JPS63218298A - Process for preventing activated sludge from occurrence of abnormal phenomenon - Google Patents

Abstract

PURPOSE:To prevent activated sludge from generation of tacky materials therein, by adding a water-soluble cationic polymer prepd. by the reaction of dialkylamine and occasionally ammonia with epihalohydrin to waste water contg. activated sludge. 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 the dialkylamine) with epihalohydrin is added to activated sludge or waste water contg. activated sludge. By this method, generation of tacky materials in the activated sludge is prevented. The above described water-soluble cationic polymer is added to the activated sludge or waste water at the time when a symptom of increase of SVI (sludge volume index) is observed. Thus, the SVI is held immediately at an original level or below without causing further increase of the SVI. Moreover, the above described water-soluble cationic polymer influences the effect durable for a long time by once addition.

Description

[Detailed Description of the Invention] [Background of the Invention] Technical Field The present invention relates to an abnormal phenomenon of activated sludge, that is, activated sludge generates and accumulates sticky substances consisting of highly viscous polysaccharides and crude proteins; Regarding how to prevent this. More specifically, the present invention relates to a method for preventing abnormal phenomena in activated sludge 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. It is known that during treatment using this method, fluctuations in the flow rate of inflowing wastewater and fluctuations in the a-organisms in the inflowing wastewater occur, and the microbial flora in activated sludge changes in response to these fluctuations. There is. When this change in the microbial flora is rapid, the sludge swells, sedimentation becomes poor, the sludge rises to near the water surface, the amount of sludge overflow increases, and the treatment capacity decreases and in some cases, it becomes impossible to treat, so-called bulking. A phenomenon occurs. When this phenomenon occurs, the sludge becomes whitish, very light, and difficult to settle, resulting in BOD
The removal rate is also extremely reduced.

As an indicator of whether activated sludge is functioning normally, SVI (Sludge VOIL) 110
There is a sludge index). This SVI is 1
It is expressed as the volume occupied by g of activated sludge in 30 minutes of settling.

The SVI of activated sludge that functions normally is 50 to 150.
, especially less than 100, 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 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 significant impact on the factory's production plans. In the case of public sewage systems, this could similarly become a 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, a composition containing these active ingredients is added to the influent wastewater at a rate of 0. It has the disadvantage that it needs to be added continuously for 3 hours or more at a large amount of 5 to 3 kg ZTIi, and that it takes 24 hours or more to take effect.

The bulking phenomenon of activated sludge is 5phaOrOtll
us (Sphaerochilus spp.), Th1othrix
(Thiotrix sp.), Aspergllus
(Aspergillus sp.), Pen1c4111u (
In addition to abnormal growth of filamentous fungi such as Penicillium (genus Penicillium), a highly viscous jelly-like substance is generated in activated sludge depending on the season or nutritional status, which makes it difficult for the sludge to settle, resulting in a bulking phenomenon. There is also. 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.

Possible Solution The present inventors have already made a proposal to solve the problems observed in the conventional bulking prevention method by adding drugs (Japanese Patent Application Laid-Open No. 61-204092 and (Specification No. 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 has been caused by filamentous bacteria, such as Sphaerochilus (natans) and Begiatoa (Beg.
giatoa) are said to be representative of the causative microorganisms (Journal of Sewage Heat Treatment Society, Vol. 22, No. 252, No. 2-
12 pages (1985)).

By the way, with the recent development of sewerage systems, rainwater and domestic wastewater have come to be separated and treated. the result,
It is assumed that changes have occurred in the filamentous bacteria that cause bulking when municipal sewage, which is domestic wastewater, is treated using the activated sludge method.

[Summary of the invention]

Summary The present invention aims to specifically prevent specific abnormal phenomena of activated sludge in response to recent changes in urban sewage, and the present invention uses the water-soluble cationic polymer of the present inventors to prevent this abnormal phenomenon. The aim is to achieve this goal by using it as a drug.

That is, the method for preventing abnormal phenomena in activated sludge according to the present invention is as follows:
In the treatment of wastewater by the activated sludge method, activated sludge or wastewater containing the same is added with 0.05 to 25 parts by weight of dialkylamine and optionally ammonia (dialkylamine and This method is characterized in that it prevents the generation of sticky substances in activated sludge by adding a water-soluble cationic polymer obtained by the reaction of (equimolar or less) and epihalohydrin.

Effects According to the present invention, the above-mentioned objects are achieved, and stickiness of activated sludge is specifically prevented.

That is, according to the low molecular weight polymer according to the present invention, S
Adding this polymer at the point when there are signs of an increase in VI can quickly maintain the SVI value at or below the original level without substantial further increase in SVI.

Moreover, 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, simply adding a water-soluble cationic polymer to the activated sludge treatment system can suppress the increase in Sv■ of activated sludge in a short time.

(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 specifically preventing certain abnormal phenomena of activated sludge.

Target activated sludge The activated sludge that is the target of the present invention produces sticky substances that are abnormal secretions.

Such sticky substances are also secreted by useful activated sludge bacteria, such as Zoogloea, when the environment changes. The bulking phenomenon caused by the viscous material created by Zoojiroa is called Zoojiroa bulking.

If it is necessary to isolate such microorganisms, they can easily be obtained from activated sludge of sewage.

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.)

In addition, the "water-soluble cationic polymer obtained by the reaction of a dialkylamine, optionally ammonia (equal mole or less as the dialkylamine), and shrimp halohydrin" as used in the present invention refers to 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.

20H Here, R1-R2 is an alkyl group derived from a dialkylamine, X- is a halogen or other anion derived from shrimp halohydrin, or 0H-1n is a polymer (2 or more, preferably 3 or more) such a polymer The dialkylamine 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 in the range of 0.0001 to 1.0, with a particularly preferred molar ratio of 0.0001 to 1.0.
001~0. The range is 1.

As shrimp halohydrin, 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 shrimp halohydrin, the number of moles of dialkylamine and ammonia and the number of moles of shrimp halohydrin are approximately equal, and a closed reaction vessel equipped with a stirrer is used to react with an inert Under a gas atmosphere, the internal temperature of the reaction vessel is set to 30-10
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 shrimp halohydrin continuously or in batches while controlling the temperature inside the reaction vessel so that it does not rise too much. When adding ammonia, it is preferable to first add shrimp halohydrin to the dimethylamine aqueous solution and then add ammonia. After adding epihalohydrin and dialkylamine (and ammonia) to the reaction vessel, add oxides or hydroxides of alkali metals and alkaline earth metals to the reaction vessel at a rate of 0.00001 to 0.0 per mole of epichlorohydrin. If .01 mol is added and maintained at a temperature range of 30-60°C for several hours, the molecular weight of the resulting 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 shrimp halohydrin) 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.

As mentioned above, the main feature of the present invention compared to the prior invention of the present inventors is that the molecular weight is low. The polymer obtained as above is 2 mol/
The size of the molecular weight can be determined by the intrinsic viscosity [η] measured and calculated by dissolving it in a liter of KBr aqueous solution, and in the method of the present invention, [η] is 0.001 dl/g or more, more preferably 0. .01 dl/g or more, use later.

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 to use the solution produced as an aqueous solution as it is or after diluting or concentrating as necessary to prevent bulking of activated sludge.
It is also normal.

Prevention of abnormal phenomena in activated sludge Except for the target activated sludge to be prevented from abnormal phenomena as described above and the changes in treatment conditions that should occur as a result, bulking of activated sludge by the addition of chemicals according to the present invention The prevention method is essentially the same as the conventional one.

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 the water-soluble cationic polymer used is too small, the object of the invention will not be achieved, which is not preferable, and if it is too large, it will be washed out of the system together with wastewater, which is not preferable. The amount used is preferably selected within the range of 0.05 to 25 parts by weight based on 100 parts by weight of 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 to activated sludge in the above range, no increase in SVI is observed for 6 months or more. When signs of an increase in SVI are observed, it is advisable to add the water-soluble cationic polymer within the above range at that point.

Experimental Example Example 1 Monthly average of 500 m/day, lactose wastewater with BOD of 1500 ppm flows in, suspended solids (S S) is 260 ppm
At a wastewater treatment plant of a food company, factory wastewater containing 88% of organic matter is treated with activated sludge using a 1000rd aeration tank and a 500H final settling tank. Aeration tank sedimentation sludge volume index (S
VI value) exceeds 250, and the dry sludge concentration (M
LSS) becomes 4500 ppm or less, and the ML in the aeration tank
SS also fell below 2200 ppm, the separation 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.

The operating conditions are that the return ratio of returned sludge to treated raw water is 70.
%, the air magnification is 15 times the raw water, and a diffuser pipe is used to introduce air. When the sludge in the aeration tank and settling tank at this treatment plant was stained with Durham staining and observed using a phase contrast microscope, it was found that:
Except for a small amount of mold, almost no filamentous bacteria was observed inside and around the sludge. However, sludge has considerable viscosity, and the sludge was sampled from the outlet of the aeration tank, concentrated by centrifugation at 100G for 10 minutes, and the collected sludge was washed three times with water, and then washed with lN-NaOH. After extraction and neutralization with sulfuric acid, a viscous substance consisting of about 26% sugars and about 25% crude proteins was extracted from the activated sludge.

At this treatment plant, the molar ratio of epichlorohydrin and 50% dimethylamine aqueous solution becomes 1:1.05.
A mixed reaction composition obtained by adding epichlorohydrin to a 0% dimethylamine aqueous solution while maintaining the reaction temperature at 90°C and stirring and mixing (intrinsic viscosity [η] measured with a 2 mol/liter KBr aqueous solution) When a composition of 0.02 dl/g) was continuously added to the return sludge line at a rate of 70 g/min while diluting it 100 times with tap water for 50 hours, the activated sludge became thinner than before addition. It has formed a stiff flock. As a result, the SVI value reached 150, and after 100 hours, the sedimentation column was significantly improved and the SV
The I value becomes 85, and the returned sludge concentration increases to MLS.
The S value rose to 8,500 ppm, and the sludge concentration in the aeration tank also decreased to ML.
The SS value has increased to 4800 ppm. Even though raw water treatment is able to obtain good quality treated water under normal operation, and the amount of raw water flowing in increases significantly in the evening, the concentration of returned sludge has increased, so the return rate must be temporarily adjusted. By simply changing the sludge concentration in the aeration tank, the sludge interface in the settling tank will no longer rise and flow out, and the BOD value will also be 20 ppm.
It became below.

Example 2 At the wastewater treatment plant of the food company in Example 1, the monthly average of 400
yd/day, wastewater containing various sugars, mainly lactose, with a BOD of 1500 ppm flows in, and suspended solids (SS)
10,001! At a wastewater treatment plant of a food company that processes wastewater with activated sludge using an aeration tank and a 500 Wt final settling tank, the settled sludge volume index (SVI value) of the aeration tank exceeded 250, and the dried sludge of the returned sludge The concentration (MLSS) becomes 4500 ppm or less, and the MLSS in the aeration tank also becomes 2200 ppm or less, and the separation of treated water and sludge in the final settling tank deteriorates significantly, the treated water becomes cloudy, and the treated water from the final settling tank becomes cloudy. BOD value of 20
Exceeded ppm. The operating conditions are that the return ratio of returned sludge to treated raw water is 70%, the air ratio to raw water is 15 times,
A diffuser pipe is used to introduce air. When the sludge in the aeration tank and settling tank at this treatment plant was stained with Durham and observed using a phase contrast microscope, it was found that almost all filamentous bacteria were found inside and around the sludge, with the exception of a small amount of mold. There wasn't. However, sludge has a considerable viscosity, and the sludge was sampled from the outlet of the aeration tank, centrifuged at 100G for 10 minutes, concentrated, and the collected sludge was washed three times with water.
After extraction with -NaOH and neutralization with sulfuric acid, a viscous substance consisting of about 25% sugars and about 25% crude proteins was extracted from the activated sludge.

At this treatment plant, epichlorohydrin was added to a 50% dimethylamine aqueous solution while maintaining the reaction temperature at 85°C until the molar ratio of epichlorohydrin and 50% dimethylamine aqueous solution was 1:1, and the mixture was stirred. The mixed reaction composition obtained by
was continuously added to the return sludge line for 60 hours at a rate of 70 g/min while diluting it 100 times with tap water.
The activated sludge formed a firmer floc than before addition. As a result, the SVI value becomes 130, which is 1
After 50 hours, the sedimentation properties were significantly improved and the SVI value was 90.

Furthermore, the concentration of returned sludge has increased to an MLSS value of 8000 ppm, and the sludge concentration in the aeration tank has also increased to an MLSS value of 4000 ppm. Even though raw water treatment is able to obtain good quality treated water under normal operation, and the amount of raw water flowing in increases significantly in the evening, the concentration of returned sludge has increased, so the return rate must be temporarily adjusted. The sludge concentration in the aeration tank could be changed by simply using this method, and the sludge interface in the settling tank no longer rose and flowed out, and the BOD value was reduced to 20 ppm or less.

In addition, when dewatering excess raw sludge, cationic polyacrylamide was used as a flocculant at 1.2% by weight based on the dry weight of the sludge and dewatered using a centrifugal decanter, but the amount of flocculant used was 0. Dehydration became possible at .6% by weight.

Example 3 At the wastewater treatment plant of the food company in Example 1, the monthly average of 400
rIt/day, wastewater containing various sugars, mainly lactose with a BOD of 1600 ppm, flows in, and suspended solids (S S
) is 260 ppm, and the 88th component is 90% or more organic matter. At a food company's wastewater treatment plant where wastewater is treated with activated sludge using a final settling tank, the settled sludge volume index (SVI value) of the aeration tank exceeds 250, and the dry sludge concentration (MLSS) of the returned sludge is The MLSS in the aeration tank also fell below 2200 ppm, and 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. The operating conditions are that the return ratio of return sludge to treated raw water is 70%, and the air ratio to raw water is 15.
A diffuser tube is used to introduce air. When the sludge in the aeration tank and settling tank at this treatment plant was stained with Durham and observed using a phase contrast microscope, it was found that almost all filamentous bacteria were found inside and around the sludge, with the exception of a small amount of mold. There wasn't.

However, sludge has considerable viscosity, and after sampling the sludge from the outlet of the aeration tank, centrifuging it at 100G for 10 minutes, concentrating it, and washing the collected sludge three times with water,
After extraction with 1N-NaOH and neutralization with sulfuric acid, a viscous substance consisting of about 26% sugars and about 25% crude proteins was extracted from the activated sludge.

At this treatment plant, the molar ratio of epichlorohydrin, 50% dimethylamine aqueous solution, and 12% ammonia aqueous solution is 1:1.
．． A mixed reaction obtained by adding epichlorohydrin to a mixed amine of 50% dimethylamine aqueous solution and 12% ammonia water while maintaining the reaction temperature at 90°C and stirring and mixing until the ratio becomes 05:0.1. The reaction composition obtained by stirring and mixing the composition for an additional 10 hours (intrinsic viscosity [η] measured with a 2 mol/liter KBr aqueous solution was 0.02 d)
1/g composition) was continuously added to the return sludge line for 60 hours while diluting it 100 times with tap water at a rate of 80 g/min. As a result, the activated sludge formed firmer flocs than before addition. It has been formed. As a result, the SVI value was 130, and after 100 hours, the sedimentation property was significantly improved and the SVI value was 90. Furthermore, the concentration of returned sludge has increased to an MLSS value of 80'OOppm, and the sludge concentration in the aeration tank has also increased to an MLSS value of 4000 ppm. Even though raw water treatment is able to obtain good quality treated water under normal operation, and the amount of raw water flowing in increases significantly in the evening, the concentration of returned sludge has increased, so the return rate must be temporarily adjusted. By just doing this, the sludge concentration in the aeration tank was changed, the sludge interface in the settling tank rose and no longer flowed out, and the BOD value was also reduced to 20 ppm.
It is now possible to discharge the following good quality treated water.

Example 4 At the wastewater treatment plant of the food company in Example 1, despite the temperature of the aeration tank dropping to 15°C in December, the monthly average
0 doors/day, a factory where wastewater containing various sugars, mainly lactose, with a BOD of 1600 ppm flows in, and the suspended solid content (SS) is 260 ppm, and 88 of the components are 90% or more organic. At a wastewater treatment plant of a food company where wastewater is treated with activated sludge using a 1000 Trt aeration tank and a 500 Trt final settling tank, the settled sludge volume index (SVI value) of the aeration tank exceeds 250. The dry sludge concentration (MLSS) of returned sludge is 4500 ppm or less,
The MLSS in the aeration tank also fell below 2200 ppm, the separation 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 was 20p.
exceeded pm. The operating conditions are that the return ratio of returned sludge to treated raw water is 70%, the air ratio to raw water is 15 times, and air is introduced using a diffuser pipe. When the sludge in the aeration tank and settling tank at this treatment plant was stained with Durham and observed using a phase contrast microscope, it was found that almost all filamentous bacteria were found inside and around the sludge, with the exception of a small amount of mold. There wasn't. However, sludge has considerable viscosity, and after sampling the sludge from the outlet of the aeration tank, centrifuging it at 100G for 10 minutes, concentrating it, and washing the collected sludge three times with water, the sludge was washed with water three times.
After extraction with NaOH and neutralization with sulfuric acid, a viscous substance consisting of about 25% sugars and about 25% crude proteins was extracted from the activated sludge.

At this 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 maintaining the reaction temperature at 90°C until the ratio becomes 0.1, and stir and mix to the resulting mixed reaction composition. While adding 12% ammonia water,
The reaction composition obtained by stirring and mixing for 10 hours (2 mol/
The intrinsic viscosity [η] measured with liter of KBr aqueous solution is 0.
．． 12 dl/g of composition) was diluted 100 times with tap water at a rate of 75 g/min to the return sludge line at a rate of 60 dl/g.
When the activated sludge was added continuously over a period of time, the activated sludge formed a firmer floc than before addition. As a result, S
The VI value became 140, and after 100 hours, the sedimentation property was significantly improved and the SVI value became 90. Furthermore, the concentration of returned sludge has increased to an MLSS value of 7500 ppm, and the sludge concentration in the aeration tank has also increased to an MLSS value of 4000 ppm.

Even though raw water treatment is able to obtain good quality treated water under normal operation, and the amount of raw water flowing in increases significantly in the evening, the concentration of returned sludge has increased, so the return rate must be temporarily adjusted. The sludge concentration in the aeration tank could be changed by simply using this method, and the sludge interface in the settling tank no longer rose and flowed out, and the BOD value was reduced to 20 ppm or less.

In addition, when dewatering excess raw sludge, cationic polyacrylamide was used as a coagulant at 162% by weight based on the dry weight of the sludge and dewatered using a centrifugal decanter, but the amount of coagulant used was 0.6%. It became possible to dehydrate by weight%.

Comparative Example 1 At the wastewater treatment plant of the food company in Example 1, despite the temperature of the aeration tank dropping to 15°C in December, the monthly average
0 situation/day, a factory where wastewater containing various sugars, mainly lactose, with a BOD of 1600 ppm flows in, and the suspended solid content (SS) is 260 ppm, and the 88th component of the wastewater is 90% or more of organic matter. At a wastewater treatment plant of a food company where wastewater is treated with activated sludge using a 1000 m aeration tank and a 500 m final settling tank, the settled sludge volume index (SVI value) of the aeration tank was 250. exceeded, the dry sludge concentration (MLSS) of the returned sludge becomes 4500 ppm or less, the MLSS in the aeration tank also becomes 2200 ppm or less, the separability of treated water and sludge in the final settling tank deteriorates significantly, and the treated water becomes cloudy. BOD value of treated water from final settling tank is 20pp
exceeded m. The operating conditions are that the return ratio of returned sludge to treated raw water is 70%, the air ratio to raw water is 15 times, and air is introduced using a diffuser pipe. When the sludge in the aeration tank and settling tank at this treatment plant was stained with Durham and observed using a phase contrast microscope, it was found that almost all filamentous bacteria were found inside and around the sludge, with the exception of a small amount of mold. There wasn't. but,
Sludge has a considerable viscosity, so the sludge was sampled from the outlet of the aeration tank, centrifuged at 100G for 10 minutes to concentrate, and the collected sludge was washed three times with water, then 1N-N.
After extraction with aOH and neutralization with sulfuric acid, a viscous substance consisting of about 25% sugars and about 25% crude proteins was extracted from the activated sludge.

At this treatment plant, zinc chloride was dissolved in wastewater to a concentration of 1100 pp and continuously added, and from the 4th day onwards,
The SVI value was high at 180 and showed a gradual decreasing trend, but no sudden decrease occurred. After 7 days, SVI
The value decreased to 150, but cloudy treated water started to be discharged, and when it was observed under a microscope, it was found that:
A large amount of destroyed activated sludge was seen flowing out.

With activated sludge, the outside of the flocs became more transparent compared to before addition. Therefore, although it showed a good trend in improving sedimentation, the sludge was severely damaged and
It was discontinued on day 0.

Comparative Example 2 At the wastewater treatment plant of the food company in Example 1, despite the temperature of the aeration tank dropping to 15°C in December, the monthly average
0rrl/day, wastewater containing various sugars mainly lactose with a BOD of 1600 ppm flows in, and suspended solids (S S
) is 260ppm, and the 88th component of the wastewater is 90% or more organic matter.This wastewater treatment is carried out by a food company using activated sludge using a 1000m aeration tank and a 500I final settling tank. At the site, the settled sludge volume index (SVI value) of the aeration tank exceeded 250, and the dry sludge concentration (MLSS) of the returned sludge fell below 4500 ppm.
The MLSS in the aeration tank also fell below 2200 ppm, the separation 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 was 20p.
exceeded pm. The operating conditions are that the return ratio of returned sludge to treated raw water is 70%, the air ratio to raw water is 15 times, and air is introduced using a diffuser pipe. When the sludge in the aeration tank and settling tank at this treatment plant was stained with Durham and observed using a phase contrast microscope, it was found that almost all filamentous bacteria were found inside and around the sludge, with the exception of a small amount of mold. There wasn't. However, sludge has considerable viscosity, and after sampling the sludge from the outlet of the aeration tank, centrifuging it at 100G for 10 minutes, concentrating it, and washing the collected sludge three times with water, the sludge was washed with water three times.
After extraction with NaOH and neutralization with sulfuric acid, a viscous substance consisting of about 25% sugars and about 25% crude proteins was extracted from the activated sludge.

At this treatment plant, when a cationic polymer flocculant (Sankyo Kasei Kobunshi "Sanpoli Ni-ichi 601J") was dissolved in the wastewater to a concentration of 1100 pp and continuously added, the SVI value decreased from the 4th day onward. 150, but a sudden decrease did not occur.After 7 days, a large number of activated sludge containing air bubbles was observed floating at the top of the settling tank. In other words, the activated sludge coagulated to form large flocs, and the size of the flocs became good, but since the sludge floated up, the addition was discontinued.

After 5 days, the flocculation deteriorated, so this flocculant was added again to promote sedimentation.

When this addition was repeated, 19 sludge entrained air bubbles and floated to the surface in the aeration tank and settling tank, and the sludge flowed out together with the treated water from the final settling tank, causing problems in wastewater treatment.

Claims (1)

[Claims] In the treatment of wastewater by the activated sludge method, activated sludge or wastewater containing the same is added with 0.05 to 25 parts by weight of dialkylamine and optionally ammonia (dialkylamine and An abnormal phenomenon in activated sludge characterized by preventing the generation of sticky substances in activated sludge by adding a water-soluble cationic polymer obtained by the reaction of epihalohydrin and epihalohydrin. Prevention method.