JP4421372B2 - Sewage treatment equipment - Google Patents

Description

  The present invention relates to a sewage treatment apparatus using an activated sludge method.

  Currently, in many sewage treatment facilities, sewage is purified by the activated sludge method. This is because the activated sludge method uses the metabolic action of microorganisms, so that the treatment efficiency is high and economical. Here, the activated sludge method will be described below.

  First, sewage is continuously supplied to a biological treatment tank (aeration tank) where it contacts a population of aerobic microorganisms. Thereby, the substrate (BOD component) of sewage is oxidatively decomposed by a population of aerobic microorganisms. This population of aerobic microorganisms is commonly referred to as “activated sludge”. Sewage treated in the biological treatment tank flows into the sedimentation tank together with the microbial population.

  In the settling tank, the microbial populations stick together to form a floc and settle. On the other hand, the supernatant (separated liquid) overflows. The microbial population settled in the sedimentation tank, that is, sludge is returned again to the biological treatment tank by the pump (return sludge), and the substrate is oxidatively decomposed again.

  However, since microorganisms multiply, returning all of the sludge may result in insufficient oxygen in the biological treatment tank or difficulty in solid-liquid separation in the sedimentation tank. For this reason, the proliferated portion is taken out of the system as surplus sludge and subjected to processing such as dehydration and incineration. Eventually, excess sludge is disposed of in landfills.

  However, in recent years, the number of sewage treatment facilities has increased, and along with this, the amount of excess sludge generated has also increased steadily. For this reason, it has become difficult year by year to secure a final disposal site for landfill. In each municipality, the cost for transporting and processing surplus sludge is increasing. Under such circumstances, various studies have been conducted on methods for reducing excess sludge.

  As a means for reducing surplus sludge, for example, it has been proposed to add a re-substrateing process to the treatment process of the activated sludge method (see, for example, Non-Patent Document 1). The re-substrateing process is a process in which a part of sludge (concentrated sludge) settled in a sedimentation tank is converted again into a biodegradable substrate (re-substrate). FIG. 6 is a diagram showing an outline of the activated sludge method to which a re-substrateing process is added.

  As shown in FIG. 6, the sludge generated in the biological treatment tank 51 is sent to a precipitation tank 53 where it is settled and concentrated. A part of the sludge settled in the sedimentation tank 53 is sent as it is to the biological treatment tank 51 as a return sludge, and another part is sent to the re-substrate forming apparatus 52.

  The re-substrate forming apparatus 52 performs killing of microorganisms in sludge, destruction of cell walls, solubilization / reduction in molecular weight, etc. by physical, chemical or biological methods. As a result, microorganisms in the sludge are killed, and the sludge is re-substrateed. Further, this re-substrate sludge (hereinafter referred to as “re-substrate sludge”) is sent again to the biological treatment tank 51 and is oxidatively decomposed by the microbial population. As a result, excess sludge can be reduced.

  Specific methods for re-substrate formation include ozone oxidation method, thermophilic bacteria method, bead mill method, hydrothermal treatment method, ultrasonic method, high-speed rotating disk method, water jet method, electrolysis method, high pressure treatment method, acid / alkali Processing methods, microwave methods, and the like are known. Among these, Non-Patent Document 1 discloses a method using a hydrothermal treatment method.

  Further, in Non-Patent Document 1, an attempt is made to theorize the mechanism of sludge reduction when a re-substrateing process by a hydrothermal treatment method is introduced. In addition, simulation analysis of a model constructed based on this theory is performed, thereby determining operating conditions such as the amount of resubstrate.

Further, in Non-Patent Document 1, the accuracy of the simulation analysis is also verified by comparing the value obtained from the simulation analysis with the actual measurement value. From this, it is considered that sludge can be reduced by incorporating a re-substrateing apparatus into an existing sewage treatment apparatus that implements the activated sludge process and operating the sewage treatment apparatus under the operating conditions disclosed in Non-Patent Document 1.
Tokuaki Okuda “Study on development of activated sludge process with reduced excess sludge by hydrothermal reaction”, Doctoral degree dissertation, Graduate School of Engineering, Osaka Institute of Technology, December 2002

  However, in a sewage treatment apparatus that incorporates a re-substrateing device, it is necessary to execute a re-substrateing process, which increases the burden on the administrator compared to a sewage treatment device that does not incorporate a re-substrateing device. End up. For this reason, even if the cost for disposal of surplus sludge can be reduced, an increase in operation cost due to an increase in the number of managers or the like is caused.

  Moreover, the operation conditions disclosed in Non-Patent Document 1 are conditions for reducing surplus sludge to the last, and do not contribute to labor saving of the sewage treatment apparatus. Furthermore, in Non-Patent Document 1, a model is constructed on the assumption that no excess sludge is generated, and an analysis simulation is performed based on the model. For this reason, when the sewage treatment apparatus is actually operated for a long time, the analysis result and the actual situation may be different.

  An object of the present invention is to provide a sewage treatment apparatus that can perform a re-substrate treatment in consideration of the generation of excess sludge and can suppress an increase in operation cost.

  In order to achieve the above object, the sewage treatment apparatus according to the present invention is a sewage treatment apparatus for purifying sewage by the activated sludge method, and separates the biological treatment tank and the sewage treated in the biological treatment tank from the concentrated sludge. A solid-liquid separation means for separating the concentrated sludge, a re-substrate forming means for re-substrateing the concentrated sludge, and a first re-substrate forming line for sending the concentrated sludge to the re-substrate forming means A second re-substrateing line for sending re-substrate sludge generated by the re-substrate treatment to the biological treatment tank, and a return line for returning the concentrated sludge to the biological treatment tank A discharge line for discharging the concentrated sludge to the outside as surplus sludge, a control means, and the resubstrateization means of the concentrated sludge by the first resubstrateization line according to an instruction of the control means Introduction and discharge Line switching means for switching to any one of the discharge of the excess sludge to the outside by the tank, the control means, in a state where the discharge to the outside by the discharge line is stopped by the line switching means, From the concentration Xd1 of the inactive sludge in the biological treatment tank, the concentration Sd of the inflowing substrate in the biological treatment tank and the separation liquid, and the solubilized component concentration Se of the re-substrate in the biological treatment tank and the separation liquid The daily amount Qr of the re-substrate sludge that can be supplied to the biological treatment tank and the daily amount Qe of the excess sludge that needs to be discharged when the Qr is achieved are calculated and calculated. The line switching unit is switched so that the Qr and the Qe are satisfied.

  As described above, according to the sewage treatment apparatus of the present invention, the amount of re-substrate sludge that can be supplied to the biological treatment tank per day is calculated by the control means. In addition, the calculation of the daily amount of re-substrate sludge that can be supplied to the biological treatment tank is performed in consideration of the generation of excess sludge. Furthermore, the control means also calculates the amount of surplus sludge per day that needs to be discharged in order to achieve the calculated amount of re-substrate sludge per day. For this reason, it is possible to perform the re-substrate treatment in consideration of the generation of excess sludge, and the deviation between the actual situation and the calculation result is suppressed. In addition, since the calculation can be performed by the control means in this way, the supply of the calculated re-substrate sludge to the biological treatment tank and the discharge of the surplus sludge for the calculated amount can be easily automated. Can also be suppressed.

In the sewage treatment apparatus according to the present invention, the substrate concentration Sa of sewage flowing from the outside to the biological treatment tank on the inflow side of the sewage in the biological treatment tank, and the sewage flowing from the outside to the biological treatment tank. A first measuring means for measuring the amount Qa per day is provided, the sludge concentration X4 in the re-substrate sludge and the re-substrate in the re-substrate sludge in the second re-substrate sludge A second measuring means for measuring the solubilized component concentration Sc is provided, and the biological treatment tank has a sum of the activated sludge concentration Xa1 in the biological treatment tank and the non-activated sludge concentration Xd1 in the biological treatment tank. A third measuring means for measuring the sludge concentration X1 in the biological treatment tank is provided, and the sludge concentration X2 in the separated liquid and the Sd are disposed on the separation liquid discharge side of the solid-liquid separating means. The biological treatment which is the sum of Se And a fourth measurement means for measuring the substrate concentration S in the separation liquid, and a fifth measurement for measuring the sludge concentration X3 in the concentrated sludge on the discharge side of the concentrated sludge of the solid-liquid separation means. Means, and the control means has a storage unit, and the storage unit has a sludge conversion rate a ₁ of the substrate in the sewage flowing from the outside into the biological treatment tank, and the re-substrate in the biological treatment tank. The sludge conversion rate a ₂ of the suspended component of the activated sludge, the sludge conversion rate a ₃ of the solubilized component of the resubstrate sludge in the biological treatment tank, and the decomposition of the substrate in the sewage flowing into the biological treatment tank from the outside The rate k ₁ , the decomposition rate k ₂ of the suspended component of the resubstrate sludge in the biological treatment tank, the decomposition rate k _{3 of} the solubilized component of the resubstrate sludge in the biological treatment tank, and the biological treatment tank from the outside Saturation constant Ks ₁ of substrate in wastewater flowing into The saturation constant Ks ₂ of the suspended component of the resubstrate sludge in the biological treatment tank, the saturation constant Ks _{3 of} the solubilized component of the resubstrate sludge in the biological treatment tank, the autooxidation rate b of the activated sludge, The volume V1 of sewage in the biological treatment tank, the ratio between Se and S (Se / S), the ratio between Xa1 and X1 (Xa1 / X1) are stored, and the control means includes the first The value measured by the fifth measuring means from one measuring means and the value stored in the storage unit are supplied to the biological treatment tank by substituting them into the following formulas (1) to (8) It is preferable to calculate the daily amount Qr of the re-substrate sludge that can be produced and the daily amount Qe of the excess sludge that needs to be discharged when the Qr is achieved. According to this aspect, appropriate Qr and Qe can be easily calculated.

  In the sewage treatment apparatus of the present invention, the control means includes a detection unit, and the first measurement means, the second measurement means, the third measurement means, the fourth measurement means, Preferably, at least one of the fifth measurement means outputs a signal corresponding to each measurement value to the detection unit, and the detection unit detects the measurement value from the signal. In this case, the coefficient can be automatically detected by the control means.

  Further, it is preferable that the re-substrate forming means is an ultrasonic treatment device or a hydrothermal treatment device. In this case, the certainty of the re-substrate treatment can be increased.

  In the sewage treatment apparatus of the present invention, the daily amount of the concentrated sludge introduced into the re-substrateing means by the first re-substrate forming line is measured in the first re-substrate forming line. A first flow meter is provided, and a second flow meter for measuring a daily amount of the excess sludge discharged from the discharge line is provided in the discharge line, and the control means includes It is determined whether or not the value measured by the first flow meter has reached the daily amount Qr of the re-substrate sludge that can be supplied to the biological treatment tank. The introduction of the concentrated sludge by the first resubstrate line is stopped, and further, whether the value measured by the second flow meter has reached the daily amount Qe of the excess sludge If the result is The down switching means, preferably in the manner to stop the discharge of the excess sludge by the discharge line. According to this aspect, a necessary amount of concentrated sludge can be automatically supplied to the re-substrate forming means. Moreover, a necessary amount of excess sludge can be automatically discharged.

  Hereinafter, an example of the sewage treatment apparatus of the present invention will be described with reference to FIGS. First, a material balance model of the sewage treatment apparatus of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a material balance model of the sewage treatment apparatus of the present invention.

  As shown in FIG. 1, when sewage flows into the biological treatment tank 1 from the outside of the sewage treatment apparatus, the substrate in the sewage is oxidatively decomposed by microorganisms in the biological treatment tank 1. Thereby, sludge is generated. The biologically treated sewage is sent to a solid-liquid separation means (not shown in FIG. 1) and separated into a separation liquid and concentrated sludge. The separated liquid is discharged as treated water.

  On the other hand, a part of the concentrated sludge is sent to the re-substrate forming apparatus 2 as a drawn sludge and re-substrate. The concentrated sludge that has been re-substrate (re-substrate sludge) can be oxidatively decomposed again, and is returned to the biological treatment tank 1. Although the other part of the concentrated sludge is not shown in FIG. 1, it is sent directly to the biological treatment tank 1 as return sludge and used for biological treatment. The remaining concentrated sludge is discharged to the outside as excess sludge.

  Therefore, in order to reduce the daily amount Qe (L / day) of excess sludge, the daily amount Qr (L / day) of concentrated sludge (drawn sludge) to be sent to the re-substrateing device 2 is appropriately set. Must be a value. Table 1 shows the definition of each parameter described in FIG.

  In the parameters shown in Table 1, XN = XaN + XdN (N = 1, 2, 3, 4) and S = Sd + Se.

  The growth and decomposition of sludge in the biological treatment tank 1 shown in FIG. 1 can be expressed by the following formulas (1) to (3) using the parameters shown in Table 1. Moreover, decomposition | disassembly of the soluble substrate in the biological treatment tank 1 shown in FIG. 1 can be shown by following formula (4)-(6) using the parameter shown in Table 1. FIG.

  Table 2 shows definitions of various coefficients used in the following formulas (1) to (6).

The units a ₁ , a ₂ , and a ₃ in Table 2 are not particularly limited, but these units include “g-SS / g-BOD” and “g-SS / g-SS”. , “G-SS / g-COD”, “g-SS / g-TOC” and the like.

  FIG. 2 is a diagram conceptually showing the re-substrate sludge. As shown in FIG. 2, some of the concentrated sludge (activated sludge) sent to the re-substrate forming apparatus 2 (see FIG. 1) can be oxidatively decomposed by microorganisms by re-substrate treatment. It becomes chemical sludge. The remainder remains unsubstrate sludge that cannot be oxidatively decomposed by microorganisms. At this time, assuming that the re-substrateization rate of the concentrated sludge is ε and the non-substrate conversion rate of the concentrated sludge is δ, ε + δ = 1.

  In FIG. 2, γ represents a conversion coefficient of concentrated sludge to re-substrate sludge. The conversion factor γ to resubstrate sludge can be obtained by measuring the sludge concentration and substrate concentration of the resubstrate sludge and calculating the ratio. Examples of the unit of the conversion coefficient γ to re-substrate sludge include [g-BOD / g-SS], [g-COD / g-SS], [g-TOC / g-SS] and the like. Usually, the conversion factor γ of the re-substrate sludge is about 0.4 [g-TOC / g-SS].

  Moreover, as shown in FIG. 2, the re-substrate sludge is divided into a suspended component and a solubilized component. If the suspension rate of the re-substrate sludge is ζ and the solubilization rate of the re-substrate sludge is η, ζ + η = 1. Furthermore, the solubilized component includes a dissolved component and a gas component dissolved in the waste water. When the dissolution rate of the solubilized component of the re-substrate sludge is θ and the gasification rate is ι, θ + ι = 1.

  Here, the material balance in the material balance model shown in FIG. 1 is examined. When paying attention to the sludge concentration X1 (mg / L) in the biological treatment tank 1, the mass balance is expressed by the following equations (9) and (10). Further, the following formula (7) is derived from the above formula (3) and the following formulas (9) and (10).

  Further, when paying attention to the biological treatment tank 1 and the substrate concentration S (mg / L) in the separation liquid, the mass balance is expressed by the following equations (11) and (12). Further, the following formula (8) is derived from the above formula (6) and the following formulas (11) and (12).

  Therefore, the amount Qr (L / day) of re-substrate sludge that can be supplied to the biological treatment tank 1 in consideration of the generation of surplus sludge (ie, the amount of concentrated sludge that is sent to the re-substrate formation device 2 per day) ) Is considered to be an appropriate value, it is desirable to operate the sewage treatment apparatus so that Qr satisfies the above mass balance equations (7) and (8). For this reason, in an example of the sewage treatment apparatus of the present invention shown in FIG. 3 below, the daily amount Qr of re-substrate sludge that can be supplied to the biological treatment tank 1 using the above formulas (1) to (8). (L / day) and surplus sludge amount Qe (L / day) are determined.

  Next, the configuration of the sewage treatment apparatus of the present invention will be described with reference to FIGS. FIG. 3 is a block diagram showing an example of the sewage treatment apparatus of the present invention. 4A and 4B are diagrams showing an example of the re-substrate forming apparatus. FIG. 4A is a side view and FIG. 4B is a bottom view.

  As shown in FIG. 3, the sewage treatment apparatus includes a biological treatment tank 1 for performing an activated sludge method, a re-substrateing apparatus 2, a sedimentation tank 3, and a control apparatus 15. Microorganisms are present in the biological treatment tank 1. Therefore, the substrate in the wastewater flowing from the outside is oxidatively decomposed by this microorganism. Sewage treated by the biological treatment tank 1 flows into the sedimentation tank 3.

  The sedimentation tank 3 functions as a solid-liquid separation means for separating the sewage treated in the biological treatment tank 1 into the concentrated sludge 22 and the separation liquid 21. The separation liquid 21 is discharged to the outside by overflow. On the other hand, the concentrated sludge 22 is discharged out of the sedimentation tank 3 by suction by the pump 4 through a drawing line 27 connected to the bottom of the sedimentation tank 3.

  In the present invention, the line means a flow path. In the example of FIG. 3, the precipitation tank 3 is used as the solid-liquid separation means, but the solid-liquid separation means is not limited to this. In the present invention, a membrane separation device, a pressurized flotation separation device, a centrifugal separation device, or the like may be used as the solid-liquid separation means. Furthermore, instead of the biological treatment tank 1 and the sedimentation tank 3, a batch processing apparatus in which the biological treatment tank and the solid-liquid separation means are integrated may be used.

  The resubstrate forming apparatus 2 performs a resubstrate forming process on the concentrated sludge 22 obtained in the settling tank 3. In the present invention, the type of the resubstrate forming apparatus 2 is not particularly limited, and may be a hydrothermal apparatus that performs resubstrate by hydrothermal treatment, or an ultrasonic processing apparatus that performs resubstrate by ultrasonic treatment. It may be. Furthermore, as the re-substrate forming apparatus 2, ozone oxidation method, thermophilic bacteria method, bead mill method, high-speed rotating disk method, water jet method, electrolysis method, high pressure treatment method, acid / alkali treatment method, microwave method, etc. It is also possible to use an apparatus for performing a re-substrateing treatment.

  In the example of FIG. 3, the ultrasonic treatment apparatus shown in FIG. 4 is used as the re-substrate forming apparatus 2. In the example of FIG. 4, the ultrasonic processing apparatus is configured by attaching a plurality of ultrasonic transducers 32 to the bottom surface of a processing tank 31 that stores concentrated sludge. With this configuration, in the concentrated sludge sent into the treatment tank 31, cavitation is generated by the ultrasonic waves from the ultrasonic vibrator 32. As a result, microorganisms in the concentrated sludge are destroyed and solubilized. In the example of FIGS. 3 and 4, the operation and output adjustment of the re-substrate forming apparatus 2 are performed by the control device 15.

  Moreover, when using an ultrasonic treatment apparatus as the re-substrate forming apparatus 2, it is preferable to set the ultrasonic frequency to 20 kHz to 100 kHz, particularly 20 kHz to 40 kHz. Note that the ultrasonic treatment apparatus that can be used as the re-substrate forming apparatus 2 is not limited to the example shown in FIG.

  Moreover, when using the hydrothermal processing apparatus which performs re-substrate-izing by hydrothermal processing as the re-substrate-forming apparatus 2, it is preferable to set reaction temperature to 100 to 300 degreeC, especially 100 to 200 degreeC. The configuration of the hydrothermal treatment apparatus is not particularly limited. Further, in the hydrothermal treatment apparatus, the heating method is not particularly limited, and may be a continuous type or a batch type. Further, a heating unit for performing the hydrothermal treatment is not particularly limited, and a boiler, a heater, an electromagnetic induction device, a microwave irradiation device, or the like can be used as the heating unit.

  Further, as shown in FIG. 3, the drawing line 27 branches into a return line 23, a first re-substrate line 24, and a discharge line 26. The return line 23 is a line for returning the concentrated sludge 22 to the biological treatment tank 1 as it is. The first resubstrate forming line 24 is a line for introducing concentrated sludge into the resubstrate forming apparatus 2. The discharge line 26 is a line for discharging the concentrated sludge 22 to the outside as excess sludge.

  Each branch line is provided with valves 5 to 7. The valves 5 to 7 are automatic valves that can be opened and closed by inputting signals, and function as line switching means. In the example of FIG. 3, the opening / closing of the valves 5 to 7 is controlled by the control device 15. Reference numeral 25 denotes a second re-substrate forming line for sending the sludge (re-substrate sludge) re-substrateed by the re-substrate forming apparatus 2 to the biological treatment tank 1.

  Further, in the sewage treatment apparatus shown in FIG. 3, five measuring means from the first measuring means 8 to the fifth measuring means 12 are provided. Further, in the example of FIG. 3, each measurement unit, except for the second measurement unit 9, has a function of outputting a signal corresponding to the measured value to the detection unit 16 of the control device 15. The value measured by the second measuring means 9 is input from the input unit 20 to the control device 15 by the operator of the sewage treatment apparatus. The input value is stored in the storage unit 18.

  The second measuring means 9 can be given a function of outputting a signal corresponding to the measured value to the detecting unit 16 of the control device 15. In addition, the measurement means other than the second measurement means 9 may not have a function of outputting a signal to the control device 15, and in this case, the measured value is the operator of the sewage treatment apparatus. Is input from the input unit 20.

  The first measuring means 8 is provided on the sewage inflow side in the biological treatment tank 1. The first measuring means 8 includes a load measuring device for measuring the substrate concentration Sa (mg / L) of sewage flowing into the biological treatment tank 1 from the outside, and the daily sewage flowing into the biological treatment tank from the outside. And a flow meter for measuring the amount Qa (L / day) of the gas.

  The second measuring means 9 is attached to a line branched from the second re-substrateing line 25. The second measuring means 9 measures the sludge concentration X4 (mg / L) in the re-substrate sludge and the solubilized component concentration Sc (mg / L) of the re-substrate in the re-substrate sludge. In the example of FIG. 3, the second measuring means 9 includes a first measuring tank (not shown) and a second measuring tank (not shown). Each measurement tank is provided with a load measuring device.

  The supply port of the first measuring tank is equipped with a filter (not shown) having a particle holding capacity of 5 μm or more, preferably 1.2 μm or more. It is measured as the solubilized component concentration Sc (mg / L) of the re-substrate in the sludge. Furthermore, the supply port of the second measuring tank is provided with a filter (not shown) having a particle holding capacity of 125 μm or more, preferably 37 μm or more. It is measured as sludge concentration X4 (mg / L) in the activated sludge.

  Further, the measurement of X4 and Sc by the second measuring means 9 is performed in a state where the discharge by the discharge line 26 is stopped by the line switching means, that is, only the valve 7 is closed. The value measured by the second measuring means 9 is input to the control device 15 from the input unit 20 by the operator of the sewage treatment apparatus as described above.

  Further, from the X4 and Sc measured by the second measuring means, the re-substrateization rate ε of the concentrated sludge, the suspension rate ζ of the re-substrate sludge described above with reference to FIG. The solubilization rate η (see FIG. 2) can be calculated. The dissolution rate θ of the solubilized component of the resubstrate sludge and the gasification rate ι (see FIG. 2) of the solubilized component of the resubstrate sludge can be calculated from the amount of TOC loss in the resubstrate treatment. However, when an ultrasonic treatment device or a hydrothermal treatment device is used as the re-substrate forming device 2, gasification does not usually occur, and θ = 1 and ι = 0.

  The third measuring means 10 is attached to the biological treatment tank 1. The third measuring means 10 is an SS meter, and measures the sludge concentration X1 (mg / L) in the biological treatment tank 1. The fourth measuring means 11 is provided on the discharge side of the separation liquid 21 in the settling tank 3. The fourth measuring means 11 is composed of an SS meter for measuring the sludge concentration X2 (mg / L) in the separation liquid 21 and a load measuring device for measuring the substrate concentration S (mg / L) in the separation liquid 21. Has been. X2 measured at this time also corresponds to the sludge concentration in the biological treatment tank 1. S also corresponds to the substrate concentration in the biological treatment tank 1.

  The fifth measuring means 12 is provided on the discharge side of the concentrated sludge 22 in the settling tank 3, that is, on the drawing line 27. The fifth measuring means 12 is an SS meter that measures the sludge concentration X3 in the concentrated sludge 22.

  In addition, the load measuring device used in the example of FIG. 3 is not particularly limited. Examples of the load measuring device include a BOD meter, a COD meter, an SS meter, and a TOC meter. Moreover, when using SS meter, the measuring method is not specifically limited. As the SS meter, for example, one using an absorbance measurement method or a scattered light measurement method can be used. Also, when a COD meter is used, the measurement method is not particularly limited. As the COD meter, for example, one using an absorbance measurement method can be used.

  Further, as shown in FIG. 3, a flow meter 13 is provided between the valve 6 and the resubstrate forming apparatus 2 in the first resubstrate forming line 24. The flow meter 13 measures the amount (L / day) of the concentrated sludge sent to the re-substrateing apparatus 2. Furthermore, a flow meter 14 is provided on the downstream side of the valve 7 in the discharge line 26. The flow meter 14 measures the amount (L / day) of excess sludge that passes through the discharge line 26. Further, the flow meters 13 and 14 output a signal corresponding to the measured value to the detection unit 16. The types of the flow meters 13 and 14 are not particularly limited. Specifically, an ultrasonic flowmeter or an electromagnetic flowmeter can be used.

  In the example of FIG. 3, the control device 15 includes a detection unit 16, a calculation unit 17, a storage unit 18, a drive unit 19, and an input unit 20. The detection unit 16 is connected to the first measurement unit 8 to the fifth measurement unit 12 (excluding the second measurement unit 9) and the flow meters 13 and 14, and signals output from the respective measurement units and the flow meter. Is input to the detector 16.

  Moreover, the detection part 16 is the quantity Qr (L / day) of the re-substrate-ized sludge which can be supplied to the biological treatment tank 1 from the input signal, and the quantity Qe (L / day) of the excess sludge to be discharged. The coefficient necessary for the calculation of is detected. Specifically, the detection unit 16 detects the substrate concentration Sa (mg / L) of sewage flowing into the biological treatment tank 1 from the outside and the biological treatment tank 1 from the outside by a signal from the first measuring means 8. And the amount Qa (L / day) per day of the inflowing sewage is detected.

  Furthermore, the detection unit 16 detects the sludge concentration X1 (mg / L) in the biological treatment tank 1 based on the signal from the third measurement unit 10, and in the separated liquid based on the signal from the fourth measurement unit 11. The sludge concentration X2 (mg / L) and the substrate concentration S (mg / L) in the separation liquid 21 are detected. Further, the detection unit 16 detects the sludge concentration X3 (mg / L) in the concentrated sludge 22 based on the signal from the fifth measuring means 12.

  The detection unit 16 also measures the sludge concentration X4 (mg / L) in the resubstrate sludge and the solubilized component concentration Sc (mg in the resubstrate sludge) measured by the second measuring means 9. / L) is also detected. However, in the example of FIG. 3, the detection of X4 and Sc is performed by the detection unit 16 reading X4 and Sc from the storage unit 18. In the example of FIG. 3, the detection unit 16 also determines whether X4 and Sc are stored in the storage unit 18.

  The storage unit 18 is necessary to calculate the daily amount Qr (L / day) of re-substrate sludge that can be supplied to the biological treatment tank 1 and the daily amount Qe (L / day) of excess sludge to be discharged. Which are coefficients that cannot be obtained from each measuring means. The storage unit 18 also stores the above-described formulas (1) to (8). In the example of FIG. 3, the coefficient that cannot be obtained from each measurement means is input by the operator via the input unit 20. The storage unit 18 can also store the coefficient detected by the detection unit 16.

In the example of FIG. 3, as the coefficients stored in the storage unit 18, the inflow substrate sludge conversion rate a ₁ (g-SS / g-TOC), the re-substrate suspended component sludge conversion rate a ₂ (g-SS / g -SS), and resubstrate solubilization component sludge conversion rate a ₃ (g-SS / g-TOC). Also included are the inflowing substrate decomposition rate k ₁ (1 / day), the re-substrate suspension component decomposition rate k ₂ (1 / day), and the re-substrate solubilizing component decomposition rate k ₃ (1 / day).

Furthermore, the coefficients stored in the storage unit 18 include the inflow substrate saturation constant Ks ₁ (mg / L), the re-substrate suspension component saturation constant Ks ₂ (mg / L), and the re-substrate solubilization component saturation constant Ks ₃ ( mg / L), and the autooxidation rate b (1 / day) of activated sludge. The storage unit 18 also stores the volume V1 of sewage in the biological treatment tank 1, the ratio between Se and S (Se / S), and the ratio between Xa1 and X1 (Xa1 / X1).

  The calculation unit 17 uses the measurement value detected by the detection unit 16 and the coefficient stored in the other storage unit 18 to send the amount Qr (L / day) of the concentrated sludge to be sent to the re-substrateing apparatus 2. And the amount Qe (L / day) of excess sludge to be discharged. In the example of FIG. 3, the calculation by the calculation unit 17 is performed by substituting the detected measurement value and the read coefficient into the above-described equations (1) to (8).

  The drive unit 19 outputs a signal for performing an opening / closing operation of the valves 5, 6, and 7 that function as a line switching unit in response to an instruction from the calculation unit 17. For example, when the arithmetic unit 17 instructs to introduce the concentrated sludge into the re-substrate forming apparatus 2, the driving unit 19 opens the valve 6 and closes the valve 7. When the calculation unit 17 instructs to discharge the excess sludge, the drive unit 19 closes the valve 6 and opens the valve 7.

  Further, the amount of concentrated sludge introduced into the re-substrateing apparatus 2 via the first re-substrateing line 24 is measured by the flow meter 13 and detected by the detection unit 16. Similarly, the amount of excess sludge discharged from the discharge line 26 is measured by the flow meter 14 and detected by the detection unit 16. For this reason, the arithmetic unit 17 performs feedback control so that the calculated Qr and Qe are achieved.

  Next, operation | movement of the sewage treatment apparatus shown in FIG. 3 is demonstrated using FIG. FIG. 5 is a flowchart showing the operation of the sewage treatment apparatus shown in FIG. In the following description, FIG. 3 is taken into consideration as appropriate.

As shown in FIG. 5, first, the calculation unit 17 reads out coefficients necessary for calculating the concentrated sludge amount Qr and the excess sludge amount Qe from the storage unit 18 (step S <b> 1). The coefficients to be read are a ₁ (g-SS / g-TOC), a ₂ (g-SS / g-SS), a ₃ (g-SS / g-TOC), k ₁ (1 / day) described above. ), K ₂ (1 / day), k ₃ (1 / day), Ks ₁ (mg / L), Ks ₂ (mg / L), Ks ₃ (mg / L), b (1 / day), V1 , Se / S, Xa1 / X1.

  Next, the calculation unit 17 gives an instruction to the drive unit 19 to close only the valve 7 (step S2). Next, in this state, the calculation unit 17 causes the detection unit 16 to perform the following steps S3 to S6. Note that the order of steps S3 to S6 is not particularly limited, and these can be performed simultaneously.

  In step S <b> 3, the detection unit 16 flows into the biological treatment tank 1 and the substrate concentration Sa (mg / L) of sewage flowing into the biological treatment tank 1 from the outside by a signal from the first measuring means 8. The amount of sewage per day Qa (L / day) is detected.

  In step S4, the detection unit 16 determines the sludge concentration X2 (mg / L) in the separation liquid 21 and the substrate concentration S (mg / L) in the separation liquid 21 based on a signal from the fourth measurement unit 11. To detect. In step S <b> 5, the detection unit 16 detects the sludge concentration X <b> 1 (mg / L) in the biological treatment tank 1 by the third measuring means 10. In step S <b> 6, the detection unit 16 detects the sludge concentration X <b> 3 (mg / L) in the concentrated sludge 22 by the fifth measuring unit 12.

  Next, the detection unit 16 inputs the sludge concentration X4 (mg / L) in the resubstrate sludge and the solubilized component concentration Sc (mg / L) of the resubstrate in the resubstrate sludge. It is determined whether it is stored in the storage unit 18 (step S7). If stored, the detection unit 16 reads X4 and Sc from the storage unit 18 (step S8). When not stored, the detection unit 16 enters a standby state.

  Steps S7 and S8 can also be executed before any of steps S3 to S6. Further, measurement and input of X4 and Sc may be performed before execution of the steps shown in FIG.

  Next, the calculation unit 17 reads the equations (1) to (8) stored in the storage unit 18, and substitutes the measurement values and coefficients obtained in steps S1, S3 to S6, and S8 into these equations. (Step S9). As a result, the amount Qr (L / day) of the re-substrate sludge per day that can be supplied to the biological treatment tank 1 and the amount Qe (L / day) of the excess sludge that needs to be discharged when Qr is achieved. And are calculated. Since the values of Xa1 and Xd1 are X1 = Xa1 + Xd1 as described above, they are calculated from the detected value of X1 and the read value of (Xa1 / X1). The same applies to the values of Se and Sd.

  Next, the calculation unit 17 gives an instruction to the drive unit 19 so that the resubstrate line valve 6 is opened and the discharge line valve 7 is closed (step S10). As a result, the concentrated sludge 22 flows through the first re-substrateization line 24, the re-substrate sludge flows through the second re-substrate formation line 25, and the re-substrate sludge flows into the biological treatment tank 1. Moreover, the discharge of excess sludge is stopped. In this case, the valve 5 may be in an open state or a closed state.

  Next, the calculation unit 17 determines whether or not the amount of concentrated sludge measured by the flow meter 13 and detected by the detection unit 16 has reached the amount Qr (L / day) of concentrated sludge calculated in step S8. Is determined (step S11). If not, the calculation unit 17 enters a standby state while the drive unit 19 maintains the state of step S10.

  When it arrives, the calculating part 17 gives the instruction | indication to the drive part 19 so that the valve | bulb 6 for re-substrate formation lines may be in a closed state, and the valve | bulb 7 for discharge lines may be in an open state (step S11). In addition, the arithmetic unit 17 outputs a signal to the resubstrate forming apparatus 2 to stop the operation. In this case as well, the valve 5 may be open or closed.

  Next, the calculation unit 17 determines whether or not the amount of excess sludge measured by the flow meter 14 and detected by the detection unit 16 has reached the amount Qe (L / day) of excess sludge calculated in step S8. Is determined (step S13). If not, the calculation unit 17 enters a standby state while the drive unit 19 maintains the state of step S12. When it arrives, the calculating part 17 gives an instruction | indication to the drive part 19 so that the valve | bulb 7 for discharge lines may be closed, and complete | finishes a process.

As described above, according to the sewage treatment apparatus shown in FIG. 3, the control device 15 automatically discharges the re-substrate sludge that can be supplied to the biological treatment tank 1 per day, Qr, and Qr. A necessary amount Qe of excess sludge per day is calculated. The control device 15 automatically supplies the calculated re-substrate sludge to the biological treatment tank 1 and discharges the calculated excess sludge. For this reason, it is possible to perform the re-substrate treatment in consideration of the generation of excess sludge, and at the same time, it is possible to suppress an increase in the burden on the administrator, so it is possible to suppress an increase in operation cost. The coefficient to be set will be described. In the present invention, the value of the coefficient stored in advance in the storage unit 18 can be set as appropriate by experiment according to the type of sewage. For example, the inflow substrate sludge conversion rate a ₁ , the resubstrate suspension component sludge conversion rate a ₂ , the resubstrate solubilization component sludge conversion rate a ₃ , and the autooxidation rate b are the same as those described in “Non-Patent Document 1”. It can be determined by measuring the amount of change in substrate and the amount of change in sludge by batch-type biological treatment experiments described on pages 91 to 102.

Similarly, inflow substrate decomposition rate k ₁ , resubstrate suspension component decomposition rate k ₂ , resubstrate solubilization component decomposition rate k ₃ , inflow substrate saturation constant Ks ₁ , resubstrate suspension component saturation constant Ks _2. , And the resubstrate solubilization component saturation constant Ks ₃ can also be determined. An example of coefficients obtained by the biological treatment experiment described in Non-Patent Document 1 is shown in Table 3 below.

  The ratio of Se to S (Se / S) is the ratio of the solubilizing component of the re-substrate sludge. (Se / S) can be calculated from, for example, the following equation (13) using data obtained when the sewage treatment apparatus is operated on the day before the day of executing the steps shown in FIG.

  In the following formula (13), PQr is the amount Qr (g / day) per day of the re-substrate sludge that can be supplied to the biological treatment tank 1 calculated on the previous day. Moreover, PQa is the amount Qa (g / day) per day of sewage that flows into the biological treatment tank 1 from the outside, detected on the previous day. PSc is the solubilized component concentration Sc (mg / L) of the re-substrate in the re-substrate sludge detected on the previous day. PSa is the substrate concentration Sa (mg / L) of sewage that flows into the biological treatment tank 1 from the outside, detected the previous day.

  Further, the calculation by the equation (13) can be performed by the calculation unit 17. The calculation step using the equation (13) by the calculation unit 17 may be performed before the execution of the step shown in FIG. 5 or after any one of the steps S1 to S6 shown in FIG. You can go.

  However, when there is no data on the day before the day of executing the step shown in FIG. 5, the calculation unit 17 uses the data acquired in steps S <b> 3 to S <b> 8 and the predicted re-substrate sludge amount input in advance to step S <b> 9. It is preferable that (Se / S) is calculated before execution. Specifically, the calculation unit 17 substitutes Qa and Sa detected in step S3 for the above equation (13) instead of PQa and PSa. Further, instead of PSc, Sc detected (read) in step S8 is substituted into the above equation (13). Further, the predicted re-substrate sludge amount is substituted in place of PQr.

The predicted re-substrate sludge amount is obtained by multiplying the substrate concentration Sa (mg / L) of the sewage flowing into the biological treatment tank 1 by the inflow substrate sludge conversion rate a ₁ to obtain the predicted surplus sludge amount. Can be calculated by multiplying by an arbitrary coefficient. The coefficient by which the predicted surplus sludge amount is multiplied can be appropriately set within the range of 1 to 10, preferably within the range of 2 to 4, taking into consideration the performance of the re-substrateing apparatus.

  Moreover, the ratio (Xa1 / X1) of Xa1 and X1 has shown the ratio of the activated sludge in the sludge in the biological treatment tank 1. FIG. In the example of FIG. 3, (Xa1 / X1) is obtained by considering activated sludge as non-resubstrate sludge. Specifically, the ratio of the suspended component inhibited by a filter having a particle holding capacity of 125 μm or more, preferably 37 μm or more is measured, and this measured value is input to the storage unit 18 as (Xa1 / X1). In addition, the number of viable bacteria in the suspension component in the biological treatment tank 1 or ATP (adenosine triphosphate) or the like can be measured, and this measured value can be input to the storage unit 18 as (Xa1 / X1).

  Note that the values of (Se / S) and (Xa1 / X1) vary with variations in the operating conditions of the biological treatment tank 1 and the re-substrate forming apparatus 2. For this reason, these values are preferably measured and updated as needed.

  In the present invention, the control device 15 can be realized by installing a program for implementing steps S1 to S13 shown in FIG. 5 in a computer having an input / output interface and executing the program. In this case, a central processing unit (CPU) of the computer functions as a detection unit, a calculation unit, and a drive unit, and performs processing. A storage device such as a memory or a hard disk provided in the computer functions as a storage unit. In addition, a mouse, a keyboard, and the like provided in the computer function as an input unit. The data input to the control device 15 can also be performed from another computer connected by wire or wirelessly.

  As described above, according to the sewage treatment apparatus of the present invention, it is possible to perform the re-substrate treatment in consideration of the generation of excess sludge, and as a result, the generation of excess sludge can be minimized. For this reason, the cost concerning disposal of surplus sludge can be reduced, and it can also contribute to the solution of the problem that securing of the disposal site of surplus sludge is difficult. Furthermore, since an increase in operation cost is suppressed, introduction is easy.

It is a figure which shows the material balance model of the sewage treatment apparatus of this invention. It is a figure which shows notionally re-substrate sludge. It is a block diagram which shows an example of the sewage treatment apparatus of this invention. It is a figure which shows an example of the re-matrixization apparatus, Fig.4 (a) is a side view, FIG.4 (b) is a bottom view. It is a flowchart which shows operation | movement of the sewage treatment apparatus shown in FIG. It is a figure which shows the outline of the activated sludge method to which the re-substrate formation process was added.

Explanation of symbols

1 Biological treatment tank 2 Re-substrateing device 3 Precipitation tank (Solid-liquid separation means)
4 Pump 5, 6, 7 Valve 8 First measurement means 9 Second measurement means 10 Third measurement means 11 Fourth measurement means 12 Fifth measurement means 13, 14 Flow meter 15 Control device 16 Detection unit 17 Arithmetic unit 18 Storage unit 19 Drive unit 20 Input unit 21 Separation liquid 22 Concentrated sludge 23 Return line 24, 48 First resubstrate line 25, 49 Second resubstrate line 26 Discharge line 27 Extraction line 31 Treatment tank 32 Ultrasonic transducer

Claims (5)

A sewage treatment apparatus for purifying sewage by an activated sludge method,
A biological treatment tank, solid-liquid separation means for separating sewage treated in the biological treatment tank into concentrated sludge and a separation liquid, a re-substrateing means for performing a re-substrate treatment on the concentrated sludge, and the concentration A first re-substrateing line for sending sludge to the re-substrateing means, and a second re-substrateing line for sending the re-substrateing sludge generated by the re-substrateing treatment to the biological treatment tank A return line for returning the concentrated sludge to the biological treatment tank, a discharge line for discharging the concentrated sludge to the outside as excess sludge, a control means, and according to instructions from the control means And at least line switching means for switching to any one of introduction of the concentrated sludge to the resubstrateization means by the first resubstrateization line and discharge of the excess sludge to the outside by the discharge line,
The control means has a non-activated sludge concentration Xd1 in the biological treatment tank and an inflow substrate in the biological treatment tank and the separation liquid in a state where the discharge by the discharge line is stopped by the line switching means. The amount Qr of the resubstrate sludge that can be supplied to the biological treatment tank Qr and the Qr from the concentration Sd of the biological treatment tank and the solubilized component concentration Se of the resubstrate in the biological treatment tank and the separation liquid A wastewater treatment apparatus that calculates the amount Qe of the surplus sludge per day that needs to be discharged when it is achieved, and causes the line switching means to perform switching so that the calculated Qr and Qe are satisfied. On the inflow side of the sewage in the biological treatment tank, the substrate concentration Sa of the sewage flowing into the biological treatment tank from the outside and the daily amount Qa of the sewage flowing into the biological treatment tank from the outside are measured. A first measuring means is provided;
The second re-substrateization line is provided with second measurement means for measuring the sludge concentration X4 in the re-substrate sludge and the solubilized component concentration Sc of the re-substrate in the re-substrate sludge,
The biological treatment tank is configured to measure a sludge concentration X1 in the biological treatment tank that is the sum of the concentration Xa1 of activated sludge in the biological treatment tank and the concentration Xd1 of inactive sludge in the biological treatment tank. Measuring means are provided,
On the discharge side of the separation liquid of the solid-liquid separation means, the sludge concentration X2 in the separation liquid, and the biological treatment tank that is the sum of Sd and Se and the substrate concentration S in the separation liquid are measured. A fourth measuring means is provided;
A fifth measuring means for measuring a sludge concentration X3 in the concentrated sludge is provided on the concentrated sludge discharge side of the solid-liquid separation means,
The control means has a storage unit, and in the storage unit, the sludge conversion rate a ₁ of the substrate in the sewage flowing into the biological treatment tank from the outside, the suspension of the re-substrate sludge in the biological treatment tank The sludge conversion rate a _{2 of} the component, the sludge conversion rate a ₃ of the solubilized component of the resubstrate sludge in the biological treatment tank, the decomposition rate k ₁ of the substrate in the sewage flowing into the biological treatment tank from the outside, Decomposition rate k ₂ of the suspended component of the resubstrate sludge in the biological treatment tank, decomposition rate k _{3 of} the solubilized component of the resubstrate sludge in the biological treatment tank, sewage flowing from the outside into the biological treatment tank Saturation constant Ks _{1 of} the substrate, saturation constant Ks ₂ of the suspended component of the resubstrate sludge in the biological treatment tank, saturation constant Ks _{3 of} the solubilized component of the resubstrate sludge in the biological treatment tank, activity Sludge autooxidation rate b, the biological treatment The volume V1 of the sewage in the bath, the ratio of the Se and the S (Se / S), the ratio of the said Xa1 X1 (Xa1 / X1) is stored,
By the control means substituting the value measured by the fifth measurement means from the first measurement means and the value stored in the storage section into the following formulas (1) to (8) The daily amount Qr of the re-substrate sludge that can be supplied to the biological treatment tank and the daily amount Qe of the excess sludge that needs to be discharged when the Qr is achieved are calculated. The sewage treatment apparatus described in 1.

The control means has a detection unit;
At least one of the first measuring unit, the second measuring unit, the third measuring unit, the fourth measuring unit, and the fifth measuring unit outputs a signal corresponding to each measured value. Output to the detection unit,
The sewage treatment apparatus according to claim 2, wherein the detection unit detects the measurement value from the signal.   The sewage treatment apparatus according to any one of claims 1 to 3, wherein the re-substrate forming means is an ultrasonic treatment apparatus or a hydrothermal treatment apparatus. The first re-substrateing line is provided with a first flow meter for measuring a daily amount of the concentrated sludge introduced into the re-substrateing means by the first re-substrateing line, and the discharge The line is provided with a second flow meter for measuring the daily amount of the excess sludge discharged from the discharge line,
The control means determines whether or not the value measured by the first flow meter has reached a daily amount Qr of the resubstrate sludge that can be supplied to the biological treatment tank. The line switching means stops the introduction of the concentrated sludge through the first resubstrate line, and the value measured by the second flow meter is the amount Qe of surplus sludge per day. The sewage treatment apparatus according to any one of claims 1 to 4, wherein when it reaches, the line switching means stops the discharge of the excess sludge by the discharge line.

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