JP3067993B2 - Method and apparatus for biological dephosphorization of wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for biologically removing phosphorus from wastewater.
The present invention relates to an improved method and an apparatus for injecting a chemical flocculant in wastewater treatment using a chemical flocculation action in combination with a biological dephosphorization action.

[0002]

2. Description of the Related Art Conventionally, as a method for removing phosphorus from domestic wastewater or industrial wastewater, an activated sludge treatment system using biological dephosphorization has been adopted. In this system, BOD in inflowing wastewater is used. When the (biological oxygen demand) concentration is lowered, there is a disadvantage that the phosphorus removing action becomes unstable, for example, the phosphorus removal efficiency is lowered. In order to improve this point, a flocculant-added activated sludge method using a chemical flocculant in combination with a biological dephosphorization method has been put to practical use. However, in a system using a chemical flocculant in combination, there is a problem that it is difficult to add an appropriate amount of a flocculant for the following reasons. First, it is difficult to predict the mechanism of biological dephosphorization because it has not been sufficiently elucidated, and it takes about an hour to perform the analysis operation even if it is attempted to predict it from the analytical value of the phosphorus component of the treated water. An obstacle is that it is not possible to add an appropriate amount of coagulant to wastewater during inflow treatment.

In order to solve this problem, for example, Japanese Patent Application Laid-Open
No. 89993 has been proposed. In this method, an excess or deficiency predicted value of the phosphorus removal amount of the treatment process is calculated based on the degree of change in the phosphorus concentration value of the treated water detected by the phosphorus detector provided in the final treatment tank of the water treatment system, The amount of the coagulant to be added is controlled.
Then, according to the system of the embodiment (FIG. 2), the aeration tank 11 has the injection point 12 of the coagulant (aluminum sulfate), and the final settling tank 13 has the detection point 14 and the treated water outlet 1.
In the wastewater treatment system equipped with the above-mentioned method 5, the detected water collected from the detection point 14 is monitored by a colorimetric phosphorus detector 16 for phosphorus, and the concentration signal is transmitted to the programmable operation controller 1.
7, and the arithmetic and control unit 17 calculates the expected amount of the flocculant,
On the basis thereof, a pump control signal is sent to the injection pump 18 so that a controlled amount of the coagulant is supplied from the coagulant storage tank 19 to the injection point 12.
It is configured to be sent to.

[0004]

In the above dephosphorization method and apparatus, the change rate of the phosphorus concentration value after the final coagulation treatment is measured and fed back to the coagulant to be injected in the previous stage. The purpose is to control the amount and, as a result, to cope with fluctuations in the phosphorus concentration, and it is possible to cope with fluctuations in the phosphorus concentration over a long period with a large fluctuation cycle, but not to cope with fluctuations occurring in a short time. was there. In addition, since the injection amount of the flocculant is controlled based on a large fluctuation of the cycle, it is necessary to expect a somewhat excessive safety factor for the injection amount, so that there is a problem that the running cost is increased. The present invention has been made in order to solve such problems, and can cope with fluctuations in phosphorus concentration occurring in a short period of time, and can reduce the amount of coagulant to be injected to a minimum necessary amount. Abstract: A method for dephosphorization and an apparatus therefor are provided.

[0005]

SUMMARY OF THE INVENTION The above-mentioned problem is solved by claim 1.
In a wastewater treatment method using a chemical coagulation action in combination with a biological dephosphorization action, the activated sludge mixed water in the biological reaction tank or the activated sludge mixed water sampled from the biological reaction tank is subjected to solid-liquid separation and separated. The process includes measuring the concentration of phosphorus using the liquid portion, and injecting a required amount of a flocculant calculated from the phosphorus concentration and the flow rate of the treated water into the water to be treated in the biological reaction tank. It can be solved by the biological dephosphorization method of wastewater.

In the activated sludge treatment system having a biological reaction tank and a final sedimentation tank according to claim 2, the activated sludge mixed water in the biological reaction tank or the activated sludge mixed water collected from the biological reaction tank is solid-liquid. A solid-liquid separator to be separated, a phosphorus concentration meter for measuring the concentration of phosphorus in the separated liquid portion, and a concentration value transmitted from the phosphorus concentration meter and a flow rate value of the treated water in the biological reaction tank. Calculate the amount of phosphorus component that requires treatment, and calculate the required amount of coagulant corresponding to it,
The present invention can also be solved by a biological dephosphorization device for wastewater, which is provided with a coagulant injection amount control device for injecting the required amount of coagulant from an injection point provided in the biological reaction tank.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Next, an embodiment of the biological dephosphorization apparatus for wastewater of the present invention will be described with reference to a conceptual diagram (FIG. 1) showing the outline of the apparatus. The present invention provides a biological reaction tank 2 having an anaerobic tank 21 and an aerobic tank 22 arranged side by side, into which wastewater first flows from a sedimentation tank (not shown), and the treated water is finally treated and discharged as treated water. In the activated sludge treatment system provided with the final sedimentation basin 3, a dephosphorization apparatus in which the chemical decoupling action is added to the biological dephosphorization action of the wastewater. As a characteristic portion of this device, a device group divided into a phosphorus concentration measurement system, a flow rate measurement system, and a coagulant injection system is provided.

First, in this embodiment, as a phosphorus concentration measuring system for measuring the amount of phosphorus to be removed by the coagulation action, activated sludge mixed water is collected from a water sampling point 44 in the aerobic tank 22 and solidified. A pump 43 for feeding into the liquid separator 42, and a solid-liquid separator 42 for removing solids from the activated sludge mixed water.
And a phosphorus concentration meter 41 for measuring the concentration of dissolved phosphorus using the liquid from which solids have been removed as a sample. The measured density value is transmitted as an electric signal to the coagulant injection amount control device 61 described later.

In this case, the sampling point 44, which is the collecting position of the activated sludge mixed water, is set upstream of the later-described injection point 64 for injecting the flocculant in the latter part of the aerobic tank 22, It is preferable to set the position near the drainage port of the aerobic tank 22 where the biological dephosphorization is almost completed. The distance between the water sampling point 44 and the injection point 64 is determined by the condensing agent injected into the injection point 64.
It is necessary to provide an interval that does not disturb the flow in the vicinity of 4 so that the phosphorus concentration does not fluctuate. In addition, the activated sludge mixed water flows between the water sampling point 44 and the injection point 64. The time required is one of the phosphorus concentration meters 41 used in this device.
It is preferable that the distance is set so as not to be shorter than the required time per measurement.

In the present invention, the solid-liquid separator 42 is set so that the phosphorus component to be removed by the coagulant can be measured based on the liquid content obtained by separating the solid content from the activated sludge mixed water. Since the phosphorus component treated by the biological dephosphorization is fixed in solids of various forms, the solids are separated by the solid-liquid separator 42,
The remaining untreated dissolved phosphorus component, that is, only the phosphorus component to be removed by the coagulant, can be measured by the phosphorus concentration meter 41 .

Here, as the solid-liquid separator 42, one using membrane filtration such as an ultrafiltration membrane device or a microfiltration membrane device, or a centrifugal separator can be used. Further, in this embodiment, the solid-liquid separator 42 is independently provided outside the biological reaction tank, but the filtration device formed of the hollow fiber membrane is used as the solid-liquid separator to treat the water to be treated in the biological reaction tank. It can also be immersed in the device.

In the present invention, as for the timing of collecting the activated sludge mixed water from the water sampling point 44, it is preferable to provide a time interval according to the expected concentration fluctuation of the wastewater, for example, an appropriate interval within 12 hours. However, when the phosphorus concentration meter 41 is a single measurement unit, it is preferable to provide a water sampling interval corresponding to the time required for one measurement, for example, about 30 minutes to 2 hours. It is not necessary to set a shorter water sampling interval in ordinary wastewater dephosphorization treatment, but in such a case, a plurality of measurement units of the phosphorus concentration meter 41 are prepared and each measurement operation is performed. If a time difference is provided and measurement is performed in parallel, the water sampling interval can be set to an arbitrary time. As the phosphorus concentration meter 41 , a densitometer based on an absorption spectrophotometer or a colorimetry can be appropriately used.

As a flow rate measuring system for calculating the quantity of the phosphorus component from the above-mentioned phosphorus concentration, a flow meter 51 having a detection point 52 is provided in a communication channel between the biological reaction tank and the final sedimentation basin. The flow rate of the treated water flowing in the biological reaction tank per hour can be measured. Then, the measured flow rate value is transmitted as an electric signal to the coagulant injection amount control device 61 described later. The mounting position of the detection point 52 is not limited to the above position, but may be any point as long as the flow rate of the wastewater to be subjected to chemical dephosphorization can be properly measured.

As a coagulant injection system for injecting the coagulant into the biological reaction tank, a storage tank 63 for storing the coagulant is provided.
And a pump 62 for taking out the flocculant from the storage tank 63 and injecting it from an injection point 64 provided on the outlet side of the aerobic tank 22.
And a coagulant injection amount control device 61 capable of controlling the operation of the pump 62. In this case, the coagulant injection amount control device 61 has a function of calculating the amount of phosphorus to be removed based on the concentration signal from the phosphorus concentration meter 41 and the flow rate signal from the flow meter 51, And a function of controlling the operation of the pump 62 so as to inject the required amount of the flocculant at a predetermined timing.

Here, as the coagulant, an aluminum or iron-based inorganic coagulant such as polyaluminum chloride (PAC) is preferable. Further, the amount of phosphorus per hour to be removed can be obtained as a value obtained by multiplying the difference between the measured phosphorus concentration value and its target value by the flow rate. The required amount of the coagulant corresponding thereto is PO ₄
Since the chemical equivalent relationship between the converted phosphorus and the flocculant is in a molar ratio determined by the type of the flocculant, since the type and concentration of the flocculant to be used are known in advance, the phosphorus amount is divided. For example, the required amount of the coagulant corresponding thereto can be known. The calculation of the phosphorus amount and the calculation of the required amount of the coagulant or the setting of the injection timing are programmed so that the coagulant injection amount control device 61 automatically performs the calculation.

The flocculant calculated as described above is injected at a predetermined timing from an injection point 64 provided on the outlet side of the aerobic tank 22.
It is preferable to select the timing so that the above-mentioned coagulant is injected at the time when the water to be treated, which has been sampled and subjected to the measurement of the phosphorus concentration, flows to the injection point 64. Such timing is determined by the flow meter 51 by the aerobic tank 22.
Since the flow rate of the inside treated water is known, it can be predicted.
The set position of the injection point 64 is preferably the aerobic tank 2
2 is an outlet side, but is not necessarily limited thereto, and further includes an aerobic tank 22 or a biological reaction tank 2
, For example, in the anaerobic tank 21.

(Embodiment 2) Next, with reference to the above-described dephosphorization apparatus and the conceptual diagram of FIG. 1, one embodiment of the biological dephosphorization method for wastewater of claim 1 of the present invention will be described. The dephosphorization method of the present invention is a wastewater treatment method which uses a chemical coagulation action in combination with a biological dephosphorization action, at least a first step of solid-liquid separation of the activated sludge mixed water to be treated, From the second step of measuring the concentration of phosphorus using the method, and the third step of calculating the required amount of the flocculant from the phosphorus concentration and the flow rate of the treated water, and injecting it into the activated sludge mixed water to be treated. It is configured.

In the step of solid-liquid separation of the activated sludge mixed water to be treated in the first step, the activated sludge mixed water is supplied from a water sampling point 44 provided in the aerobic tank 22 of the biological reaction tank 2 as shown in FIG. A method of collecting and sending the solid matter to the solid-liquid separator 42 by a pump 43 to separate the solid matter may be used. Alternatively, a filtration device composed of a hollow fiber membrane is immersed in treated water in the aerobic tank 22 (see the figure). It is also possible to employ a method in which the activated sludge mixed water is directly solid-liquid separated. In this case, the description of the dephosphorization apparatus is applied as it is to the type of the apparatus for solid-liquid separation, the relationship between the water sampling position and the injection point, or the timing of water sampling.

In the step of measuring the phosphorus concentration using the separated liquid portion in the second step, the liquid portion of the activated sludge mixed water is measured using a phosphorus concentration meter 41 based on an absorption spectrophotometric method or a colorimetric method. Since the dissolved phosphorus component is measured, the phosphorus component that is treated by biological dephosphorization and is fixed in solids in various forms is excluded, so only the phosphorus component to be removed by the flocculant is used. Can be measured by the phosphorus concentration meter 41 .

In the third step, in the step of calculating the required amount of the flocculant from the phosphorus concentration and the flow rate of the treated water, and injecting it into the activated sludge mixed water to be treated, the first step is obtained in the second step. The amount of the phosphorus component to be treated with the flocculant is calculated from the phosphorus concentration and the flow rate of the treated water measured by a separate means. Next, the required amount of the flocculant is calculated using the fact that the phosphorus content and the required amount of the flocculant are in a chemical equivalent relationship. Further, at a predetermined timing, the calculated amount of the coagulant is injected into the treated water of the aerobic tank 22 via the injection point 64 from the coagulant storage tank 63 separately prepared by operating the pump 62. These calculation steps or control steps can be embodied as an automatic control device like the flocculant injection amount control device 61 in the dephosphorization device, and the above description can be applied to this case as it is. .

(Action) In any of the dephosphorization method and apparatus according to the present invention, when the phosphorus concentration of the wastewater to be treated fluctuates in a short time due to a change in the properties of the inflow wastewater or a change in the biological dephosphorization action. However, the amount of the phosphorus component removed by the chemical aggregation can be calculated at appropriate time intervals,
The required amount of the coagulant is calculated based thereon, and the coagulant can be accurately injected into the wastewater of the predetermined treatment target, so that the amount of the injected coagulant can be minimized. It has the effect that.

[0022]

The method and apparatus for biologically removing phosphorus in wastewater of the present invention are configured as described above, and therefore can cope with fluctuations in the concentration of phosphorus in wastewater generated in a short time. It becomes possible, and the treated water quality does not decrease,
Further, since the amount of the injected coagulant can be reduced to the minimum necessary, there is an excellent effect that the running cost can be reduced. Therefore, the present invention has a biological dephosphorization method and a wastewater biological solution which has solved the conventional problems and has a great industrial value.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a conventional example.

[Explanation of symbols]

2 biological reactor, 3 final sedimentation basin, 41 phosphorus concentration meter,
42 solid-liquid separator, 44 water sampling point, 51 flow meter, 61
Collecting dose control device, 64 injection points.

────────────────────────────────────────────────── (5) References JP-A-7-88497 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/30 C02F 1/52 WPI (DIALOG) )

Claims (2)

(57) [Claims] 1. A wastewater treatment method which uses a chemical coagulation action in combination with a biological dephosphorization action, wherein the activated sludge mixed water in the biological reaction tank or the activated sludge mixed water sampled from the biological reaction tank is subjected to solid-liquid separation. Each process of measuring the phosphorus concentration using the separated liquid portion and injecting a required amount of a flocculant calculated from the phosphorus concentration and the flow rate of the treated water into the water to be treated in the biological reaction tank. A biological dephosphorization method for wastewater characterized. 2. An activated sludge treatment system comprising a biological reaction tank and a final sedimentation basin, wherein a solid-liquid separation for solid-liquid separation of the activated sludge mixed water in the biological reaction tank or the activated sludge mixed water sampled from the biological reaction tank. Vessel, a phosphorus concentration meter that measures the concentration of phosphorus in the separated liquid portion, and a phosphorus component that requires treatment based on the concentration value transmitted from the phosphorus concentration meter and the flow rate value of the treated water in the biological reaction tank. Calculating a physical quantity, calculating a required amount of the coagulant corresponding thereto, and a coagulant injection amount control device for injecting the required amount of the coagulant from an injection point provided in the biological reaction tank. And wastewater biological dephosphorizer.