JPH0631291A - Sewage treatment device - Google Patents

Abstract

PURPOSE:To make it possible to control the injection of a flocculant by quantifying a state in which sludge flock is formed and estimating a phosphorus removal rate rapidly based on the quantified state. CONSTITUTION:An image of a state in which sludge flock is formed is measured using an image recognition device 30, then a relationship between the increase rate of a flock particle diameter and a phosphorus removal rate in a control means 40 is obtained, and the phosphorus removal rate is estimated based on the determined relation. Then the phosphorus removal rate is maintained at an appropriate level by controlling the injection amount of a flocculant to be injected into an aerophilic aeration tank 1 from a flocculant storage tank 70. Consequently, an image of a state in which the sludge flock is formed is measured, so that the injection of the flocculant is performed without a shortage of an excess. Thus a treated water is always obtained stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage treatment device,
In particular, it relates to a sewage treatment apparatus suitable for efficiently removing phosphorus in sewage.

[0002]

2. Description of the Related Art In order to properly inject the coagulant in accordance with the phosphorus load in the waste water, it is necessary to accurately grasp the phosphorus load in the waste water and appropriately control the injection amount of the coagulant accordingly. Is effective. Therefore, at present, the coagulant is generally injected by converting it from the measured value of the phosphorus concentration in the waste water or the treated water and the inflow water amount.

For example, Japanese Examined Patent Publication (Kokoku) No. 3-22935 / 1990, when a flocculent is mixed with a flocculant to flocculate and settle the pollutant in the treated water, the shape of the floc is measured by an image and the flocculation is performed based on this value. It is described that the agent injection machine is controlled to optimize the injection amount of the coagulant. According to the invention, the flocculant is injected directly into the pond. In addition, the present inventors
A method has been proposed in which microbial flora in activated sludge is image-measured and a coagulant and an inhibitor are injected according to the result (JP-A-1-111491).

[0004]

The coagulation sedimentation method, which is one of the sewage treatment techniques, removes phosphorus from sewage by injecting a coagulant. Therefore, by measuring the phosphorus concentration in the treated water, it is possible to determine the quality of the coagulant injection amount. However, the literature (environmental technology: July 1984, 538-541
(See page), the measurement of phosphorus concentration requires complicated operations such as pressurization, heat decomposition, cooling, and reagent addition of the sample, and one measurement usually takes about 1 hour. There is a problem that it takes time.

The present invention has been made in view of the above problems, and its purpose is, in particular, a predicting means capable of quantifying the state of sludge floc formation and rapidly determining the phosphorus removal rate from the result. It is to provide a sewage treatment device provided with.

[0006]

In order to solve the above problems, the sewage treatment apparatus of the present invention basically comprises a biological reaction tank containing a mixed liquid of inflowing sewage and activated sludge, and the biological reaction tank. Settling tank for solid-liquid separating the activated sludge from the mixed solution flowing out from the sludge, sludge returning means for returning the activated sludge solid-liquid separated in the settling tank to the biological reaction tank, and aggregating phosphorus in the mixed solution Sewage having a chemical injection means for injecting a chemical into a biological reaction tank for this purpose, an imaging means for imaging the activated sludge in a plurality of locations in the mixed solution, and a measurement means for measuring the image feature amount of the imaged activated sludge The treatment apparatus is characterized by including a predicting unit for predicting a phosphorus removal rate by obtaining the particle size increase rate from the average particle size of the activated sludge in the mixed liquid measured by the measuring unit.

As a more specific example, the sewage treatment apparatus is provided with a control means for controlling the chemical injection amount of the chemical injection means based on the result obtained by the prediction means. And those equipped with means for displaying the relationship between the particle size increase rate of the activated sludge obtained by the prediction means and the phosphorus removal rate.

[0008]

In the sewage treatment apparatus of the present invention having the above characteristics, the mixed liquid of the inflowing sewage and the activated sludge, which is discharged from the biological reaction tank, is solid-liquid separated in the settling tank. Most of the activated sludge settled there is returned to the biological reaction tank by the returning sludge means. The image feature amount of the activated sludge in the mixed liquid imaged by the plurality of image pickup means is measured by the measuring means. Then, the prediction means predicts the phosphorus removal rate by obtaining the particle size increase rate from the measured average particle size of the activated sludge in the mixed liquid. Based on the result obtained by the predicting means, the chemical injecting means is controlled so that the coagulant injection amount to be supplied to the biological reaction tank is appropriate in order to aggregate the phosphorus in the mixed solution.

As described above, the phosphorus removal rate can be properly maintained by controlling the injection of the coagulant using the average particle size increase rate of the activated sludge as an index.

[0010]

Embodiments of the activated sludge sewage treatment apparatus according to the present invention will be described below with reference to the drawings. In all the drawings for explaining the embodiments, those having the same function are designated by the same reference numerals, and overlapping description will be omitted. Example 1 FIG. 1 is an overall schematic view schematically showing an overall outline of an activated sludge sewage treatment apparatus according to the present invention. FIG. 2 is a schematic diagram of a control device for controlling the coagulant injection amount. Also, in FIG.
Is a correlation diagram between the phosphorus removal rate and the floc particle size increase rate in the condensate injection, and Fig. 4 shows the relationship between the phosphorus removal rate and the floc particle size increase rate shown in Fig. 3. Also, the figure
Fig. 5 is a diagram showing the measurement results of sludge settling property during coagulant injection.

In FIG. 1, an aerobic aeration tank 1, which is a biological reaction tank, is connected to a settling tank 2 by a pipe or the like, while inflowing water 3 containing organic substances flows in. The sedimentation basin 2 and the aerobic aeration tank 1 are connected by the returning sludge means 4. In addition, treated water 5 and excess sludge 6 treated in the settling basin 2 are discharged to the outside of the system. Further, air diffusers 8a and 8b for ejecting the air 7 fed into the aerobic aeration tank 1 are provided, whereby the mixed liquid 9 is stirred and oxygen is supplied.

Imaging devices 20a and 20b are installed in the rear stage of the aerobic aeration tank 1 and in the front stage of the settling basin 2, respectively. An image recognition device 30 is provided as a measuring unit that calculates the image feature amount of the flocs imaged by the imaging devices 20a and 20b. Further, in order to optimize the coagulant to be injected into the aerobic aeration tank 1, the control device 40, the display device 50, the coagulant adjusting device.
60 and a flocculant storage tank 70 are provided.

Next, the operation of the sewage treatment apparatus of the first embodiment thus constructed will be described. Inflow water 3 containing organic matter and return sludge 4 containing activated sludge are introduced into the aerobic aeration tank 1.
The mixed liquid9 of sewage and activated sludge is the diffuser pipe at the bottom of the aerobic aeration tank.
Stirring and oxygen supply are performed by the air 7 injected from 8a and 8b. The mixed liquid 9 flowing out from the aerobic aeration tank 1 is the sedimentation tank 2
The solid-liquid separation is carried out with and the supernatant is discharged as treated water 5. On the other hand, most of the settled activated sludge is returned to the aerobic aeration tank 1 as the return sludge 4, and the activated sludge corresponding to the growth is discharged to the outside of the system as excess sludge 6.

When the inflow water is aerobically treated, a part of phosphorus is decomposed by activated sludge to become phosphoric acid phosphorus (PO ₄ ³⁻ ). Phosphorous phosphate is PAC (polyaluminum chloride (A
l ₂ (OH) nCl ₆ ) _n ) and sulfuric acid band (Al ₂ (SO
₄ ) React with a flocculant such as ₃ · n H ₂ O) to precipitate as insoluble aluminum phosphate ( _Al PO ₄ ) as shown in formula (1). A coagulant is injected into the end of the aerobic aeration tank 1 to remove phosphorus from water.

PO ₄ ³⁻ + Al ³⁺ − → AlPO ₄ −−−− (1) According to this principle, a coagulant is injected into the end of the aerobic aeration tank 1 to remove phosphorus from water. The coagulant from the coagulant reservoir 70 is injected by the coagulant adjusting device 60. Imaging device 20
The purpose of a is to monitor sludge flocs that do not show a coagulation effect because they are close to the coagulant injection position. On the other hand, the imaging device
In 20b, sludge flocs that show the flocculating effect of coagulant injection are monitored. The image recognition device 30 calculates the image feature amount such as the shape of the flocs imaged by both the imaging devices 20a and 20b. The image processing of the image feature amount in the floc formation state in the suspension is performed by the image recognition apparatus according to the invention of the present inventors (for example, “Materials Suspended in Water” described in Japanese Patent Publication No. 3-22935). "Monitoring device", "Waterworks flock image recognition device" described in Japanese Examined Patent Publication No. 3-22936, "Microbiota detection device" described in Japanese Examined Patent Publication No. 3-2037).

As a result of analyzing the temporal change of the floc formation state at the time of injecting the coagulant using these image processing techniques, it was found that the floc shape was changed by the coagulant injection (this change cannot be visually judged). Therefore, the quantitative effect of coagulant injection can be grasped by measuring the floc formation state. Here, as one of the flock image feature amounts, the average particle size of the flock is calculated, and both values imaged by the imaging devices 20a and 20b are compared,
A signal is transmitted to the coagulant regulator 60 via the controller 40 to control the coagulant injection amount from the coagulant reservoir 70. At the same time, the display device 50 displays the relationship between the floc particle size and the phosphorus removal rate, which will be described later, via the control device 40.

Next, details of the control device 40 will be described with reference to FIG. In FIG. 2, 41 is a comparison circuit, 42 is an arithmetic unit,
43 is a control circuit. From the image recognition device 30, the flock particle size increase rate Rf is input to the comparison circuit 41. On the other hand, the operator inputs the phosphorus removal rate target value Rp * to the arithmetic unit 42.
From the target value Rp *, the flock particle size increase rate target value Rf * is obtained from the operation line A. Next, Rf * is input to the proportional circuit 41, where it is compared with the flock particle size increase rate Rf and the deviation ΔR
Calculate f. The control circuit 43 receives ΔRf and transmits a signal for controlling the coagulant injection amount to the coagulant regulator 60.

Next, the relationship between the phosphorus removal rate and the floc particle size increase rate in the coagulant injection will be described with reference to FIGS. Figure 3 shows the relationship between the phosphorus removal rate and the floc particle size increase rate at the coagulant injection rate. This is obtained from experiments at the target processing plant. As shown in Figure 3, both the phosphorus removal rate and the floc particle size increase rate increase proportionally within a certain range corresponding to the coagulant injection rate. Also,
Since the phosphorus removal rate and the increase in floc particle size increase proportionally, the relationship between the phosphorus removal rate and the floc particle size increase rate shown in Fig. 4 can be obtained by rearranging Fig. 3. The relationship shown in FIG. 4 is used in the arithmetic unit 42 shown in FIG. 2 to control proper coagulant injection. In this way, by monitoring the floc formation state, it is possible to grasp the progress of sludge flocculation and the state of phosphorus removal by coagulant injection. Then, the phosphorus removal rate can be predicted from the flock particle size increase rate, and the predicted value of the phosphorus removal rate is displayed on a display device such as a CRT 50. Therefore, the control device 40 also has a function as a prediction unit.

FIG. 5 shows the result of measurement of the sludge settling property in the coagulant injection. As a result, although there is an upper limit of the coagulant injection rate, it is apparent that the sludge settability is improved by increasing the coagulant injection rate. Second Embodiment In the first embodiment shown in FIG. 1, the imaging devices 20a and 20b are installed at two locations in the liquid in the aerobic tank 1 and the settling tank 2, but the present invention is not particularly limited to this. As an example of FIG.
The imaging device 20 can be installed outside the liquid as shown in FIG.

In FIG. 6, 10 is a liquid sampling pump, 11a, 11b and 11c are liquid sampling valves, and 12 is a liquid discharge after measurement. In such a configuration, 11a, 11b
Alternatively, by sampling the liquid through the valve of 11c, it is possible to monitor flocs that do not show a flocculation effect by coagulant injection (11a) and flocs that show a flocculation effect (11b, 11c). The image feature amount can be measured. Hereinafter, the operation is the same as that shown in FIG.

Embodiment 3 Another embodiment is shown in FIG. In FIG. 7, the imaging device 20
A is configured so that it can be moved to the rear part of the aerobic tank 1 (shown with a solid line) and the middle part of the aerobic tank 1 (shown with a dotted line). In such a configuration, in the imaging device 20a indicated by the solid line,
The floc showing the aggregation effect can be monitored, and the image feature amount of the floc not showing the aggregation effect can be measured by the imaging device 20a described by the dotted line after the movement. By such measurement, the increase rate of the floc particle size can be calculated. The operation thereafter is the same as that of the first embodiment shown in FIG.

Embodiment 4 Another embodiment is shown in FIG. In the case of this embodiment, the imaging device 20a is installed in the rear part of the aerobic tank 1, and the coagulant adjusting device 60
From the rear part of the aerobic tank 1 where the coagulant injection position from is indicated by the solid line,
There are two locations, one in the middle of the aerobic tank 1 and the settling tank 2 indicated by the dotted line. In such a configuration, when the coagulant injection position is indicated by a solid line, the floc measurement in which the coagulant effect is not shown in the aerobic tank 1 is shown, and the aerobic tank 1 in which the coagulant injection position is shown by the dotted line is shown. When the area between the sedimentation tank 2 and the sedimentation tank 2 is located, the floc feature amount showing the aggregation effect can be measured. As a result, the increase rate of the floc particle size can be calculated.
Hereinafter, the operation is similar to that of the first embodiment (FIG. 1).

Example 5 In the example of FIG. 9, the advanced treatment of coagulant injection was applied.
It is a method of controlling the process. In Fig. 9, 4a is a returning sludge control device, 6a is an excess sludge control device, 8c and 8d are aeration air control devices, 21a is an inflow water flow meter, 21b is a dissolved oxygen meter, 21c is a sludge concentration meter, and 21d is an organic matter concentration. A total of 80 is an evaluation device, and 90 is a process control device.

In such a configuration, the control device 40 can measure floc characteristic amounts as well as flocculent microorganisms and filamentous microorganisms in the activated sludge, and the appearance ratio of both can be measured by the evaluation device 80. It predicts and evaluates sedimentation characteristics and activity status. For example, as the evaluation of the sedimentation property, it is evaluated that the sedimentation property tends to deteriorate when the area and the perimeter of the aggregating microorganism are large. On the other hand, the evaluation method of the activity state of microorganisms is good if the appearance ratio of the above two kinds of microorganisms is within a predetermined range, and if either of them is a priority species, excess or deficiency of air or excess or insufficient of organic matter is determined. The process control device 90 selects the operation target and sets the operation amount based on the output result of the evaluation device 80 and the water quality measurement value in the process. As the water quality meter, the above-mentioned dissolved oxygen meter 21a, sludge concentration meter
21b and an organic matter concentration meter 21c. In addition, the aeration air 7, return sludge 4 and surplus sludge 6 are used as control variables, respectively.
Operated by 8c, 8d, 4a, 6a. In addition, the inflow water flow meter 21
The signal from a is transmitted to the process control device 90. At the same time, the flock image feature amount is transmitted to the process control device 90 via the evaluation device 70, and the inflow water flow rate can be corrected from the flock image feature amount (correction means such as an adjusting device is not shown). it can. Further, the flock image feature amount can be transmitted to the process control device 90 via the evaluation device 80, from which the aeration air amount can be manipulated by the aeration air adjusting device 8c or 8d. Hereinafter, other actions are similar to those of the first embodiment (FIG. 1).

Example 6 Microorganisms in activated sludge can generally be represented by C ₆₀ H ₈₇ O ₂₃ N ₁₂ P with a phosphorus content of about 2.2%. However, if activated sludge is made into an atmosphere of anaerobic (a state in which not only dissolved oxygen but also bound oxygen is not present in water), aerobic, anaerobic, and aerobic, the sludge absorption capacity of activated sludge greatly increases and a large amount of phosphorus is contained in the body. The phosphorus content rate is 5% or more. In the biological reaction tank, such microorganisms are selectively grown to allow the microorganisms to take up phosphate phosphorus, and the microorganisms having an increased phosphorus concentration are discharged as excess sludge out of the system to remove phosphorus. In FIG. 10 of the present embodiment, a coagulant injection operation is performed in the anaerobic / aerobic biological phosphorus removal method (AO method) to further increase the phosphorus removal efficiency.

In FIG. 10, 1a is an anaerobic tank and 1 is an aerobic tank. First, in the anaerobic tank 1a, phosphorus is released under anaerobic conditions, and under aerobic conditions in the aerobic tank 1, more phosphorus is ingested. It is a thing. Other operations are the same as in FIG. Further, also in FIG. 10 of this embodiment, it is possible to appropriately carry out the embodiments 2, 3, 4 and 5 shown in FIGS. 6, 7, 8 and 9 described above.

EXAMPLE 7 Simultaneous treatment of nitrogen and phosphorus using microorganisms is A ₂
It is the O method. Influent water contains ammonia nitrogen caused by urine and organic nitrogen caused by proteins. These nitrogens are oxidized by microorganisms in the aeration tank (nitrification effect). The generated nitrification ions are reduced to nitrogen gas by microorganisms and removed from the waste water in a state where there is no dissolved oxygen (anoxic state). Therefore, the mixed liquid containing nitrification ions is circulated without oxygen, and the nitrification ions are released as nitrogen gas into the atmosphere to remove nitrogen in the wastewater. The phosphorus removal is as described in Example 6 shown in FIG.

[0028] In this embodiment, as shown in FIG. 11, the A ₂
In addition to the O method, a coagulant injection operation is performed to increase the phosphorus removal efficiency. In FIG. 11, 1a is an anaerobic tank, 1b is an anoxic tank, 1 is an aerobic tank, and 13 is a mixed liquid circulation. First, in the phosphorus removal action, phosphorus is released in the anaerobic tank 1a under anaerobic conditions and phosphorus is taken in under the aerobic conditions in the aerobic tank 1, and the flocculating agent is injected into the aerobic tank 1 to increase the phosphorus removal efficiency. On the other hand, in the nitrogen removal, in the anoxic tank 1b and the aerobic tank 1, as described above, the mixed solution containing nitrification ions is circulated from the aerobic tank to the anoxic tank to remove nitrogen. Other operations are the same as in FIG. In addition, in FIG. 11 of the present embodiment, as shown in FIGS.
It is possible to appropriately carry out the embodiments 2, 3, 4 and 5 shown in FIGS.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various designs can be made without departing from the present invention described in the claims. It is possible to make changes. For example, the operator can perform a manual coagulant injection operation in addition to the coagulant injection operation by the control circuit 43 described above, according to the predicted display value.

As the flock image feature amount, the flock particle size has been described in the above embodiment, but the number of flock particles or the like can be used. Further, the coagulant injection operation includes a continuous supply method and an impulse supply method, and either method can correct the coagulant injection rate based on the floc image feature amount.

[0031]

As is clear from the above description, according to the present invention, the correlation between the floc formation characteristic amount and the phosphorus removal rate can be clarified by measuring the sludge floc formation state in the coagulant injection operation. Therefore, it is possible to control coagulant injection for the purpose of removing phosphorus by using the image measurement information of flocs. At the same time, the sedimentation characteristics of sludge can be estimated. With these, the operation of the sewage treatment apparatus can be efficiently operated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall outline of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a control device.

FIG. 3 is a diagram showing a relationship between a phosphorus removal rate and a floc particle size increase rate in coagulant injection.

FIG. 4 is a diagram showing a relationship between a phosphorus removal rate and a floc particle size increase rate.

FIG. 5 is a diagram showing sedimentation characteristics of activated sludge.

FIG. 6 is a schematic configuration diagram of a second embodiment.

FIG. 7 is a schematic configuration diagram of a third embodiment.

FIG. 8 is a schematic configuration diagram of a fourth embodiment.

FIG. 9 is a schematic configuration diagram of a fifth embodiment.

FIG. 10 is a schematic configuration diagram of a sixth embodiment.

FIG. 11 is a schematic configuration diagram of Example 7.

[Explanation of symbols]

1 ... Aerobic aeration tank, 1a ... Anaerobic tank, 1b ... Oxygen-free tank, 2 ...
Settling tank, 20, 20a, 20b ... Imaging device, 30 ... Image recognition device, 40 ... Control device, 50 ... Display device, 60 ... Coagulant adjusting device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Yoda 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Factory (72) Naoki Hara 5-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Incorporated company Hitachi Ltd. Omika factory (72) Inventor Fumichi Kure 52-1 Omika-cho, Hitachi City, Ibaraki prefecture Incorporated company Hitachi Ltd. Omika factory (72) Inventor Enshiro Ichiro Hitachi City, Ibaraki prefecture 4026 Kuji Town, Hitachi Research Laboratory, Hitachi Co., Ltd. (72) Misako Obuchi 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Co., Ltd.

Claims (7)

[Claims] 1. A biological reaction tank containing a mixed liquid of inflowing sewage and activated sludge, a settling tank for solid-liquid separating the activated sludge from the mixed liquid flowing out of the biological reaction tank, and a solid-liquid separation in the settling tank. Sludge returning means for returning the activated sludge to the biological reaction tank, chemical injection means for injecting a chemical into the biological reaction tank to agglomerate phosphorus in the mixed solution, and activated sludge at a plurality of locations in the mixed solution In the sewage treatment apparatus having an image capturing means for capturing an image and a measuring means for measuring the image feature amount of the imaged activated sludge, the average particle size of the activated sludge in the mixed liquid measured by the measuring means A sewage treatment apparatus comprising a predicting unit that predicts the phosphorus removal rate by obtaining the particle size increase rate. 2. A biological reaction tank containing a mixed solution of influent sewage and activated sludge, a settling tank for solid-liquid separating the activated sludge from the mixed solution flowing out of the biological reaction tank, and a solid-liquid separation in the settling tank. Sludge returning means for returning the activated sludge to the biological reaction tank, chemical injection means for injecting a chemical into the biological reaction tank to agglomerate phosphorus in the mixed solution, and activated sludge at a plurality of locations in the mixed solution In the sewage treatment apparatus having an image capturing means for capturing an image and a measuring means for measuring the image feature amount of the imaged activated sludge, the average particle size of the activated sludge in the mixed liquid measured by the measuring means It is characterized by further comprising: predicting means for predicting the phosphorus removal rate by obtaining the particle size increasing rate, and control means for controlling the chemical injection amount of the chemical injecting means based on the result obtained by the predicting means. Sewage treatment equipment. 3. A biological reaction tank containing a mixed liquid of influent sewage and activated sludge, a settling tank for solid-liquid separating the activated sludge from the mixed liquid flowing out of the biological reaction tank, and a solid-liquid separation in the settling tank. Sludge returning means for returning the activated sludge to the biological reaction tank, chemical injection means for injecting a chemical into the biological reaction tank to agglomerate phosphorus in the mixed solution, and activated sludge at a plurality of locations in the mixed solution In the sewage treatment apparatus having an image capturing means for capturing an image and a measuring means for measuring the image feature amount of the imaged activated sludge, the average particle size of the activated sludge in the mixed liquid measured by the measuring means It is characterized by further comprising: a prediction unit that predicts the phosphorus removal rate by obtaining the particle size increase rate, and a display unit that displays the relationship between the particle size increase rate and the phosphorus removal rate of the activated sludge obtained by the prediction unit. Sewage treatment equipment. 4. A biological reaction tank containing a mixed solution of influent sewage and activated sludge, a settling tank for solid-liquid separating the activated sludge from the mixed solution flowing out of the biological reaction tank, and a solid-liquid separation in the settling tank. Sludge returning means for returning the activated sludge to the biological reaction tank, chemical injection means for injecting a chemical into the biological reaction tank to agglomerate phosphorus in the mixed solution, and activated sludge at a plurality of locations in the mixed solution In the sewage treatment apparatus having an image capturing means for capturing an image and a measuring means for measuring the image feature amount of the imaged activated sludge, the average particle size of the activated sludge in the mixed liquid measured by the measuring means A predicting means for predicting the phosphorus removal rate by obtaining the particle size increase rate, a display means for displaying the relationship between the particle size increase rate and the phosphorus removal rate of the activated sludge obtained by the predicting means, and the predicting means. Based on the results obtained A sewage treatment apparatus comprising a control means for controlling the amount of chemical injection of the injection means. 5. A biological reaction tank containing a mixed solution of influent sewage and activated sludge, a settling tank for solid-liquid separating the activated sludge from the mixed solution flowing out of the biological reaction tank, and a solid-liquid separation in the settling tank. Sludge returning means for returning the activated sludge to the biological reaction tank, chemical injection means for injecting a chemical into the biological reaction tank to agglomerate phosphorus in the mixed solution, and activated sludge at a plurality of locations in the mixed solution In the sewage treatment apparatus having an image capturing means for capturing an image and a measuring means for measuring the image feature amount of the imaged activated sludge, the average particle size of the activated sludge in the mixed liquid measured by the measuring means Prediction means for predicting the phosphorus removal rate by obtaining the particle size increase rate, control means for controlling the chemical injection amount of the chemical injection means based on the result obtained by the prediction means, and coagulation and sedimentation of sludge Sludge properties such as properties Evaluating means to be evaluated, returning sludge amount adjusting means, surplus sludge amount adjusting means, aeration air amount adjusting means, and status measuring instrument such as inflow water flow meter, dissolved oxygen meter, sludge concentration meter, organic matter concentration meter, etc. Sewage treatment equipment characterized by. 6. Measured values of the flow rate of water flowing into the reaction tank, dissolved oxygen in the reaction tank, sludge concentration of the reaction tank, organic matter concentration of treated water flowing out from the settling tank, and activity obtained by the image measuring means. The sewage system according to any one of claims 1 to 5, further comprising a sludge settling property evaluation means for evaluating the settling property of the activated sludge based on the image feature amounts of the filamentous microorganisms and the aggregating microorganisms in the sludge. Processing equipment. 7. The measured values of the flow rate of water flowing into the reaction tank, the dissolved oxygen in the reaction tank, the sludge concentration of the reaction tank, the organic matter concentration of the treated water flowing out from the sedimentation tank, and the image measurement means. At least one of returned sludge amount, excess sludge amount, and aeration air amount is controlled by a sludge sedimentation evaluation means that evaluates the sedimentation property of activated sludge based on the image feature amount of filamentous microorganisms and coagulant microorganisms in activated sludge. The sewage treatment apparatus according to any one of claims 1 to 5, further comprising: