JP2002001333A - Organic wastewater treatment method - Google Patents

Abstract

(57) [Problem] To provide a method for recovering deterioration of separation performance due to the presence of an inhibitory component when performing solid-liquid separation treatment of organic wastewater using a separation membrane. SOLUTION: In treating organic wastewater using a microorganism treatment and a solid-liquid separation treatment using a separation membrane, a filterable inhibitory component composed of a high molecular weight organic compound present in a biological treatment tank is reduced and then separated. A method for treating organic wastewater, comprising performing solid-liquid separation using a membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating organic wastewater using a separation membrane, and to a method for improving the solid-liquid separation performance of the separation membrane.

[0002]

2. Description of the Related Art Conventionally, in performing organic wastewater treatment, a method of purifying by using microorganisms and then separating and purifying solids has been widely used. At this time, as a method of performing solid-liquid separation, sand filtration, gravity precipitation, and the like are performed. However, the solid-liquid separation by these methods has disadvantages that the SS concentration of the obtained treated water tends to be high, and that a large site is required for solid-liquid separation.

As a method for solving such inconveniences, various methods have recently been studied for performing solid-liquid separation of water to be treated using a membrane module provided with a separation membrane such as a microfiltration membrane or an ultrafiltration membrane. I have. When the water to be treated is filtered using the separation membrane, treated water containing almost no SS can be obtained.

However, when the treatment is performed using a microfiltration membrane or an ultrafiltration membrane having a small fraction pore size, at least a part of the organic compound is blocked by the separation membrane. At this time, when the organic compound is hardly decomposable by microorganisms, such a compound accumulates due to a long-term membrane separation treatment, which tends to cause blockage of the membrane and impair the filterability. In addition, if the wastewater to be treated is mixed with substances such as antibiotics and bactericides, or if the temperature drops, or if the BOD load sharply increases, the environment may adversely affect the metabolism of microorganisms. It is known that when stress is applied, a change occurs in the metabolic pattern of microorganisms, and organic substances may be released outside the cells of the microorganisms. Such organics can also cause membrane blockage and impair filterability. The inhibition of the filtration property of the separation membrane by such an organic compound tends to increase as the molecular weight of the organic substance increases, and the molecular weight is 300
It is remarkably recognized in a high molecular weight organic compound of 0 dalton or more. Inhibition of filterability occurs even at such a low concentration of the high-molecular organic matter as several tens of ppm or less.

[0005]

When the filterability inhibiting component comprising such a high molecular weight organic compound is present in the liquid to be treated under the same filtration conditions as when the component is not present, the separation membrane is not treated. Since the blockage progresses rapidly, it is necessary to frequently perform a washing operation for recovering the filtration performance, which causes a disadvantage that the life of the separation membrane is shortened. Also,
To prevent rapid blockage, it is effective to reduce the filtration rate of the separation membrane, but in that case, the processing capacity is reduced, so that an extra membrane area is required to make up for it, and equipment cost is reduced. However, there is a problem that the bulk increases.

As disclosed in Japanese Patent Application Laid-Open No. 10-309567, a method has been devised in which an adsorbent such as activated carbon is added to adsorb and remove the filterability inhibiting component in order to improve the filterability. In general, as an adsorbent, a low molecular weight organic compound can be satisfactorily adsorbed and removed, but a high molecular weight organic compound is difficult to adsorb and remove. Also, even if an adsorbent such as activated carbon is added to a system containing miscellaneous substances such as organic wastewater,
Since it is impossible to remove only the substance that inhibits the filterability, it is necessary to add a very large amount of adsorbent in order to obtain a sufficient effect. Further, since the adsorbing capacity of the adsorbent is saturated, frequent renewal is required to maintain the effect, which is an economic problem. The present invention has been made in order to solve such inconveniences, and a method for recovering deterioration of separation performance due to the presence of an inhibitory component when performing solid-liquid separation treatment of organic wastewater using a separation membrane. Is provided.

[0007]

That is, the gist of the present invention is to provide a method for treating organic wastewater using a microorganism treatment and a solid-liquid separation treatment using a separation membrane. And a solid-liquid separation using a separation membrane after reducing the filterability-inhibiting component.

The means for reducing the filterability inhibiting component comprising a high molecular weight organic compound separates the liquid in the biological treatment tank into a liquid containing the filterability inhibitory component and a suspension component, and discards the liquid. Thereafter, it is preferable to re-disperse the suspended component in a liquid having less filterability-inhibiting components as compared with the discarded liquid, since this does not adversely affect the microbial activity. Further, means for reducing the filterability inhibiting component consisting of a high molecular weight organic compound,
Separating the liquid in the biological treatment tank into a liquid containing a filterability inhibiting component and a suspended component, subjecting the liquid to an oxidizing treatment, and then remixing the liquid and the suspended component, is discharged. Is preferred in that organic components are minimized. Further, the means for separating the liquid in the biological treatment tank into a liquid containing the filterability inhibiting component and a suspension component performs centrifugation or performs a coagulation treatment on the suspension component of the liquid in the biological treatment tank. After that, it is preferable to carry out filtration using a separation material larger than the fractional pore size of the separation membrane because the treatment time can be shortened.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto. Figure 1
1 is a schematic diagram showing an example of an embodiment of the present invention.

First, the liquid to be treated is purified in the biological treatment tank 1. A plurality of biological treatment tanks can be installed according to the purpose. Next, a solid-liquid separation process is performed using the membrane separation device 2 installed inside the biological treatment tank 1. The separation membrane used in the present invention is not particularly limited, and a separation membrane having a shape such as a flat membrane type, a hollow fiber membrane type, a tubular membrane type, and a bag-like membrane type can be applied. There is no particular limitation on the material thereof, and cellulosic, polyolefin,
Polysulfone, polyvinyl alcohol, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, ceramic, and the like can be used. The pore size of the membrane used in the present invention is not particularly limited, and a pore size of 0.001 to 0.1 μm, which is generally called an ultrafiltration membrane, or a pore size of 0.1 to 0.1 μm, which is generally called a microfiltration membrane. It is possible to use those having a pore size of 1 to 1 μm or larger.

In the biological treatment tank 1 when water treatment is being performed well, purified water 3 and suspended components 4 mainly composed of microorganisms to be subjected to biological treatment are turbid. Here, when the filterability inhibiting component 5 composed of a high-molecular organic substance accumulates in the biological treatment tank 1 due to the above-described cause,
Blockage of the separation membrane occurs, resulting in problems in the solid-liquid separation process, such as an increase in differential pressure or a decrease in flux.

At this time, if the filterability inhibiting component 5 is removed from the biological treatment tank 1, the filterability is improved. At this time, in order to perform the subsequent water treatment smoothly, it is necessary to remove the filterability inhibiting component 5 without adversely affecting the microorganisms to be subjected to biological treatment. It is effective to separate the suspension component 4 and the liquid component containing the filterability inhibiting component 5 by the separation unit 6 first.

The filterability inhibiting component 5 contained in this liquid component
The concentration of water is very small, about several tens of ppm at most, and most of the other water is purified water by microorganisms. Therefore, there is no particular problem if this liquid component is discarded as it is.

With respect to the liquid component containing the filterability inhibiting component 5,
For example, when the filterability-inhibiting component 5 is removed by means of performing a decomposition treatment using an oxidizing agent such as ozone or hypochlorite, it is not necessary to discard the liquid component, and after performing the decomposition treatment, The liquid component and the suspension component 4 may be mixed again.

As a processing flow, for example, an internal liquid is supplied from the biological treatment tank 1 to the separation means 6, and the separated suspended component 4 is temporarily stored in a separately prepared container. Thereafter, the liquid component containing the filterability inhibiting component 5 is discarded, and the suspended component 4
Is returned to the original biological treatment tank 1, and thereafter, the biological treatment tank 1
Alternatively, a method of supplying another liquid 7 having less filterability inhibiting component 5 than the discarded liquid component and redispersing the same can be used.

Further, the liquid inside the biological treatment tank 1 is temporarily transferred to another tank, the liquid is supplied therefrom to the separation means 6, and the liquid component containing the filterability inhibiting component 5 is discarded. The turbid component 4 is returned to the original biological treatment tank 1, and then the filterability inhibiting component 5 is added to the biological treatment tank 1 as compared with the discarded liquid component.
It is possible to use a method of supplying and redispersing another liquid 7 with a small amount.

Alternatively, the internal liquid is supplied from the biological treatment tank 1 to the separation means 6, and the separated suspended component 4 is returned to the biological treatment tank 1, and the liquid component containing the filterability inhibiting component 5 is concentrated while being concentrated. A method of disposing and then supplying another liquid 7 having less filterability inhibiting component 5 to the biological treatment tank 1 than the discarded liquid component 5 and redispersing the liquid component can be used.

The other liquid 7 for redispersing the suspended substance 4 is not particularly limited as long as the content of the filterability inhibiting component 5 is smaller than that of the liquid component to be discarded. Any one of a liquid, a filtrate of a separation membrane, tap water, river water, well water and the like can be used.

The separating means 6 is not particularly limited. For example, gravity sedimentation, centrifugal separation, filtration with a separating material, etc. can be used. However, it is economical and efficient to carry out the separation operation in as short time as possible. Therefore, it is preferable to perform centrifugal separation with good separation efficiency and filtration with a separating material.

In the case of performing filtration using a separation material, the fractional pore size of the separation pore size of the separation membrane used in the membrane separation device 2 should be larger than that of the separation membrane used in the membrane separation device 2 so as not to block the filterability inhibiting component 5 composed of a high molecular organic substance. It is necessary to use a large one. The larger the fraction pore size, the larger the filtration amount per unit time, so that the separation process can be carried out quickly. If the pore diameter is too large, even the suspended component 4 will slip through. In this case, the separation pore diameter of the separation material is preferably 1 μm or less.

Furthermore, when the suspension component 4 is subjected to a flocculation treatment to form flocs and increase the particle size, separation is facilitated. The flocculant used for the flocculation treatment is not particularly limited, and inorganic flocculants such as iron chloride, polyiron, and PAC, anionic, cationic, or amphoteric polymer flocculants can be used. Making the floc of the suspended component as large and robust as possible is effective for the subsequent separation, and preferably has a particle size of several mm or more. Therefore, it is preferable to use a polymer flocculant capable of forming a larger floc.

As a separating material after the coagulation treatment,
It is possible to use nonwoven fabric, paper, cloth, mesh, slits, punching plates, and other materials with coarse openings.
In consideration of the work efficiency at the time of separation, the lower limit of the fractionation pore diameter is preferably 30 μm, and more preferably 100 μm.
μm. In consideration of the solid content recovery rate, the upper limit of the fractional pore diameter is preferably 5 mm, and more preferably 3 mm.

Since the microorganism in the suspension component retains a considerable amount of water inside and around its cells, the suspension component 4 and the liquid component can be combined with one another without impairing the microbial activity.
It is practically impossible to completely separate the liquid component from the liquid component contained in the suspension component 4.
Will remain.

For this reason, it is important to reduce the liquid component in the suspended component 4 after separation and to reduce the amount of the remaining filterability inhibiting component 5. Therefore, when the suspended component 4 is separated into the liquid component, The volume of the liquid component after the separation is preferably １ ／ or more, more preferably ／ or more, of the total volume before the separation.

Further, the suspension component 4 and the liquid component are separated, and the suspension component 4 is redispersed in a liquid having less filterability inhibiting component 5 than the discarded liquid component. An operation of separating the liquid component from the liquid component may be performed. By performing such an operation, the amount of the remaining filterability inhibiting component 5 can be further reduced.

[0026]

According to the present invention, when performing the microbial treatment and the solid-liquid separation treatment by the separation membrane, it is possible to avoid the deterioration of the solid-liquid separation property due to the accumulation of the filterability inhibiting component and to continue the stable treatment. Become.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention.

[Explanation of symbols]

 1: biological treatment tank 2: membrane separation device 3: purified water 4: suspended component 5: filterability inhibiting component 6: separation means 7: another liquid

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Yanone 4-160 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi F-term in Mitsubishi Rayon Co., Ltd. Product Development Laboratory (reference) 4D006 GA06 GA07 HA93 KA02 KA03 KA16 KA31 KA41 KA62 KB13 KB14 KB20 KB22 KB30 KD01 KD08 KD21 KD24 MA01 MA02 MA03 MA22 MC03 MC11 MC22 MC29 MC30 MC33 MC37 MC62 PA01 PB08 PC62 4D028 AA02 AB01 AC01 BD17 BE01 4D062 BA22 BA23 BB05 CA01 DB01 EA37 FA01 FA02 FA17 FA24

Claims (5)

[Claims] Claims: 1. An organic wastewater treatment using a microorganism treatment and a solid-liquid separation treatment with a separation membrane, after reducing a filterability inhibiting component composed of a high molecular organic compound present in a biological treatment tank, A method for treating organic wastewater, comprising performing solid-liquid separation using a separation membrane. 2. A means for reducing the filterability inhibiting component comprising a high molecular weight organic compound separates the liquid in the biological treatment tank into a liquid containing the filterability inhibitory component and a suspension component, and discards the liquid. 2. The method for treating organic wastewater according to claim 1, wherein the suspended component is redispersed in a liquid having less filterability-inhibiting components than the discarded liquid. 3. A means for reducing the filterability inhibiting component comprising a high molecular weight organic compound separates the liquid in the biological treatment tank into a liquid containing the filterability inhibitory component and a suspension component, and oxidizes the liquid. 2. The method for treating organic waste water according to claim 1, wherein the liquid and the suspended component are re-mixed after the application. 4. The method for treating organic wastewater according to claim 2, wherein the means for separating the liquid in the biological treatment tank into a liquid containing a filterability inhibiting component and a suspension component is centrifugation. 5. A means for separating a liquid in a biological treatment tank into a liquid containing a filterability-inhibiting component and a suspension component, after performing a coagulation treatment on the suspension component of the liquid in the biological treatment tank, Filtration using a separation material larger than the fractional pore size of the membrane,
The method for treating organic wastewater according to claim 2.