JPH03224694A - Chlorine dosing control device in water purification plant - Google Patents

Abstract

PURPOSE:To maintain the target value of the concn. of a residual chlorine by making correction according to the change in the water temp. obtd. from experiment so that the fluctuation in the chlorine decomposition rate by a fluctuation in the water temp. is compensated in the computation to change a chlorine dosage in proportion to a quantity of solar radiation. CONSTITUTION:The correction value Rt of the quantity of solar radiation obtd. by correcting the predicted sunshine quantity of solar radiation REt after the prescribed time is determined in a means 17 for computing the correction value of the sunshine quantity of solar radiation. A means 18 for computing the chlorine decomposition rate determines the decomposition rate DSt of the residual chlorine by the solar radiation corresponding to the correction value Rt and the actually measured value Tempt. of the water temp. Further, the chlorine injection rate CLt is determined from the deviation between the actually measured value Rc of the concn. of the residual chlorine in the water and the target concn. of the residual chlorine corrected by the decomposition rate of the residual chlorine in a means 19 for computing the chlorine injection rate. The corrected value DVt of the manipulated variable is determined from the change rate of the quantity of solar radiation with time at the present point of the time of the correction value Rt in a means 20 for computing the correction value of the manipulated variable. Further, the set value of the chlorine injection rate is determined by adding the chlorine injection rate CLt and the correction value DVt in a means 21 for computing the chlorine injection rate.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a chlorine injection control device for a water purification plant.

(Prior art) In general, a receiving well that introduces raw water, a mixing pond that mixes chlorine from a chlorine injection means with the raw water, and a floc that forms a TRJ turbid substance floc in the chlorine-injected water from the mixing pond. A formation pond, a settling basin that settles the flocs and other pollutants and separates them from the water, a filtration basin that filters the supernatant water from the settling basin, and a water purification basin that stores the treated water from the filtration basin as purified water. In a water treatment plant consisting of
Since raw water contains inorganic substances, organic substances, and microorganisms including pathogens, the chlorine injected is used to decompose and remove these substances and microorganisms. Generally, settling tanks have a long residence time, and while the treated water passes through the settling tank, residual chlorine in the treated water is broken down by sunlight and some of it is scattered. If chlorine is always injected at a constant injection rate, it may become impossible to obtain a residual chlorine concentration above the specified value. This effect is particularly noticeable in the summer when there is a lot of solar radiation.

Therefore, conventionally, chlorine injection means installed in the mixing pond,
The chlorine concentration measuring means installed in the flocculation pond and the solar radiation measuring means installed in the settling basin are used to measure the chlorine concentration at each preset time from sunrise to sunset, and at each predetermined time before that time. a predicted solar radiation calculation means for calculating a predicted solar radiation amount for each time; a predicted solar radiation amount at the current time obtained by the predicted solar radiation calculation means before the predetermined time; and a predicted solar radiation amount at the current time measured by the solar radiation measurement means. a solar radiation correction calculation means for calculating a solar radiation correction value obtained by correcting the predicted solar radiation after a predetermined time obtained at the current time using the solar radiation actual measurement value; A chlorine decomposition amount calculation means for determining the amount of residual chlorine decomposition due to solar radiation, an actual value of the residual chlorine concentration in water measured by the chlorine concentration measuring means, and a target residual chlorine concentration corrected by the residual chlorine decomposition amount. a chlorine injection rate calculation means for calculating a chlorine injection rate from the deviation; a manipulated variable correction value calculation means for calculating a manipulated variable correction value from the temporal change in solar radiation at the current moment of the solar radiation correction value; A chlorine injection control device is used, which includes a chlorine injection amount calculation means for calculating a chlorine injection amount setting value by adding a chlorine injection amount correction value to the chlorine injection amount setting value and applying it to the chlorine injection means.

In this conventional chlorine injection control device, chlorine is injected from a mixing pond for a predetermined period of time at each preset time from sunrise to sunset using a predicted solar radiation calculation means. The predicted amount of solar radiation at each time is determined before h hours, which is the delay time for the chlorine to reach the settling tank.

In addition, the solar radiation correction value calculation means uses the predicted solar radiation amount at the current time obtained by the predicted solar radiation amount calculation means a predetermined time ago and the actual solar radiation amount at the current time, A correction calculation is performed on the predicted solar radiation amount at each time to obtain a solar radiation correction value.

Further, the chlorine decomposition amount calculation means calculates the amount of residual chlorine concentration decomposed by solar radiation based on the solar radiation amount correction value.

Further, the chlorine injection rate calculation means calculates the chlorine injection rate from the deviation between the actual measured value of the residual chlorine concentration in water and the target residual chlorine concentration, which is corrected by the amount of residual chlorine decomposition.

In addition, the manipulated variable correction value calculation means calculates the manipulated variable correction value from the trend of change in the solar radiation amount at the present time of the solar radiation amount correction value.

Then, the chlorine injection amount calculation means adds the above chlorine injection rate and the manipulated variable correction value to obtain a chlorine injection amount set value, and provides this to the chlorine injection means to control the amount of chlorine injection into the raw water in the mixing pond. In addition, the residual chlorine concentration in the settling basin was maintained at the target value.

(Problems to be Solved by the Invention) Such conventional chlorine injection control devices for water purification plants predict changes in the amount of solar radiation per day, and use the amount of chlorine decomposed by this solar radiation as a correction value to determine the residual chlorine concentration in water. However, the amount of chlorine decomposed by solar radiation is not simply proportional to the amount of solar radiation, but is also greatly influenced by water temperature.

Therefore, in the conventional device, the amount of chlorine decomposition due to solar radiation obtained by the chlorine decomposition amount calculating means is multiplied by the solar radiation amount correction value obtained by the solar radiation amount correction value calculating means and the parameter. This parameter was manually changed according to changes in water temperature.

However, when parameters are adjusted manually in this way, the parameters must be adjusted only once per season, making it impossible to respond to minute fluctuations in water temperature, and because it is done manually, changes may be forgotten or errors may occur. Sometimes,
It has been desired to develop a chlorine injection control device that can automatically adjust parameters according to the actual water temperature.

This invention was made in view of such conventional problems, and in the calculation of changing the chlorine injection rate in proportion to the amount of solar radiation, it is corrected according to the water temperature change obtained from experience, It is an object of the present invention to provide a chlorine injection control device for a water purification plant that can compensate for fluctuations in the amount of chlorine decomposed and accurately maintain the residual chlorine concentration at a settling tank outlet position at a target value.

[Structure of the Invention] (Means for Solving the Problems) A chlorine injection control device for a water purification plant of the present invention includes: a water temperature measuring means provided in a receiving well; a chlorine injection means provided in the mixing pond; A chlorine concentration measuring means provided in the floc formation pond and a solar radiation measuring means provided in the sedimentation pond are used to measure the chlorine concentration at each preset time from sunrise to sunset. a predicted solar radiation calculation means for calculating a predicted solar radiation amount for each time; a predicted solar radiation amount for the current time obtained by the predicted solar radiation calculation means before the predetermined time; and a current time measured by the solar radiation measurement means. solar radiation amount correction value calculating means for calculating a solar radiation amount correction value obtained by correcting the predicted solar radiation amount after a predetermined time obtained at the current time using the solar radiation amount actual measurement value; and the solar radiation amount correction value and the water temperature. a chlorine decomposition amount calculation means for determining the amount of residual chlorine decomposed by solar radiation based on the actual water temperature measured by the measuring means; an actual value of the residual chlorine concentration in water measured by the chlorine concentration measuring means; and a target. a chlorine injection rate calculation means for calculating a chlorine injection rate from the deviation from the residual chlorine concentration corrected by the residual chlorine decomposition amount; and a manipulated variable correction value for calculating the manipulated variable correction value from the temporal change amount of the solar radiation amount at the current time of the solar radiation amount correction value. The apparatus includes: a manipulated variable correction value calculation means; and a chlorine injection amount calculation means for adding the chlorine injection rate and the manipulated variable correction value to obtain a chlorine injection amount set value and supplying the set value to the chlorine injection means.

(Function) In the chlorine injection control device for a water purification plant of the present invention, the predicted solar radiation calculation means predicts in advance the change in solar radiation on the 11th for a predetermined period of time.

Then, the solar radiation correction value calculation means corrects the predicted solar radiation predicted a predetermined amount of time ago by comparing it with the actual measured solar radiation at the current time. Further, the chlorine decomposition amount calculation means calculates the amount of residual chlorine decomposition based on the amount of solar radiation at the current time based on the actual water temperature value of the mixing pond actually measured by the water temperature measurement means and the solar radiation amount correction value by the solar radiation amount correction value calculation means. seek.

The chlorine injection rate calculation means calculates a new chlorine injection rate from this residual chlorine decomposition amount, the current residual chlorine concentration in the sedimentation tank measured by the chlorine concentration measuring means, and the target residual chlorine concentration, and calculates this as the chlorine injection amount. It is given to the calculation means.

On the other hand, the manipulated variable correction value calculation means obtains a manipulated variable correction value from the temporal change in the solar radiation amount at the current time of the solar radiation amount correction value, and similarly provides this to the chlorine injection amount calculation means.

Therefore, the chlorine injection amount calculation means adds the chlorine injection rate and the manipulated variable correction value to obtain a chlorine injection amount set value, and provides this to the chlorine injection means.

The chlorine injection means controls the chlorine injection amount based on the chlorine injection amount set value given from the chlorine injection amount calculation means.

, 2. Therefore, the residual chlorine concentration in the sedimentation basin after a predetermined h hours from the current time will always be approximately the target residual chlorine concentration, even if there are fluctuations in solar radiation or seasonal changes in water temperature. It is possible to control the amount of chlorine injection in the mixing pond.

(Example) Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention, and shows a landing well 1 into which raw water is initially introduced, chlorine from a chlorine injection pump 2 as a chlorine injection means, and raw water from the landing well 1. A rapid mixing pond 4 receives the injection of an alkali agent for pH adjustment and a flocculant for turbidity from an alkaline agent injection means that is not used, and rapidly stirs the treated water using a flash mixer 3. A floc formation pond 5 that forms flocs from pollutants in the treated water into which chlorine has been injected from the mixing pond 4, a settling tank 6 that settles the flocs and other pollutants and separates them from the treated water, and this settling tank 6. It is equipped with a filtration oil 7 that filters the supernatant water from the filtration oil 7, and a water purification pond 8 that stores the treated water from the filtration oil 7 as purified water.

In addition, the receiving well 1 is provided with a water test pump 9 and a water temperature gauge 10 as water temperature measuring means for measuring the temperature of raw water, and the floc formation pond 5 is provided with a water test pump 11 as a means for measuring residual chlorine concentration. A residual chlorine concentration meter 12 is provided. Further, the settling tank 6 is provided with a solar radiation meter 13 as a means for measuring solar radiation, and is further provided with a water test pump 14 and a residual chlorine concentration meter 15 for measuring the residual chlorine concentration.

Furthermore, the entire computer is incorporated as a software program, and is equipped with the following means as a chlorine injection control system.

In other words, by inputting calendar information, each time from sunrise to sunset on the corresponding month and day is set for a predetermined time h (this time is the time when chlorine injected in mixing tank 4 comes out to settling tank 6). The predicted solar radiation amount for the current time calculated by the f-side solar radiation amount calculation means 16 and the predicted solar radiation amount calculation means 16 before a predetermined time. A solar radiation correction value Rt obtained by correcting the predicted solar radiation Ret after a predetermined time determined at the current time using Ret-h and the measured solar radiation value Rpv at the current time measured by the solar radiation meter 13. and a solar radiation correction calculating means 17 for calculating the amount of solar radiation.

Also, based on the solar radiation correction value Rt, a chlorine decomposition amount calculating means 18 calculates the residual chlorine concentration decomposition amount DSt due to solar radiation in the settling tank 6, and a residual chlorine concentration meter 12 measures the residual chlorine concentration in the water in the floc formation pond 5. chlorine injection rate calculation means 19 that calculates the chlorine injection rate CLt from the deviation between the actual measured value RC of the residual chlorine concentration and a preset target residual chlorine concentration, corrected by the residual chlorine decomposition amount DSt;
Manipulated variable correction value calculating means 2o for calculating the manipulated variable correction value DVt from the temporal change amount of the solar radiation amount at the current moment of the solar radiation amount corrected value Rt.
and an addition means 21 that adds the chlorine injection rate CLt and the manipulated variable correction value DVt to obtain a new chlorine injection rate Cut.

The chlorine injection rate CLt from the addition means 21 is given to the controller 22, and the controller 22 calculates the chlorine injection amount setting value from the chlorine injection rate CLt, and controls the chlorine injection pump 2 based on the chlorine injection rate CLt. It is controlled to adjust the amount of chlorine injection.

In addition, the water temperature Te1llpt measured by the water temperature gauge 10 installed in the landing well 1 is subjected to a correction operation of 2 on the parameters described below, and this is applied to the chlorine decomposition amount calculation means 18 and the manipulated variable correction value calculation means 2o. The residual chlorine concentration measured by the residual chlorine concentration meter 15 in the sedimentation tank 6 is determined by the parameter correction calculating means 23 for providing the residual chlorine concentration in the sedimentation tank 6 whether the actual measured value of solar radiation Rpv is less than or equal to a preset value or before sunset and after the set time. It also includes a determining means 24 that determines whether the actual measured value RC' is greater than or equal to a preset value and determines whether the solar radiation correction calculation is to be terminated.

Next, the operation of the chlorine injection control device for a water purification plant having the above configuration will be explained.

At the outlet of the landing well 1, raw water is injected with chlorine from a chlorine injection pump 2 and an alkali agent from an alkali agent injection device (not shown), and furthermore, at the entrance of the rapid mixing basin 4, flocculant injection control (not shown) is performed. The flocculant is injected from the device and rapidly stirred by the flash mixer 3 in the rapid mixing pond 4.

In the floc formation tank 5, the flocs are slowly further stirred to grow the flocs, and in the settling tank 6, most of the grown flocs are settled and removed.

The water flowing out of the sedimentation tank 6 is made clear in a filtration area 7, chlorine is injected by a post-chlorination machine (not shown), and the water is stored in a water purification tank 8.

The inlet water of the landing well 1, the inlet water of the flocculation pond 5, and the outlet water of the settling basin 6 are respectively guided by a water test pump 9°11.14 to a water temperature meter 10 and a residual chlorine concentration meter 12.15, and the water temperature is measured. TerApt and residual chlorine concentrations RC and RC' are measured.

The amount of solar radiation irradiated onto the settling tank 6 is measured by a solar radiation meter 13.

The predicted solar radiation calculation means 16 calculates the predicted solar radiation Ret from a predetermined early time before sunrise, when actual solar radiation starts, based on the input calendar information. This predicted amount of solar radiation Ret is the direction p1 of the water treatment plant.
Function Ret −f (p, m, t) of calendar m and current time t
- (1), and specifically, for example, use data from the Science Chronology (edited by Tokyo Astronomical Observatory, each year edition) as calendar information, calculate the sunrise and sunset times, and calculate the sunshine hours calculated from these two times. Calculation is performed according to the following equation (2) from Ts and the daily maximum solar radiation Rmax expressed by a sine wave function with a period of one year.

Here, t represents the elapsed time from sunrise to the current time. Further, Rmax is calculated using the following equation (3).

However, α, β, and γ are parameters, which are obtained from the solar radiation data of the past several years. Further, d is the number of days counted from New Year's Day to the current day.

The solar radiation amount correction value calculation means 17 is the predicted solar radiation amount calculation means 16.
The predicted solar radiation Ret-h for the current time, which is the output obtained a predetermined time ago, is compared with the indicated value Rpv of the pyranometer 13 at the current time, and the corrected solar radiation amount Rt is calculated as follows: Calculate according to formula (4).

Rt-Ret-h 10kl-(RpV -Ret-h
) ・(4) However, 1 is a constant here, and is a value specific to the water purification plant.

Next, in the chlorine decomposition amount calculation means 18, based on the solar radiation amount correction value Rt which is the output of the solar radiation amount correction value calculation means 17,
The residual chlorine decomposition amount DSt depending on the amount of solar radiation is calculated by the following equations (5) and (6).
).

DSt −DSt−1+ to 2・(Rt−Rt−1)
... (5) k2- Tempt II
k3 + k4 = - (6) Here, in equation (5), k2 is a parameter for converting the amount of solar radiation into residual chlorine concentration, and the one calculated by equation (6) in the parameter correction calculation means 23 is used. Therefore, this parameter 2 varies with water temperature.

Moreover, Rt-1 is the solar radiation amount correction value at the previous sampling time.

In equation (6), 3 is in the range of 0.03 to 0.07, and k4 is a value specific to the water purification plant. Furthermore, the value of 3 is determined empirically.

One chlorine injection rate calculation means receives as input the chlorine decomposition amount DSt due to the amount of solar radiation obtained by the chlorine decomposition amount calculation means 18 and the actually measured residual chlorine concentration Re, and calculates the chlorine injection rate CLt by feedback.

However, the deviation Et used here is not only the difference between the preset target residual chlorine concentration Rs and the actually measured residual chlorine concentration Re, but also the residual chlorine decomposition as shown by the following equation (7). It is corrected by the amount DSt.

Et −Rsv −Rc+DSt
-(7) Further, the chlorine injection rate calculation means 19 uses this deviation Et to calculate the chlorine injection rate CLt as follows (8), (9)
) Calculate based on the formula.

CLt theory CLt-1+ΔCL
... (8) ΔCL=kc fkp (Et-Et-
1) +ki-Et)... (9) Here, kc, kp, and ki are control gains.

However, even if chlorine is injected at the chlorine injection rate CLt determined by the chlorine injection rate calculation means 19, there is a response delay of h hours before the effect appears. The manipulated variable correction value calculating means 2o executes correction calculations for the following equations (10) and (11).

DVt −DVt−1+ DMt
−(10) DMt −DMt−1, + k2・k5・
(Rt-21?t-1+Rt-1)... (11
) However, here, 5 is a constant specific to the water treatment plant.

The addition means 21 calculates the chlorine injection rate C obtained in this way.
ut and the manipulated variable correction value DVt, a new chlorine injection rate CLt is calculated, and this chlorine injection rate CLt is calculated by the controller 22.
The controller 22 multiplies this value Cut by the inflow flow rate into the rapid mixing tank 4 to obtain the amount of chlorine injection, and controls the amount of chlorine injection by the chlorine injection pump 2.

In this way, taking into account the time delay, the predicted solar radiation calculated a predetermined time ago is compared with the actual solar radiation at the current time, and the solar radiation is corrected. In addition to correcting the amount of residual chlorine decomposed, the amount of residual chlorine decomposed that depends on changes in water temperature is also corrected based on water temperature information. It is possible to perform accurate chlorine injection control that compensates for variations in the amount of chlorine decomposition and makes the actual residual chlorine concentration almost match the target residual chlorine concentration.

Note that the judgment means 24 determines that residual chlorine decomposition due to solar radiation is determined from the chlorine injection rate CLt by terminating the solar radiation correction calculation when the measured value of solar radiation is less than the set value even after sunset or before sunset. By subtracting the amount DSt, a new chlorine injection rate CLt is obtained and given to the controller 22.

[Effects of the Invention] As described above, according to the present invention, the change in solar radiation in a day is predicted, the predicted solar radiation in parentheses is corrected by the solar radiation actually measured on the control implementation day, and the water temperature is measured. Based on these parameters, calculate the amount of residual chlorine decomposed in the settling tank,
By compensating for this value, the amount of chlorine injection in the mixing pond is controlled so that the residual chlorine concentration matches the target value, so even if there are large seasonal fluctuations in water temperature, there is no need for human intervention. Residual chlorine concentration can be controlled so that the residual chlorine concentration matches the target value without excess or deficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. 1... Water landing well 2... Chlorine injection pump 4
... Rapid mixing tank 6 ... Sedimentation tank 7 8 ... Water purification pond 10 2 ... Residual chlorine concentration meter 6 ... Predicted solar radiation calculation means 7 ... Solar radiation correction value calculation means 8 ...・Chlorine decomposition amount calculation means 9...Chlorine injection rate calculation means 0...Manipulated amount correction value calculation means 1...Addition means 22 5. Flock formation pond...Suitable area...Water temperature meter...Controller

Claims (1)

[Claims] A landing well to which raw water is initially supplied, a mixing pond to which chlorine is supplied and mixed with the raw water from the landing well, and a floc formation pond to form flocs of pollutants in the raw water. , a chlorine injection control device for a water purification plant comprising a sedimentation basin for settling the flocs, a filtration basin for filtering the treated water from the floc formation basin, and a water purification basin for storing the treated water from the filtration basin; A water temperature measuring means provided in the water well, a chlorine injection means provided in the mixing pond, a chlorine concentration measuring means provided in the floc formation pond, a solar radiation measurement means provided in the settling pond, and Predicted solar radiation calculation means for calculating the predicted solar radiation for each set time from sunrise to sunset before a predetermined time; The predicted solar radiation amount obtained at the current time after a predetermined time is corrected using the predicted solar radiation amount for the current time obtained and the actual solar radiation measurement value at the current time measured by the solar radiation measurement means. a solar radiation correction value calculation means for calculating a solar radiation correction value, and a chlorine decomposition amount calculation for calculating the residual chlorine decomposition amount due to solar radiation based on the solar radiation correction value and the water temperature actual value measured by the water temperature measuring means. and chlorine injection rate calculation means for calculating a chlorine injection rate from the deviation between the actual value of the residual chlorine concentration in water measured by the chlorine concentration measuring means and the target residual chlorine concentration, which is corrected by the residual chlorine decomposition amount. , a manipulated variable correction value calculation means for calculating a manipulated variable correction value from the temporal change in solar radiation at the current moment of the solar radiation correction value; and a chlorine injection amount set value by adding the chlorine injection rate and the manipulated variable correction value. A chlorine injection control device for a water purification plant, comprising a chlorine injection amount calculation means for calculating the amount of chlorine injection and giving it to the chlorine injection means.