JPH06206077A - Chlorine injection rate controller for water supply - Google Patents

Abstract

(57) [Summary] [Purpose] To keep the residual chlorine concentration at the target point at an optimum level. [Configuration] Pipe network model, forecast and actual demand, target concentration time series value, temporary set injection rate, injection rate upper and lower limit data are input to the computing device 1, and the network model and forecast / actual demand are calculated. The residual water concentration distribution in the pipe network when the chlorine injection rate was set to the value of the provisional injection rate was calculated by the dynamic water quality analysis calculation used, and then the dynamics using the network model and forecast / actual demand were calculated. The change of residual chlorine concentration distribution in the pipe network is repeatedly calculated when the chlorine injection rate is increased by a unit amount per unit time by the dynamic water quality analysis calculation. From the relationship between the obtained chlorine injection rate and residual chlorine concentration distribution, calculate the injection rate schedule that makes the residual chlorine concentration at the target point on the pipe network close to the target concentration time-series value, and then to the injection ratio controller 5. Controls the injection rate of feed chlorine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chlorine injection rate control device for maintaining an appropriate residual chlorine concentration in a water distribution network in a chlorine injection facility installed for disinfecting waterworks.

[0002]

2. Description of the Related Art In waterworks, it is obligatory to inject chlorine for disinfection, and the amount of injection must also be detected at a prescribed residual chlorine concentration of 0.1 mg / l or more at a water tap at the end. Therefore, conventionally, an appropriate injection rate is determined by manually analyzing the concentration of residual chlorine at the water tap at the end or by using a sensor, and a schedule of the injection rate of chlorine is determined on a daily or monthly basis.

[0003]

By the way, since the injected chlorine is attenuated with the passage of time, if the flow rate in the pipeline is small, the stagnation time becomes long and the residual chlorine concentration drops remarkably. On the other hand, when the flow rate of water is large, on the contrary, the decrease is small. In other words, if chlorine was injected at the same injection rate,
The residual chlorine concentration at the terminal will change depending on the amount of water distribution.

Since the actual water distribution varies greatly during the day, when the chlorine injection rate is determined on a daily basis, the injection rate is determined on the basis of the time zone with the smallest water distribution. Therefore, the concentration of residual chlorine becomes an excessively high value during the time when the amount of water distribution is large. If the concentration of residual chlorine is high,
The water becomes so-called chlorine-smelling water, which gives uncomfortable feeling to the user, and trihalomethane which is a carcinogen is generated. Moreover, injecting chlorine excessively is uneconomical because it is an unnecessary expense for the water supply business.

Therefore, a method of controlling the chlorine injection rate is required so that the minimum residual chlorine concentration can be always maintained at the water tap at the end in consideration of the temporal variation of the residual chlorine concentration decreasing characteristic in the water distribution network. Become. For that purpose, a method of installing a sensor for measuring the residual chlorine concentration at a target end and feeding back this signal to control the residual chlorine concentration to a target value can be considered.

However, in this case as well, since the phenomenon to be targeted is the movement of the substance itself, the dead time is generally very long and its fluctuation range is large, and the residual chlorine concentration is reduced so as to reduce the deviation from the target value. It was impossible to control. The present invention has been made to solve the above problems, and an object of the present invention is to control a chlorine injection rate capable of always maintaining a residual chlorine concentration at a terminal at a reference value, even if there is a variation in water distribution. To provide a device.

[0007]

In order to achieve the above object, a first aspect of the present invention provides a pipe network model, a forecast and actual demand amount, a target concentration time series value, a temporary set injection rate, an injection rate upper and lower limit values. Means to input each data, pipe network model and prediction
Means to calculate the residual chlorine concentration distribution in the pipe network when the chlorine injection rate is set as the value of the provisional injection rate by the dynamic water quality analysis calculation using the actual demand, the pipe network model, and the forecast / actual demand A method for repeatedly calculating changes in the residual chlorine concentration distribution in the pipe network when the chlorine injection rate is increased by a unit amount per unit time by the dynamic water quality analysis calculation using By means of the least squares method using the simultaneous equations obtained from the relationship with the chlorine concentration distribution or the relationship, means for calculating the injection rate schedule in which the residual chlorine concentration at the target point on the pipe network is close to the target concentration time series value, When the calculated value of the infusion rate schedule exceeds the upper and lower limits of the infusion rate, a means for correcting the value within the upper and lower limits is provided.

A second invention is characterized in that, in the first invention, there is provided means for calculating an injection rate schedule within the upper and lower limits of the injection rate by using a linear programming method.

Here, it is possible to provide a plurality of target points and / or chlorine injection points on the pipe network. Further, when there are a plurality of chlorine injection points, the chlorine injection intervals may be different from each other.

[0010]

In the first aspect of the invention, when the pipe network model, the forecast and actual demand, the target concentration time series value, the temporary set injection rate, and the injection rate upper and lower limit values are input, the pipe network model and the prediction are obtained. -The distribution of residual chlorine concentration in the pipe network is calculated by the dynamic water quality analysis calculation using the actual demand when the chlorine injection rate is set to the value of the provisional injection rate. Then, the change in residual chlorine concentration distribution in the pipe network is repeatedly calculated by the dynamic water quality analysis calculation using the pipe network model and the forecast / actual demand amount when the chlorine injection rate is increased by the unit amount per unit time. .

The residual chlorine concentration at the target point on the pipe network is determined by the least squares method using the simultaneous equations obtained from the relation between the calculated chlorine injection rate and the residual chlorine concentration distribution, or the target concentration time series. An infusion rate schedule close to the value is calculated. When the calculated infusion rate schedule value exceeds the infusion rate upper and lower limits, the schedule value is corrected within the upper and lower limits.

In the second aspect of the invention, the injection rate schedule is calculated using the linear programming so that the injection rate is within the upper and lower limit values. It should be noted that the injection rate schedule is calculated at either one or a plurality of target points and chlorine injection points on the pipe network. Further, when there are a plurality of chlorine injection points and the chlorine injection intervals are different from each other, the injection rate schedule is similarly calculated.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, the procedure for determining the time schedule of the optimum chlorine injection rate up to T hours ahead will be described. The chlorine injection rate here means the residual chlorine concentration at the outlet of a water treatment plant or distribution reservoir. Therefore, after the chlorine is added to the filtered water, the chlorine consumed up to the outlet of the pond shall be compensated by the on-site control.

(1) Similar to using a pipe network for pipe network calculation, modeling is performed with nodes and pipe lines. As a pipeline model,
For example, a model as shown in FIG. 4 is set. (2) The demand water amount for each node is determined for each Δt ₁ hour before the T time by the demand forecast or the planned water amount. (3) T time ahead of the chlorine injection rate at the chlorine injection point,
Temporarily set a time schedule for every Δt ₂ hours. Here, for example, the time schedule is set to a constant chlorine injection rate.

(4) Using the data of (1), (2), and (3), the time variation of the residual chlorine concentration at each node for each Δt ₁ hour up to the time T is calculated. It is called water quality analysis calculation). However, since the residual chlorine concentration also affects the past history, it is calculated from the time before the last L time when it has an influence. The actual value is used as the chlorine injection rate in the past time, and the actual value or estimated value is used as the demand water amount for each node.

The dynamic water quality analysis calculation is calculated as follows. 1) Pipe network calculation is performed under the conditions such as the nodal demand and injection point head at that time, and the flow distribution of each pipeline is calculated. 2) The residence time t _s and the concentration decrease rate R are calculated for each pipeline by the following formula.

[0017]

[Equation 1]

[0018]

[Number 2] _{R = exp (-k · t s} )

Where k is the residual chlorine concentration reduction rate coefficient, t
Is time, t ₀ is the time, Q (t) is the pipe flow rate, D is the pipe inner diameter, and L is the pipe section length. t _s determine the value that satisfies the equation (1) in the numerical solution. 3) by interpolation on the upstream side (t ₀ -t _s) time of residual chlorine concentration C _A from the concentration calculation points before and after sandwiching the time according to the flow direction of the conduit, to calculate. 4) Calculate the residual chlorine concentration C _B of the downstream side at the time concerned by the following formula.

[0020]

## EQU3 ## C _B (t ₀ ) = R · C _A (t ₀ −t _s ).

5) For each node, the residual chlorine concentration C _C of the outflow pipe upstream is calculated from the concentration of the residual chlorine downstream of the inflow pipe by the following formula, assuming that they are completely mixed after merging. However,
C ₀ is the injection concentration at the chlorine injection point.

[0022]

[Equation 4]

The steps 1) to 5) are repeatedly calculated for each calculation time interval from -L time to T time.

(5) Let the concentrations of the target nodes at Δt ₁ time intervals obtained by the dynamic water quality analysis be x ⁰ (i), (i = 1 to n). The injection rate at Δt ₂ time interval at that time is u ⁰ (j),
(J = 1 to m). Here, n and m are n =
T / Δt ₁ and m = T / Δt ₂ . However, in general, n ≧ m.

The relationship between the injection point concentration u (j) at the time j and the concentration x (i) at the target point at the time i is formulated by the following numerical calculation. Then, the injection point concentration u at time j
In order to obtain the sensitivity of the density x (i) of the target point at time i with respect to (j), u (j) is sequentially changed from j = 1 to j = m by Δu.
Incremented by 1 and calculated sequentially for dynamic water quality analysis, x
The variation Δx (i, j) of (i) is obtained. However, Δx
(I, j) is the increment of x (i) from x ⁰ (i) when u (j) is incremented by Δu. That is, these relationships are as follows.

[0026]

[Equation 5]

Here, a (i, j) ≧ 0. From Expression 5, x (i) can be expressed as the following expression.

[0028]

[Equation 6]

However, Δx and Δu are respectively expressed by the following equations.

[0030]

Δx (i) = x (i) −x ⁰ (i)

[0031]

Δu (j) = u (j) −u ⁰ (j)

Here, when the target node is a plurality of N points, X _I , X _I ⁰ , A
Let _I (j) and ΔX _I be the following equations, respectively.

[0033]

[Formula 9] X _I = [x _I (1) ... x _I (n)] ^T

[0034]

[Expression 10] X _I ⁰ = [x _I ⁰ (1) ... x _I ⁰ (n)] ^T

[0035]

[Expression 11] A _I (j) = [a _I (1, j) ... a _I (n, j)] ^T

[0036]

[Expression 12] ΔX _I = X _I −X _I ⁰

[Mathematical formula-see original document] Therefore, the equation 6 is expressed as the following equation.

[0038]

[Equation 13]

When the chlorine injection points are a plurality of M points, U
_{Let J} , U _J ⁰ , A _J (i), and ΔU _{J be} as follows.

[0040]

[Equation 14] U _J = [u _J (1) ... u _J (m)] ^T

[0041]

[Equation 15] U _J ⁰ = [u _J ⁰ (1) ... u _J ⁰ (m)] ^T

[0042]

## EQU16 ## A _J (i) = [a _J (i, 1) ... a _J (i, m)]

[0043]

[Expression 17] ΔU _J = U _J −U _J ⁰

Accordingly, Equation 6 is expressed as follows.

[0045]

[Equation 18]

When the target nodes are a plurality of N points and the chlorine injection points are a plurality of M points, A _IJ is expressed by the following equation.

[0047]

[Formula 19]

Further, equations 9, 10, 12, 14, 1
From the relationship of Nos. 5 and 17, Formula 6 is expressed as the following formula.

[0049]

[Equation 20]

When there are a plurality of chlorine injection points (M points) and the injection rate schedules have different time intervals. When the time interval of the J-th injection point is Δt _2J , m _J = T / Δ
In addition to t _2J , U _J , U _J ⁰ , ΔU _J , and A _J (i) are respectively set as in the following equations.

[0051]

[Expression 21] U _J = [u _J (1) ... u _J (m _J )] ^T

[0052]

[Equation 22] U _J ⁰ = [u _J ⁰ (1) ... u _J ⁰ (m _J )] ^T

[0053]

[Expression 23] ΔU _J = U _J −U _J ⁰

[0054]

A _J (i) = [a _J (i, 1) ... a _J (i, m _J )]

Accordingly, the equation 6 is expressed as the following equation.

[0056]

[Equation 25]

When there are a plurality of target nodes (N points), a plurality of chlorine injection points (M points), and the time intervals of the injection rate schedules are different, _AIJ is set as follows.

[0058]

[Equation 26]

Further, equations 9, 10, 12, 21, 21
From the relationship of 2 and 23, Equation 6 is expressed as the following equation.

[0060]

[Equation 27]

Here, equations 6, 13, 18, 20, 2
5,27 can be generally expressed by the following equation.

[0062]

X-X ⁰ = A · (U-U ⁰ )

Here, the elements of X, U and A are re-established as x _i ,
When expressed as u _j and a _ij , the following expressions are respectively obtained.

[0064]

X = [x ₁ ... X _p ] ^T

[0065]

[Equation 30] U = [u ₁ ... u _q ] ^T

[0066]

[Equation 31]

The numbers p and q of the elements of X and U are expressed by the following equations in the most general case.

[0068]

[Expression 32] p = N · n

[0069]

[Expression 33]

Furthermore,

[0071]

[Equation 34]

[0072]

[Equation 35] B = [b ₁ ... B _p ] ^T

Then, X is given by the following equation.

[0074]

[Equation 36] X = A ・ U + B

By the way, from the relationship of the delay time between the chlorine injection point and the target point, there is a case where there is a relationship of the following formula for a certain x _i .

[0076]

[Equation 37]

At this time, all the elements in the i-th row of A are 0, and x _i is out of control (x _i = x _i ⁰ ). Therefore,
Delete the corresponding element in row i from X, A, B. Those after deletion are represented as X ', A', B '. The number of elements of X'after deletion is p '. On the other hand, for some u _i, there is a case where the following relationship is established.

[0078]

[Equation 38]

At this time, all the elements of the j column of A are 0, and u _j is irrelevant to the control of X and cannot be determined. Therefore, the corresponding element in column j is deleted from U and A '. Those after deletion are represented as U ′ and A ″. The number of elements of U ′ after deletion is q ′. From these, Equation 36
Is as follows.

[0080]

X '= A' '· U' + B '

Based on the equations 6 and 39, the optimum solution U _{s of} U ′ is obtained for the target X ′. Hereafter, in order to simplify the symbols, X ', A'',U', B ',
If p ′ and q ′ are set again as X, A, U, B, p and q, X is expressed by the following equation.

[0082]

[Formula 40] X = AU + B

Further, X = [ x ₁ ... X _p ], and x _i is x _i
The target concentration of

1) Optimal injection for making the residual chlorine concentration at the target point as close as possible to the target value. When p = q and the matrix A is regular (there is an inverse matrix), X =
If X is set, the equation 40 can be solved for U = U _s , and the following equation can be obtained.

[0085]

[Expression 41] U _s = A ^-1 · ( X −B)

[0086] However, if there is a limitation on the value of u _j, u _j>
When u _j ′, u _j = u _j ′. When u _j < u _j , u _j
= U _j . Here, u _j ′ is the upper limit value of the injection rate and u _j is the lower limit value of the injection rate. When p> q and rank of the matrix A is q, the evaluation function is as follows.

[0087]

(42) J = (X− X ) ^T · (X− X ) = (A · U + B− X ) ^T · (A · U + B− X )

Then, U _s that minimizes the equation 42 can be solved by the least squares method, and the solution is as follows.

[0089]

[Expression 43] U _s = (A ^T · A) ⁻¹ · A ^T · ( X −B)

However, when the value of u _j is restricted, the process is the same as. 2) Optimal injection to keep the residual chlorine concentration at the target point at the required minimum residual chlorine concentration. The following objective function J is minimized in order to make the concentration of each time as close to the target value as possible and reduce the amount of injected chlorine.

[0091]

[Equation 44]

However, e _i and f _j are respective weights, and, for example, are values proportional to the flow rate at the corresponding time. If the upper and lower limits of the injection rate are taken into consideration as a constraint condition, U will be as follows.

[0093]

(45) U ≦ U ′ (u _j ≦ u _j ′)

[0094]

(46) U ≧ U (u _j ≧ u _j )

Further, in order to make the density equal to or higher than the target value, X
As follows.

[0096]

(47) X ≧ X (x _i ≧ x _i )

At this time, the evaluation function of Expression 44 is as follows.

[0098]

[Equation 48]

However, E and F are expressed as the following equations.

[0100]

[Equation 49] E = [e ₁ ... E _p ]

[0101]

F = [f ₁ ... f _q ]

EQUATION 40 Equal sign constraint and EQUATION 4
If there is a pair of solutions of X and U that satisfy the constraint conditions under the inequality constraint conditions of 5, 46, 47, the solution X _s , U _s that minimizes the evaluation function of Expression 48 is obtained by linear programming. Can be solved.

FIG. 1 shows a block diagram of an embodiment of the present invention. The optimum injection schedule is calculated by the arithmetic unit 1 such as a computer based on the pipe network model, the predicted demand, and the actual demand. This calculation calculates a plan up to 24 hours ahead at a fixed time once a day, or starts it at a fixed time cycle and updates the optimal infusion schedule in order.

From the optimum injection schedule, the target residual chlorine concentration at the time is periodically measured by the regular transmission device 2 by the constant time transmitter 2.
It transmits to the injection ratio controller 5 of a water purification plant via the telemeters 3 and 4. The injection ratio controller 5 is the clean water reservoir 12
The residual chlorine concentration signal from the residual chlorine concentration meter 13 installed at is fed back, the injection ratio is calculated and output so as to match the target, and the result is given to the ratio setter 6. The ratio setter 6 multiplies the amount of filtered water from the flow meter 10 at the outlet of the filter basin 9 by the injection ratio to instruct the chlorine injector 7 about the chlorine injection amount. The chlorine injecting machine 7 injects chlorine into the mixing basin 11 based on the injection amount command.

2 and 3 are flow charts showing an embodiment of the calculation procedure for obtaining the time schedule of the infusion rate. FIG. 2 shows the calculation procedure of the first invention, and FIG.
The calculation procedure of the invention of is shown.

According to these embodiments, the residual chlorine concentration at the target point can be made as close as possible to the target value. Alternatively, it can be made as low as possible above the target value. As a result, it is possible to always obtain an appropriate residual chlorine concentration distribution in the water distribution network and to reduce the amount of chlorine injection at the injection point. This is shown by computer simulation results.

FIG. 4 shows a network diagram of a target area.
In this example, there is one target point and one injection point. FIG. 5 shows the injection rate at a temporarily set injection point in the network diagram (constant at 0.5 mg / l). FIG. 6 shows the change over time in the residual chlorine concentration at the target point at that time. It can be seen that the residual chlorine concentration at the target site changes due to the change in the remaining time due to the change in demand.

FIG. 7 shows the change over time in the injection rate at the injection point when the residual chlorine concentration at the target point in the same network is equal to or higher than the target value and is as low as possible by linear programming. FIG. 8 shows the change over time in the residual chlorine concentration at the target node at that time. From these facts, it is understood that the residual chlorine concentration at the target node is controlled to be almost constant, the injection rate at the injection point is lowered, and the chlorine injection amount can be reduced.

[0109]

As described above, according to the first and second inventions, the input pipe network model, the predicted and actual demand amount, the target concentration time series value, the temporarily set injection rate, and the injection rate upper and lower limit values. It becomes possible to calculate the injection rate schedule that obtains the residual chlorine concentration at the target point close to the target concentration time-series value based on each data of. As a result, the residual chlorine concentration at the target point is always kept stable and optimal. In addition, the excessive injection of chlorine is prevented even at the injection point, improving the economic efficiency.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of first and second inventions.

FIG. 2 is a flowchart showing the operation of the first invention.

FIG. 3 is a flowchart showing the operation of the second invention.

FIG. 4 is a diagram showing an example of a pipe network model to which the embodiment is applied.

FIG. 5 is a graph showing an example of a temporarily set injection amount.

FIG. 6 is a graph showing an example of a temporal change of a target nodal residual concentration at the time of temporary setting injection.

FIG. 7 is a graph showing an example of an optimal infusion schedule.

FIG. 8 is a graph showing an example of time variation of the target residual chlorine concentration in the target node at the time of optimum injection.

[Explanation of symbols]

 1 Computing Device 2 Time Transmitter 3 Telemeter Master Station 4 Telemeter Slave Station 5 Injection Ratio Controller 6 Ratio Setting Device 7 Chlorine Injector 8 Chlorine Storage Tank 9 Filtration Tank 10 Flowmeter 11 Mixing Pond 12 Purification Tank 13 Residual Chlorine Concentration Meter

Claims (7)

[Claims] 1. A means for inputting each data of a pipe network model, forecast and actual demand, target concentration time series value, temporary set injection rate, upper and lower limits of injection rate, and a network model and forecast / actual demand A means for calculating the residual chlorine concentration distribution in the pipe network when the chlorine injection rate is set to the value of the provisional injection rate by the dynamic water quality analysis calculation used, and the dynamics using the pipe network model and forecast / actual demand. Means for repeatedly calculating changes in the residual chlorine concentration distribution in the pipe network when the chlorine injection rate is increased by a unit amount per unit time by dynamic water quality analysis calculation, and the calculated chlorine injection rate and residual chlorine concentration distribution. By means of the simultaneous equations obtained from the relationship or the least squares method using the relationship, the means for calculating the injection rate schedule in which the residual chlorine concentration at the target point on the pipe network is close to the target concentration time series value, and the calculated injection If the value of the schedule exceeds infusion rate upper and lower limit values, the chlorine injection rate control apparatus for water supply, characterized in that it comprises a means for correcting within the upper and lower limit value. 2. The chlorine injection rate control device for water supply according to claim 1, further comprising means for calculating an injection rate schedule within an upper and lower limit of the injection rate by using a linear programming method. Chlorine injection rate control device. 3. The chlorine injection rate control device for water supply according to claim 1 or 2, wherein a plurality of target points on the pipe network are provided. 4. The chlorine injection rate control device for waterworks according to claim 1, wherein the chlorine injection rate control device for waterworks has a plurality of chlorine injection points. 5. The chlorine injection rate control device for waterworks according to claim 3, wherein the chlorine injection rate control device for waterworks has a plurality of chlorine injection points. 6. The chlorine injection rate control device for water supply according to claim 4, wherein chlorine injection intervals at a plurality of chlorine injection points are different from each other. 7. The chlorine injection rate control device for water supply according to claim 5, wherein chlorine injection intervals at a plurality of chlorine injection points are different from each other.