JP2007326047A - Water treatment control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment control device effectively suppressing trihalomethane formation concentration in chlorine treatment based on trihalomethane forming capacity of water to be treated. <P>SOLUTION: The water treatment control device is used for a water treatment plant in which raw water is introduced into a water receiving well 20, a flocculant is added to the introduced water to be treated to cause chemical precipitation and the supernatant is filtered. In this device, fluorescence intensity of water to be treated is measured by a fluorescence analyzer 24, and the trihalomethane forming capacity of the water to be treated is predicted by a trihalomethane forming capacity predicting means 41, based on the measured fluorescence intensity of the water to be treated and a correlation found in advance of the fluorescence intensity to the trihalomethane forming capacity. The trihalomethane formation concentration based on chlorine injection to the water to be treated is calculated based on the predicted trihalomethane forming capacity, and a chlorine agent injection rate operation means 42 is provided for finding the chlorine injection rate making the trihalomethane formation concentration equal to or less than the allowable concentration of trihalomethane. A chlorine injection device 10 is controlled by a control means 43 based on the injection rate of the calculated chlorine agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is applied to a water treatment plant such as a water purification plant, and relates to a water treatment control device for suppressing production of harmful trihalomethanes produced by chlorination.

  In a water treatment plant such as a water purification plant, groundwater or surface water is introduced into a receiving well as raw water, and a floc is formed by adding a flocculant in a coagulation sedimentation facility, and this is coagulated and precipitated. By this coagulation sedimentation, turbid colloids, inorganic substances, organic substances, bacteria, organisms, etc. in the raw water are precipitated and removed. Thereafter, the supernatant is passed through a sand filtration device to remove the suspended matter, and finally subjected to chlorine treatment for disinfection and supplied to consumers.

  In recent years, some water purification plants have introduced advanced water purification treatment using ozone for the purpose of removing and reducing odorous substances and trihalomethanes. In these water purification plants, pre-chlorination is performed by injecting a chlorine agent into the water in the treatment process before the coagulation sedimentation as part of the water purification treatment of the raw water where water pollution has progressed. Pre-chlorination is effective in removing ammonia nitrogen and microorganisms in raw water, or oxidizing and removing iron and manganese, and the algicidal effect of algae breeding in water treatment plants.

  However, it has been found that the injected chlorine agent reacts with organic substances in the raw water to produce trihalomethane and the like. The amount of trihalomethane produced increases when the amount of chlorinated agent injected is large, and the amount produced is also affected by the concentration and type of organic matter.

  Here, there is trihalomethane generating ability as an index indicating how much trihalomethane is generated by chlorinating raw water. For raw water with a high trihalomethane production capacity, it is desirable to employ an intermediate chlorination method in which a chlorine agent is injected between the sedimentation basin and the filtration basin in order to reduce the trihalomethane production concentration. This is because the organic substance is removed to some extent by the precipitation treatment, so that the amount of organic substance that becomes the source of trihalomethane is smaller between the precipitation basin and the filtration basin, and the risk of generation of trihalomethane is small.

  In general, the injection rate of the chlorinating agent in the pre-chlorination is mainly determined by injecting the raw water at a constant rate or by feedback control based on the residual chlorine concentration at the sedimentation tank outlet. In addition, switching from pre-chlorination to intermediate chlorination is currently performed by operators relying on intuition and experience while monitoring raw water quality rather than automatic control.

  The fluorescence intensity that is an indicator of the organic matter contained in the raw water has a very high correlation with the trihalomethane production ability of the raw water, and the trihalomethane production ability can be predicted by measuring the fluorescence intensity of the raw water. The trihalomethane generating ability is a trihalomethane concentration generated when chlorine is injected into the raw water, and is an index for measuring how much a substance that changes to trihalomethane exists. It can be said that raw water having a high trihalomethane production capacity is likely to produce trihalomethane by chlorination.

As a method of controlling the water treatment process in consideration of the trihalomethane production ability of raw water, there is a method of injecting powdered activated carbon by predicting the trihalomethane production ability with a fluorescence analyzer (see, for example, Patent Document 1). Powdered activated carbon has the ability to adsorb organic substances that cause trihalomethanes and remove them from raw water.
JP 2003-047956 A

  Thus, in the field of water treatment, particularly water purification, chlorination is widely used for disinfection and iron / manganese removal. However, when a trihalomethane precursor is mixed in the raw water, trihalomethane is generated by chlorination. Since trihalomethane is a carcinogen, it is necessary to suppress the production of trihalomethane in the water treatment process. However, conventional chlorinating apparatuses do not have a function of calculating an appropriate chlorine injection rate considering the trihalomethane generating ability of raw water.

  The generation of trihalomethane in a water treatment plant includes the generation in pre-chlorination, the generation in intermediate chlorination, and the generation in post-chlorination as a disinfectant during water distribution. In addition, the trihalomethane production capacity of raw water (how much substances contain trihalomethane) varies in the effect of the water purification process up to the point of each chlorination.

  The objective of this invention is providing the water treatment control apparatus which can suppress effectively the trihalomethane production | generation density | concentration in chlorination based on the trihalomethane production ability of to-be-processed water.

  The water treatment control device of the present invention is a water treatment control device that controls a water treatment plant that introduces raw water into a landing well, coagulates and precipitates the treated water introduced into the landing well, and filters the supernatant water. A fluorescence analyzer for measuring the fluorescence intensity of the water to be treated, and the fluorescence intensity and the trihalomethane production ability determined in advance using the fluorescence intensity of the water to be treated measured by the fluorescence analyzer. A trihalomethane production capacity predicting means for predicting the trihalomethane production capacity of the water to be treated based on the trihalomethane production capacity, and a trihalomethane production based on the injection of a chlorine agent into the water to be treated based on the trihalomethane production capacity predicted by the trihalomethane production capacity prediction means A chlorine agent injection rate calculating means for calculating a concentration and obtaining a chlorine agent injection rate at which the trihalomethane production concentration is below the allowable trihalomethane concentration; Based on the injection rate injection rate of the chlorine agent calculated by the calculating means, and wherein the and control means for controlling the chlorine injection device into the water to be treated.

In the present invention, the chlorine injection device is configured to inject a chlorine agent into the water to be treated before coagulation sedimentation, and the chlorine agent injection rate calculation means is based on the trihalomethane production ability predicted by the trihalomethane production ability prediction means. The chlorine agent injection rate at which the trihalomethane production concentration is below the allowable concentration of trihalomethane after injection of disinfecting chlorine for the treated water after filtration is determined, and the chlorine injection device is controlled via the control means by this chlorine agent injection rate. In the present invention, a water quality indicator measuring device for measuring various water quality indicators relating to the treated water is provided, and the trihalomethane production ability predicting means generates the trihalomethane production using the fluorescence intensity of the treated water and the water quality indicator of the treated water as factors. Predict trihalomethane production potential using a function-based prediction formula.

  In the present invention, the water quality index measuring device provides at least one of the water temperature, pH, and ammonia nitrogen as the water quality index of the treated water to the trihalomethane generating ability predicting means.

  In the present invention, at least one of liquefied chlorine, sodium hypochlorite, and calcium hypochlorite is used as the chlorinating agent used in the chlorinating apparatus.

  Further, in the present invention, the trihalomethane production capacity predicting means includes the trihalomethane production capacity predicted from the fluorescence intensity of the treated water, or the fluorescence intensity and the water quality index of the treated water, respectively, and the trihalomethane production concentration in the past chlorine agent injection. The measured value is used to predict the trihalomethane production ability of the treated water.

  In the present invention, switching means for changing the injection point of the chlorinating agent in the water treatment plant to an injection point at which the production of trihalomethane is lower is provided on the basis of the predicted generation capacity by the trihalomethane generation capacity prediction section.

  Furthermore, in this invention, a fluorescence analyzer irradiates to-be-processed water the excitation light which exists in the wavelength range of 340-350 nm, and measures the fluorescence intensity which exists in the wavelength range of 420-430 nm.

  According to the present invention, in the water treatment plant that performs chlorine treatment by injecting chlorine into the water to be treated, the injection rate of the chlorinating agent is controlled based on the trihalomethane producing ability in the water to be treated. Can be effectively suppressed.

  Hereinafter, an embodiment of a water treatment control device according to the present invention will be described in detail with reference to the drawings. 1 to 6 are diagrams relating to the present embodiment, and FIG. 1 shows the overall configuration of the water treatment control device.

  First, the structure of the water treatment plant in a water purification plant etc. is demonstrated. In FIG. 1, the water treatment plant includes a landing well 20, a mixing basin 21, a coagulation sedimentation facility 22, and a sand filtration facility 23. The landing well 20 is provided at the inlet of raw water in the water purification plant, and raw water flows in from a water source such as a river (not shown). The mixing basin 21 is provided in the subsequent stage of the landing well 20, and a pre-chlorination chlorine agent is injected into the water to be treated (raw water) flowing from the landing well 20. In the coagulation sedimentation facility 22, although not shown, a coagulant is added to the water to be treated. By injecting the flocculant, organic substances, turbidity, etc. in the water to be treated are flocked and removed from the water to be treated by the coagulation sedimentation treatment. The supernatant water of the coagulation sedimentation facility 22 flows into the sand filtration facility 23 as treated water. Suspended substances in the water to be treated are removed by filtration (attachment to the filter medium and sieving in the filter layer).

  A pre-chlorine injection apparatus 10 injects a chlorine agent into the water to be treated in the mixing basin 21 to perform chlorination of the water to be treated. Although not shown in the drawing, the mixing basin 21 is provided with equipment for sufficiently mixing the chlorine agent and the water to be treated. Moreover, although not shown in figure, the chlorine injection apparatus is provided also in the exit side of the sand filtration equipment 23, and a chlorine agent is inject | poured into the treated water filtered through the road material for disinfection. This chlorination injection for disinfection is called post-chlorination, and after this chlorination, water is distributed to customers.

  A fluorescence analyzer 24 is provided in the landing well 20 and measures the fluorescence intensity of the water to be treated. The fluorescence intensity measured by the fluorescence analysis method is an effective means for quantifying and identifying low-concentration substances contained in water. In the fluorescence analysis method, it is possible to measure various substances by using a specific excitation wavelength and fluorescence wavelength. If the excitation wavelength is 345 nm and the fluorescence wavelength is 425 nm, the concentration of organic substances contained in the raw water of the water purification plant can be determined. It is possible to measure indirectly. Therefore, the fluorescence analyzer 24 irradiates the water to be treated with excitation light in the wavelength range of 340 to 350 nm, measures the fluorescence intensity in the wavelength range of 420 to 430 nm from the water to be treated, and based on the measured value. Indirectly measure the organic matter concentration in the treated water.

  Reference numeral 25 denotes a water quality indicator measuring device which is provided in the landing well 20 and measures various water quality indicators of the water to be treated. The water quality indicator measuring device 25 includes a plurality of measuring devices corresponding to each water quality indicator, such as a water temperature measuring device 26 that measures the temperature of the water to be treated, a pH measuring device 27 that measures the pH of the water to be treated, and the water to be treated. It comprises a measuring instrument 28 for measuring the ammoniacal nitrogen concentration. In addition, the water quality index measuring device 25 includes an alkalinity measuring device that measures the alkalinity of the water to be treated (not shown), a total organic carbon concentration measuring device that measures the total organic carbon concentration of the water to be treated, and the flow rate of the water to be treated. Further, a residence time measuring device that measures the residence time of the water to be treated from the volume of the water treatment plant, an ultraviolet absorbance measuring device that measures the ultraviolet absorbance of the water to be treated, and the like may be provided.

  A controller 60 for controlling the chlorine agent injection rate into the water to be treated is connected to the pre-chlorine injection device 10, the fluorescence analyzer 24, and the water quality indicator measurement device 25. The control device 60 controls the pre-chlorine injection device 10 to optimally control the injection rate of the chlorine agent, thereby suppressing the production concentration of trihalomethane in the pre-chlorination treatment. The control device 60 includes a trihalomethane production capability prediction unit 41, an optimum chlorine agent injection rate calculation unit 42, and a chlorine injection device control unit 43.

  The trihalomethane production capacity predicting means 41 predicts the trihalomethane production capacity of the water to be treated based on the fluorescence intensity of the water to be treated measured by the fluorescence analyzer 24, and the water quality index measuring device 25 measures the water quality index measurement apparatus 25 as necessary. Corrections are made using the treated water quality index. That is, the trihalomethane production capacity predicting means 41 inputs the fluorescence intensity of the water to be treated measured by the fluorescence analyzer 24, and based on the correlation shown in FIG. 2 obtained in advance between the fluorescence intensity and the trihalomethane production capacity. Estimate the trihalomethane production capacity of water to be treated. Moreover, since this trihalomethane production ability changes with the water quality of to-be-processed water, it correct | amends with this water quality as needed. For example, regarding the water temperature, which is one of the water qualities, as shown in FIG. 3, even if the fluorescence intensity is the same, there is a difference in trihalomethane production ability between the low water temperature and the high water temperature. Therefore, correction is performed as necessary using the value measured by the water quality indicator measuring device 25 so as to obtain the correct trihalomethane production ability.

  The chlorinating agent injection rate calculating means 42 calculates the optimum chlorine injection rate in the pre-chlorination based on the trihalomethane generating ability of the water to be treated predicted by the trihalomethane generating ability predicting unit 41. That is, the chlorinating agent injection rate calculating means 42 calculates the trihalomethane producing concentration by the chlorinating agent injection into the water to be treated based on the trihalomethane producing ability predicted by the trihalomethane producing ability predicting means 41, and this trihalomethane producing concentration is Obtain the chlorine agent injection rate that is below the allowable concentration of trihalomethane.

  The chlorine injection device control means 43 controls the pre-chlorine injection device 10 that injects the chlorine agent into the mixing basin 21 based on the chlorine injection rate of the pre-chlorine treatment calculated by the chlorine agent injection rate calculation means 42.

  Hereinafter, the operational effects of the present embodiment will be described with reference to FIGS. 1 to 6. First, raw water (treated water) sent from a water source is stored in the landing well 20. At this time, the fluorescence intensity of the water to be treated is measured by the fluorescence analyzer 24. In addition, various water quality indexes of the water to be treated are measured by the water quality index measuring device 25. Next, the water to be treated is injected with chlorine in the mixing basin 21 and pre-chlorinated. The water to be treated is added with a flocculant in the next coagulation sedimentation equipment 22 to form flocs, and components such as turbidity are removed by the coagulation sedimentation treatment. The supernatant water by this coagulation sedimentation process is sent to the sand filtration equipment 23 as treated water, where suspended substances and the like are removed. The treated water that has passed through the sand filtration facility 23 is then disinfected by post-chlorination in a distribution reservoir (not shown) and distributed to customers. In a water purification plant where advanced water treatment using ozone or the like is introduced, advanced water treatment by ozone treatment or activated carbon adsorption treatment is performed.

  In the mixing basin 21, when pre-chlorination is performed on the water to be treated, organic substances in the water to be treated react with the injected chlorine to generate trihalomethane. This trihalomethane is a harmful substance and it is necessary to suppress its production. FIG. 2 is a diagram showing the relationship between the fluorescence intensity of the water to be treated and the trihalomethane production ability of the water to be treated. As shown in FIG. 2, there is a correlation between the fluorescence intensity of the water to be treated and the trihalomethane production ability of the water to be treated. For this reason, by measuring the fluorescence intensity, it is possible to estimate how much a substance that changes to trihalomethane is contained by injecting chlorine into the water to be treated.

  FIG. 3 is a diagram illustrating the influence of the water temperature of the water to be treated on the relationship between the fluorescence intensity of the water to be treated and the trihalomethane production ability of the water to be treated. As shown in FIG. 3, the higher the temperature of the water to be treated, the higher the trihalomethane generating ability even with the same fluorescence intensity. This is thought to be due to the fact that the reaction between the injected chlorine and organic matter is promoted due to the high water temperature.

  In addition, it has been found that the relationship between fluorescence intensity and trihalomethane production ability is also affected by other water qualities. For example, the lower the pH of the water to be treated, the higher the oxidizing power of the chlorinating agent, and the higher the risk of trihalomethane formation. Ammonia nitrogen reacts with chlorine to produce combined chlorine. For this reason, when there is much ammonia nitrogen, the chlorine which reacts with organic substance will reduce, As a result, even if it is raw water of the same fluorescence intensity, the risk of trihalomethane production will become small.

  Therefore, by measuring the water quality data of the treated water and using it for correcting the predicted value of trihalomethane production ability, it is possible to calculate the more accurate trihalomethane production ability of the treated water.

  Hereinafter, regarding the control of the pre-chlorination, the operation of the control device 60 will be mainly described. The trihalomethane production ability prediction means 41 inputs the fluorescence intensity of the water to be treated measured by the fluorescence analyzer 24. In addition, at least one of the water quality data of the water to be treated measured by the water quality index measuring device 25 is input. And the trihalomethane production | generation ability of to-be-processed water is calculated with the fluorescence intensity of these to-be-processed water, and the water quality parameter | index from the water quality parameter | index measuring device 25. FIG. Hereinafter, the calculation method (prediction method) will be described with reference to FIG.

  A function Z1 in FIG. 4 represents the relationship between the fluorescence intensity of the water to be treated and the trihalomethane generating ability when the water quality is a predetermined standard (water temperature or the like). If the actual water quality data is all the same as the standard water quality data, the trihalomethane production capacity of the treated water is calculated as Y1 from the fluorescence intensity X1 of the treated water.

  Among the water quality data of the water to be treated measured by the water quality index measuring device 25, for example, when the water temperature is higher than the standard water temperature, the value of trihalomethane production capacity with respect to the fluorescence intensity is high, and the fluorescence intensity and trihalomethane production capacity are Is a function Z2. At this time, if the water quality data other than the water temperature is the same as the standard state, the trihalomethane generating ability of the water to be treated having a high water temperature is calculated as Y2.

  Specifically, the predicted value of trihalomethane production ability is calculated by the following formula (1) from FIG.

Predicted value of trihalomethane production ability = Y {fluorescence intensity X, function Z (function Z1-Σ correction value i for standard water quality)}
(I = 1 to 3) (1)
Here, i = 1 means the water temperature correction value, i = 2 means the pH correction value, and i = 3 means the ammonia nitrogen correction value. In addition, as described above, when using the alkalinity, total organic carbon concentration, residence time, ultraviolet absorbance of the water to be treated as the water quality index, the correction values related to these are, for example, the alkalinity correction value when i = 4, Correction may be performed with i = 5 as the total organic carbon concentration correction value, i = 6 as the residence time correction value of the water to be treated, and i = 7 as the ultraviolet absorbance correction value.

  That is, the trihalomethane production capacity predicting means 41 inputs various water quality indexes relating to the water to be treated from the water quality indicator measuring device 25, and generates trihalomethanes using the fluorescence intensity X of the water to be treated and the water quality indicator of the water to be treated as factors. The prediction formula (1) based on the function Z is used to predict the trihalomethane production ability Y.

  Next, the operation of the chlorinant injection rate calculating means 42 of the control device 60 will be described with reference to FIG.

  The chlorinating agent injection rate calculating means 42 calculates the chlorinating agent injection rate based on the predicted value of the trihalomethane generating ability calculated by the trihalomethane generating ability predicting means 41. The relationship between the chlorine injection rate and the concentration of the actually produced trihalomethane is as shown in FIG. That is, at a stage where the injection rate of chlorine is low, the production concentration of trihalomethane slightly increases. When the injection rate of chlorine increases, the reaction between organic matter and chlorine proceeds and the production concentration of trihalomethane increases. When the chlorine injection becomes excessive, the production of trihalomethane is saturated and the trihalomethane production concentration reaches its peak. The maximum trihalomethane production concentration here can be regarded as the trihalomethane production capacity calculated by the trihalomethane production capacity prediction means 41.

  In clean water, there is a permissible concentration of trihalomethane (for example, water quality reference value of trihalomethane) a1, so it is necessary to keep the trihalomethane production concentration by chlorine injection below this permissible concentration a1. In addition, as described above, post-chlorination is performed at the water purification plant outlet for disinfection. As a result, the chlorine injection in the pre-chlorination is performed in consideration of the trihalomethane concentration expected to be generated by the chlorine injected in the chlorination. Calculate the rate. As a result, the range of b in FIG. 5 becomes the injectable range of the chlorine injection rate in the pre-chlorination process. In the range of b, the injection rate that enables removal of ammonia nitrogen and microorganisms in raw water, oxidation and removal of iron and manganese, and the algicidal effect of algae breeding in the water treatment plant Is determined as the chlorine injection rate in the pre-chlorination.

  That is, the chlorinating agent injection rate calculating unit 42 calculates the trihalomethane concentration produced by the chlorinating agent injection into the water to be treated based on the trihalomethane producing ability predicted by the trihalomethane producing ability predicting unit 41, and this trihalomethane producing concentration. Is determined as a chlorinant injection rate b that gives an allowable trihalomethane concentration of a1 or less. When post-chlorination is performed, a chlorine agent injection rate b at which the trihalomethane production concentration is less than or equal to the allowable trihalomethane concentration a1 after post-chlorination (after disinfection of chlorine for the treated water after filtration) is obtained.

  Next, FIG. 6 shows a case where the predicted concentration of the trihalomethane generating ability calculated by the trihalomethane generating ability predicting means 41 is lower than the allowable concentration a1 of trihalomethane. In the case of raw water as shown in FIG. 6, the risk of generating trihalomethane by chlorine injection is low. Therefore, in this case, as described above, the chlorine in the pre-chlorination treatment is considered in consideration of the removal of ammonia nitrogen and microorganisms in the raw water, the oxidation removal of iron and manganese, and the algicidal effect of algae breeding in the water treatment plant. Determine the injection rate.

  Next, the operation of the chlorine injection device control means 43 will be described.

  The chlorine injection device control means 43 controls the pre-chlorine injection device 10 based on the injection rate of the chlorine agent injected into the mixing basin 21 calculated by the chlorine agent injection rate calculation means 42. That is, the chlorine injection device control means 43 controls the pre-chlorine injection device 10 so that the injection rate of the chlorine agent injected into the mixing basin 21 becomes the calculated target injection rate by, for example, a known PI control method. To do. In addition, as a chlorine agent used in the pre-chlorine injection apparatus 10, at least any one of liquefied chlorine, sodium hypochlorite, and calcium hypochlorite is used.

  As described above, the control device 60 according to the present embodiment predicts the trihalomethane generating ability of the water to be treated based on the fluorescence intensity of the water to be treated or the fluorescence intensity and the water quality data, and sets the predicted concentration. Accordingly, the optimum chlorine injection rate in pre-chlorination is calculated. The control device 60 controls the prechlorine injection device 10 by the chlorine injection device control means 43 based on the calculated optimum chlorine injection rate, thereby suppressing the trihalomethane generated in the prechlorination treatment within an allowable range. Can do.

  Next, the embodiment shown in FIG. 7 will be described. In this embodiment, the trihalomethane production capacity predicting means 71 is provided with a function of inputting past trihalomethane actual measurement value data 50 and water quality data storage in which water quality data when actual measurement of trihalomethane is performed is stored. This is a configuration having a part 51. Since other configurations are the same as those of the embodiment shown in FIG. 1, the same reference numerals are given and description thereof is omitted.

  This trihalomethane production capacity predicting means 71 uses the fluorescence intensity of the water to be treated or the fluorescence intensity of the water to be treated and the water quality index of the water to be treated, and the measured value data 50 of the trihalomethane production concentration in the past chlorine agent injection. Use to predict trihalomethane production capacity of treated water. The method will be described below.

  The trihalomethane production ability predicting means 71 uses the fluorescence intensity of the water to be treated measured by the fluorescence analyzer 24, the water quality of the water to be treated measured by the water quality indicator measuring device 25, and the actual measurement data 50 of the past trihalomethane production concentration. Based on this, the ability to produce trihalomethanes is estimated. That is, when calculating the trihalomethane production capacity, the water quality data storage unit 51 in which past water quality data is stored is searched based on the actual fluorescence intensity and the actual measurement value of the water quality data, and similar fluorescence intensity and water quality data are searched. To extract. If there is relevant past data, the actual measured value of trihalomethane production ability at that time is extracted. The actual measurement data 50 of the past trihalomethane production concentration input to the trihalomethane production capacity predicting means 41 is specifically an actual measurement value when the past trihalomethane production capacity is measured by hand analysis or the like, and the treated water at that time The measured value of the fluorescence intensity and the measured value of other water quality data are stored in the water quality data storage unit 51.

  Then, the extracted past measured trihalomethane production capacity is compared with the predicted concentration calculated from the function, and the higher one is set as the predicted trihalomethane production capacity. In other words, the trihalomethane production ability can be predicted more accurately on the safe side by making corrections by comparing with past actual measurement values.

  As a result, the control device 60 can calculate the optimal injection rate of the chlorine agent to be injected into the mixing basin 21 by the chlorine injection device control means 43 based on the predicted value of the trihalomethane production ability on the safer side.

  Next, the embodiment in which the injection point of the chlorinating agent in the water treatment plant is changed to an injection point where the production of trihalomethane is lower, that is, from pre-chlorination to intermediate chlorination, according to the predicted trihalomethane production capacity, This will be described with reference to FIG.

  In the present embodiment, in addition to the pre-chlorine injection device 10 for injecting a chlorine agent into the water to be treated before coagulation and precipitating the water to be treated, the chlorine agent is injected into the supernatant water after the coagulation and precipitation. An intermediate chlorine injection device 11 that performs chlorination is provided. The intermediate chlorine injection device 11 is provided between the coagulation sedimentation facility 22 and the sand filtration facility 23, and injects a chlorine agent into the supernatant water of the coagulation sedimentation facility, that is, the water to be treated flowing into the sand filtration facility 23. Perform chlorination of treated water.

  Further, pre-chlorine / intermediate chlorine switching means 44 for switching between pre-chlorination and intermediate chlorination is provided.

  The control device 60 is basically the same as the configuration shown in FIG. 7 except that the optimum chlorinating agent injection calculating means 72 switches the prechlorine treatment to the intermediate chlorine treatment with respect to the prechlorine / intermediate chlorine switching means 44. It has a function to output commands. That is, the optimum chlorinating agent injection calculating unit 72 switches the chlorinating point in the water treatment plant to the intermediate chlorinating process in which the production of trihalomethane is lower, based on the predicted forming ability of the trihalomethane generating ability predicting unit 71. The command is output to the switching means 44.

  Since other configurations are the same as those of the embodiment shown in FIG. 7, the same reference numerals are given and description thereof is omitted.

  The pre-chlorine / intermediate chlorine switching means 44 outputs the optimum chlorinating agent injection calculating means 72 when the predicted concentration of the trihalomethane generating ability calculated by the trihalomethane generating ability predicting section 71 is significantly higher than the allowable concentration of trihalomethane. Switch from pre-chlorination to medium chlorination by switching command. The operation in this case will be described with reference to FIG.

  As shown in FIG. 9, in the raw water in which the predicted concentration of the trihalomethane generation capacity calculated by the trihalomethane generation capacity prediction means 71 is significantly higher than the allowable concentration a1 of trihalomethane, a large amount of trihalomethane is generated when chlorine is injected excessively. . In this case, considering the allowable trihalomethane concentration a1 and the concentration of trihalomethane generated in the post-chlorination, the range indicated by c1 is the injectable range of the chlorine injection rate in the pre-chlorination. However, chlorine that reacts with organic matter competes with chlorine necessary for removal of ammonia nitrogen and microorganisms in the raw water, oxidation removal of iron and manganese, and algal killing of algae. The required chlorine injection rate is c2. However, when chlorine is injected at this chlorine injection rate c2, the trihalomethane production concentration becomes a2, which greatly exceeds the allowable concentration a1.

  In such a case, the optimum chlorinating agent injection rate calculating means 72 determines to switch the chlorine injection point from pre-chlorination to intermediate chlorination. That is, as shown in FIG. 9, when the chlorine injection rate c2 required for algal killing and the like is such that the trihalomethane production concentration a2 exceeds the allowable range a1, the injection point of the chlorine agent in the water treatment plant is determined as the production of trihalomethane. A switching command is issued to the switching means 44 in order to switch from an injection point (a pre-chlorination treatment to an intermediate chlorination treatment) at which the lowering is made. As a result, when the switching means 44 performs the switching operation, the intermediate chlorine injection device 11 injects chlorine between the coagulation sedimentation facility 22 and the sand filtration facility 23. In the treated water into which chlorine is injected, that is, the supernatant water of the coagulation sedimentation facility 22, most of the organic substances are removed by the coagulation sedimentation, so that the trihalomethane production concentration is also lowered.

  In this way, by detecting the risk of trihalomethane formation from the predicted value of trihalomethane formation ability, and having the function of switching the point of chlorine injection from pre-chlorination to intermediate chlorination, the production of trihalomethane can be suppressed more safely. can do.

  Although the chlorine injection control method in intermediate chlorination is not mentioned here, most of the substances that are the source of trihalomethane have been removed at the point of intermediate chlorination, so it does not require as strict control as pre-chlorination. .

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a system block diagram which shows the structure regarding one Embodiment of the water treatment control apparatus by this invention. It is a characteristic view which shows the relationship between the fluorescence intensity of to-be-processed water regarding one Embodiment same as the above, and trihalomethane production ability. It is a figure which shows the relationship between the fluorescence intensity of to-be-processed water and trihalomethane production ability by the difference in the water temperature of to-be-processed water regarding one Embodiment same as the above. It is a figure which shows the relationship between the fluorescence intensity of to-be-processed water, and the prediction density | concentration of trihalomethane production ability of the trihalomethane production ability prediction formula regarding one Embodiment same as the above. It is a figure which shows the relationship between the chlorine injection rate regarding one Embodiment same as the above, and the density | concentration of the produced | generated trihalomethane. It is a figure which shows the relationship between the chlorine injection rate regarding one Embodiment same as the above, and the density | concentration of the produced | generated trihalomethane, when the predicted value of trihalomethane production ability is low. It is a block diagram of the water treatment control apparatus regarding other embodiment of this invention. It is a block diagram of the water treatment control apparatus regarding other embodiment of this invention. It is a figure which shows the relationship between the chlorine injection rate regarding this invention, and the density | concentration of the produced | generated trihalomethane, when the predicted value of trihalomethane production ability is high.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Prechlorination apparatus 11 Intermediate chlorine injection apparatus 20 Landing well 21 Mixing basin 22 Coagulation sedimentation equipment 23 Sand filtration equipment 24 Fluorescence analyzer 25 Water quality indicator measuring device 26 Water temperature measuring device 27 pH measuring device 28 Concentration measuring device 41, 71 Trihalomethane production Performance prediction means 42, 72 Chlorine agent injection calculation means 43 Control means 44 for chlorine injection equipment 44 Switching means

Claims (8)

A water treatment control device that controls a water treatment plant that introduces raw water into a landing well, coagulates and precipitates the water to be treated introduced into the landing well, and filters the supernatant water,
A fluorescence analyzer for measuring the fluorescence intensity of the water to be treated;
Using the fluorescence intensity of the treated water measured by the fluorescence analyzer, the trihalomethane generating ability for predicting the trihalomethane producing ability of the treated water based on a predetermined correlation between the fluorescence intensity and the trihalomethane producing ability Prediction means,
Based on the trihalomethane production ability predicted by the trihalomethane production ability predicting means, a trihalomethane production concentration based on the chlorination agent injection into the water to be treated is calculated, and a chlorination agent injection rate at which the trihalomethane production concentration is less than or equal to the allowable trihalomethane production concentration is calculated. A chlorinant injection rate calculating means to be obtained
A water treatment control device comprising: control means for controlling a chlorine agent injection device into the water to be treated based on the injection rate of the chlorine agent calculated by the chlorine agent injection rate calculating means.   The chlorine injection device is configured to inject a chlorine agent into the treated water before coagulation sedimentation, and the chlorine agent injection rate calculation means has a trihalomethane production concentration based on the trihalomethane production ability predicted by the trihalomethane production ability prediction means. A chlorine agent injection rate that is equal to or lower than an allowable concentration of trihalomethane after injecting chlorine for disinfection with respect to treated water after filtration is obtained, and the chlorine injection device is controlled via the control means based on the chlorine agent injection rate. Item 2. A water treatment control device according to item 1.   A water quality indicator measuring device for measuring various water quality indicators relating to the treated water is provided, and the trihalomethane production capacity predicting means is based on the fluorescence intensity of the treated water and the trihalomethane production function based on the water quality indicator of the treated water. The water treatment control apparatus according to any one of claims 1 and 2, wherein a trihalomethane production ability is predicted using a prediction formula.   The water quality index measuring device provides at least one information of water temperature, pH, and ammonia nitrogen as water quality index of the treated water to the trihalomethane generating ability predicting means. 3. The water treatment control device according to 3.   Any one of liquefied chlorine, sodium hypochlorite, and calcium hypochlorite is used as the chlorine agent used in the chlorine agent injection device. A water treatment control device according to claim 1.   The trihalomethane production capacity prediction means uses the fluorescence intensity of the treated water, or the trihalomethane production capacity predicted from the fluorescence intensity and the treated water quality index, respectively, and the measured value of the trihalomethane production concentration in the past chlorinating agent injection. The water treatment control device according to any one of claims 1 to 5, wherein a trihalomethane production ability of the treated water is predicted.   The switching means for changing the injection point of the chlorinating agent in the water treatment plant to an injection point at which the production of trihalomethane is lower is provided based on the predicted generation capacity by the trihalomethane generation capacity prediction section. The water treatment control device according to claim 6.   The fluorescence analyzer irradiates the water to be treated with excitation light in the wavelength range of 340 to 350 nm, and measures the fluorescence intensity in the wavelength range of 420 to 430 nm. Water treatment control device according to

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