JP2017013014A - Organic wastewater treatment system, organic wastewater treatment method, and control program of organic wastewater treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic wastewater treatment system that is capable of efficiently removing nitrogen and phosphorus from organic wastewater, an organic wastewater treatment method, and a control program of the organic wastewater treatment system.SOLUTION: According to an embodiment, an organic wastewater treatment system comprises: a biological reaction tank equipped with an anaerobic treatment region, an adjustment treatment region and an aerobic treatment region in order; an ammonia concentration measuring device; a total nitrogen concentration measuring device; a total phosphorus concentration measuring device or a phosphate phosphorus concentration measuring device; and a control part. The adjustment treatment region is switchable to one or two or more atmospheres of anaerobic atmosphere, microaerobic atmosphere or aerobic atmosphere. Further, the region is a region where a range occupied with each atmosphere is adjustable. The control part has a control program which controls the adjustment treatment region so as to put priority to nitrification in removal of nitrogen, and remove phosphorus in the case where nitrification is sufficiently done.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an organic wastewater treatment system, an organic wastewater treatment method, and a control program for an organic wastewater treatment system.

  Conventionally, the standard activated sludge method has been adopted as the most typical process in sewage treatment plants that purify domestic wastewater. The standard activated sludge method oxidizes and decomposes organic pollutants in water by aerobic microorganisms in an aeration tank that supplies air into the water by a blower. In this standard activated sludge method, organic substances can be decomposed and removed.

However, nitrogen and phosphorus that cause eutrophication problems at the discharge destination cannot be removed by the standard activated sludge method. Therefore, as a method for decomposing organic substances and removing nitrogen and phosphorus, a nitrogen removal type circulatory nitrification denitrification method, a phosphorus removal type anaerobic-aerobic activated sludge method (AO method), which is a modification of the standard activated sludge method. ), Advanced treatment processes such as an anaerobic-anoxic-aerobic activated sludge method (A ₂ O) method of simultaneous removal of nitrogen and phosphorus are being promoted.

  In such an advanced treatment process, primary treated water from which the settled sludge has been removed from the influent sewage in the first settling tank is sent to the biological reaction tank. Next, organic substances, nitrogen, and phosphorus are removed from the primary treated water by the reaction of microorganisms in the anaerobic tank, anoxic tank, and aerobic tank in the biological reaction tank. At the same time, flocs that are aggregates of microorganisms are formed in the bioreactor. Then, secondary treated water containing floc is sent to the final sedimentation basin. In the final sedimentation basin, flocs are settled and removed from the secondary treated water. Most of the sediment is returned to the biological reaction tank from the final sedimentation basin as return sludge containing activated sludge. Part of the sediment is discharged as surplus sludge from the final sedimentation basin and incinerated after concentration and dehydration.

  The process for removing ammonia as nitrogen in organic wastewater is as follows. First, ammonia is oxidized (nitrified) into nitrate ions in an aerobic tank. Oxidized nitrate ions are returned to the anoxic tank. In the anaerobic tank, nitrate ions are reduced (denitrified) to nitrogen gas by the action of microorganisms. Further, in the phosphorus removal process, phosphorus is discharged from microorganisms in an anaerobic tank. Next, in the aerobic tank, the microorganisms absorb phosphorus, and the microorganisms that have absorbed phosphorus are precipitated and removed as floc. The amount of phosphorus absorbed by the microorganisms in the aerobic tank is larger than the amount of phosphorus discharged by the microorganisms in the anaerobic tank. Phosphorus removal is performed based on the difference between the discharge amount and the absorption amount.

  However, in order to introduce the above-described advanced treatment method into an existing wastewater treatment apparatus, it is necessary to newly provide an anaerobic tank, an oxygen-free tank, and an aerobic tank in the biological reaction tank. Specifically, it is necessary to introduce new equipment such as a stirrer and a pump, and newly install a new concrete frame. For this reason, the modification of the existing equipment takes time and labor, and there is a problem that the cost is high.

  In order to respond to these issues, for example, there are a first sedimentation basin that separates solids and liquids in organic wastewater into solid-liquid separation, a biological reaction tank that treats the overflow water of the first sedimentation basin with activated sludge, and activated sludge. In an activated sludge treatment facility that separates solid and liquid, a zone that can be switched between anaerobic, microaerobic and aerobic operation by adjusting the opening of the adjustment valve of the diffuser pipe arranged in the direction of water flow in the biological reaction tank ( An organic wastewater treatment system provided with an adjustment treatment area) is known. Then, according to the measured values of nitrogen, phosphorus concentration and ammonia concentration in the treated water, this adjustment treatment area is anaerobic operation when the treatment performance of phosphorus is bad, the treatment performance of nitrogen is bad and the treatment performance of ammonia is bad. In some cases, it is said that nitrogen and phosphorus can be removed by aerobic operation, and in other cases, microaerobic operation. However, in such an organic wastewater treatment system, when nitrogen removal and phosphorus removal are both compatible, it may be difficult to efficiently remove nitrogen and phosphorus depending on the amount of treated water flowing in and the water quality conditions. There was also.

Japanese Patent Laying-Open No. 2015-097976

  The problem to be solved by the present invention is to provide an organic wastewater treatment system, an organic wastewater treatment method, and a control program for an organic wastewater treatment system that enable efficient removal of nitrogen and phosphorus from organic wastewater. It is.

  The organic wastewater treatment system of the embodiment includes an adjustment processing region that can be switched to one or more of an anaerobic atmosphere, a microaerobic atmosphere, or an aerobic atmosphere, and adjusts the range of the atmosphere of the adjustment processing region. The control unit prioritizes nitrification in nitrogen removal, and determines that the nitrification is sufficient based on values measured by the ammonia concentration measuring device and the total phosphorus concentration measuring device or the phosphorous phosphorus concentration measuring device. In this case, a control program is provided for controlling the adjustment processing area so as to remove phosphorus.

The schematic diagram which shows the organic waste water treatment system which concerns on embodiment. The schematic diagram which shows an example of the atmosphere control of an adjustment process area | region. The schematic diagram which shows an example of the atmosphere control of an adjustment process area | region. The schematic diagram which shows an example of the atmosphere control of an adjustment process area | region. The schematic diagram which shows an example of the atmosphere control of an adjustment process area | region.

  Hereinafter, an organic wastewater treatment system, an organic wastewater treatment method, and an organic wastewater treatment system control program according to embodiments will be described with reference to the drawings.

  The organic waste water treatment system 1 of this embodiment shown in FIG. 1 includes a first sedimentation basin 2 (sedimentation basin), a biological reaction tank 3 and a final sedimentation basin 4 in order from the upstream side. The organic waste water treatment system 1 is provided with a control unit 9.

  The biological reaction tank 3 is a reaction vessel for purifying sewage using a decomposition action by microorganisms. The biological reaction tank 3 is provided with an anaerobic treatment area 11, an adjustment treatment area 12, and an aerobic treatment area 13. The adjustment processing area 12 is disposed between the anaerobic processing area 11 and the aerobic processing area 13. Here, “arranged between” is not a spatial concept, but the order of processing in the adjustment processing region 12 is favorably compared with the anaerobic processing region 11 from the upstream side to the downstream side along the flow of the water to be treated. This means that it is between the gas processing region 13.

  The biological reaction tank 3 has an inflow portion through which organic waste water (treated water) before purification treatment flows from the introduction flow path 51 and an outflow portion from which organic waste water (purified water) after purification treatment flows out. The inflow portion is installed in the vicinity of the anaerobic treatment region 11. The outflow part is installed in the vicinity of the aerobic treatment region 13.

  The water surface height of the organic waste water in the anaerobic treatment region 11 is higher than the water surface height of the organic waste water in the adjustment treatment region 12. The water surface height of the organic waste water in the adjustment treatment region 12 is higher than the water surface height of the organic waste water in the aerobic treatment region 13. Thus, the water surface height in the anaerobic processing region 11, the adjustment processing region 12, and the aerobic processing region 13 is configured to be lowered stepwise.

  The anaerobic treatment region 11 is a region that occupies, for example, 15 to 30% of the internal volume of the biological reaction tank 3. The aerobic treatment region 13 is, for example, a region that occupies 40 to 60% of the internal volume of the biological reaction tank 3. The remainder of the internal volume of the biological reaction tank 3 is used as the adjustment processing region 12.

  The first sedimentation basin 2 is a primary treatment facility that accepts organic waste water (treated water) and precipitates suspended matter (SS). The sedimentation basin 2 is initially provided with a weir, and the supernatant water passes over the weir and flows into the overflow line, and further flows into the biological reaction tank 3 from the overflow line. In addition, the sludge discharge line which is not shown in figure communicates with the bottom part of the first sedimentation tank 2, and sludge is discharged | emitted regularly or at any time.

  The control unit 9 is a computer in which a control program for controlling the adjustment processing area 12 is stored. Based on the measurement results of the ammonia concentration measuring device 5, the total nitrogen concentration measuring device 7, and the total phosphorus concentration measuring device 8, which will be described later, the control unit 9 changes the state of the adjustment processing region 12 to an anaerobic atmosphere, a microaerobic atmosphere, Switch to one or more atmospheres. The operation of the control unit 9 according to such a control program will be described later.

  The biological reaction vessel 3 is provided with an aeration device 20 as an aeration means. The aeration apparatus 20 includes a blower 21, an air pipe 22 extending from the blower 21, a flow rate adjusting valve 23 provided in the air pipe 22, a branch pipe 24 branched from the air pipe 22, and each branch pipe 24. The on / off valves 25a to 25d and diffuser plates 26a to 26d attached to the tips of the branch pipes 24 are configured. The diffuser plates 26 a to 26 d are installed inside the biological reaction vessel 3.

  The diffuser plate 26 a is installed in the anaerobic treatment region 11 of the biological reaction vessel 3. The diffuser plates 26b and 26c are installed in the adjustment processing region 12 along the direction in which the treated water flows. Further, the diffuser plate 26d is installed in the aerobic treatment region 13 along the direction in which the treated water flows.

  Of the on-off valves 25 a to 25 d provided on each branch pipe 24, the on-off valve 25 a installed on the branch pipe 24 toward the anaerobic treatment region 11 is always “closed”. In addition, you may abbreviate | omit installation of the branch pipe 24, the on-off valve 25a, and the diffuser board 26a. Further, the on-off valve 25d installed in the branch pipe 24 toward the aerobic treatment region 13 is always “open”. Further, the opening / closing valves 25b and 25c installed in the branch pipe 24 toward the adjustment processing region 12 can be freely set. The on-off valves 25b and 25c are connected to the control unit 9 described later.

  The opening / closing valves 25b and 25c are controlled based on instructions from the control unit 9. By controlling the opening degree of these on-off valves 25b and 25c, the range of the atmosphere in the adjustment processing region 12 can be adjusted. For example, the atmosphere of the adjustment processing region 12 can be set to one or more of an anaerobic atmosphere, a slight aerobic atmosphere or an aerobic atmosphere.

  Further, the flow rate adjusting valve 23 provided in the air pipe 22 is connected to the air volume controller 30. The air flow rate in the air pipe 22 can be adjusted by the control of the air volume controller 30.

  Since the valve is fully closed, the anaerobic treatment region 11 becomes an anaerobic atmosphere (ORP value is on the negative side) so that the activity of the anaerobic microorganisms is increased during steady operation. More specifically, the ORP value is −200 mV or less. Here, the ORP value means a redox potential. If the ORP value of the treated water is negative, it can be said that the treated water is in a reduced state. In other words, the sewage that is placed in an anaerobic state without aeration has a low potential (negative ORP value). In the anaerobic treatment region 11, the discharge of phosphorus from the microorganism proceeds and the reduction reaction from nitrate ions to nitrogen proceeds.

  On the other hand, the aerobic treatment region 13 is adjusted to an aerobic atmosphere (ORP value is on the positive side) so that the activity of aerobic microorganisms is increased during steady operation. More specifically, the ORP value is adjusted to be in a range of 50 mV or more. When the ORP value is positive, it can be said that the treated water is in an oxidized state. That is, the treated water placed in an aerobic state with sufficient aeration has a high potential. In the aerobic treatment region 13, the absorption of phosphorus by microorganisms proceeds and the oxidation reaction from ammonia to nitrate ions proceeds.

  In the adjustment processing region 12, the atmosphere can be switched to one or more of an anaerobic atmosphere, a slight aerobic atmosphere, and an aerobic atmosphere. Moreover, the adjustment process area | region 12 can adjust the range which each atmosphere of an anaerobic atmosphere, a micro aerobic atmosphere, and an aerobic atmosphere occupies. In the present embodiment, the adjustment processing area 12 is divided into two areas, a first area 12a and a second area 12b.

  The first region 12a is a region corresponding to the installation location of the diffuser plate 26b, and the second region 12b is a region corresponding to the installation location of the diffusion plate 26c. The first region 12a and the second region 12b can be switched independently of each other.

  Here, the slightly aerobic atmosphere refers to an atmosphere adjusted so that the ORP value is in the range of −50 to 50 mV. Since the anaerobic atmosphere is an atmosphere in a range of −200 mV or less and the aerobic atmosphere is an atmosphere in a range of 50 mV or more, it can be said that the slightly aerobic atmosphere is in an intermediate state between the anaerobic atmosphere and the aerobic atmosphere. In this slightly aerobic atmosphere, the reduction reaction from nitrate ions to nitrogen and the oxidation reaction from ammonia to nitrate ions proceed simultaneously.

  Switching the atmosphere in the adjustment processing region 12 is performed by operating the aeration apparatus 20. The aeration apparatus 20 is controlled by a command from the control unit 9 described later. When air is not supplied from each diffuser plate of the aeration apparatus 20, an anaerobic atmosphere is created. When a large amount of air is supplied from each diffuser plate of the aeration apparatus 20, an aerobic atmosphere is obtained. When a small amount of air is supplied from each diffuser plate of the aeration apparatus 20, a slightly aerobic atmosphere is obtained.

  Switching between the aerobic atmosphere and the slightly aerobic atmosphere is performed by adjusting the opening degree of the on-off valves 25b and 25c provided in the branch pipe 24. For example, in the case of an aerobic atmosphere, the opening degree of the on-off valves 25b and 25c is fully opened (100% open). When the slightly aerobic atmosphere is used, the opening degree of the on-off valves 25b and 25c is set to 5 to 15% with respect to the full opening.

  Moreover, in order to adjust the range which each atmosphere occupies, it carries out by controlling independently the air supply amount from the two diffuser plates 26b and 26c with which the adjustment process area | region 12 was equipped. For example, when the air supply of both of the diffuser plates 26b and 26c is stopped, the entire adjustment processing region 12 becomes an anaerobic atmosphere. When the air supply to the diffuser plate 26b is stopped and a small amount of air is supplied from the diffuser plate 26c, the first region 12a becomes an anaerobic atmosphere, and the second region 12b becomes a slightly aerobic atmosphere. When a small amount of air is supplied from the diffuser plate 26b and a large amount of air is supplied from the diffuser plate 26c, the first region 12a becomes a slightly aerobic atmosphere and the second region 12b becomes an aerobic atmosphere.

  Further, when a large amount of air is supplied from both of the diffuser plates 26b and 26c, the entire adjustment processing region 12 becomes an aerobic atmosphere. In the present embodiment, the adjustment processing region 12 is further divided into two regions (first region and second region) by installing the two diffuser plates 26b and 26c in the adjustment processing region 12. By installing more plates and dividing the adjustment processing region 12 into more regions, the atmosphere in the adjustment processing region 12 can be adjusted more flexibly.

  A disinfection facility (not shown) is provided on the downstream side of the final sedimentation basin 4 so that the sterilized treated water is discharged to a river or ocean through a discharge channel.

  The final sedimentation basin 4 is provided with a return pipe 40. A pump 41 is provided in the middle of the return pipe 40. Return sludge and part of the treated water are always returned from the final sedimentation basin 4 to the upstream portion of the biological reaction tank 3 by the return pipe 40.

  The organic waste water treatment system 1 is provided with an ammonia concentration measuring device 5, a dissolved oxygen measuring device 6, and a total phosphorus concentration measuring device 8. It is also preferable that a total nitrogen concentration measuring device 7 is provided. The ammonia concentration measuring device 5 measures the ammonia concentration of the treated water flowing through the aerobic treatment region 13. The dissolved oxygen measuring device 6 measures the dissolved oxygen amount of the treated water flowing through the aerobic treatment region 13. The total nitrogen concentration measuring device 7 and the total phosphorus concentration measuring device 8 measure the total nitrogen concentration and the total phosphorus concentration of the treated water discharged from the biological reaction tank 3 and the final sedimentation basin 4, respectively. In addition, it can replace with the total phosphorus concentration measuring device 8, and a phosphoric acid state phosphorus concentration measuring device can also be used.

  The ammonia concentration measuring device 5 and the dissolved oxygen measuring device 6 are connected to the air volume controller 30. Further, the ammonia concentration measuring device 5 is also connected to the control unit 9. Furthermore, the total nitrogen concentration measuring device 7 and the total phosphorus concentration measuring device 8 are connected to the control unit 9.

  The control unit 9 stores a control program for controlling the biological reaction vessel 3. This control program includes a first step and a second step. The first step issues a command to measure the ammonia concentration of the treated water in the aerobic treatment region 13, the total nitrogen concentration of the treated water discharged from the biological reaction tank, and the total phosphorus concentration at each predetermined time. The second step issues a command to adjust the range of the anaerobic atmosphere, the microaerobic atmosphere, and the aerobic atmosphere in the adjustment processing region 12 based on the measurement results of the ammonia concentration, the total phosphorus concentration, and preferably the total nitrogen concentration. The first and second steps of the control program are realized, for example, by functions provided in the central processing unit that constitutes the control unit 9. The organic waste water treatment method by the operation of such a control program will be described later.

Next, an organic wastewater treatment method using the organic wastewater treatment system of the present embodiment and a control program for the organic wastewater treatment system will be described.
The organic waste water (treated water) is first separated into a solid content and a liquid content in the sedimentation basin 2. The liquid component is introduced into the biological reaction tank 3 through the introduction channel. In the biological reaction tank 3, the activated sludge, which is an agglomerate of microorganisms, simultaneously removes organic substances and removes nitrogen and phosphorus by the following principle.

First, the principle of nitrogen removal will be described.
Most of the nitrogen components in organic wastewater exist in the form of ammonia ions (NH ₄ ⁺ ). This nitrogen content is oxidized to nitrate nitrogen (NO ₃ ⁻ ) by the reaction of the formula (1) by the action of nitrifying bacteria present in the activated sludge under conditions where oxygen is present. This reaction proceeds mainly in the aerobic treatment region 13.

Conditions where oxygen is present (aerobic conditions)
NH ₄ ⁺ + 2O ₂ → NO ₃ ⁻ + H ₂ O + 2H ⁺ (1)

  This nitrate nitrogen is reduced to nitrogen gas by the reaction of formula (2) by the action of denitrifying bacteria in the absence of oxygen. This reaction proceeds mainly in the anaerobic treatment region 11. Since (H) in the formula (2) is given from an organic substance (hydrogen donor) in sewage, an organic substance is required to promote this reaction. The organic matter may be an organic matter in organic waste water, or may supply alcohol, carboxylic acid or the like to the anaerobic treatment region 11.

Conditions without oxygen (anaerobic conditions)
2NO ₃ ⁻ + 10H → N ₂ + 2OH ⁻ + 4H ₂ O (2)

  As described above, the reaction of the formula (1) mainly proceeds in an aerobic atmosphere. In the anaerobic atmosphere, the reaction of the formula (2) mainly proceeds. Further, in the slightly aerobic atmosphere, the reactions of formulas (1) and (2) proceed simultaneously.

  Here, when the progress of the reaction from ammonia in formula (1) to nitrate ions is insufficient, the reaction in formula (2) does not proceed and the total nitrogen concentration in the organic waste water cannot be reduced. Therefore, when the ammonia concentration and the total nitrogen concentration in the organic waste water are high, it is necessary to promote the formula (1), and it is necessary to increase the aerobic atmosphere.

  On the other hand, even if the reaction of the formula (1) is sufficiently advanced, if the reaction of the formula (2) does not proceed, the total nitrogen concentration in the organic waste water cannot be reduced. Therefore, when the total nitrogen concentration is high despite the low ammonia concentration in the organic waste water, it is necessary to promote the formula (2), and thus it is necessary to increase the slightly aerobic atmosphere.

Next, the principle of phosphorus removal will be described.
Phosphorus is removed by the action of phosphorus accumulating bacteria present in the activated sludge. Phosphorus-accumulating bacteria discharge phosphorus accumulated in the cells in an anaerobic atmosphere. On the other hand, in an aerobic atmosphere, it absorbs more phosphorus than was discharged from the cells in an anaerobic atmosphere. Phosphorus corresponding to the difference between the discharge amount and the absorption amount is removed from the water. The phosphorus accumulating bacteria that store phosphorus in the body are removed by being extracted as excess sludge in the final sedimentation basin 4. Moreover, removal of phosphorus by phosphorus accumulating bacteria often proceeds more effectively as the volume of the anaerobic atmosphere increases. In addition, under the microaerobic condition where the nitrification / denitrification reaction is promoted, phosphorus is not discharged by the phosphorus accumulating bacteria.

Based on the above principle of nitrogen removal and phosphorus removal, the organic wastewater treatment method of the present embodiment will be described together with the operation of the control program executed by the control unit 9.
In the present embodiment, the adjustment treatment region 12 of the biological reaction tank 3 is an aerobic treatment region, so that nitrification (oxidation from ammonia to nitrate ions) is performed before denitrification (reduction of nitrate ions to nitrogen gas). Next, when this nitrification is sufficient, the control program performs an operation of removing phosphorus by setting the adjustment processing region 12 of the biological reaction tank 3 to an anaerobic atmosphere, and nitrogen (ammonia). Removal and phosphorus removal.

  Specifically, the ammonia concentration measuring device 5 installed on the outflow side of the biological reaction tank 3 measures the ammonia concentration on the outflow side of the biological reaction tank 3. Further, the total phosphorus concentration on the outflow side of the final sedimentation basin 4 is measured by the total phosphorus concentration measuring device 8 installed on the outflow side of the final sedimentation basin 4. In addition, when using a phosphate phosphorus concentration measuring device instead of the total phosphorus concentration measuring device 8, the phosphate phosphorus concentration is measured.

  The atmosphere switching (anaerobic atmosphere, slightly aerobic atmosphere, aerobic atmosphere) function of the adjustment processing region 12 is performed on the outflow side of the biological reaction tank 3 measured by the ammonia concentration measuring device 5 installed on the outflow side of the biological reaction tank 3. Ammonia concentration and total phosphorus concentration on the outflow side of the final precipitation basin 4 measured by the total phosphorus concentration measuring device 8 installed on the outflow side of the final precipitation basin 4 (in place of the total phosphorus concentration measuring device 8, phosphate phosphorus concentration When the measuring device is used, the adjustment processing region 12 of the biological reaction tank 3 is switched between an anaerobic atmosphere and an aerobic atmosphere based on the phosphoric acid state phosphorus concentration).

  The basic condition of the atmosphere switching control in the adjustment processing region 12 is that nitrogen removal is performed before the denitrification (reduction of nitrate ions to nitrogen gas) by making the adjustment processing region 12 of the biological reaction tank 3 an aerobic atmosphere. Only by nitrification (oxidation from ammonia to nitrate ions) and then, if it is judged that this nitrification is sufficient, the adjustment treatment area 12 of the biological reaction tank 3 is made anaerobic atmosphere to thereby reduce the phosphorus content. Remove. Ammonia related to nitrogen removal causes a rise in the BOD concentration of the treated water, and is controlled so as to perform oxidation (nitrification) to nitrate ions that do not affect the BOD concentration.

A specific atmosphere switching control example of the adjustment processing region 12 in the present embodiment will be described with reference to the schematic diagram of FIG.
The atmosphere switching control in the adjustment treatment region 12 is performed according to the state of the treated water (treated water quality state (I) to (IV)). The following determination is performed at the timing of control based on the control cycle. The control period is preferably a day order rather than a time order, but is not limited. In the following example, there is a margin (control redundancy) with respect to the NH ₄ -N target value and the PO ₄ -P target value. The NH ₄ -N target value and the PO ₄ -P target value are, for example, 1 mg / L and 2 mg / L, respectively, and a margin can be set for each NH ₄ -N target value and PO ₄ -P target value. Adjustable parameters such as 0.1 and 0.2.

<Processed water quality I>
In the treated water quality state I, the treated water NH ₄ -N exceeds the target upper limit value (NH ₄ -N target value + margin), and the treated water PO ₄ -P is the target lower limit value (PO ₄ -P target value). -Margin) The water quality is as follows. In this case, since nitrification is insufficient and phosphorus removal is sufficient, in order to promote nitrification, the adjustment processing region 12 is controlled so that the aerobic atmosphere increases.

<Processed water quality II>
In the treated water quality state II, NH ₄ -N of the treated water exceeds the target upper limit value (NH ₄ -N target value + allowance margin), and PO ₄ -P of the treated water is the target upper limit value (PO ₄ -P target value). The water quality is over +). In this case, since nitrification is insufficient and phosphorus removal is insufficient, in order to give priority to nitrification, the adjustment processing region 12 is controlled so that the aerobic atmosphere increases.

<Processed water quality III>
In the treated water quality state III, NH ₄ -N of the treated water is equal to or less than the target lower limit (NH ₄ -N target value−allowance), and PO ₄ -P of the treated water is the target upper limit (PO ₄ -P target value). The water quality is over +). In this case, since nitrification is sufficient and phosphorus removal is insufficient, the adjustment processing region 12 is controlled to increase the anaerobic atmosphere in order to promote phosphorus removal.

<Treatment water quality IV>
In the treated water quality state IV, the treated water NH ₄ -N is equal to or lower than the target lower limit value (NH ₄ -N target value-allowance), and the treated water PO ₄ -P is the target lower limit value (PO ₄ -P target value). -Margin) The water quality is as follows. In this case, since nitrification is sufficient and phosphorus removal is sufficient, the atmosphere of the adjustment processing region 12 is maintained as it is.

  An example of switching the adjustment processing region 12 of the biological reaction tank 3 will be described with reference to FIG. In FIG. 3, the first section is the anaerobic processing area 11, and the fourth section is the aerobic processing area 13. The second section is the first area 12 a of the adjustment processing area 12, and the third section is the second area 12 b of the adjustment processing area 12.

The processing atmosphere that can be taken by the first compartment, the second compartment, the third compartment, and the fourth compartment of the biological reaction tank 3 is defined as the following three patterns.
(State 1) 1st section: Anaerobic, 2nd section: Aerobic, 3rd section: Aerobic, 4th section: Aerobic (State 2) 1st section: Anaerobic, 2nd section: Anaerobic, 3rd section: Aerobic, fourth compartment: aerobic (state 3) first compartment: anaerobic, second compartment: anaerobic, third compartment: anaerobic, fourth compartment: aerobic

When the adjustment processing region 12 of the biological reaction tank 3 is set to an aerobic atmosphere in the treated water quality state I and the treated water quality state II at the timing of control, the biological reaction tank 3 is in the order of state 3 → state 2 → state 1 described above. Switch one step.
When the adjustment treatment region 12 of the biological reaction tank 3 is set in an anaerobic atmosphere in the treated water state III, the biological reaction tank 3 is switched in one stage in the order of the state 1 → the state 2 → the state 3 described above.
When the adjustment treatment region 12 of the biological reaction tank 3 is maintained as it is in the treated water quality IV, the state of the biological reaction tank 3 is maintained without being switched.

  Switching of the state of the adjustment processing region 12 of the biological reaction tank 3 is performed in one step at one control timing. At the timing of control, it is necessary to make the adjustment processing region 12 of the biological reaction tank 3 an aerobic atmosphere. When the current biological reaction tank 3 is in the state 1, the adjustment processing region 12 should be an aerobic atmosphere any more. Therefore, the biological reaction tank 3 remains in the state 1 without switching the state of the biological reaction tank 3.

  At the timing of control, it is necessary to make the adjustment processing region 12 of the biological reaction tank 3 an anaerobic atmosphere. When the current biological reaction tank 3 is in the state 3, the adjustment processing region 12 cannot be made an anaerobic atmosphere any more. Therefore, the biological reaction tank 3 is left in the state 3 without switching the state of the biological reaction tank 3.

As an example of switching of the adjustment processing region 12 of the biological reaction tank 3, a case where the initial state of the biological reaction tank 3 is set to the state 1 in FIG. In the case of the treated water quality state I and the treated water quality state II, it is necessary to make the adjustment treatment region 12 of the biological reaction tank 3 an aerobic atmosphere. The reaction vessel 3 remains in state 1.
In the case of the treated water quality state III, the biological reaction tank 3 is switched from the state 1 to the state 2 in order to make the adjustment treatment region 12 of the biological reaction tank 3 an anaerobic atmosphere.
In the case of the treated water quality state IV, the biological reaction tank 3 is left in the state 1 in order to maintain the adjustment treatment region 12 of the biological reaction tank 3 as it is.

By providing a margin with respect to the NH ₄ -N target value and the PO ₄ -P target value, useless opening of the on-off valves 25 b and 25 c formed on the way from the aeration apparatus 20 to the adjustment processing region 12 Since adjustment can be made unnecessary, it is possible to extend the device life of the on-off valves 25b and 25c.

That is, in the case of the initial treated water quality state II, in order to give priority to nitrification, the nitrification is improved by making the adjustment treatment region 12 of the biological reaction tank 3 an aerobic atmosphere, and the treatment water quality state III is headed. When a margin is provided when moving from the treated water quality state II to the treated water quality state III, the NH ₄ −N target upper limit value (NH ₄ −N target value + allowance margin) of the treated water is changed to NH ₄ − of the treated water. During the N target lower limit value (NH ₄ −N target value−allowance margin), there is no control, so there is no useless adjustment of the opening / closing valves 25b and 25c.

In the treated water quality state III, in order to promote the removal of phosphorus, by making the adjustment treatment region 12 of the biological reaction tank 3 an anaerobic atmosphere, the removal of phosphorus is improved, and the treated water quality state IV or treated water quality state I is changed. Head. In addition, there is a possibility that the nitrification will deteriorate due to the anaerobic atmosphere. When an allowance is provided when moving from the treated water quality state III to the treated water quality state IV, the treated water PO ₄ −P target upper limit value (PO ₄ −P target value + allowed margin) is changed from the treated water PO ₄ − During the P target lower limit value (PO ₄ −P target value−allowance margin), it becomes an uncontrolled region, so that unnecessary opening adjustment of the on-off valves 25b and 25c is eliminated.

Further, when an allowance is provided when moving from the treated water quality state III to the treated water quality state I, the treated water PO is reduced from the treated water PO ₄ -P target upper limit value (PO ₄ -P target value + margin). _{Between the 4-} P target lower limit (PO ₄ -P target value-margin) and the NH ₄ -N target lower limit (NH ₄ -N target value-margin) of the treated water, NH ₄ -N of treated water. Between the target upper limit values (NH ₄ −N target value + allowance margin), the regions are not controlled. Therefore, useless opening adjustment of the on-off valves 25b and 25c is eliminated.
When the treated water quality state IV is reached, the adjustment treatment region 12 of the biological reaction tank 3 maintains the current state.

In the treated water quality state I, in order to promote nitrification, nitrification is improved by making the adjustment treatment region 12 of the biological reaction tank 3 an aerobic atmosphere, and the treated water quality state I moves toward the treated water quality state IV. . When an allowance is provided when going from the treated water quality state I to the treated water quality state IV, the NH ₄ −N target upper limit value of the treated water (NH ₄ −N target value + allowable margin) is changed from the treated water NH ₄ − During the N target lower limit value (NH ₄ −N target value−allowance margin), there is no control, so there is no useless adjustment of the opening / closing valves 25b and 25c.

Next, the case where there is no margin for the NH ₄ -N target value and the PO ₄ -P target value will be described with reference to the schematic diagram of FIG. The control period is preferably a day order rather than a time order, but is not limited.

<Processed water quality I>
The treated water quality state I is a water quality state in which the treated water NH ₄ -N exceeds the target value and the treated water PO ₄ -P is equal to or lower than the target value. In this case, since nitrification is insufficient and phosphorus removal is sufficient, in order to promote nitrification, the adjustment processing region 12 is controlled so that the aerobic atmosphere increases.

<Processed water quality II>
The treated water quality state II is a water quality state where NH ₄ -N of the treated water exceeds the target value and PO ₄ -P of the treated water exceeds the target value. In this case, since nitrification is insufficient and phosphorus removal is insufficient, in order to give priority to nitrification, the adjustment processing region 12 is controlled so that the aerobic atmosphere increases.

<Processed water quality III>
The treated water quality state III is a water quality state where NH ₄ -N of the treated water is equal to or lower than the target value and PO ₄ -P of the treated water exceeds the target value. In this case, since nitrification is sufficient and phosphorus removal is insufficient, the adjustment processing region 12 is controlled to increase the anaerobic atmosphere in order to promote phosphorus removal.

<Treatment water quality IV>
The treated water quality state IV is a water quality state where the treated water NH ₄ -N is equal to or lower than the target value and the treated water PO ₄ -P is equal to or lower than the target value. In this case, since nitrification is sufficient and phosphorus removal is sufficient, the atmosphere of the adjustment processing region 12 is maintained as it is.

The NH ₄ -N target value and the PO ₄ -P target value are, for example, 1 mg / L and 2 mg / L, respectively, as in the case where there is a margin, but the adjustment process of the biological reaction tank 3 after exceeding the target value When the region 12 is changed, the timing is late. Therefore, when the values slightly smaller than the target values (NH ₄ -N target value and PO ₄ -P target values are 1 mg / L and 2 mg / L, respectively, for example, 0. When it becomes 5 mg / L and 1.5 mg / L, the adjustment process area | region 12 of the biological reaction tank 3 is changed, and a timing is advanced.

  Next, the schematic diagram of FIG. 5 shows an embodiment in which the occurrence frequency of a phenomenon in which phosphorus removal temporarily deteriorates when the adjustment processing region 12 of the biological reaction tank 3 is set in an anaerobic atmosphere in order to improve phosphorus removal. Will be described with reference to FIG.

In the following treatment by treatment water quality state, basically, the adjustment treatment region 12 of the biological reaction tank 3 is changed based on the treatment water NH ₄ -N, and the adjustment treatment region 12 of the biological reaction vessel 3 is aerobic. In order to maintain the atmosphere or to maintain the current state, the adjustment treatment region 12 of the biological reaction tank 3 is set to an anaerobic atmosphere only when the treated water quality state D is reached.

The control period is preferably a time order rather than a day order, but is not limited to this. In addition, the case where there is a margin with respect to the NH ₄ -N target value and the PO ₄ -P target value of the treated water is shown below. The NH ₄ -N target value and the PO ₄ -P target value are, for example, 1 mg / L and 2 mg / L, respectively. The margin is an adjustable parameter such as 0.1 or 0.2, although only in the case of the NH ₄ -N target value.

The significance of setting a margin is the same as that of the embodiment shown in FIG. Further, there is a case where there is no margin for the NH ₄ -N target value, and the significance when there is no margin is the same as in the embodiment shown in FIG. In addition, when there is no allowance for the NH ₄ -N target value, the adjustment processing region 12 of the biological reaction tank 3 may be changed when the value becomes slightly smaller than the target value to advance the timing. It is the same as that described in the embodiment.

<Processed water quality state A>
The treated water quality state A is a water quality state where the treated water NH ₄ -N exceeds the target upper limit value (NH ₄ -N target value + margin) of the treated water NH ₄ -N, and in this case, nitrification is insufficient. In order to improve nitrification, the aerobic atmosphere is increased in the adjustment processing region 12 of the biological reaction tank 3.

<Processed water quality state B>
In the treated water quality state B, the treated water NH ₄ -N is equal to or higher than the target lower limit value of the treated water NH ₄ -N (NH ₄ -N target value-allowance), and the treated water NH ₄ -N is treated water NH ₄ -N. Since the water quality is below the N target upper limit (NH ₄ −N target value + allowance margin) and nitrification is sufficient, the adjustment treatment region 12 of the biological reaction tank 3 is maintained as it is.

<Processed water quality state C>
In the treated water quality state C, the treated water NH ₄ -N is below (below) the target lower limit value of the treated water NH ₄ -N (NH ₄ -N target value−allowance), and the treated water PO ₄ -P is PO. It is determined that the water quality is lower than the _4- P target value, nitrification is sufficient, and phosphorus is not so bad, and the adjustment treatment area 12 of the biological reaction tank 3 is maintained as it is.

<Processed water quality state D>
In the treated water quality state D, the treated water NH ₄ -N is less than (below) the target lower limit value of the treated water NH ₄ -N (NH ₄ -N target value-allowance), and the treated water PO ₄ -P is PO. _{Since the} water quality is higher than the _4- P target value and nitrification is sufficient but phosphorus is deteriorated, the adjustment treatment region 12 of the biological reaction tank 3 is obtained in advance by simulation or the like in order to improve phosphorus removal. The processing atmosphere is effective for removing phosphorus.

According to at least one embodiment described above, the control unit prioritizes nitrification in nitrogen removal, and controls the adjustment processing region to perform phosphorus removal when nitrification is sufficient, thereby removing nitrogen and It is possible to provide an organic wastewater treatment system, an organic wastewater treatment method, and a control program for the organic wastewater treatment system that can efficiently remove phosphorus and reduce the total nitrogen concentration and the total phosphorus concentration in the organic wastewater.
Further, it is possible to remove nitrogen and phosphorus at low cost by eliminating useless opening adjustment of the on-off valve that controls the atmosphere in the adjustment processing region.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Organic waste water treatment system, 2 ... First sedimentation basin (precipitation basin), 3 ... Biological reaction tank, 5 ... Ammonia concentration measuring device, 7 ... Total nitrogen concentration measuring device, 8 ... Total phosphorus concentration measuring device, 9 ... Control part 11 anaerobic processing region 12 adjustment processing region 13 aerobic processing region

Claims (5)

From the upstream side to the downstream side along the flow of the water to be treated, a biological reaction tank comprising an anaerobic treatment region, an adjustment treatment region, and an aerobic treatment region in order,
An ammonia concentration measuring device for measuring the ammonia concentration of treated water in the aerobic treatment region;
A total nitrogen concentration measuring device for measuring the total nitrogen concentration of the treated water flowing out of the biological reaction tank;
A total phosphorus concentration measuring device or a phosphorous phosphorus concentration measuring device for measuring the total phosphorus concentration or phosphate phosphorus concentration of the treated water flowing out of the biological reaction tank;
A control unit that adjusts the atmosphere range of the adjustment processing region based on values measured by the ammonia concentration measuring device, the total nitrogen concentration measuring device, and the total phosphorus concentration measuring device or the phosphoric phosphorus concentration measuring device. When,
Comprising
The adjustment processing area can be switched to at least one kind of atmosphere among anaerobic atmosphere, slightly aerobic atmosphere or aerobic atmosphere, and the range occupied by each atmosphere can be adjusted,
The control unit prioritizes nitrification in nitrogen removal, and the nitrification is sufficient based on the values measured by the ammonia concentration measuring device and the total phosphorus concentration measuring device or the phosphorous phosphorus concentration measuring device. An organic wastewater treatment system comprising a control program for controlling the adjustment treatment area so as to remove phosphorus when it is determined that From the upstream side to the downstream side along the flow of the water to be treated, a biological reaction tank comprising an anaerobic treatment region, an adjustment treatment region, and an aerobic treatment region in order,
An ammonia concentration measuring device for measuring the ammonia concentration of treated water in the aerobic treatment region;
A total nitrogen concentration measuring device for measuring the total nitrogen concentration of the treated water flowing out of the biological reaction tank;
A total phosphorus concentration measuring device or a phosphorous phosphorus concentration measuring device for measuring the total phosphorus concentration or phosphate phosphorus concentration of the treated water flowing out of the biological reaction tank;
A control unit that adjusts the atmosphere range of the adjustment processing region based on values measured by the ammonia concentration measuring device, the total nitrogen concentration measuring device, and the total phosphorus concentration measuring device or the phosphoric phosphorus concentration measuring device. When,
Comprising
The adjustment treatment area is an area that can be switched to one or more atmospheres of an anaerobic atmosphere, a slight aerobic atmosphere or an aerobic atmosphere, and the range occupied by each atmosphere can be adjusted,
The control unit prioritizes nitrification in nitrogen removal, and the nitrification is sufficient based on the values measured by the ammonia concentration measuring device and the total phosphorus concentration measuring device or the phosphorous phosphorus concentration measuring device. And an organic wastewater treatment system having a control program for controlling the adjustment processing region so that phosphorus removal is performed when the phosphorus concentration exceeds a specified value. The controller is
A target value setter for storing a target value set in advance for the ammonia concentration and the total phosphorus concentration or the phosphate phosphorus concentration;
Switch to adjust the range of the atmosphere in the adjustment processing area by illuminating the target value and the measured values measured by the ammonia concentration measuring device and the total phosphorus concentration measuring device or the phosphorous phosphorus concentration measuring device. A determination unit;
The organic waste water treatment system according to claim 1 or 2 comprising. From the upstream side to the downstream side along the flow of the water to be treated, a biological reaction tank comprising an anaerobic treatment region, an adjustment treatment region, and an aerobic treatment region in order,
An ammonia concentration measuring device for measuring the ammonia concentration of treated water in the aerobic treatment region;
A total nitrogen concentration measuring device for measuring the total nitrogen concentration of the treated water flowing out of the biological reaction tank;
A total phosphorus concentration measuring device or a phosphorous phosphorus concentration measuring device for measuring the total phosphorus concentration or phosphate phosphorus concentration of the treated water flowing out of the biological reaction tank;
A control unit that adjusts the atmosphere range of the adjustment processing region based on values measured by the ammonia concentration measuring device, the total nitrogen concentration measuring device, and the total phosphorus concentration measuring device or the phosphoric phosphorus concentration measuring device. When,
Comprising
The adjustment treatment area can be switched to one or more of anaerobic atmosphere, slightly aerobic atmosphere or aerobic atmosphere, and an organic wastewater treatment system which can adjust the range occupied by each atmosphere. An organic wastewater treatment method using
Prioritizing nitrification in nitrogen removal with respect to the adjustment treatment region, the nitrification is performed based on values measured by the ammonia concentration measuring device and the total phosphorus concentration measuring device or the phosphate phosphorus concentration measuring device. An organic wastewater treatment method comprising a step of controlling so as to remove phosphorus when it is determined that is sufficient. From the upstream side to the downstream side along the flow of the water to be treated, a biological reaction tank comprising an anaerobic treatment region, an adjustment treatment region, and an aerobic treatment region in order,
An ammonia concentration measuring device for measuring the ammonia concentration of treated water in the aerobic treatment region;
A total nitrogen concentration measuring device or a phosphorous phosphorus concentration measuring device for measuring the total nitrogen concentration or phosphate phosphorus concentration of the treated water flowing out of the biological reaction tank;
A total phosphorus concentration measuring device for measuring the total phosphorus concentration of treated water flowing out of the biological reaction tank;
A control unit that adjusts the atmosphere range of the adjustment processing region based on values measured by the ammonia concentration measuring device, the total nitrogen concentration measuring device, and the total phosphorus concentration measuring device or the phosphoric phosphorus concentration measuring device. When,
Comprising
The adjustment treatment area can be switched to one or more of anaerobic atmosphere, slightly aerobic atmosphere or aerobic atmosphere, and an organic wastewater treatment system which can adjust the range occupied by each atmosphere. A control program for causing the control unit to execute
Prioritizing nitrification in nitrogen removal with respect to the adjustment treatment region, the nitrification is performed based on values measured by the ammonia concentration measuring device and the total phosphorus concentration measuring device or the phosphate phosphorus concentration measuring device. A control program comprising a step of performing control to remove phosphorus when it is determined that is sufficient.

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