the ASM model, and ASM-mDON-DIN models 1 and 2 at different carbon/nitrogen ratios were constructed by using mDON and DIN as objects.

[0053] S1-3: Model initialization was performed on the ASM-mDON-DIN models 1 and 2.

[0054] S1-4: The influences of parameter changes on mDON and DIN were calculated by using an absolute-relative sensitivity equation after model initialization, and the parameter estimation function was calibrated based on the initially simulated mDON and DIN concentrations and the result of sensitivity analysis. The calibrated values of the models were shown in Table 3.

TABLE-US-00003 TABLE 3 Calibrated values of the ASMN-mDON-DIN models Parameter Unit Numerical value Chemometric coefficient Y.sub.H mg(COD.sub.XH)/mg(N) 0.591 f.sub.H, DON mg(N)/mg(COD.sub.XH) 0.081 Kinetic parameter μ.sub.H 1/h 0.296 K.sub.NO.sub.3 mg (N)/L 0.098 K.sub.H, mDON mg (N)/L 2.08 K.sub.I4S.sub.s mg (COD)/L 117

[0055] S1-5: The initial values of parameters in the models were replaced with the calibrated parameter values to obtain the rate equation of each component in the models 1 and 2:

[0056] Model 1:

[00028]$S_{\mathrm{DIN}}:\frac{{\mathrm{dS}}_{\mathrm{DIN}}}{\mathrm{dt}}=-0.22(0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,I,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right))+0.01.Math.X_H\left(t\right).Math.M_{H,\mathrm{mDON}}\left(t\right)-0.03.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)$$S_{\mathrm{mDON}}:\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=0.14(0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,I,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right)+0.17.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.$$M_{H,O}\left(t\right))-0.01.Math.X_H\left(t\right).Math.M_{H,\mathrm{mDON}}\left(t\right)$$X_H:\frac{{\mathrm{dX}}_H}{\mathrm{dt}}=0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.$$M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,I,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.$$M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right)+0.17.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.62.Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.X_H\left(t\right)$$X_I:\frac{{\mathrm{dX}}_I}{\mathrm{dt}}=0.124.Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.X_H\left(t\right)$$S_S:\frac{{\mathrm{dS}}_s}{\mathrm{dt}}=-1.69(0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,I,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right)+0.17.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.$$M_{H,O}\left(t\right))-0.114.Math.M_{\mathrm{ANRA},{\mathrm{NO}}_3}\left(t\right).Math.M_{I,\mathrm{NH}}\left(t\right).Math.M_{I7,{\mathrm{NO}}_2}\left(t\right)\left(V_1+V_2+V_3+V_4-V_6\right)-0.343.Math.$$M_{\mathrm{ANRA},{\mathrm{NO}}_2}\left(t\right).Math.M_{I,\mathrm{NH}}\left(t\right)\left(V_1+V_2+V_3+V_4-V_6\right)$$S_{\mathrm{NO}}:\frac{{\mathrm{dS}}_{\mathrm{NO}}}{\mathrm{dt}}=1.9(0.17.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right))$$S_{N2O}:\frac{{\mathrm{dS}}_{N2O}}{\mathrm{dt}}=1.9(0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.37.Math.X_H\left(t\right).Math.M_{H,I,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right))$$S_{\mathrm{ALK}}:\frac{{\mathrm{dS}}_{\mathrm{ALK}}}{\mathrm{dt}}=-0.005.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.02.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)-0.006.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)-0.006.Math.X_H\left(t\right).Math.M_{H,I,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.$$M_{H,O}\left(t\right)+0.07.Math.{\kappa }_a.Math.X_H\left(t\right).Math.M_{H,\mathrm{mDON}}\left(t\right)+0.141\text{.2}.Math.i_{\mathrm{XB}}.Math.M_{\mathrm{ANRA},{\mathrm{NO}}_2}\left(t\right).Math.M_{I,\mathrm{NH}}\left(t\right)(V_1+$$V_2+V_3+V_4-V_6)$

[0057] Model 2:

[00029]$S_{\mathrm{DIN}}:\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=-0.22(0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right))+0.01.Math.X_H\left(t\right).Math.M_{H,\mathrm{mDON}}\left(t\right)-0.048.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)$$S_{\mathrm{Mdon}}:\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=0.14(0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right))+0.3.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.$$M_{H,O}\left(t\right))-0.01.Math.X_H\left(t\right).Math.M_{H,\mathrm{mDON}}\left(t\right)$$X_H:\frac{{\mathrm{dX}}_H}{\mathrm{dt}}=0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.$$M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.$$M_{H,O}\left(t\right))+0.3.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)-0.62.Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.$$X_H\left(t\right)$$X_I:\frac{{\mathrm{dX}}_I}{\mathrm{dt}}=0.124.Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.X_H\left(t\right)$$S_S:\frac{{\mathrm{dS}}_s}{\mathrm{dt}}=-1.69(0.296.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)+$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)+0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right))+0.3.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.$$M_{H,O}\left(t\right))-0.114.Math.M_{\mathrm{ANRA},{\mathrm{NO}}_3}\left(t\right).Math.M_{I,\mathrm{NH}}\left(t\right).Math.M_{I7,{\mathrm{NO}}_2}\left(t\right)\left(V_1+V_2+V_3+V_4-V_6\right)-$$0.343.Math.M_{\mathrm{ANRA},{\mathrm{NO}}_2}\left(t\right).Math.M_{I,\mathrm{NH}}\left(t\right)\left(V_1+V_2+V_3+V_4-V_6\right)$$S_{\mathrm{NO}}:\frac{{\mathrm{dS}}_{\mathrm{NO}}}{\mathrm{dt}}=1.9.Math.(0.3.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right))$$S_{N2O}:\frac{{\mathrm{dS}}_{N2O}}{\mathrm{dt}}=1.9.Math.(0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.37.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.M_{H,O}\left(t\right))$$S_{\mathrm{ALK}}:\frac{{\mathrm{dS}}_{\mathrm{ALK}}}{\mathrm{dt}}=-0.005.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_3}\left(t\right).Math.M_{H,O}\left(t\right)-$$0.036.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,{\mathrm{NO}}_2}\left(t\right).Math.M_{H,O}\left(t\right)-0.006.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.$$M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,\mathrm{NO}}\left(t\right).Math.M_{H,O}\left(t\right)-0.006.Math.X_H\left(t\right).Math.M_{H,S_s}\left(t\right).Math.M_{H,\mathrm{NH}}\left(t\right).Math.M_{H,N_{2}O}\left(t\right).Math.$$M_{H,O}\left(t\right)+0.007.Math.X_H\left(t\right).Math.M_{H,\mathrm{mDON}}\left(t\right)+0.014.Math.M_{\mathrm{ANRA},{\mathrm{NO}}_2}\left(t\right).Math.M_{I,\mathrm{NH}}\left(t\right)(V_1+V_2+V_3+$$V_4-V_6);$

[0058] where M.sub.H,S.sub.s(t) was the Monod item of the substrate limit using the dissolved biodegradable organic matters of heterotrophic bacteria; M.sub.H,I,S.sub.s(t) was the inhibition Monod item of the dissolved biodegradable organic matters of heterotrophic bacteria; M.sub.H,NH(t) was the Monod item of the substrate limit using ammonia nitrogen; M.sub.H,O(t) was the Monod item of the oxygen limit of heterotrophic bacteria; M.sub.H,NO.sub.3(t) was the Monod item of the nitrate nitrogen limit; M.sub.H,NO.sub.2(t) was the Monod item of the nitrite nitrogen limit; M.sub.H,NO(t) was the Monod item of the nitric oxide limit; M.sub.H,N.sub.2.sub.O(t) was the Monod item of the nitrous oxide limit; M.sub.ANRA,NO.sub.3(t) was the Monod item of the nitrate nitrogen limit during the assimilative reduction of nitrate into nitrite nitrogen; M.sub.I,NH(t) was the inhibition Monod item of ammonia nitrogen during the assimilative reduction of nitrate into nitrite nitrogen; M.sub.I7,NO.sub.2(t) was the inhibition Monod item of nitrite during the assimilative reduction of nitrate into nitrite nitrogen; M.sub.ANRA,NO.sub.2(t) was the Monod item of the nitrite limit during the assimilative reduction of nitrite nitrogen into ammonia nitrogen; and, M.sub.H,mDON(t) was the Monod item of the mDON limit produced by heterotrophic bacteria.

[0059] The degree of fitting between the calibrated simulated value and the measurement value of mDON and DIN in the effluent was 0.937 (p<0.05) and 0.901 (p<0.05), respectively, indicating that the accuracy of model simulation was high and the models had been established.

[0060] S2: According to the carbon/nitrogen ratio, the ASM-mDON-DIN models of different kinetic equations were selected for collaborative optimization of mDON and DIN in the effluent in the denitrification process to obtain best parameter values, specifically comprising the following steps.

[0061] According to the central composite design rule, the value of the process operation parameter carbon/nitrogen ratio was set as 2.5, 4.5 and 6.5, the value of pH was set as 6.5, 7.5 and 8.5, and the value of DO was set as 0 mg/L, 0.25 mg/L and 0.5 mg/L.

[0062] When the value of the carbon/nitrogen ratio was 2.5, the model 1 was selected; and, when the value of the carbon/nitrogen ratio was 4.5 and 6.5, the model 2 was selected.

[0063] By using the carbon/nitrogen ratio, pH and DO in the process operation parameter values as design factors of the response surface methodology and the sum of the concentration of mDON and the concentration of DIN in the effluent as a response value (See FIGS. 1A-1C), the predicted value of the sum of the concentration of mDON and the concentration of DIN was shown in Table 4:

TABLE-US-00004 TABLE 4 Predicted value of the sum of the concentration of mDON and the concentration of DIN in the effluent under different process parameters C/N pH DO (mg/L) mDON + DIN (mg/L) 2.50 6.50 0.00 10.58 6.50 6.50 0.00 6.04 2.50 6.50 1.00 18.56 6.50 6.50 1.00 13.37 4.50 7.50 0.50 10.24 2.50 8.50 0.00 10.66 6.50 8.50 0.00 6.40 2.50 8.50 1.00 17.62 6.50 8.50 1.00 14.32

[0064] The minimum value of the sum of the concentration of mDON and the concentration of DIN in the effluent and the corresponding process operation parameters were obtained. When the minimum value of the sum of the concentration of mDON and the concentration of DIN was 5.56 mg/L, the carbon/nitrogen ratio was 5.65, pH was 6.74, and DO was 0.30 mg/L.

[0065] It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.