CN115630473A

CN115630473A - Sewage treatment plant optimized operation method considering sewage reuse

Info

Publication number: CN115630473A
Application number: CN202210980706.3A
Authority: CN
Inventors: 赵霞; 石诗义; 毛杨; 王骆; 刘丁溢
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2022-08-16
Filing date: 2022-08-16
Publication date: 2023-01-20

Abstract

The invention discloses an optimized operation method of a sewage treatment plant considering sewage reuse, which comprises the following steps; 1) Acquiring basic parameters of a sewage treatment plant; 2) According to basic parameters of a sewage treatment plant, modeling equipment units of the sewage treatment plant to obtain an equipment unit model of the sewage treatment plant; 3) Establishing an optimized operation model of the sewage treatment plant considering sewage reuse according to the equipment unit model of the sewage treatment plant; 4) And solving the optimal operation model of the sewage treatment plant in consideration of sewage reuse to obtain the optimal operation scheme of the sewage treatment plant. The invention fully excavates the flexibility of the sewage treatment plant, can make the load stable and carry out peak clipping and valley filling, and improves the economy and the load stability.

Description

Sewage treatment plant optimized operation method considering sewage reuse

Technical Field

The invention relates to the field of optimized operation of a multi-energy system, in particular to an optimized operation method of a sewage treatment plant considering sewage reuse.

Background

At present, with the acceleration of urbanization process and the continuous improvement of water-energy relation research, sewage treatment has become the key point of renewable energy utilization research. In a water system, a sewage treatment plant belongs to an energy-intensive facility, the operation cost is high, and the power consumption accounts for 3% -4% of the load of a power grid in the United states.

In the places of water shortage and drought, the water resources are effectively recycled, and the water, energy and land can be greatly saved. These regions are under water resource pressure due to irregular water resource supply throughout the year, and recycling nutrients and water in municipal sewage to agriculture is a key to effectively construct a water-energy-food-climate network.

At present, the research of managing sewage treatment plants mainly focuses on the aspects of ensuring the best quality of sewage water so as to ensure the health of citizens, complying with the rules of sanitation and environment and the like; most of the research on energy conservation thereof still stays in process flow optimization; for the sewage recycling, more heat energy and chemical energy contained in the recycled sewage are remained, and a few researches only discuss the aspects of recycling the sewage, but do not consider the influence of the recycling on the energy utilization behavior of a sewage treatment plant.

Disclosure of Invention

The invention aims to provide an optimized operation method of a sewage treatment plant considering sewage reuse, which comprises the following steps;

1) Acquiring basic parameters of a sewage treatment plant;

further, the basic parameters of the sewage treatment plant comprise time-of-use electricity price, gas price, sewage load, irrigation water price, secondary emission income, tertiary emission income, industrial general water load, industrial general water price and other parameters.

2) According to basic parameters of a sewage treatment plant, modeling equipment units of the sewage treatment plant to obtain an equipment unit model of the sewage treatment plant;

further, the equipment unit model of the sewage treatment plant comprises a treatment unit model, a sludge biogas production model, a CHP unit model and an energy storage device model.

Further, the treatment unit model comprises a primary sewage treatment unit model, a secondary sewage treatment unit model and a deep sewage treatment model;

wherein, the primary sewage treatment unit model is as follows:

P _t,clar ＝γ _s Q _t H _t /1000η (1)

H _t ＝aQ _t ² +bQ _t r+cr ² (2)

in the formula, subscript t represents time t; p _t,clar Clearing the power of the pump for the time t; eta is the efficiency of the cleaning pump; q _t The flow rate of wastewater entering the regulating reservoir at the moment t; gamma ray _s Is the sewage specific gravity; h _t Clearing the pump lift at the moment t; r is the relative speed of the cleaning pump; a, b and c are empirical coefficients of pump head curves of the water pump;

the secondary sewage treatment unit model is as follows:

in the formula, P _t,Aer Blower power at time t; r is the air gas constant; t is _in Is the fan inlet temperature; eta _B The mechanical efficiency of the blower; p _a Is at atmospheric pressure; p _t,stat Static pressure at the outlet of the blower diffuser; p _t,dyn Is a dynamic pressure; q _t,air Is the air mass flow rate; m _air Is the molecular mass of air;

wherein the dynamic pressure P _t,dyn Air mass flow rate Q _t,air Respectively as follows:

P _t,dyn ＝(Q _t,air /A _dif ) ² k _p (4)

in the formula, A _dif Is the diffuser cross-sectional area; coefficient k _p ＝275N s ² /m ⁴ ；K _La Being a standard transfer of oxygenThe efficiency of the process is improved, and the efficiency is improved,

is the mass of oxygen in a unit mass of air,

is the standard oxygen transfer rate;

standard oxygen transfer rate

As follows:

m _t,BOD ＝Q _t,2 (BOD _t,in -BOD _t,out )ConB (7)

m _t,TKN ＝Q _t,2 (TKN _t,in -TKN _t,out )ConN (8)

in the formula, m _t,BOD And m _t,TKN Oxidizing oxygen demand and nitrifying oxygen demand for the aeration tank; beta is the mass of oxygen in the unit mass of air; c _T And C _T ⁰ At a temperature T and a reference temperature T, respectively ⁰ Oxygen saturation concentration in the lower fresh water; c _d Is the dissolved oxygen concentration; alpha is the oxygen transfer ratio in the wastewater; theta is a constant; BOD _t,in And BOD _t,out The BOD concentration of inlet water and outlet water of a sewage treatment plant; TKN _t,in And TKN _t,out TKN concentration of inlet water and outlet water of a sewage treatment plant; conN is the required oxygen ratio for oxidation of TKN; conB is the oxygen ratio required to oxidize BOD; q _t,2 The sewage flow is treated in the second stage;

the advanced wastewater treatment model is as follows:

P _t,3 ＝η ₃ V _t,3 (9)

in the formula eta ₃ The volume coefficient of sewage treated by unit electric energy in a three-stage treatment link; v _t,3 At time t by three stagesTreating the volume of water entering the clean water basin; p _t,3 The power consumption of the three-stage treatment at the time t.

Further, the sludge-to-biogas model comprises a biogas yield calculation equation, a heat loss calculation equation of the digester wall and a heat energy calculation equation required by sludge heating;

wherein, the biogas yield calculation equation is as follows:

in the formula, subscript t represents time t; m is _sl,t The sludge mass at the time t; beta is a beta _wsl The sludge coefficient after standing and precipitating the sewage is obtained; p is a radical of _t,BG The amount of biogas generated at time t;

is a reference temperature T ⁰ The sewage sludge methane yield coefficient; f. of _t (T _dig ) The fermentation temperature T of the biogas pool at the time T _dig The gas production rate of the lower methane; f. of _t (T ⁰ ) For the methane tank to reference the temperature T at the moment T ₀ The gas production rate of the lower methane; rho _wsl Is the average density of the sewage after standing and precipitation;

wherein the gas production rate f _t (T _dig ) And fermentation temperature T _dig The relationship of (a) is as follows:

f _t (T _dig )＝m(T _dig -T ₀ ) ² +n (11)

in the formula, m and n are coefficients in a quadratic expression respectively;

the heat loss calculation equation of the digester wall and the heat energy calculation equation required by sludge heating are respectively as follows:

heat loss H from digester wall _t,loss And the heat energy H required by heating the sludge _t,sludge Comprises the following steps:

in the formula, H _t,loss 、H _t,sludge Respectively the heat loss of the digester wall and the heat energy required by sludge heating; cp (p) _sludge The specific heat capacity of the sludge; t is a unit of _t,air And T _t,soil Measuring the temperature of the air and the soil at the time t respectively; k is a radical of _air And k _soil Air and soil heat transfer coefficients, respectively; t is _dig Fermentation temperature for anaerobic digestion; t is _so Is the average influent sludge temperature; a. The _sup And A _base The side area and the base area of the digester are respectively.

Further, the CHP unit model is as follows:

P _{t,CHP_G} ＝p _t,gas L _gas η _CHP,e (13)

H _t,CHP ＝p _t,gas L _gas η _CHP,h (14)

in the formula, P _{t,CHP_G} The CHP total power generation power at the time t; h _t,CHP CHP thermal power at time t; p is a radical of _t,gas The flow rate of the biogas consumed by the CHP at the moment t; l is _gas The heat value of the biogas is obtained; eta _CHP,e And η _CHP,h The electrical and thermal efficiencies of CHP, respectively.

Further, the energy storage device model comprises a storage battery model and a phase change heat storage tank model;

the storage battery model is as follows:

in the formula, E _t,bat And E _t-Δt,bat The storage battery stores electric quantity at the time t and the time t-delta t respectively; Δ t is the time; p is _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power;

the charging power is the upper and lower limits;

the upper and lower limits of the discharge power; 0-1 variable I _t,cha To represent the state variable of charging, I _t,cha =1 denotes charging, I _t,cha =0 represents no charging; 0-1 variable I _t,dis To represent the state variable of the discharge, I _t,dis =1 for discharge, I _t,dis =0 denotes no discharge; eta _cha And η _dis Respectively charging and discharging efficiencies of the storage battery;

and

respectively an upper limit and a lower limit of the energy storage capacity of the storage battery; e _t,bat The energy storage capacity of the storage battery at the moment t; e _0,bat And E _T’,bat The starting value and the end value of the storage battery in the dispatching cycle are obtained; t' is the total number of time segments of one scheduling period.

The phase change heat storage tank model is as follows:

in the formula, H _t,bat And H _t-Δt,bat Storing heat in the phase change heat storage tanks at the time t and the time t-delta t respectively; h _{t,bat_cha} And H _{t,bat_dis} Respectively storing and releasing heat power;

the upper and lower limits of the heat storage power;

the upper and lower limits of the heat release power; 0-1 variable I _t,hcha Is a state variable for representing heat storage, I _t,hcha =1 for heat storage, I _t,hcha =0 means no heat storage; 0-1 variable I _t,hdis Is a state variable for representing the heat release, I _t,hdis =1 denotes exotherm, I _t,hdis =0 indicates no exotherm; eta _hcha And η _hdis Respectively the storage efficiency and the heat release efficiency of the phase-change heat storage tank；

And

respectively is the upper limit and the lower limit of the heat storage capacity of the phase change heat storage tank; h _t,bat Storing heat capacity of the phase change heat storage tank at the time t; h _0,bat And H _T’,bat The starting value and the ending value of the phase change heat storage tank in the scheduling period are obtained.

3) Establishing an optimized operation model of the sewage treatment plant considering sewage reuse according to the equipment unit model of the sewage treatment plant;

further, an objective function of the optimized operation model of the sewage treatment plant considering sewage reuse is as follows:

in the formula (f) _t,gas Trading costs for the air network; f. of _t,gird Trading costs for the grid; f. of _t,W Earning for selling water; f. of _t,en Is an environmental benefit.

Wherein the cost f of the gas network transaction _t,gas Power grid transaction cost f _t,gird Income f from selling water _t,W Environmental gain f _t,en Respectively as follows:

in the formula, c _t,gird And c _gas Time-of-use electricity price and gas price at the moment t respectively; p is _t,gird And P _t,gas Respectively, interaction quantity with the power grid and the gas grid at the time t; c. C _W2 And c _W3 Respectively a second-level water price and a third-level water price; q _t,I And Q _t,D The secondary water demand and the tertiary water demand at the time t are respectively; k _en2 And K _en3 Respectively converting coefficients of second-level discharge and third-level discharge; q _t,en2 The water flow discharged by secondary treatment at the time t; q _t,en3 Is at t timeThe water flow discharged by the three-stage treatment is carved.

Further, the constraint conditions of the optimized operation model of the sewage treatment plant considering sewage reuse comprise electric power balance constraint, gas balance constraint, thermal power balance constraint, secondary water treatment balance constraint, tertiary water treatment balance constraint, CHP output upper and lower limit constraint, regulating reservoir constraint, secondary reservoir constraint and clean water reservoir constraint;

wherein the electric power balance constraint is as follows:

P _t,wind +P _{t,CHP_G} +P _t,gird +P _{t,bat_dis} +P _t,PV ＝P _{t,bat_cha} +P _t,clar +P _t,Aer +P _t,3 (19)

in the formula, P _t,PV Generating power for the photovoltaic unit; p _t,wind Generating power for the wind turbine; p _t,Aer Blower power for time t; p _{t,CHP_G} The CHP total power generation power at the time t; p _t,gird The interaction quantity with the power grid at the moment t is shown; p _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power; p _t,clar Clearing the power of the pump at time t; p _t,3 The power consumption of the tertiary treatment at the time t;

the gas balance constraints are as follows:

p _t,BG -p _t,gas ＝P _t,gas (20)

in the formula, p _t,gas The flow rate of the biogas consumed by the CHP at the moment t; p is a radical of _t,BG The amount of biogas generated at time t;

the thermal power balance constraint is as follows:

H _t,CHP +H _{t,bat_dis} ＝H _t,loss +H _t,sludge +H _{t,bat_cha} (21)

in the formula, H _t,CHP CHP thermal power at time t; h _{t,bat_cha} And H _{t,bat_dis} Respectively storing and releasing heat power; h _t,loss 、H _t,sludge Respectively the heat loss of the digester wall and the heat energy required by sludge heating;

the secondary water treatment equilibrium constraints are as follows:

Q _t,2 ＝α ₂ Q _t,se2 (22)

in the formula, Q _t,se2 The flow rate after the secondary water treatment at the time t is shown; alpha (alpha) ("alpha") ₂ The flow ratio of secondary water treatment is adopted; q _t,2 For the secondary treatment of sewage flow at the time t

The three-stage water treatment equilibrium constraints are as follows:

Q _t,3 ＝α ₃ Q _t,th3 (23)

in the formula, Q _t,th3 The flow rate after the three-stage water treatment at the moment t is shown; alpha is alpha ₃ The flow rate ratio of three-stage water treatment is adopted; q _t,3 The flow of the three-stage treatment sewage at the time t;

the CHP upper and lower force limits are constrained as follows:

in the formula (I), the compound is shown in the specification,

and

the upper limit and the lower limit of CHP electric power output are respectively;

and

respectively an upper limit and a lower limit of CHP thermal power output. P _t,CHP And Q _t,CHP CHP electric power and thermal power at the time t respectively;

the regulation pool constraints are as follows:

in the formula, R _t,1 And R _t-1,1 Is time t,Regulating the water storage capacity of the pool at the t-1 moment;

the maximum water storage capacity of the regulating reservoir; r is _0,1 And R _T,1 Respectively the initial value and the final value in the dispatching cycle of the regulating pool; q _t The flow rate of wastewater entering the regulating reservoir at the moment t;

the secondary reservoir constraints are as follows:

in the formula, R _t,2 And R _t-1,2 The water storage capacity of the secondary reservoir at the time t and the time t-1;

the maximum water storage capacity R of the secondary reservoir _0,2 And R _T,2 Respectively representing the starting value and the ending value in the second-level reservoir scheduling period; q _t,I The secondary water demand at the time t; q _t,en2 Water flow discharged by secondary treatment at time t;

and (3) restricting the clean water tank:

in the formula, R _t,3 And R _t-1,3 The water storage capacity of the clean water tank at the t moment and the t-1 moment;

is the maximum water storage capacity of the clean water tank, R _0,3 And R _T,3 Respectively are the initial value and the final value in the clear pool scheduling period; q _t,D The water demand is three-level at the time t; q _t,en3 The water flow discharged by the three-stage treatment at the time t.

4) And solving the optimal operation model of the sewage treatment plant in consideration of sewage reuse to obtain the optimal operation scheme of the sewage treatment plant.

Further, a tool for solving the optimal operation model of the sewage treatment plant considering sewage reuse includes CPLEX.

The technical effect of the invention is undoubted, aiming at the problem that the existing sewage treatment plant neglects the reuse of water resources during operation, the invention fully considers the flexibility and the sewage reuse of the sewage treatment plant, and provides the optimized operation method of the sewage treatment plant considering the sewage reuse.

The invention fully excavates the flexibility of the sewage treatment plant, can lead the load to be stable, carries out peak clipping and valley filling and improves the economy and the load stability.

Drawings

FIG. 1 is a block diagram of the solution flow of the method of the present invention.

FIG. 2 is a structural view of energy flow of a sewage treatment plant in consideration of sewage reuse according to the present invention.

FIG. 3 is a schematic view of a sewage treatment plant stage treatment considering sewage reuse according to the present invention.

FIG. 4 is a graph comparing the secondary treatment water flow for three scenarios.

FIG. 5 is a graph comparing three stages of process water flow for three scenarios.

FIG. 6 is a graph showing the temperature comparison of the biogas digester under three scenes.

Detailed Description

The present invention is further illustrated by the following examples, but it should not be construed that the scope of the above-described subject matter is limited to the following examples. Various substitutions and alterations can be made without departing from the technical idea of the invention and the scope of the invention is covered by the present invention according to the common technical knowledge and the conventional means in the field.

Example 1:

referring to fig. 1 to 6, a method for optimizing an operation of a sewage treatment plant in consideration of sewage reuse includes the following steps;

1) Acquiring basic parameters of a sewage treatment plant;

the basic parameters of the sewage treatment plant comprise time-of-use electricity price, gas price, sewage load, irrigation water price, secondary discharge income, tertiary discharge income, industrial water use load, industrial water use price and the like.

the sewage treatment plant equipment unit model comprises a treatment unit model, a sludge biogas production model, a CHP unit model and an energy storage device model.

The treatment unit model comprises a primary sewage treatment unit model, a secondary sewage treatment unit model and an advanced sewage treatment model;

wherein, the primary sewage treatment unit model is as follows:

P _t,clar ＝γ _s Q _t H _t /1000η (1)

H _t ＝aQ _t ² +bQ _t r+cr ² (2)

in the formula, subscript t represents time t; p _t,clar Clearing the power of the pump at time t; eta is the efficiency of the cleaning pump; q _t The flow rate of wastewater entering the regulating reservoir at the moment t; gamma ray _s Is the sewage specific gravity; h _t Clearing the pump lift at the moment t; r is the relative speed of the cleaning pump; a, b and c are empirical coefficients of a water pump lift curve; the coefficient mentioned in this embodiment is a predetermined constant.

The secondary sewage treatment unit model is as follows:

in the formula, P _t,Aer Blower power at time t; r is the air gas constant; t is _in Is the fan inlet temperature; eta _B To the mechanical efficiency of the blower; p _a Is at atmospheric pressure; p _t,stat Static pressure at the outlet of the blower diffuser; p _t,dyn Is a dynamic pressure; q _t,air Is the air mass flow rate; m is a group of _air Is the molecular mass of air;

P _t,dyn ＝(Q _t,air /A _dif ) ² k _p (4)

in the formula, A _dif Is the diffuser cross-sectional area; coefficient k _p ＝275N s ² /m ⁴ ；K _La In order to be the standard transfer efficiency of oxygen,

is the mass of oxygen in a unit mass of air,

standard oxygen transfer rate;

standard oxygen transfer rate

As follows:

m _t,BOD ＝Q _t,2 (BOD _t,in -BOD _t,out )ConB (7)

m _t,TKN ＝Q _t,2 (TKN _t,in -TKN _t,out )ConN (8)

in the formula, m _t,BOD And m _t,TKN Oxidizing oxygen demand and nitrifying oxygen demand for the aeration tank; beta is the mass of oxygen in the unit mass of air; c _T And C _T ⁰ At a temperature T and a reference temperature T, respectively ⁰ Oxygen saturation concentration in the lower fresh water; c _d Is the dissolved oxygen concentration; alpha is the oxygen transfer ratio in the wastewater; theta is a constant; BOD _t,in And BOD _t,out BOD (biochemical oxygen demand) concentrations of inlet water and outlet water of a sewage treatment plant; TKN _t,in And TKN _t,out For sewage treatment plant to enterTKN (total kjeldahl nitrogen in wastewater) concentration of water and effluent; conN is the required oxygen ratio for oxidation of TKN; conB is the oxygen ratio required to oxidize BOD; q _t,2 The sewage flow is treated in the second stage;

the advanced wastewater treatment model is as follows:

P _t,3 ＝η ₃ V _t,3 (9)

in the formula eta ₃ The volume coefficient of sewage treated by unit electric energy in a three-stage treatment link; v _t,3 The volume of water entering the clean water tank after three-stage treatment at the moment t; p _t,3 The power consumption of the three-stage treatment at the time t.

The sludge biogas production model comprises a biogas yield calculation equation, a heat loss calculation equation of the wall of the digestion tank and a heat energy calculation equation required by sludge heating;

wherein, the biogas yield calculation equation is as follows:

in the formula, subscript t represents time t; m is _sl,t The sludge mass at the time t; beta is a _wsl The sludge coefficient after standing and precipitating the sewage is obtained; p is a radical of _t,BG The amount of biogas generated at time t;

is a reference temperature T ⁰ The sewage sludge generates biogas coefficient; f. of _t (T _dig ) The fermentation temperature T of the methane tank at the time T _dig The gas production rate of the lower methane; f. of _t (T ⁰ ) For the methane tank to reference the temperature T at the moment T ₀ The gas production rate of the lower methane; rho _wsl Is the average density of the sewage after standing and precipitation;

f _t (T _dig )＝m(T _dig -T ₀ ) ² +n (11)

in the formula, H _t,loss 、H _t,sludge Respectively the heat loss of the digester wall and the heat energy required by sludge heating; cp (p) _sludge The specific heat capacity of the sludge is adopted; t is _t,air And T _t,soil Measuring the temperature of the air and the soil at the time t respectively; k is a radical of _air And k _soil Air and soil heat transfer coefficients, respectively; t is _dig Fermentation temperature for anaerobic digestion; t is _so Is the average influent sludge temperature; a. The _sup And A _base The side area and the base area of the digester are respectively.

The CHP (Combined Heat and Power) unit model is as follows:

P _{t,CHP_G} ＝p _t,gas L _gas η _CHP,e (13)

H _t,CHP ＝p _t,gas L _gas η _CHP,h (14)

in the formula, P _{t,CHP_G} The CHP total power generation power at the t moment; h _t,CHP CHP thermal power at time t; p is a radical of formula _t,gas The flow rate of the biogas consumed by the CHP at the moment t; l is _gas The heat value of the biogas is obtained; eta _CHP,e And η _CHP,h The electrical and thermal efficiencies of CHP, respectively.

The energy storage device model comprises a storage battery model and a phase change heat storage tank model;

the storage battery model is as follows:

in the formula, E _t,bat And E _t-Δt,bat The storage battery stores electric quantity at the time t and the time t-delta t respectively; Δ t is the time; p _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power;

the charging power is the upper and lower limits;

the upper and lower limits of the discharge power; 0-1 variable I _t,cha To represent the state variable of charging, I _t,cha =1 denotes charging, I _t,cha =0 means no charging; 0-1 variable I _t,dis To represent the state variable of the discharge, I _t,dis =1 for discharge, I _t,dis =0 denotes no discharge; eta _cha And η _dis Respectively charging and discharging efficiencies of the storage battery;

and

The phase change heat storage tank model is as follows:

in the formula, H _t,bat And H _t-Δt,bat Storing heat in the phase change heat storage tank at the time t and the time t-delta t respectively; h _{t,bat_cha} And H _{t,bat_dis} Respectively storing and releasing heat power;

the upper and lower limits of the heat storage power;

the upper and lower limits of the heat release power; 0-1 variable I _t,hcha Is a state variable for representing heat storage, I _t,hcha =1 for heat storage, I _t,hcha =0 indicates no heat storage; 0-1 variable I _t,hdis Is a state variable for representing the heat release, I _t,hdis =1 denotes exotherm, I _t,hdis =0 means no exotherm; eta _hcha And η _hdis Respectively the storage efficiency and the heat release efficiency of the phase change heat storage tank;

and

the objective function of the optimized operation model of the sewage treatment plant considering sewage reuse is as follows:

Wherein the cost f of the gas network transaction _t,gas Grid transaction cost f _t,gird Profit f from sale of water _t,W Environmental gain f _t,en Respectively as follows:

in the formula, c _t,gird And c _gas Time-of-use electricity price and gas price at the moment t respectively; p is _t,gird And P _t,gas Respectively, interaction quantity with the power grid and the gas grid at the time t; c. C _W2 And c _W3 Respectively a second-level water price and a third-level water price; q _t,I And Q _t,D The secondary water demand and the tertiary water demand at the time t are respectively; k _en2 And K _en3 Respectively converting coefficients of secondary emission and tertiary emission; q _t,en2 The water flow discharged by secondary treatment at the time t; q _t,en3 The water flow discharged by the three-stage treatment at the time t.

The constraint conditions of the optimized operation model of the sewage treatment plant considering sewage reuse comprise electric power balance constraint, gas balance constraint, thermal power balance constraint, secondary water treatment balance constraint, tertiary water treatment balance constraint, CHP output upper and lower limit constraint, regulating reservoir constraint, secondary reservoir constraint and clear water reservoir constraint;

wherein the electric power balance constraint is as follows:

in the formula, P _t,PV Generating power for the photovoltaic unit; p _t,wind Generating power for the wind turbine generator; p _t,Aer Blower power at time t; p _{t,CHP_G} The CHP total power generation power at the t moment; p is _t,gird The interaction quantity with the power grid at the moment t is shown; p _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power; p _t,clar Clearing the power of the pump for the time t; p is _t,3 The power consumption of the tertiary treatment at the time t;

the gas balance constraints are as follows:

p _t,BG -p _t,gas ＝P _t,gas (20)

the thermal power balance constraint is as follows:

H _t,CHP +H _{t,bat_dis} ＝H _t,loss +H _t,sludge +H _{t,bat_cha} (21)

the secondary water treatment equilibrium constraints are as follows:

Q _t,2 ＝α ₂ Q _t,se2 (22)

in the formula, Q _t,se2 The flow rate after the secondary water treatment at the time t is shown; alpha is alpha ₂ The flow ratio of secondary water treatment is adopted; q _t,2 For the secondary treatment of sewage flow at the time t

The three-stage water treatment equilibrium constraints are as follows:

Q _t,3 ＝α ₃ Q _t,th3 (23)

the CHP upper and lower force limits are constrained as follows:

in the formula (I), the compound is shown in the specification,

and

and

the adjustment tank constraints are as follows:

in the formula, R _t,1 And R _t-1,1 Regulating the water storage capacity of the pool at the t moment and the t-1 moment;

the maximum water storage capacity of the regulating reservoir; r _0,1 And R _T,1 Respectively the initial value and the final value in the dispatching cycle of the regulating pool; q _t The flow rate of wastewater entering the regulating reservoir at the moment t;

the secondary reservoir constraints are as follows:

the maximum water storage capacity of the second-stage reservoir, R _0,2 And R _T,2 Respectively representing the starting value and the ending value in the second-level reservoir scheduling period; q _t,I The secondary water demand at the time t; q _t,en2 The water flow discharged by secondary treatment at the time t;

and (3) restricting the clean water tank:

The tool for solving the optimal operation model of the sewage treatment plant considering sewage reuse comprises CPLEX.

Example 2:

an optimized operation method of a sewage treatment plant considering sewage reuse comprises the following steps;

1) Acquiring basic parameters of a sewage treatment plant;

4) And solving the optimal operation model of the sewage treatment plant in consideration of sewage reuse to obtain an optimal operation scheme of the sewage treatment plant.

Example 3:

the main content of the optimized operation method of the sewage treatment plant considering sewage reuse is shown in an embodiment 2, wherein basic parameters of the sewage treatment plant comprise time-of-sale electricity price, gas price, sewage load, irrigation water price, secondary discharge income, tertiary discharge income, industrial miscellaneous water load, industrial miscellaneous water price and other parameters.

Example 4:

the main content of the optimized operation method of the sewage treatment plant considering sewage reuse is shown in an embodiment 2, wherein the equipment unit model of the sewage treatment plant comprises a treatment unit model, a sludge biogas production model, a CHP unit model and an energy storage device model.

Example 5:

a sewage treatment plant optimization operation method considering sewage reuse mainly includes embodiment 4, wherein the treatment unit model includes a primary sewage treatment unit model, a secondary sewage treatment unit model, and a deep sewage treatment model;

wherein, the first-level sewage treatment unit model is as follows:

P _t,clar ＝γ _s Q _t H _t /1000η (1)

H _t ＝aQ _t ² +bQ _t r+cr ² (2)

in the formula, subscript t represents time t; p _t,clar Clearing the power of the pump at time t; eta is the efficiency of the cleaning pump; q _t The flow rate of wastewater entering the regulating reservoir at the moment t; gamma ray _s Is the sewage specific gravity; h _t Clearing the pump lift at the moment t; r is the relative speed of the cleaning pump; a, b and c are empirical coefficients of a water pump lift curve;

the secondary sewage treatment unit model is as follows:

in the formula, P _t,Aer Blower power at time t; r is the air gas constant; t is _in Is the fan inlet temperature; eta _B To the mechanical efficiency of the blower; p _a Is at atmospheric pressure; p _t,stat Static pressure at the outlet of the blower diffuser; p _t,dyn Is a dynamic pressure; q _t,air Is the air mass flow rate;

P _t,dyn ＝(Q _t,air /A _dif ) ² k _p (4)

in the formula (I), the compound is shown in the specification,A _dif is the diffuser cross-sectional area; coefficient k _p ＝275N s ² /m ⁴ ；K _La In order to be the standard transfer efficiency of oxygen,

is the mass of oxygen in a unit mass of air,

is the standard oxygen transfer rate;

standard oxygen transfer rate

As follows:

m _t,BOD ＝Q _t,2 (BOD _t,in -BOD _t,out )ConB (7)

m _t,TKN ＝Q _t,2 (TKN _t,in -TKN _t,out )ConN (8)

the advanced wastewater treatment model is as follows:

P _t,3 ＝η ₃ V _t,3 (9)

Example 6:

a sewage treatment plant optimization operation method considering sewage reuse mainly includes an embodiment 4, wherein the sludge biogas production model includes a biogas yield calculation equation, a heat loss calculation equation of a digester wall and a heat energy calculation equation required by sludge heating;

wherein, the biogas yield calculation equation is as follows:

in the formula, subscript t represents time t; m is _t,sl The sludge mass at the time t; beta is a _wsl The sludge coefficient after standing and precipitating the sewage is obtained; p is a radical of _t,BG The amount of biogas generated at time t;

is a reference temperature T ⁰ The sewage sludge generates biogas coefficient; f. of _t (T _dig ) The fermentation temperature T of the biogas pool at the time T _dig The gas production rate of the lower methane; f. of _t (T ⁰ ) For the methane tank to reference the temperature T at the moment T ₀ The gas production rate of the lower methane;

f _t (T _dig )＝m(T _dig -T ₀ ) ² +n (2)

in the formula, H _t,loss 、H _t,sludge Respectively the heat loss of the digester wall and the heat energy required by sludge heating; cp (p) _sludge The specific heat capacity of the sludge is adopted; t is _t,air And T _t,soil Measuring the temperature of the air and the soil at the time t respectively; k is a radical of _air And k _soil Air and soil heat transfer coefficients, respectively; t is _dig Fermentation temperature for anaerobic digestion; t is a unit of _so Is the average influent sludge temperature; a. The _sup And A _base The side area and the base area of the digester are respectively.

Example 7:

the optimized operation method of the sewage treatment plant considering sewage reuse mainly comprises the following steps of example 4, wherein a CHP unit model is as follows:

P _{t,CHP_G} ＝p _t,gas L _gas η _CHP,e (1)

H _t,CHP ＝p _t,gas L _gas η _CHP,h (2)

Example 8:

the main content of the optimized operation method of the sewage treatment plant considering sewage reuse is shown in embodiment 4, wherein the energy storage device model comprises a storage battery model and a phase change heat storage tank model;

the storage battery model is as follows:

the charging power upper limit and the charging power lower limit;

the upper and lower limits of the discharge power; 0-1 variable I _t,cha To represent the state variable of charging, I _t,cha =1 denotes charging, I _t,cha =0 means no charging; 0-1 variable I _t,dis To represent the state variable of the discharge, I _t,dis =1 for discharge, I _t,dis =0 means no discharge; eta _cha And η _dis Respectively charging and discharging efficiencies of the storage battery;

and

The phase change heat storage tank model is as follows:

the upper and lower limits of the heat storage power;

and

respectively is the upper limit and the lower limit of the heat storage capacity of the phase change heat storage tank; h _t,bat Storing heat capacity of the phase change heat storage tank at the moment t; h _0,bat And H _T’,bat The starting value and the ending value of the phase change heat storage tank in the scheduling period are obtained.

Example 9:

the main content of a sewage treatment plant optimization operation method considering sewage reuse is shown in example 2, wherein an objective function of a sewage treatment plant optimization operation model considering sewage reuse is as follows:

Wherein the cost f of the gas network transaction _t,gas Power grid transaction cost f _t,gird Profit f from sale of water _t,W Environmental gain f _t,en Respectively as follows:

in the formula, c _t,gird And c _gas Are respectively astime-of-use electricity price and gas price at time t; p _t,gird And P _t,gas Respectively, interaction quantity with the power grid and the gas grid at the time t; c. C _W2 And c _W3 Respectively a second-level water price and a third-level water price; q _t,I And Q _t,D The secondary water demand and the tertiary water demand at the time t are respectively; k _en2 And K _en3 Respectively converting coefficients of secondary emission and tertiary emission; q _t,en2 The water flow discharged by secondary treatment at the time t; q _t,en3 The water flow discharged by the three-stage treatment at the time t.

Example 10:

a sewage treatment plant optimization operation method considering sewage reuse is disclosed in an embodiment 2, wherein constraint conditions of an optimization operation model of the sewage treatment plant considering sewage reuse comprise electric power balance constraint, gas balance constraint, thermal power balance constraint, secondary water treatment balance constraint, tertiary water treatment balance constraint, CHP output upper and lower limit constraint, regulating reservoir constraint, secondary reservoir constraint and clear water reservoir constraint;

wherein the electric power balance constraint is as follows:

P _t,wind +P _{t,CHP_G} +P _t,gird +P _{t,bat_dis} +P _t,PV ＝P _{t,bat_cha} +P _t,clar +P _t,Aer +P _t,3 (1)

in the formula, P _t,PV Generating power for the photovoltaic unit; p _t,wind Generating power for the wind turbine; p _t,Aer Blower power for time t; p _{t,CHP_G} The CHP total power generation power at the t moment; p is _t,gird The interaction quantity with the power grid at the moment t is shown; p _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power; p _t,clar Clearing the power of the pump for the time t; p _t,3 The power consumption of the tertiary treatment at the time t;

the gas balance constraints are as follows:

p _t,BG -p _t,gas ＝P _t,gas (2)

the thermal power balance constraint is as follows:

H _t,CHP +H _{t,bat_dis} ＝H _t,loss +H _t,sludge +H _{t,bat_cha} (3)

the secondary water treatment equilibrium constraints are as follows:

Q _t,2 ＝α ₂ Q _t,se2 (4)

in the formula, Q _t,se2 The flow rate after the secondary water treatment at the time t; alpha (alpha) ("alpha") ₂ The flow ratio of secondary water treatment is adopted; q _t,2 For the secondary treatment of sewage flow at the time t

The three-stage water treatment equilibrium constraints are as follows:

Q _t,3 ＝α ₃ Q _t,th3 (5)

in the formula, Q _t,th3 The flow rate after the three-stage water treatment at the moment t is shown; alpha is alpha ₃ The flow rate ratio of three-stage water treatment is adopted; q _t,2 The flow of the three-stage treatment sewage at the time t;

the CHP upper and lower force limits are constrained as follows:

in the formula (I), the compound is shown in the specification,

and

respectively the upper limit and the lower limit of CHP electric power output;

and

respectively an upper limit and a lower limit of CHP thermal power output. P is _t,CHP And Q _t,CHP CHP electric power and thermal power at the time t respectively;

the adjustment tank constraints are as follows:

the maximum water storage capacity of the regulating tank is obtained; r _0,1 And R _T,1 Respectively the initial value and the final value in the dispatching cycle of the regulating pool; q _t The flow rate of wastewater entering the regulating reservoir at the moment t;

the secondary reservoir constraints are as follows:

and (3) restricting the clean water tank:

in the formula, R _t,3 And R _t-1,3 The water storage capacity of the clean water tank at the t moment and the t-1 moment; r _max3 Is the most important part of a clean water poolLarge water storage capacity, R _0,3 And R _T,3 Respectively are the initial value and the final value in the clear pool scheduling period; q _t,D The water demand is three-level at the time t; q _t,en3 The water flow discharged by the three-stage treatment at the time t.

Example 11:

the main content of the method is shown in embodiment 2, wherein a tool for solving an optimized operation model of the sewage treatment plant considering sewage reuse comprises CPLEX.

Example 12:

an optimized operation method of a sewage treatment plant considering sewage reuse comprises the following steps:

a sewage treatment plant considering sewage reuse, which comprises treatment units and equipment units at all levels; each stage of treatment unit comprises a regulating tank, a cleaning pump, a primary sedimentation tank, a blower, a biological denitrification tank, a secondary sedimentation tank, a secondary reservoir, a deep treatment unit, a clean water tank and a filter membrane; the equipment unit comprises a photovoltaic generator set, a wind generating set, a methane generator, a methane tank, an electric boiler, a storage battery and a heat storage tank; the method is characterized in that: the sewage treatment plant is also provided with lines and pipelines to realize interaction with a power grid and an air grid; the electric boiler transfers heat energy to the heat storage tank and the methane tank through the heat pipeline.

The technical scheme for realizing the invention is as follows: an optimized operation method of a sewage treatment plant considering sewage reuse. The method mainly comprises the following steps: step 1: the basic parameters of a sewage treatment plant are first entered. Step 2: and modeling each unit in the sewage treatment plant. And step 3: and establishing an objective function and constraint conditions for optimizing operation of the sewage treatment plant in consideration of sewage reuse, carrying out piecewise linearization treatment on the nonlinear constraint, and then solving by using a commercial solver CPLEX to obtain an optimal solution of the optimization problem. The specific implementation steps are as follows:

inputting basic data

1.1 input basic data

Basic parameters input into a sewage treatment plant include: time-of-use purchase electricity price, time-of-use sale electricity price, gas price, sewage load, irrigation water price, secondary discharge income, tertiary discharge income, industrial general water load, industrial general water price and other parameters.

Each unit model of sewage treatment plant

2.1 Process models at levels

The power consumption of the primary treatment mainly comprises a cleaning pump:

P _t,clar ＝γ _s Q _t H _t /1000η (1)

H _t ＝aQ _t ² +bQ _t r+cr ² (2)

in which the subscript t denotes time t, P _t,clar Clearing the power of the pump at time t; eta is the efficiency of the cleaning pump; q _t The flow rate of wastewater entering the regulating reservoir at the moment t; gamma ray _s Is the sewage specific gravity; h _t Clearing the pump lift at the moment t; r is the relative speed of the cleaning pump; and a, b and c are empirical coefficients of pump head curves of the water pump.

The aeration unit in the power consumption of the secondary sewage treatment model mainly consumes the power of a blower:

in which the subscript t denotes time t, P _t,Aer Blower power at time t; r is the air gas constant; t is a unit of _in Is the fan inlet temperature; eta _B To the mechanical efficiency of the blower; p _a Is at atmospheric pressure; p _t,stat Is the static pressure at the exit of the blower diffuser.

Dynamic pressure P _t,dyn Can be calculated from the following formula:

P _t,dyn ＝(Q _t,air /A _dif ) ² k _p (4)

in the formula, the subscript t represents time t, Q _t,air Is the air mass flow rate; a. The _dif Is the diffuser cross-sectional area; k is a radical of formula _p ＝275N s ² /m ⁴

Air mass flow rate Q _t,air Can be calculated from the following formula:

in the formula, the subscript t represents time t, K _La For the standard transfer efficiency of oxygen, n _O2 Is the mass of oxygen in the unit mass of air, m _t,O2 Standard oxygen transfer rate.

The standard oxygen transfer rate can be calculated by the following formula:

m _t,BOD ＝Q _t,2 (BOD _t,in -BOD _t,out )ConB (7)

m _t,TKN ＝Q _t,2 (TKN _t,in -TKN _t,out )ConN (8)

in which the subscript t denotes time t, m _t,BOD And m _t,TKN The oxidation oxygen demand and the nitrification oxygen demand of the aeration tank are obtained, beta is the oxygen mass in unit mass of air, C _T And C _T ⁰ Oxygen saturation concentration in fresh water at T temperature and reference temperature, C _d Alpha is the oxygen transfer ratio in the wastewater, theta is a constant, BOD for the dissolved oxygen concentration _t,in And BOD _t,out The BOD concentration, TKN of inlet water and outlet water of a sewage treatment plant _t,in And TKN _t,out TKN concentration of inlet water and outlet water of a sewage treatment plant, conN is required oxygen ratio for oxidation of TKN, CONB is required oxygen ratio for oxidation of BOD, Q _t,2 The flow rate of the secondary treatment sewage is shown.

Deep processing model:

P _t,3 ＝η ₃ V _t,3 (9)

in the formula eta ₃ The volume coefficient of sewage treated by unit electric energy in a three-stage treatment link; v _t,3 The volume of water entering the clean water tank after three-stage treatment at the moment t; p _t,3 For three-stage treatment at time tThe power consumption.

2.2 sludge Marsh model

Carrying out anaerobic digestion treatment on the sludge obtained in the secondary treatment process to obtain biogas, wherein the yield of the biogas is as follows:

in the formula, subscript t represents time t; m is a unit of _t,sl The sludge mass at the time t; beta is a beta _wsl The sludge coefficient after standing and precipitating the sewage is obtained; p is a radical of _t,BG The amount of biogas generated at time t; beta is a beta _S2B,T0 Is T ₀ Lower sludge biogas production coefficient, T ₀ Typically 35 deg.c. f. of _t (T _dig ) The fermentation temperature T of the methane tank at the time T _dig And lowering the gas production rate of the methane.

The relationship between biogas yield and fermentation temperature can be expressed as:

f _t (T _dig )＝m(T _dig -T ₀ ) ² +n (11)

in the formula, m and n are coefficients in a quadratic expression respectively.

in the formula (II b) _sludge The specific heat capacity of the sludge is 3.62kJ/kg ℃; t is _air And T _soil Measuring the temperature of air and soil respectively; k is a radical of _air And k _soil Air and soil heat transfer coefficients, respectively; t is _dig The fermentation temperature for anaerobic digestion, and the average influent sludge temperature T _so Should be 15 ℃; a. The _sup And A _base Respectively the side area and the base area of the digestion tank, m ² 。

2.3CHP Unit model

The CHP unit model is as follows:

P _{t,CHP_G} ＝p _t,gas L _gas η _CHP,e (13)

H _t,CHP ＝p _t,gas L _gas η _CHP,h (14)

in the formula, P _{t,CHP_G} The CHP total power generation power at the time t; h _t,CHP CHP thermal power at time t; p is a radical of _t,gas The flow rate of the biogas consumed by the CHP at the moment t; l is _gas The heat value of the biogas is; eta _CHP,e And η _CHP,h The electrical and thermal efficiencies of CHP, respectively.

2.4 energy storage device

The sewage treatment plant is provided with a storage battery and a phase change heat storage tank;

the storage battery model is as follows:

in the formula, E _t,bat And E _t-Δt,bat The storage battery stores electric quantity at the t moment and the t-delta t moment respectively; Δ t is the time; p is _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power;

the charging power is the upper and lower limits;

and

respectively an upper limit and a lower limit of the energy storage capacity of the storage battery; _Et,bat the energy storage capacity of the storage battery at the moment t; e _0,bat And E _T’,bat The starting value and the end value of the storage battery in the dispatching cycle are obtained; t' is the total number of time segments of one scheduling period.

The phase change heat storage tank model is as follows:

the upper and lower limits of the heat storage power;

the upper and lower limits of the heat release power; 0-1 variable I _t,hcha Is a state variable for representing heat storage, I _t,hcha =1 for heat storage, I _t,hcha =0 indicates no heat storage; 0-1 variable I _t,hdis Is a state variable for representing the heat release, I _t,hdis =1 denotes exotherm, I _t,hdis =0 indicates no exotherm; eta _hcha And η _hdis Respectively the storage efficiency and the heat release efficiency of the phase change heat storage tank;

and

Establishing an objective function and constraint conditions for optimizing operation and solving

3.1 establishing an objective function with minimal operating cost

The following objective function is established according to the model:

in the formula, f _t,gas Cost for trading with the air grid; f. of _t,gird Trading costs for the grid; f. of _t,W Earning for selling water; f. of _t,en Is an environmental benefit.

Each cost and benefit is calculated by:

in the formula, c _t,gird And c _gas Time-of-use electricity price and gas price at the moment t respectively; p _t,gird And P _t,gas Respectively, interaction quantity with the power grid and the gas grid at the time t; c. C _W2 And c _W3 Respectively a second-level water price and a third-level water price; q _t,I And Q _t,D The secondary water demand and the tertiary water demand at the time t are respectively; k _en2 And K _en3 Respectively converting coefficients of second-level discharge and third-level discharge; q _t,en2 The water flow discharged by secondary treatment at the time t; q _t,en3 The water flow discharged by the three-stage treatment at the time t.

3.2 establishing various constraints

The electric power balance constraint is:

in the formula, P _t,PV Generating power for the photovoltaic unit; p _t,wind The generated power of the wind turbine generator is obtained.

And (3) gas balance constraint:

p _t,BG -p _t,gas ＝P _t,gas (20)

thermal power balance constraint:

H _t,CHP +H _{t,bat_dis} ＝H _t,loss +H _t,sludge +H _{t,bat_cha} (21)

and secondary water treatment balance constraint:

Q _t,2 ＝α ₂ Q _t,se2 (22)

in the formula, Q _t,se2 The flow rate after the secondary water treatment at the time t is shown; alpha is alpha ₂ Is the flow ratio of secondary water treatment

And (3) three-stage water treatment balance constraint:

Q _t,3 ＝α ₃ Q _t,th3 (23)

in the formula, Q _t,th3 The flow rate after the three-stage water treatment at the moment t is shown; alpha is alpha ₃ Is a three-stage water treatment flow ratio

And (3) CHP (Chronic acid phosphate) output upper and lower limit constraint:

in the formula (I), the compound is shown in the specification,

and

and

respectively an upper limit and a lower limit of CHP thermal power output.

Regulating the regulating pool:

in the formula, R _t,1 Regulating the water storage capacity of the pool at the moment t;

for regulating the maximum water storage capacity of the tank, R _0,1 And R _T,1 Respectively the beginning and end values in the regulation pool scheduling period.

And (3) secondary reservoir restraint:

in the formula, R _t,2 The water storage capacity of the secondary reservoir at the moment t; r _max2 The maximum water storage capacity R of the secondary reservoir _0,2 And R _T,2 And the initial value and the final value in the scheduling period of the secondary reservoir are respectively.

And (3) restricting the clean water tank:

in the formula, R _t,3 The water storage capacity of the clean water tank at the moment t; r _max3 Is the maximum water storage capacity of the clean water tank, R _0,3 And R _T,3 Respectively, the starting value and the ending value in the clear pool scheduling period.

3.3 constraint handling and solving

And solving by adopting a solver CPLEX after carrying out piecewise linearization processing on the formulas (1) - (8) and the formulas (10) - (11).

Example 13:

a verification test of the optimal operation method of the sewage treatment plant considering sewage reuse in the embodiments 1 to 12 comprises the following steps:

1) The classification treatment equipment for the sewage treatment plant considering sewage reuse is determined, and comprises a regulating reservoir, a secondary reservoir, a clean water reservoir, primary treatment, secondary treatment and tertiary treatment, wherein the primary treatment comprises the following steps: a pump and a primary sedimentation tank. The secondary treatment comprises the following steps: an air blower, an anoxic/aerobic (A/O) tank and a secondary sedimentation tank. The three-stage treatment comprises the following steps: and a third-stage treatment tank. Wherein: sewage firstly enters a regulating tank to ensure that the water quality is consistent, and is pumped to a primary sedimentation tank for filtration, and then enters an A/O tank for anoxic denitrification, aerobic organic matter removal and aeration treatment in a nitrification stage, so as to obtain sludge in a secondary sedimentation tank; the water after secondary treatment can be used for agricultural irrigation and for discharge to obtain pollution discharge benefits; the sludge is then anaerobically treated to reduce the volume of the sludge and produce biogas for power generation or heating. Finally, the sewage subjected to the tertiary treatment is used for industrial miscellaneous use and for discharge to obtain a pollution discharge benefit. The sewage treatment plant is provided with a regulating reservoir, a secondary reservoir and a clean water reservoir so as to realize flexible graded regulation and control.

As shown in the attached figure 2, the energy flow of the sewage treatment plant considering sewage reuse comprises electric energy, heat energy, water and methane. Wherein: the electric bus is connected with a power grid, a storage battery, a wind-solar generator set, a CHP (Chronic Hydrogen phosphate) and energy consumption equipment of a sewage treatment plant; the heat pipeline is connected with the CHP, the heat storage tank and the methane tank; the gas pipe is connected with the CHP, the methane tank and the gas network; the sewage enters a sewage treatment plant for treatment and then is recycled through a water pipe.

2) The operation of a sewage treatment plant is optimized by the method of the invention for the sewage treatment plant:

2.1 Input basic data

Basic parameters input into a sewage treatment plant include: time-of-use electricity price purchasing, time-of-use electricity price selling, gas price, sewage load, irrigation water price, secondary discharge income, tertiary discharge income, industrial water load, industrial water price and wind and light output.

The time-of-use purchase electricity price and the time-of-use sale electricity price are given in table 1; gas prices, irrigation water prices, secondary discharge gains, tertiary discharge gains, and industrial miscellaneous water prices are given in table 2; the sewage load, irrigation water load, and industrial utility water load are given in table 3;

TABLE 1 time of use electricity price

TABLE 2 cost benefits

Irrigation water price	0.1 yuan/m ³
		Second order emission yield	0.01 yuan/m ³
Price of gas purchase	1.5 yuan/m ³
		Price of gas sale	1.0 yuan/m ³
Three stage emission yield	0.09 yuan/m ³
		Water price for industrial waste	0.5 yuan/m ³

TABLE 3 Water load in scheduling period

Time period	Sewage load/m ³	Irrigation water load/m ³	Load of industrial miscellaneous Water/m ³
				0	1500	85.40	10
1	1360	70.55	0
				2	1356	87.68	10
3	1360	109.59	10
				4	1320	70.55	20
5	1300	109.36	180
				6	1260	109.36	70
7	1220	90.02	60
				8	1280	119.43	50
9	1276	161.34	50
				10	1362	264.56	90
11	1450	432.22	90
				12	1540	514.01	20
13	1520	546.81	20
				14	1480	538.38	30
15	1530	513.99	30
				16	1510	408.48	20
17	1450	324.36	20
				18	1420	204.00	70
19	1430	163.48	40
				20	1426	149.56	60
21	1460	135.89	60
				22	1480	94.28	0
23	1490	114.83	10

2.2 Modeling and solving a wastewater treatment plant for wastewater reuse

Through the unit models, the objective functions and the constraint conditions of the sewage treatment plant listed above, the equations (1) - (8) and (10) - (11) are subjected to piecewise linearization processing and then solved by a solver CPLEX, so that the operation cost errors and the solving time under different segmentation numbers are obtained, as shown in Table 4.

TABLE 4 running cost error and solution time for different number of stages

Number of segments	Total cost/element	Relative error	Solution time/s
				5	1198.7	0.016％	50
10	1198.6	0.0083％	169
				15	1198.5	/	891

2.3 Effect of experiment)

Three operation modes are provided for a certain sewage treatment plant, and the effectiveness and superiority of the method are contrastively verified. Scene 1: and sewage reuse is considered. Scene 2: the reuse of sewage is not considered. Scene 3: the clear water tank, the secondary reservoir and the regulating tank are not arranged, and the temperature of the methane is constant.

(a) Running cost comparison

Table 5 shows the operating costs of the sewage treatment plants and the total operating cost for the three scenarios.

TABLE 5 running costs under different scenarios

Comprehensive comparison can show that the scene 1 has higher electricity transaction cost compared with the scene 2 because of the requirement of water recycling, and higher water selling income is obtained by sacrificing less electricity cost; scenario 3 results in higher electricity transaction costs because no elements such as a water reservoir can reduce the load during periods of high electricity prices. Scenario 1 has the least total operating cost compared to the rest of the scenarios, highlighting the effectiveness and economy of the present invention.

(b) Comparison of operating states of primary equipment units

As shown in fig. 4 and 5, in the scene 3, no elements such as a reservoir or the like are arranged, so that the load can not be reduced in a high electricity price period, and the treated water amount is consistent with the sewage load; in scenes 1 and 2, because the wind-solar generator set has low output and low electricity price in the period of 6-00-9; and in the section 12. Because the tertiary treatment is more energy-consuming, the tertiary treatment is mainly carried out in the valley period of electricity price, and the tertiary water treatment is required in the period of flat period of electricity price in the scene 1 due to the requirement of water use. In the scenario 2, since water reuse is not considered, the tertiary treatment is not performed in a time period when the electricity price is high. As shown in fig. 6, scenes 1 and 2 produce more gas at a higher temperature for sale at a lower electricity price, and keep the temperature low while using more biogas for electricity generation at a higher electricity price; 20. Therefore, the flexibility of the sewage treatment plant is fully exploited, so that the load is stable, the peak clipping and the valley filling are carried out, and the economy and the load stability are improved.

Claims

1. An optimized operation method of a sewage treatment plant considering sewage reuse is characterized by comprising the following steps;

1) And acquiring basic parameters of the sewage treatment plant.

2) And modeling the equipment unit of the sewage treatment plant according to the basic parameters of the sewage treatment plant to obtain an equipment unit model of the sewage treatment plant.

2. The method as claimed in claim 1, wherein the basic parameters of the sewage treatment plant include time-of-sale electricity price, gas price, sewage load, irrigation water price, secondary discharge income, tertiary discharge income, industrial utility water load, and industrial utility water price.

3. The optimal operation method of the sewage treatment plant considering sewage reuse according to claim 1, wherein the equipment unit model of the sewage treatment plant comprises a treatment unit model, a sludge biogas production model, a CHP unit model and an energy storage device model.

4. The optimal operation method of sewage treatment plant considering sewage reuse according to claim 3, wherein the treatment unit models include a primary sewage treatment unit model, a secondary sewage treatment unit model, a deep sewage treatment model;

wherein, the primary sewage treatment unit model is as follows:

P _t,clar ＝γ _s Q _t H _t /1000η (1)

H _t ＝aQ _t ² +bQ _t r+cr ² (2)

in the formula, subscript t represents time t; p _t,clar Clearing the power of the pump at time t; eta is the efficiency of the cleaning pump; q _t The flow rate of wastewater entering the regulating reservoir at the moment t; gamma ray _s Is the sewage specific gravity; h _t Clearing the pump lift at the moment t; r is the relative speed of the cleaning pump; a, b and c are empirical coefficients of pump head curves of the water pump;

the secondary sewage treatment unit model is as follows:

in the formula, P _t,Aer Blower power for time t; r is the air gas constant; t is a unit of _in Is the fan inlet temperature; eta _B To the mechanical efficiency of the blower; p _a Is at atmospheric pressure; p is _t,stat Static pressure at the outlet of the blower diffuser; p _t,dyn Is a dynamic pressure; q _t,air Is the air mass flow rate; m is a group of _air Is the molecular mass of air;

P _t,dyn ＝(Q _t,air /A _dif ) ² k _p (4)

is the mass of oxygen in a unit mass of air,

standard oxygen transfer rate;

standard oxygen transfer rate

As follows:

m _t,BOD ＝Q _t,2 (BOD _t,in -BOD _t,out )ConB (7)

m _t,TKN ＝Q _t,2 (TKN _t,in -TKN _t,out )ConN (8)

in the formula, m _t,BOD And m _t,TKN Oxidizing oxygen demand and nitrifying oxygen demand for the aeration tank; beta is the mass of oxygen in the unit mass of air; c _T And C _T ⁰ At a temperature T and a reference temperature T, respectively ⁰ Oxygen saturation concentration in the lower fresh water; c _d Is the dissolved oxygen concentration; alpha is the oxygen transfer ratio in the wastewater; theta is a constant; BOD _t,in And BOD _t,out The BOD concentration of inlet water and outlet water of a sewage treatment plant; TKN _t,in And TKN _t,out Is a sewage placeTKN concentration of inlet water and outlet water of a treatment plant; conN is the required oxygen ratio for oxidation of TKN; conB is the oxygen ratio required to oxidize BOD; q _t,2 The sewage flow is treated in the second stage;

the advanced wastewater treatment model is as follows:

P _t,3 ＝η ₃ V _t,3 (9)

in the formula eta ₃ The volume coefficient of sewage treated by unit electric energy in a three-stage treatment link; v _t,3 The volume of water entering the clean water tank after three-stage treatment at the time t; p _t,3 The power consumption of the three-stage treatment at the time t.

5. The optimal operation method of a sewage treatment plant considering sewage reuse according to claim 3, wherein the sludge-to-biogas model includes a biogas production calculation equation, a heat loss calculation equation of a digester wall, and a heat energy calculation equation required for sludge heating;

wherein, the biogas yield calculation equation is as follows:

is a reference temperature T ⁰ The sewage sludge methane yield coefficient; f. of _t (T _dig ) The fermentation temperature T of the methane tank for anaerobic digestion at the moment T _dig The gas production rate of the lower methane; f. of _t (T ⁰ ) For the methane tank to reference the temperature T at the moment T ₀ The gas production rate of the lower methane; rho _wsl Is the average density of the sewage after standing and precipitation;

f _t (T _dig )＝m(T _dig -T ₀ ) ² +n (11)

in the formula, H _t,loss 、H _t,sludge Respectively the heat loss of the wall of the digestion tank and the heat energy required by heating the sludge; cp (p) _sludge The specific heat capacity of the sludge; t is _t,air And T _t,soil Measuring the temperature of the air and the soil at the time t respectively; k is a radical of _air And k _soil Air and soil heat transfer coefficients, respectively; t is _so Is the average influent sludge temperature; a. The _sup And A _base The side area and the base area of the digester are respectively.

6. The method for optimizing operation of a sewage treatment plant considering sewage reuse according to claim 3, wherein the CHP unit model is as follows:

P _{t,CHP_G} ＝p _t,gas L _gas η _CHP,e (13)

H _t,CHP ＝p _t,gas L _gas η _CHP,h (14)

7. The optimal operation method of a sewage treatment plant considering sewage reuse according to claim 3, wherein the energy storage device model comprises a storage battery model and a phase-change heat storage tank model;

the storage battery model is as follows:

the charging power upper limit and the charging power lower limit;

and

The phase change heat storage tank model is as follows:

the upper and lower limits of the heat storage power;

the upper and lower limits of the heat release power; 0-1 variable I _t,hcha Is a state variable for representing heat storage, I _t,hcha =1 for heat storage, I _t,hcha =0 means no heat storage; 0-1 variable I _t,hdis Is a state variable for representing the heat release, I _t,hdis =1 denotes exotherm, I _t,hdis =0 indicates no exotherm; eta _hcha And η _hdis Respectively the storage efficiency and the heat release efficiency of the phase change heat storage tank;

and

8. The method for optimizing operation of a wastewater treatment plant considering wastewater reuse according to claim 1, wherein an objective function of an optimized operation model of a wastewater treatment plant considering wastewater reuse is as follows:

Wherein, the cost of the air network transaction f _t,gas Grid transaction cost f _t,gird Income f from selling water _t,W Environmental gain f _t,en Respectively as follows:

9. The optimal operation method of the sewage treatment plant considering sewage reuse according to claim 1, wherein the constraint conditions of the optimal operation model of the sewage treatment plant considering sewage reuse include electric power balance constraint, gas balance constraint, thermal power balance constraint, secondary water treatment balance constraint, tertiary water treatment balance constraint, CHP upper and lower output limit constraint, regulation pool constraint, secondary reservoir constraint and clean water pool constraint;

wherein the electric power balance constraint is as follows:

in the formula, P _t,PV Generating power for the photovoltaic unit; p _t,wind For wind-power unitsGenerating power; p _t,Aer Blower power at time t; p _{t,CHP_G} The CHP total power generation power at the time t; p _t,gird The interaction quantity with the power grid at the moment t is obtained; p _{t,bat_cha} And P _{t,bat_dis} Respectively charge and discharge power; p is _t,clar Clearing the power of the pump at time t; p _t,3 The power consumption of the tertiary treatment at the time t;

the gas balance constraints are as follows:

p _t,BG -p _t,gas ＝P _t,gas (20)

in the formula, p _t,gas The flow rate of the biogas consumed by the CHP at the moment t; p is a radical of _t,BG The amount of biogas generated at time t; p is _t,gas The interaction quantity with the air network at the time t;

the thermal power balance constraint is as follows:

H _t,CHP +H _{t,bat_dis} ＝H _t,loss +H _t,sludge +H _{t,bat_cha} (21)

the secondary water treatment equilibrium constraints are as follows:

Q _t,2 ＝α ₂ Q _t,se2 (22)

in the formula, Q _t,se2 The flow rate after the secondary water treatment at the time t; alpha is alpha ₂ The flow ratio of secondary water treatment is adopted; q _t,2 For the secondary treatment of sewage flow at the time t

The three-stage water treatment equilibrium constraints are as follows:

Q _t,3 ＝α ₃ Q _t,th3 (23)

the CHP upper and lower force limits are constrained as follows:

in the formula (I), the compound is shown in the specification,

and

and

the adjustment tank constraints are as follows:

in the formula, R _t,1 And R _t-1，1 Regulating the water storage capacity of the pool at the t moment and the t-1 moment;

secondary reservoir constraints are as follows:

the maximum water storage capacity R of the secondary reservoir _0,2 And R _T,2 Respectively representing the starting value and the ending value in the second-level reservoir scheduling period; q _t,I The secondary water demand at the time t; q _t,en2 The water flow discharged by secondary treatment at the time t;

and (3) restricting the clean water tank:

10. The method for optimizing the operation of a sewage treatment plant considering sewage reuse according to claim 1, wherein: tools for solving the optimal operation model of the sewage treatment plant considering sewage reuse include CPLEX.