JP2007253011A - Biological treatment method and apparatus for organic liquid waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose an aerobic treatment method for organic liquid waste, with which the amount of sludge to be volume-reduced and then discharged to the outside of a system is reduced and the increase/decrease of the amount of sludge to be held is recognized and the proper amount of sludge to be modified is set and controlled quickly and correctly even when a load is fluctuated to treat organic liquid waste stably and obtain the treated water having excellent quality, and an aerobic treatment apparatus for the organic liquid waste. <P>SOLUTION: The aerobic treatment method for the organic liquid waste comprises the steps of: introducing organic liquid waste into an aeration tank 2 to perform aerobic biological treatment on the introduced organic liquid waste; subjecting a part of a liquid mixture in the aeration tank 2 to solid-liquid separation in a solid-liquid separation tank 3; returning the separated sludge of the preset amount to the aeration tank as return sludge; and introducing the remainder of the separated sludge into an ozonization tank 22 to ozonize the introduced sludge and return the ozonized sludge to the aeration tank 2. The amount M of sludge to be held in the system is calculated by using concentration of sludge in the liquid mixture in the aeration tank 2, the amount of the liquid mixture, concentration of sludge precipitated in the solid-liquid separation tank 3 and the amount of the precipitated sludge. The increased/decreased amount ΔM of sludge to be held is calculated by using a difference between the calculated amount M of sludge to be held and the target amount M0 of sludge to be held. The increased/decreased amount ΔS of sludge to be modified is calculated by multiplying the calculated increased/decreased amount ΔM by a VSS conversion factor and a coefficient of the amount of sludge to be modified. The amount of sludge to be modified is controlled so as to be increased/decreased correspondingly to the calculated increased/decreased amount ΔS of sludge. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for aerobic biological treatment of organic effluent in the presence of activated sludge, and more particularly to a method for treating organic effluent to reduce excess sludge in an activated sludge treatment system.

  The aerobic biological treatment method that treats organic wastewater under aerobic conditions using the action of aerobic microorganisms, such as the activated sludge treatment method, is low in processing cost and excellent in processing performance. Although widely used in general, since a large amount of hardly dewatering excess sludge is generated, a volume reduction treatment method for reducing the amount of sludge has been performed. As a treatment method for reducing the volume of such sludge, Patent Document 1 discloses that sludge is extracted from an aeration tank or a solid-liquid separation tank (precipitation tank), and this extracted sludge is subjected to ozone treatment, heat treatment, acid or alkali treatment, etc. There has been proposed a method of reforming easily biodegradable by the reforming treatment and returning the modified sludge to an aeration tank for biodegradation.

  In such a treatment method, since the amount of generated sludge is proportional to the inflow load BOD, the inflow load amount is measured, and when the amount of sludge multiplied by a certain coefficient is extracted and reformed, a stable treatment is performed. be able to. However, since the amount, concentration, and the like of the liquid to be treated that fluctuates vary, it is difficult to accurately grasp the load BOD, and therefore it is difficult to accurately grasp the amount of generated sludge.

  When the sludge reduction capacity is larger than the amount of production, the MLSS concentration gradually decreases, and the processing deteriorates. On the other hand, when the capacity is small, the MLSS concentration increases, and when the flow rate is increased, sludge flows out of the solid-liquid separation tank and the quality of the treated water is deteriorated. In order to improve this point, in Patent Document 1, the amount of sludge withdrawn is controlled so that the VSS / SS and MLSS of the activated sludge in the aeration tank are kept constant. However, the measurement of MLSS requires time and effort, and it is difficult to respond quickly to changes in the processing system.

  As a method for improving such a point, Patent Document 2 monitors the sludge interface in the solid-liquid separation tank, and the sludge interface in the solid-liquid separation tank has a predetermined upper limit so that the sludge interface is maintained in a certain range. Whether the amount of sludge to be reformed is increased when the value is higher than the value, and the amount of sludge to be reformed is controlled to be decreased when the value is lower than the predetermined lower limit, and the subsequent processing is continued under the increased or decreased conditions. Alternatively, a method of controlling to increase or decrease for a predetermined time has been proposed.

  However, when the amount of sludge reforming is changed by such a method, the amount of sludge decomposition (decreased capacity) changes, but it is a biological reaction and changes gradually rather than responding immediately. Therefore, for example, when the sludge interface becomes higher than a predetermined height, even if the sludge reforming amount is controlled to increase, the sludge increase tendency does not stop immediately, and the sludge interface remains at a position higher than the predetermined height for a while. Will exist. After that, the sludge decreases and the sludge interface decreases in about 2 to 4 days.

Thus, it takes time from the change of the sludge reforming amount until the result appears, and the amount, concentration, etc. of the liquid to be treated fluctuate during this time. Conventionally, the amount of sludge reforming determined when performing sludge reduction operation is calculated assuming the amount of sludge generated at that time. However, during the weight reduction operation, the amount of sludge generated is controlled by sludge reforming, so it is difficult to grasp the amount of sludge generated that varies depending on various conditions such as the influent water quality, water temperature, SRT, and supply oxygen amount. Therefore, it is difficult to maintain an appropriate amount of sludge reforming, and the amount of sludge increases or decreases too much, and the appropriate amount of retained sludge cannot be maintained. For this reason, the conventional method has a problem in that the amount of sludge reforming cannot be controlled quickly and accurately to perform a stable treatment.
Japanese Unexamined Patent Publication No. 7-116687 Japanese Patent Laid-Open No. 11-10185

  The problem of the present invention is to reduce the amount of sludge that is discharged out of the system by reducing the volume of sludge, and always grasp the increase or decrease in the amount of retained sludge, and quickly set the appropriate sludge reforming amount even if there is a load fluctuation. The present invention also proposes an aerobic treatment method and apparatus for organic effluent that can accurately control the amount of sludge reforming and perform stable treatment to obtain good treated water quality.

The present invention is the following organic wastewater biological treatment method and apparatus.
(1) A biological treatment process for introducing an organic drainage liquid into an aeration tank and aerobic biological treatment in the presence of activated sludge;
Solid-liquid separation of the mixed liquid in the aeration tank in the solid-liquid separation tank, discharging the separated liquid as a treatment liquid, and returning at least a part of the separated sludge to the aeration tank;
A modification step of extracting a set amount of the activated sludge from the separated sludge or the mixed liquid, and modifying the extracted sludge to be easily biodegradable,
A return process for returning the modified sludge to the aeration tank,
The amount of retained sludge in the system is obtained from the sludge concentration and the amount of liquid mixture in the aeration tank, and the sludge concentration and the amount of separated sludge in the solid-liquid separation tank,
Obtain the amount of retained sludge from the difference between the retained sludge amount thus obtained and the target retained sludge amount,
Multiply the increase / decrease amount of this retained sludge by the VSS conversion factor per unit weight and the sludge reforming amount coefficient per unit weight of the reduced sludge, to obtain the increase / decrease amount of the reformed sludge,
When the retained sludge amount is larger than the target retained sludge amount, the set amount is increased by the sludge amount corresponding to the increase / decrease amount of the reforming treatment, and when the retained sludge amount is smaller than the target retained sludge amount, the setting is performed. An aerobic treatment method for organic drainage, characterized in that the amount is controlled to be reduced by the amount of sludge corresponding to the amount of increase / decrease in the reforming treatment.
(2) The method according to (1) above, wherein the sludge concentration of the separated sludge in the solid-liquid separation tank is obtained from the sludge concentration in the mixed liquid in the aeration tank and the concentration ratio of the solid-liquid separation tank.
(3) a biological treatment apparatus that introduces organic drainage liquid into an aeration tank and performs aerobic biological treatment in the presence of activated sludge;
Including a solid-liquid separation tank for solid-liquid separation of the liquid mixture in the aeration tank, discharging the separation liquid as a processing liquid, and returning at least a part of the separated sludge to the aeration tank;
A reformer that draws a set amount of the activated sludge from the separated sludge or the mixed liquid and reforms the extracted sludge to be easily biodegradable;
A return means for returning the modified sludge to the aeration tank;
Measuring means for measuring the sludge concentration of the mixed liquid in the aeration tank and the sludge concentration of the separated sludge in the solid-liquid separation tank, and the amount of separated sludge in the solid-liquid separation tank;
The amount of retained sludge in the system is obtained from the measured value, the increase / decrease amount of retained sludge is obtained from the difference between the retained sludge amount thus obtained and the target retained sludge amount, and the increase / decrease amount of retained sludge is calculated as VSS per sludge unit weight. Multiplying the conversion coefficient and the sludge reforming amount coefficient per unit weight of the sludge to be reduced, the amount of increase or decrease in the reformed sludge is obtained. Is increased by the amount of sludge corresponding to the control amount, and when the retained sludge amount is smaller than the target retained sludge amount, the control device controls to decrease the set amount by the amount of sludge corresponding to the increase / decrease amount of the reforming process. An aerobic treatment apparatus for organic drainage, comprising:
(4) The apparatus according to (3), wherein the sludge concentration of the separated sludge in the solid-liquid separation tank is determined from the sludge concentration in the mixed liquid in the aeration tank and the concentration ratio of the solid-liquid separation tank.

  The organic effluent to be treated in the present invention is an effluent containing an organic substance treated by a normal aerobic biological treatment method, but may contain a hardly biodegradable organic substance or an inorganic substance. In addition, ammonia nitrogen may be contained. Such organic effluents include sewage, human waste, food factory effluents and other industrial effluents.

  The aerobic biological treatment in the present invention is configured to introduce an organic waste liquid into an aeration tank and perform the aerobic biological treatment in the presence of activated sludge. In addition, the solid-liquid separation step and the apparatus guide the mixed liquid from the aeration tank to the precipitation tank as a solid-liquid separation tank and perform solid-liquid separation (precipitation separation), discharge the separated liquid as a processing liquid, and at least part of the separated liquid Although it can comprise so that it may return to an aeration tank, membrane separation can also be performed using separation membranes, such as a UF membrane. As such a treatment system, organic waste liquid is mixed with activated sludge in an aeration tank and aerated, and the mixed liquid is separated into solid and liquid in a solid-liquid separation tank, and a part of the separated sludge is returned to the aeration tank. The aerobic biological treatment in the standard activated sludge treatment method is common, but other treatments obtained by modifying this may be used. When treating the drainage liquid containing ammonia nitrogen, it can be treated in combination with a nitrification denitrification step.

  In the present invention, a set amount is extracted from the biological sludge from the treatment system in such an aerobic biological treatment, and a reforming step is performed to modify the extracted sludge to be easily biodegradable. When extracting biological sludge, it is preferable to extract a part of the separated sludge separated by the solid-liquid separator, but it may be extracted from the aeration tank in a mixed liquid state. When extracting from the separated sludge, part or all of the portion discharged as excess sludge can be extracted as extraction sludge, but in addition to the excess sludge, a part of the return sludge returned to the aeration tank as return sludge is further added. It can also be modified by drawing. In this case, the amount of excess sludge generated outside the system can be reduced, and in some cases, it can be reduced to zero.

  Any method can be adopted as a reforming step for reforming the extracted sludge into a property that is easily decomposed by organisms. For example, modification by ozone treatment, modification by acid treatment, modification by alkali treatment, modification by heat treatment, modification by high-pressure pulse discharge treatment, modification by grinding treatment using a mill such as a ball mill or a colloid mill, It is possible to employ reforming or the like combining these. Among these, the modification by ozone treatment is preferable because the treatment operation is simple and the treatment efficiency is high.

  In the ozone treatment as the reforming step, the sludge extracted from the aerobic biological treatment system may be brought into contact with ozone, and the sludge is easily biodegradable by the oxidizing action of ozone. When the ozone treatment is performed in an acidic region having a pH of 5 or less, the oxidative decomposition efficiency is increased. The pH adjustment at this time is preferably performed by adding an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid to the biological sludge as a pH adjusting agent, adjusting the biological sludge by an acid fermentation treatment, or a combination thereof. . When adding a pH adjuster, it is preferable to adjust pH to 3-4, and when performing an acid fermentation process, it is preferable to carry out so that pH may become 4-5.

The ozone treatment can be performed by adjusting the extracted sludge or its acid fermentation treatment solution as it is or by concentrating it with a centrifugal separator or the like if necessary, and bringing it into contact with ozone. As a contact method, a method of introducing sludge into an ozone treatment tank and blowing ozone, a method of mechanical stirring, a method of using a packed bed, or the like can be employed. In addition to ozone gas, ozone-containing gas such as ozone-containing air or ozonized air can be used as ozone. The use of ozone is 0.02 to 0.06 g-O ₃ / g-VSS, preferably 0.02 to 0.05 g-O ₃ / g-VSS. Biological sludge is oxidized and decomposed by ozone treatment and converted into BOD components.

  In the acid treatment as the reforming step, the drawn sludge drawn from the aerobic biological treatment system is guided to the reforming tank, and a mineral acid such as hydrochloric acid or sulfuric acid is added, and the pH is 2.5 or lower, preferably pH 1-2. It is only necessary to hold for a predetermined time. The residence time is, for example, 5 to 24 hours. At this time, it is preferable to heat the sludge, for example, to 50 to 100 ° C., because the reforming is promoted. By treatment with such an acid, the sludge becomes readily biodegradable and can be easily decomposed and removed by returning to the aerobic biological treatment system.

  In addition, in the alkali treatment as the sludge reforming step, the extracted sludge extracted from the aerobic biological treatment system is guided to the reforming tank, and the alkali such as sodium hydroxide and potassium hydroxide is 0.1 to 1 with respect to the sludge. What is necessary is just to add weight% and hold | maintain for a predetermined time. The residence time is about 0.5 to 2 hours, and the sludge is easily biodegradable. At this time, it is preferable to heat the sludge, for example, to 5 to 100 ° C., since the reforming is promoted.

  The heat treatment as the reforming step can be performed by heat treatment alone, but is preferably performed in combination with acid treatment or alkali treatment. In the case of performing the heat treatment alone, for example, the temperature can be set to 70 to 100 ° C. and the residence time can be set to 2 to 3 hours.

  In the high voltage pulse discharge treatment, sludge is present between a positive electrode such as tungsten / thorium alloy having an electrode interval of 3 to 10 mm, preferably 4 to 8 mm, and a negative electrode such as stainless steel, and an applied electricity of 10 to 50 kV, preferably Can perform pulse discharge at 20 to 40 kV and a pulse interval of 20 to 80 Hz, preferably 40 to 60 Hz, and the sludge can be processed while being circulated sequentially.

  The modified sludge modified to be readily biodegradable in this way is introduced into the aeration tank of the aerobic biological treatment process in the return process to perform the aerobic treatment, and assimilate to the aerobic biological material. In the aeration tank, the biological sludge is controlled so that the VSS / SS ratio is maintained at 0.2 to 0.7, preferably 0.3 to 0.6, and the MLVSS is maintained at 500 to 10,000 mg / L, preferably 1000 to 5000 mg / L. By doing so, the sedimentation property and dewatering property of sludge can be improved.

  In the present invention, the amount of retained sludge in the system is determined from the sludge concentration and amount of the mixed liquid in the aeration tank, and the sludge concentration and amount of separated sludge in the solid-liquid separation tank, and the amount of retained sludge thus obtained, Determine the amount of retained sludge increase / decrease based on the difference from the target retained sludge amount, and multiply this retained sludge increase / decrease by the VSS conversion factor per sludge unit weight and sludge reforming amount coefficient per unit weight of sludge reduction. When the amount of retained sludge is larger than the target retained sludge amount, the set amount of sludge to be extracted for reforming is increased by the amount of sludge corresponding to the increase / decrease amount of the reforming treatment, and the retained sludge amount When the amount is less than the target retained sludge amount, a control device is provided to control the set amount so as to decrease by the amount of sludge corresponding to the increase / decrease amount of the reforming process.

  The measuring means measures the sludge concentration of the mixed solution in the aeration tank, the sludge concentration of the separated sludge in the solid-liquid separation tank, and the separated sludge amount in the solid-liquid separation tank. The amount of sludge retained in the aeration tank is calculated from the SS concentration and the amount of the liquid mixture in the aeration tank, but since the amount of the liquid mixture in the aeration tank is determined, only the sludge concentration in the liquid mixture in the aeration tank is used here. Can be measured. The sludge concentration of the mixed solution in the aeration tank can be measured by an SS densitometer provided in the aeration tank or the transfer path.

  The retained sludge amount in the solid-liquid separation tank is calculated from the sludge concentration in the separated sludge in the solid-liquid separation tank and the separated sludge amount in the solid-liquid separation tank. The sludge concentration of the separated sludge can be measured by the SS concentration meter provided in the solid-liquid separation tank or the return path, but can also be obtained from the sludge concentration of the mixed liquid in the aeration tank and the concentration ratio of the solid-liquid separation tank. . In this case, the sludge concentration of the liquid mixture in the aeration tank is measured, the integrated flow rate of the treatment liquid flowing out from the solid-liquid separation tank, and the return sludge returned to the aeration tank from the solid-liquid separation tank The integrated flow rate can be measured with a flow meter, and the concentration ratio can be determined from the flow rate ratio. The amount of separated sludge in the solid-liquid separation tank can be measured by a sludge interface meter provided in the solid-liquid separation tank.

  In the control device, the amount of retained sludge in the system is obtained from the measurement value measured by the measuring means, and the increase / decrease amount of retained sludge is obtained from the difference between the retained sludge amount thus obtained and the target retained sludge amount. Is multiplied by the VSS conversion coefficient per sludge unit weight and the sludge reforming coefficient per unit weight of sludge reduction to determine the amount of reformed sludge increase / decrease, and if the retained sludge amount is larger than the target retained sludge amount, reforming is performed. The amount of sludge to be extracted is increased by the amount of sludge corresponding to the amount of increase / decrease in the reforming process, and when the retained sludge amount is less than the target retained sludge amount, the set amount is increased / decreased in the reforming process. It is set as the structure controlled so that it may reduce by the amount of sludge equivalent to the quantity.

  The retained sludge amount in the system is calculated as the total amount of the mixed sludge amount in the aeration tank and the precipitated sludge amount in the solid-liquid separation tank, and is neglected because there is little sludge in the transfer path and the return path. This amount of retained sludge can be calculated by equation (1) or equation (2). In Formula (1) or Formula (2), the capacity conversion function is a function that converts the capacity of the precipitated sludge in accordance with the separation sludge interface height of the solid-liquid separation tank, and the capacity correction by the shape of the solid-liquid separation tank Is a function that performs The concentration gradient function is a function for correcting the concentration gradient of the precipitated sludge and the sludge near the interface. In the formula (2), the treated water flow rate and the returned sludge flow rate indicate an integrated flow rate for a predetermined time, preferably 1 day.

M = X ・ V + Xr ・ H ・ A ・ B (1)
Or M = X · V + X · (Q + Qr) / (Qr + Qw) · H · A · B (2)
Here, M is the retained sludge amount (g), X is the aeration tank MLSS (g / m ³ ), V is the aeration tank volume (m ³ ), Xr is the return sludge concentration (g / m ³ ), and H is the solid liquid The separation sludge interface height (m) of the separation tank, A is a volume conversion function (-), B is a concentration gradient function (-, usually 0.5 to 1), Q is the raw water flow rate (m ³ / day), Qw is excess sludge Amount (m ³ / day, zero at 100% volume reduction), Qr is the amount of returned sludge (m ³ / day).

The increase / decrease amount ΔM of the sludge retention amount can be calculated by the equation (3) from the difference between the retained sludge amount M in the system thus obtained and the target retained sludge amount M0.
ΔM = M−M0 (3)

  When the increase / decrease amount ΔM of the sludge retention amount obtained from the equation (3) is positive, the amount of sludge to be reformed is increased, and when the increase / decrease amount ΔM of the sludge retention amount is negative, the sludge to be reformed. Control to reduce the amount. In this case, the amount of the modified sludge to be increased / decreased can be obtained by multiplying the increase / decrease amount ΔM of the sludge retention amount by the VSS conversion coefficient per sludge unit weight and the sludge reforming amount coefficient per unit weight of reduced sludge. In this case, the increase / decrease amount ΔS of the modified sludge can be calculated by the following equation (4).

ΔS = ΔM × k1 × k2 (4)
However, ΔS is the increase / decrease amount of sludge supplied to the reforming tank (kg-VSS / day),
k1 is VSS conversion factor (kg-VSS / kg-SS) per SS unit weight of sludge,
k2 is sludge reforming coefficient per unit weight of sludge reduction (kg-VSS / kg-VSS)

  K1 in the above formula (4) is a VSS conversion factor (kg-VSS / kg-SS) per unit weight of sludge, which varies according to the properties of the activated sludge in the treatment system. The processing conditions are almost constant. In formula (4), k1 is usually 0.5 to 0.9 kg-VSS / kg-SS in the activated sludge treatment system for general organic wastewater, and 0.8 kg-VSS / kg-SS in the examples described later. It is.

  K2 in the equation (4) is a sludge reforming coefficient (kg−VSS / kg−VSS) per unit weight of the sludge to be reduced, and the amount of sludge to be reformed relative to the sludge to be reduced (kg−VSS) (kg− VSS). This coefficient k2 varies depending on the type of reforming treatment, etc., but in general sludge reforming, it is usually 2 to 5, and in sludge reforming with ozone, k2 is usually 2.9 when zero surplus sludge is zero. It is.

  In the control device, the retained sludge amount M in the system is obtained from the measured values of the measuring means by the equations (1) and (2), and the difference between the retained sludge amount M thus obtained and the target retained sludge amount M0 is obtained from the equation (3). Thus, by obtaining the increase / decrease amount ΔM of the retained sludge, it is possible to always grasp the increase / decrease in the sludge in the system. Then, the increase / decrease amount of retained sludge is obtained by multiplying the increase / decrease amount ΔM of the retained sludge by the VSS conversion coefficient per sludge unit weight and the sludge reforming amount coefficient per unit weight of the reduced sludge by the equation (4) to obtain the increase / decrease amount ΔS of the reformed sludge. When ΔM is positive, it increases by the amount of sludge corresponding to the increase / decrease amount ΔS of the reforming process, and when ΔM is negative, the amount of sludge corresponding to the increase / decrease amount ΔS of the reforming process increases by ΔS. Control is performed to decrease, and the reforming process is performed according to the increase / decrease amount ΔS. Since the modified sludge modified in the reforming process is easily biodegradable, it is biodegraded by supplying it to the biological treatment process and aerobic biological treatment, and a part thereof is converted into sludge.

  By performing the treatment as described above, the amount of sludge in the system can be controlled quickly and accurately, and a stable treatment can be performed. By controlling the increase / decrease amount ΔM of the retained sludge and the increase / decrease amount ΔS of the modified sludge at predetermined time intervals, for example, at intervals of one day, the sludge generation amount that fluctuates according to various conditions is controlled following a delay of one day. This makes it possible to secure an appropriate amount of retained sludge.

  According to the present invention, the retained sludge amount in the system is determined from the sludge concentration and the mixed liquid amount in the aeration tank and the sludge concentration and the precipitated sludge amount in the solid-liquid separation tank, and the retained sludge amount thus obtained. The amount of retained sludge increase / decrease is calculated from the difference from the target retained sludge amount, and the increase / decrease amount of retained sludge is multiplied by the VSS conversion coefficient per unit weight and sludge reforming amount coefficient per unit weight of reduced sludge. When the increase / decrease amount of retained sludge is greater than the target retained sludge amount, the set amount is increased by the amount of sludge corresponding to the increase / decrease amount of the reforming treatment, and the increase / decrease amount of retained sludge is retained sludge. When the amount is smaller than the target retained sludge amount, the set amount is controlled so as to decrease by the amount of sludge corresponding to the increase / decrease amount of the reforming treatment, so that the sludge is reduced and discharged out of the system. Reduces sludge volume and retains sludge The increase or decrease constantly grasp the sludge modifying amount controlled quickly and accurately by setting the appropriate sludge modifying amount even if a load change by performing a stable treatment can be obtained good processing quality.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are flow sheets showing an aerobic biological treatment apparatus according to another embodiment, and is an example in which ozone treatment is adopted as a reforming step.

  1 and 2, reference numeral 1 denotes an aerobic biological treatment system, which includes an aeration tank 2 as a biological treatment apparatus and a solid-liquid separation tank 3 as a solid-liquid separation apparatus. The aeration tank 2 communicates with the liquid passage 4 to be treated, the return sludge passage 5 and the ozone treatment sludge introduction passage 6, and the air diffuser 7 is provided at the bottom and the air supply passage 8 communicates therewith. A communication path 9 communicates from the aeration tank 2 to the solid-liquid separation tank 3. The treatment liquid path 10 and the separated sludge discharge path 11 communicate with the solid-liquid separation tank 3, and the return sludge path 5 branches from the separated sludge discharge path 11. A pump 12 is provided in the return sludge path 5.

  Reference numeral 21 denotes a reforming treatment system, which includes an ozone treatment tank 22 and an ozone generator 23. An extraction sludge passage 24 and a waste ozone passage 25 communicate with the upper portion of the ozone treatment tank 22. A pump 26 is provided in the extraction sludge passage 24. In addition, an ozone supply path 27 and an ozone treatment sludge introduction path 6 communicate with the lower part of the ozone treatment tank 22. 23a is a raw material air supply path.

  30 is a control unit constituting the control device. In the embodiment of FIG. 1, the sludge concentration signal of the aeration tank 2 is input by the SS concentration meter 31 provided in the aeration tank 2, and is provided in the solid-liquid separation tank 3. The separated sludge interface 33 of the solid-liquid separation tank 3 is measured by the interface meter 32 and the interface signal is input, and the sludge concentration signal of the separated sludge of the solid-liquid separation tank 3 is obtained by the SS densitometer 34 provided in the return sludge channel 5. And the sludge retention amount in the system is calculated according to the equation (1).

  In the embodiment of FIG. 2, the control unit 30 constituting the control device inputs the sludge concentration signal of the aeration tank 2 from the SS concentration meter 31 provided in the aeration tank 2, and the flow meter provided in the treatment liquid path 10. 35, a daily flow rate signal of the treatment liquid flowing out is input, a daily flow rate signal of the returned sludge is input by the flow meter 36 provided in the return sludge passage 5, and sludge in the system is obtained by the above equation (2). The holding amount is calculated.

  In the aerobic biological treatment method of organic waste liquid by the above apparatus, the organic waste liquid is introduced into the aeration tank 2 from the liquid passage 4 to be treated, and the return sludge is returned from the return sludge passage 5 by driving the pump 12. Then, it is mixed with the activated sludge in the aeration tank 2, and the air supplied from the air supply path 8 is diffused from the diffuser 7 to perform the aerobic biological treatment. Thereby, the organic matter in the drainage is decomposed by the biooxidation reaction.

  A part of the mixed liquid (aerobic treatment liquid) in the aeration tank 2 is introduced into the solid-liquid separation tank 3 through the communication path 9 and separated into the separated liquid and the precipitated sludge by solid-liquid separation. The separation liquid is discharged out of the system from the processing liquid passage 10 as a processing liquid. The concentrated separated sludge is taken out from the separated sludge discharge passage 11, and a part thereof is returned to the aeration tank 2 from the return sludge passage 5 as return sludge.

  The remainder of the separated sludge is introduced into the ozone treatment tank 22 from the extraction sludge passage 24 by driving the pump 26. When surplus sludge is generated, it can be discharged out of the system from the surplus sludge discharge passage 28. However, if sludge larger than the sludge generation amount is introduced into the ozone treatment tank 22 for ozone treatment and returned to the aeration tank 2, the surplus is produced. Since the amount of sludge generated becomes zero, the excess sludge discharge path 28 can be omitted. In the ozone treatment tank 22, ozone generated by the ozone generator 23 is introduced from an ozone supply path 27 and is contacted with sludge for ozone treatment. Thereby, sludge is made into BOD. Ozone exhaust gas is discharged from the exhaust ozone passage 25 to the outside of the system.

  The ozone-treated sludge is introduced into the aeration tank 2 from the ozone-treated sludge introduction path 6. Since the sludge is easily biodegradable by the ozone treatment, it is assimilated by the microorganisms in the activated sludge in the aeration tank 2 together with the BOD flowing from the liquid channel 4 to be treated by returning it to the aeration tank 2. Disassemble. When processing a liquid to be treated containing ammonia nitrogen, a denitrification tank is provided in front of the aeration tank 2, and the liquid to be treated, the return sludge, and the ozone treatment sludge are introduced into the denitrification tank. The nitrification liquid is circulated to perform denitrification and BOD removal, and the aeration tank 2 performs processing so as to mainly perform nitrification.

  In the embodiment of FIG. 1, the sludge concentration in the aeration tank 2 is measured by the SS concentration meter 31 provided in the aeration tank 2, and the sludge concentration signal of the aeration tank 2 is input to the control unit 30, and the solid-liquid separation tank 3 The interface 33 of the sludge in the solid-liquid separation tank 3 is measured by the interface meter 32 provided in the vessel, the interface signal is input to the control unit 30, and the SS concentration meter 34 provided in the return sludge passage 5 is further used as the solid-liquid. The sludge concentration of the precipitated sludge in the separation tank 3 is measured, the sludge concentration signal is input to the control unit 30, and the sludge retention amount in the system is calculated by the above equation (1).

In this case, in the control unit 30, the amount of sludge retained in the aeration tank 2 is the product of the aeration tank sludge concentration indicated by the sludge concentration signal of the aeration tank 2 and the aeration tank capacity (capacity of the mixed liquid in the aeration tank 2). The amount of sludge retained in the solid-liquid separation tank 3 is calculated as follows: the precipitated sludge concentration indicated by the sludge concentration signal of the return sludge passage 5, and the solid-liquid separation tank sludge interface height (precipitation sludge height) indicated by the interface signal. It is calculated as the product of the capacity conversion function and the concentration gradient function, and the retained sludge amount M in the system is calculated as the sum of these. The volume conversion function is based on the surface area of the solid-liquid separation tank 3, but is a function for correcting the volume due to the conical shape of the lower part.
The concentration gradient function is a function for correcting the concentration gradient of the precipitated sludge concentration and the interface sludge concentration.

  In the embodiment of FIG. 2, the sludge concentration in the aeration tank 2 is measured by the SS concentration meter 31 provided in the aeration tank 2, and the sludge concentration signal of the aeration tank 2 is input to the control unit 30, and the solid-liquid separation tank 3 The interface of the sedimentation sludge in the solid-liquid separation tank 3 is measured by the interface meter 32 provided in the process, and the interface signal is input to the control unit 30, and the processing liquid flowing out by the flow meter 35 provided in the process liquid path 10 The daily flow rate is measured, the flow rate signal is input to the control unit 30, the daily flow rate of the returned sludge is measured by the flow meter 36 provided in the return sludge channel 5, and the signal is input to the control unit 30. Then, the sludge retention amount in the system is calculated by the equation (2).

  In this case, in the control unit 30, the amount of sludge retained in the aeration tank 2 is the product of the aeration tank sludge concentration indicated by the sludge concentration signal of the aeration tank 2 and the aeration tank capacity (capacity of the mixed liquid in the aeration tank 2). Calculated, the retained sludge amount in the solid-liquid separation tank 3 is converted into the above-mentioned aeration tank sludge concentration, the ratio of (treatment liquid flow rate + return sludge flow rate) / return sludge flow rate, solid-liquid separation tank sludge interface height and capacity conversion. The amount of retained sludge M in the system is calculated as the sum of these.

  In the case of FIGS. 1 and 2, the control unit 30 holds the above equation (3) from the difference between the retained sludge amount M in the system and the target retained sludge amount M0 obtained by the above equations (1) and (2). By obtaining the sludge increase / decrease amount ΔM, it is possible to always grasp the sludge increase / decrease in the system. Further, the increase / decrease amount ΔS of the reformed sludge is obtained by multiplying the increase / decrease amount ΔM of the retained sludge by the VSS conversion coefficient per sludge unit weight and the sludge reforming amount coefficient per unit weight of the reduced sludge by the above formula (4), When the increase / decrease amount ΔM is positive, the set amount of sludge extracted for reforming is increased by the amount of sludge corresponding to the increase / decrease amount ΔS of the reforming process, and the increase / decrease amount ΔM of retained sludge is negative. Is controlled to decrease by the amount of sludge corresponding to the increase / decrease amount ΔS of the reforming process, and is supplied to the reforming process according to the increase / decrease amount ΔS for reforming. Since the modified sludge modified in the reforming process is easily biodegradable, it is biodegraded by supplying it to the biological treatment process and aerobic biological treatment, and a part thereof is converted into sludge.

  By performing the treatment as described above, the amount of sludge in the system can be controlled quickly and accurately, and a stable treatment can be performed. By performing the calculation of the retained sludge increase / decrease amount ΔM and the modified sludge increase / decrease amount ΔS at a predetermined time interval, the sludge generation amount that fluctuates according to various conditions can be controlled following the delay of the predetermined time, A proper amount of retained sludge can be secured and stable treatment can be performed.

Example 1:
Using the apparatus of FIG. 1, sewage (BOD: 200 mg / L, flow rate 500 m ³ / day) was aerobically treated with a sludge load of 0.1 kg-BOD / kg-VSS / day in the presence of activated sludge. The set amount of sludge to be extracted from the solid-liquid separation tank 3 and sludge reformed was 200 kg-VSS / day, and the amount of ozone used was 13.4 kg-O ₃ / day, which was 6.7% of VSS. After 24 hours, the retained sludge amount M was 50 kg-SS higher than the target retained sludge amount M0. At this time, the VSS per SS is 80% by weight in the analysis value of this sludge, and as a result, 40kg-VSS sludge is increased in the system.
50kg-SS × 0.8kg-VSS / kg-SS = 40kg-VSS

  Therefore, in order to return the retained sludge amount to the target retained sludge amount, the sludge reforming amount was increased. In the case of the ozone reduction method, the amount of ozone treatment is 2.9 times the amount to be reduced, so the set amount of sludge for sludge reforming is controlled to increase by 116 kg-VSS / day, and the amount of ozone treatment sludge is 316 kg. -VSS / day. As a result, from the sludge concentration analysis result, the sludge retention amount after 24 hours became the target retained sludge amount.

Example 2:
The same sewage as in Example 1 (BOD: 200 mg / L, flow rate 500 m ³ / day) was subjected to aerobic biological treatment with a sludge load of 0.1 kg-BOD / kg-VSS / day using the apparatus shown in FIG. 2 in the presence of activated sludge. . The set amount of sludge to be extracted from the solid-liquid separation tank 3 and sludge reformed was 200 kg-VSS / day, and the amount of ozone used was 13.4 kg-O ₃ / day, which was 6.75% of VSS. After 24 hours, the retained sludge amount M was 50 kg more than the target retained sludge amount M0. Therefore, the ozone treatment sludge amount was increased to 116kg-VSS and controlled to 316kg-VSS / day. As a result, after 24 hours, the amount of retained sludge was reduced by 25 kg-SS. This was thought to be due to a decrease in the inflow BOD amount. Therefore, in order to increase the amount of retained sludge by 25 kg-SS, the ozone-treated sludge amount was reduced to 58 kg-VSS as shown in the following formula and set to 142 kg-VSS / day. According to the sludge concentration analysis result, the retained sludge amount became the target retained sludge amount after 24 hours.
25kg-SS × 0.8 kg-VSS / kg-SS × 2.9 ＝ 58kg-VSS

  The organic effluent can be used in an organic effluent treatment method in which the aerobic biological treatment is performed in the presence of activated sludge and the volume of excess sludge in the activated sludge treatment system is reduced.

It is a flow sheet which shows the aerobic biological treatment device of an embodiment. It is a flow sheet which shows an aerobic biological treatment device of other embodiments.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aerobic biological treatment system 2 Aeration tank 3 Solid-liquid separation tank 4 Processed liquid path 5 Return sludge path 6 Ozone treatment sludge introduction path 7 Air diffuser 8 Air supply path 9 Connection path 10 Treatment liquid path 11 Separation sludge discharge path 12 26 Pump 21 Ozone treatment system 22 Ozone treatment tank 23 Ozone generator 23a Raw material air supply path 24 Extracted sludge path 25 Exhaust ozone path 27 Ozone supply path 28 Surplus sludge discharge path 30 Control units 31, 34 SS concentration meter 32 Interface meter 33 Interface 35, 36 flow meter

Claims (4)

A biological treatment process for introducing an organic effluent into an aeration tank, and aerobic biological treatment in the presence of activated sludge;
Solid-liquid separation of the mixed liquid in the aeration tank in the solid-liquid separation tank, discharging the separated liquid as a treatment liquid, and returning at least a part of the separated sludge to the aeration tank;
A modification step of extracting a set amount of the activated sludge from the separated sludge or the mixed liquid, and modifying the extracted sludge to be easily biodegradable,
A return process for returning the modified sludge to the aeration tank,
The amount of retained sludge in the system is obtained from the sludge concentration and the amount of liquid mixture in the aeration tank, and the sludge concentration and the amount of separated sludge in the solid-liquid separation tank,
Obtain the amount of retained sludge from the difference between the retained sludge amount thus obtained and the target retained sludge amount,
Multiply the increase / decrease amount of this retained sludge by the VSS conversion coefficient per unit weight and the sludge reforming amount coefficient per unit weight of the reduced sludge to obtain the increase / decrease amount of the reformed sludge,
When the retained sludge amount is larger than the target retained sludge amount, the set amount is increased by the sludge amount corresponding to the increase / decrease amount of the reforming treatment, and when the retained sludge amount is smaller than the target retained sludge amount, the setting is performed. An aerobic treatment method for organic drainage, characterized in that the amount is controlled to be reduced by the amount of sludge corresponding to the amount of increase / decrease in the reforming treatment.   The method according to claim 1, wherein the sludge concentration of the separated sludge in the solid-liquid separation tank is determined from the sludge concentration in the mixed liquid in the aeration tank and the concentration ratio of the solid-liquid separation tank. A biological treatment apparatus that introduces organic waste liquid into the aeration tank and performs aerobic biological treatment in the presence of activated sludge;
Including a solid-liquid separation tank for solid-liquid separation of the liquid mixture in the aeration tank, discharging the separation liquid as a processing liquid, and returning at least a part of the separated sludge to the aeration tank;
A reformer that draws a set amount of the activated sludge from the separated sludge or the mixed liquid and reforms the extracted sludge to be easily biodegradable;
A return means for returning the modified sludge to the aeration tank;
Measuring means for measuring the sludge concentration of the mixed liquid in the aeration tank and the sludge concentration of the separated sludge in the solid-liquid separation tank, and the amount of separated sludge in the solid-liquid separation tank;
The amount of retained sludge in the system is obtained from the measured value, the increase / decrease amount of the retained sludge amount is obtained from the difference between the retained sludge amount thus obtained and the target retained sludge amount, and the increase / decrease amount of the retained sludge amount is expressed as VSS per sludge unit weight. Multiplying the conversion coefficient and the sludge reforming amount coefficient per unit weight of the sludge to be reduced, the amount of increase or decrease in the reformed sludge is obtained. Is increased by the amount of sludge corresponding to the control amount, and when the retained sludge amount is smaller than the target retained sludge amount, the control device controls to decrease the set amount by the amount of sludge corresponding to the increase / decrease amount of the reforming process. An aerobic treatment apparatus for organic drainage, comprising: The apparatus according to claim 3, wherein the sludge concentration of the separated sludge in the solid-liquid separation tank is obtained from the sludge concentration in the mixed liquid in the aeration tank and the concentration ratio of the solid-liquid separation tank.

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