JPH07116661A - Waste water treatment apparatus using ultrafiltration membrane - Google Patents

Abstract

PURPOSE:To always obtain a definite amt. of membrane permeating by low energy by providing an ultrafiltration membrane module in the sludge within a reaction tank subjecting waste water to microbiological treatment and arranging an air diffusion device under the module and providing a culture tank reactivating the sludge to return the same to the reaction tank. CONSTITUTION:An ultrafiltration membrane module 4 constituted of a large number of hollow yarn membranes is immersed in a reaction tank 3 allowing active bacteria microbiologically treating raw water to live. The sludge in the reaction tank 3 is subjected to solid-liquid separation by the membrane module 4 by operating a treated water pump 40 to take out only treated water. An air diffusion device 5 is arranged under the membrane module 4 to inject air from a blower 7 and an air lift 10 is operated to take out the sludge in the reaction tank 3 to the outside through a return pipe 11 and a part of sludge is introduced into a sludge reactivating culture tank 9 and the culture soln. containing bacteria cultured in a culture tank 9 is returned to the reaction tank 3 through a sludge pipe 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus using a submerged type ultrafiltration membrane module, and more specifically, it stabilizes a microbial treatment reaction in a reaction tank to effectively achieve solid-liquid separation performance by a membrane. The present invention relates to a wastewater treatment device that can be fully utilized.

[0002]

BACKGROUND OF THE INVENTION Generally, when biological treatment of waste water is performed, a gravity sedimentation type sedimentation tank is adopted as a solid-liquid separation means. In biological treatment, the presence of bacterial cells that oxidize is essential, but these bacterial cells are treated under treatment conditions (for example, concentration of wastewater, temperature,
However, there was a problem that the sludge flowed out from the settling basin and the cell concentration in the bioreactor could not be maintained.

For this reason, an ultrafiltration membrane using pressure as a driving force has been introduced in place of the gravity sedimentation type sedimentation basin (see, for example, JP-A-61-146397). In the conventional process of such membrane treatment, waste water is received in a reaction tank, the suspension after the reaction is sent to a circulation tank, and this circulating liquid is separated into a membrane permeate and a concentrated liquid by an ultrafiltration membrane.

However, in this membrane treatment process, the ultrafiltration membrane is provided separately from the reaction tank, and a circulation tank is required. Therefore, there is a problem that a large amount of space is required.

For this reason, conventionally, a technique has been proposed in which a hollow fiber type ultrafiltration membrane and a circulation portion are provided in a reaction tank to save space.

However, when a hollow fiber type ultrafiltration membrane is used, an adhering layer such as a gel layer or a cake layer which suppresses filtration is easily formed on the membrane surface, so that a constant amount of permeated water is maintained. Has a drawback in that it requires a large-capacity pressurizing pump and increases power cost.

Therefore, in order to save space and reduce power costs, in Japanese Patent Laid-Open No. 1-168304, not only a hollow fiber type ultrafiltration membrane and a circulation unit are provided in the reaction tank, but also
A technique of installing an air diffuser below the submerged hollow fiber membrane has been proposed. That is, a turbulent flow is formed on the film surface by the bubbles supplied by the air diffuser, and the film adhesion layer can be effectively separated. Therefore, the amount of water permeated through the membrane can be kept constant without using a large-capacity pressure pump.

However, it has been found that there is a limit in the process for treating a hollow fiber membrane in liquid using such an air diffuser. That is, in this membrane treatment process, the solid sludge in the reaction tank is completely blocked by the membrane, and the blocked solid sludge is gradually concentrated. Considering only the concentration balance, the solid sludge in the reaction tank may be pulled out in a fixed amount, but the amount of pulling out is usually the multiplication sludge (the amount of organic matter converted into microbial sludge) and BOD (biological oxygen demand). Amount) and C
It is an amount considering inorganic solid components other than the OD (chemical oxygen consumption) component.

However, the components of the waste water also include a hardly decomposable substance which is difficult to decompose by microorganisms. Since such a hardly decomposable substance cannot be converted into microbial sludge and cannot be extracted as solid sludge in the reaction tank, it is blocked by the membrane and remains in the system.

Further, since the wastewater does not always have a certain property, the wastewater having the changed property must also be received in the reaction tank.

Due to such changes in drainage properties and accumulation of the above-mentioned hardly-decomposable substances, sludge in the reaction tank becomes a sol-gel state, and the activity of microorganisms in the reaction tank is lost, resulting in clogging of the membrane filtration surface and membrane thinning. There is a problem that the conventional membrane treatment process cannot deal with, such as clogging in the pores and foaming outflow from the reaction tank.

It has been recognized that the membrane conventionally used as a substitute for the sedimentation tank is effective because it does not cause sludge outflow from the sedimentation tank when used when the microbial activity or sedimentation property in the reaction tank is poor. I had. In other words, he knew that if membranes were used, biological treatment would not have to be considered specially. However, although the sludge did not flow out of the settling tank, a new problem of foaming outflow from the reaction tank arose as described above.

The present inventor believes that the conventional recognition does not complete the membrane treatment process at all, and the idea is completely different from the conventional perception, that is, improvement of biological treatment does not make the membrane effectively function. As a result of further research, the reaction system in the reaction tank was always kept in a fixed direction by recovering the microbial activity in the reaction tank even if the drainage property changed or the above-mentioned persistent substances accumulated. By doing so, it was found that as a result, the air diffuser functions effectively, and a constant amount of permeated water can be obtained with low energy, and the present invention has been completed.

[0014]

Therefore, the object of the present invention is not only to realize space saving, but also to improve the microbial activity in the reaction tank due to changes in drainage properties and accumulation of hardly decomposable substances. By recovering, the reaction system in the reaction tank is always directed in a fixed direction, and as a result, the air diffuser functions effectively, and an ultrafiltration membrane that can obtain a constant amount of permeated water with low energy is provided. It is to provide a wastewater treatment device used.

[0015]

That is, a wastewater treatment apparatus using an ultrafiltration membrane according to the present invention that achieves the above object has a reaction tank for treating wastewater with microorganisms, and the sludge in the reaction tank contains An ultrafiltration membrane module composed of a plurality of hollow fiber membranes that separates into a membrane permeate and a concentrate using pressure as a driving force is installed, and an air diffuser is installed below the membrane module, and the reaction is performed. A culture tank for introducing sludge in the tank to reactivate the sludge and returning the sludge to the reaction tank is provided.

[0016] In a preferred embodiment of the present invention, the culture tank is a granular material containing at least a humic substance and a substance having an andesite or rhyolitic composition in an activated or unstable state in the body or It is to fill these moldings and to arrange an air diffuser below the filling.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wastewater treatment device using an ultrafiltration membrane according to the present invention will be described with reference to the drawings.

FIG. 1 is a flow sheet showing an embodiment of the waste water treatment equipment according to the present invention.

In FIG. 1, 1 is a raw water adjusting tank that receives sewage, night soil, pig house drainage, various plant drainage, domestic drainage, etc. after or without pretreatment, and 2 feeds the raw water by a predetermined amount. It is a raw water pump.

Reference numeral 3 is a reaction tank for treating raw water with a microorganism.
The reaction tank 3 is a tank in which an active microorganism is inhabited, and is preferably a group of soil-facultative anaerobic bacteria or a group of bacteria in which a soil-facultative anaerobic bacterium and a soil aerobic bacterium coexist (hereinafter,
These are called "soil bacteria group". ) Is inhabited.

The soil-based bacterial group does not need to exist from the beginning of the treatment, and the soil-based bacterial group occupies the priority species since the reaction tank initially contains microorganisms other than the soil-based bacterial group. You can also get used to it. Moreover, you may be accustomed using the seed sludge of soil-borne bacteria group. The seed sludge of the soil bacteria group can be produced using a culture tank described later.

Reference numeral 4 denotes an ultrafiltration membrane module composed of a plurality of hollow fiber membranes, which is provided by being immersed in the reaction tank 3. The number of modules is calculated from the required filtration area. The material of the hollow fiber is not particularly limited, but for example, polyethylene-based, polyamide-based, polysulfone-based, cellulose-based, polyvinyl-based, polystyrene-based, acrylamide-based, polyvinyl alcohol-based, etc. can be used.
A treated water pump 40 is connected to each membrane module 4 through a pipe, and when the treated water pump 40 is operated, sludge in the reaction tank 3 is solid-liquid separated by the membrane module 4 and only treated water can be taken out. it can.

Reference numeral 5 denotes an air diffuser installed below the membrane module 4, and air is supplied to the air diffuser 5 from a blower 7 via an air diffuser pipe 6 connected to the device 5. .

Reference numeral 8 is an air diffuser for supplying air to the reaction tank 3. Oxygen is supplied to the microorganisms in the reaction tank by the air diffuser 8, and the pollutants in the raw water and the microorganisms are mixed and stirred in the reaction tank, so that the microbial reaction can be favorably set.

Reference numeral 9 is an air lift for sludge in the reaction tank 3.
Is a culture tank which is transferred and introduced through the return pipe 11 to reactivate the sludge and returns it to the reaction tank 3.

The culture tank 9 has a main body 90 filled with a granular material containing at least a humic substance and an activated or unstable andesite or rhyolitic composition or a molded product thereof. An air diffuser tube 92 is arranged below the filling material 91.

In the present specification, a humus is a mixture of humus and a humus precursor, and a humus precursor is a general term for an intermediate substance in the process of converting organic matter into humus.

The culture solution (culture sludge) containing the microorganisms or the metabolites of the microorganisms cultured in the culture tank 9 is returned to the reaction tank 3 through the culture sludge pipe 12. The amount of liquid sent to the reaction tank is preferably in the range of 10 to 50 vol% with respect to the amount of raw water.

When the culture sludge is sent to the reaction tank 3, the microorganisms in the reaction tank 3 are activated, which allows a steady treatment even if the properties of the raw water change, and the adsorption of hardly decomposable substances. It is possible to occlude and adsorb or decompose it, and further prevent sludge foaming in the reaction tank 3. Further, the culture tank 9 serves as a seed sludge supply source for soil bacteria.

By supplying the culture sludge to the reaction tank 3 from the culture tank 9 as in the present embodiment, the soil bacteria group occupy the priority species in the reaction tank 3.

The metabolites of this soil bacterial group are bound, granulated, aggregated, and aggregated by a physicochemical reaction with a soluble substance in raw water.
Condensation, polymerization, etc. will proceed rapidly, and at the same time, the enlarging of fine sludge will proceed rapidly. Wastewater can be purified by adsorbing and occluding and adsorbing soluble components by the sludge-like substance, that is, by rapidly incorporating soluble components and advancing sludge formation (JP-A-59-166293).
No.

According to the treatment using the metabolites of the soil-based bacteria group, it is possible to take in the soluble and hardly decomposable substances and promote the sludge formation, which may cause the clogging of the membrane. Disappear.

The sludge in the reaction tank 3 is preferably sent to the raw water adjusting tank 1 via the return pipe 13. Odor components originating from raw water are adsorbed on and absorbed by sludge to prevent odor generation. It is also preferable to feed the sludge in the reaction tank 3 to a drainage source (not shown). As for the method of returning wastewater to the discharge source, in the case of public sewers, a return pipe can be installed in the upper space of the buried sewer pipe and used to return. In the case of human waste, it can be returned to the toilet, collection tank, or lorry of each house. In the case of factory wastewater, it can be returned to the discharge source or discharge route of each factory.

At the time of returning the raw water to the raw water adjusting tank 1, it is preferable to add a facility for supplying air together. In this embodiment, the raw water adjusting tank 1 is provided with the air diffuser 14, and the raw water adjusting tank 1 also serves as a reaction tank.

Excess sludge in the reaction tank is drawn out and dehydrated through the drawing line 11A, if necessary. The use of soil bacteria makes sludge enormous and lumpy to improve the solid-liquid separation property, which enables chemical-free dehydration. In addition, sludge can be used as a fertilizer by allowing chemical-free dehydration. The effect of the present embodiment is remarkable as compared with the conventional case where sludge cannot be used as a fertilizer when a chemical is used for dehydration.

The means for attaching the hollow fibers in the membrane module 4 is not particularly limited, but, for example, as shown in FIG. 2, a fixed number of hollow fibers are fixed between the header pipes 15 that are placed opposite to each other so that they can be conducted to each header pipe 15. It is also preferable to

Although one embodiment of the present invention has been described above, the present invention is not limited to this, and it is also preferable to feed the culture sludge to the raw water adjusting tank 1 from the viewpoint of preventing odor or reducing the load on the reaction tank. .

When the sludge in the reaction tank is returned to the raw water adjusting tank 1, it can be returned as solid sludge without returning it as it is. Compared to returning liquid sludge,
Since the amount of treated water in the system can be reduced and the capacity of each tank can be reduced, the cost of the entire device can be reduced and the site area can be reduced. Furthermore, compared to incinerating dehydrated sludge (cake) as is commonly done, not only is cost saving, but effective use of sludge becomes possible. Even if the dehydrated cake is returned to the raw water tank, etc., there are no adverse effects because it is chemical-free (for example, it inhibits microbial activity in the reaction tank or increases sludge in the system due to excessive accumulation of inorganic components). . In the past, polymer flocculants and inorganic flocculants were always used in dehydration, but using polymer flocculants has the adverse effect of inhibiting microbial activity in the reaction tank, and using inorganic flocculants results in inorganic flocculants. There is an adverse effect that sludge in the system increases due to excessive accumulation of components.

It is also a preferable embodiment to construct the culture tank 9 so that the silica solution can be supplied. In this case, it is possible to omit any one or all of the substances having a composition of humic substance, andesite, or rhyolite in the filling material in the culture tank. The silica solution is supplied from the silica solution tank 93 using the silica solution pump 94. The silica solution is a solution containing monomer silica, and is obtained by dissolving blast furnace slag, cristobalite, etc. in an acid, or by alkali silicate or the like.

[0040]

[Experimental Example] The present invention will be described in more detail with reference to Experimental Examples of the present invention.

Experimental Example 1 The following raw water was treated using the apparatus shown in FIG. The fluctuation of the raw water condition was tested by changing the concentration.

(Raw water: mixed urine) Human waste 17 m ³ / D + septic tank sludge 3 m ³ / D Mixed urine BOD 12500 ppm (variation rate 0 to 40)
%) Mixed urine pH 7-8 As a hollow fiber, polyethylene membrane (pore size 0.1 micron,
A filtration area of about 40 m ² ) was used. Air was constantly supplied from the air diffuser.

The culture tank used was a 1 m ³ tank, and the culture time of the concentrated solution was 500 liters / 24 hr. Specifically, 500 liters / D of the culture solution is returned to the reaction tank, and 500 liters / D of the uncultured concentrated solution is introduced from the circulation tank to carry out the culture, and 500 liters of the culture solution and the uncultured solution are each added. I changed it.

As a result of the experiment, the fluctuation of the raw water content was 0 to 40%, and the BOD and pH of the membrane-permeated water were the treated water conditions (BOD) even when the raw water containing a large amount of hardly decomposable substances such as human waste was treated.
The content was 10 ppm or less and the pH was 5.8 to 8.6), and the amount of permeated water (flux) was stable. The membrane cleaning effect of the air diffuser was confirmed.

For comparison, when the same experiment was carried out in the case where the culture sludge was not used and the culture sludge was not supplied to the reaction tank, foaming was observed in the sludge in the reaction tank, the viscosity was improved, and the amount of membrane permeated water was April. After a lapse of time, it began to decrease and the effect of cleaning the membrane by the air diffuser was not observed.

Further, an experiment was also conducted in which the circulating sludge was returned to the receiving sand settling tank or the raw water storage tank, and it was found that after returning the culture sludge, the smell of night soil was significantly reduced.

[0047]

EFFECTS OF THE INVENTION According to the present invention, not only space saving can be realized, but also the microbial activity in the reaction tank is recovered by the fluctuation of drainage property or accumulation of hardly decomposable substance. A wastewater treatment device using an ultrafiltration membrane that keeps the reaction system inside always in a certain direction, and as a result the air diffuser functions effectively and can obtain a constant amount of permeated water with low energy. Can be provided.

The apparatus of the present invention can be applied not only to new construction but also to improvement of existing treatment facilities.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an embodiment of a wastewater treatment device according to the present invention.

FIG. 2 is an explanatory view showing a mounted state of a submerged hollow fiber membrane module.

[Explanation of sign]

 1: Raw water adjusting tank 2: Raw water pump 3: Reaction tank 4: Ultrafiltration membrane module 40: Treated water pump 5: Air diffuser 6: Air diffuser 7: Blower 8: Air diffuser 9: Culture tank 90: Main body 91 : Filler 92: Air diffuser 93: Silica solution tank 94: Silica solution pump 10: Air lift 11: Return pipe 12: Culture sludge pipe 13: Return pipe 14: Air diffuser 15: Header pipe

Claims (2)

[Claims] 1. An ultrafiltration having a reaction tank for treating wastewater with microorganisms, and comprising a plurality of hollow fiber membranes for separating a membrane permeate and a concentrated solution into sludge in the reaction tank by using pressure as a driving force. A membrane module is installed, and an air diffuser is installed below the membrane module, and a culture tank for introducing sludge in the reaction tank to reactivate the sludge and returning it to the reaction tank is provided. A wastewater treatment device using an ultrafiltration membrane. 2. A culture tank having a main body filled with a granular material or a molded product thereof containing at least a humus and an activated or unstable andesite or rhyolitic composition substance. The waste water treatment apparatus using the ultrafiltration membrane according to claim 1, wherein an air diffuser is arranged below the filling material.