JPH11169885A - Control method by water treatment process and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control the injection time and injection quantity of a flocculant necessary for maintaining the concentration of phosphorus in a treating water to a desired value from a phosphorus excess intake state of a biological reaction vessel. SOLUTION: The sewerage disposal equipment is provided with a biological reaction vessel 1 having an anaerobic vessel 1A and an aerobic vessel 1C, a sedimentation pond 2, a flocculant injection equipment 9 for removing phosphorus in the aerobic vessel IC and a computer 30 for controlling the flocculant injection. The computer 30 has a phosphorus removal judging part 37 for judging whether the biological reaction vessel 1 has good phosphorous removing ability by judging >=2 measured values of a rainfall SR, a flowing-in water DO1, a flowing-water ORP1 and an aerobic vessel DOK corresponding to the judging indexes, computing parts 31-34 for obtaining the injecting quantity of the flocculant based on a logarithmic ratio of the phosphorus concentration Pi to the desired value Pm of a water to be treated at the upstream position from a flocculant injection part of the aerobic vessel 1C when the resultant judgment is bad and the phosphorus concentration is not kept to the desired value Pm and a flocculant quantity control part 36 for operating a flocculant injection equipment 9 by the computed result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment system for removing organic matter, nitrogen, and phosphorus from municipal sewage, industrial wastewater, lake water or dam lake water by a combination of biological treatment and physicochemical coagulation. The present invention relates to a water treatment control method and apparatus that appropriately adjusts a coagulant to be injected for the purpose of chemical flocculation and maintains a phosphorus concentration in treated water at a target value.

[0002]

2. Description of the Related Art In recent years, eutrophication has been progressing in lakes, marshes, dam lakes, bays, and the like, and it is necessary to reduce the inflow of nitrogen and phosphorus, which cause this, and conserve water quality. At the sewage treatment plant,
Organic matter is mainly removed from domestic wastewater and industrial wastewater by microbial treatment called the activated sludge method. Sewage contains nitrogen and phosphorus in addition to organic matter, and phosphorus flows into sewage treatment plants as orthophosphoric acid (PO4-P) and nitrogen as ammonia nitrogen. If the water is released without removing these phosphorus and nitrogen, eutrophication will proceed in the discharge water area, and the water quality will be further deteriorated due to abnormal growth of algae. Therefore, sewage treatment plants are also required to remove phosphorus and nitrogen in addition to organic matter.

[0003] In a sewage treatment plant, a microbial reaction tank is used in which an aeration tank, which is one facility of an activated sludge process, is divided into an aerobic region and an anaerobic region in order to remove phosphorus and nitrogen in inflowing sewage. . Microbial reaction tanks include the anaerobic-anoxic-aerobic method (A2O method), anaerobic-aerobic method (AO method), and modified activated sludge circulation method. It is arranged at the latter stage. Of these methods, A2
The O method can be expected to improve nitrogen and phosphorus, the AO method can be phosphorus, and the modified activated sludge circulation method can improve nitrogen removal rate.

[0004] The A2O method and the AO method utilize a phosphorus excess intake function of activated sludge (general term of complex microorganisms) by arranging an anaerobic tank at the front and an aerobic tank at the latter. Release and biological intake of phosphorus in the influent water by ingesting more phosphorus than released in the aerobic tank. However, the excess sludge phosphorous intake function varies depending on the quality of the influent water, plant operating conditions, or the activated sludge management conditions, and may result in poor discharge or poor intake, resulting in an increase in the phosphorus concentration in the treated water. .

[0005] For this reason, a method of injecting a coagulant such as a metal salt and removing it physicochemically is also used in the sewage treatment plant. If the injection amount of the coagulant is insufficient, the removal of phosphorus becomes insufficient, and the concentration of phosphorus in the treated water is increased. On the other hand, excessive injection has an effect on the operation cost, the amount of sludge generated, and the activity of microorganisms. Therefore, the injection amount of the coagulant must be minimized.

[0006] When phosphorus is removed by physicochemical coagulation in a sewage treatment plant, an aluminum or iron metal salt or slaked lime is used as a coagulant. Phosphorus in the liquid exists in the form of orthophosphoric acid or condensed phosphoric acid, and forms a sparingly soluble salt upon injection of a flocculant. Further, the flocculant reacts with the bicarbonate to form a floc of hydroxide and further adsorbs and removes phosphorus. The reaction formula when an aluminum-based flocculant is used is represented by Chemical Formula 1.

[0007]

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In order to convert the phosphorus in the solution into a poorly soluble salt, it is theoretically sufficient to inject 1 mole ratio of aluminum from the formula (1). However, since it is also consumed by other substances as in the formula (f2), it is necessary to make the molar ratio larger than 1 (cited example 1: edited by Tsuneo Murata; "Advanced Sewage Treatment Technology", Science and Engineering Books, May 1992).

As a well-known method for controlling the coagulant injection amount for the purpose of removing phosphorus, a change rate d (= (Pi−Po) is calculated based on the current phosphorus concentration Pi of the treated water and the phosphorus concentration Po of the treated water before a predetermined time b. /
b) is determined, and it is predicted that the phosphorus concentration change ΔPc (= dc) of the treated water after c hours assuming that the change will continue in the future,
There is a proposal to set the injection amount based on a deviation from a target value (cited example 2: Japanese Patent Application Laid-Open No. 3-89993). Alternatively, the phosphorus component amount is determined from the phosphorus concentration of the liquid portion obtained by solid-liquid separation of the activated sludge mixed water sampled from the aerobic tank and the flow rate of the treated water flowing out of the aerobic tank,
A method of controlling the amount of flocculant by calculating the required amount of flocculant from the amount of the phosphorus component using the chemical equivalent relationship (Cited Example 3: JP-A-9-74086). Is controlled to be constant in terms of molar ratio, and the phosphorus-containing floc is separated by sand filtration (Cited Example 4: JP-A-63-242392). The coagulant is injected by multiplying the phosphorus concentration of the dehydrated filtrate by an equivalent conversion coefficient. There are proposals such as a method for setting the amount (Cited Example 5: Japanese Patent Application Laid-Open No. 7-88497).

[0010]

The above cited examples 2 to 5
In the control of the coagulant injection amount, the molar ratio or the concentration ratio of aluminum and phosphorus is set in advance based on the equations (1) and (2), and a constant ratio control method for controlling the coagulant is adopted. I have.

For example, in the cited example 2, the test results (first
According to Table, the aluminum injection rate is almost proportional to the phosphorus concentration of the inflow water, and can be estimated to be about 1.3 in terms of molar ratio. However, as is clear from FIG. 2 of Reference 2, the phosphorus concentration in the influent water of a sewage treatment plant or the like greatly changes depending on the life cycle of a human. Therefore, it is difficult to properly control the coagulant by the prediction method in which the future phosphorus concentration of the treated water changes at the same rate as in the past.

Further, the coagulant injection amount is controlled in proportion to the phosphorus concentration in the inflow water. However, as in a microbial reaction tank comprising an anaerobic tank and an aerobic tank, the phosphorus concentration in the reaction tank is determined by the phosphorus concentration in the inflow water. However, there is a problem in applying a control method with a constant molar ratio to a treatment process in which the ratio may increase. In Reference Examples 2 to 5, the phosphorus concentration in the upstream part near the coagulant injection position is measured, and the deviation from the phosphorus concentration or the target value of the phosphorus concentration after the coagulant injection is multiplied by a constant value to obtain the coagulant injection amount. You have set. However, according to the test results of the present inventors,
In the coagulant control method as in the cited example in which the concentration ratio between aluminum and phosphorus is kept constant, the phosphorus concentration in the treated water cannot be maintained below the target value.

In addition, the biological reaction tank can maintain the phosphorus concentration in the normal range of the influent water below a target value by the phosphorus excess intake function when the biological state of the activated sludge is normal.
However, the excess sludge phosphorus intake function varies greatly depending on the quality of influent water and plant operating conditions.
Attempts to control the phosphorus concentration below the target value result in excessive injection of the coagulant, which not only increases running costs but also adversely affects activated sludge. Therefore, it is necessary to quantitatively evaluate the excess phosphorus intake function of the biological reaction layer, that is, the ability to remove phosphorus, and to inject a flocculant when the ability to remove phosphorus is reduced to such an extent that the target value cannot be maintained.

An object of the present invention is to consider the state of the prior art described above and predict the phosphorus removal capacity in a biological reaction tank, and when the capacity is reduced, inject an appropriate amount of a coagulant to reduce the phosphorus concentration in the treated water. It is an object of the present invention to provide a biological water treatment method and apparatus for maintaining the water content below a target value.

[0015]

A biological water treatment control method according to the present invention comprises a biological reaction tank and a sedimentation tank in which an anaerobic tank is located in the first stage and an aerobic tank is located in the second stage. In a biological water treatment process equipped with a coagulant injection facility for removing phosphorus, the ability of the biological reaction tank to remove phosphorus is determined based on a preset determination index, and the phosphorus of the treated water in the sedimentation basin is determined. When it is predicted that the concentration cannot be maintained below the target value, the water to be treated (hereinafter referred to as water to be treated) before the coagulant is injected into the aerobic tank or the measured phosphorus concentration in the treated water and the target value The injection amount of the coagulant is obtained based on the logarithmic ratio of the above, and the coagulant injection equipment is controlled.

Further, the biological water treatment control method of the present invention comprises:
In the biological water treatment process, when the total rainfall (SR1) within a predetermined period in the environment of the influent flowing into the biological reaction tank exceeds a certain amount, the phosphorus removal ability of the biological reaction tank is determined. Determined based on the index, when it is predicted that the preset phosphorus concentration target value of the treated water (Pm) cannot be maintained, the phosphorus concentration in the treated water before the injection of the coagulant in the aerobic tank ( Pi) and / or the phosphorus concentration in the treated water (Po), and the concentration of the coagulant injected into the treated water from the phosphorus concentration target value (Pm) is calculated, and the product of the injected concentration and the flow rate of the water to be treated, A coagulant injection amount necessary to maintain the target value is obtained, and the coagulant injection equipment is controlled.

In the present invention, at least one of a dissolved oxygen concentration (DOI), an oxidation-reduction potential (ORPI) and a dissolved oxygen concentration (DOK) in the aerobic tank is set in advance. The determined index is compared with the measured value, and if the measured value exceeds the determined index, it is predicted that the phosphorus concentration target value cannot be maintained.

In the case where the time during which the measured value continuously exceeds the judgment index is equal to or longer than a first reference time,
The injection control of the coagulant is started.

Further, one or both of the measured values of the dissolved oxygen concentration and the oxidation-reduction potential of the influent water flowing into the biological reaction tank are compared with a second judgment index set in advance, and the measured value is compared with the second judgment index. When the value is lower than the second constant index, the injection control of the coagulant is stopped after a lapse of a second reference time based on the total rainfall (SRt) after the start of the injection control.

The biological water treatment control device of the present invention has at least an anaerobic tank, an aerobic tank, and a sedimentation tank, and is equipped with a facility for injecting a flocculant into the outlet (outlet or near) of the aerobic tank. Determining means for determining the quality of the phosphorus removal capacity of the biological reaction tank according to a predetermined determination index, and water to be treated before the coagulant is injected into the aerobic tank (hereinafter referred to as water to be treated). Or calculating means for calculating the coagulant injection amount based on the logarithmic ratio between the measured value of the phosphorus concentration in the treated water and the target value, and when the determining means determines that the phosphorus removing ability is defective, the calculating means The coagulant injection equipment is operated in response to an output signal from the apparatus.

The water treatment control device includes a measuring means for measuring the amount of rainfall in the environment of the inflow of the inflow water into the biological reaction tank, and a concentration of the inflow water-soluble oxygen concentration, the inflow hydroxylation-reduction potential, and the aerobic tank dissolved oxygen concentration. Measuring means for measuring at least one, the determining means for determining whether the phosphorus removal ability is good or not, and for instructing the coagulant injection control, the rainfall determination index; The determination index is set to at least one of a concentration, the inflow hydroxylation reduction potential, and the dissolved oxygen concentration in the aerobic tank.

In the case where the result of determination of the phosphorus removal ability (good / fail) by the determination means and the result of calculation of the logarithmic ratio (greater than 0 / less than 0) by the calculation means conflict with each other, the biological reaction tank is A display means for outputting a message for assisting the driving operation is provided. The message is "change of return sludge flow rate" and / or "change of set value (determination index) of dissolved oxygen concentration in aerobic tank".

The operation of the present invention will be described. According to the present invention, (1) the ability of the biological reaction tank to remove phosphorus by releasing and ingesting phosphorus is influenced by the quality of the incoming sewage, and changes in accordance with the quality of the incoming water or the amount of rainfall affecting this quality, and further, the quality of the incoming water. It can be determined from the aerobicity of the biological reaction tank and the like. (2) The phosphorus concentration of the water to be treated or treated water before / after the injection of the flocculant is determined by the flocculant injection concentration (the initial value is the injection concentration =
0) that the logarithmic relationship decreases after a predetermined time,
This is based on two experimental findings. Hereinafter, the phosphorus removal characteristics by the biological treatment of the present invention and the reaction characteristics by the coagulant injection will be described.

FIG. 2 shows changes in the concentration of soluble phosphorus and the amount of rainfall in treated water obtained by biological treatment. The concentration of phosphorus in the influent is 2
It fluctuates every day at 5 mg / L, but the phosphorus concentration of treated water rises when there is more than a specified amount of rainfall.

In a biological reaction tank in which an anaerobic tank is provided in the first stage and an aerobic tank is provided in the second stage, orthophosphoric acid is released from the body of the activated sludge in the anaerobic tank, and is ingested in the aerobic tank in excess of the released amount and accumulated in the body. . It is essential for phosphorus intake to release phosphorus sufficiently in the preceding anaerobic tank, and when this release is insufficient, intake in the aerobic tank becomes insufficient, resulting in an increase in the phosphorus concentration of the treated water. This phenomenon is called phosphorus removal failure.

FIG. 3 shows the amount of phosphorus released from the anaerobic tank and the inflow water D.
It shows the relationship between O and ORP. In any case, when the amount exceeded a specific value, the release amount worsened and the intake amount was also reduced. FIG. 4 shows changes in the inflow water DO, ORP and the aerobic tank DO in the case where the phosphorus concentration of the treated water has increased during the elapsed days of 90 to 120 days in FIG. In this test, the amount of air supplied to the aerobic tank was adjusted by the deviation between the measured value of the DO meter installed at the outlet of the aerobic tank and a preset target value KO *.

The phosphorus concentration in the treated water increased with the rise of the inflow water DO and ORP, and several days after the recovery, the concentration A was below the target value (0.5 mg / L). The target value of aerobic tank DO is 1.5mg / L
However, due to the influence of the residence time, the ascent of the inflow water DO was increased, and the recovery was similarly delayed. The reason why the aerobic tank DO exceeded the control target value was that the organic matter and nitrogen in the inflow water were diluted by the rain to a low concentration, and the water to be treated was low in oxygen demand. This is because the operation was performed at the preset lower limit of the amount of air to prevent clogging.

From these results, it is possible to determine the poor phosphorus removal in the biological reaction tank based on the amount of rainfall, the DO value of the influent water, and the ORP value. When the air amount in the aerobic tank is controlled by the DO value, the aerobic tank DO value can be applied to the determination index. Indices for predicting poor phosphorus removal and determining injection / stop of the coagulant include the above-mentioned total rainfall, inflow DO value, and inflow ORP.
It is not necessary to use all of the values and the aerobic tank DO values, and it is basically necessary to use one index of the inflow DO value or the inflow ORP value on the premise of rainfall.

The coagulant injection concentration during the coagulant injection period can be determined based on the following experimental findings.

FIG. 5 shows the relationship between the concentration of soluble phosphorus in the treated water and the concentration of aluminum injection. Aluminum-based flocculant (PA
C: polyaluminum chloride) was injected, and the measured values of the soluble phosphorus concentration and the aluminum injection concentration in the treated water 30 minutes after the injection, the phosphorus concentration on the vertical axis is a logarithmic value.

If the phosphorus concentration P at the injection concentration of 0 is used as a parameter, as shown in FIG. 6, the phosphorus concentration P expressed by a logarithmic value with respect to the injection concentration R decreases in a proportional relationship. Therefore, the necessary coagulant injection concentration Rm can be obtained by the equation (1) based on the measured phosphorus concentration Pi of the water to be treated and the target phosphorus concentration Pm of the treated water.

[0032]

Rm = k1 · (LogPi−LogPm) = k1 · Log (Pi / Pm) (1) where k1 is a coefficient (reciprocal of the gradient tan θ). (1)
In the equation, when the logarithmic ratio is 0 or less, since the measured value of the phosphorus concentration of the water to be treated is equal to or less than the target value Pm, it is not necessary to inject the coagulant.

Since equation (1) can be regarded as an added value of points A and B in FIG. 6, when converted using the measured phosphorus concentration Po of the treated water, the coagulant injection concentration shortage (correction) Expression (2) for determining the value) ΔRm can be derived.

[0034]

ΔRm = Rm−Rm ′ = k1 · {(LogPi−LogPm) − (LogPi−LogPo)} = k1 · Log (Po / Pm) (2) That is, the measured value of the phosphorus concentration of the treated water and the target The correction value ΔRm of the coagulant injection concentration can be determined according to the logarithmic ratio of the values.

Since the measurement accuracy of the phosphorus concentration is higher in the treated water than in the mixed solution in the reaction tank, the response is inferior to the case of the formula (1), but the control accuracy can be improved. When the logarithmic ratio is equal to or less than 0 in the equation (2), no correction is required, and the coagulant injection amount is maintained at the current value.

Further, by using the measured phosphorus concentration Pi of the water to be treated and the measured phosphorus concentration Po of the treated water, it is possible to perform control capable of improving both accuracy and responsiveness. As shown in FIG. 7, the coagulant injection concentration is set to the point C (Rm ') by a linear relationship of the coefficient k1 so that the measured phosphorus concentration Pi of the water to be treated becomes the target value Pm. On the other hand, if the measured phosphorus concentration Po of the treated water at this time is point A, the target value Pm is point B according to the coefficient k2, so that a correction of ΔRm is required. Therefore, the required coagulant injection concentration Rm is expressed by equation (3) from both measured values Pi and Po.

[0037]

Rm = Rm + ΔRm = k1 · (LogPi−LogPm) + k2 · (LogPo−LogPm) = k3 · Log (Pi · Po / Pm2) (3) In the expressions (1) to (3), The deviation from the numerical value and the logarithmic value from the ratio are equivalent, and the definition of the logarithmic ratio described in the present invention includes both.

According to the present invention, the poor phosphorus removal in the biological reaction tank is not directly affected by the activated sludge, and is determined by a reliable gauge such as a rain gauge, a DO meter, or an ORP meter. In this case, by controlling the coagulant injection amount based on the logarithmic ratio of the measured value of the phosphorus concentration in the water to be treated or the treated water and the target value of the treated water, the amount of phosphorus in the treated water can be reduced to a minimum necessary amount. The concentration can be maintained at or below the target value, and low-cost operation management can be realized in which an adverse effect on activated sludge due to coagulant excess injection can be prevented.

If the logarithmic ratio in the expressions (1) to (3) is 0 or more, despite the determination result that phosphorus removal is normal, there is an abnormality in the measuring instrument or microorganisms in the activated sludge. It is possible to judge that the phase change or the operation condition of the reaction tank is inappropriate, and to issue an alarm. With this alarm, maintenance of the measuring instrument and proper management of the microorganisms can be supported in a timely manner.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be described in detail with reference to the drawings. Note that the same components are denoted by the same reference numerals throughout the drawings.

Example 1 FIG. 1 shows an anaerobic-aerobic method (AO
2) is a block diagram of the sewage treatment equipment according to the present invention, and a flocculant control device for controlling the phosphorus concentration of treated water to a target value or less is provided.
Example 1 The sewage treatment equipment of Example 1 is a biological reaction tank 1 composed of an anaerobic tank 1A and an aerobic tank 1C, a final sedimentation tank 2, an underwater stirrer 3, a blower 5, a sludge return equipment 6, a sludge discharge equipment 7, and a flocculant tank 8. And a coagulant injection equipment 9.

Inflow sewage discharged from homes and factories is first settled and removed in a sedimentation basin (not shown), and flows into the biological reaction tank 1. Return sludge 12, which is a group of microorganisms called activated sludge, is supplied from the final sedimentation tank 2 to the anaerobic tank 1A into which the inflow sewage 11 is led through the sludge return equipment 6, and the inflow sewage 11 and the return sludge 12 are mixed with the submerged stirrer 3 With stirring. In the anaerobic tank 1A under the anaerobic condition, the activated sludge hydrolyzes the polyphosphoric acid accumulated in the cells and orthophosphoric acid (PO4-
Released into the liquid as P). Activated sludge adsorbs organic matter when phosphorus is released and accumulates in cells. Therefore, in the anaerobic tank 1A, the phosphorus concentration increases, and the organic matter decreases.

The mixed solution in the anaerobic tank 1A is supplied to the aerobic tank via the partition wall 19.
Led to 1C. A diffuser pipe 4 is provided at the bottom of the aerobic tank 1C to diffuse the air 16 from the blower 5 to agitate the mixed liquid and supply the oxygen source of the activated sludge. In the aerobic tank 1C, the activated sludge decomposes the adsorbed organic matter into water and carbon dioxide in the presence of oxygen. It oxidizes ammonia nitrogen to nitric or nitrite nitrogen. Further, orthophosphoric acid in the solution is taken into cells as polyphosphate. Since this intake amount is usually an excess intake amount that was released in the anaerobic tank 1A, phosphorus was reduced and removed in the entire process.

The effluent 13 of the aerobic tank 1C is led to the final sedimentation basin 2, where the activated sludge in the mixed solution is settled by gravity. The supernatant liquid is discharged to rivers and oceans after chlorine sterilization as treated water 14. On the other hand, most of the precipitated high-concentration activated sludge is returned to the biological reaction tank 1 as returned sludge 12 by the sludge return facility 6, and a part corresponding to the multiplied portion is converted into excess sludge 15 via the sludge discharge facility 7. To discharge out of the system. The surplus sludge 15 contains phosphorus removed in the biological reaction tank 1.

In the process of biologically removing phosphorus as described above, it is necessary to maintain the anaerobic state in the anaerobic tank 1A and release phosphorus appropriately. If the release of phosphorus is insufficient, the intake of phosphorus in the aerobic tank 1C is poor, and the overdose is not required. Deterioration of the phosphorus removal capacity leads to a decrease in the phosphorus removal rate in the whole process, and the phosphorus concentration of the treated water 14 may be higher than that of the inflow sewage 11.

According to the present invention, when the phosphorus removing ability is deteriorated, it is difficult to rapidly recover by the biological treatment. Therefore, the state of the deterioration is quickly detected, and the phosphorus concentration in the treated water 14 is maintained at a target value or less. A chemical coagulation treatment for injecting a coagulant such as a salt is used together.

For this reason, the water treatment equipment of the present embodiment is provided with a coagulant tank 8 and a coagulant injection equipment 9, and is operated and controlled by the computer 30 at the outlet of the aerobic tank 1C which does not require stirring and mixing. The required amount of coagulant 17 is injected. Hereinafter, the configuration and operation of the coagulant injection control device realized by the computer 30 will be described.

A water sampling facility 20 is installed in the aerobic tank 1C, and water is sent to a phosphorus concentration meter 21. In the phosphorus concentration meter 21, the aerobic tank
The activated sludge of the mixed liquid of 1C is separated, and the concentration of soluble phosphorus in the liquid is measured and input to the computer 30. The installation position of the water sampling facility 20 is at least upstream of the injection position of the coagulant 17, and the phosphorus concentration of the water to be treated before the coagulant injection (in this example, the mixed solution in the aerobic tank) is measured. For the activated sludge separation of the aerobic tank 1C mixed solution, a membrane filtration method such as a flat membrane or a hollow membrane can be applied.

The rainfall SR measured by the rain gauge 29, the flow meter 22
And the inflow sewage flow rate Qi and return sludge flow rate Qr measured at 23,
Inflow water DO measured by dissolved oxygen concentration meter (DO meter) 25,27
Value (DOI) and aerobic tank DO (DOK), oxidation-reduction potentiometer (ORP meter)
The inflow water ORP value (ORPI) measured at 26 is also taken into the computer 30.

Based on these input values, the phosphorus removal determination unit 37 of the computer 30 determines whether the phosphorus removal ability of the biological reaction tank 1 is good. When the phosphorus removal ability is normal, the phosphorus concentration of the treated water in the sedimentation basin 2 can be maintained below the phosphorus concentration target value Po stored in the computer 30 in advance. On the other hand, if the phosphorus removal ability is poor, the required coagulant injection amount is calculated and the coagulant injection equipment 9 is controlled because the phosphorus concentration of the treated water exceeds the target value Po.

FIGS. 8 and 9 show flowcharts of the determination process of the phosphorus removal determination unit. FIG. 8 shows a determination process at the start of injection. The phosphorus removal determination unit 37 starts this process at the time of rainfall based on the measured value SR of the rain gauge 29. First, the total rainfall SR for a preset period (within 5 days) exceeds the set amount SR1 (s10
1) Further, when the inflow water DO value, the ORP value, and the aerobic tank DO value exceed the set values ID1, IO1, and KO *, respectively (s10).
2), when the phosphorus removal ability is determined to be defective and the state reaches the set duration T1n (s103), the injection of the flocculant is started.

Here, the set amount SR1 of the total rainfall is 10 mm or more, the inflow water DO set value ID1 is 1.0 mg / L or more, and the inflow water ORP set value IO1 is -300 mV or more. Also, aerobic tank DO set value KO *
Uses the DO target value at the time of performing the air amount control. The duration TIn continuously exceeding each set value is set within a range of 24 hours or less in consideration of the residence time of the biological reaction tank 1 up to the coagulant injection position. Each set value used for the determination is input in advance to the target value input unit 32.

FIG. 9 shows a process for judging when injection is stopped, which is started when rain stops. First, it is checked whether the inflow water DO value and the ORP value have become equal to or less than the set values ID2 and IO2, respectively, and whether the aerobic tank DO value has become about KO * (s201). Set value ID
2. For IO2, a DO value or an ORP value before the start of injection and before rainfall is stored, or a value obtained by subtracting a predetermined offset value from the set values ID1 and IO1 at the time of injection start determination processing is used. When the measured value becomes equal to or less than the set value, the total rainfall SRt during the coagulant injection period is calculated based on the time (s202). Total rainfall SRt
In the case of <SR2 (s203), the injection of the flocculant is stopped when the duration time reaches T2n (s204). Total rainfall SRt
If ≧ SR2 (s205), the injection of the flocculant is stopped when the duration time reaches T3n (s206). The total rainfall determination value SR2 is set to 20 to 80 mm, and the durations T2n and T3n are set within 5 days.

A plurality of determination indices are used for the determination of deterioration and recovery of the phosphorus removal ability in the phosphorus removal determination section 37 described above.
Although used under the ND condition, the present invention is not limited to this. For example, when assuming the determination of the total rainfall SR as described above, the OR of the inflow water DO value and the ORP value and the aerobic tank DO value is used.
Conditions may be used. Alternatively, the total rainfall SR may not be included in the determination index, and may be any two AND conditions of the inflow water DO value, the ORP value, and the aerobic tank DO value, or all OR conditions.

The ORP of the anaerobic tank is used as one of the judgment indices.
Values can also be considered. According to the experiments of the present inventors, the anaerobic tank
The indication value of ORP is unstable, and it is difficult to use this as the sole indicator of phosphorus removal ability. But anaerobic tank ORP
Indicates a change that is linked to the inflow water DO and the inflow water ORP to some extent, and can be added to the determination index as an AND condition with one or more of the above determination indexes. In addition, when a plurality of ORP meters are installed in the anaerobic tank and the interoperability can be confirmed among them, the indicated value can be considered to be stable, and thus can be used in the same column as the above-mentioned determination index.

Upon receiving an instruction to start the coagulant injection from the phosphorus removal determination unit 37, the injection concentration calculation unit 37 determines the phosphorus concentration target value Pm of the treated water input from the target value input unit 32 and the processing target of the aerobic tank 1C. The phosphorus concentration Pi measured from water is compared, and if Pi> Pm, the metal salt injection concentration Rm is calculated from the above equation (1). The coefficient k1 is set in the range of 5 to 20 when the metal salt is PAC.

The injection amount calculator 33 calculates the metal salt injection amount M from the injection concentration Rm, the inflow sewage flow rate Qi, and the return sludge flow rate Qr (4).
Calculate from the formula.

[0058]

## EQU4 ## M = Rm. (Qi + Qr) (4) The concentration Cm of the metal salt contained in the coagulant differs depending on the coagulant used and the dissolution conditions. The coagulant amount calculation unit 34 calculates the coagulant amount G including the required metal salt injection amount M from the equation (6).

[0059]

G = M / Cm (5) The coagulant amount control unit 36 adjusts the coagulant injection equipment 9 to provide an aerobic tank.
Control is performed so that the amount of coagulant G to be injected into 1C is obtained. The injection equipment 9 in this example is a pump, and the control unit 36 sets the pump rotation speed or the stroke length so that the measured value of the flow meter 24A becomes the flow value of the coagulant amount G.

In the logarithmic term of the equation (1), the ratio Pi / Pm ≦
If 1 or Pi / (Pm + ΔP) ≦ 1, it is determined that the phosphorus concentration of the treated water satisfies the target value, and the injection of the flocculant is stopped during that period. By this intermittent operation, the injection of an extra flocculant is suppressed, the operating cost is reduced, and the adverse effect on the activated sludge is avoided. Here, ΔP is a soluble phosphorus concentration that decreases between the water sampling facility 20 and the treated water 14 when the phosphorus removal capacity is normal, and can be set as a unique value of the process, and may be included in the target value in advance. Further, the phosphorus concentration at the time of stopping or restarting the intermittent control usually includes an allowable error with respect to the target value.

As a function of the computer 30, the air amount control unit 39A
And a return amount control unit 39B for controlling the blower 5 and the sludge return equipment 6. The air amount control unit 39A adjusts the blower 5 in accordance with the deviation between the DO measurement value KO of the aerobic tank 1C measured by the DO meter 28 and the DO target value KO * from the target value input unit 32, and To control the flow rate. The return amount control unit 39B includes the target value input unit 32
The sludge return facility 6 is adjusted so that the flow rate is obtained by multiplying the operation ratio η1 set in the above and the inflow sewage flow rate Qi, and the flow rate of the returned sludge 12 is controlled.

By this operation, the activated sludge concentration in the biological reaction tank 1 is stabilized, the influence of the activated sludge concentration on the release and intake of phosphorus can be eliminated, and the quality of the phosphorus removing ability can be accurately determined. In addition, when the phosphorus removal ability is deteriorated, the operation ratio η is increased to enhance the degree of reduction of the anaerobic tank and promote the recovery, so that the injection time of the flocculant and the injection amount are also reduced.

Further, a display unit 38 is provided as a function of the computer 30, and outputs a process state, a measured value, an alarm, and the like as necessary. For example, if contradictory results such as Pi> Pm are obtained when the phosphorus removal determining section 37 determines that the phosphorus removal capability is normal, the cause of deterioration in phosphorus removal is more in the biological reaction tank than in the inflow water quality. Since it is considered that the influence is caused by the operating conditions, the operation of changing the return sludge flow rate and the DO set value are performed, and then the control by the determination of the phosphorus removal capacity and the calculation of the flocculant amount are performed again.

Therefore, when an inconsistent result is obtained, the display unit 38 displays “change the return sludge flow rate” and “DO target value =
Display a message such as "Enhance KO *". At this time, as the related process amount, the measured value and the set value of the returned sludge flow rate Qr, and the flow rate of the air 16 are maintained at the air amount lower limit set value (target value input section), but exceed the target value KO *. It can also output the state of the DO measurement value etc.

[Embodiment 2] FIG. 10 is a block diagram of a sewage treatment facility based on an anaerobic-aerobic method, in which a coagulant control device using a measured value of the concentration of treated water phosphorus is provided. 1 is different from the configuration of FIG. 1 in that a water sampling facility 20 and a phosphorus concentration meter 21 are installed for the treated water 14, a measured phosphorus concentration Po of the treated water is input to a computer 30, and a calculation of the amount of the flocculant is performed. In the formula.

The injection concentration calculator 31 calculates the metal salt injection concentration correction value ΔRm from the phosphorus concentration measurement value Po and the target value Pm of the treated water by the above equation (2). The injection amount calculation unit 33 calculates the metal salt injection correction amount ΔM from equation (6), and the coagulant correction amount calculation unit 35 calculates the coagulant correction amount ΔG from equation (7).

[0067]

ΔM = ΔRm · (Qi + Qr) (6) ΔG = ΔM / Cm (7) The coagulant amount calculation unit 34 calculates an operation amount G ′ from the current coagulant amount G and the correction amount ΔG. The coagulant injection equipment 9 is adjusted based on the deviation from the signal value of the flow meter 25 corresponding to the current coagulant amount G to control the coagulant 17 to the aerobic tank 1C.

The system of the second embodiment causes a control delay corresponding to the residence time of the final sedimentation tank 2 as compared with the first embodiment. However, the treated water sent by the water sampling facility 20 has a very low concentration of activated sludge, the maintenance frequency of the pretreatment separation device is improved, and the flocculant control based on more accurate measurement information is possible.

[Embodiment 3] FIG. 11 is a block diagram of a sewage treatment system based on an anaerobic-aerobic method, in which a coagulant control device using the phosphorus concentration of the water to be treated and the treated water is provided. Example 3 is a combination of FIG. 1 and FIG. 10 in which water sampling facilities 20 and 20A are installed for aerobic tank 1C and treated water 14, and phosphorus concentration meters 21 and 21 are used.
Measure each phosphorus concentration with A. Based on the phosphorus concentration Pi of the aerobic tank 1C, the phosphorus concentration Po of the treated water, and the target value Pm, the injection concentration calculation circuit 31 calculates the metal salt injection concentration Rm by the above equation (3). Thereafter, in the same manner as in the first embodiment, the coagulant injection amount G is determined, and the coagulant injection unit 9 is adjusted by the coagulant control unit 36 to control the coagulant into the aerobic tank 1C.

According to this embodiment, the error of the phosphorus concentration in the aerobic tank 1C can be corrected by the measured value of the treated water, and the control accuracy is improved because the control by the final sedimentation basin 2 is not accompanied.

[Embodiment 4] FIG. 12 is a block diagram of a sewage treatment facility using an anaerobic-anoxic-aerobic method (A2O method).
A flocculant control device using the phosphorus concentration of the C water to be treated is provided. In this sewage treatment equipment, the biological reaction tank 1 is divided into three chambers: an anaerobic tank 1A, an oxygen-free tank 1B, and an aerobic tank 1C. To the oxygen-free tank 1B. The anoxic tank 1B has a denitrification function of reducing nitric or nitrite nitrogen generated in the aerobic tank 1C to nitrogen gas.

The coagulant injection control method in Example 4 is as follows.
This is the same as FIG. 1 except for the calculation of the injection amount calculation unit 33. The injection amount calculation unit 33 calculates the metal salt injection amount M by the equation (8) in which the circulating fluid flow rate Qj from the flow meter 24 is also added.

[0073]

M = Rm · (Qi + Qr + Qj) (8) In the present sewage treatment equipment, when the phosphorus concentration of the treated water is used instead of the water to be treated, the correction value ΔM of the metal salt injection concentration is calculated by the equation (6). The second embodiment is the same as the second embodiment except that the circulating fluid flow rate Qj is added. Further, when the phosphorus concentration of the water to be treated and the treated water is used, the third embodiment differs from the third embodiment in that the metal salt injection amount M is calculated by the equation (4) based on the metal salt injection concentration Rm obtained by the equation (3). Is the same.

It should be noted that the function of the computer 30 is as follows.
39A, a circulation amount control unit 39C is provided in addition to the return amount control unit 39B,
The water supply equipment 10 is controlled. The circulation amount control unit 39C adjusts the water supply equipment 10 so that the flow rate obtained by multiplying the operation ratio η2 set in the target value input unit 32 and the inflow sewage flow rate Qi, and controls the flow rate of the circulating fluid 18. By controlling the amount of air, the amount of returned sludge, and the amount of circulating liquid, the efficiency of removing organic substances and nitrogen is stabilized, and the above-described control of the coagulant injection amount is performed to reduce the concentration to a predetermined value or less including the phosphorus concentration. Can maintain water.

As described above, in the practical examples 1-4 of the present invention, the anaerobic-aerobic method and the anaerobic-anoxic-aerobic method were targeted.
Applicable to the anaerobic-aerobic-anaerobic-aerobic method (AOAO method). In the AOAO method, a coagulant is injected into the downstream aerobic tank outlet, and the metal salt injection amount M is calculated from the inflow sewage amount and the returned sludge amount.

[0076]

According to the present invention, the change in the state of phosphorus release / uptake in the biological reaction tank is predicted at an early stage, and when the phosphorus removal ability cannot maintain the target phosphorus value of the treated water, the injection of the flocculant is promptly performed. The effect is that the deterioration of water quality can be prevented by starting.

Further, the coagulant injection amount can be limited to a necessary minimum amount based on the logarithmic ratio characteristic between the phosphorus concentration in the water to be treated and / or the treated water and the coagulant injection concentration, and is limited to the period when the phosphorus removal ability deteriorates. Therefore, it is possible to reduce the operating cost and suppress the adverse effect of the flocculant on the activated sludge.

Further, when a result that is inconsistent with the need for coagulant injection is obtained between the predicted result of the phosphorus removal ability and the logarithmic ratio based on the measured value of the phosphorus concentration, the process state or the like that causes this is determined. Since the display is performed and appropriate operation support is performed, it is possible to quickly recover the biological treatment plant to an appropriate operation state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sewage treatment facility including a flocculant control device according to a first embodiment of the present invention.

FIG. 2 is a graph showing an example of a test result of a treated water phosphorus concentration in a sewage treatment facility.

FIG. 3 is a graph showing an example of a test result of phosphorus release characteristics of an anaerobic tank.

FIG. 4 is a graph showing an example of detailed test results at the time of deterioration of phosphorus release / intake.

FIG. 5 is an explanatory diagram showing a change characteristic of an aluminum injection concentration and a soluble phosphorus concentration.

FIG. 6 is an explanatory diagram explaining a calculation method of a coagulant injection concentration.

FIG. 7 is an explanatory diagram explaining another calculation method of the coagulant injection concentration.

FIG. 8 is a processing flowchart of a coagulant injection determination method in Examples 1 to 4.

FIG. 9 is a processing flowchart of a flocculant stop determination method in Examples 1 to 4.

FIG. 10 is a configuration diagram of a sewage treatment facility including a flocculant control device according to a second embodiment.

FIG. 11 is a configuration diagram of a sewage treatment facility including a flocculant control device according to a third embodiment.

FIG. 12 is a configuration diagram of a sewage treatment facility including a flocculant control device according to a fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Biological reaction tank, 1A ... Anaerobic tank, 1B ... Oxygen-free tank, 1C ... Aerobic tank, 2 ... Sedimentation tank, 5 ... Blower, 6 ... Sludge return equipment, 7 ...
Sludge discharge equipment, 8 ... flocculant tank, 9 ... flocculant injection equipment, 10 ... circulation equipment, 20 ... water sampling equipment, 21 ... phosphorus concentration meter, 2
2, 23, 24 ... flow meter, 25, 27 ... dissolved oxygen concentration meter, 26 ... oxidation-reduction potentiometer, 29 ... rain gauge, 30 ... computer, 31 ... injection concentration calculation unit, 32 ... target value input unit, 33 ... Injection amount calculation unit, 34 ... flocculant amount calculation unit, 65 ... flocculant correction amount calculation unit, 36 ... flocculant amount control unit, 37 ... phosphorus removal determination unit, 38 ... display unit, 39A ... air amount control unit, 39B ... Return amount control unit, 39C ... Circulation amount control unit.

[Procedure amendment]

[Submission date] January 19, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Title: Method and apparatus for controlling a water treatment process

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

TECHNICAL FIELD The present invention relates to a water treatment process for biologically treating municipal sewage, industrial wastewater or tap water.
In particular, a system that stably removes phosphorus in the influent water.
It relates to a control method and an apparatus .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

An object of the present invention is to consider the state of the prior art described above and predict the phosphorus removal capacity in a biological reaction tank, and when the capacity is reduced, inject an appropriate amount of a coagulant to reduce the phosphorus concentration in the treated water. To control the water treatment process so that
It is to provide a method and an apparatus .

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

SUMMARY OF THE INVENTION The water treatment process of the present invention
Is a biological treatment tank and a sedimentation tank in which an anaerobic tank is located in the first stage and an aerobic tank is located in the second stage, and the water treatment process includes a coagulant injection facility for removing phosphorus in the aerobic tank. When the phosphorus removal capacity of the biological reaction tank is determined based on a preset determination index, and it is predicted that the phosphorus concentration of the treated water of the settling basin cannot be maintained below its target value. Calculating the coagulant injection amount based on the water to be treated before injection of the coagulant in the aerobic tank (hereinafter, the water to be treated) or the logarithmic ratio of the measured phosphorus concentration in the treated water and the target value, The coagulant injection equipment is controlled.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Further, the control method of the present invention, the water treatment flop
In the process , when the total rainfall (SR1) within a predetermined period in the environment of the influent flowing into the biological reaction tank exceeds a certain amount, the phosphorus removal capacity of the biological reaction tank is determined based on a determination index. When it is predicted that the preset phosphorus concentration target value of the treated water (Pm) cannot be maintained, the phosphorus concentration (Pi) in the water to be treated before the injection of the flocculant in the aerobic tank.
And / or calculating the concentration of the coagulant injected into the treated water from the phosphorus concentration (Po) in the treated water and the target phosphorus concentration (Pm), and calculating the target by the product of the injected concentration and the flow rate of the water to be treated. The amount of coagulant injection required to maintain the value is obtained, and the coagulant injection equipment is controlled.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

The control device of the water treatment process of the present invention has at least an anaerobic tank, an aerobic tank, and a sedimentation tank, and is equipped with a facility for injecting a flocculant into an outlet (outlet or near) of the aerobic tank. In the water treatment equipment, determining means for determining whether or not the phosphorus removal ability of the biological reaction tank is good or not according to a predetermined determination index, and water to be treated (hereinafter, water to be treated) before injection of the flocculant into the aerobic tank. Provision is made for a calculating means for determining the coagulant injection amount based on the logarithmic ratio of the measured phosphorus concentration in the treated water and the target value, and when the determining means determines that the phosphorus removal capability is defective, the calculating means The coagulant injection equipment is operated in response to the output signal of (1).

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

The control device for the water treatment process includes a measuring means for measuring rainfall in the environment of the inflowing water into the biological reaction tank, an inflowing water-soluble oxygen concentration, an inflowing hydroxylation reduction potential, and an aerobic tank dissolved oxygen. Measuring means for measuring at least one of the concentrations; the judging means judges the quality of the phosphorus removal ability, and instructs the coagulant injection control; The determination index is set to at least one of the dissolved oxygen concentration, the inflow hydroxylation reduction potential, and the aerobic tank dissolved oxygen concentration.

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁶ Identification code FI C02F 3/12 C02F 3/12 K (72) Inventor Fumichi Kimura 5-2-1 Omikacho, Hitachi City, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (72) Inventor Yoshiaki Tashiro 2-8-1, Nishishinjuku, Shinjuku-ku, Tokyo (72) Inventor Yoshiyuki Osawa 25-1, Arakawa, Arakawa-ku, Tokyo Tokyo Sewerage Bureau Mikawashima Treatment Plant (72) 72) Inventor Saburo Ando 2-1-1-14 Miyagi, Adachi-ku, Tokyo Inside the Tokyo Sewerage Bureau Kodai Treatment Plant

Claims (9)

[Claims] 1. Biological water having a biological reaction tank and a sedimentation tank in which an anaerobic tank is located at a preceding stage and an aerobic tank is located at a later stage, and a coagulant injection facility for removing phosphorus in the aerobic tank. In the treatment process, the phosphorus removal capacity of the biological reaction tank is determined based on a preset determination index, and if the phosphorus concentration of the treated water (hereinafter, treated water) of the sedimentation basin cannot be maintained below its target value. When predicted, the coagulant is injected based on the water to be treated (hereinafter referred to as water to be treated) before the coagulant is injected into the aerobic tank or the logarithmic ratio of the measured phosphorus concentration in the treated water to the target value. A method for controlling biological water treatment, comprising determining an amount and controlling the coagulant injection equipment. 2. Biological water having a biological reaction tank and a sedimentation tank in which an anaerobic tank is located in the first stage and an aerobic tank in the second stage, and wherein the aerobic tank is equipped with a coagulant injection facility for removing phosphorus. In the treatment process, when the total rainfall (SR1) within a predetermined period in the environment of the inflowing water flowing into the biological reaction tank exceeds a certain amount, the phosphorus removal capacity of the biological reaction tank is determined based on the determination index. However, when it is predicted that the preset phosphorus concentration target value (Pm) of the treated water cannot be maintained, the water to be treated (hereinafter, the treated water) in the aerobic tank before the coagulant injection is performed. Phosphorus concentration
(Pi) and / or the phosphorus concentration in the treated water (Po) and the phosphorus concentration target value (Pm) to calculate the coagulant injection concentration into the treated water from the product of the injected concentration and the flow rate of the water to be treated, A method for controlling biological water treatment, comprising: obtaining a coagulant injection amount required to maintain the target value; and controlling the coagulant injection equipment. 3. The method according to claim 1, wherein at least one of a dissolved oxygen concentration (DOI), an oxidation-reduction potential (ORPI), and a dissolved oxygen concentration (DOK) of the inflow water into the biological reaction tank is provided. Comparing the measured value with a judgment index which is set in advance, and predicting that the phosphorus concentration target value cannot be maintained when the measured value exceeds the judgment index. . 4. The coagulant injection control according to claim 3, wherein the coagulant injection control is started when a time during which the measured value continuously exceeds the determination index is equal to or longer than a first reference time. Biological water treatment control method. 5. The method according to claim 4, wherein a measured value of one or both of a dissolved oxygen concentration and an oxidation-reduction potential of the inflow water into the biological reaction tank is compared with a second determination index preset for each of the measured values. When the measured value falls below the second constant index, the injection control is started, and after a second reference time based on the total rainfall (SRt) has elapsed, the injection control of the coagulant is stopped. A biological water treatment control method, comprising: 6. Biological water having a biological reaction tank and a sedimentation tank in which an anaerobic tank is located in the first stage and an aerobic tank in the second stage, and wherein the aerobic tank is equipped with a coagulant injection facility for removing phosphorus. In the treatment equipment, a determination unit that determines the quality of the phosphorus removal ability of the biological reaction tank according to a predetermined determination index, and water to be treated (hereinafter, water to be treated) before the injection of the flocculant into the aerobic tank. Arithmetic means for calculating the coagulant injection amount based on the logarithmic ratio between the measured phosphorus concentration in the treated water and the target value is provided.When the phosphorus removal ability is determined to be poor by the determination means, A biological water treatment control device, wherein the coagulant injection equipment is operated in response to an output signal. 7. The method according to claim 6, wherein a measuring means for measuring a rainfall in the environment of the inflow of the inflow water into the biological reaction tank, the inflow water-soluble oxygen concentration, the inflow hydroxylation reduction potential, and the aerobic tank dissolved oxygen concentration. Measuring means for measuring at least one; the determining means determines whether the phosphorus removing ability is good or not, and instructs the injection control of the coagulant; A biological water treatment control device having a determination index set to at least one of a concentration, an inflow hydroxylation reduction potential, and an aerobic tank dissolved oxygen concentration. 8. The determination result (good / good) of the phosphorus removal ability by the determination means according to claim 6 or 7.
No) and display means for outputting a message for supporting the operation of the biological reaction tank when the calculation result (greater than 0 / less than 0) of the log ratio by the calculation means conflicts with each other. A biological water treatment control device characterized. 9. The biological water treatment control device according to claim 8, wherein the message is “change of return sludge flow rate” and / or “change of set value of dissolved oxygen concentration in aerobic tank”. .