JPS6158236B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a method and apparatus for controlling chlorine injection in a water treatment plant, and is particularly suitable for automating chlorine injection, and is suitable for automating chlorine injection in a water treatment plant and fully takes into account the consumption characteristics of injected chlorine in an actual water treatment plant. The present invention relates to an injection control method and apparatus. [Background of the Invention] Chlorine injection treatment is one of the chemical treatments in water treatment plants. The main purpose of this chlorine injection is to sterilize water, which is one of the important roles of a water treatment plant, but it also removes iron, manganese, moss, ammonia, and microorganisms. To achieve this objective, the Water Supply Act requires that the amount of residual chlorine at the demand end be maintained at 0.1 ppM or higher. On the other hand, at the demand end
If the concentration is 0.9ppM, a chlorine odor will be produced, which is not only unpleasant but may also harm the health of consumers. Therefore, in water treatment plants, the amount of chlorine injection must be adjusted so that the amount of residual chlorine at the demand end is within the range of 0.1 to 0.9 ppM. Conventionally, the distribution reservoir within a water treatment plant was regarded as the demand end located at the shortest distance from the chlorine injection point, and the residual salt in this distribution reservoir was
It was adjusted to 0.8ppM. However, in actual water treatment plants, residual salt in distribution tanks is greatly influenced not only by the chlorine injection rate at the receiving pond, but also by disturbance factors such as the amount of treated water, weather, and time of day. However, it takes a long time for the effects to be seen in the residual salt in the distribution reservoir. Therefore,
It is difficult to automate chlorine injection, and in the past, it relied solely on the intuition of the operator, so optimal control was not always possible and the amount of chlorine consumed tended to be high. [Object of the Invention] The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a method and apparatus for controlling chlorine injection in a water purification plant, which can be automated and consumes less chlorine. [Summary of the Invention] The present invention provides, in a water purification plant having a catch basin, a sedimentation basin, a filtration basin, etc., at least a target value for residual salt in filtrate, and a correction target value and a measurement that corrects the target value according to the amount of water to be treated. Considering the deviation of the values and the environmental conditions,
The above objective was achieved by adjusting the chlorine injection rate in the landing pond. The principle of the present invention will be explained below. The following relationship holds between the chlorine injection rate and residual chlorine. In other words, even if the chlorine injection rate remains unchanged, (1) the amount of water to be treated, (2) the content of manganese, ammonia, etc. in the treated water, (3) environmental conditions (mainly weather and time of day), (4) sedimentation ponds, The amount of residual chlorine changes depending on the shape of the filter. Of the four items above, (4) remains constant once the water treatment plant is determined, and the amount of this influence can be determined experimentally.
In addition, (2) can be considered to be almost constant if the water intake route is constant, but currently there is no online instrument that can accurately measure manganese, ammonia, etc., so it remains as a disturbance. Figure 1 shows the results of field experiments regarding (3).
Shown in Figure 2. The figure shows a step change K to the chlorine injection rate P (solid line B) while keeping the treated water amount Q (broken line A) constant.
Residual salt in treated water (dotted chain line C) when given
Figure 1 shows the changes over time in the residual salt of filtrate (broken line D) and the residual salt in the distribution pond (solid line E).
The figure shows the case of a rainy and cloudy day. This can be summarized as shown in the table below.

[Table] Therefore, it can be seen that when the residual salt in the distribution reservoir is set to 0.1 to 0.9 ppM, the target value of residual chlorine at each point can be determined as follows.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The chlorine injection control device of this embodiment includes a filtrate residual salt meter 20 installed in a pump well 8 of a water treatment plant, and a sedimentation tank 4.
a treated water residual salt meter 22 installed at , a clock 28 that outputs different outputs during the day and night, and a filtrate residual salt target value corrector 30 that corrects the set filtrate residual salt target value according to the flow rate of treated water.
A treated water measurement value recording device 32 that retains the treated water residual salt measured by the treated water residual salt meter 22 for the flow delay time from the sedimentation tank 4 to the pump well 8, and a treated water residual salt meter 20 output/processing device. Water measurement value storage device 32 outputs
A treated water residual salt target value calculator 34 calculates the treated water residual salt target value from the weather meter 26 output, clock 28 output, and filtrate residual salt target value corrector 30 output, and a treated water residual salt target value calculator 34 that calculates the chlorine injection rate from the landing pond 2 to the settling pond. A chlorine injection rate storage device 36 that holds only the flow delay time up to 4, output of the treated water residual salt meter 22, output of the chlorine injection rate storage device 36, output of the weather meter 26, output of the clock 28, and target value of residual salt in the treated water. a chlorine injection rate calculator 38 that calculates the chlorine injection rate from the output of the calculator 34; and a chlorine injection rate controller 40 that controls the chlorine injection rate according to the deviation between the output of the chlorine injection rate calculator 38 and the chlorine injection rate. , a chlorine injection amount regulator 42 that adjusts the amount of chlorine injection according to the output of the chlorine injection rate controller 40, and a chlorine injection valve 44. In addition, 6 is a filtration pond, 10 is a distribution reservoir, 12
14 is a residual salt meter for the water distribution reservoir for monitoring purposes, and 14 is a chlorine storage tank. The weather meter 26 has, for example, a photoelectric light intensity meter 261, and as shown in FIG. 4, when it is sunny,
Output X=0, and output X=1 when it is not sunny. The clock 28 outputs Y=0 if the current time T is daytime, and outputs Y=1 if it is nighttime.
In this embodiment, daytime is defined as 6:00 to 18:00, and as shown in FIG. 5, Y=0 if it is between 6:00 and 18:00, and Y=1 otherwise. The filtrate residual salt value corrector 30 includes a treated water flow meter 2
Based on the treated water amount d measured in step 4, the preset treated water amount d and filtrate residual salt target value e
Correct the filtrate residual salt target value e based on the relative relationship between
decide. For example, when d=80000m ³ /h or less,
When e = 1.1ppM, d = 8000m ³ /h ~ 14000m ³ /h, e = 1.0ppM, d = 14000m ³ /h ~ 20000m ³ /
When h, e=0.9ppM. The treated water residual salt target value calculator 34 calculates the treated water residual salt target value f in the following manner. That is, as shown in FIG. 6, first, the subtractor 341 calculates the actual filtrate residual salt b detected by the filtrate residual salt meter 20 and the target value corrected by the filtrate residual salt target value corrector 30. Find the deviation (eb) from e. From this, the target residual salt value f of the treated water is determined, and at this time, the coefficient α of (eb) is selected based on the experimental results according to the following three conditions. (1) Weather: Clear, Time: Daytime (2) Weather: Clear, Time: Night (3) Weather: Other than clear In other words, a logic circuit is constructed according to the outputs of the weather meter output X and clock output Y, and the above Coefficient α corresponding to three cases can be selected. That is, the AND circuit 342 in FIG.
It turns on when Y=0. Therefore, the coefficient setter 3
43, the coefficient α for the case where the weather is clear and the time is daytime can be determined. Similarly, the AND circuit 344 calculates that X=
Since it is turned on when 0 and Y=1, the coefficient α can be determined when the weather is clear and the time is night. or,
The AND circuit 346 is turned on if the weather is other than clear, that is, if X=1, regardless of the state of time Y.
The coefficient α in case (3) can be determined by the coefficient setter 347. When the coefficient α of the coefficient multiplier 348 is determined as described above, α・(eb) is calculated, and the adder 349 adds the pump from the sedimentation tank 4 inputted from the treated water measurement value storage device 32. Measured value C of residual salt in treated water before flow delay time T ₁ up to #8
(−T ₁ ) is added. That is, f = α (e - b) + C ( - T ₁ ) Here, the reason why we did not use the current value as the measured value of residual salt in the treated water, but used the value before T ₁ was due to the flow rate according to the experimental results. This takes into account delays. The chlorine injection rate calculator 38 calculates a target value g of the chlorine injection rate in the landing pond. That is, as shown in FIG. 7, the subtracter 381 calculates the deviation (f) between the current target residual salt value f of the treated water and the measured value C by the residual salt meter.
Find C). To correct this, g is determined, but the coefficient β is selected and determined based on external conditions, as in the case of the treated water residual salt target value calculator. Once the coefficient β is determined, β・(f−C) is calculated, and an adder 389 adds the values input from the chlorine injection rate storage device 36 from the landing pond 2 to the sedimentation basin 4.
Chlorine injection rate _h (-
T ₂ ). The basis for this is the same as that of the treated water residual salt target value calculator 34. Therefore, the chlorine injection rate target value g is as follows: g=β·(f−C)+h(−T ₂ ). 382, 384, 386, 383, 385, 387, and 388 are the same AND circuits, coefficient setters, and coefficient multipliers as described above, respectively. The operation will be explained below. First, the treated water flow meter 24
Measure the treated water flow rate d. The final target value is corrected by the filtrate residual salt target value corrector 30 according to the treated water flow rate d, and an appropriate filtrate residual salt corrected target value e is determined. Next, the corrected filtrate residual salt target value e,
Based on the filtrate residual salt meter 20 output b and the treated water residual salt C (-T ₁ ) from the flow delay time T ₁ before, the current target value for the residual salt in the treated water is calculated by considering the current weather X and the current time Y. f
seek. Next, from the treated water residual salt target value f, the current treated water residual salt measurement value C, the chlorine injection rate h (-T ₂ ) just ₂ hours before the flow delay time T, and the current weather X and time Y. , the target chlorine injection rate g is calculated by the chlorine injection rate calculator 38. The chlorine injection rate controller 40 controls the chlorine injection amount regulator 42 according to the deviation between the chlorine injection rate target value g and the current chlorine injection rate h. The opening degree of the chlorine injection valve 44 is adjusted by the chlorine injection amount regulator 42 to obtain the optimum chlorine injection amount. In this example, the target value of chlorine injection rate is not immediately determined from the target value of residual salt in the filtrate, but the target value of residual salt in the treated water is determined once during the process, and this is compared with the measured value of residual salt in the treated water to determine the chlorine injection rate. Since the injection rate is re-corrected, it is resistant to external disturbances and allows for fine-grained control. In addition, in this example, optimal control is performed taking into account the flow delay time of treated water, but the shape and stirring condition of each pond in the water treatment plant are excellent, so there is almost no flow delay. In some cases, the control device can be simplified by ignoring the flow delay time and omitting the storage device. [Effects of the Invention] As described above, the present invention provides a chlorine injection control method and device for a water purification plant, in which at least residual salt in filtrate is set as a target value, and the target value is measured as a corrected target value corrected according to the amount of water to be treated. Since the chlorine injection rate in the landing pond is adjusted in consideration of the value deviation and environmental conditions, automation is possible and there is an excellent effect that there is almost no wasted chlorine consumption.

[Brief explanation of the drawing]

1 and 2 are diagrams showing experimental results of chlorine consumption characteristics in a water treatment plant, FIG. 3 is a block diagram showing a chlorine injection control device that is an embodiment of the present invention, and FIG. FIG. 5 is a flow diagram showing the operation flow of the weather meter in this embodiment, and FIG. 6 is a flow diagram showing the operation flow of the clock in this embodiment.
The figure is a flow diagram showing the operation flow of the treated water residual salt target value calculator in this embodiment, and FIG. 7 is a flow diagram showing the operation flow of the chlorine injection rate calculator in this embodiment. Explanation of symbols, 2... Landing pond, 4... Sedimentation pond, 6
... Filtration pond, 10 ... Distribution reservoir, 14 ... Chlorine storage tank, 20 ... Filtered water residual salt meter, 24 ... Treated water flow meter, 26 ... Weather meter, 28 ... Clock, 30 ...
Filtered water residual salt target value corrector, 36... Chlorine injection rate storage device, 38... Chlorine injection rate calculator, 40... Chlorine injection rate controller, 42... Chlorine injection amount regulator, 44
...Chlorine injection valve.

Claims (1)

[Claims] 1. In a water purification plant having a catch basin, a sedimentation basin, a filtration basin, a distribution basin, etc., the target value of residual salt in filtrate is corrected by at least the amount of treated water, and the corrected target value of residual salt in filtrate is measured. A chlorine injection control method for a water purification plant, characterized in that the chlorine injection rate is adjusted according to the deviation from a residual salt value based on . 2 Correct the filtrate residual salt target value based on the amount of treated water, find the deviation between the corrected filtrate residual salt target value and the measured value by the filtrate residual salt meter, and calculate the deviation from the installed position of the treated water residual salt meter to this value. The target value for residual salt in treated water is calculated by adding the measured value from the treated water residual salt meter that was measured by the flow delay time of the treated water to the water residual salt meter installation position, and the calculated value and the measurement by the treated water residual salt meter are calculated. Calculate the target value of the chlorine injection rate by calculating the deviation from the value and adding to this value the measured value of the chlorine injection rate just before the flow delay time of the treated water from the landing pond to the installed position of the treated water residual salt meter. A chlorine injection control method for a water purification plant according to claim 1, wherein the deviation between the calculated value and the chlorine injection rate at the time of chlorine injection in the landing pond is determined, and the chlorine injection amount is adjusted according to the deviation. . 3 At water purification plants that have catch basins, sedimentation basins, filtration basins, distribution reservoirs, etc., the target value of residual salt in filtrate is corrected based on the amount of treated water and environmental conditions, and the corrected target value of residual salt in filtrate and the residual salt based on the measurement are calculated. A chlorine injection control method for a water treatment plant, the method comprising: adjusting the chlorine injection rate according to the deviation from the value of . 4 A patent that corrects the target value of residual salt in filtrate based on the amount of treated water, time of day and weather at the time of measurement, and adjusts the chlorine injection rate according to the deviation between the corrected target value of residual salt in filtrate and the measured value of residual salt. A method for controlling chlorine injection in a water purification plant according to claim 3. 5. Correct the target value for residual salt in filtrate based on the amount of treated water, find the deviation between the corrected target value for residual salt in filtrate and the measured value by the residual salt in filtrate meter, and add the weather and time at the time of measuring the residual salt in filtrate to the deviation. Multiply by a preset coefficient that is selected according to the combination with the belt and takes into account the change in residual salt in the filtrate due to the combination of whether the weather is sunny or not and whether the time is daytime or not. To the obtained value, add the value measured by the treated water residual salt meter from the previous treatment water flow delay time from the installed position of the treated water residual salt meter to the filtrate residual salt meter installation position to obtain the target value of treated water residual salt. Calculate the difference between the calculated value and the measured value by the treated water residual salt meter, and determine whether the deviation is selected according to the combination of the weather and time zone at the time of measuring the treated water residual salt and whether the weather is clear or not. The value obtained by this multiplication is multiplied by a preset coefficient that takes into account the change in chlorine injection rate due to the combination of daytime and whether the time zone is daytime or not. Calculate the target value of the chlorine injection rate by adding the measured value of the chlorine injection rate before the flow delay time of the treated water, and find the deviation between the calculated value and the chlorine injection rate at the time of chlorine injection in the landing pond. The method of controlling chlorine injection in a water purification plant according to claim 3, wherein the amount of chlorine injection is adjusted according to the deviation. 6 In a chlorine injection control device for a water purification plant that has a chlorine injection regulator that adjusts the amount of chlorine injection in a water treatment plant having a landing pond, a sedimentation basin, a filtration basin, a distribution reservoir, etc. , a filtrate residual salt target value corrector that corrects a set filtrate residual salt target value according to at least the amount of treated water; and a residual salt meter that is installed in the pond and measures the residual salt value of the installed pond. A chlorine injection control device for a water purification plant, comprising: the filtrate residual salt target value corrector; and a controller that controls the chlorine injection regulator based on the output of the residual salt meter. 7 A treated water residual salt meter that measures residual salt in treated water;
A filtrate residual salt meter that measures residual salt in filtrate, and treated water from the measured value by the treated water residual salt meter to the installation position of the filtrate residual salt meter based on the measured value by the treated water residual salt meter. a residual salt value calculator that calculates the residual salt value at the installation position of the filtrate residual salt meter in consideration of the flow delay time and the transition characteristics of the residual salt value; the filtrate residual salt target value corrector; The chlorine injection control device for a water purification plant according to claim 6, further comprising a chlorine injection amount calculator that calculates the chlorine injection amount based on the output of the salt value calculator.