JP2002282881A - Waste water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve effective waste water treatment without short-circuit. SOLUTION: In a nitration tank 1, circulation flow in the counter direction is took place by alternate aeration through diffusion air pipes 5a, 5b by alternate opening of auto valves 6a, 6b. Raw water inlet part 3 and treated water outlet part 4 are arranged to the orthogonal direction of circulation low in order to avoid short-circuit. Alkaline chemicals are also injected dispersively from the top coming across the circulation flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for treating wastewater,
Particularly, the present invention relates to an aerobic biological treatment using microorganisms grown on a fixed bed.

[0002]

2. Description of the Related Art Conventionally, treatments utilizing aerobic microorganisms have been used for treating various wastewaters. In the treatment of organic wastewater and nitrogen-containing wastewater, such aerobic microorganism treatment has become the mainstream. I have.

[0003] For example, in a process of manufacturing a semiconductor device such as an IC, hydrofluoric acid, ammonia, nitric acid and the like are used, so that waste water 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, fluorine (hydrofluoric acid), nitrogen (ammonia, nitric acid) are used as cleaning waste liquid when the semiconductor substrate is washed with ultrapure water or the like. ) Is discharged. 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.

[0004] Fluorine in the wastewater is generally removed as calcium fluoride by adding calcium, and the above-mentioned wastewater is also precipitated by adding calcium hydroxide or the like 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.

The removal of fluorine by calcium is a reaction of 2F ⁻ + Ca ²⁺ = CaF ₂ . Usually, the target concentration of fluorine in the fluorine removal treatment water is about 10 mg / L or less, and in such a case, the residual calcium concentration in the treatment water is reduced to 100 to 100 mg / L.
It is necessary to be about 1000 mg / L. The presence of silicon or phosphoric acid in the waste water has an adverse effect on the precipitation of calcium fluoride, in which case more calcium is added or coagulation treatment with an inorganic coagulant or polymer coagulant is required. May be required.

[0006] On the other hand, as described above, biological denitrification is usually employed for nitrogen removal. In this biological denitrification, nitrogen is removed by utilizing nitrate respiration of an anoxic state of a denitrifying bacterium, a facultative anaerobic bacterium.

[0007] In this biological denitrification, first, wastewater is nitrified to convert ammonium nitrogen in the wastewater into nitrite nitrogen and / or nitrate nitrogen, and then a hydrogen donor such as methanol is added. The denitrification treatment is performed by making it anoxic. In this specification, nitrite nitrogen and / or nitrate nitrogen is simply referred to as nitrate nitrogen or simply nitric acid as appropriate.

[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 bonding to various ions, and is likely to be precipitated as a solid during the biological treatment process. When calcium precipitates as a solid, it is present together with microorganisms in biological treatment, and the amount of inorganic sludge in the biologically treated sludge increases. 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, in addition to a floating activated sludge method for treating microorganisms in a suspended state, a fixed bed type using a filler for holding microorganisms is used. There is processing. This fixed-bed treatment can maintain the concentration of microorganisms in the treatment tank at a high level, not only increase the volume load, but also has the advantage that basically no sedimentation tank is required 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, calcium is likely to precipitate on the microorganism-holding filler and cause clogging. If clogging occurs, the clogging will be eliminated by air cleaning or chemical cleaning.However, if such a cleaning treatment is performed, the microorganisms retained on the microorganism retaining filler will also be removed. Will be removed. 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 frequently performed, the concentration of microorganisms in the fixed bed cannot be maintained at a high level. The nitrification load on the tank cannot be increased.

Further, in the nitrification treatment, an alkaline agent is added since 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.

[0014] For this reason, the present applicant has filed Japanese Patent Application No. 2000-9.
No. 2372 proposes an aeration unit for sequentially switching the aeration locations for a plurality of locations in the nitrification treatment unit to perform aeration. With this configuration, a circulating flow is generated in the fixed bed, and the mixing is improved. Further, the flow of the circulating flow 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 also be dissolved in the next stage, and thus the scale Generation can be prevented.

However, in this configuration, the inflowed wastewater flows along the circulating flow and reaches the outflow portion without being sufficiently contacted with the microorganisms in the fixed bed. Worsens.

The injected alkali is well mixed in the circulating flow direction, but in the direction perpendicular to the circulating flow, the pH is high near the alkali injection point, and as the distance from the alkali injection point increases, nitrification proceeds. Decrease. Therefore, the distribution of pH is large in the direction perpendicular to the circulating flow, and scale generation is inevitable.

Furthermore, since the alkali is injected from the upper part of the nitrification tank, the pH is high in the upper part and the nitrification proceeds in the lower part, and
H decreases. Therefore, when the treated water is allowed to flow out from the upper part, the injected alkaline agent flows out without being sufficiently mixed, which is inefficient.

The present invention has been made in view of the above problems, and has as its object to provide a wastewater treatment apparatus that can efficiently treat wastewater when a circulating flow is generated by aeration.

[0019]

According to the present invention, there is provided a fixed bed processing tank for aerobic biological treatment of inflowing waste water by microorganisms grown on a fixed bed, and a plurality of aeration sites in the fixed bed processing tank. Aeration means for sequentially switching and performing aeration, and sequentially generating a circulating flow in a substantially opposite direction in the fixed bed processing tank, wherein the aeration means is generated in the fixed bed processing tank by the aeration means. The drainage inflow portion is provided on one side surface substantially perpendicular to the flow direction of the circulating flow, and the treated water outflow portion is provided on the other side surface opposite to the one side surface.

With such a configuration, the flow of water (hereinafter referred to as the flow of water to be treated) due to the flow of wastewater into and out of the fixed-bed treatment tank as treated water, and the circulation flow generated by aeration Cross in the vertical direction. As a result, a helical flow is generated due to the synthesis of the two flows, but the circulating flow is much faster than the flow of the water to be treated. After mixing, it reaches the outlet. Therefore, effective processing can be performed by effectively utilizing the tank capacity of the fixed bed processing tank.

[0021] Further, there is further provided a medicine injecting means for injecting a medicine into the fixed bed treatment tank, wherein the medicine injecting means is provided in the direction perpendicular to the direction of the circulating flow, over the entire circulating flow. Preferably, the drug is dispersed and injected. With this configuration, the drug can be injected little by little in the direction perpendicular to the circulating flow, and the occurrence of the pH distribution in the direction perpendicular to the circulating flow that has occurred in the conventional method can be eliminated.

Further, it is preferable that the medicine injecting means injects the medicine while diluting the medicine with dilution water. With this configuration, it is possible to prevent the drug concentration from becoming extremely high in the vicinity of the drug injection point. In addition, since the medicine can be stored in a concentrated 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 a rapid increase in pH at the drug injection point, and to more effectively prevent the generation of scale.

It is preferable that the inflow portion of the wastewater is provided at an upper portion of the fixed bed treatment tank, and the treated water outflow portion is provided at a lower portion of the fixed bed treatment tank. As a result, the wastewater crosses the inside of the tank and flows from the upper part to the lower part, so that the occurrence of a short circuit can be effectively prevented.

Further, when nitrification is performed in a fixed-bed treatment tank and an alkali agent is added, the alkali agent injected at the top is diluted along the circulating flow, and is consumed as nitrification proceeds. After that, since it is discharged from the lower part, it is possible to use it efficiently without injecting extra alkali agent.

Preferably, the wastewater 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 alkali agent.

It is preferable that pH is measured in the lower part of the fixed-bed treatment tank, and the injection amount of the alkaline agent is controlled based on the measurement result. Since the alkaline agent is injected at the top of the fixed bed processing tank, the pH is
When is measured, the influence of the alkaline agent is easily perceived and the fluctuation of pH is large, so that stable pH control is difficult. On the other hand, in the lower part of the fixed-bed treatment tank, the alkali agent is sufficiently diluted and the pH is stable, so that the alkali agent injection means can be controlled accurately.

[0027]

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

FIG. 1 is a diagram showing the configuration of the present 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. Wastewater containing calcium and nitrogen is obtained as treated water from which fluorine has been removed.

The fixed-bed nitrification tank 1 has a rectangular parallelepiped shape. Inside the fixed-bed nitrification tank 1, a filler 2 for holding microorganisms is arranged. In addition, a raw water inflow section 3 into which drainage flows is provided at an upper portion of one side surface of the fixed-bed nitrification tank 1,
A treated water outflow portion 4 is provided at a lower portion of a side surface of the fixed bed nitrification tank 1 opposite to a side surface on which the raw water inflow portion 3 is provided. In addition, as is clear from the plan view, the raw water inflow section 3 and the treated water outflow section 4 are arranged shifted from the center of the tank so as to be close to a diagonal line. Therefore, in the front view, it flows in from the upper left of the fixed bed nitrification tank 1 and flows out from the lower right.

A plurality of air diffusers 5a, 5b are arranged at the bottom of the fixed-bed nitrification tank 1, and air is supplied to these from automatic blowers 6a, 6b from a blower serving as an air supply source. The automatic valves 6a and 6b are opened alternately, and a circulating flow as shown by arrows in the figure is generated alternately. Therefore, the overall flow of the water to be treated from the raw water inflow section 3 to the treated water outflow section 4 in the fixed bed treatment tank 1 is in a direction orthogonal to the circulating flow.

At the center above the fixed-bed nitrification tank 1, a gutter 7 which is open upward in a direction crossing the circulating flow of the fixed-bed nitrification tank 1 is disposed. Is supplied by the alkaline agent pump 9, and at the same time, working water (tap water or the like may be used as dilution water). The gutter 7 has a plurality of cutouts formed on both side walls thereof, so that the alkaline agent can be dispersed and injected into the entire tank.

Further, the pH at the bottom of the fixed bed nitrification tank 1 is measured by the pH sensor 10, and the alkali pump 9 is controlled based on the measurement result.

The waste water containing calcium and nitrogen (ammonia nitrogen: NH ₄ -N) is introduced from a 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 subjected to aeration treatment to be maintained in an aerobic state. Therefore, nitrifying bacteria adhere and grow on the surface of the microorganism-holding filler 2, and the nitrifying bacteria nitrify the ammonium nitrogen in the wastewater. Then, the nitrified treated water flows out of the treated water outlet 4 of the fixed-bed nitrification tank 1.
The nitrifying bacteria in the fixed-bed nitrifying tank 1 can be maintained at a sufficiently high concentration by adhering and growing nitrifying bacteria on the surface of the microorganism-holding filler 2, so that efficient nitrification treatment can be performed. it can.

The filler 2 for holding microorganisms is shown in FIG.
As shown in (1), a material obtained by alternately laminating corrugated plate members 2b and flat plate members 2a in which a nonwoven fabric is formed into a corrugated plate shape is suitably used. By arranging a plurality of the microorganism-holding fillers 2 in a vertical direction such that a passage is formed in the tank in a vertical direction, or by rolling and arranging them, the periphery of the nonwoven fabric becomes a vertical water passage. In addition, such a filler for holding microorganisms is disclosed in, for example, JP-A-7-24489.

Here, the water to be treated introduced into the fixed-bed nitrification tank 1 contains, for example, about 100 to 1000 mg / L not only ammonia nitrogen but also calcium ions. 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, the calcium compound precipitates on the microorganism-holding filler 2, and the microorganism-holding filler 2 is easily clogged.

On the other hand, in the fixed-bed nitrification tank 1, the pH is lowered by nitrification of ammonia nitrogen. Also, p
When H decreases, 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 1 so that the pH in the tank is maintained near neutrality. . That is, the alkali agent from the alkali agent storage tank 8 is supplied to the fixed-bed nitrification tank 1 by the alkali pump 9.

As described above, the addition of the alkali agent prevents the pH in the fixed-bed nitrification tank 1 from lowering. However, by the addition of the alkali agent, the pH of the portion where the alkali agent is added is concentrated. To rise. Therefore, in this portion, the calcium compound precipitates and the microorganism-retaining filler 2
Clogging tends to occur.

Further, if frequent washing is performed to eliminate such clogging, nitrifying bacteria are also washed together. Therefore, if frequent washing is performed, nitrification that can be held in the fixed-bed nitrification tank 1 can be maintained. The amount of bacteria becomes small, so that sufficient nitrification treatment cannot be performed.

In this embodiment, the alkaline pump 9
Is diluted with working water and dispersed by a gutter 7 serving as a dispersion means, and then added from the upper part of the fixed-bed nitrification tank 1.

As described above, by diluting, dispersing and injecting the alkali agent, the amount of the alkali agent injected into one place can be reduced. Therefore, an increase in pH at the portion can be made relatively small, and precipitation of calcium at the portion can be prevented.

It is preferable that the distance between each part when dispersing the alkaline agent is about several hundred mm to 1,000 mm.
For example, the distance between the notches provided in the gutter 7 may be set to this level.

Further, as described above, if the raw water inflow portion 3 is the upper portion of the tank and the treated water outflow portion 4 is the lower portion of the tank, the alkaline agent injected from the upper portion is diluted, and after being consumed by the nitrification reaction, is withdrawn from the lower portion. Thus, leakage of the alkali agent can be prevented.

On the other hand, at the bottom of the fixed bed nitrification tank 1, a plurality of air diffusers are divided into 5a and 5b, and air is diffused from one of the air diffusers 5a and 5b by automatic valves 6a and 6b. In addition, in the fixed-bed nitrification tank 1, the place to be diffused can be switched. Air is blown out of the air diffuser, and this air is usually pumped from a blower or the like. The arrow shown by the solid line in FIG. 1 indicates the flow of water that occurs when 6a is closed and 6b is opened. in this case,
The air diffuses only from the air diffuser 5b, causing an upward flow above 5b and a downward flow above 5a. For this reason,
In the example of the front view of FIG. 1, as indicated by an 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, scale is likely to occur in the upper left part, but scale is likely to dissolve in the upper right part. The broken arrows in FIG. 1 indicate the flow of water that occurs when 6b is closed and 6a is opened.

Then, by sequentially switching the automatic valves 6a and 6b, the circulating flow becomes almost in the opposite direction, and the place where the pH is low and the place where the pH is high alternate in the tank. It can be prevented from dissolving and fixing the scale as a whole.

In the lower part of the microorganism-holding filler 2, scale generation and scale dissolution do not occur much, or the scale is dissolved on the upward flow side and the scale is generated on the downward flow side. However, also in this portion, it is possible to prevent the scale from being fixed.

The raw water inflow section 3 is provided on the side of the nitrification tank perpendicular to the circulating flow generated by the aeration generated in the tank as described above, and the treated water outflow section 4 is provided on the side opposite thereto.

As a result, a flow of water (hereinafter, referred to as a treated water flow) caused by the flow of wastewater into the fixed-bed nitrification tank 1 and the flow of treated water, and a circulation flow generated by aeration are provided. They will cross vertically. as a result,
A helical flow is generated by the synthesis of these two flows, but the circulating flow is much faster than the flow of the water to be treated, so the incoming wastewater is sufficiently mixed while flowing along the circulating flow. Later, it reaches the outlet.

In this embodiment, the pH is measured by the pH sensor 10 in the lower part of the fixed-bed nitrification tank 1, and the injection amount of the alkaline agent is controlled based on the measurement result.

As a means for measuring the pH below the fixed-bed nitrification tank 1, a sampling cock may be installed below the fixed-bed nitrification tank 1 to measure the sample water. The pH sensor 10 may be installed directly below the fixed-bed nitrification tank 1 by providing a pipe or the like that penetrates the filler as described above. Further, the pH of the treated water flowing out from the lower part of the fixed-bed nitrification tank 1 may be measured.

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 can be easily sensed,
Is also large, so that stable pH control is difficult.
On the other hand, in the lower part of the fixed-bed nitrification tank 1, the alkali agent is sufficiently diluted and the pH is stable, so that the alkali agent injection means can be controlled accurately.

[Overall Configuration] In this embodiment, FIG. 3 shows an overall flow of treating wastewater containing fluorine and nitrogen to remove fluorine and nitrogen.

As described above, the waste water 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) The concentration is about 10 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 11 by a pump or the like. Calcium is added to the fluorine removing unit 11. 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 11, it is general that an aluminum-based flocculant, an acrylic polymer flocculant and the like are also 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 is present together with fluorine in the wastewater, and when it is desired to remove phosphorus together with fluorine, a method of adding calcium to the wastewater and adjusting the pH of the wastewater to, for example, 9 to 11 to remove phosphorus is used. 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.
mg / L or more.

The fluorine removing unit 11 thus obtained
Is introduced into the fixed-bed nitrification tank 1. Then, as described above, the nitrification treatment is effectively performed without generating scale or short circuit.

Next, the nitrification treatment water is introduced into the USB denitrification tank 12. The USB denitrification tank 12 is an upward sludge blanket (USB) type denitrification tank, in which a sludge blanket of denitrifying bacteria is formed, and wastewater is circulated in the upflow. 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.

Then, a hydrogen donor such as methanol is supplied to the USB denitrification tank 12, and oxygen of nitrate contained in the nitrification-treated water is removed by facultative anaerobic denitrifying 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 nitrification treatment water flowing into the USB denitrification tank 12 contains a relatively large amount of calcium, and 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. At that time, carbon dioxide is generated according to the following equation. I do. 2NO ₂ ⁻ + CH ₃ OH → N ₂ ↑ + CO ₂ + 2OH ⁻ +
H ₂ O ₂ NO ₃ ⁻ + (5/3) CH ₃ OH → N ₂ ↑ + (5 /
3) CO ₂ + 2OH ⁻ + (7/3) H ₂ O

The carbon dioxide generated in this manner is dissolved in water to form bicarbonate ions as shown in the following formula, which reacts with calcium in the water to be treated to form insoluble calcium carbonate. CO ₂ + OH ⁻ → HCO ₃ ⁻ Ca ²⁺ + HCO ₃ ⁻ → CaCO ₃ ↓ + H ⁺

In this way, calcium carbonate is generated and trapped in the sludge blanket in the USB denitrification tank 12. 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 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 washing operation and the sludge can be easily pulled out, the sludge concentration in the tank can be appropriately adjusted to perform an efficient treatment.

Next, the denitrification treatment water in the USB denitrification tank 12 is:
It is introduced into the fixed-bed oxidation tank 13, where it is subjected to aeration treatment to remove residual methanol. As the filler for holding microorganisms in the fixed-bed oxidation tank 13, a material filled with a large number of mesh-like plastic pipes is preferable. By filling such a microorganism-holding filler, efficient oxidation treatment can be performed in the oxidation tank, and the precipitation tank can be omitted.

[0062] In this manner, treated water from which nitrogen has been removed can be obtained under the condition where a high concentration of calcium is present. According to this embodiment, nitrification treatment can be performed in the fixed-bed nitrification tank 1 while preventing precipitation of calcium. Therefore, the concentration of the nitrifying bacteria in the fixed-bed nitrification tank 1 is increased, so that the nitrification treatment can be performed efficiently. Also, the next US
In the B denitrification tank 12, calcium can be removed while performing a denitrification treatment, and further, the precipitation of calcium promotes the formation of granules, thereby enabling effective denitrification.

Incidentally, the denitrification tank and the oxidation tank after the fixed-bed nitrification tank 1 may be of a floating type, and a solid-liquid separation device such as a sedimentation tank may be provided after the oxidation tank.

[0064]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example A simulated wastewater containing calcium and nitrogen shown in Table 1 was treated with the apparatus shown in FIG. Water temperature 20
C., nitrification load was set to 1.0 kg-N / m ³ / d, and 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. did.

As a result, the pH in the upper part of the nitrification tank was 7.5 to 7.5.
It was 8.0, but as a result of passing water for 100 days, no scale was found on the filler at the end of the test. At this time, the ammonia removal rate was 98% or more throughout the test, and very good treated water quality was obtained.

Comparative Example 1 Similar to the example, simulated wastewater containing calcium and nitrogen shown in Table 1 was treated with the apparatus shown in FIG. However, the raw water inflow section and the treated water outflow section are each moved clockwise in the horizontal plane from the position shown in FIG.
It was installed at a position rotated by 0 degrees.

As a result, the pH of the upper part of the nitrification tank became 7.5 to 8.0 as in the example. However, as a result of passing water for 100 days, at the end of the test, the scale was placed on the filler. No outbreaks were noted. However, the ammonia removal rate was about 90% throughout the test, and the quality of treated water deteriorated as compared with the examples. This was thought to be because part of the raw water short-circuited along the circulation flow due to aeration.

"Comparative Example 2" Similar to the example, simulated wastewater containing calcium and nitrogen shown in Table 1 was treated by the apparatus shown in FIG. However, sodium hydroxide was added as an alkali agent at one point from an alkali agent addition pipe.

As a result, the pH rose to 9 to 10 in the vicinity of the alkali addition section in the upper part of the nitrification tank. As a result of passing water for 100 days, partial scale generation was observed on the filler near the alkali-added portion about one month after the start of water passing. The occurrence of this scale became more remarkable with the passage of the water flow test, and the range of occurrence expanded. At this time, the ammonia removal rate was 98% or more throughout the test, and very good treated water quality was obtained. However, in the long term, clogging due to scale and accompanying reduction in nitrification performance were expected.

[Table 1]

[0071]

As described above, according to the present invention,
In the fixed-bed treatment tank, a flow of water (hereinafter referred to as a treated water flow) caused by inflow of wastewater and outflow as treated water, and a circulating flow generated by aeration cross vertically. . As a result, a helical flow occurs due to the synthesis of these two flows, but the circulating flow is much faster than the flow of the treated water, so that the incoming wastewater flows along the circulating flow, After reaching the outlet. Therefore, effective processing can be performed by effectively utilizing the tank capacity of the fixed bed processing tank.

Further, by dispersing and injecting the medicine throughout the entire circulating flow in a direction perpendicular to the direction of the circulating flow, the medicine is injected little by little in the direction perpendicular to the circulating flow. It is possible to eliminate the occurrence of a pH distribution in a direction perpendicular to the circulating flow generated in the conventional method.

Further, by injecting the drug while diluting it with the dilution water, it is possible to prevent the drug concentration from becoming extremely high in the vicinity of the drug injection point. In addition, since the medicine can be stored in a concentrated 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 a rapid increase in pH at the drug injection point, and to more effectively prevent the generation of scale.

Further, by providing the inflow part of the wastewater at the upper part of the fixed-bed treatment tank and providing the outflow part of the treated water at the lower part of the fixed-bed treatment tank, the wastewater crosses the inside of the tank and flows from the upper part to the lower part. Since it flows, the occurrence of a short circuit can be effectively prevented.

In the lower part of the fixed bed processing tank, the alkali agent is sufficiently diluted and the pH is stable, so that the alkali agent injection means can be controlled accurately.

[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-holding filler.

FIG. 3 is a diagram showing an overall flow of processing.

[Explanation of symbols]

1 fixed bed nitrification tank, 2 microbial holding filler, 3 raw water inlet, 4 treated water outlet, 5 (5a, 5b) diffuser,
6 (6a, 6b) Automatic valve, 7 gutter, 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)

[Claims] 1. A fixed bed processing tank for aerobic biological treatment of inflowing waste water by microorganisms grown on a fixed bed, and aeration is performed by sequentially switching from a plurality of aeration locations in the fixed bed processing tank. Aeration means for sequentially generating a circulating flow in the floor treatment tank in a substantially opposite direction, wherein the fixed-bed treatment tank has a flow direction of a circulating flow generated by aeration by the aeration means. On the other hand, a wastewater treatment apparatus in which a drainage inflow portion is provided on one side surface which is substantially vertical and a treated water outflow portion is provided on another side surface opposite to the one side surface. 2. The apparatus according to claim 1, further comprising a medicine injecting means for injecting a medicine into the fixed bed processing tank, wherein the medicine injecting means is provided in a direction perpendicular to the direction of the circulating flow. A wastewater treatment device that disperses and injects chemicals throughout the circulating flow. 3. The wastewater treatment apparatus according to claim 2, wherein the medicine injection means injects the medicine while diluting the medicine with dilution water. 4. The apparatus according to claim 1, wherein the inflow portion of the wastewater is provided in an upper portion of the fixed-bed treatment tank, and the treated water outflow portion is provided in a lower portion of the fixed-bed treatment tank. Processing equipment. 5. The wastewater treatment device according to claim 1, wherein the wastewater contains calcium and nitrogen, and the chemical is an alkaline agent. 6. The wastewater treatment apparatus according to claim 4, wherein the pH is measured at a lower portion of the fixed bed treatment tank, and the injection amount of the alkaline agent is controlled based on the measurement result.