JPH11179371A - Apparatus for treating water containing manganese and organic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain treated water of good quality stably and efficiently by removing manganese and organic components in raw water simultaneously without requiring excess ozone and without causing the reduction of membrane permeation flux. SOLUTION: Manganese is oxidized with ozone in the first ozone contact tank 1, the produced manganese dioxide is removed by a solid-liquid separation means 2. After organic components being oxidation-decomposed in the second ozone contact tank 3, the treated water is subjected to membrane separation with a membrane separator 4. By the ozone-oxidation of raw water containing manganese and the organic components, manganese is oxidized to be insolubilized and the organic components such as humic acid can be decomposed into low molecular weight compounds. By the decomposition of the organic components, in the membrane separator 4 in the succeeding stage, the formation of a cake layer or a gel layer on the membrane which causes the reduction of membrane permeation flux is prevented to keep a high membrane permeation flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for efficiently treating water in which manganese coexists mainly with an organic substance such as humic acid, such as groundwater and spring water.

[0002]

2. Description of the Related Art Since manganese-containing water causes discoloration, its removal is regarded as important, especially in water systems. As a method for removing manganese, soluble Mn ²⁺
Is most commonly oxidized and removed as insoluble manganese dioxide (MnO ₄ ). As a method of oxidizing Mn ²⁺ , contact filtration method (commonly known as manganese sand method) using chlorine as an oxidizing agent and hydrated manganese dioxide as an autocatalyst, and potassium permanganate as an oxidizing agent are in the practical stage. There is a coagulation sedimentation method. Further, as an application technique of the manganese sand method, Japanese Patent Application Laid-Open No. 9-57263 discloses a method in which water to which a chlorinating agent is added is subjected to membrane separation treatment using a membrane separation apparatus in which hydrated manganese dioxide is adhered to the membrane surface. Methods for removing manganese have been proposed.

There is also a method using ozone as an oxidizing agent. However, in this method, when excessive ozone is injected, the produced manganese dioxide is further oxidized to permanganate ions, so that the removing effect is not improved. There's a problem.
For this reason, in actual equipment, in order to treat permanganate ions generated by excessive ozone injection, a method of reducing permanganate ions to manganese dioxide by providing a retention tank or a filtration device as a post-treatment of the ozone treatment. Is adopted.

On the other hand, as a method for treating an organic component, which is a problem of disinfection by-products due to chlorine such as humic acid, there is a limit in the treatment by the coagulation sedimentation / sand filtration method which has been widely performed conventionally. , Ozone and activated carbon treatment have come to be used. As a result, it becomes possible to treat soluble organic components which were difficult to remove by the coagulation sedimentation / sand filtration method, and the quality of treated water was improved. Also,
In such a process, by introducing a membrane separation process as a solid-liquid separation unit, the entire apparatus can be simplified.

[0005] An apparatus combining the ozone / activated carbon treatment and the membrane separation treatment is proposed in, for example, JP-A-6-328069 and JP-A-8-89959.
As a technology that replaces the conventional coagulation sedimentation and sand filtration, it has recently been adopted in the field of water purification and the like.

[0006]

As described above, a method of removing soluble manganese as insoluble precipitate by oxidizing soluble manganese with chlorine or the like is generally adopted for raw water containing manganese. In this method, for example, when removing insoluble matter of manganese in a membrane separation device,
When an organic component coexists in raw water, a cake layer or a gel layer of the organic component is formed on the membrane surface, and the permeation flux of the membrane is reduced. Therefore, it is necessary to remove the organic components in the raw water in advance.
In addition, for example, if humic acid is present in raw water, chlorine added as an oxidizing agent may react with humic acid to generate trihalomethane. Therefore, it is necessary to remove organic components from this point as well.

On the other hand, as a method for removing organic components, a method using coagulation sedimentation and sand filtration or a method combining ozone / activated carbon treatment and membrane separation treatment has recently been adopted, as described above.

However, conventionally, it has not been considered to remove manganese together with the organic component. For example, in the method of treating the organic component by coagulation sedimentation and sand filtration, the manganese is further removed separately from the organic component treatment step. A processing step is added. In addition, in the method using the combination of the ozone / activated carbon treatment and the membrane separation treatment, the main purpose is not to remove manganese, so that manganese cannot always be removed efficiently.

An object of the present invention is to solve the above-mentioned conventional problems and to provide an apparatus for treating manganese and organic component-containing water that efficiently removes organic components and manganese in raw water.

[0010]

The manganese and organic component-containing water treatment apparatus according to the present invention is a manganese and organic component treatment system in which water containing manganese and organic components is sequentially passed through an ozone contact device and a membrane separation device for treatment. An apparatus for treating contained water,
The ozone contact device has a first ozone contact tank and a second ozone contact tank into which the effluent of the first ozone contact tank is introduced. A solid-liquid separation means is provided between the contact tank and the contact tank.

By subjecting raw water in which manganese and organic components coexist to be subjected to ozone oxidation treatment, manganese in the raw water can be ozone-oxidized and insolubilized, and organic components such as humic acid can be oxidatively decomposed and reduced in molecular weight. . Since organic components such as humic acid are oxidatively decomposed, a cake layer or a gel layer for lowering the membrane permeation flux does not develop on the membrane surface in the subsequent membrane separation device, and a high membrane permeation flux is maintained.

When water containing both manganese and an organic component is ozone-oxidized, manganese is preferentially oxidized first, and then the organic component is oxidized and decomposed. Therefore,
When excessive ozone is injected for oxidative decomposition of organic components, manganese dioxide generated by the oxidation is further oxidized to generate permanganate ions, and the manganese removal effect is reduced, and the treated water becomes pink. The problem of coloring occurs.

However, according to the present invention, manganese is oxidized with ozone in the first ozone contact tank, and insoluble manganese dioxide generated by the oxidation is removed by solid-liquid separation means. In the first ozone contact tank, the amount of ozone necessary to oxidize manganese into manganese dioxide may be supplied in order to perform oxidative decomposition of manganese, and the greater the amount of organic components oxidized, the greater the amount of ozone supplied to manganese. No need. Since the manganese dioxide generated by oxidation in the first ozone contact tank is separated and removed by the solid-liquid separation means, ozone and manganese do not coexist for a long time until the organic matter is oxidized. Even if ozone is excessively present in the tank, almost no permanganate ion is generated. In the second ozone contact tank, organic components can be efficiently oxidatively decomposed without generating permanganese ions. Such an operation and effect can be obtained.

[0014] Further, in the case where the ozone-resistant membrane material is used in the treatment combining the ozone oxidation and the membrane separation treatment, the membrane is subjected to the condition that ozone is detected in the injection water of the membrane separation device. Separation can be performed, and organic components that cause membrane fouling, such as organic substances deposited on the membrane surface and microbial slime that adheres and grows, are eliminated by the remaining ozone, and stable membrane filtration is achieved. Can be continued.

However, when raw water contains a large amount of manganese, ozone in the ozone oxidation treatment is preferentially consumed for the oxidation of manganese. In order to allow ozone to remain in the treated water, it is necessary to supply more ozone than oxidizes the organic components. On the other hand, in the present invention, an ozone contact tank for manganese oxidation and an ozone contact tank for oxidative decomposition of organic components are separated, and excess ozone is supplied by removing insoluble matter of manganese between the two tanks. Without leaving ozone in the ozone-oxidized water, it is possible to perform stable membrane separation with the effect of eliminating and poisoning ozone.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of an apparatus for treating water containing manganese and organic components according to the present invention.

This treatment device for water containing manganese and organic components comprises a first ozone contact tank 1, a solid-liquid separation means 2, a second ozone contact tank 3, a membrane separation device 4, and an activated carbon adsorption tower 5. .

Raw water is first introduced into the first ozone contact tank 1, and manganese in the raw water is preferentially oxidized by ozone. The amount of ozone injected into the first ozone contact tank 1 may be an amount capable of oxidizing manganese in raw water to manganese dioxide, and varies depending on the quality of raw water. It is preferably about 3 mg / L. Further, the residence time in the first ozone contact tank 1 is preferably set to about 5 to 15 minutes.

The treated water in the first ozone contact tank 1 is then introduced into a solid-liquid separation means 2 to separate and remove insoluble manganese dioxide generated by ozone oxidation. As the solid-liquid separation means 2, a sedimentation basin or a suitable filtration means can be used. Among them, the filtration means is composed of a filter cloth having ozone corrosion resistance, a filter medium such as sand, ceramic, etc. Any material that can efficiently capture and remove the manganese dioxide particles generated in the ozone contact tank 1 can be used.

The separated water from which manganese dioxide has been removed by the solid-liquid separation means 2 is then introduced into a second ozone contact tank 3, where organic components are oxidized and decomposed by ozone. This second
The amount of ozone injected into the ozone contact tank 3 is an amount at which organic components in raw water are oxidized and decomposed or slightly larger than that, and varies depending on the quality of raw water. It is preferred to be about 0.5 to 2 mg / L. The residence time of the second ozone contact tank 3 is preferably set to about 5 to 15 minutes.

[0022] The treated water in the second ozone contact tank 3 is then introduced into a membrane separation device 4 and subjected to a membrane separation treatment.

As described above, by leaving ozone in the influent water of the membrane separation device 4, organic components that cause membrane fouling, such as organic substances deposited on the membrane surface and microorganisms slime that adheres and grows, are removed. Since ozone is eliminated by the poisoning effect, and efficient membrane separation can be performed,
It is preferable that about 0.1 to 1 mg / L of ozone remain in the inflow water of the membrane separation device 4.

When ozone is left in this way, the membrane of the membrane separator 4 may be a metal-inorganic membrane made of stainless steel, copper, aluminum, titanium, or the like, a glass or alumina ceramic membrane, or other PEEK. (Polyetheretherketone), tetrafluoroethylene,
It is necessary to use a film having high resistance to ozone oxidation such as polyvinylidene fluoride. Further, as the membrane type of the membrane separation device 4,
A microfiltration (MF) membrane, an ultrafiltration (UF) membrane, or the like can be used.

This membrane separation device 4 is provided with a backwashing means (not shown), which is periodically backwashed with treated water, gas or the like, and is a component which has not been removed by the solid-liquid separation means 2 at the preceding stage and passed therethrough. As a result, efficient membrane separation can be maintained by excluding the inorganic components blocked by the membrane surface and adhering to the membrane surface to the outside of the system.

Next, the permeated water of the membrane separation device 4 adsorbs and removes residual ozone in the activated carbon adsorption tower 2 and adsorbs and removes low molecular weight organic components generated by oxidative decomposition of organic components.

The treated water of the activated carbon adsorption tower 5 is a highly purified water containing manganese dioxide and other turbid substances which are solid-liquid separated and contain no ozone, and are discharged out of the system as treated water.

In the apparatus for treating water containing manganese and organic components according to the present invention, the ozone discharged from the second ozone contact tank 3 and the treated water tank (not shown) of the membrane separation apparatus 4 are collected, and the collected ozone is collected. Is preferably sent to the first ozone contact tank 1 for reuse. By doing so, in the case of raw water having a relatively low manganese ion concentration, manganese ozone oxidation can be performed without performing new ozone injection in the first ozone contact tank 1. In this case,
When the amount of ozone for ozone oxidation of manganese is insufficient with only the exhausted ozone, only the insufficient amount may be newly injected. In particular, when ozone is left in the inflow water of the membrane separation device 4, the amount of ozone used can be reduced by collecting and reusing the exhausted ozone, which is extremely advantageous.

FIG. 1 shows an example of an embodiment of the present invention, and the present invention does not depart from the gist of the present invention.
It is not limited to the device shown in FIG.

For example, the activated carbon adsorption tower may be provided in front of the membrane separation device. In this case, the residual ozone due to the ozone oxidation is removed by the activated carbon adsorption tower. And a film having no ozone oxidation resistance, such as polyacrylonitrile, polyethylene, polypropylene, and cellulose acetate.

When an activated carbon adsorption tower is provided at the subsequent stage of the membrane separation apparatus, a fixed bed type activated carbon adsorption tower can be used because there is no danger of the activated carbon adsorption tower being clogged by suspended substances. If the adsorption tower is installed in front of the membrane separation device, the activated carbon adsorption tower will not be clogged with suspended matter in the water, so that the activated carbon adsorption tower will be suspended in water, such as in the case of an upflow fluidized bed type of granular activated carbon. It is preferable to adopt a type that does not capture suspended substances.

The activated carbon treatment may be carried out by providing an activated carbon adsorption tower or by adding powdered activated carbon directly to a water supply line and thereafter separating the activated carbon.

[0033]

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

Example 1 Bentonite, sodium humate and manganese sulfate were suspended in tap water at a concentration of 10 mg / L and 2.5 m, respectively.
g / L and water dissolved to 1 mg-Mn / L were treated as raw water in the apparatus shown in FIG.

The raw water is treated at 10 m ³ / day, the first ozone contact tank is treated at an ozone injection rate of 2 mg-O ₃ / L, the residence time is 5 minutes, and the treated water of the first ozone contact tank is sand. Solid-liquid separation was performed with a filter. Second ozone injection rate 5mg-O ₃ / L in the ozone contact tank, is treated with a residence time of 10 minutes, the residual ozone concentration of 0.5~1.5mg-O ₃ / L.

As the membrane separation device, MF membrane (membrane material PV)
DF) Using a separator, the treated water in the second ozone contact tank was treated at a permeation flux of the membrane of 2 m ³ / m ² / day. The permeated water of the membrane separation device was passed through a fixed bed activated carbon adsorption tower to obtain treated water.

The ozone discharged from the second ozone contact tank and the treated water tank of the membrane separator was collected and injected into the first ozone contact tank. At this time, in the first ozone contact tank, only this exhausted ozone was sufficient, and there was no need to separately inject new ozone.

At this time, the quality of the effluent of each treatment tank was examined, and the results are shown in Table 1.

Further, the degree of increase of the transmembrane pressure after the treatment for 30 days is represented by the ratio of transmembrane pressure (ΔPa) / permeation flux (flux), and the results are shown in FIG.

Table 1 shows the amount of ozone required for treating 1 L of raw water.

Comparative Example 1 In Example 1, except that only one ozone contact tank was provided, and no solid-liquid separation means was provided, the treated water in the ozone contact tank was treated with a membrane separation device, and further activated carbon adsorption treatment was performed. Was treated in the same manner, and the quality of the effluent of each tank, the degree of increase in the membrane differential pressure, and the amount of ozone were examined. The results are shown in Table 1.

[0042]

[Table 1]

As can be seen from Table 1, according to the apparatus for treating water containing manganese and organic components of the present invention, both manganese and organic components can be efficiently removed with a small amount of injected ozone.
It can also be seen that an increase in the membrane differential pressure is also prevented.

[0044]

As described above in detail, according to the apparatus for treating water containing manganese and organic components of the present invention, manganese and organic components in raw water can be treated without requiring an excessive amount of ozone, The water can be removed at the same time without causing the problem of reduction of the permeation flux, and the treated water having good quality can be obtained stably and efficiently.

The apparatus for treating manganese and organic component-containing water of the present invention particularly contains a large amount of manganese ions,
It is effective for treating groundwater and spring water in which organic components such as humic acid coexist, and it is possible to efficiently and economically obtain purified water with high clarity.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a treatment device for water containing manganese and organic components of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st ozone contact tank 2 Solid-liquid separation means 3 2nd ozone contact tank 4 Membrane separation apparatus 5 Activated carbon adsorption tower

Claims (1)

[Claims] 1. An apparatus for treating manganese and organic component-containing water, wherein water containing manganese and an organic component is sequentially passed through an ozone contact device and a membrane separation device to treat the manganese and organic component-containing water. A contact tank, and a second ozone contact tank into which the effluent of the first ozone contact tank is introduced; solid-liquid separation between the first ozone contact tank and the second ozone contact tank An apparatus for treating water containing manganese and organic components, characterized in that a means is provided.