JP6444574B1 - Water treatment system and water treatment method - Google Patents

Abstract

The water treatment system (100) includes an aeration tank (1), an aeration tank (1), an aeration device (2), an ozone purification tank (8), an ozone generator (11), and an ozone from the aeration tank (1). A transfer pipe (103) for transferring the sludge-containing treated water (5) to the septic tank (8), and a return pipe (105) for returning the sludge-containing treated water (5) injected with ozone gas to the aeration tank (1); The aeration tank (1) includes an aeration promoting unit (13) in which the aeration device (2) is disposed below and an aeration suppressing unit (14) in which the aeration device (2) does not exist below. The end port (103t) provided in the aeration tank (1) of the transfer pipe (103) is defined on the boundary K between the aeration promoting unit (13) and the aeration suppressing unit (14) or the aeration suppressing unit ( 14) Located in the surface layer of sludge-containing treated water.

Description

  The present application relates to a water treatment system and a water treatment method for treating water, and particularly to a water treatment system and a water treatment method for treating waste water containing an organic substance using ozone.

  Conventionally, a water treatment method such as a standard activated sludge method using microorganisms is known as a method for treating water such as wastewater containing organic matter. In this treatment method, wastewater is treated using sludge containing microorganisms. As wastewater treatment progresses, purification of wastewater is promoted, while microorganisms grow. When the microorganisms in the sludge grow while the treatment of the wastewater proceeds, sludge containing microorganisms and other suspended matters may be excessively generated as waste. The sludge generated excessively in this way is called surplus sludge.

  In the above-mentioned treatment method in which wastewater is treated using sludge containing microorganisms, specifically, microorganisms are present in a biological treatment tank for aeration, and biological treatment is performed by flowing wastewater into this biological treatment tank. Do. At this time, because sludge can be generated excessively in the biological treatment tank due to biological treatment, sludge that is necessary for purification of wastewater in the biological treatment tank and excessively generated sludge that is not necessary for purification of wastewater (excess sludge) Sludge-containing treated water containing both of these is produced.

  Excess sludge is sludge that is unnecessary for water treatment and must be discharged outside the wastewater treatment system. The discharged surplus sludge is subjected to incineration, landfill disposal, or fermentation under anaerobic conditions as industrial waste. Disposal of excess sludge requires significant energy, cost, and new land. Therefore, in the water treatment system and the water treatment method, reduction of the generated amount of excess sludge is required.

  As one method for reducing the amount of excess sludge generated, sludge volume reduction treatment using ozone gas is known. Specifically, sludge containing treated water containing sludge is transferred from the biological treatment tank to the outside of the tank, and ozone gas is injected into the transferred sludge containing treated water (for example, refer to Patent Documents 1 and 2). Moreover, you may inject | pour ozone gas with respect to the sludge isolate | separated from the treated water in the solid-liquid separation tank instead of the sludge containing treated water transferred from the biological treatment tank (for example, refer patent document 2, 3). The sludge-containing treated water that has been transferred from the biological treatment tank to the outside of the tank and injected with ozone gas is returned again to the biological treatment tank.

  Wastewater and other water that is subject to biological treatment includes not only organic substances but also inorganic substances such as sand and metals.Thus, sludge in biological treatment tanks is composed of organic sludge from which microorganisms and organic substances are collected, as well as sand and metals. It consists of inorganic sludge composed of inorganic substances. Inorganic substances are divided into oxide-forming inorganic substances that react with ozone gas such as iron and manganese to form oxides, and non-reactive inorganic substances that do not consume ozone gas such as sand and aluminum phosphate.

  By the way, since ozone gas cannot decompose inorganic substances in sludge and decomposes only organic sludge in sludge, the amount of excess sludge can be reduced by the amount of decomposed organic sludge. At this time, a portion of the injected ozone gas is consumed by the oxide-forming inorganic substance that reacts with ozone gas such as iron and manganese to form oxides, so only the amount of ozone gas consumed is injected into the sludge-containing treated water. The amount of ozone gas that needs to be increased.

  In sludge volume reduction treatment using ozone gas, if the amount of ozone gas to be injected is excessive, organic sludge necessary for purification of wastewater in the biological treatment tank is also decomposed and the quality of the treated water can be deteriorated. Thereby, the procurement cost of ozone gas increases. On the other hand, if the amount of ozone gas to be injected is insufficient, there is a possibility that the organic sludge generated excessively cannot be decomposed, and the disposal cost of the sludge increases. Therefore, it is important to inject a sufficient amount of ozone gas so that only the excessively generated organic sludge that is not necessary for wastewater purification can be decomposed. Therefore, in Patent Document 1, the microbial activity of the sludge-containing treated water in the biological treatment tank is measured, and the amount of ozone gas to be injected is controlled according to the microbial activity. Moreover, in patent document 3, the amount of sludge in the sludge containing treated water in a biological treatment tank is measured, and the quantity of ozone gas to inject | pour is controlled according to the amount of sludge.

JP 2013-226536 A JP 2004-141746 A Japanese Patent Laid-Open No. 11-347596

  In conventional water treatment systems that apply sludge volume reduction treatment using ozone gas, sludge-containing treated water containing sludge composed of organic sludge, oxide-forming inorganic substances, and non-reactive inorganic substances is stored in the biological treatment tank. Although the ozone treatment is carried out by transferring it outside, it does not have a mechanism for suppressing the transfer of the oxide-forming inorganic substance that consumes ozone gas to the outside of the tank. Therefore, a part of the injected ozone gas is consumed by the oxide-forming inorganic substance, and there is a problem that the amount of ozone gas that needs to be injected into the sludge-containing treated water increases, thereby increasing the procurement cost of the ozone gas.

  The present application discloses a technique for solving the above-mentioned problems. Sludge-containing treated water containing sludge is transferred from a biological treatment tank to the outside of the tank, and ozone gas is injected into the transferred sludge-containing treated water. In the water treatment system and the water treatment method to suppress the increase in the amount of ozone gas that needs to be injected into the sludge-containing treated water by suppressing the transfer amount of the oxide-forming inorganic substance that consumes ozone gas to the outside of the tank, An object of the present invention is to provide a water treatment system and a water treatment method capable of reducing the risk that the amount of ozone gas injected is excessive or insufficient relative to the amount of organic sludge to be ozone-treated in sludge-containing treated water. To do.

The water treatment system disclosed in the present application is
An aeration tank to fill the wastewater,
An aeration device disposed at the bottom of the aeration tank and releasing gas into the aeration tank;
An ozone clarification tank that performs reaction purification treatment with ozone gas by transferring sludge-containing treated water generated from the wastewater in the aeration tank;
An ozone generator for supplying ozone gas to the ozone septic tank;
A transfer pipe for transferring the sludge-containing treated water from the aeration tank to the ozone purification tank;
A return pipe for returning the sludge-containing treated water injected with the ozone gas from the ozone purification tank to the aeration tank;
The aeration tank is divided into an aeration promoting unit in which the aeration device is disposed below and an aeration suppressing unit in which the aeration device does not exist below,
The end port provided in the aeration tank of the transfer pipe is located on the boundary between the aeration promoting unit and the aeration suppressing unit or in the aeration suppressing unit, and in the surface layer portion of the sludge containing treated water , The terminal opening is open upward .

The water treatment method disclosed in the present application is:
An aeration process in which aeration apparatus for releasing gas in an aeration tank is used to aerate wastewater and grow microorganisms;
A biological treatment process for producing sludge-containing treated water using the sludge containing microorganisms;
A transfer step of transferring the sludge-containing treated water from the aeration tank to an ozone purification tank;
An ozone treatment step of injecting ozone gas into the sludge-containing treated water in the ozone septic tank;
In the ozone purifying tank, a return step for returning the sludge-containing treated water into which the ozone gas has been injected to the aeration tank,
In the transfer step, a boundary between an aeration promoting unit, which is a region where the aeration device is disposed below, and an aeration suppressing unit, which is a region where the aeration device does not exist below, inside the aeration tank The sludge-containing treated water is drawn from the top or inside the aeration suppressing part and from the surface layer part of the sludge-containing treated water, and is transferred from the top to the bottom and transferred to the ozone septic tank.

  According to the water treatment system and the water treatment method disclosed in the present application, in the water treatment system for transferring sludge-containing treated water containing sludge from the biological treatment tank to the outside of the tank, and injecting ozone gas into the transferred sludge-containing treated water. By suppressing the amount of oxide-forming inorganic substances that consume ozone gas to the outside of the tank, the increase in the amount of ozone gas that needs to be injected into sludge-containing treated water should be suppressed, and ozone treatment in sludge-containing treated water should be performed It is possible to provide a water treatment system and a water treatment method capable of reducing the risk that the amount of ozone gas injected becomes excessive or insufficient with respect to the amount of organic sludge.

It is a schematic diagram which shows the structure of the water treatment system which concerns on Embodiment 1. FIG. 2 is a flowchart of a water treatment method according to Embodiment 1. It is a schematic diagram which shows the structure of the water treatment system which concerns on Embodiment 2. FIG. It is a schematic diagram which shows the structure of the water treatment system which concerns on Embodiment 3. FIG. It is a schematic diagram which shows the structure of the water treatment system which concerns on Embodiment 4. FIG. It is a schematic diagram which shows the structure of the water treatment system which concerns on Embodiment 5. FIG. It is a figure explaining the relationship between the quantity of ozone gas per unit weight of the organic sludge used for the water treatment system which concerns on Embodiment 5, and the ultraviolet light absorbency of a supernatant liquid. 10 is a flowchart of a water treatment method according to Embodiment 5. 10 is another flowchart of the water treatment method according to the fifth embodiment. It is a figure which shows the other example of an aeration cutoff wall.

Embodiment 1 FIG.
Hereinafter, the water treatment system and the water treatment method according to Embodiment 1 will be described with reference to the drawings.
In this specification, when referring to the height, when referring to the height, the height in the vertical direction is meant. In addition, when referring to the upper and lower relationships such as the upper, lower, and upper surfaces, the vertical relationship is assumed.
FIG. 1 is a schematic diagram showing the configuration of the water treatment system 100. The water treatment system 100 includes an aeration tank 1, an air diffuser 2, a first solid-liquid separation tank 6, an ozone purification tank 8, and the like.

  The aeration tank 1 is filled with untreated wastewater 4 containing organic matter. Waste water 4 is an example of water to be treated.

  A diffuser 2 is provided at a predetermined portion of the bottom of the aeration tank 1. The air diffuser 2 is connected to an air supply device 3 installed outside the aeration tank 1. The air diffuser 2 discharges and supplies the air acquired from the air supply device 3 into the aeration tank 1 and puts the aeration tank 1 under an aerobic condition. As the air supply device 3, a blower, a compressor, a pump, or the like is used, depending on a necessary air supply amount.

  In the aeration tank 1, the wastewater 4 is treated under aerobic conditions by sludge that is an aggregate of cultivated microorganisms and the like, and sludge-containing treated water 5 containing sludge is generated.

  The sludge-containing treated water 5 generated in the aeration tank 1 is discharged to a first solid-liquid separation tank 6 connected to the aeration tank 1. The first solid-liquid separation tank 6 separates the sludge-containing treated water 5 into purified treated water 7 and concentrated sludge. The concentrated sludge separated in the first solid-liquid separation tank 6 is transported to the outside of the solid-liquid separation tank via an excess sludge pipe 101. A part of the concentrated sludge is returned to the aeration tank 1 through the concentrated sludge return pipe 102.

  The outflow method of the treated water 7 flowing out from the first solid-liquid separation tank 6 is not particularly limited. However, when the overflow method is adopted, the treated water 7 is removed from the first solid-liquid separation tank 6 without requiring power such as a pump. Can be drained.

  As the first solid-liquid separation tank 6, a precipitation tank or a membrane separation tank is used. When using a membrane separation tank, a membrane module used in a so-called membrane separation activated sludge method may be used.

  The ozone purification tank 8 is connected to the aeration tank 1 via the transfer pipe 103. In the ozone purification tank 8, a reaction purification process using ozone gas is performed on the sludge-containing treated water 5 transferred from the aeration tank 1. A pump 9 is installed on the transfer pipe 103. The end of the transfer pipe 103 on the side of the aeration tank 1 is a terminal port 103t.

  The sludge-containing treated water 5 in the aeration tank 1 is transferred to the ozone purification tank 8 through the transfer pipe 103 by driving the pump 9 from the place where the end port 103t is located. The sludge containing treated water 5 can be continuously transferred to the ozone septic tank 8. The pump 9 is an example of means for transferring the sludge-containing treated water 5 to the ozone purification tank 8.

  The ozone purification tank 8 is connected to the ozone generator 11 via the ozone gas pipe 104. The ozone generator 11 is a device that generates gaseous ozone. The ozone gas generated by the ozone generator 11 is supplied to the ozone purification tank 8 from the ozone gas pipe 104 and reacted with the organic sludge in the sludge containing treated water 5 transferred to the ozone purification tank 8 to decompose it.

  The sludge-containing treated water 5 obtained by decomposing organic sludge with ozone gas is returned to the aeration tank 1 via the return pipe 105. A return pump 12 is installed on the return pipe 105, and the sludge-containing treated water 5 in the ozone purification tank 8 can be continuously returned to the aeration tank 1 by driving the return pump 12.

  The return pump 12 is an example of means for returning the sludge-containing treated water 5 to the aeration tank 1, and is not limited to this return means. As the return means, for example, when the ozone purification tank 8 is located higher than the aeration tank 1, it may be returned by natural fall.

  In addition, the structure of the ozone purification tank 8 should just use the well-known technique which can supply ozone gas to the sludge containing treated water 5, and is not specifically limited. For example, the ozone purification tank 8 can store the sludge-containing treated water 5 and is provided with an air diffuser and an ejector that is a gas-liquid mixer. Ozone gas is supplied to the tank via the air diffuser and the ejector. Alternatively, the ozone purification tank 8 may be a gas-liquid mixer itself such as an ejector, and ozone gas may be directly supplied from the ozone gas pipe 104 into the tank.

  The reaction method of ozone gas and organic sludge in the ozone purification tank 8 may be any known technique such as a batch method, a CSTR (continuous tank reactor) method, or a PFR (plug flow) method, and is not particularly limited.

  For example, the ozone purification tank 8 is a tank that can store the sludge-containing treated water 5, and the sludge-containing treated water 5 is stored and held in the ozone purification tank 8 by the pump 9, and the sludge-containing treated water 5 is stored in the ozone generator 11. When the generated ozone gas is supplied via a gas-liquid mixer such as an air diffuser or an ejector and then the sludge-containing treated water 5 is returned to the aeration tank 1 using the return pump 12, a batch system is used.

  Further, for example, the ozone purification tank 8 is a tank capable of storing the sludge-containing treated water 5, and the sludge-containing treated water 5 is aerated with the pump 9 at the same time as the sludge-containing treated water 5 flows into the ozone purification tank 8. When returning to the tank 1 and supplying the ozone gas generated by the ozone generator 11 during that time via a gas-liquid mixer such as an air diffuser or an ejector, the CSTR system is used.

  Furthermore, when the ozone purification tank 8 is a gas-liquid mixer itself such as an ejector, the PFR method is used.

  The ozone generator 11 is connected to a raw material supply device (not shown) that supplies a raw material of ozone gas to the ozone generator 11 and a cooling device (not shown) that cools the ozone generator 11.

  The raw material of ozone gas supplied to the ozone generator 11 is not particularly limited. For example, liquid oxygen, oxygen generated by PSA (Pressure Swing Adsorption), or PVSA (Pressure Vacuum Swing Adsorption) can be used. You may arrange | position the additional gas supply part which adds 0.05 to 5% of nitrogen, air, or a carbon dioxide with respect to the flow volume of the oxygen supplied as needed.

  The cooling device includes a circulation pump that circulates a cooling medium for cooling the ozone generator 11 and a cooler that cools the cooling medium that has increased in temperature by absorbing heat generated in the ozone generator 11. As the cooler, a heat exchange type cooler selected from a liquid-liquid type and a liquid-gas type, or a liquid-fluorocarbon refrigerant type chiller may be used.

  In addition, a refrigerator may be used when cooling at an extremely low temperature. As an example of the cooling medium, general tap water may be used. In addition, water mixed with antifreeze or scale remover, ion-exchanged water, or pure water may be used. Further, ethylene glycol or ethanol may be used.

  The concentration of ozone gas generated by the ozone generator 11 is not particularly limited, but the organic sludge in the sludge-containing treated water 5 is efficiently decomposed to improve biodegradability and promote the reduction of excess sludge in the aeration tank 1. In consideration of this and the ozone gas concentration that can be generated only by the current ozone generator 11, the ozone gas concentration is preferably 100 g / Nm 3 or more and 400 g / Nm 3 or less, more preferably 250 g / Nm 3 or more and 400 g / Nm 3 or less.

  When the ozone gas concentration is lower than the above range, the biodegradability of the organic sludge in the sludge-containing treated water 5 is not improved, and there is a possibility that excess sludge cannot be reduced in the aeration tank 1. In addition, at present, it is difficult to generate ozone gas having a concentration of 400 g / Nm 3 or more with the ozone generator 11 alone.

  The inside of the aeration tank 1 is partitioned into an aeration promoting unit 13 that is a region where the aeration device 2 is disposed below and an aeration suppressing unit 14 that is a region where the aeration device 2 does not exist below.

  The end port 103t provided in the aeration tank 1 of the transfer pipe 103 is on the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 and the surface layer portion of the water surface of the sludge-containing treated water 5 in the aeration tank 1. Located in. Therefore, the sludge-containing treated water 5 in the aeration tank 1 is discharged from the surface layer portion of the water surface of the aeration tank 1 on the boundary K between the aeration promoting section 13 where the end port 103t is located and the aeration suppressing section 14. It is sent to the ozone purification tank 8 through the transfer pipe 103. Then, ozone gas is injected into the sludge-containing treated water 5 in the ozone purification tank 8.

  In a standard activated sludge method, which is a sewage treatment method, the density of organic sludge in which microorganisms and organic substances in the aeration tank 1 are collected is about 1.1 g / cm 3, which is almost the same density as water. On the other hand, oxide-forming inorganic substances that react with ozone gas such as iron and manganese to form oxides and non-reactive inorganic substances that do not consume ozone gas such as sand and aluminum phosphate are generally compared to water and organic sludge. For example, the oxide-forming inorganic substance is 5.0 g / cm 3 or more, and the non-reacting inorganic substance is 2.0 g / cm 3 or more. These substances tend to have higher settling properties as the density of the substance increases.

  Therefore, in the aeration suppressing unit 14 in which the aeration device 2 does not exist below, convection of the sludge-containing treated water 5 due to gas is suppressed, so that the sludge-containing treated water 5 has a ratio of organic sludge and inorganic matter in the vertical direction. Is different. That is, in the aeration suppression unit 14, the presence ratio of the organic sludge with respect to the inorganic matter is increased on the surface layer side, and the presence ratio of the inorganic matter with respect to the organic sludge is increased toward the bottom.

  In addition, the growth rate of microorganisms (organic sludge) that grow under aerobic conditions where oxygen such as air is supplied by aeration is generally microorganisms that grow under anaerobic conditions where oxygen such as air is not supplied. The growth rate is about 20 times. Therefore, in the region on the side of the aeration suppressing unit 14 that is away from the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14, the further away from the boundary K, the closer to anaerobic conditions, so that it grows under aerobic conditions. The abundance ratio of microorganisms that grow under anaerobic conditions for microorganisms increases. From the viewpoint of efficiency in reducing the amount of excess sludge generated, it is desirable to inject and decompose ozone gas into microorganisms that grow under aerobic conditions with a high growth rate.

  Therefore, the position of the end port 103t from which the sludge-containing treated water 5 is discharged from the aeration tank 1 is on the boundary K between the aeration promoting part 13 and the aeration suppressing part 14, and the surface layer part of the aerated tank 1 sludge-containing treated water. As a result, the sludge-containing treated water 5 having a high abundance ratio of organic sludge to inorganic substances and a high abundance ratio of microorganisms growing under anaerobic conditions to anaerobic conditions is transferred to the ozone septic tank 8. Then, ozone gas can be injected into the sludge-containing treated water 5.

  Thereby, the organic sludge containing many microorganisms that grow under aerobic conditions with a high growth rate is efficiently decomposed, and the transfer amount of the oxide-forming inorganic substance that consumes ozone gas to the ozone clarification tank 8 is suppressed. It becomes possible. Moreover, since the transfer amount of the oxide-forming inorganic substance to the ozone purification tank 8 is suppressed, the injection amount of ozone gas is necessarily excessive with respect to the amount of organic sludge to be ozone-treated in the sludge-containing treated water 5. Or the risk of shortage is reduced.

  As described above, from the viewpoint of efficiency in reducing the amount of excess sludge generated, the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 having a high abundance ratio of microorganisms that grow under aerobic conditions with a high growth rate. Although it is desirable to provide the terminal port 103t on the top, the amount of inorganic matter transferred to the ozone clarification tank 8 is suppressed, for example, when the water temperature is lowered in winter and the activity of microorganisms is reduced and the amount of excess sludge generated in the aeration tank 1 is small. If the efficiency of reducing the amount of surplus sludge generated is maintained even if only the emphasis is placed on the end, the end port 103t may be positioned in the aeration suppressing unit 14.

  By the way, as described above, a part of the concentrated sludge separated in the first solid-liquid separation tank 6 is returned to the aeration tank 1 through the concentrated sludge return pipe 102. The concentrated sludge flows into the aeration tank 1 from the return pipe connection portion 15 of the aeration tank 1. The return pipe connecting portion 15 is desirably located on the side surface of the aeration tank 1 and on the aeration suppressing portion 14 side.

  Next, the positional relationship between the end port 103t of the transfer pipe 103 and the return pipe connecting portion 15 will be described. The end port 103t is preferably located at a higher position than the return pipe connecting portion 15, and more preferably at a position higher by 1 m or more than the height of the return pipe connecting portion 15. That is, conversely, if the end port 103t is provided at a position lower than the return pipe connecting portion 15, the inorganic substance contained in the concentrated sludge that has flowed into the aeration tank 1 from the return pipe connecting portion 15 This is because there is a risk of being transferred from 103 t to the ozone purification tank 8.

  Moreover, it is preferable that the terminal port 103t is 0.5 m or more below in the vertical direction from the water surface of the sludge containing treated water 5 of the aeration tank 1. If the position of the terminal port 103t is less than 0.5 m downward from the surface of the sludge-containing treated water 5 in the aeration tank 1, scum (bacteria, E. coli, urea-decomposing bacteria, Suspended substances, fibers, oil lipids, carbon dioxide gas, etc. float with sludge, and bubbles derived from aeration in a sponge-like thick film may be transferred to the ozone clarification tank 8, and the pump This is because there is a high risk that the scum may cause deterioration or failure of the pump 9 due to mixing of scum, or the contact efficiency between ozone gas and organic sludge in the ozone septic tank 8 may be hindered by scum.

The length of the aeration suppression unit 14 in the horizontal direction (the direction perpendicular to the vertical direction), that is, the horizontal distance from the return pipe connection unit 15 to the boundary K between the aeration promotion unit 13 and the aeration suppression unit 14 is It is preferable that the following formula 1 is satisfied, and it is more preferable that the formula 2 is satisfied. Expressions 1 and 2 are relational expressions obtained from Expression 3 in which Stokes' law is applied to particles having a particle diameter of 0.00005 m using water (20 ° C.) as a dispersion medium.
[Expression 3: ρS = 1100] (m) ≧ horizontal distance (m) ≧ [Expression 3: ρS = 5000] from the return pipe connecting portion 15 to the boundary K between the aeration promoting portion 13 and the aeration suppressing portion 14 (M) ... Formula 1
[Equation 3: ρS = 1100] (m) ≧ horizontal distance (m) ≧ [Equation 3: ρS = 2000] from the return pipe connecting portion 15 to the boundary K between the aeration promoting portion 13 and the aeration suppressing portion 14 (M) ... Formula 2
(Q / A) × 18 × η × H / (ρS−1000) / g / (0.00005) 2.
Here, in Equation 3, Q is the flow rate (m3 / s) of the concentrated sludge in the concentrated sludge return pipe 102, A is the cross-sectional area (m2) of the side surface of the aeration tank 1, and η is the viscosity of water (Pa · s) and H are the height (m) from the bottom of the aeration tank 1 to the return pipe connecting portion 15, and g is the gravitational acceleration (m / s2). In each equation, ρS is the particle density (kg / m 3), ρS1100 is a representative value of the particle density of sludge (floc), ρS2000 is a representative value of the particle density of the non-reactive inorganic substance, ρS5000 represents a representative value of the particle density of the above-described oxide-forming inorganic substance.

  FIG. 2 is a flowchart of a water treatment method executed by the water treatment system 100, that is, a flowchart of a process for reducing excess sludge (volume reduction process). The left side of the figure is a flowchart of a batch system, and the right side is a flowchart of a CSTR (continuous tank reactor) system and a PFR (plug flow) system. The water treatment method using the water treatment system 100 includes a transfer process, an ozone treatment process, and a return process. Further, each flowchart of FIG. 2 shows the flow of starting and stopping of each device, and the progress of each process is indicated by “S1 start”, “S1 end”, and the like.

  Although not shown in FIG. 2, the water treatment process includes an aeration process in which the wastewater 4 that has flowed into the aeration tank 1 is aerated by the aeration device 2 to grow microorganisms, and microorganisms that exist in the aeration tank 1. A biological treatment process for producing a sludge-containing treated water 5 by biologically treating the wastewater 4 with sludge. After the biological treatment process, the pump 9 is activated and the sludge-containing treated water 5 is transferred from the aeration tank 1 to the ozone purification tank 8 (step S1, transfer process). The pump 9 may be operated manually or automatically controlled according to a preset control program. This step S1 is an example of a transfer process.

  Subsequently, the ozone generator 11 is activated to generate ozone gas by discharge. The ozone gas is supplied to the ozone purification tank 8 through the ozone gas pipe 104, and the ozone gas is injected into the sludge containing treated water 5 in the ozone purification tank 8 (step S2, ozone treatment process). This step S2 is an example of an ozone treatment process.

  In the ozone purification tank 8, the sludge-containing treated water 5 into which ozone gas has been injected is returned to the aeration tank 1 by the operation of the return pump 12 (step S3, return process). This step S3 is an example of a return process. For example, as described above, the ozone purification tank 8 may be provided at a position higher than the aeration tank 1, and the treated sludge-containing treated water 5 may be returned to the aeration tank 1 using natural fall.

  A water treatment method including a series of steps of transferring sludge-containing treated water 5 from the inside of the aeration tank 1, injecting ozone gas, and returning it, specifically, the volume reduction process for reducing excess sludge is the batch method described above. The start and end timings of the transfer process, the ozone treatment process, and the return process differ depending on the CSTR method and the PFR method.

  As shown in FIG. 2, in the batch method, each process proceeds in the order of start of step S1, end of step S1, start of step S2, end of step S2, start of step S3, end of step S3. In the CSTR (continuous tank reactor) method and the PFR (plug flow) method, the start of step S1, the start of step S2, the start of step S3, the end of step S2, the end of step S1, and the end of step S3 are referred to. Proceed with each process in order.

  The excess sludge volume reduction process is preferably performed periodically and intermittently. The interval of the volume reduction process is not particularly limited, and may be set as appropriate according to the organic matter load of microorganisms in the aeration tank 1 and the amount of excess sludge generated. However, when considering both the bioactivity maintaining ability of the activated sludge containing microorganisms and the excess sludge volume reducing ability, an interval of 1 hour to 24 hours is preferable, and an interval of 2 hours to 12 hours is more preferable. More preferably, the interval is not less than 6 hours and not more than 6 hours.

  When the interval of the volume reduction process performed periodically and intermittently is smaller than the above range, even microorganisms contributing to wastewater treatment in the aeration tank 1 may be transferred more than necessary and decomposed by ozone gas.

  Therefore, the activity of microorganisms contributing to wastewater treatment is reduced, wastewater treatment in the aeration tank 1 is not sufficiently performed, and the water quality of the treated water 7 after treatment may be deteriorated. On the other hand, when ozone treatment is performed, microorganisms in the sludge are decomposed and components in the microorganisms (soluble organic substances) are released into the sludge-containing treated water 5. Therefore, if the interval between volume reduction processes performed periodically and intermittently is larger than the above range, the amount of microbial growth that increases by using the microbial components released by decomposition as a substrate becomes larger, and the excess sludge as a whole There is a possibility that the amount cannot be reduced.

  According to the water treatment system 100 and the water treatment method according to the present embodiment, the position of the end port 103t from which the sludge-containing treated water 5 is discharged from the aeration tank 1 is determined between the aeration promoting unit 13 and the aeration suppressing unit 14. By making the surface layer portion on the boundary K or in the aeration control unit 14 and on the water surface of the aeration tank 1, the sludge-containing treated water 5 having a high ratio of organic sludge to inorganic substances is transferred to the ozone purification tank 8. It is possible to inject ozone gas. Therefore, the transfer amount of the oxide-forming inorganic substance that consumes ozone gas to the ozone purification tank 8 is suppressed, and an increase in the amount of ozone gas that needs to be injected into the sludge-containing treated water 5 is suppressed, and the sludge-containing treated water 5 It is possible to provide a water treatment system and a water treatment method capable of reducing the risk that the amount of ozone gas injected is excessive or insufficient relative to the amount of organic sludge to be ozone-treated.

Embodiment 2. FIG.
Hereinafter, the water treatment system according to Embodiment 2 will be described.
FIG. 3 is a schematic diagram showing the configuration of the water treatment system 200.
In the figure, the same components and members as those of the water treatment system 100 according to Embodiment 1 are denoted by the same reference numerals, and description thereof is omitted unless particularly necessary.

  The basic configuration and operation of the water treatment system 200 are the same as those in the first embodiment, but upward on the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 and on the bottom of the aeration tank 1. The aeration blocking wall 16 is provided, and the difference is that the sediment discharge pipe 106 is provided at the bottom of the region on the aeration suppressing unit 14 side adjacent to the aeration blocking wall 16.

  In the water treatment system 200, as described above, the aeration blocking wall 16 is provided on the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 and at the bottom of the aeration tank 1. Thereby, it is possible to prevent the inorganic matter that has settled at the bottom of the aeration suppressing unit 14 near the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 from being lifted again by the aeration of the aeration device 2. Therefore, the risk that the oxide-forming inorganic substance that consumes ozone gas is transferred to the ozone purification tank 8 via the transfer pipe 103 can be reduced as compared with the first embodiment.

  Further, the sediment at the bottom of the aeration suppressing unit 14 near the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 is periodically discharged from the precipitate discharge pipe 106 by a pump (not shown) or the like. Is discharged outside. This discharge operation may be performed manually or may be automatic control for opening and closing the valve in accordance with a preset control program.

FIG. 10 is a view showing another example of the aeration blocking wall.
The configuration of the aeration blocking wall 16 is not particularly limited. As shown in the exposure blocking walls 16a and 16b in FIG. 10, the aeration blocking wall may be configured to be curved or inclined toward the aeration suppressing unit 14 side. If comprised in this way, the effect which prevents the inorganic substance which settled on the bottom part of the aeration suppression part 14 vicinity of the boundary K of the aeration promotion part 13 and the aeration suppression part 14 from being re-levitated by aeration can be enlarged further. it can.

  Further, the height of the upper surface of the aeration blocking wall 16 is not particularly limited, but is preferably higher than the height of the air diffuser 2 and lower than the height of the return pipe connecting portion 15. When the height of the upper surface of the aeration blocking wall 16 is lower than the height of the aeration device 2, the gas such as air released from the aeration device 2 is blocked from flowing into the bottom of the aeration suppression unit 14. The effect of preventing the inorganic matter precipitated at the bottom of the aeration suppressing unit 14 near the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 from re-floating due to aeration of the aeration device 2 is obtained. Because there is no fear.

  In addition, when the height of the upper surface of the aeration barrier 16 is higher than the height of the return pipe connection 15, not only the high density inorganic substance contained in the concentrated sludge flowing into the aeration tank 1 from the return pipe connection 15, Organic sludge having a low density tends to settle on the bottom of the aeration suppressing unit 14 near the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 and aeration to the bottom of the aeration suppressing unit 14 near the boundary K is performed. It is because there exists a possibility that sludge may rot because it will be interrupted | blocked excessively and oxygen will not spread to the sludge containing treated water 5. FIG.

  In general, the height of the air diffuser 2 is lower than the height of the return pipe connecting portion 15. When the height of the air diffuser 2 is higher than the height of the return pipe connection 15, oxygen does not spread over the sludge existing between the air diffuser 2 and the return pipe connection 15, and the sludge can be spoiled. Because.

  According to the water treatment system 200 according to the second embodiment, the same effects as those of the first embodiment can be obtained.

  Further, since the aeration blocking wall 16 is provided on the boundary K between the aeration promoting unit 13 and the aeration suppressing unit 14 and at the bottom of the aeration tank 1, the boundary between the aeration promoting unit 13 and the aeration suppressing unit 14. It is possible to prevent the inorganic matter that has settled at the bottom of the aeration suppressing unit 14 near K from re-floating due to the aeration of the aeration device 2. Therefore, it is possible to reduce the risk that the oxide-forming inorganic substance that consumes ozone gas is transferred to the ozone purifying tank 8 through the terminal port 103t.

Embodiment 3 FIG.
Hereinafter, the water treatment system according to Embodiment 3 will be described.
FIG. 4 is a schematic diagram showing the configuration of the water treatment system 300. In the figure, the same components and members as those of the water treatment system 200 according to Embodiment 2 are denoted by the same reference numerals, and description thereof is omitted unless particularly required.

  The basic configuration and operation of the water treatment system 300 are the same as those of the water treatment system 200 of the second embodiment, but the lower end portion of the transfer pipe 303 is bent in a U shape toward the aeration suppressing unit 14 side. The end port 303t is different in that it opens upward.

  Thus, since the lower end portion of the transfer pipe 303 is bent in a U shape toward the aeration suppressing unit 14, the end port 303 t is located in the aeration suppressing unit 14. In addition, the sludge-containing treated water 5 in the aeration tank 1 is drawn from the top to the bottom with respect to the end port 303 t that opens upward in the aeration suppressing unit 14 and transferred to the ozone purification tank 8. For this reason, it can suppress that gas, such as air which floats upwards from the bottom by the diffuser 2, is directly transferred to the ozone purification tank 8 by the pump 9 from the terminal end 303t.

  Thereby, while the noise and vibration of the pump 9 become small, the transfer flow rate of the sludge containing treated water 5 by the pump 9 can be stabilized. Thus, by stabilizing the amount of organic sludge transferred to the ozone septic tank 8, the risk that the amount of ozone gas injected becomes excessive or insufficient relative to the amount of organic sludge can be further reduced.

  In addition, since it is only necessary to suppress the transfer of gas such as air that rises from the bottom to the top by the air diffuser 2 directly from the end port to the ozone purification tank 8 by the pump 9, in the aeration tank 1, As long as the sludge-containing treated water 5 is not sucked into the transfer pipe from the top to the top, the configuration of the lower end of the transfer pipe is not limited to the U-shape, and the end port only needs to be at least upward from the horizontal.

  According to the water treatment system 300 according to the third embodiment, the same effect as in the second embodiment can be obtained.

  Further, the lower end portion of the transfer pipe 303 is bent in a U shape toward the aeration suppressing unit 14 side, and the end port 303t is opened upward and is located in the aeration suppressing unit 14. The sludge-containing treated water 5 in the aeration tank 1 can be sucked from the top to the bottom in the aeration suppression unit 14 and transferred to the ozone purification tank 8, and is levitated from the bottom to the top by the air diffuser 2. It is possible to prevent the gas such as air from entering the pump 9 directly from the end port 303t. Thereby, the transfer flow rate of the sludge containing treated water 5 of the pump 9 can be stabilized, and the risk that the injection amount of ozone gas is excessive or insufficient with respect to the amount of organic sludge can be further reduced.

Embodiment 4 FIG.
Hereinafter, the water treatment system according to Embodiment 4 will be described.
FIG. 5 is a schematic diagram showing the configuration of the water treatment system 400. In the figure, the same components and members as those of the water treatment system 300 according to the third embodiment are denoted by the same reference numerals, and the description thereof is omitted unless particularly necessary.

  The basic configuration and operation of the water treatment system 400 are the same as those of the water treatment system 300 of the third embodiment, but the water treatment system 400 determines the sludge concentration at a position in the vicinity of the end port 303t in the aeration tank 1. The first sensor 17 to be measured, the first pump control device 18 (transfer amount control device) for controlling the pump 9 based on the measurement result of the first sensor 17, and the organic at a position in the vicinity of the end port 303t in the aeration tank 1 The difference is that a second sensor 19 for measuring the concentration of sludge and an ozone generator control device 20 for controlling the ozone generator 11 based on the measurement result of the second sensor 19 are provided.

  Since the water treatment system 400 includes the first sensor 17 that measures the sludge concentration of the sludge-containing treated water 5 in the aeration tank 1, the organic load in the aeration tank 1 (the amount of organic matter processed by microorganisms in the aeration tank 1). = Changes in the sludge concentration of the sludge-containing treated water 5 accompanying changes in the amount of the sludge-containing treated water 5 in the aeration tank 1 x the concentration of organic matter).

  The sludge concentration value measured by the first sensor 17 is input to the first pump control device 18. The first pump control device 18 changes the flow rate of the sludge-containing treated water 5 that the pump 9 transfers from the aeration tank 1 to the ozone purification tank 8 according to the input sludge concentration value.

  A quotient obtained by dividing the amount of the sludge-containing treated water 5 that the pump 9 transfers to the ozone clarification tank 8 per day by the surplus sludge generation amount per day is defined as the sludge treatment ratio. The sludge treatment ratio of the water treatment system 400 is appropriately set according to the organic matter load of microorganisms in the aeration tank 1, the amount of excess sludge generated, and the like.

  Here, the amount of excess sludge is determined as follows. That is, first, as the amount of necessary sludge, there is a general standard value or a design value based on the experience of the site manager. The sludge concentration in the aeration tank 1 that satisfies the standard value or the design value can be calculated. A value obtained by multiplying the calculated value by the volume of the aeration tank 1 is the amount of necessary sludge. Then, the value obtained by subtracting the necessary amount of sludge from the value obtained by multiplying the actual sludge concentration measured by the first sensor 17 and the volume of the aeration tank 1 is the surplus sludge amount.

  The above sludge treatment ratio is not particularly limited. However, 2.0 or more and 4.0 or less are preferred, and 2.6 or more and 3.4 or less are more preferred. When the sludge treatment ratio is less than 2.0, there is a possibility that the amount of sludge reduced due to the injection of ozone gas is small and the amount of excess sludge cannot be reduced sufficiently. On the other hand, when the sludge treatment ratio exceeds 4, the amount of microorganisms in the aeration tank 1 is excessively reduced, the activity of microorganisms is lowered, and the water quality of the treated water 7 may be deteriorated. When the sludge treatment ratio is in the range of 2.6 to 3.4, excess sludge can be efficiently reduced while maintaining the activity of microorganisms in the aeration tank 1.

  The first pump controller 18 (1) the value of the sludge concentration measured by the first sensor 17, (2) the amount of excess sludge generated by the above calculation, and (3) the set sludge treatment ratio. From the value, the flow rate of the sludge containing treated water 5 that the pump 9 transfers to the ozone purification tank 8 is calculated to control the pump 9.

  This control method is not particularly limited, and the flow rate may be adjusted by controlling the number of revolutions of the pump by an inverter, or an electric valve is installed on the transfer pipe 303 and the pressure loss of the transfer pipe 303 is changed by the electric valve. The flow rate may be adjusted accordingly.

  The configuration of the first sensor 17 is not particularly limited as long as the sludge concentration of the sludge-containing treated water 5 in the aeration tank 1 can be measured, and a known sensor such as an SS (Suspended Solids) densitometer or a turbidimeter is used. can do. Further, manual measurement by manual analysis or automatic measurement using an automatic measuring device may be used.

  In addition, since the water treatment system 400 includes the second sensor 19 that measures the concentration of organic sludge in the sludge-containing treated water 5 in the aeration tank 1, organic load in the aeration tank 1 (microorganisms in the aeration tank 1 are treated). Change in the amount of organic matter) and the change in the concentration of organic sludge in the sludge-containing treated water 5 due to the change in the amount of inorganic matter contained in the inflowing wastewater 4 can be detected.

  The concentration value of the organic sludge measured by the second sensor 19 is input to the ozone generator control device 20. The ozone generator control device 20 controls the amount of ozone gas that the ozone generator 11 injects into the sludge-containing treated water 5 transferred to the ozone clarification tank 8 according to the input organic sludge concentration value.

  The “amount of ozone gas per unit weight of the organic sludge” necessary for decomposing the organic sludge is not particularly limited as long as the organic sludge in the sludge-containing treated water 5 can be efficiently decomposed. However, considering the utilization efficiency of ozone gas, the amount of ozone gas per 1 g of organic sludge is preferably 30 mg or more and 85 mg or less, and more preferably 40 mg or more and 55 mg or less.

  When the amount of ozone gas per gram of organic sludge is smaller than the above range, the organic sludge in the sludge-containing treated water 5 is not sufficiently decomposed, and the excess sludge cannot be reduced in the aeration tank 1 There is sex. In addition, when the amount of ozone gas per gram of organic sludge is larger than the above range, it is possible to increase the residual ozone gas in the water by injecting more ozone gas than necessary, and increase unreacted ozone gas. There is.

  The ozone generator controller 20 includes (1) the concentration value of the organic sludge measured by the second sensor 19 and (2) the sludge that the pump 9 determined by the first pump controller 18 transfers to the ozone clarification tank 8. The ozone generator 11 should be injected into the sludge-containing treated water 5 transferred to the ozone purification tank 8 from the amount of the treated water 5 and (3) the amount of ozone gas per unit weight of the organic sludge set in advance. The amount of ozone gas is calculated, and the ozone gas concentration, ozone gas flow rate, and ozone treatment time of the ozone generator 11 are adjusted.

  As described above, the concentration of ozone gas generated by the ozone generator 11 is preferably 100 g / Nm3 or more and 400 g / Nm3 or less, and more preferably 250 g / Nm3 or more and 400 g / Nm3 or less. When the ozone gas concentration is lower than the above range, the biodegradability of the organic sludge in the sludge-containing treated water 5 does not improve, and the surplus sludge may not be reduced in the aeration tank 1. In addition, at present, it is difficult to generate ozone gas having a concentration of 400 g / Nm 3 or more with the ozone generator 11 alone.

  The ozone treatment time per time is not particularly limited, but is preferably 20 minutes or longer and 90 minutes or shorter, and more preferably 30 minutes or longer and 50 minutes or shorter. When the ozone treatment time per one time is shorter than the above range, the size and power of the pump 9 and the return pump 12 are increased, so that the initial cost and running cost may increase.

  Moreover, when the ozone treatment time per time is longer than the above range, the microorganisms in the organic sludge are decomposed along with the ozone treatment, and the microbial components (soluble organic matter) released into the sludge-containing treated water 5 are long. Since it continues to flow out into the sludge containing treated water 5 over time, the water quality of the treated water 7 may be deteriorated.

  The 2nd sensor 19 will not be specifically limited if the density | concentration of the organic sludge of the sludge containing process water 5 in the aeration tank 1 can be measured, Well-known techniques, such as an ignition loss test, can be used.

  The first pump control device 18 controls the pump 9 according to the measured value of the sludge concentration of the first sensor 17, and the ozone generator control device 20 corresponds to the measured value of the organic sludge concentration of the second sensor 19. The ozone generator 11 is controlled, but when the agitation of the sludge in the aeration tank 1 is insufficient or the measurement accuracy of the first sensor 17 and the second sensor 19 is low, the first sensor 17, In addition, the measured values of the second sensor 19 may vary greatly.

  If these measured values vary, the flow rate of the pump 9 controlled by the first pump control device 18 and the amount of ozone gas generated by the ozone generator 11 controlled by the ozone generator control device 20 are excessively large. Fluctuate and the sludge volume reduction process can become unstable.

  Therefore, the first pump control device 18 and the ozone generator control device 20 record the measurement values sent from the first sensor 17 and the second sensor 19 respectively for a certain period, for example, for one week. The average value of the measured values obtained for each period may be calculated, and the pump 9 and the ozone generator 11 may be controlled based on the average value.

  Since the measured value is smoothed by adopting an average value for every certain period, the risk that the pump 9 and the ozone generator 11 operate according to the abnormal values of the sludge concentration and the organic sludge concentration is reduced. This makes it possible to stabilize the excess sludge volume reduction process.

  In addition, when the density | concentration of the organic sludge of an excess sludge can be measured, the ozone generator control apparatus 20 is (1) the value of the density | concentration of the organic sludge measured with the 2nd sensor 19, and (2) of the excess sludge. The pump 9 may be controlled by calculating the flow rate of the sludge-containing treated water 5 that the pump 9 transfers to the ozone purification tank 8 from the generated amount of organic sludge and (3) the value of the set sludge treatment ratio.

  According to the water treatment system 400 according to the fourth embodiment, the same effect as in the third embodiment can be obtained.

  Moreover, the 1st sensor 17 which measures the sludge density | concentration of the sludge containing treated water 5 in the aeration tank 1, and the flow rate of the sludge containing treated water 5 which the pump 9 transfers to the ozone purification tank 8 based on the measured value are controlled. Since one pump control device 18 is provided, the amount of the sludge-containing treated water 5 that is transferred to the ozone clarification tank 8 and into which ozone gas is injected can be controlled.

  Furthermore, a second sensor 19 that measures the concentration of organic sludge in the sludge-containing treated water 5 in the aeration tank 1, and an ozone generator controller 20 that controls the amount of ozone gas in the ozone generator 11 based on the measured value. Therefore, the risk that the amount of ozone gas injected becomes excessive or insufficient with respect to the amount of organic sludge to be ozone-treated in the sludge-containing treated water 5 can be greatly reduced.

Embodiment 5. FIG.
Hereinafter, the water treatment system according to Embodiment 5 will be described.
FIG. 6 is a schematic diagram showing the configuration of the water treatment system 500. In the figure, the same components and members as those of the water treatment system 400 according to the fourth embodiment are denoted by the same reference numerals, and description thereof is omitted unless particularly necessary.

  The basic configuration and operation of the water treatment system 500 are the same as those in the fourth embodiment, but the return pipe 105 is separated from the solid liquid of the treated sludge-containing treated water 5 via the sampling pipe 107. The solid-liquid separation tank 21 is connected, the sampling valve 22 is provided on the sampling pipe 107, and the absorbance of the ultraviolet light of the sludge-containing treated water 5 in the tank is further measured in the second solid-liquid separation tank 21. The difference is that a third sensor 23 is provided.

  In the water treatment system 500, a part of the sludge-containing treated water 5 that is injected with ozone gas in the ozone purification tank 8 and returned to the aeration tank 1 is recovered in the second solid-liquid separation tank 21 by opening the sampling valve 22. be able to.

  In the second solid-liquid separation tank 21, the collected sludge-containing treated water 5 after the ozone treatment is separated into a precipitate and a supernatant liquid. Then, the absorbance of the ultraviolet light of the supernatant is measured by the third sensor 23. The absorbance value measured by the third sensor 23 is input to the ozone generator controller 20 and fed back to the next ozone treatment. That is, the amount of ozone gas in the next ozone treatment based on the absorbance value of the supernatant obtained as a result of injecting the ozone amount calculated by the ozone generator controller 20 into the sludge-containing treated water 5 of the ozone purification tank 8. Feedback control is performed on the ozone generator controller 20 so as to adjust the above.

  More specifically, the ozone generator control device 20 (1) the concentration value of the organic sludge measured by the second sensor 19, and (2) the pump 9 determined by the first pump control device 18 is ozone. The amount of the sludge-containing treated water 5 to be transferred to the septic tank 8, (3) the amount of ozone gas calculated from the amount of ozone gas per unit weight of the set organic sludge, and (4) the amount of ozone gas of the calculated amount containing sludge Based on the absorbance value obtained as a result of the injection into the treated water 5, the set value ((3) in this paragraph) of the amount of ozone gas per unit weight of the organic sludge in the next ozone treatment is corrected.

  As described above, the amount of ozone gas per gram of organic sludge is preferably 30 mg or more and 85 mg or less, and more preferably 40 mg or more and 55 mg or less in order to sufficiently decompose the organic sludge in the sludge-containing treated water 5. However, the amount of the inorganic substance contained in the wastewater 4, particularly the amount of the oxide-forming inorganic substance that consumes ozone gas varies, so that the amount of the oxide-forming inorganic substance contained in the sludge-containing treated water 5 in the aeration tank 1 is greatly increased. In the case where the oxide-forming inorganic substance transferred to the ozone purification tank 8 through the transfer pipe 303 greatly increases or decreases, even if ozone gas in an amount within the above range is injected per 1 g of organic sludge, The ozone gas injected by the oxide-forming inorganic substance is consumed more or less than expected, and the amount of ozone gas per unit weight of the organic sludge that is actually required becomes larger or smaller than the above range. There is a risk that.

  The present inventors have found that there is a correlation between the amount of ozone gas per unit weight of organic sludge and the ultraviolet absorbance value of the supernatant of the sludge-containing treated water 5 after the ozone treatment. The amount of oxide-forming inorganic substances contained in the sludge-containing treated water 5 in the aeration tank 1 greatly increased and decreased, and the oxide-forming inorganic substances transferred to the ozone purification tank 8 via the transfer pipe 303 significantly increased and decreased. Even in this case, the set value of the amount of ozone gas per unit weight of the organic sludge in the next ozone treatment can be corrected to an appropriate value by feedback control according to the measurement result of the third sensor 23.

  Therefore, the amount of the oxide-forming inorganic substance contained in the sludge-containing treated water 5 in the aeration tank 1 is greatly increased or decreased as the amount of the oxide-forming inorganic substance contained in the waste water 4 fluctuates. Even when the amount of oxide-forming inorganic substances transferred to the ozone purification tank 8 via the transfer pipe 303 is greatly increased or decreased, the injection of ozone gas with respect to the amount of organic sludge to be ozone-treated in the sludge-containing treated water 5 The risk of excessive or insufficient amounts can be greatly reduced.

  FIG. 7 is a diagram showing the correlation between the amount of ozone gas per gram of organic sludge and the ultraviolet absorbance value of the supernatant of the sludge-containing treated water 5 after the ozone treatment. For each wastewater treatment plant where the present water treatment system 500 is introduced, the value of ultraviolet absorbance is uniquely determined with respect to the amount of ozone gas per unit weight of organic sludge. Moreover, according to the increase / decrease in the quantity of the oxide formation inorganic substance transferred to the ozone purification tank 8 via the transfer piping 303, the value of the ultraviolet light absorbency of the supernatant liquid of the sludge containing treated water 5 after the ozone treatment also increases / decreases.

  Therefore, in the amount of ozone gas per unit weight of the same organic sludge, the amount of oxide-forming inorganic matter in the sludge-containing treated water 5 indirectly increased when the ultraviolet absorbance value decreased below an arbitrary reference value. I understand that. For this reason, in the next ozone treatment, the ozone generator control device 20 performs correction to increase the amount of ozone gas per unit weight of the organic sludge so that the value of the ultraviolet absorbance becomes the reference value.

  On the other hand, in the amount of ozone gas per unit weight of the same organic sludge, when the value of ultraviolet absorbance increased from an arbitrary reference value, the amount of oxide-forming inorganic substances in the sludge-containing treated water 5 decreased indirectly. Therefore, in the next ozone treatment, the ozone generator control device 20 performs correction to reduce the amount of ozone gas per unit weight of the organic sludge so that the ultraviolet absorbance value becomes the reference value.

  If the 3rd sensor 23 can measure the ultraviolet light absorbency of the supernatant liquid of the sludge containing treated water 5 after ozone treatment, the structure will not be specifically limited, A spectrophotometer etc. can be used in a well-known range. The wavelength of the ultraviolet light is preferably 230 nm or more and 300 nm or less, and more preferably 260 nm or more and 280 nm or less. In the case of ultraviolet light having a wavelength not included in the above range, there is a possibility that the absorbance and the amount of ozone gas per unit weight of the organic sludge cannot be correlated.

  Further, since there is a correlation between the ultraviolet absorbance and TOC (Total Organic Carbon), COD (Chemical Oxygen Demand), etc., the ultraviolet absorbance may be calculated indirectly using a TOC meter or a COD meter.

FIG. 8 is a flowchart of a water treatment method (batch method) executed by the water treatment system 500.
FIG. 9 is a flowchart of a water treatment method (CSTR method and PFR method) executed by the water treatment system 500.
The water treatment method according to the present embodiment includes a sludge concentration measurement step, an organic sludge concentration measurement step, a transfer step, an ozone treatment step, a return step, a sampling step, an ultraviolet absorbance measurement step, and a feedback step.

  The waste water 4 that has flowed into the aeration tank 1 is subjected to biological treatment in the aeration tank 1 to become sludge containing treated water 5 containing sludge. The sludge concentration in the sludge-containing treated water 5 is measured by the first sensor 17 (step C1, sludge concentration measuring step). The timing of measurement is not particularly limited, and may be measured intermittently, such as once a day, or may be continuously measured.

  Moreover, the density | concentration of the organic sludge in the sludge containing treated water 5 is measured by the 2nd sensor 19 (step C2, organic sludge density | concentration measurement process). The timing of measurement is not particularly limited, and may be measured intermittently, such as once a day, or may be continuously measured.

  According to the value of the sludge concentration obtained in the sludge concentration measurement step, the flow rate of the sludge-containing treated water 5 that the pump 9 transfers from the aeration tank 1 to the ozone purification tank 8 is calculated by the first pump controller 18 and calculated. The pump 9 is operated at the flow rate value. The sludge-containing treated water 5 is discharged from the aeration tank 1 and transferred to the ozone purification tank 8 (step S1, transfer process).

  According to the concentration value of the organic sludge obtained in the organic sludge concentration measuring step, the ozone generator 11 controls the ozone gas to be injected into the sludge-containing treated water 5 that the ozone generator 11 has transferred to the ozone septic tank 8. The amount is calculated and the ozone generator 11 is operated to produce the amount. The ozone gas is supplied to the ozone purification tank 8 through the ozone gas pipe 104, and the calculated amount of ozone gas is injected into the sludge containing treated water 5 in the ozone purification tank 8 (step S2, ozone treatment process).

  In the ozone purification tank 8, the sludge-containing treated water 5 into which ozone gas has been injected is returned to the aeration tank 1 by the operation of the return pump 12 (step S3, return process).

  Subsequently, a part of the sludge-containing treated water 5 that is injected with ozone gas in the ozone purification tank 8 and returned to the aeration tank 1 is collected in the second solid-liquid separation tank 21 by opening the sampling valve 22 (step S4, Sampling process).

  In the second solid / liquid separation tank 21, the sludge-containing treated water 5 after the ozone treatment is separated into a precipitate and a supernatant liquid, and then the third sensor 23 uses the ultraviolet light of the supernatant liquid of the sludge-containing treated water 5 after the ozone treatment. Absorbance is measured. The absorbance value measured by the third sensor 23 is input to the ozone generator control device 20 (step S5, ultraviolet absorbance measurement step).

  Based on the input absorbance value, the ozone generator control device 20 adjusts the set value of the amount of ozone gas per unit weight of the organic sludge in the next ozone treatment process (step S6, feedback process).

  A water treatment method including a series of steps of transferring sludge-containing treated water 5 from the inside of the aeration tank 1, injecting ozone gas, and returning it, specifically, the volume reduction process for reducing excess sludge is the batch method described above. In the CSTR (continuous tank reactor) system and the PFR (plug flow) system, the start timing and end timing of the transfer process, the ozone treatment process, the return process, and the sampling process are different.

  In the batch method shown in FIG. 8, start / end of step C1, start / end of step C2, start of step S1, end of step S1, start of step S2, end of step S2, start of step S3, start of step S4 Processing is performed in the order of start / end, end of step S3, start / end of step S5, and start / end of step S6.

  On the other hand, in the CSTR (continuous tank reactor) method and the PFR (plug flow) method shown in FIG. 9, the start / end of step C1, the start / end of step C2, the start of step S1, the start of step S2, the step S3 Start, end of step S4, end of step S2, end of step S1, end of step S3, start / end of step S5, start / end of step S6.

  According to the water treatment system 500 according to the fifth embodiment, the same effect as in the fourth embodiment can be obtained.

  Moreover, the 3rd sensor 23 which can measure the light absorbency of the ultraviolet light of the supernatant liquid of the sludge containing treated water 5 after ozone treatment is provided, and according to the measurement result of the 3rd sensor 23, the unit weight of the organic sludge in the next ozone treatment Since the set value of the amount of ozone gas per unit can be adjusted by feedback control, the amount of oxide-forming inorganic substances contained in the waste water 4 varies, and the sludge containing treated water 5 in the aeration tank 1 Even in the case where the amount of the oxide-forming inorganic substance contained is greatly increased and decreased and the amount of the oxide-forming inorganic substance transferred to the ozone clarification tank 8 via the transfer pipe 303 is greatly increased or decreased, the ozone in the sludge-containing treated water 5 The risk of excessive or insufficient ozone gas injection relative to the amount of organic sludge to be treated can be greatly reduced.

  This application is not limited to the specific details and exemplary embodiments described and described above. Variations and effects that can be easily derived by those skilled in the art are also included. For example, it can also be used for known water treatment techniques such as an A2O method (anaerobic / anoxic / aerobic method) and an OD method (OXIDATION DITCH method) including an anaerobic tank and an anaerobic tank. At that time, the sludge-containing treated water 5 into which ozone gas is injected in the ozone purification tank 8 may be returned to any one of an anaerobic tank, an oxygen-free tank, and an aeration tank. Accordingly, various modifications can be made without departing from the spirit or scope of the general concept as defined by the scope of the claims and their equivalents.

Although this application describes various exemplary embodiments and examples, various features, aspects, and functions described in one or more embodiments may be applied to particular embodiments. The present invention is not limited to this, and can be applied to the embodiments alone or in various combinations.
Accordingly, innumerable modifications not illustrated are envisaged within the scope of the technology disclosed in the present application. For example, the case where at least one component is deformed, the case where the component is added or omitted, the case where the at least one component is extracted and combined with the component of another embodiment are included.

  100, 200, 300, 400, 500 Water treatment system, 1 aeration tank, 2 air diffuser, 3 air supply device, 4 waste water, 5 sludge-containing treated water, 6 first solid-liquid separation tank, 7 treated water, 8 ozone Septic tank, 9 pump, 11 ozone generator, 12 return pump, 13 aeration promoting part, 14 aeration suppressing part, K boundary, 15 return pipe connection part, 16 aeration blocking wall, 17 first sensor, 18 first pump control device, 19 Second sensor, 20 Ozone generator control device, 21 Second solid-liquid separation tank, 22 Sampling valve, 23 Third sensor, 101 Excess sludge piping, 102 Concentrated sludge return piping, 103, 303 Transfer piping, 103 t, 303 t End port, 104 ozone gas piping, 105 return piping, 106 sediment discharge piping, 107 sampling piping.

Claims (13)

An aeration tank to fill the wastewater,
An aeration device disposed at the bottom of the aeration tank and releasing gas into the aeration tank;
An ozone clarification tank that performs reaction purification treatment with ozone gas by transferring sludge-containing treated water generated from the wastewater in the aeration tank;
An ozone generator for supplying ozone gas to the ozone septic tank;
A transfer pipe for transferring the sludge-containing treated water from the aeration tank to the ozone purification tank;
A return pipe for returning the sludge-containing treated water injected with the ozone gas from the ozone purification tank to the aeration tank;
The aeration tank is divided into an aeration promoting unit in which the aeration device is disposed below and an aeration suppressing unit in which the aeration device does not exist below,
The end port provided in the aeration tank of the transfer pipe is located on the boundary between the aeration promoting unit and the aeration suppressing unit or in the aeration suppressing unit, and in the surface layer portion of the sludge containing treated water , The end port is a water treatment system that opens upward . The water treatment system according to claim 1, wherein an aeration blocking wall is provided upward on the boundary between the aeration promoting unit and the aeration suppressing unit and on the bottom of the aeration tank. The water treatment system according to claim 2, wherein the aeration blocking wall is curved or inclined toward the aeration suppressing unit side. The sediment discharge piping which discharges the sediment of the bottom part of the said aeration suppression part is provided in the bottom part of the said aeration tank of the area | region by the side of the said aeration suppression part adjacent to the said aeration blocking wall. Water treatment system as described in. A first solid-liquid separation tank connected to the aeration tank and separating the sludge-containing treated water into purified treated water and concentrated sludge;
Concentrated sludge return piping for returning a part of the concentrated sludge to the aeration tank,
The water treatment system according to any one of claims 1 to 4 , wherein a connection portion of the concentrated sludge return pipe with the aeration tank is located on a side surface of the aeration tank and on the aeration suppression unit side. The water treatment system according to claim 5 , wherein the position of the end port is higher than the connection portion. A first sensor for measuring a sludge concentration of the sludge-containing treated water at the position of the terminal port;
The water treatment according to any one of claims 1 to 6 , further comprising a transfer amount control device that controls an amount of the sludge-containing treated water transferred to the ozone septic tank based on a measurement result of the first sensor. system. 8. The water according to claim 7 , wherein the transfer amount control device controls the amount of the sludge-containing treated water transferred to the ozone septic tank based on an average value of the measured values of the first sensor recorded at regular intervals. Processing system. A second sensor for measuring the concentration of the organic sludge in the sludge-containing treated water at the position of the end opening;
The water treatment system according to any one of claims 1 to 8 , further comprising an ozone generator control device that controls the ozone generator based on a measurement result of the second sensor. The water treatment system according to claim 9 , wherein the ozone generator control device controls the amount of ozone injected into the ozone septic tank based on an average value of the measurement values of the second sensor recorded at regular intervals. A second solid-liquid separation tank that separates the sludge-containing treated water that has been treated by the ozone purification tank into a precipitate and a supernatant, and a third sensor that measures the absorbance of ultraviolet light of the supernatant,
The water treatment system according to claim 9 or 10 , wherein the absorbance value is input to the ozone generator control device. An aeration process in which aeration apparatus for releasing gas in an aeration tank is used to aerate wastewater and grow microorganisms;
A biological treatment process for producing sludge-containing treated water using the sludge containing microorganisms;
A transfer step of transferring the sludge-containing treated water from the aeration tank to an ozone purification tank;
An ozone treatment step of injecting ozone gas into the sludge-containing treated water in the ozone septic tank;
In the ozone purifying tank, a return step for returning the sludge-containing treated water into which the ozone gas has been injected to the aeration tank,
In the transfer step, a boundary between an aeration promoting unit, which is a region where the aeration device is disposed below, and an aeration suppressing unit, which is a region where the aeration device does not exist below, inside the aeration tank A water treatment method for extracting the sludge-containing treated water from above or in the aeration suppressing part and from a surface layer part of the sludge-containing treated water , and transferring the sludge-containing treated water from above to the ozone purification tank. In the ozone treatment step, after separating the sludge-containing treated water into which ozone gas has been injected, into a precipitate and a supernatant liquid, the ultraviolet light measurement step of measuring the ultraviolet light absorbance of the supernatant liquid,
The water treatment method according to claim 12, wherein a set value of the amount of the ozone gas per unit weight of the organic sludge in the ozone treatment step is adjusted based on the absorbance value.

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