JP2009119406A - Wastewater treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment method and apparatus which enables the efficient removal of hardly decomposable organic substances in the wastewater. <P>SOLUTION: The wastewater treatment apparatus 10 includes a fluidized-bed bioreactor 12 for treating the wastewater containing the hardly decomposable organic substances biologically with organism-deposited carriers 18, and a flocculation-separation tank 14 disposed downstream of the fluidized-bed bioreactor 12 for flocculating and separating the hardly decomposable organic substances by adding a flocculating agent to the treated water obtained in the fluidized-bed bioreactor 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method and apparatus, and more particularly to a wastewater treatment method and apparatus for treating paint wastewater discharged from a painting factory.

  In general, paint wastewater discharged from a coating factory is biologically treated by an activated sludge method after removing hardly decomposable organic substances in the wastewater by coagulation separation treatment (see Patent Document 1). However, in recent years, the paint used has shifted from oily to water-soluble as a measure against VOC, and as a result, resins and pigments, which are hardly decomposable organic substances, have shifted from hydrophobic to hydrophilic. Degradable organic matter is dissolved. Such resins and pigments are stable in dispersion state due to the polymer dispersant and surfactant contained in the paint, and therefore are difficult to agglomerate and separate and have poor biodegradability. Therefore, in recent years, the quality of water after treatment has deteriorated, and there has been a problem that conventional wastewater treatment methods cannot adequately cope with it.

In order to solve such problems, many methods using physical / chemical treatment methods such as an ozonolysis method, a Fenton oxidation method, and a UV irradiation method have been proposed. For example, Patent Document 2 discloses a treatment method for irradiating ultraviolet rays or visible light in the presence of a photooxidation catalyst to oxidatively decompose waste water containing organic matter. Patent Document 3 discloses an oxidation method using a metal catalyst.
JP 2000-84568 A JP-A-8-155308 JP-A-9-1162

  However, these methods have a problem that it is difficult to sufficiently decompose the hard-to-decompose organic substance, and there is a problem that even if it can be decomposed, the processing is very expensive.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a wastewater treatment method and apparatus that can efficiently remove hardly decomposable organic substances contained in wastewater.

  In order to achieve the above object, the invention according to claim 1 is a wastewater treatment method for removing hardly decomposable organic substances contained in wastewater, wherein the wastewater is discharged by a fluidized bed biological reaction tank to which a carrier to which microorganisms are fixed is added. The biologically treated water is subjected to a biological treatment, and the biologically treated water is subjected to agglomeration and separation treatment, whereby the hardly decomposable organic matter is agglomerated and separated and removed from the waste water.

  The inventor of the present invention has intensively studied to solve the above-mentioned problems. As a result, wastewater containing hardly decomposable organic matter (for example, water-soluble paint wastewater) is first biologically treated in a fluidized bed bioreactor, and then the flocculant is used. It has been found that the addition of the aggregation separation treatment allows the separation and removal of the hardly decomposable organic matter in the waste water sufficiently and easily. The present invention has been made in view of such circumstances, and since the agglomeration and separation treatment is performed after the biological treatment in the fluidized bed biological reaction tank, the persistent organic matter in the wastewater is sufficiently and easily obtained. Can be separated and removed.

  The invention according to claim 2 is the invention according to claim 1, wherein the agglomeration and separation treatment includes a hardly decomposable organic substance that cannot be decomposed in the fluidized bed bioreactor, and a microbial floc discharged from the fluidized bed bioreactor. Are coagulated and precipitated simultaneously. According to the present invention, it is possible to agglomerate a hardly decomposable organic substance using a microbial floc as a nucleus of aggregation.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the carrier is sand, activated carbon, a resin carrier or a polymer hydrogel, and the fluidized bed bioreactor has a COD _Mn volume load of 1 It is characterized by operating at ˜2 kg / m ³ · d. According to the present invention, by operating the fluidized bed biological reaction tank under the above-mentioned conditions, it is possible to separate and remove easily decomposable organic substances in the waste water, and at the same time, fine microbial flocs are generated in the reaction tank. As a result, in the aggregating and separating process at the latter stage of the biological treatment, it is possible to efficiently perform the aggregating and separating process of the hardly decomposable organic substance using the fine microbial floc as the nucleus.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the diameter of the microbial floc discharged from the fluidized bed biological reaction tank is 10 μm or less. According to the present invention, the microbial floc has a small diameter and is used as an agglomeration nucleus, whereby the aggregating effect in the aggregating / separating process can be improved, and the separation and removal efficiency of the hardly decomposable organic matter can be greatly improved.

  In order to achieve the above object, the invention according to claim 5 is a fluidized bed biological reaction tank for biological treatment of wastewater containing a hard-to-decompose organic substance to which a carrier immobilizing microorganisms is added, and the fluidized bed biological organism. A flocculant separation tank that is provided in a subsequent stage of the reaction tank and adds a flocculant to the biologically treated water obtained in the fluidized bed biological reaction tank, and agglomerates and separates the hardly decomposable organic matter. Features. The present invention is an apparatus invention for carrying out the method invention of claim 1, wherein the flocculation separation treatment is performed in the flocculation separation tank after the biological treatment is performed in the fluidized bed type bioreaction tank, so Decomposable organic substances can be separated and removed sufficiently and easily.

  According to the present invention, since the agglomeration separation process is performed after the biological treatment is performed in the fluidized bed biological reaction tank, the hardly decomposable organic matter in the waste water can be separated and removed sufficiently and easily.

  Hereinafter, preferred embodiments of a wastewater treatment method and apparatus according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 schematically shows the configuration of the waste water treatment apparatus of the present embodiment. The following will be described with an example of treating water-soluble paint wastewater, but the present invention is not limited to this, and is used as an apparatus for treating wastewater containing hardly decomposable organic substances (components such as resins and hard pigments). be able to. Examples of the paint wastewater include water-soluble paint coating lines for automobiles and various industrial products, paint booth water at sheet metal plants, and wastewater containing water-soluble paint components from paint production plants. These effluents have a relatively low BOD / COD _Mn ratio (for example, effluents in water-soluble paint lines of automobiles have a BOD / COD _Mn ratio of about 0.3) and are poorly biodegradable.

  As shown in FIG. 1, the waste water treatment apparatus 10 is mainly composed of a fluidized bed biological reaction tank 12 and a coagulation separation tank 14.

  A raw water pipe 16 is connected to the fluidized bed biological reaction tank 12, and raw water (painted wastewater in the present embodiment) is supplied through the raw water pipe 16 and stored in the fluidized bed biological reaction tank 12. The Inside the fluidized bed biological reaction tank 12, a carrier 18 to which microorganisms are adhered and fixed is put. As the carrier 18, a hollow one, a concave-convex one, a porous one having a large surface area per unit volume, a one that swells by absorbing water, and the like can be used. A carrier having a large surface area and a large amount of attached microorganisms is preferred. Further, as the material of the carrier 18, various conventionally known organic and inorganic carriers can be used, for example, activated carbon, zeolite, sand particles, resin, ceramics, polymer hydrous gel such as polyethylene glycol, and the like. One type or two or more types can be used in combination.

An air diffuser 20 is disposed at the bottom of the fluidized bed biological reaction tank 12. A blower 22 is connected to the diffuser tube 20, and air can be supplied to the diffuser tube 20 by the blower 22. The air sent to the air diffuser 20 becomes a myriad of bubbles and is diffused into the fluidized bed bioreactor 12, and the bubbles rise to cause the carrier 18 to flow, and to the microorganisms of the carrier 18. Is supplied. Thereby, the waste water in the fluidized bed biological reaction tank 12 is biologically treated. At this time, in the present embodiment, the operation is controlled so that the COD _Mn volumetric load in the fluidized bed biological reaction tank 12 becomes 1 to 2 kg / m ³ · d. As a result, fine microbial floc having a particle diameter of 1 to 10 μm is generated in the reaction tank, and the particles are contained in the treated water after biological treatment (hereinafter, biologically treated water).

  A pipe 24 is connected to the outlet of the fluidized bed biological reaction tank 12, and a screen 26 is provided so as to surround the connection with the pipe 24. The screen 26 prevents the carrier 18 from flowing out, the carrier 18 is separated by the screen 26, and only biologically treated water flows out into the pipe 24. The pipe 24 is connected to the flocculation / separation tank 14, and the biologically treated water flowing out from the fluidized bed biological reaction tank 12 is supplied to the flocculation / separation tank 14.

  The agglomeration separation tank 14 is provided with two stirring tanks 14A and 14B and a precipitation tank 14C, and the two stirring tanks 14A and 14B are each provided with a stirring device 28. In the stirring tank 14A, an inorganic flocculant is added to the biologically treated water, and this biologically treated water is stirred by the stirring device 28 and supplied to the stirring tank 14B. In the stirring tank 14B, the polymer is added to the biologically treated water, and this biologically treated water is stirred by the stirring device 28 and supplied to the precipitation tank 14C. As described above, the flocculant is added to the biologically treated water and stirred to produce an aggregate with fine microbial flocs in the biologically treated water as a nucleus, and the aggregate is precipitated in the precipitation tank 14C. A treated water pipe 30 is connected to the upper part of the settling tank 14C, and the supernatant liquid is discharged from the treated water pipe 30 as treated water, and aggregates are separated and removed. Thereby, the hardly decomposable organic substance contained in the waste water is separated and removed from the waste water. In this embodiment, the aggregates are separated by precipitation. However, the aggregates may be separated by floating and removed. In addition, the flocculant is not limited to the above-mentioned examples. For example, inorganic flocculants represented by aluminum sulfate, polyaluminum chloride, ferric chloride, etc., anionic, nonionic or cationic polymer flocculants An agent or the like can be used, and these can be used alone or in combination of two or more according to the type of drainage.

  Next, the operation of the waste water treatment apparatus 10 configured as described above will be described.

  The fluidized bed biological reaction tank 12 described above is a device that performs biological treatment in a fluidized bed by adding a carrier 18 on which microorganisms are attached and propagated. Compared to an activated sludge device that is a general biological treatment device, Maintenance such as sludge concentration and condition is not required and maintenance is easy. On the other hand, when the fluidized bed biological reaction tank 12 is in a high load state, a naturally occurring microorganism or a microorganism film peeled off from the carrier 18 flows out together with the treated water, and the treated water becomes cloudy. For this reason, the operation | movement of a low load process is normally performed so that treated water may not become cloudy.

On the other hand, in the fluidized bed biological reaction tank 12 of the present embodiment, the operation is performed such that the COD _Mn volumetric load becomes 1 to 2 kg / m ³ · d. As a result, only easily decomposable organic substances are removed from the wastewater, and fine flocs having a particle diameter of 1 to 10 μm are generated and become cloudy. In this way, when the cloudy water is agglomerated and separated after actively creating a cloudy state, the cloudy component becomes the nucleus of the agglomerated material, and separation and removal of the hardly decomposable organic matter becomes possible.

FIG. 2 shows the relationship between the sludge floc diameter during the coagulation / separation treatment and the COD _Mn after the coagulation / separation treatment. In this test, activated sludge whose particle diameter was changed by homogenization was mixed with supernatant water obtained by solid-liquid separation of biologically treated water of water-soluble paint wastewater so that the SS concentration became 500 mg / L, An aluminum chloride solution (alumina 11%) 1 ml / L and a strong anion polymer 2 mg / L were added for aggregation separation. As can be seen from FIG. 2, when the particle size of the sludge floc is large, the COD _{Mn of the} coagulated and separated water is high, and the hardly decomposable organic matter remains. On the other hand, when the particle diameter of the sludge floc is less than 10 μm, COD _Mn is reduced due to aggregation of the sludge floc. In the case of sludge floc having a particle diameter of less than 10 μm, unlike the case of normal activated sludge floc (over 10 μm), the charge of the sludge floc particles affects the aggregation of persistent organic substances, and the sludge floc is agglomerated. This is considered to be a nucleus.

In the wastewater treatment apparatus 10 of the present embodiment, biologically treated water containing fine floc having a particle diameter of 1 to 10 μm is obtained by the fluidized bed biological reaction tank 12. Therefore, by subjecting this biologically treated water to agglomeration and separation treatment, it is possible to obtain a treated water with a small amount of COD _Mn by aggregating the hardly decomposable organic matter remaining in the biologically treated water using fine microbial flocs as the nucleus of aggregation.

  As described above, according to the wastewater treatment apparatus 10 of the present embodiment, biologically treated water containing fine flocs is obtained by biologically treating wastewater containing hardly decomposable organic matter in the fluidized bed biological reaction tank 12. Is produced, and this is subjected to agglomeration and separation treatment, so that the hardly decomposable organic substance can be separated and removed sufficiently and easily.

The test was conducted using water-soluble paint drainage (COD _Mn 5500 mg / L, BOD 1400 mg / L) discharged from a paint booth for water-based paint for automobiles. In Example 1, the biological treatment was performed in the order of the aggregating separation process, and in Comparative Examples 1 and 2, the aggregating separation process was performed in the order of the biological treatment. The conditions and results at that time are shown in the table of FIG.

In the biological treatment of Example 1, 10% of a hollow cylindrical polypropylene carrier (with respect to the reaction vessel) was added to a reaction vessel made of vinyl chloride having an actual volume of 2 L, and the fluidized bed biological reaction in which the carrier was fluidized by a diffused ball. A tank was used. The treatment load was 1 kg-COD _Mn / m ³ · d. By this biological treatment, readily degradable organic substances were treated, and BOD was removed to 10 mg / L or less. However, since the hard-to-decompose organic matter cannot be biodegraded, the COD _Mn removal rate is as low as about 70%, and 1600 mg / L of COD _Mn remained in the biologically treated water.

After the biological treatment, 1 ml / L of a polyaluminum chloride solution (alumina 11%) and 2 mg / L of a strong anion polymer were added as agglomeration separation treatment, and the mixture was agitated and reacted to cause aggregation precipitation. As a result, there was no white turbidity in the biologically treated water, and a transparent supernatant separation water was obtained. As shown in FIG. 3, the coagulation separation treated water had a BOD of less than 10 mg / L and COD _{Mn of} 96 mg / L, which was sufficiently low.

On the other hand, in Comparative Example 1, 1 ml / L of a polyaluminum chloride solution (11% alumina) (referred to as PAC) and 2 mg / L of a strong anion polymer were added as agglomeration separation treatment, and the mixture was agitated to cause aggregation precipitation. The coagulation / separation treated water was able to remove only 10% of COD _Mn . Therefore, as Comparative Example 2, the PAC was increased to 5 ml / L. However, no significant improvement was observed in the aggregation state, and the COD _Mn removal rate was as low as 15%. Thereafter, these coagulated and separated water were treated with activated sludge.

The activated sludge treatment was performed under the condition of COD _Mn volumetric load 0.5 kg / m ³ · d. Thereby, BOD of the treated water of the comparative examples 1 and 2 was able to be processed to less than 10 mg / L similarly to Example 1. However, COD _{Mn of} Comparative Example 1 was 730 mg / L, and COD _{Mn of} Comparative Example 2 was as high as 500 mg / L, and a new activated carbon treatment was required for the discharge treatment.

The figure which shows typically the structure of the waste water treatment equipment of this Embodiment. The figure explaining the effect | action of the waste water treatment equipment of this invention The figure which shows the result of the example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Waste water treatment apparatus, 12 ... Fluidized bed type biological reaction tank, 14 ... Coagulation separation apparatus, 16 ... Raw water piping, 18 ... Carrier, 20 ... Aeration pipe, 22 ... Blower, 24 ... Pipe, 26 ... Screen, 28 ... Stirring Equipment, 30 ... treated water pipe

Claims (5)

In the wastewater treatment method to remove the hardly decomposable organic matter contained in the wastewater,
The wastewater is biologically treated by a fluidized bed bioreactor to which a carrier immobilizing microorganisms is added,
A wastewater treatment method characterized in that the biologically treated biologically treated water is subjected to coagulation and separation treatment, whereby the hardly decomposable organic matter is aggregated and separated and removed from the wastewater.   2. The coagulation separation treatment simultaneously coagulates and precipitates a hardly decomposable organic substance that cannot be decomposed in the fluidized bed biological reaction tank and a microbial floc discharged from the fluidized bed biological reaction tank. Wastewater treatment method. The carrier is sand, activated carbon, a resin carrier or a polymer hydrogel,
The wastewater treatment method according to claim 1 or 2, wherein a COD _Mn volumetric load of the fluidized bed type bioreactor is operated at 1 to 2 kg / m ³ · d.   The wastewater treatment method according to any one of claims 1 to 3, wherein the diameter of the microbial floc discharged from the fluidized bed biological reaction tank is 10 µm or less. A fluidized bed type bioreactor to which a carrier in which microorganisms are fixed is added and biologically treating waste water containing persistent organic substances,
A flocculent separation tank that is provided downstream of the fluidized bed bioreactor, adds a flocculant to the biologically treated water obtained in the fluidized bed bioreactor, and agglomerates and separates the hardly decomposable organic matter;
A wastewater treatment apparatus comprising:

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