JPH0523664A - Method for automatically controlling backwashing of biological activated-carbon treating tower - Google Patents

Abstract

PURPOSE:To improve a cleaning effect by passing cleaning water backward through an activated-carbon treating tower in accordance with the water level in the tower and supplying air from the lower part of the tower. CONSTITUTION:The backwashing of a downward-flow biological activatedcarbon treating tower is automatically controlled by a controller 24, and the system is formed with a level gage 23 (backwashing is started at a water level L2, air cleaning is started at a level L3, and the backwashing is finished at a level L1), a backwashing pipeline (a backwashing motor-operated valve 17, a backwashing flowmeter 18 and a backwashing pump 19) and an air cleaning pipeline (an air cleaning motor-operated valve 20, an air cleaning flowmeter 21 and a cleaning air pump 22). When backwashing is started, activated carbon- treated water is sent to the tower to raise the water level and to secure the space permitting the fluidization of the mixed part of activated carbon. However, this operation is omitted when the water head is sufficient at the start of backwashing. When a combination of aeration and water backwashing is applied, the activated-carbon tank is fluidized by aeration to increase the water backwashing effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic backwashing control method for a biological activated carbon treatment tower in a water purification treatment device.

[0002]

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

In the water purification process of FIG. 2, raw water taken from rivers and lakes enters the landing well 1. Next, the flocculation basin 4 is entered through the mixing basin 2 in which a flocculant is injected and mixed for the purpose of removing turbid components (viscosity, organic matter, etc.) in raw water. In the floc formation pond 4, stay for a certain period of time, and
Grow larger flocs by gentle agitation. After that, the flocs grown in the flocculation basin are separated in the sedimentation basin 6, and fine flocs that cannot be separated in the sedimentation 6 are removed in the filtration basin 7. In this water purification process, algae killing treatment, iron removal, manganese removal, and chlorine injection for the purpose of removing chromaticity are performed.

In recent years, water pollution in rivers and lakes is advancing due to the deterioration of water environment in urban areas, and the chromaticity in raw water for tap water can be improved only by combining conventional coagulation sedimentation, filtration and chlorine treatment. There is a limit to the removal of odors, and there is a concern that trihalomethane, which is a carcinogenic substance, is an organochlorine compound generated due to an increase in chlorine injection amount accompanying the deterioration of water quality of raw water. Furthermore, the inclusion of trace amounts of harmful substances is also a problem. Against this background, there has been a strong demand for “safe and delicious water”.
Therefore, as a method of effectively removing or reducing these, a method of incorporating an advanced treatment combining ozone treatment, activated carbon treatment and the like into a water purification process has come to be implemented.
Activated carbon treatment adsorbs and removes trace organic substances in the water to be treated with activated carbon, and depending on the water purification process, it is also possible to reproduce microorganisms on the surface of activated carbon and remove ammonia in the water (called biological activated carbon treatment). ). There are two types of activated carbon treatment methods: fixed tank type and fluidized tank type, and they are distinguished depending on whether the activated carbon is used in a fixed tank state or in a fluidized state. Move in countercurrent. The fixed tank type and the fluidized tank type each have advantages and disadvantages. The downflow (fixed tank) type activated carbon treatment has the advantage that the operation is simpler and the outflow of activated carbon particles is smaller than the fluidized-bed type, but in order to remove the head loss due to the accumulation of suspended suspended matter, It is necessary to wash the activated carbon tank regularly.

[0005]

In the downward flow type biological activated carbon treatment tower, when water is continuously supplied, the water resistance is increased due to the influence of suspended substances accumulated in the activated carbon tank or microorganisms propagating in the activated carbon tank. The water head (water level at the upper end of activated carbon) rises. For this reason, it is necessary to regularly wash the activated carbon tank to remove suspended substances and the like that cause resistance to water flow. Examples of the cleaning method include backwashing with water and air cleaning. In backwashing with water, stop the passage of water to be treated, and use the activated carbon-treated water as water for backwashing from the bottom of the treatment tower so that the tank expansion rate of the activated carbon tank is usually about 30-40%. It is adjusted and the backwashing operation is continued for a certain period of time. The backwash drainage flows out from the upper part of the treatment tower due to overflow and is returned to the raw water of the water treatment plant. Further, in the air cleaning, like the backwashing with water, the flow of the water to be treated is stopped, and air is sent from the lower part of the processing tower to vigorously mix the entire activated carbon tank. When only backwashing is insufficient, it is effective and has a large cleaning effect, but there is a problem that abrasion of activated carbon particles and separation of microorganisms occur when biological activated carbon treatment is performed. Normally, air washing is not carried out alone, but is used as an aid for 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 the 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 thereof is to obtain a high-performance cleaning action by efficiently controlling the combination of water backwashing and air backwashing. ..

[0007]

In order to achieve the above object, the present invention relates to a method of treating raw water by passing the raw water to be treated through an activated carbon treatment tower and then introducing the raw water into a treatment tank. Washing water is caused to flow backward to the activated carbon treatment tower corresponding to the water level of the activated carbon treatment tower, and air is supplied from below the activated carbon treatment tower.

[0008]

[Function] The controller automatically controls the backwashing of the downward flow type biological activated carbon treatment tower, and the system configuration consists of a level meter (backwash start water level, air wash start water level, backwash end water level) and water backwash. It consists of a washing pipe system (motor valve for backwashing, flow meter for backwashing, pump for backwashing) and an air washing pipe system (motorized valve for air washing, air flow meter for air washing, air pump for air washing). At the start of the backwash operation, the activated carbon treated water is sent to the treatment tower to raise the water level in order to secure a flow space for the activated carbon mixed portion. However, this operation can be omitted if there is sufficient head at the start of backwashing. The backwashing method is a method that combines air aeration and water backwashing to minimize the separation of the microbial film on the surface of the activated carbon particles, and a method that improves the backwashing effect by combining air washing and water backwashing. Is possible. In the usual backwashing method that combines air aeration and water backwashing, the activated carbon tank is fluidized by air aeration in order to improve the water backwashing effect. The water level for starting air cleaning is set to a position lower than the overflow level so that activated carbon particles do not flow out from the upper part of the tower during air aeration and air cleaning.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a system for carrying out an automatic backwashing control method for 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 portion 13 and The backwash water collecting section 14 is provided. That is, there is a treated water collecting portion 13 at the bottom of the tower, and a filter 1 that holds the activated carbon 11 at the upper portion thereof and allows 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 that collects the backwash drainage that overflows during water backwashing.
The backwash drainage that overflows here is discharged as backwash water 15.

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

In the system of FIG. 1, in the normal activated carbon treatment, raw water for activated carbon treatment is supplied from the upper part of the activated carbon treatment tower 10 to adsorb a trace amount of organic substances, suspended matter components, etc. in the raw water by the activated carbon to treat the treated water. The treated water is collected in the treated water collecting section 13, the treated water electric valve 16 is opened, and the treated water is sent to the treated water tank. When water flow is continued, the water head gradually increases due to adsorption of suspended matter components and the like to the activated carbon layer 11. L1 is the water level at the end of backwash, L2 is the backwash start water level, and L3 is the air wash start water level. The position of this head is detected by the backwash control level meter 23, and when the preset backwash start level L2 is reached, the backwash automatic wash is started.

In the automated backwash cleaning, the system cleaning controller 24 operates each device in the following sequence.

That is, (step 1) When the level meter 23 detects the backwash start water level L2, (step 2)
The activated carbon treatment raw water is stopped, and the controller 24 closes the treated water electric valve 16 and (step 3) opens the backwash electric valve 17 and operates the backwash pump 19 to operate the activated carbon treatment layer 11. Back wash. When the water level of the activated carbon treatment tower 10 rises to reach the level L3 (air cleaning backwash start water level level) by this backwashing action, the controller 24 controls the backwash motor-operated valve 17 based on the detection signal of the level meter 23. At the same time as closing and stopping the backwashing pump 19, (step 4) the air washing motor-operated valve 20 is opened and the air washing pump 22 is operated to perform air aeration. The operator sets the duration of the air aeration operation in advance.

(Step 5) The backwash motor-operated valve 17 is opened, the backflow pump 10 is operated, and the backwash motor 18 is operated so that the flow signal of the backwash flow meter 18 becomes a preset value. The opening degree of the valve 17 is adjusted to control the flow rate. The operator sets the duration of backwashing with water in advance. The backwash waste water overflows from the upper part of the activated carbon treatment tower 10, flows into the backwash water collecting portion 14, and is discharged as backwash water 15. After the backwash set time has elapsed, the backwash electric valve 17 is closed and the backwash pump is stopped.

(Step 6) As an operation for starting water flow, the treated water motor valve 16 is opened, and the activated carbon tower 1 after backwashing with water is washed.
When the water head of 0 decreases and reaches the water level L1 (water level at the end of backwashing), the supply of raw water for activated carbon treatment is started.

In order to enhance the effect of the backwash cleaning, "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 rate signal of the air cleaning air flow meter 21 becomes a preset value. The operator sets beforehand the duration of backwashing with air.

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

(1) Step 3 [Treatment of treated water] 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 such that the activated carbon is in a fluidized state, and wear of activated carbon particles and microbial detachment on the surface are minimized.

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

(4) It is possible to set [air cleaning] every several backwashing operations as a judgment as to whether or not to carry out [airwashing] in step 4. It is also possible to carry out 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 set values (level meter water level, flow rate, air volume,
If the time setting is set, the backwash operation can be performed automatically. In addition, by combining backwashing with water and air aeration, backwashing can be performed with minimal separation of the microbial membrane on the surface of activated carbon particles, and air washing can be performed according to the degree of accumulation of pollutants in the activated carbon layer. Can be incorporated to improve the cleaning effect. Furthermore, by performing automatic backwash control of the downward flow type biological activated carbon treatment tower in the advanced water purification treatment, the reliability of the activated carbon treatment operation and the reliability of the entire water purification process can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an automatic backwash control system for carrying out an automatic backwash 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 part, 14 ... Backwash water collecting part, 15 ...
Backwash water, 16 ... Electric valve for treated water, 17 ... Electric valve for backwash,
18 ... Flowmeter for backwashing, 19 ... Pump for backwashing, 20 ... Electric valve for air washing, 21 ... Air meter for air washing, 22 ... Air pump, 23 ... Level meter for backwashing control, 24 ... Controller for system control ..

Claims (1)

Claim: What is claimed is: 1. A raw water to be treated is passed through an activated carbon treatment tower, which is then introduced into a treatment tank to treat the raw water, which corresponds to the water level of the activated carbon treatment tower. A method for automatically controlling backwashing of a biological activated carbon treatment tower, characterized in that washing water is allowed to flow back into the activated carbon treatment tower and air is supplied from below the activated carbon treatment tower.