WO2012077381A1 - Wastewater treatment device - Google Patents

Wastewater treatment device Download PDF

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Publication number
WO2012077381A1
WO2012077381A1 PCT/JP2011/068317 JP2011068317W WO2012077381A1 WO 2012077381 A1 WO2012077381 A1 WO 2012077381A1 JP 2011068317 W JP2011068317 W JP 2011068317W WO 2012077381 A1 WO2012077381 A1 WO 2012077381A1
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Prior art keywords
biological treatment
treatment tank
sludge
tank
biological
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PCT/JP2011/068317
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French (fr)
Japanese (ja)
Inventor
裕章 目黒
泰彦 嶌田
長谷部　吉昭
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オルガノ株式会社
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Priority to CN201180054810.XA priority Critical patent/CN103209931B/en
Publication of WO2012077381A1 publication Critical patent/WO2012077381A1/en

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/30—Aerobic and anaerobic processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/32—Nature of the water, waste water, sewage or sludge to be treated from the food or foodstuff industry, e.g. brewery waste waters
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C02F2103/346—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from semiconductor processing, e.g. waste water from polishing of wafers

Definitions

  • the present invention relates to a wastewater treatment apparatus for biologically treating organic wastewater containing BOD components with biological sludge.
  • the standard activated sludge method which is a continuous type, has a so-called “bulking” problem that makes it difficult to separate biological sludge due to poor sedimentation of biological sludge. Since the treatment capacity of the activated sludge method strongly depends on the amount of biological sludge that can be retained, the problem that biological sludge flows out into treated water due to poor sedimentation caused by bulking is a major issue. Many techniques called modified activated sludge have been developed for such problems (see, for example, Non-Patent Document 1).
  • Wastewater treatment by batch activated sludge process using granule is beneficial in that it has no bulking problems, has high sedimentation of biological sludge, and has a high treatment capacity. Since the operation control requires many sensors, the apparatus becomes complicated, which is disadvantageous in terms of initial cost and operation management.
  • the conventional treatment equipment does not have a mechanism that can form granules from biological sludge, so if the granule collapses for some reason, it is acclimatized by adding the granule again as seed sludge. There is a problem in operation management.
  • an object of the present invention is to provide a wastewater treatment apparatus that can enhance the sedimentation property of biological sludge.
  • an object is to provide a wastewater treatment apparatus that can granulate sludge and enhance the sedimentation property of biological sludge.
  • the present invention is a wastewater treatment apparatus having a reaction tank for biologically treating organic wastewater containing BOD components with biological sludge, and a sludge separation tank for separating treated water obtained in the reaction tank from the sludge.
  • the reaction tank includes an oxygen-free biological treatment tank, a first biological treatment tank and a second biological treatment tank to which oxygen necessary for the biological treatment is supplied, and the organic wastewater is the first biological treatment tank. It is continuously flowed into one biological treatment tank and biologically treated in the first biological treatment tank and the second biological treatment tank, and the sludge in the sludge separation tank is treated with the second biological treatment tank and the anoxic biological treatment.
  • the sludge in the oxygen-free biological treatment tank is returned to the tank, and is supplied to at least the first biological treatment tank.
  • the MLSS load of the first biological treatment tank is higher than the MLSS load of the second biological treatment tank. It is.
  • the MLSS load of the first biological treatment tank is in a range of 0.8 kgBOD / kgMLSS / d or more, and the MLSS load of the second biological treatment tank is 0.00.
  • the range is preferably 5 kg BOD / kg MLSS / d or less.
  • the total residence time of the water to be treated in the first biological treatment tank and the second biological treatment tank is 3 hours or more.
  • the sedimentation property of biological sludge can be enhanced.
  • FIG. 1 It is a schematic block diagram which shows an example of the waste water treatment apparatus which concerns on this embodiment. It is a figure which shows the relationship between BOD density
  • granule in this specification refers to a microbial self-granulated body, and there is no particular limitation, but for example, the particle diameter is 100 ⁇ m or more.
  • the “continuous type” is a system in which waste water is continuously supplied to the reaction tank and operated, but the reaction tank is operated by a pump using a principle such as a reciprocating motion such as a diaphragm pump.
  • a system in which waste water is supplied to the vehicle may be used.
  • a raw water tank is installed in front of the reaction tank, and the operation of the pump is controlled according to the water level of the raw water tank (the pump is operated when the water level is high, and the pump is stopped when the water level is low).
  • a simulated continuous water supply method for supplying wastewater to the reaction tank may be used. This method is distinguished from batch-type treatment and semi-batch-type treatment in that it does not involve aggressive drainage in the reaction tank.
  • Wastewater to be treated is wastewater containing biodegradable organic substances such as food processing factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, sewage, human waste, river water and the like. Moreover, when processing a biologically indegradable organic substance, a physicochemical process is performed beforehand and it can process by converting into a biodegradable substance.
  • FIG. 1 is a schematic configuration diagram illustrating an example of a wastewater treatment apparatus according to the present embodiment.
  • the waste water treatment apparatus 1 shown in FIG. 1 includes an anoxic biological treatment tank 10, a first biological treatment tank 12, a second biological treatment tank 14, and a sludge separation tank 16.
  • a drainage inflow line 18a is connected to the first biological treatment tank 12, a drainage inflow line 18b is connected between the first biological treatment tank 12 and the second biological treatment tank 14, and the second A drainage inflow line 18c is connected between the biological treatment tank 14 and the sludge separation tank 16, and a sludge return line 20a is connected between the sludge separation tank 16 and the anoxic biological treatment tank 10, Between the sludge separation tank 16 and the second biological treatment tank 14, a sludge return line 20b is directly connected or a sludge return line 20b branched from the sludge return line 20a is connected. A sludge return line 20 c is connected to the treatment tank 12. Further, a treated water discharge line 22 is connected to the sludge separation tank 16.
  • FIG. 2 is a diagram showing the relationship between one batch of BOD concentration and time in the batch activated sludge method.
  • the batch activated sludge method treats the raw water inflow process, reaction process, sedimentation process, and discharge process as one cycle.
  • the BOD concentration decreases due to the decomposition action of microorganisms.
  • the processing speed is faster than when the BOD concentration is low. That is, the MLSS load is high and the microorganism is in a satiety state.
  • the reaction process when biological treatment with microorganisms progresses and the BOD concentration in the reaction tank becomes low, the treatment speed decreases and eventually becomes zero. That is, the MLSS load is low and the microorganism is starved. Then, after an oxygen-free state, the process proceeds to a biological sludge sedimentation process and a treated water discharge process. By repeating this cycle, granulation of biological sludge occurs in the reaction tank. That is, in order to granulate biological sludge, it is important to control the transition from the satiety state to the starvation state in addition to the oxygen-free state.
  • the oxygen-free state, satiety state, and starvation state by the batch activated sludge method are reproduced by the continuous activated sludge method, and the conditions under which sludge granulation can easily occur. Enabled to set.
  • the oxygen-free state necessary for sludge granulation is executed by the oxygen-free biological treatment tank 10 of this embodiment. Specific biological treatment of the anoxic biological treatment tank 10 will be described later.
  • the anoxic biological treatment tank 10 microorganisms such as denitrifying bacteria and biological sludge supplied from a sludge separation tank 16 described later are retained. And they are in anoxic state due to the endogenous respiration of their biological sludge.
  • the oxygen-free state is a state where dissolved oxygen does not exist, but nitrous acid, oxygen derived from nitric acid, and the like exist.
  • the satiety state necessary for granulating sludge is executed by the first biological treatment tank 12 of this embodiment.
  • the first biological treatment tank 12 microorganisms and biological sludge supplied from the anoxic biological treatment tank 10 to be described later are retained.
  • oxygen is supplied by explosion or stirring, and the biological sludge is in a satiety state by applying a higher MLSS load than the second biological treatment tank 14.
  • the second biological treatment tank 14 microorganisms and biological sludge supplied from the first biological treatment tank 12 described later are retained.
  • oxygen is supplied by explosion or stirring, and the biological sludge is starved by applying an MLSS load lower than that of the first biological treatment tank 12.
  • an oxygen-free biological treatment tank 10 the 1st biological treatment tank 12, and the 2nd biological treatment tank 14 are connected in series, and an anoxic state, a satiety state, and a starvation state are carried out by a continuous activated sludge method. It is reproduced.
  • Wastewater containing BOD components discharged from food factories or the like flows continuously into the first biological treatment tank 12 through the wastewater inflow line 18a.
  • a raw water storage tank (not shown) to stabilize the quality of the waste water.
  • a stirring device mechanical stirring, air stirring, etc.
  • various BOD components are targeted.
  • oil and fat are attached to sludge and granules and adversely affected, they are floated and agglomerated in advance before being supplied to the first biological treatment tank 12. It is desirable to remove fats and oils to about 150 mg / L or less by an existing method such as a pressure levitation device or an adsorption device.
  • the BOD component in the wastewater is decomposed by the microorganisms in the tank and the biological sludge supplied from the anoxic biological treatment tank 10 under aerobic conditions (oxygen supply by aeration, stirring, etc.).
  • the sludge from the anoxic biological treatment tank 10 is diluted with the waste_water
  • the MLSS load of the first biological treatment tank 12 is preferably in the range of 0.8 kg BOD / kg MLSS / d to less than 1.8 kg BOD / kg MLSS / d, depending on the BOD component, the volume of the tank, and the like.
  • the inflow BOD component is almost decomposed in the first biological treatment tank 12.
  • the MLSS load of the first biological treatment tank 12 is in the range of 1.8 kgBOD / kgMLSS / d or more to less than 5.0 kgBOD / kgMLSS / d, the BOD component remains in the treated water discharged from the first biological treatment tank 12. Since the amount is small, the influence of the MLSS load on the second biological treatment tank 14 in the subsequent stage is small.
  • the MLSS load in the first biological treatment tank 12 is 5.0 kgBOD / kgMLSS / d or more, depending on the type of BOD component, the BOD component flowing into the second biological treatment tank 14 in the subsequent stage increases, and the second biological treatment tank It may be difficult to make the MLSS load of 14 smaller than the MLSS load of the first biological treatment tank 12.
  • the wastewater (including sludge) treated in the first biological treatment tank 12 continuously flows into the second biological treatment tank 14 through the wastewater inflow line 18b.
  • the second biological treatment tank 14 is supplied from the microorganisms in the tank, the biological sludge supplied from the first biological treatment tank 12 and the subsequent sludge separation tank 16 under aerobic conditions (oxygen supply by aeration or stirring).
  • the unreacted BOD component in the waste water is decomposed by the biological sludge.
  • the MLSS concentration increases due to the inflow of biological sludge supplied from the subsequent sludge separation tank 16.
  • the MLSS load can be controlled to be lower than that of the biological treatment tank 12.
  • the MLSS load of the second biological treatment tank 14 is preferably in the range of 0 kgBOD / kgMLSS / d to 0.5 kgBOD / kgMLSS / d or less, depending on the BOD component, the volume of the tank, and the like. If there are many unreacted BOD components flowing in from the first biological treatment tank 12, the MLSS load of the second biological treatment tank 14 may exceed 0.5 kgBOD / kgMLSS / d.
  • MLSS load of the second biological treatment tank 14 exceeds 0.5 kgBOD / kgMLSS / d, a high MLSS load will continue to be applied through the first biological treatment tank 12, so that bulking is induced by granulation of biological sludge. May increase the likelihood of doing so.
  • the wastewater (including sludge) treated in the second biological treatment tank 14 passes through the wastewater inflow line 18 c and continuously flows into the sludge separation tank 16.
  • the biological sludge is settled and separated from the waste water discharged from the second biological treatment tank 14.
  • the waste water from which the biological sludge was separated is discharged from the treated water discharge line 22 as treated water.
  • the biological sludge concentrated in the sludge separation tank 16 is supplied from the sludge return line 20a to the anoxic biological treatment tank 10, and is also supplied from the sludge return line 20b to the second biological treatment tank 14.
  • a pump or the like in the sludge return line 20a When adjusting the amount of sludge returned, it is preferable to install a pump or the like in the sludge return line 20a.
  • the sludge separation tank 16 is not limited to sedimentation separation, and may be, for example, membrane separation.
  • anoxic biological treatment tank 10 a denitrification process is performed to convert nitrogen-containing substances in the anoxic biological treatment tank 10 into nitrogen gas by microorganisms such as denitrifying bacteria and biological sludge supplied from the sludge separation tank 16. Is called.
  • the oxygen-free biological treatment tank 10 is in an oxygen-free state due to endogenous respiration of biological sludge. Stirring at this time is preferable because the sludge concentration in the tank becomes uniform.
  • the residence time of the biological sludge in the anoxic biological treatment tank 10 is remarkably short, oxygen contained in the biological sludge supplied from the sludge separation tank 16 cannot be consumed by endogenous respiration, and an anoxic state can be maintained.
  • the biological sludge treated in the oxygen-free state is continuously supplied from the sludge return line 20c to the first biological treatment tank 12.
  • the anaerobic biological treatment tank 10 of the present embodiment may be in an anaerobic state. That is, the anaerobic biological treatment tank 10 may be an anaerobic tank. In the anaerobic tank, denitrification, methane fermentation, and the like are performed in an anaerobic state.
  • the anaerobic state is a condition in which not only dissolved oxygen but also nitrous acid or nitric acid-derived oxygen does not exist.
  • organic substances are required in the reaction process, it is necessary to allow a part of the waste water to flow into the anaerobic tank and add the organic substances in the waste water. However, if a part of the waste water is introduced, the residence time of the waste water in the anaerobic tank is shortened, and it is necessary to ensure the residence time.
  • the BOD concentration in the reaction tank becomes high and satiety at the initial stage of the reaction step, but the BOD concentration in the reaction tank increases as the decomposition of the BOD component proceeds. It will decline and move to starvation.
  • it is considered important that the time of starvation at this time is sufficiently long compared to the satiety state, in addition to the subsequent oxygen-free process. ing.
  • the optimum value of this ratio is considered to vary depending on the BOD component to be processed, but in many cases, the starvation state requires a longer time than the satiation state.
  • fills the range of the MLSS load mentioned above will be in a satiety state, and the 2nd biological treatment tank 14 will be in a starvation state. Therefore, the amount of sludge returned is controlled and the volume of the first biological treatment tank 12 and the second biological treatment tank 14 is designed so that the ratio of the fed state to the starved state (satiated state / starved state) is less than 1. It is desirable to do.
  • the reaction occurs in the same reaction tank, so the MLSS amount in the satiety state and the starvation state is the same. Therefore, the ratio of the satiety state to the starvation state (satiate state / starvation state) may be determined by applying the time of the satiety state and the time of the starvation state.
  • the saturable state and the starved state tanks are different from each other, and therefore the MLSS amount to be held is different. Therefore, the ratio of the satiety state to the starvation state is calculated as follows.
  • the cycle interval between the starved state and the satiety state is also known as a factor necessary for granulating biological sludge.
  • the first biological treatment tank 12 and the second biological treatment tank 14 are set so that the total residence time of the water to be treated in the first biological treatment tank 12 and the second biological treatment tank 14 is at least 3 hours. It is desirable to set the volume of water, the flow rate of treated water, and the return sludge flow rate so that the cycle interval between the starved state and the satiety state is not shortened.
  • the first biological treatment tank 12 and the second biological treatment tank 14 are each divided into a plurality of parts, and the wastewater containing the BOD component is allowed to flow into the divided first biological treatment tanks 12, respectively. It is preferable to supply each of the second biological treatment tanks 14 into which the biological sludge is divided.
  • the biological treatment tank is divided, the volume of at least one of the first biological treatment tank 12 and the second biological treatment tank 14 satisfies the preferable conditions for granulation of the biological sludge described above. I just need it.
  • the entire sludge flow rate discharged from the sludge separation tank 16 and the sludge flow rate flowing into the anoxic biological treatment tank 10 are the satiety state in the first biological treatment tank 12 with respect to the starvation state in the second biological treatment tank 14 described above. It is preferable that the ratio (satiated / starved state) is less than 1 and that the residence time of the anaerobic biological treatment tank is secured for 30 minutes or more. For example, if the sludge flow rate flowing into the anaerobic biological treatment tank 10 is increased, the residence time of the anoxic biological treatment tank 10 and the first biological treatment tank 12 is reduced, while the MLSS concentration in the first biological treatment tank 12 is increased. descend.
  • the residence time of the anoxic biological treatment tank 10 and the first biological treatment tank 12 is increased, while the MLSS concentration in the first biological treatment tank 12 is increased.
  • the residence time of the anoxic biological treatment tank 10, the first biological treatment tank 12, and the second biological treatment tank 14 decreases, the MLSS concentration in the first biological treatment tank 12 increases, 2 The MLSS concentration in the biological treatment tank 14 also increases.
  • the residence time of the anoxic biological treatment tank 10, the first biological treatment tank 12, and the second biological treatment tank 14 increases, and the MLSS concentration in the first biological treatment tank 12 increases, 2
  • the MLSS concentration in the biological treatment tank 14 also increases.
  • the oxygen-free state, satiety state, and starvation state which are important factors for granulating biological sludge, can be arbitrarily set by operating the return flow rate. It is beneficial in that it can be controlled.
  • the pH in each biological treatment tank is not particularly specified, but the pH in each biological treatment tank is preferably in the range of 6-8 as in the case of normal activated sludge. Depending on the type of BOD component to be treated, the pH in the tank may fluctuate. In that case, the pH in the tank should be controlled within the above range using sodium hydroxide, hydrochloric acid, sulfuric acid, etc. Is preferred.
  • Nucleus is required for granulation of sludge. Since normal effluent contains such fine particles as nuclei, it is not necessary to add them in particular, but hydroxides such as Fe 2+, Fe 3+, Ca 2+ and Mg + are used in order to promote nucleation. It is preferred to add ions as they are formed. In addition, when adding Fe2 +, it is preferable to add to the anoxic biological treatment tank 10. Thereby, in addition to the promotion formation of a nucleus, an oxygen-free state can be promoted.
  • nitrate or nitrite it is preferable to add nitrate or nitrite to the anaerobic biological treatment tank 10.
  • This embodiment is also effective for suppressing bulking.
  • it is effective to create an environment that makes it difficult for the filamentous microorganisms that cause it to selectively grow.
  • a method that introduces a substrate concentration gradient or starvation conditions is called kinetic selection, and makes it difficult for filamentous microorganisms to ingest the substrate.
  • kinetic selection a method that introduces a substrate concentration gradient or starvation conditions
  • a method for introducing environmental changes such as aerobic, anaerobic and anaerobic is called metabolic selection (see Non-Patent Document 1).
  • biological sludge is brought into an oxygen-free state or a starved state, an environment in which the action of kinetic selection and metabolic selection is easy to work, and thus bulking can be suppressed.
  • the wastewater treatment apparatus 1 shown in FIG. 1 (the volume of the anoxic biological treatment tank 10 is 10L, the volume of the first biological treatment tank 12 is 30L, the volume of the second biological treatment tank 14 is 40L), Biological treatment of water to be treated was performed by diluting the components to an arbitrary concentration of BOD 130 to 300 mg / L. The water to be treated was continuously supplied to the first biological treatment tank 12. The sludge used in the standard activated sludge method was used as seed sludge. After acclimatization, the MLSS load was controlled by changing the flow rate.
  • the anoxic biological treatment tank 10 was only stirred by a stirrer, and the DO was maintained at less than 1 mg / L during the test period.
  • the first biological treatment tank 12 and the second biological treatment tank 14 were subjected to air explosion using a diffuser, and the DO was maintained in the range of 5 to 8 mg / L during the test period.
  • Water temperature was measured at room temperature without any particular control, and changed in the range of 25 to 28 ° C during the test period.
  • the entire sludge flow rate discharged from the sludge separation tank 16 was set to the same amount as the flow rate of the water to be treated supplied to the first biological treatment tank 12. Moreover, the ratio of the sludge flow rate supplied to the anoxic biological treatment tank 10 and the sludge flow rate supplied to the second biological treatment tank 14 was adjusted to 3:10. The percentage of MLSS concentration in each tank is determined by the mass balance, and the overall sludge flow rate increases in proportion to the flow rate of the water to be treated. State / starvation ratio) was fixed at about 0.34.
  • the water surface area load of the sludge separation tank 16 was in the range of 0.2 m / h to 2.0 m / h.
  • the BOD concentration of the treated water and the BOD concentration of the final treated water obtained from the sludge separation tank 16 are shown.
  • index the sum total of the residence time of the 1st biological treatment tank 12 and the 2nd biological treatment tank 14, and the residence time (median value) of the anoxic biological treatment tank 10 are shown.
  • Table 1 shows.
  • the particle size distribution of the sludge in each test period is shown.
  • the MLSS load of the first biological treatment tank 12 is set to 0.3 kgBOD / kgMLSS / d
  • the MLSS load of the second biological treatment tank 14 is 0.04 kgBODkgMLSS / d.
  • SVI30 in this test period was lower than that of seed sludge, and the sedimentation property of the sludge was improved.
  • the particle size distribution during this test period did not change much compared to the seed sludge, and no granule formation was observed.
  • the biological sludge in the first biological treatment tank 12 is unlikely to be sufficiently satiety, and it is considered that granulation of the biological sludge did not occur during the test period (10 days).
  • the MLSS load of the first biological treatment tank 12 was set to 0.8 kgBOD / kgMLSS / d by increasing the inflow flow rate of the water to be treated.
  • SVI30 during this test period was greatly reduced compared to seed sludge.
  • the particle diameter in this test period is larger than that of seed sludge, and it can be said that granulation of biological sludge is progressing.
  • the amount of inflow water to be treated and the BOD concentration of the water to be treated were increased to set the MLSS load of the first biological treatment tank 12 to 1.8 kgBOD / kgMLSS / d.
  • SVI30 during this test period remained low as in the test period from 10 days to 20 days after the start of the test.
  • the particle diameter was further increased during this test period.
  • the MLSS load of the first biological treatment tank 12 is set to 1.8 kgBOD / kgMLSS / d, and the amount of inflow water to be treated is increased as the MLSS concentration increases.
  • the total residence time of the first biological treatment tank 12 and the second biological treatment tank 14 was set to 1.8 h.
  • SVI30 in this test period increased compared to the test period from 20 days to 30 days after the start of the test.
  • the dilution ratio of the BOD concentration of the treated water is changed to 300 mg / L, the amount of inflow water of the treated water is decreased, and the MLSS load of the first biological treatment tank 12 is 1.9 kgBOD. / KgMLSS / d, and the total residence time of the first biological treatment tank 12 and the second biological treatment tank 14 was set to 3.2 h.
  • Table 1 the SVI30 increased during the test period from 30 days to 40 days after the start of the test decreased during this test period, and an improvement trend was observed in the sedimentation property of biological sludge.
  • flocs adhering to the granules decreased during the test period from the 30th day to the 40th day.
  • the sedimentation property of sludge when the MLSS load of the first biological treatment tank 12 is set to 0.3 kgBOD / kgMLSS / d and the MLSS load of the second biological treatment tank 14 is set to 0.04 kgBODkgMLSS / d, the sedimentation property of sludge However, granulation of biological sludge did not occur during the 10-day test period. And when the MLSS load of the 1st biological treatment tank 12 was raised to 0.8 kgBOD / kgMLSS / d or more, granulation of the biological sludge occurred in a short period of 10 days. In addition, if the total residence time of the first biological treatment tank 12 and the second biological treatment tank 14 is low, flocs may adhere around the granules and the sedimentation property of the biological sludge may decrease.
  • the oxygen-free biological treatment tank 10 is omitted in FIG. 1, the MLSS load of the first biological treatment tank 12 is 1.4 kgBOD / kgMLSS / d, and the second biological treatment.
  • the MLSS load of the tank 14 was raised to 0.1 kg BOD kg MLSS / d, and operation was performed for 20 days at this load.
  • the state of the sludge at this time was observed with an electron microscope, and sludge was granulated with the start-up, but a large amount of micro-animals were observed during the operation for 20 days. Has been destroyed.
  • Table 2 SVI30 was higher than the granulated condition.
  • the anoxic biological treatment tank 10 was added and the operation was performed for 10 days without changing the load conditions.
  • the results after 10 days of operation are summarized in Table 2.
  • Table 2 the SVI30 after 10 days of operation was greatly reduced as compared to the case where the anoxic biological treatment tank 10 was omitted.
  • the state of the sludge at this time was observed with an electron microscope, the number of micro-animals decreased, and granules having a diameter of about 200 ⁇ m were formed. From this, it is considered that the oxygen-free biological treatment tank 10 greatly contributes to granulation.
  • wastewater treatment equipment 10 anoxic biological treatment tank, 12 first biological treatment tank, 14 second biological treatment tank, 16 sludge separation tank, 18a-18c drainage inflow line, 20a-20c sludge return line, 22 treated water discharge line .

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Abstract

Provided is a wastewater treatment device capable of increasing the precipitation of biological sludge by: having a reaction tank that biologically treats with biological sludge organic wastewater that includes a BOD component, and a sludge separation tank (16) that separates the processed water obtained in the reaction tank from sludge; the reaction tank including an anaerobic biological processing tank (10), and a first biological processing tank (12) and a second biological processing tank (14) to which the oxygen required for the biological processing is supplied; the organic wastewater continuously flowing into the first biological processing tank (12) and being biologically processed in the first biological processing tank (12) and the second biological processing tank (14); the sludge inside the sludge separation tank (16) being returned to the second biological processing tank (14) and the anaerobic biological processing tank (10); the sludge inside the anaerobic biological processing tank (10) being supplied to at least the first biological processing tank (12); and the MLSS load in the first biological processing tank (12) being higher than the MLSS load in the second biological processing tank (14). <0}

Description

排水処理装置Wastewater treatment equipment
　本発明は、ＢＯＤ成分を含む有機性排水を生物汚泥により生物処理する排水処理装置に関する。 The present invention relates to a wastewater treatment apparatus for biologically treating organic wastewater containing BOD components with biological sludge.
　好気性の活性汚泥法が排水処理装置として適用され始めた頃、処理対象のＢＯＤ成分を含んだ有機性排水をバッチ毎に処理する回分式活性汚泥法による排水処理が行われていた。回分式活性汚泥法とは、原水の流入工程、反応工程、沈降工程、排出工程を１サイクルとして処理するものである。しかし、回分式活性汚泥法では、水量や負荷の大きな変動に対応することが難しく、また、当初は自動化技術が無かったために、運転サイクルを手動で行わなくてはならず、操作が煩雑となる欠点等があった。このため、連続的に有機性排水を流入させることができる標準活性汚泥法が開発された。 When the aerobic activated sludge method began to be applied as a wastewater treatment device, wastewater treatment by a batch activated sludge method in which organic wastewater containing BOD components to be treated was treated in batches was performed. In the batch activated sludge process, the raw water inflow process, reaction process, sedimentation process, and discharge process are treated as one cycle. However, with the batch activated sludge method, it is difficult to cope with large fluctuations in water volume and load, and since there was no automation technology at the beginning, the operation cycle must be performed manually, and the operation is complicated. There were drawbacks. For this reason, a standard activated sludge method that allows continuous flow of organic wastewater has been developed.
　しかしながら、連続式である標準活性汚泥法では、生物汚泥の沈降不良によって、生物汚泥の分離が困難になる、いわゆる「バルキング」の問題がある。活性汚泥法の処理能力は、保持できる生物汚泥量に強く依存するため、バルキングに起因する沈降不良によって、処理水に生物汚泥が流出する問題は大きな課題である。このような課題に対し、活性汚泥の変法と呼ばれる技術が数多く開発されてきた（例えば、非特許文献１参照）。 However, the standard activated sludge method, which is a continuous type, has a so-called “bulking” problem that makes it difficult to separate biological sludge due to poor sedimentation of biological sludge. Since the treatment capacity of the activated sludge method strongly depends on the amount of biological sludge that can be retained, the problem that biological sludge flows out into treated water due to poor sedimentation caused by bulking is a major issue. Many techniques called modified activated sludge have been developed for such problems (see, for example, Non-Patent Document 1).
　近年、回分式活性汚泥法において、非常に速い沈降速度をもつ「グラニュール」と呼ばれる微生物自己造粒体を用いることで、汚泥濃度を高めて高い処理能力が実現できることが報告されている（例えば、特許文献１参照）。 In recent years, in batch activated sludge processes, it has been reported that by using a microbial self-granulated material called “granule” having a very fast sedimentation rate, a high treatment capacity can be realized by increasing the sludge concentration (for example, , See Patent Document 1).
　また、連続法の活性汚泥法においても、グラニュールを種汚泥として生物汚泥をグラニュール化させる手法が提案されている（例えば、特許文献２参照）。 Also in the continuous activated sludge method, a method of granulating biological sludge using granule as seed sludge has been proposed (for example, see Patent Document 2).
特表２００５－５３８８２５号公報JP 2005-538825 A 特開２００２－３３６８８５号公報JP 2002-336885 A
　グラニュールを用いた回分式活性汚泥法による排水処理は、バルキングの課題がなく、また、生物汚泥の沈降性が高く、高い処理能力が得られる点で、有益であるが、回分式活性汚泥法の運転制御には、多くのセンサーを必要とするため、装置が複雑になり、初期コスト、運転管理の面で不利である。 Wastewater treatment by batch activated sludge process using granule is beneficial in that it has no bulking problems, has high sedimentation of biological sludge, and has a high treatment capacity. Since the operation control requires many sensors, the apparatus becomes complicated, which is disadvantageous in terms of initial cost and operation management.
　連続式の活性汚泥法において、生物汚泥をグラニュール化させるためには、グラニュールを種汚泥として添加する必要がある。すなわち、従来の処理装置では、生物汚泥からグラニュールを形成することができる機構を備えていないため、何らかの原因でグラニュールが崩壊してしまった場合、再度種汚泥としてグラニュールを添加して馴養しなくてはならず、運転管理上に問題がある。 In the continuous activated sludge process, it is necessary to add granule as seed sludge in order to granulate biological sludge. In other words, the conventional treatment equipment does not have a mechanism that can form granules from biological sludge, so if the granule collapses for some reason, it is acclimatized by adding the granule again as seed sludge. There is a problem in operation management.
　そこで、本発明は、生物汚泥の沈降性を高めることができる排水処理装置を提供することを目的とする。あるいは、連続式の活性汚泥法において、汚泥をグラニュール化させ、生物汚泥の沈降性を高めることができる排水処理装置を提供することを目的とする。 Therefore, an object of the present invention is to provide a wastewater treatment apparatus that can enhance the sedimentation property of biological sludge. Alternatively, in a continuous activated sludge method, an object is to provide a wastewater treatment apparatus that can granulate sludge and enhance the sedimentation property of biological sludge.
　（１）本発明は、ＢＯＤ成分を含む有機性排水を生物汚泥により生物処理する反応槽と、前記反応槽で得られた処理水を前記汚泥と分離する汚泥分離槽と、を有する排水処理装置であって、前記反応槽は、無酸素生物処理槽と、前記生物処理に必要な酸素が供給される第１生物処理槽及び第２生物処理槽と、を含み、前記有機性排水は前記第１生物処理槽に連続的に流入され、前記第１生物処理槽及び前記第２生物処理槽で生物処理され、前記汚泥分離槽内の汚泥は、前記第２生物処理槽及び前記無酸素生物処理槽へ返送され、前記無酸素生物処理槽内の汚泥は、少なくとも前記第１生物処理槽に供給され、前記第１生物処理槽のＭＬＳＳ負荷は、前記第２生物処理槽のＭＬＳＳ負荷より高いものである。 (1) The present invention is a wastewater treatment apparatus having a reaction tank for biologically treating organic wastewater containing BOD components with biological sludge, and a sludge separation tank for separating treated water obtained in the reaction tank from the sludge. The reaction tank includes an oxygen-free biological treatment tank, a first biological treatment tank and a second biological treatment tank to which oxygen necessary for the biological treatment is supplied, and the organic wastewater is the first biological treatment tank. It is continuously flowed into one biological treatment tank and biologically treated in the first biological treatment tank and the second biological treatment tank, and the sludge in the sludge separation tank is treated with the second biological treatment tank and the anoxic biological treatment. The sludge in the oxygen-free biological treatment tank is returned to the tank, and is supplied to at least the first biological treatment tank. The MLSS load of the first biological treatment tank is higher than the MLSS load of the second biological treatment tank. It is.
　（２）上記（１）の排水処理装置において、前記第１生物処理槽のＭＬＳＳ負荷は、０．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以上の範囲であり、前記第２生物処理槽のＭＬＳＳ負荷は、０．５ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以下の範囲であることが好ましい。 (2) In the wastewater treatment apparatus of (1), the MLSS load of the first biological treatment tank is in a range of 0.8 kgBOD / kgMLSS / d or more, and the MLSS load of the second biological treatment tank is 0.00. The range is preferably 5 kg BOD / kg MLSS / d or less.
　（３）上記（１）または（２）の排水処理装置において、前記第１生物処理槽及び前記第２生物処理槽の被処理水の滞留時間の合計が３時間以上であることが好ましい。 (3) In the waste water treatment apparatus according to (1) or (2), it is preferable that the total residence time of the water to be treated in the first biological treatment tank and the second biological treatment tank is 3 hours or more.
　本発明によれば、生物汚泥の沈降性を高めることができる。 According to the present invention, the sedimentation property of biological sludge can be enhanced.
本実施形態に係る排水処理装置の一例を示す概略構成図である。It is a schematic block diagram which shows an example of the waste water treatment apparatus which concerns on this embodiment. 回分式活性汚泥法における１バッチのＢＯＤ濃度と時間との関係を示す図である。It is a figure which shows the relationship between BOD density | concentration of 1 batch and time in a batch type activated sludge process. 実施例の各試験期間における汚泥の粒径分布を示す。The particle size distribution of the sludge in each test period of an Example is shown.
　以下、本発明の実施の形態について説明する。なお、本実施形態は本発明を実施する一例であって、本発明は本実施形態に限定されるものではない。 Hereinafter, embodiments of the present invention will be described. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.
　ここで、本明細書において「グラニュール」とは微生物自己造粒体のことをいい、特に制限はないが、例えばその粒径が１００μｍ以上のものをいう。 Here, “granule” in this specification refers to a microbial self-granulated body, and there is no particular limitation, but for example, the particle diameter is 100 μm or more.
　また、本明細書において、「連続式」とは、連続して反応槽に排水を供給して運転する方式であるが、ダイヤフラムポンプ等の往復運動のような原理を利用したポンプにより、反応槽に排水を供給して運転する方式等であってもよい。また、反応槽の前段に原水槽を設置し、その原水槽の水位に応じてポンプの稼動－停止を制御（水位が高い場合にはポンプを稼動、水位が低い場合にはポンプを停止）して、反応槽に排水を供給する模擬連続通水方式等であってもよい。かかる方式は反応槽内の積極的な排水を伴わない点で、回分式処理、半回分式処理と区別される。 In the present specification, the “continuous type” is a system in which waste water is continuously supplied to the reaction tank and operated, but the reaction tank is operated by a pump using a principle such as a reciprocating motion such as a diaphragm pump. For example, a system in which waste water is supplied to the vehicle may be used. In addition, a raw water tank is installed in front of the reaction tank, and the operation of the pump is controlled according to the water level of the raw water tank (the pump is operated when the water level is high, and the pump is stopped when the water level is low). In addition, a simulated continuous water supply method for supplying wastewater to the reaction tank may be used. This method is distinguished from batch-type treatment and semi-batch-type treatment in that it does not involve aggressive drainage in the reaction tank.
　処理対象となる排水は食品加工工場排水、化学工場排水、半導体工場排水、機械工場排水、下水、し尿、河川水等、生物分解性有機物を含有した排水である。また、生物難分解性の有機物を処理する場合には、予め物理化学的処理を施し、生物分解性の物質に変換することによって処理が可能となる。 Wastewater to be treated is wastewater containing biodegradable organic substances such as food processing factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, sewage, human waste, river water and the like. Moreover, when processing a biologically indegradable organic substance, a physicochemical process is performed beforehand and it can process by converting into a biodegradable substance.
　以下に食品工場排水を処理対象とした場合を一例として、本実施形態に係る排水処理方法及び排水処理装置の適用について説明する。 Hereinafter, application of the wastewater treatment method and wastewater treatment apparatus according to this embodiment will be described by taking as an example the case where food factory wastewater is treated.
　図１は、本実施形態に係る排水処理装置の一例を示す概略構成図である。図１に示す排水処理装置１は、無酸素生物処理槽１０、第１生物処理槽１２、第２生物処理槽１４、汚泥分離槽１６、を備えるものである。 FIG. 1 is a schematic configuration diagram illustrating an example of a wastewater treatment apparatus according to the present embodiment. The waste water treatment apparatus 1 shown in FIG. 1 includes an anoxic biological treatment tank 10, a first biological treatment tank 12, a second biological treatment tank 14, and a sludge separation tank 16.
　第１生物処理槽１２には、排水流入ライン１８ａが接続されており、第１生物処理槽１２と第２生物処理槽１４との間には、排水流入ライン１８ｂが接続されており、第２生物処理槽１４と汚泥分離槽１６との間には、排水流入ライン１８ｃが接続されており、汚泥分離槽１６と無酸素生物処理槽１０との間には、汚泥返送ライン２０ａが接続され、汚泥分離槽１６と第２生物処理槽１４との間には、汚泥返送ライン２０ｂが直接接続もしくは汚泥返送ライン２０ａから分岐した汚泥返送ライン２０ｂが接続され、無酸素生物処理槽１０と第１生物処理槽１２との間には、汚泥返送ライン２０ｃが接続されている。また、汚泥分離槽１６には、処理水排出ライン２２が接続されている。 A drainage inflow line 18a is connected to the first biological treatment tank 12, a drainage inflow line 18b is connected between the first biological treatment tank 12 and the second biological treatment tank 14, and the second A drainage inflow line 18c is connected between the biological treatment tank 14 and the sludge separation tank 16, and a sludge return line 20a is connected between the sludge separation tank 16 and the anoxic biological treatment tank 10, Between the sludge separation tank 16 and the second biological treatment tank 14, a sludge return line 20b is directly connected or a sludge return line 20b branched from the sludge return line 20a is connected. A sludge return line 20 c is connected to the treatment tank 12. Further, a treated water discharge line 22 is connected to the sludge separation tank 16.
　本実施形態の排水処理装置１の動作説明に先立って、生物汚泥のグラニュール化の条件について説明する。 Prior to explaining the operation of the wastewater treatment apparatus 1 of the present embodiment, conditions for granulating biological sludge will be described.
　図２は、回分式活性汚泥法における１バッチのＢＯＤ濃度と時間との関係を示す図である。前述した通り回分式活性汚泥法とは、原水の流入工程、反応工程、沈降工程、排出工程を１サイクルとして処理するものである。図２に示すように、原水の流入工程を経て、反応工程に移ると、ＢＯＤ濃度が微生物の分解作用により減少していく。この時、微生物の一般的性質として、ＢＯＤ濃度が高い時は、ＢＯＤ濃度が低い時と比べて、同一のＭＬＳＳ濃度であるならば、その処理速度は速くなる。すなわち、ＭＬＳＳ負荷が高く、微生物は飽食状態となっている。反応工程において、微生物による生物処理が進み、反応槽内のＢＯＤ濃度が低くなると、処理速度が低下し、やがては０となる。すなわち、ＭＬＳＳ負荷が低く、微生物は飢餓状態となっている。その後、無酸素状態を経て、生物汚泥の沈降工程、処理水の排出工程に移行する。このサイクルを繰り返すことにより、反応槽内では生物汚泥のグラニュール化が起こる。すなわち、生物汚泥のグラニュール化には、無酸素状態に加え、飽食状態から飢餓状態への遷移を制御することが重要である。 FIG. 2 is a diagram showing the relationship between one batch of BOD concentration and time in the batch activated sludge method. As described above, the batch activated sludge method treats the raw water inflow process, reaction process, sedimentation process, and discharge process as one cycle. As shown in FIG. 2, when the raw water inflow process proceeds to the reaction process, the BOD concentration decreases due to the decomposition action of microorganisms. At this time, as a general property of microorganisms, when the BOD concentration is high, if the same MLSS concentration is used, the processing speed is faster than when the BOD concentration is low. That is, the MLSS load is high and the microorganism is in a satiety state. In the reaction process, when biological treatment with microorganisms progresses and the BOD concentration in the reaction tank becomes low, the treatment speed decreases and eventually becomes zero. That is, the MLSS load is low and the microorganism is starved. Then, after an oxygen-free state, the process proceeds to a biological sludge sedimentation process and a treated water discharge process. By repeating this cycle, granulation of biological sludge occurs in the reaction tank. That is, in order to granulate biological sludge, it is important to control the transition from the satiety state to the starvation state in addition to the oxygen-free state.
　そこで、本実施形態の排水処理装置では、回分式活性汚泥法による無酸素状態、飽食状態、飢餓状態を連続式の活性汚泥法にて再現し、汚泥のグラニュール化が起こりえる条件を容易に設定できるようにした。 Therefore, in the wastewater treatment apparatus of this embodiment, the oxygen-free state, satiety state, and starvation state by the batch activated sludge method are reproduced by the continuous activated sludge method, and the conditions under which sludge granulation can easily occur. Enabled to set.
　まず、汚泥のグラニュール化に必要な無酸素状態は、本実施形態の無酸素生物処理槽１０によって、実行される。無酸素生物処理槽１０の具体的な生物処理については後述するが、無酸素生物処理槽１０内には、脱窒菌等の微生物、後述する汚泥分離槽１６から供給される生物汚泥が滞留しており、それらの生物汚泥の内生呼吸で無酸素状態となっている。ここで、無酸素状態とは、溶存酸素は存在しないが、亜硝酸や硝酸由来の酸素等は存在している状態である。 First, the oxygen-free state necessary for sludge granulation is executed by the oxygen-free biological treatment tank 10 of this embodiment. Specific biological treatment of the anoxic biological treatment tank 10 will be described later. In the anoxic biological treatment tank 10, microorganisms such as denitrifying bacteria and biological sludge supplied from a sludge separation tank 16 described later are retained. And they are in anoxic state due to the endogenous respiration of their biological sludge. Here, the oxygen-free state is a state where dissolved oxygen does not exist, but nitrous acid, oxygen derived from nitric acid, and the like exist.
　次に、汚泥のグラニュール化に必要な飽食状態は、本実施形態の第１生物処理槽１２によって、実行される。第１生物処理槽１２内には、微生物、後述する無酸素生物処理槽１０から供給される生物汚泥が滞留している。第１生物処理槽１２内では、爆気や攪拌等で酸素を供給し、また、第２生物処理槽１４よりも高いＭＬＳＳ負荷をかけることによって、生物汚泥が飽食状態とされている。第２生物処理槽１４内は、微生物、後述する第１生物処理槽１２から供給される生物汚泥が滞留している。第２生物処理槽１４内では、爆気や攪拌等で酸素を供給し、第１生物処理槽１２よりも低いＭＬＳＳ負荷をかけることによって、生物汚泥が飢餓状態とされている。 Next, the satiety state necessary for granulating sludge is executed by the first biological treatment tank 12 of this embodiment. In the first biological treatment tank 12, microorganisms and biological sludge supplied from the anoxic biological treatment tank 10 to be described later are retained. In the first biological treatment tank 12, oxygen is supplied by explosion or stirring, and the biological sludge is in a satiety state by applying a higher MLSS load than the second biological treatment tank 14. In the second biological treatment tank 14, microorganisms and biological sludge supplied from the first biological treatment tank 12 described later are retained. In the second biological treatment tank 14, oxygen is supplied by explosion or stirring, and the biological sludge is starved by applying an MLSS load lower than that of the first biological treatment tank 12.
　そして、このような無酸素生物処理槽１０、第１生物処理槽１２、第２生物処理槽１４を直列に連結させて、無酸素状態、飽食状態、飢餓状態を連続式の活性汚泥法にて再現している。 And such an oxygen-free biological treatment tank 10, the 1st biological treatment tank 12, and the 2nd biological treatment tank 14 are connected in series, and an anoxic state, a satiety state, and a starvation state are carried out by a continuous activated sludge method. It is reproduced.
　以下に、本実施形態の排水処理装置１の動作について説明する。 Hereinafter, the operation of the wastewater treatment apparatus 1 of the present embodiment will be described.
　食品工場等から排出されたＢＯＤ成分を含む排水は、排水流入ライン１８ａを通り、第１生物処理槽１２に連続的に流入する。食品工場等から排出された排水は、第１生物処理槽１２に供給される前に、原水貯留槽（不図示）へと送られ、排水の水質安定化が行われることが好ましい。また、この際、排水中に固形物が含まれている場合には、スクリーン等によって、固形物を取り除いておくことが望ましい。また、原水貯留槽では排水の均一化を行うため、攪拌装置（機械攪拌、空気攪拌等）を設置することが望ましい。 Wastewater containing BOD components discharged from food factories or the like flows continuously into the first biological treatment tank 12 through the wastewater inflow line 18a. Before the waste water discharged from the food factory or the like is supplied to the first biological treatment tank 12, it is preferably sent to a raw water storage tank (not shown) to stabilize the quality of the waste water. At this time, when solid matter is contained in the waste water, it is desirable to remove the solid matter with a screen or the like. Moreover, in order to make the wastewater uniform in the raw water storage tank, it is desirable to install a stirring device (mechanical stirring, air stirring, etc.).
　本実施形態では、様々なＢＯＤ成分を対象としているが、油脂分に関しては汚泥やグラニュールに付着して悪影響を及ぼすため、第１生物処理槽１２に供給される前に、予め浮上分離、凝集加圧浮上装置、吸着装置等の既存の手法にて、油脂分を１５０ｍｇ／Ｌ以下程度まで除去しておくことが望ましい。 In this embodiment, various BOD components are targeted. However, since oil and fat are attached to sludge and granules and adversely affected, they are floated and agglomerated in advance before being supplied to the first biological treatment tank 12. It is desirable to remove fats and oils to about 150 mg / L or less by an existing method such as a pressure levitation device or an adsorption device.
　第１生物処理槽１２では、好気条件下で（曝気や攪拌等による酸素供給）、槽内の微生物及び無酸素生物処理槽１０から供給される生物汚泥により、排水中のＢＯＤ成分が分解される。このように、第１生物処理槽１２では、無酸素生物処理槽１０からの汚泥がＢＯＤ成分を含む排水で希釈されるため、槽内のＭＬＳＳ濃度を低く保つことができる。すなわち前述した高いＭＬＳＳ負荷を確保し、生物汚泥を飽食状態としている。第１生物処理槽１２のＭＬＳＳ負荷は、ＢＯＤ成分や槽の容積等にもよるが、０．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以上～１．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ未満の範囲が好ましく、この場合には、流入したＢＯＤ成分は第１生物処理槽１２でほとんど分解される。第１生物処理槽１２のＭＬＳＳ負荷が１．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以上～５．０ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ未満の範囲では、第１生物処理槽１２から排出される処理水にＢＯＤ成分が残存するものの、その量は少ないため、後段の第２生物処理槽１４に与えるＭＬＳＳ負荷の影響は小さい。すなわち、第１生物処理槽１２のＭＬＳＳ負荷より大きくなることはない。第１生物処理槽１２でのＭＬＳＳ負荷が５．０ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以上の場合、ＢＯＤ成分の種類によっては後段の第２生物処理槽１４へ流入するＢＯＤ成分が多くなり、第２生物処理槽１４のＭＬＳＳ負荷を第１生物処理槽１２のＭＬＳＳ負荷より小さくすることが困難になる場合がある。 In the first biological treatment tank 12, the BOD component in the wastewater is decomposed by the microorganisms in the tank and the biological sludge supplied from the anoxic biological treatment tank 10 under aerobic conditions (oxygen supply by aeration, stirring, etc.). The Thus, in the 1st biological treatment tank 12, since the sludge from the anoxic biological treatment tank 10 is diluted with the waste_water | drain containing a BOD component, the MLSS density | concentration in a tank can be kept low. That is, the above-mentioned high MLSS load is ensured and the biological sludge is in a satiety state. The MLSS load of the first biological treatment tank 12 is preferably in the range of 0.8 kg BOD / kg MLSS / d to less than 1.8 kg BOD / kg MLSS / d, depending on the BOD component, the volume of the tank, and the like. The inflow BOD component is almost decomposed in the first biological treatment tank 12. When the MLSS load of the first biological treatment tank 12 is in the range of 1.8 kgBOD / kgMLSS / d or more to less than 5.0 kgBOD / kgMLSS / d, the BOD component remains in the treated water discharged from the first biological treatment tank 12. Since the amount is small, the influence of the MLSS load on the second biological treatment tank 14 in the subsequent stage is small. That is, it does not become larger than the MLSS load of the first biological treatment tank 12. When the MLSS load in the first biological treatment tank 12 is 5.0 kgBOD / kgMLSS / d or more, depending on the type of BOD component, the BOD component flowing into the second biological treatment tank 14 in the subsequent stage increases, and the second biological treatment tank It may be difficult to make the MLSS load of 14 smaller than the MLSS load of the first biological treatment tank 12.
　次に、第１生物処理槽１２で処理された排水（汚泥も含む）は、排水流入ライン１８ｂを通り、第２生物処理槽１４に連続的に流入する。第２生物処理槽１４では、好気条件下で（曝気や攪拌等による酸素供給）、槽内の微生物、第１生物処理槽１２から供給される生物汚泥及び後段の汚泥分離槽１６から供給される生物汚泥により、排水中の未反応のＢＯＤ成分が分解される。第２生物処理槽１４では、第１生物処理槽１２よりも流入するＢＯＤ成分が少ないことに加え、ＭＬＳＳ濃度が後段の汚泥分離槽１６から供給される生物汚泥の流入により増加するため、第１生物処理槽１２よりもＭＬＳＳ負荷が低くなるように制御することができる。すなわち、第２生物処理槽１４のＭＬＳＳ負荷はほとんどない状態か非常に低い状態を確保することができるため、生物汚泥を飢餓状態とすることができる。第２生物処理槽１４のＭＬＳＳ負荷は、ＢＯＤ成分や槽の容積等にもよるが、０ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ～０．５ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以下の範囲とすることが好ましい。第１生物処理槽１２から流入する未反応のＢＯＤ成分が多いと、第２生物処理槽１４のＭＬＳＳ負荷が０．５ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄを超える場合がある。第２生物処理槽１４のＭＬＳＳ負荷が０．５ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄを超えると、第１生物処理槽１２を通して高いＭＬＳＳ負荷が与え続けられることになるので、生物汚泥のグラニュール化よりバルキングを誘発する可能性が高まる場合がある。 Next, the wastewater (including sludge) treated in the first biological treatment tank 12 continuously flows into the second biological treatment tank 14 through the wastewater inflow line 18b. The second biological treatment tank 14 is supplied from the microorganisms in the tank, the biological sludge supplied from the first biological treatment tank 12 and the subsequent sludge separation tank 16 under aerobic conditions (oxygen supply by aeration or stirring). The unreacted BOD component in the waste water is decomposed by the biological sludge. In the second biological treatment tank 14, in addition to less BOD components flowing in than the first biological treatment tank 12, the MLSS concentration increases due to the inflow of biological sludge supplied from the subsequent sludge separation tank 16. The MLSS load can be controlled to be lower than that of the biological treatment tank 12. That is, since the MLSS load of the second biological treatment tank 14 is almost zero or very low, the biological sludge can be brought into a starved state. The MLSS load of the second biological treatment tank 14 is preferably in the range of 0 kgBOD / kgMLSS / d to 0.5 kgBOD / kgMLSS / d or less, depending on the BOD component, the volume of the tank, and the like. If there are many unreacted BOD components flowing in from the first biological treatment tank 12, the MLSS load of the second biological treatment tank 14 may exceed 0.5 kgBOD / kgMLSS / d. If the MLSS load of the second biological treatment tank 14 exceeds 0.5 kgBOD / kgMLSS / d, a high MLSS load will continue to be applied through the first biological treatment tank 12, so that bulking is induced by granulation of biological sludge. May increase the likelihood of doing so.
　次に、第２生物処理槽１４で処理された排水（汚泥も含む）は、排水流入ライン１８ｃを通り、汚泥分離槽１６に連続的に流入する。汚泥分離槽１６内では、第２生物処理槽１４から排出された排水から生物汚泥が沈降分離される。そして、生物汚泥が分離された排水は、処理水として処理水排出ライン２２から排出される。汚泥分離槽１６において濃縮された生物汚泥は、汚泥返送ライン２０ａから無酸素生物処理槽１０に供給され、また、汚泥返送ライン２０ｂから第２生物処理槽１４に供給される。汚泥の返送量を調整する場合等においては、汚泥返送ライン２０ａ等にポンプ等を設置することが好ましい。また、汚泥分離槽１６は、沈降分離に制限されるものではなく、例えば、膜分離等でもよい。 Next, the wastewater (including sludge) treated in the second biological treatment tank 14 passes through the wastewater inflow line 18 c and continuously flows into the sludge separation tank 16. In the sludge separation tank 16, the biological sludge is settled and separated from the waste water discharged from the second biological treatment tank 14. And the waste water from which the biological sludge was separated is discharged from the treated water discharge line 22 as treated water. The biological sludge concentrated in the sludge separation tank 16 is supplied from the sludge return line 20a to the anoxic biological treatment tank 10, and is also supplied from the sludge return line 20b to the second biological treatment tank 14. When adjusting the amount of sludge returned, it is preferable to install a pump or the like in the sludge return line 20a. Further, the sludge separation tank 16 is not limited to sedimentation separation, and may be, for example, membrane separation.
　無酸素生物処理槽１０内では、脱窒菌等の微生物、汚泥分離槽１６から供給される生物汚泥によって、無酸素生物処理槽１０内の窒素含有物質を窒素ガスに変換する脱窒処理等が行われる。無酸素生物処理槽１０内は、前述したように生物汚泥の内生呼吸により無酸素状態となっている。この時に攪拌を行うと、槽内汚泥濃度が均一となるので好ましい。また、無酸素生物処理槽１０の生物汚泥の滞留時間が著しく短いと、汚泥分離槽１６から供給された生物汚泥中に含まれる酸素が内生呼吸で消費されきれず、無酸素状態が維持できなくなる場合があるため、無酸素生物処理槽１０の生物汚泥の滞留時間は３０分以上確保することが望ましい。無酸素状態で処理された生物汚泥は、汚泥返送ライン２０ｃから第１生物処理槽１２に連続的に供給される。 In the anoxic biological treatment tank 10, a denitrification process is performed to convert nitrogen-containing substances in the anoxic biological treatment tank 10 into nitrogen gas by microorganisms such as denitrifying bacteria and biological sludge supplied from the sludge separation tank 16. Is called. As described above, the oxygen-free biological treatment tank 10 is in an oxygen-free state due to endogenous respiration of biological sludge. Stirring at this time is preferable because the sludge concentration in the tank becomes uniform. Moreover, if the residence time of the biological sludge in the anoxic biological treatment tank 10 is remarkably short, oxygen contained in the biological sludge supplied from the sludge separation tank 16 cannot be consumed by endogenous respiration, and an anoxic state can be maintained. Since it may disappear, it is desirable to ensure the residence time of the biological sludge in the oxygen-free biological treatment tank 10 for 30 minutes or more. The biological sludge treated in the oxygen-free state is continuously supplied from the sludge return line 20c to the first biological treatment tank 12.
　本実施形態の無酸素生物処理槽１０は、嫌気状態であってもよい。すなわち、無酸素生物処理槽１０は嫌気槽であってもよい。嫌気槽では、嫌気状態で、脱窒、メタン発酵等が行われる。ここで嫌気状態とは、溶存酸素のみならず、亜硝酸や硝酸由来の酸素も存在しない条件である。嫌気槽の場合には、反応過程で有機物が必要となるため、排水の一部を嫌気槽に流入させ、排水中の有機物を添加する必要がある。但し、排水の一部を流入させると、嫌気槽での排水の滞留時間が短くなり、滞留時間を確保する必要がある。 The anaerobic biological treatment tank 10 of the present embodiment may be in an anaerobic state. That is, the anaerobic biological treatment tank 10 may be an anaerobic tank. In the anaerobic tank, denitrification, methane fermentation, and the like are performed in an anaerobic state. Here, the anaerobic state is a condition in which not only dissolved oxygen but also nitrous acid or nitric acid-derived oxygen does not exist. In the case of an anaerobic tank, since organic substances are required in the reaction process, it is necessary to allow a part of the waste water to flow into the anaerobic tank and add the organic substances in the waste water. However, if a part of the waste water is introduced, the residence time of the waste water in the anaerobic tank is shortened, and it is necessary to ensure the residence time.
　このように、飽食状態の第１生物処理槽１２、飢餓状態の第２生物処理槽１４、無酸素状態の無酸素生物処理槽１０を経由するように生物汚泥を循環させていくと、生物汚泥のグラニュール化が起こり、生物汚泥の沈降性を高めることができる。その結果、排水の処理速度を高めることが可能となる。また、活性汚泥の管理上重要な汚泥沈降性管理がし易くなる。 In this way, when biological sludge is circulated through the first biological treatment tank 12 in the satiety state, the second biological treatment tank 14 in the starvation state, and the anoxic biological treatment tank 10 in the anoxic state, the biological sludge is obtained. Granulation of the slag occurs and the sedimentation of biological sludge can be enhanced. As a result, it is possible to increase the wastewater treatment speed. In addition, it becomes easy to manage sludge settling which is important in managing activated sludge.
　以下に、汚泥のグラニュール化における好ましい条件等について説明する。 Hereinafter, preferable conditions for granulating sludge will be described.
　図２に示すように、回分式活性汚泥法の場合、反応工程における反応初期では、反応槽内のＢＯＤ濃度が高く飽食状態となるが、ＢＯＤ成分の分解が進むに従って反応槽内のＢＯＤ濃度が低下し、飢餓状態へと移行していく。汚泥の沈降性改善、汚泥のグラニュール化等には、その後の無酸素状態の工程に加え、この時の飢餓状態の時間が、飽食状態に対して十分に長いことが重要であると考えられている。この割合の最適値は、処理対象のＢＯＤ成分によって異なると考えられるが、多くの場合、飢餓状態の方が飽食状態より長い時間必要である。本実施形態において、前述したＭＬＳＳ負荷の範囲を満たす第１生物処理槽１２は飽食状態となり、第２生物処理槽１４は飢餓状態となっている。従って、飢餓状態に対する飽食状態の割合（飽食状態／飢餓状態）が１未満となるように、汚泥返送量を制御すること、及び第１生物処理槽１２と第２生物処理槽１４の容積を設計することが望ましい。 As shown in FIG. 2, in the case of the batch activated sludge method, the BOD concentration in the reaction tank becomes high and satiety at the initial stage of the reaction step, but the BOD concentration in the reaction tank increases as the decomposition of the BOD component proceeds. It will decline and move to starvation. In order to improve the sedimentation of sludge and granulate the sludge, it is considered important that the time of starvation at this time is sufficiently long compared to the satiety state, in addition to the subsequent oxygen-free process. ing. The optimum value of this ratio is considered to vary depending on the BOD component to be processed, but in many cases, the starvation state requires a longer time than the satiation state. In this embodiment, the 1st biological treatment tank 12 which satisfy | fills the range of the MLSS load mentioned above will be in a satiety state, and the 2nd biological treatment tank 14 will be in a starvation state. Therefore, the amount of sludge returned is controlled and the volume of the first biological treatment tank 12 and the second biological treatment tank 14 is designed so that the ratio of the fed state to the starved state (satiated state / starved state) is less than 1. It is desirable to do.
　回分式活性汚泥法の場合は同一の反応槽内で反応が起こるので、飽食状態と飢餓状態とのＭＬＳＳ量は同一である。したがって、飢餓状態に対する飽食状態の割合（飽食状態／飢餓状態）は、飽食状態の時間と飢餓状態の時間を当てはめればよい。一方、連続式の活性汚泥法の場合、飽食状態と飢餓状態の槽は別であるため、保持するＭＬＳＳ量はそれぞれ異なる。そのため、飢餓状態に対する飽食状態の割合は、以下のように計算される。
Figure JPOXMLDOC01-appb-M000001
 In the case of the batch activated sludge method, the reaction occurs in the same reaction tank, so the MLSS amount in the satiety state and the starvation state is the same. Therefore, the ratio of the satiety state to the starvation state (satiate state / starvation state) may be determined by applying the time of the satiety state and the time of the starvation state. On the other hand, in the case of the continuous activated sludge method, the saturable state and the starved state tanks are different from each other, and therefore the MLSS amount to be held is different. Therefore, the ratio of the satiety state to the starvation state is calculated as follows.
Figure JPOXMLDOC01-appb-M000001
　また、回分式活性汚泥法において、飢餓状態と飽食状態のサイクル間隔も生物汚泥のグラニュール化に必要な因子として知られている。一般的に、飢餓状態と飽食状態のサイクル間隔が短いほど、生物汚泥のグラニュール化が困難になることが分かっている。これは、連続式の活性汚泥法においても同様である。本実施形態では、第１生物処理槽１２及び第２生物処理槽１４の被処理水の滞留時間の合計が少なくとも３時間以上となるように、第１生物処理槽１２と第２生物処理槽１４の容積、被処理水流量、及び返送汚泥流量を設定し、飢餓状態と飽食状態のサイクル間隔が短くならないようにすることが望ましい。 In the batch activated sludge method, the cycle interval between the starved state and the satiety state is also known as a factor necessary for granulating biological sludge. In general, it has been found that the shorter the cycle interval between starvation and satiety, the more difficult it is to granulate biological sludge. The same applies to the continuous activated sludge method. In the present embodiment, the first biological treatment tank 12 and the second biological treatment tank 14 are set so that the total residence time of the water to be treated in the first biological treatment tank 12 and the second biological treatment tank 14 is at least 3 hours. It is desirable to set the volume of water, the flow rate of treated water, and the return sludge flow rate so that the cycle interval between the starved state and the satiety state is not shortened.
　生物汚泥のグラニュール化の点では、第１生物処理槽１２、第２生物処理槽１４をそれぞれ複数に分割し、ＢＯＤ成分を含む排水を分割した第１生物処理槽１２それぞれに流入させ、また、生物汚泥を分割した第２生物処理槽１４それぞれに供給することが好ましい。生物処理槽を分割させた場合には、それらのうちの少なくとも１つの第１生物処理槽１２及び第２生物処理槽１４の容積が、前述した生物汚泥のグラニュール化の好ましい条件を満たすものであればよい。 In terms of granulation of biological sludge, the first biological treatment tank 12 and the second biological treatment tank 14 are each divided into a plurality of parts, and the wastewater containing the BOD component is allowed to flow into the divided first biological treatment tanks 12, respectively. It is preferable to supply each of the second biological treatment tanks 14 into which the biological sludge is divided. When the biological treatment tank is divided, the volume of at least one of the first biological treatment tank 12 and the second biological treatment tank 14 satisfies the preferable conditions for granulation of the biological sludge described above. I just need it.
　汚泥分離槽１６から排出される全体の汚泥流量及び無酸素生物処理槽１０へ流入する汚泥流量は、前述した第２生物処理槽１４での飢餓状態に対する第１生物処理槽１２での飽食状態の割合（飽食状態／飢餓状態）が１未満、無酸素生物処理槽の滞留時間が３０分以上確保できるように設定されることが好ましい。例えば、無酸素生物処理槽１０へ流入する汚泥流量を増加させると、無酸素生物処理槽１０及び第１生物処理槽１２の滞留時間が減少する一方で、第１生物処理槽１２のＭＬＳＳ濃度が低下する。無酸素生物処理槽１０へ流入する汚泥流量を減少させると、無酸素生物処理槽１０及び第１生物処理槽１２の滞留時間が増加する一方で、第１生物処理槽１２のＭＬＳＳ濃度が上昇する。全体の汚泥流量が増加すると、無酸素生物処理槽１０、第１生物処理槽１２及び第２生物処理槽１４の滞留時間が減少し、第１生物処理槽１２のＭＬＳＳ濃度が上昇すると共に、第２生物処理槽１４のＭＬＳＳ濃度も上昇する。全体の汚泥流量が減少すると、無酸素生物処理槽１０、第１生物処理槽１２及び第２生物処理槽１４の滞留時間が増加し、第１生物処理槽１２のＭＬＳＳ濃度が増加するとともに、第２生物処理槽１４のＭＬＳＳ濃度も上昇する。このような返送流量の操作により無酸素生物処理槽１０、第１生物処理槽１２及び第２生物処理槽１４の滞留時間、第１生物素処理槽１２のＭＬＳＳ濃度及び第２生物処理槽１４のＭＬＳＳ濃度等を変化させることができるので、飢餓状態に対する飽食状態の割合を任意にコントロールすることが可能となる。本実施形態の連続式の活性汚泥法では、回分式活性汚泥法と異なり、生物汚泥のグラニュール化に重要な因子である無酸素状態、飽食状態、飢餓状態を、返送流量の操作により任意にコントロール可能である点で有益である。 The entire sludge flow rate discharged from the sludge separation tank 16 and the sludge flow rate flowing into the anoxic biological treatment tank 10 are the satiety state in the first biological treatment tank 12 with respect to the starvation state in the second biological treatment tank 14 described above. It is preferable that the ratio (satiated / starved state) is less than 1 and that the residence time of the anaerobic biological treatment tank is secured for 30 minutes or more. For example, if the sludge flow rate flowing into the anaerobic biological treatment tank 10 is increased, the residence time of the anoxic biological treatment tank 10 and the first biological treatment tank 12 is reduced, while the MLSS concentration in the first biological treatment tank 12 is increased. descend. When the sludge flow rate flowing into the anoxic biological treatment tank 10 is decreased, the residence time of the anoxic biological treatment tank 10 and the first biological treatment tank 12 is increased, while the MLSS concentration in the first biological treatment tank 12 is increased. . As the overall sludge flow rate increases, the residence time of the anoxic biological treatment tank 10, the first biological treatment tank 12, and the second biological treatment tank 14 decreases, the MLSS concentration in the first biological treatment tank 12 increases, 2 The MLSS concentration in the biological treatment tank 14 also increases. When the overall sludge flow rate decreases, the residence time of the anoxic biological treatment tank 10, the first biological treatment tank 12, and the second biological treatment tank 14 increases, and the MLSS concentration in the first biological treatment tank 12 increases, 2 The MLSS concentration in the biological treatment tank 14 also increases. By operating the return flow rate, the residence time of the anoxic biological treatment tank 10, the first biological treatment tank 12 and the second biological treatment tank 14, the MLSS concentration of the first biological element treatment tank 12, and the second biological treatment tank 14 Since the MLSS concentration and the like can be changed, the ratio of the satiety state to the starvation state can be arbitrarily controlled. In the continuous activated sludge method of this embodiment, unlike the batch activated sludge method, the oxygen-free state, satiety state, and starvation state, which are important factors for granulating biological sludge, can be arbitrarily set by operating the return flow rate. It is beneficial in that it can be controlled.
　各生物処理槽内のｐＨについては特に規定されるものではないが、通常の活性汚泥と同様に各生物処理槽内のｐＨは６～８の範囲とすることが好ましい。処理対象のＢＯＤ成分の種類によっては槽内のｐＨが変動する場合があるが、その場合には、水酸化ナトリウムや塩酸、硫酸等を用いて、槽内のｐＨを上記範囲内に制御することが好ましい。 The pH in each biological treatment tank is not particularly specified, but the pH in each biological treatment tank is preferably in the range of 6-8 as in the case of normal activated sludge. Depending on the type of BOD component to be treated, the pH in the tank may fluctuate. In that case, the pH in the tank should be controlled within the above range using sodium hydroxide, hydrochloric acid, sulfuric acid, etc. Is preferred.
　汚泥のグラニュール化には核が必要とされている。通常の排水中にはこのような核となるような微粒子が含まれているので特に添加する必要はないが、核形成を促進させる点で、Ｆｅ２＋、Ｆｅ３＋、Ｃａ２＋、Ｍｇ＋等の水酸化物が形成されるようなイオンを添加することが好ましい。なお、Ｆｅ２＋を添加する場合は、無酸素生物処理槽１０に添加することが好ましい。これにより、核の促進形成に加えて無酸素状態を促進することができる。 核 Nucleus is required for granulation of sludge. Since normal effluent contains such fine particles as nuclei, it is not necessary to add them in particular, but hydroxides such as Fe 2+, Fe 3+, Ca 2+ and Mg + are used in order to promote nucleation. It is preferred to add ions as they are formed. In addition, when adding Fe2 +, it is preferable to add to the anoxic biological treatment tank 10. Thereby, in addition to the promotion formation of a nucleus, an oxygen-free state can be promoted.
　また、無酸素生物処理槽１０に硝酸塩もしくは亜硝酸塩を添加することが好ましい。これにより、嫌気性細菌である脱窒菌が無酸素生物処理槽１０内で増殖しやすくなり、無酸素状態が良好に保たれる。 In addition, it is preferable to add nitrate or nitrite to the anaerobic biological treatment tank 10. Thereby, denitrifying bacteria which are anaerobic bacteria are easily grown in the anoxic biological treatment tank 10, and the anoxic state is kept good.
　本実施形態は、バルキングの抑制にも有効である。バルキングの抑制には、原因となる糸状微生物を選択的に増殖させにくくなるような環境をつくることが有効とされている。一般的に、基質濃度が低い飢餓状態に耐性がない糸状微生物を排除するために、基質の濃度勾配や飢餓状態などを導入する方法をキネティックセレクションと呼び、糸状微生物が基質を摂取しにくくするために、好気、無酸素及び嫌気などの環境変化を導入する方法をメタボリックセレクションと呼ぶ（非特許文献１参照）。本実施形態は、生物汚泥を無酸素状態や飢餓状態とするため、キネティックセレクション及びメタボリックセレクションの作用が働き易い環境となるため、バルキングを抑制することができる。 This embodiment is also effective for suppressing bulking. In order to suppress bulking, it is effective to create an environment that makes it difficult for the filamentous microorganisms that cause it to selectively grow. In general, in order to eliminate filamentous microorganisms that are not resistant to starvation conditions with low substrate concentrations, a method that introduces a substrate concentration gradient or starvation conditions is called kinetic selection, and makes it difficult for filamentous microorganisms to ingest the substrate. In addition, a method for introducing environmental changes such as aerobic, anaerobic and anaerobic is called metabolic selection (see Non-Patent Document 1). In this embodiment, since biological sludge is brought into an oxygen-free state or a starved state, an environment in which the action of kinetic selection and metabolic selection is easy to work, and thus bulking can be suppressed.
　以下、実施例を挙げ、本発明をより具体的に詳細に説明するが、本発明は、以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
　図１に示した排水処理装置１（無酸素生物処理槽１０の容積１０Ｌ、第１生物処理槽１２の容積３０Ｌ、第２生物処理槽１４の容積４０Ｌ）を用いて、工水で有機性ＢＯＤ成分をＢＯＤ１３０～３００ｍｇ／Ｌの任意の濃度に希釈した被処理水の生物処理を行った。被処理水は、第１生物処理槽１２に連続的に供給した。標準活性汚泥法に用いられる汚泥を種汚泥として使用した。馴養後、ＭＬＳＳ負荷のコントロールは流量変化によって行った。 Using the wastewater treatment apparatus 1 shown in FIG. 1 (the volume of the anoxic biological treatment tank 10 is 10L, the volume of the first biological treatment tank 12 is 30L, the volume of the second biological treatment tank 14 is 40L), Biological treatment of water to be treated was performed by diluting the components to an arbitrary concentration of BOD 130 to 300 mg / L. The water to be treated was continuously supplied to the first biological treatment tank 12. The sludge used in the standard activated sludge method was used as seed sludge. After acclimatization, the MLSS load was controlled by changing the flow rate.
　無酸素生物処理槽１０は攪拌機による攪拌のみを行い、試験期間中、ＤＯを１ｍｇ／Ｌ未満に維持した。第１生物処理槽１２及び第２生物処理槽１４は散気管による空気爆気を行い、試験期間中、ＤＯを５～８ｍｇ／Ｌの範囲に維持した。 The anoxic biological treatment tank 10 was only stirred by a stirrer, and the DO was maintained at less than 1 mg / L during the test period. The first biological treatment tank 12 and the second biological treatment tank 14 were subjected to air explosion using a diffuser, and the DO was maintained in the range of 5 to 8 mg / L during the test period.
　水温は特にコントロールせず室温で行い、試験期間中、２５～２８℃の範囲で推移した。 Water temperature was measured at room temperature without any particular control, and changed in the range of 25 to 28 ° C during the test period.
　汚泥分離槽１６から排出される全体の汚泥流量を第１生物処理槽１２に供給する被処理水の流量と同量に設定した。また、無酸素生物処理槽１０に供給する汚泥流量と第２生物処理槽１４に供給する汚泥流量との割合を３：１０に調整した。物質収支により各槽のＭＬＳＳ濃度割合が決定され、全体の汚泥流量は被処理水の流量に比例して同様の割合で上昇させていくため、試験期間中の飢餓状態に対する飽食状態の割合（飽食状態／飢餓状態の割合）は約０．３４に固定された。 The entire sludge flow rate discharged from the sludge separation tank 16 was set to the same amount as the flow rate of the water to be treated supplied to the first biological treatment tank 12. Moreover, the ratio of the sludge flow rate supplied to the anoxic biological treatment tank 10 and the sludge flow rate supplied to the second biological treatment tank 14 was adjusted to 3:10. The percentage of MLSS concentration in each tank is determined by the mass balance, and the overall sludge flow rate increases in proportion to the flow rate of the water to be treated. State / starvation ratio) was fixed at about 0.34.
　汚泥分離槽１６の水表面積負荷は、０．２ｍ／ｈ～２．０ｍ／ｈの範囲とした。 The water surface area load of the sludge separation tank 16 was in the range of 0.2 m / h to 2.0 m / h.
　試験期間中における、被処理水のＢＯＤ濃度及び汚泥分離槽１６から得られる最終処理水のＢＯＤ濃度、各槽のＭＬＳＳ濃度、第１生物処理槽１２と第２生物処理槽１４のＭＬＳＳ負荷、汚泥沈降性の指標となるＳＶＩ３０（第２生物処理槽１４のみ）、第１生物処理槽１２と第２生物処理槽１４の滞留時間の合計、無酸素生物処理槽１０の滞留時間（中央値）を表１に示す。また、図３に、各試験期間における汚泥の粒径分布を示す。 During the test period, the BOD concentration of the treated water and the BOD concentration of the final treated water obtained from the sludge separation tank 16, the MLSS concentration of each tank, the MLSS load of the first biological treatment tank 12 and the second biological treatment tank 14, sludge SVI30 (only 2nd biological treatment tank 14) used as a sedimentation parameter | index, the sum total of the residence time of the 1st biological treatment tank 12 and the 2nd biological treatment tank 14, and the residence time (median value) of the anoxic biological treatment tank 10 are shown. Table 1 shows. Moreover, in FIG. 3, the particle size distribution of the sludge in each test period is shown.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１に示すように、試験開始から１０日までは、第１生物処理槽１２のＭＬＳＳ負荷を０．３ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄに設定し、第２生物処理槽１４のＭＬＳＳ負荷を０．０４ｋｇＢＯＤｋｇＭＬＳＳ／ｄに設定した。この試験期間でのＳＶＩ３０は、種汚泥と比較して低下し、汚泥の沈降性は向上した。しかし、図３に示すように、この試験期間での粒度分布は種汚泥と比較して大きな変化はなく、グラニュールの形成は認められなかった。ＭＬＳＳ負荷０．３ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄでは、第１生物処理槽１２の生物汚泥が充分な飽食状態となり難く、上記試験期間（１０日間）では、生物汚泥のグラニュール化が起こらなかったと考えられる。 As shown in Table 1, from the start of the test to 10 days, the MLSS load of the first biological treatment tank 12 is set to 0.3 kgBOD / kgMLSS / d, and the MLSS load of the second biological treatment tank 14 is 0.04 kgBODkgMLSS / d. SVI30 in this test period was lower than that of seed sludge, and the sedimentation property of the sludge was improved. However, as shown in FIG. 3, the particle size distribution during this test period did not change much compared to the seed sludge, and no granule formation was observed. With an MLSS load of 0.3 kg BOD / kg MLSS / d, the biological sludge in the first biological treatment tank 12 is unlikely to be sufficiently satiety, and it is considered that granulation of the biological sludge did not occur during the test period (10 days).
　試験開始１０日後～２０日までは、被処理水の流入流量を増加させて第１生物処理槽１２のＭＬＳＳ負荷を０．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄに設定した。表１に示すように、この試験期間でのＳＶＩ３０は種汚泥と比較して大きく低下した。また、図３に示すように、この試験期間での粒径は種汚泥と比較して大きくなっており、生物汚泥のグラニュール化が進行していると云える。 From the 10th day to the 20th day after the start of the test, the MLSS load of the first biological treatment tank 12 was set to 0.8 kgBOD / kgMLSS / d by increasing the inflow flow rate of the water to be treated. As shown in Table 1, SVI30 during this test period was greatly reduced compared to seed sludge. Moreover, as shown in FIG. 3, the particle diameter in this test period is larger than that of seed sludge, and it can be said that granulation of biological sludge is progressing.
　試験開始２０日後～３０日までは、被処理水の流入水量、被処理水のＢＯＤ濃度を増加させて第１生物処理槽１２のＭＬＳＳ負荷を１．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄに設定した。表１に示すように、この試験期間でのＳＶＩ３０は、試験開始１０日後～２０日までの試験期間と同様に低い値を維持した。また、図３に示すように、この試験期間では、さらに粒子径が大きくなっていた。この試験期間の生物汚泥を電子顕微鏡で観察したところ、直径約２００μｍのグラニュールが形成されていた。 From 20 days to 30 days after the start of the test, the amount of inflow water to be treated and the BOD concentration of the water to be treated were increased to set the MLSS load of the first biological treatment tank 12 to 1.8 kgBOD / kgMLSS / d. As shown in Table 1, SVI30 during this test period remained low as in the test period from 10 days to 20 days after the start of the test. Further, as shown in FIG. 3, the particle diameter was further increased during this test period. When the biological sludge during this test period was observed with an electron microscope, granules having a diameter of about 200 μm were formed.
　試験開始３０日後～４０日までは、第１生物処理槽１２のＭＬＳＳ負荷を１．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄに設定し、ＭＬＳＳ濃度の上昇に合わせて被処理水の流入水量を増加させることで、第１生物処理槽１２と第２生物処理槽１４の滞留時間の合計を１．８ｈに設定した。その結果、表１に示すように、この試験期間でのＳＶＩ３０は、試験開始後２０日後～３０日までの試験期間と比較して上昇した。試験開始３０日後～４０日までの試験期間の生物汚泥を電子顕微鏡で観察したところ、試験開始２０日後～３０日までの試験期間に形成されたグラニュールは維持されているものの、その周りにフロックが付着していた。この付着したフロックが原因で、生物汚泥の沈降性が悪化したものと考えられる。 From the 30th day to the 40th day from the start of the test, the MLSS load of the first biological treatment tank 12 is set to 1.8 kgBOD / kgMLSS / d, and the amount of inflow water to be treated is increased as the MLSS concentration increases. The total residence time of the first biological treatment tank 12 and the second biological treatment tank 14 was set to 1.8 h. As a result, as shown in Table 1, SVI30 in this test period increased compared to the test period from 20 days to 30 days after the start of the test. When biological sludge was observed with an electron microscope from 30 days to 40 days after the start of the test, granules formed during the test period from 20 days to 30 days after the start of the test were maintained, but flocks around them Was attached. It is considered that the sedimentation property of biological sludge deteriorated due to the attached floc.
　試験開始４０日後～５０日までは、被処理水のＢＯＤ濃度の希釈割合を３００ｍｇ／Ｌに変更し、被処理水の流入水量を減少させ、第１生物処理槽１２のＭＬＳＳ負荷を１．９ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄに設定し、第１生物処理槽１２と第２生物処理槽１４の滞留時間の合計を３．２ｈに設定した。その結果、表１に示すように、試験開始３０日後～４０日までの試験期間で上昇したＳＶＩ３０が、この試験期間で低下し、生物汚泥の沈降性に改善傾向がみられた。試験開始４０日後～５０日までの試験期間の生物汚泥を電子顕微鏡で観察したところ、試験開始３０日後～４０日までの試験期間中にグラニュールに付着したフロックが減少していた。 From the 40th day to the 50th day after the start of the test, the dilution ratio of the BOD concentration of the treated water is changed to 300 mg / L, the amount of inflow water of the treated water is decreased, and the MLSS load of the first biological treatment tank 12 is 1.9 kgBOD. / KgMLSS / d, and the total residence time of the first biological treatment tank 12 and the second biological treatment tank 14 was set to 3.2 h. As a result, as shown in Table 1, the SVI30 increased during the test period from 30 days to 40 days after the start of the test decreased during this test period, and an improvement trend was observed in the sedimentation property of biological sludge. When biological sludge during the test period from the 40th day to the 50th day of the test was observed with an electron microscope, flocs adhering to the granules decreased during the test period from the 30th day to the 40th day.
　以上のように、第１生物処理槽１２のＭＬＳＳ負荷を０．３ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄに設定し、第２生物処理槽１４のＭＬＳＳ負荷を０．０４ｋｇＢＯＤｋｇＭＬＳＳ／ｄに設定した場合、汚泥の沈降性は向上するものの、１０日間の試験期間では、生物汚泥のグラニュール化が起こらなかった。そして、第１生物処理槽１２のＭＬＳＳ負荷を０．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以上に上昇させると、１０日間という短期間で生物汚泥のグラニュール化が起こった。また、第１生物処理槽１２と第２生物処理槽１４の滞留時間の合計が低いと、グラニュールの周りにフロックが付着し、生物汚泥の沈降性が低下する場合がある。 As described above, when the MLSS load of the first biological treatment tank 12 is set to 0.3 kgBOD / kgMLSS / d and the MLSS load of the second biological treatment tank 14 is set to 0.04 kgBODkgMLSS / d, the sedimentation property of sludge However, granulation of biological sludge did not occur during the 10-day test period. And when the MLSS load of the 1st biological treatment tank 12 was raised to 0.8 kgBOD / kgMLSS / d or more, granulation of the biological sludge occurred in a short period of 10 days. In addition, if the total residence time of the first biological treatment tank 12 and the second biological treatment tank 14 is low, flocs may adhere around the granules and the sedimentation property of the biological sludge may decrease.
　次に、新たに同様の種汚泥を使用し、図１において無酸素生物処理槽１０を省略した上で、第１生物処理槽１２のＭＬＳＳ負荷を１．４ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ、第２生物処理槽１４のＭＬＳＳ負荷を０．１ｋｇＢＯＤｋｇＭＬＳＳ／ｄとなるまで立ち上げ、この負荷で２０日間の運転を行った。この時の汚泥の状況を電子顕微鏡で観察したところ、立ち上げに応じて汚泥のグラニュール化がみられたが、２０日間の運転中に多量の微小動物の増殖が見られ、これらによりグラニュールが破壊されてしまった。２０日間運転後の結果を表２にまとめた。表２に示したように、ＳＶＩ３０はグラニュール化している条件と比較して高い値となった。 Next, the same kind of sludge is newly used, the oxygen-free biological treatment tank 10 is omitted in FIG. 1, the MLSS load of the first biological treatment tank 12 is 1.4 kgBOD / kgMLSS / d, and the second biological treatment. The MLSS load of the tank 14 was raised to 0.1 kg BOD kg MLSS / d, and operation was performed for 20 days at this load. The state of the sludge at this time was observed with an electron microscope, and sludge was granulated with the start-up, but a large amount of micro-animals were observed during the operation for 20 days. Has been destroyed. The results after 20 days of operation are summarized in Table 2. As shown in Table 2, SVI30 was higher than the granulated condition.
　その後、無酸素生物処理槽１０を付加して、負荷条件を変えずに１０日間の運転を行った。１０日間運転後の結果を表２にまとめた。表２に示すように、１０日間の運転後のＳＶＩ３０は、無酸素生物処理槽１０を省略した場合に比べて大きく低下した。この時の汚泥の状況を電子顕微鏡で観察したところ、微小動物の減少が見られ、さらには直径約２００μｍのグラニュールが形成されていた。このことから、無酸素生物処理槽１０がグラニュール化に大きく寄与していると考えられる。 Then, the anoxic biological treatment tank 10 was added and the operation was performed for 10 days without changing the load conditions. The results after 10 days of operation are summarized in Table 2. As shown in Table 2, the SVI30 after 10 days of operation was greatly reduced as compared to the case where the anoxic biological treatment tank 10 was omitted. When the state of the sludge at this time was observed with an electron microscope, the number of micro-animals decreased, and granules having a diameter of about 200 μm were formed. From this, it is considered that the oxygen-free biological treatment tank 10 greatly contributes to granulation.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　１　排水処理装置、１０　無酸素生物処理槽、１２　第１生物処理槽、１４　第２生物処理槽、１６　汚泥分離槽、１８ａ～１８ｃ　排水流入ライン、２０ａ～２０ｃ　汚泥返送ライン、２２　処理水排出ライン。 1 wastewater treatment equipment, 10 anoxic biological treatment tank, 12 first biological treatment tank, 14 second biological treatment tank, 16 sludge separation tank, 18a-18c drainage inflow line, 20a-20c sludge return line, 22 treated water discharge line .

Claims (3)

  1. 　ＢＯＤ成分を含む有機性排水を生物汚泥により生物処理する反応槽と、前記反応槽で得られた処理水を前記汚泥と分離する汚泥分離槽と、を有する排水処理装置であって、
    　前記反応槽は、無酸素生物処理槽と、前記生物処理に必要な酸素が供給される第１生物処理槽及び第２生物処理槽と、を含み、
    　前記有機性排水は前記第１生物処理槽に連続的に流入され、前記第１生物処理槽及び前記第２生物処理槽で生物処理され、
    　前記汚泥分離槽内の汚泥は、前記第２生物処理槽及び前記無酸素生物処理槽へ返送され、
    　前記無酸素生物処理槽内の汚泥は、少なくとも前記第１生物処理槽に供給され、
    　前記第１生物処理槽のＭＬＳＳ負荷は、前記第２生物処理槽のＭＬＳＳ負荷より高いことを特徴とする排水処理装置。     A wastewater treatment apparatus having a reaction tank for biologically treating organic wastewater containing BOD components with biological sludge, and a sludge separation tank for separating treated water obtained in the reaction tank from the sludge,
    The reaction tank includes an oxygen-free biological treatment tank, and a first biological treatment tank and a second biological treatment tank to which oxygen necessary for the biological treatment is supplied,
    The organic waste water is continuously flowed into the first biological treatment tank, biologically treated in the first biological treatment tank and the second biological treatment tank,
    The sludge in the sludge separation tank is returned to the second biological treatment tank and the anoxic biological treatment tank,
    The sludge in the anoxic biological treatment tank is supplied to at least the first biological treatment tank,
    The waste water treatment apparatus, wherein an MLSS load of the first biological treatment tank is higher than an MLSS load of the second biological treatment tank.
  2. 　前記第１生物処理槽のＭＬＳＳ負荷は、０．８ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以上の範囲であり、前記第２生物処理槽のＭＬＳＳ負荷は、０．５ｋｇＢＯＤ／ｋｇＭＬＳＳ／ｄ以下の範囲であることを特徴とする請求項１記載の排水処理装置。 The MLSS load of the first biological treatment tank is in a range of 0.8 kgBOD / kgMLSS / d or more, and the MLSS load of the second biological treatment tank is in a range of 0.5 kgBOD / kgMLSS / d or less. The waste water treatment apparatus according to claim 1.
  3. 　前記第１生物処理槽及び前記第２生物処理槽の被処理水の滞留時間の合計が３時間以上であることを特徴とする請求項１又は２記載の排水処理装置。 The waste water treatment apparatus according to claim 1 or 2, wherein the total retention time of water to be treated in the first biological treatment tank and the second biological treatment tank is 3 hours or more.
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