JP3377949B2 - Method and apparatus for treating organic wastewater - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wastewater treatment process such as a sewage treatment plant and a human waste treatment plant, or a method for treating organic wastewater discharged from a food factory, a chemical factory and the like.

[0002]

As a method for treating organic wastewater as described above, wastewater is aerobically digested and decomposed in an aeration tank equipped with an immersion type membrane separation apparatus, and solid-liquid separation is performed by the membrane separation apparatus. A method for discharging separated treated water has been proposed (Japanese Patent Laid-Open No. 8-24597, Utility Model Registration No. 2556521, etc., FIG. 2 shows an outline of this apparatus). This method can perform aerobic digestion and decomposition of organic wastewater and isolation of treated water by membrane separation in parallel, so the space occupied by the device is small,
It is preferable in that the labor of the treatment is not complicated. Further, since the sludge concentration in the aeration tank can be maintained at a high concentration, there is an advantage that the sludge load becomes small and the amount of excess sludge generated is small. However, with this method, the quality of the treated water is often unfavorable unless the sludge is properly drawn out, and it may not be possible to discard it without further treatment. Such a decrease in treated water quality is caused by microbial cells in sludge (particularly aerobic microorganisms) proliferating, resulting in a fine sterilized body derived from a dead sterilized body resulting from a high concentration of sludge in the aeration tank, a gel-like substance, It is considered that soluble organic substances, etc., pass through the submerged membrane and mix into the treated water, and it is shown that the biological / chemical oxygen demand of the treated water and the concentration of soluble / suspending organic compounds are high. Be done. As described above, dumping both sludge and treated water generated by the above treatment into the ocean, rivers, lakes and the like could cause environmental problems.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art.
The purpose is to improve the quality of the treated water generated in the above-mentioned organic wastewater treatment method, that is, reduce the biological / chemical oxygen demand of the treated water and the concentration of soluble / suspendable organic compounds. At the same time, it is to provide a treatment method capable of reducing the amount of excess sludge generated.

[0004]

In order to achieve the above object, the present invention provides a method for treating an organic wastewater containing organic sludge in the following steps: Process of aerobically treating wastewater and membrane separation in the aeration tank installed in (2), and (2) a step of solubilizing a part of the mixed solution in the aeration tank with thermophilic bacteria in the solubilization tank only including, solubilizing reagent in step (2) after the completion of return to the aeration tank
Provided is a processing method (first invention of the present application), which is characterized by being sent and processed in a circulating system . By this method, a part of the mixed solution containing sludge containing the organic matter derived from the microorganisms grown in the aeration tank under aerobic conditions and the dead sterilized body after the growth is guided to the solubilization tank and solubilized. By doing so, the water quality in the treated water discharged from the aeration tank is improved. That is, by pulling out the mixed liquid in the aeration tank to reduce the amount of sludge, the above-mentioned microorganisms, soluble organic substances derived from dead sterilized bodies and the like, gel-like substances, solids having a fine and membrane-permeable size, etc. It is possible to reduce the amount mixed in the discharged treated water. The mixed liquid containing the sludge extracted from the aeration tank is solubilized, and the volume reduction of the excess sludge is finally achieved.

[0005] solubilization treatment liquid after the pre-Symbol step (2) is returned to the aeration tank, that is processed in the circulatory system, the aerobic digestion degradation and solubilization, further reducing the amount of sludge It is possible to reduce the amount of the treated water contaminants as described above, which improves the treated water quality.

[0006] Before SL solubilization step (2) is accomplished by digestion with thermophilic bacteria. Such thermophiles are generally contained in compost, excess sewage sludge, soil, etc.,
It is preferable because sludge can be solubilized with high efficiency.

The second invention of the present application relates to an organic wastewater treatment apparatus for carrying out the above treatment method, which comprises an aeration tank in which a membrane separation device is disposed in the tank and a thermophilic bacterium. Melting
Solubilization tank for performing solubilization, a route for introducing sludge from the aeration tank to the solubilization tank, and solubilization treatment from the solubilization tank to the aeration tank
Provided is a processing device including a path for returning a liquid . With such a treatment device, it is possible to implement the above treatment method in which the quality of treated water is improved and the generation of excess sludge is reduced with a device having a relatively simple structure.

[0008] By further comprising a path for returning the solubilized treated liquid to the aeration tank from said solubilizing tank, the organic waste water by circulating process, a reduction in the generation of improved and excess sludge further treated water Ru can be realized.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG. 1 which shows an outline of an apparatus of the present invention. First, in the aeration tank 1 provided with the membrane separation device 2, solid-liquid separation is performed by the membrane separation device 2 in parallel with biological digestion by aeration treatment. The mixed liquid containing sludge during the aeration process is appropriately extracted and introduced into the next solubilization tank 3. In the solubilization tank 3, the solid component of sludge is converted into a water-soluble component, the treated liquid after solubilization is returned to the aeration tank 1, and the organic component is converted into gas as much as possible by biological digestion. Therefore, the amounts of soluble organic substances, gel-like components, and fine solid components contained in the treated water after membrane separation discharged from the aeration tank 1 are much reduced as compared with the conventional method shown in FIG. That is, the quality of treated water is remarkably improved.

In the present invention, the structure of each tank for performing aeration treatment, membrane separation and solubilization and the route connecting these tanks are not particularly limited, and essentially those conventionally used are used. (See Japanese Patent Application Laid-Open No. 9-10791 by the present applicant).

The aeration tank used in the apparatus of the present invention may be any one provided with aeration means and provided with a membrane separation device. The aeration treatment is preferably carried out at room temperature with an aeration amount of 0.1 to 0.5 vvm so that aerobic digestion and decomposition are allowed, but depending on the load, an aeration amount higher than this may be applied to a higher temperature. May be processed. The liquid to be treated is preferably adjusted to a pH of 5.0 to 8.0. Also,
In the aeration tank, in order to promote aerobic digestion and decomposition, microorganisms such as yeast, and flocculating agents such as aluminum sulfate, polyaluminum chloride, ferric chloride, ferrous sulfate, etc. May be added.

The membrane separator provided in the aeration tank has, for example, a pore size of 0.1 to 2.5 μm, preferably 0.3 to 0.
Membranes with 5 μm are preferably used, and those formed from one or more membrane module structures are preferred. As a preferred membrane separation device, a product made by Yuasa Corporation and an immersion type membrane separation device equipped with a T-type filter element can be mentioned.

Further, in the above membrane separation device, preferably,
It is preferable that a cleaning means such as pressurization by water pressure, air pressure, or the like, scrubbing, vibration, chemical injection, or the like be included or provided side by side to prevent substances that do not pass through the membrane from adhering to the membrane surface as much as possible.

The mixed solution is withdrawn from the aeration tank in order to subject a part of the mixed solution to the next solubilization step, but preferably, the concentration of the mixed solution suspension substance (MLSS) in the aeration tank is kept constant, It is advisable to withdraw the mixed solution while controlling the amount intermittently or constantly so that digestion and decomposition by aerobic treatment can be carried out smoothly, and to carry out the next solubilization step.

In the solubilization step, a thermophilic bacterium (for example, cells such as Bacillus stearothermophilus may be added)
Decomposition, ozone decomposition, electrolysis, thermal alkali decomposition,
It may be carried out by selecting from various conventionally known methods such as enzymatic degradation (for example, addition of protease, lipase, glycosidase, etc. alone or in combination).

[0016] Currently, the preferred solubilization step is decomposition by thermophilic bacterium treatment in terms of the achieved solubilization rate, maintenance and economic efficiency, and the like. In this case, 50-9
It is advisable to proceed solubilization at 0 ° C., preferably 60 to 70 ° C., under normal pressure, preferably at a pH of around neutral to weakly alkaline. The solubilization by the thermophilic bacterium may be anaerobic or aerobic.

The above-described wastewater treatment method of the present invention may be performed in either a batch type or a continuous type, and the treatment time is appropriately set in consideration of the physical properties of the wastewater and the scale and shape of each treatment tank. .

Thus, according to the treatment method of the present invention, the treated water finally obtained by passing through the membrane separator in the aeration tank is
The quality of the water has improved so that it can be disposed of as it is.

[0019]

EXAMPLES Examples of the present invention will be described below, but the scope of the present invention should not be limited by these examples.

[Example 1] An artificial wastewater prepared by diluting a mixture of peptone: glucose: yeast extract in a weight ratio of 4: 4: 1 with tap water to a BOD of about 1200 mg / L. Used as raw water.

A volume load of this raw water was applied to an aeration tank (a rectangular tank made of transparent vinyl chloride having an internal volume of 40 L) equipped with an immersion type membrane separator (T-type filter element manufactured by Yuasa Corporation). It was charged at 4 kg-BOD / m ³ / day, and maintained at room temperature (25 ° C.) with an aeration rate of 0.5 vvm. Then, the MLSS concentration in the aeration tank is set to about 12,
A fixed amount of the mixed solution was constantly withdrawn from the aeration tank so as to be maintained at 300 mg / L, and introduced into a solubilization tank (a glass cylindrical tank having an internal volume of 2 L). Aeration rate is 0.5v
vm at 65 ° C. The solubilization tank uses sewage surplus sludge for 3 years or more under high temperature conditions (6
2% by volume of seed sludge cultured at 5 ° C. was added. The treatment liquid after solubilization was constantly returned to the aeration tank and the treatment was continued for 100 days in the circulation system.

[Comparative Example 1] The same aeration treatment as in Example 1 was carried out except that the extraction, solubilization and return from the aeration tank were not carried out. The MLSS concentration in the aeration tank was approximately 12,040 mg / L.

The amount of sludge produced by each of the above treatments was measured, and the quality of treated water was inspected for the following items. The results are shown in Table 1.

BOD: 2 according to JIS K 0102
Based on the amount of dissolved oxygen consumed after leaving the diluted solution at 0 ° C. for 5 days, biological oxygen consumption measurement S-TOC: JISK 0102 according to a filtrate filtered through a glass fiber filter paper having a pore size of 1 μm
Measurement of the amount of soluble total organic compounds by combustion oxidation-infrared TOC analysis method according to 0102: SS: JISK 0102, the residue on the filter paper filtered with a glass fiber filter paper having a pore size of 1 μm is 105 to 110 ° C.
Weigh the suspended solids by drying with

[0025]

[Table 1]

From Table 1, it is clear that the treated water produced in Example 1 has a lower content of soluble organic substances and suspended solids and improved water quality as compared with that of Comparative Example 1. Is. And the amount of sludge was also zero.

[0027]

EFFECTS OF THE INVENTION According to the present invention, while maintaining the advantages such as space saving and simplicity of the treatment of organic wastewater using an aeration tank provided with a membrane separation, the quality of the obtained treated water is improved and excess sludge is generated. The effect that the amount can be reduced is achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an organic wastewater treatment apparatus of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional organic wastewater treatment apparatus.

[Explanation of symbols]

1 ... Aeration tank 2. Membrane separation device 3 ... Solubilization tank

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-10791 (JP, A) JP-A-61-129094 (JP, A) JP-A-5-185092 (JP, A) JP-A-8- 215695 (JP, A) JP 6-206088 (JP, A) JP 9-253699 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/12 C02F 11 / 02

Claims (2)

(57) [Claims] 1. A method for treating organic wastewater, comprising the following steps: (1) aerobic treatment and membrane separation of wastewater in an aeration tank in which a membrane separation device is disposed in the tank. , And (2) A part of the mixed solution in the aeration tank is stored in the solubilization tank by thermophilic bacteria.
Look including the step of solubilized I, solubilizing reagent in step (2) after the end is returned to the aeration tank,
A processing method characterized by being processed in a circulatory system . 2. A treatment apparatus for organic wastewater, comprising an aeration tank in which a membrane separation device is disposed in the tank, and solubilization by thermophilic bacteria.
A solubilizing tank for performing a path for introducing sludge solubilization tank from該曝gas tank, solubilizing reagent to the aeration tank from solubilization tank
A processing device including a route for returning the .