JP2002172386A - Washing method for activated carbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the quantity of washing water and washing time in the case of washing activated carbon packed in a tower, by increasing the discharge efficiency of very fine activated carbon particles remained in the tower. SOLUTION: An activated carbon-packed bed is extended by back washing (a first back washing process). After the first back washing process, another back washing is carried out at a flow velocity lower than that of the first back washing process (a second back washing process). After the second washing process, washing is performed by feeding washing water (a washing process).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning activated carbon filled in a column, by improving the efficiency of discharging ultra-fine activated carbon particles remaining in the column, thereby reducing the amount of cleaning water and shortening the cleaning time. The present invention relates to a method for cleaning activated carbon.

[0002]

2. Description of the Related Art In various water treatment apparatuses such as a wastewater treatment apparatus and a pure water production apparatus, activated carbon is often used to adsorb and remove organic substances such as chromaticity and odor components in water, or remove residual chlorine and the like. An activated carbon tower filled with activated carbon is installed for the purpose of decomposing and removing oxidizing substances. In this activated carbon tower,
By continuing the treatment, adhesion and deposition of turbidity in water,
Alternatively, the activated carbon packed bed is clogged due to miniaturization at the time of decomposition of the oxidizing substance, and the pressure difference in the tower increases. Therefore, in order to eliminate the rise in the differential pressure, it is necessary to periodically perform backwashing to discharge the turbidity and the fine activated carbon in the column.

[0003] The backwashing of the activated carbon tower is performed by stopping the flow of raw water and then introducing backwashing water in an upward flow to expand the activated carbon packed bed. After standing, washing water is passed under the same conditions as in the water passing step, and a washing step is performed in which turbidity and fine activated carbon in the tower are discharged into the washing wastewater. Usually, raw water is used as cleaning water, and cleaning wastewater is collected in a raw water tank or discharged out of the system.

[0004] This washing step is continued until turbidity and finely divided activated carbon in the column are almost completely discharged, that is, until these SS are hardly detected in the washing wastewater.
After that, the water passage process is restarted.

[0005]

In the backwashing step of the activated carbon tower prior to the washing step, the activated carbon particles come into contact with each other due to the backwash water flow, and extremely fine activated carbon particles are generated. In particular, in this backwashing step, when backwash water is introduced at a high flow rate in order to efficiently remove turbidity adhering to activated carbon,
The contact efficiency between activated carbon particles is high, and turbidity is efficiently removed and removed, but at the same time, a large amount of activated carbon fine particles are generated.

[0006] When a large amount of fine particles of activated carbon are generated in the tower due to backwashing, it is not easy to discharge the fine particles to the outside of the tower in the washing step. A large amount of water is required, a long cleaning time is required, and the processing cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for cleaning activated carbon, which has a remarkably high cleaning efficiency and can reach a water-collectable value with a short cleaning time and a small amount of cleaning water. I do.

[0008]

Means for Solving the Problems The method for cleaning activated carbon of the present invention is a method for cleaning activated carbon packed in a tower, comprising the steps of: ), And a second backwashing step (hereinafter referred to as “backwashing”) in which after the first backwashing step, backwashing is performed at a lower flow rate than the backwashing flow rate in the first backwashing step. ), And a washing step of washing by passing washing water after the second back washing step.

According to the method of the present invention, by carrying out light backwashing after the main backwash, ultra-fine activated carbon particles remaining in the column are discharged, and the discharge is facilitated in the subsequent washing step. Thus, the amount of washing water in the washing step can be reduced, and the washing time can be shortened.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the method for cleaning activated carbon of the present invention will be described in detail.

FIG. 1 is a system diagram showing an embodiment of a method for cleaning activated carbon of the present invention.

In the activated carbon tower 1, raw water is passed through for treatment.
In the flowing water process, the valve V₁, V ₅Open other buses
The lube is closed and the raw water is activated via pipes 11, 12, and 13.
Water is passed through the charcoal tower in a downward flow, and treated water is taken out from the pipe 14.
You.

By continuing the flow of the raw water, the pressure difference in the activated carbon tower 1 increases, so that the processing of the raw water (water collection of the treated water) is periodically stopped, and Activated carbon is washed.

In the present invention, washing is performed in the following (1) to (1).
This is performed by performing the step (4).

(1) Main backwashing step The valves V ₂ and V ₃ are opened and the other valves are closed, and raw water is introduced into the activated carbon tower 1 via pipes 11 and 15 in an upward flow, and the activated carbon packed bed 2 is removed. The main backwash is performed by developing and discharging the backwash drainage from the top of the tower via pipes 13, 16, and 17. The backwash water flow rate in this main backwash is LV 10-25.
It is preferable that the activated carbon-filled layer 2 is developed at a development rate of 7 to 25% at m / hr.
~ 20 minutes, the amount of main backwash water is 10 ~ 30B. V. It is preferable to set the degree. In addition, it is preferable to use the treated water of the activated carbon tower 1 as the backwash water, but a sufficient effect can be obtained even with raw water. By performing this main backwash,
The turbidity and the like adhering to the activated carbon particles can be separated and removed, and the turbidity and the like between the activated carbon particles can be suspended and discharged. This backwash wastewater is usually discharged outside the system for wastewater treatment.

(2) Light backwashing step After the main backwashing step, the valves V ₆ and V ₃ are opened and the other valves are closed, and the raw water is supplied to the activated carbon tower 1 through the pipes 18 and 15.
To the pipes 13 and 1 from the top of the tower.
A light backwash is performed by draining through 6,17.
Incidentally, the valve V ₆ is of a small flow rate of the valve V _2, therefore, in this light backwash process, the raw water flows at a low flow rate than the above-mentioned present backwash step of flowing the raw water from the valve V _2. This light backwash has a smaller flow rate than the main backwash,
The backwash water is lightly backwashed so that the activated carbon packed bed 2 slightly flows, and the backwash water flow rate of this light backwash is LV 2 to 5 m / h.
r, it is preferable that the activated carbon packed bed 2 is slightly developed to a developing rate of 3% or less.
~ 20 minutes, light backwash water flow rate is 1-5B. V. It is preferable to set the degree. In addition, although the treated water of the activated carbon tower 1 is preferably used as the backwash water for the light backwash, a sufficient effect can be obtained even with raw water. By performing such a light backwashing after the main backwashing, the ultra-fine activated carbon particles generated in the main backwashing step and remaining in the activated carbon tower 1 are effectively discharged, and in the subsequent washing step, It is easy to discharge. This backwash wastewater is usually discharged outside the system for wastewater treatment.

(3) Standing Step After the light backwashing step, the sheet is once left standing. In a normal case, the standing time is about 5 to 10 minutes.

(4) Washing Step After the standing step, the valves V ₁ and V ₄ are opened, the other valves are closed, and raw water, treated water or pure water is supplied to the pipes 11 and 1.
The water is introduced into the upper part of the activated carbon tower 1 from 2 and 13 and washed by passing water downward. Washing drainage is discharged via pipes 15, 19, and 17. In this washing step, turbid substances such as ultra-fine activated carbon particles remaining in the tower 1 are discharged to the outside of the system. Since the particles are discharged and easily discharged, the amount of cleaning water and the cleaning time in this cleaning step can be significantly reduced as compared with the conventional method without light backwashing. The flow rate of the washing water in this washing step is LV10
The washing time and the flow rate of the washing water are preferably set so that the inside of the tower 1 is sufficiently washed and the concentration of the turbid substance in the washing water reaches a water-collectable value at or below a predetermined value. Generally, the washing time is 60 to 180 minutes and the amount of washing water is 60 to 180 B. V. And a sufficient cleaning effect can be obtained. As this washing water, it is preferable to use treated water, but raw water may be used. This washing drainage
It is usually discharged to the outside of the system for wastewater treatment, or returned to the raw water tank for treatment.

FIG. 1 shows an example of an activated carbon tower to which the present invention is applied, and the activated carbon tower to which the present invention is applied is not limited to the illustrated activated carbon tower.

The activated carbon tower to be washed in the present invention may be one that adsorbs and removes organic substances such as chromaticity and odor components of raw water, and one that decomposes oxidizing substances such as residual chlorine. And both of these functions may be performed. The type (raw material) of the activated carbon to be filled is not particularly limited, and the present invention is applicable to all activated carbons such as coconut husks and coal. Usually, the activated carbon filled in the activated carbon tower has a particle size of about 10 to 32 mesh.

[0021]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 200 mL of activated carbon (particle size: 10 to 32 mesh) was filled, and factory wastewater was passed at LV 20 m / hr to remove organic substances (TOC) and residual chlorine.
(In the water passing step, the valve V
_1, V ₅ only opened, other valves are closed), after 24 hours of continuous water passage, according to the present invention, was washed activated carbon packed bed 2. The opening and closing of the valves, the flow rate, the flow rate and the flow time of each step, and the development rate of the activated carbon packed bed at the time of backwashing were as shown in Table 1. Note that raw water was used as the backwash water, and pure water was used as the wash water. In the washing step, the TOC concentration of the washing wastewater is measured, and the possible water sampling value (washing end time) is set to 400 ppb-T, which is almost the same as the TOC concentration of the raw water.
The cleaning effect was examined as OC. As a result, the TOC concentration of the washing wastewater with respect to the flow rate (BV) in the washing step is as shown in FIG.
V. It was confirmed that the water flow rate reached the water sampling possible value.

Comparative Example 1 The same cleaning effect as in Example 1 was carried out except that the main backwash was performed under the same conditions, and then the light backwash was not performed, but the main backwash was allowed to stand and the washing step was performed. Was examined. The opening and closing of the valves, the flow rate, the flow rate and the flow time of each step, and the development rate of the activated carbon packed bed at the time of backwashing are as shown in Table 1. as a result,
The TOC concentration of the washing wastewater with respect to the water flow rate (BV) in the washing step is as shown in FIG.
200 B. in the washing process until the water sampling possible value is reached.
V. Water was required.

[0024]

[Table 1]

From this result, by performing light backwashing,
It can be seen that the amount of washing water and the washing time can be reduced to 1/10 of the conventional amount.

[0026]

As described above in detail, according to the method for cleaning activated carbon of the present invention, light backwashing is performed after main backwashing, thereby facilitating discharge of extremely fine activated carbon particles remaining in the column. This makes it possible to reduce the amount of washing water in the subsequent washing step and shorten the washing time. For this reason, according to the present invention, it is possible to shorten the period until water flow is restarted and to significantly reduce the amount of drainage, thereby reducing the cost of water treatment.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a method for cleaning activated carbon of the present invention.

FIG. 2 is a graph showing the TOC concentration of the washing wastewater with respect to the amount of passing water (BV) in the washing process of Example 1 and Comparative Example 1.

[Explanation of symbols]

 1 activated carbon tower 2 activated carbon packed bed

Claims (1)

[Claims] 1. A method for washing activated carbon packed in a column, comprising: a first backwashing step of developing an activated carbon packed bed by backwashing; and after the first backwashing step, the first backwashing A second backwash step of performing backwash at a lower flow rate than the backwash flow rate of the step; and a washing step of performing washing by passing washing water after the second backwash step. A featured method for cleaning activated carbon.