JPH1170393A - Agent for preventing bulking of activated sludge and wastewater treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily control treatment regardless of causes of bulking, lower the SVI within a short time, and keep the effect continuously by using a composition having a specified formula. SOLUTION: This bulking preventing agent has a formula R1 -Y. In the formula, R1 is a compound residue containing a cationic group which has a property of easily adhering to bulking generating bacteria. Cations, functional groups with low electron density or the like is an example of the cationic group. In this case, it is preferable to add a cationic group, for example quaternary ammonium compounds, which is easy to adhere especially to filamentous bacteria, to the bulking preventing agent. Y is a group which affects the bulking generating bacteria, especially attaches the bulking generating bacteria. For example, -OSO3 M group (wherein M is hydrogen or a metal element), a guanidine residue the like which can disinfect the bulking generating bacteria such as filamentous bacteria, etc., can be used. In this case, a group having a formula; -OSO3 M; is especially preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bulking inhibitor for activated sludge and a method for treating wastewater using the bulking inhibitor.

[0002]

BACKGROUND OF THE INVENTION Wastewater from sewage, night soil and various organic industrial wastes is usually treated by the activated sludge process. The activated sludge method is one of the biological treatment methods for treating wastewater using microorganisms such as bacteria and protozoa, but has had the following problems. That is, during the activated sludge treatment, the microbial flora in the activated sludge changes with the fluctuation of the flow rate of the inflow wastewater and the fluctuation of the organic matter in the inflow wastewater. When these changes are rapid, sludge swells, sedimentation worsens, sludge rises near the water surface, sludge overflow increases, treatment capacity decreases, and in some cases, treatment becomes impossible. A phenomenon was occurring. When this phenomenon occurs, the sludge becomes whitish, very light and difficult to settle, and the BOD removal rate is extremely reduced. Such a phenomenon is referred to as a so-called bulking phenomenon, and is considered to be one of the biggest causes of reducing wastewater purification efficiency and treatment capacity in the activated sludge method.

[0003] For example, SVI (Sl) is an indicator of whether or not activated sludge normally performs a wastewater treatment function.
udge Volume Index, sludge index). This SVI
Is expressed as the volume occupied by 1 g of activated sludge for 30 minutes. The SVI of activated sludge that exhibits normal functions is 5
It is from 0 to 150, especially below 100, but that of activated sludge with bulking can be as high as 300 to 1000. In addition, activated sludge that has caused such bulking is not easy to recover its function, and in the worst case sludge needs to be replaced. Processing must be stopped,
This will have a significant effect on the factory production plan. In addition, in a sewage treatment plant, the water amount fluctuates generally in a day, and sludge flows out during a time period when the water amount fluctuates in the morning and afternoon, and the water quality is remarkably deteriorated and the water cannot be treated.

Conventionally, as a method for preventing the occurrence of bulking of activated sludge, a method of dissolving one or more dithiocarbamates having a specific structure in water and adding the same to activated sludge (Japanese Patent Publication No. 58-14274) Gazette), valine in wastewater,
A method has been proposed in which a composition containing one or more of amino acids such as leucine, isoleucine, phenylalanine L-glutamate, and tyrosine as an active ingredient is added to activated sludge (Japanese Patent Publication No. 58-14275). . Also, a cationic polymer obtained by reaction with a secondary amine, a difunctional epoxy compound and a polyfunctional amine and having a solution viscosity of at least 800 cSt at 25 ° C. and a concentration of 37% by weight aqueous solution is added to the activated sludge. A method (US Pat. No. 3,894,948) and the like have been proposed. However, none of these methods was sufficient for preventing bulking for a long time.

In recent years, the present inventors have proposed a series of bulking inhibitors having a quaternized ammonium salt in the main chain of the polymer (JP-B 3-56118, JP-B 3-56119,
Japanese Patent Publication No. 7-41263) has been proposed as a persistent anti-bulking agent.

[0006]

However, bulking inhibitors having a quaternary ammonium salt in the main chain of the polymer are not always sufficient in terms of persistence and immediate action when the molecular weight of the water-soluble cationic polymer is reduced. . In addition, when the intrinsic viscosity increases, the effect on the bulking bacteria decreases, and the effect of lowering the SVI decreases. It is effective only in combination with anaerobic and aerobic driving. This is because there is an effect on bulking by the type 021N filamentous bacteria, but otherwise there is almost no effect. As described above, there is a problem that a bulking inhibitor which reduces SVI in a short time with respect to occurrence of bulking, which may vary depending on the season such as summer and winter, and maintains its effect has not been found.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and an anti-bulking agent capable of easily reducing the SVI in a short time regardless of the cause of occurrence and reducing the SVI and maintaining its effect, An object of the present invention is to provide a wastewater treatment method using a bulking inhibitor.

[0008]

The anti-bulking agent for activated sludge according to claim 1 is an anti-bulking agent for activated sludge represented by the general formula R ₁ -Y, wherein R ₁ contains a cationic group. Y is a compound residue, and Y is a group that acts on bulking bacteria. Here, the compound residue containing a cationic group refers to the remaining portion of the compound containing a cationic group bonded to Y. In addition, the bulking bacteria refers to bacteria that cause a bulking phenomenon in the process of treating wastewater with activated sludge, and particularly refers to filamentous bacteria. The group acting on the bulking bacteria refers to the action of attacking and destroying the bulking bacteria.

The anti-bulking agent for activated sludge according to claim 2 is characterized in that, in claim 1, Y is -OSO ₃ M group, and M is hydrogen or a metal element.

The anti-bulking agent for activated sludge according to claim 3 is characterized in that in claim 1 or 2, the cationic group is a group having quaternized nitrogen.

[0011] The bulking inhibitor for activated sludge according to claim 4 may be any one of claims 1 to 3,
The general formula R ₁ -Y is an organic polymer having an intrinsic viscosity of 0.6 dl / g or less. Here, the intrinsic viscosity is determined by dissolving a sample in a 2 mol / l KBr aqueous solution and measuring the temperature.
It means the value measured at ° C.

The anti-bulking agent for activated sludge according to claim 5 is an activated sludge anti-bulking agent which is a mixture of a compound represented by the general formula R ₂ -Y and a compound containing at least a cationic group. , R ₂ are unsaturated bond residues of hydrocarbons having at least an unsaturated bond in the molecule and derivatives thereof, and Y is a group acting on bulking bacteria. Here, the unsaturated bond residue refers to a portion excluding an unsaturated bond involved in the reaction, and specifically refers to a remaining portion to which at least Y is bonded. The group acting on the bulking bacteria refers to the action of attacking and destroying the bulking bacteria.

[0013] bulking agents of activated sludge according to claim 6 resides in that in Claim 5, Y is at -OSO ₃ M group, wherein the said M is hydrogen or a metal element.

The wastewater treatment method of the present invention is a wastewater treatment method for treating wastewater with activated sludge, wherein at least one bulking agent selected from the above-mentioned anti-bulking agents is used for 100 parts by weight of dry solid content of activated sludge. 0.01 ~ 2 inhibitor
It is characterized by adding 5 parts by weight.

The anti-bulking agent of the present invention is the result of many years of research on the bulking phenomenon. That is, the bulking phenomenon of activated sludge is caused by bulking-producing bacteria, for example, Sphaertilus (genus Spherotilus), Thio
thrix, genus Aspergillus, Aspergillus, Penicillum, Actinomyces, Type 0803, Type 1701, Type 021N, Type 0961, and other generally sheathed filamentous bacteria and sheathed sulfur-containing filamentous bacteria. This is mostly caused by abnormal growth of filamentous bacteria and filamentous fungi, but especially in winter, activated sludge produces a viscous jelly-like substance, which makes it difficult for the sludge to settle out and causes a bulking phenomenon. May be shown. In this case, it is said that it is effective to add a metal salt such as zinc chloride or a cationic polyacrylamide-based polymer coagulant to the wastewater. In an air tank or the like, it was found that the activated sludge easily contained air bubbles, and the activated sludge containing air bubbles had an extremely low ability to treat wastewater, and had no remarkable effect in preventing the occurrence of bulking. Also, a method of adding fine inorganic particles as a mass additive is known, but in this case, it is necessary to add at least 5% by weight to sludge,
Poor sedimentation also occurs due to the increase in true volume and sedimentation volume of sludge, and the effect is small. Further, since the sludge must be extracted again as a surplus, the disposal cost is greatly increased, which is disadvantageous. In addition, when filamentous bacteria and filamentous fungi contributing to bulking are treated with a chemical having strong bactericidal activity, filamentous bacteria are temporarily destroyed, but at the same time, activated sludge is dismantled, and filamentous bacteria are generated again. Easier to do,
It was found that there was little sustained effect on preventing bulking. In addition, there is often a tendency for bulking to occur frequently.

The present invention has been made based on such findings. That is, the anti-bulking agent of the present invention is, as described above, an anti-bulking agent for activated sludge represented by the general formula R ₁ -Y or a compound represented by the general formula R ₂ -Y and at least a cationic group. It has been found that the use of an activated sludge bulking inhibitor, which is a mixture with a compound containing, can mainly kill filamentous bacteria while maintaining the activity of activated sludge regardless of the type of wastewater and its state. It was done by doing.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION R _{1 according to the} present invention is a compound residue containing a cationic group, and the cationic group portion has a property of easily adhering to bulking bacteria. Examples of the cationic group include a cationic group and a functional group having a low electron density. In the present invention, it is particularly preferable that the bulking inhibitor has a cationic group which easily adheres to filamentous bacteria. The cationic group is preferably a group having a quaternized nitrogen, and examples thereof include a quaternized ammonium group, a quaternized pyridine group, and a quaternized amino group.

An example of R ₁ is an organic group represented by the following chemical formula 1.

Embedded image

R ₃ represents hydrogen or a lower alkyl group, and hydrogen which gives more hydrophilicity is suitable for the present invention.
The term "lower alkyl group" refers to a linear or branched alkyl group having 1 to 4 carbon atoms. R ₄ represents a cationic group and preferably has a functional group that easily adheres to filamentous bacteria, and is preferably a group containing, for example, a quaternary ammonium salt or a tertiary amine. It can be mentioned as a base for forming these -CONH ₂ group, or a derivative group thereof. Further, it may be a derivative group of a -COOH group.
These derivative groups are groups in which a hydrogen atom of an amide group or a carboxyl group is substituted, and examples thereof include the following functional groups.

-CONHCH ₂ OH, -CON (C
_{H 3) 2, -CONHCH 2 OCH} 2 CH (C
_{H 3) 2, -CONHCH 2 CH} (CH 3) 2 CH 2 S
_{O 3 H, -CONHCH 2 C (} CH 3) 2 CH 2 SO 3
_{H, -CONHC (CH 3) 2} CH 2 SO 3 H, -CO
OCH ₂ CH ₂ N (CH ₃ ) ₂ , —COOC ₂ H ₄ N ⁺
(CH ₃ ) ₃ Cl ⁻ .

Further, R ₁ may be a copolymer containing at least one unit represented by the following chemical formula 2 in a polymer chain.

Embedded image R ₅ represents the same hydrogen or lower alkyl group as in Chemical formula 1,
R ₆ represents a carboxyl group, an alkoxyl group, an amino group, a sulfo group, a group having these functional groups at the terminal, and a derivative of these groups. The unit having R ₆ is obtained, for example, by copolymerizing a vinyl monomer. Examples of such a vinyl monomer include acrylic acid, methacrylic acid, n-butyl acrylate, 2-methoxyethyl acrylate, and 2-ethoxyethyl. Acrylate,
Acrylic acids such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, quaternary dimethylaminoethyl ester acrylate, styrenesulfonic acid, ethylenesulfonic acid, 2-acrylamide- Sulfonic acids such as 2-methylpropanesulfonic acid and the like can be mentioned. Since it is suitable as a bulking inhibitor, it is suitable as an anti-bulking agent because it is inexpensive in cost, easy to use industrially, has high defoaming properties, and is excellent in water solubility, and is gradually decomposed by active oxygen. Acrylic esters and methacrylic esters can be mentioned.

Y is a group acting on bulking bacteria, and particularly a group capable of attacking bulking bacteria. For example, mention may be made of or -OSO ₃ M group which can sterilize the bulking occurrence bacteria such as filamentous bacteria, guanidine residue, a carboxyl group, an ester residue, a nitro group, a nitroso group, a halogen group, and an aromatic group. In the present invention, a group having a general formula of —OSO ₃ M is particularly preferable. M represents hydrogen or a metal element. As the metal element, an alkali metal is preferable, for example, Na,
K and Li can be exemplified. As preferred M, the produced salt has high water solubility and is industrially inexpensive.
Na and K can be mentioned. Such -OSO ₃
By having an M group, filamentous bacteria can be mainly killed.

The bulking inhibitor represented by the general formula R ₁ -Y is preferably a high molecular weight substance, and its polymerization degree is preferably 0.001 to 0.6 dl / g or less in intrinsic viscosity. By selecting a polymerization degree at which the intrinsic viscosity falls within this range, filamentous bacteria can be continuously sterilized. In addition, the anti-bulking agent is not preferable to act as an emulsifier, and preferably has an antifoaming effect,
Those having an HLB value of 30 or less, more preferably 10 or less in the whole molecule are preferred.

The bulking inhibitor represented by the general formula R ₁ -Y can be used, for example, in water and a hydrophilic solvent such as methanol or ethanol, for example, with a monomer having a quaternized nitrogen alone or an acrylamide monomer or an acrylate ester monomer. Is polymerized by a method such as redox polymerization or radical polymerization in the presence of a large amount of peroxodisulfate such as potassium peroxodisulfate (K ₂ S ₂ O ₈ ), so that a —OSO ₃ M group is added to the molecular terminal. Can be introduced. Thus, the present invention is to always added to the end groups -OSO ₃ M group, peroxodisulfuric acid potassium (K ₂ S
_Use peroxodisulfate such as ₂ O ₈ ) in a larger amount than the concentration of the initiator.

It should be noted, group acting on bulking generating bacteria, for example, -OSO ₃ M group, not only the molecular chain terminals bulking agents as described above, may be included as a side chain in the molecular chain. When a —OSO ₃ M group is introduced as a side chain into the molecular chain, a compound having a double bond in the main chain as R ₁ is used, and potassium peroxodisulfate (K ₂
It is obtained by reacting a peroxodisulfate such as S ₂ O ₈ ) or sulfuric acid.

Another bulking inhibitor of the present invention is a mixture of a compound represented by the general formula R ₂ -Y and a compound containing at least a cationic group. The general formula R ₂ is a portion obtained by removing at least a hydrocarbon having an unsaturated bond in a molecule and a derivative thereof from the unsaturated bond involved in the reaction. Potassium peroxodisulfate (K ₂ S
By reacting with peroxodisulfate such as ₂ O ₈ ) or sulfuric acid, a —OSO ₃ M group which becomes Y in the molecule can be introduced. Examples of the starting material for R ₂ include unsaturated fatty acids and aliphatic hydrocarbons having an unsaturated group. Examples of unsaturated fatty acids include myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, cis vacenoic acid, vaccenic acid, erucic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, sardine oil, and docosahexaenoic acid. Can be. Examples of the aliphatic hydrocarbon having an unsaturated group include unsaturated higher alcohols corresponding to unsaturated fatty acids.

Y is a group acting on bulking bacteria, particularly a group capable of attacking bulking bacteria, and is preferably a group having a general formula of -OSO ₃ M, as described above. Y is a compound such as —OSO ₃ M group introduced into the molecule by reacting an unsaturated group of R ₂ with sulfuric acid or a peroxodisulfate such as potassium peroxodisulfate (K ₂ S ₂ O ₈ ). be able to. Specifically, a peroxodisulfate such as potassium peroxodisulfate (K ₂ S ₂ O ₈ ) is added in an amount of 0.01 to 1.5 moles per mole of the monomer having an unsaturated group, and is added at 50 to 80 ° C. It is obtained by raising the temperature and reacting for 2 to 8 hours.

The compound containing at least a cationic group mixed with the compound represented by R ₂ -Y includes a polymerizable compound containing a cationic group in the main chain or side chain. As the cationic group, a group having a quaternized nitrogen is preferable, and examples thereof include a polymer of dimethylamine and epichlorohydrin and a polymer having a quaternized nitrogen in a side chain. The molecular weight of such a polymer is preferably a molecular weight that does not inhibit the activity of the activated sludge. When the molecular weight is small, the bactericidal property of the cationic group is exhibited, and the activated sludge may be destroyed. Specifically, the intrinsic viscosity of the compound containing a cationic group is 0.001.
It is preferably about 0.6 dl / g.

The anti-bulking agent of the present invention thus obtained can be used as a solid by removing the solvent at the time of the synthesis reaction, or can be used as water or a hydrophilic solution. Particularly, use as an aqueous solution is suitable as a bulking inhibitor in wastewater treatment.

The wastewater treatment method of the present invention is characterized by using the above-mentioned bulking inhibitor. The amount of addition is 0.01 to 25 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the dry solid content of the activated sludge. When the addition amount is within this range, the occurrence of the bulking phenomenon can be suppressed, and the bulking suppression effect can be maintained continuously without being dissolved in the wastewater and flowing out of the system.

The method of adding the anti-bulking agent is as follows: (a) a method of mixing and mixing with the inflow wastewater and sending the mixture to an aeration tank;
(B) Direct addition to the tank where activated sludge is foaming and scumming in the aeration tank or settling tank, (c) Addition to returned sludge, or a combination of two or more of these Can be done in a way. When the anti-bulking agent of the present invention is added, it is possible to suppress an increase in SVI for 6 months or more. In addition, when signs of increasing SVI are observed, at that time, the anti-bulking agent of the present invention is used.
It is preferable to add in the range of 0.01 to 25 parts by weight. Furthermore, since the anti-bulking agent of the present invention has almost no adverse effect on activated sludge, it is continuously added and always used in activated sludge to be used as an agent for preventing bulking while maintaining normal wastewater treatment. be able to.

[0032]

【Example】

Example 1 In a closed reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and the like, 5 L of an aqueous solution containing 0.5 mol of potassium peroxodisulfate (K ₂ S ₂ O ₈ ) was added to dimethylaminoethyl methyl acrylate acrylate. Monomer [(CH ₂ ＣＨCHCOO)
^{_{C 2 H 4 N + (CH}} 3) 3 Cl -] 5 mol, while keeping turn were charged reaction vessel methyl monomer 5 mol acrylic acid under a nitrogen atmosphere and reacted for 8 hours at 60 ° C.. The obtained reaction product was dropped into a large amount of acetone to obtain a white powdery polymer. This polymer was dissolved in a 2 mol / l KBr aqueous solution and the intrinsic viscosity was measured at a temperature of 25 ° C. As a result, the intrinsic viscosity was 0.15 dl / g. This polymer contains -OSO ₃ K group at the molecular terminal is a polymer containing a cationic group quaternized nitrogen in the molecule chain.

Example 2 282 g of oleic acid and 200 g of sodium benzenesulfonate were charged into a closed reaction vessel equipped with a stirrer, a reflux condenser, a jacket-type condenser, a thermometer, etc., and the inside of the reaction vessel was kept in a nitrogen atmosphere. While adding 120g of concentrated sulfuric acid, 1
After reacting at 5 ° C. for 5 hours, the mixture was neutralized with potassium hydroxide to obtain a solution 1. On the other hand, 50% by weight of dimethylamine
100 g of the aqueous solution was charged into a closed reaction vessel equipped with a stirrer, reflux condenser, thermometer, etc., and 102 g of epichlorohydrin was gradually added while maintaining the inside of the reaction vessel in a nitrogen atmosphere while maintaining the temperature at 30 to 80 ° C. Thus, solution 2 was obtained. Solution 1 and solution 2 were mixed at a weight ratio of 1: 1 to obtain a bulking inhibitor.

Example 3 A bulking inhibitor was obtained in the same manner as in Example 1 except that a dimethylaminoethyl methyl methacrylate chloride monomer was used instead of the dimethylaminoethyl methyl acrylate acrylate monomer.

Example 4 A bulking inhibitor was obtained in the same manner as in Example 2, except that linoleic acid was used instead of oleic acid and paratoluenesulfonic acid was used instead of sodium benzenesulfonate.

Example 5 A sealed reaction vessel equipped with a stirrer, a reflux condenser, a thermometer and the like was charged with 5 liters of an aqueous solution containing 0.5 mol of potassium peroxodisulfate (K ₂ S ₂ O ₈ ), and added with dimethylamino acrylate. Ethyl methyl chloride monomer [(CH ₂ ＣＨCHCOO)
^{_{C 2 H 4 N + (CH}} 3) 3 Cl -] were sequentially the charged reaction vessel 10 mol while maintaining the nitrogen atmosphere, reacted for 8 hours at 60 ° C.. The obtained reaction product was dropped into a large amount of acetone to obtain a white powdery polymer. This polymer is
It was dissolved in 2mol / l KBr aqueous solution and the intrinsic viscosity was measured at a temperature of 25 ° C. As a result, the intrinsic viscosity was 0.20dl / g. This polymer contains -OSO ₃ K group at the molecular terminal is a polymer containing a cationic group quaternized nitrogen in the molecule chain.

Example 6 Dimethylaminoethyl methyl acrylate monomer [(CH ₂ ＣＨCHCOOC ₂ H ₄ N ⁺ (CH ₃ ) _3]
Cl ^-] dimethylaminoethylmethacrylate methyl chloride monomer in place of _{[(CH 2 = C (CH} 3) CO
A bulking inhibitor was obtained in the same manner as in Example 5, except that OC ₂ H ₄ N ⁺ (CH ₃ ) ₃ Cl ⁻ ] was used.

Example 7 A sealed reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, etc., was charged with 5 liters of an aqueous solution containing 0.5 mol of potassium peroxodisulfate (K ₂ S ₂ O ₈ ), and added with dimethylamino acrylate. Ethyl methyl chloride monomer [(CH ₂ ＣＨCHCOO)
C ₂ H ₄ N ⁺ (CH ₃ ) ₃ Cl ⁻ ] 5 mol, dimethylaminoethyl methyl methacrylate chloride monomer [(CH ₂ ＣC (CH ₃ ) COOC ₂ H ₄ N ⁺ (C
H ₃ ) ₃ Cl ⁻ ] 5 mol was charged in order, and the reaction was carried out at 60 ° C. for 8 hours while keeping the inside of the reaction vessel in a nitrogen atmosphere. The obtained reaction product was dropped into a large amount of acetone to obtain a white powdery polymer. As a result of dissolving this polymer in a 2 mol / l KBr aqueous solution and measuring the intrinsic viscosity at a temperature of 25 ° C.,
The intrinsic viscosity was 0.18 dl / g. This polymer contains -OSO ₃ K group at the molecular terminal is a polymer containing a cationic group quaternized nitrogen in the molecule chain.

EXAMPLE 8 Raw waste water having a COD of 380 ppm was sent to four aeration tanks having a capacity of 370 m ³ at a rate of 80 m ³ / hour per unit, and an activated sludge concentration of 3500 ppm (meaning a dry solid content relative to the waste water) And then adjust the raw water in the aeration tank to COD: nitrogen element: phosphorus element ratio of 100: 5: 1, pH to 7 and then supply air to each aeration tank at 800 m ³ / hour. Infused at the speed of. After this treatment, the feed to the settling tank capacity 500 m ^3,
The sludge was allowed to settle, and the supernatant liquid and the concentrated liquid phase of the activated sludge were separated, and the supernatant liquid was flown to the river as effluent. The activated sludge concentrate is returned to the aeration tank at a rate of 80 m ³ / hour as return sludge, and 1 m ³ / hour of the activated sludge concentrate is used as excess activated sludge, and a flocculant is added to this to add sludge. Was aggregated and dehydrated with a centrifugal dehydrator to obtain a dehydrated cake having a water content of 90% by weight. When this wastewater treatment operation was continued for a long time, the SVI of the activated sludge in the aeration tank reached 320.

The amount of the anti-bulking agent obtained in Example 1 corresponding to 120 kg as the dry weight of the polymer solid content was added to the undiluted wastewater sent to the aeration tank at the above-mentioned rate.
It was added over time. After the addition of the anti-bulking agent, the activated sludge in the aeration tank was examined for SVI.
It dropped sharply to 86. In addition, the activated sludge concentration inside the settling tank installed after the aeration tank increased significantly from 5500 ppm before the addition of the bulking inhibitor to 12000 ppm after the addition. Also, the amount of returned sludge was reduced to 47 m ³ / hour to suppress the rise of MLSS. Furthermore, there was no change in the change in dissolved oxygen concentration and the rate of decrease in BOD due to the addition of the anti-bulking agent. In addition, the level of the settling interface of the activated sludge in the settling tank does not rise even after one month has passed since the addition of the anti-bulking agent, so the amount of excess sludge to be withdrawn is reduced and the operating time of the dehydrator is reduced by half. At the same time, the amount of dewatered cake to be incinerated was reduced. The wastewater treatment was performed under the same conditions as in Example 1 except that the anti-bulking agent obtained in Examples 5 to 7 was used instead of the anti-bulking agent obtained in Example 1. The same results as in Example 1 were obtained.

Example 9 From the aeration tank in Example 8, the solid content concentration after drying was
Activated sludge of 3500 ppm and SVI of 320 was collected in a beaker. The anti-bulking agent obtained in Example 1 was used in an amount of 50 to 400 pp based on the dry weight of the polymer solid based on the volume of the aeration tank.
The addition amount was changed within the range of m and the state of reduction in SVI of the activated sludge was observed. When the anti-bulking agent obtained in Example 1 is added to the activated sludge in the above range, SVI
Dropped to 160. Therefore, the sludge from the wastewater treatment plant
In an activated sludge small model having an aeration tank capacity of 3 m ³ and a settling tank capacity of 1 m ³ assuming an actual wastewater treatment plant, raw wastewater of Example 8 was subjected to COD: nitrogen: phosphorus element in the aeration tank. Was added continuously so that the ratio became 100: 5: 1, the dissolved oxygen concentration in the aeration tank was adjusted to 1 to 2 ppm, and the sludge was continuously returned with the sludge return rate set to 50%. In this activated sludge model, the anti-bulking agent was continuously added for 24 hours while diluting 100 times with tap water so that the dry weight of the polymer solids was 50 ppm based on the volume of the aeration tank. After the addition of the bulking inhibitor, the SV of activated sludge in the aeration tank
I was reduced to 120, and the separability between the supernatant and the concentrated liquid of the activated sludge in the settling tank was improved. The BOD in the treated water was in a good condition without any change. Even 11 months after the addition of the bulking inhibitor, the level of the activated sludge settling surface in the settling tank did not rise.

Example 10 From the aeration tank in Example 8, the solid content concentration after drying was
Activated sludge of 3500 ppm and SVI of 320 was collected in a beaker. To the activated sludge in this beaker, the anti-bulking agent obtained in Example 2 was added in varying amounts within the range of 50 to 400 ppm in terms of the dry weight of the polymer solid content to reduce the SVI of the activated sludge. The situation was observed. When the anti-bulking agent is added to the collected activated sludge in the above range,
The SVI has dropped to 130. Therefore, the sludge from the above wastewater treatment plant was put into a small model of activated sludge treatment similar to that in Example 9, and the amount of dissolved oxygen in the aeration tank described in Example 9 was determined.
The continuous operation was performed under the same conditions as the amount of raw wastewater added and the sludge return rate. In this small model of activated sludge, the anti-bulking agent is used as the dry weight of polymer solids for the aeration tank volume.
While diluting 100 times with tap water to 150 ppm 2
It was added continuously for 4 hours. After the addition of the bulking inhibitor,
The SVI of the activated sludge in the aeration tank dropped to 120, and 3 days after the end of the addition, the SVI dropped to 80, and the separability between the supernatant and the concentrated liquid of the activated sludge in the settling tank was reduced. Improved. One month after the addition of the bulking inhibitor, the rapid increase of filamentous bacteria was suppressed, and the level of the settling interface of the activated sludge in the settling tank did not increase. The BOD of the treated water was in a good condition without any change.

Example 11 From the aeration tank in Example 8, the solid content concentration after drying was
Activated sludge of 3500 ppm and SVI of 320 was collected in a beaker. With respect to the activated sludge in this beaker, the anti-bulking agent obtained in Example 3 was added to the sludge collected from the aeration tank with the addition amount being changed in the range of 50 to 400 ppm as the dry weight of the polymer solid content. The state of reduction of SVI of activated sludge was observed. When the anti-bulking agent was added in the above range to the collected activated sludge, the SVI was reduced to 160. Therefore, the sludge from the wastewater treatment plant described above was put into a small model of activated sludge treatment similar to that in Example 9, and the same as the dissolved oxygen amount, wastewater raw water addition amount, and sludge return rate of the aeration tank described in Example 9 Was operated continuously under the following conditions. In this small model of activated sludge, tap water was added to the sludge using tap water so that the anti-bulking agent would be 150 ppm by dry weight of polymer solids.
It was added continuously for 24 hours while diluting it 00 times. After the addition of the bulking inhibitor, the SVI of the activated sludge in the aeration tank is
After 3 days from the end of addition, SVI was 1
It decreased to 10 and the separability between the supernatant and the concentrated solution of activated sludge in the settling tank was improved. One month after the addition of the bulking inhibitor, the rapid increase of filamentous bacteria was suppressed, and the level of the settling interface of the activated sludge in the settling tank did not increase. The BOD of the treated water was in a good condition without any change. The wastewater treatment was performed under the same conditions as in Example 11 except that the anti-bulking agent obtained in Example 4 was used instead of the anti-bulking agent obtained in Example 3; Similar results were obtained.

Comparative Example 1 In place of the bulking inhibitor used in Example 8, a commercially available cationic polyacrylamide-based flocculant (for example, Diaclear (manufactured by Mitsubishi Chemical Corporation, trade name), Hymoloc (Himo Corporation) Sanfloc (manufactured by Sanyo Chemical Industries, trade name), Diafloc (manufactured by Diaflock, trade name), Cliff Lock (manufactured by Kurita Industries,
Using the aqueous solution of (trade name), the amount of addition was changed in the same manner as in Example 9, and the state of reduction in SVI of the activated sludge was observed. In the case of the above commercially available disposal liquids, all exhibited almost the same behavior, and the activated sludge collected from the aeration tank exhibited good sedimentation floc when the dry weight of solids in the treatment liquid was around 20 ppm. SVI of the activated sludge was about 130 after the formation was started and the solid content in the treatment liquid was added so that the dry weight was 60 ppm. However, if you put an airstone into this graduated cylinder,
After aeration for a minute, the settled sludge entrained air bubbles and all floated, making it impossible to settle and separate. In the wastewater treatment plant of Example 8, the SVI of the activated sludge in the aeration tank rose to 300 due to the generation of a large amount of filamentous bacteria, making it difficult to separate the sludge layer and the supernatant in the settling tank. At that time, the cationic methacrylate coagulant (molecular weight Mw: about 5,000,000) was adjusted to a concentration of 0.5% by weight, and an amount corresponding to a dry weight of polymer solids of 60 kg was added continuously for 24 hours. However, after the addition of the treatment liquid, the SVI of the activated sludge in the aeration tank dropped to 120, but bubbles adhered to flocs flocculated in the final sedimentation tank, causing a large amount of sludge to float and flowing out with the treated water. It became impossible to process. Also, three days after the completion of the addition, the SVI again exceeded 300, making it difficult to separate the supernatant and the activated sludge concentrate in the settling tank.

Comparative Example 2 In place of the anti-bulking agent used in Example 8, an anti-bulking agent prepared by the following method was used.
I was observed to be in a reduced state. Preparation of Comparative Sample: Equimolar 50% dimethylamine was continuously added to epichlorohydrin over 5 hours while maintaining the temperature at 60 ° C. under cooling. After completion of the addition, the mixture was aged for 12 hours while maintaining the temperature at 40 ° C. Using a preparative GPC, a polymer having an intrinsic viscosity of 0.40 measured at a temperature of 25 ° C. from a 2 mol / l KBr aqueous solution was fractionated from the resulting mixed reaction composition as a comparative sample.

The activated sludge described in Example 9 was put into a small model of the activated sludge described in Example 9, and continuously rotated under the same conditions as in Example 9. In this small model of activated sludge, 100% of the anti-bulking agent of the comparative sample was added to the sludge with tap water so that the dry weight of the polymer solid content was 100 ppm.
It was added continuously for 24 hours while diluting 2-fold. Eleven hours after the addition of the bulking inhibitor of the comparative sample, the SVI of the activated sludge in the aeration tank dropped to 140. Observation of the sludge at this time with a microscope revealed that the sludge contained filamentous bacteria and formed large flocs. However, from the addition
Three days later, the SVI exceeded 300 again, making it difficult to separate the supernatant and the concentrated activated sludge in the settling tank. When the sludge at this time was observed with a microscope, the large sludge flocs returned to the size before the addition of the bulking inhibitor of the comparative sample, and a large amount of long filamentous bacteria was observed.

[0047]

The bulking inhibitor of the present invention contains a cationic group and a group acting on a bulking bacterium, or a hydrocarbon or the like having an unsaturated bond in the molecule and a group acting on a bulking bacterium. And a compound containing a cationic group, the filamentous bacteria can be mainly killed while maintaining the activity of the activated sludge. Therefore, an increase in the SVI of the activated sludge can be suppressed in a short time by simply adding the bulking inhibitor. In addition, this effect can be maintained for a long time. As a result, the activated sludge in the aeration tank does not expand, the sedimentation volume is reduced, the activated sludge concentration is kept high, and the effect of removing BOD can be significantly increased.

Since the wastewater treatment method of the present invention uses the above-described bulking inhibitor, the sedimentation and separation of activated sludge becomes extremely easy even in a settling tank. In addition, since the volume of the sediment (the settling volume) can be made extremely small, surplus activated sludge is hardly generated, and there is no need to frequently perform surplus activated sludge removal and incineration, which is an extremely excellent wastewater treatment method.

Claims (7)

[Claims] An anti-bulking agent for activated sludge represented by the general formula R ₁ -Y, wherein R ₁ is a compound residue containing a cationic group, and Y acts on a bulking-producing bacterium. Activated sludge bulking inhibitor characterized by being a base. 2. The bulking inhibitor of activated sludge according to claim 1, wherein said Y is a —OSO ₃ M group, and said M is hydrogen or a metal element. 3. The bulking inhibitor of activated sludge according to claim 1, wherein the cationic group is a group having quaternized nitrogen. 4. The activated sludge according to claim 1, wherein the general formula R ₁ -Y is an organic polymer having an intrinsic viscosity of 0.6 dl / g or less. Anti-bulking agent. 5. An anti-bulking agent for activated sludge which is a mixture of a compound represented by the general formula R ₂ -Y and a compound containing at least a cationic group, wherein said R ₂ has at least one molecule in the molecule. The unsaturated bond residue of a hydrocarbon having an unsaturated bond and a derivative thereof,
Y is a group that acts on bulking bacteria, and is a bulking inhibitor for activated sludge. 6. The bulking inhibitor of activated sludge according to claim 5, wherein said Y is a —OSO ₃ M group, and said M is hydrogen or a metal element. 7. A wastewater treatment method for treating wastewater with activated sludge, wherein at least one of the bulking inhibitors selected from claims 1 to 6 is used for 100 parts by weight of dry solid content of the activated sludge. A method for treating wastewater, comprising adding 0.01 to 25 parts by weight of a bulking inhibitor for activated sludge.