JP7186639B2 - Water treatment method and water treatment equipment - Google Patents

Description

The present invention relates to a water treatment apparatus, for example, a water treatment apparatus for removing manganese from manganese-containing water, which includes a treatment tank in which raw water is treated while forming an expanded bed by passing an upward flow of raw water through a packed bed of granular packing. It relates to water treatment equipment.

Patent Document 1 discloses a water treatment method for removing manganese from raw water containing manganese. According to this document, an oxidation treatment tank comprising a packed bed filled with particles of a manganese oxide catalyst is used. Raw water to which an oxidizing agent has been added is passed through the oxidation treatment tank in an upward flow, and manganese in the raw water is oxidized and precipitated while forming an expanded bed. Then, the oxidized precipitate is removed by the filtration membrane in the latter stage.

Patent Documents 2 to 4 also disclose such methods, and these documents refer to the rate of catalyst development. The deployment rate is defined as follows.
{(height of packed bed when passing water) - (height of packed bed when not passing water)}/(height of packed bed when not passing water)

JP 2003-266085 A JP 2017-18918 A JP 2015-003316 A JP 2015-147156 A

In the water treatment method as described above, if the expansion rate of the packed bed is small, a one-sided flow (short pass) may occur in the packed bed. If the expansion rate is large, the contact time between the raw water and the catalyst may be shortened, and the catalyst particles may flow out of the packed bed. Such a phenomenon can cause deterioration in the quality of treated water. Therefore, it is desirable to design the oxidation treatment tank such that the spread rate of the packed bed is within a desired range. However, the raw water temperature may change depending on the environmental temperature, and the expansion rate may change depending on the raw water temperature. Therefore, the rate of expansion may deviate from the desired range due to changes in raw water temperature.

Not only in oxidation treatment tanks used for manganese removal, but also in treatment tanks in which raw water is treated while forming an expanded bed by passing raw water in an upward flow through a packed bed of granular packing, it depends on the temperature of the raw water. As a result, the expansion rate of the packed bed may change.

It is an object of the present invention to provide a water treatment method and a water treatment method that can reduce the change in the expansion rate of the packed bed depending on the raw water temperature and keep the expansion rate of the packed bed within a desired range even if the raw water temperature changes. It is to provide a processing device.

According to one aspect of the invention,
A water treatment method using a treatment tank which comprises a packed bed of granular packing inside a container and treats the raw water while forming an expanded bed by passing raw water in an upward flow through the packed bed,
including a flow rate adjustment step of adjusting the flow rate of raw water to the treatment tank,
In the flow rate adjusting step, the water flow rate is changed according to the raw water temperature,
When the raw water temperature changes from a value less than the upper threshold value TH _i to a value equal to or higher than the upper threshold value TH _i , if the water flow rate is Q _i , the water flow rate Q _i is maintained until it changes to the upper threshold value TH _i . After maintaining the water flow rate is changed stepwise to Q _{i + 1} ,
When the raw water temperature changes from a value exceeding the lower threshold value TL _i to a value equal to or lower than the lower threshold value TL _i , if the water flow rate is Q _{i + 1} , the water flow rate Q _{i + 1} is increased until it changes to the lower threshold value TL _i . After maintaining the water flow rate is changed stepwise to _Qi ,
Here, i represents an integer from 1 to n, n is an integer of 1 or more, Q _i < Q _{i + 1} , TL _i < TH _i , and when n is 2 or more, TH _i ≤ TL A water treatment method is provided, characterized in that _i+1 .

According to another aspect of the invention,
A water treatment apparatus comprising a treatment tank provided with a packed bed of granular packing inside a container, and treating the raw water while forming an expanded bed by passing an upward flow of raw water through the packed bed,
including a flow rate adjusting means for adjusting the flow rate of raw water to the treatment tank,
The flow rate adjusting means changes the water flow rate according to the raw water temperature ,
When the raw water temperature changes from a value less than the upper threshold value TH _i to a value equal to or higher than the upper threshold value TH _i , if the water flow rate is Q _i , the water flow rate Q _i is maintained until it changes to the upper threshold value TH _i . After maintaining the water flow rate is changed stepwise to Q _{i + 1} ,
When the raw water temperature changes from a value exceeding the lower threshold value TL _i to a value equal to or lower than the lower threshold value TL _i , if the water flow rate is Q _{i + 1} , the water flow rate Q _{i + 1} is increased until it changes to the lower threshold value TL _i . After maintaining the water flow rate is changed stepwise to _Qi ,
Here, i represents an integer from 1 to n, n is an integer of 1 or more, Q _i < Q _{i + 1} , TL _i < TH _i , and when n is 2 or more, TH _i ≤ TL A water treatment device is provided, characterized in that _i+1 .

According to the present invention, a water treatment method and a water treatment method are capable of reducing the change in the expansion rate of the packed bed depending on the temperature of the raw water and maintaining the expansion rate of the packed bed within a desired range even if the temperature of the raw water changes. A processing device is provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows an example of the water treatment apparatus which concerns on embodiment of this invention. It is a graph which shows the example of the correlation of the expansion rate of a packed bed, and a water flow linear velocity for every raw-water temperature. 4 is a flowchart for explaining an example of a flow rate adjustment process; It is a figure which shows the example of the step-like change of water flow volume. FIG. 10 is a diagram showing another example of a stepwise change in water flow rate;

One aspect of the present invention relates to a water treatment method using a treatment tank. A treatment tank is a tank having a packed bed of granular packing inside the container. In the treatment tank, by passing raw water in an upward flow through the packed bed, the granular packing is developed in a fluidized state to form an expanded bed. Then, the expanded granular packing and raw water come into contact with each other, and the raw water is treated (for example, oxidation treatment or ion exchange treatment).

This water treatment method includes a flow rate adjustment step of adjusting the water flow rate of raw water to the packed bed (hereinafter sometimes simply referred to as "water flow rate"). In the flow rate adjustment step, the change in the expansion rate of the packed bed depending on the raw water temperature is reduced, and the water flow rate is changed according to the raw water temperature so that the expansion rate of the packed bed falls within a desired range. This is effective to prevent the occurrence of short pass, to prevent the contact time between the raw water and the catalyst from decreasing, and to prevent the catalyst particles from flowing out of the packed bed. .

Hereinafter, the present invention will be described by taking as an example a water treatment apparatus and a water treatment method for treating manganese-containing water containing at least manganese using an oxidation treatment tank filled with a granular oxidation catalyst containing manganese dioxide as a treatment tank. The invention is not limited thereby.

The water treatment apparatus shown in FIG. 1 has an oxidation treatment tank 20 . The oxidation treatment tank 20 includes a packed bed 22 of an oxidation catalyst inside a container 21 . Raw water is supplied to the water treatment apparatus from line L1. A line L1 is connected to the inlet of the oxidation treatment tank 20 . A line L2 is connected to the outlet of the oxidation treatment bath 20 . Line L2 is connected to the inlet of a membrane filtration device (not shown). The line L1 is provided with flow rate adjusting means 10 for adjusting the flow rate of the raw water.

The height of the packed bed 22 depends on the upward linear velocity of the raw water (hereinafter sometimes referred to as "LV"), and therefore the flow rate of the raw water supplied from the line L1 to the oxidation treatment tank 20. Depends and changes. In order to supply raw water to which an oxidant has been added in advance to the oxidation treatment tank 20, the water treatment apparatus can include an oxidant addition means (not shown). The oxidant addition means can be provided in the line L1, for example upstream or downstream of the flow control means 10 in the line L1. It should be noted that the flow control means 10 is not limited to the case where the flow control means 10 includes the flow control valve 13 as shown in FIG. oxidant addition means can be used. In the filling layer 22, manganese dissolved in the raw water is oxidized and deposited. Oxidation treated water is discharged from the oxidation treatment tank 20 to the line L2. In the downstream of the oxidation treatment tank 20, precipitates contained in the oxidation treated water are removed by a membrane filtration device to obtain treated water with a reduced manganese concentration.

FIG. 2 shows an example of the correlation between the expansion rate of the packed bed 22 and the linear water flow velocity LV in such an oxidation treatment tank for each raw water temperature. Industrial water and groundwater are assumed here as raw water, and their typical temperature is 1 to 30°C. According to this figure, for example, in order to achieve a deployment rate of 25 to 40%, the LV should be within the range of 53 to 75 m/h at a water temperature of 30°C, and the LV should be 35 at a water temperature of 1°C. The value should be in the range of ~49 m/h. In other words, depending on the temperature of the raw water, the range of LV required to achieve a desired range of deployment rate differs. Specifically, the higher the raw water temperature, the larger the LV should be. With respect to the same device, the same argument holds for the water flow rate, since the LV is proportional to the water flow rate.

In the flow rate adjustment step, the water flow rate is changed so that the higher the temperature of the raw water supplied from the line L1, the larger the water flow rate (however, in some temperature ranges, the raw water temperature change is It is acceptable that the water flow rate does not change). As a result, it is possible to reduce the change in the rate of expansion of the filling layer 22 that depends on the temperature of the raw water.

The flow control means 10 includes a temperature sensor 11 , a flow sensor 12 , a flow control valve 13 , a temperature indicator 14 , a flow indicator controller 15 and a controller 16 . An output signal (corresponding to raw water temperature) from temperature sensor 11 is sent to control device 16 via temperature indicator 14 . A signal corresponding to the target value of the water flow rate is sent from the controller 16 to the flow indicator controller 15 . The control device 16 changes the output signal (the control target value of the water flow rate) according to the raw water temperature so as to reduce the change in the expansion rate of the packed bed depending on the raw water temperature.

A measured value (current value) of the water flow rate is sent from the flow sensor 12 to the flow indicator controller 15 . A signal (manipulated amount) corresponding to the degree of opening of the valve is sent from the flow indicator controller 15 to the flow control valve 13 . By using the flow sensor 12, the flow control valve 13, and the flow indicator controller 15, the water flow rate can be controlled to the control target value by closed loop control. The temperature indicator 14 can be omitted, and the flow rate indicating function of the flow rate indicating controller 15 can be omitted.

In the flow rate adjustment step, from the viewpoint of preventing hunting, it is preferable to change the water flow rate with hysteresis in accordance with the raw water temperature. In particular, it is preferable to change the water flow rate stepwise with hysteresis between _Qi and Qi ₊₁ . n is an integer of 1 or more, and i represents an integer from 1 to n (i=1, 2, . . . n). Both Q _i and Q _i+1 are water flow rates, where Q _i <Q _i+1 .

In order to know the change in the raw water temperature, the raw water temperature can be repeatedly measured at suitable sampling intervals and the previous measured value and the latest measured value can be compared. Previous measurements of raw water temperature can be stored in controller 16 .

An example of the flow rate adjustment process will be described with reference to FIG. First, in step S1, the raw water temperature (T) is measured. In step S1, the raw water flow rate (Q) can also be measured. Since the change in the raw water temperature cannot be determined at the time of the first measurement, the process returns to step S1 without performing the subsequent steps (steps S2 to S5), and the raw water temperature and flow rate are measured again.

In step S2, when the previous measured value of the raw water temperature is less than TH _i and the latest measured value of the raw water temperature is equal to or higher than the upper threshold value TH _i , "from the value where the raw water temperature T is less than the upper threshold value TH _i changed to a value greater than or equal to the upper limit threshold TH _i' . This means that the raw water temperature has risen and reached the upper threshold TH _i . Further, it is determined whether or not the water flow rate Q (latest measured value) is _Qi . If both of these conditions are met, go to step S3, otherwise go to step S4. In step S3, the water flow rate Q is changed to Qi ₊₁ , and then the process returns to step S1.

In step S4, when the previous measured value of the raw water temperature exceeds TL _i and the latest measured value of the raw water temperature is equal to or lower than TL _i , "from the value where the raw water temperature T exceeds the lower limit threshold TL _i to the lower limit threshold TL changed to a value less than or equal to _i' . This means that the raw water temperature has dropped and reached the lower threshold TL _i . Further, it is determined whether or not the water flow rate Q (latest measured value) is Qi ₊₁ . If both of these conditions are met, go to step S5, otherwise go back to step S1. In step S5, the water flow rate is changed to _Qi , and then the process returns to step S1.

Note that TL _i <TH _i for any i, and TH _i ≤ TL _i+1 when n is 2 or more. In addition, Q _i , TH _i and TL _i are based on the correlation between the expansion rate, LV (or water flow rate), and raw water temperature as shown in FIG. can be determined in advance so as to fall within the range of .

[Example of n = 1]
FIG. 4 shows an example of a stepwise change in water flow rate. In this example, n=1 and the only possible value for i is 1. The water flow rate is changed stepwise with hysteresis between _Q1 and _Q2 .

When the raw water temperature changes from a value less than the upper threshold value _TH1 to a value equal to or higher than the upper threshold value _{TH1, if the water flow rate is Q1 ,} the water flow rate is changed to _Q2 (when the water flow rate is _Q2 If so, keep the flow rate at _Q2 ). Also, when the raw water temperature changes from a value exceeding the lower limit threshold TL ₁ to a value equal to or lower than the lower limit threshold TL ₁ , if the water flow rate is Q ₂ , the water flow rate is changed to Q ₁ (the water flow rate is Q If it is ₁ , the water flow rate is maintained at _Q1 ). Note that TL ₁ <TH ₁ .

In normal operation, the water flow rate is not changed except for the above cases. However, the water flow rate can be changed during operation other than normal operation, such as when an abnormality occurs.

At the start of the flow rate adjustment process, for example, the water flow rate can be set as follows. That is, if the raw water temperature is equal to or lower than the lower limit threshold value _TL1 , the water flow rate is set to _Q1 . If the raw water temperature is equal to or higher than the upper threshold value _TH1 , the water flow rate is set to _Q2 . If the raw water temperature exceeds the lower limit threshold value _TL1 and is lower than the upper limit threshold value _TH1 , the water flow rate is set to _Q1 or _Q2 .

[Example of n = 4]
From the viewpoint of keeping the expansion ratio within a narrower range, it is preferable to change the water flow rate in a stepwise manner in a plurality of stages. That is, n is preferably 2 or more. An example of n=4 will be described below with reference to FIG. Possible values for i are 1, 2, 3 and 4. That is, since the water flow rate is changed stepwise in four stages, there are five water flow rates (Q ₁ to Q ₅ ).

FIG. 5 shows the raw water temperature range from 0° C. to 30° C. Usually, it is _sufficient to assume this temperature range. The water flow rate at that time can be set to _Q5 . Alternatively, the number of steps can be further increased to step change the water flow rate to a higher temperature region.

In this example, TH _i =TL _i+1 for all i. That is, in this example, TH ₁ and TL ₂ have the same value, TH ₂ and TL ₃ have the same value, and TH ₃ and TL ₄ have the same value. However, it is not limited to this, and it is sufficient if TH _i ≤ TL _i+1 for all i when n is 2 or more. Also, in this example, the width of each hysteresis region (the difference between the upper limit threshold and the lower limit threshold) is the same at 5° C., but it is not limited to this. The water flow rate, upper limit threshold value, and lower limit threshold value for each stage have values shown in FIG. Incidentally, when the water flow rates Q ₁ to Q ₅ in this example are converted to LV, they correspond to 44, 46, 48, 50 and 51 m/h, respectively.

When the raw water temperature changes from a value lower than the upper threshold value _TH1 to a value higher than the upper threshold value _{TH1, if the water flow rate is Q1 ,} the water flow rate is changed to _Q2 . Also, when the raw water temperature changes from a value exceeding the lower threshold value _TL1 to a value equal to or lower than the lower threshold value _TL1 , if the water flow rate is _Q2 , the water flow rate is changed to _Q1 . In this manner, the water flow rate is changed stepwise between _Q1 and _Q2 with hysteresis.

Also, when the raw water temperature changes from a value less than the upper threshold value _TH2 to a value equal to or higher than _the upper threshold value TH2, if the water flow rate is _Q2 , the water flow rate is changed to _Q3 . Also, when the raw water temperature changes from a value exceeding the lower threshold value _TL2 to a value equal to or lower than the lower threshold value _TL2 , if the water flow rate is _Q3 , the water flow rate is changed to _Q2 . In this manner, the water flow rate is changed stepwise between _Q2 and _Q3 with hysteresis.

Similarly, using the upper threshold value _TH3 and the lower threshold value _TL3 , the water flow rate is changed stepwise between _Q3 and _Q4 with hysteresis. Also, using the upper threshold value _TH4 and the lower threshold value _TL4 , the water flow rate is changed stepwise between _Q4 and _Q5 with hysteresis. In normal operation, the water flow rate is not changed except for the above cases.

At the start of the flow rate adjustment process, for example, the water flow rate can be set as follows. That is, if the raw water temperature is equal to or lower than TL ₁ (the smallest of TL _i ), the water flow rate is set to Q ₁ (the smallest of Q _i ). If the raw water temperature is equal to or higher than the upper threshold value TH ₄ (the largest of TH _i , ie, TH _n ), the water flow rate is set to Q ₅ (the largest of Q _i+1 , ie, Q _n+1 ). When the raw water temperature exceeds the lower threshold value TL _i and is lower than the upper threshold value TH _i , the water flow rate is set to Q _i or Q _i+1 .

[Another example of means for changing the water flow rate]
When changing the water flow rate to the oxidation treatment tank 20, the flow control valve 13 does not necessarily have to be used. For example, a pump (not shown) for transporting raw water is provided on the line L1, and the number of revolutions of the pump is controlled by an inverter (not shown), thereby adjusting the water flow rate. In this case, the output signal from the flow indicator controller 15 can be sent to the inverter instead of the flow control valve 13 to control the rotation speed of the pump. Also in this case, the closed loop control can control the water flow rate to the control target value.

Alternatively, instead of using the flow rate control valve 13, a plurality of on/off valves (not shown) such as solenoid valves may be provided in parallel and the opening and closing of these valves may be controlled to adjust the water flow rate. In this case, a flow rate indicator (without an adjustment function) can be used instead of the flow rate indicator controller 15, and a signal corresponding to the measured raw water flow rate can be sent to the controller 16 from the flow rate indicator. The controller 16 can determine the water flow rate (Q _i ) according to the temperature of the raw water, and open/close each on/off valve so as to realize the Q _i . A signal for opening and closing the valve can be sent from the control device 16 to each on/off valve. The control in this case is open loop control.

[Conditions for manganese removal treatment]
As shown in FIG. 1, the oxidation treatment tank filled with an oxidation catalyst containing manganese dioxide as a particulate packing can be subjected to the aforementioned flow control step. In the oxidation treatment tank, at least one component of iron and manganese contained in the raw water can be oxidized and precipitated.

In the oxidation treatment tank for removing manganese, the spread rate of the packed layer of the oxidation catalyst is preferably 25% or more and 40% or less.

Examples of oxidation catalysts include granulated manganese dioxide oxidation catalysts and manganese sand. The density of the oxidation catalyst is, for example, 2.8 g/cm ³ or more. The particle size of the oxidation catalyst is preferably 0.4 mm or more from the viewpoint of preventing the outflow of the catalyst, and is preferably 2.0 mm or less from the viewpoint of preventing the catalyst surface area from becoming small. The amount of oxidation catalyst can be determined, for example, so that the space velocity of water in the catalyst layer is 200 h ⁻¹ or less.

The temperature in the oxidation treatment bath is, for example, in the range of 1 to 50.degree. The pH of raw water supplied to the oxidation treatment tank is, for example, 7.0 to 8.6.

The oxidizing agent added to the raw water upstream of the oxidation treatment tank is, for example, sodium hypochlorite. The content of soluble manganese in raw water is, for example, 0.01 to 5 mg/L, and the content of soluble iron is, for example, 0.1 to 20 mg/L or less. The amount of the oxidizing agent to be added is, for example, 0.5 to 2 mol per 1 mol of the soluble iron content, and 1 to 4 mol per 1 mol of the soluble manganese content.

Precipitates deposited by oxidation can be removed by filtering the water treated in the oxidation treatment tank by membrane filtration or the like. For this purpose, downstream of the oxidation treatment tank, for example, a membrane filtration device with a filtration membrane can be provided. Any filter membrane may be used as long as it can filter deposits such as iron and manganese that have been oxidized and deposited, and examples thereof include UF (ultrafiltration) membranes and MF (microfiltration) membranes. Thus, the water treatment apparatus including the oxidation treatment tank and the membrane filtration apparatus, that is, the iron/manganese-containing water treatment apparatus can be suitably applied to, for example, water treatment plants and underground water treatment.

[About ion exchange treatment]
Ion-exchanged water can also be produced using an ion-exchange resin as the granular filler. The treatment tank in this case is an ion exchange resin tower. A known ion exchange resin can be appropriately used as the granular ion exchange resin. As the structure of the ion-exchange resin tower, a known structure can be appropriately adopted.

10 flow control means 11 temperature sensor 12 flow sensor 13 flow control valve 14 temperature indicator 15 flow indicator controller 16 controller 20 oxidation treatment tank 21 vessel 22 packed bed

Claims (4)

A water treatment method using a treatment tank which comprises a packed bed of granular packing inside a container and treats the raw water while forming an expanded bed by passing raw water in an upward flow through the packed bed,
including a flow rate adjustment step of adjusting the flow rate of raw water to the treatment tank,
In the flow rate adjusting step, the water flow rate is changed according to the raw water temperature,
When the raw water temperature changes from a value less than the upper threshold value TH _i to a value equal to or higher than the upper threshold value TH _i , if the water flow rate is Q _i , the water flow rate Q _i is maintained until it changes to the upper threshold value TH _i . After maintaining the water flow rate is changed stepwise to Q _{i + 1} ,
When the raw water temperature changes from a value exceeding the lower threshold value TL _i to a value equal to or lower than the lower threshold value TL _i , if the water flow rate is Q _{i + 1} , the water flow rate Q _{i + 1} is increased until it changes to the lower threshold value TL _i . After maintaining the water flow rate is changed stepwise to _Qi ,
Here, i represents an integer from 1 to n, n is an integer of 1 or more, Q _i < Q _{i + 1} , TL _i < TH _i , and when n is 2 or more, TH _i ≤ TL _i+1 , a water treatment method. 2. The water treatment method according to claim 1 , wherein the particulate filler is an oxidation catalyst containing manganese dioxide or an ion exchange resin. A water treatment apparatus comprising a treatment tank provided with a packed bed of granular packing inside a container, and treating the raw water while forming an expanded bed by passing an upward flow of raw water through the packed bed,
including a flow rate adjusting means for adjusting the flow rate of raw water to the treatment tank,
The flow rate adjusting means changes the water flow rate according to the raw water temperature ,
When the raw water temperature changes from a value less than the upper threshold value TH _i to a value equal to or higher than the upper threshold value TH _i , if the water flow rate is Q _i , the water flow rate Q _i is maintained until it changes to the upper threshold value TH _i . After maintaining the water flow rate is changed stepwise to Q _{i + 1} ,
When the raw water temperature changes from a value exceeding the lower threshold value TL _i to a value equal to or lower than the lower threshold value TL _i , if the water flow rate is Q _{i + 1} , the water flow rate Q _{i + 1} is increased until it changes to the lower threshold value TL _i . After maintaining the water flow rate is changed stepwise to _Qi ,
Here, i represents an integer from 1 to n, n is an integer of 1 or more, Q _i < Q _{i + 1} , TL _i < TH _i , and when n is 2 or more, TH _i ≤ TL _i+1 , a water treatment device. 4. The water treatment device according to claim 3 , wherein the particulate packing is an oxidation catalyst containing manganese dioxide or an ion exchange resin.

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