JP4400721B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment system that injects a flocculant to remove suspensions and / or lysates in raw water.

  In irrigation water treatment and wastewater treatment, an inorganic or organic flocculant is injected into the raw water to be treated to agglomerate the suspension or dissolved matter contained in the raw water and removed as agglomerated floc. . At this time, after the suspension in the flocculation process is guided to a measurement tank and subjected to solid-liquid separation using means such as subsidence and filtration, the turbidity of the treated water is measured, or a turbidimeter is used. It is used to measure the treatment water turbidity after solid-liquid separation and control the injection amount of the flocculant (see, for example, Patent Document 1).

On the other hand, the present inventors irradiate laser light into a solid-liquid mixed suspension in which aggregated flocs are formed, and scattered light generated by the collision of the laser light with the suspension in the suspension. Is detected in a very small measurement region, and the scattered light components due to the aggregates (floc) and non-aggregates are distinguished from each other so that the state of the particles in the suspension can be accurately detected. It was proposed to control the injection of the flocculant into the raw water based on the output of the sensor (see, for example, Patent Document 2).
JP-A-7-204412 JP 2002-257715 A

  However, in the method of measuring the treatment water turbidity after coagulation treatment and solid-liquid separation and controlling the injection amount of the flocculant, there is a time delay between the injection position of the flocculant and the measurement position of the treatment water turbidity. Large, unable to cope with rapid fluctuations in raw water quality. In addition, when measuring the turbidity of treated water that has undergone solid-liquid separation treatment, even if the coagulation treatment itself is good, solid-liquid separation is caused by floc leaks due to a decrease in sedimentation rate due to an increase in the amount of treated water and an increase in the interface. Turbidity of treated water after treatment may increase. Therefore, there is a problem that it is difficult to distinguish between an increase in turbidity due to an increase in the amount of treated water and an increase in turbidity due to poor aggregation. Furthermore, as described above, in order to separate the suspension into solid and liquid using the measuring tank, it is unavoidable that equipment and time are lost, and that it is impossible to quickly cope with fluctuations in the quality of raw water. There's a problem.

  The present invention has been made in view of such circumstances. The purpose of the present invention is to eliminate fluctuations in water quality due to the injection of the flocculant when the flocculant is injected to remove the suspension and / or dissolved matter in the raw water. Water treatment that can distinguish and detect other water quality fluctuation factors such as the amount of treated water and changes in pH, for example, and can control the injection of the flocculant appropriately and quickly based on the detection result To provide a system.

In order to achieve the above-described object, a water treatment system according to the present invention includes a flocculation reaction tank for injecting a flocculant into raw water to agglomerate a suspension and / or a dissolved material in the raw water, and the flocculation reaction tank. A solid-liquid separation device such as a precipitation tank that obtains treated water from which the suspended suspension and / or dissolved matter has been removed by subjecting the discharged suspension to solid-liquid separation,
The suspension and / or turbidity is measured by measuring a floc formation state and turbidity in the suspension provided in a suspension supply path from the aggregation reaction tank or the aggregation reaction tank to the solid-liquid separation device. Or an aggregation state measuring means for detecting the aggregation state of the lysate;
A water quality evaluation means, such as a turbidimeter, which is provided in a discharge path of the treated water from the solid-liquid separation device and measures the floc formation state and turbidity in the treated water to evaluate the quality of the treated water; ,
By referring to a database that preliminarily organizes and stores changes in the state of suspension and treated water according to their factors, the state of aggregation of the suspension and / or dissolved matter obtained by the aggregation state measuring means and the water quality evaluation means ; and a factor determining means for determining the cause of quality variations in the treated water in accordance with a combination of the quality of the treated water obtained by,
The aggregation state measuring unit and the water quality evaluating unit detect scattered light in a minute region of the laser light irradiated into the measurement target water, and measure floc formation state and turbidity in the measurement target water. It consists of an aggregation sensor as shown in
The factor determination means responds to the water quality fluctuation factor in advance based on the fact that the floc formation state and / or the relative relationship between the turbidity obtained by each of the agglomeration sensors exhibits a behavior unique to the water quality fluctuation factor. In addition, referring to a database in which the state of floc formation and turbidity in the suspension and treated water are registered, the water quality fluctuation caused by the injection of the flocculant and other water quality fluctuation factors such as the amount of treated water are distinguished. <br/> It is characterized by that.

  That is, the water treatment system according to the present invention pays attention to the fact that the cause of the water quality fluctuation of the treated water is caused not only by the amount of flocculant injected but also by the amount of treated water and pH, etc. Detects the state of liquid aggregation (turbidity, floc particle size, number of flocs, etc.), and also detects the quality of water (turbidity, etc.) of the treated water obtained by subjecting the above suspension to solid-liquid separation. By comparing each other and examining the correlation, it is determined whether the water quality fluctuation due to the treated water is due to inappropriate injection of the flocculant or due to factors other than the flocculant such as changes in the amount of treated water It is characterized by doing so.

Further, in the water treatment system according to the present invention, when the determination result by the factor determination means is a change in water quality due to the injection of the flocculant, the floc formation state obtained by each of the flocculant sensors and / or It is preferable to provide control means for optimizing and controlling the injection amount of the flocculant according to the turbidity of the liquid layer and prohibiting the injection amount control of the flocculant in the case of water quality fluctuations other than the injection of the flocculant . Specifically, the injection amount is optimized and controlled only when the water quality fluctuation is caused by the injection of the flocculant, and if it is a factor other than the flocculant, the alarm output, sludge extraction amount control, and pH control are performed. By taking measures such as these, the injection amount of the flocculant, which is a basic control target, is not changed unintentionally.

  According to the water treatment system configured as described above, not only the state of aggregation of the suspension in the aggregation reaction tank, but also the quality of the treated water obtained by subjecting the suspension to solid-liquid separation treatment is detected. By comparing the turbidity and flock status of the treated water, the relative relationship between the detection information that varies depending on the cause of the water quality fluctuation may be caused by the excess or deficiency of the flocculant injection amount, It can be easily distinguished and determined whether it is a factor other than the injection amount of the flocculant. Therefore, the injection amount can be appropriately controlled only when the water quality changes due to the excessive or insufficient amount of the flocculant injection.

  Specifically, it is possible to determine whether the increase in turbidity of the treated water is due to poor aggregation due to the amount of flocculant injected or due to floc leaks, etc. From the increasing tendency of the turbidity of the treated water, it is possible to specify the factor of the increase in turbidity. Therefore, it is possible to perform appropriate water treatment control according to the cause of water quality fluctuation.

Hereinafter, a water treatment system according to an embodiment of the present invention will be described with reference to the drawings, taking a coagulation sedimentation process as an example.
FIG. 1 is a schematic configuration diagram of a water treatment system that performs coagulation / sedimentation treatment on water / drainage (treated water), and 1 accepts raw water (treated water) and uses a flocculant injected into the raw water. This is an agglomeration reaction tank for agglomerating flocs by aggregating suspensions and dissolved substances contained in raw water. Reference numeral 2 denotes a sedimentation tank (solid-liquid separation device) that obtains treated water obtained by subjecting the suspension introduced from the agglomeration reaction tank 1 to precipitation treatment and solid-liquid separation.

  The injection of, for example, the inorganic flocculant A into the raw water is performed via the pump 4 under the control of the chemical injection control device 3 composed of a computer with respect to the raw water supply water system to the agglomeration reaction tank 1. Further, the pH adjusting agent B is injected into the aggregation reaction tank 1 through a pump 5. The injection of the pH adjusting agent B by the pump 5 is performed based on the pH value of the suspension measured by the pH meter 6 provided in the aggregation reaction tank 1 under the control of the pH controller 7. To be done. In addition, a polymer flocculant C is appropriately injected into the suspension guided from the agglomeration reaction tank 1 to the precipitation tank 2 via a pump 8.

  Basically, in the water treatment system configured to include the agglomeration reaction tank 1 and the precipitation tank 2 described above, the water treatment system according to the present invention is characterized in that the agglomeration reaction tank 1 agglomerates the suspension. A first agglomeration sensor 11 is provided as an agglomeration state measuring means for detecting a state, and a second agglomeration sensor 12 is provided as a water quality evaluation means for evaluating the quality of the treated water on the outlet side of the settling tank 2, This is because the information (turbidity and floc formation state) detected by each of these aggregation sensors 11 and 12 is taken into the drug injection control device 3.

  The agglomeration sensors 11 and 12 are introduced in detail in the above-mentioned Patent Document 2, but briefly described. For example, as shown in FIG. 2, a light projecting unit and a light receiving unit are arranged close to each other to be measured. A probe 13 provided in water (sample water), a light emitting unit 14 that irradiates laser light amplitude-modulated (AM-modulated) into the sample water via the probe 13, and collision of the laser beam with particles in the sample water And a detector 15 for detecting the turbidity and flock formation state of the measurement target water by detecting the scattered light generated by the above-described probe 13. In particular, in the detection unit 15, only the frequency component F that has been amplitude-modulated from the output of the photoelectric converter that generates an electric signal corresponding to the amount of received light (the received light intensity) of the scattered light S through the band-pass filter (BPF). After extraction, the amplitude modulation frequency component is detected and the envelope component E is obtained.

  Considering the scattered light generated in the minute region S irradiated with the laser light in this way, the intensity of the scattered light generated by the minute colloidal particles made of the suspended material in this region S is equal to the number of the minute colloidal particles. Increase proportionally. The number of microcolloid particles decreases as the aggregation progresses and flocs having a large particle diameter are generated. On the other hand, since flocs are formed by agglomerating fine colloidal particles, the number increases as the agglomeration proceeds, but the number is much smaller than that of fine colloidal particles. Therefore, the possibility that the flock exists in the above-described minute region S is low, and only enters the minute region S temporarily. However, the frequency at which the floc enters the minute region S increases as the number of flocs increases with the progress of aggregation.

  Therefore, when the intensity of the scattered light in the minute region S is measured as described above, the aggregation of suspended substances in the test water proceeds, the number of minute colloidal particles decreases, and the number of flocs gradually increases in the minute region S. Although the intensity of the scattered light may temporarily increase due to the flocs, it generally decreases. Therefore, except for the case where the scattered light intensity is temporarily increased due to the presence of flocs, if we focus on the intensity of the scattered light, the scattered light intensity at that time is an unaggregated colloid that is not flocked. It can be regarded as indicating the number of particles. Moreover, if the minimum value of the envelope component according to the intensity of the scattered light described above is detected, the number of unaggregated colloidal particles in the test water can be obtained. Furthermore, if attention is paid to the period in which the intensity of scattered light temporarily increases due to flocs, the number of flocs generated by aggregation (the density of flocs in the test water) can be obtained, and the temporary scattered light intensity is increased. From this, the particle diameter of the floc can be obtained.

Now, the above-mentioned chemical injection control device 3 for inputting the aggregation state of the suspension detected by using the aggregation sensors 11 and 12 and the water quality information of the treated water respectively processes the processing by performing information processing as follows. Monitor the water quality and, if there is a change in water quality, find the cause of the change.
<Normal>
When the coagulation sedimentation process is normally performed, the floc in the coagulation reaction tank 1 grows by taking in the suspended components in the raw water. Therefore, the turbidity of the liquid phase from which the aggregated floc has been removed (turbidity due to unaggregated colloidal particles or the like) is in the lowest state. At this time, out of the floc information and turbidity detected through the aggregation sensors 11 and 12 respectively, the turbidity of the suspension detected through the first aggregation sensor 11, in particular, the influence of the floc has not been eliminated. Turbidity due to agglomerated colloidal particles is the lowest value. Further, the information detected via the first aggregation sensor 11 includes a lot of information about the grown floc, so that the intensity of scattered light temporarily increased due to the floc described above.

On the other hand, the turbidity of the treated water obtained through the second aggregation sensor 12 is sufficiently low when the aggregation process and the solid-liquid separation process are performed efficiently. Further, if no floc leak occurs, temporarily high scattered light due to the floc cannot be detected. That is, when the agglomeration process and the solid-liquid separation process are normally performed, floc growth (formation) in the agglomeration reaction tank 1 and solid-liquid separation (removal of the agglomeration floc) in the precipitation tank 2 are performed. Since it is performed satisfactorily, the turbidity detected by the first and second aggregation sensors 11 and 12 is the lowest value. The temporarily high scattered light due to the flocs becomes large in the first aggregation sensor 11 and is hardly detected by the second aggregation sensor 12.
<Insufficient aggregation chemical solution>
On the other hand, when the injection amount of the inorganic flocculant is insufficient, floc formation in the agglomeration reaction tank 1 becomes immature. As a result, the flocs are reduced, so that the scattered light intensity is temporarily reduced due to the aforementioned flocs. In addition, since suspended substances that are not taken into flocs increase in the liquid, the turbidity of the suspension, particularly turbidity due to unaggregated colloidal particles that eliminate the influence of flocs, increases. Therefore, the change in the information detected by the first aggregation sensor 11 is monitored, and the scattered light intensity temporarily increased by the floc is reduced, or the turbidity of the suspension, particularly the influence of the floc is eliminated. If it is detected that the turbidity due to unaggregated colloidal particles or the like has increased, it can be determined that the cause is the lack of the flocculant.

<Excessive flocculant>
Further, when the inorganic flocculant is excessively injected, the intensity of the scattered light due to the flocs changes to some extent as the flocs grow. However, the suddenly large floc is easily broken, and as a result, a large amount of fine floc (pin floc) is formed. Since the pin flocs are very small and many, it is difficult for the first aggregation sensor 11 to distinguish them from unaggregated colloidal particles. For this reason, the turbidity due to the turbidity of the suspension detected by the first aggregation sensor 11 and the non-aggregated colloidal particles and the like excluding the influence of floc (excluding pin floc) is increased. In other words, when the flocculant is excessive, the turbidity caused by unaggregated colloidal particles that exclude the influence of floc (excluding pin floc), etc. Although it rises, the intensity of the temporarily high scattered light by the floc has a certain magnitude. Therefore, by determining the difference in intensity of the scattered light, it is possible to distinguish whether the coagulant is excessive or conversely insufficient.
<PH variation>
By the way, when the pH of the suspension deviates from a predetermined value (when pH fluctuation occurs), the amount of the flocculant injected into the suspension is excessive or insufficient as compared with the case where the pH is at the predetermined value. In contrast, the state of aggregation of the suspension reacts more sensitively. For this reason, the turbidity and floc information of the suspension detected using the first aggregation sensor 11 changes abruptly at short time intervals. However, paying attention to the treated water solid-liquid separated in the sedimentation tank 2, the rapid fluctuation of the suspension state due to the pH fluctuation is averaged by the buffer function in the sedimentation tank 2 having a large capacity. The information detected by the second aggregation sensor 12 is hardly affected by the pH fluctuation.

  On the other hand, when the pH is controlled to a predetermined value, when the injection amount of the flocculant is excessive or insufficient, the turbidity of the suspension gradually increases as compared with the case where the pH fluctuation occurs. fluctuate. Therefore, the turbidity of the treated water solid-liquid separated in the precipitation tank 2 is not as fast as the increase in the turbidity of the suspension in the agglomeration reaction tank 1, but gradually increases. The difference between the increase in the turbidity of the suspension in the agglomeration reaction tank 1 and the increase in the turbidity of the treated water separated into solid and liquid is the turbidity of the treated water by the residence time of the suspension in the precipitation tank 2. It can be distinguished from the fact that the peak occurs late.

Accordingly and degree of variation in the aggregation state of suspension to be detected by the first aggregation sensor 11, although the time delay of the residence time of the suspension in the precipitation tank 2 is, by the second aggregation sensor 12 By examining the information of the detected treated water, it is possible to easily determine the presence or absence of pH fluctuation. Further, the turbidity of the suspension detected by the first agglomeration sensor 11 provided in the agglomeration reaction tank 1, particularly the degree of increase in turbidity due to unaggregated colloidal particles and the like excluding the influence of floc (variation signal) The average value) can be monitored to determine the degree of collapse of the aggregated flocs. Accordingly, since it is possible to predict how much the turbidity detected by the second aggregation sensor 12 will increase based on the determination result, it is determined whether the coagulant is excessive or insufficient in consideration of pH fluctuation. It becomes possible.
<Influence of treated water volume and interface fluctuation>
By the way, the increase in the turbidity of the treated water due to the increase in the amount of treated water and the increase of the interface caused by the inclusion of floc into the treated water will be discussed. The increase in the amount of treated water and the increase in the interface hardly involve the aggregation state in the aggregation reaction tank 1, so there is almost no change in information (signal) detected by the first aggregation sensor 11. However, the number of flocs detected by the second aggregation sensor 12 increases due to the floc leak. Therefore, when there is no change in the information detected by the first agglomeration sensor 11 and only the number of flocs of treated water detected by the second agglomeration sensor increases, the amount of treated water increases and the interface rises. Accordingly, it can be determined that a floc leak has occurred.

  In such a case, it is desirable to wait for the floc leak to settle, or to notify the operator of the occurrence of the floc leak and not to control the injection of the flocculant. If the amount of treated water is monitored using a flow meter or the like, the above-mentioned flock leak may cause an increase in the amount of treated water using the information on the flow rate fluctuation, or may be caused by an abnormal rise in the interface. It is possible to determine whether or not to do.

  In the medicine injection control device 3 described above, the turbidity and leak information of the suspension and the treated water respectively detected by the factor determination function 3a using the first and second aggregation sensors 11 and 12 described above are obtained. By comparing and determining each other and examining the relative relationship, the factors of the water quality fluctuations of the solid-liquid separation treated water described above are respectively determined. When such factor determination is performed, the state changes of the suspension and treated water described above are arranged in advance according to the factor and registered in the database (DB) 10 as shown in FIG. 3, for example. The database 10 may be searched according to the relative relationship between the signals detected by the first and second agglomeration sensors 11 and 12 to determine the factor of water quality fluctuation.

  The chemical injection control device 3 feedback-controls the operation of the pump 4 only when the water quality fluctuation factor is excessive or insufficient of the flocculant in accordance with the water quality fluctuation factor (determination result) obtained as described above. Thus, the injection amount of the flocculant is optimized. In other words, when the water quality fluctuates due to a factor other than the excess or deficiency of the flocculant, the injection amount control of the flocculant is prohibited and the injection amount at that time is maintained. Therefore, it is possible to appropriately take measures according to the factor against fluctuations in the agglomeration conditions, and it becomes possible to perform stable injection control of the aggregating agent.

  The present invention is not limited to the embodiment described above. Here, a water treatment system that performs coagulation sedimentation has been described as an example, but the present invention can be similarly applied to a water treatment system that performs solid-liquid separation by pressure flotation treatment. If the flocculant is excessive in this pressure floating process, the floc breaks during the pressure process due to the low floc strength, resulting in a fine flock (pin flock). On the contrary, when the coagulant is insufficient, a large amount of suspended matter that is not taken into the floc remains as in the case of the above-described coagulation sedimentation treatment. Accordingly, even in this case, if two systems of aggregation sensors are provided to detect the suspension in the aggregation reaction tank 1 and the turbidity and floc information of the treated water solid-liquid separated by the pressure flotation process, The same effects as those of the embodiment described above can be obtained.

  In the embodiment, the agglomeration sensor 12 similar to the agglutination sensor 11 incorporated in the agglutination reaction tank 1 is used to inspect the treated water, but a conventional optical turbidimeter can also be used. In addition, when the water quality fluctuates due to a factor other than the excess or deficiency of the flocculant, it is of course possible to control the amount of sludge withdrawn from the settling tank 2 or the injection amount of the pH adjusting agent according to the factor. is there. Furthermore, it is possible to configure the factor of the water quality fluctuation more accurately while inputting the operation information of the water treatment facility (treatment water amount, interface position, pH value, etc.). In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The waist part schematic block diagram of the water treatment system which concerns on one Embodiment of this invention. The figure which shows the example of the aggregation sensor used for the water treatment system shown in FIG. The figure which shows the example of the information memorize | stored beforehand in the database for determining the factor of water quality fluctuation | variation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coagulation reaction tank 2 Settling tank 3 Chemical injection control apparatus 3a Factor determination function 7 pH controller 10 Database 11 1st aggregation sensor 12 2nd aggregation sensor

Claims (2)

An agglomeration reaction tank for injecting a flocculant into the raw water to agglomerate the suspension and / or dissolved matter in the raw water;
A solid-liquid separation device for obtaining treated water from which the suspension and / or dissolved matter has been removed by subjecting the suspension discharged from the agglomeration reaction vessel to solid-liquid separation, and
The suspension and / or turbidity is measured by measuring a floc formation state and turbidity in the suspension provided in a suspension supply path from the aggregation reaction tank or the aggregation reaction tank to the solid-liquid separation device. Or an aggregation state measuring means for detecting the aggregation state of the lysate;
Water quality evaluation means for measuring the floc formation state and turbidity in the treated water and evaluating the measured value as the quality of the treated water provided in the treated water discharge path from the solid-liquid separator,
By referring to a database that preliminarily organizes and stores changes in the state of suspension and treated water according to their factors, the state of aggregation of the suspension and / or dissolved matter obtained by the aggregation state measuring means and the water quality evaluation means ; and a factor determining means for determining the cause of quality variations in the treated water in accordance with a combination of the quality of the treated water obtained by,
The aggregation state measuring means and the water quality evaluating means comprise an aggregation sensor that detects scattered light in a minute region of the laser light irradiated into the measurement target water and measures the floc formation state and turbidity in the measurement target water. ,
The factor determination means determines whether the flocs in the suspension and the treated water are associated with factors of water quality fluctuations in advance from the floc formation state and / or the relative turbidity of the liquid layer obtained by the respective aggregation sensors. A water treatment system that distinguishes between water quality fluctuations caused by the injection of the flocculant and other water quality fluctuation factors with reference to databases in which the formation state and turbidity of water are registered . The water treatment system according to claim 1 ,
When the determination result by the factor determination means is a change in water quality due to the injection of the flocculant, the amount of the flocculant injected according to the floc formation state and / or the turbidity of the liquid layer respectively obtained by the respective flocculence sensors And a control means for prohibiting the control of the injection amount of the flocculant when the water quality changes due to other than the injection of the flocculant.

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