JPH054093A - Treatment of organic polluted waste water - Google Patents

Abstract

PURPOSE:To improve the efficiency in purifying an org. polluted waste water by using the fine powder of a copolymer of acrylonitrile and vinyl acetate or a body coated with the powder as the biological adsorption carrier or bed. CONSTITUTION:The org. polluted waste water in a raw waste water tank 2 is transferred to an aeration tank 1 and brought into contact with the biological adsorption carrier or bed by aeration and agitation, and the microbes are adsorbed and removed from the waste water. In this case, the fine powder of a copolymer of acrylonitrile and vinyl acetate or a body coated with the powder, the random-shaped lump of the fiber consisting of the copolymer or the cut materials of the nonwoven fabric consisting of the fiber are used as the biological adsorption carrier or bed. Consequently, biological sludge is adsorbed on the fine powder of the copolymer to reduce the dispersed sludge, biological flocculation is excellently carried out at the final stage of the aeration tank, and the compactness of the settled sludge is enhanced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a substance which can be suitably used as an adsorption carrier or an adsorption bed for adsorbing and purifying microorganisms from organic polluted wastewater, in other words, microorganisms involved in purification. The present invention relates to a method for purifying an organic polluted wastewater using a biological adsorption carrier and an adsorption bed, which have not been used in the past.

[0002]

BACKGROUND ART When biologically treating organic polluted wastewater, biofilms such as a sprinkling filter method, a dipping filter method and a rotating disk method are used as a method for fixing and treating microorganisms involved in purification. The law is well known. Further, as a method for allowing the microbial granules to grow without fixing the bed on which the microorganisms grow, there are a moving bed and a floating fluidized bed treatment method in which the microorganisms are brought into contact with the organic polluted wastewater for treatment.

By the way, the final stage of the activated sludge method of organic polluted wastewater is solid-liquid separation of treated water and biological sludge in a settling tank. Therefore, the sedimentation characteristics of the sludge mixed liquid at the final stage of the aeration tank are an index for evaluating the progress of biological purification in the activated sludge aeration tank.

The evaluation method will be described below. When the sludge mixture at the final stage of the aeration tank is put in a graduated cylindrical tube and allowed to stand, the biological sludge shows biological coagulation within 2 to 3 minutes immediately after standing and forms flocs to cause interference sedimentation, resulting in uniform velocity. Settle at. This layer sedimentation keeps a constant value until the sludge concentration reaches the boundary surface exceeding the critical concentration, and as the height of the deposited sludge layer increases, the sludge that settles begins to compress the lower layer and the sedimentation velocity decreases, Consolidate sludge settling at the bottom. The volume (%) of the sedimented sludge layer after 30 minutes of standing is read. The volume of sedimented sludge after 30 minutes of standing is SV30.

After measuring this SV30, the sludge mixture is filtered and dried at 100 ° C. or below, and the sludge weight is calculated to obtain M
It is expressed in LSS mg / l, and the sludge volume index SVI is calculated from this MLSS and SV30 by the following formula. SVI (ml) = (SV30 × 10000) / MLSS (mg / l) This SVI shows the volume occupied by 1 g of sludge in ml when the sludge is allowed to settle. It is preferably within the range of 100.

However, in the conventional activated sludge method in practical equipment, the SVI is in the range of 100 to 120, but as a result of measuring the sludge sedimentation characteristics, the sludge sedimentation speed is slow and the sludge is not compacted and is supernatant. When the amount of liquid is small, the SVI is 200 or more, indicating that the sludge has expanded, that is, in a state generally called bulking, and solid-liquid separation becomes difficult, and sludge flows out into the overflow water of the final settling tank. Things happen.

In such a case, there is a method of adding iron chloride, iron sulfate, aluminum sulfate, polyaluminum chloride or a polymer coagulant to the aeration tank in order to forcibly coagulate the sludge and lower the SVI. However, the activated sludge method with the addition of these flocculants aims to remove phosphorus contained in the wastewater to be treated, while these agents also kill protozoa and microbes, so these The reduction of sludge considered as a role and improvement of treated water cannot be expected, and metals such as aluminum and iron accumulate in the sludge, increasing the amount of sludge generated. There are problems such as coloring.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a substance which can be used very effectively as a biosorbent carrier or a biosorbent bed in the treatment of organic polluted wastewater, for example, in the aeration tank in the above-mentioned activated sludge method. It is intended to develop a very useful method for treating organic polluted wastewater, for example, by adding substances, sludge settling characteristics can be improved and SVI value can be lowered very effectively.

[0009]

Means for Solving the Problems In the process of producing an acrylic fiber from a copolymer of acrylonitrile and vinyl acetate, the present inventor, in the two-stage treatment of the sprinkling filter of the waste water and the activated sludge method, It was found that this copolymer polymer has a very excellent adsorption function for microorganisms, and the utilization of this acrylonitrile-vinyl acetate copolymer was studied in order to achieve the above object. As a result, they arrived at the present invention by knowing that this copolymer has an adsorption function superior to any other biological adsorption carrier as an adsorption carrier for microorganisms involved in purification of organic polluted wastewater.

That is, according to the present invention, a fine powder or a coated body of a copolymer of acrylonitrile and vinyl acetate, a random agglomerate of fibers made of the copolymer, or a cut product of a nonwoven fabric made of the fibers is used as a bioadsorption carrier. A method of treating organic polluted wastewater, which is characterized by being used as a body or a biological adsorption bed.

When the copolymer obtained by the copolymerization reaction of acrylonitrile and vinyl acetate is washed with water,
Only a small amount of this copolymer is contained in the wash water. When the copolymerized polymer in water is observed with a microscope, it is recognized that it has a fine ellipsoidal shape. When observing the sprinkling filter biofilm after treating the wastewater containing this copolymer by a two-stage treatment method using a sprinkling filter-activated sludge method together with bacteria, bacteria are adsorbed to the above elliptic spherical polymer. The condensed state was confirmed.

[0012] In addition, in the microorganisms constituting the activated sludge in the aeration tank that receives the water flowing down from the sprinkling filter, the oval spheres of the copolymerized polymer adsorb organisms to form flocs. It was observed under a microscope. Based on these results, it was determined that this acrylonitrile-vinyl acetate copolymer has excellent microbial adsorption performance, and no technology utilizing this characteristic has existed at all in the past, and this copolymer was used for wastewater purification. It was considered to be a new and useful usage.

Considering why this copolymer has excellent microbial adsorption performance, the following reasons can be given. That is, the fine powder of a copolymer of acrylonitrile and vinyl acetate provides an important field for electrochemical adsorption at the interface with respect to adsorption between microorganisms and each other. That is, since the acrylic fiber obtained by melt spinning this copolymer is dyed with a cationic dye, the surface of this copolymer is negatively charged in water, while the surface charge of the microorganism is Is usually positively (+) charged (pH acidic),
Both are electrochemically adsorbed to each other.

On the surface of the body of the microorganism, the ionization state changes due to the change in pH due to the ionization of its carboxyl group, phosphate group, amino group, etc., and it is positively (+) charged on the acidic side where the pH is low, and the pH is high. It is negatively (−) charged on the alkaline side. Bacteria originally include positive (+)-charged Gram-positive bacteria and negative (-)-charged Gram-negative bacteria, but in most cases, the charge changes with pH as described above and adsorption With respect to, the electrochemical adsorption between the organisms adsorbed on the biosorbent bed is observed.

A suspension of fine powder of acrylonitrile / vinyl acetate copolymer is added to the aeration tank in the activated sludge method so that the amount of the fine powder is about 50 mg / l and aeration is carried out. The biological sludge is adsorbed on the fine powder of the copolymer, the amount of the dispersed sludge is reduced, the biological flocculation in the final stage of the aeration tank is improved, and the compaction property of the sedimentation sludge is increased, and the sedimentation sludge exhibits good sedimentation characteristics. This adsorption phenomenon showed stable adsorption without being separated even if the adsorption was repeated after drawing out from the final settling tank, returning to the aeration tank, and repeating aeration. Although the amount of the copolymerized polymer added varies depending on the state of sludge, it is determined that the above-mentioned 50 mg / l is suitable, and if it is too small, the effect on the sedimentation property is low and the amount added is too large. However, it is not possible to obtain an effect higher than a predetermined value.

Next, the acrylic fiber obtained by melt-spinning the acrylonitrile / vinyl acetate copolymer also has a negative (-) surface charge in water, and therefore, it is capable of electrochemically adsorbing microorganisms and the organic polluted wastewater. It can be used as a biosorbent carrier or a biosorbent bed. In this case, it is appropriate to use this acrylic fiber in a random lump form or use it as a nonwoven fabric cut product obtained by making a nonwoven fabric from this acrylic fiber and cutting it into small pieces.

For example, if an adsorbent bed is made of random lumps of acrylic fibers and the adsorbent bed is used to purify the organic polluted wastewater, biological sludge is adsorbed to the adsorbent bed very effectively and the wastewater is purified. Is done. The biosorbent bed consisting of random lumps made of acrylic fiber has the drawback that the adsorbed microorganisms are not subdivided even when the biosorbent beds come into contact with each other by agitation during aeration, and biological aggregation is inhibited. There is no.

That is, in the conventionally used adsorption beds such as anthracite and blast furnace slag, the adhering organisms adsorbed are rubbed into contact with each other during aeration to be subdivided and the aggregation of microorganisms is disturbed during solid-liquid separation. However, there is a problem that the treated water becomes cloudy in the sedimentation tank and the transparency is lowered, but such a phenomenon does not occur at all in the lumps of acrylic fibers.

Also, in the case of circulating and filtering pond water in a closed static pond that is eutrophication, fine algae floating in the pond water are removed by purifying by using the random lumps of acrylic fibers in the present invention. You can do it. Normally, when circulating and filtering pond water, a pressure-type rapid filter, which is widely used for filtering industrial water, is used, but various algae and microorganisms floating in pond water are collected on the filter medium and adhere Therefore, various obstacles occur. However, for example, a pulsating adsorbent bed type biological filtration device is filled with a random lump of acrylic fibers in the present invention and operated, algae and microorganisms are trapped in the biological adsorbent bed, and not only physical trapping is performed. , Biological purification proceeds due to the living metabolism in the living environment in the bioadsorption bed, and the purification of pond water is surely performed.

The acrylonitrile-vinyl acetate copolymer of the present invention can be used as a fine powder, a random lump of fibers, or a cut product of a non-woven fabric, and the copolymer is dissolved in a solvent to obtain a suitable solid. It can be applied as a biological adsorption bed even when applied to an object.
The point is that this copolymer is used as an adsorption carrier or adsorption bed in the state of having a large surface area and its surface charge is negatively (-) charged, and it is possible to obtain a negative charge in the organic polluted wastewater by electrochemical adsorption. The microorganisms are fixed and captured and purified.

[0021]

Example 1 SV30 = 68%, MLSS = 2590 mg / l, by measuring sedimentation characteristics at the final stage of the aeration tank,
Swelling sludge showing a value of SVI = 268 ml was used for the experiment. When the sludge was observed under a microscope, actinomycetes were observed, and a small amount of filamentous fungus, spherochylus, was observed. However, it was considered that the sludge caused by actinomycetes was not considered to be bulking due to the filamentous fungus, based on the amount generated.
A few other fungi, caterpillars, rotifers, etc. were also observed.

With respect to this sludge which tends to expand, in the aeration apparatus as shown in FIG. 1, a fine powder suspension of acrylonitrile / vinyl acetate copolymer is placed in the aeration tank (1) from the addition position (s). Was added until the fine powder concentration reached 50 mg / l, and the operation was continued. The copolymerized polymer added to the aeration tank (1) acts as an adsorption carrier for the sludge-constituting organisms, and when the concentration in the aeration tank (1) reaches a certain amount, it is not necessary to add it thereafter.

After completion of the addition of the fine powder of copolymerized polymer,
The experiment was completed by setting the aeration time in the aeration tank (1) to 4 hours. When the sedimentation characteristics of this sludge mixture were measured, S
V30 = 32%, MLSS = 3500 mg / l, SVI =
A value of 91.4 ml was obtained, the SVI was greatly reduced compared to the value before treatment, and the solid-liquid separation ability in the precipitation tank (3) was greatly improved.

[0024]

Example 2 Using acrylic fibers obtained by melt spinning from an acrylonitrile / vinyl acetate copolymer,
A large number of random agglomerates having a volume of about 1 cm ³ and a weight of about 0.2 g were produced. A sludge liquid having a biological sludge concentration of 2 g / l was used in an aeration tank in which an adsorbent bed was previously prepared in which the sludge liquid was used at a ratio of 30 pieces / l of the above random agglomerates.

Next, when aeration was performed from below and the system was operated for 6 hours, the organisms were completely adsorbed on this adsorption bed.
Moreover, the random lumps of acrylic fibers were not subdivided at all even when they contacted each other by agitation during aeration, and there was no defect that biological aggregation was inhibited.

[0026]

[Example 3] On a ceramic filter medium (5) of the treatment tank (4) in the pulsating fluidized bed pond water purification apparatus shown in FIG. Acrylic bio-adsorption bed (6) was laminated, and pond water with advanced eutrophication was sent. Purification was performed by repeating the operation of passing water and backwashing by switching the valve, and purified water containing almost no microorganisms or algae was obtained in the treated water receiving tank (7).

[0027]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a copolymer of acrylonitrile and vinyl acetate, which has never been used as a sludge purification substance by biological adsorption, has a very excellent microbial adsorption ability. It is an invention achieved by the discovery.

The present invention uses a fine powder of this copolymer, a coated body thereof, a random agglomerate of fibers made of this polymer, or a cut product of a non-woven fabric of the fibers, etc. By using as
A highly effective purification treatment of organic polluted wastewater is achieved. The electrochemical adsorption capacity of the copolymer of the present invention for microorganisms in water is, as shown in Examples, biological purification of organic polluted wastewater and elimination of various obstacles caused by fine algae generated in pond water. It has a very high utility in the present day when the importance of preventing environmental damage is being emphasized.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram when the treatment method of the present invention is applied to aeration-type sludge purification.

FIG. 2 is a cross-sectional explanatory view when the treatment method of the present invention is applied to a pulsating fluidized bed system pond water purification device.

[Explanation of sign]

 (1) Aeration tank (2) Raw wastewater tank (3) Precipitation tank (4) Treatment tank (5) Ceramic filter medium (6) Acrylic organism adsorption bed (7) Treated water receiving tank

Claims (1)

Claim: What is claimed is: 1. A fine powder of a copolymerized polymer of acrylonitrile and vinyl acetate, a coated body, a random lump of fibers made of the copolymerized polymer, or a cut product of a nonwoven fabric made of the fiber, A method for treating organic polluted wastewater, which is used as a biosorbent carrier or a biosorbent bed.