JPH0824886A - Activated sludge bulking eliminator - Google Patents

Abstract

PURPOSE:To obtain a bulking eliminator which prevents an aqueous alkylpyridinium halide solution from solidifying at a low temperature and can be continuously supplied by a constant volume pump even in winter by blending an aqueous alkylpyridinium halide solution with isopropyl-alcohol. CONSTITUTION:In the bulking eliminator, consisting of alkylpyridinium halide as an effective component, which is used in an activated sludge method for treating waste water containing an organic substance, isopropyl alcohol is blended which prevents an aqueous alkylpyridinium halide solution from solidifying at a low temperature and does not give any adverse effect upon microbes in activated sludge and a treated water without blocking a sterilization action to filiform bacteria by alkylpyridinium halide. In addition, butyldiglycol is blended with the aqueous alkylpyridinium halide solution, if necessary. Thus, it is possible to achieve a continuous constant volume supply of a chemical liquid even at a low temperature and, thereby, eliminate the bulking phenomenon efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agent for eliminating bulking of activated sludge in a wastewater treatment apparatus.

[0002]

2. Description of the Related Art The activated sludge method is widely used as a method for treating wastewater containing organic substances such as general household wastewater and industrial wastewater. The activated sludge method uses an aeration process that absorbs and decomposes and removes organic matter by contacting the wastewater to be treated with activated sludge, which is an aggregate of microorganisms, and the activated sludge is treated from the treated water using the difference in specific gravity between the treated water and the treated water. It is composed of a separation process for sedimentation separation. However, the activated sludge swells in the treatment process, and the specific gravity of the sludge with respect to the treated water is reduced, so that the phenomenon that the treated water and the activated sludge are not smoothly separated in the separation step frequently occurs.

Such a phenomenon is called bulking. In particular, when bulking is caused by the propagation of filamentous bacteria, the sedimentation of the activated sludge is extremely reduced. In addition to overflowing, not only water pollution at the discharge destination occurs, but also continuous use of the wastewater treatment device may not be possible.

As a method for eliminating bulking caused by the reproduction of filamentous bacteria, a method of sterilizing the filamentous bacteria itself has been adopted, and a method of adding a mixture of chlorhexidine hydrochloride, gluconic acid and chlorhexidine (Japanese Patent Publication No. 37764), a method of adding a water-soluble cationic polymer obtained by reaction with dialkylamine, ammonia and epihalohydrin, or reaction between polyalkylenepolyamine and epihalohydrin (JP-A-63-218299 and JP-A-2-21899). No. 169096) has been proposed, but in order to maintain an effective concentration of each of these agents, which exerts the bactericidal effect of filamentous bacteria,
Since it is necessary to continuously add a large amount of chemicals, it has a bactericidal effect on other useful activated sludge fungi, and there are drawbacks in environmental impact and economical efficiency.

Therefore, the present inventor has already added a method of adding an alkylpyridinium halide as a method for eliminating bulking by sterilizing filamentous bacteria (Japanese Patent Laid-Open No. 6-242242).
-71287). According to this method, the bulking is eliminated by using a small amount of the chemical, and the bulking can be eliminated without affecting the microorganisms in the activated sludge and the treated water.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In using a bulking elimination agent containing an alkylpyridinium halide as an active ingredient, powdered bulking is used in an aeration tank of an activated sludge device in which filamentous bulking occurs and in a returning sludge line. A scavenger is directly added to the activated sludge, or a solution of a bulking scavenger dissolved in water is added dropwise or added, or an inorganic porous carrier is impregnated and added, but preferably the drug is This is a method of continuously supplying a solution of a bulking elimination agent dissolved in water to the aeration tank of the activated sludge treatment device and the return sludge line using a constant supply pump so that the filamentous bacteria in the activated sludge can be uniformly adsorbed. .

However, the solubility of an alkylpyridinium halide in water largely depends on the temperature, and when the temperature of the solution is below the Kraft point, the solubility is drastically lowered, and the precipitation and crystallization of the alkylpyridinium halide cause the entire solution to dissolve. Becomes a solidified state. In particular, this phenomenon is constantly observed in the winter when the temperature is low, and there is a problem that the solution cannot be supplied at all due to the precipitation of the composition in the metering pump channel portion and the inside of the hose and the solidification of the solution. When such a phenomenon occurs, a method of using a heater or a heating device such as hot water may be considered, but the operation is complicated and is not a realistic method considering the application in an outdoor wastewater treatment facility. There wasn't.

An object of the present invention is to provide a bulking elimination agent for activated sludge which prevents solidification of an alkylpyridinium halide aqueous solution at low temperatures and can be continuously supplied by a metering pump even in winter.

[0009]

[Means for Solving the Problems] The present inventor has found that an alkylpyridinium halide aqueous solution is prevented from solidifying at a low temperature, does not inhibit the bactericidal action of the alkylpyridinium halide on filamentous bacteria, and is a microorganism and treatment in activated sludge. As a result of various experiments of drug compositions that do not affect water, it was found that the intended purpose can be achieved by adding isopropyl alcohol to an alkylpyridinium halide aqueous solution, and the present invention has been completed. .

Further, they have found that the intended purpose can be achieved by adding butyldiglycol to an aqueous solution of alkylpyridinium halide, and have completed the present invention.

The alkylpyridinium halide used in the present invention is represented by the general formula shown in Chemical formula 1, and representative examples thereof include ethylpyridinium bromide, n-butylpyridinium chloride, dodecylpyridinium chloride, Hexadecylpyridinium chloride, hexadecylpyridinium bromide and the like can be mentioned. These alkylpyridinium halides can be obtained by reacting an alkyl halide with pyridine under heating and stirring, and after the reaction is completed, the product is steam distilled to remove unreacted pyridine and recrystallized.

[0012]

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The aqueous solution of alkylpyridinium halide used in the present invention is obtained by dissolving the above alkylpyridinium halide in water at a temperature not lower than the Kraft point. At a temperature below the Kraft point, an aqueous solution having a high concentration cannot be prepared due to its low solubility, but at a temperature above the Kraft point, an aqueous solution having a high concentration can be obtained due to the micellar action. And, the concentration is preferably 20 to 40 wt%.

The isopropyl alcohol used in the present invention is an alcohol having a boiling point of 82.3 ° C. and is industrially produced and used as a solvent for organic compounds and the like. The compounding amount of isopropyl alcohol with respect to the aqueous alkylpyridinium halide solution varies depending on the type of the alkylpyridinium halide and the concentration of the aqueous solution, but the concentration of the commonly used aqueous alkylpyridinium halide solution is 2
In the case of 0 to 40 wt%, it may be added in a proportion of 15 to 60 parts by weight with respect to 100 parts by weight of this aqueous solution. When the amount of isopropyl alcohol to be added to the alkylpyridinium halide aqueous solution is lower than these, the effect of preventing solidification of the aqueous solution at low temperature does not appear sufficiently, and conversely, when the amount is high, the concentration of alkylpyridinium halide decreases. , Because the bactericidal effect against filamentous bacteria cannot be expected, and other activated sludge bacteria will be adversely affected,
Not preferred.

The butyl diglycol used in the present invention is a polyhydric alcohol derivative having a boiling point of 230.4 ° C., which is industrially produced and used as a solvent for inks and paints. For the same reason as above, the concentration of butyldiglycol in the alkylpyridinium halide aqueous solution is 2% for the concentration of the alkylpyridinium halide aqueous solution.
In the case of 0 to 40 wt%, it may be added in a ratio of 20 to 80 parts by weight with respect to 100 parts by weight of this aqueous solution.

Addition of isopropyl alcohol and butyldiglycol to the aqueous solution of alkylpyridinium halide can be carried out individually or as a mixture of both.

In using the bulking elimination agent of the present invention, a method of continuously supplying it to the aeration tank and the return sludge line of the activated sludge treatment device in which filamentous bulking is generated is used.

The amount of the bulking elimination agent of the present invention used varies depending on the propagation status of filamentous bacteria, but is usually 0.2 to 20 parts by weight based on 100 parts by weight of the dry solid content of the activated sludge. It may be added. If the bulking eliminating agent added at this time is less than 0.2 parts by weight, it is difficult to eliminate the filamentous bulking because the bactericidal action against filamentous bacteria is low. It is not preferable because it adversely affects sludge bacteria and normal treatment cannot be performed.

The continuous supply rate of the bulking elimination agent varies depending on operating conditions such as the amount of treated water in the wastewater treatment device and the rate of returned sludge, but normally the above-mentioned amount used may be supplied at a rate of 24 to 96 hours.

[0020]

[Function] Filamentous bacteria that cause the occurrence of bulking are cells that are covered by the sheath, which is the core of the nucleus, and are less susceptible to external influences than ordinary microorganisms.
In addition, since the sheath cells are destroyed and the sheath cells are actively activated even when they are released to the outside to reform the filaments, the sheath cells that are the nucleus of filamentous bacteria are killed in order to eliminate bulking. Need to let.

The bactericidal effect on the filamentous bacteria propagated in the activated sludge appears in 2 to 5 hours after the addition of the alkylpyridinium halide of the present invention, and the filamentous bacterial cells regularly housed in the sheath are destroyed. The appearance can be observed, and it can be observed that the sheath is cut at various places and released as fine fragments with the passage of time. As the filamentous bacteria are killed, bulking is eliminated, and a sludge index value (hereinafter, SVI: Sluge) indicating the sedimentation of activated sludge
The volume index) drops rapidly, and activated sludge is in a normal state with good sedimentation.

Since alkylpyridinium halide is a cationic compound, it is easily adsorbed by filamentous bacteria whose surface is anionic, and therefore, when alkylpyridinium halide is added to activated sludge, it is adsorbed unevenly. It is easy to sterilize the filamentous bacteria in a portion where the drug is adsorbed by a predetermined amount or more, but the filamentous bacterium is not sterilized in a portion where the drug adsorption amount is small. In particular, this tendency becomes more remarkable as the size of the wastewater treatment device becomes larger, and it is necessary to continuously supply the aqueous solution of the chemical using a metering pump to uniformly adsorb the chemical to the activated sludge.

Since alkylpyridinium halide is a kind of cationic surfactant, its solubility in water largely depends on the temperature. When the temperature of the solution is above the Kraft point, the solubility is large and the aqueous solution of 20 to 40 wt%. Can be easily obtained. However, at temperatures below the Kraft point, the solubility drops sharply, causing the deposition of alkylpyridinium halides,
With the crystallization, the whole solution is in a solidified state.

For example, the craft points are dodecylpyridinium chloride 18 ° C., dodecylpyridinium iodide 24 ° C., hexadecylpyridinium chloride 35 ° C., hexadecylpyridinium bromide 31 ° C., and hexadecylpyridinium iodide 45 ° C. on the other hand,
The temperature around the wastewater treatment system in winter is generally 10 ° C or lower, so 20% of the alkylpyridinium halide is used.
The ~ 40 wt% aqueous solution was in a precipitated and solidified state, and it was impossible to quantitatively supply this. According to the composition of the present invention, a stable solution state can be maintained at a temperature of 0 ° C. or higher without depositing and solidifying a 20 to 40 wt% solution of an alkylpyridinium halide.
The filamentous bulking can be eliminated by the fixed amount supply method.

A method of adding a large excess of water to the alkylpyridinium halide to prepare a low-concentration solution and supplying the solution in a fixed amount can be considered. In this case, 100 to 500 times the weight of the alkylpyridinium halide is required. So
Since the supply device becomes large and the operation becomes complicated, workability,
Economically unsuitable for implementation.

[0026]

【Example】

(Example 1) Various additives for preventing precipitation and solidification of an aqueous solution of an alkylpyridinium halide at low temperature were investigated. From the viewpoint of adding to activated sludge treatment equipment, alcoholic compounds, polyhydric alcohols and their derivatives were tested in consideration of effects on activated sludge organisms, degradability in activated sludge, and effects on discharged water quality.

Hexadecylpyridinium chloride was used as the alkylpyridinium halide, and the additives shown in Table 1 were added to 100 parts by weight of the hexadecylpyridinium chloride aqueous solution (34 wt%).
100 g of each sample was prepared by adding 0, 60 parts by weight, and these were placed in a constant temperature bath set at a temperature of 1 ° C. for 24, 48, 96.
Table 1 shows the state of precipitation of the composition and solidification of the aqueous solution after standing for a while.

[0028]

[Table 1]

From the experimental results shown in Table 1, it was confirmed that the aqueous solution of alkylpyridinium halide to which isopropyl alcohol and butyldiglycol were added was excellent in precipitation of alkylpyridinium halide at low temperature and prevention of solidification of the aqueous solution.

Example 2 Monthly average treated water amount 3000 m ³ /
Biochemical oxygen demand (hereinafter referred to as BOD) 18
At a public sewage treatment plant (standard activated sludge system) that processes 0 mg / l sewage effluent, the dry solid content (hereinafter referred to as MLSS) of activated sludge in the aeration tank is 2300 mg / l, SVI.
Was 370, and the test was conducted using a treatment device in which the separation of the treated water and the activated sludge in the settling tank was deteriorated. The aeration tank volume of this device is 1200 m ³ , and the precipitation tank volume is 27.
It is 0 m ³ . When the activated sludge in the aeration tank was collected and observed with a phase-contrast microscope (× 400), it was found that Spherocillus natans was proliferating and that filamentous bulking had occurred.

Hexadecylpyridinium chloride 3
Bulking elimination agent 4 in which 30 parts by weight of butyl diglycol is mixed with 100 parts by weight of 0% aqueous solution (liquid temperature 30 ° C.)
8 kg was prepared and was supplied to the returning sludge line in a fixed amount at a rate of 1 kg per hour using a diaphragm metering pump.
The period of continuous supply was mid-February, the temperature around the processing equipment was 9 ° C. at the highest and 2 ° C. at the lowest, and the temperature of the bulking elimination agent was within 4 ° C. ± 2 ° C.

The activated sludge after 24 hours from the supply time is M
The LSS value was 2370 mg / l and the SVI value was 190.
When the appearance of filamentous bacteria at this time was observed, it was found that the cells of Spherocillus natans contracted in the sheath and some cells fell out of the sheath.

3 days after the start of the test, the activated sludge was MLSS.
The value was 2400 mg / l and the SVI value had dropped to 140, indicating that the sludge had good sedimentation properties. When the appearance of filamentous bacteria at this time was observed, the filamentous bacterial sheaths were cut at various places and became fragments, which were liberated from the flocs of the activated sludge. Most of the cells in the sheath were shed from the sheath.

The SVI value of the activated sludge after 6 days from the start of the test was stable at 120 to 140, and the state of good sedimentation was maintained. When the state of the filamentous bacteria was observed, no new filamentous bacteria grew. Further, the water quality of the treated water during this test period had a BOD value of 20 ppm or less, and the addition of the bulking elimination agent of the present invention had no adverse effect on the treatment function.

Comparative Example 1 In Example 2, a 30% aqueous solution of hexadecylpyridinium chloride (liquid temperature 3
48 kg of a drug prepared by mixing 30 parts by weight of water with 100 parts by weight of (0 ° C.) was prepared, and an attempt was made to quantitatively supply it using a diaphragm metering pump. Fifteen minutes after the start of the quantitative supply, solidification of the drug solution was observed at the tip of the dropping tube, and one hour later, the drug solution solidified in the entire tube, and the drug solution could not be supplied. At this point, the test was terminated. .

(Example 3) Monthly average treated water amount 120 m ³ /
Daily, chemical oxygen demand (hereinafter referred to as COD) 630mg
It is a standard activated sludge type treatment device that treats tofu manufacturing wastewater of 1 / l, and the MLSS value of activated sludge in the aeration tank is 5540 mg /
l, SVI value was 175, and the test was conducted using a treatment device in which separation of treated water and activated sludge in the settling tank was deteriorated. The aeration tank volume of this device is 172 m ³ , and the precipitation tank volume is 56 m ³ . When the activated sludge in the aeration tank was collected and observed with a phase-contrast microscope (× 400), it was found that type 021N filamentous bacteria were growing and filamentous bulking had occurred.

30% of dodecylpyridinium chloride
Bulking elimination agent 9 in which 25 parts by weight of isopropyl alcohol is mixed with 100 parts by weight of an aqueous solution (liquid temperature 25 ° C.)
5 kg was prepared and supplied to the returning sludge line in a fixed amount at a rate of 1 kg per hour using a diaphragm metering pump.
During the continuous feeding, no precipitation of the composition and no solidification of the aqueous solution appeared, and the feeding could be performed smoothly. The test was conducted in early March, the temperature around the processing apparatus was 10 ° C. at the highest and 1 ° C. at the lowest, and the temperature of the bulking elimination agent was within 5 ° C. ± 2 ° C.

After 24 hours from the supply time, the activated sludge is M
The LSS value was 5220 mg / l and the SVI value was 110.
Observing the appearance of filamentous bacteria at this time, type 021
It was found that N cells contracted and were destroyed in the sheath.

The activated sludge after 3 days had an MLSS value of 6300.
The mg / l and SVI values had dropped to 64, and the activated sludge had good sedimentation properties. The SVI value of the activated sludge after 6 days was 57, and the good sedimentability was maintained. When the state of the filamentous bacteria was observed, no new filamentous bacteria grew. In addition, the quality of the treated water during this test period had a COD value of 30 ppm or less, and there was no adverse effect on the treatment function due to the addition of the bulking elimination agent of the present invention.

(Comparative Example 2) When the bulking eliminating agent used in Example 3 was mixed with 25 parts by weight of water in place of isopropyl alcohol, the chemical solution in the tube and the metering pump within 2 hours after the start of feeding. It was found that the solidification occurred and it became impossible to supply the chemical solution.

[0041]

By using the bulking elimination agent of the present invention,
The chemical solution can be continuously supplied in a constant amount even in a low temperature period, the bulking can be efficiently eliminated, and the bulking can be eliminated without affecting other microorganisms in the activated sludge and the treated water.

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Claims (2)

[Claims] 1. A bulking elimination agent for activated sludge, which comprises isopropyl alcohol mixed with an aqueous solution of alkylpyridinium halide. 2. A bulking elimination agent for activated sludge, which comprises butyldiglycol mixed with an aqueous solution of alkylpyridinium halide.