JPS63218296A - Process for preventing activated sludge from bulking - Google Patents

Abstract

PURPOSE:To prevent activated sludge from bulking, by adding a water-soluble polymer prepd. by the reaction of dialkylamine and occasionally ammonia with epihalohydrin to waste water contg. activated sludge which has caused bulking. CONSTITUTION:0.05-25pts.wt. (basing on 100pts.wt. dry solid in activated sludge) of a water-soluble cationic polymer prepd. by the reaction of dialkylamine and occasionally ammonia (<= equimolar amt. to dialkylamine) with epihalohydrin, is added to activated sludge to be bulked or having been already bulked by the Hyphomycetes of type 0041, or to waste water contg. said sludge. As the result, the activated sludge is prevented specifically from bulking due to the Hyphomycetes of type 0041. Further, the increase of SVI (sludge volume index) of the activated sludge is retarded in a short time, the concn. of the activated sludge is held at a high level, and the reducing effect for 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.

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

Sewage, frozen ground and various organic industrial wastewaters are usually treated by activated sludge methods. During treatment using this method, fluctuations in the flow rate of inflowing wastewater, changes in the eating behavior of organic matter in inflowing wastewater, and changes in the types of microorganisms such as various molds and filamentous bacteria that grow in sewer pipes occur. It is known that the microbial flora in activated sludge changes in response to these changes. When this filamentous bacteria increases, the sludge expands and
Sedimentation worsens, sludge rises close to the water surface, the amount of sludge overflow increases, and a so-called bulking phenomenon occurs, which reduces treatment capacity and, in some cases, makes treatment impossible. 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 Volume I)
ndex s sludge index) value. This SVI is 1g
It is expressed as the volume occupied by activated sludge in 30 minutes of settling. The SVI value of activated sludge that functions normally is 50.
-150, especially below 100, but that of activated sludge that has undergone bulking can reach as high as 300-800.

It is not easy to restore the function of activated sludge that has undergone such bulking, and in the worst case, it may be necessary to replace the sludge.In factories, when replacing the sludge, it is recommended that the sludge is not used until the sludge has become acclimatized. This would have to be canceled, which would have a serious impact on the factory's production plan. Even at 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. Sho 58-14274 is a method in which one or more dithiocarbamates that foster 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 1 day after day 0 and must be continued to be added every day.

The method described in Japanese Patent Publication No. 58-14275 contains valine, leucine, isoleucine, glutamic acid,
A composition containing 11 or 2 or more types of amino acids such as phenylalanine and tyrosine as active ingredients 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/Trt for more than 3 hours, and the effect cannot be obtained. The drawback is that it takes more than 24 hours to show its full potential.

The bulking phenomenon of activated sludge is 5phacrot11u
s (Sphaerochilus spp.), Th1othr1x (
Thiothrix), Aspcrgillus (
In addition to abnormal growth of filamentous fungi such as Aspergillus (genus Aspergillus) and Pcnlellium (Penicillium r14), a highly viscous jelly-like substance is generated in activated sludge depending on the season and nutritional status, which makes it difficult for the sludge to settle. , may also exhibit 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 experiments conducted by the present inventors, this method has shown that activated sludge tends to contain air bubbles in an aeration tank, etc., and that activated sludge that contains air bubbles has an extremely reduced ability to treat wastewater, preventing bulking from occurring. It was found that there was no significant effect.

In addition, attempts have been made to restore normal microbiota without relying on the addition of chemicals, using only operating conditions such as anaerobic and aerobic treatment, or adding a large amount of floating solids (SS) without using an initial settling tank. However, no satisfactory method has yet been proposed for bulking caused by abnormal growth of type 0041 filamentous bacteria.

Possible Solutions However, the addition of drugs is effective against bulking due to overgrowth of type 0041 filamentous bacteria.

The present inventors have already made a proposal to solve the problems observed in the conventional bulking prevention method by adding chemicals (Japanese Patent Laid-Open No. 61-204092 and Japanese Patent Application No. 1983-1982). 295890). 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 commonly caused by filamentous bacteria, and conventionally bulking caused by filamentous bacteria such as Sphaerochilus and Beggiatoa (1'3 eggiatoa
) are said to be representative of the causative microorganisms (Journal of the Japan Sewage Works Association, Vol. 22, No. 252, pp. 2-12 (19
1985)).

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 method for preventing bulking of activated sludge according to the present invention is to add 100 parts by weight of dry solids of activated sludge to activated sludge or wastewater containing bulking that should or has been caused by filamentous bacteria of type 0041. 0.05 to 25 ffl parts of dialkylamine and optionally ammonia (equal mole or less to dialkylamine)
It is characterized by the addition of a water-soluble cationic polymer obtained by the reaction of 100% and epihalohydrin.

Effects According to the present invention, the above objects are achieved and the type 00
Bulking of activated sludge caused by 41 filamentous bacteria is specifically prevented.

That is, according to the polymer of the present invention, when this 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 by L, The SVI value can quickly be maintained at or below the original level without substantial further increase in the SVI value. Moreover, according to the agent 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, almost no increase in BOD is observed, so it is possible to provide good treated water. Can be done. 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 control.

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, l is added to the activated sludge treatment system.
By simply adding a water-soluble cationic polymer to it, the increase in SVI of activated sludge can be suppressed in a short period of time.

(2) When the method of the present invention is used, the activated sludge in the Ill air tank does not expand, the sedimentation 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.

Activated sludge vs. activated sludge The activated sludge to which the present invention is directed is one that causes bulking due to type 0041 filamentous bacteria.

Type 0041 filamentous bacteria is 0.1+.

Eikclboom+Prog, vatar Tcch
, Vol. 8, No. 6, pp. 153-161 (1977).

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 No such presumption shall be construed as binding.)

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.

R20H Here, R1-R2 is an alkyl group derived from dialkylamine, X- is a halogen or other anion derived from epihalohydrin or OH'', n is a polymer, and 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 two alkyl groups do not have to be the same in the molecule. Specific examples of such dialkylamine include dimethylamine, diethylamine, dipropylamine, methylethylamine, methylpropylamine, ethylpropylamine, methylbutylamine, ethylbutylamine, dibutylamine, 2-ethylhexylamine, and the like.

When ammonia is used in combination, it is only necessary to add a very small amount to the dialkylamine. The amount can be selected in the molar ratio of ammonia/dialkylamine-〇,0001 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 batchwise while controlling the internal temperature of 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~
Holding in the temperature range of 60°C for several hours may increase the molecular weight of the resulting polymer. 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 in 1 above has an intrinsic viscosity [
η], the molecular weight can be determined by
In the method of the present invention, [η] is 0.001 dl/g or more, more preferably 0.01 dl/g or more. 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 that the aqueous solution produced as an aqueous solution is used as it is or after being diluted or concentrated if necessary, for use as an aqueous solution for bulking prevention of activated sludge.

Prevention of Bulking of Activated Sludge The present invention is applicable to the present invention, except that the target activated sludge to be prevented from bulking contains specific filamentous bacteria as described above, and that the treatment conditions are changed accordingly. The method of preventing bulking of activated sludge by adding chemicals is essentially the same as the conventional method.

Specifically, the water-soluble cationic polymer is added to an appropriate concentration, for example 0. An aqueous solution having a concentration of about 1 to 10% by weight may be prepared, and this aqueous solution may be added according to any of the following methods or a combination of two or more of these methods.

(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 activated dirt 0.05
It is preferable to choose between 25 parts by weight. More preferably,
The range is 0.1 to 10Tf1 part.

When a water-soluble cationic polymer is added to activated sludge once in the above range per 100 parts by weight of dry solid content of the mud, 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 Example Example 1 Monthly 87yen 2500 rIt/day, BOD 280ppm
.

The suspended solid content (S S) is 220 ppm, and moreover, organic matter accounts for 50% or more of the 88 components, and 1
Most of the sewage discharge comes from apartment complexes, where the daily inflow raw water has a very large temporal change, and the amount of treated water at 9 a.m. and 10 p.m. is approximately six times the lowest at 9 a.m. and 10 p.m. Separate urban sewerage drainage, which occupies 1,000m of
At a public sewage treatment plant where wastewater is treated with activated sludge using an aeration tank and a 500m final settling tank, the settled sludge volume index (SVI value) of the aeration tank exceeds 350, and the dry sludge concentration ( MLSS) becomes less than 3000 ppm, MLSS in the aeration tank also becomes less than 1200 ppm, the separation of treated water and sludge in the final settling tank deteriorates significantly, the treated water becomes cloudy, and the BOD of the treated water from the final settling tank decreases. value is 20
Exceeded ppm. The operating conditions are that the return ratio of returned sludge to treated raw water is 5G%, the air ratio to raw water is 8 times, and a diffuser plate is used to introduce air. When the sludge in the aeration tank and settling tank at this treatment plant was Durham stained and observed using a phase contrast microscope, it was found that the sludge contained typical type 0041 filaments attached to floc-forming bacteria in and around the sludge. Many bacteria were observed.

At this treatment plant, until the molar ratio of epichlorohydrin and 50% dimethylamine aqueous solution becomes 1:1.05,
096 A mixed reaction composition obtained by adding epichlorohydrin to a 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 is 0) A composition of 0.02 dl/min) was continuously added to the return sludge line for 50 hours while diluting it 100 times with tap water at a rate of 70 g/min. A large number of destroyed filamentous bacteria such as 0041 were observed, as well as type 004 in the aeration tank.
As the first class began to be destroyed, the SVI value decreased to 150, and the position of the sludge interface in the final settling tank also decreased. After 50 hours, the SVI value was 90. It was confirmed that filamentous bacteria such as type 0041 were extremely reduced in the sludge present in the aeration tank at this time. Furthermore, the activated sludge formed firmer flocs than before addition. As a result, after 100 hours, the sedimentation properties were significantly improved and the SV
The I value becomes 80, and the returned sludge concentration decreases to MLS.
The S value has increased to 5500 ppm, and the sludge concentration in the aeration tank has also decreased to ML.
Since the SS value has increased to 2,300 ppm, it is now possible to obtain good quality treated water during normal operation, and therefore even if the amount of raw water inflow varies greatly between morning and evening, the concentration of returned sludge remains high. As a result, the sludge concentration in the aeration tank can be changed simply by temporarily adjusting the return rate, and the sludge interface in the settling tank rises, eliminating the possibility of outflow.

Filamentous bacteria such as type 0041 are destroyed and flow out, but the suspended solids concentration at this time is less than 5 ppm,
The BOD and COD values of the effluent after chlorination were each less than 20 ppm, and were in good condition as effluent.

Example 2 In the treatment plant of Example 1, a large amount of filamentous bacteria such as type 0041 occurred, and the SVI value exceeded 250. The dry sludge concentration (MLSS) of the returned sludge is 3500 ppm or less, and the MLSS in the aeration tank is also 1200 ppm or less.
Separability of treated water and sludge in the final sedimentation tank deteriorated significantly, the treated water became cloudy, and the BOD value of the treated water from the final sedimentation tank decreased to 2.
Exceeded 0 ppm. The operating conditions are that the return ratio of return sludge to treated raw water is 50%, the air ratio to raw water is 8 times,
A diffuser plate is used to introduce air.

When the sludge in the aeration tank and sedimentation tank of this treatment plant was Duram-stained and observed under a daylight microscope, it was found that in the sludge and around the sludge, typical type 0041 filaments attached to floc-forming bacteria were observed. Many sexually transmitted bacteria were observed.

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 by
was continuously added to the return sludge line for 45 hours at a rate of 70 g/min while diluting it 100 times with tap water.
After 8 hours, type 004 was added to the treated water from the final settling tank.
Many filamentous bacteria of type 0041 in the aeration tank were observed to be destroyed, and the SVI value decreased to 160, causing the sludge in the final settling tank to decrease. The interface position has also decreased. After 50 hours, the SVI value was 90. It was confirmed that the filamentous bacteria present in the aeration tank at this time (1: It was confirmed that the destroyed filamentous bacteria flowed out together with the treated water, and that almost no filamentous bacteria such as type 0041 remained in the activated sludge remaining in the aeration tank and sedimentation tank. , activated sludge formed firmer flocs than before addition.

As a result, the sedimentation properties of activated sludge were significantly improved, and SVI
The value becomes 80, and the returned sludge concentration reaches the MLSS value of 7000p.
pm and the sludge concentration in the aeration tank also reached an MLSS value of 2600.
ppm”-H. Furthermore, the sludge is thickened in a gravity-type thickening tank, and the thick sludge can be sent to the digestion tank.
The rate of production of digester gas increased to , and the efficiency of the digester increased. In addition, when dewatering digested sludge, cationic polyacrylamide is used as a flocculant to dry sludge TiI! Dehydration was performed using a centrifugal decanter using 0.6ffiE1% for :i, but now dehydration can be performed using 0.5% by weight of flocculant.

Filamentous bacteria such as type 0041 are destroyed and flow out, but the suspended solids concentration at this time is less than 5 ppm,
The BOD and COD values of the effluent after chlorine sterilization were each less than 20 ppm, and were in good condition as effluent.

For about a month after the addition of the water-soluble cationic conjugate, although it is thought that the drainage water from the water supply system contains filamentous cells such as type 0041, the growth of filamentous bacteria rapidly increases. This increase was suppressed.

Example 3 In the treatment plant of Example 1, a large amount of filamentous bacteria such as type 0041 occurred, and the SVI value exceeded 250. The dry sludge concentration (MLSS) of the returned sludge is 3500 ppm or less, and the MLSS in the aeration tank is also 1200 ppm or less.
Separability of treated water and sludge in the final sedimentation tank deteriorated significantly, the treated water became cloudy, and the BOD value of the treated water from the final sedimentation tank decreased to 2.
Exceeded 0 ppm. The operating conditions are that the return ratio of return sludge to treated raw water is 50%, the air ratio to raw water is 8 times,
A diffuser plate is used to introduce air.

When the sludge in the aeration tank and sedimentation tank at this treatment plant was stained with Durham and observed using a phase contrast microscope, it was found that the inside and surrounding area of the sludge contained typical type 0 bacteria attached to floc-forming bacteria.
Many filamentous bacteria of 041 were observed.

In this treatment plant, the molar ratio of epichlorohydrin, 50% dimethylamine aqueous solution, and 1296 ammonia aqueous solution is 1:
1. A mixture obtained by adding epichlorohydrin to a mixed amine in a 50% dimethylamine aqueous solution and 1296 ammonia water while maintaining the reaction temperature at 90°C until the ratio of o5:o, 1 is reached, and stirring and mixing. The reaction composition further comprises:
The reaction composition obtained by mixing after 100 hours (2 mol/
The intrinsic viscosity [η] measured with liter of KBr aqueous solution is 0.
．． 0.2 dl/g composition) was added to the return sludge line at a rate of 70 g/min while diluting it 100 times with tap water.
After 8 hours of continuous addition, many types of type 0041 filamentous bacteria that were thought to have been destroyed were observed in the treated water from the final settling tank, and type 0041 filamentous bacteria in the aeration tank were also destroyed. For the first time, the SVI value decreased to ]30, and the position of the sludge interface in the final settling tank also decreased. After 50 hours, the SVI value was 80. It was confirmed that the number of type 0041 filamentous bacteria in the sludge present in the aeration tank at this time was extremely reduced. Also,
The activated sludge formed a firmer floc than before addition.

As a result, after 100 hours, the sedimentation properties were significantly improved and the SVI value reached 70. Returned sludge concentration is MLSS
The value rose to 6,500 ppm, and the sludge concentration in the aeration tank also reached MLS.
Since the S value has increased to 2,400 ppm, it has become possible to obtain good quality treated water with normal operation. In addition, even if the amount of raw water flowing in changes greatly between morning and evening, the concentration of the returned sludge becomes high, so by temporarily adjusting the return rate, the sludge concentration in the aeration tank can be changed, and the sedimentation The sludge interface in the tank no longer rises by -1- and flows out.

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.

Filamentous bacteria such as type 0041 are destroyed and flow out, but the suspended solids concentration at this time is less than 5 ppm,
The BOD and COD values of the effluent after chlorine sterilization were each less than 20 ppm, and were in good condition as effluent.

Example 4 In the treatment plant of Example 1, a large amount of filamentous bacteria such as type 0041 occurred, and the SVI value exceeded 250. The dry sludge concentration (MLSS) of the returned sludge is 3500 ppm or less, and the MLSS in the aeration tank is also 1200 ppm or less.
Separability of treated water and sludge in the final sedimentation tank deteriorated significantly, the treated water became cloudy, and the BOD value of the treated water from the final sedimentation tank decreased to 2.
Exceeded 0 ppm. The operating conditions are that the return ratio of returned sludge to treated raw water is 5096, the air ratio to raw water is 8 times, and a diffuser plate is used to introduce air.

When the sludge in the aeration tank and sedimentation tank at this treatment plant was Durham stained and observed using a phase contrast microscope, it was found that typical type 0041 filamentous bacteria attached to the sludge flocs were found in and around the sludge flocs. observed a lot.

At the second treatment plant, the molar ratio of epichlorohydrin, 50% dimethylamine aqueous solution, and 12% ammonia aqueous solution was 1:1.
: Add epichlorohydrin to a 50% dimethylamine aqueous solution while keeping the reaction temperature at 90°C until the ratio is 0.1, and stir and mix to the resulting mixed reaction composition, without further stirring. While stirring, add 12% ammonia water,
The reaction composition obtained by mixing after 100 hours (2 mol/
A composition with an intrinsic viscosity [η] of 0.12 dl/g determined by M1 with 1 liter of KBr aqueous solution was added to the return sludge line at a rate of 70 g/min while diluting it 100 times with tap water.
When the addition was continued for 0 hours, a large number of destroyed type 0041 filamentous bacteria were observed in the treated water from the final settling tank after 8 hours, and type 0041 filamentous bacteria in the aeration tank were observed. began to be destroyed, and the SVI value decreased to 160, and the position of the sludge interface in the final settling tank 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 70 hours, the filamentous form of type 0041 bacteria was destroyed;
Furthermore, it was confirmed that the destroyed filamentous bacteria flowed out together with the treated water, and that almost no type 0041 filamentous bacteria remained in the activated sludge remaining in the aeration tank and sedimentation tank. Furthermore, the activated sludge formed firmer flocs than before addition. As a result, the sedimentation properties of the activated sludge were significantly improved and the SVI value reached 80, the return sludge concentration increased to an MLSS value of 7000 ppm, and the sludge concentration in the aeration tank also increased to an MLSS value of 2800 ppm. Furthermore, it became easier to thicken the sludge in the gravity-type thickening tank, making it possible to send thick sludge to the anaerobic digestion tank, increasing the rate of gas generation in the digestion tank, and increasing the efficiency of the digestion tank.

In addition, when dewatering digested sludge, cationic polyacrylamide was added at 0.0% relative to the dry weight of the sludge. After adding 6% by weight of flocculant, dehydration was performed in a centrifugal decanter, but now dehydration can be achieved even if the amount of flocculant used is reduced to 0.5% by weight.

Type 0041 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, The water was in good condition as effluent.

For about one month after the addition of the water-soluble cationic polymer, there was a rapid increase in the number of type 0041 filamentous bacteria, even though it is thought that there were type 0041 filamentous bacteria in the sewage wastewater. was suppressed.

Comparative Example 1 In Example 1, a large amount of filamentous bacteria of type 0041 occurred, and the SVI value exceeded 350.

Dry sludge concentration (MLSS) of returned 16 mud is 3500pp
MLSS in the aeration tank is also 1200ppm.
The separability of treated water and sludge in the final settling tank deteriorated significantly, the treated water became cloudy, and the BOD value of the treated water from the final settling tank exceeded 20 ppm. When an aqueous sodium hypochlorite solution (5% effective chlorine concentration) was added to the return sludge line at a rate of 50 liters/day for 5 days, the filamentous bacteria existing in the sludge began to decrease. , SVI
The value is 80, which is not sufficient for sedimentation, so add a sodium hypochlorite aqueous solution (cultivating chlorine concentration 596).
When added for 5 days at a rate of 80 liters/mouth, S
Although the VI value decreased to 90, 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 white cloudiness was due to the fact that not only type 0041 filamentous bacteria were destroyed by li and leaked out, but also many of the useful floc-forming bacteria were destroyed, losing their floc-forming ability, becoming microscopic, and leaking out. . This cloudy state lasts not only while adding sodium hypochlorite aqueous solution (effective chlorine concentration: 5%) to the return sludge line, but also for 30 minutes after the addition is completed, and the formation of useful flocs that has been destroyed. Bacteria were observed to be leaking out. As a result, the discharged water remained cloudy and was not in good condition. Further, after the addition was completed, as soon as the treated water was released from its cloudy state, filamentous bacteria such as type 0041 were observed again. After 8 days, the SVI value reached 150.

Since sodium hypochlorite aqueous solution (effective chlorine concentration 596) is highly toxic, sufficient equipment and care must be taken when adding it. Furthermore, since it also promotes corrosion of equipment, there are restrictions on where it can be added.

Comparative Example 2 In Example 1, there were many filamentous bacteria of type 0041;
The SVI value exceeded 250.

Dry sludge concentration (MLSS) of returned sludge is 3500 ppm
As a result, the MLSS in the aeration tank became less than 1200 ppm, the separation of treated water and sludge in the final settling tank deteriorated significantly, the treated water became cloudy, and the BO of the treated water from the final settling tank deteriorated.
D value exceeded 20 ppm. When cationic polyacrylamide (C402 manufactured by Diafloc Co., Ltd.) was added at a rate of 3 ppm for 8 days to the sludge flowing from the aeration tank to the final settling tank, it was found that it contained type 0041 filamentous bacteria. Aggregation occurred resulting in an SVI value of 120. However, after the addition was stopped, the sedimentation properties gradually worsened, and the SVI value increased to 180 after 80 minutes.

Therefore, this flocculant was added again to promote sedimentation. When this addition was repeated, the sludge entrained air bubbles in the aeration tank and settling tank and rose to the top, and the sludge flowed out of the final settling tank together with the treated water, causing problems in wastewater treatment.

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 0041. 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.