JPH11262799A - Waste water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of times of the backwashing work of the adsorbent of the fixed bed of an adsorption tower by adding a sterilizing agent to membrane permeated water between a biological treatment tank and the adsorption tower. SOLUTION: A sodium hypochlorite aq. soln. is stored in a sterilizing agent storage tank 1 2. Sodium hypochlorite is added to the membrane permeated water within an intermediate tank 30 by a sterilizing agent supply pump 13 so that the concn. of effective chlorine in the membrane permeated water to which biological treatment and membrane separation treatment are applied becomes about 10 mg/l to be mixed therewith by a stirrer 15 to perform sterilizing treatment. When the pressure loss of an adsorption tower 5 exceeds about 0.5 kg/cm<2> by this treatment, the adsorbent of the fixed bed 10 of the adsorption tower 5 is backwashed. By this constitution, bacteria permeated through the flat membranes of a filter membrane unit 3 are killed and the generation frequency of the clogging of the fixed bed 10 is reduced and backwashing can be dispensed with until about 90 days are elapsed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating wastewater such as sewage, industrial wastewater, domestic wastewater and the like.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional wastewater treatment method.

In FIG. 3, raw wastewater put in a flow control tank (1) is sent at a constant flow rate to a biological treatment tank (4) having a filtration membrane unit (3) by a drainage supply pump (2). The biological treatment tank (4) contains a suspension in which aerobic microorganisms are dispersed. Although not shown, the filtration membrane unit (3) is made up of a plurality of hollow flat membrane modules, and each flat membrane module is provided between two flat membranes arranged in opposition and the periphery of both flat membranes. It consists of a framed spacer arranged. A suction tube is connected to each flat membrane module so as to communicate with the inside of the hollow portion. Each suction pipe is connected to a membrane permeated water pipe (6) extending from an adsorption tower (5) arranged downstream of the biological treatment tank (4). A suction pump (7) is provided in the middle of the membrane permeated water pipe (6), and the water in the biological treatment tank (4) passes through the flat membrane and is sucked into the flat membrane module by the suction pump (7). And the permeated water is
(5). As the flat membrane of the flat membrane module, an ultrafiltration membrane or a microfiltration membrane is used.
Among them, it is preferable to use a microfiltration membrane having relatively low suction resistance and low cost. In addition, filtration membrane unit
In (3), a capillary module using a hollow fiber membrane can be applied instead of a flat membrane module using a flat membrane.

Then, air is blown into the aeration device (9) by the blower (8) to aerate the raw wastewater from below the filtration membrane unit (3), and the air is sucked by the suction pump (7). Then, the organic matter in the raw wastewater is decomposed by aerobic microorganisms and subjected to biological treatment, and sludges and suspensions such as decomposed organic matter and inorganic matter are filtered by the flat membrane module of the filtration membrane unit (3). Separated and subjected to a membrane separation treatment, the permeated water permeating the flat membrane is sent to the adsorption tower (5) through the permeated water pipe (6). The adsorption tower (5) is equipped with a fixed bed (10) filled with an adsorbent such as activated carbon, and the membrane permeated water sent to the adsorption tower (5) passes through the fixed bed (10) while passing through the fixed bed (10). Trace components remaining in water are adsorbed and removed. The permeated water passing through the fixed bed (10) is sent to the discharge tank (11).

Thereafter, the germicide stored in the germicide storage tank (12) is added to the membrane permeated water in the discharge tank (11) by the germicide supply pump (13), and the stirrer is driven by the motor (14). According to (15), the membrane permeated water and the germicide are mixed and sterilized. The treated water subjected to the sterilization treatment is discharged from the discharge tank (11) to the outside of the system. Thus, the wastewater is treated.

The pressure loss in the adsorption tower (5) is measured with a pressure gauge (1).
When the pressure loss reaches a certain value, the operation of the drainage supply pump (2) and the suction pump (7) is stopped to stop drainage treatment, and the backwash pump (17) By discharge tank
The water in (11) is fed from the outlet side of the adsorption tower (5) through the conduit (18) to backwash the adsorbent of the fixed bed (10), and the water used for the backwash is passed through the conduit (19). Send it to the flow control tank (1). A conduit (18) for sending water in the discharge tank (11) to the adsorption tower (5), and a flow control tank for water used for backwashing
The conduit (19) that feeds to (1) is provided with valves (20) and (21),
These valves (20) and (21) are opened only when the adsorbent of the fixed bed (10) is backwashed.

[0007]

Since the permeated water fed into the adsorption tower (5) contains no sludge or suspended matter, there is almost no clogging of the fixed bed (10) in the adsorption tower (5). It is believed that. However, bacteria smaller than the pore diameter of the flat membrane of the filtration membrane unit (3) penetrate the flat membrane, and the bacteria grow by utilizing nutrients in the permeated water, thereby fixing the adsorption tower (5). The floor (10) becomes clogged in a relatively short period of time. Therefore, the conventional method requires frequent backwashing of the adsorbent of the fixed bed (10), and there is a problem that the operation is troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to reduce the frequency of occurrence of clogging of the fixed bed of the adsorption tower as compared with the conventional method. An object of the present invention is to provide a wastewater treatment method capable of reducing the number of times.

[0009]

Means for Solving the Problems and Effects of the Invention A wastewater treatment method according to the present invention comprises subjecting wastewater to biological treatment and membrane separation in a biological treatment tank provided with a filtration membrane unit, and then treating the wastewater with fixed beds. A wastewater treatment method in which an adsorption treatment is performed in an adsorption tower, wherein a bactericide is added to the membrane permeated water in a portion between the biological treatment tank and the adsorption tower.

According to the method of the present invention, after subjecting wastewater to biological treatment and membrane separation treatment in a biological treatment tank provided with a filtration membrane unit, the membrane permeated water is subjected to adsorption treatment in a fixed-bed adsorption tower. Since a bactericide is added to the membrane permeated water in the portion between the biological treatment tank and the adsorption tower, bacteria that have passed through the filtration membrane of the filtration membrane unit are killed before the membrane permeated water is sent to the adsorption tower, The frequency of clogging of the fixed bed of the adsorption tower due to bacterial growth is reduced. Therefore, the number of backwashing operations of the adsorbent in the fixed bed can be greatly reduced.

In the wastewater treatment method of the present invention, an intermediate tank may be provided between the biological treatment tank and the adsorption tower, and the membrane permeated water and the germicide may be mixed in the intermediate tank. In this case, the germicidal effect of the germicide is further improved.

In the wastewater treatment method of the present invention, the germicide may be used in the form of an aqueous solution. An example of this is, for example, an aqueous solution of sodium hypochlorite.

Further, in the wastewater treatment method of the present invention,
The germicide may be solid or ozone. In these cases, it is desirable to provide an intermediate tank between the biological treatment tank and the adsorption tower, and to use it as a mixture of the membrane permeated water and the disinfectant in the intermediate tank. Has an excellent bactericidal effect.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. In FIG. 1, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1 showing the wastewater treatment method of the present invention, the biological treatment and membrane separation treatment in the biological treatment tank (4)
This is performed in the same manner as in the case of the conventional method shown in FIG. The permeated water subjected to the biological treatment and the membrane separation treatment in the biological treatment tank (4) is sent to an intermediate tank (30) located at a higher position than the biological treatment tank (4) and the adsorption tower (5). And
The disinfectant stored in the disinfectant storage tank (12) is added to the permeated water in the intermediate tank (30) by the disinfectant supply pump (13), and the disinfectant is stirred by the agitator (15) driven by the motor (14). The permeated water and the bactericide are mixed and sterilized. Next, the sterilized membrane permeated water is sent to the adsorption tower (5) by the pump (31), and the trace components remaining in the membrane permeated water while passing through the fixed bed (10) are adsorbed and removed. The permeated water that has passed through the fixed bed (10) is sent to the discharge tank (11), and then discharged out of the system. Thus, the wastewater is treated.

According to the above method, the permeated water is transferred to the adsorption tower (5).
Before being sent to the filtration unit, the sterilizing agent added in the intermediate tank (30) and mixed with the permeated water causes
Bacteria that have permeated the flat membrane of (3) are killed, and the frequency of clogging of the fixed bed (10) of the adsorption tower (5) due to bacterial growth is reduced. Therefore, the number of backwashing operations of the adsorbent of the fixed bed (10) can be greatly reduced.

Hereinafter, specific examples of the present invention will be described together with comparative examples.

[0018]

[Example] In treating wastewater, a disinfectant storage tank (12)
An aqueous solution of sodium hypochlorite is stored in the water, and the germicide is supplied using the germicide supply pump (13) so that the effective chlorine concentration in the permeated water subjected to the biological treatment and the membrane separation treatment becomes 10 mg / l. While adding sodium hypochlorite to the membrane permeated water in the intermediate tank (30) from the storage tank (12) and mixing it with the membrane permeated water, the wastewater was treated as described in the above embodiment. . The pressure loss of the adsorption tower (5) is 0.5 kg / c.
When m ² was exceeded, the adsorbent in the fixed bed (10) of the adsorption tower (5) was backwashed. As a result, there was no need to perform backwashing until about 90 days had elapsed.

[0019]

[Comparative Example] Drainage treatment is performed without supplying a sterilizing agent to the intermediate tank. When the pressure loss of the adsorption tower exceeds 0.5 kg / cm ² , backwashing of the adsorbent on the fixed bed of the adsorption tower is performed. I did it. As a result, backwashing needs to be performed about every 20 days.

FIG. 2 shows the change over time in the pressure loss of the adsorption tower in the above specific examples and comparative examples. In FIG. 2, the pressure loss becomes 0.1 kg / cm ² or less when the backwashing is performed.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a graph showing changes over time in pressure loss of an adsorption tower in specific examples and comparative examples.

FIG. 3 is a flowchart showing a conventional method.

[Explanation of symbols]

 (3): Filtration membrane unit (4): Biological treatment tank (5): Adsorption tower (30): Intermediate tank

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Claims (6)

[Claims] 1. A wastewater treatment method comprising subjecting wastewater to biological treatment and membrane separation treatment in a biological treatment tank provided with a filtration membrane unit, and then subjecting the permeated water to adsorption treatment in a fixed-bed adsorption tower. A wastewater treatment method comprising adding a bactericide to a membrane permeated water in a portion between a treatment tank and an adsorption tower. 2. An intermediate tank is provided between the biological treatment tank and the adsorption tower, and the membrane permeated water and the bactericide are mixed in the intermediate tank.
Wastewater treatment method as described. 3. The wastewater treatment method according to claim 1, wherein the germicide is in the form of an aqueous solution. 4. The wastewater treatment method according to claim 1, wherein the germicide is an aqueous sodium hypochlorite solution. 5. The fungicide according to claim 1, wherein the fungicide is solid.
Wastewater treatment method as described. 6. The method according to claim 1, wherein the germicide is ozone.
Wastewater treatment method as described.