JP4400720B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment system that injects a flocculant to remove suspensions and / or dissolved matters in water to be treated.

  In irrigation water treatment and wastewater treatment, inorganic or organic flocculants are injected into the raw water to be treated (treated water) to agglomerate suspensions and dissolved substances contained in the treated water, thereby forming aggregated flocs. Removing is done. At this time, the suspension in the flocculation process is sampled and guided to a measuring tank, and after performing solid-liquid separation using means such as sedimentation and filtration, the turbidity of the treated liquid is measured, or turbidity is measured. The treated water turbidity after the flocculation solid-liquid separation is measured using a dynamometer and the injection amount of the flocculating agent is controlled (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

By the way, the state of aggregation of the suspension and dissolved matter in the coagulation tank is influenced not only by the amount of the coagulant injected, but also by the pH value, water temperature, and further the amount of treated water. Therefore, exclusively, the operating conditions are kept constant, and a pH adjuster is added to the agglomerated water to make the pH constant.
However, when the aggregation state detected by the aggregation sensor changes in a short time, it is possible to determine whether the cause is due to excessive or insufficient injection amount of the flocculant or excessive or insufficient injection amount of the pH adjusting agent. There is a problem that you can't. Therefore, the pH of the flocculated water is measured with a pH meter provided in the flocculation tank. However, in order to ensure stable operation of the pH meter, periodic calibration such as pH meter calibration and electrode cleaning is required. There is a problem that maintenance is necessary and it is difficult to always grasp the pH of the agglomerated water with good responsiveness and reliability.

The present invention has been made in view of such circumstances, and its purpose is to change the water quality due to the injection of the flocculant when the flocculant is injected to remove the suspension and / or dissolved matter in the water to be treated. And other factors such as water quality fluctuation factors, such as changes in the amount of treated water and pH, are detected separately, and the injection control of the coagulant is performed appropriately and quickly in a state where the pH of the treated water is stabilized. It is to provide a water treatment system that can be used.

In order to achieve the above-described object, the water treatment system according to the present invention injects a flocculant and a pH adjuster into the water to be treated and removes suspended matter and / or dissolved matter in the water to be treated by flocculation and flocking. A system,
(a) a pH meter that measures the pH of water to be treated into which a flocculant and a pH adjuster have been injected;
(b) pH for selectively controlling the injection of the pH adjusting agent into the water to be treated so that the pH of the water to be treated becomes a target value according to the pH of the water to be treated measured by the pH meter. Adjusting agent injection control means;
(c) an aggregation state measuring means for detecting the state of the aggregation floc in the water to be treated in which the aggregation agent and the pH adjusting agent are injected;
(d) comprising a flocculant injection control means for controlling the injection of the flocculant according to the aggregation state of the treated water measured by the aggregation state measuring means,
(e) Whether the pH adjusting agent is being injected based on the injection information of the pH adjusting agent by the pH adjusting agent injection control means, within a preset monitoring time after stopping the injection, or after stopping the injection Determine whether the monitoring time has elapsed,
If it is within a preset monitoring time during or after the injection is stopped , the injection of the flocculant is controlled by the flocculant injection control means, assuming that the pH of the water to be treated is adjusted to an appropriate range, and the injection is performed. When the aggregation state of the water to be treated is changed from the state of the aggregation floc measured by the aggregation state measuring means after the elapse of a preset monitoring time after the stop, the pH adjusting agent injection control The control target value in the means is corrected, and the pH adjuster injection control by the pH adjuster injection control means is executed, thereby optimizing the pH of the water to be treated and then the flocculant injection control means by the flocculant injection control means. It is characterized by comprising control management means for executing injection control.

That is, in the water treatment system according to the present invention, the pH of the water to be treated at that time and the aggregation state of the water to be treated measured by the agglomeration state measuring means according to the injection state of the pH adjuster to the water to be treated. From this correlation, it is determined whether or not the change in the aggregation state is due to excessive or insufficient injection amount of the pH adjusting agent, and it is recognized that the pH adjusting agent injection is appropriate and the pH of the water to be treated is stable. It is characterized by controlling the injection of flocculant only in cases .

In the water treatment system according to the present invention, the state of aggregation of the water to be treated is changed from the state of the aggregation floc measured by the aggregation state measuring unit after the monitoring time has elapsed after stopping the injection of the pH adjuster. If it is determined that the control target value in the pH adjuster injection control means is corrected, injection control of the pH adjuster by the pH adjuster injection control means is executed, whereby the treated water is After the pH is optimized, the flocculant injection control by the flocculant injection control means is executed.
In other words, in the case where the aggregation state is changed without injection of the pH adjusting agent, it is determined that the injection amount of the pH adjusting agent is insufficient, and the control target value is corrected or the pH is adjusted. It is characterized in that the injection of the pH adjusting agent is promoted by performing calibration of the meter, and the injection control of the flocculant is performed after the pH adjustment of the water to be treated is optimized.

Preferably, after the control management means corrects the control target value and operates the pH adjuster injection control means to optimize the pH of the water to be treated, the control target value is set to the original target value. Configured to restore.

In the case where the water treatment system according to the present invention includes means for measuring the flow rate and / or temperature of the water to be treated, the aggregation state measurement means causes the change in flow rate and / or temperature. It is preferable to determine whether or not the aggregation state of the measured water to be measured is changed, and when the change in the aggregation state is detected , the operation of the flocculant injection control unit is preferably prohibited .

  According to the water treatment system configured as described above, the coagulant is added according to the relative relationship between the state of injection of the pH adjuster into the water to be treated and the state of aggregation of the water to be treated which is obtained by the coagulation state detection means. Since the injection is controlled, for example, when pH adjustment of the water to be treated is not appropriate, wasteful injection of the flocculant is prevented by prohibiting the control of the injection amount of the flocculant until the pH adjustment is appropriate. It becomes possible. For example, when the pH adjusting agent is not injected and the aggregation state is poor, it is determined that the pH adjustment is inappropriate, and the pH adjusting agent injection target value is corrected quickly. After the optimization, the original injection target value is restored and the flocculant injection control is started. 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.

  When the flow rate and / or temperature of the water to be treated is monitored, it is easily determined that the aggregation state of the water to be treated required by the aggregation state detecting means is changed due to the change. Therefore, it is possible to control the flocculant injection after suppressing the fluctuation factor.

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 and wastewater (treated water). 1 is a water treatment system that accepts treated water and uses a flocculant injected into the treated water. This is an agglomeration reaction tank for agglomerating flocs by aggregating suspensions and dissolved substances contained in water. Reference numeral 2 denotes a sedimentation tank for obtaining treated water obtained by subjecting the suspension introduced from the agglomeration reaction tank 1 to precipitation treatment and solid-liquid separation.

  For example, the inorganic flocculant A is injected into the water to be treated via the pump 4 under the control of the flocculant injection control device 3 comprising a computer with respect to the feed water system of the water to be treated into the agglomeration reaction tank 1. Done. In addition, a pH adjusting agent (for example, caustic soda) B is injected into the agglomeration reaction tank 1 through a pump 5. The injection of the pH adjusting agent B by the pump 5 is basically based on the pH value of the water to be treated (suspension) measured by the pH meter 6 provided in the aggregation reaction tank 1. The control is performed so as to obtain a predetermined pH value under control. 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.

The aggregation reaction tank 1 is provided with an aggregation sensor 11 as an aggregation state measuring means for detecting the aggregation state of the suspension. Information (turbidity and floc formation state) detected by the aggregation sensor 11 is taken into the flocculant injection control device 3.
The agglomeration sensor 11 is introduced in detail in the above-mentioned Patent Document 2, but briefly described, for example, as shown in FIG. Generated by collision of the laser beam with particles in the test water, a probe 13 provided in the test water, a light emitting unit 14 that irradiates laser light amplitude-modulated (AM-modulated) into the test water via the probe 13 And a detector 15 for detecting the turbidity and floc formation state of the measurement target water by detecting scattered light to be detected through the 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 water treatment system according to the present invention is characterized in that the operation of the flocculant injection control device 3 for controlling the injection of the inorganic flocculant A described above depends on the operating state of the pH controller 7 (injection state of the pH adjusting agent). ) Is taken in and controlled . In the chemical injection control device 3, the inorganic coagulation via the pump 4 is performed according to the injection state of the pH adjusting agent in the control management means 3 a and the aggregation state in the aggregation reaction tank 1 detected by the aggregation sensor 11. In addition to controlling the injection of the agent A, the operation of the pH controller 7 for controlling the injection of the pH adjusting agent B is controlled.

That is, in the control management means 3a of the flocculant injection control device 3, the operation of the pump 4 is controlled on condition that the pH of the suspension is stable within a predetermined range, and a predetermined aggregation state (turbidity) ) To control the injection of the inorganic flocculant A. If the pH of the suspension is stable at a low level even when a predetermined amount of pH adjusting agent B is injected, the control target value in the pH controller 7 is corrected (for example, the pH is increased). The control target value is restored after the pH of the suspension is stabilized at a predetermined level, and the injection control of the inorganic flocculant A described above is started.

Specifically, the management control means 3a is injecting the pH adjusting agent B from the drug injection information obtained from the pH controller 7, is within a preset monitoring time after stopping the injection, or after stopping the injection. It is determined whether the above monitoring time has elapsed. And the control is managed as follows according to the injection | pouring state of this pH adjuster.
<After a lapse of a predetermined time after stopping the injection of pH adjuster B>
That is, when it is determined that the pH adjusting agent B has not been injected, the control management unit 3a determines whether or not the output of the aggregation sensor 11 has fluctuated beyond a preset width. When the output of the aggregation sensor 11 has changed greatly, the control management means 3a follows the relationship between the output of the aggregation sensor 11 and the pH of the suspension as shown in FIG. 3, for example. It is determined that the change in output is caused by a decrease in pH. Then, it is determined that the cause of the aggregation failure is a change in pH, the control target value in the pH controller 7 described above is corrected, and injection of the pH adjusting agent B is promoted. Then, after confirming that the pH of the suspension is within a predetermined appropriate range, injection control of the inorganic flocculant A is executed based on the output of the first aggregation sensor 11.
<During the injection of the pH adjuster B or within a preset monitoring time after stopping the injection>
On the other hand, when the pH adjusting agent B is injected, the pH of the suspension is normally adjusted within a predetermined appropriate range based on the output of the pH meter 6. Therefore, in this case, the control management means 3a executes the injection control of the inorganic flocculant according to the relationship between the injection amount of the flocculant A and the output of the flocculant sensor 11 shown in FIG. 4, for example, and stabilizes the aggregation state. Plan.

Thus, if it is determined whether or not the pH adjusting agent B is injected from the operating state of the pH controller 7 as described above, the change in the aggregation state of the suspension detected by the aggregation sensor 11 is the pH adjusting agent B. It is possible to easily determine whether or not it is caused by excess or deficiency, and the injection of the inorganic flocculant A can be efficiently controlled after adjusting the pH of the suspension to an appropriate range. Therefore, when the cause of the deterioration of the aggregation state detected via the aggregation sensor 11 is the lack of the pH adjusting agent B, there is an effect such as no waste of excessive injection of the inorganic aggregation agent A. It is done.
<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, the turbidity of the suspension detected through the aggregation sensor 11, particularly the turbidity caused by unaggregated colloidal particles and the like excluding the influence of floc, becomes the lowest value. Further, the information detected via the 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.

< Insufficient aggregation chemical solution>
On the other hand, when the injection amount of the inorganic flocculant A is insufficient, floc formation in the flocculation 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 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 colloidal particles or the like has increased, it can be determined that the cause is the lack of the flocculant.

<Excessive flocculant>
When the inorganic flocculant A is excessively injected, the intensity of the scattered light due to the flocs described above 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 these pin flocs are very small and many, it is difficult for the 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 aggregation sensor 11 and the unaggregated colloidal particles and the like excluding the influence of the 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 agglomeration sensor 11 changes drastically at short time intervals. However, paying attention to the treated water solid-liquid separated in the sedimentation tank 2, the rapid fluctuation of the aggregation state of the suspension 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 aggregation sensor provided in the sedimentation tank 2 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 , if the state of the treated water (aggregation state) in the sedimentation tank 2 is examined, the degree of fluctuation of the aggregation state of the suspension detected by the aggregation sensor 11 and the convection time of the suspension in the precipitation tank 2 Although there is a time delay, it is possible to easily determine the presence or absence of pH fluctuation. Further, the turbidity of the suspension detected by the agglutination sensor 11 provided in the agglomeration reaction tank 1, especially the degree of increase in turbidity due to unaggregated colloidal particles and the like excluding the influence of floc (average value of fluctuation signal) ) Can be monitored to determine the degree of collapse of the aggregated floc .
<Influence of treated water volume and interface fluctuation>
Here, the increase in the turbidity of the treated water due to the increase in the amount of treated water and the rise of the interface caused by the inclusion of floc in the treated water will be considered. 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 aggregation sensor 11. However, the number of flocs in the sedimentation tank 2 increases due to the leak of flocs. Therefore, when there is no change in the information detected by the aggregation sensor 11 and only the number of flocs in the sedimentation tank 2 increases, a floc leak occurs as the amount of treated water increases and the interface rises. Can be determined.

  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 flocculant injection control device 3, the operation of the pump 4 is feedback-controlled only when the water quality fluctuation factor is the excess or deficiency of the flocculant according to the water quality fluctuation factor (determination result) obtained as described above. Therefore, 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. In this pressurization flotation process, if the flocculant is excessive, the floc breaks during the pressurization process due to the low floc strength, resulting in a 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.

  In the embodiment, 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 according to the factor. 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 relationship between pH of coagulation reaction process water, and the output of an aggregation sensor. The figure which shows the relationship between the injection amount of the aggregation chemical | medical solution, and the output of an aggregation sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coagulation reaction tank 2 Precipitation tank 3 Coagulant injection | pouring control apparatus 3a Control management means 7 pH controller 11 Aggregation sensor

Claims (2)

In a water treatment system for injecting a flocculant and a pH adjuster into water to be treated to agglomerate and remove suspensions and / or dissolved matters in the water to be treated,
A pH meter for measuring the pH of the water to be treated into which the flocculant and the pH adjuster are injected;
PH adjuster injection for selectively controlling injection of the pH adjuster into the treated water so that the pH of the treated water reaches a target value according to the pH of the treated water measured by the pH meter Control means;
A coagulation state measuring means for detecting a state of coagulation floc in the water to be treated into which the coagulant and the pH adjusting agent are injected;
A flocculant injection control means for controlling the injection of the flocculant according to the aggregation state of the water to be treated measured by the aggregation state measuring means;
Control management means for controlling the operation of the pH adjuster injection control means and the flocculant injection control means,
When the control management means is injecting the pH adjusting agent based on the injection information of the pH adjusting agent by the pH adjusting agent injection control means, or within a preset monitoring time after stopping the injection , The flocculant injection control by the flocculant injection control means is executed as the pH of the water to be treated is adjusted to an appropriate range ,
On the other hand, when the aggregation state of the water to be treated from the state of the measured flocs in the aggregated state measuring means even after the monitoring time has elapsed after injection stop of the pH adjusting agent is changed, The control target value in the pH adjuster injection control means is corrected to execute the pH adjuster injection control by the pH adjuster injection control means, thereby optimizing the pH of the water to be treated, and then the flocculant injection A water treatment system characterized in that the control means performs injection of the flocculant.   The control management means restores the control target value to the original target value after correcting the control target value and operating the pH adjuster injection control means to optimize the pH of the treated water. The water treatment system according to claim 1 which is a thing.

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