JP2006305552A - Method and inhibitor for inhibiting filamentous bulking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and inhibitor for inhibiting filamentous bulking in an activated sludge treatment system having an excellent proliferation inhibiting effect on filamentous bacteria in small concentrations and a little adverse effect on bacteria other than the filamentous bacteria and being thus capable of effectively inhibiting filamentous bulking. <P>SOLUTION: The method inhibits the filamentous bulking by adding ortho-phthalaldehyde or the ortho-phthalaldehyde together with a surface active agent to the activated sludge treatment system. The inhibitor inhibits the filamentous bulking which contains the ortho-phthalaldehyde or the ortho-phthalaldehyde together with the surface active agent. The bulking activated sludge consists of a floc with the filamentous bacteria stretching outward. The inhibiting action of the ortho-phthalaldehyde against bacteria takes place at a high speed, resulting in the decomposition of the ortho-phthalaldehyde. Therefore, the filamentous bacteria around the floc is inhibited while the filamentous bacteria composing the floc are not sterilized and remain active, since the ortho-phthalaldehyde does not penetrate the floc. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an inhibitor for suppressing filamentous bulking in an activated sludge treatment system.

  In the activated sludge treatment method for organic wastewater, wastewater is mixed with activated sludge in an aeration tank and aerated, and sludge is separated in a solid-liquid separation tank, and the separated liquid is discharged as treated water, while a part of the separated sludge is discharged. Is returned to the aeration tank as return sludge, and the remainder is discharged as excess sludge. In such an activated sludge treatment method, organic substances are decomposed by activated sludge in which bacteria such as zoom glare have prevailed, but depending on the properties of raw water and various treatment conditions, filamentous bacteria such as Sphaerotilus natans may be contained in the activated sludge. May grow and filamentous bulking may occur. Filamentous bulking is a phenomenon in which activated sludge is lightened by the growth of filamentous bacteria and the separability deteriorates. When such bulking occurs, it becomes difficult to separate the sludge in the solid-liquid separation tank, and the sludge flows out together with the treated water, so that a sufficient return sludge cannot be secured and the processing performance deteriorates.

  Conventionally, in order to prevent such filamentous bulking, there is a method of suppressing the growth of filamentous bacteria by adding various bactericides, and quaternary ammonium salts (alkyl, trimethyl, ammonium, chloride, etc.) are used as bactericides. ) Is used. JP-A-59-112902 discloses that benzalkonium chloride, benzethonium chloride and a mixture thereof can sterilize only filamentous bacteria and suppress bulking without affecting other sterilizations. Has been.

  However, in general, quaternary ammonium salts are bactericides, so that the growth of bacteria other than filamentous bacteria can be suppressed when used in a large amount (for example, JP-A-61-35895).

  Therefore, as an inhibitor of filamentous bacteria that does not kill microorganisms other than filamentous bacteria, an anionic or nonionic surfactant is used (Japanese Patent Application Laid-Open No. 7-116686), or specific to filamentous bacteria. Utilization of acting lytic enzyme-producing bacteria has been made (Japanese Patent Laid-Open No. 61-35895).

  However, when an anionic or nonionic surfactant is put into an aeration tank, there is a problem that foaming is remarkable and sedimentation of activated sludge is not sufficient. On the other hand, the use of a lytic enzyme-producing bacterium has been put to practical use because it is effective only for specific filamentous bacteria and is not universal, or it is very expensive to apply to an actual activated sludge facility. The current situation is not.

For this reason, there is a need for a bulking inhibitor that acts more specifically on filamentous bacteria to suppress its growth and has less adverse effects on bacteria other than filamentous bacteria compared to quaternary ammonium salts. It was.
JP 59-112902 A JP 61-35895 A Japanese Patent Laid-Open No. 7-116686

  It is an object of the present invention to show a good growth inhibitory effect at a low concentration against filamentous bacteria in an activated sludge treatment system, and has little adverse effect on bacteria other than the filamentous bacteria, and effectively inhibits filamentous bulking. An object of the present invention is to provide a method and an inhibitor for suppressing filamentous bulking.

  The method for suppressing filamentous bulking according to the present invention (Claim 1) is characterized in that orthophthalaldehyde is added to the activated sludge treatment system in the method for inhibiting filamentous bulking in the activated sludge treatment system.

  The method for suppressing filamentous bulking according to claim 2 is characterized in that, in claim 1, orthophthalaldehyde and a surfactant are added to the activated sludge treatment system.

  The inhibitor of filamentous bulking of the present invention (Claim 3) is an inhibitor of filamentous bulking in an activated sludge treatment system, and is characterized by containing orthophthalaldehyde.

  The suppressor for filamentous bulking according to claim 4 is characterized in that, in claim 3, it contains orthophthalaldehyde and a surfactant.

  That is, as a result of evaluating various drugs, the present inventors have found that when orthophthalaldehyde is employed, the rate of decrease in the respiration rate of activated sludge is small in a concentration range that effectively inhibits filamentous bacteria. I found it.

  Moreover, it discovered that a more favorable effect could be acquired when ortho phthalaldehyde and surfactant were used together rather than ortho phthalaldehyde single agent.

  In addition, in this invention, the inhibitory effect of the filamentous bacteria by chemical | medical agent addition was evaluated by active dyeing. This is due to the following reason. That is, in the conventional evaluation method, a method of observing the state in which the filamentous bacteria are physically destroyed, such as the lysis effect, the detachment of cells from the sheath, and the cleavage of the filamentous body, has been mainly used. However, the conventional method overlooks filamentous bacteria that have not been physically disrupted but have reduced activity. On the other hand, by using the activity staining method, the presence or absence of the activity of such bacteria that are not physically destroyed can be easily evaluated in a short time.

  Moreover, the presence or absence of the activity fall of the whole activated sludge by chemical | medical agent addition was evaluated by the measurement of the respiration rate.

  The mechanism of action of selective and specific inhibitory effects on filamentous bacteria by the combination of orthophthalaldehyde or orthophthalaldehyde and a surfactant is presumed as follows.

In other words, the bulking activated sludge has a structure in which filamentous bacteria extend outside the floc.
Surfactants and quaternary ammonium salts denature the cell membrane. Addition of a low concentration does not lead to lysis of filamentous bacteria, but affects the cell membrane of filamentous bacteria protruding from the activated sludge. In addition, since the concentration is low, filamentous bacteria around the floc are suppressed, but do not penetrate into the floc. Therefore, the non-filamentous bacteria forming flocs are maintained without being sterilized.

  On the other hand, orthophthalaldehyde denatures bacterial proteins. Then, the inhibitory action of orthophthalaldehyde on bacteria occurs at an extremely fast rate, and as a result, orthophthalaldehyde is decomposed. Therefore, although the filamentous bacteria around the floc are suppressed, orthophthalaldehyde does not penetrate into the floc, so that the non-filamentous bacteria forming the floc are not sterilized and the activity is maintained. .

  In addition, as a result of evaluating glutaraldehyde, m-phthalaldehyde, p-phthalaldehyde, and benzaldehyde as chemical substances similar to orthophthalaldehyde, the characteristics as described above are apparent from Comparative Examples 1 to 4 described later. Was most prominent in orthophthalaldehyde and was confirmed to be specific to orthophthalaldehyde.

  Moreover, the effect by using surfactant together is as follows. That is, as described above, the surfactant denatures the cell membrane and does not lead to lysis of filamentous bacteria when added at a low concentration, but affects the cell membrane of filamentous bacteria protruding from the activated sludge. On the other hand, orthophthalaldehyde denatures bacterial proteins. Although the effect is not sufficient on the one hand, filamentous bacteria can be efficiently lysed by synergizing the effects in this way.

  According to the present invention, the growth of filamentous bacteria is specifically and preferentially suppressed, and bacteria other than the filamentous bacteria are hardly suppressed. Therefore, the filamentous bulking generated in the activated sludge treatment is suppressed, and the filamentous bulking is caused. A reduction in processing efficiency can be prevented.

  Embodiments of the method for suppressing filamentous bulking and the inhibitor of the present invention will be described in detail below.

  In the present invention, orthophthalaldehyde or orthophthalaldehyde and a surfactant are added to the activated sludge treatment system to suppress filamentous bulking.

  As the surfactant, various types such as those shown in Table 1 below can be used. These surfactants may be used alone or in combination of two or more.

  As the surfactant, those with * in Table 1 are particularly preferable, and benzalkonium chloride is particularly preferable.

  In the present invention, the activated sludge treatment system means a treatment system in any method that performs aerobic treatment using activated sludge, and in addition to the standard activated sludge treatment method, the modification and combinations with other treatment methods. Including processing systems in processing methods. Here, the processing system means the entire system for performing the above-described processing, and in the present invention, from any place (for example, the aeration tank, the return sludge line, etc.) of this processing system to the mixed liquid in the aeration tank. Thus, filamentous bulking can be suppressed by adding orthophthalaldehyde, or orthophthalaldehyde and a surfactant. In addition, in the present invention, the term “suppressing” means not only suppressing the occurrence of bulking, but also suppressing the progress and expansion of the bulking that has already occurred.

  Orthophthalaldehyde or orthophthalaldehyde and a surfactant can be added to any place in the activated sludge treatment system, but it is particularly preferable to add them to an aeration tank. When the amount of sludge accumulated in the settling tank is large, it is preferable to add it to the settling tank or the return line. The amount of orthophthalaldehyde or orthophthalaldehyde and surfactant added varies depending on the addition position, method, MLSS, and the amount of filamentous bacteria in the activated sludge. For the liquid containing activated sludge, for example, about 1 to 100 mg / L, preferably about 5 to 50 mg / L is appropriate for the mixed liquid in the aeration tank. Moreover, when adding orthophthalaldehyde and surfactant, generally it is 1-100 mg / L in total with respect to the liquid containing activated sludge, for example, the liquid mixture in an aeration tank, and 2-200 mg / L in total. Preferably, the total is about 5 to 50 mg / L and about 10 to 100 mg / L in total. Further, regarding the addition ratio of orthophthalaldehyde and surfactant, surface activity with respect to orthophthalaldehyde 1 by weight from the viewpoint of preventing sludge foaming and avoiding outflow of sludge outside the system. The agent is preferably 10 or less, and more preferably 5 or less. Further, from the viewpoint of expressing the lysis effect of filamentous bacteria and sufficiently suppressing the filamentous bulking, the surfactant is preferably at least 1 with respect to orthophthalaldehyde 1, and more preferably at least 2. preferable.

  The addition method may be added continuously, or may be added intermittently so as to achieve the above concentration at a predetermined time, for example, once a day. A high concentration may be added at one time (however, when a surfactant is used, the concentration is preferably such that foaming does not occur), or the low concentration may be added in several portions. In addition, when the bulking is slight, only one addition may be necessary. Orthophthalaldehyde and the surfactant may be mixed and added in advance, or may be added separately. Moreover, not only simultaneous addition but you may add separately, for example alternately, and may add to another location.

  In particular, when orthophthalaldehyde and a surfactant are used in combination, it is desirable to determine the addition method and the addition amount by evaluating foamability in advance. As an evaluation method, put the sludge liquid to which the drug is applied into a 500 mL graduated cylinder, send a fixed amount of air from a porous stone and aerate, and check the foaming amount and foaming duration. It is desirable to determine the addition amount.

  By adding orthophthalaldehyde or orthophthalaldehyde and a surfactant in this way, filamentous bacteria in the activated sludge lose respiratory activity, lose their ability to grow, and gradually decrease their abundance. At this time, for the bacteria other than the filamentous bacteria in the activated sludge, the decrease in the respiratory activity is small compared to the case where other fungicides are used, so that the organic substance decomposition activity is maintained.

  In the case of severe bulking in which the amount of filamentous bacteria is extremely high, bulking is performed by using a cationic polymer flocculant or an amphoteric polymer flocculant and an inorganic carrier such as activated carbon, iron salt, aluminum salt or lime. A synergistic effect in inhibition is obtained.

  Therefore, the inhibitor of filamentous bulking of the present invention is orthophthalaldehyde, or orthophthalaldehyde and a surfactant, and these cationic polymer aggregating agent and amphoteric polymer aggregating agent, and activated carbon, iron salt, aluminum salt, It may include one or more inorganic carriers such as lime.

  The filamentous bulking inhibitor of the present invention containing orthophthalaldehyde and a surfactant may be a mixture of orthophthalaldehyde and a surfactant to form a single agent. The activator may be provided separately. The content of orthophthalaldehyde and the surfactant is preferably the above-described ratio of preferred additions.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

<Example 1, Comparative Examples 1-11>
Into a 300 mL Erlenmeyer flask, 100 mL of bulking sludge predominating with filamentous bacteria was added, and the chemicals shown in Table 2 were added to a predetermined concentration. After stirring for 3 hours at 26 ° C., the respiratory rate and the presence or absence of dehydrogenase activity of filamentous bacteria were evaluated.

  The respiration rate was measured by the method for measuring the oxygen utilization rate described in “Sewage test method (1997 version)”, Volume 274, edited by Japan Sewerage Association. That is, after the bulking sludge brought into contact with the drug as described above is aerated to be supersaturated with oxygen, a medium (peptone 1 g / L, yeast extract 1 g / L, adjusted to pH 7.0) is added, and the oxygen consumption rate The respiratory rate was determined by

  On the other hand, the dehydrogenase activity of filamentous bacteria was evaluated by the INT (2-p-iodophenyl) -3- (p-nitrophenyl) -5-phenyltetrazoliumchloride) staining method. INT is oxidized in the electron transport system within the breathing cell, producing a red INT-formazan deposit. The presence or absence of this deposit was observed with a bright field microscope, and it was determined that the cells in which no deposit was confirmed were suppressed.

  Specifically, the bulking sludge contacted with the drug as described above is diluted with 20 mM phosphate buffer (pH 7) so that the MLSS becomes 100 to 500 mg / L, and the INT aqueous solution is diluted to a final concentration of 0.02 It added so that it might become weight%, and it was made to react for 30 minutes in the dark place after sealing so that air might not enter. Formaldehyde was added to a final concentration of 0.17% by weight to stop the reaction. The reaction solution of sludge and INT (hereinafter, the reaction solution prepared in this way may be referred to as “reaction solution I”) is double-stained with malachite green to produce INT-formazan in filamentous bacteria. Was observed with a bright-field microscope, and the minimum concentration for inhibiting filamentous bacteria in each drug was determined. Here, the minimum concentration that inhibits filamentous bacteria refers to the minimum concentration of the bactericide in which the deposit of INT-formazan is not recognized in the filamentous bacteria in the above staining method.

  Table 2 shows the minimum inhibitory concentration of each drug against filamentous bacteria and the respiratory activity remaining rate (respiration rate remaining rate (vs. blank)) at the minimum inhibitory concentration.

  From Table 2, it was found that orthophthalaldehyde has a remarkably low minimum concentration for inhibiting filamentous bacteria as compared with other fungicides, and can suppress the degree of decrease in the respiration rate of activated sludge to a low level.

<Examples 2 to 12, Comparative Examples 12 and 13>
In Example 1, evaluation was performed in the same manner except that the drugs shown in Table 3 were added so as to have the concentrations shown in Table 3.

  However, the evaluation of the dehydrogenase activity of filamentous bacteria was evaluated by the deposit residual rate in the filamentous bacteria. That is, the reaction solution I prepared in the same manner as in Example 1 was double-stained with malachite green, the remaining amount of deposit was confirmed, the amount of deposit in the blank to which no drug was added was set to 100%, The rate was calculated.

  Furthermore, foaming evaluation was performed as follows. That is, by the diffuser-stone method described in the interfacial chemistry research edition “Foam Trouble and Defoaming Technology”, page 122, the sludge liquid brought into contact with the drug as described above is placed in a 500 mL graduated cylinder. A certain amount of air was sent from a quality stone and aerated, and the volume of the foam was read.

  Table 3 shows the deposit residual rate of INT-formazan, the foaming amount, and the residual respiratory activity rate of sludge (remaining rate of respiratory rate (vs. blank)) in filamentous bacteria of each drug. In Table 3, the results in Example 1 are also shown.

  From Table 3, the deposit amount of INT-formazan in filamentous bacteria was halved by adding orthophthalaldehyde 10 mg / L (Example 1). However, it has been found that even if the amount of orthophthalaldehyde added is doubled, the amount of deposit does not decrease and the respiratory activity of sludge decreases (Example 12). Further, it was confirmed that the amount of deposit does not decrease even when potassium sorbate, which is a known bulking inhibitor other than the surfactant, is used in combination with orthophthalaldehyde (Comparative Examples 12 and 13).

  In contrast, polyoxyethylene-n-dodecyl ether (7 mol of ethylene oxide added) and trialkylamine salts, which are a kind of surfactant, are used together with orthophthalaldehyde, so that a single agent of orthophthalaldehyde is used. It is possible to reduce the amount of deposit (Examples 2 to 5). Moreover, it became clear that dioctyl didecyl ammonium chloride and benzethonium chloride, which are one kind of quaternary ammonium salts, can suppress the foaming amount to the same level or less as the above surfactants (Examples 6 and 8). Furthermore, it has been found that when benzalkonium chloride is used in combination, the activity of filamentous bacteria can be greatly reduced while reducing the amount of deposits compared to other quaternary ammonium salts. It has also been found that by reducing the concentration of the concomitant agent, the amount of foaming and sludge respiratory activity are reduced to a small extent. In particular, benzalkonium chloride was found to have a significant decrease in the activity of filamentous bacteria and a small decrease in the foaming amount and sludge respiratory activity compared to the surfactant (Examples 10 and 11).

<Example 13>
Filamentous bulking sludge (MLSS2210mg / L, SVI1283mL / g) is put into a 1 liter beaker, and orthophthalaldehyde is added to this so as to be 10mg / L once every two days, and artificial waste water is passed through. At 25 ° C., the activated sludge was treated by aeration at 1 L / min.

  Artificial wastewater was composed of 10% by weight glucose, 10% by weight peptone, 5% by weight potassium monophosphate, and 10% by weight monosodium phosphate, and the pH was adjusted to 7.0. The TOC load was 0.5 kg / day.

  As a result, after addition of orthophthalaldehyde, the deposit of the filamentous bacterium INT-formazan was not observed in 1 day, and after 6 days, the SVI decreased to 569 mL / g, and almost no filamentous bacterium was observed. In addition, there was no decrease in respiratory rate due to the addition of orthophthalaldehyde. The changes over time in SVI and respiratory rate at this time were as shown in Table 4.

<Example 14>
Example 13 except that orthophthalaldehyde and benzalkonium chloride were added to the filamentous bulking sludge (MLSS2210 mg / L, SVI1385 mL / g) once every two days to 10 mg / L respectively. When activated sludge treatment of artificial wastewater was performed, deposits of filamentous bacteria INT-formazan were not recognized in 1 day after addition of orthophthalaldehyde and benzalkonium chloride, and SVI reached 356 mL / g after 6 days The number of filamentous bacteria was hardly recognized. The changes over time in SVI and respiration rate were as shown in Table 5.

<Comparative example 14>
When activated sludge treatment of artificial wastewater was carried out in the same manner as in Example 13 except that filamentous bulking sludge (MLSS 2370 mg / L, SVI997 mL / g) was used and orthophthalaldehyde was not added, operation 6 Even after the day, no decrease in filamentous bacteria was observed, and an increase in SVI was observed. The changes over time in SVI and respiration rate were as shown in Table 6.

<Comparative Example 15>
Activated sludge of artificial wastewater as in Example 14, except that filamentous bulking sludge (MLSS 2450 mg / L, SVI997 mL / g) was used and only benzalkonium chloride was added and orthophthalaldehyde was not added. When the treatment was carried out, the deposit of the filamentous bacterium INT-formazan decreased in one day, but the effect was found to be lower than that of Example 14. Similar results were obtained after 6 days of operation. The changes over time in SVI and respiration rate at this time were as shown in Table 7.

<Comparative Example 16>
When activated sludge treatment of artificial wastewater was performed in the same manner as in Example 13 except that filamentous bulking sludge (MLSS 2370 mg / L, SVI965 mL / g) was used and orthophthalaldehyde was not added, operation 6 No decrease was observed even on the day, and an increase in SVI was observed. The changes over time in SVI and respiratory rate were as shown in Table 8.

Claims (4)

  A method for suppressing filamentous bulking, wherein orthophthalaldehyde is added to the activated sludge treatment system in a method for inhibiting filamentous bulking in an activated sludge treatment system.   The method for suppressing filamentous bulking according to claim 1, wherein orthophthalaldehyde and a surfactant are added to the activated sludge treatment system.   An inhibitor of filamentous bulking in an activated sludge treatment system, characterized by containing orthophthalaldehyde.   The inhibitor of filamentous bulking according to claim 3, comprising orthophthalaldehyde and a surfactant.