JPH08112591A - How to treat foam scum - Google Patents

Abstract

PURPOSE: To obviate the generation of scum in spite of reaeration by physically defoaming the suspended scum by directly adding a hydrolase to defoaming water for physically disintegrating suspended scum or using an immobilized lysozyme and causing bacteriolysis of actinomycetes or selective sterilization by the hydrolase. CONSTITUTION: The treatment of the suspended scum (in activated sludge microorgaisms of water treatment) suspended on the water surface in a sewer treatment is executed by adding the hydrolase to cause the bacteriolysis of the actinomycetes to the defoaming water 2, 4 for physically defoaming the suspended scum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a sewage treatment, in which a hydrolase suitable for decomposing foamed scum derived from actinomycetes is added directly to defoaming water, or the enzyme is immobilized for water treatment. The present invention relates to a method for surely treating foamed scum by introducing and mixing it into activated sludge microorganisms.

[0002]

2. Description of the Related Art In sewage treatment, a large amount of scum floats on the water surface of a treatment tank, and the floating scum damages the landscape and is blown away by the wind to cause pollution. It is a serious problem such as deterioration.
Therefore, as a method of removing the scum floating on the water surface, as shown in FIG. 4, defoaming water is sprayed from above the floating scum to physically break it to remove the defoaming, or
It was removed by scum skimmer in the final settling tank and returned to the raw water tank and the first settling tank as scum return water.

[0003]

However, effervescent scum is formed by actinomycetes, which is the causative microorganism, and usually foams in the aeration tank and floats as scum in the aeration tank or the precipitation tank. Therefore, in the physical defoaming by the defoaming water, the scum is generated again by the aeration again, and the scum cannot be completely removed. Moreover, residual actinomycetes that could not be completely removed simply circulate in the sewage treatment system and could not be a fundamental solution. In addition to this, there is a method of using a bactericide, but there is a risk that useful bacteria for treating water are also killed at the same time.

According to the present invention, hydrolyzing enzyme is added directly to antifoaming water for physically crushing floating scum, or immobilized lysozyme is used to physically defoam scum, and The purpose is to lyse or selectively sterilize actinomycetes so that scum does not occur even if aeration is performed again.

[0005]

Means for Solving the Problems The present invention has been made in order to achieve the above-mentioned object, and in straywater treatment, floating scum floating on the water surface is physically defoamed. The essence is to suppress foaming scum by adding a hydrolytic enzyme that lyses lysozyme, immobilize lysozyme that hydrolyzes the cell wall of Gram-positive bacteria, and add and mix it into water-treated activated sludge microorganisms. .

[0006]

A large amount of effervescent scum floats on the water surface when sewage is aerobically agitated and treated. This effervescent scum is caused by actinomycetes such as Rhodococcus and Nocardia. In order to solve this floating foam scum, the physiological action of lysozyme, which selectively kills actinomycetes, is utilized. This is because the hydrolytic enzyme (lysozyme) was added to the defoaming water that physically crushes the foam scum to defoam it so that the foam scum was not physically defoamed. Since actinomycetes in scum are also lysed by the action of hydrolase in scum, even if this sewage is aerated again, scum does not recur and sewage treatment can be performed efficiently. Furthermore, even if this lysozyme is put into a sewage treatment facility, it will be diluted with the inflowing sewage and will not flow out of the system as treated water, so this lysozyme will be immobilized for the purpose of containing it in the treatment facility system. The particle size is increased to prevent outflow by means such as a screen and contain it in the aeration tank. This minimizes the effect on useful activated sludge microorganisms and can selectively sterilize actinomycetes over a long period of time, so that foaming scum can be suppressed without adversely affecting water treatment.

[0007]

EXAMPLE A method for treating foam scum according to the present invention will be described below. An enzyme is known as a biocatalyst, and since it can repeatedly use its action, it exhibits a high activity even in a trace amount, selectively decomposes a substrate, and its effect stops after a certain amount of reaction. On the other hand, bacteria are roughly classified into positive bacteria and negative bacteria by Gram staining depending on the difference in cell wall structure. Most of floc activated sludge, which is the center of water treatment, is Gram-negative bacteria and actinomycetes is Gram-positive bacteria. The present invention utilizes the characteristic of the enzyme that selectively decomposes this Gram-positive bacterium to perform scum treatment in sewage more effectively,
Hydrolyzing enzyme is added directly or immobilized to defoaming water that physically breaks and removes floating scum so that the concentration becomes suitable for the properties of sewage.

As this hydrolase, lysozyme,
Examples include trypsin and cellulase. This trypsin and cellulase are known as digestive enzymes and digest and decompose bacteria. Work actively against activated sludge. Since lysozyme is industrially used for biochemical tests and is expensive, it is effective to apply it to water treatment as an immobilized enzyme in the water treatment system. In addition, when directly acting on live bacteria, the anti-osmotic effect of the cell wall is lost, causing lysis. Utilizing this effect, it is used for sterilization of sake burn-off bacteria, eradication of Gram-positive bacteria in foods, and pharmaceuticals. Therefore, lysozyme acts actively on the activated sludge and has no adverse effect, and the amount of hydrolyzing enzyme such as lysozyme added is 0.01 to 1000 mg / l, ph6.
It is desirable to adjust the concentration within the range of to 8 so that the concentration is suitable for the property of sewage.

Lysozyme (N-acetylmuramidoglycanohydrolase: commonly known as muramidase) has a molecular weight of 14037.12.
It is a hydrolase consisting of 9 amino acids.It is widely distributed in various animal tissues, secretions, egg white, etc., and is known to be contained in some plants such as cabbage and turnip. Manufactured. This lysozyme has the property of specifically degrading the cell wall of some Gram-negative bacteria such as Gram-positive bacteria, Escherichia coli, and Salmonella. This specific action is due to the cell wall constituents of the above microorganisms. In other words, the main component of the cell wall is N-acetyl-D-glycosamine,
An aggregate of N-acetylmuramic acid and a peptide chain forms a strong film as a kind of complex polysaccharide called murein, and lysozyme is one of these N-acetyl-D-glycosamine and N-acetylmuramic acid. It is an enzyme that hydrolyzes the β1 → 4 bond and decomposes the cell wall into disaccharides and tetrasaccharides.

As shown in FIG. 5 (1), lysozyme hydrolyzes the cell wall of Gram-positive bacteria (actinomycetes) in the absence of lipopolysaccharide, while activated sludge microorganisms show Gram-negative bacteria as shown in FIG. 5 (2). Since the lipopolysaccharide is present on the cell wall surface, the cell wall is not dissolved even by the lysozyme molecule.

Next, the method for removing foam scum according to the present invention will be described with reference to FIG. 1 showing an embodiment applied to the standard activated sludge method. In FIG. 1, reference numeral 1 is an aeration tank for aerobically treating the sewage from which solids have been removed by a dust remover or the like in the previous step.
Above the inside of the aeration tank 1, a defoaming nozzle 2 for injecting defoaming water toward the water surface at a required pressure is provided for the scum layer generated and floating in the aeration tank, and the aeration process is performed. A final settling tank 3 is connected to the aeration tank 1 so as to send the sewage from the aeration tank to the next treatment step.

The final settling tank 3 is also provided with a defoaming nozzle 4 for injecting defoaming water toward the water surface at a required pressure, and each of the defoaming nozzles 2 and 4 has a hydrolytic enzyme such as lysozyme. Is connected via a pipe 6 to a chemical dissolution tank 5 for dissolving water, a pump 7 for pressurized water supply is connected to this pipe 6, and defoaming water to which a hydrolase is added at an appropriate concentration is supplied to a nozzle. It has become so. This defoaming water can be used directly as tap water, but can also be used after disinfecting the treated water discharged from the final settling tank in the disinfection tank 8 to save water.

The treated water thus sterilized in the disinfection tank is mixed with the hydrolase in the chemical dissolution tank, and nozzles are sprayed in the aeration tank 1 and the final settling tank 3 to crush and lyse floating scum (actinomycetes). It is completely removed by the combined action with.

FIG. 2 shows an embodiment in which the method for removing foam scum according to the present invention is applied to the oxidation ditch method. Sewage is caused to flow into the ditch 10 having a circulation water channel, and scum is generated in the sewage circulating in the ditch 10 to float. In order to crush this scum, a defoaming nozzle 14 is provided at one or two places of the ditch 10, and a pump 16 is connected to this defoaming nozzle 14 via a pipe 15. A defoaming nozzle 1 is connected to the ditch 10 and a final settling tank 11 is connected to the pump 16 as well.
7 is provided. The pump 16 has a chemical dissolution tank 12 into which a part of the treated water flows in through the disinfection tank 13 and dissolves the hydrolase.
Make sure to supply more water.

When defoaming water containing a hydrolyzing enzyme added at an appropriate concentration is sprayed from such a defoaming nozzle toward the water surface, the scum floating at the nozzle water pressure is physically crushed. However, the scum is not completely defoamed only with this nozzle water, and when flowing down downstream and aerating again, some residual actinomycetes grow and scum occurs. Since the hydrolase is added to the nozzle water, the scum that has not been crushed lyses the actinomycetes by the hydrolase and is completely defoamed as shown in FIG.

[0016]

[Chemical formula 1]

Expensive lysozyme, which is industrially used for biochemical tests, is effectively kept in the water treatment system as an immobilized enzyme in the application to water treatment. As shown in the figure, the methods for immobilizing enzymes and microorganisms are roughly classified into three methods: carrier binding method, cross-linking method and encapsulation method. Further, as the carrier binding method, physical adsorption method, ionic binding method, covalent method It can be classified as a binding method, and is classified into a lattice type and a microcapsule type as a comprehensive method. Its purpose is (1) Utilizing high concentrations of enzymes and microorganisms to enhance the physiological reaction of each. (2) To stabilize the physiological reaction. (3) Contain microorganisms with a slow growth rate and expensive enzymes in the reaction tank. Etc.

The immobilization of the enzyme is preferably carried out under conditions of high temperature, strong acid and strong alkali, in which the enzyme is denatured and inactivated, and which is very mild even with an organic solvent and concentrated salts.

A method using polyvinyl alcohol (PVA) will be described below by taking the comprehensive fixing method as an example.
PVA is industrially manufactured by adding (saponifying) alkali from polyvinyl acetate, and its molecular structure is as shown in Chemical Formula 2. The higher the degree of polymerization and the degree of saponification, the higher the viscosity and the lower the solubility. There is.

[0020]

[Chemical formula 2]

The fixing agent has a degree of polymerization of 1000 to 400.
0, a completely saponified product having a saponification degree of 98% or more is suitable, but a partially saponified product having 87 to 98% may be used.

As the immobilization procedure, first, an aqueous PVA solution is prepared. PVA does not readily dissolve at room temperature, and is sufficiently stirred while being heated to form a 20% aqueous solution. Next, after cooling the PVA aqueous solution, it is mixed with lysozyme at the same weight ratio. At this stage, PVA is pasty and shows fluidity. Further, this PVA-lysozyme mixture is added to a 10% sodium sulfate solution. A polymer or protein in an aqueous solution has a phenomenon of precipitating a solute in a salt solution, which is called salting out. PVA is solidified again by this salting out and returns to the original state in which it is hardly dissolved in water at room temperature. At this time, lysozyme is comprehensively immobilized on PVA.

The size of the pellets of entrapping immobilization lysozyme is formed according to the purpose. As a method for keeping the pellets in the water treatment system, when a screen is installed at the outlet of the aeration tank, , It must be larger than the eye width.

The molding method is as follows. When the PVA-lysozyme mixture is added to the sodium sulfate aqueous solution, it is added in the form of water drops.
The size of the pellet can be adjusted to an arbitrary size by adjusting the size, or the PVA-lysozyme mixture can be added all at once and the solidified product can be shredded and molded.

In the molded immobilizing pellets, the larger the size, the lower the enzyme activity becomes, but this is because it becomes difficult for water to permeate the inside of the pellets, and it depends on the activity of the enzyme and the size of the screen. It is desirable to mold it to about 3 to 7 mm.

[0026]

EFFECT OF THE INVENTION The method for treating foam scum of the present invention comprises adding a hydrolase that lyses actinomycetes to defoaming water that physically defoams the floating scum that floats on the water surface during sewage treatment. As a result, the actinomycetes in the scum are lysed by the action of the hydrolase even in the scum that was not physically defoamed by the spray pressure of the defoaming water, so this sewage is aerated again and retreated. Even so, there is an advantage that the sewage treatment can be efficiently performed without the recurrence of scum. In addition, the method for treating foam scum of the present invention is a method of immobilizing lysozyme that hydrolyzes the cell wall of Gram-positive bacteria, and introducing and mixing it in water-treated activated sludge microorganisms, so that it becomes a useful activated sludge microorganism. Since the effect of the above can be minimized and actinomycetes can be selectively sterilized for a long period of time, there is an advantage that the foam scum can be suppressed without adversely affecting the water treatment.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example in which the method for removing foam scum of the present invention is applied to a standard activated sludge method.

FIG. 2 is an explanatory diagram of an example applied to the oxidation ditch method.

FIG. 3 is an explanatory diagram showing defoaming of scum according to the present invention.

FIG. 4 is an explanatory diagram showing defoaming of scum by conventional defoaming water.

FIG. 5 is an explanatory view of the lytic action according to the present invention.

FIG. 6 is a primary structural diagram of lysozyme.

FIG. 7 is an explanatory diagram of an example in which immobilization of lysozyme of the present invention is performed by a lattice type comprehensive method.

FIG. 8 is an explanatory diagram of an example performed by the same microcapsule type encapsulation method.

FIG. 9 is an explanatory diagram of immobilizing lysozyme of the present invention by a carrier binding method.

FIG. 10 is an explanatory view of immobilizing lysozyme of the present invention by a crosslinking method.

[Explanation of symbols]

 1 Aeration tank 2 Defoaming nozzle 3 Final sedimentation tank 4 Defoaming nozzle 5 Chemical dissolution tank 6 Piping 7 Pump 8 Disinfection tank 10 Ditch 11 Final sedimentation tank 12 Chemical dissolution tank 13 Disinfection tank 14 Defoaming nozzle 15 Piping 16 Pump 17 Defoaming tank nozzle

Claims (3)

[Claims] 1. A method in which a hydrolytic enzyme that lyses actinomycetes is added to defoaming water that physically defoams floating scum (in water-treated activated sludge microorganisms) that floats on the water surface during sewage treatment. A method for treating foam scum, which is characterized by the following. 2. A method for treating foam scum, which comprises immobilizing a hydrolase that hydrolyzes the cell wall of Gram-positive bacteria, and introducing and mixing the enzyme into water-treated activated sludge microorganisms to suppress foam scum. 3. The hydrolyzing enzyme lysozyme.
The method for treating foamed scum described.