JPH0468003B2 - - Google Patents

Description

Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to a filter control device in a water purification plant.

(Prior Art) Generally, in a water purification plant, water flowing into a sedimentation basin outflow culvert from a sedimentation basin is filtered through a plurality of filtration basins and then supplied to a water distribution basin.

Conventionally, the filters have been controlled by automatically or manually adjusting a flow rate regulating valve provided in each filter depending on the amount of water to be treated. Further, the flow rate may be adjusted only by opening and closing an on-off valve without providing a flow control valve.

(Problems to be Solved by the Invention) However, the conventional filter control system as described above has the following problems.

With a system that automatically adjusts the flow rate control valve provided in each filtration basin, it is difficult to perform PID control in response to large fluctuations in the amount of treated water.

In other words, each filtration basin has a maximum and minimum throughput value determined in order to perform a suitable filtration action, so if the throughput decreases significantly, one of the filtration basins must be manually stopped. I will have to. Furthermore, in this case, the control conditions vary significantly depending on the number of stopped filters, so the remaining filters may become uncontrollable. on the other hand,
If the throughput increases significantly, PID control may not be able to keep up, and overflow may occur unless a backup filter is added through manual intervention.

Furthermore, since flow control valves are prone to failure, it is necessary to take measures such as installing alternative valves in parallel and securing personnel to deal with abnormal situations.

In the method of manually operating the flow rate control valve or on-off valve provided in each filtration basin, an engineer is required to be permanently present for manual operation. Further, since the operation of the flow rate control valve or the on-off valve must follow the fluctuation of the throughput, it is time consuming and difficult.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a filter control device for a water purification plant that can maintain all filters in a suitable state and control them fully automatically according to the amount of water to be treated.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention filters water flowing from a sedimentation basin into a sedimentation basin outflow channel through a plurality of filtration basins and flows it into a distribution basin. In a filter control device in a water purification plant to be supplied, a pond number determining means determines a pond number of a filter to be started/stopped, a water level detecting means detects a water level of the sedimentation basin outflow drain, and the sedimentation basin outflow drain a water level change amount detection means for detecting a water level change amount per unit time; an excess/deficiency state determining means for determining an excess/deficiency state of the current total throughput of the filtration basin based on the detected water level; a period determining means for determining a control circumference for starting/stopping the filtration basin based on the detected excess/deficiency state and the detected amount of change in water level; The filter includes a stop command means, and a valve control means for controlling the opening and closing of the on-off valve provided in the filtration pond having the determined pond number based on the command from the means.

(Function) In the present invention, a control cycle is determined based on the current excess/deficiency status of the total throughput and the amount of change in the water level, and based on this control cycle, the determined filter among all the filters is started/stopped. Control. This allows the multiple filtration basins connected to the sedimentation basin outflow drain to be maintained in a suitable condition.
Fully automatic control is possible.

(Example) Hereinafter, an example of the present invention will be described using the accompanying drawings.

FIG. 1 is a block diagram showing a filter control device according to an embodiment of the present invention together with a water purification plant.

First, the configuration of a water purification plant is shown as follows: Sedimentation tank 1
A flow meter 2 connected to a water receiving well (not shown) is connected to the input side of the flow meter 2, and water to be purified flows through the flow meter 2.

On the other hand, on the output side of the settling tank 1, there is a settling tank outflow conduit 3 into which water overflowed from the settling tank 1 flows.
is located. Let the amount of water flowing into the outflow channel per unit time be Q (m ³ /hour), and the current water level be h. Further, it is assumed that the horizontal cross-sectional area of the outflow conduit 3 is A (m ² ).

A plurality of filtration basins 5 are connected in parallel to the sedimentation basin outflow conduit 3 via an electromagnetic on-off valve 4, and a water distribution basin 8 is connected to the filtration basin 5 through a flow meter 6 and an electromagnetic on-off valve 7. A conduit 9 is connected thereto.

On the output side of the water distribution reservoir 8, there are a water distribution pump 10 and a flow meter 11 for supplying purified water to consumers.
is connected.

Water level detectors 12 are installed in the outflow culvert 3 and each pond 5, 8.
and 13 and 14 are attached, respectively.

In the water purification plant with the above configuration, each filtration basin 5
If the throughput of is qi (i = 1 to n, there are n filters from No. 1 to No. n filters), the change in water level h with respect to time t is dh/dt = ( It is expressed as Q-Σqi)/A...(1). In other words, the water treatment flow rate Q of the water treatment plant
Compared to , when the sum Σqi of the filtration flow rate of each filtration basin is large, the water level h of the sedimentation basin outflow conduit 3 falls, and conversely, when it is small, the water level h rises.

Further, the relationship between the water level h of the sedimentation basin outflow conduit 3 and the water level H of the water distribution reservoir 8 is expressed as h-H=Ri(qi)+ri(qi)...(2). Here, Ri (qi): Head loss of the No. I filtration basin Ri (qi): Head loss of the valves of the No. I filtration basin Therefore, the opening degree of the filtration flow rate control valve is constant,
If the number of operating filtration basins is also constant, if the difference between the water level h of sedimentation basin outflow channel 3 and the water level of water distribution area 8 increases, the filtration flow rate qi will increase, and conversely, if the difference decreases, the filtration flow rate qi will decrease. do. In other words, water with a flow rate Q flowing into the sedimentation basin outflow channel 3 from the sedimentation basin 1 is affected by the head loss according to the expression (2), and causes a water level fluctuation dh/dt according to the expression (1).

Therefore, by adjusting the total processing amount Σqi,
It is necessary to absorb water level fluctuations dh/dt and keep the water level h within a predetermined range.

Next, a filter control device connected to the water purification plant will be explained.

The reference water level setting unit 12 sets reference values h H , _{h L} of two levels, high and low, as values with predetermined intervals above and below the control center value for the water level h of the sedimentation basin outflow channel 3.
This is to set.

The water level status determination logic 13 is the sedimentation pond outflow culvert 3
The detected value h of the water level detector 12 and the reference value h _H ,
h _L and determines the following three states A, B, and C, and depending on each state, three types of signals "+1", "0", "-"
1" is output.

h＞h _H (State A)..."+1" h _L ≦h≦h _H (State B)..."0"h<h _L (State C)..."-1" ...(3) The signal "+1" is the water level This means that the total throughput Σqi should be increased in order to lower the water level _h in view of the fact that h has exceeded the upper limit hH. Similarly, the signal "0" means that it should be left as is, and the signal "-1" means that it should be decreased.

The water level change detection logic 14 detects the water levels h ₁ and h ₂ after a predetermined observation time Δt, and detects the difference between the two water levels, that is, the water level change Δh.

△h=h ₁ −h ₂ (4) The control cycle setting logic 15 inputs the water level change amount △h with respect to the observation time △T, sets the parameter value to α, and sets the control period for controlling the on-off valves 4 and 7. The control period T is calculated using the following equation.

T=|(ΔT/Δh)|·α (5) Here, the calculated control period T is a value inversely proportional to the water level change amount Δh. Therefore, when the amount of water level change Δh is large, the control period T becomes short and the filter starts immediately. On the other hand, when the water level change amount Δh is small, the control period T becomes long,
Filtration start-up will be delayed.

The pond number determination logic 16 determines the number of the filtration ponds to be started/stopped, depending on the configuration of the water purification plant, for example, cyclically determining a plurality of filtration ponds in order for the purpose of uniform control. It is something to do.

The start/stop command unit 17 issues a start/stop command to the filter having the determined number using the control cycle T.

The valve opening/closing control logic 18 controls opening and closing of the opening/closing valves 4 and 6 based on command signals from the start/stop command section 17.

That is, in the case of filtration activation, the output of the filtration activation command is waited until T time has elapsed from the previous filtration activation time, and after the T time has elapsed, the filtration activation command is output. Similarly, in the case of stopping the filter, the output of the filter stop command is waited until T time has elapsed from the previous filter stop time, and after the T time has elapsed, the filter stop command is output.

FIG. 2 is an explanatory diagram showing the operation of the filter control device according to the present invention.

The process in step 201 is executed by the water level state change logic 13, and the states A, B, and C shown in equation (3) are determined according to the detected water level h. If the state is A or C, the process moves to step 202, and if the state is C, the process ends here.

The process of step 202 is executed by the control cycle setting logic 15, and calculates the control cycle T shown by equation (5) according to the water level change amount Δh detected by the water level change amount detection logic 14.

In step 203, the pond number determination logic 16 determines the pond number to be activated/deactivated.

Step 204 is executed by the start/stop command section 17 to classify the states A and C, and if the state is A, the process goes to step 205, and if the state is C, the process goes to step 206.

Steps 205 and 206 are executed by the valve opening/closing control logic, and in step 205, a startup command is output for the filter with the determined number. In step 206, a stop command is output for the filter with the determined number.

However, in the case of starting the filter, the output of the filter starting command is waited until T time has elapsed since the previous starting of the filter, and after the T time has elapsed, the filter starting command is output. Similarly, in the case of stopping the filtration, the output of the filtration stop command is waited until T time has elapsed from the previous filtration stop time, and after the T time has elapsed, the filtration stop command is output.

To explain the operation of this embodiment in more detail,
Now, the flow rate Q to the sedimentation pond outflow culvert 3 increases, and the water level h
If it exceeds the upper limit h _H , the water level state determination logic 13 outputs a signal "+1" (state A) in order to increase the total throughput Σqi of the filter 5.

Therefore, the start/stop control section 17 uses the control period T calculated by the control period setting logic 15 to
Regarding the filtration basins 5 determined by the pond number determination logic 16, the currently stopped filtration basins 5 are controlled to be activated in response to an increase in the water level h. The opposite is true for lowering the water level, and a predetermined filter is controlled to stop.

Therefore, in this embodiment, the start/stop control section 17
By detecting the flow rate qi of each filter 5, the control status of each valve 4, 6, and the water level of the filter 5, and starting/stopping the filter 5 each time the set control cycle T arrives, The throughput qi of each filter 5 is controlled to be between the maximum and minimum allowable amounts qmax and qmin.

qmin≦qi≦qmax …(6) In other words, if the filtration flow rate per filtration basin exceeds the maximum filtration flow rate, the sedimentation basin outflow culvert 3
The water level h rises. When the water level h reaches or exceeds the maximum water level, the control period T is calculated based on the water level change rate Δh. Then, when the control cycle T comes, one predetermined filter is activated. In this case, 1
Since the number of ponds is increased, the filtration flow rate per pond decreases, but since each filter pond 5 cannot flow a flow rate lower than the minimum filtration flow rate, the water level h of the sedimentation basin outflow culvert 3 decreases. When the water level h becomes below the minimum water level, the control period T is calculated based on the water level change rate Δh.
Then, when the control cycle T comes, one predetermined filter 5 is stopped. Therefore, the number of fluctuations in the filtration flow rate of each filtration basin becomes small, and the water level of the sedimentation basin outflow channel 3 can be adjusted by controlling the start/stop of the filtration basins 5 while maintaining the throughput of all the filtration basins 5 in an optimal state. h can be converged within the reference values h _H and hL, and the filter can be maintained in a more suitable state.

In addition, in the above example, although the number of starting/stopping filter basins 5 is shown as being singular, the number of starting/stopping may be plural.

Further, although the starting/stopping filter 5 is shown as being singular in a certain time period, a plurality of filters 5 may be changed cyclically at the control period T.

Further, although the start/stop duty is shown as being constant with respect to the control period T calculated according to the water level change amount Δh, the duty may be changed while the control period T is constant.

FIG. 3 is an explanatory diagram showing another embodiment.

In this embodiment, in contrast to the embodiment shown in FIG.
A flow rate regulating valve 19 is provided next to the on-off valve 7 provided in each filter basin 5, and start/stop control is performed in accordance with the flow rate control of each filter basin 5.

The control device includes a flow rate target value setting unit 20 that sets a target flow rate value qo, and a filtration flow rate control device that controls the opening of the flow rate control valve 19 of each filtration basin 5 so that the throughput amount qi matches the target value qo. 21 are provided.

In this embodiment, the flow rate control can only be performed by starting/stopping in the embodiment shown in FIG.
can be maintained at the target value qo, so the water level h can be converged within the upper limit h _H and lower limit h _L by adding start/stop control to this while completely observing the conditions shown in equation (6). I can do it.

In this example, the target value qo is kept constant, but the water level h
The target value ho is set to the allowable value _{qmax ,} so that the
A target value correction section that changes the target value within the range of qmin may be provided.

In this case, it is possible to maintain the water level h at the target value ho as long as there is no large variation in the flow rate Q.

Note that the present invention is not limited to the above-mentioned embodiments, but can be implemented in other embodiments by making appropriate design changes.

[Effects of the Invention] As described above, according to the present invention, multiple filters connected to a sedimentation tank outflow drain are controlled to start/stop, so all filters are maintained in a suitable state and controlled fully automatically. be able to.

In addition, the only requirement for the plant configuration is to equip each filtration basin with an electromagnetic on-off valve.
It can also be easily applied to existing plants that are not equipped with a filtration flow control valve.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a filter control device according to an embodiment of the present invention together with a water purification unit, Fig. 2 is a flowchart showing the operation of the above embodiment, and Fig. 3 is a block diagram showing another embodiment. be. 1... Sedimentation basin, 3... Sedimentation basin outflow drain, 5... Filtration basin, 4, 7... Electromagnetic shut-off valve, 8... Distribution reservoir,
Q... Inflow amount, qi... Processing amount of each filter.

Claims (1)

[Scope of Claims] 1. In a filtration control device in a water purification plant where water flowing from a sedimentation basin to a sedimentation basin outflow drain is filtered through a plurality of filtration basins and supplied to a distribution basin, the filtration basin to be started/stopped is pond number determining means for determining a pond number; water level detecting means for detecting the water level of the sedimentation pond outflow drain; water level change amount detection means for detecting the amount of change in water level per unit time of the sedimentation basin outflow drain; Excess/deficiency determining means for determining whether the current total throughput of the filtration basin is excessive or insufficient based on the detected water level; and activating the filtration basin based on the over/deficit status determined by the means and the detected water level change amount. /Period determining means for determining a stop control cycle; and activation for the filter pond with the determined pond number/
Filtration in a water purification plant comprising: a start/stop command means for instructing stoppage; and a valve control means for controlling opening/closing of an on-off valve provided in the filtration basin with the determined pond number based on a command from the means. Pond control device.