JP2969927B2 - Water treatment control device - Google Patents

Description

The present invention relates to activated carbon injection control in a water treatment apparatus.

B. Summary of the Invention According to the present invention, a treated water photographing machine is installed in a sedimentation basin, and the average particle size and the pulverized coal per unit amount in the treated water are determined based on image information from the treated water photographing machine. At the same time, these amounts are guided to an arithmetic processing unit as a feedback signal, and the activated carbon injection amount is controlled based on the arithmetic signal, thereby increasing control accuracy and reducing control delay time.

C. Conventional technology At present, water purification plants are subject to significant pollution of rivers, lakes and marshes.
The generation of chromaticity, odor, etc. in the raw water is difficult, and as a countermeasure, a method of injecting and removing powdered activated carbon is generally used.

Determining the injection rate of powdered activated carbon is very difficult. The reason is that not only the substance to be removed but also other substances are adsorbed at the same time, so it cannot be determined from the ability experimentally obtained using a single substance, and the mixing contact conditions which are a major influencing factor for adsorption And the contact time cannot be the same as the actual scale.

Therefore, in practice, raw water for the purpose of treatment is used, powder activated carbon is added thereto at various injection rates, and a jar test is performed.

Also, the longer the mixing and contacting time, the better. However, in the existing water treatment plant, it is far from short in terms of site and power. Therefore, there are various restrictions when applying to existing water treatment plants.

D. Problems to be Solved by the Invention In order to obtain a sufficient contact time, the injection site is important. Some water treatment plants adopt a method of injecting water at the water intake point and making contact while flowing down the waterway along the way to prolong the contact time.However, such conditions are rarely obtained. Usually, it is injected during the appropriate process in the water treatment plant. At present, the injection points of powdered activated carbon generally available in water treatment plants are as follows.

(1) Landing well and rapid mixing pond (2) Floc formation pond entrance (3) Settlement pond exit and filtration pond entrance. However, in the landing well and the rapid mixing pond of (1), there is a risk that the contact efficiency is reduced because the powdered activated carbon is injected at the same time as the coagulant or the pre-chlorination treatment.
At the entrance of the floc formation pond in (2), since the reaction between the flocculant and the turbidity is almost completed in the stage (1), there is a risk that pulverized coal which cannot be coagulated flows out and passes through the filtration pond. At the outlet of the settling basin and the inlet of the filtration basin of (3), the activated carbon powder accumulates in the sand layer, so that the filtration speed is rapidly reduced, and there is a risk that pulverized coal may pass through.

As mentioned above, although there are various problems at the time of powdered activated carbon injection in actual water treatment plants, most of them do not implement feedback control (FB) by feedforward (FF) control.

The present invention has been made in view of the above points, and an object of the present invention is to solve various problems in water treatment by performing feedback control during powder activated carbon injection control.

E. Means for Solving the Problems The present invention provides, in order to achieve the above object, a landing well for entering treated water, and a mixing pond for adding and mixing a coagulant into treated water supplied from the landing well. A floc forming pond that forms flocs by stirring the treated water from the mixing pond; and a sedimentation pond that precipitates the flocs. A method for controlling the turbidity of the treated water flowing out of the sedimentation basin to a set turbidity of the treated water, wherein the injected turbidity is based on a treated water photographing machine installed in the sedimentation pond and image information from the treated water photographing machine. The fine pulverized coal in which the activated carbon was not agglomerated or adsorbed was identified, and the particle size distribution of the pulverized coal in the treated water was determined. From the particle size distribution, the average particle size of pulverized coal and the amount of pulverized coal per unit volume Pulverized coal measuring unit An arithmetic processing unit that calculates the predicted runoff turbidity of the settling basin from the amount of pulverized coal per unit amount from the pulverized coal measurement unit, and compares the set runoff turbidity with the predicted runoff turbidity. And an activated carbon injection controller for controlling the amount of activated carbon to be injected based on the activated carbon.

F. Action A fine pulverized coal particle size distribution in which activated carbon was not agglomerated or adsorbed was determined based on image information from the treated water photographing machine installed in the sedimentation basin. The average particle size and the amount of pulverized coal per unit amount are obtained, and the amount of pulverized coal per unit amount is led to an arithmetic processing unit as a feedback signal to calculate a predicted turbidity of the runoff. Control the inflow.

G. Embodiment An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of an activated carbon injection control device of a water treatment apparatus according to an embodiment of the present invention, wherein 1 is a landing well for receiving treated water, and 2 is a coagulant injected into treated water supplied from the landing well. 3 is a floc forming pond for forming flocs, 4 is a sedimentation pond for sedimenting flocs 6, and 5 is a filtration pond. Activated carbon is injected into the landing well 1, the mixing pond 2 or the floc forming pond 3. A flocculant is mixed into the mixing pond 2 from a flocculant controller (not shown). 7
Is a stirrer rotationally driven by a motor 8, and 10 is a motor for rotating the paddle 9, and the motor 10 is controlled by a rotation speed controller (not shown) based on a measurement signal of a floc measuring device (not shown). The rotation is controlled.

For example, an underwater camera 11 which is also used as a floc measuring device (not shown) is provided at an entrance (in the vicinity of the rectifying wall) in the sedimentation basin 4. The installation site of the underwater camera 11 is not limited to the entrance of the sedimentation basin, but may be any position where image processing by the underwater camera can be performed. As a back screen of the underwater camera 11, a white board is used.

Reference numeral 12 denotes a pulverized coal measuring device, which processes an image from the underwater camera 11 to identify pulverized coal, performs statistical processing to create various data on pulverized coal, and inputs the data to the arithmetic processing unit 13. . Numeral 13 denotes an arithmetic processing unit which comprises an arithmetic computer or the like, executes a required arithmetic processing based on various data from the pulverized coal measuring device 12 and gives an operation instruction to the activated carbon injection device 14. The activated carbon injection device 14 appropriately injects activated carbon into the landing well 1, the mixing pond 2 and the floc forming pond 3 based on a command from the arithmetic processing unit 13.

In the floc formation pond 3, sedimentation, activated carbon, etc. are mixed at a high density, so that it is very difficult to recognize pulverized coal due to the effects of particles overlapping and stirring, etc. It was installed near the water surface at the entrance. The underwater camera detection unit can use the one used for the flock measurement device, and replaces the back screen, which is the background of the camera, from the black board to the white board. The reason was considered that the activated carbon was black, and that pulverized coal was clearly projected to facilitate image processing.

In the image measurement processing flow, the average particle size and the amount of pulverized coal (volume of tens of microns of pulverized coal per unit volume) are obtained by binarizing the background into white and pulverized coal into black, contrary to the floc measuring device. Is measured. FIG. 2 shows the measurement results.
The histogram is obtained by plotting the volume amount (product of the particle volume and the number corresponding to the classified diameter on the horizontal axis) on the vertical axis and the particle diameter every 100 microns on the horizontal axis. In this histogram, a threshold is set at a boundary of 300 microns, which is at risk of flowing out of the sedimentation basin, and the number of particles less than 300 microns and the total volume are output. The setting of the threshold value is given from a surface area load factor which is an index for evaluating how much particles can be removed when the particles flow into the sedimentation basin 5.

Specifically, as shown in equation (1), the surface area load factor is an index of the minimum particles that can be removed 100% in the sedimentation basin by dividing the flow rate (Q) flowing into the sedimentation basin by the surface area of the sedimentation basin.

WO = Q / A (1) where, WO: surface area load factor (cm / sec) Q: sedimentation tank inflow (cm ³ / sec) A: sedimentation tank surface area (cm ³ )

That is, equation (1) is a basic value that gives the removal rate of the sedimentation velocity W (cm / sec) of single particles smaller than the surface area loading rate (WO).

 It can be removed by the ratio of W <WO.

 W ≧ WO: 100% can always be removed.

Generally, the flow velocity of the chemical sedimentation basin is 0.66 cm / sec or less, and that of the slant plate sedimentation basin is 1.0 cm / sec or less. It is possible that floc particles of up to 200 microns may flow out. In fact, it is possible to apply this principle directly to pulverized coal particles by confirming a high correlation between the turbidity of the sedimentation basin and the floc diameter. This is because powdered activated carbon always passes through the floc agglomeration process, and is considered to have substantially the same characteristics (effective density and the like) as fine floc.

(1) Pulverized coal amount per unit volume in image measurement Here, Mg: amount of pulverized coal (g /), X: volume of floc by series from 50 to 300μ (cm ³ ), Gc: number of measurement screens, Gs: capacity of screen viewing range (), ρE2: average fine powder Charcoal density (150μm
Is 0.074 g / cm ³ ).

(2) Predicted outflow turbidity of sedimentation basin obtained from image measurement T _TB = Mg · {1- (AVEWG / WO)} × 1000 (3) where, T _TB : predicted outflow turbidity of sedimentation basin (mg /), Mg: Pulverized coal amount (g /), AVEWG: Sedimentation speed of average pulverized coal diameter (150
μm sedimentation velocity = 0.04 cm / sec), WO: surface load rate (cm / sec) during image measurement.

Example 1, Mg = 0.00457, AVEWG = 0.0 in actual image measurement
4, When WO = 0.05 Predicted runoff turbidity = 0.00457 · {1- (0.04 / 0.05)] · 1000 = 0.914 mg / Example-2, Mg = 0.0004 in actual image measurement, AVEWG = 0.0
4, When WO = 0.05 Predicted runoff turbidity = 0.0004 • {1- (0.04 / 0.05)} • 1000 = 0.1mg /

The results show that the predicted turbidity of runoff from the sedimentation basin changes significantly depending on the amount of pulverized coal (Mg). Furthermore, it was confirmed that the predicted runoff turbidity had a considerably high correlation with the measured runoff turbidity after the residence time of the sedimentation basin.

(3) Feedback control of injection amount of powdered activated carbon (slurry is also possible) In this control, predicted runoff turbidity (T _TB ) calculated from pulverized coal amount obtained by image measurement and set runoff turbidity (TB _SET threshold) , The amount of powdered activated carbon to be injected is determined, and the correction term of the injection rate formula is increased or decreased. Table 1 shows the criteria.

If the difference between the set value and the image measurement value is large based on the three judgments, the injection amount is significantly reduced to TB _SET << T _TB .

The point of this judgment is the characteristic amount of pulverized coal particles (pulverized coal amount of 50 to 300 microns) based on image information obtained from the underwater camera 11 installed at the entrance of the sedimentation basin 4 (near the rectifying wall).
And predict the runoff turbidity (T _TB ) of the sedimentation basin. Judgment is made from the predicted outflow turbidity and a preset turbidity to perform feedback control.

[Reason for control]

The measured pulverized coal amount tended to increase, and as a result, information with a high predicted turbidity was obtained. Therefore, the injection amount of powdered activated carbon is reduced.

The measured amount of pulverized coal had a tendency to decrease, and as a result, information that the predicted turbidity was lower than the set value was obtained. Therefore,
Increase the amount of powdered activated carbon injected.

 Consider the contact efficiency and maintain the status quo.

Substituting the above criteria feedforward coagulant injection amount (4) the correction term of equation becomes _{D = a · Q ± B x} (TB DIFF) ...... (4).

Here, D: powder activated carbon injection amount formula (mg / or g / m ³ ),
Q: Water intake (m ³ / h), a: Coefficient, B _x : Correction term pulverized coal increase / decrease ratio, TB _DIFF : Difference in runoff turbidity.

Feed forward injection type D = a · Q, constant injection,
Feedback control is performed based on the difference between the predicted turbidity and the set turbidity obtained by calculating the correction term ± B _x (pulverized coal increase / decrease ratio) from the image measurement.

As described above, the feedback control of the amount of powdered activated carbon injected using the image processing technology is possible in consideration of the clogging of the filtration pond or the like with the pulverized coal using the powdered activated carbon injection amount (1) capable of feedback control. is there. Furthermore, the feedback control by image measurement is basically performed by sampling control (at intervals of about 10 to 30 minutes), and based on the amount of pulverized coal (Mg) of the equation (2) obtained at the time of image measurement, the predicted outflow turbidity ( 3) The equation is calculated, and the predicted value is compared with a preset turbidity value (upper limit value) to determine the activated carbon powder injection amount.

According to the present embodiment, unremovable pulverized coal is detected at the entrance of the settling basin at the stage of terminating the contact between the substance to be removed and the activated carbon powder. In addition, a criterion for controlling the coagulant injection rate is determined from the amount of pulverized coal (below the threshold of 300 microns) obtained from the image measurement and the predicted turbidity of the outflow.

H. Effects of the Invention As described above, in the water treatment control device according to the present invention, the amount of pulverized coal per unit amount is obtained from the image information in the sedimentation basin, and the predicted runoff turbidity in the sedimentation basin is calculated from the amount of pulverized coal. Then, the injection amount of the activated carbon powder is controlled using the predicted flow turbidity as a feedback control factor.

Therefore, there is an advantage that it is possible to derive the amount of pulverized coal (Mg) and the predicted turbidity of runoff (T _TB ) from the information from the underwater camera in the sedimentation basin.

Conventionally, the turbidity of runoff from the sedimentation basin is measured using a turbidity meter.
Took two to three hours. In this control, unremovable pulverized coal is detected at a predetermined position in the sedimentation basin at the stage when the contact between the removal target substance and the powdered activated carbon is completed. Further, there is an advantage that the delay time of the feedback control can be reduced to 30 to 60 minutes.

In addition, the criterion for controlling the coagulant injection rate can be determined from the amount of pulverized coal obtained from the image measurement and the estimated turbidity of the runoff, and the criterion can be further subdivided by changing the difference interval between the set value and the image measurement value. There are advantages that can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a powdered activated carbon injection control device of a water treatment apparatus according to an embodiment of the present invention, and FIG. 2 is a distribution diagram of an average particle size of pulverized coal. 1 ... landing well, 2 ... mixing pond, 3 ... floc formation pond,
4 ... sedimentation basin, 5 ... filtration basin, 7 ... stirrer, 8 ... motor, 9 ... paddle, 10 ... motor, 11 ... underwater camera, 12 ... pulverized coal measuring device, 13 ... Arithmetic computer,
14 ... Activated carbon injection device.

Continuation of the front page (56) References JP-A-2-218408 (JP, A) JP-A-1-199608 (JP, A) JP-A-64-15107 (JP, A) JP-A-63-218217 (JP) JP-A-62-250919 (JP, A) JP-A-62-214331 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 1/28 B01D 21/30

Claims (3)

(57) [Claims] 1. A landing well for receiving treated water, a mixing pond for introducing and mixing a flocculant into treated water supplied from the landing well,
A flocculation pond for forming flocs by stirring the treated water from the mixing pond; and a sedimentation pond for sedimentation of the flocs. A method for controlling the turbidity of treated water flowing out of a pond to a set turbidity of treated water, comprising: a treated water photographing machine installed in the sedimentation pond; and the injected activated carbon based on image information from the treated water photographing machine. Identify fine pulverized coal that has not been agglomerated or adsorbed, determine the particle size distribution of pulverized coal in the treated water, and determine the average particle size of pulverized coal and the amount of pulverized coal per unit volume from this particle size distribution. A pulverized coal measurement unit, an arithmetic processing unit that calculates a predicted outflow turbidity of the settling basin from the amount of pulverized coal per unit amount from the pulverized coal measurement unit, and compares the set outflow turbidity and the predicted outflow turbidity. , These comparisons A water treatment control device, comprising: an activated carbon injection control unit that controls an injection amount of activated carbon based on a result. 2. The apparatus according to claim 1, wherein said treated water photographing machine is installed at an entrance in said sedimentation basin.
The water treatment control device according to Item. 3. The water treatment according to claim 1, wherein a criterion for controlling the coagulant injection is determined from the amount of pulverized coal per unit volume and the predicted turbidity of the settling basin. Control device.