JPS63218294A - Process for preventing activated sludge from bulking - Google Patents

Abstract

PURPOSE:To prevent activated sludge from bulking, by adding a water-soluble cationic polymer obtd. by the reaction of dialkylamine, occasionally ammonia, with epihalohydrin, to waste water contg. already bulked activated sludge. CONSTITUTION:0.05-25pts.wt. of a water-solube cationic polymer obtd. by the reaction of dialkylamine, occasionally ammonia (<= equimolar amt. to dialkylamine) with epihalohydrin, per 100pts.wt. dry solid of the activated sludge is added to activate sludge in which bulking has already caused or in which bulking is to be caused by the Hyphomycetes of type 021N, or to waste water contg. such activated sludge. As the result, bulking of activated sludge caused by the type 021N Hyphomycetes is prevented specifically. Further, the increase of SVI (sludge volume index) of the activated sludge is retarded in a short time. Moreover, the concn. of activated sludge is held at a high level, and the reducing effect of BOD is enhanced remarkably.

Description

[Detailed Description of the Invention] [Background of the Invention] Technical Field The present invention relates to the expansion phenomenon of activated sludge, that is, bulking (
Bulking).

More specifically, the present invention relates to a method for effectively preventing bulking of activated sludge caused by specific bacteria in a method for preventing bulking by adding chemicals.

Active l as one of the biological methods used for wastewater treatment
There is a ri mud method. This method utilizes the properties of activated sludge, a slurry produced by blowing air into wastewater containing organic matter and propagating microorganisms.Activated sludge produces highly adsorbent flocs. This method takes advantage of the phenomenon that since its specific gravity is higher than that of water (for example, it is said to be around 1.003), it settles when left to stand, leaving behind transparent treated water. The settled activated sludge is reused as return sludge.

Sewage, urine and various organic industrial wastewaters are usually treated by the activated sludge process. During treatment using this method, changes occur in the flow rate of inflowing wastewater, changes in organic matter in inflowing wastewater, and changes in the types of microorganisms such as various molds and filamentous bacteria that grow in sewer pipes. It is known that the microbial flora in activated sludge changes in response to changes in When this filamentous bacteria increases, the sludge swells, sedimentation becomes poor, the sludge rises to near the water surface, the amount of sludge overflow increases, and the so-called bulking phenomenon occurs, which reduces treatment capacity and in some cases makes treatment impossible. occurs. When this phenomenon occurs, the sludge becomes whitish, very light, and difficult to settle, and the BOD removal rate is also extremely reduced.

As an indicator of whether activated sludge is functioning normally, SVI (Sludge Volus+e
There is an Index sludge index) value. This SVI value is
It is expressed as the volume occupied by 1 g of activated sludge during 30 minutes of settling. The SVI of activated sludge that functions normally is 5.
It is 0 to 150, especially 100 or less, but that of activated sludge that has undergone bulking can be as high as 300 to 800.

It is not easy to restore the function of activated sludge that has caused such bulking, and in the worst case, it becomes necessary to replace the sludge.In factories, etc., when replacing the sludge, the sludge must be used until it has become acclimatized. This will have a serious impact on the factory's production plan.Even in public sewage treatment plants, B
The OD removal efficiency decreases, leading to environmental pollution, which may become a major social problem.

Prior art methods for preventing bulking of activated sludge are disclosed in Japanese Patent Publications No. 58-14274 and Japanese Patent Publication No. 58-14275.
The method described in the above publication has been proposed.

The method described in Japanese Patent Publication No. 58-14274 is a method in which one or more dithiocarbamates having a specific structure are dissolved in water and added to activated sludge. However, this method is only applicable when the cause of bulking is abnormal growth of filamentous fungi, and is not effective when there are other causes. In addition, when using this method, it takes more than 4 days, or even 1 day in some cases, even if the degree of damage to the activated sludge is relatively minor, before the effect appears.
It has the disadvantage that it is necessary for more than 0 days and must continue to be added in large amounts every day.

The method described in Japanese Patent Publication No. 58-14275 contains valine, leucine, isoleucine, glutamic acid,
A composition containing one or more amino acids such as phenylalanine and tyrosine as an active ingredient is added to activated sludge. When using this method, it is necessary to continuously add a composition containing these active ingredients to the inflowing wastewater at a high level of 0.5 to 3 kg/m for more than 3 hours, and the effect cannot be obtained. 2 to demonstrate
The disadvantage is that it requires more than 4 hours.

The bulking phenomenon of activated sludge is 5phaerot11u
s (Sphaerochilus spp.), Th1othrlx (
Thiothrix), Aspergillus (
In addition to abnormal growth of filamentous fungi such as Aspergillus (genus Aspergillus) and Pcnlclllum (genus Penicillium),
Depending on the season and nutritional status, a highly viscous jelly-like substance may be generated in activated sludge, making it difficult for the sludge to settle and causing a bulking phenomenon. In the latter case, it is said to be effective to add Z n C12 or a cationic polyacrylamide-based polymer flocculant to the wastewater. However, according to the inventor's experiments,
It has been found that this method has no significant effect on preventing bulking, as activated sludge tends to contain air bubbles in aeration tanks, etc., and activated sludge containing air bubbles has an extremely reduced ability to treat wastewater. Ta.

In addition, the normal microbial flora can be restored to normal microbiota without relying on the addition of chemicals, for example, using only operating conditions such as anaerobic and aerobic treatment or a method of mixing a large amount of suspended solids (S, S) without using an initial settling tank. Although attempts have been made, no satisfactory method has yet been proposed for bulking caused by abnormal growth of type 021N filamentous bacteria.

Possible Solutions However, the addition of drugs is effective against bulking due to overgrowth of type 021N filamentous bacteria.

The present inventors have already made a proposal to solve the problems observed in the conventional bulking prevention method by adding drugs (Japanese Patent Laid-Open No. 61-204092 and Japanese Patent Application No. 1983). -295890 specification). These proposals are based on the use of water-soluble cationic polymers obtained by the reaction of dialkylamines and epichlorohydrin, or water-soluble cationic polymers obtained by the reaction of dialkylamines, ammonia, and epichlorohydrin as anti-bulking agents. The main feature is the use of merging.

Where the problem lies At general final treatment plants for urban sewage, bulking is most often caused by filamentous bacteria, and conventionally, bulking is caused by filamentous bacteria, such as Sphaerochilus and BegglatOa.
are said to be representative of the causative microorganisms (Journal of the Japan Sewage Works Association, Vol. 22, No. 252, pp. 2-12 (1985)
Year)).

By the way, with the recent development of sewerage systems, rainwater and domestic wastewater have come to be separated and treated. As a result, it is presumed that changes have occurred in the filamentous bacteria that cause bulking when urban sewage, such as domestic wastewater, is treated by the activated sludge method.

[Summary of the invention]

Summary The present invention aims to specifically kill specific bulking-forming filamentous bacteria in response to recent changes in urban sewage. The aim is to achieve this goal by using it as a drug.

That is, the activated sludge bulking prevention method according to the present invention applies to activated sludge in which bulking should occur or has occurred due to type 021N filamentous bacteria, or wastewater containing the same, based on 100 parts by weight of dry solid content of the activated sludge. It is characterized by the addition of 0.05 to 25 parts by weight of a water-soluble cationic polymer obtained by the reaction of a dialkylamine, optionally ammonia (equal mole or less to the dialkylamine), and epihalohydrin. be.

Effects According to the present invention, the above objects are achieved and type 02
Bulking of activated sludge due to 1N filamentous bacteria is specifically prevented.

That is, according to the polymer according to the present invention, if the polymer is added at the time when signs of an increase in the SVI value due to abnormal proliferation of filamentous bacteria are observed, or after the SVI value has increased, the polymer can be added quickly. The SVI value can be maintained at or below the original level without substantial further increase in the SVI value. Moreover, according to the drug of the present invention,
Although the filamentous forms of filamentous bacteria are destroyed and the products flow out of the treatment tank together with the treated water, there is hardly any increase in BOD, so it is possible to provide good treated water. Furthermore, the drug of the present invention has a long duration of effect after one addition.

Therefore, implementing the present invention will be extremely beneficial in terms of activated sludge process management.

In addition to these unique effects, the present invention also has the following effects derived from the prior invention of the present inventors.

(1) When using the method of the present invention, an increase in the SVI of activated sludge can be suppressed in a short time by simply adding a water-soluble cationic polymer to the activated sludge treatment system.

(2) When using the method of the present invention, the activated sludge in the aeration tank does not expand, the settling volume can be reduced, the activated sludge concentration can be kept high, and the BOD removal effect can be significantly increased.

(3) When the method of the present invention is used, the sedimentation and separation of activated sludge becomes extremely easy even in a sedimentation tank. Moreover, since the volume of sedimented material (sedimentation volume) can be significantly reduced, excess activated sludge is less likely to be produced, and there is no need to frequently remove or incinerate excess activated sludge.

[Detailed description of the invention]

As mentioned above, the present invention relates to a method for preventing bulking of activated sludge due to certain filamentous bacteria.

Target Activated Sludge The activated sludge targeted by the present invention is one that causes bulking due to type 021N filamentous bacteria.

Type 021N filamentous bacteria are D, I! .

EikelbooII: Prog,vater Tec
h, vol. 8, no. 6 - pp. 153-161 (1977
It is defined in 2013).

As mentioned above, urban sewage activated sludge containing this filamentous bacteria has recently become more common, and if it is necessary to isolate this microorganism, it can be easily obtained from these sewage activated sludges. .

Water-soluble cationic polymer The drug used in the present invention is a water-soluble cation whose chemical substance is obtained by the reaction of a dialkylamine and epihalohydrin, or a dialkylamine and an equimolar amount or less of ammonia and epihalohydrin. Polymer.

Although the chemical structure of this polymer is not necessarily clear, it is assumed that the nitrogen atom of the dialkylamine is quaternized and the halogen ion derived from epihalohydrin serves as its counter ion (however, the present invention (We are not in any way limited by such estimates.)

Furthermore, in the present invention, the "water-soluble cationic polymer obtained by the reaction of a dialkylamine, optionally ammonia (equal molar or less to the dialkylamine), and epihalohydrin" is a water-soluble cationic polymer obtained by reacting an epihalohydrin with the above counterion (halogen). It is intended to include substitutes for ions and the corresponding hydroxides.

Therefore, the possible predicted structure of this water-soluble cationic polymer when it does not contain ammonia is as follows.

SakiN"-CH-CH-CH2+□ 1X-1 R20H Here, R1-R2 is an alkyl group derived from sial"kylamine, X- is a halogen or other anion or OH-" derived from epihalohydrin, and n is a polymer. (2 or more, preferably 3 or more) The dialkylamine from which such a polymer is to be produced is preferably one in which the alkyl group has about 1 to 8 carbon atoms, particularly about 1 to 2 carbon atoms. The alkyl groups may not be identical within the molecule. Specific examples of such dialkylamines include dimethylamine, diethylamine, dipropylamine, methylethylamine, methylpropylamine, ethylpropylamine, methylbutylamine, ethyl Examples include butylamine, dibutylamine, 2-ethylhequinylamine, and the like.

When ammonia is used in combination, it is only necessary to add a very small amount to the dialkylamine. The molar ratio of ammonia/dialkylamine can be selected from the range of 0.0001 to 1.0, with a particularly preferred molar ratio of 0.0001 to 1.0.
It is in the range of 001 to 0.1.

In epihalohydrin, the halogens are fluorine, chlorine,
Bromine or iodine compounds are generally targeted, but epichlorohydrin is preferred at least for economic reasons.

To react dialkylamine, ammonia (when used), and epihalohydrin, the number of moles of dialkylamine and ammonia is approximately equal to the number of moles of epihalohydrin, a closed reaction vessel equipped with a stirrer is used, and an inert Under a gas atmosphere, the internal temperature of the reaction vessel is set to 30-11
The temperature range is preferably 0°C.

More specifically, a 20-70% strength by weight aqueous solution of dialkylamine or dialkylamine and optionally ammonia,
Pour into a closed reaction container equipped with a stirrer, reflux condenser, thermometer, etc., replace the atmosphere inside the container with nitrogen gas, and while stirring,
It is preferable to add epihalohydrin continuously or in quarters while controlling the temperature inside the reaction vessel to prevent it from rising too much. When adding ammonia, it is preferable to first add epihalohydrin to the dimethylamine aqueous solution and then add ammonia. After adding epihalohydrin and dialkylamine (and ammonia) to the reaction vessel, add alkali metal or alkaline earth metal oxides or hydroxides to the reaction vessel at a rate of 0.00001 to 0.00 per mole of epichlorohydrin. .01 mol added, 30~
When kept in the temperature range of 60° C. for several hours, the molecular weight of the produced polymer may increase. Note that when this reaction product is maintained as an aqueous solution at a temperature of about 30° C. under a nitrogen gas atmosphere, a reaction in which the molecular weight increases slowly proceeds for about two months. During this time, if air or oxygen is introduced into the container, the reaction that increases the molecular weight will not proceed.

The polymer thus obtained can be further processed to replace the halogen (derived from epihalohydrin) as a counterion with another anion or to remove the counterion and convert this cationic polymer into a hydroxide. It is clear from the above that it is also possible to do this.

The polymer obtained as described above has an intrinsic viscosity [η
In the method of the present invention, [η] of 0.001 dl/g or more, more preferably 0.01 dl/g or more, is used.

If [η] is too small, the adsorption to activated sludge will decrease and the sustainability of the bulking prevention effect will decrease, which is not preferable.

The water-soluble cationic polymer thus obtained can also be converted into a solid by removing the solvent (usually water). However, it is preferable and usual to use the aqueous solution produced as an aqueous solution as it is or after diluting or concentrating as necessary to prevent bulking of activated sludge.

Prevention of bulking of activated sludge The agent according to the present invention, except for the fact that the target activated sludge to be prevented from bulking contains the specific filamentous bacteria as mentioned above, and for any changes in treatment conditions that may occur thereby. The method of preventing bulking of activated sludge by addition is essentially the same as the conventional method.

Specifically, a water-soluble cationic polymer is made into an aqueous solution with an appropriate concentration, for example, about 0.1 to 10% by weight, and this aqueous solution is processed by one of the following methods or two methods.
It may be added according to the method of combining more than one species.

(1) Method of mixing with inflowing wastewater and sending it to an aeration tank.

(2) Method of adding directly to an aeration tank or settling tank where bulking of activated sludge is occurring.

(3) Method of adding to returned sludge.

If the amount of this water-soluble cationic polymer used is too small, the purpose of the invention will not be achieved, so it is undesirable. On the other hand, if it is too large, filamentous bacteria will be rapidly destroyed and the treated water will deteriorate rapidly. This is not preferable because it may become cloudy or be washed out of the system together with the wastewater, possibly causing an increase in the COD of the treated water. The amount used is preferably selected within the range of 0.05 to 25 parts by weight based on 100 parts by weight of the dry solid content of the activated sludge. More preferably, it is in the range of 0.1 to 10 parts by weight.

When a water-soluble cationic polymer is added once within the above range to activated sludge, no increase in the SVI value is observed for one month or more. Thereafter, when signs of an increase in the SVI value are observed, the water-soluble cationic polymer is preferably added within the above range.

Experimental Examples Example 1 At a public sewage treatment plant that processes separated urban sewerage wastewater with a monthly average of 3000 m/day and a BOD of 2 ooppm and a suspended solids (SS) of 120 ppm, the settled sludge volume index (SVI) of the aeration tank was value) exceeded 700, the dry sludge concentration (MLSS) of the returned sludge fell below 2000 ppm, the MLSS in the aeration tank also fell below 11000 ppm, and the separability of treated water and sludge in the final settling tank deteriorated significantly. Therefore, we temporarily changed the operating conditions by using two 1000 rIt aeration tanks in series, and the final settling tank was two 500 rIt tanks in parallel, doubling the aeration time and settling time. The BOD and SS values of treated water were maintained. The return rate of returned sludge to treated raw water is 100%.
The air magnification ratio for raw water is 6 times, and a diffuser plate is used to introduce air. When the sludge in the aeration tank and sedimentation tank of this treatment plant was Durham stained and observed using a phase contrast microscope, it was found that there were not floc-forming bacteria in the sludge between the flocs, but rather type 021N filamentous bacteria. Volume was observed more often.

At this treatment plant, until the molar ratio of epichlorohydrin and 50% dimethylamine aqueous solution becomes 1:1.05,
The mixed reaction composition obtained by adding epichlorohydrin to a 0% dimethylamine aqueous solution while maintaining the reaction temperature at 90°C and mixing with stirring (intrinsic viscosity [η] measured with a 2 mol/liter KBr aqueous solution) When 0.02 dl/g of composition) was continuously added to the return sludge line for 50 hours while diluting it 100 times with tap water at a rate of 100 sr/min, 9 hours later, it was added to the treated water from the final settling tank. A large number of type 021N filamentous bacteria that were thought to have been destroyed were observed, as well as type 021N bacteria in the aeration tank.
began to be destroyed and the SVI value decreased to 200, and the position of the sludge interface in the final settling tank also decreased. After 50 hours, S
VI value reached 80. It was confirmed that the number of filamentous bacteria in the sludge present in the aeration tank at this time was extremely reduced. Furthermore, the activated sludge formed firmer flocs than before addition. After 100 hours, the sedimentation property was significantly improved and the SVI value became 75, so the concentration of returned sludge increased to the MLSS value of 5500 ppm, and the sludge concentration in the aeration tank also increased to the MLSS value of 2300 ppm. It is now possible to operate by switching each tank to use one pond. Therefore, the raw water inflow system was changed to two-line parallel operation, and the raw water could now be treated.
Processing capacity has been doubled.

Type 021N filamentous bacteria are destroyed and flowed out, but the suspended solids concentration at this time is less than 5 ppm, and the BOD and COD values of the effluent after chlorine sterilization are each less than 20 ppm, The water was in good condition as effluent.

Example 2 Monthly average: 7,000m/unit, BOD: 150ppm.

At a public sewage treatment plant that processes partially combined urban sewerage wastewater with a suspended solids content (SS) of 110 ppm,
The settled sludge volume index (SVI value) of the aeration tank with a capacity of 0 m exceeds 400, and the dry sludge concentration (MLSS) of the returned sludge
) became less than 2000 ppm, the MLSS in the aeration tank also became less than 11000 ppm, and the separability of treated water and sludge in the final settling tank with a volume of 1000 m deteriorated significantly. The operating conditions are that the return ratio of returned sludge to treated raw water is 309
6. The air magnification is 5 times the raw water, and a diffuser plate is used to introduce air. When the sludge in the aeration tank and sedimentation tank of this treatment plant was Durham stained and observed using a phase contrast microscope, it was found that there were not floc-forming bacteria in the sludge between the flocs, but rather type 021N filamentous bacteria. Volume was observed more often.

At this treatment plant, epichlorohydrin was added to a 50% dimethylamine aqueous solution while maintaining the reaction temperature at 85°C, and the mixture was stirred until the molar ratio of epichlorohydrin and 50% dimethylamine aqueous solution was 1=1. The mixed reaction composition obtained (a composition with an intrinsic viscosity [η] of 0.12 dl/g measured with a 2 mol/liter KBr aqueous solution) was diluted 100 times with tap water at a rate of 150 g/min. When it was continuously added to the return sludge line for 45 hours,
After 6 hours, Type 021 was added to the treated water from the final settling tank.
A large number of N filamentous bacteria that were thought to have been destroyed were observed, and the type 021N in the aeration tank began to be destroyed, causing the SVI value to drop to 210, and the position of the sludge interface in the final settling tank also decreased. After 50 hours, the SVI value was 110. It was confirmed that the number of filamentous bacteria in the sludge present in the aeration tank at this time was extremely reduced.

After 60 hours, the filamentous form of type 021N was destroyed;
Moreover, the destroyed filamentous bacteria flow out together with the treated water,
It was confirmed that almost no filamentous bacteria remained in the activated sludge remaining in the aeration tank and settling tank. Furthermore, the activated sludge formed firmer flocs than before addition. As a result, the sedimentation properties of activated sludge were significantly improved, with an SVI value of 80, and a return sludge concentration of MLSS value of 60.
00ppm, and the sludge concentration in the aeration tank also decreased to MLSS value 2.
It has increased to 300 ppm. In addition, the sludge was thickened in a gravity-type thickening tank, allowing thicker sludge to be sent to the digester, increasing the rate of digestion gas production, and increasing the efficiency of the digester. In addition, when dewatering digested sludge, cationic polyacrylamide was used as a flocculant in a centrifugal decanter using 0.6% by weight based on the dry weight of the sludge, but the amount of flocculant used was 0.6% by weight based on the dry weight of the sludge. It became possible to dehydrate at 5% by weight.

Type 021N filamentous bacteria are destroyed and flowed out, but the suspended solids concentration at this time is less than 5 ppm, and the BOD and COD values of the effluent after chlorine sterilization are each less than 20 pprn. It was in good condition as water.

For about two months after the addition of the water-soluble cationic polymer, the rapid increase in filamentous bacteria was suppressed despite the presence of type 021N in the sewerage wastewater.

Example 3 At a public sewage treatment plant that processes separated urban sewerage wastewater with a monthly average of 3000 Wl, BOD of 250 ppm, and suspended solids (SS) of 140 ppm, the settled sludge volume index (SVI value) of the aeration tank is 700. The dry sludge concentration CMLSS) of the returned sludge was below 2000 ppm, and the MLSS in the aeration tank was also below 11000 ppm, and the separability of treated water and sludge in the final settling tank was significantly deteriorated. Therefore, we temporarily changed the operating conditions by using two 1000m aeration tanks in series, and the final settling tank was two 500m tanks in parallel, doubling the aeration time and settling time. , the BOD value and SS value of the treated water were ensured. The return ratio of returned sludge to treated raw water is 100%, the air ratio to raw water is 6 times, and a diffuser plate is used to introduce air.

When the sludge in the aeration tank and sedimentation tank of this treatment plant was Durham stained and observed using a phase contrast microscope, it was found that there were not floc-forming bacteria in the sludge between the flocs, but rather type 021N filamentous bacteria. Volume was observed more often.

At this treatment plant, the molar ratio of epichlorohydrin, 50% dimethylamine aqueous solution, and 12% ammonia aqueous solution was 1.
: 1. 05:0. Add epichlorohydrin to the mixed amine of 50% dimethylamine aqueous solution and 12% ammonia water until the ratio becomes 1, while keeping the reaction temperature at 90 ° C., and further mix the obtained mixed reaction composition with stirring. The reaction composition obtained by mixing after 100 hours (2 mol/
The intrinsic viscosity [η] measured with liter of KBr aqueous solution is 0.
．． 02dl/g composition) was diluted 100 times with tap water at a rate of 100g/min to the return sludge line.
When the addition was continued for 0 hours, a large number of destroyed type 021N filamentous bacteria were observed in the treated water from the final settling tank after 8 hours, and type 021N in the aeration tank began to be destroyed and SVI value is 180
, and the position of the sludge interface in the final settling tank has also decreased.

After 50 hours, the SVI value was 95.

It was confirmed that the number of filamentous bacteria in the sludge present in the aeration tank at this time was extremely reduced. After 100 hours, the sedimentation properties were significantly improved and the SVI value was 85. Furthermore, the activated sludge formed firmer flocs than before addition. As a result, the return sludge concentration was MLSS
The value rose to 6,500 ppm, and the sludge concentration in the aeration tank also reached MLS.
As the S value increased to 2,400 ppm, we were able to switch to using one aeration tank and one settling tank for operation, so we changed to two-line parallel operation and were able to process raw water, thus increasing the processing capacity. It doubled. The sludge in the river was thickened in a gravity-type thickening tank, and the thick sludge could now be sent to the digester, increasing the rate of digestion gas production and increasing the efficiency of the digester.

Type 021N filamentous bacteria are destroyed and flowed out, but the suspended solids concentration at this time is less than 5 ppm, and the BOD and COD values of the effluent after chlorine sterilization are each less than 20 ppm, The water was in good condition as effluent.

Example 4 Monthly average: 7,500m/unit, BOD: 160ppm.

At a public sewage treatment plant that treats partially combined urban sewerage wastewater with a suspended solids (SS) of 120 ppm,
The settled sludge volume index (SVI value) of the aeration tank with a capacity of 0 m exceeds 400, and the dry sludge concentration (MLSS) of the returned sludge
) becomes 2000 ppm or less, and the MLSS in the aeration tank
The amount of sludge decreased to below 11,000 pp, and the separability of treated water and sludge in the final sedimentation tank with a volume of 1,200 m deteriorated significantly. The operating conditions are that the return ratio of returned sludge to treated raw water is 3.
0%, the air magnification is 5 times the raw water, and a diffuser plate is used to introduce air. When the sludge in the aeration tank, 1ν, and sedimentation tank at this treatment plant was Durham stained and observed using a phase contrast microscope, it was found that in the lTi mud, there were filamentous type 021N bacteria between the flocs, rather than floc-forming bacteria. A larger volume of sexual bacteria was observed.

In this treatment plant, the molar ratio of epichlorohydrin, 50% dimethylamine aqueous solution, and 12% ammonia aqueous solution is 1:
Add epichlorohydrin to the 5026 dimethylamine aqueous solution while maintaining the reaction temperature at 90°C until the ratio is 1:0.1, and stir and mix to the resulting mixed reaction composition. While adding 12% aqueous ammonia, the mixture was mixed after 10 hours to obtain a reaction composition (intrinsic viscosity [η] measured with a 2 mol/liter KBr aqueous solution).
When 150 g/min of a composition with a composition of Many types of type 021N filamentous bacteria that were thought to have been destroyed were observed, and the type 021N in the aeration tank began to be destroyed and the SVI value decreased to 2.
00, and the position of the sludge interface in the final settling tank has also decreased. After 50 hours, the SVI value reached 100. It was confirmed that the number of filamentous bacteria in the sludge present in the aeration tank at this time was extremely reduced.

After 60 hours, the filamentous form of type 021N was destroyed;
Moreover, the destroyed filamentous bacteria flow out together with the treated water,
It was confirmed that almost no filamentous bacteria remained in the activated sludge remaining in the aeration tank and settling tank. Furthermore, the activated sludge formed firmer flocs than before addition. As a result, the sedimentation properties of activated sludge were significantly improved and the SVI value reached 70, the return sludge concentration increased to the MLSS value of 6000 ppm, and the sludge concentration in the aeration tank also increased to MLSS.
The value has increased to 2300 ppm. In addition, the sludge was thickened in a gravity-type thickening tank, which made it possible to send thick sludge to the digester, increasing the rate of digestion gas generation and increasing the efficiency of the digester. In addition, when dewatering digested sludge, cationic polyacrylamide was used as a flocculant in a centrifugal decanter using 0.66% by weight of the dry sludge, but the amount of flocculant used was 0.66% by weight. It became possible to dehydrate at 5ffi amount%.

Type 021N filamentous bacteria are destroyed and flow out, but the suspended solids concentration at this time is less than 5 ppm, and the BOD and COD values of the effluent after chlorine sterilization are each less than 20 ppm, and the effluent is not discharged. It was in good condition as water.

For about two months after the addition of the water-soluble cationic polymer, the rapid increase in filamentous bacteria was suppressed despite the fact that type 021N was contained in the sewage wastewater.

Comparative Example 1 In Example 1, when type 021N filamentous bacteria was mixed into the sludge and the SVI value exceeded 600,
Without adding the reaction composition of the present invention, a sodium hypochlorite aqueous solution (l!ir effective chlorine concentration 5%) was added to the return sludge line.
) was added for 8 u at a rate of 50 liters/day,
The filamentous bacteria contained in the sludge began to decrease, but
The SVI value is 350, which is still not enough, so should I add aqueous sodium hypochlorite? When i1 (available chlorine concentration 5%) was added at a rate of 80 liters/day for 5 days, the SV
Although the I value decreased to 150, the treated water became extremely cloudy and the suspended solids concentration exceeded 15 ppm. The BOD of the effluent after chlorine sterilization was less than 20 ppm, but the COD value exceeded 30 ppm.

When the state of the activated sludge was observed under a microscope, the flocs were destroyed and became extremely fine, with no protozoa present at all. The cloudiness was due to not only the filamentous bacteria being destroyed and flowing out, but also the useful floc-forming bacteria being destroyed and flowing out. This cloudy state is caused by a sodium hypochlorite aqueous solution (effective chlorine concentration 5%) in the return sludge line.
) was observed to be destroyed and useful floc-forming bacteria were observed to flow out not only during the addition but also for 3 days after the addition was completed. As a result, the discharged water remained cloudy and was not in good condition.

After stopping the addition of sodium hypochlorite aqueous solution (available chlorine concentration: 5%) to the return sludge line, as soon as the treated water is no longer cloudy, the sterilizing power of Type 021N, which flows in from the outside, will be lost. However, the filamentous bacteria contained in the sludge began to rapidly increase again, and five days later S
The VI value became 350.

Next, sodium chlorate aqueous solution (chlorine concentration: 5%) is highly toxic, so sufficient equipment and care must be taken when adding it. Furthermore, it also promotes corrosion of equipment.
There are restrictions on where it can be added.

Comparative Example 2 In Example 1, when a large amount of type 021N filamentous bacteria was mixed into the sludge and the SVI value exceeded 600,
When 5 ppm of cationic polyacrylamide (C402 manufactured by Diafloc Co., Ltd.) was added continuously for 3 days to the sludge flowing from the aeration tank to the settling tank, condensation occurred in a state containing type 021N, resulting in an SVI value. is 15
It became 0. However, after the addition of the flocculant was stopped, the sedimentation properties gradually deteriorated, and the SVI value reached 300 after 7 days. Furthermore, the flocculant did not destroy Type 021N and cause it to rapidly flow out of the activated sludge, thereby reducing the amount of filamentous bacteria. When this flocculant is added continuously, 1
After several months, air bubbles were easily trapped in the aeration tank, and the sludge rose to the surface in the settling tank.

Claims (1)

[Claims] 0.05 to 25 parts by weight of dialkylamine per 100 parts by weight of dry solids of the activated sludge is added to activated sludge or wastewater containing bulking which is to be or has been bulked by filamentous bacteria of type 021N. A method for preventing bulking of activated sludge, which is characterized by adding a water-soluble cationic polymer obtained by the reaction of ammonia (equal mole or less with dialkylamine) and epihalohydrin.