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.

Description

CROSS-REFERENCE TO RELAYED APPLICATIONS

Pursuant to 35 U.S.C. § 119 and the Paris Convention Treaty, this application claims foreign priority to Chinese Patent Application No. 202111652401.1 filed Dec. 30, 2021, the contents of which, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, MA 02142.

BACKGROUND

The disclosure relates to the field of wastewater treatment, and more particularly to a method for collaborative control of organic nitrogen and inorganic nitrogen in a denitrification process.

The total dissolved nitrogen in sewage includes inorganic nitrogen (DIN) and dissolved organic nitrogen (DON). In many areas, a high standard is required for the discharge threshold of total nitrogen (TN) in the effluent from municipal sewage treatment plants, so as to control the eutrophication and anoxia of the received water body. For this standard, some sewage plants adopt post denitrification or other processes to improve the denitrification efficiency. When the concentration of the total nitrogen is low (<10 mg/L), 20% to 40% of the total nitrogen in the effluent from the sewage treatment plant exists in the form of DON. Therefore, the DON in the effluent is one of key factors to limit the lower concentration of total nitrogen in the effluent from the sewage treatment plant. The total nitrogen in the effluent from the sewage plant is affected by the removal rage of DIN and is also directly related to the concentration of DON. Therefore, in order to realize the standard discharge of total nitrogen in the effluent from the sewage plant under high standards, it is necessary to collaboratively control organic nitrogen and inorganic nitrogen.

At present, the researches on the control of total nitrogen in the effluent mainly focus on the simulation and optimization control of organic nitrogen, but do not focus on the collaborative control of inorganic nitrogen and organic nitrogen. The International Water Association (IWA) has been committed to the construction and practice of the mathematical denitrification model for activated sludge in sewage treatment for a long term. The IWA pays more attention to the transformation kinetic parameters of inorganic nitrogen and the nitrogen balance in wastewater biological treatment systems. For example, the activated sludge nitrogen model issued in 2008 by the IWA described the transformation and removal of DIN components (ammonia nitrogen, nitrate nitrogen and nitrite nitrogen) during the complete denitrification process of the activated sludge but did not consider microbial dissolved organic nitrogen (mDON) produced by microbial metabolism in the denitrification effluent, so the DIN and DON in the effluent could not be simulated simultaneously.

SUMMARY

An objective of the disclosure is to solve the problem that the total nitrogen in the effluent from a sewage plant is difficult to satisfy the standard discharge under high standards. Based on the activated sludge denitrification model of the IWA, a transformation mathematical model for simultaneous simulation of DON and DIN in a sewage biological treatment system is firstly constructed to realize the simultaneous simulation and collaborative operation control of DON and DIN in the effluent from a sewage plant, so that a new method is provided to satisfy the standard discharge of total nitrogen in the sewage plant under high standards.

A method for collaborative optimization control method for organic nitrogen and inorganic nitrogen in a denitrification process is provided, the 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 the concentration values of mDON and DIN in the effluent in the denitrification process, to obtain best process operation parameter values.

In a class of this embodiment, in S1, operations for establishing the ASM-mDON-DIN models comprise:

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

In a class of this embodiment, in S3, operations for selecting collaborative optimization parameters comprise:

• • S2-1: setting process parameter values: determining the 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 the numerical value of the carbon/nitrogen ratio in S2-1;
  • S2-3: collaborative optimization: based on the model selected in S2-2, obtaining the minimum value of the sum of the concentration of organic nitrogen and the 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 the 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, i.e., carbon/nitrogen ratio, pH and dissolved oxygen, obtained in S2-3.

In a class of this embodiment, the measured values of model parameters comprise the initial values of the yield coefficient (Y_H) of anoxic growth of heterotrophic bacteria measured based on the data collected in S1-1, the proportion (f_H,DON) of mDON formed by heterotrophic bacteria based on organism growth, the ammoniated mDON half-saturation constant (K_H,DON) of heterotrophic bacteria, the maximum specific growth rate (μ_H) of heterotrophic bacteria and the nitrate half-saturation constant (K_NO3) of heterotrophic bacteria.

In a class of this embodiment, the inorganic nitrogen component S_DIN comprises ammonia nitrogen, nitrate nitrogen and nitrite nitrogen.

In a class of this embodiment, the ASM-mDON-DIN model 1 comprises 10 components, 8 processes, 22 parameters and a kinetic parameter, i.e., the inhibition constant (K_I4Ss) 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_H, particulate inert substance Xi, dissolved biodegradable organic matter S_S, microbial organic nitrogen S_mDON, ammonia nitrogen S_NH, nitrate nitrogen S_NO3, nitrite nitrogen S_NO2, nitric oxide S_NO, nitrous oxide S_N2O and alkalinity S_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: the yield coefficient Y_H of anoxic S_s-based growth of heterotrophic bacteria, the oxygen containing proportion i_XB of organism, the proportion f_H,DON of mDON formed by heterotrophic bacteria based on organism growth, the proportion f_I of inert substances produced by organism, the maximum specific growth rate μ_H of anoxic growth of heterotrophic bacteria, the half-saturation utilization constant K_s of the substrate of heterotrophic bacteria, the ammonia half-saturation constant K_H,NH of heterotrophic bacteria, the anoxic growth factor η₂ of heterotrophic bacteria in the process 2, the anoxic growth factor η₃ of heterotrophic bacteria in the process 3, the anoxic growth factor η₄ of heterotrophic bacteria in the process 4, the nitrate nitrogen half-saturation constant K_NO3, the nitrite nitrogen half-saturation constant K_NO2, the nitric oxide half-saturation constant K_NO, the nitrous oxide half-saturation constant K_N2O, the decay coefficient b_H of heterotrophic bacteria, the ammoniated mDON half-saturation constant K_H,DON of heterotrophic bacteria, the ammonification rate κ_α of microbial dissolved organic nitrogen, the NO₃⁻—N half-saturation constant K_7,NO3 of ANRA, the inhibition constant K_I7NH of ammonia nitrogen in the ANRA process, the inhibition constant K_I8NO2 of nitrite nitrogen in the ANRA process, the half-saturation constant K_8,NO2 of nitrite nitrogen in the ANRA process and the oxygen half-saturation constant K_H,O of heterotrophic bacteria.

In a class of this embodiment, 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:

$\mathrm{DIN}\left(S_{\mathrm{DIN}}\right):\frac{{\mathrm{dS}}_{\mathrm{DIN}}}{\mathrm{dt}}=\left(-i_{\mathrm{XB}}-\frac{f_{H,\mathrm{DON}}}{Y_H}\right)\left(V_1+V_2+V_3+V_4\right)+V_6+(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+$ $\frac{1}{0.571})V_2;$ $\mathrm{mDON}\left(S_{\mathrm{mDON}}\right):\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=\frac{f_{H,\mathrm{DON}}}{Y_H}\left(V_1+V_2+V_3+V_4\right)-V_6;$ $\mathrm{heterotrophic}\mathrm{bacteria}\left(X_H\right):\frac{{\mathrm{dX}}_H}{\mathrm{dt}}=V_1+V_2+V_3+V_4-V_5;$ $\mathrm{particulate}\mathrm{inert}\mathrm{substance}\left(X_I\right):\frac{{\mathrm{dX}}_I}{\mathrm{dt}}=f_I{V}_5;$ $\mathrm{dissolved}\mathrm{biodegradable}\mathrm{organic}\mathrm{matter}\left(S_S\right):\frac{{\mathrm{dS}}_s}{\mathrm{dt}}=-\frac{1}{Y_H}(V_1+V_2+V_3+$ $V_4)-1.14V_7-3.43V_8;$ $\mathrm{nitric}\mathrm{oxide}\left(S_{\mathrm{NO}}\right):\frac{{\mathrm{dS}}_{\mathrm{NO}}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_2+\left(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+\frac{1}{0.571}\right)V_3;$ $\mathrm{nitrous}\mathrm{oxide}\left(S_{N2O}\right):\frac{{\mathrm{dS}}_{N2O}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_3+\left(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+\frac{1}{0.571}\right)V_4;$ $\mathrm{alkalinity}\left(S_{\mathrm{ALK}}\right):\frac{{\mathrm{dS}}_{\mathrm{ALK}}}{\mathrm{dt}}=\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_1-(\frac{i_{\mathrm{XB}}}{14}+\frac{f_{H,\mathrm{DON}}}{14Y_H}-$ $\frac{1+2.86f_{H,\mathrm{DON}}-Y_H}{14·\left(0.571Y_H\right)})V_2+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_3+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_4+\frac{1}{14}{V}_6+\frac{1}{7}{V}_8;$

• • (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:

$\mathrm{DIN}\left(S_{\mathrm{DIN}}\right):\frac{{\mathrm{dS}}_{\mathrm{DIN}}}{\mathrm{dt}}=\left(-i_{\mathrm{XB}}-\frac{f_{H,\mathrm{DON}}}{Y_H}\right)\left(V_1+V_2^{\prime }+V_3+V_4^{\prime }\right)+V_6+(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+$ $\frac{1}{0.571})V_2^{\prime };$ $\mathrm{mDON}\left(S_{\mathrm{mDON}}\right):\frac{{\mathrm{dS}}_{\mathrm{mDON}}}{\mathrm{dt}}=\frac{f_{H,\mathrm{DON}}}{Y_H}\left(V_1+V_2^{\prime }+V_3+V_4^{\prime }\right)-V_6;$ $\mathrm{heterotrophic}\mathrm{bacteria}\left(X_H\right):\frac{{\mathrm{dX}}_H}{\mathrm{dt}}=V_1+V_2^{\prime }+V_3+V_4^{\prime }-V_5;$ $\mathrm{particulate}\mathrm{inert}\mathrm{substance}\left(X_I\right):\frac{{\mathrm{dX}}_I}{\mathrm{dt}}=f_I{V}_5;$ $\mathrm{dissolved}\mathrm{biodegradable}\mathrm{organic}\mathrm{matter}\left(S_S\right):\frac{{\mathrm{dS}}_s}{\mathrm{dt}}=-\frac{1}{Y_H}(V_1+V_2^{\prime }+V_3+$ $V_4^{\prime })-1.14V_7-3.43V_8;$ $\mathrm{nitric}\mathrm{oxide}\left(S_{\mathrm{NO}}\right):\frac{{\mathrm{dS}}_{\mathrm{NO}}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_2^{\prime }+\left(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+\frac{1}{0.571}\right)V_3;$ $\mathrm{nitrous}\mathrm{oxide}\left(S_{N2O}\right):\frac{{\mathrm{dS}}_{N2O}}{\mathrm{dt}}=\left(\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}-\frac{1}{0.571}\right)V_3+(-\frac{1+2.86f_{H,\mathrm{DON}}}{0.571Y_H}+$ $\frac{1}{0.571})V_4^{\prime };$ $\mathrm{alkalinity}\left(S_{\mathrm{ALK}}\right):\frac{{\mathrm{dS}}_{\mathrm{ALK}}}{\mathrm{dt}}=\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_1-(\frac{i_{\mathrm{XB}}}{14}+\frac{f_{H,\mathrm{DON}}}{14Y_H}-$ $\frac{1+2.86f_{H,\mathrm{DON}}-Y_H}{14·\left(0.571Y_H\right)})V_2^{\prime }+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_3+\left(-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}\right)V_4^{\prime }+\frac{1}{14}{V}_6+\frac{1}{7}{V}_8.$

In a class of this embodiment, the ASMN-mDON-DIN models 1 and 2 comprise 8 process rate expressions respectively, i.e., V₁-V₈ and V₁′-V₈′:

• • (1) the anoxic growths (V₁ and V₁′) of heterotrophic bacteria based on dissolved biodegradable organic matters (Ss) are:V₁=μ_H·X_H(t)·M_H,Ss(t)·M_H,NH(t)·M_H,NO3(t)·M_H,O(t)V₁′=V₁
  • (2) the anoxic growths (V₂ and V₂′) of heterotrophic bacteria based on dissolved biodegradable organic matters are:V₂=μ_H·η₂·X_H(t)·M_H,Ss(t)·M_H,NH(t)·M_H,NO2(t)·M_H,O(t)V₂′=α·μ_H·η₂·X_H(t)·M_H,Ss(t)·M_H,NH(t)·M_H,NO2(t)·M_H,O(t)
  • (3) the anoxic growths (V₃ and V₃′) of heterotrophic bacteria based on dissolved biodegradable organic matters are:V₃=μ_H·η₃·X_H(t)·M_H,Ss(t)·M_H,NH(t)·M_H,NO(t)·M_H,O(t)V₃′=V₃
  • (4) the anoxic growths (V₄ and V₄′) of heterotrophic bacteria based on dissolved biodegradable organic matters are:V₄=μ_H·η₄·X_H(t)·M_H,I,Ss(t)·M_H,NH(t)·M_H,N2O(t)·M_H,O(t)V₄′=α·μ_H·η₄·X_H(t)·M_H,Ss(t)·M_H,NH(t)·M_H,N2O(t)·M_H,O(t)
  • (5) the decays (V₅ and V₅′) of heterotrophic bacteria are:V₅=b_H·M_H,NO3(t)·X_H(t)V₅′=V₅
  • (6) the ammonification (V₆ and V₆′) of microbial dissolved organic nitrogen is:V₆=κ_α·X_H(t)·M_H,mDON(t)V₆′=V₆
  • (7) the assimilative reduction (V₇ and V₇′) of nitrate into nitrite is:V₇=1.2·i_XB·M_ANRA,NO3(t)·M_I,NH(t)·M_I7,NO2(t)(V₁+V₂+V₃+V₄−V₆)V₇′=V₇

(8) the assimilative reduction (V₈ and V₈′) of nitrite into ammonia nitrogen is:V₈=1.2·i_XB·M_ANRA,NO2(t)·M_I,NH(t)(V₁+V₂+V₃+V₄−V₆)V₈′=V₈

where M_H,Ss(t) is the Monod item of the substrate limit using the dissolved biodegradable organic matters of heterotrophic bacteria; M_H,I,Ss(t) is the inhibition Monod item of the dissolved biodegradable organic matters of heterotrophic bacteria; M_H,NH(t) is the Monod item of the substrate limit using ammonia nitrogen; M_H,O(t) is the Monod item of the oxygen limit of heterotrophic bacteria; M_H,NO3(t) is the Monod item of the nitrate nitrogen limit; M_H,NO2(t) is the Monod item of the nitrite nitrogen limit; M_H,NO(t) is the Monod item of the nitric oxide limit; M_H,N2O(t) is the Monod item of the nitrous oxide limit; M_ANRA,NO3(t) is the Monod item of the nitrate nitrogen limit during the assimilative reduction of nitrate into nitrite nitrogen; M_I,NH(t) is the inhibition Monod item of ammonia nitrogen during the assimilative reduction of nitrate into nitrite nitrogen; M_I7,NO2(t) is the inhibition Monod item of nitrite during the assimilative reduction of nitrate into nitrite nitrogen; M_ANRA,NO2(t) is the Monod item of the nitrite limit during the assimilative reduction of nitrite nitrogen into ammonia nitrogen; and, M_H,mDON(t) is the Monod item of the mDON limit produced by heterotrophic bacteria.

In a class of this embodiment, the sensitivity analysis uses an absolute-relative sensitivity equation to calculate the influences of parameter changes on mDON and DIN.

Preferably, except for five model parameter values to be measured, the initial values of the common chemometric coefficients and kinetic parameters of the ASM-mDON-DIN models 1 and 2 are shown in Table 1 below.

TABLE 1
Initial values of common chemometric coefficients and kinetic
parameters of the ASM-mDON-DIN models 1 and 2
Parameter	Unit	Numerical value
Chemometric
coefficients
iXB	mg (N)/mg (CODXH)	0.086
f1	mg (CODXI)/mg (CODXH)	0.2
Kinetic
parameters
Ks	mg (COD)/L	20
NH, NH	mg (NH3-N)/L	0.05
KH, O	mgO2/L	0.2
n2	—	0.57
n3	—	1.25
n4	—	1.25
KNO2	mg N/L	0.15
KI4Ss	mg (COD)/L	120
KNO	mg N/L	0.0003
KN2O	mg N/L	1.1
bH	mg (COD)/L	0.62
K7, NO3	mg N/L	0.1
KINH	mg N/L	0.05
K8, NO2	mg N/L	0.1
ka	L/(mg (N) · d)	0.010
KI8NO2	mg N/L	0.05
KI4Ss	mg (COD)/L	120

Preferably, the Gujer matrix of the ASM-mDON-DIN models 1 and 2 is shown by Table 2:

TABLE 2
Gujer Matrix of the ASMN-DIN-mDON models 1 and 2
	SS	SH	X1	SmDON	SNH	SNO3	SNO2	SNO	SN2O	SALK
V1	$-\frac{1}{Y_H}$	1		$\frac{f_{H,\mathrm{DON}}}{Y_H}$	$\begin{array}{c}-i_{\mathrm{XB}}-\\ \frac{f_{H,\mathrm{DON}}}{Y_H}\end{array}$	$\begin{array}{c}-\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{1.14Y_H}+\\ \frac{1}{1.14}\end{array}$	$\begin{array}{c}\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{1.14Y_H}-\\ \frac{1}{1.14}\end{array}$			$\begin{array}{c}-\frac{i_{\mathrm{XB}}}{14}-\\ \frac{f_{H,\mathrm{DON}}}{14Y_H}\end{array}$
V2	$-\frac{1}{Y_H}$	1		$\frac{f_{H,\mathrm{DON}}}{Y_H}$	$\begin{array}{c}-i_{\mathrm{XB}}-\\ \frac{f_{H,\mathrm{DON}}}{Y_H}\end{array}$		$\begin{array}{c}-\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{0.571Y_H}+\\ \frac{1}{0.571}\end{array}$	$\begin{array}{c}\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{1.14Y_H}-\\ \frac{1}{1.14}\end{array}$		$\begin{array}{c}-\frac{i_{\mathrm{XB}}}{14}-\frac{f_{H,\mathrm{DON}}}{14Y_H}+\\ \frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}-\\ Y_H\end{array}}{14·\left(0.571Y_H\right)}\end{array}$
V3	$-\frac{1}{Y_H}$	1		$\frac{f_{H,\mathrm{DON}}}{Y_H}$	$\begin{array}{c}-i_{\mathrm{XB}}-\\ \frac{f_{H,\mathrm{DON}}}{Y_H}\end{array}$			$\begin{array}{c}-\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{0.571Y_H}+\\ \frac{1}{0.571}\end{array}$	$\begin{array}{c}\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{1.14Y_H}-\\ \frac{1}{1.14}\end{array}$	$\begin{array}{c}-\frac{i_{\mathrm{XB}}}{14}-\\ \frac{f_{H,\mathrm{DON}}}{14Y_H}\end{array}$
V4	$-\frac{1}{Y_H}$	1		$\frac{f_{H,\mathrm{DON}}}{Y_H}$	$\begin{array}{c}-i_{\mathrm{XB}}-\\ \frac{f_{H,\mathrm{DON}}}{Y_H}\end{array}$				$\begin{array}{c}-\frac{\begin{array}{c}1+\\ 2.86f_{H,\mathrm{DON}}\end{array}}{0.571Y_H}+\\ \frac{1}{0.571}\end{array}$	$\begin{array}{c}-\frac{i_{\mathrm{XB}}}{14}-\\ \frac{f_{H,\mathrm{DON}}}{14Y_H}\end{array}$
V5		−1	f1
V6				−1	1					$\frac{1}{14}$
V7	−1.14					−1	1
V8	−3.43				1		−1			$\frac{1}{7}$

In a class of this embodiment, the influent of the denitrification process in the target sewage plant should satisfy 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.

Compared with the prior art, the following advantages are associated with the method for collaborative control of organic nitrogen and inorganic nitrogen in a denitrification process of the disclosure:

• • (1) The ASMN-mDON-DIN models established in the disclosure can realize the simultaneous simulation and collaborative operation control of mDON and DIN, so that a new method is provided to satisfy the standard discharge of total nitrogen in the sewage plant under high standards.
  • (2) The ASMN-mDON-DIN models established in the disclosure are high in accuracy, and the degree of fitting R² between the simulated value and the measured value is greater than or equal to 0.9 (p<0.05).

BRIEF DESCRIPTION OF THE DRAWINGS

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);

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

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

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.

• • S1: ASM-mDON-DIN models for simultaneous prediction of microbial dissolved organic nitrogen (mDON) and inorganic nitrogen (DIN) in denitrification processes were established.
  • S1-1: The measurement results of model parameters were calculated according to the collected data: Y_H=0.58, f_H,DON=0.068, μ_H=0.35, K_NO3=0.12, K_H,mDON=1.55. The initial values of the remaining kinetic and chemometric parameters were shown in Table 1.
  • 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.
  • S1-3: Model initialization was performed on the ASM-mDON-DIN models 1 and 2.
  • 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 3
Calibrated values of the ASMN-mDON-DIN models
Parameter	Unit	Numerical value
Chemometric
coefficient
YH	mg(CODXH)/mg(N)	0.591
fH, DON	mg(N)/mg(CODXH)	0.081
Kinetic parameter
μH	1/h	0.296
KNO3	mg (N)/L	0.098
KH, mDON	mg (N)/L	2.08
KI4Ss	mg (COD)/L	117

• • 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:

Model 1:

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

Model 2:

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

where M_H,Ss(t) was the Monod item of the substrate limit using the dissolved biodegradable organic matters of heterotrophic bacteria; M_H,I,Ss(t) was the inhibition Monod item of the dissolved biodegradable organic matters of heterotrophic bacteria; M_H,NH(t) was the Monod item of the substrate limit using ammonia nitrogen; M_H,O(t) was the Monod item of the oxygen limit of heterotrophic bacteria; M_H,NO3(t) was the Monod item of the nitrate nitrogen limit; M_H,NO2(t) was the Monod item of the nitrite nitrogen limit; M_H,NO(t) was the Monod item of the nitric oxide limit; M_H,N2O(t) was the Monod item of the nitrous oxide limit; M_ANRA,NO3(t) was the Monod item of the nitrate nitrogen limit during the assimilative reduction of nitrate into nitrite nitrogen; M_I,NH(t) was the inhibition Monod item of ammonia nitrogen during the assimilative reduction of nitrate into nitrite nitrogen; M_I7,NO2(t) was the inhibition Monod item of nitrite during the assimilative reduction of nitrate into nitrite nitrogen; M_ANRA,NO2(t) was the Monod item of the nitrite limit during the assimilative reduction of nitrite nitrogen into ammonia nitrogen; and, M_H,mDON(t) was the Monod item of the mDON limit produced by heterotrophic bacteria.

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.

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.

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.

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.

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 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

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.

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.

Claims

1. A method, comprising: S1: establishing a model 1 and a model 2 for simultaneous simulation of microbial dissolved organic nitrogen (mDON) and inorganic nitrogen (DIN) in denitrification processes; andS2: selecting the model 1 or the model 2 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 S2 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; andS2-4: 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.

3. The method of claim 1, wherein the calculated values of model parameters comprise initial values of a yield coefficient (YH) of anoxic growth of heterotrophic bacteria calculated based on the data collected in S1-1, a proportion (fH,DON) of mDON formed by heterotrophic bacteria based on organism growth, an ammoniated mDON half-saturation constant (KH,DON) of heterotrophic bacteria, a maximum specific growth rate (μH) of heterotrophic bacteria and a nitrate half-saturation constant (KNO3) of heterotrophic bacteria.

4. The method of claim 1, wherein inorganic nitrogen component SDIN comprises ammonia nitrogen, nitrate nitrogen and nitrite nitrogen.

5. The method of claim 1, wherein models 1 and 2 comprise 8 process rate expressions respectively, which are V1-V8 and V1′-V8′: (1) anoxic growths (V1 and V1′) of heterotrophic bacteria based on dissolved biodegradable organic matters (Ss) are: V1=μH·XH(t)·MH,Ss(t)·MH,NH(t)·MH,NO3(t)·MH,O(t);V1′=V1;(2) anoxic growths (V2 and V2′) of heterotrophic bacteria based on dissolved biodegradable organic matters are: V2=μH·η2·XH(t)·MH,Ss(t)·MH,NH(t)·MH,NO2(t)·MH,O(t);V2′=α·μH·η2·XH(t)·MH,Ss(t)·MH,NH(t)·MH,NO2(t)·MH,O(t);(3) anoxic growths (V3 and V3′) of heterotrophic bacteria based on dissolved biodegradable organic matters are: V3=μH·η3·XH(t)·MH,Ss(t)·MH,NH(t)·MH,NO(t)·MH,O(t);V3′=V3;(4) anoxic growths (V4 and V4′) of heterotrophic bacteria based on dissolved biodegradable organic matters are: V4=μH·η4·XH(t)·MH,I,Ss(t)·MH,NH(t)·MH,N2O(t)·MH,O(t);V4′=α·μH·η4·XH(t)·MH,Ss(t)·MH,NH(t)·MH,N2O(t)·MH,O(t);(5) decays (V5 and V5′) of heterotrophic bacteria are: V5=bH·MH,NO3(t)·XH(t);V5′=V5;(6) ammonification (V6 and V6′) of microbial dissolved organic nitrogen V6=κα·XH(t)·MH,mDON(t);V6′=V6;(7) assimilative reduction (V7 and V7′) of nitrate into nitrite is: V7=1.2·iXB·MANRA,NO3(t)·MI,NH(t)·MI7,NO2(t)(V1+V2+V3+V4−V6);V7′=V7;(8) assimilative reduction (V8 and V8′) of nitrite into ammonia nitrogen V8=1.2·iXB·MANRA,NO2(t)·MI,NH(t)(V1+V2+V3+V4−V6);V8′=V8;where MH,Ss(t) is a Monod item of the substrate limit using the dissolved biodegradable organic matters of heterotrophic bacteria; HM,I,Ss(t) is an inhibition Monod item of the dissolved biodegradable organic matters of heterotrophic bacteria; MH,NH(t) is a Monod item of the substrate limit using ammonia nitrogen; MH,O(t) is a Monod item of the oxygen limit of heterotrophic bacteria; MH,NO3(t) is a Monod item of the nitrate nitrogen limit; MH,NO2(t) is a Monod item of the nitrite nitrogen limit; MH,NO(t) is a Monod item of the nitric oxide limit; MH,N2O(t) is a Monod item of the nitrous oxide limit; MANRA,NO3(t) is a Monod item of the nitrate nitrogen limit during the assimilative reduction of nitrate into nitrite nitrogen; MI,NH(t) is an inhibition Monod item of ammonia nitrogen during the assimilative reduction of nitrate into nitrite nitrogen; M17,NO2(t) is an inhibition Monod item of nitrite during the assimilative reduction of nitrate into nitrite nitrogen; MANRA,NO2(t) is a Monod item of the nitrite limit during the assimilative reduction of nitrite nitrogen into ammonia nitrogen; and, MH,mDON(t) is a Monod item of the mDON limit produced by heterotrophic bacteria.

6. The method of claim 1, 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.

7. The method of claim 1, wherein the sensitivity analysis uses an absolute-relative sensitivity equation to calculate the influences of parameter changes on mDON and DIN.

8. A method, comprising: S1: establishing a model 1 and a model 2 for simultaneous simulation of microbial dissolved organic nitrogen (mDON) and inorganic nitrogen (DIN) in denitrification processes; andS2: selecting the model 1 or the model 2 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;