JP2001276888A - Drain treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove nitrogen in a drain containing calcium and nitrogen. SOLUTION: The drain containing calcium and nitrogen is admitted into a fixed bed nitrification tank 10 and is subjected to nitrification treatment. An alkal agent is injected to plural points from an alkaline agent tank 14. Places where the pH of packing materials 30 for holding the microorganisms rises are dispersed to prevent the formation of scale. Changing of the places, where the agent is injected, temporally is also adequate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for treating wastewater containing calcium and nitrogen, and more particularly to an apparatus for nitrifying nitrogen using a microorganism.

[0002]

2. Description of the Related Art Conventionally, hydrofluoric acid, ammonia, nitric acid, and the like are used in a process of manufacturing a semiconductor device such as an IC, so that wastewater containing fluorine and nitrogen is discharged.
In other words, these chemicals are used for etching etc.
The concentrated waste liquid is disposed of as waste, but wastewater containing fluorine (hydrofluoric acid) and nitrogen (ammonia, nitric acid) is discharged as a cleaning waste liquid when the semiconductor substrate is cleaned with ultrapure water or the like. The LCD (liquid crystal display) manufacturing process basically has the same process as that of the semiconductor device, and generates the same drainage. Furthermore, wastewater containing fluorine and nitrogen is generated in coal-fired power plants, glass surface processing plants, and the like.

[0003] Fluorine in wastewater is generally removed as calcium fluoride by adding calcium, and calcium fluoride is also added to the above wastewater to precipitate calcium fluoride. Has been removed. Calcium fluoride tends to be very fine particles, and to remove it, an inorganic coagulant such as aluminum or an acrylic polymer coagulant is added to form flocs, and calcium fluoride is precipitated and removed. ing.

Here, fluorine removal by calcium is a reaction of 2F ⁻ + Ca ²⁺ = CaF ₂ , in which case the solubility product Ksp = 3.45.
× 10 ⁻¹¹ . Therefore, unless the conditions are such that considerable calcium ions remain, fluorine cannot be sufficiently removed.

Usually, the target concentration of fluorine in the fluorine-removed water is about 10 mg / L or less. In such a case, the residual calcium concentration in the treated water is reduced to 100 to 100 mg / L.
It is necessary to be about 0 mg / L.

The presence of silicon, phosphoric acid, etc. in the waste water has an adverse effect on the precipitation of calcium fluoride. In this case, more calcium is added or an inorganic coagulant or polymer coagulant is used. Coagulation treatment may be required.

On the other hand, as the nitrogen removal, biological denitrification is usually employed. In this biological denitrification, nitrogen is removed by utilizing nitrate respiration in an anoxic state of a denitrifying bacterium, a facultative anaerobic bacterium. In this biological denitrification, first, the wastewater is nitrified to convert the ammonia nitrogen in the wastewater into nitrite nitrogen and / or nitrate nitrogen, and then a hydrogen donor such as methanol is added, and the oxygen-free state is added. To perform a denitrification treatment. In this specification,
Nitrite nitrogen and / or nitrate nitrogen will be referred to simply as nitrate nitrogen or simply nitric acid.

[0008] Combining such fluorine removal and nitrogen removal removes fluorine and nitrogen in wastewater.

[0009]

Here, wastewater containing a large amount of fluorine has an adverse effect on biological treatment. For this reason, the biological denitrification treatment is performed on the wastewater from which fluorine has been removed. Therefore, wastewater to be subjected to biological denitrification treatment is wastewater containing a large amount of calcium.

[0010] Calcium is likely to be precipitated by binding to various ions, and is likely to be precipitated as a solid during the biological treatment process. If calcium precipitates as a solid, it will be present together with the microorganisms in the biological treatment, and the amount of inorganic sludge in the biologically treated sludge will increase. Therefore, it is difficult to maintain a high concentration of microorganisms in biological treatment, and efficient treatment cannot be performed.

In biological treatment such as biological denitrification treatment, a fixed-bed treatment using a filler for holding microorganisms is used in addition to a floating activated sludge method in which treatment is performed while microorganisms are suspended. There is. The fixed-bed treatment not only can maintain the concentration of microorganisms in the treatment tank at a high level and can increase the volume load, but also has the merit of basically eliminating the need for a sedimentation tank because the microorganisms are held in the fixed bed. Therefore, there is a demand to use a fixed bed in order to improve processing efficiency.

However, in the case of the present wastewater, the wastewater to be subjected to the biological denitrification treatment contains a large amount of calcium. Therefore, during the biological denitrification treatment, there is a high possibility that calcium precipitates on the filler for holding microorganisms and causes clogging.

When clogging occurs, the clogging is eliminated by washing with air or chemicals. However, if such a cleaning treatment is performed, the microorganisms retained on the microorganism-retaining filler material are removed. Is also removed at the same time. Nitrifying bacteria, which are the main components of nitrification treatment, are autotrophic bacteria and their growth rate is slow.If the above-mentioned washing treatment is performed frequently, the concentration of microorganisms in the fixed bed cannot be kept high, and nitrification occurs. The nitrification load on the treatment tank cannot be increased.

Further, in the nitrification treatment, an alkaline agent is added because the pH decreases with the generation of nitric acid. By the addition of such an alkaline agent, a local increase in pH occurs, and calcium precipitation is likely to occur in that portion, and clogging is likely to occur. Then, the portion where clogging occurs cannot contribute to the nitrification reaction.
Calcium combines with carbonate ions, phosphate ions, hydroxide ions, sulfate ions, and the like present in the wastewater and precipitates.

The present invention has been made in view of the above problems, and has as its object to provide a wastewater treatment apparatus capable of efficiently treating wastewater containing calcium and nitrogen.

[0016]

SUMMARY OF THE INVENTION The present invention relates to an apparatus for treating wastewater containing calcium and nitrogen, wherein the wastewater containing calcium and nitrogen flows in and is subjected to nitrification treatment by microorganisms grown on a fixed bed. And an alkaline agent injecting means for separately injecting an alkaline agent into a plurality of locations in the nitrification treatment section.

As described above, by dividing and injecting the alkaline agent into a plurality of locations, it is possible to prevent an increase in pH at a particular location, and to effectively prevent the generation of calcium scale in the nitrification treatment section using a fixed bed. Can be prevented.

It is preferable that the alkaline agent injecting means injects an alkaline agent into a plurality of locations in a time-division manner.
In this way, by injecting in a time-sharing manner, once a high pH
Then, even if the scale is generated, the pH is lowered by the nitrification reaction in the next time, the scale is dissolved, and thus the generation of the scale can be prevented.

The present invention also relates to an apparatus for treating wastewater containing calcium and nitrogen, wherein the wastewater containing calcium and nitrogen flows in and is subjected to nitrification treatment by microorganisms grown on a fixed bed. It is characterized by having aeration means for sequentially switching the aeration locations for a plurality of locations in the processing unit to perform aeration, and an alkali agent injection means for injecting an alkali agent into the nitrification processing unit.

With such a configuration, the direction of the circulating flow in the fixed bed varies with time. Nitrification progresses to the lowest pH at the site located on the most downstream side of the circulating flow, but since the site is changed with time, the scale once generated will be dissolved at a later stage, and therefore the scale will be dissolved. Can be prevented from occurring.

It is preferable that the alkaline agent injecting means injects the alkaline agent from the alkaline agent storage tank into the nitrification section while diluting the alkaline agent with dilution water. The dilution can effectively prevent the generation of a high pH portion. In addition, since the dilution is performed at the time of injection, the capacity of the alkaline agent storage tank does not increase.

[0022]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a view showing a configuration of a wastewater treatment apparatus according to a first embodiment. Fluorine and nitrogen-containing wastewater generated in semiconductor manufacturing factories, LCD manufacturing factories, coal-fired power plants, glass (surface processing) factories, and the like are first subjected to fluorine removal. This fluorine removal is performed by adding calcium to precipitate and remove calcium fluoride. Thus, waste water containing calcium and nitrogen is obtained as the treated water from which fluorine has been removed.

The waste water containing such calcium and nitrogen flows into the fixed-bed nitrification tank 10 as water to be treated.
The inside of the fixed-bed nitrification tank 10 is filled with a filler 30 for holding microorganisms. Then, the water to be treated flows into the upper part of the fixed-bed nitrification tank 10, and the treated water is discharged from the lower part. Therefore, the to-be-processed water flows in the downflow as a whole through the microorganism-holding filler 30. The flow of the water to be treated to the fixed-bed nitrification tank 10 may be an upward flow.

As the filler 30 for holding microorganisms, one having a configuration as shown in FIG. 2 is preferably employed. The filler 30 for holding microorganisms is formed by adhering an activated carbon nonwoven fabric 34 in which a mixture of activated carbon fibers and polypropylene is formed in a felt shape to the surface of a flat nonwoven fabric 32 made of polypropylene in a corrugated shape. . Accordingly, the activated carbon nonwoven fabric 34 forms a vertical passage 36. By arranging a plurality of the microorganism-holding fillers 30 in the tank such that the passages 36 are formed vertically in the tank, or by rolling and arranging them, the activated carbon nonwoven fabric 3
The periphery of 4 becomes a vertical water passage. In addition, such a filler for holding microorganisms is disclosed in, for example, JP-A-7-24489.

On the other hand, an air diffuser 12 is arranged at the bottom of the fixed-bed nitrification tank 10, from which air is blown out. This air is usually pumped from a blower or the like. As a result, the inside of the fixed-bed nitrification tank 10 is aerated and stirred, oxygen is dissolved in the liquid in the tank, and the inside of the tank is maintained under aerobic conditions. Then, the water to be treated flowing into the fixed bed nitrification tank 10, because ammonia nitrogen (NH 4 _-N) is contained, nitrifying bacteria adheres grows on the surface of a microorganism retaining filler 30. As described above, by holding the nitrifying bacteria on the microorganism-holding filler 30, the nitrifying bacteria in the fixed-bed nitrification tank 10 can be maintained at a sufficiently high concentration, and an efficient nitrification treatment can be performed. .

Here, the water to be treated introduced into the fixed-bed nitrification tank 10 contains, for example, about 100 to 1000 mg / L of calcium ions as well as ammonia nitrogen. When the pH is high, calcium ions are precipitated by binding to carbonate ions, phosphate ions, hydroxide ions, sulfate ions, and the like. Therefore, when the pH is high, a calcium compound precipitates on the microorganism-holding filler 30, and the microorganism-holding filler 30 is easily clogged.

On the other hand, in the fixed-bed nitrification tank 10, the pH is lowered by nitrification of ammonia nitrogen. However, when the pH is lowered, the activity of the nitrifying bacteria is inhibited, so that an alkali agent such as sodium hydroxide is added to the fixed-bed nitrification tank 10 so that the pH in the tank is maintained near neutrality. I have to. That is, the alkali agent from the alkali agent storage tank 14 is supplied to the fixed-bed nitrification tank 10 by the alkali pump 16.

As described above, the addition of the alkali agent prevents the pH in the fixed-bed nitrification tank 10 from lowering. However, the addition of the alkali agent mainly increases the pH of the portion where the alkali agent is added. To rise. Therefore, in this part, the calcium compound precipitates, and the microorganism-holding filler 3
At 0, clogging is likely to occur.

Further, if frequent washing is performed to eliminate such clogging, nitrifying bacteria will be eliminated together. Nitrifying bacteria have a slow growth rate,
If frequent washing is performed, the amount of nitrifying bacteria that can be held in the fixed-bed nitrification tank 10 decreases, and it becomes impossible to perform a sufficient nitrification treatment.

In the present embodiment, the alkaline pump 1
6 is divided into a plurality of branch pipes 18a, 1
8b, which are divided into a plurality of locations in the fixed-bed nitrification tank 10 and injected.

As described above, by dividing and injecting the alkaline agent into a plurality of locations, the amount of the alkaline agent injected into one location can be reduced. Thus, the increase in pH at that portion can be made relatively small, and calcium precipitation at that portion can be prevented.

The distance between the plurality of locations into which the alkali agent is injected is preferably about 0.1 to 4 m.

[Second Embodiment] FIG. 3 shows an apparatus according to a second embodiment. In this embodiment, the branch pipes 18a, 1
8b are provided with valves 20a and 20b, respectively. Then, by sequentially opening the valves 20a and 20b, the location where the alkaline agent is added is changed with time.

With such a configuration, scale can be prevented in the filler 30 for holding microorganisms. In particular, by successively switching the locations where the alkali agent is added, not only is it difficult to form a local high pH region in the fixed-bed nitrification tank 10, but also the injection of the alkali agent results in a high pH, and once the scale is generated. However, in the next stage, nitrification lowers the pH and dissolves the scale. Therefore, it is possible to finally prevent the occurrence of scale. The switching time is not particularly limited, but is preferably in the range of 1 minute to 24 hours.

FIG. 4 is a plan view of the fixed-bed nitrification tank 10 as viewed from above, and shows a configuration in which the alkaline agent is injected by sequentially switching to four injection locations. In this case, the valves 20a-
There are four valves of 20d, which are sequentially switched to add an alkali agent sequentially to the four parts of the fixed bed nitrification tank 10. In the example of FIG. 4A, the valve 20a is opened, and an alkali agent is added to a lower left portion. Further, FIG. 4B shows that the valve 20d is opened and the alkali agent is added to the lower right portion.

FIG. 5 shows two valves 20b and 20d.
One valve is shown in an open state, and in the next state, the valve 20 is opened.
By opening a and 20c, the addition position of the alkaline agent is sequentially changed. Even with such a configuration, it is possible to prevent the partial high pH state from continuing, and to effectively prevent the occurrence of calcium scale based on the high pH.

Third Embodiment Next, FIG. 6 shows the configuration of the third embodiment. As shown in FIG. 6, in this embodiment, the dilution water is supplied to the branch pipe 18a via the valves 22a and 22b.
18b can be added to the alkaline agent. As the dilution water, water having a low calcium concentration such as industrial water or city water is used. Then, when the alkali agent is added, it is diluted and added to a plurality of locations in the fixed-bed nitrification tank 10. In this case, the alkali agent and the dilution water may be supplied sequentially or may be supplied continuously.

Thus, while diluting the alkaline agent,
By adding to a plurality of locations of the fixed-bed nitrification tank 10,
The diluted alkaline agent can be supplied to each part of the fixed-bed nitrification tank 10 without increasing the capacity of the alkaline agent storage tank 14 so much. Therefore, it is possible to prevent the generation of scale by reducing an increase in pH of the portion where the alkali agent is added.

In general, the sodium hydroxide stored in the alkaline agent storage tank 14 is a 10 to 40% aqueous solution, and the dilution ratio is preferably about 10 to 1000 times.

"Fourth Embodiment" FIG. 7 shows a configuration of a fourth embodiment. In the present embodiment, the air diffuser is divided into a plurality of air diffusers 12a and 12b, and the locations where air is diffused can be switched by valves 24a and 24b. Therefore,
As shown in FIG. 7A, air is diffused from the air diffuser 12b by opening the valve 24b and closing the valve 24a. As a result, an upward flow is generated above the air diffuser 12b,
A downward flow is formed above the air diffuser 12a. Therefore, FIG.
In the example of (a), a counterclockwise circulation flow is generated, and the upper left portion (shown by oblique lines) has the highest pH, and the upper right portion (shown by hatching) has the lowest pH. Therefore, scale is likely to occur in the upper left part, but scale is likely to dissolve in the upper right part.

On the other hand, in the example of FIG. 7B, air is diffused from the air diffuser 12a by opening the valve 24a and closing the valve 24b, and a clockwise circulation flow is generated. (Shown) indicates the highest pH, and the upper left portion (shaded by dots) indicates the lowest pH. Therefore, scale is likely to occur in the upper right part, but scale is likely to dissolve in the upper left part.

Then, by sequentially switching the valves 24a and 24b, the scale once generated is also dissolved in the next stage, and it is possible to prevent the scale from being fixed as a whole.

In the lower part of the microorganism-holding filler 30, scale generation and scale dissolution do not occur much, or scale dissolution occurs on the upward flow side and scale generation occurs on the downward flow side. However, also in this portion, it is possible to prevent the scale from being fixed.

The alkaline agent is preferably supplied from the upper part of the fixed-bed nitrification tank 10 as shown in the figure.
Although not particularly limited, the aeration LV (linear velocity) is 10 to 50 with respect to the bottom area of the fixed-bed nitrification tank 10.
m / h is preferable.

[Overall Configuration] In the present embodiment, wastewater containing fluorine and nitrogen is treated to remove fluorine and nitrogen. FIG. 8 shows this overall flow.

As described above, the wastewater containing fluorine and nitrogen is discharged in a semiconductor manufacturing process and the like.
The concentration of fluorine (F) in the wastewater is not limited, but is 10 to 1000 mg / L, ammonia nitrogen (NH ₄ −
N) concentration: 10 to 10000 mg / L, nitrate nitrogen (N
O ₃ -N) concentration is about 0 to 10000 mg / L.
In a normal case, the wastewater is temporarily stored in a wastewater storage tank, and then introduced into the fluorine removing unit 50 by a pump or the like. Calcium is added to the fluorine removing unit 50. This calcium is preferably added in the form of calcium hydroxide (Ca (OH) ₂ ) or calcium chloride (CaCl ₂ ).

By the addition of such calcium, fluorine (fluorine ion) and calcium (calcium ion) in water react with each other to precipitate calcium fluoride (CaF ₂ ). Therefore, fluorine is removed by solid-liquid separation of the precipitated calcium fluoride. In addition, in the fluorine removing section 50, it is general that an aluminum-based coagulant, an acrylic-based polymer coagulant, and the like are added to perform a precipitation treatment. In addition, the pH of the wastewater is often low, and in that case, for precipitation of calcium fluoride, the pH is adjusted to, for example, 4 to 7 by adding sodium hydroxide (NaOH) or the like. In addition, when phosphorus and phosphorus coexist in the wastewater, and when it is desired to remove phosphorus together with the fluorine, the pH of the wastewater is adjusted to, for example, 9 to 11 by adding calcium to the wastewater, and the fluorine and phosphorus are combined in one step. How to remove at the same time,
A method of adding calcium to waste water to adjust the pH to 4 to 7 and precipitating fluorine as calcium fluoride, and further adding calcium to adjust the pH of the waste water to 9 to 11 to remove phosphorus. Good to adopt. This fluorine removal treatment water contains a large amount of calcium ions. This is because the calcium ion concentration must be considerably high in order to sufficiently reduce the fluorine ions in the water. For example, the calcium ion concentration is 200 mg / L.
That is all.

The fluorine removing section 50 may employ a method in which granular calcium carbonate is brought into contact with waste water containing fluorine. In this method, fluorine-containing wastewater is circulated in a column filled with granular calcium carbonate. As a result, the fluorine in the wastewater is replaced with the carbonic acid of the calcium carbonate to form granular calcium fluoride, which is removed. And the fluorine removal treatment water from which fluorine was removed is obtained. Even in such treatment, the fluorine removal rate cannot be increased unless the calcium concentration in the fluorine removal treatment water is increased to some extent, and the fluorine removal treatment water is waste water containing calcium.

The fluorine removing unit 50 thus obtained is
Is introduced into the fixed-bed nitrification tank 10. Then, as described above, the nitrification treatment is performed without generating scale.

Next, the nitrification-treated water is introduced into the USB denitrification tank 52. The USB denitrification tank 52 is an upward sludge blanket (USB) type denitrification tank, in which a sludge blanket of denitrifying bacteria is formed, and wastewater is circulated upward in this tank. When the sludge blanket is formed by the denitrifying bacteria in this way, granular materials (referred to as granules) in which the denitrifying bacteria are aggregated at a high concentration are formed, and the denitrifying bacteria are maintained at a high concentration to perform an efficient denitrification treatment. Such a USB denitrification tank is disclosed in Japanese Patent Application Laid-Open No. 62-22529.
No. 4 and the like.

Then, a hydrogen donor such as methanol is supplied to the USB denitrification tank 52, and oxygen of nitrate contained in the nitrification-treated water is removed by facultative anaerobic denitrification bacteria forming a sludge blanket. The methanol used is oxidized, and nitric acid is reduced to nitrogen gas and removed. Since the denitrification reaction raises the pH, the pH is adjusted by adding an acid such as hydrochloric acid as needed.

Here, the fluorine removal treatment water flowing into the USB denitrification tank 52 contains a large amount of calcium, and this calcium is removed in the USB denitrification tank 52.

That is, in the USB denitrification tank 52, as described above, a hydrogen donor such as methanol is oxidized using oxygen such as nitrous acid (NO ₂ ⁻ ) or nitric acid (NO ₃ ⁻ ) to reduce nitrogen. However, at that time, carbon dioxide CO ₂ is generated according to the following equation.

2NO ₂ ⁻ + CH ₃ OH → N ₂ ↑ + CO ₂ + 2OH ⁻ + H ₂ O 2NO ₃ ⁻ + (5/3) CH ₃ OH → N ₂ ↑ + (5/3) CO ₂ + 2OH ⁻ + (7 / 3) H ₂ O The carbon dioxide thus generated dissolves in water and becomes bicarbonate ion as shown in the following formula, and this reacts with calcium Ca ^{2+ in the} water to be treated and becomes insoluble calcium carbonate C.
the aCo _3.

[0056] _{^{CO 2 + OH - → HCO 3}} - Ca 2+ + HCO 3 - → CaCo 3 ↓ + H + Thus, the calcium carbonate is generated are captured here in the sludge blanket in the USB denitrification tank 52. The generation of such calcium carbonate promotes the formation of granules, and can form a stable sludge blanket. Thereby, an efficient denitrification process can be performed.

In this way, in this USB denitrification tank 52, denitrification treatment and calcium removal are performed. In particular, in the USB denitrification tank 52, the formation of granules is promoted due to the presence of calcium, the concentration of denitrifying bacteria in the tank can be increased, and efficient treatment can be performed. Further, since the USB denitrification tank 52 does not require a washing operation and the sludge can be easily pulled out, the sludge concentration in the tank can be appropriately adjusted to perform efficient treatment.

Incidentally, an acid as a pH adjuster is added to the USB denitrification tank 52 as needed. To complete the denitrification, methanol is added so that a small amount of methanol remains.

Next, the denitrification treatment water in the USB denitrification tank 52 is
It is introduced into a fixed-bed oxidation tank 54, where it is subjected to aeration treatment to remove residual methanol. As the filling material for holding microorganisms in the fixed-bed oxidation tank 54, the same material as that in the fixed-bed nitrification tank 10 described above can be used.
It is also preferable to fill a large number of mesh-like plastic pipes. By filling such a microorganism-holding filler, efficient oxidation treatment can be performed in the oxidation tank, and the precipitation tank can be omitted.

Thus, treated water from which fluorine and nitrogen have been removed is obtained. According to this embodiment, nitrification treatment can be performed in the fixed-bed nitrification tank 10 while preventing generation of scale. Therefore, by increasing the concentration of nitrifying bacteria in the fixed-bed nitrification tank 10, the nitrification treatment can be performed effectively. Further, in the USB denitrification tank 52 at the next stage, calcium can be removed while performing the denitrification treatment, and further, the precipitation of calcium promotes the formation of granules, thereby enabling effective denitrification.

Incidentally, a denitrification tank after the fixed-bed nitrification tank 10,
The oxidation tank may be of a floating type, and a sedimentation tank or a submerged membrane separation device may be provided downstream of the oxidation tank.

[0062]

EXAMPLES As raw water, pH 3, fluorine compound 1434
_{mgF / L, NH 4 -N51mg /} L, NO 3 -N32
mg / L wastewater from a semiconductor manufacturing plant
Processing experiments were performed on the devices of the second and third embodiments. Further, as a comparative example, an experiment was performed using a device having the same configuration as that of the first embodiment and adding a necessary alkali agent to one point on the upper part of the fixed-bed nitrification tank.

For pH adjustment, a 40% aqueous solution of NaOH was used, and as a filler for retaining microorganisms, a nonwoven fabric containing activated carbon fibers processed into a corrugated plate was used. Nitrification load is
1.0 kg-N / m ³ / d.

The switching of the alkali agent injection point and the switching of the aeration in Embodiments 2 and 3 are performed once an hour. In the third embodiment, industrial water is used as the dilution water, and the dilution ratio is set to 50 times. Further, in any of the examples, Ca (OH) ₂
Calcium concentration of water is 500m
g / L, and the pH during the reaction was 10
Was controlled. The solid after the reaction was removed by precipitation and used as inflow water to the nitrification tank. Therefore, the calcium concentration of the inflow water into the nitrification tank was 500 mg / L.

When scale is generated in the filler, the outflow calcium concentration is reduced compared to the inflow calcium concentration. Therefore, the presence or absence of scale generation in the filler can be determined by calculating the balance of calcium. In addition,
In each case, sodium hydroxide was added so that the pH of the nitrification-treated water was in the range of 6 to 7.

Table 1 shows the experimental results.

[0067]

[Table 1]

As described above, in the case of the devices of the first to third embodiments, there is almost no difference between the inflow calcium concentration and the outflow calcium concentration. Therefore, the device of this embodiment can effectively prevent the generation of calcium scale. Understand.

On the other hand, in the case of the comparative example, the outflow calcium concentration is reduced to about の of the inflow calcium concentration, and it is estimated that the difference in calcium is precipitated as calcium scale.

[0070]

As described above, according to the present invention,
By dividing and injecting the alkali agent into a plurality of locations, it is possible to prevent a rise in pH at a specific location, and to effectively prevent the generation of calcium scale in the nitrification treatment section using the fixed bed.

Further, by injecting the alkaline agent into a plurality of locations in a time-division manner, once the pH becomes high and the scale is generated, the pH becomes low in the next time and the scale is dissolved,
Therefore, generation of scale can be prevented.

Further, by sequentially switching and aerating a plurality of locations in the nitrification treatment section, the direction of the circulating flow in the fixed bed varies with time. Nitrification progresses to the lowest pH at the site located on the most downstream side of the circulating flow, but since the site is changed with time, the scale once generated will be dissolved at a later stage, and therefore the scale will be dissolved. Can be prevented from occurring.

Further, by injecting the alkaline agent from the alkaline agent storage tank into the nitrification section while diluting it with diluting water, it is possible to effectively prevent the generation of a high pH portion. Further, since the liquid is diluted at the time of injection, the capacity of the storage tank for the alkaline agent does not increase.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment.

FIG. 2 is a diagram showing a configuration of a filler for holding microorganisms.

FIG. 3 is a diagram illustrating a configuration of a second embodiment.

FIG. 4 is a diagram showing a configuration of a modification of the second embodiment.

FIG. 5 is a diagram showing a configuration of another modification of the second embodiment.

FIG. 6 is a diagram illustrating a configuration of a third embodiment.

FIG. 7 is a diagram illustrating a configuration of a fourth embodiment.

FIG. 8 is a diagram showing an overall processing flow.

[Explanation of symbols]

10 fixed-bed nitrification tank, 12 (a, b) diffuser, 14
Alkaline agent storage tank, 16 alkaline pumps, 18 (a, b)
Alkali agent addition piping, 30 Microorganism retention filler.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Era 1-2-8 Shinsuna, Koto-ku, Tokyo Organo Corporation F-term (reference) 4D028 AA08 AB00 AC03 BB02 BB07 BC13 BD06 CA00 CA09 CB08 4D040 BB02 BB42 BB52 BB82 BB91

Claims (4)

[Claims] An apparatus for treating wastewater containing calcium and nitrogen, wherein the wastewater containing calcium and nitrogen flows in and is subjected to nitrification treatment by microorganisms grown on a fixed bed; and a plurality of places in the nitrification treatment part. A wastewater treatment apparatus comprising: an alkali agent injection means for separately injecting an alkali agent into the water. 2. The wastewater treatment apparatus according to claim 1, wherein the alkaline agent injecting unit injects the alkaline agent into a plurality of locations in a time-division manner. 3. An apparatus for treating wastewater containing calcium and nitrogen, wherein the wastewater containing calcium and nitrogen flows in and is subjected to nitrification treatment by microorganisms grown on a fixed bed. A wastewater treatment apparatus comprising: aeration means for sequentially switching aeration locations for aeration to perform aeration; and alkali agent injection means for injecting an alkali agent into a nitrification treatment unit. 4. The apparatus according to claim 1, wherein the alkaline agent injecting means injects the alkaline agent from the alkaline agent storage tank into the nitrification unit while diluting the alkaline agent with dilution water. And wastewater treatment equipment.