Microbial reaction tank

Abstract

DC60 (05 / 09 / 57) What was revealed was a microbial reaction tank, which, despite having a larger capacity,... It is also possible to treat with anaerobic / oxygen-dependent microorganisms, and it can also reduce costs. The expenses for construction and the wastewater treatment process that uses that include two external tanks, An inner cylindrical tank 3, with upper / lower openings, is positioned inside this outer tank. The circulation control device 4 controls the circulation rate within the tank of treated water and is installed. Placed on top of the inner tank of this cylinder is a cylindrical control plate, number 5, which is mounted around the circumference. Outside the top of the cylindrical tank, a sediment settling device is installed, along with a quality measurement device. The treated water (6 units) is installed on the outside and inside of the cylindrical inner tank, along with the wastewater outlet. 10. These are installed in the recirculation path of the treated water that circulates in the outer and inner tanks. The inlet and outlet for treated water 11 are installed on top of the external tank with a protective device. Solidification agent 12 prevents the solidified sludge from hardening.

Description

[0001] The present invention relates to a microbial reaction tank, and more particularly to a device for preventing the accumulation of sludge in a microbial reaction tank.

[0002] Wastewater containing high concentrations of nitrogen, phosphorus, and organic pollutants that increase biochemical oxygen demand (hereinafter referred to as BOD) and suspended solids concentration (hereinafter referred to as SS) is a cause of environmental pollution, such as river pollution and red tide outbreaks. Conventionally, the so-called modified Barnard process, which is one of the aerobic-anaerobic circulation methods, has been known as a method for treating wastewater containing such high concentrations of pollutants. In this method, in order to reuse the alkali released during the denitrification reaction in the nitrification reaction, the denitrification process in the activated sludge treatment process is divided into two stages: a first denitrification tank and a second denitrification tank located before and after the first nitrification tank, and a second nitrification tank is provided after the second denitrification tank, and the mixed liquid flowing out from the first and second nitrification tanks is circulated to the first denitrification tank.

[0003] However, this method of wastewater treatment has the following problems. (1) High concentrations of ammoniacal nitrogen have bactericidal properties themselves, and therefore often inhibit the activity of activated sludge in the activated sludge treatment process. As a result, the activated sludge treatment becomes insufficient. (2) In so-called modified Barnard processes, the hydrogen ion concentration (hereinafter referred to as pH) decreases as the nitrification reaction progresses in the nitrification tank. However, since the nitrification reaction is pH-dependent, a decrease in pH slows down the nitrification reaction. As a result, activated sludge treatment becomes insufficient, and phosphorus removal also becomes insufficient. (3) If activated sludge treatment is insufficient and the denitrification reaction is slowed, the concentrations of residual ammonia, nitrate ions, and nitrite ions will increase, resulting in a higher BOD that depends on these nitrogen compounds, and insufficient wastewater treatment. (4) In wastewater containing high concentrations of pollutants, high concentrations of activated sludge are required, which inevitably leads to a tendency for the concentration of activated sludge suspended solids (MLSS) and other factors to be high. As a result, supplying oxygen becomes difficult, as does stirring the activated sludge and solid-liquid separation in the sedimentation tank. (5) When denitrification and denitrification are performed by activated sludge treatment on wastewater that has a high nitrogen content despite a low concentration of organic pollutants, problems such as pH reduction and sludge floating due to denitrification may occur.

[0004] In order to address the above method, the present inventors have proposed a microbial reaction tank and a wastewater treatment method using the same that can efficiently treat activated sludge in wastewater containing high concentrations of nitrogen components, phosphorus components, organic substances, and other pollutants (Patent Document 1). This microbial reaction tank has an inner tank having a nitrification reaction section and a denitrification reaction section connected vertically by turbine blades.

[0005] Japanese Patent Application Publication No. 11-128987

[0006] However, in the conventional microbial reaction tank described above, the anaerobic tank for denitrification, which is formed in the lower part of the inner tank, and the aerobic tank for nitrification, which is formed in the upper part of the inner tank, are connected only by turbine blades. As the capacity of the reaction tank increases, there is a problem that stirring in each tank becomes insufficient and the anaerobic or aerobic reaction does not proceed sufficiently. In addition, there is a problem that the construction cost of the reaction tank increases, and the cost of fixing the inner tank inside the outer tank also increases.

[0007] Furthermore, as the capacity of the reaction tank increases, the problem arises that activated sludge accumulates inside the tank. When sludge accumulates, it can become difficult to circulate the treated water and sludge in the reaction tank. In particular, when solids such as oil and sludge, and adhesive suspended solids are mixed in, the circulation of the sludge becomes difficult. The present invention was made to address these problems and aims to provide a microbial reaction tank that can efficiently treat activated sludge in wastewater containing high concentrations of pollutants, can continuously perform anaerobic and aerobic microbial treatment while maintaining a high internal circulation rate even when the reaction tank capacity is large, and can prevent the accumulation of activated sludge in the tank.

[0008] The microbial reaction tank of the present invention comprises an outer tank, a cylindrical inner tank disposed inside the outer tank and having openings at the top and bottom, a circulation rate control device provided at the top of the cylindrical inner tank for controlling the circulation rate of the water to be treated inside the tank, a cylindrical control plate provided on the outer circumference of the top of the cylindrical inner tank for settling sludge, a water quality measuring device provided on the outside and inside of the cylindrical inner tank, and a raw water supply port provided in the circulation path of the water to be treated circulating inside the outer tank and the inner tank, and a treated water discharge port provided at the top of the outer tank. The cylindrical inner tank constituting the microbial reaction vessel is divided into an upper and lower cylindrical section by a partition wall having a communication hole in the center. The upper cylindrical section is an aerobic microbial treatment tank with a truncated cone shape at its apex, with open top and bottom surfaces, and multiple air inlets provided around the communication hole inside the upper cylindrical section and around the periphery of the partition wall. The lower cylindrical section is an anaerobic microbial treatment tank with an opening at its bottom. A stirring device for agitating the contents of the aerobic and anaerobic microbial treatment tanks, and a sedimentation and immobilization prevention device for preventing the settling and immobilization of the settled sludge, are provided inside and outside the outer and inner tanks. The microbial reaction tank includes means for detecting at least one measurement value selected from the pH, oxidation-reduction potential (hereinafter referred to as ORP), and dissolved oxygen content (hereinafter referred to as DO) of the water to be treated, as measured by the water quality measuring device described above, and means for controlling the circulation rate of the water to be treated in the tank to 3 to 20 by controlling at least one amount selected from the opening and closing of a liquid level adjustment valve, the vertical movement of a liquid level adjustment control plate, and the amount of air blown in from the air inlet, provided in the circulation rate control device described above, according to the detected measurement value. Here, the circulation rate of the water to be treated in the reaction tank refers to the amount defined by the following formula. Water circulation rate = Amount of water to be treated discharged from the top of the inner tank (m³) 3 / day) / Raw water supply amount (m 3 / day) The microbial reaction tank is characterized in that raw water supplied from the raw water inlet circulates within the tank along with activated sludge through the inside of the cylindrical inner tank, the outer surface of the cylindrical inner tank, and the activated sludge settled at the bottom of the outer tank, thereby enabling continuous anaerobic and aerobic microbial treatment. In particular, the raw water supply port is characterized by having multiple discharge ports or slits provided in an annular raw water supply section located at the bottom of the opening of the anaerobic microbial treatment tank. Furthermore, the lower part of the cylinder is characterized by having a volume of 1 / 10 to 1 times that of the upper part of the cylinder. ​​

[0009] The sedimentation and immobilization prevention device attached to the above-mentioned microbial reaction tank is characterized by: (1) a vibrating device provided on the inner wall or outer wall of the lower part of the outer tank where the sludge settles; (2) a device comprising a vibrating plate provided near the inner wall and a vibration generator provided on the upper part of the outer tank that transmits vibrations to the vibrating plate; (3) a scraper provided on the inner wall of the lower part of the outer tank where the sludge settles; (4) an agitation flow generating device that generates an agitation flow of sludge along the inner wall of the lower part of the outer tank, and in particular is a movable fluid spray nozzle that sprays fluid while moving along the inclined surface of the inner wall, or a fluid spray nozzle fixed at predetermined intervals on the inclined surface of the inner wall; (5) a pump that sucks up the sludge settled in the lower part of the outer tank and discharges it into the anaerobic microbial treatment tank while the agitation flow generating device moves along the inclined surface or lower surface of the inner wall, or a pump that is fixed at predetermined intervals on the inclined surface or lower surface of the inner wall and sucks up the sludge settled in the lower part of the outer tank and discharges it into the anaerobic microbial treatment tank.

[0010] The microbial reaction tank of the present invention is equipped with a sedimentation and immobilization prevention device consisting of a vibrator, a vibrating plate provided near the inner wall, a scraper provided on the inner wall, or a stirring flow generator on the inner wall of the lower part of the outer tank where the sludge settles, so that the sludge can be prevented from settling and becoming immobilized in the lower part of the microbial reaction tank. As a result, anaerobic and aerobic microbial treatment of raw water containing high concentrations of pollutants can be carried out continuously while maintaining a high circulation rate within the tank. Furthermore, because a sedimentation and immobilization prevention device is provided, the cylindrical inner tank can be made into a simple shape, and the installation of the microbial reaction tank becomes easier even when the capacity of the reaction tank is increased.

[0011] This is a cross-sectional view of a microbial reaction tank. This is a cross-sectional view of a microbial reaction tank equipped with a vibrator. This is a cross-sectional view of a microbial reaction tank equipped with another vibrator. This is a cross-sectional view of a microbial reaction tank equipped with a self-propelled scraper. This is a cross-sectional view of a microbial reaction tank equipped with a mobile fluid spray nozzle. This is a cross-sectional view of a microbial reaction tank equipped with a fixed fluid spray nozzle. This is a cross-sectional view of a microbial reaction tank equipped with a mobile fluid discharge pump. This is a cross-sectional view of a microbial reaction tank equipped with a fixed fluid discharge pump. This is a diagram showing the circulation path of the treated water and activated sludge in the microbial reaction tank.

[0012] The microbial reaction vessel of the present invention will be explained with reference to Figure 1. Figure 1 is a cross-sectional view of the microbial reaction vessel. The microbial reaction tank 1 consists of an outer tank 2, a cylindrical inner tank 3 located inside the outer tank 2, a circulation rate control device 4 provided at the top of the cylindrical inner tank 3, a cylindrical control plate 5 provided on the outer circumference of the cylindrical inner tank 3, and a water treatment quality measuring device 6. A sludge outlet 13 may be provided. This invention does not limit the volume of the water tank in the microbial treatment equipment, and can be applied to both small-scale and large-scale systems. However, its effects are most pronounced when the microbial reaction tank 1 is 20 m³. 3 Preferably 30 to 6000 m 3 This is the case when applied to a microbial reaction vessel having an internal volume of 6000 m³. 3 When it exceeds 20m, it becomes difficult to create a circulating flow. 3 In the case of smaller-scale systems, the advantages of circulating the sludge up and down within the microbial reaction tank 1 diminish.

[0013] The outer tank 2 has a cylindrical appearance consisting of a base 2a which forms the bottom, a cylindrical side surface 2b and an upper surface 2c. A rotating shaft 7 for attaching stirring blades, etc., is provided at the center of the cylinder. This rotating shaft 7 is rotatably fixed by a frame 2d provided at the center of the base 2a and a bearing 2e provided at the center of the upper surface 2c. The rotating shaft 7 is also rotated by a drive device 2f. The upper surface 2c rotatably fixes the rotating shaft 7 and also holds the cylindrical inner tank 3 with a support, etc. A raw water supply port 10 is provided at the bottom of the outer tank 2, which is below the cylindrical inner tank 3. The raw water supply port 10 consists of multiple discharge ports 10b or slits provided in the annular raw water supply section 10a, which is located below the lower opening 3f of the cylindrical inner tank 3. By arranging the raw water supply port 10 in this way, the anaerobic sludge is sufficiently agitated. Note that this raw water supply port 10 can be provided in locations other than the bottom of the cylindrical inner tank 3, as long as it is part of the circulation path of the water to be treated. Furthermore, a treated water outlet 11 is provided at the top of the outer tank 2, and a sedimentation and solidification prevention device 12 is provided on the inner and outer surfaces of the outer tank to prevent the settled sludge from settling and becoming fixed.

[0014] The sedimentation and solidification prevention device 12 for preventing the sedimentation and solidification of settled sludge will be described below. The sedimentation and immobilization prevention device 12 may be one of the devices described below, or it may be a sedimentation and immobilization prevention device that combines multiple such devices. (1) A vibrating device installed on the inner or outer wall of the lower part of the outer tank where the sludge settles. Figure 2 shows a cross-sectional view of a microbial reaction tank equipped with a vibration device. The vibration generator 12a can be fixedly installed on the inclined portion of the lower part of the outer tank. Examples of this vibration generator include an electromagnetic vibrator and a knock-type hammer. It is preferable that these vibration devices operate intermittently using a timer. The vibration of the lower surface of the outer tank itself can prevent the sludge from settling and becoming fixed.

[0015] (2) A sedimentation and immobilization prevention device having a vibrating plate provided near the inner wall and a vibration generator that transmits vibrations to the vibrating plate Figure 3 shows a cross-sectional view of a microbial reaction tank equipped with other vibration devices. Figure 2 shows a vibration device installed on the outer wall of the lower part of the outer tank. However, if the vibrating plate or hammer is attached to the inner wall of the lower part of the outer tank, sludge tends to accumulate around the vibrating plate, etc. Therefore, when attaching a vibrating plate to the inner wall of the lower part of the outer tank, as shown in Figure 3, a vibration generator 12a is installed at the top of the outer tank, and the vibration is transmitted to the vibrating plate 12b via a rod 12c. The vibration of the vibrating plate 12b prevents the sludge from settling and becoming fixed.

[0016] (3) A scraper provided on the inner wall of the lower part of the outer tank where the sludge settles Figure 4 shows an example of a cross-sectional view of a microbial reaction tank equipped with a self-propelled scraper. A mobile device 12e that can move along the upper periphery of the outer tank is attached to the upper periphery of the outer tank, and a scraper 12d is attached to the tip of this mobile device 12e. By making this scraper 12d self-propel along the inner wall of the lower part of the outer tank, the settled sludge is loosened and given fluidity. Sludge that has been given fluidity will no longer settle and become fixed.

[0017] (4) Agitation flow generating device that generates a sludge agitation flow along the inner wall of the lower part of the outer tank Figures 5 to 8 show the sludge agitation flow generation device. Figure 5 is a cross-sectional view of a microbial reaction tank equipped with a movable fluid spray nozzle that sprays fluid while moving along the inclined surface of the inner wall, and Figure 6 shows an example of fluid spray nozzles fixed at predetermined intervals on the inclined surface of the inner wall. Figures 7 and 8 show examples of discharge pumps that can be used instead of nozzles. As shown in Figure 5, the nozzle 12f, positioned on the inclined surface of the lower part of the inner wall of the outer tank, can spray fluid supplied from a blower or pump mounted on a mobile device 12e attached to the upper periphery of the outer tank onto the accumulated sludge. Examples of fluids include air, water, and sludge. By spraying fluid from the nozzle 12f onto the accumulated sludge, fluidity can be given to the accumulated sludge, preventing it from settling and becoming fixed. The nozzles 12g shown in Figure 6 are fixed at predetermined intervals in the circumferential and inclined directions of the inclined surface at the lower part of the inner wall of the outer tank, so that fluid can be uniformly sprayed onto the pre-accumulated sludge. By continuously or intermittently spraying fluid from these nozzles 12g, fluidity can be given to the accumulated sludge, preventing it from settling and becoming fixed. It is important that the fixed nozzles 12g are positioned above the inclined surface at the lower part of the inner wall of the outer tank, and that the piping is installed in the direction of the circulation flow, so as not to obstruct the circulation flow of the sludge as much as possible.

[0018] As shown in Figure 7, the mobile discharge pump 12h, which is positioned on the inclined surface or bottom surface of the lower part of the inner wall of the outer tank, can self-propel along the lower part of the inner wall of the outer tank by means of a moving device 12e attached to the upper periphery of the outer tank. The discharge pump 12h is equipped with a suction nozzle 12i for sucking up sludge that has settled in the lower part of the outer tank, and a discharge port 12j for discharging the sucked-up sludge into the anaerobic microbial treatment tank. By self-propelling along the lower part of the inner wall of the outer tank while sucking up and discharging sludge, fluidity can be given to the accumulated sludge, preventing it from settling and becoming fixed. The fixed discharge pump 12h, shown in Figure 8, is positioned to be fixed to the inclined surface or bottom surface of the lower part of the inner wall of the outer tank. It is positioned in a location where sludge accumulation is likely to occur. This discharge pump 12h is equipped with a suction nozzle 12i for sucking up sludge that has settled at the bottom of the outer tank, and a discharge port 12j for discharging the sucked-up sludge into the anaerobic microbial treatment tank. It is important that the fixedly positioned discharge pump 12h is installed in a manner that does not obstruct the sludge circulation flow. For example, all pump piping should be installed parallel to the flow direction of the sludge circulation flow.

[0019] The cylindrical inner tank 3 is placed inside the outer tank, which is equipped with the above-mentioned sedimentation and immobilization prevention device 12. The cylindrical inner tank 3, which has a nearly circular cross-section, is divided into an upper cylindrical section 3c and a lower cylindrical section 3d by a partition wall 3a. A communication hole 3b is provided in the center of the partition wall 3a, connecting the upper cylindrical section 3c and the lower cylindrical section 3d. The presence of this partition wall 3a ensures that even when the volume of the microbial reaction tank increases, the upper cylindrical section 3c and the lower cylindrical section 3d are sufficiently separated, allowing activated sludge treatment to be carried out in each section. Aerobic microbial treatment reactions can be carried out sufficiently in the upper cylindrical section 3c, and anaerobic microbial treatment reactions can be carried out sufficiently in the lower cylindrical section 3d. If the area of ​​the partition wall 3a increases, it can be reinforced with a support member 3g or the like. The connecting hole 3b has a diameter large enough to allow the activated sludge treated with anaerobic microorganisms to move from the lower part of the cylinder 3d to the upper part of the cylinder 3c, which is the aerobic microorganism treatment area. The diameter of this connecting hole 3b is adjusted according to the volume of the microbial reaction tank, the properties and amount of raw water to be treated, etc.

[0020] The upper part 3c of the cylinder has a frustoconical apex with an open top and bottom. That is, the tip of the cylindrical part is shaped to narrow in diameter at a predetermined angle in the height direction. The inclination angle of the cross-section in the height direction passing through the center of the frustoconical is 40 to 60 degrees, preferably 45 degrees. By setting the inclination angle within this range, the sludge contained in the water to be treated discharged from the upper part of the aerobic tank flows down the outer surface of the frustoconical, making it easier for the sludge to coagulate and enabling rapid forced settling of the sludge. In addition, the coagulation of the sludge makes it easier to separate the sludge from the purified treated water. The upper cylindrical part 3c is an aerobic microbial treatment tank with air inlets 8 and 8a inside. The air inlets 8 are located around the central axis 7 and around the communication hole 3b, and can be fixed on the partition wall 3a by support columns (not shown). Preferably, the air outlet of the air inlets 8 is positioned downwards, as this contributes to stirring the water to be treated and the sludge in the aerobic tank. The air inlet 8a can be an air blowing section 8b arranged in an annular shape in plan view on the peripheral edge of the partition wall inside the upper part 3c of the cylinder, with multiple air holes 8c provided in this air blowing section 8b, or a slit formed on the upper or side surface of the air blowing section 8b. By adjusting the amount of air blown in from air inlets 8 and 8a and the control amount of the circulation rate control device described later, the circulation rate of the water to be treated can be varied within the range of 3 to 20 without using a circulation pump. This makes it easy to set appropriate nitrification conditions for aerobic microbial treatment and appropriate denitrification conditions for anaerobic microbial treatment. Furthermore, since the forced sedimentation principle on the outer surface of the aerobic microbial treatment tank with the above-mentioned inclination angle allows for extremely efficient solid-liquid separation of sludge, aerobic and anaerobic microbial treatment reactions can be efficiently carried out in the same vertical tank. Furthermore, an alkali supply port or an acid supply port, not shown in the diagram, may be provided inside the aerobic tank.

[0021] The lower cylindrical part 3d is an anaerobic microbial treatment tank having a volume of 1 / 10 to 1 times that of the upper cylindrical part. Within this volume range, for example, aerobic microbial treatment reactions and anaerobic microbial treatment reactions can be efficiently carried out on raw water containing high-concentration nitrogen-containing pollutants. A denitrifying bacteria nutrient supply port, not shown in the figure, can be provided inside the anaerobic microbial treatment tank. Furthermore, when there are few hydrogen donors in the raw water and denitrification is performed by supplying hydrogen donors such as methanol or acetic acid to remove nitrogen from nitrates, it is preferable to make the volume of the anaerobic microbial treatment tank larger than that of the aerobic microbial treatment tank. The shape of the lower part 3d of the cylinder is an inverted frustoconical shape with an opening 3f that is larger in area than the opening 3e of the upper part 3c of the cylinder. In other words, the tip of the cylindrical part is shaped to narrow in diameter at a predetermined angle downwards. By increasing the area of ​​the opening 3f, the agitation of sludge in the anaerobic microbial treatment tank can be facilitated. When the shape of the lower part 3d of the cylinder is the inverted truncated cone shape described above, it is preferable that the lower inner surface 2g of the outer tank 2 be at the same angle as the predetermined angle described above, in order to prevent the sludge from settling and becoming fixed.

[0022] The cylindrical inner tank 3 is equipped with a stirring device to ensure that the treatment reaction between the water to be treated and the activated sludge is carried out sufficiently in the aerobic microbial treatment tank which is the upper part of the cylinder 3c and the anaerobic microbial treatment tank which is the lower part of the cylinder 3d. The stirring device is preferably a stirring blade 7a or 7b fixed to a rotating shaft 7 attached to the center of the cylindrical inner tank 3. The stirring blade 7a is preferably a turbine blade provided in the upper part 3c of the cylinder that can sufficiently carry out the aerobic microbial treatment reaction. In addition to a turbine blade, any device that can mix air and water with a relatively low rotational speed and without significantly reducing aeration performance depending on the amount of air blown in can be used. The stirring blade 7b is located inside the lower part 3d of the cylinder. Any stirring blade capable of carrying out the anaerobic microbial treatment reaction can be used, but turbine blades or propeller blades are preferred.

[0023] The partition wall 3a provided inside the cylindrical inner tank 3 is supported by support columns 9 that are fixed to and erected on the base 2a which forms the bottom surface of the outer tank 2. The cylindrical inner tank 3 is held inside the outer tank by the support of the support column 9 and by a support device that bridges across the upper part of the outer tank 2.

[0024] A circulation rate control device 4 for controlling the circulation rate of the water to be treated within the reaction tank is provided at the top of the cylindrical inner tank 3. Specifically, the circulation rate of the water to be treated within the reaction tank is controlled by the circulation rate control device 4 by opening and closing a liquid level adjustment valve or by moving a liquid level adjustment plate up and down. The water level of the water to be treated is lowest when the liquid level adjustment valve is fully open or when the liquid level adjustment plate is at its lowest position. The water level is indicated by A. The circulation rate within the reaction vessel can also be controlled by the amount of air injected from the air inlets 8 and / or 8a. Increasing the amount of air injected increases the circulation rate. This can also be done by combining the opening and closing of the liquid level control valve with the adjustment of the air volume. As anaerobic and aerobic microbial treatment tanks become larger, aeration air alone may not be sufficient to maintain the sludge circulation flow rate, and excessive air injection may cause adverse effects. To address such situations, the air inlet shown in Figure 1, 8a, is necessary. This air inlet 8a, which has poor aeration efficiency, has the advantage of making it significantly easier to adjust the air injection volume and ORP. For example, the air inlet 8a is installed in the aerobic portion of the upper surface of the partition wall 3a, with the stirring blade 7a at its center, and an annular air injection section 8b in plan view that communicates with an external blower, etc., and this air injection section 8b is provided with holes or slits. This not only simply increases the amount of air, but also exerts the baffling effect of the stirring blade 7a, resulting in a synergistic effect that enables efficient stirring.

[0025] By opening and closing the liquid level adjustment valve and / or adjusting the amount of air injected, the circulation rate of the water to be treated can be varied without using a pump. As will be described later, the water to be treated is circulated from the aerobic microbial treatment tank 3c through the cylindrical control plate 5 located outside this tank to the anaerobic microbial treatment tank 3d, and then from the anaerobic microbial treatment tank 3d back to the aerobic microbial treatment tank 3c, thereby performing denitrification, dephosphorization, etc. Therefore, by controlling the circulation rate of the water to be treated according to the detected value based on a predetermined control program, optimal denitrification, dephosphorization, etc. can be performed.

[0026] A cylindrical control plate 5 is positioned on the upper outer circumference of the cylindrical inner tank 3. The cylindrical control plate 5 is a cylinder with an open top and bottom, and the bottom surface 5a of the cylindrical control plate 5 is positioned close to the inclined surface of the cylindrical inner tank 3. A sludge settling section is formed in this close-proximity inclined surface portion, where sludge is concentrated and treated water is separated. Furthermore, by positioning the bottom surface 5a close, rapid forced settling of the sludge becomes possible. It is preferable that the distance of the bottom surface 5a from the inclined surface of the cylindrical inner tank 3 can be adjusted. The shape of the cylindrical control plate 5 can be a straight cylinder with the same area of ​​openings on the top and bottom surfaces, or an inverted truncated cone shape where the opening area of ​​the top surface is larger than the opening area of ​​the bottom surface. Within the microbial reaction tank, water quality measuring devices 6 are installed both inside and outside the cylindrical inner tank 2. These water quality measuring devices 6 measure the pH, ORP, and DO of the water being treated.

[0027] The water circulation rate in the microbial reaction tank of the present invention is 3 to 20, preferably 5 to 20. If the water circulation rate is less than 3, the aerobic microbial treatment reaction will occur more easily, and if it exceeds 20, the balance between the aerobic microbial treatment reaction and the anaerobic microbial treatment reaction will be disrupted, making it impossible to denitrify and dephosphorize the raw water. In other words, by setting the water circulation rate within this range, the ORP of the water to be treated, as measured by the water quality measuring device, can be maintained at -10 mV or less, preferably -50 mV or less, in the anaerobic microbial treatment reaction tank, and at +10 mV or more, preferably +100 mV or more, in the aerobic microbial treatment reaction tank. As a result, the aerobic microbial treatment reaction and the anaerobic microbial treatment reaction are carried out sufficiently, and denitrification and dephosphorization are performed continuously. Under these conditions, the pH in the aerobic microbial treatment reaction tank is in the range of 4.5 to 8.5, preferably 5.5 to 7.5.

[0028] The wastewater treatment method using the microbial reaction tank 1 is a wastewater treatment method that treats raw water by a treatment process including an activated sludge treatment step, the activated sludge treatment step includes a sludge circulation step that forms a circulating flow of activated sludge and a raw water addition step that adds raw water to the circulating flow of activated sludge. The circulating flow of the activated sludge circulates from the anaerobic microorganism treatment tank through the aerobic microorganism treatment tank, and the treated water is separated in the sludge sedimentation section and the sludge is concentrated, and this concentrated sludge is sent to the anaerobic microorganism treatment tank. Further, the activated sludge treatment process is a sludge circulation process and a raw water addition process that are treated using the above-described microorganism reaction tank.

[0029] The wastewater treatment method using the microorganism reaction tank 1 has the following excellent characteristics as compared with the conventional wastewater treatment method. In the conventional wastewater treatment method, the raw water and the returned sludge are mixed at a certain ratio and flow into the aeration tank, and until the returned sludge contacted at that time and the sludge and the treated water are separated in the sedimentation tank, which is the next process, until the activated sludge and the raw water that were first contacted and mixed are discharged, only the same activated sludge bacteria are contacted and the raw water is pushed out and flows. The wastewater treatment method using the microorganism reaction tank 1 is a method of forming a circulating flow of activated sludge that circulates up and down and adding raw water into the circulating flow. To create the circulating flow of the activated sludge, without using a circulation pump, the upward flow by the aeration air used for microorganism treatment is utilized to form the circulating flow of the sludge, so it is an energy-saving wastewater treatment method. Further, it is a treatment method capable of efficiently performing the aeration of the aerobic microorganism treatment tank. The addition position of the raw water may be anywhere within the path of the circulating flow, but preferably it is the aerobic microorganism treatment tank. More preferably, the anaerobic microorganism treatment tank is suitable. In the case of the treatment using the circulating flow in the wastewater treatment method of the present invention, even for raw water with a BOD of at least 800 mg / L or more and a total nitrogen amount (hereinafter referred to as T-N) of 40 mg / L or more, the BOD of the treated water is usually extremely low, 20 mg / L or less, and generally, as the quality of the discharged water, it can be operated with a BOD of 10 mg / L or less. Furthermore, if raw water is added to the sludge sedimentation section in the circulating flow path formed on the outer surface of the cylindrical inner tank, which is an aerobic microbial treatment tank, contact between the sludge and the raw water may become insufficient, resulting in insufficient adsorption of pollutants. In such cases, some untreated pollutants from the raw water may be mixed into the treated water, leading to deterioration of the treated water. However, in cases where water quality regulations are lax, for example, in primary treatment facilities for sewage discharge where the BOD is 300 mg / L or less or 600 mg / L or less, it may be possible to add raw water to the sludge sedimentation section in the circulating flow path.

[0030] The following describes in detail the method for treating raw water containing high-concentration nitrogen-containing pollutants using the microbial reaction tank 1 with reference to Figure 9. Figure 9 is a diagram showing the circulation pathway of the water to be treated and activated sludge in the microbial reaction tank 1. In Figure 9, the shaded areas are areas with high concentrations of activated sludge, and the arrows indicate the circulation direction of the water to be treated and activated sludge. The raw water to be treated, which contains pollutants from which solid components have been separated by a wedge wire screen or the like, is continuously supplied from a raw water supply port 10 located at the bottom of the microbial reaction tank 1. It is preferable that the BOD and SS of the supplied raw water be measured in advance. The wastewater treatment method using the microbial reaction tank 1 of the present invention is suitable for treating wastewater discharged from food factories, and suitable raw water for this purpose is, for example, raw water containing a BOD of 800 mg / L or more, a chemical oxygen demand (hereinafter referred to as COD) of 300 mg / L or more, and a T-N of 40 mg / L or more. It is also suitable for treating raw water containing a n-hexane extractable oil concentration (hereinafter referred to as n-Hex) in the range of 50 mg / L or more.

[0031] The microbial reaction tank 1 is filled with activated sludge at a concentration of 5,000 to 12,000 mg / L in terms of solid content. The raw water first comes into contact with the activated sludge in an anaerobic state within the lower part of the cylinder 3d, where a denitrification reaction takes place. The raw water to be treated, supplied from the raw water supply port 10, and the circulating activated sludge are circulated within the lower part of the cylinder 3d by the rotation of the stirring blades or the ejection of air from the diffuser pipes, where an anaerobic microbial treatment reaction takes place. Next, raw water and activated sludge move through the communication hole 3b into the upper part 3c of the cylinder into which air is being blown, and while contacting the activated sludge in the upper part 3c of the cylinder in an aerobic state, the interior of the upper part 3c of the cylinder circulates due to the rotation of the stirring blade or the ejection of air from the air injection port, and a nitrification reaction, which is an aerobic microbial treatment reaction, proceeds. As the nitrification reaction progresses, the pH etc. of the treated water decreases. The pH, ORP, and DO of the treated liquid are measured by the treated water quality measuring device 6, and based on these values, the circulation amount of the raw water or the treated water is determined. Specifically, the air blowing amount etc. is adjusted so that the ORP can be maintained at +10 mV or more in the aerobic reaction treatment section where the nitrification reaction is carried out and at -10 mV or less in the anaerobic reaction treatment section where the denitrification reaction is carried out, and the treated water is circulated. The circulation amount can be easily carried out without using a circulation pump etc. by controlling the air amount and / or the circulation rate control device. Therefore, the wastewater treatment method of the present invention is an energy-saving type wastewater treatment method. Further, since each unit of the microbial reaction can be adjusted in the facility including the microbial reaction tank of the present invention, it is easy to program these controls in advance and perform unmanned automatic operation, and it has the characteristics as a labor-saving plant.

[0032] The circulation rate is controlled by the circulation rate control device 4, and a part of the treated water and activated sludge discharged from the upper part of the upper part 3c of the cylinder flows down along the outer peripheral surface of the frustum of a cone having a 45-degree inclination angle. The discharged treated water and activated sludge pass through the sludge concentration section 5b formed by the cylindrical control plate 5 disposed close to the inclined surface of the outer peripheral surface of the frustum of a cone, enabling rapid forced sedimentation of the activated sludge. Also, separation of the purified treated water and the activated sludge becomes easy, and the separated treated water is discharged from the treated water discharge port 11. The rapidly forced sedimented activated sludge is concentrated and deposited between the inner surface of the outer tank and the outer peripheral surface of the inner tank. This deposited activated sludge moves to the anaerobic microbial treatment reaction section while being mixed with the treated water and circulates within the microbial reaction tank. The wastewater treatment method of the present invention can easily absorb fluctuations in the load of the raw water by circulating the activated sludge while being concentrated in the anaerobic / aerobic tank at a circulation rate of 3 to 20. Also, since the circulation rate is maintained within this range, the activated sludge is domesticated and becomes the activated sludge optimal for wastewater treatment.

[0033] In the microbial reaction tank, even when the BOD load of the raw water is low, if the nitrogen concentration is high, it is preferable to add a denitrifying bacteria nutrient composed of an organic substance such as a proton donor, for example, methanol, to the anaerobic reaction treatment section for treatment. In this case, since the pH of the treated water tends to rise, it is preferable to add a mineral acid such as hydrochloric acid.

[0034] The wastewater treatment method using the microbial reaction tank of the present invention may use one microbial reaction tank, or a plurality of tanks may be used. In this case, the effluent from the first tank is introduced into the raw water supply port of the second tank. Also, for example, when two microbial reaction tanks are connected in series, by changing the ratio of the volume of the nitrification reaction section to the volume of the denitrification reaction section in the second tank from the ratio in the first tank, wastewater treatment can be performed more effectively. Specifically, by making the volume ratio smaller than that of the first tank, denitrification and dephosphorization can be performed.

[0035] Further, the wastewater treatment method using the microbial reaction tank of the present invention can be combined with a conventional wastewater treatment method. For example, in a wastewater treatment facility consisting of the connection of an existing aerobic nitrification tank and an anaerobic denitrification tank, by supplying the effluent from each tank to the microbial reaction tank of the present invention, digestion of pollutants and denitrification / dephosphorization can be performed more effectively.

[0036] Examples The wastewater discharged from a food manufacturing factory was treated using the microbial reaction tank shown in FIG. 1. The wastewater before treatment had a BOD of 1200 mg / L, a chemical oxygen demand (hereinafter referred to as COD) of 750 mg / L, a T-N of 130 mg / L, an n-Hex of 250 mg / L, and an SS of 200 mg / L, and the amount of wastewater to be treated was 1500 m 3 / day.

[0037] The microbial reaction tank has an anaerobic microbial treatment section with a volume of 250 m 3 and an aerobic microbial treatment section with a volume of 650 m 3 . The treatment raw water circulation rate in the microbial reaction tank was circulated within the range of 3 to 6. As a pretreatment, the raw water was aerated and adjusted in a raw water aeration adjustment tank so that the ORP (Orientation Reduction Potential) was positive, and then sent to the microbial reaction tank for treatment. In the microbial reaction tank, the pH in the anaerobic microbial treatment tank was 6.9, the ORP was -350 mV, and the DO (Dose Oxygen) was 0, while the pH in the aerobic microbial treatment tank was 7.1, the ORP was +210 mV, and the DO was 1.1 mg / L. The microbial concentration in both the aerobic and anaerobic microbial treatment tanks was 6400 mg / L. Two 25 kW blowers were used for this process; one was connected to the piping of air inlet 8a in commercial operation, and the other was connected to air inlet 8, which is part of the aeration equipment, and operated with an inverter to adjust the air volume. The normal air volume for both blowers was 18 m³. 3 It was / minutes. The water quality of the effluent discharged from the microbial reaction tank was as follows: BOD 8 mg / L, COD 11 mg / L, n-Hex 0.8 mg / L, T-N 2 mg / L, and SS 8 mg / L. Furthermore, virtually no dehydrated cakes were observed. Next, vibration generators 12a, as shown in Figure 2, were fixed to the outside of the inclined section at the bottom of the outer tank of the microbial reaction tank at 1m intervals in the circumferential direction. These vibration generators are called vibration motors, have a voltage of 200V and 6 poles, and a vibration frequency of 15.6Hz. Sludge settling was prevented by a cycle of 20 minutes of vibration followed by 1 hour of rest. As a result, the sludge circulation flow improved, and the amount of water treated increased by 2000 m³ compared to when the vibration generator 12a was not used. 3 It improved day by day.

[0038] The wastewater treatment method described above allows for anaerobic-aerobic operation in the microbial reaction tank while suppressing the generation of harmful gases, thereby improving the self-digestion efficiency of the microbial cells. Furthermore, through the circulation of sludge, microbial cells capable of selectively decomposing sludge substances in the raw water are cultivated, making it possible to easily treat difficult-to-decompose pollutants. As a result, the effect of reducing the amount of dewatered cake discharged to almost zero was observed. Furthermore, compared to the conventional push-flow treatment method shown in the comparative example below, the wastewater treatment method according to this embodiment can reduce the amount of aeration airflow, so the electricity cost can be reduced by at least half, thus making a significant contribution to energy conservation.

[0039] Comparative Example 1 Comparative Example 1 of the present invention shows the treatment status before the introduction of the microbial reaction tank of the present invention in the same factory as the example. The water quality of the raw wastewater before treatment was the same as in the example, with BOD of 1200 mg / L, COD of 750 mg / L, T-N of 130 mg / L, n-Hex of 250 mg / L, and SS of 200 mg / L, and the amount of water to be treated was 1500 m³. 3 It is / day. Wastewater discharged from food manufacturing plants, 500m 3 After adjusting the raw water flow rate in the raw water treatment tank, 850 mg / L of polyaluminum chloride (PAC), 380 mg / L of 25% by weight caustic soda, and 1.5 mg / L of anionic polymer flocculant are added in the coagulation reaction tank to create coagulated flocs, which are then processed at a rate of 120 m 3 In a pressurized flotation tank, the flocculated flocs are separated by flotation, and after removing oil and suspended solids, the tank is filled to 1400m. 3 After treatment in an aerobic activated sludge treatment tank using an extrusion flow method, 350m 3 Sludge and treated water were separated in a sedimentation tank and discharged. Four 25kW aeration blowers were used to maintain the DO level at 1.5 mg / L or higher near the outlet of the aeration tank. The treated water quality after pressurized flotation treatment was BOD 900 mg / L, COD 550 mg / L, T-N 130 mg / L, n-Hex 10 mg / L, and SS 20 mg / L. Furthermore, the floating scum separated by pressurized flotation produced 22.8 tons of sludge with a water content of 96% by weight per day. Using cationic and anionic polymer flocculants, 6 tons of dewatered cake with a water content of 85% by weight were generated daily. Therefore, sludge disposal was required daily, and outsourced disposal of more than 150 tons of dewatered cake was required every month.

[0040] The water quality of the effluent separated in the sedimentation tank was as follows: BOD 18 mg / L, COD 25 mg / L, n-Hex 1 mg / L, T-N 25 mg / L, and SS 5 mg / L. Due to aeration conditions and fluctuations in the raw water, it was often difficult to maintain a pH of 6 or higher at all times when trying to reduce the BOD of the effluent to 20 mg / L or less.

[0041] Comparative Example 2 Comparative Example 2 shows the treatment conditions in the same factory as in the example, but without the use of a vibration generator, in order to clarify the effects of the present invention. The water quality of the raw wastewater before treatment was the same as in the example, with BOD of 1200 mg / L, COD of 750 mg / L, T-N of 130 mg / L, n-Hex of 250 mg / L, and SS of 200 mg / L, and the amount of water to be treated was 1500 m³. 3 It is / day. When the system was operated without the vibration generator 12a, the microbial concentration in the anaerobic and aerobic microbial treatment tanks fell below 4000 mg / L, the sludge interface increased, and the suspended solids (SS) in the treated water exceeded 50 mg / L. This is thought to be due to a decrease in the sludge sedimentation and separation capacity in the sedimentation section. Foaming also occurred on the outlet surface of the aerobic microbial treatment tank. In some cases, the BOD of the treated water exceeded 20 mg / L. Clearly, the amount of oil and undegraded substances adsorbed onto the circulating sludge increased, changing it into sludge that was more prone to adhesion, and in some cases, sludge circulation problems gradually progressed, resulting in treatment failures.

[0042] The microbial reaction tank of the present invention can continuously perform anaerobic and aerobic microbial treatment of raw water in a simple form, even when the reaction tank capacity is large, without substantially discharging excess sludge, and can therefore be used as a wastewater treatment facility containing high concentrations of pollutants. Furthermore, the wastewater treatment method using the microbial reaction tank of the present invention can be used as an environmentally friendly wastewater treatment method that causes less environmental damage. Compared to conventional push-flow activated sludge treatment methods, this method requires less aeration airflow, produces better treated water quality, generates almost no excess sludge, and consumes less electricity. Therefore, it is a particularly desirable wastewater treatment facility for factories manufacturing international products that aim for a clean factory environment.

[0043] 1 Microbial reaction tank 2 Outer tank 3. Cylindrical inner tank 4. Circulation Rate Control Device 5. Cylindrical control plate 6. Water quality measurement device for treated water 7. Rotation axis 8. Air intake 9 Support pillar 10. Raw water supply port 11 Treated water outlet 12. Device to prevent sedimentation and immobilization 13. Sludge outlet