JP2017202473A - Water treatment method and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method and system capable of drawing a nitrifying bacteria carrying carrier from a nitrification tank while sufficiently suppressing a decrease in nitrification efficiency.SOLUTION: In a water treatment method, ammonia nitrogen-containing water to be treated is treated to obtain first treated water in a first nitrification tank 10 into which a nitrifying bacteria carrying carrier 200 has been charged in a drawable state, the first treated water is treated to obtain second treated water in a second nitrification tank 20 into which the nitrifying bacteria carrying carrier 200 has been charged, the concentration of ammonia or ammonia nitrogen in the second treated water is measured, and when drawing the nitrifying bacteria carrying carrier 200 from the first nitrification tank, 50 vol% or less of the nitrifying bacteria carrying carrier 200 charged in the first nitrification tank 10 is drawn from the first nitrification tank 10 and at the same time the first nitrification tank 10 is replenished with a carrier not carrying nitrifying bacteria, in a state where the ammonia concentration or the ammonia nitrogen concentration has been kept at or below a preset threshold value for a preset time or longer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment method and a water treatment system for water to be treated containing ammoniacal nitrogen.

Groundwater often contains ammoniacal nitrogen. When drinking groundwater containing ammonia nitrogen, the ammonia nitrogen is reduced.
As a method for treating water to be treated containing ammonia nitrogen, for example, the following method has been proposed.
(1) A water treatment method in which water to be treated containing ammoniacal nitrogen is subjected to nitrification by a catalytic oxidation method using a nitrifying bacteria-supporting carrier (Patent Document 1).

  When treating water to be treated using a nitrifying bacteria-supporting carrier, the nitrifying bacteria-supporting carrier can be extracted from the nitrification tank of an existing water treatment system, and placed in the nitrification tank of a new water treatment system, that is, nitrifying bacteria can be transplanted Done. For this reason, the nitrifying bacteria-supporting carrier is often extracted from the nitrification tank. However, in the water treatment method of (1), since the nitrifying bacteria-supporting carrier having a dendritic structure with branches branched from the trunk is fixed in the nitrification tank, a part of the nitrifying bacteria-supporting carrier is removed from the nitrifying tank. It cannot be extracted easily.

On the other hand, as a water treatment method that does not fix the microorganism-supporting carrier in the biological treatment tank, for example, the following method has been proposed.
(2) A water treatment method in which water to be treated is introduced into a biological treatment tank, and the water to be treated is brought into contact with a microorganism-supporting carrier flowing in the biological treatment tank (Patent Documents 2 and 3).

JP2015-226892A JP 2000-42584 A JP 2005-161227 A

  If the microorganism-supporting carrier in the water treatment method (2) is applied to the nitrifying bacteria-supporting carrier in the water treatment method (1), the nitrifying bacteria-supporting carrier can be easily extracted from the nitrification tank. However, the absolute amount of nitrifying bacteria remaining in the nitrification tank when the nitrifying bacteria supporting carrier is withdrawn from the nitrification tank in a state where the amount of nitrifying bacteria supported is insufficient, or when a large amount of the nitrifying bacteria supporting carrier is withdrawn from the nitrification tank at once. There is a significant shortage. Since the growth rate of nitrifying bacteria is low, the nitrification efficiency in the nitrification tank is greatly reduced until the nitrifying bacteria sufficiently grow on the surface and inside of the carrier.

  The present invention provides a water treatment method and a water treatment system capable of extracting a nitrifying bacteria-supporting carrier from a nitrification tank while sufficiently suppressing a decrease in nitrification efficiency.

The present invention has the following aspects.
<1> In a first nitrification tank filled with a nitrifying bacteria-supporting carrier that can be extracted, treated water containing ammonia nitrogen is treated as first treated water; In the second nitrification tank, the first treated water is treated as a second treated water; the ammonia concentration or ammoniacal nitrogen concentration of the second treated water is measured; the nitrifying bacteria from the first nitrifying tank When the support carrier is extracted, the nitrification charged in the first nitrification tank in a state where the ammonia concentration or the ammonia nitrogen concentration is lower than a preset threshold value continues for a preset time or longer. A water treatment method wherein 50% by volume or less of the bacterium-supporting carrier is extracted from the first nitrification tank, and the first nitrification tank is supplemented with a carrier on which nitrifying bacteria are not supported.
<2> The water treatment method according to <1>, wherein the carrier is a sponge carrier.
<3> The water treatment method according to <1> or <2>, wherein the second treated water is ion-exchanged into a third treated water in an ion exchange apparatus filled with an ion exchange resin.
<4> Measure the amount of water to be treated supplied to the first nitrification tank; ammonia mass calculated from the ammonia concentration or ammonia nitrogen concentration and the integrated value of the amount of water to be treated <3> The water treatment method according to <3>, wherein the ion exchange resin of the ion exchange device is regenerated when becomes equal to or greater than a preset threshold value.
<5> The water treatment method according to any one of <1> to <4>, wherein the nitrifying bacteria-supporting carrier is extracted from the first nitrification tank using an air lift pump.
<6> a first nitrification tank filled with the nitrifying bacteria-supporting carrier in a state where it can be extracted and treating water to be treated containing ammoniacal nitrogen to form a first treated water; A second nitrification tank that treats the first treated water to form a second treated water; a concentration measuring device that measures an ammonia concentration or an ammoniacal nitrogen concentration of the second treated water; and the first A pump for extracting the nitrifying bacteria-carrying carrier from the nitrification tank; a concentration measuring device and a control device electrically connected to the pump; the control device presets the ammonia concentration or the ammonia nitrogen concentration A determination unit that determines whether or not a state that is equal to or less than a predetermined threshold value is maintained for a preset time; and 50% by volume or less of the nitrifying bacteria-supporting carrier filled in the first nitrification tank And a control unit for driving the pump so as to extract from the first nitrification tank, a water treatment system.
<7> The water treatment system according to <6>, wherein the carrier is a sponge carrier.
<8> The water treatment system according to <6> or <7>, further comprising an ion exchange device that is filled with an ion exchange resin and ion-exchanges the second treated water into a third treated water.
<9> The apparatus further includes a water flow rate measuring device that measures the amount of the water to be treated supplied to the first nitrification tank; the determination unit in the control device includes the ammonia concentration or the ammoniacal nitrogen concentration; It is determined whether the ammonia mass calculated from the integrated value of the amount of water to be treated is equal to or greater than a preset threshold; the control unit in the control device regenerates the ion exchange resin in the ion exchange device The water treatment system according to <8>, wherein the operation is started.
<10> The water treatment system according to any one of <6> to <9>, wherein the pump is an air lift pump.

  According to the water treatment method and the water treatment system of the present invention, the nitrifying bacteria-supporting carrier can be extracted from the nitrification tank while sufficiently suppressing the decrease in nitrification efficiency.

It is a schematic block diagram which shows an example of the water treatment system of this invention. It is a graph which shows the time change of the ammonia nitrogen density | concentration of the to-be-processed water and treated water after extracting the nitrifying bacteria support | carrier in Example 1 from the 1st nitrification tank. It is a graph which shows the time change of the ammonia nitrogen concentration of to-be-processed water and treated water after extracting the nitrifying bacteria support | carrier in the comparative example 1 from the 1st nitrification tank.

The following definitions of terms apply throughout this specification and the claims.
“Ammonia nitrogen” refers to nitrogen contained in water as an ammonium salt. Also called ammonia nitrogen.
The “stable state” refers to a state where the state where the ammonia concentration or the ammoniacal nitrogen concentration is equal to or lower than a preset threshold value continues for a preset time.

<One Embodiment of Water Treatment System>
FIG. 1 is a schematic configuration diagram showing an example of a water treatment system of the present invention.
The water treatment system 1 is a first nitrification tank that treats water to be treated containing ammoniacal nitrogen supplied from a raw water tank (not shown) through the water to be treated water supply channel 100 to obtain first treated water. 10; a second nitrification tank 20 that treats the first treated water transferred from the first nitrification tank 10 through the first treated water transfer flow path 101 into a second treated water; An ion exchange device 30 that performs ion exchange treatment of the second treated water transferred from the second nitrification tank 20 through the second treated water transfer flow path 102 to form third treated water; A transfer pump (not shown) provided in the middle of the channel 100; a water flow measurement for measuring the amount of water to be treated provided in the middle of the treated water supply channel 100 and supplied to the first nitrification tank 10 An ammonia concentration of the second treated water, which is provided in the middle of the second treated water transfer channel 102; Or a concentration measuring device 50 for measuring the ammonia nitrogen concentration; an air lift pump 60 that is immersed in the first nitrification tank 10 and withdraws it from the first nitrification tank 10; Means, a transfer pump, an ion exchange device 30, a water flow rate measuring device 40, a concentration measuring device 50, and a control device (not shown) electrically connected to the air lift pump 60.

(First nitrification tank)
The first nitrification tank 10 is provided in a container-shaped tank body 11 filled with a nitrifying bacteria support carrier 200 in a state where it can be extracted; and at a location where the first treated water transfer channel 101 is connected to the tank body 11. Furthermore, a so-called fluidized bed aerobic organism comprising a solid-liquid separation device 12 for separating the nitrifying bacteria-supporting carrier 200 and the first treated water; and an aeration device 13 inserted in the bottom of the tank body 11. It is a reaction tank.

Examples of the solid-liquid separation device 12 include a screen.
The air diffuser 13 includes an air diffuser 14 located at the bottom of the tank body 11; an air supply pipe 15 that supplies air to the air diffuser 14; a blower 16 provided in the air supply pipe 15; An air amount adjusting means 17 provided in the middle of the air supply pipe 15 between the air section 14 and the blower 16 is provided.
Examples of the air diffuser 14 include an air diffuser tube, an air diffuser bulb, and the like in which air diffuser holes (not shown) are formed.
Examples of the air amount adjusting means 17 include a gate valve and a butterfly valve.

(Second nitrification tank)
The second nitrification tank 20 is provided in a container-like tank main body 21 filled with a nitrifying bacteria-supporting carrier 200 in a state where it can be extracted; and a place where the second treated water transfer channel 102 is connected to the tank main body 21. In addition, a so-called fluidized bed aerobic organism comprising a solid-liquid separation device 22 for separating the nitrifying bacteria-supporting carrier 200 and the second treated water; and an air diffuser 23 inserted at the bottom of the tank body 21. It is a reaction tank.

Examples of the solid-liquid separator 22 include a screen.
The air diffuser 23 includes an air diffuser 24 located at the bottom of the tank body 21; an air supply pipe 25 that supplies air to the air diffuser 24; a blower 26 provided in the air supply pipe 25; An air amount adjusting means 27 provided in the middle of the air supply pipe 25 between the air section 24 and the blower 26 is provided.
Examples of the air diffuser 24 include an air diffuser tube, an air diffuser bulb, and the like in which air diffuser holes (not shown) are formed.
Examples of the air amount adjusting means 27 include a gate valve and a butterfly valve.

(Ion exchange device)
The ion exchange device 30 includes an ion exchange column (not shown); and an ion exchange resin (not shown) filled in the ion exchange column.
As an ion exchange resin, a strong acid cation exchange resin is used from the standpoint of further suppressing a decrease in nitrification efficiency caused by a reduction in the amount of nitrifying bacteria after the nitrifying bacteria supporting carrier 200 is extracted from the first nitrification tank 10. preferable.

(Water flow measurement device)
Examples of the water flow rate measuring device 40 include a rotor meter and an electromagnetic flow meter.

(Concentration measuring device)
Examples of the concentration measuring device 50 include an ion selective sensor.

(Air lift pump)
The air lift pump 60 includes an air supply means (not shown); a pumping pipe 61 having a lower end opened as a suction port; an upper end connected to the air supply means, and a lower end connected to the vicinity of the lower end of the pumping pipe 61. An air supply pipe 62; and a discharge pipe 63 extending laterally from the vicinity of the upper end of the pumping pipe 61.

(Control device)
The control device includes an interface unit (not shown), a storage 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 blower and air amount adjusting means of the air diffuser, the transfer pump, the ion exchange device 30, the water flow rate measuring device 40, the concentration measuring device 50, the air lift pump 60 and the like to the control unit. Is.

  The storage unit includes a threshold value and time for determining a stable state of the ammonia concentration or ammonia nitrogen concentration of the second treated water, an ammonia mass threshold value for determining regeneration of the ion exchange resin of the ion exchange device 30, water The operating conditions of the processing system 1 are stored.

  The treatment unit integrates the amount of water to be treated measured by the water flow measuring device 40; the mass of ammonia from the ammonia concentration or ammonia nitrogen concentration measured by the concentration measuring device 50 and the integrated value of the amount of water to be treated. The calculation such as calculation is performed.

  The determination unit is configured so that the state in which the ammonia concentration or ammonia nitrogen concentration measured by the concentration measuring device 50 is preset and less than or equal to the threshold value stored in the storage unit is longer than the preset time and stored in the storage unit. Determination of whether it is in a sustained state, that is, a stable state; determination of whether or not the ammonia mass calculated by the processing unit is greater than or equal to a threshold value set in advance and stored in the storage unit.

  The control unit controls the water treatment system 1 based on the determination result in the determination unit, the operation conditions of the water treatment system 1 stored in the storage unit, and the like. For example, in a state where the determination unit determines that it is in a stable state, the air lift pump 60 so that 50% by volume or less of the nitrifying bacteria-supporting carrier 200 filled in the first nitrification tank 10 is extracted from the first nitrification tank 10. When the determination unit determines that the ammonia mass is equal to or greater than a preset threshold value, causes the ion exchange device 30 to start an operation of regenerating the ion exchange resin; The transfer pump is controlled based on the stored amount of water to be treated; the blower of the air diffuser and the air amount adjusting means are controlled based on the air amount set in advance and stored in the storage unit. is there.

The processing unit, the determination unit, and the control unit may be realized by dedicated hardware, and are configured by a memory and a central processing unit (CPU) to realize functions of the processing unit, the determination unit, and the control unit. The function may be realized by loading the program for loading into the memory and executing the program.
An input device, a display device, or the like may be connected to the control device as a peripheral device. Examples of the input device include input devices such as a display touch panel, a switch panel, and a keyboard. Examples of the display device include a liquid crystal display device and a CRT.

(Nitrifying carrier support)
The nitrifying bacteria-supporting carrier 200 has nitrifying bacteria supported on the surface of the carrier. When the carrier is porous, nitrifying bacteria may be carried inside the carrier.

Examples of the shape of the carrier include a rectangular parallelepiped, a sphere, a cylinder, and a filament.
As the carrier, it is possible to carry nitrifying bacteria on the surface and inside of the carrier, that is, from the point that many nitrifying bacteria can be carried and nitrification efficiency is improved, porous ones are preferable, and the carrying of nitrifying bacteria can be maintained well. In addition, a sponge carrier is more preferable because damage to the pump and piping can be minimized.
Examples of the material for the sponge carrier include polyvinyl alcohol, polyethylene glycol, and polyurethane.

Examples of nitrifying bacteria include known nitrifying bacteria used for biological nitrification of ammoniacal nitrogen. A nitrifying bacterium represented by Nitrobacter is autotrophic and basically uses carbon dioxide as the sole carbon source and can grow in the presence of ammonia without the need for an organic substrate, but its growth rate is extremely low. Therefore, in order to keep the biological nitrification reaction high, an operation for holding a large amount of nitrifying bacteria in the nitrification tank is required. Therefore, it is preferable to hold the nitrifying bacteria in a state where they are supported on a carrier instead of suspended cells.
Examples of the method for supporting the nitrifying bacteria on the carrier include a method of introducing the carrier into a nitrifying tank of an existing water treatment system and growing the nitrifying bacteria on the surface of the carrier.

<One Embodiment of Water Treatment Method>
Hereinafter, an example of the water treatment method using the water treatment system 1 will be described.

(Ammonia nitrogen reduction)
The transfer pump provided in the middle of the to-be-processed water supply flow path 100 is driven, and the to-be-processed water containing ammonia nitrogen is passed through the to-be-treated water supply flow path 100 from the raw water tank (not shown). Supplied to the nitrification tank 10 and the water to be treated is stored in the first nitrification tank 10. Further, the water to be treated in the first nitrification tank 10 is transferred to the second nitrification tank 20 through the first treated water transfer channel 101, and the water to be treated is stored in the second nitrification tank 20.
Examples of water to be treated include groundwater, river water, lake water, and the like, and groundwater is preferable.

The nitrifying bacteria support carrier 200 extracted from the nitrification tank of the existing water treatment system is put into the first nitrification tank 10 and the second nitrification tank 20 of the water treatment system 1.
The filling rate of the nitrifying bacteria-supporting carrier 200 is preferably 20 to 50% by volume with respect to the effective water amount of the first nitrifying tank 10 or the second nitrifying tank 20.

While supplying the water to be treated to the first nitrification tank 10 with a predetermined amount of water, the air diffuser 13 is driven, and air is preset from the air diffuser 14 into the first nitrification tank 10. Aerate by volume.
When air is diffused from the bottom of the first nitrification tank 10, a swirl flow consisting of an upward flow and a downward flow is generated in the first nitrification tank 10, and nitrifying bacteria are supported in the water to be treated in the first nitrification tank 10. The carrier 200 flows freely.
The flow rate of the upward flow in the swirling flow is preferably 0.1 to 0.5 m / s.
The amount of air diffused from the diffuser 14 of the diffuser 13 can be adjusted to an arbitrary amount of air by the air amount adjusting means 17.

The first treated water discharged from the first nitrification tank 10 through the solid-liquid separation device 12 is diffused while being transferred to the second nitrification tank 20 through the first treated water transfer channel 101. The device 23 is driven, and air is diffused from the air diffuser 24 into the second nitrification tank 20 with a preset amount of air.
When air is diffused from the bottom of the second nitrification tank 20, a swirl flow consisting of an upward flow and a downward flow is generated in the second nitrification tank 20, and nitrification is performed in the first treated water of the second nitrification tank 20. The fungus carrier 200 flows freely.
The flow rate of the upward flow in the swirling flow is preferably 0.1 to 0.5 m / s.
The air amount diffused from the air diffuser 24 of the air diffuser 23 can be adjusted to an arbitrary air amount by the air amount adjusting means 27.

In the first nitrification tank 10, oxygen-containing air is supplied from the air diffuser 14 of the air diffuser 13. When oxygen is supplied into the first nitrification tank 10, the ammoniacal nitrogen in the water to be treated is ammonia oxidized (nitrified) by the nitrifying bacteria of the nitrifying bacteria-supporting carrier 200 in the first nitrification tank 10 and converted into nitric acid. Become. Thus, the to-be-processed water containing ammonia nitrogen is processed in the 1st nitrification tank 10, and it is set as 1st treated water.
In the second nitrification tank 20, oxygen-containing air is supplied from the air diffuser 24 of the air diffuser 23. When oxygen is supplied into the second nitrification tank 20, ammonia nitrogen remaining in the first treated water is oxidized with ammonia (nitrification) by the nitrifying bacteria of the nitrifying bacteria-supporting carrier 200 in the second nitrification tank 20. To nitric acid. Thus, the 1st treated water containing ammonia nitrogen is processed with the 2nd nitrification tank 20, and it is set as the 2nd treated water.
Ammonia oxidation is represented by the following formula.
NH ₄ ⁺ + 2O ₂ + HCO ₃ ⁻ → HNO ₃ + H ₂ CO ₃ + H ₂ O

  The whole or part of the second treated water discharged from the second nitrification tank 20 through the solid-liquid separation device 22 passes through the second treated water transfer channel 102 and is filled with ion exchange resin. It is transferred to the exchange device 30. In the ion exchange device 30, the second treated water is ion-exchanged to become third treated water in which ammonia nitrogen is further reduced. The third treated water discharged from the ion exchange device 30 is discharged to the outside of the water treatment system 1 through the third treated water transfer channel 103. The second treated water that has not passed through the ion exchange device 30 bypasses the ion exchange device 30 through the detour channel 104 and then passes through the third treated water transfer channel 103 to the outside of the water treatment system 1. Discharged.

(Extraction of nitrifying bacteria carrier)
When the second treated water discharged from the second nitrification tank 20 through the solid-liquid separator 22 is transferred to the ion exchange device 30 through the second treated water transfer channel 102, the concentration is measured. Pass through device 50. When the second treated water passes through the concentration measuring device 50, the ammonia concentration or ammonia nitrogen concentration of the second treated water is measured.
It is preferable to continuously measure the ammonia concentration or ammonia nitrogen concentration of the second treated water. Only one of the ammonia concentration and the ammonia nitrogen concentration of the second treated water may be measured, or both may be measured.

When it is necessary to extract the nitrifying bacteria carrier 200 from the first nitrification tank 10, a state in which the ammonia concentration or the ammonia nitrogen concentration measured by the concentration measuring device 50 is equal to or lower than a preset threshold is preset. The determination unit of the control device determines whether or not the state has been maintained for more than a predetermined time, that is, whether the state is stable.
The threshold value of ammonia concentration or ammonia nitrogen concentration is appropriately determined according to the use of treated water (drinking, industrial use, etc.).

  When the determination unit of the control device determines that the ammonia concentration or ammonia nitrogen concentration is in a stable state, the operator drives the air lift pump 60 manually or automatically by the control device. 50% by volume or less of the nitrifying bacteria-supporting carrier 200 filled in the first nitrification tank 10 is extracted from the first nitrification tank 10. Further, the first nitrification tank 10 is replenished with approximately the same amount of the nitrifying bacteria-supporting carrier 200 extracted from the first nitrification tank 10 and not supporting the nitrifying bacteria.

  In the air lift pump 60, the air supplied from the air supply means passes through the air supply pipe 62 and is supplied from the vicinity of the lower end of the pumping pipe 61 to the pumping pipe 61 and rises in the pumping pipe 61. At this time, water containing the nitrifying bacteria supporting carrier 200 is sucked up from the suction port at the lower end of the pumping pipe 61 and rises while mixing with the air rising in the pumping pipe 61. A mixture of water and air containing the nitrifying bacteria carrier 200 rising in the pumping pipe 61 is discharged from a discharge pipe 63 extending laterally from the vicinity of the upper end of the pumping pipe 61. In this manner, the nitrifying bacteria-supporting carrier 200 is extracted from the first nitrification tank 10. When a predetermined amount of the nitrifying bacteria carrier 200 is extracted, the air lift pump 60 is stopped, that is, the supply of air from the air supply means is stopped, whereby the nitrifying bacteria carrier 200 from the first nitrification tank 10 is stopped. Stop extraction.

  When the determination unit of the control device determines that the ammonia concentration or the ammonia nitrogen concentration is not in a stable state, the control unit determines whether the ammonia concentration or the ammonia nitrogen concentration in the second treated water is in a stable state. The extraction of the nitrifying bacteria-supporting carrier 200 from one nitrification tank 10 is suspended.

(Regeneration of ion exchange resin)
The treated water supplied from the raw water tank through the treated water supply channel 100 to the first nitrification tank 10 passes through the water flow rate measuring device 40 provided in the middle of the treated water supply channel 100. When the water to be treated passes through the water flow measuring device 40, the amount of water to be treated is measured.

In the processing unit of the control device, the ammonia mass is calculated from the ammonia concentration or ammonia nitrogen concentration measured by the concentration measuring device 50 and the integrated value of the amount of water to be treated measured by the water flow measuring device 40.
The determination unit of the control device determines whether the ammonia mass calculated by the processing unit is equal to or greater than a preset threshold value.
The ammonia mass threshold value is appropriately determined according to the type of ion exchange resin of the ion exchange device 30, the filling amount, and the like.

When it is determined by the determination unit of the control device that the ammonia mass is equal to or greater than a preset threshold value, the ion exchange of the ion exchange device 30 is performed manually by the operator or automatically by the control device. Recycle the resin.
The regeneration of the ion exchange resin in the ion exchange device 30 is preferably performed when the determination unit of the control device determines that the ammonia concentration or the ammoniacal nitrogen concentration is in a stable state.
During the regeneration of the ion exchange resin of the ion exchange device 30, the entire amount of the second treated water discharged from the second nitrification tank 20 passes through the bypass channel 104 and then bypasses the ion exchange device 30. 3 is discharged to the outside of the water treatment system 1 through the treated water transfer passage 103.

<Action mechanism>
(Α) In the water treatment method described above, for the following reasons (i) to (iii), the nitrifying bacteria-supporting carrier can be extracted from the nitrification tank while sufficiently suppressing a decrease in nitrification efficiency.
(I) Since the first two-stage treatment of the first nitrification tank 10 and the second nitrification tank 20 is performed and the nitrification bacteria support carrier 200 is extracted from the first nitrification tank 10, the nitrification bacteria support carrier Even if 200 is extracted from the first nitrification tank 10, the lowering of the nitrification efficiency in the first nitrification tank 10 can be compensated by the second nitrification tank 20 in the subsequent stage.
(Ii) Since the amount of the nitrifying bacteria supporting carrier 200 extracted from the first nitrifying tank 10 is limited to 50% by volume or less of the nitrifying bacteria supporting carrier 200 filled in the first nitrifying tank 10, the nitrifying bacteria supporting The absolute amount of nitrifying bacteria remaining in the first nitrification tank 10 after the carrier 200 is extracted is not greatly deficient, and a decrease in nitrification efficiency in the first nitrification tank 10 is suppressed as much as possible.
(Iii) Extraction of the nitrifying bacteria-supporting carrier 200 from the first nitrification tank 10 is performed for a preset time when the ammonia concentration or ammoniacal nitrogen concentration of the second treated water is equal to or lower than a preset threshold value. Since the nitrification bacteria are sufficiently present in the first nitrification tank 10, the absolute amount of nitrification bacteria remaining in the first nitrification tank 10 after the nitrification bacteria-supporting carrier 200 is extracted is determined. A decrease in nitrification efficiency in the first nitrification tank 10 can be suppressed as much as possible without a significant shortage.

(Β) In the water treatment method described above, if the carrier of the nitrifying bacteria supporting carrier 200 is a sponge carrier, nitrifying efficiency can be improved because a large number of nitrifying bacteria can be supported. Can be maintained well, and damage to the pump and piping can be minimized.
(Γ) Moreover, in the water treatment method described above, if the second treated water is ion-exchanged into the third treated water in the ion exchange device 30 filled with the ion exchange resin, the treated water is treated. The ammoniacal nitrogen is further reduced.
(Δ) In the water treatment method described above, the amount of water to be treated supplied to the first nitrification tank 10 is measured; the ammonia concentration or ammonia nitrogen concentration of the second treated water; Treated water in which ammonia nitrogen is reduced by regenerating the ion exchange resin of the ion exchange device 30 when the ammonia mass calculated from the integrated value of the amount of water to be treated is equal to or greater than a preset threshold value. Can be obtained stably.

  Moreover, in the water treatment system 1 demonstrated above, since it is set as the structure mentioned above, one Embodiment of the water treatment method mentioned above can be implemented by using the water treatment system 1, As a result, the action mechanisms (α) to (δ) can be exhibited.

<Other embodiments>
In the water treatment method of the present invention, the water to be treated containing ammoniacal nitrogen is treated in the first nitrification tank filled with the nitrifying bacteria-supporting carrier so that it can be extracted to form the first treated water; The first treated water is treated in the second nitrification tank filled with the second treated water; the ammonia concentration or the ammonia nitrogen concentration of the second treated water is measured; nitrification from the first nitrification tank When the fungus-carrying carrier is extracted, the nitrifying bacteria-carrying carrier filled in the first nitrification tank in a state where the ammonia concentration or the ammoniacal nitrogen concentration is lower than a preset threshold value continues for a preset time or longer. Of 50% by volume or less of the first nitrification tank and a method of replenishing the first nitrification tank with a carrier on which no nitrifying bacteria are supported, and is limited to the above-described embodiment. No.

  In addition, the water treatment system of the present invention includes a first nitrification tank in which a nitrifying bacteria-supporting carrier is filled in a state where it can be extracted and treated water containing ammoniacal nitrogen is treated as first treated water; A second nitrification tank filled with a fungus-carrying carrier and treating the first treated water to form a second treated water; a concentration measuring device for measuring the ammonia concentration or ammonia nitrogen concentration of the second treated water; A pump for extracting the nitrifying bacteria carrier from the first nitrification tank; a concentration measuring device and a control device electrically connected to the pump; the control device is preset with an ammonia concentration or ammonia nitrogen concentration A determination unit for determining whether or not the state of being equal to or less than the threshold value has been maintained for a preset time or longer; and 50% by volume or less of the nitrifying bacteria-supporting carrier filled in the first nitrification tank in the first nitrification tank Unplug Suyo as long as it has a control unit for driving the pump, but is not limited to the water treatment system 1 of the illustrated embodiment.

For example, the number of nitrification tanks is not limited to two and may be three or more.
The air diffuser is not limited to the illustrated example, and a known device can be adopted.
The installation location of the concentration measuring device is not limited to the middle of the second treated water transfer channel, and may be directly immersed in the second nitrification tank. Measurement efficiency can be improved by immersing the concentration measuring device directly in the second nitrification tank.
The measurement of the ammonia concentration or ammonia nitrogen concentration may be performed for the first treated water or the third treated water.
The pump for extracting the nitrifying bacteria-supporting carrier from the first nitrification tank is not limited to the air lift pump. As the pump, an air lift pump is preferable from the viewpoint of high energy efficiency and miniaturization of the apparatus.
The ion exchange device is not necessarily provided when ammoniacal nitrogen in the treated water is sufficiently reduced by the nitrification tank.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Example 1
A water treatment system similar to the water treatment system 1 shown in FIG. 1 was prepared except that the installation location of the concentration measuring device was different.
As the tank body of the nitrification tank, a complete mixing tank type transparent acrylic water tank was used. The water tank is a one-sided swirl flow square water tank having a width of 120 mm, a depth of 60 mm, a height of 270 mm, and an effective water volume of 1.75 L. An air balloon was provided at the bottom of the water tank.

Ammonium chloride and sodium bicarbonate were added to the ground water to prepare water to be treated having an ammoniacal nitrogen concentration: 4.4 mg / L and alkalinity: 70 mg / L.
Water temperature: treated water at 18 ° C. was supplied to the first nitrification tank and the second nitrification tank, and the treated water was stored in the first nitrification tank and the second nitrification tank.

  The nitrifying bacteria supporting carrier extracted from the nitrification tank of the existing water treatment system was put into the first nitrification tank and the second nitrification tank. The filling rate of the nitrifying bacteria-supporting carrier was 30% by volume with respect to the effective amount of water in each nitrifying tank. As the carrier, a foamed polyurethane sponge carrier (Inoac Corporation, Waterflex, 5 mm square, product number: AQ-14) was used.

While supplying the water to be treated to the first nitrification tank, air was diffused from the air balloon into the first nitrification tank. In addition, air was diffused from the air balloon into the second nitrification tank while the first treated water discharged from the first nitrification tank was transferred to the second nitrification tank. The water to be treated was supplied so that the water retention time (HRT) was 0.43 hours. The ammoniacal nitrogen load was 0.25 kg-N / m ³ / d. Excess air was diffused so that the dissolved oxygen in each nitrification tank was saturated.

  An ion selective sensor (Endless Hauser Japan, ISEmax CAS40D) was introduced into the second nitrification tank, and the ammonia nitrogen concentration of the second treated water was measured. After about one month, the stable state, that is, the ammonia nitrogen concentration of the second treated water in the second nitrification tank showed 0.1 mg / L or less for 7 consecutive days.

  After confirming that it was in this stable state, 50% by volume of the nitrifying bacteria carrier was extracted from the first nitrification tank, the same amount of a new sponge carrier was introduced, and the supply of water to be treated was resumed. did. FIG. 2 shows changes in the ammoniacal nitrogen concentration of the water to be treated and the treated water from immediately after the restart to the third day. As a result, the ammoniacal nitrogen concentration of the second treated water in the second nitrification tank immediately after resumption is about 2 mg / L, and 0.1 mg / L before extracting the nitrifying bacteria-supporting carrier on the second day. As shown, the decrease in nitrification efficiency was sufficiently suppressed.

Then, the second treated water discharged from the second nitrification tank is converted into a strongly acidic cation exchange resin (manufactured by Dow Chemical Co., Ltd., Duolite IMAC HP 1220 regenerated with saturated saline) on the ion exchange column. Water was allowed to pass through the filled ion exchanger at SV: 10 h ⁻¹ .

Again, 50% by volume of the nitrifying bacteria carrier was extracted from the first nitrification tank, the same amount of a new sponge carrier was added, and the supply of water to be treated was resumed. The second treated water discharged from the second nitrification tank was passed through the ion exchange device.
The ammoniacal nitrogen concentrations of the second treated water in the second nitrification tank and the third treated water at the outlet of the ion exchange apparatus after 1 hour of water flow were 0.8 mg / L and 0.1 mg / L, respectively. It was. It was confirmed that ammonia nitrogen could be reduced by passing the second treated water through the ion exchanger even immediately after the nitrifying bacteria-supporting carrier was extracted.

(Comparative Example 1)
Water treatment was performed in the same manner as in Example 1 except that the amount of the nitrifying bacteria-supporting carrier extracted from the first nitrification tank was changed to 75% by volume.
FIG. 3 shows the transition of ammonia nitrogen concentration in the water to be treated and the treated water from the first day after the nitrifying bacteria supporting carrier was extracted from the first nitrification tank and the supply of the water to be treated was resumed. Even after 4 days of restart, the ammonia nitrogen concentration of the second treated water in the second nitrification tank never became 1 mg / L or less, and the decrease in nitrification efficiency could not be sufficiently suppressed. .

  INDUSTRIAL APPLICABILITY The water treatment method and the water treatment system of the present invention are useful for a water treatment method and a water treatment system that reduce ammoniacal nitrogen by treating water to be treated containing a large amount of ammonia nitrogen, in particular, groundwater by a bionitrification reaction.

  DESCRIPTION OF SYMBOLS 1 Water treatment system, 10 1st nitrification tank, 11 tank main body, 12 solid-liquid separator, 13 air diffuser, 14 air diffuser, 15 air supply pipe, 16 blower, 17 air quantity adjustment means, 20 2nd Nitrification tank, 21 tank body, 22 solid-liquid separator, 23 air diffuser, 24 air diffuser, 25 air supply pipe, 26 blower, 27 air amount adjusting means, 30 ion exchange device, 40 water flow measuring device, 50 concentration Measuring device, 60 air lift pump, 61 pumping pipe, 62 air supply pipe, 63 discharge pipe, 100 treated water supply flow path, 101 first treated water transfer flow path, 102 second treated water transfer flow path, 103 third Treated water transfer channel, 104 bypass channel, 200 nitrifying bacteria support carrier.

Claims (10)

Treating water to be treated containing ammoniacal nitrogen in the first nitrification tank filled with the nitrifying bacteria-supporting carrier in a state where it can be extracted,
Treating the first treated water in a second nitrification tank filled with a nitrifying bacteria-supporting carrier to form second treated water;
Measuring the ammonia concentration or ammoniacal nitrogen concentration of the second treated water;
When extracting the nitrifying bacteria-supporting carrier from the first nitrification tank, the state in which the ammonia concentration or the ammoniacal nitrogen concentration is lower than a preset threshold value continues for a preset time or longer. A water treatment in which 50% by volume or less of the nitrifying bacteria-supporting carrier filled in one nitrification tank is extracted from the first nitrification tank, and the first nitrification tank is supplemented with a carrier not supporting nitrifying bacteria. Method.   The water treatment method according to claim 1, wherein the carrier is a sponge carrier.   The water treatment method according to claim 1 or 2, wherein the second treated water is ion-exchanged into a third treated water in an ion exchange apparatus filled with an ion exchange resin. Measuring the amount of water to be treated supplied to the first nitrification tank;
When the ammonia mass calculated from the ammonia concentration or the ammoniacal nitrogen concentration and the integrated value of the amount of water to be treated exceeds a preset threshold value, the ion exchange resin of the ion exchange device is The water treatment method according to claim 3, which is regenerated.   The water treatment method according to any one of claims 1 to 4, wherein the nitrifying bacteria-supporting carrier is extracted from the first nitrification tank using an air lift pump. A first nitrification tank filled with a nitrifying bacteria-supporting carrier in a state where it can be withdrawn and treating water to be treated containing ammoniacal nitrogen to form first treated water;
A second nitrification tank filled with a nitrifying bacteria-supporting carrier and treating the first treated water into a second treated water;
A concentration measuring device for measuring an ammonia concentration or ammonia nitrogen concentration in the second treated water;
A pump for extracting the nitrifying bacteria-supporting carrier from the first nitrification tank;
A control device electrically connected to the concentration measuring device and the pump;
The control device is
A determination unit for determining whether the state in which the ammonia concentration or the ammoniacal nitrogen concentration is equal to or lower than a preset threshold value is in a state in which the ammonia concentration or the ammonia nitrogen concentration is maintained for a preset time;
A water treatment system, comprising: a controller that drives the pump so that 50% by volume or less of the nitrifying bacteria-supporting carrier filled in the first nitrification tank is extracted from the first nitrification tank.   The water treatment system according to claim 6, wherein the carrier is a sponge carrier.   The water treatment system according to claim 6 or 7, further comprising an ion exchange device that is filled with an ion exchange resin and ion-exchanges the second treated water into a third treated water. A water flow rate measuring device for measuring the amount of water to be treated supplied to the first nitrification tank;
The determination unit in the control device determines whether the ammonia mass calculated from the ammonia concentration or the ammoniacal nitrogen concentration and an integrated value of the amount of water to be treated is equal to or greater than a preset threshold; The water treatment system according to claim 8, wherein the control unit in the control device causes the ion exchange device to start an operation of regenerating the ion exchange resin.   The water treatment system according to any one of claims 6 to 9, wherein the pump is an air lift pump.

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