JP7255342B2 - Water treatment device and water treatment method - Google Patents

Description

The present invention relates to a water treatment device and a water treatment method.

As a method for treating organic wastewater, a method using a treatment tank in which organic matter is decomposed and removed by microorganisms is known. For example, an activated sludge method and a biofilm method are well known. The activated sludge method uses an activated sludge tank equipped with an aerator to cause aerobic microorganisms in the activated sludge to decompose contaminants such as organic matter in the water to be treated, followed by solid-liquid separation in a subsequent sedimentation tank. The biofilm method is a method of decomposing contaminants such as organic substances in water to be treated by microorganisms adhered to the surface or inside of a carrier.

As the activated sludge method, for example, the methods described in Patent Documents 1 and 2 are known.
Patent Document 1 discloses a first biological treatment process in which BOD in organic wastewater is treated under a high load to convert it into dispersed bacteria, and a second process in which the converted dispersed bacteria are flocculated and micro-organisms coexist. In the biological treatment method for organic wastewater having the biological treatment steps of (1) and (2), a biological treatment method for organic wastewater is described in which the second biological treatment step is performed under pH 5-6 conditions.
In Patent Document 2, organic wastewater is introduced into the first biological treatment tank of the biological treatment tanks provided in three or more stages and biologically treated with bacteria, and the dispersed bacteria from the first biological treatment tank are removed. A biological treatment method for organic wastewater in which the first biologically treated water containing , the third biological treatment tank is a floating biological treatment tank, the first biological treated water is passed through the second biological treatment tank in a transient manner to obtain the second biological treated water, and the second biological treated water is the third The third biological treated water obtained by passing water through the biological treatment tank is solid-liquid separated into sludge and treated water, part of the separated sludge is drawn out of the system as excess sludge, and at least part of the remaining separated sludge is A method for biological treatment of organic wastewater to be returned to the third biological treatment tank as return sludge is described.

Japanese Patent Application Laid-Open No. 2005-211879 Japanese Patent Application Laid-Open No. 2009-202115 JP 2015-039691 A JP 2013-138976 A

In the activated sludge method described in Patent Documents 1 and 2, it is assumed that high-load water to be treated is used in a two-stage or more biological treatment process that utilizes the predatory action of microorganisms, and sedimentation is used as a solid-liquid separation process. Use separation. The methods described in Patent Documents 1 and 2 do not take measures when using low-load water to be treated, and when treating water to be treated whose water quality fluctuates greatly over time, the activated sludge malfunctions at low loads. was what occurred.

On the other hand, there is known a method of treating water to be treated whose water quality fluctuates over time using a membrane separation activated sludge method in which the solid-liquid separation process of the activated sludge method is replaced from the conventional sedimentation separation to membrane separation (for example, See Patent Documents 3 and 4).
In Patent Document 3, a carrier tank containing a fluidized bed carrier on which aerobic microorganisms are immobilized, and a membrane separation device into which treated water treated in the carrier tank can flow, and a membrane separation device and activated sludge are contained. A wastewater treatment method for treating raw water using a wastewater treatment apparatus comprising a sludge treatment tank, comprising a load measurement step of measuring the load of raw water (organic pollution load), a carrier tank and membrane separation activated sludge treatment. a supply amount control step for controlling the supply amount of raw water to the tank, wherein a set value used in the supply amount control step is set in advance, and the supply amount control step is performed when the load of the raw water measured by the load measurement step is If the load is less than the set value, the raw water is not supplied to the carrier tank, and the raw water is supplied to the membrane separation activated sludge treatment tank without being supplied to the low load control process. and a high load control step of supplying at least a portion of the raw water to the carrier tank.

In Patent Document 4, a first biological treatment apparatus for treating wastewater by a membrane separation activated sludge method, a second biological treatment apparatus for treating wastewater by a biofilm method, a first biological treatment apparatus and a second A measurement unit that measures the load concentration (organic matter concentration) and flow rate in the wastewater flowing upstream of the biological treatment equipment, and calculates the load amount (organic pollutant load amount) from the load concentration and flow rate, and according to the load amount to determine the distribution ratio between the flow rate of wastewater to be supplied to the first biological treatment apparatus and the flow rate of wastewater to be supplied to the second biological treatment apparatus, and based on the distribution ratio, the first biological treatment apparatus A wastewater treatment system is described that includes a controller that regulates the flow rate of wastewater delivered to the second biological treatment system and the flow rate of wastewater delivered to the second biological treatment system.

However, in Patent Document 3, the raw water load (organic pollutant load) must be measured in the supply amount control process for controlling the amount of raw water supplied to the carrier tank and the membrane separation activated sludge treatment tank. Patent Document 3 further describes finely adjusting the control of the supply amount of raw water in a constant load control step based on the reduction rate of the load of the treated water in the carrier tank with respect to the load of the raw water (BOD removal rate, etc.). In both cases, it was essential to measure the load of raw water.
Also in Patent Document 4, the distribution ratio between the flow rate of wastewater supplied to the first biological treatment apparatus and the flow rate of wastewater supplied to the second biological treatment apparatus is It was essential to measure the wastewater load (organic pollutant load) flowing upstream of the biological treatment equipment.
Thus, when the organic pollution load of the water to be treated (raw water) cannot be measured, there has been no known method of treating the water to be treated whose water quality fluctuates over time.

The problem to be solved by the present invention is to suppress the malfunction of activated sludge when treating water to be treated whose quality fluctuates greatly over time without measuring the organic pollution load of the water to be treated, and stably To provide a water treatment apparatus capable of obtaining treated water of good quality.

As a result of intensive studies to solve the above problems, the present inventors found that the load measuring unit between the carrier tank and the activated sludge tank measures the organic pollution load of the treated water in the carrier tank, It has been found that the above problem can be solved by controlling the inflow ratio of the water to be treated to the carrier tank and the activated sludge tank according to the organic pollution load measured by the load measuring part.
Specifically, the present invention and preferred configurations of the present invention are as follows.

[1] A water treatment apparatus comprising a carrier tank and an activated sludge tank in this order,
An inflow ratio control unit is provided upstream of the carrier tank,
Equipped with a load measuring unit between the carrier tank and the activated sludge tank,
The load measurement unit measures the organic pollution load of the treated water in the carrier tank,
1. A water treatment apparatus, wherein an inflow ratio control unit controls an inflow ratio of water to be treated into the carrier tank and the activated sludge tank according to the organic pollution load measured by the load measuring unit.
[2] The load measuring unit measures the concentration of organic matter in the treated water in the carrier tank as the organic pollution load,
When the concentration of organic substances in the water treated in the carrier tank is equal to or higher than the set value, the inflow ratio control unit causes all of the water to be treated to flow into the carrier tank,
The water treatment apparatus according to [1], wherein the inflow ratio control unit causes part of the water to be treated to flow into the activated sludge tank when the concentration of organic substances in the treated water in the carrier tank is less than a set value.
[3] The water treatment apparatus according to [1] or [2], wherein each of the carrier tank and the activated sludge tank has an inflow pipe for the water to be treated.
[4] The water treatment apparatus according to any one of [1] to [3], wherein the inflow ratio control section includes an inflow pipe for the water to be treated to the activated sludge tank and an activated sludge tank feed valve.
[5] The load measuring unit measures the concentration of organic matter in the treated water in the carrier tank as the organic pollution load,
When the concentration of organic substances in the treated water in the carrier tank is higher than the set value, the feed valve for the activated sludge tank is closed to allow all the water to be treated to flow into the carrier tank,
The water treatment apparatus according to [4], wherein the activated sludge tank feed valve is opened to allow part of the water to be treated to flow into the activated sludge tank when the concentration of organic substances in the treated water in the carrier tank is less than the set value.
[6] The water treatment apparatus according to any one of [1] to [5], in which the BOD of the water to be treated fluctuates over time.
[7] The water treatment apparatus according to any one of [1] to [6], which comprises a sedimentation tank downstream of the activated sludge tank.
[8] The water treatment apparatus according to [7], comprising means for returning sludge from the sedimentation tank to the activated sludge tank.
[9] A water treatment method for treating water to be treated using a water treatment apparatus equipped with a carrier tank and an activated sludge tank in this order,
The water treatment device has an inflow ratio control unit upstream of the carrier tank,
The water treatment equipment has a load measuring unit between the carrier tank and the activated sludge tank,
The load measurement unit measures the organic pollution load of the treated water in the carrier tank,
A water treatment method, wherein an inflow ratio control unit controls an inflow ratio of water to be treated into the carrier tank and the activated sludge tank according to the organic pollution load measured by the load measuring unit.

According to the present invention, when treating water to be treated whose quality fluctuates greatly over time without measuring the organic pollution load of the water to be treated, the malfunction of activated sludge is suppressed, and stable and good water quality is obtained. A water treatment apparatus from which treated water can be obtained can be provided.

FIG. 1 is a schematic cross-sectional view of an example of the water treatment apparatus of the present invention. FIG. 2 is a schematic cross-sectional view of another example of the water treatment apparatus of the present invention.

The present invention will be described in detail below. Although the constituent elements described below may be described based on representative embodiments and specific examples, the present invention is not limited to such embodiments. In the present specification, a numerical range represented by "-" means a range including the numerical values described before and after "-" as lower and upper limits.

[Water treatment equipment]
The water treatment apparatus of the present invention comprises a carrier tank and an activated sludge tank in this order, an inflow ratio control section is provided upstream of the carrier tank, and a load measuring section is provided between the carrier tank and the activated sludge tank. The load measuring unit measures the organic pollutant load of the treated water in the carrier tank, and the inflow ratio controller measures the organic pollutant load measured by the load measuring unit. controls the inflow ratio of
With this configuration, the water treatment apparatus of the present invention suppresses the malfunction of the activated sludge and stabilizes the activated sludge when treating the water to be treated, the water quality of which greatly fluctuates over time, without measuring the organic pollution load of the water to be treated. Then, treated water of good quality can be obtained. Since the treated water in the carrier tank is water after being treated in the carrier tank, which is resistant to time fluctuations of the organic contaminant load, the time fluctuation range of the organic contaminant load is smaller than that of the water to be treated. By measuring the organic pollutant load of the treated water in the carrier tank, which has a small temporal fluctuation of the organic pollutant load, the frequency of measuring the organic pollutant load can be reduced. can be introduced. In addition, since the frequency of opening and closing the valves of the inflow ratio control section can be suppressed, the consumption speed of the valves used in the inflow ratio control section can be suppressed. Due to the above advantages, industrial applicability is high.
The water treatment apparatus of the present invention is not limited to the activated sludge method, and can also be applied to the case of using activated sludge in the biofilm method. That is, the water treatment apparatus of the present invention does not necessarily require a solid-liquid separation tank such as a sedimentation tank.
The organic pollutant load can be measured from the values of general water quality indicators such as the concentration of organic matter. The concentration of organic matter includes BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), TOC (Total Organic Carbon), DOC (Dissolved Organic Carbon), Turbidity and chromaticity are preferably used as standards. For example, waste water containing organic matter such as food processing waste water has a high BOD value. The water treatment apparatus of the present invention is preferably used, for example, when the BOD of the treated water in the carrier tank fluctuates greatly with time due to the treatment of the water to be treated whose BOD fluctuates greatly with time.
In addition, it is preferable to use a fluid bed carrier as a carrier in the carrier tank. By using a fluidized bed carrier, the biophase can be retained in the fluidized bed carrier, high BOD volume load treatment can be performed in a small volume (reduced installation space of the carrier tank), and equipment costs can be reduced. can be lowered.
Other preferred embodiments of the water treatment apparatus of the present invention will be described below.

<Overall composition>
First, the overall configuration of the water treatment apparatus of the present invention will be described.

FIG. 1 is a schematic cross-sectional view of an example of the water treatment apparatus of the present invention.
The water treatment apparatus shown in FIG. 1 is a water treatment apparatus having a carrier tank 11 and an activated sludge tank 12 in this order. The water treatment apparatus includes an inflow ratio control unit 32 upstream of the carrier tank 11 and a load measuring unit 31 between the carrier tank 11 and the activated sludge tank 12. The load measuring unit 31 measures the organic property of the treated water 2 in the carrier tank. The pollution load is measured, and the measured numerical value is transmitted to the inflow ratio controller 32 by means of the control signal 33 . The inflow ratio control unit 32 controls the inflow ratio of the water 1 to be treated into the carrier tank 11 and the activated sludge tank 12 according to the organic pollution load measured by the load measuring unit 31 .
As shown in FIG. 1, carrier tank 11 preferably comprises aeration means 22 and fluidized bed carrier 21 . It is preferred that the activated sludge tank is equipped with aeration means 22 and contains no carrier.
In the water treatment apparatus, it is preferable that each of the carrier tank 11 and the activated sludge tank 12 has an inflow pipe (not shown) for the water 1 to be treated. It is preferable that an inflow ratio control unit 32 comprising an inflow pipe for the water to be treated to the activated sludge tank and an activated sludge tank feed valve is provided by branching from the inflow pipe for the water to be treated 1 to the carrier tank 11 .
The water treatment equipment may be equipped with a flow meter (not shown) upstream of the carrier tank 11 .

A water treatment method using the water treatment apparatus shown in FIG. 1 will be described. In FIG. 1, the flow of water is indicated by solid arrows. In the water treatment apparatus shown in FIG. 1, the load measuring unit 31 measures the organic pollution load of the treated water 2 in the carrier tank. The inflow ratio control unit 32 controls the inflow ratio of the water 1 to be treated into the carrier tank 11 and the activated sludge tank 12 according to the organic pollution load measured by the load measuring unit 31. and/or sent to the activated sludge tank 12 .
In the carrier tank 11, the water to be treated 1 is biologically treated by the fluidized bed carrier 21 while being aerated by the gas from the aeration means 22, and then sent as the carrier tank treated water 2 from the carrier tank 11 to the activated sludge tank 12. be. The carrier tank 11 preferably has a screen 23 capable of restricting movement of the fluidized bed carrier 21 to the activated sludge tank 12 .
In the activated sludge tank 12, the water to be treated 1 and/or the treated water 2 in the carrier tank are aerated with gas from the aeration means 22, and then discharged from the activated sludge tank 12 as treated water 3 and treated water 4 in the activated sludge tank. . The treated water 3 and the treated water 4 in the activated sludge tank may be discharged to an external area such as the ocean or a river as they are, may be recovered and reused as industrial water, or may be further subjected to wastewater treatment.

FIG. 2 is a schematic cross-sectional view of another example of the water treatment apparatus of the present invention.
The water treatment apparatus shown in FIG. 2 has a sedimentation tank downstream of the activated sludge tank in the water treatment apparatus shown in FIG.

A water treatment method using the water treatment apparatus shown in FIG. 2 will be described.
In the water treatment apparatus shown in FIG. 2, the activated sludge tank treated water 3 is sent from the activated sludge tank 12 to the downstream sedimentation tank 13 . A portion of the sludge that has undergone solid-liquid separation in the sedimentation tank 13 is returned to the activated sludge tank 12 as return sludge 41, and the rest is discharged as excess sludge 42 to the outside area.
The treated water 4 from the sedimentation tank 13 may be discharged as it is to an external area such as the ocean or a river, may be recovered and reused as industrial water, or may be further subjected to wastewater treatment.

<Load measurement part>
In the water treatment apparatus of the present invention, the load measuring section measures the organic pollution load of the treated water in the carrier tank. The load measurement unit includes an organic pollution index measurement unit that directly measures the organic pollution load, an arbitrary meter such as a flow meter; a storage unit that stores input signals from the meter; an output unit capable of outputting data stored in the storage unit and parameters calculated by the calculation unit as an output signal (control signal) to the inflow ratio control unit; other input units and control units; may be provided.
The water to be treated used in the water treatment apparatus is not particularly limited, and various types of wastewater such as domestic wastewater, sewage, and factory wastewater can be used as the water to be treated. Wastewater from factories includes wastewater from food factories and pulp and paper factories. In the present invention, it is preferable to use water to be treated whose water quality fluctuates greatly over time, and more preferably to use water to be treated whose organic contaminant load greatly fluctuates over time. The water treatment apparatus of the present invention can be used particularly preferably when the BOD of the water to be treated fluctuates over time. Here, the water treatment apparatus of the present invention can be used even when the organic pollution load of the water to be treated cannot be measured (especially when it cannot be continuously monitored or monitored), but the organic pollution load of the water to be treated or The time variation of the organic pollutant load may be measured by some means.
The BOD of the water treated in the carrier tank is preferably 1-1000 mg/L, more preferably 5-200 mg/L, and particularly preferably 10-150 mg/L. When the BOD of the treated water in the carrier tank is equal to or lower than the upper limit of the preferred range, the organic pollution load can be within the range of the organic pollution load that can be treated in the activated sludge tank, and the water quality of the treated water in the activated sludge tank can be improved. When the BOD of the treated water in the carrier tank is equal to or higher than the lower limit of the preferable range, it is possible to suppress the malfunction of the activated sludge and improve the water quality of the treated water in the activated sludge tank.
Variation of BOD of the water to be treated need not be measured in the present invention, but is preferably 50 to 2000 mg/L, more preferably 100 to 1000 mg/L, and 200 to 800 mg/L. is particularly preferred.
Fluctuations in the BOD volume load with respect to the volume of the entire carrier tank and activated sludge tank of the water to be treated need not be measured in the present invention, but are found to be 0.2 to 4.0 kg-BOD/m ³ /day. It is preferably from 0.3 to 2.0 kg-BOD/m ³ /day, more preferably from 0.5 to 1.8 kg-BOD/m ³ /day. Incidentally, "kg-BOD/m ³ /day" as a unit of BOD volume load is synonymous with "kg/m ³ /day".

<Inflow ratio controller>
In the water treatment apparatus of the present invention, the inflow ratio control section controls the inflow ratio of the water to be treated into the carrier tank and the activated sludge tank according to the organic pollution load measured (monitored) by the load measuring section. The inflow ratio control unit is a storage unit that stores the control signal from the load measurement unit and set values used for control; A control section capable of opening and closing, etc.; other input section, output section, and calculation section; may be provided.
The inflow ratio control unit controls the inflow ratio of the water to be treated into the carrier tank and the activated sludge tank according to the organic pollution load obtained by the load measuring unit, based on preset values stored in advance. is preferred.
In the present invention, the load measurement unit measures the concentration of organic substances in the treated water in the carrier tank as the organic pollution load, and when the concentration of organic substances in the treated water in the carrier tank is equal to or higher than the set value, the inflow ratio control unit removes all of the water to be treated from the carrier. It is more preferable that the inflow ratio control unit causes part of the water to be treated to flow into the activated sludge tank when the concentration of organic substances in the treated water in the carrier tank is less than the set value.

The configuration of the inflow ratio control section is not particularly limited. It is preferable that the inflow ratio control unit includes an inflow pipe for the water to be treated to the activated sludge tank and an activated sludge tank feed valve.
In this case, the load measuring unit measures the concentration of organic matter in the treated water in the carrier tank as the organic pollution load. is allowed to flow into the carrier tank, and when the concentration of organic matter in the treated water of the carrier tank is less than the set value, it is more preferable to open the activated sludge tank feed valve to allow part of the water to be treated to flow into the activated sludge tank.

When monitoring the concentration of organic matter in the water treated in the carrier tank, the inflow ratio of the water to be treated into the activated sludge tank can be set as follows so that the BOD setting value of the treated water in the carrier tank is 70 mg/L. Especially preferred.
(1-1) When the BOD of the treated water in the carrier tank is 70 mg/L or more: The feed valve of the activated sludge tank is closed, and the water to be treated does not flow into the activated sludge tank.
(1-2) When the BOD of the treated water in the carrier tank is less than 70 mg/L: Open the activated sludge tank feed valve, let a certain amount of the water to be treated flow into the activated sludge tank, and let the remaining amount flow into the carrier tank. Let
In (1-2) above, "a certain amount of the water to be treated" is not particularly limited. From the above, it is possible to set the amount to be less than the total amount. Control of "a certain amount of the water to be treated" can be controlled by adjusting the opening of the feed valve for the activated sludge tank, adjusting the cross-sectional area of the inflow pipe for the water to be treated to the activated sludge tank, and the like.

<Carrier tank>
The water treatment apparatus of the present invention comprises a carrier tank. Also, in the present invention, it is preferred that the carrier tank comprises an aeration means, a fluidized bed carrier and a screen.
The volume of the carrier tank is not particularly limited. By using a fluidized bed carrier, the volume of the carrier tank can be reduced even when water quality fluctuates and high BOD volume load treatment is performed, and the site area required for installation of the carrier tank can also be reduced.
Examples of materials for the carrier tank include concrete, metal, and resin. Among them, it is preferably made of resin, and for example, vinyl chloride, fiber-reinforced plastic, or the like can be preferably used.

(Aeration means)
The aeration means for the carrier tank is not particularly limited, and known aeration means can be used. It is preferable that the air volume is variable and that the backflow prevention function is provided.
Even if the amount of water to be treated that flows into the carrier tank is temporarily reduced to 0.0 m ³ /day, no problem will occur because the microorganisms are immobilized on the fluidized bed carrier. However, in this case, in order to avoid anaerobic putrefaction, it is preferable to continue supplying oxygen to the carrier tank by aeration means.

(Fluid bed carrier)
It is preferable that the carrier tank comprises a fluidized bed carrier, and specifically the carrier tank is filled with the fluidized bed carrier. Since the fluidized bed carrier is packed in a fluidized state (without being fixed), high BOD volume load treatment can be performed when water quality fluctuates, and preferably BOD can be reduced in a short time.
In the present invention, the packing rate of the fluidized bed carrier is preferably 10-50%, more preferably 20-40%.
It is more preferable that the fluidized bed carrier has a shape and material that allow the microorganisms to congregate inside the fluidized bed carrier from the viewpoint of enabling biological treatment in the carrier tank even at low water temperatures (around 10°C).

The shape of the fluidized bed carrier is preferably cubic (cube-shaped), rectangular parallelepiped, columnar, strip-shaped, confetti-shaped, tetrahedral, spherical, soccer-ball-like shape, etc., and more preferably columnar. A columnar shape is a shape in which the bottom surface and the top surface have the same shape, and side surfaces connect the bottom surface and the top surface. In the present invention, it is particularly preferred that the fluidized bed carrier has a substantially cylindrical shape. In the case of a substantially cylindrical shape, the bottom surface and the top surface may be completely circular, partially deformed circles, or a plurality of overlapping circles in a plane.

Inorganic substances such as resins and ceramics can be used as materials for the fluidized bed carrier. Examples of resins used for the fluidized bed carrier include thermoplastic resins, thermosetting resins, rubbers, elastomers, and the like.
Among these, thermoplastic resins are preferable from the viewpoint of facilitating high BOD volume load treatment. Among thermoplastic resins, it is more preferable to use polyvinyl alcohol, polyurethane, polypropylene, and polyethylene.

(screen)
In the present invention, the carrier tank is preferably equipped with a screen capable of restricting the movement of the fluidized bed carrier into the activated sludge tank. With this configuration, the activated sludge tank can be easily maintained in a carrier-free state, the BOD volume load in the activated sludge tank can be reduced, and the effect of sludge reduction in the activated sludge tank can be enhanced. The screen is not particularly limited, and known screens such as film-shaped and cylindrical screens can be used.

<Activated sludge tank>
A water treatment apparatus of the present invention comprises an activated sludge tank. Moreover, in the present invention, it is preferable that the activated sludge tank has an aeration means. The activated sludge tank preferably contains no carrier. The term "carrier-free" for the activated sludge tank is not strictly limited to the case where it does not contain any substance that can serve as a carrier, and it is sufficient that it does not substantially contain a carrier. The problem to be solved by the present invention can be solved if the carrier can be positively added. In addition, it is easy to extend the system by, for example, putting the carrier into an activated sludge tank.
The volume of the activated sludge tank is not particularly limited. For example, a configuration in which the volume of the activated sludge tank is approximately the same as the volume of the carrier tank can be mentioned.
The material of the activated sludge tank is not particularly limited. For example, the material of the activated sludge tank may be the same as the material of the carrier tank.

(Aeration means)
As the aeration means for the activated sludge tank, known aeration means may be used, but an aeration means capable of intermittent aeration is preferred.

<Sedimentation tank>
Since the water treatment apparatus of the present invention is used for both the activated sludge process and the membrane separation activated sludge process, it may or may not have a sedimentation tank.
The water treatment apparatus of the present invention is preferably used for the activated sludge process and has a sedimentation tank downstream of the activated sludge tank. It is preferable that the treated water from the activated sludge tank is sent to the sedimentation tank, solid-liquid separated in the sedimentation tank, and then discharged to an external area such as the ocean or river, or recovered and reused as industrial water. .
The water treatment apparatus of the present invention preferably comprises means for returning sludge from the sedimentation tank to at least one of the carrier tank and the activated sludge tank, and more preferably comprises means for returning sludge from the sedimentation tank to the activated sludge tank. preferable. By combining means for returning sludge with the above-described load measuring unit and inflow ratio control unit, when treating water whose quality fluctuates greatly over time, the malfunction of activated sludge can be further suppressed and the system can be stabilized. Treated water of good quality can be obtained.

<Other devices>
The water treatment device may have other devices.
When the water treatment apparatus of the present invention is used in a membrane separation activated sludge process, a filtration membrane may be provided downstream of the activated sludge tank to separate treated water and activated sludge.
The water treatment apparatus is preferably equipped with known liquid transfer means such as a pump for transferring the water to be treated, the treated water in the carrier tank and the treated water.
It is preferable that the water treatment apparatus include an adjustment tank. By providing the adjustment tank upstream of the carrier tank, it becomes easier to control the water quality of the water to be treated.
It is preferable that the water treatment apparatus does not have a flocculating means between the carrier tank and the activated sludge tank, from the viewpoint of further simplification of the water treatment apparatus itself and avoiding chemical costs due to the flocculant.
The water treatment equipment may or may not have a washing facility. When washing the fluidized bed carrier, the fluidized bed carrier may be washed after being removed from the water treatment apparatus, or may be washed by backflow washing in the water treatment apparatus, or washed under load by a washing machine or the like. good too. It is preferable that the water treatment apparatus does not have a washing facility, because the water treatment apparatus itself can be further simplified. The fluidized bed carrier preferably has excellent strength and durability. When using a fluidized bed carrier with excellent durability, the water treatment apparatus preferably does not have a washing facility.

<Treatment water>
The BOD of the treated water is preferably less than 40 mg/L, more preferably 30 mg/L or less, and particularly preferably 20 mg/L or less.

[Water treatment method]
The water treatment method of the present invention is a water treatment method in which water to be treated is treated using a water treatment apparatus equipped with a carrier tank and an activated sludge tank in this order, and the water treatment apparatus is upstream of the carrier tank with an inflow ratio of The water treatment equipment has a load measuring part between the carrier tank and the activated sludge tank, the load measuring part measures the organic pollution load of the treated water in the carrier tank, and the inflow ratio control part is the load measuring part. The inflow ratio of the water to be treated to the carrier tank and the activated sludge tank is controlled according to the measured organic pollutant load.
Preferred aspects of the water treatment method of the present invention are the same as the preferred aspects of the water treatment apparatus of the present invention.

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

[Examples 1 and 2]
A carrier tank, an activated sludge tank and a sedimentation tank were connected, and a load measuring section was provided in the piping from the carrier tank to the activated sludge tank. Further, an inflow ratio control unit comprising an inflow pipe for the water to be treated to the activated sludge tank and an activated sludge tank feed valve is branched from the inflow pipe for the water to be treated to the carrier tank. bottom. The load measuring unit has an automatic COD measuring device that measures COD, which is an index of the concentration of organic matter, and can obtain BOD by converting the measured value of the COD meter. The outline of the water treatment apparatus of Example 1 is as shown in FIG. 2, and the details are as follows.
As a carrier tank, a fluidized bed biological treatment tank containing a substantially cylindrical polyethylene carrier was used. In the carrier tank, the filling rate of the fluid bed carrier was set to 25%. A screen was provided in front of the flow path to the activated sludge tank to prevent movement of the fluidized bed carrier from the carrier tank to the activated sludge tank.
The activated sludge tank was equipped with an aeration means but contained no carrier. No sludge was returned from the activated sludge tank to the carrier tank.
A solid-liquid separation tank was used as a sedimentation tank. Sludge was returned from the sedimentation tank to the activated sludge tank.
The load measuring unit is equipped with an automatic COD measuring device, and obtains the BOD value from the measured COD value based on the COD-to-BOD conversion ratio previously obtained and stored. Furthermore, the load measuring section can control the amount of water to be treated flowing into the carrier tank and the activated sludge tank by transmitting the calculated BOD value to the inflow ratio control section by means of a control signal.
The inflow ratio control unit controls the inflow ratio of the water to be treated into the activated sludge tank based on preset values stored in advance according to the organic pollution load (BOD value) obtained by the load measurement unit. can. Specifically, the opening and closing of the activated sludge tank feed valve provided in the inflow pipe of the water to be treated to the activated sludge tank was controlled. The set values are as follows.
(1-1) When the BOD of the treated water in the carrier tank is 70 mg/L or more: The feed valve of the activated sludge tank is closed, and the water to be treated does not flow into the activated sludge tank.
(1-2) When the BOD of the treated water in the carrier tank is less than 70 mg/L: Open the activated sludge tank feed valve, let a certain amount of the water to be treated flow into the activated sludge tank, and let the remaining amount flow into the carrier tank. Let

Using the water treatment apparatus of Example 1, while measuring the organic pollution load of the treated water in the carrier tank as described above, based on the set value according to the organic pollution load (BOD value) obtained by the load measuring unit Water treatment was performed while controlling the inflow ratio control unit with the Example 1 is the step of using carrier tank treated water with a BOD of 131 mg/L, and Example 2 is the step of using the carrier tank treated water with a BOD of 12 mg/L because the BOD of the water to be treated fluctuates. In Example 2, the "fixed amount of the water to be treated" in (1-2) above was an amount of about 2/3 or more to less than the total amount of the water to be treated.
The BOD of the treated water in the activated sludge tank was measured and shown in Table 1 below. Specifically, in Example 1, the above (1-1) “When the BOD of the treated water in the carrier tank is 70 mg / L or more: Close the activated sludge tank feed valve, and the inflow of the water to be treated into the activated sludge tank is , None”, and the BOD of the treated water in the activated sludge tank that passed through the activated sludge tank was 18 mg/L. In Example 2, the above (1-2) "When the BOD of the treated water in the carrier tank is less than 70 mg/L: Open the activated sludge tank feed valve, let a certain amount of the water to be treated flow into the activated sludge tank, The BOD of the treated water in the activated sludge tank that passed through the activated sludge tank was 19 mg/L.
In addition, each BOD density|concentration was measured based on JISK010221.

[Example 3]
Using the water treatment apparatus of Example 1, when using the water to be treated that can obtain the treated water in the carrier tank with a BOD of 12 mg / L in the same manner as in Example 2, the activated sludge tank feed valve is closed and the flow to the activated sludge tank Water treatment was performed so that the inflow of the water to be treated was eliminated. Here, in Example 3, "when the BOD of the treated water in the carrier tank is less than 70 mg/L", it means that the control satisfying the above (1-2) was not performed.
The BOD of the treated water in the activated sludge tank was measured and shown in Table 1 below. Specifically, in the water treatment of Example 3 in which the entire amount of water to be treated with a low BOD flowed into the carrier tank, the BOD of the treated water in the activated sludge tank that passed through the activated sludge tank was 38 mg/L.

[Example 4]
Using the water treatment apparatus of Example 1, water treatment was carried out by opening the activated sludge tank feeding valve when using the water to be treated which yields BOD 800 mg/L treated water in the carrier tank. Here, although Example 4 is "when the BOD of the treated water in the carrier tank is 70 mg/L or more", it means that the control satisfying the above (1-1) was not performed.
The BOD of the treated water in the activated sludge tank was measured and shown in Table 1 below. Specifically, in the water treatment of Example 4 in which a certain amount of water to be treated with a high BOD flowed into the activated sludge tank, the BOD of the treated water in the activated sludge tank that passed through the activated sludge tank was 33 mg/L.

From Table 1 above, according to the present invention, when treating water whose quality fluctuates greatly over time (large load fluctuation) without measuring the organic pollution load of the treated water, activated sludge malfunction It was found that it is possible to provide a water treatment apparatus capable of suppressing , and stably obtaining treated water (treated water from the activated sludge tank) of good quality.
Especially when the organic pollution load of the treated water in the carrier tank is low, the total amount of the water to be treated is treated in two stages in the carrier tank and the activated sludge tank without controlling the inflow ratio of the water to be treated to the carrier tank and the activated sludge tank. Compared to Example 3, Example 2, in which a portion of the water to be treated was controlled to directly flow into the activated sludge tank based on the organic pollution load of the treated water in the carrier tank, passed through the activated sludge tank. The water quality of the treated water in the activated sludge tank was good.
When the organic pollutant load of the treated water in the carrier tank is high, preferable conditions (1-1) and (1-2) are satisfied rather than Example 4 in which preferable condition (1-1) is not satisfied. In Examples 1 and 2, which were controlled, the water quality of the treated water in the activated sludge tank after passing through the activated sludge tank was better.

1 Water to be treated 2 Carrier tank treated water 3 Activated sludge tank treated water 4 Treated water 11 Carrier tank 12 Activated sludge tank 13 Sedimentation tank 21 Fluid bed carrier 22 Aeration means 23 Screen 31 Load measurement section 32 Inflow ratio control section 33 Control signal 41 Returned sludge 42 Excess sludge

Claims (9)

A water treatment apparatus comprising a carrier tank and an activated sludge tank in order from upstream ,
An inflow ratio control unit is provided upstream of the carrier tank,
A load measuring unit is provided between the carrier tank and the activated sludge tank,
The load measuring unit measures the organic pollution load of the treated water in the carrier tank,
A water treatment apparatus, wherein the inflow ratio control section controls the inflow ratio of the water to be treated to the carrier tank and the activated sludge tank according to the organic pollution load measured by the load measuring section. The load measuring unit measures the concentration of organic substances in the treated water in the carrier tank as the organic pollution load,
when the concentration of organic substances in the treated water in the carrier tank is equal to or higher than a set value, the inflow ratio control unit causes all of the water to be treated to flow into the carrier tank;
2. The water treatment apparatus according to claim 1, wherein when the concentration of organic matter in the water treated in the carrier tank is less than a set value, the inflow ratio control section causes part of the water to be treated to flow into the activated sludge tank. 3. The water treatment apparatus according to claim 1, wherein said carrier tank and said activated sludge tank each have an inflow pipe for said water to be treated. The water treatment apparatus according to any one of claims 1 to 3, wherein said inflow ratio control unit includes an inflow pipe for said water to be treated to said activated sludge tank and an activated sludge tank feed valve. The load measuring unit measures the concentration of organic substances in the treated water in the carrier tank as the organic pollution load,
when the concentration of organic substances in the treated water in the carrier tank is equal to or higher than a set value, closing the feed valve for the activated sludge tank to allow all of the water to be treated to flow into the carrier tank;
5. The water treatment apparatus according to claim 4, wherein when the concentration of organic substances in the treated water in the carrier tank is less than a set value, the feed valve for the activated sludge tank is opened to allow part of the water to be treated to flow into the activated sludge tank. The water treatment apparatus according to any one of claims 1 to 5, wherein the BOD of the water to be treated varies with time. The water treatment apparatus according to any one of claims 1 to 6, comprising a sedimentation tank downstream of said activated sludge tank. 8. A water treatment system according to claim 7, comprising means for returning sludge from said sedimentation tank to said activated sludge tank. A water treatment method for treating water to be treated using a water treatment apparatus comprising a carrier tank and an activated sludge tank in order from upstream ,
The water treatment device comprises an inflow ratio control section upstream of the carrier tank,
The water treatment equipment comprises a load measuring unit between the carrier tank and the activated sludge tank,
The load measuring unit measures the organic pollution load of the treated water in the carrier tank,
The water treatment method, wherein the inflow ratio control unit controls the inflow ratio of the water to be treated into the carrier tank and the activated sludge tank according to the organic pollution load measured by the load measuring unit. .

Images