JP4676082B2 - Wastewater treatment equipment - Google Patents

Description

【００７１】
【発明の効果】
以上説明したように、本発明によれば、固定床処理槽内には、排水が流入され、処理水として流出されることによる水の流れ（以下、被処理水流れと呼ぶ）と、曝気によって生じる循環流とが垂直方向に交わることとなる。その結果、この二つの流れの合成によるらせん状の流れが生じるが、循環流は被処理理水の流れよりも非常に流れが早いため、流入した排水は、循環流に沿って流れながら、十分に混合された後に、流出部に到達する。従って、固定床処理槽の槽容量を有効に利用して効果的な処理を行うことができる。
【００７２】
また、前記循環流の流れの方向と垂直な方向において、循環流の全体に渡って、薬剤を分散注入することで、薬剤を、循環流に対して垂直方向に少量づつ注入することが可能であり、従来法において生じた循環流に対する垂直な方向におけるｐＨ分布の発生を解消することができる。
【００７３】
また、薬剤を希釈水により希釈しながら注入することで、薬剤注入点近傍において、薬剤濃度が非常に高くなることを防止することができる。また、薬剤の貯槽には濃厚な状態で薬剤を貯留できるため、貯槽の容量を有効利用できる。特に、薬剤がアルカリ剤である場合には、薬剤注入点における急激なｐＨ上昇を防止することが可能であり、スケールの発生をより効果的に防止することができる。
【００７４】
また、前記排水の流入部を固定床処理槽の上部に設け、前記処理水流出部を固定床処理槽下部に設けることで、排水は、槽内を横切るとともに、上部から下部へと流れるため、短絡の発生を有効に防止できる。
【００７５】
また、固定床処理槽下部ではアルカリ剤は十分に希釈されｐＨが安定しているため、的確にアルカリ剤注入手段を制御することができる。
【図面の簡単な説明】
【図１】 実施形態の装置の構成を示す図である。
【図２】 微生物保持充填材の構成を示す図である。
【図３】 処理の全体フローを示す図である。
【符号の説明】
１ 固定床硝化槽、２ 微生物保持充填材、３ 原水流入部、４ 処理水流出部、５（５ａ，５ｂ） 散気管、６（６ａ，６ｂ） 自動弁、７ 樋、８ アルカリ剤貯槽、９ アルカリポンプ、１０ ｐＨセンサ、１１ フッ素除去部、１２ ＵＳＢ脱窒槽、１３ 固定床酸化槽。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment apparatus, and particularly to an aerobic biological treatment by microorganisms grown on a fixed bed.
[0002]
[Prior art]
Conventionally, treatment using aerobic microorganisms has been used for the treatment of various types of wastewater, and such aerobic microorganism treatment has become mainstream in the treatment of organic wastewater and nitrogen-containing wastewater.
[0003]
For example, in a manufacturing process of a semiconductor device such as an IC, hydrofluoric acid, ammonia, nitric acid, and the like are used, so that wastewater containing fluorine and nitrogen is discharged. That is, these chemicals are used for etching and the like, and the concentrated waste liquid is disposed of as waste. However, as cleaning waste liquid when the semiconductor substrate is cleaned with ultrapure water, fluorine (hydrofluoric acid), nitrogen (ammonia, nitric acid) ) Is discharged. The LCD (liquid crystal display) manufacturing process basically has the same process as that of the semiconductor device, and the same waste water is generated. Furthermore, wastewater containing fluorine and nitrogen is also generated in coal-fired power plants, glass surface processing plants, and the like.
[0004]
Fluorine in the wastewater is generally removed as calcium fluoride by adding calcium, and the wastewater as described above is also removed by adding calcium hydroxide to precipitate calcium fluoride. Yes. Calcium fluoride tends to become very fine particles. To remove this, an inorganic flocculant such as aluminum or an acrylic polymer flocculant is added to form a floc to precipitate and remove calcium fluoride. ing.
[0005]
Here, fluorine removal by calcium is
2F⁻+ Ca²⁺= CaF₂
It is a reaction. Usually, the target concentration of the fluorine concentration in the fluorine removal treated water is about 10 mg / L or less. In such a case, the residual calcium concentration in the treated water needs to be about 100 to 1000 mg / L. In addition, if silicon, phosphoric acid, etc. are present in the wastewater, there is an adverse effect on the precipitation of calcium fluoride. In that case, more calcium can be added, or agglomeration treatment with an inorganic flocculant or polymer flocculant can be performed. It may be necessary.
[0006]
On the other hand, as described above, biological denitrification is usually employed as nitrogen removal. In this biological denitrification, nitrogen is removed by using nitrate respiration in the anoxic state of denitrifying bacteria, which are facultative anaerobic bacteria.
[0007]
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 to the oxygen free state. By performing the denitrification process. In the present specification, nitrite nitrogen and / or nitrate nitrogen is simply referred to as nitrate nitrogen or simply nitric acid as appropriate.
[0008]
Then, fluorine and nitrogen in waste water are removed by combining such fluorine removal and nitrogen removal.
[0009]
[Problems to be solved by the invention]
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 waste water after the fluorine is removed. Therefore, the wastewater to be subjected to biological denitrification is wastewater containing a large amount of calcium.
[0010]
Calcium is highly likely to be precipitated by binding to various ions, and is likely to be precipitated as a solid in the biological treatment process. And when calcium precipitates as a solid substance, this will exist with the microorganisms in biological treatment, and the amount of inorganic sludge in biological treatment sludge will increase. Therefore, it becomes difficult to maintain a high microorganism concentration in biological treatment, and efficient treatment cannot be performed.
[0011]
In addition, in biological treatment such as biological denitrification, there is a fixed bed type treatment using a microorganism-retaining filler in addition to a floating activated sludge method in which microorganisms are suspended. . This fixed bed type treatment has the advantage that the microorganism concentration in the treatment tank can be kept high, the volumetric load can be increased, and a sedimentation tank is basically not required because the microorganisms are held on the fixed bed. . Therefore, there is a demand to use a fixed bed for improving processing efficiency.
[0012]
However, in the case of this waste water, the waste water that is the target of biological denitrification treatment contains a large amount of calcium. Therefore, in the biological denitrification treatment, calcium is likely to deposit on the microorganism holding filler and cause clogging. When clogging occurs, the clogging can be eliminated by air cleaning or chemical cleaning. However, when such cleaning treatment is performed, the microorganisms retained on the microorganism-retaining filler are also brought together. It will be removed. The nitrifying bacteria that are the main nitrifiers are self-feeding bacteria and their growth rate is slow, and if the washing process as described above is frequently performed, the microbial concentration in the fixed bed cannot be maintained high. The nitrification load on the tank cannot be increased.
[0013]
Furthermore, in the nitrification treatment, an alkaline agent is added because the pH decreases as nitric acid is generated. By adding such an alkaline agent, a local increase in pH occurs, calcium is likely to precipitate in that portion, and clogging is likely to occur. Then, the portion where the clogging occurs cannot contribute to the nitrification reaction. Calcium is precipitated by combining with carbonate ions, phosphate ions, hydroxide ions, sulfate ions, etc. present in the waste water.
[0014]
For this reason, the present applicant has proposed an aeration means for performing aeration by sequentially switching the aeration locations for a plurality of locations in the nitrification unit in Japanese Patent Application No. 2000-92372. With this configuration, a circulation flow is generated in the fixed bed and mixing is improved. Furthermore, the flow of the circulating flow varies with time. Nitrification progresses to the lowest pH in the part located at the most downstream side of the circulation flow, but the part is changed with time, so the scale once generated is dissolved in the next stage. Occurrence can be prevented.
[0015]
However, in this configuration, the drained water that flows in flows along the circulating flow and reaches the outflow part without sufficiently contacting with the microorganisms in the fixed bed, so that it is easy to short-circuit and the quality of the treated water is deteriorated. .
[0016]
The injected alkali is well mixed in the circulating flow direction, but in the direction perpendicular to the circulating flow, the pH is high in the vicinity of the alkali injection point, and nitrification progresses as the distance from the alkali injection point increases, and the pH decreases. . Therefore, the distribution of pH is large in the direction perpendicular to the circulation flow, and scale generation is unavoidable.
[0017]
Furthermore, since the alkali is injected from the upper part of the nitrification tank, the pH is high in the upper part, and nitrification progresses in the lower part and the pH is lowered. Therefore, when the treated water flows out from the upper part, the injected alkaline agent flows out without being sufficiently mixed, which is inefficient.
[0018]
This invention is made | formed in view of the said subject, and when a circulation flow arises by aeration, it aims at providing the waste_water | drain processing apparatus which can process waste_water | drain efficiently.
[0019]
[Means for Solving the Problems]
The present invention provides a fixed bed treatment tank for treating aerobic organisms with inflow wastewater by microorganisms grown on a fixed bed, and aeration is performed by sequentially switching from a plurality of aeration locations in the fixed bed treatment tank. A wastewater treatment apparatus that sequentially generates a circulation flow in a substantially opposite direction in the treatment tank, wherein the wastewater treatment apparatus has a flow direction of the circulation flow generated by aeration by the aeration means in the fixed bed treatment tank. The waste water inflow portion is provided on one side surface substantially in the vertical direction, and the treated water outflow portion is provided on the other side surface facing the one side surface.
[0020]
With such a configuration, the flow of water (hereinafter referred to as the water to be treated) that flows out from the fixed-bed treatment tank and flows out as treated water is perpendicular to the circulation flow generated by aeration. It will cross in the direction. As a result, a spiral flow is generated by the combination of these two flows, but the circulation flow is much faster than the water to be treated. After mixing, it reaches the outflow part. Therefore, effective processing can be performed by effectively using the tank capacity of the fixed bed processing tank.
[0021]
The medicine injection means for injecting the medicine into the fixed bed processing tank further disperses the medicine throughout the circulation flow in a direction perpendicular to the direction of the circulation flow. Injection is preferred. With this configuration, it is possible to inject a medicine in small amounts in a direction perpendicular to the circulating flow, and it is possible to eliminate the occurrence of pH distribution in the direction perpendicular to the circulating flow that occurs in the conventional method.
[0022]
Further, it is preferable that the medicine injection means injects the medicine while diluting the medicine with dilution water. With this configuration, it is possible to prevent the drug concentration from becoming very high in the vicinity of the drug injection point. In addition, since the medicine can be stored in a rich state in the medicine storage tank, the capacity of the storage tank can be effectively used. In particular, when the drug is an alkaline agent, it is possible to prevent an abrupt increase in pH at the drug injection point, and scale can be more effectively prevented.
[0023]
Moreover, it is preferable that the inflow part of the waste water is provided in the upper part of the fixed bed treatment tank and the outflow part of the treated water is provided in the lower part of the fixed bed treatment tank. As a result, the drainage flows across the tank and flows from the upper part to the lower part, so that the occurrence of a short circuit can be effectively prevented.
[0024]
Furthermore, when nitrification is performed in a fixed bed treatment tank and an alkali agent is added, the alkali agent injected at the upper part is diluted along the circulation flow and further consumed as nitrification proceeds, and then the lower part is added. Therefore, it can be used efficiently without injecting extra alkali agent.
[0025]
Moreover, it is preferable that the waste water contains calcium and nitrogen, and the chemical is an alkaline agent. Precipitation of calcium can be effectively prevented while suppressing a decrease in pH due to nitrification with an alkaline agent.
[0026]
Moreover, it is preferable to measure pH at the lower part of the fixed bed treatment tank and to control the injection amount of the alkaline agent based on the measurement result. Since the alkaline agent is injected at the upper part of the fixed bed treatment tank, when the pH is measured at the upper part of the fixed bed treatment tank, the influence of the alkaline agent is easy to sense and the fluctuation in pH is large, so stable pH control is possible. It is difficult. On the other hand, since the alkaline agent is sufficiently diluted and the pH is stable at the lower part of the fixed bed treatment tank, the alkaline agent injection means can be controlled accurately.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0028]
FIG. 1 is a diagram showing the configuration of this embodiment. Fluorine is first removed from wastewater containing fluorine and nitrogen generated in semiconductor manufacturing plants, LCD manufacturing plants, coal-fired power plants, glass (surface processing) plants, and the like. This fluorine removal is performed by adding calcium and precipitating and removing calcium fluoride. Waste water containing calcium and nitrogen is obtained as treated water from which fluorine has been removed.
[0029]
The fixed bed nitrification tank 1 has a rectangular parallelepiped shape. Inside the fixed bed nitrification tank 1, a microorganism holding filler 2 is disposed. In addition, a raw water inflow portion 3 into which drainage flows is provided at an upper portion of one side surface of the fixed bed nitrification tank 1, and a side surface facing one side surface where the raw water inflow portion 3 of the fixed bed nitrification tank 1 is provided. The treated water outflow part 4 is provided in the lower part. As is clear from the plan view, the raw water inflow portion 3 and the treated water outflow portion 4 are arranged shifted from the center of the tank so as to be positioned close to the diagonal line. Therefore, in a front view, it flows in from the upper left of the fixed bed nitrification tank 1, and flows out from the lower right.
[0030]
A plurality of diffuser tubes 5a and 5b are arranged at the bottom of the fixed-bed nitrification tank 1, and air is supplied to these from automatic blowers 6a and 6b from a blower as an air supply source. The automatic valves 6a and 6b are alternately opened, and a circulation flow as indicated by arrows in the figure is alternately generated. Therefore, the flow of the treated water as a whole from the raw water inflow portion 3 to the treated water outflow portion 4 in the fixed bed treatment tank 1 is in a direction orthogonal to the circulation flow.
[0031]
Further, in the central portion above the fixed bed nitrification tank 1, an upwardly opened basket 7 is arranged in a direction crossing the circulating flow of the fixed bed nitrification tank 1. Here, the alkaline agent from the alkaline agent storage tank 8 is disposed. Is supplied by the alkaline agent pump 9 and industrial water (or tap water may be used if diluted) is supplied. In addition, the cage | basket 7 can carry out the dispersion | distribution injection | pouring of the alkaline agent in the whole inside of a tank by forming a some notch in the both side wall.
[0032]
Further, the pH of the bottom of the fixed bed nitrification tank 1 is measured by the pH sensor 10, and the alkaline pump 9 is controlled based on the measurement result.
[0033]
Calcium and nitrogen (ammonia nitrogen: NH₄The wastewater containing -N) flows in from the raw water inflow section 3. The inside of the fixed bed nitrification tank 1 is filled with a filler 2 for holding microorganisms, and the inside of the tank is aerated and maintained in an aerobic state. Therefore, nitrifying bacteria adhere to and grow on the surface of the microorganism-retaining filler 2, and ammonia nitrogen in the waste water is nitrated by the nitrifying bacteria. And the nitrified treated water flows out from the treated water outflow part 4 of the fixed bed nitrification tank 1. In addition, by attaching and growing nitrifying bacteria on the surface of the microorganism-retaining filler 2, the nitrifying bacteria in the fixed bed nitrification tank 1 can be maintained at a sufficiently high concentration, and an efficient nitrification treatment can be performed. it can.
[0034]
As the microorganism-retaining filler 2, a material constituted by alternately laminating corrugated sheet material 2b and flat sheet material 2a obtained by forming a nonwoven fabric into corrugated sheets as shown in FIG. 2 is preferably used. Then, the surroundings of the nonwoven fabric become vertical water passages by arranging a plurality of the microorganism-retaining fillers 2 in the tank so as to form a passage in the vertical direction or by rolling them up. Such a microorganism-retaining filler is disclosed, for example, in JP-A-7-24489.
[0035]
Here, the water to be treated introduced into the fixed bed nitrification tank 1 contains not only ammonia nitrogen but also calcium ions, for example, in an amount of about 100 to 1000 mg / L. When the pH is high, calcium ions bind to carbonate ions, phosphate ions, hydroxide ions, sulfate ions, and the like, and are precipitated. Therefore, when the pH is high, the calcium compound is deposited on the microorganism-retaining filler 2, and the microorganism-retaining filler 2 is likely to be clogged.
[0036]
On the other hand, in the fixed bed nitrification tank 1, the pH is lowered by nitrification of ammonia nitrogen. Moreover, since the activity of nitrifying bacteria is inhibited when the pH is lowered, an alkaline agent such as sodium hydroxide is added to the fixed bed nitrification tank 1 so that the pH in the tank is maintained near neutrality. ing. That is, the alkaline agent from the alkaline agent storage tank 8 is supplied to the fixed bed nitrification tank 1 by the alkaline pump 9.
[0037]
Thus, although the fall of pH in the fixed bed nitrification tank 1 is prevented by the addition of the alkaline agent, the pH of the portion to which the alkaline agent has been added increases mainly by the addition of the alkaline agent. Therefore, the calcium compound is precipitated in this portion, and clogging is likely to occur in the microorganism-retaining filler 2.
[0038]
In addition, in order to eliminate such clogging, if frequent washing is performed, nitrifying bacteria are also washed together. Therefore, if frequent washing is performed, the amount of nitrifying bacteria that can be held in the fixed bed nitrification tank 1 As a result, the nitrification treatment cannot be performed sufficiently.
[0039]
In the present embodiment, the alkaline agent from the alkaline pump 9 is diluted with the working water, and further dispersed by the basket 7 as a dispersing means, and then added from the upper part of the fixed bed nitrification tank 1.
[0040]
Thus, by diluting, dispersing and injecting the alkali agent, the amount of the alkali agent injected into one place can be reduced. Therefore, the increase in pH at that portion can be made relatively small, and precipitation of calcium at that portion can be prevented.
[0041]
In addition, as for the distance of each location at the time of disperse | distributing an alkaline agent, about several hundred mm-1000 mm are preferable. For example, the distance between the notches provided in the ridge 7 may be set to this level.
[0042]
Furthermore, as described above, when the raw water inflow part 3 is the tank upper part and the treated water outflow part 4 is the tank lower part, the alkaline agent injected from the upper part is diluted and extracted from the lower part after being consumed by the nitrification reaction. Leakage of the alkaline agent can be prevented.
[0043]
On the other hand, a plurality of diffuser tubes are divided into 5a and 5b at the bottom of the fixed bed nitrification tank 1, and are diffused from either of the diffuser tubes 5a and 5b by automatic valves 6a and 6b. In the floor nitrification tank 1, the place where aeration is diffused can be switched. Air is ejected from the air diffuser, and this air is usually pumped from a blower or the like. The arrows shown by solid lines in FIG. 1 indicate the flow of water that occurs when 6a is closed and 6b is opened. In this case, the air is diffused only from the air diffuser 5b, and an upward flow is generated above 5b, and a downward flow is generated above 5a. For this reason, in the example of the front view of FIG. 1, as shown by the arrow, a counterclockwise circulation flow is generated, but the upper left portion has the highest pH and the upper right portion has the lowest pH. Therefore, there is a high possibility that a scale is generated in the upper left part, but there is a high possibility that the scale is dissolved in the upper right part. In addition, the arrow shown with a broken line in FIG. 1 shows the flow of water that occurs when 6b is closed and 6a is opened.
[0044]
And by switching the automatic valves 6a and 6b sequentially, the circulation flow is almost in the opposite direction, and the place where the pH is low and the place where the pH is high alternately in the tank, so once generated scale is dissolved in the next stage, The scale can be prevented from fixing as a whole.
[0045]
In the lower part of the microorganism-retaining filler 2, scale generation and scale dissolution do not occur so much, or scale dissolution occurs on the upward flow side and scale generation occurs on the downward flow side. However, it is possible to prevent the scale from being fixed in this portion.
[0046]
In this way, the raw water inflow portion 3 is provided on the side surface of the nitrification tank in the direction perpendicular to the circulating flow caused by aeration, and the treated water outflow portion 4 is installed on the side surface facing the nitrification tank.
[0047]
Thereby, in the fixed bed nitrification tank 1, the flow of water (hereinafter referred to as the water to be treated) due to the inflow of the wastewater and the outflow as treated water and the circulation flow generated by aeration in the vertical direction. Will be exchanged. As a result, a spiral flow is generated by the combination of these two flows, but the circulation flow is much faster than the water to be treated. After mixing, it reaches the outflow part.
[0048]
In the present embodiment, the pH sensor 10 measures the pH below the fixed bed nitrification tank 1 and controls the injection amount of the alkaline agent based on the measurement result.
[0049]
Here, as a means for measuring pH in the lower part of the fixed bed nitrification tank 1, it may be performed on sample water collected by installing a sampling cock in the lower part of the fixed bed nitrification tank 1, as shown in FIG. A pipe or the like penetrating the filler may be provided, and the pH sensor 10 may be directly installed at the lower part of the fixed bed nitrification tank 1. Furthermore, you may measure the pH of the treated water which flows out out of the fixed bed nitrification tank 1 lower part.
[0050]
In particular, since the alkaline agent is injected into the upper part of the fixed bed nitrification tank 1, when the pH is measured at the upper part of the fixed bed nitrification tank 1, the influence of the alkaline agent is easily sensed, and the fluctuation in pH is large. Stable pH control is difficult. On the other hand, in the lower part of the fixed bed nitrification tank 1, since the alkaline agent is sufficiently diluted and the pH is stable, the alkaline agent injection means can be accurately controlled.
[0051]
"overall structure"
In this embodiment, this whole flow which processes the waste_water | drain containing a fluorine and nitrogen and removes a fluorine and nitrogen is shown in FIG.
[0052]
Thus, the wastewater containing fluorine and nitrogen is discharged in the semiconductor manufacturing process and the like, and the fluorine (F) concentration of the wastewater is not limited, but is 10 to 1000 mg / L, ammonia nitrogen. (NH₄-N) Concentration is about 10 to 10000 mg / L. In a normal case, the waste water is once stored in a waste water storage tank and is introduced into the fluorine removing unit 11 by a pump or the like from here. Calcium is added to the fluorine removing unit 11. This calcium is calcium hydroxide (Ca (OH)₂) And calcium chloride (CaCl₂) And the like.
[0053]
Fluorine (fluorine ion) in water reacts with calcium (calcium ion) by the addition of such calcium, and calcium fluoride (CaF)₂) Precipitates. Thus, fluorine removal is performed by solid-liquid separation of the precipitated calcium fluoride. In this fluorine removing section 11, it is common to perform precipitation by adding an aluminum flocculant or an acrylic polymer flocculant. Moreover, the pH of the waste water is often low. In that case, sodium hydroxide (NaOH) or the like is added to adjust the pH to, for example, 4 to 7 in order to precipitate calcium fluoride. In addition, when phosphorus and phosphorus coexist in the wastewater and it is desired to remove phosphorus together with fluorine, a method of removing phosphorus by adjusting the pH of the wastewater to, for example, 9 to 11 by adding calcium to the wastewater. Adopt it. This fluorine removal treated 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 water. For example, the calcium ion concentration is 200 mg / L or more.
[0054]
The treated water in the fluorine removing unit 11 thus obtained is introduced into the fixed bed nitrification tank 1. Then, as described above, nitrification is effectively performed without generating a scale and without generating a short circuit.
[0055]
Next, the nitrification water is introduced into the USB denitrification tank 12. This USB denitrification tank 12 is an upflow sludge blanket (USB) type denitrification tank. A sludge blanket for denitrifying bacteria is formed in the tank, and the wastewater is circulated in an upward flow. When the sludge blanket is formed by denitrifying bacteria as described above, a granular material (called granules) in which the denitrifying bacteria aggregate at a high concentration is formed, and the denitrifying bacteria are maintained at a high concentration and an efficient denitrification treatment is performed.
[0056]
The USB denitrification tank 12 is supplied with a hydrogen donor such as methanol, and methanol using the oxygen of nitric acid contained in the nitrification water by the facultative anaerobic denitrifying bacteria forming the sludge blanket. Then, nitric acid is reduced to nitrogen gas and removed. Since the pH is increased by this denitrification reaction, an acid such as hydrochloric acid is added as necessary to adjust the pH.
[0057]
Here, the nitrification water flowing into the USB denitrification tank 12 contains a relatively large amount of calcium, but this calcium is removed in the USB denitrification tank 12. That is, in the USB denitrification tank 12, as described above, a hydrogen donor such as methanol is oxidized using oxygen of nitrous acid or nitric acid to reduce nitrogen, and carbon dioxide is generated according to the following equation. To do.
2NO₂ ⁻+ CH₃OH → N₂↑ + CO₂+ 2OH⁻+ H₂O
2NO₃ ⁻+ (5/3) CH₃OH
→ N₂↑ + (5/3) CO₂+ 2OH⁻+ (7/3) H₂O
[0058]
The carbon dioxide generated in this way dissolves in water and becomes bicarbonate ions as in the following formula, which reacts with calcium in the water to be treated to become insoluble calcium carbonate.
CO₂+ OH⁻→ HCO₃ ⁻
Ca²⁺+ HCO₃ ⁻→ CaCO₃↓ + H⁺
[0059]
In this manner, calcium carbonate is generated in the sludge blanket in the USB denitrification tank 12 and captured here. Such generation of calcium carbonate promotes the formation of granules and can form a stable sludge blanket. Thereby, an efficient denitrification process can be performed.
[0060]
In this manner, in the USB denitrification tank 12, denitrification treatment and calcium removal are performed. In particular, in the USB denitrification tank 12, 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 12 does not require a cleaning operation and the sludge can be easily extracted, the sludge concentration in the tank can be appropriately adjusted to perform an efficient treatment.
[0061]
Next, the denitrification water in the USB denitrification tank 12 is introduced into the fixed bed oxidation tank 13, where aeration treatment is performed to remove residual methanol. As the filler for holding microorganisms in the fixed bed oxidation tank 13, a filler filled with a large number of mesh-like plastic pipes is suitable. By filling such a microorganism-retaining filler, an efficient oxidation treatment can be performed in the oxidation tank, and the precipitation tank can be omitted.
[0062]
In this way, treated water from which nitrogen has been removed is obtained under conditions where high concentration of calcium is present. According to this embodiment, the nitrification treatment can be performed in the fixed bed nitrification tank 1 while preventing the precipitation of calcium. Therefore, the concentration of nitrifying bacteria in the fixed bed nitrification tank 1 can be increased to perform efficient nitrification treatment. Further, in the USB denitrification tank 12 in the next stage, calcium can be removed while performing denitrification treatment, and further, the precipitation of calcium promotes the formation of granules, and effective denitrification can be performed.
[0063]
The denitrification tank and the oxidation tank at the subsequent stage of the fixed bed nitrification tank 1 may be a floating type, and a solid-liquid separation device such as a precipitation tank may be provided at the subsequent stage of the oxidation tank.
[0064]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples.
[0065]
"Example"
The simulated waste water containing calcium and nitrogen shown in Table 1 was treated with the apparatus shown in FIG. Water temperature 20 ° C, nitrification load 1.0kg-N / m³/ D, sodium hydroxide was added as an alkaline agent from the upper part of the nitrification tank to adjust the pH of the treated water flowing out from the lower part of the nitrification tank to 7.0.
[0066]
As a result, the pH of the upper part of the nitrification tank became 7.5 to 8.0. As a result of passing water over 100 days, no scale was observed on the filler at the end of the test. At this time, the ammonia removal rate was 98% or more throughout the test, and a very good treated water quality was obtained.
[0067]
"Comparative Example 1"
Similar to the example, the simulated waste water containing calcium and nitrogen shown in Table 1 was treated with the apparatus shown in FIG. However, the raw water inflow portion and the treated water outflow portion were respectively installed at positions rotated 90 degrees clockwise in the horizontal plane from the position shown in FIG.
[0068]
As a result, the pH of the upper part of the nitrification tank became 7.5 to 8.0, as in the example. As a result of passing water over 100 days, generation of scale was observed on the filler at the end of the test. I couldn't. However, the ammonia removal rate was about 90% throughout the test, and the treated water quality deteriorated as compared with the Examples. This was thought to be because some of the raw water was short-circuited along the circulation flow by aeration.
[0069]
"Comparative Example 2"
Similar to the example, the simulated waste water containing calcium and nitrogen shown in Table 1 was treated with the apparatus shown in FIG. However, sodium hydroxide as an alkali agent was added at one point from the alkali agent addition pipe.
[0070]
As a result, the pH rose to 9-10 in the vicinity of the alkali addition part at the top of the nitrification tank. As a result of water passing over 100 days, partial scale generation was observed on the filler in the vicinity of the alkali-added portion about one month after the start of water passage. The occurrence of this scale became more noticeable as the water flow test progressed, and the generation range expanded. At this time, the ammonia removal rate was 98% or more throughout the test, and a very good treated water quality was obtained. However, in the long term, clogging due to the scale and the accompanying decrease in nitrification performance were expected.
[Table 1]

[0071]
【The invention's effect】
As described above, according to the present invention, the flow of water (hereinafter referred to as the water to be treated) caused by the inflow of the wastewater into the fixed bed treatment tank and the outflow as treated water, and aeration. The resulting circulating flow intersects in the vertical direction. As a result, a spiral flow is generated by the synthesis of these two flows, but the circulation flow is much faster than the flow of treated water, so that the influent wastewater flows along the circulation flow, After being mixed, it reaches the outflow part. Therefore, effective processing can be performed by effectively using the tank capacity of the fixed bed processing tank.
[0072]
In addition, in a direction perpendicular to the direction of the flow of the circulation flow, the drug can be injected little by little in the direction perpendicular to the circulation flow by dispersing and injecting the drug over the entire circulation flow. Yes, it is possible to eliminate the occurrence of pH distribution in the direction perpendicular to the circulating flow generated in the conventional method.
[0073]
Also, by injecting the drug while diluting with dilution water, it is possible to prevent the drug concentration from becoming very high in the vicinity of the drug injection point. In addition, since the medicine can be stored in a rich state in the medicine storage tank, the capacity of the storage tank can be effectively used. In particular, when the drug is an alkaline agent, it is possible to prevent an abrupt increase in pH at the drug injection point, and scale can be more effectively prevented.
[0074]
In addition, by providing the inflow part of the waste water in the upper part of the fixed bed treatment tank and providing the treated water outflow part in the lower part of the fixed bed treatment tank, the waste water flows through the tank and flows from the upper part to the lower part. The occurrence of a short circuit can be effectively prevented.
[0075]
Moreover, since the alkaline agent is sufficiently diluted and the pH is stable at the lower part of the fixed bed treatment tank, the alkaline agent injection means can be accurately controlled.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an apparatus according to an embodiment.
FIG. 2 is a diagram showing a configuration of a microorganism-retaining filler.
FIG. 3 is a diagram showing an overall flow of processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed bed nitrification tank, 2 Microbe holding | maintenance filler, 3 Raw water inflow part, 4 Treated water outflow part, 5 (5a, 5b) Aeration pipe, 6 (6a, 6b) Automatic valve, 7kg, 8 Alkaline agent storage tank, 9 Alkali pump, 10 pH sensor, 11 fluorine removal unit, 12 USB denitrification tank, 13 fixed bed oxidation tank.

Claims (6)

A fixed-bed treatment tank for treating the influent wastewater with aerobic organisms by microorganisms grown on the fixed bed;
Aeration means for performing aeration by sequentially switching from a plurality of aeration locations in this fixed bed treatment tank, and sequentially generating a circulation flow in substantially the opposite direction in the fixed bed treatment tank;
A wastewater treatment device having
A drainage inflow portion is provided on one side surface that is substantially perpendicular to the direction of the flow of the circulating flow generated by aeration by the aeration means in the fixed bed treatment tank, and treated water is provided on the other side surface that faces the one side surface. Wastewater treatment equipment that provides an outflow part. The apparatus of claim 1.
A drug injection means for injecting a drug into the fixed bed treatment tank;
This chemical injection means is a wastewater treatment apparatus for injecting chemicals over the entire circulating flow in a direction perpendicular to the direction of the circulating flow. The apparatus of claim 2.
The said chemical | medical agent injection | pouring means is a waste_water | drain processing apparatus which inject | pours, diluting a chemical | medical agent with dilution water. The apparatus according to claim 2 or 3 ,
The waste water contains calcium and nitrogen, and the chemical is an alkaline agent. The apparatus according to claim 4.
A wastewater treatment apparatus that measures pH at a lower part of the fixed bed treatment tank and controls an injection amount of the alkaline agent based on a measurement result. The device according to any one of claims 1 to 5 ,
A waste water treatment apparatus in which the inflow part of the waste water is provided in an upper part of a fixed bed treatment tank and the outflow part of the treated water is provided in a lower part of the fixed bed treatment tank.

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