JP3268876B2 - How to purify river or lake water - 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 purifying river water and lake water. More specifically, the present invention relates to a method for purifying unchlorinated river water and lake water, which is characterized by treating with a hollow fiber type ultrafiltration membrane and biological activated carbon.

[0002]

2. Description of the Related Art Conventionally, a water purification system for obtaining tap water from river water or lake water generally involves a pre-chlorination-coagulation-sedimentation-sand filtration-chlorine sterilization process. In order to realize such a process, a coagulation pond, a sedimentation pond, a sand filtration pond, a chlorine sterilization facility, and the like are required, and there is a problem that a large installation space is required. In addition, since the pollution of water sources such as rivers has been increasing in recent years, development of a new advanced water purification treatment system has been required, and it has been proposed to add an activated carbon treatment system or an ozone treatment system to the above process.

However, the addition of the above-mentioned activated carbon treatment system and ozone treatment system to the conventional water purification treatment system causes a further increase in installation space and a new problem requiring complicated measurement control technology. Occurs.

[0004] The pre-chlorination is performed before the coagulation sedimentation step. The purpose of the pre-chlorination is to oxidize soluble iron, manganese, ammonia and the like contained in river water or lake water by the action of chlorine, and further to coagulate sedimentation. To remove by precipitation. However, there has been a problem that trace organic substances contained in river water and lake water are oxidized by chlorine in pre-chlorination, and harmful substances such as trihalomethane having carcinogenicity are generated. Therefore, a method of purifying river water and lake water without performing pre-chlorination has been required.

[0005] On the other hand, techniques for utilizing a new material called an ultrafiltration membrane have been proposed in various fields, and a hollow fiber type capable of coping with the problems of the installation space for obtaining tap water and contamination of a water source. Practical application of a water purification system using an ultrafiltration membrane module is being studied.

As a method of purifying groundwater and wastewater suitable for a case where the degree of contamination of water fluctuates considerably or a case where the composition of pollutants varies widely, Japanese Patent Laid-Open No. 22709/1992 is disclosed.
No. 9 discloses a method of subjecting water to be treated to membrane separation between a biological treatment step and activated carbon adsorption.

[0007]

When treating river water or lake water using a hollow fiber type ultrafiltration membrane, an ultrafiltration membrane treatment is carried out without pre-chlorination for the purpose of preventing the formation of trihalomethane. In this case, the soluble iron, manganese, ammonia and the like are not removed by the ultrafiltration membrane, and the low molecular weight organic substances are not sufficiently removed by the ultrafiltration membrane treatment. Not only makes it difficult to control chlorine and sodium hypochlorite, etc. added for the purpose of the above, but also produces insoluble substances and trihalomethane, etc., and increases the odor of chlorine due to the production of chloramine. May be undesirable.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies on the above-mentioned problems relating to the treatment of river water or lake water using a hollow fiber type ultrafiltration membrane capable of preventing the generation of trihalomethane and achieving high purification. The present inventors have found that the above problem can be easily solved by combining a hollow fiber type ultrafiltration membrane with a biological activated carbon treatment, and completed the present invention.

That is, the present invention relates to a chlorine-free river water.
Alternatively, treat lake water using a hollow fiber type ultrafiltration membrane ,
Previously treated with bacteria-containing liquid or ultrafiltration membrane
A method for purifying river water or lake water , characterized by treating with untreated river water or lake water using biological activated carbon.

[0010] River water using the purification method according to the present invention.
FIG. 1 shows a process diagram of the treatment of lake or lake water . FIG. 1 shows only the main steps. In FIG. 1, reference numeral 1 denotes a pretreatment step for a filtration device for removing coarse suspended matters and a sand basin for removing sand, etc., 2 a treatment step using a hollow fiber type ultrafiltration membrane, and 3 a biological activated carbon treatment step. And 4 is a sterilization step. In addition, the present invention does not include a step in which the positions of the biological activated carbon treatment step and the treatment step using the hollow fiber type ultrafiltration membrane are switched as shown in FIG . However,
Although not shown in Fig. 1, the river water is temporarily
Or surface water such as lake water through an activated carbon treatment process
After being attached, treated with a hollow fiber type ultrafiltration membrane,
Passing the treated water through the activated carbon treatment step is included in the present invention.
You.

As the biological activated carbon filtration device used in the biological activated carbon treatment step of the present invention, a known apparatus can be used as it is. To capture and fix bacteria in high concentration,
A filter aid carrier such as cellulose may be filled together with the activated carbon. Bacteria adsorbed and fixed on activated carbon are not particularly limited, but typical examples include ammonia-oxidizing bacteria that require oxygen when oxidizing ammonia. Activated carbon treatment of river water or lake water containing organic matter usually causes bacteria existing in surface water to be captured and immobilized on activated carbon, and the activated carbon is gradually changed to biological activated carbon. In a preferred embodiment of the present invention shown in FIG.
Since the river water or lake water after passing through the hollow fiber type ultrafiltration membrane is treated with biological activated carbon, the fixation of bacteria is usually difficult to proceed. In that case, a liquid containing bacteria is separately flowed into the activated carbon layer, or river water or lake water not treated with the hollow fiber type ultrafiltration membrane is allowed to flow through the activated carbon filtration device for a predetermined time in advance, and the bacteria are removed. When is fixed, use as a processing step of the present invention can be started.

The biological activated carbon filtration apparatus is usually a fixed-bed type treatment tower, in which water to be treated is injected from above and treated water is extracted from below. As the use continues, the pressure loss may increase due to the proliferated bacteria and viscous substances secreted by the bacteria. Therefore, it is desirable to periodically wash as necessary.

The process for treating river water or lake water using the hollow fiber type ultrafiltration membrane used in the present invention is not particularly limited. A preferred example of the process includes a process in which a raw fiber is entirely filtered while performing a cross flow during a normal operation using a hollow fiber type filtration membrane module as shown in FIG. 3, and intermittent backwashing is performed. It can be operated at a recovery rate of 90% or more and 99% or less from raw water. In the process of FIG. 3, in addition to the check valve 10, pump 11, hollow fiber type ultrafiltration membrane module 12, automatic permeated water valve 13, and automatic valve 14 for washing water discharge, permeation for accumulating permeated water is performed. A water tank 17, a pump 18 for returning the accumulated permeated water to the outlet side of the hollow fiber type ultrafiltration membrane module 12, and performing backwashing, a backwash automatic valve 19, and a washing water discharge path 1
5 are provided. The washing water discharge path 15 is the pump 1
1 and the hollow fiber type ultrafiltration membrane module 12.

The operation of the hollow fiber type ultrafiltration membrane treatment step is performed as follows. During normal operation, the permeated water automatic valve 13 is opened, the concentrated water discharge automatic valve 14, the backwash automatic valve 1
9 are both closed, and the pump 18 is stopped. In this way, the river water or lake introduced through the check valve 10
The raw water of the swamp is pressurized by a pump 11 and supplied to a hollow fiber type ultrafiltration membrane module 12. In the hollow fiber type ultrafiltration membrane module 12, the permeated water from which the turbid components have been removed by the filtration action of the ultrafiltration membrane is accumulated in the permeated water tank 17 through the permeated water automatic valve 13. During the normal operation, a crossflow of more than zero and about six times or less with respect to the inflow amount of the raw water through the circulation path 16 is performed, but the permeated water amount is equal to the raw water amount.

The backwashing is performed at regular time intervals of, for example, about 30 minutes to 1 hour for 30 to 60 seconds. In this case, the supply of raw water is stopped, the automatic permeated water valve 13 is closed, the automatic cleaning water discharge valve 14 and the automatic backwash valve 19 are both opened, the pump 11 is stopped, and the pump 18 is operated. In this manner, the hollow fiber ultrafiltration membrane module 12 is backwashed by utilizing a part of the permeated water accumulated in the permeated water tank 17, and is stripped from the inner surface of the hollow fiber membrane by the backwash. The turbid component is discharged out of the system through a cleaning water discharge automatic valve 14 through a cleaning water discharge path 15 as cleaning water. The backwash water amount is equal to the washwater discharge water amount.

The filtration membrane module is most preferably made of cellulose acetate, and an internal pressure system for supplying raw water to the inside of the hollow fiber membrane is preferred.

Preferably, the predetermined pressure at the time of the backwash is substantially 1.0 to 3 times the operating pressure at the time of the normal operation. More preferably, it is 1.3 times or more.

The water used for backwashing may be membrane permeated water, or purified water such as tap water finally obtained may be separately supplied, but the former is preferred. The backwashing may be time control or pressure control at a predetermined cycle. In the case of pressure control, the backwash may be operated at substantially 1.3 times or more the operating pressure. Assuming that the flow rate of the permeated water is P and the amount of water discharged together with the thickened mud is C according to the above-mentioned treatment step, the recovery rate is 100 × P / (P
+ C) (%), and can be operated at a recovery rate of 95% or more and 99% or less.

In the processing method of the present invention shown in FIG.
Soluble iron chlorine untreated river water or lake in water, manganese, ammonia, even in such a molecular weight of 1,000 or less organic matter is not removed by hollow fiber ultrafiltration membrane is removed by the biological activated carbon treatment process The Rukoto. This allows
These components, which were conventionally rendered insoluble by pre-chlorination and removed in the precipitation and aggregation step, can now be effectively removed without pre-chlorination. According to the purification method of the present invention, the obtained purified water has turbidity, TOC (total organic carbon),
Excellent chromaticity. In addition, since chlorination is not performed in the course of the presence of a relatively large amount of organic substances, the generation of trihalomethane, which has conventionally been considered as a problem when mixed into tap water, can be prevented.

[0020]

As described above, according to the present invention, the purification method according to the present invention, by treatment with hollow fiber type ultrafiltration membrane and biological activated carbon treatment, effectively river without performing prechlorination
Pollution product and solubility of the components in water or lake in water it becomes possible to remove. And because it doesn't do pre-chlorination,
Highly purified treated water suitable for tap water and the like is obtained with little generation of carcinogenic trihalomethane.

[Brief description of the drawings]

FIG. 1 shows a river water or a river which adopts the purification method according to the present invention.
FIG. 3 is a diagram showing an example of a lake water treatment process.

FIG. 2 is a processing step not included in the purification method according to the present invention.
Is a diagram illustrating an example of a degree.

FIG. 3 is a process diagram illustrating a configuration and an operation method of a hollow fiber type ultrafiltration membrane module used in the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C02F 1/44 C02F 1/44 H

Claims (4)

(57) [Claims] Claims 1. A chlorine-free river water or lake water is treated using a hollow fiber type ultrafiltration membrane.
Or river water not treated with an ultrafiltration membrane
Or a method for purifying river water or lake water , wherein the treatment is performed using biological activated carbon into which lake water or lake water has flowed . 2. The method of purifying river water or lake water according to claim 1 , wherein the treatment using the hollow fiber type ultrafiltration membrane includes an internal pressure type hollow fiber type ultrafiltration membrane module using cellulose acetate as a membrane material. The river water or lake that is the treatment used
Water purification method. 3. A method of purifying river water or lake water according to claim 1, purifying river water or lake water treatment using the biological activated carbon is a treatment with biological activated carbon filtration device immobilized with ammonium oxidizing bacteria Method. 4. The method according to claim 1, further comprising treating in a sterilization step.
3. The method for purifying river water or lake water according to any one of 3.