JP7584937B2 - Water treatment system and water treatment method - Google Patents

Description

An embodiment of the present invention relates to a water treatment system and a water treatment method that injects powdered activated carbon and a flocculant into the water to be treated to remove odorous substances, dissolved organic matter, and turbidity substances from the water to be treated.

In general, the water to be treated (hereinafter also referred to as "raw water") taken from rivers, lakes, reservoirs, etc. contains odorous substances, soluble natural organic matter such as humin (hereinafter also referred to as "soluble organic matter"), and suspended solids such as fine particles.

Meanwhile, at water purification plants, chemicals such as sodium hypochlorite are injected for the purpose of removing metals such as iron and manganese and for disinfection treatment. However, when raw water contains soluble organic matter, the soluble organic matter reacts with the chemicals to produce trihalomethanes and haloacetic acids (hereinafter also referred to as "disinfection by-products"). These disinfection by-products are carcinogenic, so their production must be suppressed.

Many water purification plants inject powdered activated carbon to remove odorous substances and dissolved organic matter from the raw water, and coagulants to remove turbidity. In this type of water treatment system, the injection rate of powdered activated carbon must be determined according to the quality of the raw water.

The jar test (hereafter also referred to as the "beaker test") is often used to determine the powdered activated carbon injection rate. In the jar test, raw water is collected in multiple beakers, and different amounts of powdered activated carbon are injected into each of the collected raw water samples to evaluate the removal rate of odorous substances and soluble organic matter, and the minimum powdered activated carbon injection rate required to reduce the odor concentration and soluble organic matter after treatment to below the target concentration is determined.

However, the above method of determining the powdered activated carbon injection rate by jar testing makes it extremely difficult to inject powdered activated carbon in response to changes in the raw water quality, and there is a risk of the injection rate being either too high or too low. In addition, since the jar test takes time to determine the optimal injection rate of powdered activated carbon, it is possible that the quality of the raw water has already changed by the time the optimal injection rate of powdered activated carbon is obtained.

In particular, it is known that the adsorption characteristics of odorous substances by powdered activated carbon are affected by the concentration and molecular structure of coexisting soluble organic substances, which can inhibit the adsorption of odorous substances.

In addition, when deciding the actual injection rate of powdered activated carbon to be added, the injection rate is determined on the safe side compared to the injection rate obtained by the jar test, resulting in overinjection.

Powdered activated carbon has a very high unit price compared to other chemicals such as coagulants, sulfuric acid, and sodium hypochlorite. Therefore, excessive injection of powdered activated carbon can lead to a sharp rise in chemical costs. From an economic standpoint, there is a need for a method to prevent excessive injection of powdered activated carbon and to control the optimal injection rate of powdered activated carbon in response to changes in the quality of the raw water.

One method for controlling the powdered activated carbon injection rate is to use an odor sensor to detect odorous substances in the air near the water surface of the raw water in the powdered activated carbon treatment tank, calculate the powdered activated carbon injection rate for the raw water flow rate based on the odor intensity reading obtained, and control the powdered activated carbon based on this powdered activated carbon injection rate (see, for example, Patent Document 1).

Another method is to observe the state of the pulverized coal in the raw water after the powdered activated carbon is injected, and use the observation results as a feedback signal to send the injection rate of the activated carbon to a calculation unit in the previous stage, thereby controlling the injection rate of the powdered activated carbon to achieve the target set effluent turbidity (see, for example, Patent Document 2).

However, these conventional methods do not take into account the quality of the raw water, and are not accurate enough to optimize the injection rate of powdered activated carbon. In particular, they do not take into account the effect of coexisting soluble organic substances on the adsorption characteristics of odorous substances.

To address this issue, there is a method for determining the coefficients that affect the residual rate of odorous substances and organic substances when powdered activated carbon is injected, and then determining the required powdered activated carbon injection rate (see, for example, Patent Document 3).

However, when powdered activated carbon is injected, it is necessary to carry out a subsequent coagulation and sedimentation and filtration process to remove the powdered activated carbon that has adsorbed the target substances.

In this case, odorous substances and soluble organic substances that are the targets of adsorption by powdered activated carbon are also removed in the coagulation treatment process, but because this is not taken into consideration in conventional powdered activated carbon injection control, in most cases, powdered activated carbon ends up being injected in excess. This not only results in excessive chemical costs, but also leads to increased costs due to the increased injection rate of coagulant required for removal, as well as increased treatment costs due to the increased amount of sludge discharged.

Japanese Patent Application Publication No. 2-284687 Patent No. 2969927 Patent No. 4153893

The problem that this invention aims to solve is to provide a water treatment system and a water treatment method that can optimize the injection rate of powdered activated carbon.

The water treatment system of the embodiment includes a first flocculant injection rate calculation unit and an activated carbon injection rate calculation unit. The first flocculant injection rate calculation unit calculates a first flocculant injection rate, which is the injection rate of flocculant required for flocculation and precipitation of turbidity in the raw water, based on the quality of the raw water. The activated carbon injection rate calculation unit calculates a first powdered activated carbon injection rate, which is the injection rate of powdered activated carbon required to remove odorous substances in the raw water, based on the odorous substance concentration in the raw water, at least one of the ultraviolet absorbance, the fluorescent intensity, and the soluble organic carbon concentration of the raw water, and the first flocculant injection rate.

FIG. 1 is a conceptual diagram showing an example in which a water treatment system to which a water treatment method common to each embodiment of the present invention is applied is applied to a rapid filtration type water treatment facility. 3 is a block diagram showing an example of the configuration of an activated carbon injection rate calculation unit in the water treatment system of the first embodiment. FIG. 1 is a diagram showing a flow of treatment by a water treatment system to which a water treatment method according to a first embodiment is applied; FIG. 13 is a diagram showing an example of the relationship between the coagulant injection rate _Ipacl and the ultraviolet light absorbance residual rate _RUVpacl by the coagulation treatment. FIG. 13 is a diagram showing the relationship between the coagulant injection rate _Ipacl and the combined treatment coefficient _FDOM . FIG. 1 is a graph showing the relationship between the specific absorbance SUVA in raw water and the coefficient f. FIG. 1 is a graph showing the relationship between the powdered activated carbon injection rate I _car and the odorant concentration residual rate RC _car after powdered activated carbon treatment. FIG. 13 is a diagram showing the relationship between the coagulant injection rate I _pacl and the odorant concentration residual rate RC _car/pacl in the combined treatment of powdered activated carbon and a coagulant. 13 is a block diagram showing an example of the configuration of a flocculant injection rate calculation unit in the water treatment system of the second embodiment. FIG. FIG. 11 is a diagram showing a flow of treatment by a water treatment system to which a water treatment method according to a second embodiment is applied.

The water treatment system and water treatment method according to each embodiment of the present invention will be described below with reference to the drawings.

(composition)
First, a configuration of a water treatment system to which a water treatment method, which is common to each embodiment of the present invention, is applied will be described.

Figure 1 is a conceptual diagram showing an example of a water treatment system to which a water treatment method common to each embodiment of the present invention is applied, applied to a rapid filtration type water treatment facility.

The water treatment system of each embodiment of the present invention is not limited to rapid filtration water treatment facilities, but can also be applied to other types of water treatment facilities, such as water treatment facilities using membrane filtration or sand filtration methods.

As shown in FIG. 1, the water treatment system 1 is incorporated into a water treatment facility 3 together with a water treatment device 2.

The water treatment device 2 performs adsorption treatment and coagulation and sedimentation on the raw water A. The adsorption treatment is a process in which odorous substances and soluble organic matter in the raw water A are adsorbed and removed using powdered activated carbon. The coagulation and sedimentation is a process in which turbid matters in the raw water A are coagulated and sedimented using a coagulant.

The water treatment device 2 includes a receiving well 20, a powdered activated carbon injection device 21, a coagulant mixing basin 30, a coagulant injection device 31, a flocculation basin 40, a settling basin 50, a filtration basin 60, and a purified water basin 70.

The receiving well 20 stores raw water A, which is the water to be treated by the water treatment facility 3. The receiving well 20 is connected to the coagulant mixing basin 30 by piping 91, and the raw water A is led from the receiving well 20 to the coagulant mixing basin 30 via piping 91. The piping 91 before the receiving well 20 is equipped with a water quality meter set 10 that measures the water quality of the raw water A, an odor sensor 11 that measures the concentration of odorous substances in the raw water A, a soluble organic substance indicator meter set 12 that measures the organic substance concentration indicator in the raw water A, and a flow meter 13 that measures the flow rate of the raw water A.

The water quality meter set 10 includes, but is not limited to, a turbidity meter 10a, an alkalinity meter 10b, a water temperature meter 10c, and a pH meter 10d, and these sensors measure various water qualities and then transmit the measurement data to the water treatment system 1.

The dissolved organic matter indicator instrument set 12 includes, but is not limited to, an ultraviolet spectrophotometer 12a, a fluorescence intensity meter 12b, and a dissolved organic carbon concentration (DOC) meter 12c, and these sensors transmit measurement data to the water treatment system 1.

Powdered activated carbon C is injected into the receiving well 20 from a powdered activated carbon injection device 21 to adsorb odorous substances and soluble organic matter in the raw water A.

The powdered activated carbon injection device 21 stores powdered activated carbon C. The powdered activated carbon injection device 21 injects the powdered activated carbon C into the raw water A that has landed in the water receiving well 20, based on the control from the water treatment system 1.

In the flocculant mixing basin 30, suspended matter (turbidity) such as clay, bacteria, and algae contained in the raw water A and powdered activated carbon C injected in the receiving well 20 are flocculated by flocculant P injected from a flocculant injection device 31 to generate fine flocs. The flocculant mixing basin 30 is equipped with an agitator 32, such as a flash mixer.

The coagulant mixing pond 30 is provided with a pH meter 14. The pH meter 14 measures the pH of the mixed water B, which is the raw water A to which coagulant P has been injected, and transmits the measurement data to the water treatment system 1.

The flocculant injection device 31 stores flocculant P. The flocculant injection device 31 is also connected to the water treatment system 1, and injects the flocculant P into the mixed water B in the flocculant mixing pond 30 based on the control of the water treatment system 1.

As the coagulant P, it is preferable to use an aluminum-based coagulant or an iron-based coagulant. Examples of aluminum-based coagulants include aluminum sulfate (aluminum sulfate) and polyaluminum chloride (PACl). Examples of iron-based coagulants include iron chloride, iron sulfate, and polysilica iron.

In the flocculation basin 40, the size of the fine flocs contained in the mixed water B supplied from the flocculant mixing basin 30 grows. In the example shown in FIG. 1, the flocculation basin 40 has, for example, two mixing basins 40a and 40b, but the number of mixing basins is not limited to two.

The settling basin 50 is provided downstream of the flocculation basin 40, and in the settling basin 50, the flocs that have grown in the flocculation basin 40 are sedimented and separated. The floc-mixed water is retained in the settling basin 50 for a predetermined period of time or more. This causes the flocs in the floc-mixed water to settle and settle at the bottom of the settling basin 50. The flocs that have settled in the settling basin 50 are discharged as sludge from the bottom of the settling basin 50 and are treated.

The filtration basin 60 is provided downstream of the settling basin 50. The filtration basin 60 is supplied with the supernatant water Z obtained by retaining the water in the settling basin 50 for a predetermined period of time or more. The supernatant water Z supplied to the filtration basin 60 passes through a filtration layer 60a formed in the filtration basin 60, thereby removing minute flocs that were not removed by settling in the settling basin 50. The filtered water W from which the minute flocs have been removed in this manner is sent to the purified water basin 70 as purified water.

The receiving well 20 and the coagulant mixing pond 30 are connected to an oxidizing agent injection device 23 for injecting sulfuric acid and other agents used as chemicals to adjust the pH of the raw water A and the mixed water B, and an injection device 22 for injecting sodium hypochlorite and other agents to disinfect algae and bacteria.

Similarly, the filtration tank 60 is connected to an alkaline agent injection device 61 for injecting caustic soda 72 and other agents used to adjust the pH of the supernatant liquid Z.

The purified water reservoir 70 is also connected to an alkaline agent injection device 72 for injecting caustic soda and other agents used to adjust the pH of the purified water W, and an injection device 71 for injecting sodium hypochlorite and other agents to disinfect algae and bacteria.

The pipe 92 that discharges the filtered water from the filtration tank 60 is equipped with a filtered water ultraviolet transmittance meter 15 that measures the ultraviolet absorbance of the filtered water W.

The purified water reservoir 70 is equipped with a tap water quality meter set 80, which includes a turbidity/color sensor 80a, a residual salt concentration sensor 80b, a pH sensor 80c, and a water temperature sensor 80d for measuring the turbidity/color, residual salt concentration, pH, water temperature, etc., of the water quality of the filtered treated water W discharged as tap water.

(First embodiment)
Next, a water treatment system to which the water treatment method according to the first embodiment of the present invention is applied will be described.

As shown in FIG. 1, the water treatment system 1 is applied to a water treatment facility 3 including a water treatment device 2 that sequentially performs an adsorption process to remove odorous substances and soluble organic matter in raw water A using powdered activated carbon, and a coagulation and sedimentation process to coagulate and settle turbid matters in raw water A using a coagulant, and includes as its components a treated water quality target setting unit 100, an activated carbon injection rate calculation unit 200, and a coagulant injection rate calculation unit 300.

The activated carbon injection rate calculation unit 200 and the coagulant injection rate calculation unit 300 realize these functions by recording a program that realizes these functions on a computer-readable recording medium and having the program recorded on this recording medium read by a computer system.

The term "computer system" as used herein includes hardware such as the OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" can include devices that dynamically store programs for a short period of time, such as communication lines when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and devices that store programs for a certain period of time, such as volatile memory within a computer system that serves as a server or client in such cases. Furthermore, the above-mentioned program may be one that realizes part of the functions described above, or may be one that can realize the functions described above in combination with a program already recorded in the computer system.

The flocculant injection rate calculation unit 300 receives measurement data from the water quality meter set 10 and the pH measuring device 14, and uses the received measurement data to calculate the flocculant injection rate _Ipacl , which is the injection rate of flocculant P injected into the raw water A in the coagulation and sedimentation treatment, based on the water quality of the raw water A before the adsorption treatment. The calculated flocculant injection rate _Ipacl is then output to the activated carbon injection rate calculation unit 200 and the flocculant injector 31.

On the other hand, the activated carbon injection rate calculation unit 200 receives the setting data from the treated water quality target setting unit 100, the measurement data from the odor sensor 11 and the soluble organic matter indicator instrument set 12, and the calculation results from the coagulant injection rate calculation unit 300, and uses these received data to calculate the powdered activated carbon injection rate I car, _which is the injection rate of powdered activated carbon C to be injected into the raw water A for adsorption treatment, based on the odorous substance concentration C R in the raw water A before adsorption treatment, and at least one of the ultraviolet absorbance UV _R , _fluorescence intensity FL _R , and soluble organic carbon concentration DOC _R of the raw water A before adsorption treatment, and the coagulant injection rate I _pacl , and outputs it to the powdered activated carbon injection device 21.

For this reason, the activated carbon injection rate calculation unit 200 has a configuration as shown in FIG. 2.

Figure 2 is a block diagram showing an example of the configuration of the activated carbon injection rate calculation unit in the water treatment system of the first embodiment.

The activated carbon injection rate calculation unit 200 includes a data receiving unit 200a, a data processing unit 200b, an organic matter-specific activated carbon injection rate calculation unit 203, an odorant concentration remaining rate estimation unit 204 after combined treatment, an odor-specific activated carbon injection rate calculation unit 207, and an activated carbon injection rate determination unit 209.

The data receiving unit 200a receives measurement data from the odor sensor 11 and the soluble organic matter indicator instrument set 12, setting data set by the treated water quality target setting unit 100 (e.g., target odor intensity, target soluble organic carbon concentration, ultraviolet absorbance, etc.), and calculation results (flocculant injection rate _Ipacl ) from the flocculant injection rate calculation unit 300.

The data processing unit 200b receives the data received by the data receiving unit 200a from the data receiving unit 200a, stores it, and performs necessary data processing such as calculations using the stored data, and also stores the results. The data stored in the data processing unit 200b in this way can be used by the organic matter-specific activated carbon injection rate calculation unit 203, the odorant concentration remaining rate after combined treatment estimation unit 204, the odor-specific activated carbon injection rate calculation unit 207, and the activated carbon injection rate determination unit 209.

The results calculated by the organic matter-compatible activated carbon injection rate calculation unit 203, the odorant concentration remaining rate after combined treatment estimation unit 204, and the odor-compatible activated carbon injection rate calculation unit 207 are also sent to the data processing unit 200b. As a result, the results calculated by the organic matter-compatible activated carbon injection rate calculation unit 203, the odorant concentration remaining rate after combined treatment estimation unit 204, and the odor-compatible activated carbon injection rate calculation unit 207 are shared by the organic matter-compatible activated carbon injection rate calculation unit 203, the odorant concentration remaining rate after combined treatment estimation unit 204, the odor-compatible activated carbon injection rate calculation unit 207, and the activated carbon injection rate determination unit 209.

The odorant concentration remaining rate after combined treatment estimation unit 204 uses the data stored in the data processing unit 200b to calculate the odorant concentration remaining rate RCcar/pacl after combined treatment in which powdered activated carbon treatment and coagulation treatment are performed consecutively. The calculation result is sent from the odorant concentration remaining rate after combined treatment estimation unit 204 to the data processing unit 200b and stored in the data processing unit 200b.

The odor-resistant activated carbon injection rate calculation unit 207 uses the data stored in the data processing unit 200b to calculate the powdered activated carbon injection rate I car _-D , which is the injection rate of powdered activated carbon C injected into the raw water A for the adsorption treatment of odorants, based on the target odorant concentration remaining rate R C _T obtained by dividing the target odorant concentration _{C D for} the raw water A in the coagulation and sedimentation treatment by the odorant concentration C R. The calculation result is sent from the odor-resistant activated carbon injection rate calculation unit 207 to the data processing unit 200b and stored in the data processing unit 200b.

The organic matter corresponding activated carbon injection rate calculation unit 203 uses the data accumulated in the data processing unit 200b to calculate the powdered activated carbon injection rate I car- _UV , which is the injection rate of powdered activated carbon C to be injected into the raw water A for the adsorption treatment of _{soluble organic matter, based on the target ultraviolet absorbance remaining rate RUV T obtained} by dividing the target ultraviolet absorbance _{UV D} for the raw water A in the coagulation and sedimentation treatment by the ultraviolet absorbance UV R. The calculation result is sent from the organic matter corresponding activated carbon injection rate calculation unit 203 to the data processing unit 200b and stored in the data processing unit 200b.

The activated carbon injection rate determination unit 209 determines the larger of the powdered activated carbon injection rates I _car-D and I _car-UV stored in the data processing unit 200b as the powdered activated carbon injection rate for the adsorption treatment, and outputs the determined powdered activated carbon injection rate to the powdered activated carbon injection device 21 as the powdered activated carbon injection rate I _car .

Next, an example of the operation of a water treatment system to which the water treatment method of the first embodiment of the present invention configured as described above is applied will be described.

Figure 3 is a diagram showing the process flow of a water treatment system to which the water treatment method of the first embodiment is applied.

First, the treated water quality target setting unit 100 sets the target odorant concentration C _D , target ultraviolet absorbance UV _D , target turbidity Tu _D , target residual chlorine concentration RCl _D , target hydrogen ion concentration index pH _D and the like as target values for the treated filtered water W (S100). These set data are transmitted to the activated carbon injection rate calculation unit 200, received by the data receiving unit 200a, and stored in the data processing unit 200b.

In the data processing unit 200b, a target odorant concentration residual rate _RCT is calculated from the target odorant concentration CD and the odorant concentration _CR in the raw water measured by the odor sensor 11 according to the following formula (1) (S201).

RC _T = C _D /C _R ... (1)
The data processing unit 200b also calculates a target ultraviolet absorbance remaining rate RUV _T from the target ultraviolet absorbance UVD and the ultraviolet absorbance _UVR of the raw water measured by the ultraviolet absorptiometer 12a according to the following formula (2) (S201).

RUV _T =UV _D /UV _R ... (2)
In parallel, the coagulant injection rate calculation unit 300 calculates the target turbidity Tu _D and the raw water turbidity measured by the turbidity meter 10 a, alkalinity meter 10 b, water temperature meter 10 c, and pH meter 10 d of the water quality meter set 10. The pH value Tu _R of the raw water, the alkalinity Alk _R of the raw water, the water temperature T _R , and the hydrogen ion concentration index pH _R are used together with the pH measuring device 14 installed in the coagulant mixing basin 30 to obtain the pH value _F of the mixing basin. Then, the coagulant injection rate _Ipacl for achieving the target turbidity _TUD is calculated according to the following formula (3) (S300).

I _pacl = f(Tu _D , Tu _R , Alk _R , _TR , pH _R , pH _F ) ... (3)
Here, the ultraviolet absorbance RUV _{car /pacl} when the powdered activated carbon treatment and the coagulation treatment are used in combination is calculated using the ultraviolet absorbance remaining rate RUV _car after the powdered activated carbon treatment, the ultraviolet absorbance remaining rate RUV _pacl after the coagulation treatment, and the combined treatment coefficient F _DOM. and is defined as in the following formula (4).

RUV _car/pacl = F _DOM × RUV _car × RUV _pacl ... (4)
FIG. 4 is a diagram showing an example of the relationship between the coagulant injection rate _Ipacl and the ultraviolet light absorbance remaining rate _RUVpacl in the coagulation treatment.

4 shows the results of a test conducted by the inventors in which the coagulant P was added to raw water adjusted to a soluble organic carbon concentration DOC _R =2.5 (mg/L) and a mixed water pH _F =6.5, followed by rapid stirring at a rotation speed of 150 (rpm) for 10 minutes and then slow stirring at a rotation speed of 80 (rpm) for 60 minutes, in which the residual ultraviolet absorbance RUV _{p acl} on the vertical axis indicates the value obtained by dividing the post-treatment ultraviolet absorbance UV _{p acl} by the raw water ultraviolet absorbance UV _R (i.e., RUV _{p acl} =UV _{p acl} /UV _R ). In this test, humic acid and fulvic acid were added as soluble organic matter at an adjusted mixing ratio.

Figure 4 shows three cases: 100% humic acid, a mixture of 50% humic acid and 50% fulvic acid, and 100% fulvic acid, and shows that the fulvic acid mixture ratio affects the soluble organic matter removal performance of the coagulation treatment.

Therefore, the ultraviolet absorbance _RUVpacl after the flocculation treatment is calculated in the flocculant injection rate calculation unit 300 according to the following formulas (5) and (6) using the relationship in FIG. 4 (S301).

RUV _pacl = α × I _pacl + β... (5)
β=f(pH _F , UV _R , DOC _R , FL _R )...(6)
Therefore, the ultraviolet absorbance RUV _{p acl} after the aggregation treatment is expressed as the following function:

RUV _pacl = f(I _pacl , pH _F , UV _R , DOC _R , FL _R ) (6a)
Here, _Ipacl is the coagulant injection rate (mg/L), α is the injection rate constant (-), β is the intercept corresponding to _Ipacl = 0 (mg/L) in FIG. pH _F , the pH index of the pond; E260 _R , the ultraviolet absorbance (abs/cm) of the raw water at a wavelength of 260 (nm); DOC _R , the dissolved organic carbon concentration (mg/L); and FL _R, the fluorescence intensity of the raw water. The excitation wavelength and the fluorescence wavelength are preferably 300 (nm) to 350 (nm) and 400 (nm) to 450 (nm), respectively. In the embodiment, the excitation wavelength is 345 (nm) and the fluorescence wavelength is 425 (nm).

The combined treatment coefficient _FDOM shown in the above-mentioned formula (4) is a coefficient that indicates the combined treatment effect of the powdered activated carbon treatment and the coagulation treatment.

FIG. 5 is a diagram showing the relationship between the coagulant injection rate _Ipacl and the combined treatment coefficient _FDOM .

The results shown in Figure 5 were obtained through testing by the inventors. In this test, the powdered activated carbon treatment was performed by rapidly stirring at 150 rpm for 60 minutes, adjusting the pH to a specified value, adding coagulant P, rapidly stirring at 150 rpm for 10 minutes, and then slowly stirring at 80 rpm for 60 minutes.

As shown in the figure, the combined treatment coefficient _FDOM changes greatly depending on the mixing ratio of humic acid and fulvic acid in the added organic matter. When there is a large amount of humic acid, the ultraviolet absorbance remaining rate RUV _{car/p acl} of the combined treatment is smaller ( _FDOM < 1) than the product of the ultraviolet absorbance remaining rate RUV _car after treatment with powdered activated carbon alone and the ultraviolet absorbance remaining rate RUV _{p acl} after treatment with a coagulant alone (RUV _car ×RUV _{p acl} ), showing a combined treatment promoting effect. However, when the ratio of fulvic acid increases, the ultraviolet absorbance remaining rate RUV _{car/p acl} of the combined treatment becomes larger (FDOM ≥ 1) than (RUV _car ×RUV _{p acl} ), showing an inhibiting effect on the combined treatment.

In FIG. 5, if the relationship between the combined treatment coefficient _FDOM and the coagulant injection rate _Ipacl for each mixture ratio of humic acid and fulvic acid is approximated by the following formula (7), a different coefficient f and index n for each mixture ratio can be obtained.

F _DOM = f x I _pacl ⁿ ... (7)
Therefore, the relationship between the specific absorbance SUVA defined by the following formula (8), which is an index close to the mixture ratio of humic acid and fulvic acid in the dissolved organic matter in the raw water A, and the coefficient f was investigated. As a result, the relationship shown in FIG. Such a relationship is obtained (S202).

Figure 6 shows the relationship between the specific absorbance SUVA in the raw water and the coefficient f.

SUVA=E260 _g /DOC _R (abs・L/m・mg)...(8)
Here, E260R is the ultraviolet absorbance (abs/m) of raw water A at a wavelength of 260 (nm), and DOCR is the dissolved organic carbon concentration (mg/L) of raw water A.

The organic matter-compatible activated carbon injection rate calculation unit 203 uses the relationships in the above equations (3) to (8) to calculate the powdered activated carbon injection rate Icar-UV for soluble organic matter in the following procedure (S203).

In order to calculate the powdered activated carbon injection rate Icar-UV, the organic matter corresponding activated carbon injection rate calculation unit 203 first sets the target ultraviolet absorbance remaining rate RUV _T as RUV _car/pacl after the combined treatment with the powdered activated carbon and the coagulant, and calculates the ultraviolet absorbance remaining rate RUV _car after the powdered activated carbon treatment process using the following equations (9) and (10).

RUV _T = RUV _car/pacl = F _DOM × RUV _car × RUV _pacl ... (9)
RUV _car = RUV _T (F _DOM × RUV _pacl )...(10)
Next, the powdered activated carbon injection rate I _car-UV for soluble organic substances is calculated using the isothermal adsorption equation shown in the following formula (11).

I _car-UV = f(K _UV , RUV _car , E260 _R , DOC _R )...(11)
Here, _KUV is an adsorption constant that is determined by the performance of the powdered activated carbon and the properties of the substance to be adsorbed, and is set after being investigated in advance.

In this manner, the organic matter-compatible activated carbon injection rate calculation unit 203 calculates the soluble organic matter-compatible powdered activated carbon injection rate I _car-UV required to reduce the ultraviolet absorbance UVR of the raw water to UVD.

Next, the odorant removal effect is estimated when the powdered activated carbon injection rate I _car-UV for soluble organic substances calculated by the above formula (11) is set to the powdered activated carbon injection rate I _car .

FIG. 7 is a diagram showing the relationship between the powdered activated carbon injection rate I _car and the odorant concentration remaining rate RC _car after powdered activated carbon treatment.

FIG. 8 is a diagram showing the relationship between the coagulant injection rate _Ipacl and the odorant concentration residual rate RC _car/pacl in the combined treatment of powdered activated carbon and a coagulant.

Figures 7 and 8 are both results obtained from tests conducted by the inventors, with Figure 7 showing test results on the odorous substance removal characteristics of a single treatment with powdered activated carbon C, and Figure 8 showing test results on the odorous substance removal characteristics of a combined treatment with powdered activated carbon C and coagulant P.

The test was performed using 2-methylisoborneol, which is known as a mold odorous substance in raw water for tap water, as the odorous substance, and raw water to which humic acid and fulvic acid were further added as coexisting organic matter. FIG. 7 shows the relationship between the odorous substance concentration remaining rate RC _car and the powdered activated carbon injection rate I _{car after powdered activated carbon treatment with rapid stirring at a rotation speed of 150 (rpm) for 60 minutes, and FIG. 8 shows the relationship between the odorous substance concentration remaining rate RC car/pacl} and the coagulant injection rate I pacl after powdered activated carbon treatment with rapid stirring at a rotation speed of 150 (rpm) for 60 minutes, adjusting the pH to a specified value, adding coagulant _P , rapid stirring at a rotation speed of 150 (rpm) for 10 minutes, and slow stirring at a rotation speed of 80 ( _rpm ) for 60 minutes.

In Fig. 8, the odorant concentration remaining rate RC _car/pacl after powdered activated carbon treatment before coagulation treatment is shown on the y-axis of the coagulant injection rate _Ipacl = 0 (mg/L), but the odorant concentration remaining rate RC car/ _pacl after coagulation treatment is greater than the odorant concentration remaining rate RC _car after powdered activated carbon treatment. This suggests that the odorant once adsorbed in the powdered activated carbon treatment is released in the subsequent coagulation treatment process, and the higher the ratio of fulvic acid in the composition of the coexisting organic matter, the higher the release rate.

Based on the above results, the odorant concentration remaining rate after combined treatment estimating unit 204 estimates the odorant concentration remaining rate RC _car/pacl after combined treatment in which powdered activated carbon treatment and coagulation treatment are performed consecutively, using the powdered activated carbon injection rate I _car (mg/L), the coagulant injection rate I _pacl (mg/L), the ultraviolet absorbance E260 _R (abs/cm) of the raw water at a wavelength of 260 (nm) which is an index of coexisting organic matter, the soluble organic carbon concentration DOC _R (mg/L) of the raw water, the fluorescence intensity FL _R at 425 (nm) emitted by the excitation wavelength 345 (nm) to detect fulvic acid, and the hydrogen ion concentration index pH _F of the mixing tank (S204). Please refer to the following formula (12).

RC _car/pacl = f (I _car , I _pacl , E260 _R , DOC _R , FL _R , pH _F ) (12)
Next, as shown in FIG. 3 again, the data processing unit 200b calculates the odorant concentration remaining rate RC _car/pacl estimated in step S204 and the target odorant concentration remaining rate RC _T calculated in step S201. are compared (S205).

As a result of the comparison in step S205, when the odorant concentration residual rate RC _car/pacl is equal to or less than the target odorant concentration residual rate RC _T (S205: Yes), the data processing unit 200b sets the powdered activated carbon injection rate I _car to the powdered activated carbon injection rate I _car-UV required for removing soluble organic matter obtained in step S203, as shown in the following formula (13) (S206).

I _car = I _{car - UV} (mg/L)... (13)
On the other hand, if the comparison result in step S205 shows that the odorant concentration residual rate RC _car/pacl is greater than the target odorant concentration residual rate RC _T (S205: No), the odor-controlling activated carbon injection rate calculation unit 207 Thus, RC _T is substituted for RC _car/pacl in the following equation (13a), and the powdered activated carbon injection rate I _car-D required for odorous substance removal is calculated by back calculation (S207).

I _car−D = f(RC _T , RC _car/pacl , UV _R , DOC _R , I _pacl ) (13a)
Then, the data processing unit 200b sets the powdered activated carbon injection rate I _car to the powdered activated carbon injection rate I _car-D required for odorous substance removal, which was obtained in step S207 (S208).

Next, in the activated carbon injection rate determination unit 209, the larger of the powdered activated carbon injection rate I _car-D required for removing odorous substances and the powdered activated carbon injection rate I _car-UV required for removing soluble organic matter is determined as the powdered activated carbon injection rate for adsorption treatment (S209), and the powdered activated carbon injection device 21 is controlled at the determined powdered activated carbon injection rate I _car .

In the above explanation, the residual rate RUV of ultraviolet absorbance E260 at 260 (nm) is used as a representative index of soluble organic matter. However, since the calculation formula uses the soluble organic carbon concentration and the fluorescence intensity at a fluorescence wavelength of 425 (nm) relative to an excitation wavelength of 345 (nm), the residual rate RUV of ultraviolet absorbance E260 at 260 (nm) can be universally applied as a representative index of soluble organic matter even when the raw water varies or the water source is different.

In the above explanation, the calculation formula was derived based on the test results in Figures 7 and 8, in which 2-methylisoborneol was used as the odorant. However, it is possible to deal with other odors in the same way by understanding the relationship between the odor sensor output and the substance concentration in advance and using the conversion coefficient for 2-methylisoborneol.

Furthermore, in the above description, an example is described in which the soluble organic matter in the raw water is monitored by three types of instruments, the ultraviolet spectrometer 12a, the fluorescence intensity meter 12b, and the soluble organic carbon concentration (DOC) meter 12c, but the soluble organic carbon concentration DOC _R and the fluorescence intensity FL _R are expressed as linear functions of the ultraviolet absorbance E260 _R , as shown in the following formulas (14) and (15). Therefore, when there is little variation in the organic matter composition in the raw water in a single raw water system, it is possible to obtain values of other indicators with one representative instrument by using a single representative instrument, the ultraviolet spectrometer, and calculating the raw water organic carbon concentration DOC _R and the raw water fluorescence intensity FL _R from the obtained ultraviolet absorbance E260 _R according to the conversion formulas shown in the following formulas (14) and (15).

DOC _R = a x UV _R + b... (14)
FL _R =c×UV _R +d (15)
Where:
DOC _R : raw water organic carbon concentration (mg/L),
FL _R : raw water fluorescence intensity (-),
UV _R : raw water ultraviolet absorbance (abs/cm),
a: ultraviolet absorbance, soluble organic carbon concentration conversion coefficient,
b: ultraviolet absorbance, soluble organic carbon concentration conversion constant;
c: UV absorbance, fluorescence intensity conversion coefficient,
d: UV absorbance, fluorescence intensity conversion constant,
It is.

As described above, when the soluble organic matter and odorous substances adsorbed to the powdered activated carbon C are removed by capturing the powdered activated carbon C with the coagulant P, an appropriate and highly accurate evaluation can be performed by using the ultraviolet absorbance E260 at a wavelength of 260 nm as an evaluation index for the remaining state of the powdered activated carbon C. In other words, by evaluating the state of the powdered activated carbon C using the ultraviolet absorbance E260 and then determining the powdered activated carbon injection rate, a highly accurate powdered activated carbon injection rate that follows fluctuations in the water quality of the raw water can be determined, and soluble organic matter and odorous substances can be removed. As a result, it is also possible to prevent the soluble organic matter concentration and odorous substances in the filtered water from exceeding the target value due to insufficient injection of powdered activated carbon, and to prevent waste of chemical costs due to excessive injection.

As described above, in the water treatment system 1 to which the water treatment method of the first embodiment is applied, when both soluble organic matter and odorous substances are removed by using powdered activated carbon C and coagulant P in combination, a target odorous substance concentration residual rate RC _T , which is the ratio of the odorous substance concentration C _D after treatment to the odorous substance concentration C _R in the raw water (= C _D / C _R ), and a target ultraviolet light absorbance residual rate RUV _T , which is the ratio of the ultraviolet light absorbance UV _D after treatment to the raw water ultraviolet light absorbance UV _R (= UV _D / UV _R ) are calculated (S201).

In parallel, the coagulant injection rate Ipacl for achieving the target turbidity TU _D is calculated based on the target turbidity Tu _{D , the raw water turbidity Tu R ,} the raw water alkalinity Alk _R , the water temperature _{T R ,} the hydrogen ion concentration index pH _R , and the mixing basin hydrogen ion concentration index pH _F according to the above-mentioned formula (3) (S300).

Thereafter, the powdered activated carbon injection rate I _car-UV corresponding to the soluble organic matter is calculated from the relationships of the above-mentioned equations (3) to (10) and the isothermal adsorption equation f shown in the above-mentioned equation (11) (S203).

Next, the powdered activated carbon injection rate I _car-UV corresponding to soluble organic matter is set as the powdered activated carbon injection rate I _car , and the odorous substance concentration remaining rate RC car/pacl after combined treatment with powdered activated carbon and coagulant is calculated based on the coagulant injection rate _{I pacl ,} ultraviolet absorbance E260R, soluble organic carbon concentration DOC _R , fluorescence intensity FL _R , and mixing tank pH _F according to the above-mentioned formula (12) (S204).

Then, if the value of the odorant concentration residual rate after combined treatment RC _car/pacl is equal to or less than the value of the target odorant concentration residual rate RC _T (S205: Yes), the value of the powdered activated carbon injection rate I _car is set to the powdered activated carbon injection rate I _car-UV corresponding to soluble organic matter (S206).

On the other hand, if the odorant concentration residual rate after combined treatment RC _car/pacl is greater than the target odorant concentration residual rate RC _T (S205: No), the odorant-specific powdered activated carbon injection rate I _car-D is calculated according to the above-mentioned formula (13a) (S207), and the value of the powdered activated carbon injection rate I _car is set to the odorant-specific powdered activated carbon injection rate I _car-D (S208).

Then, of the powdered activated carbon injection rate I _car-D and the powdered activated carbon injection rate I _car-UV , the larger value is determined as the powdered activated carbon injection rate for the adsorption treatment (S209), and the powdered activated carbon injection device 21 can be controlled with the determined powdered activated carbon injection rate I _car .

In this way, according to the water treatment system to which the water treatment method of the first embodiment is applied, the injection rate I _car of the powdered activated carbon C can be controlled to an optimal value in response to changes in the water quality of the treated water by injecting the powdered activated carbon while taking into consideration the combined effect of the powdered activated carbon C and the coagulant P on the removal of soluble organic matter and odorous substances.

This prevents unnecessary injection of powdered activated carbon C, significantly reducing the amount of powdered activated carbon C that previously needed to be injected, while also avoiding the soluble organic matter concentration and odorous substances in the filtered water exceeding the target level due to insufficient injection of powdered activated carbon C, and the waste of chemical costs due to excessive injection, making it possible to achieve economical water treatment.

Second Embodiment
Next, a water treatment system to which the water treatment method of the second embodiment is applied will be described.

In this embodiment, the same parts as in the first embodiment are designated by the same reference numerals to avoid duplication of explanation.

Figure 9 is a block diagram showing an example of the configuration of the coagulant injection rate calculation unit in the water treatment system of the second embodiment.

The flocculant injection rate calculation unit 300 has a data receiving unit 300a, a data processing unit 300b, an odorant concentration residual rate estimation unit 302, a flocculant injection rate calculation unit 304, and a flocculant injection rate determination unit 306.

The data receiving unit 300a receives measurement data from the water quality meter set 10, the odor sensor 11, and the pH measuring instrument 14.

The data processing unit 300b receives the data received by the data receiving unit 300a from the data receiving unit 300a, and performs necessary data processing such as calculations using the received data, and also stores the results. The data stored in the data processing unit 300b in this way (the data from the data receiving unit 300a and the results of the data processing performed by the data processing unit 300b) can be used by the odor substance concentration residual rate estimation unit 302, the flocculant injection rate calculation unit 304, and the flocculant injection rate determination unit 306.

The results calculated by the odorant concentration remaining rate estimation unit 302, the flocculant injection rate calculation unit 304, and the flocculant injection rate determination unit 306 are also sent to the data processing unit 300b. As a result, the results calculated by the odorant concentration remaining rate estimation unit 302, the flocculant injection rate calculation unit 304, and the flocculant injection rate determination unit 306 are shared by the odorant concentration remaining rate estimation unit 302, the flocculant injection rate calculation unit 304, and the flocculant injection rate determination unit 306.

The odorant concentration residual rate estimation unit 302 calculates an odorant concentration residual rate estimate value RC _{car/ pacl} in the raw water A after the combined treatment with the powdered activated _carbon and the coagulant according to the _above -mentioned formula ( ₁₂ ) using the powdered activated carbon injection rate I _car , which is the injection rate of powdered activated carbon C injected into the raw water for the adsorption treatment of soluble organic matter, calculated based on the target odorant concentration residual rate RC _T (=C D /C _R ) obtained by dividing the target odorant concentration CD for the raw water in the coagulation and sedimentation treatment by the odorant concentration CR, the specific absorbance SUVA (=E260 _R /DOC _R ) obtained by dividing the ultraviolet absorbance E260 R by the soluble organic carbon concentration DOC R, and the coagulant injection rate I _pacl obtained according to the above-mentioned formula (3 ₎ .

When the odorant concentration residual rate estimated value RC _car/pacl is greater than the target odorant concentration residual rate RC _T , the flocculant injection rate calculation unit 304 calculates the flocculant injection _rate I _{pacl-D, which is the flocculant injection rate required to make the odorant concentration residual rate estimated value RC car/pacl coincide with the target odorant concentration residual rate RC T, using a preset odorant concentration residual rate characteristic prediction equation by combined processing (I pacl-D = f (} RC _T , RC _{car/pacl ,} UV R , DOC _R , I _car-UV )).

When the value of the flocculant injection rate _Ipacl is equal to or greater than the value of the flocculant injection rate _Ipacl-D ( _Ipacl-D ≦ _Ipacl ), the flocculant injection rate determination unit 306 determines the value of the flocculant injection rate _Ipacl as the flocculant injection rate in coagulation sedimentation, and conversely, when the value of the flocculant injection rate _Ipacl-D is greater than the flocculant injection rate _Ipacl ( _Ipacl-D > _Ipacl ), the flocculant injection rate determination unit 306 determines the value of the flocculant injection rate _Ipacl-D as the flocculant injection rate in coagulation sedimentation.

Next, we will explain an example of the operation of a water treatment system to which the water treatment method of the second embodiment configured as described above is applied.

Figure 10 is a diagram showing the process flow of a water treatment system to which the water treatment method of the second embodiment is applied.

The processing flow in this embodiment differs from that in the first embodiment in the response when odorous substance removal is insufficient at the soluble organic matter-compatible powdered activated carbon injection rate, but is otherwise the same, so in Figure 10, the same processing parts as in Figure 3 are given the same step numbers.

Therefore, the following will explain the differences from Figure 3.

In this embodiment, unlike the first embodiment, the powdered activated carbon injection device 21 is controlled by the powdered activated carbon injection rate Icar-UV corresponding to the soluble organic substances calculated in step S203.

In this embodiment, the odorant concentration residual rate estimation unit 302 calculates the odorant concentration residual rate estimation value RC _car/pacl in the raw water A after the powdered activated carbon C and the coagulant P are used in combination (S204a). The details of the calculation method are as described in step S204.

In addition, in this embodiment, unlike the first embodiment, if RCcar/pac _l is equal to or less than RCT in step S205 (S205: Yes), the coagulant injector 31 is controlled at the coagulant injection rate Ipac _l calculated in step S300 (S218: Yes, S219).

On the other hand, in step S205, if RCcar/pac _l is greater than RCT (S205: No), the flocculant injection rate calculation unit 304 calculates the flocculant injection rate Ipac _l- D corresponding to the odorant, where RCcar/pac _l coincides with the target odorant concentration remaining rate RCT, using the odorant concentration remaining rate characteristic prediction formula (Ipac _l-D = f (RC _T , RC _{car/pac l} , UV _R , DOC _R , I _car-UV )) by the combined treatment according to the relationship between the flocculant injection rate Ipac l and the odorant concentration remaining rate RCcar/pac _l after the combined treatment in Fig. 8 (S217). The calculated flocculant injection rate Ipac _l -D corresponding to the odorant is sent to _the data processing unit 300b and is held in the data processing unit 300b. The data processing unit 300b also holds the coagulant injection rate Ipac _l calculated in step S300.

After step S217, in step S218, the value of the flocculant injection rate Ipacl _- D corresponding to the odorant held in the data processing unit 300b is compared with the value of the flocculant injection rate _Ipacl by the flocculant injection rate determination unit 306. Then, if the value of the flocculant injection rate _Ipacl is equal to or greater than the value of the flocculant injection rate _Ipacl-D corresponding to the odorant (S218: Yes), the value of the flocculant injection rate _Ipacl is set as the flocculant injection rate in the coagulation sedation, and the flocculant injector 31 is controlled by the value of the flocculant injection rate _Ipacl (S219). On the other hand, if the flocculant injection rate Ipac _{- D} corresponding to the odorous substance is greater than the flocculant injection rate Ipac (S218: No), the value of the flocculant injection rate _Ipac-D corresponding to the odorous substance is set as the flocculant injection rate in coagulation sedimentation, and the flocculant injector 31 is controlled by the value of the flocculant injection rate _Ipac-D (S220).

As described above, according to the water treatment system to which the water treatment method of the second embodiment is applied, when the powdered activated carbon injection rate Icar-UV for soluble organic matter is insufficient to remove odorous substances, the injection rate of the relatively inexpensive coagulant P is increased without increasing the injection rate of the powdered activated carbon C, which has a high unit price, thereby reducing the residual odorous substance concentration rate, thereby making it possible to prevent excessive increases in chemical costs. In addition, since the injection rate of powdered activated carbon C can be minimized, it is possible to reduce the amount of sludge generated and also to prevent increases in its disposal costs.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

1. Water treatment system, 2. Water treatment equipment, 3. Water treatment facility, 10. Water quality meter set, 10a. Turbidity meter, 10b. Alkalinity meter, 10c. Water temperature meter, 10d. pH meter, 11. Odor sensor, 12. Dissolved organic matter indicator meter set, 12a. Ultraviolet absorbance meter, 12b. Fluorescence intensity meter, 12c. Dissolved organic carbon concentration (DOC) meter, 13. Flow meter, 14. pH meter, 15. Filtered water ultraviolet transmittance meter, 20 Receiving well, 21: powdered activated carbon injection device, 22: sodium hypochlorite injection device, 23: oxidant injection device, 30: coagulant mixing basin, 31: coagulant injection device, 32: agitator, 40: flocculation basin, 40a: mixing basin, 40b: mixing basin, 50: settling basin, 60: filtration basin, 60a: filtration layer, 61: alkaline agent injection device, 70: clear water basin, 71: sodium hypochlorite injection device, 72: alkaline agent injection Apparatus, 80... Tap water quality meter set, 80a... Turbidity/color sensor, 80b... Residual salt concentration sensor, 80c... pH sensor, 80d... Water temperature sensor, 91... Piping, 92... Piping, 100... Treated water quality target setting unit, 200, 200A... Activated carbon injection rate calculation unit, 200a... Data receiving unit, 200b... Data processing unit, 203... Organic matter corresponding activated carbon injection rate calculation unit, 204... Odor substance concentration remaining rate estimation unit after combined treatment, 204a... Odor substance concentration remaining rate estimation unit, 207... Odor-responsive activated carbon injection rate calculation unit, 209... Activated carbon injection rate determination unit, 230... Odor substance concentration remaining rate calculation unit, 230... Odor substance concentration remaining rate calculation unit, 240... Odor substance concentration remaining rate update unit, 300... Flocculant injection rate calculation unit, 300a... Data receiving unit, 300b... Data processing unit, 302... Odor substance concentration remaining rate estimation unit, 304... Flocculant injection rate calculation unit, 306... Flocculant injection rate determination unit

Claims (5)

A first flocculant injection rate calculation unit that calculates a first flocculant injection rate, which is an injection rate of a flocculant required for flocculation and precipitation of turbidity in the raw water, based on the water quality of the raw water;
an activated carbon injection rate calculation unit that calculates a first powdered activated carbon injection rate, which is an injection rate of powdered activated carbon required for removing odorous substances in the raw water, based on an odorous substance concentration in the raw water, at least one of an ultraviolet absorbance, a fluorescent intensity, and a dissolved organic carbon concentration in the raw water, and the first coagulant injection rate;
The activated carbon injection rate calculation unit
an odor-controlling activated carbon injection rate calculation unit that calculates a second powdered activated carbon injection rate, which is an injection rate of powdered activated carbon required for adsorption treatment of the odorant, based on a target odorant concentration remaining rate obtained by dividing a target odorant concentration for the raw water by the odorant concentration;
an organic matter-responsive activated carbon injection rate calculation unit that calculates a third powdered activated carbon injection rate, which is an injection rate of powdered activated carbon required for adsorption treatment of soluble organic matter in the raw water, based on a target ultraviolet absorbance remaining rate obtained by dividing a target ultraviolet absorbance for the raw water by the ultraviolet absorbance;
a first powdered activated carbon injection rate determining unit that determines a larger one of the second powdered activated carbon injection rate and the third powdered activated carbon injection rate as the first powdered activated carbon injection rate . A first flocculant injection rate calculation unit that calculates a first flocculant injection rate, which is an injection rate of a flocculant required for flocculation and precipitation of turbidity in the raw water, based on the water quality of the raw water;
an activated carbon injection rate calculation unit that calculates a first powdered activated carbon injection rate, which is an injection rate of powdered activated carbon required for removing odorous substances in the raw water, based on an odorous substance concentration in the raw water, at least one of an ultraviolet absorbance, a fluorescent intensity, and a dissolved organic carbon concentration in the raw water, and the first coagulant injection rate;
The first coagulant injection rate calculation unit is
an odorant concentration remaining rate estimating unit that calculates an odorant concentration remaining rate estimate value in the raw water after the powdered activated carbon and the flocculant are treated in combination based on at least the ultraviolet absorbance, the dissolved organic carbon concentration, and the first flocculant injection rate;
a second flocculant injection rate calculation unit that calculates a second flocculant injection rate, which is a flocculant injection rate required to make the odorant concentration remaining rate estimate value coincide with the target odorant concentration remaining rate when the odorant concentration remaining rate estimate value is greater than the target odorant concentration remaining rate obtained by dividing the target odorant concentration for the raw water by the odorant concentration;
a flocculant injection rate determination unit that determines the first flocculant injection rate as the flocculant injection rate when the value of the first flocculant injection rate is equal to or greater than the value of the second flocculant injection rate, and determines the second flocculant injection rate as the flocculant injection rate when the value of the second flocculant injection rate is greater than the first flocculant injection rate . A first flocculant injection rate calculation unit that calculates a first flocculant injection rate, which is an injection rate of a flocculant required for coagulation and precipitation of turbidity in the raw water, based on the water quality of the raw water;
an activated carbon injection rate calculation unit that calculates a first powdered activated carbon injection rate, which is an injection rate of powdered activated carbon required for removing odorous substances in the raw water, based on an odorous substance concentration in the raw water, at least one of an ultraviolet absorbance, a fluorescent intensity, and a dissolved organic carbon concentration in the raw water, and the first coagulant injection rate;
The activated carbon injection rate calculation unit
an organic matter-specific activated carbon injection rate calculation unit that calculates a third powdered activated carbon injection rate for soluble organic matter required to reduce the ultraviolet absorbance of the raw water to a target ultraviolet absorbance based on at least the ultraviolet absorbance and the soluble organic carbon concentration;
an odorant concentration remaining rate estimating unit that calculates an odorant concentration remaining rate estimate value in the raw water after the powdered activated carbon and the flocculant are treated in combination based on at least the ultraviolet absorbance, the dissolved organic carbon concentration, and the first flocculant injection rate;
a data processing unit that compares a target odorant concentration remaining rate obtained by dividing a target odorant concentration for the raw water by the odorant concentration with the odorant concentration remaining rate estimate, and sets the third powdered activated carbon injection rate to the first powdered activated carbon injection rate when the odorant concentration remaining rate estimate is equal to or lower than the target odorant concentration remaining rate;
an activated carbon injection rate calculation unit that calculates a second powdered activated carbon injection rate required for odorant removal based on the odorant concentration residual rate estimation value and the target odorant concentration residual rate when the odorant concentration residual rate estimation value is greater than the target odorant concentration residual rate;
and an activated carbon injection rate determination unit that determines the larger of the second powdered activated carbon injection rate and the third powdered activated carbon injection rate as the powdered activated carbon injection rate for adsorption treatment of the odorous substances. The water treatment system according to claim 1 , wherein the dissolved organic carbon concentration and the fluorescence intensity are expressed as linear functions of the ultraviolet absorbance. Calculating a first flocculant injection rate, which is an injection rate of a flocculant required for coagulation and precipitation of turbidity in the raw water, based on the water quality of the raw water;
Calculating a first powdered activated carbon injection rate, which is an injection rate of powdered activated carbon required for removing odorous substances in the raw water, based on the odorous substance concentration in the raw water, at least one of the ultraviolet absorbance, the fluorescent intensity, and the dissolved organic carbon concentration in the raw water, and the first coagulant injection rate;
Calculating the first powdered activated carbon injection rate comprises:
Calculating a second powdered activated carbon injection rate, which is an injection rate of powdered activated carbon necessary for adsorption treatment of the odorant, based on a target odorant concentration remaining rate obtained by dividing the target odorant concentration for the raw water by the odorant concentration;
Calculating a third powdered activated carbon injection rate, which is an injection rate of powdered activated carbon necessary for adsorption treatment of soluble organic matter in the raw water, based on a target ultraviolet absorbance remaining rate obtained by dividing a target ultraviolet absorbance for the raw water by the ultraviolet absorbance;
determining, as the first powdered activated carbon injection rate, one of the second powdered activated carbon injection rate and the third powdered activated carbon injection rate, which has a larger value .