JP2004344741A - Sewage treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sewage treatment method using active sludge and a bulking prevention agent where bulking caused by filamentous microorganisms as the maximum trouble on facility management can securely be prevented. <P>SOLUTION: In the sewage treatment method, sewage is stirred in a horizontal direction in the presence of the active sludge and the bulking prevention agent within a disposal tank. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５７】
第１表から、曝気槽にバルキング防除剤を添加し、曝気槽内を水平方向に撹拌した場合（実施例１）、曝気槽水とバルキング防除剤を混合槽内で４８時間水平方向に撹拌して得られた混合物を曝気槽に添加した場合（実施例２）、及び曝気槽水とバルキング防除剤を混合槽内で４８時間水平方向に撹拌して得られた混合物を曝気槽に添加し、該曝気槽内を水平方向に撹拌した場合（実施例３）では、糸状性微生物の大幅な減少が見られ、バルキングをほぼ完全に防止することができることが確認された。その一方、バルキング防除剤を添加していない比較例１では、糸状性微生物が全く減少していなかった。曝気槽にバルキング防除剤を添加したが、水平方向に撹拌をしなかった場合（比較例２）は、糸状性微生物がわずかに減少していた。
【００５８】
【発明の効果】
本発明の汚水処理方法によれば、生活排水や産業排水、廃水等の汚水処理施設において、水質を悪化させることなく、また、有用なフロック形成菌の生育を阻害することなく、糸状性微生物を減少させてバルキングの発生を確実に防止し、曝気槽内の活性汚泥を恒常的に活性化し、汚水を効率的かつ経済的に処理することができる。
【図面の簡単な説明】
【図１】図１は、本発明の実施に好適な汚水処理施設の概略図である。
【図２】図２は、図１に示す汚水処理施設の混合槽の概略図である。
【図３】図３は、本発明の実施に好適な汚水処理施設の概略図である。
【図４】図４は、従来の活性汚泥法による汚水処理施設の概略図である。
【符号の説明】
１…第１次沈殿槽、２…曝気槽、２ａ…第１の曝気槽、２ｂ…第２の曝気槽、３…最終沈澱槽、４…汚泥返送手段、５，５’…撹拌装置、６…散気装置、７…混合槽[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sewage treatment method capable of reliably preventing the occurrence of bulking due to filamentous microorganisms, which is the greatest obstacle in facility management, in a sewage treatment method using an activated sludge method.
[0002]
[Prior art]
BACKGROUND ART Conventionally, an activated sludge method using activated sludge has been widely used as a method for treating wastewater such as domestic wastewater, industrial wastewater, and wastewater. In this method, an organic substance-containing wastewater is aerated in the presence of activated sludge to adsorb and decompose organic substances by activated sludge, and then obtain supernatant water (treated water) by utilizing the property of sedimentation by gravity. Things.
[0003]
An example (schematic) of a sewage treatment facility using this activated sludge method is shown in FIG. The treatment facility shown in FIG. 4 includes a primary sedimentation tank 1, an aeration tank 2, a final sedimentation tank (secondary sedimentation tank) 3, and sludge return means 4. In this treatment facility, first, wastewater flows into the primary sedimentation tank 1 to remove large-sized sediment, and the wastewater from which the sediment has been removed is transferred to the aeration tank 2 containing activated sludge. Next, by aeration of the wastewater together with the activated sludge, organic substances contained in the wastewater are adsorbed and decomposed by the activated sludge. Next, the obtained treated water is transferred to the final sedimentation tank 3 to precipitate and remove activated sludge, and the supernatant water is discharged to the outside after being sterilized with chlorine as required. Further, a part of the settled activated sludge is returned to the aeration tank by the sludge return means 4 as returned sludge, and the remaining activated sludge is concentrated into a dewatered cake and incinerated.
[0004]
By the way, during the sewage treatment by the activated sludge method, a phenomenon may occur in which activated sludge is settled poorly in the final settling tank. The phenomenon that activated sludge becomes poor sedimentation is called bulking, and is the biggest problem in the activated sludge method. It is said that the cause is that the growth balance of the microflora in the activated sludge is disrupted, and the filamentous microorganisms predominate over the floc-forming bacteria.
[0005]
When bulking occurs, the activated sludge expands and becomes difficult to settle, and it becomes impossible to obtain an interface between the activated sludge and the treated water in the settling tank. Then, the activated sludge flows out together with the treated water, causing environmental pollution. Furthermore, due to the outflow of the activated sludge, the concentration of MLSS (suspended matter in the water of the aeration tank) in the aeration tank is not maintained, and the biological decomposition of the organic matter dissolved in the wastewater or the wastewater by the activated sludge becomes poor. Cause environmental pollution.
[0006]
Conventionally, as a method of coping with the occurrence of bulking, there are a method of increasing the sedimentation of activated sludge by adding an inorganic flocculant and a polymer flocculant, and a method of introducing chlorine, which is an inexpensive disinfectant. Are known. However, the addition of a flocculant temporarily solves the deterioration of the sedimentation of activated sludge, but it is only an emergency treatment and does not suppress the growth of filamentous microorganisms that cause bulking. It is not effective in preventing recurrence. In addition, since disinfectants such as chlorine have no selectivity, not only the growth of filamentous microorganisms that cause bulking, but also the growth of useful organisms in activated sludge, are greatly adversely affected. However, there is a problem that the bulking may be relapsed due to the extinguishing of useful microorganisms.
[0007]
Therefore, a method has been proposed in which various bulking control agents are charged into a sewage treatment tank when the sewage is transferred to an aeration tank and aerated together with activated sludge (Patent Documents 1 to 4). However, simply charging various bulking control agents into the sewage treatment tank may not completely suppress bulking, which has been a problem.
[0008]
[Patent Document 1]
JP-A-10-244287
[Patent Document 2]
JP-A-11-33583
[Patent Document 3]
JP-A-11-47883
[Patent Document 4]
JP-A-11-57762
[0009]
[Problems to be solved by the invention]
[0010]
The present invention has been made in view of the problems of the related art, and in a sewage treatment method using an activated sludge and a bulking controlling agent, bulking due to filamentous microorganisms which is the greatest obstacle in facility management can be surely controlled. It is an object to provide a sewage treatment method.
[0011]
[Means for Solving the Problems]
The inventor of the present invention has intensively studied a method capable of reliably controlling bulking in a sewage treatment method using the activated sludge method. As a result, they have found that by stirring the contents in the sewage treatment tank in the horizontal direction in the presence of the bulking control agent, the occurrence of bulking can be reliably controlled, and the present invention has been completed.
[0012]
Thus, according to the present invention, there is provided a sewage treatment method using an activated sludge method using at least one sewage treatment tank, wherein the contents are horizontally stirred in the sewage treatment tank in the presence of a bulking control agent. Wastewater treatment method is provided.
In the sewage treatment method of the present invention, the stirring is preferably performed in the presence of at least one selected from a cationic polymer flocculant, an inorganic flocculant, a clay mineral, an enzyme preparation and an aerobic microorganism.
[0013]
In the sewage treatment method of the present invention, the sewage treatment tank is used for culturing aerobic microorganisms provided in an aeration tank or separately provided from the aeration tank, and mixing the culture to flow into the aeration tank. It is preferably a tank. Further, in the mixing tank, it is more preferable to culture the aerobic microorganisms using one or more selected from returned sludge, raw sewage water, aeration tank water, and treated water.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the wastewater treatment method of the present invention will be described in detail.
The sewage treatment method of the present invention is a sewage treatment method using an activated sludge method, wherein the contents are stirred horizontally in a sewage treatment tank in the presence of a bulking control agent.
The sewage treatment method of the present invention may be any method that purifies sewage using activated sludge, and includes methods such as a long-time aeration method and a batch activated sludge method in addition to a standard activated sludge method. The present invention also includes a method capable of simultaneously removing organic matter (BOD) and nitrogen in wastewater, such as a circulating nitrification denitrification method.
[0015]
The wastewater targeted by the present invention contains organic matter, and is not particularly limited as long as purification is required. For example, water contaminated with organic matter such as domestic wastewater, industrial wastewater, and wastewater may be mentioned.
The activated sludge used in the present invention is obtained by aerating wastewater containing organic substances, and is an aggregate of aerobic bacteria and protozoa that continue to breathe and grow while adsorbing and decomposing organic substances in water. is there.
[0016]
The bulking control agent used in the present invention is not particularly limited as long as it selectively inhibits the growth of filamentous microorganisms and helps to improve the sedimentation of activated sludge. Specific examples thereof include dithiocarbamates described in JP-B-58-14274, iodopropargyl derivatives described in JP-A-55-11536, and bis-carboxylates described in JP-A-55-147196. Biguanide derivatives, benzalkonium chloride and benzethonium chloride described in JP-B-63-39562, chlorohexidine hydrochloride and chlorhexidine gluconate described in JP-B-1-37364, and JP-B1-49560. Acrylic acid hydrazide-based polymer compound or a polymer compound containing an amino group or a quaternary ammonium salt, an acid such as sulfamic acid or a salt thereof, a quaternary ammonium salt described in JP-A-62-168599, Killing of thiocyanates and halogenated acetoxyalkenes Agents, separately added alkyleneimine polymers and sodium hypochlorite described in JP-A-4-74595, cinnamaldehyde, anisaldehyde, eugenol described in JP-A-5-146790 A cationic reaction product of an imidazole compound and epihalohydrin described in JP-B-6-88889, an indazole derivative described in JP-A-6-170385, and a JP-A-6-63580 Isophthalonitrile derivatives, a mixture of a small amount of a coagulant and a small amount of a bactericide described in JP-A-6-71286, and a water solution obtained by reaction of an amine with epihalohydrin and the like described in JP-A-6-142676. Mixtures of a water-soluble polymer or an alkyleneimine polymer with aluminum sulfate, etc .; Methylene dithiocyanate described in 06089, tetramethylammonium chloride and propyltrimethylammonium bromide described in JP-A-7-8985, 1-alkylpyridinium halides described in JP-A-6-34389, A mixture of a water-soluble polymer obtained by reacting an epihalohydrin or the like with an amine described in JP-A-7-24490, an alkyleneimine polymer, a tetraalkylammonium halide or a 1-alkylpyridinium halide, Japanese Patent Publication No. 7-38991. Sorbic acid and a salt thereof described in JP-A-7-80492, a mixture of calcium carbonate and the like and a floc-forming bacterium described in JP-A-7-80492, and a dialkylamine and epihalohydrin described in JP-B-7-41263. Water of Soluble cationic polymers, mixtures of anionic surfactants and nonionic surfactants described in JP-A-7-116686, primary to tertiary amino acids described in JP-A-7-116687 A mixture of a cationic surfactant having a group and an amphoteric surfactant, a macrolide antibiotic described in JP-A-7-136684, and 1-hydroxy-2 described in JP-A-7-241590. Mixtures of (1H) -pyridinethione alkali metal salt and cationic polymer flocculant, aminoglycoside antibiotics described in JP-A-9-70595, naphthols described in JP-A-10-244287, Conventionally known bulking control agents such as naphthoquinones described in JP-A-11-33583. These bulking control agents can be used alone or in combination of two or more.
[0017]
Among these, those having excellent selectivity, which inhibit the growth of harmful filamentous microorganisms that cause bulking but do not inhibit the growth of useful floc-forming bacteria, are preferred. Examples of such a bulking controlling agent include those containing at least one kind of an indazole derivative or a salt thereof described in JP-A-6-170385.
[0018]
The bulking control agent is usually used as a powder, but can also be used as a liquid dissolved in water or the like. When used as a dust, the amount of addition is about 1 to 200 mg / liter, preferably about 2 to 50 mg / liter, based on the total volume of the sewage treatment tank.
The method of adding the bulking control agent to the sewage treatment tank is not particularly limited, and examples thereof include a method of adding the agent in a continuous manner, and a method of adding it twice or three times a day.
[0019]
In the present invention, it is preferable that at least one selected from a cationic polymer flocculant, an inorganic flocculant, a clay mineral, an enzyme preparation and an aerobic microorganism is added to the sewage treatment tank together with the bulking control agent. By using these additives in combination with the bulking control agent, the effect of improving the initial activated sludge settling property immediately after the addition of the bulking control agent and maintaining the bulking control period can be expected.
[0020]
Examples of the cationic polymer flocculant to be used include polyacrylates, polymethacrylates, vinylformaldehydes, dicyanamides, and the like, and examples of the inorganic coagulants include aluminum sulfate and ferric chloride. Can be Examples of the clay mineral include zeolite, vermiculite, and attapulgite. The addition amount of the cationic polymer flocculant is usually about 10 to 50 mg / liter based on the total capacity of the sewage treatment tank, and the addition amount of the inorganic coagulant and clay mineral is based on the total capacity of the sewage treatment tank. On the other hand, it is usually about 10 to 200 mg / liter.
[0021]
Examples of the enzyme preparation used include preparations containing one or more enzymes such as amylase, protease, cellulase, and lipase. The enzyme preparation may be a culture of aerobic microorganisms or other microorganisms, or may be extracted from plants or the like. The enzyme preparation may be a product obtained by isolating and purifying an enzyme component from these microorganisms, or a mixture thereof.
[0022]
As the aerobic microorganism, any microorganism such as bacteria, mold, and yeast can be used as long as it can be proliferated by aeration culture. These microorganisms may be used as mixed bacteria. Among these, microorganisms which have a high growth rate and produce a large amount of extracellular enzymes are preferred. Examples of such microorganisms include Bacillus subtilis, activated sludge such as zooglare, oil-decomposing bacteria when the raw water contains a large amount of oil, and various types of hard-to-decompose bacteria when the raw water contains a lot of hardly decomposable substances. Examples can be given.
These enzyme preparations and aerobic microorganisms are preferably added to a mixing tank prepared separately from the aeration tank, as described later.
[0023]
The sewage treatment method of the present invention is characterized in that contents are horizontally stirred in a sewage treatment tank in the presence of a bulking control agent.
The sewage treatment tank used in the present invention is not particularly limited as long as it has a shape capable of stirring in the horizontal direction, but is preferably a cylindrical shape having good stirring efficiency in the horizontal direction. Activated sludge is an aggregate of aerobic microorganisms, and the sewage treatment tank used is equipped with a device (aeration device) that supplies oxygen (air) necessary for the mixing and decomposition reaction of aerobic microorganisms. preferable. Specific examples include an aeration tank for aerating sewage in the presence of activated sludge and a mixing tank for flowing a culture of an enzyme agent or an aerobic microorganism into the aeration tank.
[0024]
In the present invention, agitating in the horizontal direction means that a mixture containing at least a bulking control agent (contents in the sewage treatment tank) is forcedly convected in the horizontal direction by mechanical stirring in the sewage treatment tank. Say. In addition, as long as it is capable of convection in the horizontal direction, it may be convection in multiple directions, such as a spiral shape or a combination of the horizontal direction and the vertical direction.
[0025]
As a method of stirring in the horizontal direction, for example, a method by radiation type stirring in which a stirring blade attached to the tip of a vertically provided shaft is rotated and a flow of water due to the centrifugal action of rotation is strongly generated in the radial direction of the blade. A method using an agitating blade such as a method using an axial flow type agitator that can simultaneously generate an axial flow by rotating the agitating blade by a thrust in a rotational axis direction; a jet type by a horizontal jet from a jet nozzle A method using stirring; a method using a stirrer rotated by magnetic force; and the like. Among these, the method of stirring using a stirring blade is preferable because it is possible to stir vigorously and mechanically and violently in the horizontal direction and to use existing equipment as it is.
[0026]
The method using a stirring blade can be performed using a stirring device having a stirring motor, a stirring shaft, and a stirring blade.
The stirring blade to be used is not particularly limited, and examples thereof include a paddle type, a propeller type, a turbine type, a blue-margin type, an squid type, and modified types thereof. In addition, the size and the number of stages of the stirring blade are not particularly limited. Considering the size (width and height) of the aeration tank to be used, an appropriate size and number of stages are used so that the effect of controlling bulking is best exhibited. Can be selected.
[0027]
The installation position and the number of the stirring devices are not particularly limited as long as uniform stirring in the horizontal direction is ensured, and one stirring device may be installed at an appropriate position in the sewage treatment tank. May be installed. When a plurality of sewage treatment tanks are installed, a stirrer may be installed in all sewage treatment tanks or may be installed only in a specific sewage treatment tank.
[0028]
The stirring conditions such as the stirring speed of the stirring device are not particularly limited as long as the desired bulking control effect can be obtained, and appropriate conditions can be set.
The stirring time is usually 1 to 24 hours, preferably 2 to 10 hours. The temperature during stirring is usually 0 to 40 ° C, preferably 10 to 35 ° C.
[0029]
The details of the reason why bulking can be reliably prevented by stirring the contents in the sewage treatment tank in the horizontal direction are not clear, but when stirring in the sewage treatment tank is only bubbling that causes vertical convection Cannot achieve the same effect, the following can be considered. That is, by horizontally stirring the contents in the sewage treatment tank, the filamentous microorganisms undergo mechanical damage such as cutting, bending, twisting, rupture of the cell membrane, etc. It is possible to suppress the occurrence of bulking, which is killed or becomes a fine hyphal fragment, and the addition of a bulking control agent alone was insufficient.
[0030]
According to the present invention, a synergistic effect of the action of a bulking control agent (inhibition of the growth of filamentous microorganisms) and mechanical damage due to horizontal agitation kills filamentous microorganisms in a sewage treatment tank or produces fine hyphal fragments. By doing so, the occurrence of bulking can be prevented and the sedimentation of activated sludge can be improved.
[0031]
The sewage treatment method of the present invention can be implemented, for example, by a sewage treatment facility shown in FIGS. 1 (a) and 1 (b). 1 (a) and 1 (b), 1 is a first settling tank, 2 is an aeration tank, 2a is a first aeration tank, 2b is a second aeration tank, 3 is a final settling tank, 4 is an activated sludge tank. Return means 5 is a stirring device.
[0032]
In the sewage treatment facility shown in FIG. 1 (a), first, sewage flows into a primary sedimentation tank, and large trash is removed. Next, the sewage from which the large trash has been removed is sent to the aeration tank 2.
[0033]
The aeration tank 2 may be composed of a single tank as shown in FIG. 1 (a), or may be one in which a plurality of tanks are connected as shown in FIG. 1 (b). May be provided with a partition plate inside. Furthermore, as in the case where the purpose is to remove nitrogen simultaneously with the decomposition of organic matter, it may be composed of an aeration tank that performs only agitation without aeration, and an aeration tank that performs aeration with a diffuser. . The size of the aeration tank or the mixing tank is not particularly limited, and an appropriate tank can be selected and used depending on the amount of wastewater to be treated.
[0034]
In the aeration tank 2, the sewage fed from the first settling tank 1 is horizontally stirred by the stirrer 5 together with the activated sludge and the bulking control agent while fresh air is constantly bubbled by the diffuser 6. Is done. During this time, the organic matter contained in the sewage is adsorbed and decomposed by the activated sludge, and the filamentous microorganisms are killed or become fine hyphal fragments due to the synergistic effect of the effect of the bulking control agent and the effect of horizontal stirring. , The occurrence of bulking is reliably prevented.
[0035]
The sewage in which the organic matter has been decomposed is transferred to the final settling tank 3 together with the activated sludge. In the final sedimentation tank 3, it is separated into supernatant water and activated sludge by standing and gravity separation. Part of the separated activated sludge is returned to the aeration tank 2 by the activated sludge return means 4, and is again subjected to sewage treatment. Excess activated sludge is incinerated after dehydration. On the other hand, the supernatant water is sterilized by a chlorine sterilizer (not shown) and then discharged to the outside.
[0036]
In the sewage treatment facility shown in FIG. 1B, first, in a first aeration tank 2a, a mixture containing sewage, activated sludge, and a bulking control agent is allowed to stay for a certain period of time under aeration conditions, so that organic matter contained in the sewage is removed. Is sufficiently decomposed by activated sludge. Next, the treated wastewater is transferred to the second aeration tank 2b, and is stirred in the horizontal direction by the stirring device 5 in the second aeration tank 2b. In the second aeration tank 2b, the sewage treated in the first aeration tank 2a is agitated in the horizontal direction, whereby the occurrence of bulking can be reliably prevented. According to the apparatus shown in FIG. 1 (b), the amount of activated sludge sent to the final settling tank 3 can be reduced, and the burden of the operation of separating, collecting and disposing activated sludge can be reduced.
[0037]
In the sewage treatment method of the present invention, the activated sludge obtained by horizontally stirring the bulking control agent and the sludge activating medium in a mixing tank prepared separately from the aeration tank is added to the aeration tank. You may do so. This method is particularly preferable because the installation of the stirring device is simple and the efficiency of sewage treatment with activated sludge can be further increased.
[0038]
As the sludge activation medium to be used, returned sludge, sewage raw water, aeration tank water, treated water, or one or more kinds of treated water can be mentioned. Of these, the use of returned sludge is preferred from the viewpoint of the activation efficiency of activated sludge, that is, the activation efficiency per amount of use of the bulking control agent. In addition, in facilities where raw sewage flows in all year round and the raw water concentration is stable, if the raw sewage water may contain filamentous microorganisms that cause bulking, aeration where bulking has not yet occurred In the case where the purpose is to prevent occurrence of bulking in the tank, it is preferable to use raw sewage as a sludge activating medium. When using raw sewage, foaming may occur, so it is desirable to perform a foam removal treatment or a defoaming treatment. On the other hand, if the mixing tank to be used is small, return sludge, raw sewage water, aeration tank water cannot be used due to special circumstances, or if a special treatment method such as a biofilm method is used, use tap water or treated water. Is preferred. When tap water or the like is used, it is desirable to add an enzyme / microbial preparation or the like to the sludge activation medium.
[0039]
As the mixing tank used in the present invention, any mixing tank can be used as long as the contents in the tank can be agitated in the horizontal direction while being ventilated. For example, those provided with a ventilation stirring mechanism can be mentioned. As the ventilation stirring mechanism, a mechanism capable of adjusting the amount of ventilation, the size of bubbles generated by ventilation, the speed of stirring, and the like is preferable. Further, a stirring blade or a baffle plate may be provided, but when stirring can be performed by a ventilation pipe, a diffuser pipe, or the like, the stirring blade or the like need not be provided.
[0040]
Further, as the mixing tank, a culture tank or the like provided with the above-described aeration stirring mechanism can be used. When a culture tank is used, it is preferable to add an aerobic microorganism, a sludge activation medium (preferably returned sludge) and a bulking control agent to the tank, and culture the aerobic microorganism. The obtained activated sludge enhances the treatment effect of sewage by activated sludge and is excellent in controlling bulking. In addition, when the viscosity of the returned sludge or the like is high or when the amount of the liquid is small and it is difficult to introduce a constant amount of the sludge activating medium into the mixing tank, a high-concentration quantitative pump can be used.
[0041]
As a method of stirring the contents in the mixing tank in the horizontal direction, the same method as the method of stirring the contents in the aeration tank in the horizontal direction can be adopted. FIG. 2 shows an example (schematic diagram) in which a stirrer for stirring the contents in the mixing tank in the horizontal direction is installed. One stirring device is installed at the center of the mixing tank 7. In FIG. 2, returned sewage is sent in from the left end (arrow). In the mixing tank 7, a bulking agent and, if desired, other additives are added. A diffusing device 6 is provided at the bottom of the mixing tank 7 for taking in air (oxygen) from the outside and bubbling the air from the bottom of the mixing tank 7. For the ventilation of the mixing tank, concretely, a ventilation pipe branched from the air supply pipe of the treatment facility, an aeration blower or an underwater aerator, a ventilation device with an adjustable aeration amount, or fine air bubbles are used for the entire aeration. It can be performed by providing an air diffuser such as a diffuser or an air diffuser corresponding to the amount of ventilation.
[0042]
The capacity of the mixing tank depends on the scale of the processing facility to be applied, but is usually 2 to 5 m. ³ A volume of about a volume is used, and the ventilation capacity of such a mixing tank usually needs to be about 4 times / hour of the volume of the mixing tank. The installation location of the mixing tank varies depending on the condition of the facility and the like, but usually, a convenient and safe place near the inflow side of the raw water from the aeration tank is preferable.
[0043]
In the present invention, in order to obtain an activated sludge efficiently, it is preferable to periodically replenish the mixing tank with a bulking control agent, and to replenish the bulking control agent together with an enzyme preparation and / or an aerobic microorganism. Is more preferred. In particular, when returning sludge is used as the sludge activating medium, it is preferable to periodically supply the mixing tank with the bulking control agent. When a certain amount of these bulking control agent, enzyme preparation, or aerobic microorganism (preparation) is packed in a water-soluble film in order to suppress dusting, they can be directly introduced into a mixing tank. The amount of the bulking control agent to be mixed into the mixing tank is 10 to 3000 g / m daily depending on the type. ³ Degree, preferably 400 to 2000 g / m ³ It is about.
[0044]
The contact between the bulking control agent and the sludge activating medium in the mixing tank is preferably performed under aeration and stirring conditions. The introduction of the sludge activating medium into the mixing tank may be of a batch (batch) type or a continuous type. In the case of the continuous type, the sludge activating medium can reduce the effective volume of the mixing tank by about 1/2 in 24 hours. It is desirable to introduce continuously. In any case, the contact time between the bulking control agent and the sludge activating medium in the mixing tank needs to be about 24 to 96 hours. If less than 24 hours, an activated sludge that can activate the activated sludge in the aeration tank cannot be obtained. Even if it exceeds 96 hours, an activated sludge that can activate the activated sludge in the aeration tank can be obtained. Can not be obtained.
[0045]
The inflow of the activated sludge obtained from the mixing tank into the aeration tank is preferably a quantitative inflow. Stable sewage treatment can be realized by flowing in a fixed amount. The fixed inflow may be carried out together with a bulking control agent, or may flow separately from the bulking control agent. Further, depending on the condition of the treatment facility, it is possible to flow into the returned sludge or the inflowed sewage raw water and flow into the aeration tank together therewith. However, when flowing into the incoming sewage raw water, it is necessary to confirm in advance that the activity of the activated sludge does not decrease due to a change in pH or the like. The amount flowing in quantitatively may be appropriately set according to the scale of processing. In addition, the constant inflow may be a continuous inflow or an intermittent inflow, but it is particularly desired that the inflow of the activated sludge is continued, for example, at least 5 days or more.
[0046]
As a place where the activated sludge obtained from the mixing tank flows into the aeration tank, a place where a residence time is allowed in the aeration tank, for example, a raw water inflow side of the aeration tank is desirable, but it is also possible to flow into the inflow raw water. It is preferable that the activated sludge is allowed to flow into the aeration tank at a place where the residence time is sufficient. The place where the residence time can be taken in the aeration tank is, specifically, on the side where the wastewater flows into the aeration tank from the primary sedimentation tank. Further, as shown in FIG. 1B, when a plurality of aeration tanks are installed, the aeration tank is on the side where the wastewater flows in from the primary sedimentation tank.
[0047]
FIGS. 3A to 3C show an example of a sewage treatment facility for implementing the sewage treatment method of the present invention, which has a mixing tank. 3 (a) to 3 (c), 1 is a primary sedimentation tank, 2 is an aeration tank, 3 is a final sedimentation tank, 4 is activated sludge return means, and 7 is a mixing tank. Further, the mixing tank 7 is provided with a stirrer 5 'for stirring the contents in the tank in the horizontal direction.
[0048]
In the facility shown in FIG. 3A, a part of the returned sludge is transferred to the mixing tank 7 as a sludge activating medium, and the obtained activated sludge is continuously and quantitatively flown from the mixing tank 7 into the aeration tank 2 together with the bulking control agent. It is supposed to. In the facility shown in FIG. 3B, a part of the raw sewage is transferred to the mixing tank 7 as a sludge activating medium, and the obtained activated sludge is continuously and quantitatively flown from the mixing tank 7 into the aeration tank 2 together with the bulking control agent. It is made to let. In the facility shown in FIG. 3 (c), a part of the water of the aeration tank is transferred to the mixing tank 7 as a sludge activating medium, and the obtained activated sludge is transferred from the mixing tank 7 to the aeration tank 2 together with the bulking control agent. It is designed to continuously flow in a fixed amount.
[0049]
According to the sewage treatment facilities shown in FIGS. 3A to 3C, the occurrence of bulking can be reliably prevented, and the amount of the bulking control agent and the enzyme preparation and / or aerobic microorganisms supplied to the mixing tank can be aerated. The replenishment required is very small compared to the replenishment required to achieve the same effect by direct injection into the tank, making it much more economical.
[0050]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the technical scope of the present invention is not limited to these Examples.
[0051]
(The occurrence of bulking)
In an aeration tank of a sewage treatment apparatus having an aeration tank having a capacity of 2 liters and a sedimentation tank having a capacity of 0.5 liters, artificially synthesized wastewater (glucose 870 mg / l, peptone 250 mg / l, sodium chloride 300 mg / l, Activated sludge was cultured under aeration conditions by continuously supplying 39 mg / l of potassium and 43 mg / l of ammonium nitrate.
[0052]
Filamentous bulking was generated under the conditions of a synthetic wastewater inflow rate of 1 liter / day, an MLSS concentration of 2,000 mg / liter, and a room temperature of 20 to 25 ° C., and the following experiment was performed. The filamentous microorganisms generated at this time were TYPE021N, spherothyls natans, TYPE1701, and TYPE1702. Identification of filamentous microorganisms is described in Eikelboom D. et al. H. Filamentous organsmsobserved in activated sludge. Water Research vol. 9: 365-388 (1975).
[0053]
(Test method)
Examples 1 to 3 and Comparative Examples 1 and 2 below were provided as test plots.
(A) Example 1
The above-mentioned bulking control agent was added to the aeration tank at a rate of 40 mg / day every day, and the inside of the aeration tank was stirred horizontally.
(B) Example 2
100 ml of aeration tank water was placed in a 300 ml Erlenmeyer flask containing a magnetic stirrer, 40 mg of the above-mentioned bulking control agent was added thereto, and the contents were stirred horizontally for 48 hours using a magnetic stirrer. The area where the mixture was added to the aeration tank every day (the inside of the aeration tank was not stirred horizontally)
(C) Example 3
100 ml of aeration tank water was placed in a 300 ml Erlenmeyer flask containing a magnetic stirrer, 40 mg of the above-mentioned bulking control agent was added thereto, and the contents were stirred horizontally for 48 hours using a magnetic stirrer. The mixture was added to the aeration tank daily, and the inside of the aeration tank was stirred horizontally using a stirrer equipped with a propeller-type stirring blade at the tip.
[0054]
(D) Comparative Example 1
Section where no drug is added
(E) Comparative example 2
A section in which a bulking control agent (manufactured by Nippon Soda Co., Ltd., trade name: VALKICK) containing 5-nitroimidazole as an active ingredient was added to an aeration tank every day at a rate of 40 mg / day.
[0055]
The evaluation of the anti-bulking effect was carried out by microscopic observation of the growth of filamentous microorganisms (evaluated as "++" for very large cases, "+" for large cases, and "±" for very small normal cases). . The results are shown in Table 1.
[0056]
[Table 1]

[0057]
From Table 1, when the bulking control agent was added to the aeration tank and the inside of the aeration tank was stirred horizontally (Example 1), the water of the aeration tank and the bulking control agent were horizontally stirred in the mixing tank for 48 hours. When the mixture obtained in (1) was added to the aeration tank (Example 2), and the mixture obtained by horizontally stirring the aeration tank water and the anti-bulking agent in the mixing tank for 48 hours was added to the aeration tank. When the inside of the aeration tank was agitated in the horizontal direction (Example 3), the number of filamentous microorganisms was significantly reduced, and it was confirmed that bulking could be almost completely prevented. On the other hand, in Comparative Example 1 to which no bulking control agent was added, the number of filamentous microorganisms was not reduced at all. When the bulking control agent was added to the aeration tank, but the stirring was not performed in the horizontal direction (Comparative Example 2), the number of filamentous microorganisms was slightly reduced.
[0058]
【The invention's effect】
According to the sewage treatment method of the present invention, in a sewage treatment facility for domestic wastewater, industrial wastewater, wastewater, etc., without deteriorating the water quality, and without inhibiting the growth of useful floc-forming bacteria, filamentous microorganisms By reducing the amount, the occurrence of bulking can be reliably prevented, the activated sludge in the aeration tank is constantly activated, and the wastewater can be treated efficiently and economically.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a sewage treatment facility suitable for implementing the present invention.
FIG. 2 is a schematic view of a mixing tank of the sewage treatment facility shown in FIG.
FIG. 3 is a schematic diagram of a sewage treatment facility suitable for carrying out the present invention.
FIG. 4 is a schematic view of a conventional sewage treatment facility by an activated sludge method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Primary sedimentation tank, 2 ... Aeration tank, 2a ... First aeration tank, 2b ... Second aeration tank, 3 ... Final sedimentation tank, 4 ... Sludge return means, 5,5 '... Stirring device, 6 ... aeration device, 7 ... mixing tank

Claims (4)

A sewage treatment method using an activated sludge method using at least one sewage treatment tank, wherein contents are horizontally stirred in the sewage treatment tank in the presence of a bulking control agent. The sewage treatment method according to claim 1, wherein the stirring is further performed in the presence of at least one selected from a cationic polymer flocculant, an inorganic flocculant, a clay mineral, an enzyme preparation, and an aerobic microorganism. . The sewage treatment tank is an aeration tank, or provided separately from the aeration tank, cultivates a culture of aerobic microorganisms, characterized in that it is a mixing tank for flowing the culture into the aeration tank. The sewage treatment method according to claim 1 or 2, wherein The sewage treatment method according to claim 3, wherein the aerobic microorganism is cultured in the mixing tank using one or more selected from returned sludge, raw sewage water, aeration tank water, and treated water.

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