WO2016009650A1 - Aeration calculation device and water treatment system - Google Patents
Aeration calculation device and water treatment system Download PDFInfo
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- WO2016009650A1 WO2016009650A1 PCT/JP2015/003582 JP2015003582W WO2016009650A1 WO 2016009650 A1 WO2016009650 A1 WO 2016009650A1 JP 2015003582 W JP2015003582 W JP 2015003582W WO 2016009650 A1 WO2016009650 A1 WO 2016009650A1
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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
- C02F3/02—Aerobic processes
- C02F3/12—Activated sludge processes
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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
- C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B11/00—Automatic controllers
- G05B11/01—Automatic controllers electric
- G05B11/32—Automatic controllers electric with inputs from more than one sensing element; with outputs to more than one correcting element
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B11/00—Automatic controllers
- G05B11/01—Automatic controllers electric
- G05B11/36—Automatic controllers electric with provision for obtaining particular characteristics, e.g. proportional, integral, differential
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Definitions
- the present invention relates to a water treatment system that performs purification using an activated sludge method.
- a water treatment system described in Patent Document 1 includes a raw water tank for storing raw water, a series of treatment tanks for biologically treating pollutants in raw water with activated sludge, and water to be treated in which raw water and activated sludge are mixed. And a sedimentation basin for sedimenting and separating sludge.
- the series of treatment tanks include an anaerobic tank, an anaerobic tank, and an aerobic tank provided with an air diffuser. In these treatment tanks, contaminants contained in raw water such as carbon-based organic substances, nitrogen-containing compounds, and phosphorus-containing compounds are removed.
- Wastewater standard items for sewage treatment include TN (total nitrogen), TP (total phosphorus), and BOD (biochemical oxygen demand). It is necessary to satisfy. However, a technology that can measure BOD immediately and inexpensively has not been developed yet. Therefore, in order to ensure that the BOD of the treated water satisfies the predetermined treatment standard, aeration in the aerobic tank is performed with an aeration air volume that can achieve the treatment standard with a sufficient margin.
- the BOD of the water to be treated starts to decrease from a relatively early stage after the start of the treatment, and eventually has a characteristic that the change becomes gradual. It is known that the concentration (which may be described as “NH 4 -N”) hardly changes immediately after the start of the treatment, and has a characteristic of starting to decrease when the change in BOD becomes gentle. That is, in the water treatment process by the activated sludge method, the organic matter decomposition rate is faster than the nitrification rate (first knowledge).
- the water to be treated A and B filled in the experimental vessel was aerated with a predetermined aeration air volume, and the NH4-N concentration and COD (chemical oxygen demand) were measured.
- the aeration air volume at the time of the experiment was larger than the minimum air volume, and was smaller than the aeration air volume set for the treated water having a standard NH 4 -N concentration in the conventional water treatment system.
- BOD is the required oxygen amount of only biodegradable organic matter
- COD is different in that it is the required oxygen amount of both organic and inorganic materials, but it can be measured in a shorter time than BOD.
- COD may be used as an alternative indicator for BOD.
- the results of this experiment are shown in the graph in FIG. 14 showing the time-series changes in the NH 4 —N concentration treatment behavior and the COD treatment behavior in the aerobic tank.
- the vertical axis represents the NH 4 -N concentration and COD
- the horizontal axis represents the treatment time
- the solid line represents the NH 4 -N concentration time series change
- the broken line represents the COD time series change. Yes.
- the characteristics common to the treatment behavior of NH 4 —N concentration and the treatment behavior of COD were observed for the treated waters A and B.
- the common feature is that COD starts to decrease from a relatively early stage when processing is started, and gradually changes gradually, and even if aeration is continued, the COD becomes almost unchanged. Further, the common feature is that the NH 4 -N concentration hardly changes until around a certain processing time, and starts to decrease sharply after exceeding a certain processing time.
- the COD hardly changes after the treatment time T C1 .
- the amount of change in NH 4 —N concentration of the water to be treated A from the start of treatment to the treatment time T C1 is ⁇ X 1 [mg / L].
- the COD hardly changes after the treatment time T C2 .
- the amount of change in NH 4 —N concentration of the water to be treated B from the start of treatment to the treatment time T C2 is ⁇ X 2 [mg / L].
- the water to be treated A and the water to be treated B have different water qualities and different NH 4 -N concentrations at the start of treatment, the amount of change ⁇ X 1 and the amount of change ⁇ X 2 were almost the same value. Moreover, although not described in this specification, the same tendency as the water to be treated A and B was observed for the water to be treated having a quality different from that of the water to be treated A and B. From this, even if the NH 4 -N concentration of the water to be treated at the start of treatment is different, if NH 4 -N is nitrified by ⁇ X [mg / L], the COD is at a certain level (ie, aeration more than this) (The second finding).
- an amount of oxygen necessary for decomposing organic substances can be supplied by supplying an amount of oxygen necessary for nitrification to the aerobic tank. Therefore, in the present invention, using a NH 4 -N concentration as an alternative indicator of BOD of the treated water, the NH 4 -N concentration in the treated water is controlled aeration of the aerobic tank to be equal to or less than a predetermined target value It was. In controlling such aeration air volume, no further nitrification is required if the NH 4 -N concentration of the raw water is below a predetermined target value. Therefore, if the aeration air volume in the aerobic tank is kept to the minimum air volume, aeration is achieved. The operating energy of the apparatus can be reduced.
- the target value of the aeration air volume is appropriately set, thereby reliably treating the organic matter in the water to be treated while suppressing the aeration air volume.
- the aeration air volume calculation device is: An aeration air volume calculating device for obtaining an aeration air volume to a treatment tank for purifying treated water by an activated sludge method, A target value calculation element that generates a target value smaller than the ammonia nitrogen concentration in the treatment tank, which is the ammonia nitrogen concentration of the water to be treated at the inlet of the treatment tank, and ammonia nitrogen in the treatment water treated in the treatment tank A feedback manipulated variable calculation element for generating a feedback manipulated variable based on a deviation between the treatment tank outlet ammonia nitrogen concentration that is a concentration and the target value, and an manipulated variable that is the aeration air volume based on the feedback manipulated variable It is characterized by comprising a calculation means for calculating.
- the water treatment system includes: A treatment tank including an aerobic tank equipped with an air diffuser, and purifying treated water by an activated sludge method; A raw water ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of raw water flowing into the treatment tank or a treatment tank inlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water at the inlet of the treatment tank; A treatment tank outlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water flowing out of the treatment tank; The aeration air volume calculating device; And an aeration air volume control device that controls the aeration device based on the operation amount obtained by the aeration air volume computing device.
- the target value of the treatment tank outlet NH 4 —N concentration is always lower than the NH 4 —N concentration at the treatment tank inlet. Since the manipulated variable (aeration air volume) is determined by feedback control based on the deviation between the target value and the treatment tank outlet NH 4 -N concentration (control value), the NH 4 -N concentration of the water to be treated is reduced. Therefore, sufficient aeration is continuously performed. Thereby, the situation where the amount of aeration is remarkably reduced and the organic matter in the treated water is not sufficiently decomposed can be avoided, and the treatment of the organic matter in the treated water can be performed reliably.
- the target value of NH 4 -N concentration at the treatment tank outlet changes according to the change in NH 4 -N concentration at the treatment tank inlet, the aeration air volume does not become excessive, and the aeration air volume and the operating energy of the diffuser are reduced. Can be suppressed.
- the target value is a value smaller than the treatment tank inlet ammonia nitrogen concentration by a predetermined value, and when the predetermined value becomes a constant value of COD or BOD of the water to be treated by aeration, It may be an absolute value of the amount of change in the ammonia nitrogen concentration of the water to be treated from the start of the aeration.
- COD or BOD is a constant value means that in addition to the state where COD or BOD is strictly constant, the reduction width of COD or BOD is smaller than that at the start of aeration, The state where the fluctuation of COD or BOD is small even if the operation is continued (for example, the rate of decrease per hour is 5% or less or 10% or less) is included.
- the target value may be a value that is smaller than the treatment tank inlet ammonia nitrogen concentration by a value selected from a range of 2 to 10 [mg / L].
- the aeration tank is aerated with an aeration air volume that can achieve the treatment standard with a margin. According to the arithmetic device and the water treatment system, it is possible to appropriately suppress an increase in the amount of aeration air for the water to be treated while reliably processing the organic matter in the water to be treated, thereby reducing the operating energy of the air diffuser. be able to.
- the calculation means selects a smaller one of a predetermined reference target value and the target value generated by the target value calculation element, and the feedback manipulated variable calculation element It is desirable to further include a row selector that outputs the target value.
- the target value of the treatment tank outlet NH 4 -N concentration is always less than or equal to the predetermined reference target value, which is effective when the NH 4 -N concentration is included in the water quality standard of the treated water. .
- the aeration air amount calculation device and the water treatment system are raw water ammonia nitrogen concentration which is ammonia nitrogen concentration of raw water flowing into the treatment tank, raw water inflow amount which is inflow amount of the raw water flowing into the treatment tank, It further comprises an acquisition means for acquiring a treatment tank outlet ammonia nitrogen concentration and a circulation flow rate that is a flow rate of sludge separated from the treatment water and returned to the treatment tank, and the computing means comprises the raw water ammonia nitrogen concentration,
- the treatment tank inlet ammonia nitrogen concentration may be calculated based on the raw water inflow amount, the treatment tank outlet ammonia nitrogen concentration, and the circulation flow rate.
- the calculation means In the aeration air amount calculation device and the water treatment system, the calculation means generates a feedforward operation amount based on a raw water ammonia nitrogen concentration that is an ammonia nitrogen concentration of raw water flowing into the treatment tank.
- An arithmetic element and an adder that adds the feedforward manipulated variable and the feedback manipulated variable.
- the adder is configured to calculate the manipulated variable based on the feedback manipulated variable and the feedforward manipulated variable. It is desirable that
- the calculation means increases the feedforward operation amount when the raw water inflow amount, which is the inflow amount of the raw water flowing into the treatment tank, is larger than a predetermined reference inflow amount, and the raw water inflow amount is the predetermined amount.
- the feedforward manipulated variable is corrected by multiplying the correction coefficient calculation element for obtaining a correction coefficient for decreasing the feedforward manipulated variable, the feedforward manipulated variable and the correction coefficient. And a multiplier.
- the amount of increase in the aeration air predicted based on the change in the raw water ammonia nitrogen concentration is calculated as the feedforward manipulated variable, and this can be added to the manipulated variable.
- the manipulated variable changes according to the amount of raw water flowing into the treatment tank, so that the organic matter in the treated water is reliably treated while suppressing the aeration air volume. be able to.
- the target value of the processing tank outlet NH 4 -N concentration changes according to the change of NH 4 -N concentration of the treatment tank inlet, and, NH 4 -N concentration and the treatment tank of the processing tank inlet The value is always lower than the outlet NH 4 -N concentration. Therefore, it is possible to reliably perform the treatment of the organic matter in the water to be treated by continuously performing aeration while suppressing the amount of aeration air.
- FIG. 1 is a diagram showing a schematic configuration of a water treatment system according to the first embodiment of the present invention.
- FIG. 2 is a block diagram showing a control configuration of the water treatment system according to the first embodiment.
- FIG. 3 is a block diagram showing a signal flow of the aeration air volume calculation device according to the first embodiment.
- FIG. 4 is a graph showing the characteristics of the FF manipulated variable function.
- FIG. 5 is a graph showing the characteristics of the FF manipulated variable correction function.
- FIG. 6 is a graph showing the relationship between the treatment tank inlet NH 4 -N concentration and the target value.
- FIG. 7 is a block diagram showing a signal flow of the aeration air volume calculation device according to the first modification of the first embodiment of the present invention.
- FIG. 1 is a diagram showing a schematic configuration of a water treatment system according to the first embodiment of the present invention.
- FIG. 2 is a block diagram showing a control configuration of the water treatment system according to the first embodiment.
- FIG. 8 is a graph showing the relationship between the treatment tank inlet NH 4 -N concentration and the target value.
- FIG. 9 is a diagram showing a schematic configuration of a water treatment system according to the second embodiment of the present invention.
- FIG. 10 is a block diagram showing a control configuration of the water treatment system according to the second embodiment.
- FIG. 11 is a block diagram showing a signal flow of the aeration air volume calculation device according to the second embodiment.
- FIG. 12 is a view showing a modification of the water treatment system adopting the circulation type anaerobic aerobic method.
- FIG. 13 is a view showing a modification of the water treatment system employing the membrane separation activated sludge method.
- FIG. 14 is a graph showing time-series changes in NH 4 —N concentration treatment behavior and COD treatment behavior in an aerobic tank.
- the water treatment system according to the present invention is applied to a water treatment system including a biological treatment tank (hereinafter simply referred to as “treatment tank”) for purifying treated water such as sewage using an activated sludge method.
- treatment tank a biological treatment tank
- the aeration air volume calculating device according to the present invention is for calculating an aeration air volume suitable for treating the water to be treated in the treatment tank, and may be attached to the water treatment system, You may be comprised as an arithmetic unit independent of a processing system.
- FIG. 1 is a diagram showing an overall configuration of a water treatment system 10 according to the first embodiment of the present invention.
- the water treatment system 10 according to the first embodiment of the present invention is a system that realizes a water treatment process that purifies sewage by an anaerobic aerobic method (AO method) among activated sludge methods.
- the water treatment system 10 includes a raw water tank 2, a treatment tank 3 including an anaerobic tank 31 and an aerobic tank 32, a precipitation tank 4, an aeration air volume calculating device 65 that calculates the aeration air volume of the aerobic tank 32, And a control device 6 that controls the operation of the system 10.
- the raw water tank 2 temporarily stores the inflowing sewage.
- the outlet of the raw water tank 2 is connected to the inlet of the anaerobic tank 31 by a pipe 52.
- the pipe 52 is provided with a supply pump 51 that pumps the raw water stored in the raw water tank 2 to the anaerobic tank 31.
- the amount of raw water flowing from the raw water tank 2 into the treatment tank 3 is the discharge flow rate of the supply pump 51.
- the treatment tank 3 is provided with an anaerobic tank 31 and an aerobic tank 32 in order from the upstream side.
- the anaerobic tank 31 and the aerobic tank 32 are formed by partitioning one processing tank 3 by a partition, and the anaerobic tank 31 and the aerobic tank 32 are communicated by an opening formed in the partition. ing.
- the anaerobic tank 31 and the aerobic tank 32 may be independent processing tanks.
- the aerobic tank 32 is provided with an air diffuser 9 for aeration of water to be treated.
- the air diffuser 9 includes a nozzle 91 disposed at the bottom of the aerobic tank 32 and an air diffuser 92 that pumps air to the nozzle 91.
- By the air diffuser 9 fine bubbles are blown into the water to be treated from the bottom of the aerobic tank 32.
- the treated water is agitated by the rising of the bubbles blown into the aerobic tank 32, and the treated water is aerated to increase the amount of dissolved oxygen in the treated water.
- the amount of air blown by the diffuser blower 92 (hereinafter referred to as “aeration air amount”) is controlled based on an operation signal from the control device 6.
- the aerobic tank 32 and the precipitation tank 4 are connected by a pipe 53, and treated water in the aerobic tank 32 flows into the precipitation tank 4 through the pipe 53.
- the bottom of the settling tank 4 and the bottom of the anaerobic tank 31 are connected by a sludge return pipe 55, and the sludge precipitated in the settling tank 4 is returned to the anaerobic tank 31 through the sludge return pipe 55.
- the sludge return pipe 55 is provided with a return pump 56.
- the amount of sludge (returned sludge) returned to the anaerobic tank 31 is the discharge flow rate of the return pump 56.
- a raw water NH 4 -N concentration meter 61 for measuring the NH 4 -N concentration of the raw water flowing from the raw water tank 2 into the series of treatment tanks 3 is provided.
- the raw water NH 4 -N concentration meter 61 is not limited to the raw water tank 2 as long as it can measure the NH 4 -N concentration of the raw water, and when the first settling basin is set in the previous stage of the treatment tank 3 It may be provided in the first sedimentation basin, the first sedimentation basin, or the pipe 52 that forms a common water channel between the raw water tank 2 and the treatment tank 3.
- a treatment tank outlet NH 4 -N concentration (hereinafter simply referred to as “outlet NH 4 -N concentration”) that is the NH 4 -N concentration of the treatment liquid flowing out of the aerobic tank 32. ) Is measured, and a treatment tank outlet NH 4 -N concentration meter 62 is provided.
- These NH 4 -N concentration meters 61 and 62 are connected to the control device 6, and the measured values are output from the NH 4 -N concentration meters 61 and 62 to the control device 6.
- FIG. 2 is a block diagram showing a control configuration of the water treatment system 10.
- the control device 6 controls the operations of the supply pump 51, the return pump 56, and the air diffuser 9 based on the measured values of the raw water NH 4 -N concentration meter 61 and the treatment tank outlet NH 4 -N concentration meter 62.
- an aeration air amount calculation device 65 for calculating the aeration air amount (operation amount) of the aeration device 9 is communicably connected to the control device 6, and the control device 6 performs the aeration calculated by the aeration air amount calculation device 65.
- a control signal is output to the air diffuser 9 based on the air volume. That is, the control device 6 has a function as an aeration air volume control device.
- the control device 6 and the aeration air volume calculation device 65 are so-called computers.
- Each of the control device 6 and the aeration air amount calculating device 65 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an I / F (Interface), and an I / O (Input / output). Port) and the like (none of them are shown).
- the ROM stores programs executed by the CPU, various fixed data, and the like. Programs executed by the CPU are stored in various storage media such as a flexible disk, a CD-ROM, and a memory card, and are installed in the ROM from these storage media.
- the RAM temporarily stores data necessary for program execution.
- the I / F performs data transmission / reception with an external device (for example, an input device or storage device not shown).
- I / O inputs / outputs detection signals of various sensors.
- the control device 6 and the aeration air amount calculation device 65 are configured to perform processing for realizing each function by cooperation of software such as a program stored in the ROM and hardware such as a CPU.
- software such as a program stored in the ROM and hardware such as a CPU.
- the water treatment system 10 which concerns on this embodiment is provided with the some computer of the control apparatus 6 and the aeration air volume calculating apparatus 65, these may be comprised by the single computer.
- the aeration air volume calculation device 65 will be described in detail later.
- the raw water stored in the raw water tank 2 is sent to the anaerobic tank 31 through the pipe 52 by the operation of the supply pump 51.
- the raw water (treated water) flowing into the anaerobic tank 31 is mixed with activated sludge.
- Phosphorus-accumulating bacteria in the activated sludge in the anaerobic tank 31 take in organic substances in the treated water into the body and release phosphoric acid (PO 4 ) retained in the body.
- the water to be treated in the anaerobic tank 31 flows into the aerobic tank 32 through the opening of the partition wall.
- the aerobic tank 32 In the aerobic tank 32, heterotrophic organisms contained in the activated sludge take in oxygen and decompose organic substances. Further, in the aerobic tank 32, phosphorus accumulating bacteria that excessively ingest phosphorus under aerobic conditions take in more phosphoric acid phosphorus released in the anaerobic tank 31.
- NH 4 —N in the water to be treated is oxidized into nitrite nitrogen (NO 2 —N) and nitrate nitrogen (NO 3 —N).
- the treatment liquid in the aerobic tank 32 flows into the precipitation tank 4.
- the processing liquid that has flowed into the settling tank 4 is separated into the processing liquid and the sludge as the sludge in the processing liquid is precipitated.
- the sludge is returned to the anaerobic tank 31 through the sludge return pipe 55.
- the aeration air amount calculation device 65 includes an acquisition unit 66 that acquires information (variables) necessary for calculation from the control device 6, a calculation unit 67 that calculates the aeration air amount (operation amount) of the aeration device 9, and the calculated aeration And an output unit 68 that outputs the air volume to the control device 6.
- Information acquired by the acquisition unit 66 includes raw water NH 4 -N concentration X RW that is the NH 4 -N concentration of raw water flowing into the treatment tank 3, and raw water inflow amount u that is the amount of raw water flowing into the treatment tank 3.
- NH 4 -N concentration at which the outlet NH 4 -N concentration X out of the treated water which has been processed in the processing vessel 3, and the like circulation flow rate f is the flow rate of sludge to be returned are separated to the treatment tank 3 from the treated water included.
- the raw water NH 4 -N concentration X RW is a measurement value of the raw water NH 4 -N concentration meter 61
- the raw water inflow u is the discharge flow rate of the supply pump 51
- the outlet NH 4 -N concentration X out is the treatment tank outlet NH.
- the measured value of the 4- N densitometer 62, and the circulation flow rate f is the discharge flow rate of the return pump 56.
- the aeration air volume calculating apparatus 65 acquires these information via the control apparatus 6, it is comprised so that the aeration air volume calculating apparatus 65 may acquire information directly from instruments. Also good.
- FIG. 3 is a block diagram showing a signal flow of the arithmetic processing performed in the arithmetic unit 67.
- the computing unit 67 generates a feedforward manipulated variable (hereinafter referred to as “FF manipulated variable Y F ”) based on the raw water NH 4 —N concentration X RW (hereinafter referred to as “FF manipulated variable Y F ”).
- FF control system 7 and a feedback control system (hereinafter referred to as” FB control system 8 ”) that generates a feedback manipulated variable (hereinafter referred to as” FB manipulated variable Y B ”) using the outlet NH 4 -N concentration X out as a controlled variable. ").
- the FF control system 7 and the FB control system 8 function in cooperation, and the FF operation amount Y F generated by the FF control system 7 and the FB operation amount Y B generated by the FB control system 8 are added by the adder 85. Is added to generate an operation amount Y.
- This manipulated variable Y represents the aeration air volume of the air diffuser 9.
- the output unit 68 outputs the manipulated variable signal of the manipulated variable Y calculated by the computing unit 67 to the diffuser 9, and the diffuser 9 operates the diffuser blower 92 with the aeration air volume corresponding to the manipulated variable Y. .
- the FF control system 7 and the FB control system 8 will be described in detail.
- the FF control system 7 includes an FF manipulated variable computing element 71, a dead time element 73, a feed forward gain element 74, an FF manipulated variable correction coefficient computing element 72, and a multiplier 75.
- the increase amount of the aeration air amount predicted based on the change in the raw water NH 4 -N concentration X RW is calculated as the FF manipulated variable Y F.
- the FF manipulated variable calculation element 71 is an FF manipulated variable function F 1 that calculates the FF manipulated variable Y F from the raw water NH 4 -N concentration X RW .
- the FF manipulated variable function F 1 is a function of the static characteristic relationship between the raw water NH 4 -N concentration X RW as an input value and the FF manipulated variable Y F as an output value.
- the FF manipulated variable function F 1 is preferably set for each water treatment system 10 because it is affected by the treatment capacity of the entire water treatment system 10 and the usage environment.
- the FF manipulated variable function F 1 may be determined based on experimental results or may be determined based on simulation.
- Figure 4 is a table showing the characteristics of the FF operation amount function F 1, the ordinate indicates the FF operation amount Y F (L / min), the horizontal axis represents the raw water NH 4 -N concentration X RW (mg / L) Is shown.
- the FF manipulated variable Y F (L / min) represents the aeration air volume calculated by the FF control system 7.
- the minimum air volume y 0 of the aeration air volume is the minimum air volume necessary for maintaining the entire system.
- the minimum amount of air required to maintain the entire system is heterotrophic that agitate sludge in the aerobic tank 32 and grows using carbon-based organic matter under aerobic conditions in the aerobic tank 32.
- the minimum air volume y 0 is appropriately determined according to the number of activated sludge microorganisms in the aerobic tank 32 and the capacity of the aerobic tank 32. Note that when the aeration air volume is operated at the minimum air volume y 0 , the dissolved oxygen concentration of the water to be treated in the aerobic tank 32 becomes almost zero.
- the FF manipulated variable Y F is constant at the minimum air flow y 0 .
- This first concentration x 1 is the maximum raw water NH at which the outlet NH 4 -N concentration X out is equal to or less than the reference target value X B of the NH 4 -N concentration of the treated water when the aeration air volume is the minimum air volume y 0. 4 -N concentration XRW .
- the reference target value X B of the NH 4 —N concentration of the treated water is determined as appropriate based on the environmental regulation value and the like, and is set in advance in the aeration air amount calculation device 65.
- the FF manipulated variable Y F increases as the raw water NH 4 -N concentration X RW increases.
- FF manipulated variable Y F generated by the FF operation amount calculation element 71 is adjusted by dead time element 73 and the feed-forward gain element 74.
- the dead time (also referred to as shift time) is that the raw water whose NH 4 -N concentration is measured by the raw water NH 4 -N concentration meter 61 flows into the anaerobic tank 31 and then flows into the aerobic tank 32. It takes time to complete.
- the discontinuous surface of the NH 4 -N concentration of the treated water is preferred.
- the aeration air volume is increased before reaching the air tank 32, and when the discontinuous surface reaches the aerobic tank 32, the activated sludge microorganisms are activated so as to cope with a rapid increase in NH 4 -N concentration. It is desirable to keep it. That is, the dead time is preferably set to a time shorter than the time required for the raw water whose NH 4 —N concentration is measured by the raw water NH 4 —N concentration meter 61 to flow into the aerobic tank 32. Such dead time can be obtained experimentally or computationally as a time including a residence time from flowing into the anaerobic tank 31 to flowing into the aerobic tank 32.
- Feedforward gain K f is the ratio of the FF operation amount Y
- F variation is a change amount of the output value of the input value of the FF operation amount function F 1 raw water NH 4 -N concentration X RW, is set appropriately The
- the FF manipulated variable Y F adjusted by the dead time element 73 and the feedforward gain element 74 is further corrected by the correction coefficient ⁇ .
- the correction coefficient ⁇ is for correcting the FF manipulated variable Y F based on the raw water inflow amount u.
- the correction coefficient ⁇ is calculated in the FF manipulated variable correction coefficient computing element 72 using an FF manipulated variable correction function F 2 that is a function of the relationship between the raw water inflow u as an input value and the correction coefficient ⁇ as an output value. .
- the correction coefficient ⁇ increases the FF manipulated variable Y F when the raw water inflow u is larger than the predetermined reference inflow U 1 , and the raw water inflow u to the treatment tank 3 is greater than the predetermined reference inflow U 1 . It is a correction coefficient that reduces the FF manipulated variable Y F when it is small.
- Figure 5 is a table showing the characteristics of the FF manipulated variable correction function F 2, the vertical axis represents the correction coefficient alpha, the horizontal axis represents the raw water inflow u (L / min).
- the correction coefficient ⁇ increases from ⁇ 1 smaller than 1 to ⁇ 2 larger than 1, with the raw water inflow u being equal to the reference inflow U 1 as the raw water inflow u increases.
- the reference inflow U 1 of the raw water inflow u is determined by the treatment capacity of the water treatment system 10
- the maximum inflow U 2 is determined by the capacity of the supply pump 51 in addition to the treatment capacity of the water treatment system 10.
- the FF manipulated variable Y F is corrected.
- the corrected FF manipulated variable Y F is output to the adder 85.
- the FB control system 8 includes a subtractor 83 that calculates a deviation between the outlet NH 4 -N concentration X out (control value) and the NH 4 -N concentration target value X DV of the treated water, and the FB manipulated variable Y from this deviation. And an FB manipulated variable calculating element 84 for generating B.
- the FB operation amount Y B represents the aeration air amount calculated by the FB control system 8.
- the FB operation amount calculation element 84 according to the present embodiment calculates the FB operation amount Y B using the PID control method.
- the FB operation amount calculation element 84 may be a calculation element that calculates the FB operation amount Y B using, for example, a PID control method, a P control method, or a PI control method.
- the calculated FB operation amount Y B is input to the adder 85.
- the FB control system 8 further includes a target value calculation element 81 and a low selector 82 in order to calculate the target value X DV .
- the target value calculation element 81 is a target value function F 3 for calculating the target value X DV from the raw water NH 4 -N concentration X RW , the raw water inflow u, the outlet NH 4 -N concentration X out , and the circulating flow rate f.
- the target value function F 3 includes the input values of raw water NH 4 -N concentration X RW , raw water inflow u, outlet NH 4 -N concentration X out , circulation flow rate f, and output value of target value X DV . It is a functionalized relationship.
- the outlet NH 4 -N concentration X out is the NH 4 -N concentration at the outlet of the processing tank 3 measured by the processing tank outlet NH 4 -N concentration meter 62.
- the circulation flow rate f is a flow rate of sludge separated from the treated water and returned to the treatment tank 3.
- the target value X DV calculated by the target value function F 3 is a value smaller by a predetermined value (k) than the NH 4 -N concentration at the inlet of the processing tank 3 (hereinafter referred to as “inlet NH 4 -N concentration X in ”). It is. However, the target value X DV may be a value that is smaller by a predetermined ratio (1- ⁇ ) than the NH 4 -N concentration at the inlet of the processing tank 3.
- the inlet of the treatment tank 3 is an area into which raw water and return sludge flow in the treatment tank 3 and refers to an upstream area of the anaerobic tank 31.
- a target value function F 3 is shown below [Formula 1] or [Equation 2].
- the inlet NH 4 -N concentration X in can be calculated by the following [Equation 3].
- [Formula 1] F 3 (X in ) X in ⁇ k
- F 3 (X in ) X in ⁇ ⁇
- Xin ( XRW * u + Xout * f) / (u + f)
- k [mg / L] is a constant larger than 0.
- a value selected from the range of 2 to 10 [mg / L] is preferable.
- ⁇ is a constant larger than 0 and smaller than 1, for example, 0.6 to 0.9 is preferable. It is desirable that k in the above formula 1 or ⁇ in the above formula 2 is determined based on experiments. Below, an example of the determination method of k or (beta) is demonstrated.
- B change amounts ⁇ X 1 and ⁇ X 2 of NH 4 -N concentration are known to be substantially constant regardless of the quality of the water to be treated.
- the change amount ⁇ X of the NH 4 —N concentration of the water to be treated from the start of the treatment in the treatment time in which the COD of the water to be treated hardly changes even if the aeration is continued further is a plurality of treatments having different water qualities. When experimented with water, it was almost constant at 2 to 10 [mg / L].
- the change amount ⁇ X is, NH 4 -N treated water when the NH 4 -N concentration of the treated water at the start of processing, COD of water to be treated was hardly changed even continue further aeration It can be expressed as a difference from the concentration.
- the value of the change ⁇ X is experimentally obtained so that the difference between the inlet NH 4 -N concentration X in and the target value X DV becomes ⁇ X [mg / L] or a value obtained by adding a safety factor to ⁇ X. K or ⁇ is determined.
- the value of the change amount ⁇ X is preferably an average value of a plurality of change amounts ⁇ X obtained experimentally. In the above, BOD may be used instead of COD.
- the target value X DV calculated according to the determination method of k or ⁇ is a value smaller than the inlet NH 4 -N concentration X in by a predetermined value.
- the predetermined value is when COD or BOD of the water to be treated becomes a substantially constant value (that is, when COD or BOD of the water to be treated hardly changes even if aeration is continued further). This is the absolute value of the amount of change ⁇ X from the start of the aeration treatment of the NH 4 —N concentration of the water to be treated.
- the absolute value of the change ⁇ X obtained as a result of the experiment is 2 to 10 [mg / L], but if the safety factor is expected, the absolute value of the change ⁇ X is selected from the range of 2 to 45 [mg / L].
- the value may be However, since the aeration air volume increases as the target value X DV decreases, the predetermined value is preferably a smaller value from the viewpoint of reducing the operating energy of the diffuser.
- the target value X DV calculated by the target value calculation element 81 as described above is compared with the reference target value X B by the low selector 82, and the smaller value is selected as the (new) target value X DV . It is output to the subtracter 83.
- FIG. 6 shows the relationship between the target value X DV (that is, the target value X DV input to the subtractor 83) used for calculating the FB manipulated variable Y B and the inlet NH 4 -N concentration X in.
- the chart is shown.
- the vertical axis represents the NH 4 -N concentration
- the horizontal axis represents time
- the solid line represents the target value X DV
- the chain line represents the inlet NH 4 -N concentration X in .
- the target value X DV from the start of processing to the time Ta is constant at the reference target value X B.
- the target value X DV from time Ta to time Tb changes from the inlet NH 4 -N concentration X in by a predetermined value or a value smaller by a predetermined ratio.
- the target value X DV from time Tb to the end of processing is constant at the reference target value X B.
- a larger value by a predetermined value than the reference target value X B as the threshold when the inlet NH 4 -N concentration X in is greater than the threshold reference target value X B is selected as the target value X DV, inlet When the NH 4 -N concentration X in is less than or equal to the threshold value, a value smaller than the inlet NH 4 -N concentration X in by a predetermined value is selected as the target value X DV .
- the target value X DV of the outlet NH 4 -N concentration is always lower than the inlet NH 4 -N concentration X in . Therefore, the deviation between the outlet NH 4 -N concentration X out (control value) and the target value X DV is always greater than zero.
- the FB manipulated variable Y B is calculated by feedback control based on this deviation, and the diffuser 9 is controlled based on the calculated manipulated variable Y (aeration air volume). Sufficient aeration is performed continuously to reduce the NH 4 —N concentration of the catalyst.
- the target value X DV of the outlet NH 4 -N concentration changes according to the change of the inlet NH 4 -N concentration X in .
- the target value X DV of the outlet NH 4 -N concentration appropriate for the inlet NH 4 -N concentration X in is set. Therefore, the aeration air volume in the aerobic tank 32 does not become excessive, and the aeration air volume and the operating energy of the diffuser 9 can be suppressed.
- the aeration air volume is calculated by the aeration air volume calculation device 65 according to Modification 1 described below.
- FIG. 7 is a block diagram showing a signal flow of the aeration air volume calculation device 65 according to the first modification.
- the process for calculating the target value X DV of the FB control system 8 is changed from the process according to the above-described embodiment. That is, in the FB control system 8 according to the modified example 1, the target value X DV calculated by the target value calculation element 81 is used as it is as the target value X DV without being compared with the reference target value X B. Yes.
- FIG. 8 shows a chart showing the relationship between the target value X DV calculated by the FB control system 8 according to the first modification and the inlet NH 4 -N concentration X in .
- the vertical axis represents the NH 4 -N concentration
- the horizontal axis represents time
- the solid line represents the target value X DV
- the chain line represents the inlet NH 4 -N concentration X in .
- the target value X DV changes from the inlet NH 4 -N concentration X in by a predetermined value or a value smaller by a predetermined ratio from the start to the end of the process.
- FIG. 9 is a diagram showing a schematic configuration of a water treatment system 10 according to the second embodiment of the present invention
- FIG. 10 is a block diagram showing a control configuration of the water treatment system 10 according to the second embodiment.
- the same or similar members as those in the first embodiment described above are denoted by the same reference numerals in the drawings, and the description thereof is omitted. Mainly differences from the first embodiment. explain.
- the water treatment system 10 according to the second embodiment is replaced with the raw water NH 4 -N concentration meter 61 provided in the raw water tank 2 in the water treatment system 10 according to the first embodiment.
- a treatment tank inlet NH 4 -N concentration meter 63 provided at the inlet of the treatment tank 3 is provided.
- the treatment tank inlet NH 4 -N concentration meter 63 is configured to detect the NH 4 -N concentration of the water to be treated at the inlet of the treatment tank 3 and output it to the control device 6.
- the inlet of the processing tank 3 is an area into which raw water and return sludge flow in the processing tank 3, and is an upstream area of the anaerobic tank 31.
- the processing sequence of the water treatment system 10 is a multi-lineage advantage in that the provision of the NH 4 -N concentration meter in the raw water tank 2 as in the first embodiment it is possible to reduce the number of installation of NH 4 -N concentration meter
- the number of processing series is one or two
- installing the NH 4 -N concentration meter at the inlet of the processing tank 3 can save the processing for calculating the inlet NH 4 -N concentration X in . Is reasonable.
- the processing tank inlet NH 4 directly with the -N concentration meter 63 to detect the inlet NH 4 -N concentration X in, the detected inlet NH 4 -N so that calculates the aeration amount using the concentration X in.
- FIG. 11 is a block diagram showing a signal flow of the aeration air volume calculation device 65 according to the second embodiment.
- the FF manipulated variable Y F is generated based on the raw water NH 4 —N concentration X RW detected by the raw water NH 4 —N concentration meter 61.
- the FF manipulated variable Y F is generated based on the inlet NH 4 -N concentration X in detected by the treatment tank inlet NH 4 -N concentration meter 63. That is, the FF manipulated variable calculating element 71 according to the second embodiment is an FF manipulated variable function F 1 that calculates the FF manipulated variable Y F from the inlet NH 4 -N concentration X in .
- the target value calculation element 81 of the FB control system 8 of the first embodiment is the target value X DV from the raw water NH 4 -N concentration X RW , the raw water inflow u, the outlet NH 4 -N concentration X out , and the circulation flow rate f.
- the target value calculation element 81 of the second embodiment calculates the target value X DV from the inlet NH 4 -N concentration X in detected by the treatment tank inlet NH 4 -N concentration meter 63. It is. That is, the target value function F 3 according to the second embodiment is a function of the relationship between the inlet NH 4 -N concentration X in that is an input value and the target value X DV that is an output value.
- the target value X DV calculated by the target value function F 3 is a value that is smaller than the inlet NH 4 -N concentration X in by a predetermined value.
- the water treatment system 10 which concerns on the said embodiment implement
- the anaerobic aerobic method (A2O method) which combined biological nitrogen treatment with the anaerobic aerobic method. It may be a treatment process or a treatment process of a membrane separation activated sludge method (MBR method).
- a treatment tank comprising a raw water tank 2, an anaerobic tank 31, an anaerobic tank 38, and an aerobic tank 32 in a water treatment system 10A. 3 and a settling tank 4 are provided.
- the sludge precipitated in the settling tank 4 is returned to the anaerobic tank 31.
- the circulating liquid containing the sludge precipitated in the aerobic tank 32 is returned to the anoxic tank 38.
- the circulation flow rate f for calculating the target value function F 3 is the flow rate of the sludge precipitated in the settling tank 4 returned to the anaerobic tank 31, and from the aerobic tank 32 sent to the anaerobic tank 38. A value obtained by adding the flow rate of the circulating fluid is used.
- the treatment process is the membrane separation activated sludge method
- the raw water tank 2, the anaerobic tank 31, the anaerobic tank 38, the aerobic tank 32, and the membrane separation are added to the water treatment system 10B.
- a treatment tank 3 comprising a tank 39 is provided.
- the sludge that has been membrane-separated from the treatment liquid in the membrane separation tank 39 is returned to the anaerobic tank 31.
- the circulating liquid containing the sludge precipitated in the aerobic tank 32 is returned to the anoxic tank 38.
- the circulation flow rate f for calculating the target value function F 3 is from the aerobic tank 32 sent to the anaerobic tank 38 to the flow rate of sludge precipitated in the membrane separation tank 39 returned to the anaerobic tank 31.
- a value obtained by adding the flow rate of the circulating fluid is used.
- the FF operation amount Y F is calculated by the FF control system 7
- the FB operation amount Y B is calculated by the FB control system 8.
- the operation amount Y is calculated by adding the FF operation amount Y F and the FB operation amount Y B by the adder 85.
- the operation amount Y considers only the FB operation amount Y B. There may be. In this case, the processing performed by the FF control system 7 and the adder 85 in the processing of the calculation unit 67 is omitted, and the FB operation amount Y B derived by the FB control system 8 is calculated as the operation amount Y.
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Abstract
An aeration calculation device (65) that finds aeration amounts for a treatment tank comprises a calculation unit (67) that calculates an operation amount (Y) being an aeration amount, on the basis of an FB operation amount (YB), said calculation unit (67) having: a target value calculation element (81) that generates a target value (XDV) that is smaller than the NH4-N concentration (Xin) at a treatment tank inlet; and an FB operation amount calculation element (84) that generates the FB operation amount (YB) on the basis of the deviation between the NH4-N concentration (Xout) at a treatment tank outlet and the target value (XDV). The NH4-N concentration at the treatment tank inlet is either: a value found on the basis of the NH4-N concentration (XRW) of raw water, the amount of raw water inflow (u), the NH4-N concentration (Xout) at the treatment tank outlet, and the circulation flow rate (f); or a value detected by a treatment tank inlet NH4-N concentration meter (63).
Description
本発明は、活性汚泥法を用いて浄化処理を行う水処理システムに関する。
The present invention relates to a water treatment system that performs purification using an activated sludge method.
従来、生活排水などの排水処理において、活性汚泥を用いて排水を浄化する水処理システムが用いられている。例えば、特許文献1に記載され水処理システムは、原水を貯溜する原水槽と、原水中の汚濁物質を活性汚泥で生物処理する一連の処理槽と、原水と活性汚泥が混合した被処理水から汚泥を沈殿分離する沈殿池とを備えている。上記一連の処理槽には、嫌気槽、無酸素槽、及び、散気装置を備えた好気槽が含まれている。これらの処理槽では、炭素系有機物、窒素含有化合物、リン含有化合物などの原水に含まれる汚濁物質の除去が行われる。
Conventionally, in wastewater treatment such as domestic wastewater, a water treatment system that purifies wastewater using activated sludge has been used. For example, a water treatment system described in Patent Document 1 includes a raw water tank for storing raw water, a series of treatment tanks for biologically treating pollutants in raw water with activated sludge, and water to be treated in which raw water and activated sludge are mixed. And a sedimentation basin for sedimenting and separating sludge. The series of treatment tanks include an anaerobic tank, an anaerobic tank, and an aerobic tank provided with an air diffuser. In these treatment tanks, contaminants contained in raw water such as carbon-based organic substances, nitrogen-containing compounds, and phosphorus-containing compounds are removed.
下水処理の排水基準項目には、T-N(総窒素)、T-P(総リン)、BOD(生物化学的酸素要求量)が含まれており、これらの全ての項目で所定の処理基準を満たす必要がある。ところが、BODを即時且つ安価に測定できる技術が未だ開発されていない。そこで、処理水のBODが所定の処理基準を満たすことを確保するために、処理基準を十分な余裕を持って達成できるような曝気風量で好気槽の曝気が行われている。
Wastewater standard items for sewage treatment include TN (total nitrogen), TP (total phosphorus), and BOD (biochemical oxygen demand). It is necessary to satisfy. However, a technology that can measure BOD immediately and inexpensively has not been developed yet. Therefore, in order to ensure that the BOD of the treated water satisfies the predetermined treatment standard, aeration in the aerobic tank is performed with an aeration air volume that can achieve the treatment standard with a sufficient margin.
ところで、活性汚泥法による水処理プロセスにおいて、被処理水のBODは処理開始後比較的早い段階から減少し始め、やがて変化が緩やかとなる特徴を有し、被処理水のアンモニア態窒素(以下、「NH4-N」と記載することがある)濃度は処理開始後直ぐは殆ど変化せず、BODの変化が緩やかとなるあたりから減少し始める特徴を有することが知られている。つまり、活性汚泥法による水処理プロセスでは、硝化速度と比較して有機物分解速度が速い(第1の知見)。
By the way, in the water treatment process by the activated sludge method, the BOD of the water to be treated starts to decrease from a relatively early stage after the start of the treatment, and eventually has a characteristic that the change becomes gradual. It is known that the concentration (which may be described as “NH 4 -N”) hardly changes immediately after the start of the treatment, and has a characteristic of starting to decrease when the change in BOD becomes gentle. That is, in the water treatment process by the activated sludge method, the organic matter decomposition rate is faster than the nitrification rate (first knowledge).
発明者らは、上記第1の知見を検証するために次に説明する実験を行った。この実験では、実験容器に充填された被処理水A,Bに対し所定の曝気風量で曝気を行って、NH4-N濃度とCOD(化学的酸素要求量)とを計測した。実験時の曝気風量は、最低風量より大きく、且つ、従来の水処理システムで標準的なNH4-N濃度の被処理水に対して設定される曝気風量のうち、より小さな値であった。なお、BODが生物分解性有機物のみの酸素要求量であるのに対し、CODが有機物と無機物の両方の要求酸素量であるという点で両者は相違するが、BODよりも短時間で計測可能なCODがBODの代替指標として用いられることがある。この実験結果が、図14に示す、好気槽におけるNH4-N濃度の処理挙動とCODの処理挙動の時系列変化を示すグラフに表されている。このグラフ中、縦軸がNH4-N濃度とCODとを表し、横軸が処理時間を表し、実線がNH4-N濃度の時系列変化を表し、破線がCODの時系列変化を表している。
Inventors conducted the experiment demonstrated below in order to verify the said 1st knowledge. In this experiment, the water to be treated A and B filled in the experimental vessel was aerated with a predetermined aeration air volume, and the NH4-N concentration and COD (chemical oxygen demand) were measured. The aeration air volume at the time of the experiment was larger than the minimum air volume, and was smaller than the aeration air volume set for the treated water having a standard NH 4 -N concentration in the conventional water treatment system. Although BOD is the required oxygen amount of only biodegradable organic matter, COD is different in that it is the required oxygen amount of both organic and inorganic materials, but it can be measured in a shorter time than BOD. COD may be used as an alternative indicator for BOD. The results of this experiment are shown in the graph in FIG. 14 showing the time-series changes in the NH 4 —N concentration treatment behavior and the COD treatment behavior in the aerobic tank. In this graph, the vertical axis represents the NH 4 -N concentration and COD, the horizontal axis represents the treatment time, the solid line represents the NH 4 -N concentration time series change, and the broken line represents the COD time series change. Yes.
図14のグラフによれば、被処理水A,Bについて、NH4-N濃度の処理挙動とCODの処理挙動に共通する特徴がみられた。その共通の特徴とは、CODが、処理を開始すると比較的早い段階から減少し始め、やがて変化が徐々に緩やかとなり、そのうち曝気を継続しても殆ど変化しない状態となるというものである。また、共通の特徴とは、NH4-N濃度が、或る処理時間を超えるあたりまで殆ど変化せず、或る処理時間を超えたあたりから、急激に減少を始めるというものである。
According to the graph of FIG. 14, the characteristics common to the treatment behavior of NH 4 —N concentration and the treatment behavior of COD were observed for the treated waters A and B. The common feature is that COD starts to decrease from a relatively early stage when processing is started, and gradually changes gradually, and even if aeration is continued, the COD becomes almost unchanged. Further, the common feature is that the NH 4 -N concentration hardly changes until around a certain processing time, and starts to decrease sharply after exceeding a certain processing time.
被処理水Aでは、処理時間TC1以降はCODが殆ど変化しない。被処理水Aの、処理開始時から処理時間TC1までのNH4-N濃度の変化量はΔX1[mg/L]である。一方、被処理水Bでは、処理時間TC2以降はCODが殆ど変化しない。被処理水Bの、処理開始時から処理時間TC2までのNH4-N濃度の変化量はΔX2[mg/L]である。被処理水Aと被処理水Bとは、水質が異なり、処理開始時のNH4-N濃度が異なるにも関わらず、変化量ΔX1と変化量ΔX2とがほぼ同じ値であった。また、この明細書には記載しないが、被処理水A,Bと異なる水質の被処理水についても被処理水A,Bと同様の傾向が見られた。このことから、処理開始時の被処理水のNH4-N濃度が違っていても、NH4-NがΔX[mg/L]だけ硝化されると、CODが一定水準(即ち、これ以上曝気を続けてもCODの値が殆ど変化しなくなる程度)まで処理されることが分かった(第2の知見)。
In the water to be treated A, the COD hardly changes after the treatment time T C1 . The amount of change in NH 4 —N concentration of the water to be treated A from the start of treatment to the treatment time T C1 is ΔX 1 [mg / L]. On the other hand, in the water to be treated B, the COD hardly changes after the treatment time T C2 . The amount of change in NH 4 —N concentration of the water to be treated B from the start of treatment to the treatment time T C2 is ΔX 2 [mg / L]. Although the water to be treated A and the water to be treated B have different water qualities and different NH 4 -N concentrations at the start of treatment, the amount of change ΔX 1 and the amount of change ΔX 2 were almost the same value. Moreover, although not described in this specification, the same tendency as the water to be treated A and B was observed for the water to be treated having a quality different from that of the water to be treated A and B. From this, even if the NH 4 -N concentration of the water to be treated at the start of treatment is different, if NH 4 -N is nitrified by ΔX [mg / L], the COD is at a certain level (ie, aeration more than this) (The second finding).
上記第1の知見に基づけば、硝化に必要な量の酸素を好気槽へ供給することにより、有機物の分解に必要とされる量の酸素を供給することができる。そこで、本発明では、処理水のBODの代替指標としてNH4-N濃度を用い、処理水のNH4-N濃度が所定の目標値以下となるように好気槽の曝気風量を制御することとした。このような曝気風量を制御においては、原水のNH4-N濃度が所定の目標値以下であればそれ以上の硝化が要求されないので、好気槽の曝気風量を最低風量に抑えれば散気装置の稼働エネルギーを削減することができる。しかしながら、好気槽の曝気風量が少ないと、被処理水中の有機物が十分に分解されず処理水のBODが所定の処理基準を超えるおそれがある。そこで、本発明では、更に上記第2の知見に基づき、適切に曝気風量の目標値を設定することにより、曝気風量を抑えつつ、被処理水中の有機物の処理を確実に行うこととした。
Based on the first knowledge, an amount of oxygen necessary for decomposing organic substances can be supplied by supplying an amount of oxygen necessary for nitrification to the aerobic tank. Therefore, in the present invention, using a NH 4 -N concentration as an alternative indicator of BOD of the treated water, the NH 4 -N concentration in the treated water is controlled aeration of the aerobic tank to be equal to or less than a predetermined target value It was. In controlling such aeration air volume, no further nitrification is required if the NH 4 -N concentration of the raw water is below a predetermined target value. Therefore, if the aeration air volume in the aerobic tank is kept to the minimum air volume, aeration is achieved. The operating energy of the apparatus can be reduced. However, when the amount of aeration air in the aerobic tank is small, the organic matter in the water to be treated is not sufficiently decomposed, and the BOD of the treated water may exceed a predetermined treatment standard. Therefore, in the present invention, based on the second knowledge, the target value of the aeration air volume is appropriately set, thereby reliably treating the organic matter in the water to be treated while suppressing the aeration air volume.
本発明に係る曝気風量演算装置は、
被処理水を活性汚泥法で浄化する処理槽への曝気風量を求める曝気風量演算装置であって、
前記処理槽の入口の被処理水のアンモニア態窒素濃度である処理槽入口アンモニア態窒素濃度よりも小さい目標値を生成する目標値演算要素と、前記処理槽で処理された処理水のアンモニア態窒素濃度である処理槽出口アンモニア態窒素濃度と前記目標値との偏差に基づいてフィードバック操作量を生成するフィードバック操作量演算要素とを有し、前記フィードバック操作量に基づいて前記曝気風量である操作量を算出する演算手段を備えることを特徴としている。 The aeration air volume calculation device according to the present invention is:
An aeration air volume calculating device for obtaining an aeration air volume to a treatment tank for purifying treated water by an activated sludge method,
A target value calculation element that generates a target value smaller than the ammonia nitrogen concentration in the treatment tank, which is the ammonia nitrogen concentration of the water to be treated at the inlet of the treatment tank, and ammonia nitrogen in the treatment water treated in the treatment tank A feedback manipulated variable calculation element for generating a feedback manipulated variable based on a deviation between the treatment tank outlet ammonia nitrogen concentration that is a concentration and the target value, and an manipulated variable that is the aeration air volume based on the feedback manipulated variable It is characterized by comprising a calculation means for calculating.
被処理水を活性汚泥法で浄化する処理槽への曝気風量を求める曝気風量演算装置であって、
前記処理槽の入口の被処理水のアンモニア態窒素濃度である処理槽入口アンモニア態窒素濃度よりも小さい目標値を生成する目標値演算要素と、前記処理槽で処理された処理水のアンモニア態窒素濃度である処理槽出口アンモニア態窒素濃度と前記目標値との偏差に基づいてフィードバック操作量を生成するフィードバック操作量演算要素とを有し、前記フィードバック操作量に基づいて前記曝気風量である操作量を算出する演算手段を備えることを特徴としている。 The aeration air volume calculation device according to the present invention is:
An aeration air volume calculating device for obtaining an aeration air volume to a treatment tank for purifying treated water by an activated sludge method,
A target value calculation element that generates a target value smaller than the ammonia nitrogen concentration in the treatment tank, which is the ammonia nitrogen concentration of the water to be treated at the inlet of the treatment tank, and ammonia nitrogen in the treatment water treated in the treatment tank A feedback manipulated variable calculation element for generating a feedback manipulated variable based on a deviation between the treatment tank outlet ammonia nitrogen concentration that is a concentration and the target value, and an manipulated variable that is the aeration air volume based on the feedback manipulated variable It is characterized by comprising a calculation means for calculating.
また、本発明に係る水処理システムは、
散気装置を備えた好気槽を含み、被処理水を活性汚泥法で浄化する処理槽と、
前記処理槽へ流入する原水のアンモニア態窒素濃度を計測する原水アンモニア態窒素濃度計又は前記処理槽の入口の前記被処理水のアンモニア態窒素濃度を計測する処理槽入口アンモニア態窒素濃度計と、
前記処理槽から流出する処理水のアンモニア態窒素濃度を計測する処理槽出口アンモニア態窒素濃度計と、
前記曝気風量演算装置と、
前記曝気風量演算装置で求めた前記操作量に基づいて前記散気装置を制御する曝気風量制御装置とを備えることを特徴としている。 Moreover, the water treatment system according to the present invention includes:
A treatment tank including an aerobic tank equipped with an air diffuser, and purifying treated water by an activated sludge method;
A raw water ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of raw water flowing into the treatment tank or a treatment tank inlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water at the inlet of the treatment tank;
A treatment tank outlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water flowing out of the treatment tank;
The aeration air volume calculating device;
And an aeration air volume control device that controls the aeration device based on the operation amount obtained by the aeration air volume computing device.
散気装置を備えた好気槽を含み、被処理水を活性汚泥法で浄化する処理槽と、
前記処理槽へ流入する原水のアンモニア態窒素濃度を計測する原水アンモニア態窒素濃度計又は前記処理槽の入口の前記被処理水のアンモニア態窒素濃度を計測する処理槽入口アンモニア態窒素濃度計と、
前記処理槽から流出する処理水のアンモニア態窒素濃度を計測する処理槽出口アンモニア態窒素濃度計と、
前記曝気風量演算装置と、
前記曝気風量演算装置で求めた前記操作量に基づいて前記散気装置を制御する曝気風量制御装置とを備えることを特徴としている。 Moreover, the water treatment system according to the present invention includes:
A treatment tank including an aerobic tank equipped with an air diffuser, and purifying treated water by an activated sludge method;
A raw water ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of raw water flowing into the treatment tank or a treatment tank inlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water at the inlet of the treatment tank;
A treatment tank outlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water flowing out of the treatment tank;
The aeration air volume calculating device;
And an aeration air volume control device that controls the aeration device based on the operation amount obtained by the aeration air volume computing device.
上記曝気風量演算装置及び上記水処理システムによれば、処理槽出口NH4-N濃度の目標値は常に処理槽入口のNH4-N濃度より低い値となる。そして、目標値と処理槽出口NH4-N濃度(制御値)との偏差に基づいてフィードバック制御により操作量(曝気風量)が決定されるので、被処理水のNH4-N濃度を低減するために十分な曝気が継続的に行われることとなる。これにより、曝気風量が著しく少なくなって被処理水中の有機物が十分に分解されないという事態を免れ、被処理水中の有機物の処理を確実に行うことができる。更に、処理槽出口NH4-N濃度の目標値は処理槽入口のNH4-N濃度の変化に応じて変化するので、曝気風量が過剰とならず、曝気風量及び散気装置の稼働エネルギーを抑えることができる。
According to the aeration air volume calculation device and the water treatment system, the target value of the treatment tank outlet NH 4 —N concentration is always lower than the NH 4 —N concentration at the treatment tank inlet. Since the manipulated variable (aeration air volume) is determined by feedback control based on the deviation between the target value and the treatment tank outlet NH 4 -N concentration (control value), the NH 4 -N concentration of the water to be treated is reduced. Therefore, sufficient aeration is continuously performed. Thereby, the situation where the amount of aeration is remarkably reduced and the organic matter in the treated water is not sufficiently decomposed can be avoided, and the treatment of the organic matter in the treated water can be performed reliably. Furthermore, since the target value of NH 4 -N concentration at the treatment tank outlet changes according to the change in NH 4 -N concentration at the treatment tank inlet, the aeration air volume does not become excessive, and the aeration air volume and the operating energy of the diffuser are reduced. Can be suppressed.
上記において、前記目標値は、前記処理槽入口アンモニア態窒素濃度よりも所定値だけ小さい値であって、当該所定値が、曝気により被処理水のCOD又はBODが一定値となったときの、当該被処理水のアンモニア態窒素濃度の前記曝気開始時からの変化量の絶対値であってよい。なお、上記において「COD又はBODが一定値」とあるのは、厳密にCOD又はBODが一定の値となる状態に加え、COD又はBODの減少幅が曝気開始時と比較して小さくなり、曝気を継続してもCOD又はBODの変動が小さい(例えば、1時間当たりの減少率が5%以下又は10%以下)状態が含まれる。また、前記目標値が、前記処理槽入口アンモニア態窒素濃度よりも2~10[mg/L]の範囲から選択された値だけ小さな値であってよい。
In the above, the target value is a value smaller than the treatment tank inlet ammonia nitrogen concentration by a predetermined value, and when the predetermined value becomes a constant value of COD or BOD of the water to be treated by aeration, It may be an absolute value of the amount of change in the ammonia nitrogen concentration of the water to be treated from the start of the aeration. In addition, in the above, “COD or BOD is a constant value” means that in addition to the state where COD or BOD is strictly constant, the reduction width of COD or BOD is smaller than that at the start of aeration, The state where the fluctuation of COD or BOD is small even if the operation is continued (for example, the rate of decrease per hour is 5% or less or 10% or less) is included. The target value may be a value that is smaller than the treatment tank inlet ammonia nitrogen concentration by a value selected from a range of 2 to 10 [mg / L].
従来は、処理水のBODが所定の処理基準を満たすことを確保するために、処理基準を余裕を持って達成できるような曝気風量で好気槽の曝気が行われていたが、上記曝気風量演算装置及び上記水処理システムによれば、被処理水中の有機物の処理を確実に行いつつ被処理水を曝気風量の増大を適切に抑制することができるので、散気装置の稼働エネルギーを削減することができる。
Conventionally, in order to ensure that the BOD of the treated water satisfies the predetermined treatment standard, the aeration tank is aerated with an aeration air volume that can achieve the treatment standard with a margin. According to the arithmetic device and the water treatment system, it is possible to appropriately suppress an increase in the amount of aeration air for the water to be treated while reliably processing the organic matter in the water to be treated, thereby reducing the operating energy of the air diffuser. be able to.
上記曝気風量演算装置及び上記水処理システムにおいて、前記演算手段は、所定の基準目標値と前記目標値演算要素で生成された前記目標値とのうち小さい方を選択して前記フィードバック操作量演算要素へ前記目標値として出力するローセレクタを更に有することが望ましい。この構成によれば、処理槽出口NH4-N濃度の目標値は常に所定の基準目標値以下となるので、処理水の水質基準にNH4-N濃度が含まれている場合に有効である。
In the aeration air volume calculation device and the water treatment system, the calculation means selects a smaller one of a predetermined reference target value and the target value generated by the target value calculation element, and the feedback manipulated variable calculation element It is desirable to further include a row selector that outputs the target value. According to this configuration, the target value of the treatment tank outlet NH 4 -N concentration is always less than or equal to the predetermined reference target value, which is effective when the NH 4 -N concentration is included in the water quality standard of the treated water. .
上記曝気風量演算装置及び上記水処理システムが、前記処理槽へ流入する原水のアンモニア態窒素濃度である原水アンモニア態窒素濃度、前記処理槽へ流入する前記原水の流入量である原水流入量、前記処理槽出口アンモニア態窒素濃度、及び前記処理水から分離されて前記処理槽へ戻される汚泥の流量である循環流量を取得する取得手段を更に備え、前記演算手段が、前記原水アンモニア態窒素濃度、前記原水流入量、前記処理槽出口アンモニア態窒素濃度、及び前記循環流量に基づいて前記処理槽入口アンモニア態窒素濃度を演算するように構成されていてよい。この構成によれば、原水NH4-N濃度などに基づいて処理槽入口NH4-N濃度を求めることができ、水処理システムの処理系列が多系統である場合にNH4-N濃度計の数の増加を抑えることができる。
The aeration air amount calculation device and the water treatment system are raw water ammonia nitrogen concentration which is ammonia nitrogen concentration of raw water flowing into the treatment tank, raw water inflow amount which is inflow amount of the raw water flowing into the treatment tank, It further comprises an acquisition means for acquiring a treatment tank outlet ammonia nitrogen concentration and a circulation flow rate that is a flow rate of sludge separated from the treatment water and returned to the treatment tank, and the computing means comprises the raw water ammonia nitrogen concentration, The treatment tank inlet ammonia nitrogen concentration may be calculated based on the raw water inflow amount, the treatment tank outlet ammonia nitrogen concentration, and the circulation flow rate. According to this arrangement, it is possible to determine the treatment tank inlet NH 4 -N concentration based on such raw NH 4 -N concentration, the processing sequence of the water treatment system of NH 4 -N concentration meter in the case of multiple system The increase in the number can be suppressed.
上記曝気風量演算装置及び上記水処理システムにおいて、前記演算手段が、前記処理槽へ流入する原水のアンモニア態窒素濃度である原水アンモニア態窒素濃度に基づいてフィードフォワード操作量を生成するフィードフォワード操作量演算要素と、前記フィードフォワード操作量と前記フィードバック操作量とを足し合わせる加算器とを、更に有し、前記フィードバック操作量及び前記フィードフォワード操作量に基づいて前記操作量を算出するように構成されていることが望ましい。ここで、前記演算手段は、前記処理槽へ流入する前記原水の流入量である原水流入量が所定の基準流入量より大きいときは前記フィードフォワード操作量を増加させ、前記原水流入量が前記所定の基準流入量より小さいときは前記フィードフォワード操作量を減少させるための補正係数を求める補正係数演算要素と、前記フィードフォワード操作量と前記補正係数とを掛け合わせて前記フィードフォワード操作量を補正する乗算器とを更に有していてよい。この構成によれば、原水アンモニア態窒素濃度の変化に基づいて予測される曝気風量の増加量がフィードフォワード操作量として算出され、これを操作量に付加することができる。そして、フィードフォワード操作量を補正係数で補正することにより、処理槽に流入する原水の量に応じて操作量が変化するので、曝気風量を抑えつつ、被処理水中の有機物の処理を確実に行うことができる。
In the aeration air amount calculation device and the water treatment system, the calculation means generates a feedforward operation amount based on a raw water ammonia nitrogen concentration that is an ammonia nitrogen concentration of raw water flowing into the treatment tank. An arithmetic element; and an adder that adds the feedforward manipulated variable and the feedback manipulated variable. The adder is configured to calculate the manipulated variable based on the feedback manipulated variable and the feedforward manipulated variable. It is desirable that Here, the calculation means increases the feedforward operation amount when the raw water inflow amount, which is the inflow amount of the raw water flowing into the treatment tank, is larger than a predetermined reference inflow amount, and the raw water inflow amount is the predetermined amount. The feedforward manipulated variable is corrected by multiplying the correction coefficient calculation element for obtaining a correction coefficient for decreasing the feedforward manipulated variable, the feedforward manipulated variable and the correction coefficient. And a multiplier. According to this configuration, the amount of increase in the aeration air predicted based on the change in the raw water ammonia nitrogen concentration is calculated as the feedforward manipulated variable, and this can be added to the manipulated variable. Then, by correcting the feedforward manipulated variable with the correction coefficient, the manipulated variable changes according to the amount of raw water flowing into the treatment tank, so that the organic matter in the treated water is reliably treated while suppressing the aeration air volume. be able to.
本発明によれば、処理槽出口NH4-N濃度の目標値は、処理槽入口のNH4-N濃度の変化に応じて変化し、且つ、処理槽入口のNH4-N濃度及び処理槽出口NH4-N濃度より常に低い値となる。よって、曝気風量を抑えつつ、曝気が継続的に行われることにより、被処理水中の有機物の処理を確実に行うことができる。
According to the present invention, the target value of the processing tank outlet NH 4 -N concentration changes according to the change of NH 4 -N concentration of the treatment tank inlet, and, NH 4 -N concentration and the treatment tank of the processing tank inlet The value is always lower than the outlet NH 4 -N concentration. Therefore, it is possible to reliably perform the treatment of the organic matter in the water to be treated by continuously performing aeration while suppressing the amount of aeration air.
本発明に係る水処理システムは、下水などの被処理水を活性汚泥法を用いて浄化する生物処理槽(以下、単に「処理槽」という)を備えた水処理システムに適用される。そして、本発明に係る曝気風量演算装置は、上記処理槽において被処理水を処理するために好適な曝気風量を演算するためのものであり、水処理システムに付随していてもよいし、水処理システムから独立した演算装置として構成されていてもよい。以下、図面を参照して本発明の第1及び第2実施形態を説明する。
The water treatment system according to the present invention is applied to a water treatment system including a biological treatment tank (hereinafter simply referred to as “treatment tank”) for purifying treated water such as sewage using an activated sludge method. The aeration air volume calculating device according to the present invention is for calculating an aeration air volume suitable for treating the water to be treated in the treatment tank, and may be attached to the water treatment system, You may be comprised as an arithmetic unit independent of a processing system. Hereinafter, first and second embodiments of the present invention will be described with reference to the drawings.
[第1実施形態]
図1は本発明の第1実施形態に係る水処理システム10の全体的な構成を示す図である。図1に示されるように、本発明の第1実施形態に係る水処理システム10は、活性汚泥法のうち嫌気好気法(AO法)により下水を浄化する水処理プロセスを実現するシステムである。水処理システム10は、原水槽2と、嫌気槽31及び好気槽32から成る処理槽3と、沈殿槽4と、好気槽32の曝気風量を演算する曝気風量演算装置65と、水処理システム10の運転を司る制御装置6とを備えている。 [First Embodiment]
FIG. 1 is a diagram showing an overall configuration of awater treatment system 10 according to the first embodiment of the present invention. As shown in FIG. 1, the water treatment system 10 according to the first embodiment of the present invention is a system that realizes a water treatment process that purifies sewage by an anaerobic aerobic method (AO method) among activated sludge methods. . The water treatment system 10 includes a raw water tank 2, a treatment tank 3 including an anaerobic tank 31 and an aerobic tank 32, a precipitation tank 4, an aeration air volume calculating device 65 that calculates the aeration air volume of the aerobic tank 32, And a control device 6 that controls the operation of the system 10.
図1は本発明の第1実施形態に係る水処理システム10の全体的な構成を示す図である。図1に示されるように、本発明の第1実施形態に係る水処理システム10は、活性汚泥法のうち嫌気好気法(AO法)により下水を浄化する水処理プロセスを実現するシステムである。水処理システム10は、原水槽2と、嫌気槽31及び好気槽32から成る処理槽3と、沈殿槽4と、好気槽32の曝気風量を演算する曝気風量演算装置65と、水処理システム10の運転を司る制御装置6とを備えている。 [First Embodiment]
FIG. 1 is a diagram showing an overall configuration of a
原水槽2には、流入した下水が一時的に貯えられている。原水槽2の出口は、配管52によって嫌気槽31の入口と接続されている。配管52には、原水槽2に貯えられた原水を嫌気槽31へ圧送する供給ポンプ51が設けられている。原水槽2から処理槽3への原水の流入量は、供給ポンプ51の吐出流量である。
The raw water tank 2 temporarily stores the inflowing sewage. The outlet of the raw water tank 2 is connected to the inlet of the anaerobic tank 31 by a pipe 52. The pipe 52 is provided with a supply pump 51 that pumps the raw water stored in the raw water tank 2 to the anaerobic tank 31. The amount of raw water flowing from the raw water tank 2 into the treatment tank 3 is the discharge flow rate of the supply pump 51. *
処理槽3には、上流側から順に嫌気槽31、好気槽32が設けられている。本実施の形態において、嫌気槽31及び好気槽32は一つの処理槽3を隔壁で仕切ることにより形成されており、嫌気槽31と好気槽32とは隔壁に形成された開口によって連通されている。但し、嫌気槽31と好気槽32とが各々独立した処理槽であってもよい。
The treatment tank 3 is provided with an anaerobic tank 31 and an aerobic tank 32 in order from the upstream side. In the present embodiment, the anaerobic tank 31 and the aerobic tank 32 are formed by partitioning one processing tank 3 by a partition, and the anaerobic tank 31 and the aerobic tank 32 are communicated by an opening formed in the partition. ing. However, the anaerobic tank 31 and the aerobic tank 32 may be independent processing tanks.
好気槽32には、被処理水を曝気するための散気装置9が設けられている。散気装置9は、好気槽32の底部に配置されたノズル91と、ノズル91へ空気を圧送する散気ブロワ92とを備えている。この散気装置9により、好気槽32の底部から被処理水に微細気泡が吹き込まれる。好気槽32に吹き込まれた気泡の上昇により被処理水が攪拌されるとともに、被処理水が曝気されて被処理水の溶存酸素量が高められる。散気ブロワ92の送風量(以下、「曝気風量」という)は、制御装置6からの操作信号に基づいて制御される。
The aerobic tank 32 is provided with an air diffuser 9 for aeration of water to be treated. The air diffuser 9 includes a nozzle 91 disposed at the bottom of the aerobic tank 32 and an air diffuser 92 that pumps air to the nozzle 91. By the air diffuser 9, fine bubbles are blown into the water to be treated from the bottom of the aerobic tank 32. The treated water is agitated by the rising of the bubbles blown into the aerobic tank 32, and the treated water is aerated to increase the amount of dissolved oxygen in the treated water. The amount of air blown by the diffuser blower 92 (hereinafter referred to as “aeration air amount”) is controlled based on an operation signal from the control device 6.
好気槽32と沈殿槽4とは配管53で接続されており、好気槽32の処理水が配管53を通じて沈殿槽4へ流入する。沈殿槽4の底部と嫌気槽31の底部とは汚泥返送配管55で接続されており、この汚泥返送配管55を通じて、沈殿槽4で沈殿した汚泥が嫌気槽31へ返送される。汚泥返送配管55には返送ポンプ56が設けられている。嫌気槽31へ返送される汚泥(返送汚泥)の量は、返送ポンプ56の吐出流量である。
The aerobic tank 32 and the precipitation tank 4 are connected by a pipe 53, and treated water in the aerobic tank 32 flows into the precipitation tank 4 through the pipe 53. The bottom of the settling tank 4 and the bottom of the anaerobic tank 31 are connected by a sludge return pipe 55, and the sludge precipitated in the settling tank 4 is returned to the anaerobic tank 31 through the sludge return pipe 55. The sludge return pipe 55 is provided with a return pump 56. The amount of sludge (returned sludge) returned to the anaerobic tank 31 is the discharge flow rate of the return pump 56.
原水槽2の出口近傍には、原水槽2から一連の処理槽3へ流入する原水のNH4-N濃度を計測する原水NH4-N濃度計61が設けられている。但し、原水NH4-N濃度計61は、原水のNH4-N濃度を計測できればよいので、原水槽2に限定されず、処理槽3の前段に最初沈澱池が設定されている場合には最初沈澱池や、最初沈澱池又は原水槽2と処理槽3との共通水路を形成する配管52などに設けられていてもよい。また、好気槽32の出口近傍には、好気槽32から流出する処理液のNH4-N濃度である処理槽出口NH4-N濃度(以下、単に「出口NH4-N濃度」という)を計測する処理槽出口NH4-N濃度計62が設けられている。これらのNH4-N濃度計61,62は制御装置6と接続されており、各NH4-N濃度計61,62から制御装置6へ計測値が出力される。
In the vicinity of the outlet of the raw water tank 2, a raw water NH 4 -N concentration meter 61 for measuring the NH 4 -N concentration of the raw water flowing from the raw water tank 2 into the series of treatment tanks 3 is provided. However, the raw water NH 4 -N concentration meter 61 is not limited to the raw water tank 2 as long as it can measure the NH 4 -N concentration of the raw water, and when the first settling basin is set in the previous stage of the treatment tank 3 It may be provided in the first sedimentation basin, the first sedimentation basin, or the pipe 52 that forms a common water channel between the raw water tank 2 and the treatment tank 3. Further, in the vicinity of the outlet of the aerobic tank 32, a treatment tank outlet NH 4 -N concentration (hereinafter simply referred to as “outlet NH 4 -N concentration”) that is the NH 4 -N concentration of the treatment liquid flowing out of the aerobic tank 32. ) Is measured, and a treatment tank outlet NH 4 -N concentration meter 62 is provided. These NH 4 - N concentration meters 61 and 62 are connected to the control device 6, and the measured values are output from the NH 4 - N concentration meters 61 and 62 to the control device 6.
図2は水処理システム10の制御構成を示すブロック図である。制御装置6は、原水NH4-N濃度計61及び処理槽出口NH4-N濃度計62の計測値に基づいて、供給ポンプ51、返送ポンプ56、及び散気装置9の動作を制御する。また、制御装置6には、散気装置9の曝気風量(操作量)を演算する曝気風量演算装置65が通信可能に接続されており、制御装置6は曝気風量演算装置65で算出された曝気風量に基づいて散気装置9へ制御信号を出力する。つまり、制御装置6は曝気風量制御装置としての機能を有している。
FIG. 2 is a block diagram showing a control configuration of the water treatment system 10. The control device 6 controls the operations of the supply pump 51, the return pump 56, and the air diffuser 9 based on the measured values of the raw water NH 4 -N concentration meter 61 and the treatment tank outlet NH 4 -N concentration meter 62. Further, an aeration air amount calculation device 65 for calculating the aeration air amount (operation amount) of the aeration device 9 is communicably connected to the control device 6, and the control device 6 performs the aeration calculated by the aeration air amount calculation device 65. A control signal is output to the air diffuser 9 based on the air volume. That is, the control device 6 has a function as an aeration air volume control device.
制御装置6と曝気風量演算装置65は、所謂コンピュータで構成されている。制御装置6と曝気風量演算装置65の各々は、CPU(Central Processing Unit)の他、ROM(Read Only Memory)、RAM(Random Access Memory)、I/F(Interface)、I/O(Input/output Port)等を有している(いずれも図示せず)。ROMには、CPUが実行するプログラム、各種固定データ等が記憶されている。CPUが実行するプログラムは、フレキシブルディスク、CD-ROM、メモリカード等の各種記憶媒体に保存されており、これらの記憶媒体からROMにインストールされる。RAMには、プログラム実行時に必要なデータが一時的に記憶される。I/Fは、外部装置(例えば、図示されない入力装置や記憶装置)とのデータ送受信を行う。I/Oは、各種センサの検出信号の入力/出力を行う。制御装置6と曝気風量演算装置65では、ROMに記憶されたプログラム等のソフトウェアとCPU等のハードウェアとが協働することにより、各々の機能を実現する処理を行うように構成されている。なお、本実施形態に係る水処理システム10は、制御装置6と曝気風量演算装置65との複数のコンピュータを備えているが、これらが単一のコンピュータに構成されていてもよい。曝気風量演算装置65については、後ほど詳述する。
The control device 6 and the aeration air volume calculation device 65 are so-called computers. Each of the control device 6 and the aeration air amount calculating device 65 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an I / F (Interface), and an I / O (Input / output). Port) and the like (none of them are shown). The ROM stores programs executed by the CPU, various fixed data, and the like. Programs executed by the CPU are stored in various storage media such as a flexible disk, a CD-ROM, and a memory card, and are installed in the ROM from these storage media. The RAM temporarily stores data necessary for program execution. The I / F performs data transmission / reception with an external device (for example, an input device or storage device not shown). I / O inputs / outputs detection signals of various sensors. The control device 6 and the aeration air amount calculation device 65 are configured to perform processing for realizing each function by cooperation of software such as a program stored in the ROM and hardware such as a CPU. In addition, although the water treatment system 10 which concerns on this embodiment is provided with the some computer of the control apparatus 6 and the aeration air volume calculating apparatus 65, these may be comprised by the single computer. The aeration air volume calculation device 65 will be described in detail later.
続いて、上記構成の水処理システム10による水処理プロセスについて説明する。この水処理プロセスでは、原水に含まれる有機物、窒素(NH4-Nと有機態窒素)、及びリン等の除去が行われる。
Then, the water treatment process by the water treatment system 10 of the said structure is demonstrated. In this water treatment process, organic substances, nitrogen (NH 4 —N and organic nitrogen), phosphorus, etc. contained in the raw water are removed.
原水槽2に貯えられた原水は、供給ポンプ51の稼働により配管52を通じて嫌気槽31へ送られる。嫌気槽31に流入した原水(被処理水)は、活性汚泥と混ぜ合わされる。嫌気槽31の活性汚泥中のリン蓄積細菌は、被処理水中の有機物を体内に取り込んで、体内に保持していたリン酸(PO4)を放出する。嫌気槽31の被処理水は、隔壁の開口を通じて好気槽32へ流入する。
The raw water stored in the raw water tank 2 is sent to the anaerobic tank 31 through the pipe 52 by the operation of the supply pump 51. The raw water (treated water) flowing into the anaerobic tank 31 is mixed with activated sludge. Phosphorus-accumulating bacteria in the activated sludge in the anaerobic tank 31 take in organic substances in the treated water into the body and release phosphoric acid (PO 4 ) retained in the body. The water to be treated in the anaerobic tank 31 flows into the aerobic tank 32 through the opening of the partition wall.
好気槽32では、活性汚泥に含まれる従属栄養生物が酸素を取り込み、有機物を分解する。また、好気槽32では、好気条件下でリンを過剰摂取するリン蓄積細菌が、嫌気槽31で放出された以上のリン酸態のリンを取り込む。好気槽32では、被処理水中のNH4-Nが酸化されて亜硝酸態窒素(NO2-N)、硝酸態窒素(NO3-N)となる。好気槽32の処理液は、沈殿槽4へ流入する。沈殿槽4へ流入した処理液は、処理液中の汚泥が沈殿して処理液と汚泥とに分離される。汚泥は、汚泥返送配管55を通じて嫌気槽31へ返送される。
In the aerobic tank 32, heterotrophic organisms contained in the activated sludge take in oxygen and decompose organic substances. Further, in the aerobic tank 32, phosphorus accumulating bacteria that excessively ingest phosphorus under aerobic conditions take in more phosphoric acid phosphorus released in the anaerobic tank 31. In the aerobic tank 32, NH 4 —N in the water to be treated is oxidized into nitrite nitrogen (NO 2 —N) and nitrate nitrogen (NO 3 —N). The treatment liquid in the aerobic tank 32 flows into the precipitation tank 4. The processing liquid that has flowed into the settling tank 4 is separated into the processing liquid and the sludge as the sludge in the processing liquid is precipitated. The sludge is returned to the anaerobic tank 31 through the sludge return pipe 55.
ここで、曝気風量演算装置65について詳細に説明する。曝気風量演算装置65は、演算に必要な情報(変数)を制御装置6より取得する取得部66と、散気装置9の曝気風量(操作量)を演算する演算部67と、算出された曝気風量を制御装置6へ出力する出力部68とを備えている。
Here, the aeration air volume calculation device 65 will be described in detail. The aeration air amount calculation device 65 includes an acquisition unit 66 that acquires information (variables) necessary for calculation from the control device 6, a calculation unit 67 that calculates the aeration air amount (operation amount) of the aeration device 9, and the calculated aeration And an output unit 68 that outputs the air volume to the control device 6.
取得部66が取得する情報には、処理槽3へ流入する原水のNH4-N濃度である原水NH4-N濃度XRW、処理槽3へ流入する原水の流入量である原水流入量u、処理槽3で処理された処理水のNH4-N濃度である出口NH4-N濃度Xout、及び処理水から分離されて処理槽3へ戻される汚泥の流量である循環流量fなどが含まれる。原水NH4-N濃度XRWは原水NH4-N濃度計61の測定値であり、原水流入量uは供給ポンプ51の吐出流量であり、出口NH4-N濃度Xoutは処理槽出口NH4-N濃度計62の測定値であり、循環流量fは返送ポンプ56の吐出流量である。なお、曝気風量演算装置65が制御装置6を介してこれらの情報を取得するように記載されているが、曝気風量演算装置65が計器類から直接的に情報を取得するように構成されていてもよい。
Information acquired by the acquisition unit 66 includes raw water NH 4 -N concentration X RW that is the NH 4 -N concentration of raw water flowing into the treatment tank 3, and raw water inflow amount u that is the amount of raw water flowing into the treatment tank 3. , NH 4 -N concentration at which the outlet NH 4 -N concentration X out of the treated water which has been processed in the processing vessel 3, and the like circulation flow rate f is the flow rate of sludge to be returned are separated to the treatment tank 3 from the treated water included. The raw water NH 4 -N concentration X RW is a measurement value of the raw water NH 4 -N concentration meter 61, the raw water inflow u is the discharge flow rate of the supply pump 51, and the outlet NH 4 -N concentration X out is the treatment tank outlet NH. The measured value of the 4- N densitometer 62, and the circulation flow rate f is the discharge flow rate of the return pump 56. In addition, although it describes that the aeration air volume calculating apparatus 65 acquires these information via the control apparatus 6, it is comprised so that the aeration air volume calculating apparatus 65 may acquire information directly from instruments. Also good.
図3は、演算部67で行われる演算処理の信号の流れを示すブロック線図である。図3に示すように、演算部67は、原水NH4-N濃度XRWに基づいてフィードフォワード操作量(以下、「FF操作量YF」という)を生成するフィードフォワード制御系(以下、「FF制御系7」という)と、出口NH4-N濃度Xoutを制御量としてフィードバック操作量(以下、「FB操作量YB」という)を生成するフィードバック制御系(以下、「FB制御系8」という)を備えている。FF制御系7とFB制御系8は協動して機能し、FF制御系7により生成されたFF操作量YFと、FB制御系8により生成されたFB操作量YBとが加算器85で加算されて、操作量Yが生成される。この操作量Yは散気装置9の曝気風量を表している。出力部68は、演算部67で算出された操作量Yの操作量信号を散気装置9へ出力し、散気装置9ではこの操作量Yと対応する曝気風量で散気ブロワ92が動作する。以下では、FF制御系7とFB制御系8について詳細に説明する。
FIG. 3 is a block diagram showing a signal flow of the arithmetic processing performed in the arithmetic unit 67. As shown in FIG. 3, the computing unit 67 generates a feedforward manipulated variable (hereinafter referred to as “FF manipulated variable Y F ”) based on the raw water NH 4 —N concentration X RW (hereinafter referred to as “FF manipulated variable Y F ”). FF control system 7 ") and a feedback control system (hereinafter referred to as" FB control system 8 ") that generates a feedback manipulated variable (hereinafter referred to as" FB manipulated variable Y B ") using the outlet NH 4 -N concentration X out as a controlled variable. "). The FF control system 7 and the FB control system 8 function in cooperation, and the FF operation amount Y F generated by the FF control system 7 and the FB operation amount Y B generated by the FB control system 8 are added by the adder 85. Is added to generate an operation amount Y. This manipulated variable Y represents the aeration air volume of the air diffuser 9. The output unit 68 outputs the manipulated variable signal of the manipulated variable Y calculated by the computing unit 67 to the diffuser 9, and the diffuser 9 operates the diffuser blower 92 with the aeration air volume corresponding to the manipulated variable Y. . Hereinafter, the FF control system 7 and the FB control system 8 will be described in detail.
まず、FF制御系7について詳細に説明する。FF制御系7は、FF操作量演算要素71と、無駄時間要素73と、フィードフォワードゲイン要素74と、FF操作量補正係数演算要素72と、乗算器75とを含んでいる。FF制御系7では、原水NH4-N濃度XRWの変化に基づいて予測される曝気風量の増加量がFF操作量YFとして算出される。
First, the FF control system 7 will be described in detail. The FF control system 7 includes an FF manipulated variable computing element 71, a dead time element 73, a feed forward gain element 74, an FF manipulated variable correction coefficient computing element 72, and a multiplier 75. In the FF control system 7, the increase amount of the aeration air amount predicted based on the change in the raw water NH 4 -N concentration X RW is calculated as the FF manipulated variable Y F.
FF操作量演算要素71は、原水NH4-N濃度XRWからFF操作量YFを算出するFF操作量関数F1である。FF操作量関数F1は、入力値である原水NH4-N濃度XRWと出力値であるFF操作量YFとの静特性の関係を関数化したものである。FF操作量関数F1は、水処理システム10全体の処理能力や使用環境等から影響を受けるため、各々の水処理システム10毎に設定されることが好ましい。FF操作量関数F1は、実験結果に基づいて定められてもよいし、また、シミュレーションに基づいて定められてもよい。
The FF manipulated variable calculation element 71 is an FF manipulated variable function F 1 that calculates the FF manipulated variable Y F from the raw water NH 4 -N concentration X RW . The FF manipulated variable function F 1 is a function of the static characteristic relationship between the raw water NH 4 -N concentration X RW as an input value and the FF manipulated variable Y F as an output value. The FF manipulated variable function F 1 is preferably set for each water treatment system 10 because it is affected by the treatment capacity of the entire water treatment system 10 and the usage environment. The FF manipulated variable function F 1 may be determined based on experimental results or may be determined based on simulation.
図4はFF操作量関数F1の特性を示す図表であって、縦軸はFF操作量YF(L/min)を示し、横軸は原水NH4-N濃度XRW(mg/L)を示している。FF操作量YF(L/min)は、FF制御系7により算出された曝気風量を表している。曝気風量の最低風量y0は、システム全体を維持するために最低限必要な風量である。システム全体を維持するために最低限必要な風量とは、好気槽32中の汚泥を攪拌し、好気槽32の好気的条件のもとで炭素系有機物を利用して増殖する従属栄養生物、NH4-Nを硝化する硝化細菌などの活性汚泥微生物が生体を維持するために必要な酸素を提供する、最低限の曝気風量である。最低風量y0は、好気槽32の活性汚泥微生物の数や好気槽32の容量に応じて適宜定められる。なお、曝気風量が最低風量y0で運転されているときには、好気槽32の被処理水の溶存酸素濃度はほぼ0となる。
Figure 4 is a table showing the characteristics of the FF operation amount function F 1, the ordinate indicates the FF operation amount Y F (L / min), the horizontal axis represents the raw water NH 4 -N concentration X RW (mg / L) Is shown. The FF manipulated variable Y F (L / min) represents the aeration air volume calculated by the FF control system 7. The minimum air volume y 0 of the aeration air volume is the minimum air volume necessary for maintaining the entire system. The minimum amount of air required to maintain the entire system is heterotrophic that agitate sludge in the aerobic tank 32 and grows using carbon-based organic matter under aerobic conditions in the aerobic tank 32. This is the minimum aeration volume that provides oxygen necessary for the living sludge microorganisms such as nitrifying bacteria to nitrify living organisms, NH 4 -N, to maintain the living body. The minimum air volume y 0 is appropriately determined according to the number of activated sludge microorganisms in the aerobic tank 32 and the capacity of the aerobic tank 32. Note that when the aeration air volume is operated at the minimum air volume y 0 , the dissolved oxygen concentration of the water to be treated in the aerobic tank 32 becomes almost zero.
図4の図表に示されるように、原水NH4-N濃度XRWが0から第1濃度x1までの範囲において、FF操作量YFは最低風量y0で一定である。この第1濃度x1は、曝気風量が最低風量y0であるときに、出口NH4-N濃度Xoutが処理水のNH4-N濃度の基準目標値XB以下となる最大の原水NH4-N濃度XRWである。なお、処理水のNH4-N濃度の基準目標値XBは、環境規制値などに基づいて適宜定められ、予め曝気風量演算装置65に設定されている。そして、原水NH4-N濃度XRWが第1濃度x1以上の範囲において、FF操作量YFは原水NH4-N濃度XRWの増加に伴って増加する。
As shown in the chart of FIG. 4, when the raw water NH 4 -N concentration X RW is in the range from 0 to the first concentration x 1 , the FF manipulated variable Y F is constant at the minimum air flow y 0 . This first concentration x 1 is the maximum raw water NH at which the outlet NH 4 -N concentration X out is equal to or less than the reference target value X B of the NH 4 -N concentration of the treated water when the aeration air volume is the minimum air volume y 0. 4 -N concentration XRW . The reference target value X B of the NH 4 —N concentration of the treated water is determined as appropriate based on the environmental regulation value and the like, and is set in advance in the aeration air amount calculation device 65. In the range where the raw water NH 4 -N concentration X RW is not less than the first concentration x 1 , the FF manipulated variable Y F increases as the raw water NH 4 -N concentration X RW increases.
上記FF操作量YFに動特性を付加するために、FF操作量演算要素71で生成されたFF操作量YFは無駄時間要素73とフィードフォワードゲイン要素74により調整される。無駄時間(シフト時間とも呼ばれる)は、原則として、原水NH4-N濃度計61でNH4-N濃度が計測された原水が、嫌気槽31へ流入してから、好気槽32へ流入するまでに要する時間である。但し、好気槽32においてNH4-Nを硝化する硝化細菌の増殖速度は、通常の活性汚泥中にいる従属栄養細菌より遅いので、被処理水のNH4-N濃度の不連続面が好気槽32に到達するよりも前に曝気風量を増加させ、その不連続面が好気槽32に到達したときにはNH4-N濃度の急激な増加に対応しうるように活性汚泥微生物を活性化させておくことが望ましい。つまり、無駄時間は、原水NH4-N濃度計61でNH4-N濃度が計測された原水が好気槽32に流入するまでに要する時間よりも短い時間に設定されることが望ましい。このような無駄時間は、嫌気槽31へ流入してから好気槽32へ流入するまでの滞留時間を含めた時間として、実験的又は計算的に求めることができる。フィードフォワードゲインKfは、FF操作量関数F1の入力値である原水NH4-N濃度XRWの変化量と出力値であるFF操作量YFの変化量の比であり、適宜設定される。
To add dynamics to the FF operation amount Y F, FF manipulated variable Y F generated by the FF operation amount calculation element 71 is adjusted by dead time element 73 and the feed-forward gain element 74. In principle, the dead time (also referred to as shift time) is that the raw water whose NH 4 -N concentration is measured by the raw water NH 4 -N concentration meter 61 flows into the anaerobic tank 31 and then flows into the aerobic tank 32. It takes time to complete. However, since the growth rate of nitrifying bacteria that nitrify NH 4 -N in the aerobic tank 32 is slower than that of heterotrophic bacteria in normal activated sludge, the discontinuous surface of the NH 4 -N concentration of the treated water is preferred. The aeration air volume is increased before reaching the air tank 32, and when the discontinuous surface reaches the aerobic tank 32, the activated sludge microorganisms are activated so as to cope with a rapid increase in NH 4 -N concentration. It is desirable to keep it. That is, the dead time is preferably set to a time shorter than the time required for the raw water whose NH 4 —N concentration is measured by the raw water NH 4 —N concentration meter 61 to flow into the aerobic tank 32. Such dead time can be obtained experimentally or computationally as a time including a residence time from flowing into the anaerobic tank 31 to flowing into the aerobic tank 32. Feedforward gain K f is the ratio of the FF operation amount Y F variation is a change amount of the output value of the input value of the FF operation amount function F 1 raw water NH 4 -N concentration X RW, is set appropriately The
無駄時間要素73とフィードフォワードゲイン要素74により調整されたFF操作量YFは、更に補正係数αで補正される。補正係数αは、原水流入量uに基づいてFF操作量YFを補正するためのものである。
The FF manipulated variable Y F adjusted by the dead time element 73 and the feedforward gain element 74 is further corrected by the correction coefficient α. The correction coefficient α is for correcting the FF manipulated variable Y F based on the raw water inflow amount u.
補正係数αは、FF操作量補正係数演算要素72において、入力値である原水流入量uと出力値である補正係数αの関係を関数化したFF操作量補正関数F2を用いて算出される。補正係数αは、原水流入量uが所定の基準流入量U1より大きいときにFF操作量YFを増加させ、また、処理槽3への原水流入量uが所定の基準流入量U1より小さいときにFF操作量YFを減少させるような補正係数である。
The correction coefficient α is calculated in the FF manipulated variable correction coefficient computing element 72 using an FF manipulated variable correction function F 2 that is a function of the relationship between the raw water inflow u as an input value and the correction coefficient α as an output value. . The correction coefficient α increases the FF manipulated variable Y F when the raw water inflow u is larger than the predetermined reference inflow U 1 , and the raw water inflow u to the treatment tank 3 is greater than the predetermined reference inflow U 1 . It is a correction coefficient that reduces the FF manipulated variable Y F when it is small.
図5は、FF操作量補正関数F2の特性を示す図表であって、縦軸は補正係数αを示し、横軸は原水流入量u(L/min)を示している。図5の図表に示されるように、原水流入量uが0のときに、補正係数αは1よりも小さいα1である(F2(0)=α1,α1<1)。原水流入量uが基準流入量U1のときに、補正係数αは1である(F2(U1)=1)。原水流入量uが最大流入量U2のときに、補正係数αは1よりも大きいα2である(F2(U2)=α2,α2>1)。このように、補正係数αは、原水流入量uの増加に伴って、原水流入量uが基準流入量U1のときを1として、1より小さいα1から1より大きいα2まで増加する。補正係数αの好適な一例として、α1=0.5とし、α2=1.5とすることができる。なお、原水流入量uの基準流入量U1は水処理システム10の処理能力により定まり、最大流入量U2は水処理システム10の処理能力に加えて供給ポンプ51の能力により定まる。
Figure 5 is a table showing the characteristics of the FF manipulated variable correction function F 2, the vertical axis represents the correction coefficient alpha, the horizontal axis represents the raw water inflow u (L / min). As shown in the chart of FIG. 5, when the raw water inflow u is 0, the correction coefficient α is α1 smaller than 1 (F 2 (0) = α1, α1 <1). When raw water inflow u is the reference inflow U 1, the correction coefficient α is 1 (F 2 (U 1) = 1). When the raw water inflow u is the maximum inflow U 2 , the correction coefficient α is α2 larger than 1 (F 2 (U 2 ) = α2, α2> 1). As described above, the correction coefficient α increases from α1 smaller than 1 to α2 larger than 1, with the raw water inflow u being equal to the reference inflow U 1 as the raw water inflow u increases. As a preferred example of the correction coefficient α, α1 = 0.5 and α2 = 1.5. The reference inflow U 1 of the raw water inflow u is determined by the treatment capacity of the water treatment system 10, and the maximum inflow U 2 is determined by the capacity of the supply pump 51 in addition to the treatment capacity of the water treatment system 10.
上記のように算出された補正係数αとFF操作量YFとが乗算器75で掛け合わされることにより、FF操作量YFが補正される。補正されたFF操作量YFは加算器85へ出力される。
By multiplying the correction coefficient α calculated as described above and the FF manipulated variable Y F by the multiplier 75, the FF manipulated variable Y F is corrected. The corrected FF manipulated variable Y F is output to the adder 85.
続いて、FB制御系8について詳細に説明する。FB制御系8は、出口NH4-N濃度Xout(制御値)と処理水のNH4-N濃度の目標値XDVとの偏差を算出する減算器83と、この偏差からFB操作量YBを生成するFB操作量演算要素84とを含んでいる。FB操作量YBはFB制御系8により算出された曝気風量を表している。本実施形態に係るFB操作量演算要素84はPID制御方法を用いてFB操作量YBを算出する。但し、FB操作量演算要素84は、例えば、PID制御方法、P制御方法又はPI制御方法を用いてFB操作量YBを算出する演算要素であってよい。算出されたFB操作量YBは、加算器85に入力される。
Next, the FB control system 8 will be described in detail. The FB control system 8 includes a subtractor 83 that calculates a deviation between the outlet NH 4 -N concentration X out (control value) and the NH 4 -N concentration target value X DV of the treated water, and the FB manipulated variable Y from this deviation. And an FB manipulated variable calculating element 84 for generating B. The FB operation amount Y B represents the aeration air amount calculated by the FB control system 8. The FB operation amount calculation element 84 according to the present embodiment calculates the FB operation amount Y B using the PID control method. However, the FB operation amount calculation element 84 may be a calculation element that calculates the FB operation amount Y B using, for example, a PID control method, a P control method, or a PI control method. The calculated FB operation amount Y B is input to the adder 85.
FB制御系8は、更に、目標値XDVを算出するために、目標値演算要素81と、ローセレクタ82とを備えている。目標値演算要素81は、原水NH4-N濃度XRW、原水流入量u、出口NH4-N濃度Xout、及び循環流量fから目標値XDVを算出する目標値関数F3である。目標値関数F3は、入力値である原水NH4-N濃度XRW、原水流入量u、出口NH4-N濃度Xout、及び循環流量fと、出力値である目標値XDVとの関係を関数化したものである。出口NH4-N濃度Xoutは、処理槽出口NH4-N濃度計62で測定された処理槽3の出口のNH4-N濃度である。また、循環流量fは、処理水から分離されて処理槽3へ戻される汚泥の流量である。
The FB control system 8 further includes a target value calculation element 81 and a low selector 82 in order to calculate the target value X DV . The target value calculation element 81 is a target value function F 3 for calculating the target value X DV from the raw water NH 4 -N concentration X RW , the raw water inflow u, the outlet NH 4 -N concentration X out , and the circulating flow rate f. The target value function F 3 includes the input values of raw water NH 4 -N concentration X RW , raw water inflow u, outlet NH 4 -N concentration X out , circulation flow rate f, and output value of target value X DV . It is a functionalized relationship. The outlet NH 4 -N concentration X out is the NH 4 -N concentration at the outlet of the processing tank 3 measured by the processing tank outlet NH 4 -N concentration meter 62. The circulation flow rate f is a flow rate of sludge separated from the treated water and returned to the treatment tank 3.
目標値関数F3で算出される目標値XDVは、処理槽3の入口のNH4-N濃度(以下、「入口NH4-N濃度Xin」という)から所定値(k)だけ小さい値である。但し、目標値XDVは、処理槽3の入口のNH4-N濃度から所定割合(1-β)だけ小さい値であってもよい。なお、処理槽3の入口とは、処理槽3のうち原水及び返送汚泥が流入する領域であって、嫌気槽31の上流側領域を言うこととする。
The target value X DV calculated by the target value function F 3 is a value smaller by a predetermined value (k) than the NH 4 -N concentration at the inlet of the processing tank 3 (hereinafter referred to as “inlet NH 4 -N concentration X in ”). It is. However, the target value X DV may be a value that is smaller by a predetermined ratio (1-β) than the NH 4 -N concentration at the inlet of the processing tank 3. The inlet of the treatment tank 3 is an area into which raw water and return sludge flow in the treatment tank 3 and refers to an upstream area of the anaerobic tank 31.
例えば、目標値関数F3は次に示す[式1]又は[式2]で表される。また、入口NH4-N濃度Xinは次に示す[式3]で算出することができる。
[式1] F3(Xin)=Xin-k
[式2] F3(Xin)=Xin×β
[式3] Xin=(XRW×u+Xout×f)/(u+f)
上記式1においてk[mg/L]は0より大きい定数であり、例えば、2~10[mg/L]の範囲から選択された値が好適である。また、上記式2においてβは0より大きく1より小さい定数であり、例えば、0.6~0.9が好適である。上記式1におけるk、又は、上記式2におけるβは、実験に基づいて決定されることが望ましい。以下では、k又はβの決定方法の一例について説明する。 For example, represented by a target value function F 3 is shown below [Formula 1] or [Equation 2]. Further, the inlet NH 4 -N concentration X in can be calculated by the following [Equation 3].
[Formula 1] F 3 (X in ) = X in −k
[Formula 2] F 3 (X in ) = X in × β
[Formula 3] Xin = ( XRW * u + Xout * f) / (u + f)
In the above formula 1, k [mg / L] is a constant larger than 0. For example, a value selected from the range of 2 to 10 [mg / L] is preferable. In theabove formula 2, β is a constant larger than 0 and smaller than 1, for example, 0.6 to 0.9 is preferable. It is desirable that k in the above formula 1 or β in the above formula 2 is determined based on experiments. Below, an example of the determination method of k or (beta) is demonstrated.
[式1] F3(Xin)=Xin-k
[式2] F3(Xin)=Xin×β
[式3] Xin=(XRW×u+Xout×f)/(u+f)
上記式1においてk[mg/L]は0より大きい定数であり、例えば、2~10[mg/L]の範囲から選択された値が好適である。また、上記式2においてβは0より大きく1より小さい定数であり、例えば、0.6~0.9が好適である。上記式1におけるk、又は、上記式2におけるβは、実験に基づいて決定されることが望ましい。以下では、k又はβの決定方法の一例について説明する。 For example, represented by a target value function F 3 is shown below [Formula 1] or [Equation 2]. Further, the inlet NH 4 -N concentration X in can be calculated by the following [Equation 3].
[Formula 1] F 3 (X in ) = X in −k
[Formula 2] F 3 (X in ) = X in × β
[Formula 3] Xin = ( XRW * u + Xout * f) / (u + f)
In the above formula 1, k [mg / L] is a constant larger than 0. For example, a value selected from the range of 2 to 10 [mg / L] is preferable. In the
前述の通り、図14に示す実験結果から、被処理水A,BのCODがこれ以上曝気を続けても殆ど変化しなくなる処理時間TC1,TC2における、処理開始時からの被処理水A,BのNH4-N濃度の変化量ΔX1,ΔX2は、被処理水の水質に関わらずほぼ一定であることが分かっている。そして、被処理水のCODがこれ以上曝気を続けても殆ど変化しなくなる処理時間における、処理開始時からの被処理水のNH4-N濃度の変化量ΔXは、複数の水質の異なる被処理水で実験したところ2~10[mg/L]でほぼ一定の値であった。なお、変化量ΔXは、処理開始時の被処理水のNH4-N濃度と、被処理水のCODがこれ以上曝気を続けても殆ど変化しなくなったときの被処理水のNH4-N濃度との差として表わすことができる。このような変化量ΔXの値を実験的に求めて、入口NH4-N濃度Xinと目標値XDVとの差がΔX[mg/L]又はΔXに安全率を加えた値となるように、k又はβが決定される。なお、変化量ΔXの値は、実験的に求めた複数の変化量ΔXの平均値であることが望ましい。また、上記においてCODの代わりにBODが用いられてもよい。
As described above, from the experimental results shown in FIG. 14, the water to be treated A from the start of treatment at the treatment times T C1 and T C2 at which the COD of the water to be treated A and B hardly changes even if aeration is continued further. , B change amounts ΔX 1 and ΔX 2 of NH 4 -N concentration are known to be substantially constant regardless of the quality of the water to be treated. The change amount ΔX of the NH 4 —N concentration of the water to be treated from the start of the treatment in the treatment time in which the COD of the water to be treated hardly changes even if the aeration is continued further is a plurality of treatments having different water qualities. When experimented with water, it was almost constant at 2 to 10 [mg / L]. The change amount ΔX is, NH 4 -N treated water when the NH 4 -N concentration of the treated water at the start of processing, COD of water to be treated was hardly changed even continue further aeration It can be expressed as a difference from the concentration. The value of the change ΔX is experimentally obtained so that the difference between the inlet NH 4 -N concentration X in and the target value X DV becomes ΔX [mg / L] or a value obtained by adding a safety factor to ΔX. K or β is determined. The value of the change amount ΔX is preferably an average value of a plurality of change amounts ΔX obtained experimentally. In the above, BOD may be used instead of COD.
上記k又はβの決定方法に則って算出された目標値XDVは、入口NH4-N濃度Xinよりも所定値だけ小さな値となる。ここで、前記所定値は、被処理水のCOD又はBODがほぼ一定値となったとき(即ち、これ以上曝気を続けても被処理水のCOD又はBODが殆ど変化しなくなったとき)の、当該被処理水のNH4-N濃度の曝気処理開始時からの変化量ΔXの絶対値となる。実験の結果得られた変化量ΔXの絶対値は2~10[mg/L]であるが、安全率を見込めば、変化量ΔXの絶対値は2~45[mg/L]の範囲から選択された値であってよい。但し、目標値XDVが小さくなると曝気風量が増大するので、散気装置の稼働エネルギーを削減する観点からは、前記所定値はより小さい値であることが望ましい。
The target value X DV calculated according to the determination method of k or β is a value smaller than the inlet NH 4 -N concentration X in by a predetermined value. Here, the predetermined value is when COD or BOD of the water to be treated becomes a substantially constant value (that is, when COD or BOD of the water to be treated hardly changes even if aeration is continued further). This is the absolute value of the amount of change ΔX from the start of the aeration treatment of the NH 4 —N concentration of the water to be treated. The absolute value of the change ΔX obtained as a result of the experiment is 2 to 10 [mg / L], but if the safety factor is expected, the absolute value of the change ΔX is selected from the range of 2 to 45 [mg / L]. The value may be However, since the aeration air volume increases as the target value X DV decreases, the predetermined value is preferably a smaller value from the viewpoint of reducing the operating energy of the diffuser.
以上のように目標値演算要素81で算出された目標値XDVは、ローセレクタ82で基準目標値XBと比較され、より小さいほうの値が(新たな)目標値XDVとして選択され、減算器83へ出力される。
The target value X DV calculated by the target value calculation element 81 as described above is compared with the reference target value X B by the low selector 82, and the smaller value is selected as the (new) target value X DV . It is output to the subtracter 83.
図6では、FB操作量YBを算出するために用いられる目標値XDV(即ち、減算器83に入力される目標値XDV)と、入口NH4-N濃度Xinとの関係を表した図表が示されている。この図表では、縦軸がNH4-N濃度を表し、横軸が時間を表し、実線が目標値XDVを表し、鎖線が入口NH4-N濃度Xinを表している。この図表によれば、処理開始から時刻Taまでの目標値XDVは、基準目標値XBで一定である。時刻Taから時刻Tbまでの目標値XDVは、入口NH4-N濃度Xinから所定値又は所定割合だけ小さな値で変化している。時刻Tbから処理終了までの目標値XDVは、基準目標値XBで一定である。見方を変えると、基準目標値XBより所定の値だけ大きい値を閾値として、入口NH4-N濃度Xinが閾値より大きいときは目標値XDVとして基準目標値XBが選択され、入口NH4-N濃度Xinが閾値以下のときは目標値XDVとして入口NH4-N濃度Xinよりも所定の値だけ小さな値が選択される。
FIG. 6 shows the relationship between the target value X DV (that is, the target value X DV input to the subtractor 83) used for calculating the FB manipulated variable Y B and the inlet NH 4 -N concentration X in. The chart is shown. In this chart, the vertical axis represents the NH 4 -N concentration, the horizontal axis represents time, the solid line represents the target value X DV , and the chain line represents the inlet NH 4 -N concentration X in . According to this chart, the target value X DV from the start of processing to the time Ta is constant at the reference target value X B. The target value X DV from time Ta to time Tb changes from the inlet NH 4 -N concentration X in by a predetermined value or a value smaller by a predetermined ratio. The target value X DV from time Tb to the end of processing is constant at the reference target value X B. Put differently, a larger value by a predetermined value than the reference target value X B as the threshold, when the inlet NH 4 -N concentration X in is greater than the threshold reference target value X B is selected as the target value X DV, inlet When the NH 4 -N concentration X in is less than or equal to the threshold value, a value smaller than the inlet NH 4 -N concentration X in by a predetermined value is selected as the target value X DV .
以上説明した曝気風量の演算方法によれば、出口NH4-N濃度の目標値XDVは常に入口NH4-N濃度Xinより低い値となる。よって、出口NH4-N濃度Xout(制御値)と目標値XDVとの偏差は常にゼロより大きくなる。そして、この偏差に基づいてフィードバック制御によりFB操作量YBが算出され、算出された操作量Y(曝気風量)に基づいて散気装置9が制御されるので、散気装置9では被処理水のNH4-N濃度を低減するために十分な曝気が継続的に行われる。この結果、被処理水中の有機物が十分に分解されていないのに曝気風量が最低風量y0となって被処理水中の有機物が十分に分解されないという事態を免れ、被処理水中の有機物の処理を確実に行うことができる。
According to the calculation method of the aeration air volume described above, the target value X DV of the outlet NH 4 -N concentration is always lower than the inlet NH 4 -N concentration X in . Therefore, the deviation between the outlet NH 4 -N concentration X out (control value) and the target value X DV is always greater than zero. The FB manipulated variable Y B is calculated by feedback control based on this deviation, and the diffuser 9 is controlled based on the calculated manipulated variable Y (aeration air volume). Sufficient aeration is performed continuously to reduce the NH 4 —N concentration of the catalyst. As a result, it is possible to avoid the situation where the organic matter in the treated water is not sufficiently decomposed but the aeration air volume becomes the minimum air flow y 0 and the organic matter in the treated water is not sufficiently decomposed. It can be done reliably.
更に、上記曝気風量の演算方法によれば、入口NH4-N濃度Xinの変化に応じて出口NH4-N濃度の目標値XDVが変化する。言い換えれば、入口NH4-N濃度Xinに対して適切な出口NH4-N濃度の目標値XDVが設定される。よって、好気槽32の曝気風量が過剰とならず、曝気風量及び散気装置9の稼働エネルギーを抑えることができる。
Furthermore, according to the calculation method of the aeration air volume, the target value X DV of the outlet NH 4 -N concentration changes according to the change of the inlet NH 4 -N concentration X in . In other words, the target value X DV of the outlet NH 4 -N concentration appropriate for the inlet NH 4 -N concentration X in is set. Therefore, the aeration air volume in the aerobic tank 32 does not become excessive, and the aeration air volume and the operating energy of the diffuser 9 can be suppressed.
上記実施形態では、FB制御系8で演算に用いられる出口NH4-N濃度の目標値XDVは常に所定の基準目標値XB以下となることから、処理水の水質基準にNH4-N濃度が含まれている場合に有効である。但し、水質基準にNH4-N濃度が含まれていない場合もあり、このような場合には、以下に説明する変形例1に係る曝気風量演算装置65で曝気風量が算出される。
In the above embodiment, NH 4 -N since the target value X DV outlet NH 4 -N concentration used in the calculation in the FB control system 8 always equal to or less than a predetermined reference target value X B, the water quality standards of treated water Effective when concentration is included. However, the NH 4 —N concentration may not be included in the water quality standard. In such a case, the aeration air volume is calculated by the aeration air volume calculation device 65 according to Modification 1 described below.
図7は、変形例1に係る曝気風量演算装置65の信号の流れを示すブロック線図である。この変形例1に係る曝気風量演算装置65では、FB制御系8の目標値XDVを算出する処理を前述の実施形態に係る処理から変更している。即ち、変形例1に係るFB制御系8では、目標値演算要素81で算出された目標値XDVが、基準目標値XBと比較されることなしに、そのまま目標値XDVとして用いられている。
FIG. 7 is a block diagram showing a signal flow of the aeration air volume calculation device 65 according to the first modification. In the aeration air amount calculation device 65 according to the first modification, the process for calculating the target value X DV of the FB control system 8 is changed from the process according to the above-described embodiment. That is, in the FB control system 8 according to the modified example 1, the target value X DV calculated by the target value calculation element 81 is used as it is as the target value X DV without being compared with the reference target value X B. Yes.
図8では、変形例1に係るFB制御系8で算出された目標値XDVと入口NH4-N濃度Xinとの関係を表した図表が示されている。この図表では、縦軸がNH4-N濃度を表し、横軸が時間を表し、実線が目標値XDVを表し、鎖線が入口NH4-N濃度Xinを表している。この図表では、処理開始から処理終了までを通して、目標値XDVは入口NH4-N濃度Xinから所定値又は所定割合だけ小さな値で変化している。
FIG. 8 shows a chart showing the relationship between the target value X DV calculated by the FB control system 8 according to the first modification and the inlet NH 4 -N concentration X in . In this chart, the vertical axis represents the NH 4 -N concentration, the horizontal axis represents time, the solid line represents the target value X DV , and the chain line represents the inlet NH 4 -N concentration X in . In this chart, the target value X DV changes from the inlet NH 4 -N concentration X in by a predetermined value or a value smaller by a predetermined ratio from the start to the end of the process.
[第2実施形態]
次に、本発明の第2実施形態を説明する。図9は本発明の第2実施形態に係る水処理システム10の概略構成を示す図、図10は第2実施形態に係る水処理システム10の制御構成を示すブロック図である。なお、第2実施形態の説明においては、前述の第1実施形態と同一又は類似の部材には図面に同一の符号を付して説明を省略し、主に第1実施形態からの相違点について説明する。 [Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 9 is a diagram showing a schematic configuration of awater treatment system 10 according to the second embodiment of the present invention, and FIG. 10 is a block diagram showing a control configuration of the water treatment system 10 according to the second embodiment. In the description of the second embodiment, the same or similar members as those in the first embodiment described above are denoted by the same reference numerals in the drawings, and the description thereof is omitted. Mainly differences from the first embodiment. explain.
次に、本発明の第2実施形態を説明する。図9は本発明の第2実施形態に係る水処理システム10の概略構成を示す図、図10は第2実施形態に係る水処理システム10の制御構成を示すブロック図である。なお、第2実施形態の説明においては、前述の第1実施形態と同一又は類似の部材には図面に同一の符号を付して説明を省略し、主に第1実施形態からの相違点について説明する。 [Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 9 is a diagram showing a schematic configuration of a
図9及び図10に示すように、第2実施形態に係る水処理システム10は、第1実施形態に係る水処理システム10において原水槽2に設けられた原水NH4-N濃度計61に代えて、処理槽3の入口に設けられた処理槽入口NH4-N濃度計63を備えている。この処理槽入口NH4-N濃度計63は、処理槽3の入口の被処理水のNH4-N濃度を検出し、制御装置6へ出力するように構成されている。なお、処理槽3の入口とは、処理槽3のうち原水及び返送汚泥が流入する領域であって、嫌気槽31の上流側領域である。
As shown in FIGS. 9 and 10, the water treatment system 10 according to the second embodiment is replaced with the raw water NH 4 -N concentration meter 61 provided in the raw water tank 2 in the water treatment system 10 according to the first embodiment. In addition, a treatment tank inlet NH 4 -N concentration meter 63 provided at the inlet of the treatment tank 3 is provided. The treatment tank inlet NH 4 -N concentration meter 63 is configured to detect the NH 4 -N concentration of the water to be treated at the inlet of the treatment tank 3 and output it to the control device 6. The inlet of the processing tank 3 is an area into which raw water and return sludge flow in the processing tank 3, and is an upstream area of the anaerobic tank 31.
水処理システム10の処理系列が多系統の場合は上記第1実施形態のように原水槽2にNH4-N濃度計を設けることがNH4-N濃度計の設置数を削減できる点で優位であるが、処理系列が1~2系統の場合には処理槽3の入口にNH4-N濃度計を設置する方が入口NH4-N濃度Xinを演算する処理を省くことができるので合理的である。そこで、第2実施形態に係る水処理システム10では、処理槽入口NH4-N濃度計63を用いて直接に入口NH4-N濃度Xinを検出し、この検出された入口NH4-N濃度Xinを用いて曝気風量を演算するようにしている。
When the processing sequence of the water treatment system 10 is a multi-lineage advantage in that the provision of the NH 4 -N concentration meter in the raw water tank 2 as in the first embodiment it is possible to reduce the number of installation of NH 4 -N concentration meter However, when the number of processing series is one or two, installing the NH 4 -N concentration meter at the inlet of the processing tank 3 can save the processing for calculating the inlet NH 4 -N concentration X in . Is reasonable. Therefore, the water treatment system 10 according to the second embodiment, the processing tank inlet NH 4 directly with the -N concentration meter 63 to detect the inlet NH 4 -N concentration X in, the detected inlet NH 4 -N so that calculates the aeration amount using the concentration X in.
図11は第2実施形態に係る曝気風量演算装置65の信号の流れを示すブロック線図である。図11に示すように、第1実施形態のFF制御系7では原水NH4-N濃度計61で検出された原水NH4-N濃度XRWに基づいてFF操作量YFが生成されるが、第2実施形態のFF制御系7では処理槽入口NH4-N濃度計63で検出された入口NH4-N濃度Xinに基づいてFF操作量YFが生成される。つまり、第2実施形態に係るFF操作量演算要素71は、入口NH4-N濃度XinからFF操作量YFを算出するFF操作量関数F1である。
FIG. 11 is a block diagram showing a signal flow of the aeration air volume calculation device 65 according to the second embodiment. As shown in FIG. 11, in the FF control system 7 of the first embodiment, the FF manipulated variable Y F is generated based on the raw water NH 4 —N concentration X RW detected by the raw water NH 4 —N concentration meter 61. In the FF control system 7 of the second embodiment, the FF manipulated variable Y F is generated based on the inlet NH 4 -N concentration X in detected by the treatment tank inlet NH 4 -N concentration meter 63. That is, the FF manipulated variable calculating element 71 according to the second embodiment is an FF manipulated variable function F 1 that calculates the FF manipulated variable Y F from the inlet NH 4 -N concentration X in .
また、第1実施形態のFB制御系8の目標値演算要素81は原水NH4-N濃度XRW、原水流入量u、出口NH4-N濃度Xout、及び循環流量fから目標値XDVを算出するものであるが、第2実施形態の目標値演算要素81は処理槽入口NH4-N濃度計63で検出された入口NH4-N濃度Xinから目標値XDVを算出するものである。つまり、第2実施形態に係る目標値関数F3は、入力値である入口NH4-N濃度Xinと、出力値である目標値XDVとの関係を関数化したものである。目標値関数F3で算出される目標値XDVは、入口NH4-N濃度Xinから所定値だけ小さい値である。
Further, the target value calculation element 81 of the FB control system 8 of the first embodiment is the target value X DV from the raw water NH 4 -N concentration X RW , the raw water inflow u, the outlet NH 4 -N concentration X out , and the circulation flow rate f. The target value calculation element 81 of the second embodiment calculates the target value X DV from the inlet NH 4 -N concentration X in detected by the treatment tank inlet NH 4 -N concentration meter 63. It is. That is, the target value function F 3 according to the second embodiment is a function of the relationship between the inlet NH 4 -N concentration X in that is an input value and the target value X DV that is an output value. The target value X DV calculated by the target value function F 3 is a value that is smaller than the inlet NH 4 -N concentration X in by a predetermined value.
以上に本発明の好適な実施の形態(第1実施形態及びその変形例、並びに、第2実施形態)を説明したが、上記の構成は例えば以下のように変更することができる。
The preferred embodiments of the present invention (the first embodiment and its modifications, and the second embodiment) have been described above, but the above configuration can be modified as follows, for example.
上記実施形態に係る水処理システム10は、嫌気好気法の処理プロセスを実現するものであるが、嫌気好気法に生物学的窒素処理を組み合わせた循環式嫌気好気法(A2O法)の処理プロセス、又は膜分離活性汚泥法(MBR法)の処理プロセスであってもよい。
Although the water treatment system 10 which concerns on the said embodiment implement | achieves the treatment process of an anaerobic aerobic method, the anaerobic aerobic method (A2O method) which combined biological nitrogen treatment with the anaerobic aerobic method. It may be a treatment process or a treatment process of a membrane separation activated sludge method (MBR method).
例えば、処理プロセスが循環式嫌気好気法の場合は、図12に示すように、水処理システム10Aに原水槽2と、嫌気槽31、無酸素槽38、及び好気槽32から成る処理槽3と、沈殿槽4とが設けられる。沈殿槽4で沈殿した汚泥は、嫌気槽31へ返送される。また、好気槽32で沈殿した汚泥を含む循環液は、無酸素槽38へ返送される。この場合、目標値関数F3を算出するための循環流量fには、嫌気槽31へ返送される沈殿槽4で沈殿した汚泥の流量に、無酸素槽38へ送られる好気槽32からの循環液の流量を加えた値が用いられる。
For example, when the treatment process is a circulation type anaerobic aerobic method, as shown in FIG. 12, a treatment tank comprising a raw water tank 2, an anaerobic tank 31, an anaerobic tank 38, and an aerobic tank 32 in a water treatment system 10A. 3 and a settling tank 4 are provided. The sludge precipitated in the settling tank 4 is returned to the anaerobic tank 31. Further, the circulating liquid containing the sludge precipitated in the aerobic tank 32 is returned to the anoxic tank 38. In this case, the circulation flow rate f for calculating the target value function F 3 is the flow rate of the sludge precipitated in the settling tank 4 returned to the anaerobic tank 31, and from the aerobic tank 32 sent to the anaerobic tank 38. A value obtained by adding the flow rate of the circulating fluid is used.
また、例えば、処理プロセスが膜分離活性汚泥法の場合は、図13に示すように、水処理システム10Bに原水槽2と、嫌気槽31、無酸素槽38、好気槽32、及び膜分離槽39から成る処理槽3とが設けられる。膜分離槽39で処理液と膜分離された汚泥は嫌気槽31へ返送される。また、好気槽32で沈殿した汚泥を含む循環液は無酸素槽38へ返送される。この場合、目標値関数F3を算出するための循環流量fには、嫌気槽31へ返送される膜分離槽39で沈殿した汚泥の流量に、無酸素槽38へ送られる好気槽32からの循環液の流量を加えた値が用いられる。
Further, for example, when the treatment process is the membrane separation activated sludge method, as shown in FIG. 13, the raw water tank 2, the anaerobic tank 31, the anaerobic tank 38, the aerobic tank 32, and the membrane separation are added to the water treatment system 10B. A treatment tank 3 comprising a tank 39 is provided. The sludge that has been membrane-separated from the treatment liquid in the membrane separation tank 39 is returned to the anaerobic tank 31. Further, the circulating liquid containing the sludge precipitated in the aerobic tank 32 is returned to the anoxic tank 38. In this case, the circulation flow rate f for calculating the target value function F 3 is from the aerobic tank 32 sent to the anaerobic tank 38 to the flow rate of sludge precipitated in the membrane separation tank 39 returned to the anaerobic tank 31. A value obtained by adding the flow rate of the circulating fluid is used.
また、例えば、上記実施形態に係る水処理システム10の曝気風量演算装置65の演算部67では、FF制御系7でFF操作量YFが算出され、FB制御系8でFB操作量YBが算出され、加算器85でFF操作量YFとFB操作量YBを足し合わせることにより操作量Yを算出するようにしているが、操作量YがFB操作量YBのみを考慮したものであってもよい。この場合、演算部67の処理のうち、FF制御系7及び加算器85で行われる処理が省略され、FB制御系8で導出されたFB操作量YBが操作量Yとして算出される。
Further, for example, in the calculation unit 67 of the aeration air amount calculation device 65 of the water treatment system 10 according to the above embodiment, the FF operation amount Y F is calculated by the FF control system 7, and the FB operation amount Y B is calculated by the FB control system 8. The operation amount Y is calculated by adding the FF operation amount Y F and the FB operation amount Y B by the adder 85. However, the operation amount Y considers only the FB operation amount Y B. There may be. In this case, the processing performed by the FF control system 7 and the adder 85 in the processing of the calculation unit 67 is omitted, and the FB operation amount Y B derived by the FB control system 8 is calculated as the operation amount Y.
10 水処理システム
2 原水槽
3 処理槽
31 嫌気槽
32 好気槽
38 無酸素槽
39 膜分離槽
4 沈殿槽
6 制御装置(曝気風量制御装置)
51 供給ポンプ
56 返送ポンプ
61 原水アンモニア態窒素濃度計
62 処理槽出口アンモニア態窒素濃度計
63 処理槽入口アンモニア態窒素濃度計
65 曝気風量演算装置
66 取得部(取得手段)
67 演算部(演算手段)
68 出力部
7 FF制御系
71 FF操作量演算要素(フィードフォワード操作量演算要素)
72 FF操作量補正係数演算要素(補正係数演算要素)
73 無駄時間要素
74 フィードフォワードゲイン要素
75 乗算器
8 FB制御系
81 目標値演算要素
82 ローセレクタ
83 減算器
84 FB操作量演算要素(フィードバック操作量演算要素)
85 加算器
9 散気装置
91 ノズル
92 散気ブロワ 10water treatment system 2 raw water tank 3 treatment tank 31 anaerobic tank 32 aerobic tank 38 anoxic tank 39 membrane separation tank 4 sedimentation tank 6 control device (aeration air volume control device)
51Supply Pump 56 Return Pump 61 Raw Water Ammonia Nitrogen Concentration Meter 62 Treatment Tank Exit Ammonia Nitrogen Concentration Meter 63 Treatment Tank Entrance Ammonia Nitrogen Concentration Meter 65 Aeration Air Volume Calculation Device 66 Acquisition Unit (Acquisition Means)
67 Calculation unit (calculation means)
68Output unit 7 FF control system 71 FF manipulated variable computation element (feedforward manipulated variable computation element)
72 FF manipulated variable correction coefficient calculation element (correction coefficient calculation element)
73Waste time element 74 Feed forward gain element 75 Multiplier 8 FB control system 81 Target value calculation element 82 Low selector 83 Subtractor 84 FB manipulated variable calculation element (feedback manipulated variable calculation element)
85Adder 9 Air diffuser 91 Nozzle 92 Air diffuser
2 原水槽
3 処理槽
31 嫌気槽
32 好気槽
38 無酸素槽
39 膜分離槽
4 沈殿槽
6 制御装置(曝気風量制御装置)
51 供給ポンプ
56 返送ポンプ
61 原水アンモニア態窒素濃度計
62 処理槽出口アンモニア態窒素濃度計
63 処理槽入口アンモニア態窒素濃度計
65 曝気風量演算装置
66 取得部(取得手段)
67 演算部(演算手段)
68 出力部
7 FF制御系
71 FF操作量演算要素(フィードフォワード操作量演算要素)
72 FF操作量補正係数演算要素(補正係数演算要素)
73 無駄時間要素
74 フィードフォワードゲイン要素
75 乗算器
8 FB制御系
81 目標値演算要素
82 ローセレクタ
83 減算器
84 FB操作量演算要素(フィードバック操作量演算要素)
85 加算器
9 散気装置
91 ノズル
92 散気ブロワ 10
51
67 Calculation unit (calculation means)
68
72 FF manipulated variable correction coefficient calculation element (correction coefficient calculation element)
73
85
Claims (8)
- 被処理水を活性汚泥法で浄化する処理槽への曝気風量を求める曝気風量演算装置であって、
前記処理槽の入口の被処理水のアンモニア態窒素濃度である処理槽入口アンモニア態窒素濃度よりも小さい目標値を生成する目標値演算要素と、前記処理槽で処理された処理水のアンモニア態窒素濃度である処理槽出口アンモニア態窒素濃度と前記目標値との偏差に基づいてフィードバック操作量を生成するフィードバック操作量演算要素とを有し、前記フィードバック操作量に基づいて前記曝気風量である操作量を算出する演算手段を備える、曝気風量演算装置。 An aeration air volume calculating device for obtaining an aeration air volume to a treatment tank for purifying treated water by an activated sludge method,
A target value calculation element that generates a target value smaller than the ammonia nitrogen concentration in the treatment tank, which is the ammonia nitrogen concentration of the water to be treated at the inlet of the treatment tank, and ammonia nitrogen in the treatment water treated in the treatment tank A feedback manipulated variable calculation element for generating a feedback manipulated variable based on a deviation between the treatment tank outlet ammonia nitrogen concentration that is a concentration and the target value, and an manipulated variable that is the aeration air volume based on the feedback manipulated variable An aeration air volume calculation device comprising calculation means for calculating - 前記演算手段は、所定の基準目標値と前記目標値演算要素で生成された前記目標値とのうち小さい方を選択して前記フィードバック操作量演算要素へ前記目標値として出力するローセレクタを更に有する、請求項1に記載の曝気風量演算装置。 The calculation means further includes a low selector that selects a smaller one of a predetermined reference target value and the target value generated by the target value calculation element and outputs the selected value to the feedback manipulated variable calculation element as the target value. The aeration air volume calculating device according to claim 1.
- 前記処理槽へ流入する原水のアンモニア態窒素濃度である原水アンモニア態窒素濃度、前記処理槽へ流入する前記原水の流入量である原水流入量、前記処理槽出口アンモニア態窒素濃度、及び前記処理水から分離されて前記処理槽へ戻される汚泥の流量である循環流量を取得する取得手段を更に備え、
前記演算手段が、前記原水アンモニア態窒素濃度、前記原水流入量、前記処理槽出口アンモニア態窒素濃度、及び前記循環流量に基づいて前記処理槽入口アンモニア態窒素濃度を演算するように構成されている、請求項1又は2に記載の曝気風量演算装置。 Raw water ammonia nitrogen concentration which is the ammonia nitrogen concentration of raw water flowing into the treatment tank, raw water inflow amount which is the inflow amount of the raw water flowing into the treatment tank, the treatment tank outlet ammonia nitrogen concentration, and the treated water Further comprising an acquisition means for acquiring a circulating flow rate which is a flow rate of sludge separated and returned to the treatment tank,
The calculation means is configured to calculate the treatment tank inlet ammonia nitrogen concentration based on the raw water ammonia nitrogen concentration, the raw water inflow amount, the treatment tank outlet ammonia nitrogen concentration, and the circulation flow rate. The aeration air volume calculating device according to claim 1 or 2. - 前記演算手段が、前記処理槽へ流入する原水のアンモニア態窒素濃度である原水アンモニア態窒素濃度に基づいてフィードフォワード操作量を生成するフィードフォワード操作量演算要素と、前記フィードフォワード操作量と前記フィードバック操作量とを足し合わせる加算器とを、更に有し、前記フィードバック操作量に前記フィードフォワード操作量を付加して前記操作量を算出するように構成されている、請求項1~3のいずれか一項に記載の曝気風量演算装置。 The computing means generates a feedforward manipulated variable based on the raw water ammonia nitrogen concentration which is the ammonia nitrogen concentration of the raw water flowing into the treatment tank, the feedforward manipulated variable computing element, and the feedback An adder that adds an operation amount is further provided, and the operation amount is calculated by adding the feedforward operation amount to the feedback operation amount. The aeration air volume calculating device according to one item.
- 前記演算手段は、前記処理槽へ流入する前記原水の流入量である原水流入量が所定の基準流入量より大きいときは前記フィードフォワード操作量を増加させ、前記原水流入量が前記所定の基準流入量より小さいときは前記フィードフォワード操作量を減少させるための補正係数を求める補正係数演算要素と、前記フィードフォワード操作量と前記補正係数とを掛け合わせて前記フィードフォワード操作量を補正する乗算器とを更に有する、請求項4に記載の曝気風量演算装置。 The calculation means increases the feedforward operation amount when the raw water inflow amount, which is the inflow amount of the raw water flowing into the treatment tank, is larger than a predetermined reference inflow amount, and the raw water inflow amount is increased to the predetermined reference inflow amount. A correction coefficient calculating element for obtaining a correction coefficient for reducing the feedforward manipulated variable when the amount is smaller than a quantity; a multiplier for correcting the feedforward manipulated variable by multiplying the feedforward manipulated variable and the correction coefficient; The aeration air volume calculating device according to claim 4, further comprising:
- 前記目標値は、前記処理槽入口アンモニア態窒素濃度よりも所定値だけ小さい値であって、
前記所定値が、曝気により被処理水のCOD又はBODが一定値となったときの、当該被処理水のアンモニア態窒素濃度の前記曝気開始時からの変化量の絶対値である、請求項1~5のいずれか一項に記載の曝気風量演算装置。 The target value is a value smaller than the treatment tank inlet ammonia nitrogen concentration by a predetermined value,
The predetermined value is an absolute value of the amount of change in the ammonia nitrogen concentration of the water to be treated from the start of aeration when the COD or BOD of the water to be treated becomes a constant value due to aeration. The aeration air volume calculating device according to any one of 1 to 5. - 前記目標値が、前記処理槽入口アンモニア態窒素濃度よりも2~10[mg/L]の範囲から選択された値だけ小さな値である、請求項1~6のいずれか一項に記載の曝気風量演算装置。 The aeration according to any one of claims 1 to 6, wherein the target value is a value that is smaller than a value selected from a range of 2 to 10 [mg / L] from the ammonia nitrogen concentration at the treatment tank inlet. Air volume calculation device.
- 散気装置を備えた好気槽を含み、被処理水を活性汚泥法で浄化する処理槽と、
前記処理槽へ流入する原水のアンモニア態窒素濃度を計測する原水アンモニア態窒素濃度計又は前記処理槽の入口の前記被処理水のアンモニア態窒素濃度を計測する処理槽入口アンモニア態窒素濃度計と、
前記処理槽から流出する処理水のアンモニア態窒素濃度を計測する処理槽出口アンモニア態窒素濃度計と、
請求項1~7のいずれか一項に記載の曝気風量演算装置と、
前記曝気風量演算装置で求めた前記操作量に基づいて前記散気装置を制御する曝気風量制御装置とを備える、
水処理システム。 A treatment tank including an aerobic tank equipped with an air diffuser, and purifying treated water by an activated sludge method;
A raw water ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of raw water flowing into the treatment tank or a treatment tank inlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water at the inlet of the treatment tank;
A treatment tank outlet ammonia nitrogen concentration meter for measuring the ammonia nitrogen concentration of the treated water flowing out of the treatment tank;
An aeration air volume calculating device according to any one of claims 1 to 7,
An aeration air volume control device that controls the aeration device based on the operation amount obtained by the aeration air volume computing device;
Water treatment system.
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