JP3149465B2 - Automatic backwash control method for biological activated carbon treatment tower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically controlling backwashing of a biological activated carbon treatment tower in a water purification treatment apparatus.

[0002]

2. Description of the Related Art FIG. 2 shows a water purification process which is currently generally performed. In FIG. 2, 1 is a landing well, 2 is a mixing pond, 3 is a stirrer, 4 is a floc formation pond, 5
Is a stirrer, 6 is a sedimentation basin, and 7 is a filtration pond. Reference numeral 8 denotes a water purification treatment system, which includes an ozone contact tower 9 and an activated carbon treatment tower 10.

In the water purification process shown in FIG. 2, raw water taken from a river / lake enters the landing well 1. Next, in order to remove the turbid components (viscosity, organic matter, etc.) in the raw water, the flocculant enters the flocculation pond 4 through the mixing pond 2 in which the coagulant is injected and mixed. In the floc formation pond 4, it is kept for a certain time, and
Grow larger flocks by gentle stirring. Thereafter, the flocs grown in the floc forming pond are separated in the sedimentation basin 6, and fine flocs that cannot be separated in the sedimentation basin 6 are removed in the filtration pond 7. In this water purification process, a process of injecting chlorine for the purpose of algicidal treatment, iron removal, manganese removal, and chromaticity removal is performed.

[0004] In recent years, water pollution in rivers and lakes has been progressing due to the deterioration of the water environment in urban areas, and the chromaticity of raw water for tap water has been reduced by a combination of conventional coagulation sedimentation, filtration, and chlorination. There is a limit in removing odors, and there is a concern that trihalomethane, which is a carcinogenic substance, may increase in organochlorine compounds generated by an increase in the amount of chlorine injected due to deterioration of the quality of raw water. Furthermore, contamination of trace harmful substances has become a problem. Against this background, there has been an increasing demand for safe and delicious water.
Therefore, as a method for effectively removing or reducing these, a method of incorporating advanced treatment combining ozone treatment, activated carbon treatment, and the like into a water purification process has come into practice.
Activated carbon treatment is to remove trace organic substances in the water to be treated by activated carbon by adsorption. Depending on the water purification process, it is also possible to propagate microorganisms on the surface of activated carbon and remove ammonia in the water (referred to as biological activated carbon treatment). ). There are two types of activated carbon treatment methods: fixed tank type and fluidized tank type.The type of activated carbon is distinguished depending on whether the activated carbon is used in a fixed tank state or in a fluidized state. Moving in countercurrent. Each of the fixed tank type and the fluidized tank type has advantages and disadvantages. The downflow (fixed tank) type activated carbon treatment has the advantage of easier operation and less outflow of activated carbon particles than the fluidized tank type. However, in order to remove the head loss due to the accumulation of suspended suspended solids, It is necessary to periodically clean the activated carbon tank.

[0005]

SUMMARY OF THE INVENTION In a downflow type biological activated carbon treatment tower, if water is continuously supplied, water flow resistance is affected by suspended substances accumulated in the activated carbon tank or microorganisms propagated in the activated carbon tank. The water head (water level at the top of the activated carbon) rises. For this reason, the activated carbon tank must be periodically cleaned to remove suspended substances and the like that cause water flow resistance. Washing methods include backwashing with water and air washing. In the water backwashing, the flow of the water to be treated is stopped, and from the lower part of the treatment tower, the activated carbon treated water is used as backwashing water so that the expansion rate of the activated carbon tank is usually about 30 to 40%. The backwash operation is to be continued for a certain period of time after adjustment, and the backwash wastewater flows out of the upper part of the treatment tower by overflow and is returned to the raw water of the water treatment plant. In the air cleaning, as in the case of backwashing, the flow of the water to be treated is stopped, air is sent from the lower part of the processing tower, and the entire activated carbon tank is vigorously mixed. Although backwashing alone is effective when the cleaning is not sufficient, the cleaning effect is great, but there is a problem that the activated carbon particles are worn away and the microorganisms are peeled off when biological activated carbon treatment is performed. Normally, air cleaning is not performed independently but is used as an aid to backwashing with water. Therefore, in order to operate the downflow type biological activated carbon treatment tower efficiently, it is important to combine backwashing and how to properly perform backwashing, and it is necessary to automate backwashing. Occurs.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to obtain a high-performance cleaning action by efficiently controlling the combination of water backwashing and air backwashing. .

[0007]

The present invention SUMMARY OF], in order to achieve the above object, conductive sawn to the processing tank after flowing through the raw water to be processed activated carbon treatment column, in which process the raw water, the Water level at the end of backwash in biological activated carbon treatment tower
Level, backwash start water level, and air wash start level.
The step of setting in advance and the head of the biological activated carbon treatment tower is
When the set backwash start level is reached, the biological activity
Stop the flow of the raw water to the charcoal treatment tower and backwash
Starting and then the head of the biological activated carbon treatment tower
Is reversed when the set air cleaning start level is reached.
Stopping the washing and starting air cleaning for a predetermined time;
After the air cleaning is completed, start backwashing for a predetermined time again and backwash
Wastewater overflows from the biological activated carbon treatment tower
Process and after the predetermined time of the backwash has passed, the treatment is performed in the treatment tank.
Guide the water, the head of the biological activated carbon treatment tower is set as above
When the water level reaches the end of the backwash,
And restarting the process .

[0008]

[Function] The controller automatically controls the backwashing of the downflow type biological activated carbon treatment tower using a controller. The system configuration consists of a level meter (backwashing start water level, air cleaning start water level, backwashing end water level) and water backflow. It consists of a washing pipe system (motor valve for back washing, flow meter for back washing, pump for back washing) and an air washing pipe system (motor valve for air washing, air meter for air washing, air pump for air washing). At the start of the backwashing operation, activated carbon treated water is sent to the treatment tower to increase the water level in order to secure a flow space for the activated carbon mixed portion. However, this operation can be omitted if the head at the start of backwashing is sufficient. The backwashing method is a method that combines air aeration and water backwashing to select a method that minimizes the separation of microbial membranes on the surface of activated carbon particles and a method that combines air washing and water backwashing to improve the backwashing effect. Is possible. In a normal backwashing method combining air aeration and water backwashing, the activated carbon tank is fluidized by air aeration in order to increase the water backwashing cleaning effect. The air cleaning start water level is set at a position lower than the overflow level so that activated carbon particles do not flow out of the top of the tower during air aeration and air cleaning.

[0009]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a system for implementing the method for automatically controlling backwashing of a biological activated carbon treatment tower according to the present invention. The activated carbon treatment tower 10 includes a granular activated carbon layer 11, a filter 12, a treated water collecting section 13, and It consists of a backwash water collecting part 14. That is, there is a treated water collecting section 13 at the bottom of the tower, and a filter 1 for holding activated carbon 11 and allowing only treated water to pass therethrough.
There are two. In addition, at the top of the tower, there is a backwash water collecting section 14 for collecting backwash wastewater overflowed during backwashing,
The backwash wastewater overflowed here is discharged as backwash water 15.

In FIG. 1, reference numeral 16 denotes an electric valve for treated water, 17 an electric valve for backwashing, 18 a flowmeter for backwashing, and 19 a pump for backwashing. Reference numeral 20 denotes an electric valve for air cleaning, 21 denotes an air flow meter for air cleaning, 22 denotes an air pump for air cleaning, 23
Denotes a backwash control level meter, and 24 denotes a system control controller.

In the system shown in FIG. 1, in the ordinary activated carbon treatment, raw water for activated carbon treatment is supplied from the upper part of the activated carbon treatment tower 10, and trace organic substances and turbid components in the raw water are adsorbed by the activated carbon, and the treated water is removed. The collected water is collected in the treated water collecting section 13 and the electric valve 16 for treated water is opened to be sent to the treated water tank. When the water flow is continued, the water head gradually increases due to the adsorption of the turbid components and the like to the activated carbon layer 11. L1 is a water level at the end of backwashing, L2 is a water level at the start of backwashing, and L3 is a water level at the start of air washing. The position of the water head is detected by the backwash control level meter 23, and when the backwash start level L2 is set in advance, the automatic backwashing is started.

In the automatic backwashing, each device is operated by the system washing controller 24 in the following sequence.

That is, (Step 1) When the level meter 23 detects the backwashing start water level L2, (Step 2)
The raw water for activated carbon treatment is stopped, and the controller 24 closes the electric valve 16 for treated water, (Step 3) opens the electric valve 17 for backwashing, and operates the backwash pump 19 to operate the activated carbon treatment layer 11. Backwash. When the water level of the activated carbon treatment tower 10 rises to the level L3 (air cleaning backwashing start water level) due to the backwashing action, the controller 24 activates the backwash motorized valve 17 based on the detection signal of the level meter 23. The pump 19 for closing and backwashing is stopped, and (step 4) the electric valve 20 for air cleaning is opened, and the pump 22 for air cleaning is operated to perform air aeration. The duration of the air aeration operation is set in advance by the operator.

(Step 5) The backwash motor valve 17 is opened, the backflow pump 10 is operated, and the backwash motor is operated so that the flow signal of the backwash flowmeter 18 becomes a preset value. The flow rate control is executed by adjusting the opening of the valve 17. The operator sets the water backwashing continuation time in advance. The backwash water overflows from the upper part of the activated carbon treatment tower 10, flows into the backwash water collecting section 14, and is discharged as backwash water 15. After the elapse of the set backwashing time, the backwash electric valve 17 is closed, and the backwash pump is stopped.

(Step 6) As a water flow start operation, the treated water electric valve 16 is opened, and the activated carbon tower 1 after backwashing and washing is performed.
When the water head of 0 decreases and reaches the water level L1 (water level at the end of backwashing), supply of raw water for activated carbon treatment is started.

In order to enhance the effect of the backwashing, "air cleaning" is performed in step 4. In this case, the air cleaning electric valve 20 is opened, and then the cleaning air pump 22 is opened.
To drive. The flow rate is controlled by adjusting the opening degree of the air cleaning electric valve 17 so that the flow value signal of the air cleaning air flow meter 21 becomes a preset value. The air backwashing continuation time is set in advance by an operator.

The meanings and points to be noted of the steps are as follows.

(1) Step 3 [Water treatment water supply] is an operation for securing a flow space for the activated carbon mixed portion when performing [air aeration] and [air cleaning] in step 4;
If the water head at the start of backwashing is sufficient, the water level levels L2 and L3 can be made common and step 3 can be omitted.

(2) The duration of step 4 [air aeration] is set to a minimum time so that the activated carbon is in a fluidized state, thereby minimizing wear of the activated carbon particles and microbial detachment on the surface.

(3) The backwashing flow rate in step 5 [water backwashing] is set and adjusted so that the coefficient of expansion of the activated carbon layer is usually about 30 to 40%, so that activated carbon particles do not flow out. To try.

(4) As a judgment as to whether or not to perform [air washing] in step 4, it is possible to set [air washing] every several backwash operations, or to perform a normal backwash operation. It is also possible to execute the [air cleaning] when the time interval is shortened and becomes less than a certain set time.

[0023]

The present invention is as described above, and comprises an activated carbon treatment.
After flowing the raw water to be treated into the tower,
Can, in which process the raw water, the biological activated carbon
Water level at the end of backwash in the treatment tower, water level at backwash start
Setting the air and air cleaning start level in advance,
The head of the biological activated carbon treatment tower starts backwashing at the set time
When the level is reached, the source
A step of stopping water flow and starting backwashing, and
Then, the head of the biological activated carbon treatment tower is set to the air
Stop backwashing when the cleaning start level is reached
Starting the air cleaning, and restarting after the air cleaning.
And start backwashing for a specified period of time,
A step of overflowing from the treatment tower, and
After a lapse of a fixed time, the treated water is guided to the treatment tank, and the biological activity is
The head of the charcoal treatment tower is at the water level
Restarting the flow of the raw water when the water reaches
Therefore, if an operator previously sets necessary setting values (level meter water level, flow rate, air volume, time setting), the backwashing operation can be performed automatically. In addition, by combining backwashing with water and air aeration, a backwashing operation that minimizes the separation of microbial membranes on the surface of activated carbon particles is possible, and air washing is performed according to the degree of accumulation of pollutants in the activated carbon layer. Can be incorporated to increase the cleaning effect. Further, by performing automatic backwashing control of the downflow type biological activated carbon treatment tower in the advanced water purification treatment, the reliability of the activated carbon treatment operation is improved, and the reliability of the entire water purification process is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an automatic backwashing control system for implementing an automatic backwashing control method for a biological activated carbon treatment tower according to an embodiment of the present invention.

FIG. 2 is a block diagram of a general water purification process.

[Explanation of symbols]

10 activated carbon treatment tower, 11 granular activated carbon, 12 filter, 13 treated water collecting section, 14 backwash water collecting section, 15
Backwash water, 16 ... Electric valve for treated water, 17 ... Electric valve for backwash,
18: Backwash flow meter, 19: Backwash pump, 20: Air valve for air washing, 21: Air flow meter for air washing, 22: Air pump, 23: Level meter for backwash control, 24: Controller for system control .

Claims (1)

(57) [Claims] 1. A guide sawn into the treatment tank after flowed through the raw water to be processed activated carbon treatment column, in which process the raw water backwash at the end water level of the biological activated carbon treatment tower, backwash
Set the starting water level and air cleaning start level in advance.
And the head of the biological activated carbon treatment tower is set to the set backwashing start.
When the level is reached, the source
Stopping the flow of water and starting backwashing, and then setting the head of the biological activated carbon treatment tower to the set value.
Stop backwash when the air cleaning start level is reached and
Starting air cleaning for a time, and starting backwashing again for a predetermined time after the air cleaning is completed.
The washing wastewater overflows from the biological activated carbon treatment tower.
And introducing treated water to the treatment tank after a lapse of a predetermined time of the backwashing.
When the head of the biological activated carbon treatment tower is
When the end water level is reached, restart the flow of the raw water
A method for automatically controlling backwashing of a biological activated carbon treatment tower.