JP2024057221A - Rocking biological nitrification method and rocking biological nitrification device - Google Patents

Abstract

[Problem] The object of the present invention is to provide an agitating biological nitrification method and an agitating biological nitrification device capable of treating water containing a high concentration of ammonia nitrogen at a nitrification rate higher than that of the conventional fluidized bed mixed flow method. [Solution] The following requirements 1, 2, 3, and 4 are satisfied when the water to be treated is passed through a plurality of biological retainers 6 loaded in a nitrification tank 5. Requirement 1: The three-dimensional size of one biological retainer 6 exceeds 5 mm in the maximum length direction and fits into a sphere with a diameter of 20 mm. Requirement 2: The copper ion concentration of the water to be treated is 0.1 to 300 μg/L. Requirement 3: The linear velocity ratio (LV gas/LV water) of the linear velocity of the water to be treated [m/h] to the linear velocity of the gas [m/h] is 0.3 to 6.0. Requirement 4: The following filling rate is 75% or more. Filling rate (%) = (bulk volume of multiple organism holders 6) / (available water volume in nitrification tank 5) x 100 [Selected figure] Figure 1

Description

The present invention relates to an agitated biological nitrification method and an agitated biological nitrification device.

Biological nitrification is known, in which ammonia nitrogen in the water being treated is converted to nitrate nitrogen by microorganisms. Ammonia nitrogen can be found, for example, in groundwater, well water, lake water, river water, and industrial wastewater.

A common biological nitrification method for treating water containing a low concentration of ammonia nitrogen is the fixed-bed push flow method, in which the water is passed as a push flow through a fixed bed formed by packing a filter medium on which microorganisms such as nitrifying bacteria are attached. However, the fixed-bed push flow method has a problem in that the nitrification rate per nitrification tank is low, at about 0.1 kgN/ ^m3 /d.

As a method for biological nitrification of water containing a high concentration of ammonia nitrogen, there is a fluidized bed mixed flow method in which the water to be treated is passed through a nitrification tank while circulating carriers holding microorganisms (for example, Patent Document 1).
According to the fluidized bed mixed flow type biological nitrification apparatus shown in Fig. 1 of Patent Document 1, the water to be treated can be supplied to the nitrification tank from the water to be treated supply pipe while air is supplied to the stored water in the nitrification tank from the aeration unit. When the water to be treated flows into the nitrification tank, it is instantly mixed with the stored water. As a result, the concentration of the entire stored water becomes uniform.

In the fluidized bed mixed flow method, a biological retainer carrying nitrifying bacteria and the like is fluidized in the water stored in the nitrification tank. When the biological retainer comes into contact with the water to be treated, ammonia nitrogen is converted to nitrate nitrogen and treated. The treated water flows out of the tank through the treated water outlet pipe. The fluidized bed mixed flow method can treat water to be treated that contains a high concentration of ammonia nitrogen.

JP 2017-202473 A

However, even with the conventional fluidized bed mixed flow system, the nitrification rate per nitrification tank is about 0.2 kgN/m ³ /d, and there is room for improvement in this nitrification rate.
An object of the present invention is to provide an agitating type biological nitrification method and an agitating type biological nitrification apparatus which can treat water containing a high concentration of ammonia nitrogen at a nitrification rate higher than that of the conventional fluidized bed mixed flow system.

As a result of intensive research, the inventors of the present invention have come up with the idea of setting (i) the size of the biological holder, (ii) the copper ion concentration of the water to be treated, (iii) the linear velocity ratio (LV _gas /LV _water ) between the linear velocity LV water _flow [m/h] of the water to be treated and the linear velocity LV _gas [m/h] of the gas in the stored water in the nitrification tank, and (iv) the packing rate of the biological holder within a specified range. It has been found that when the nitrification reaction is carried out under these specific conditions, a higher nitrification rate can be achieved than in the conventional fluidized bed mixed flow method, and the present invention has been completed.

The present invention has the following aspects.
[1] A rocking biological nitrification method for treating ammonia nitrogen in water to be treated, which satisfies the following requirements 1, 2, 3, and 4 when the water to be treated is passed through a plurality of biological retainers loaded in a nitrification tank.
Requirement 1: The three-dimensional size of one of the bioretainers exceeds 5 mm in the maximum length direction and fits into a sphere having a diameter of 20 mm.
Requirement 2: The copper ion concentration of the water to be treated is 0.1 to 300 μg/L.
Requirement 3: The linear velocity ratio (LV _gas /LV water flow) between the linear velocity LV _{water flow} [m/h] of the water to be treated and the linear velocity LV _gas [m/h] of the gas in the stored _water in the nitrification tank is 0.3 to 6.0.
Requirement 4: The filling rate calculated by the following formula (1) is 75% or more.
Filling rate (%) = (bulk volume of multiple biological retainers) / (available water volume in nitrification tank) × 100 ... formula (1)
[2] The rocking type biological nitrification method according to [1], wherein the biological support has a porous carrier and nitrifying bacteria supported on the carrier.
[3] The rocking type biological nitrification method according to [1] or [2], wherein the water to be treated is passed through as an upward flow.
[4] The rocking-type biological nitrification method according to any one of [1] to [3], wherein the copper ion concentration in the treated water is 0.5 to 50 μg/L.
[5] A oscillating biological nitrification apparatus comprising: a nitrification tank loaded with a plurality of biological retainers; a water-to-be-treated supply pipe for supplying water-to-be-treated into the nitrification tank; a copper supply source capable of supplying copper ions to the water-to-be-treated; a water flow rate adjustment means for adjusting the flow rate of the water-to-be-treated supplied into the nitrification tank; a gas supply device for supplying gas to water stored in the nitrification tank; and a control device electrically connected to the water flow rate adjustment means and the gas supply device; the control device performs control that satisfies the following requirements 3 and 4; and satisfies the following requirements 1 and 2.
Requirement 1: The three-dimensional size of one of the bioretainers exceeds 5 mm in the maximum length direction and fits into a sphere having a diameter of 20 mm.
Requirement 2: The copper ion concentration of the water to be treated is 0.1 to 300 μg/L.
Requirement 3: The linear velocity ratio (LV _gas /LV water flow) between the linear velocity LV _{water flow} [m/h] of the water to be treated and the linear velocity LV _gas [m/h] of the gas in the stored _water in the nitrification tank is 0.3 to 6.0.
Requirement 4: The filling rate calculated by the following formula (1) is 75% or more.
Filling rate (%) = (bulk volume of multiple biological retainers) / (available water volume in nitrification tank) × 100 ... formula (1)
[6] The rocking type biological nitrification apparatus according to [5], wherein the copper source is in contact with the water to be treated.
[7] The rocking type biological nitrification apparatus according to [5] or [6], wherein the control device controls the copper ion concentration of the water to be treated to be 0.1 to 300 μg/L.

The present invention provides an agitated biological nitrification method and an agitated biological nitrification device that can treat water containing high concentrations of ammonia nitrogen at a nitrification rate higher than that of conventional fluidized bed mixed flow methods.

FIG. 1 is a schematic diagram showing an example of a rocking type biological nitrification device. FIG. 1 is a schematic diagram for explaining a method for measuring the average density of a plurality of organism retainers. FIG. 1 is a schematic diagram for explaining a method for measuring the average density of a plurality of organism retainers. FIG. 11 is a schematic diagram showing another example of a rocking type biological nitrification device. FIG. 5 is a schematic diagram of the inside of the treated water supply pipe of the rocking type biological nitrification apparatus of FIG. 4. FIG. 11 is a schematic diagram showing another example of a rocking type biological nitrification device. FIG. 11 is a schematic diagram of the inside of a treated water supply pipe of a rocking type biological nitrification device according to another example. FIG. 11 is a schematic diagram showing another example of a rocking type biological nitrification device. FIG. 11 is a schematic diagram showing another example of a rocking type biological nitrification device. FIG. 2 is a schematic diagram showing an example of a rocking type biological nitrification device used in the examples.

As used herein, the following terms have the following meanings:
"Ammoniacal nitrogen" refers to nitrogen contained in water as ammonium salt. It is also called ammoniacal nitrogen.
The use of "to" indicating a range of numerical values means that the numerical values before and after it are included as the lower limit and upper limit.

<Water to be treated>
The water to be treated is not particularly limited as long as it contains at least ammonia nitrogen. For example, groundwater, well water, lake water, river water, industrial water, sewage, and wastewater can be mentioned. However, the water to be treated is not limited to these examples.

In addition to ammonia nitrogen, the water to be treated may further contain anions such as bicarbonate ions, nitrate ions, sulfate ions, and chloride ions, cations such as iron ions, manganese ions, calcium ions, and magnesium ions, organic matter, bacteria, etc. However, the components of the water to be treated are not limited to these.
The main components of the organic matter in the water to be treated include humic acid, fulvic acid, etc. However, the water to be treated may contain organic matter other than these exemplified components.

The content of ammoniacal nitrogen in the treated water is not particularly limited, but is, for example, within the range of 0.1 to 15 mg/L. When the content of ammoniacal nitrogen is 0.5 mg/L or more, preferably 1 mg/L or more, the advantage of applying the rocking type biological nitrification method and rocking type biological nitrification device that can realize a high nitrification rate is further increased. When a high concentration of ammoniacal nitrogen is contained (for example, when the content of ammoniacal nitrogen is more than 15 mg/L and is 50 mg/L or less), it is preferable to use multiple nitrification tanks.
The iron content of the water to be treated is not particularly limited, but is, for example, in the range of 0 to 20 mg/L. According to an embodiment of the rocking type biological nitrification method and rocking type biological nitrification device, a high nitrification rate can be achieved even when the water to be treated contains iron.

Below, several embodiments of the present invention will be described with reference to the drawings as appropriate. The dimensional ratios in the drawings are for the convenience of explanation and may differ from the actual ones. In addition, in the drawings, the same components are indicated by the same reference numerals, and descriptions of overlapping components may be omitted.

<Swing-type biological nitrification device>
The rocking type biological nitrification apparatus 1A shown in FIG. 1 includes a lifting pump 3 for pumping up raw water (well water) from a well 2; a pretreatment tank 8 for the raw water; a lifting pipe 9 having a first end connected to the lifting pump 3 and a second end connected to the inside of the pretreatment tank 8; a copper wire 10A immersed in the stored water in the pretreatment tank 8; a nitrification tank 5 for a biological nitrification reaction; a treated water supply pipe 4A having a first end connected to the inside of the pretreatment tank 8 and a second end connected to the vicinity of the bottom of the nitrification tank 5; a water supply pump 11 provided midway along the treated water supply pipe 4A; and a copper wire 10B immersed in the stored water in the pretreatment tank 8. A water flow rate adjusting means (not shown) is provided midway through A and adjusts the flow rate of the water to be treated supplied to the nitrification tank 5; a plurality of biological retainers 6 loaded in the nitrification tank 5; a blower 12 for supplying gas to the stored water in the nitrification tank 5; a gas supply pipe 13 having a first end connected to the blower 12 and a second end opening in the nitrification tank 5; a control device (not shown) electrically connected to the water flow rate adjusting means and the aeration device; a screen 28 located near the liquid level in the nitrification tank 5; and a treated water outflow pipe 7 connected to the screen 28.

The lift pipe 9 supplies well water from the well 2 into the pretreatment tank 8. The pretreatment tank 8 is a tank for pre-treating raw water (well water in this example) to produce water to be treated. The water to be treated is water that is passed through the biological retainer area 11, which is made up of multiple biological retainers 6 loaded into the nitrification tank 5.

The pretreatment tank 8 may be, for example, a simple raw water storage tank, or a tank equipped with a dissolved oxygen supply device. The dissolved oxygen supply device referred to here is an aeration device for supplying dissolved oxygen, and is different from an aeration device.
Other examples of pre-treatment include, but are not limited to, demethanization and sand filtration.

The copper wire 10A is in contact with the water stored in the pretreatment tank 8. The copper wire 10A is an example of a copper supply source capable of supplying copper ions to the water to be treated. The copper wire 10A may be made of copper alone or a copper alloy.
With the copper wire 10A, copper ions are eluted into the water stored in the pretreatment tank 8, and as a result, copper ions can be supplied to the water to be treated. In the rocking type biological nitrification device 1A, the copper ion concentration of the water to be treated falls within the range of 0.1 to 300 μg/L (requirement 2).

The water to be treated is supplied to the nitrification tank 5 through the water supply pipe 4A by a water supply pump 11. A water flow rate measuring means (not shown) for measuring the amount of water to be treated supplied to the nitrification tank 5 and a water flow rate adjusting means are provided in the water supply pipe 4A.
An example of the water flow rate adjusting means is a flow rate adjusting valve.
Examples of the water flow rate measuring means include a rotameter and an electromagnetic flowmeter.
The untreated water supply pipe 4A is provided with a water supply pump 11, but this is not essential. The untreated water may be supplied to the nitrification tank 5 by using a water level difference without providing the water supply pump 11.

The untreated water supply pipe 4A is provided with a water quality meter (not shown) for measuring the copper ion concentration, iron content and ammoniacal nitrogen of the untreated water to be supplied to the nitrification tank 5.
The treated water supply pipe 4A may be provided with a dissolved oxygen supplying means such as an aeration tank. The dissolved oxygen supplying means is for supplying dissolved oxygen to the treated water.

The nitrification tank 5 is for treating ammonia nitrogen in the water to be treated by biological nitrification reaction using the organism retainers 6. The nitrification tank 5 is loaded with a plurality of organism retainers 6.
In the nitrification tank 5, a plurality of biological retainers 6 are loaded to form a biological retainer region 11. In the biological retainer region 11, each biological retainer 6 is loaded so as to oscillate when the water to be treated is passed through it. The linear velocity of the water to be treated passed through the biological retainer 6 in the nitrification tank 5 is the LV _{water pass} [m/h].

The LV _{water flow rate} [m/h] can be calculated by dividing the water flow rate [ ^m3 /h] by the cross-sectional area S [ ^m2 ] of the nitrification tank 5. The cross-sectional area S is the average value of the horizontal cross-sectional areas at each vertical position from the bottom of the nitrification tank 5 (or the upper surfaces of support plates such as perforated blocks, strainers, screens, and grids that support the carriers at the bottom) to the water level at which water overflows when the water is flowing.

The nitrification tank 5 oxidizes the ammoniacal nitrogen in the water to be treated to produce treated water by contacting each of the biological retainers 6 in the biological retainer region 11 with the water. The biological retainer region 11 may be formed by covering the bottom of the nitrification tank 5 with multiple biological retainers 6 and stacking multiple biological retainers 6 in multiple stages in the height direction of the nitrification tank 5.

The size of the nitrification tank 5 can be designed depending on the amount of water to be treated. Therefore, the volume of the nitrification tank 5 is not particularly limited. For example, the volume of the nitrification tank 5 can be within the range of 0.1 to ¹⁰⁰ m3. In addition, the shape of the nitrification tank 5 is not particularly limited, but the nitrification tank 5 relates to a gas-liquid-solid three-phase flow reaction tank. Therefore, a shape that has as few obstacles as possible that hinder the flow of the gas-liquid-solid three phases is preferable, and a shape with few projections and recesses is particularly preferable. For example, a cylindrical shape or a square shape can be mentioned. From the viewpoint of workability, a nitrification tank having a square cross section is preferable.

The material of the nitrification tank 5 is not particularly limited. Among various materials, materials with excellent pressure resistance are preferable. Examples include concrete, iron alloys, acrylic resin, and fiber-reinforced resin. In terms of ease of processing the nitrification tank 5, a panel tank (FRP tank) is preferable.

The organism retainer 6 is a carrier that retains nitrifying bacteria. The three-dimensional size of one organism retainer 6 is such that the maximum length exceeds 5 mm and the organism retainer 6 can fit into a sphere having a diameter of 20 mm (requirement 1).
The organism holder 6 has a carrier and nitrifying bacteria held on the carrier. The shape of the carrier is not particularly limited as long as requirement 1 is satisfied. Examples of the shape of the carrier include a cube, a rectangular parallelepiped, a sphere, a cone, a polygonal pyramid, a cylinder, and a filament. However, in consideration of the ease of shaking during water flow and of loading into the nitrification tank 5, a rectangular parallelepiped, a cube, and a sphere are preferred.

In multiple organism holders 6, the shapes of the carriers do not all need to be the same, and they may be different shapes. From the viewpoint of making it easier to maintain the oscillating state and to make it easier to carry out the nitrification reaction uniformly, it is preferable that the carriers have the same shape, but this is not necessarily limited to this.

The carrier is preferably a porous carrier, since more nitrifying bacteria can be supported by supporting the nitrifying bacteria on the surface and inside of the carrier, and the nitrification rate can be further improved. When the carrier is porous, the nitrifying bacteria may be supported inside the carrier.
The pore size of the porous carrier is preferably about 0.01 to 3 mm, more preferably about 0.05 to 1 mm, and even more preferably about 0.1 to 0.5 mm.

In particular, a sponge carrier is preferred because it can maintain the support of nitrifying bacteria well and minimize damage to pumps and piping. The porosity of the sponge carrier is preferably about 85 to 99%, and more preferably about 90 to 97%.
Examples of materials for the sponge carrier include polyvinyl alcohol, polyethylene glycol, and polyurethane.
The true density of the sponge carrier is preferably 0.90 to 1.50 g/cm ³ , more preferably 1.00 to 1.40 g/cm ³ , and even more preferably 1.00 to 1.20 g/cm ³ .

The apparent surface area of the sponge carrier is preferably 300 ^m2 / ^m3 or more, more preferably 600 ^m2 / ^m3 or more. When the apparent surface area of the sponge carrier is equal to or more than the lower limit, the surface area is sufficiently large, and the contact efficiency with the water to be treated is high. In addition, it is easy to retain nitrifying bacteria, the oxygen supply efficiency is also high, and the nitrification rate is further increased.

The nitrifying bacteria include known nitrifying bacteria used in biological nitrification of ammonia nitrogen. For example, nitrifying bacteria such as Nitrosomonas are autotrophic, and basically use carbon dioxide as the only carbon source. They do not require an organic substrate and can grow in the presence of ammonia nitrogen, but their growth rate is extremely low. In order to increase the nitrification rate, an operation is required to hold a large amount of nitrifying bacteria in the nitrification tank. Therefore, it is preferable to hold the nitrifying bacteria on a carrier rather than as suspended bodies.
An example of a method for supporting nitrifying bacteria on a carrier is to introduce the carrier into a nitrification tank of an existing water treatment device and grow the nitrifying bacteria on the surface of the carrier.

The average density of the organism retainer 6 is preferably 1.00 to 2.00 g/ ^cm3 , more preferably 1.05 to 1.40 g/ ^cm3 , and even more preferably 1.10 to 1.20 g/ ^cm3 . Here, the average density of the organism retainer 6 is the average density in a wet state in which each organism retainer 6 retains nitrifying bacteria. The wet state will be described later.
If the average density of the organism retainers 6 is equal to or greater than the lower limit of the range, the organism retainers 6 are likely to settle in the stored water in the nitrification tank 5, and therefore the oscillating state can be maintained. Therefore, the organism retainers 6 do not flow excessively. As a result, the water to be treated moves toward the outlet and gradually comes into contact with a number of organism retainers 6, and the nitrification reaction is likely to proceed. If the average density of the organism retainers 6 is equal to or less than the upper limit of the range, the organism retainers 6 are likely to oscillate.
Therefore, if the average density of the organism retainers 6 is within the above range, the organism retainers 6 are easily swung in the stored water by the flow of the water to be treated. Therefore, impurities (such as SS) in the water to be treated are less likely to adhere to the organism retainers 6. As a result, the contact efficiency between the water to be treated and each organism retainer is improved, and the nitrification rate is increased.

The average density of the bioretainer can be calculated as follows.
First, the mass m [g] of the plurality of organism supports is measured. For example, as shown in Fig. 2, a container 20 with a known volume is placed on a mass meter 30, and the organism supports 6 are removed from the nitrification tank and loaded into the container 20 so that the bulk volume is constant. To make the bulk volume constant, for example, a reference line L is drawn on the side of the container 20 with a known volume, and the plurality of organism supports 6 can be loaded into the container 20 so that the reference line L coincides with the top surface of the uppermost organism support 6.

When the organism holder is removed from the nitrification tank, the retained water adhering to the carrier drips off the organism holder. The mass of the dripped retained water is not included in the mass m [g] of the multiple organism holders. In this embodiment, an organism holder with a bulk volume of about ⁵⁰⁰ cm3 is scooped out of the nitrification tank and held on the water surface. The time when water droplets stop dripping for 5 seconds or more is defined as the "wet state" of the organism holder. The organism holder in such a wet state is loaded into the container 20.
Thereafter, the operation of removing the biological retainers from the nitrification tank and loading them into container 20 is repeated, and the mass when the total bulk volume of the multiple biological retainers reaches a predetermined value is recorded as the mass m [g] of the multiple biological retainers.

Next, the volume V [ ^cm3 ] of the multiple organism supports is measured. As shown in Fig. 3, water is poured from a separately prepared beaker 40 into a container 20 loaded with wet organism supports 6 until a predetermined bulk volume is reached, i.e., up to the reference line L, filling the spaces between the organism supports 6 with water. At this time, the amount of water poured from the beaker 40 into the container 20 is measured, and the difference between the predetermined bulk volume and the amount of water poured from the beaker 40 is taken as the volume V [ ^cm3 ] of the multiple organism supports.
Finally, the mass m [g] of the plurality of biosupports is divided by the volume V [cm ³ ] of the biosupports to obtain the average density m/V [g/cm ³ ] of the biosupports 6 .

Taking into consideration the oscillation during water flow, the average volume of one organism retainer is preferably 0.03 to 5.00 ^cm3 , more preferably 0.06 to 1.00 ^cm3 , and even more preferably 0.10 to 0.30 ^cm3 . When the volume of one organism retainer is equal to or greater than the lower limit of the above range, solid-liquid separation of the organism retainer using screen 28 or the like becomes easy. When the volume of one organism retainer is equal to or less than the upper limit of the above range, the organism retainer is more likely to oscillate even with a relatively small LV _gas .
Here, the average volume of one biological retainer is the total volume of a plurality of biological retainers in the nitrification tank divided by the number of biological retainers in the nitrification tank.
Furthermore, in a plurality of bioretainers, the volumes of each bioretainer do not all need to be the same, and may be different from one another.

The bioretainer can be prepared, for example, as follows.
The carrier is cultured by passing water through the nitrification tank of an existing biological nitrification device. For example, the density of a new porous carrier is often less than 1 g/ ^cm3 because it contains air inside.
When the carrier is cultured in a nitrification tank, air gradually escapes from the carrier and the nitrifying bacteria adhere to the carrier. The carrier is cultured in a water flow until the density of the carrier containing the nitrifying bacteria and water in a wet state is within the range of 1.0 to 1.4 g/ ^cm3 , for example, to form a biological retainer.

1 again, the treated water outlet pipe 7 is for taking out the treated water from the nitrification tank 5. The treated water outlet pipe 7 is connected to a screen 28. The treated water is once collected on the screen 28 and then flows out of the nitrification tank 5 through the treated water outlet pipe 7.
An outflow volume measuring means (not shown) for measuring the volume of treated water flowing out from the nitrification tank 5 and an outflow volume adjusting means (not shown) for adjusting the flow rate of treated water flowing through the treated water outflow pipe 7 are provided midway through the treated water outflow pipe 7.
Examples of the outflow measuring means include a rotameter and an electromagnetic flowmeter.
An example of the outflow rate adjusting means is a flow rate adjusting valve.

The air diffuser equipped with the blower 12 and the gas supply pipe 13 is an example of a gas supply device. The linear velocity of the gas supplied to the stored water in the nitrification tank 5 is LV _gas [m/h].
In the rocking type biological nitrification apparatus 1A, gas is supplied to the stored water in the nitrification tank 5 from an opening of a gas supply pipe 13 extending near the bottom of the nitrification tank 5. A gas supply amount adjustment means (not shown) is provided in the middle of the gas supply pipe 13.

In principle, the aeration device is used to aerate and remove solid matter adhering to the surface of the biological retainer 6. With the aeration device, the air bubbles supplied into the nitrification tank can remove solid matter adhering to the surface of the biological retainer 6.

The gas supplied by the air diffuser is not particularly limited as long as it can agitate the organism holder 6, but a safe gas that does not inhibit the nitrification reaction and does not cause explosions or corrosion is preferable.
The gas may be, for example, air or an inert gas such as argon or nitrogen.

In the rocking type biological nitrification apparatus 1A, the opening surface of the gas supply pipe 13 is the aeration section, but in other examples the aeration section may be an aeration tube, an aeration ball, or a diffuser having a diffusion hole formed therein.
The gas supply amount adjusting means may be, for example, a gate valve, a butterfly valve, or control of blower frequency by an inverter.

The control device includes an interface unit (not shown), a memory unit (not shown), a processing unit (not shown), a determination unit (not shown), a control unit (not shown), and the like.
The interface unit electrically connects the control unit to the water flow measurement means, the water flow adjustment means, the water quality meter, the outflow measurement means, the outflow adjustment means, the blower of the air diffuser, and the gas supply adjustment means.

The memory unit stores the linear velocity ratio (LV _gas /LV _{water flow rate} ) and the operating conditions of the oscillating type biological nitrification device 1A for calculating the filling rate calculated by the following formula (1), etc.
Filling rate (%)=(bulk volume of multiple organism holders 6/available water volume in nitrification tank 5)×100 Equation (1)

LV _gas [m/h] is the linear velocity of gas in the water stored in the nitrification tank. LV _gas [m/h] is calculated by the following formula (2).
LV _gas [m/h]=amount of gas supplied by aeration device [m ³ /h]/cross-sectional area of nitrification tank S [m ² ] Equation (2)

The LV _{water flow rate} [m/h] is the linear velocity of the water being treated as it flows through the multiple organism retainers. The LV _{water flow rate} is calculated by the following formula (3).
LV _{water flow rate} =water flow rate [m ³ /h]/cross-sectional area of nitrification tank S [m ² ] Equation (3)

The operating conditions stored in the memory unit include, for example, the copper ion concentration of the water to be treated, the sum of the volumes of the multiple biological holders 6, the effective water volume in the nitrification tank 5, the cross-sectional area S of the nitrification tank 5, the bulk volume, total mass, and number of the biological holders 6 loaded in the nitrification tank 5, the average density of the biological holders 6, the supply amount of water to be treated, the outflow amount of treated water, and the amount of gas supplied into the nitrification tank 5.

In the oscillating biological nitrification device 1A, the "bulk volume of the multiple biological retainers 6" in formula (1) is the sum of the volumes of all the biological retainers 6 that make up the biological retainer region 11. In other words, the "bulk volume of the multiple biological retainers" is the volume that the assembly of the biological retainers in a stationary state occupies within the space of the effective water volume when multiple biological retainer carriers are placed in the nitrification tank.

The "bulk volume of the biological retainer" can be calculated by multiplying the distance (effective filling height hZ) from the bottom of the nitrification tank 5 (or the top surfaces of support plates such as perforated blocks, strainers, screens, and grids that support the carriers at the bottom, if any) of the nitrification tank 5 is a rectangular or cylindrical tank that is uniform in height, to the upper surface of the biological retainer when _all of the biological retainers 6 placed in the nitrification tank are allowed to stand, by the cross-sectional area S of the nitrification tank 5.

In the rocking type biological nitrification apparatus 1A, the "effective water volume in the nitrification tank 5" in formula (1) is the total volume of the water to be treated and the organism retention carrier present in the nitrification tank 5. This "effective water volume in the nitrification tank 5" is the empty volume up to the overflow water level of the nitrification tank 5. It can be calculated by multiplying the distance (effective water level hT) from the bottom of the nitrification tank 5 (if there are support plates such as perforated blocks, strainers, screens, grids, etc. that support the carriers at the bottom, the top surfaces of these support _plates ) to the water level that overflows when water is passed through by the cross-sectional area S of the nitrification tank 5.

The processing unit can perform the following operation 1.
Calculation 1: The bulk volume of the plurality of organism holders 6 and the available water volume in the nitrification tank 5 are calculated, and then the packing rate of the organism holders 6 is calculated from the above formula (1).

The processing unit can perform the following operation 2.
Calculation 2: The LV _{water flow rate} is calculated from the flow rate value of the water flow rate adjustment means and the cross-sectional area S of the nitrification tank 5, and the LV _gas is calculated from the supply value of the gas supply rate adjustment means and the cross-sectional area S of the nitrification tank 5, and the linear velocity ratio (LV _gas /LV _{water flow rate} ) is calculated.

The determination unit may determine, for example, at least one of the following items:
- Whether the copper ion concentration of the treated water measured with a water quality meter is within the range of 0.1 to 300 μg/L (requirement 2).
- Whether the linear velocity ratio (LV _gas /LV _water ) is within the range of 0.3 to 6.0 (requirement 3).
Whether or not the filling rate of the organism holder 6 calculated in the processing section is 75% or more (requirement 4).
- Whether the iron content of the treated water measured with a water quality meter is 0.5 mg/L or more.

The control unit controls the rocking type biological nitrification device 1A based on the determination result by the determination unit, the operating conditions of the rocking type biological nitrification device 1A stored in the storage unit, etc. The control unit executes control to satisfy requirements 3 and 4.
The control unit may execute control for satisfying requirement 2, that is, control for making the copper ion concentration in the water to be treated 0.1 to 300 μg/L. In addition, when the ammoniacal nitrogen content in the water to be treated is stabilized, the copper ion concentration may be secured in advance within a preferred range.

When the determining section determines that the copper ion concentration is less than 0.1 μg/L, the control section can carry out the following control.
Controlling the water flow rate adjusting means so as to reduce the supply rate of water to be treated and increase the copper ion concentration in the water to be treated.
Controlling the outflow rate adjusting means so as to reduce the outflow rate of treated water and increase the copper ion concentration in the water to be treated.

When the determining section determines that the copper ion concentration is greater than 300 μg/L, the control section can carry out the following control.
The water flow rate adjusting means is controlled so as to increase the supply rate of water to be treated and to lower the copper ion concentration in the water to be treated.
- Controlling the outflow rate adjusting means so as to increase the outflow rate of treated water and lower the copper ion concentration in the water to be treated.

When the determining unit determines that the linear velocity ratio (LV _gas /LV _{water flow} ) is less than 0.3, the control unit can carry out the following control.
- Controlling the gas supply amount adjustment means so as to increase the amount of gas supplied by the aeration device and increase the LV _gas [m/h].
Controlling the water flow rate adjustment means to reduce the supply rate of water to be treated and lower the LV _{water flow rate} [m/h].
- Controlling the outflow rate adjustment means to reduce the outflow rate of treated water and lower the LV _{water flow} rate [m/h].

When the determining unit determines that the linear velocity ratio (LV _gas /LV _{water flow} ) is greater than 6.0, the control unit can carry out the following control.
Controlling the gas supply amount adjustment means to reduce the amount of gas supplied by the aeration device and lower the LV _gas [m/h].
- Controlling the water flow rate adjustment means so as to increase the supply rate of water to be treated and increase the LV _{water flow rate} [m/h].
- Controlling the outflow rate adjustment means to increase the outflow rate of treated water and increase the LV _{water flow} rate [m3/h].

For example, when the determining section determines that the filling rate of the organism holder 6 is less than 75%, the control section can carry out the following control.
Controlling the water flow rate adjusting means so as to reduce the amount of water to be treated and thereby reduce the volume of water stored in the nitrification tank 5.
- Controlling the outflow rate adjustment means so as to increase the outflow rate of treated water and reduce the volume of stored water in the nitrification tank 5.

In addition, when the judgment section judges that the iron content of the water to be treated is 0.5 mg/L or more, the control section may carry out the following control.
Controlling the gas supply amount adjusting means to adjust the amount of gas supplied by the air diffuser.
-Adjusting the flow rate of the water flow rate adjusting means and the outflow rate adjusting means to adjust the LV _{water flow rate} .

The processing unit, the determination unit, and the control unit may be realized by dedicated hardware. The processing unit, the determination unit, and the control unit may also be configured by a memory and a central processing unit (CPU). In the case of a CPU, the functions of the processing unit, the determination unit, and the control unit may be realized by loading a program for realizing the functions of the processing unit, the determination unit, and the control unit into memory and executing the program.

The control device may be connected to peripheral devices such as an input device and a display device. Examples of the input device include a display touch panel, a switch panel, a keyboard, and the like. Examples of the display device include a liquid crystal display device, a CRT, and the like.

<Swing-type biological nitrification method>
An example of a nitrification method using the rocking type biological nitrification device 1A will be described below.
First, a plurality of organism holders 6 cultured in a nitrification tank of an existing biological nitrification apparatus are loaded into the nitrification tank 5 of the rocking type biological nitrification apparatus 1A.
The three-dimensional size of each organism retainer 6 exceeds 5 mm in the maximum length direction and fits into a sphere with a diameter of 20 mm (requirement 1). Therefore, each organism retainer 6 rocks when the water to be treated is passed through it. When the organism retainers 6 are loaded, it is advisable to leave a space between the organism retainers 6 for rocking so that the organism retainers 6 can rock when the water is passed through them.

Next, raw water containing ammonia nitrogen (well water in this example) is stored in the pretreatment tank 8. By contacting the raw water with the copper wire 10A in the pretreatment tank 8, copper ions are supplied to the water to be treated.
Thereafter, the water to be treated is supplied from the pretreatment tank 8 to the vicinity of the bottom of the nitrification tank 5 via the water to be treated supply pipe 4A and stored in the nitrification tank 5. As water is stored in the nitrification tank 5, the water also fills the spaces between the biological retainers 6 in the biological retainer region 11. As the water continues to be stored thereafter, the biological retainer 6 at the top of the biological retainer region 11 becomes immersed in the stored water.

When water is stored in the nitrification tank 5, the filling rate calculated by the following formula (1) is set to 75% or more.
Filling rate (%)=(bulk volume of multiple organism holders 6)/(available water volume in nitrification tank 5)×100 Formula (1)

(Biological nitrification reaction)
When the water to be treated is passed through the biological retainer region 11 in the nitrification tank 5, the water to be treated comes into contact with the biological retainer 6. Ammoniacal nitrogen in the water to be treated is then oxidized to nitrate nitrogen by the nitrifying bacteria in the biological retainer 6. In this way, the water to be treated containing ammoniacal nitrogen is treated in the nitrification tank 5 to produce treated water.

The apparent volume of the sponge carrier expands by aeration with gas while water is passing through it, and the expansion rate at this time is preferably within the range of 2 to 25%. The expansion rate is calculated by the following formula (4).
Expansion rate (%)=(volume [m ³ ] of the plurality of organism holders 6 in the nitrification tank 5 when water is flowing−bulk volume [m ³ ] of the plurality of organism holders 6 when left stationary)/(effective water volume [m ³ ])×100 (Equation (4))

(Copper ion concentration: requirement 2)
In this embodiment, the copper ion concentration of the water to be treated is set within the range of 0.1 to 300 μg/L when the water to be treated is passed through the treatment system.
The copper ion concentration is preferably 0.5 μg/L or more, and more preferably 1.0 μg/L or more. By setting the copper ion concentration to 0.1 μg/L or more, the biological nitrification reaction by nitrifying bacteria is activated, and as a result, a high nitrification rate can be achieved.
The copper ion concentration is preferably 100.0 μg/L or less, more preferably 50.0 μg/L or less, and even more preferably 10.0 μg/L or less. By setting the copper ion concentration to 300 μg/L or less, the biological nitrification reaction by nitrifying bacteria is less likely to be inhibited, and a high nitrification rate can be achieved.

(LV _gas /LV _{water flow} : requirement 3)
In this embodiment, when the water to be treated is passed through, the linear velocity ratio (LV _gas /LV _{water passing} ) is set to 0.3 to 6.0. The linear velocity ratio (LV _gas /LV _{water passing} ) is preferably 0.5 to 6.0, and more preferably 2.0 to 4.0.
If the linear velocity ratio (LV _gas /LV _{water flow} ) is within the above-mentioned numerical range, the nitrification rate can be increased while preventing solids such as iron from adhering to the surface of the organism holder 6. In particular, if the iron content of the water to be treated is more than 1.0 mg/L, there is a possibility that a large amount of solids such as iron hydroxide produced during the nitrification reaction will adhere to the surface of the organism holder. In this case, it may be particularly beneficial to set the linear velocity ratio (LV _gas /LV _{water flow} ) to 0.3 or more.

The LV _{water flow} can be adjusted, for example, by adjusting the flow rate of the water flow rate adjusting means and the outflow rate adjusting means.
The LV _{water flow rate} is not particularly limited, but is preferably within the range of 5 to 40 m/h, more preferably 8 to 30 m/h, and even more preferably 10 to 25 m/h. If _{the LV water flow rate} is equal to or higher than the lower limit of the range, the organism holder 6 is likely to oscillate. If the LV _{water flow rate} is equal to or lower than the upper limit of the range, the nitrification reaction efficiency is likely to be maintained, and the nitrification rate is likely to be further improved.

The LV _gas can be adjusted, for example, by the gas supply amount of the air diffuser. The amount of gas diffused from the air diffuser can be adjusted to an arbitrary amount by a gas supply amount adjusting means.
The LV _gas is not particularly limited, but in terms of agitating the biological holder 6 and reducing the electrical energy required for gas supply, the LV _gas is preferably in the range of 3 to 100 m/h, more preferably in the range of 20 to 60 m/h.

(Filling rate: requirement 4)
In this embodiment, the filling rate calculated by formula (1) is set to 75% or more when the water to be treated is passed through the treatment tank. Therefore, the nitrification rate is sufficiently high. In terms of increasing the nitrification rate, the filling rate calculated by formula (1) is preferably set to 75% or more, more preferably set to 80% or more, and even more preferably set to 85% or more.
The upper limit of the filling rate calculated by the above formula (1) is 100%, but in terms of agitating the biological holder 6 when water is passed through it, it is preferable to set it to 100% or less, more preferably 98% or less, and even more preferably 95% or less.
However, when the filling rate approaches 100%, the spatial space for oscillation is reduced, and therefore, when the water to be treated contains iron ions, suspended matter such as iron hydroxide adheres to the carrier, which may cause filtration blockage.

(Upward flow)
In the rocking type biological nitrification apparatus 1A, the water to be treated is passed as an upward flow through the multiple biological retainers 6 in the biological retainer region 11. By passing the water to be treated as an upward flow as in this embodiment, a state in which the biological retainers are easily rocked even during aeration can be achieved.

<Mechanism of action>
In the rocking biological nitrification method according to the embodiment described above, (i) the size of the biological holder, (ii) the copper ion concentration of the water to be treated, (iii) the linear velocity ratio (LV _gas /LV _{water flow} ), and (iv) the filling rate of the biological holder satisfy certain conditions. Therefore, the following advantages can be provided. Therefore, the water to be treated containing a high concentration of ammonia nitrogen can be treated at a high nitrification rate, and the treatment device can be made compact.

- Because the biological retainer can oscillate in the nitrification tank when water is passed through it, solid matter is less likely to adhere to the surface of the biological retainer, improving the efficiency of the nitrification reaction by the biological retainer.
- The copper ion concentration in the treated water is sufficiently high, but not excessively high, so a high nitrification rate can be achieved. As a result, the treated water containing a high concentration of ammonia nitrogen can also be treated. In addition, the treatment device can be made smaller.
Since the organism retainer can oscillate, the water to be treated comes into contact with the entire organism retainer efficiently when the water passes through it. As a result, even if the filling rate of the organism retainer is set to 75% or more, it is possible to prevent the occurrence of short-circuiting and the occurrence of dead spaces that do not come into contact with the organism retainer 6. This improves the nitrification rate and realizes an excellent nitrification rate.
According to the present embodiment, an excellent nitrification rate can be achieved. Therefore, there is less need to increase the number of nitrification tanks. In addition, the nitrification tanks themselves can be made smaller.

For example, in a fluidized bed mixed flow type nitrification method as described in Patent Document 1, when the packing rate reaches 75% or more, dead spaces and short-circuiting occur due to poor fluidity of the carrier, so there is a limit to how quickly the nitrification rate can be increased.
In contrast, in this embodiment, the biological retainer oscillates when water is passed through, so the treated water comes into contact with the multiple biological retainers efficiently overall. Therefore, even with a predetermined filling rate of 75% or more, it is possible to prevent the occurrence of short-circuiting flow and the occurrence of dead spaces where the water does not come into contact with the biological retainers, and as a result, the nitrification rate can be increased. The biological nitrification reaction in this embodiment can also be said to be a oscillating bed push-out flow method.

In this embodiment, the biological retainer can be swung in the water stored in the nitrification tank. Therefore, when the iron content of the water to be treated is 1.0 mg/L or less, the solid matter attached to the surface of the biological retainer can be sufficiently removed even if the LV _gas is relatively low, so that the efficiency of the nitrification reaction can be maintained high. As a result, a high nitrification rate can be achieved. In this case, the energy consumption due to aeration can be reduced.
On the other hand, as shown in the examples described later, even when the iron content of the water to be treated exceeds 1.0 mg/L, ammoniacal nitrogen can be treated at a high nitrification rate.

Furthermore, since the oscillating biological nitrification apparatus 1A described above has the configuration described above, by using the oscillating biological nitrification apparatus 1A, the oscillating biological nitrification method according to the above-mentioned embodiment can be implemented and the above-mentioned mechanism of action can be exerted.
For example, in the case of a rocking biological nitrification apparatus 1A having one nitrification tank, even if the residence time of the treated water is 30 min or less, it is possible to reduce the ammoniacal nitrogen of the treated water containing a high concentration of ammoniacal nitrogen of 5 mg/L or more to less than about 0.1 mg/L. Therefore, for example, when treating the treated water containing a high concentration of ammoniacal nitrogen of 1 mg/L or more, the present invention is particularly suitable for use in making the treated water potable.

<Other embodiment examples>
Although one embodiment has been described above by showing one embodiment, the present invention is not limited to the embodiment disclosed in this specification, and can be appropriately modified and implemented without departing from the gist of the present invention. The embodiment disclosed in this specification can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention.
Several modified examples are shown below, but the embodiments of the present invention are not limited to these modified examples.

In the above-mentioned rocking type biological nitrification apparatus 1A, the copper wire 10A of the copper supply source is in contact with the stored water in the pretreatment tank 8, but the copper supply source is not limited to this embodiment. In addition, the copper supply source may supply copper ions to the water to be treated or may supply copper ions to the raw water.
For example, in the rocking type biological nitrification apparatus 1B shown in Fig. 4, a copper wire 10A is disposed inside the treated water supply pipe 4B as shown in Fig. 5. A first end of the treated water supply pipe 4B is connected to the lifting pump 3, and a second end of the treated water supply pipe 4B is connected to the inside of the nitrification tank 5.
According to the rocking type biological nitrification apparatus 1B, copper ions can be supplied to the raw well water in the treated water supply pipe 4B. The treated water after the copper ions have been supplied to the raw water in the treated water supply pipe 4B can be passed through the biological holder 6 in the nitrification tank 5.

In addition, the method of supplying copper is not particularly limited. For example, in the rocking type biological nitrification apparatus 1C shown in FIG. 6, a copper electrode 10C is immersed as an anode in the stored water in the pretreatment tank 8. A cathode 16 is immersed in the stored water. The copper electrode 10C is connected to the positive potential side of a power source 15. The cathode 16 is connected to the negative potential side of the power source 15.
According to the rocking type biological nitrification apparatus 1C, copper ions can be supplied to the water to be treated by dissolving the anode, i.e., the copper electrode 10C, through electrolysis. Then, the water to be treated after the copper ions are supplied to the raw water in the pretreatment tank 8 can be passed through the organism holder 6 in the nitrification tank 5.

The power supply 15 is preferably electrically connected to a control device (not shown) of the rocking type biological nitrification device. In this case, the following controls can be performed by a control unit of the control device.
When the judgment unit of the control device judges that the copper ion concentration is less than 0.1 μg/L, the copper ion concentration is controlled to be increased by increasing the current value flowing through the copper electrode 10C to increase the amount of copper ions eluted.
When the judgment unit of the control device judges that the copper ion concentration is greater than 300 μg/L, the current value flowing through the copper electrode 10C is lowered to reduce the amount of copper ions eluted, thereby controlling the copper ion concentration to be higher.

The form of the copper supply source is not limited to a copper wire or a copper electrode. Other variations include, for example, making the treated water supply pipe a pipe of simple copper or a pipe of a copper alloy. Alternatively, a copper electrode connected to the positive potential side of a power source may be disposed inside the treated water supply pipe. A copper electrode 10C and a cathode 16 are disposed inside the treated water supply pipe 4A shown in FIG. 7. The copper electrode 10C is connected to the positive potential side of a power source 15. The cathode 16 is connected to the negative potential side of the power source 15.
In either variation, copper ions can be supplied to the water to be treated or to the raw water.

Alternatively, a water-soluble copper compound or an aqueous solution thereof may be added to the water to be treated or the raw water to be treated, thereby supplying the water to be treated or the raw water. For example, the rocking biological nitrification apparatus 1D shown in FIG. 8 includes a copper ion injection device 10D. In the rocking biological nitrification apparatus 1D, the first end of the water to be treated supply pipe 4A is connected to the lifting pump 3, and the second end is connected to the vicinity of the bottom of the nitrification tank 5.

The copper ion injection device 10D comprises: a tank 17 in which a water-soluble copper compound or an aqueous solution thereof is stored; an injection pipe 18 having a first end connected to the tank 17 and a second end connected to the middle of the treated water supply pipe 4A; and an injection pump 19 provided in the middle of the injection pipe 18.
According to the rocking type biological nitrification apparatus 1D, copper ions can be supplied from the tank 17 to the raw well water in the treated water supply pipe 4A by driving the injection pump 19. Then, the treated water after the copper ions have been supplied to the raw water in the treated water supply pipe 4A can be passed through the organism holder 6 in the nitrification tank 5.

The injection pump 19 is preferably electrically connected to a control device (not shown) of the rocking type biological nitrification device. In this case, the following controls can be performed by a control unit of the control device.
When the judgment section of the control device judges that the copper ion concentration is less than 0.1 μg/L, the amount of liquid supplied to the tank 17 by the injection pump 19 is increased, thereby controlling the copper ion concentration to be increased.
When the judgment section of the control device judges that the copper ion concentration exceeds 300 μg/L, the amount of liquid supplied to the tank 17 by the injection pump 19 is reduced, thereby controlling the copper ion concentration to be lower.

The location of the copper supply source is not particularly limited as long as it is a location where copper can be supplied to the water to be treated. When copper is supplied by contacting the copper supply source with the raw water or the water to be treated, it is preferable that the copper supply source is located in a position where it contacts the raw water or the water to be treated.
9, a copper wire 10A may be immersed in the water to be treated in a nitrification tank 5. Although not shown, a copper electrode 10C connected to the positive potential side of a power source may be immersed in the water to be treated in the nitrification tank 5.

When copper is eluted by contacting a copper source with the water to be treated or raw water, the form of the copper source is not particularly limited. For example, a copper element or an alloy formed into a wire shape, such as the copper wire 10A in FIG. 1, may be used, but in another example, a copper element or an alloy formed into a plate shape may be used. When copper is eluted by contacting a copper source with the water to be treated or raw water, the higher the dissolved oxygen concentration, the more the copper elution tends to be promoted.

In the above-described embodiment, the water to be treated is passed through the multiple biological retainers 6 in the biological retainer region 11 as an upward flow, but in other examples, the water to be treated may be passed through the biological retainers 6 as a downward flow from the top to the bottom of the biological retainer region 11.
The same effect can be obtained even when the water to be treated is passed through the system in a downward flow, so that a high nitrification rate can be achieved.

The number of nitrification tanks is not limited to one, and may be multiple. For example, if the ammonia nitrogen content of the water to be treated is 2 mg/L or less, the number of nitrification tanks may be one. However, if the ammonia nitrogen content of the water to be treated is 2 to 6 mg/L, the number of nitrification tanks may be increased to multiple. Also, the number of nitrification tanks equipped with an aeration device to promote the nitrification reaction may be one. For example, the number of nitrification tanks equipped with an aeration device may be increased by one for every increase of about 6 mg/L in the ammonia nitrogen content.

A dissolved oxygen (DO) meter for measuring the dissolved oxygen concentration in the water stored in the nitrification tank 5 may be used.
When there are multiple biological nitrification tanks, it is better to provide an aeration device in the pretreatment tank 8 between each biological nitrification tank, in order not to directly affect the shaking state of the biological retainer in the biological nitrification tank.

A post-treatment device may be used for subjecting treated water flowing out of the nitrification tank 5 to post-treatment. The post-treatment device may be installed appropriately depending on the quality of the water to be treated and the quality of the treated water, etc.
Examples of downstream treatment devices include an ion exchange treatment tank, a flocculant addition device, an oxidant addition device, a sand filtration tower, a membrane filtration device, and a disinfectant addition device.
The use of the final treated water after the second stage treatment is not particularly limited, and examples thereof include, but are not limited to, use as domestic water and drinking water.

The present invention has been described above with reference to several specific embodiments, but each embodiment is presented as an example and does not limit the scope of the present invention. Each embodiment described in this specification can be modified in various ways within the scope of the effects of the invention, and can be combined with features described in other embodiments within the scope of feasibility.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

<Preparation of treated water>
Raw water quality: Ferrous sulfate heptahydrate was added to the collected groundwater to prepare simulated groundwater with an iron ion concentration of 0.3 to 3.0 mg/L. Ammonium chloride and copper sulfate pentahydrate were further added to the collected groundwater to adjust the ammoniacal nitrogen concentration and copper concentration. The groundwater temperature at the time of collection was 17±1°C, the alkalinity was 85 mg/L, and the pH was 7.6±0.2.

<Construction of test equipment>
A test apparatus 50 shown in Fig. 10 was constructed. The test apparatus 50 has a nitrification tank 5, a water-to-be-treated supply pipe 14, a screen 28, and a treated water outlet pipe 7. A discharge port 14a of the water-to-be-treated supply pipe 14 opens downward in the nitrification tank 5.

(Biological Support)
As the sponge carrier, a 5 mm square cubic polyurethane sponge carrier ("Waterflex AQ-15" manufactured by Technoform Japan Co., Ltd.) was prepared. The density of the sponge carrier before the water-passing culture was 0.044 g/cm ^3. These sponge carriers were subjected to water-passing culture in the nitrification tank of an existing biological nitrification device, and about 10 kg (about 6,500 pieces) of biological holders were prepared. After the water-passing culture, the biological holders were scooped out of the nitrification tank and held on the water surface. When the water droplets stopped dripping for 5 seconds or more, the biological holders were judged to be in a wet state, and were loaded into a 10 L graduated container.

When the loading of the bioretainers into the 10 L graduated container was completed, the mass m of the bioretainers was 5785 g. Thereafter, water was poured from a separately prepared beaker into the graduated container in which the bioretainers had been loaded to fill the spaces between the bioretainers with water, and when the water level reached the 10 L mark, the water pouring was stopped. The amount of water poured from the separately prepared beaker at this time was ⁴⁷⁷⁰ cm3. The volume V of the bioretainers was set to 10000 ^cm3 (10 L) - 4770 ^cm3 = 5230 ^cm3 .
Therefore, the average density of the bioretainer was calculated to be 5785 g/5230 cm ³ ≈1.1 g/cm ³ .

(Nitrification tank)
A transparent acrylic tank with a rectangular cross section was used. The top of the tank was open to the atmosphere. The front width of the tank was 500 mm, the side depth was 150 mm, and the height was 2300 mm. The effective water volume of the tank was 150 L. When passing water, the water to be treated was supplied from the bottom of the tank, and an outlet was installed at the top of the tank, so that the water to be treated would flow upward when passing water.

The supply rate of the water to be treated was 12.5 L/min (LV _{water flow} : 10 [m3/h]). A hole was drilled at a height of 800 mm in the water tank, and the water supply pipe was extended so as to run along the side of the water tank in a vertical downward direction at 90 degrees. The length of the water supply pipe to be treated was 500 mm, and the inner diameter of the pipe was 71 mm.
The outlet of the treated water supply pipe 14 was installed at a height of 300 mm from the bottom of the tank. An aeration pipe was also placed at the bottom of the tank so that gas was supplied uniformly into the tank. The gas supply rate was 3.8 to 75 L/min (LV _gas 3 to 240 m/h).
In the examples, air (atmospheric air) that had not been subjected to any particular pretreatment was used as the gas.

(Swing-type biological nitrification device)
The amount of ammonium chloride added to the water to be treated was gradually increased while measuring the ammonia nitrogen concentration of the treated water after the nitrification reaction. The ammonia nitrogen concentration of the treated water was measured when the ammonia nitrogen concentration of the treated water reached 0.1 mg/L. In this way, the maximum nitrification rate at which the ammonia nitrogen concentration of the treated water could be maintained at 0.1 mg/L or less was determined. The nitrification rate was calculated as follows.

<Measurement method>
(Nitrification rate)
When the amount of ammonium chloride added to the raw water was gradually increased after the start of water flow, the biological nitrification reaction could not keep up, and the ammoniacal nitrogen concentration in the treated water exceeded 0.1 mg/L. The nitrification rate [kgN/ ^m3 /d] per nitrification tank at that time was calculated as follows:
Nitrification rate [kgN/m ³ /d]=(ammonia nitrogen concentration in water to be treated [kg/m ³ ]−ammonia nitrogen concentration in treated water [kg/m ³ ])×water flow rate [m ³ /d]÷water tank volume [m ³ ]

The evaluation criteria for nitrification rate are as follows:
⊚: The nitrification rate is 0.8 kgN/m ³ /d or more.
◯: The nitrification rate is more than 0.5 kgN/m ³ /d and less than 0.8 kgN/m ³ /d.
Δ: The nitrification rate is more than 0.22 kgN/m ³ /d and 0.5 kgN/m ³ /d or less.
×: The nitrification rate is 0.22 kgN/m ³ /d or less.

(Copper ion concentration)
The treated water was measured before being supplied to the water tank using an ICP optical emission spectrometer ("iCAP RQ ICP-MS" manufactured by Thermo Fisher Scientific).

(Filling rate)
The loading rate of the bioretainer was calculated from the above formula (1).

(LV _gas )
The LV _gas was calculated from the above formula (2).

(LV _{water flow} )
The LV _{water flow rate} [m/h] was calculated from the above formula (3).

(Expansion rate)
The expansion rate of the bioretainer was calculated from the above formula (4).

<Examples 1 to 8, Comparative Examples 1 and 2>
The water to be treated was passed through the organism retainer in the tank under the conditions shown in Table 1. In each example, the copper ion concentration was changed by changing the amount of copper ions added to the water to be treated. The results are shown in Table 1.

The results shown in Table 1 confirm that if the copper ion concentration is within the range of 0.1 to 300 μg/L, a higher nitrification rate can be achieved than with the conventional fluidized bed mixed flow method.

<Examples 9 to 13>
The water to be treated was passed through the organism holder in the water tank under the conditions shown in Table 2. The results are shown in Table 2. Table 2 also shows the results of Example 3 for reference.

From the results shown in Table 2, it was confirmed that by setting the linear velocity ratio (LV _gas /LV _{water flow} ) within the range of 0.3 to 6.0, a higher nitrification rate can be achieved than in the conventional fluidized bed mixed flow method.

<Examples 14 to 17>
The water to be treated was passed through the organism holder in the water tank after changing the conditions shown in Table 3. The results are shown in Table 3. Table 3 also shows the results of Example 3 for reference.

From the results shown in Table 3, it was found that when the iron concentration of the treated water is higher than 1.0 mg/L, a high nitrification rate can be achieved by setting the linear velocity ratio (LV _gas /LV _{water flow} ) to 2.0 or more.

<Examples 18 to 20>
After changing the conditions shown in Table 4, the water to be treated was passed through the organism holder in the water tank. The results are shown in Table 4. Table 4 also shows the results of Example 3 for reference.

The results shown in Table 4 indicate that the higher the loading rate of the bioretainer, the higher the nitrification rate tends to be. This is thought to be because it is able to support a large number of nitrifying bacteria.

<Comparative Examples 3 and 4>
After changing the conditions as shown in Table 5, the water to be treated was passed through the organism holder in the water tank. The results are shown in Table 5.

In Comparative Example 3, the sponge did not shake. In addition, the substrate diffusion rate to the nitrifying bacteria was also low. Furthermore, it is considered that the nitrification rate was low due to the oxygen rate limitation.
In Comparative Example 4, the sponge did not oscillate and a completely mixed flow was obtained. It is considered that the nitrification performance was reduced because the extrusion flow of the water to be treated could not be maintained.

From the results of the above-mentioned examples and comparative examples, it was found that by setting (i) the size of the bioretainer, (ii) the copper ion concentration, (iii) the linear velocity ratio (LV _gas /LV _{water flow} ), and (iv) the packing rate of the bioretainer within a predetermined range, a higher nitrification rate can be achieved than in the conventional fluidized bed mixed flow method. It was confirmed that the nitrification rate decreased when the packing rate of the bioretainer was less than 75% (Comparative Example 4) or when the linear velocity ratio (LV _gas /LV _{water flow} ) was 0 (Comparative Example 3).
Therefore, in treating a high concentration of ammoniacal nitrogen, there is little need to add two or more nitrification tanks in order to achieve a high nitrification rate, and the treatment device can be made smaller.

According to one aspect of the present invention, there is provided an agitated biological nitrification method and an agitated biological nitrification device that can treat water containing a high concentration of ammonia nitrogen at a nitrification rate higher than that of the conventional fluidized bed mixed flow method.

1 Swing-type biological nitrification device 4 Treated water supply pipe 5 Nitrification tank 6 Biological holder 7 Treated water outflow pipe 10A Copper wire (copper supply source)
12 Blower (gas (air) supply device)
13 Gas supply pipe (gas (air) supply device)

Claims (7)

A shaking biological nitrification method for treating ammonia nitrogen in treated water,
A rocking biological nitrification method, which satisfies the following requirements 1, 2, 3 and 4 when the water to be treated is passed through a plurality of biological retainers loaded in a nitrification tank.
Requirement 1: The three-dimensional size of one of the bioretainers exceeds 5 mm in the maximum length direction and fits into a sphere having a diameter of 20 mm.
Requirement 2: The copper ion concentration of the water to be treated is 0.1 to 300 μg/L.
Requirement 3: The linear velocity ratio (LV _gas /LV water flow) between the linear velocity LV _{water flow} [m/h] of the water to be treated and the linear velocity LV _gas [m/h] of the gas in the stored _water in the nitrification tank is 0.3 to 6.0.
Requirement 4: The filling rate calculated by the following formula (1) is 75% or more.
Filling rate (%) = (bulk volume of multiple biological retainers) / (available water volume in nitrification tank) × 100 ... formula (1) The shaking biological nitrification method according to claim 1, wherein the biological support has a porous carrier and nitrifying bacteria supported on the carrier. The shaking biological nitrification method according to claim 1 or 2, in which the water to be treated is passed through as an upward flow. The shaking biological nitrification method according to claim 1 or 2, wherein the copper ion concentration in the water to be treated is 0.5 to 50 μg/L. a nitrification tank loaded with a plurality of biological retainers;
a water-to-be-treated supply pipe for supplying water to be treated into the nitrification tank;
A copper supply source capable of supplying copper ions to the water to be treated;
a water flow rate adjusting means for adjusting the flow rate of the water to be treated supplied to the nitrification tank;
a gas supplying device that supplies gas to the stored water in the nitrification tank;
a control device electrically connected to the water flow rate adjusting means and the gas supply device;
Equipped with
The control device executes control that satisfies the following requirements 3 and 4,
A rocking biological nitrification device that satisfies the following requirements 1 and 2.
Requirement 1: The three-dimensional size of one of the bioretainers exceeds 5 mm in the maximum length direction and fits into a sphere having a diameter of 20 mm.
Requirement 2: The copper ion concentration of the water to be treated is 0.1 to 300 μg/L.
Requirement 3: The linear velocity ratio (LV _gas /LV water flow) between the linear velocity LV _{water flow} [m/h] of the water to be treated and the linear velocity LV _gas [m/h] of the gas in the stored _water in the nitrification tank is 0.3 to 6.0.
Requirement 4: The filling rate calculated by the following formula (1) is 75% or more.
Filling rate (%) = (bulk volume of multiple biological retainers) / (available water volume in nitrification tank) × 100 ... formula (1) The oscillating biological nitrification apparatus according to claim 5, wherein the copper source is in contact with the water to be treated. The oscillating biological nitrification device according to claim 5 or 6, wherein the control device executes control so that the copper ion concentration of the water to be treated is 0.1 to 300 μg/L.

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