JP3830505B1 - Soil denitrification equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a soil or clay for denitrifying ammonia nitrogen, and for the convenience of the facility and the ease of operation, the oxygen supply necessary for nitrification is obtained from natural aeration, The purpose is to provide denitrification that does not require stirring.
SOLUTION: The treated soil is put into a containing frame whose side is open, and the necessary oxygen for nitrifying ammonia nitrogen in the sewage is sprinkled from the upper part of the treated soil. A soil denitrification apparatus characterized in that the nitrogen component taken in and nitrified is denitrified in a denitrification tank having a clay layer filled with a water retention material and fluidized.
[Selection] Figure 2

Description

  The present invention, like sewage such as leachate at the final disposal site of waste, contains less easily decomposable organic matter (BOD), contains a lot of ammonia nitrogen, and is difficult to biologically denitrify water treatment technology. The present invention relates to a treatment apparatus for performing a series of treatments of nitrification and denitrification using general soil and clay.

In the leachate at the final disposal site, readily decomposable organic components (such as BOD) have already been decomposed in the landfill, and ammonia nitrogen converted from organic nitrogen components (NH ₄ -N) is contained in the leachate. ) Is included. In addition, in the anaerobic treatment method applied to high-concentration organic waste liquid (food factory waste liquid, livestock manure, etc.), the nitrogen component contained in the waste liquid is not treated and remains as ammoniacal nitrogen (NH ₄ -N). .

A typical method for removing nitrogen components in sewage is a biological denitrification method that combines aerobic treatment with nitrifying bacteria that live in activated sludge and anaerobic treatment with denitrifying bacteria. Finally, it is converted into inert nitrogen gas and released into the atmosphere.
Aeration (nitrification)->denitrification-> Precipitation is the typical treatment process. In the denitrification treatment of wastewater containing a lot of ammonia nitrogen, the most difficult treatment operation is the nitrification process from the scale of equipment and operation management. . In particular, when there is almost no readily decomposable organic matter (BOD) in the sewage, such as leachate at the final disposal site, nitrification may not be achieved at all. In addition, the treatment of leachate after the final disposal site has been completed is unmanned and a simple treatment method is desired. The anaerobic treatment has a small treatment scale, but cannot be discharged as it is because it is highly concentrated ammoniacal nitrogen. In order to perform the denitrification treatment, a large-scale nitrification tank or the like is required.

Activated sludge is an irregular floc of 200 to 1000 μm in which protozoa and bacteria are aggregated, and microorganisms such as nitrifying bacteria are also taken in. The aeration (nitrification) tank is constantly fluidized by air agitation for supplying oxygen, and there are many fine flocs. Fine flocs that cannot be settled in the sedimentation tank in the next process will be washed away with the treated water (washout). Bacteria with a small specific growth rate (μ) such as nitrifying bacteria are washed out with fine floc before they can grow in the aeration tank. Due to the washout of the activated sludge treatment, the number of individuals that appear as activated sludge bacteria is not large, and the treatment of BOD is often the main subject. Therefore, as a modified method of activated sludge treatment, the number of individuals that appear in the flocs of activated sludge is increased, and a long-term aeration system that reduces the sludge generated by the food chain and catalytic oxidation that fixes microorganisms to the filler. A processing method has been introduced. These treatment methods can also retain microorganisms with a low specific growth rate (μ).
In addition, in order to nitrify ammonia nitrogen in sewage, the aeration tank capacity required for normal activated sludge treatment is 3-5 times, and strong agitation to supply air for nitrification is required. In order to maintain it in the nitrification tank, a large-capacity aeration tank and precipitation tank are required, and in the water treatment operation, about three times the amount of treated water at the nitrification tank outlet is returned and circulated. .

  Specific growth rate (μ) is the growth rate per unit concentration of microorganisms, and μ when dividing once a day and growing twice is 0.693 (1 / day). . The activated sludge's BOD oxidizing bacteria μ is about 2.2 (1 / day), Nitrosomonas genus μ which is a representative species of nitrifying bacteria is 0.2-1.0 (1 / day), and subnitrifying bacteria are At 0.2 (1 / day), it is as slow as 1/10 of activated sludge bacteria, and it is difficult to maintain in the aeration tank. Nitrifying bacteria are also greatly affected by temperature, and it becomes difficult to treat sewage in cold regions and in winter when the water temperature is low.

In the biological denitrification method, ammonia nitrogen (NH ₄ -N) in sewage is nitrated (NO ₂ -N, NO ₃ -N), then placed under anaerobic conditions without dissolved oxygen, and denitrifying bacteria Nitrate nitrate and nitrite respiration are used to reduce nitrate nitrogen to inert nitrogen gas.
Most of the denitrifying bacteria are other vegetative bacteria that depend on an organic carbon source supplied from the outside, and methanol or the like is often used. In the water treatment apparatus, a re-aeration tank is additionally provided to treat the excessively injected residual methanol and the like.
The sewage denitrified through nitrification → denitrification → re-aeration is finally sent to a settling tank. Since nitrification and re-aeration tanks are stirred by air, and denitrification tanks are mechanically stirred, mixed water of sludge (bacteria) and treated water is sent to the settling tank, and the supernatant water is precipitated as treated water. The sludge must be returned and circulated in order to keep the cells in the treatment tank.

Injection of alkali such as NaOH to neutralize the nitric acid produced in the nitrification tank, and injection of acid such as H ₂ SO ₄ so that the alkalinity of water increases in the denitrification tank so as not to deviate from an appropriate pH range. Therefore, it is difficult to introduce it into facilities where simple operation is desired.

In addition to water treatment by biological denitrification, there is a soil purification method. A rich food chain is maintained in the soil by bacteria, protozoa, small animals, etc., and when organic matter contained in sewage is introduced, it is quickly decomposed and purified.
In addition, when nitrogen fertilizers such as ammonium sulfate and urea are applied to the soil, the nitrification ability of the soil is high due to rapid nitrification and accumulation of nitric acid in the surface soil in house cultivation, etc. Since it contains many clay colloids and humic plants with high exchange capacity, it has a high pH buffering capacity and has an excellent property of controlling soil acidity due to nitrification.
However, the soil is blocked by contaminants contained in the sewage, sludge generated by the decomposition of organic matter, and fine particles of cohesive soil. May not be able to continue. Moreover, since the high nitrification capacity of the soil is limited to about 10 to 30 cm from the surface layer, there is a limit to the ability to nitrate ammonia nitrogen in sewage.

In paddy fields where the supply of oxygen is blocked by filling water, it is known that when nitrate fertilizer is put into paddy soil, most of it is reduced to nitrogen gas, and nitrate fertilizer is not very useful in paddy fields.
If nitrate nitrogen in soil treated water is poured into a soil treatment tank in the form of paddy soil, it is reduced to nitrogen gas and can be denitrified. However, the soil in the water like paddy fields has not been put to practical use because it becomes consolidated as it reaches the bottom, and the ability of sewage to pass through cannot be expected. In the current treatment technology, the denitrification treatment after soil treatment is the same method as the denitrification tank of biological denitrification method, and is based on the water treatment method that aims to maintain the cells with contact materials placed in the tank. .

As a specific conventional example, for example, an oxidation tank for performing an aerobic treatment on organic wastewater and a denitrification tank for performing an anaerobic treatment on the aerobic treatment water by the oxidation tank, The soil of a predetermined depth partitioned by a water shielding sheet for preventing water leakage is used as a spray area for organic wastewater, and water spray pipes are laid on the soil surface, and air supply pipes and recovery pipes are buried in the soil. The denitrification tank is configured to contain a rice bran which is a carbon source in a pit hole whose inner surface is covered with a water shielding sheet, and a denitrification tank. Has proposed a device in which a water supply pipe for introducing aerobic treated water and a drain pipe for discharging anaerobic treated water obtained by denitrification of aerobic treated water to the outside have been proposed (patent) Reference 1).
In addition, an upper soil layer provided with a water flow device having a water spray pipe for spraying sewage is provided, and a diffusion layer is provided at a midway depth immediately below the water flow device, below the upper soil layer. A denitrification layer having a denitrification property is provided at two locations on the upper and lower sides with a breathable exhaust layer, and an exhaust passage leading from the exhaust layer to the outside of the apparatus is provided, below the denitrification layer. A device has been proposed in which a lower soil layer is provided, a water collection layer is provided below the lower soil layer, and a water collection pipe is arranged in the water collection layer (see Patent Document 2).

JP 2004-209912 A JP 2003-275780 A

However, in the technique described in Patent Document 1, the wastewater treatment is covered with a water shielding sheet other than the surface layer of the soil and an air supply pipe or the like is used, but the ventilation / exhaust efficiency in the soil is poor. In addition, when wastewater diffuses into the soil, no means for preventing the consolidation of the soil is taken, and as the treatment proceeds, the soil becomes blocked and the treatment efficiency is lowered.
Also, in the technique described in Patent Document 2, the soil is covered with a treatment tank, and ventilation and exhaust in the soil use only the surface layer of the soil and a plurality of tubes arranged in the soil. Therefore, the efficiency of ventilation and exhaust is poor, and the device itself is complicated. In addition, the means for preventing the consolidation of the soil is not specially taken, and as the treatment proceeds, the soil becomes blocked and the treatment efficiency is lowered.

Therefore, the present invention is a method and apparatus that utilizes soil with high nitrating ability for nitrating ammonia nitrogen, which is difficult to treat in water treatment operations. The purpose of oxygen is to provide natural aeration instead of air supply by a blower or the like.
Ammonia nitrogen (NH ₄ —N) converted from organic nitrogen is oxidized to NO ₂ —N or NO ₃ —N by nitrifying bacteria and nitrifying bacteria. Nitrate bacteria and nitrite bacteria are both autotrophic bacteria that synthesize cells using carbon dioxide as a carbon source.
NH ₄ ⁺ + 1.5O ₂ → NO ₂ ⁻ + H ₂ O + 2H ⁺
NO ₂ ⁻ + 0.5O ₂ → NO ₃ ⁻
The oxygen necessary for the above nitrification requires 4.6 kg of oxygen to oxidize 1 kg of NH ₄ -N. In order for the nitrogen fertilizer to be nitrated quickly in the soil, the above oxygen needs to be supplied to the soil.

Nitrification from NH ₄ -N to NO ₃ -N is a reaction due to the presence of nitrifying bacteria in the soil and is not adsorbed to soil particles, so it is a non-saturated treatment and is permanent. There is.
The nitrogen treatment capacity by adsorption or nitrification in soil varies greatly depending on the type of soil, but the nitrogen treatment capacity of soil is considered to be 0.5 to 5.0 mg / 100 g per 100 g of dry soil per day. In the case of soil deodorization in which malodor is deodorized through the soil; the ability to nitrify per day per 100 g of soil is about 10 mg NH ₃ —N / 100 g dry soil, and the soil height at this time is about 50 cm. Soil deodorization has a high nitrification capacity because air is always forcibly supplied into the soil.

In the case of nitrification by activated sludge treatment, the nitrification load factor is planned at 100 g NH ₃ -N / m ³ · day per 1 m ³ aeration tank. Although there is a difference between the retained water in the aeration tank and the retained soil in the soil treatment, the above load factor corresponds to 10 mg NH ₄ -N / 100 g · day when converted per unit volume. This is equivalent to the soil deodorization capacity for forced ventilation.
In the case of no aeration like soil deodorization, it is about 5 mg NH ₄ -N / 100 g · day, which is 1/2 of the treatment capacity of activated sludge. However, nitrifying bacteria in an aeration tank are difficult to maintain by washing out or the like, but are easily and stably maintained in soil. In addition, when power such as a blower is not used, nitrification using soil is far superior in terms of operation management and energy saving.

The air in the soil has a lower oxygen concentration than the atmosphere, and is rich in carbon dioxide and water vapor. The concentration of carbon dioxide derived from the decomposition of organic matter increases at a depth of 20 cm or more.
In the case of 5 mg / 100 g dry soil with a nitrogen treatment capacity, soil: 50%, moisture: 20%, air: 30% soil, the average amount of air contained in the soil is about 60 cc. Assuming that the total amount is ammoniacal nitrogen, about 80 cc of air is required to nitrify 5 mg of ammoniacal nitrogen, and 20 cc of air is theoretically calculated only by the amount of air present in the soil. Run short. Since the majority of soil nitrification is the surface layer, the air that is deficient is always supplied from the soil surface layer.
In order to increase the nitrification capacity of the soil, it is necessary to increase the amount of air in the soil, to increase the surface soil area, and to make active contact with the atmosphere. In addition, since nitrification is greatly affected by temperature, it is necessary to provide a scale with a margin for capacity and air supply.

If sewage is poured into the soil excessively, the surface layer will be blocked, the soil interior will be consolidated, the soil penetration capability will decrease, and the air inside the soil will also decrease.
Water entering from the soil surface is moved by gravity, capillaries in pores between soil particles, and water vapor. Movement due to gravity and capillary force is movement in the vertical and horizontal directions, and in particular, movement to a void that is an air pocket in the soil. The sewage poured from outside enters the voids in the soil by gravity and pushes out the air in the soil. This becomes more noticeable as the amount of water injection increases.
Consolidation of soil occurs because the porosity ratio in the soil decreases. The decrease in the gap ratio is caused by external pressure, the weight of the soil, the clogging of the gap due to the movement of fine particles due to the injection of excess sewage, and the like. Ordinary cultivated land is cultivated to prevent these problems and promotes soil agglomeration.
In the case of soil treatment, the ability of sewage to penetrate into soil is an important factor. The soil penetration capacity is about 20 to 60 liters / m ² · day based on the results of soil treatment. If the pore ratio can be reduced by excessive water injection into the soil, and the compaction can be prevented by the weight of the soil, the soil penetration capability can be greatly increased.
The sewage poured from the surface of the soil is collected in the lower layer by gravity. In the case of soil treatment, the soil becomes a filter, and the bacterial cells remain in the soil layer. However, when the amount of treated sewage is increased, fine particles such as clay in the soil flow out due to gravity. It is necessary to prevent the outflow of these fine particles.

Denitrification treatment with soil applies the denitrification form of paddy field.
The cross-sectional structure of the paddy field consists of an aerobic field surface, an anaerobic soil layer, and a sukibed layer and a subsoil layer below it. Oxygen in the water is consumed by the respiration of aerobic microorganisms present in the shallow water of the surface, and the oxygen consumption exceeds the supply in the soil layer below it. Active and anaerobic substance change is promoted.
There are two layers in the soil formation layer, where aerobic or semi-anaerobic facultative anaerobic bacteria are active and in which there are absolute anaerobic bacteria that are under anaerobic conditions. The reduction of nitric acid is performed in a layer where facultative anaerobes in the first stage are active, and the redox potential (Eh) is about +0.4 to +0.1 volts, which is an anaerobic condition without dissolved oxygen. . Furthermore, in the layer where the absolute anaerobic bacteria exist in the lower layer, Eh decreases to 0 to -0.3 volts.
Nitric acid is reduced to nitrogen gas while oxygen is decomposed as an oxidizing agent and decomposes organic substances. This reduction reaction of nitric acid can be represented by the following formula.
2NO ₂ +3 (H ₂ ) → N ₂ + 2OH ⁻ + 2H ₂ O
2NO ₃ +5 (H ₂ ) → N ₂ + 2OH ⁻ + 4H ₂ O
Methanol or the like is used as the organic carbon source that is (H ₂ ), and it is necessary to add three times the amount of NO ₃ —N in methanol.

When sewage is treated in the soil, there is a proliferation of bacterial cells that become excess sludge. The amount generated is 0.17 g of cells when 1 g of NH ₃ -N is nitrified, and in denitrification, in the case of methanol to which 3 times the amount of nitrate nitrogen is added, 0.15 g of cells It is believed that the body is produced. Here, suppose that the amount of bacterial cells produced at 5 mg / 100 g dry soil / day is 0.85 mg for nitrifying bacteria, 4.75 mg for denitrifying bacteria, and 5.6 mg / 100 g dry soil / day in total. This is 0.0056% per day in 100 g of dry soil, and is around 2% throughout the year.
A rich food chain is maintained in the soil, and since these cells (sludge) have a low content per dry soil, the accumulation of cells (sludge) in the soil is negligible.

In water treatment operation and soil treatment as well, in the nitrification reaction, by oxidizing 1 mg of NH ₄ -N, 7.14 mg of alkalinity is consumed and pH is lowered. When the nitrification reaction is slowed by the influence of pH and only nitritation proceeds, nitrite ions are accumulated. Since nitrite ions are highly toxic to microorganisms, the entire nitrification reaction does not proceed. The optimum pH is 7-9. In the denitrification reaction, when 1 mg of nitrate nitrogen is denitrified, 3.57 mg of alkalinity is produced.
The soil has an excellent pH buffering capacity when there are many clay colloids and humic plants. For this purpose, the soil to be treated needs to contain clay and humus having an appropriate adsorbing power. The soil in the soil treatment tank is different from natural soil, and sewage water that is more than natural rainfall is always injected, so the clay and humus, which are fine particles, are consolidated in the soil so that they will not be washed away by gravity water. It is necessary to prevent this.

In order to nitrify ammonia nitrogen in sewage by soil treatment, the air permeability and water permeability of the soil itself are important treatment elements. The nitrification capacity of the soil also affects the air in the soil, but it tends to nitrify at a depth of about 10 to 30 cm on the surface, so that most of the nitrogen is nitrated by the air supplied from the surface. It has been oxidized to reactive nitrogen.
The soil used in the present invention is sandy soil having air permeability and water permeability. In addition, in order to enlarge the contact surface with the atmosphere, the soil used for the treatment is surrounded by a storage frame and the side surface is exposed in addition to the uppermost surface so as to be in contact with the atmosphere. As a result, the surface of the soil that comes into contact with the atmosphere has five sides, with four additional sides.
In order to increase the amount of nitrifying bacteria retained, it is necessary to increase the volume of soil to be treated. However, increasing the soil capacity requires deepening. Since the air necessary for nitrification is not sufficiently supplied in a deep place in the soil, increasing the soil capacity is not effective. However, by opening the side surface to the atmosphere, air can be taken in the side surface as well as the surface soil, so that it is not necessary to increase the depth of the treated soil.

Since the soil surrounded by the storage frame opens the side, it is necessary to prevent collapse from the side. For this purpose, auxiliary tools for supplementing physical properties such as internal friction, shear resistance and compressive force of the soil are mainly embedded in the side surface of the soil. This auxiliary tool will be described below as a wedge material. A wedge material arrange | positions the several flat plate which brings about the function of an earth anchor with respect to the earth pressure from upper direction radially to a horizontal direction. The central portion of the flat plate is fixed to a short tube (called a mesh tube) made of plastic or the like that is a mesh.
The length of the flat plate is about 20 to 30 cm and is embedded around the soil side surface so that the ends of the flat plate overlap. By embedding a plurality of steps in the soil in the storage frame, the exposed side soil can be prevented from collapsing.
The soil in the upper layer of the flat plate of the wedge material is consolidated by earth pressure, but the soil pressure from above is reduced in the lower part of the flat plate, so that the soil becomes soft soil sufficiently containing air. Therefore, the lower part of the flat plate becomes a place where aerobic bacteria gather.
In addition, since the central portion is a mesh tube, it becomes a passage for air and water moving in the soil, and moderate moisture and oxygen are supplied to the cells attached to the soil particles.
Since the mesh tube in the wedge material is on the side surface in the soil, air can be easily taken in from the surface layer and the side surface, and oxygen necessary for nitrification can be supplied to the soil only by natural ventilation that does not require a blower or the like. .
In addition, if a mesh tube is arranged at the center of the soil in the storage frame, water flow and ventilation are further improved.

  The soil height stored in the storage frame needs to be about 2 m in order to secure the exposed area of the side surface. A horizontal support material is arranged at the bottom of each stage so as to receive earth pressure from above. The earth pressure of 2 m is reduced at each stage, preventing the consolidation of the soil at the bottom of the storage frame and preventing water flow failure due to consolidation.

Water is poured from the upper part of a net-like tube embedded in a depth of about 10 to 20 cm on the surface layer and arranged in two rows. Plural water inlets are arranged so that they can penetrate the treated soil evenly. Inject water continuously.
Since the soil near the corner portion of the storage frame is less susceptible to compaction due to earth pressure, it becomes relatively soft soil, and therefore, sewage from the water inlet may leak from here. A water shielding plate is embedded at a depth greater than the depth at which the reticulated pipe is embedded around the water inlet to prevent water leakage. The sewage poured into the mesh tube penetrates downward from the inner surface of the mesh tube, and is collected in the lower part through a gap portion of the wedge material. The amount of water injected per day is the amount of water permeated through the natural soil due to the fact that mesh pipes are placed in the soil, and there are horizontal support materials at the bottom of each step, and the earth pressure from above is reduced. It is possible to ensure 200 to 500 liter / m ² or more, which is about 10 times 20 to 50 liter / m ² .

At the lowermost part of the housing frame, a water collecting device is provided to prevent water collection and the fall of soil particles.
The water collecting device is a perforated tube made of plastic, and a nonwoven fabric is wound around the outer surface and arranged on the entire surface of the housing frame. The water that has passed through the soil wets the nonwoven fabric and drops it on the lower surface of the nonwoven fabric.
A water collecting cloth made of non-woven cloth is provided on the lower surface of the non-woven cloth, and water is introduced to the lower denitrification tank while wetting a thin cloth bundle made of cotton cloth or the like that becomes a water guiding cloth from the water collecting cloth. Drop the water guide cloth to the bottom of the denitrification tank. A horizontal support material will be installed just above the water collecting device to prevent the fall of soil particles and reduce the earth pressure.
A methanol diluted solution for denitrification is injected from the end of the perforated pipe serving as a water collecting device, and the water is fed through the water collecting device non-woven fabric to the denitrification tank at the lowest layer of the storage frame together with the treated water.

The denitrification tank is charged with clay (SV) about 50 to 70% as a carrier for fixing the denitrification bacteria. As for the capacity of the denitrification tank, a residence time of 2 to 5 hours is secured with respect to the processing amount, and the depth is about 1 m.
A partition plate is arranged in the denitrification tank inflow portion and the drainage portion, and an opening is provided in the lower portion of the inflow portion partition plate, so that the wastewater overflows from the upper portion of the partition plate and is treated by upward flow. The treated water is drained from the adjacent treated water tank.
The clay to be added is not special and is obtained from readily available soil. Therefore, since the clay particles are various, coarse particles and particles with a high specific gravity are deposited and consolidated in the water tank as they are. In order to prevent this, the water tank is filled with a water retaining material over the entire surface.

For the water-retaining material, use a material such as crushed stone that has a heavy specific gravity in a net-like tube, etc., so that it does not float and is wrapped with a plurality of non-woven fabrics.
Since the net-like pipes in the nonwoven fabric always have water, compaction does not occur around the water retaining material, and the water tank can be kept in a fluid clay solution. A soil layer with many facultative anaerobes in which water in the upper part of the paddy field flows can be revealed.

Since denitrifying bacteria are attached to the clay particles, nitrate nitrogen is reduced during the upward flow from the water tank inlet to the water tank outlet. In addition, the organic carbon source required by the denitrifying bacteria which are other vegetative bacteria is supplied to the denitrification tank in a well-mixed state together with the nitrified treated water by injecting a methanol diluent into the water collecting pipe.
The amount of methanol to be injected is measured by measuring the residual nitric acid concentration in the treated water tank, grasping the required amount, and adjusting the injection amount. For the methanol dilution, install a dedicated tank outside and feed a fixed amount with a metering pump. Denitrified treated water may be used for dilution of methanol.

  By filling the denitrification tank with a water retention material, the clay is fluidized. Therefore, since it is not necessary to stir the denitrification tank, a precipitation tank for solid-liquid separation is not necessary.

  The soil denitrification device surrounded by a storage frame from nitrification to denitrification is made into one unit, and the unit is increased according to the required amount of treated water. When installing a plurality of units, they are arranged with an interval at which the side surface of the treated soil surrounded by the housing frame can be exposed to the atmosphere.

Nitrification in the soil is limited to a shallow area of about 10 to 30 cm in the surface soil, and water flow to the soil is limited to 20 to 50 l / m ² per day in general soil. When there are a lot of readily decomposable organic substances or when there are foreign substances, there is a limit to practical use, such as being blocked in the soil and generating a bad odor.
In the present invention, attention is paid to the fact that the amount of air required for nitrification is intake from a shallow place in contact with the atmosphere, and the contact area with the atmosphere is increased by exposing the side surface of the treated soil. such 0.5~5.0mgNH ₄ -N / 100g dry soil which is nitrification capacity of the soil, can be exemplified 10mgNH ₄ -N / 100g dry soil until the processing capability of the actual value of the soil deodorizing of forced ventilation It becomes.

A wedge material that acts as an earth anchor is placed in the soil around the open soil side. The central portion of the wedge material has a hollow portion formed by a mesh tube, so that the air permeability and water permeability of the soil are improved, and a processing capacity of 200 to 500 liters / m ² , which is 10 times that of ordinary soil, can be secured. it can. Moreover, since ventilation is natural ventilation, power such as a blower is not used. Therefore, the structure is simple, and an apparatus that can save energy and perform unmanned management can be provided.

  The wedge material in the soil is provided with a radially horizontal flat plate that serves as an earth anchor. The back side of the flat plate becomes soil which is not consolidated by earth pressure. Appropriate water and oxygen are always supplied from the air reservoir inside the mesh tube, which is a constituent of the wedge material, to this back surface. Therefore, aerobic microorganisms having various food chains accumulate on the back surface of the horizontal material, and surplus sludge (mycelium) generated in the treatment process of sewage is decomposed by the aerobic microorganisms. Therefore, it can be set as the apparatus with little production | generation of sludge.

  At the bottom of the treated soil, a water collecting device with a non-woven fabric attached to the outside with a plastic perforated tube is installed to prevent the fall of soil particles, and by laying almost all the treated soil, a uniform water collecting area is provided. It is possible to prevent the reduction of the processing efficiency due to, for example, a road on the treated soil.

The denitrification treatment of sewage nitrified by soil treatment uses readily available clay as a carrier.
The reason why a device using soil (clay) for denitrification has not been put into practical use is because clay particles are consolidated at the bottom and water permeability cannot be secured. However, by filling the denitrification tank with a water retention material, consolidation at the bottom of the tank where clay particles are deposited can be eliminated, and denitrifying bacteria can be retained in the clay as seen in the soil formation layer with excellent denitrification ability of the paddy field. Can be performed.
In the denitrification tank of the present invention, the moisture of the surrounding clay is retained and swelled by the moisture of the water retaining material, so that stirring or the like is not required. Therefore, the subsequent precipitation treatment step is unnecessary and can be discharged as it is.

  Alternative to complex and costly biological denitrification process of current technology operation by using commonly available soil and clay, simple structure and simple operation without power Can be used as In addition, nitrification and denitrification are continuously arranged vertically, and no settling tank is required, so the installation area can be reduced.

Hereinafter, a soil denitrification apparatus according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the receiving frame 2 whose side surfaces and bottom surface are surrounded by a support material 21 and whose bottom portion is an opening is installed in a plurality of stages (three stages in FIG. 1) in the vertical direction. The lowermost layer is a water tank 7 and is composed of an inflow tank 71, a denitrification tank 72, and a treated water tank 73.
The denitrification tank 72 is provided with two partition plates 74 and 75, the partition plate 74 at the inlet has an opening on the lower surface, and the treated water that has flowed into the treated water tank 73 beyond the partition plate 75 at the outlet is supplied by a submersible pump. Drain by 76.

The storage frame 2 in FIG. 1 stores sandy soil to the top, nitrifies ammoniacal nitrogen in the sewage, and the water tank 7 functions as a denitrification unit, using clay, Then, without supplying air, nitric acid and the like are denitrified to form inert nitrogen gas, which is released to the atmosphere.
As shown in FIGS. 2 and 3, the uppermost layer is filled with the sewage sprinkler 3 and then the wedge material 5 shown in FIGS. A plurality of stages (four stages in FIG. 2) are embedded up to the water collecting device 6 in the lower layer. A support member 21 disposed in the horizontal direction that receives the earth pressure of the upper soil is provided at the bottom of each step of the storage frame 2, and an opening is provided between the support members 21.
Sandy soil is put into the storage frame 2 in order from the bottom, and the wedge material 5 is embedded at the same time.
In FIG. 3, the support material 21 arranged in the lateral direction also has a support material 22 for protecting the water collection device 6 from earth pressure at the upper part (ii ′ plane) of the third-stage water collection device 6. . For this reason, the support frame in the horizontal direction is provided with two stages of support materials 21 and 22 in the storage frame in which the water collecting device 6 is provided, and earth pressure is reduced in the soil above the water collecting device 6.

A water collecting device 6 shown in FIGS. 2 and 3 is disposed on the entire bottom surface of the housing frame 2 in FIG. The water collecting device 6 is attached so that soil particles from above do not fall into the denitrification tank 72 and so that water can be collected uniformly from the entire surface of the treated soil 4.
As shown in FIGS. 6 and 7, the non-woven fabric 62 is processed into a lantern and has a large area in order to prevent clogging due to accumulation of soil particles falling on the outer surface of a perforated tube 61 such as plastic. Cover with. The treated water wets the nonwoven fabric 62 and drops it on the lower part. The water dripped from the nonwoven fabric 62 is received by the water collecting cloth 63, and the water guiding cloth bundle 64 made of a bundle of nonwoven fabric is hung on the lower surface. The water guiding cloth bundle 64 passes through the space between the lower part of the water collecting device 6 and the water tank 7 and hangs down to the bottom of the inflow tank 74. Accordingly, the clay in the inflow portion is always wet by the water retention of the water guiding cloth bundle 64, and compaction can be prevented.
The water passing through the treated soil 4 has a water flow rate of 20 mm / hour per hour when the amount of water sprayed is 500 liters / m ² · day of continuous water per day, and the soil particles of the treated soil 4 The speed is not such that it falls with the water being passed.
The main purpose is to prevent the soil particles falling when initially placed in the storage frame 2 from being mixed into the lower water tank 7.
Further, the treated water dripped onto the water collecting device 6 at a water flow rate of 20 mm / hour per hour wets the non-woven fabric 62 of the water collecting device 6, but in the perforated pipe 61 which is an inner cylinder covered with the non-woven fabric 62. No water can penetrate. Therefore, if the pipe nozzles 65a and 65b are provided at both ends of the perforated pipe 61, and the pressurized air is supplied from one pipe nozzle 65a by the pressure air valve 66, the upper part of the nonwoven fabric 62 is in a dry state and the lower part is in a wet state. Since it is not consolidated by the support material 22 arranged horizontally immediately above, the air can blow away and remove the soil particles accumulated above.
Further, if a methanol dilution liquid that is an organic carbon source necessary for denitrification is injected from one pipe nozzle 65b by a methanol injection valve 67, methanol is passed from the hole 61a of the perforated pipe 61 through the lower wet nonwoven fabric 62. The dilution liquid is well mixed with the treated water and can be sent to the inflow tank 71.

The denitrification tank 72 partitioned by the partition plates 74 and 75 is filled with the water retaining material 8 shown in FIG. The water retaining material 8 is charged with a crushed stone or the like serving as a weight 83 in a net-like short tube 81 and the outer surface is covered with a nonwoven fabric 82. The denitrification tank 72 is charged with clay so that the SV is 50 to 70%. Clay is a variety of particles with different particle sizes and specific gravities, and if they are not stirred, they deposit on the bottom and become consolidated. By holding the water in the clay layer, the water retaining material 8 can prevent the water in the lower layer of the deposited layer from being removed and being consolidated as seen in the consolidation phenomenon.
Due to the wet water retaining material 8, the clay in the denitrification tank 72 is not consolidated.

The wedge material 5 is formed by hierarchically inserting a plurality of thin flat plates 52 so as to extend radially in the horizontal direction around a vertically placed mesh tube 51. The flat plate 52 is inserted through at least the positions of the upper surface and the lower surface of the mesh tube 51, but the number of sheets to be used is not particularly limited.
As shown in FIGS. 4 and 5, the wedge member 5 is installed such that the mesh tube 51 is vertical and the flat surface of the flat plate 52 is parallel to the horizontal plane, whereby the flat plate 52 becomes an anchor in the soil, and the flat plate 52 has a horizontal surface. Due to the upper area, pressure from above is dispersed and consolidation is prevented. Since the earth pressure from the upper side is reduced, the lower part of the flat plate 52 becomes soft soil (treated soil 4a with reduced consolidation) sufficiently containing air. Therefore, the lower part of the flat plate 52 also becomes a place where aerobic bacteria gather.
Further, since the mesh tube 51 in the center is a mesh-like hollow tube, it becomes a passage for air and water moving in the soil, and moderate moisture and oxygen are in the soil to the bacteria attached to the soil particles. Is supplied by diffusing.
The upper and lower surfaces of the mesh tube 51 of the wedge material 5 arranged horizontally are flat plates 52 that radially intersect so as to penetrate through the tube, and serve as a stopper. In the central cavity formed between the upper and lower surfaces, , The soil does not fall. On the side surface of the mesh tube 51, since the soil particles are subjected to earth pressure in the vertical direction, the soil particles do not enter from the mesh of the mesh tube 51, and the cavity is maintained.

As shown in FIG. 9, the wedge material 5 installed in the treated soil 4 is placed on the side of the treated soil 4 in a focused manner. Horizontally flat plates are partially overlapped and arranged in the vertical direction at intervals of about half the length of the flat plate 52. Since the horizontally arranged flat plates 52 of the wedge members 5 are overlapped, the earth pressure is received as a whole, and the collapse of the side soil of the treated soil 4 in the housing frame 2 can be prevented.
In addition, when the wedge material 5 is installed in the treated soil 4, a removable plate is attached to the side surface of the storage frame 4, and the soil 4 to be introduced into the side surface is compacted to some extent while applying initial pressure to the wedge material. 5 and the treated soil 4 are entangled and integrated. After the application of the initial pressure to the predetermined treated soil 4 and the wedge material 5 is completed, the outer frame plate is removed.
Since the mesh tube 51 is embedded in the treated soil 4 and disposed near the side surface, air is easily taken in from the side surface. Moreover, the mesh pipe | tube 51 is arrange | positioned also in the cross-sectional center part of the process soil 4, and water flow and ventilation | gas_flowing are ensured.

The water sprinkling device 3 is a device that pours sewage, and, as shown in FIG. 2, includes a water blocking plate 32 that surrounds a irrigation pipe 31 that pours sewage.
Water injection is performed from the water injection port 31a at the upper part of the net-like water injection pipes 31 arranged in two rows from the top of the treated soil 4 to a depth of about 10 to 20 cm on the surface layer. In addition, a plurality of water inlets 31a are arranged so as to penetrate into the treated soil 4 uniformly. Inject water continuously.
The treated soil 4 on the surface layer, in particular, the vicinity of the corner portion of the storage frame 2 is not softened by earth pressure, and therefore is relatively soft soil. May leak. A water shielding plate 32 having a depth greater than that of the water injection pipe 31 is inserted around the water injection port 31a to prevent this. If a plurality of water blocking plates 32 are installed, the water blocking effect is improved.
The sewage poured into the water injection pipe 31 penetrates downward from the inner side surface of the water injection pipe 31 and is collected in the lower part through the gap portion of the wedge material 5 and the like.

As shown in FIG. 10, a water collection device 6 for preventing water collection and the fall of soil particles is provided in the lower part of the treated soil 4 surrounded by the storage frame 2. As shown in FIG. 6, the water collecting device 6 is a perforated tube 61 made of plastic or the like and attaches a non-woven fabric 62 processed into a lantern shape to the outer surface. The perforated tube 61 is a hollow cylinder having a hole 61a on the outer peripheral surface. Further, as shown in FIG. 7, the nonwoven fabric 62 is formed by shrinking the nonwoven fabric 62 into a butterfly shape. The purpose of making the non-woven fabric 62 into a lantern is to increase the contact area of the non-woven fabric 62 and the treated water that falls, and to reduce clogging when falling soil particles accumulate on the non-woven fabric 62. Since the flow rate of the sewage to the treated soil 4 is an average speed of 10 to 20 mm per hour, the SS concentration of the treated water is 5 mg / L or less, and the soil particles fall along with the treated water. This is not the case, but it is made to correspond to the case where fine particles are accompanied with the treated water in the initial stage. The upper part of the nonwoven fabric 62 is crushed due to the accumulation of soil particles.
The treated water travels through the nonwoven fabric 62 and is collected on the lower surface. A water collecting cloth 63 made of the non-woven cloth 62 is provided on the lower surface of the non-woven cloth 62, and a thin water bunch bundle 64 made of cotton cloth or the like that becomes a water guiding cloth is further hung from the water collecting cloth 63, as shown in FIG. Water is introduced to the water tank 7 which is a denitrification part at the bottom. The purpose of conducting the water with the baffle bundle 64 is to allow the treated water to flow into the denitrification tank 72 from below the inflow tank 71 in the water tank 7 which is a denitrification section, so that the treatment can be performed in an upward flow.
In order to prevent the fall of soil particles and reduce the earth pressure immediately above the water collecting device 6, a horizontal support material 22 is installed in the housing frame 2 on the plane of FIG. 3 (ii ′).

  Both ends of the perforated pipe 61 serving as a water collecting device are shielded by plates 61b, and pipe nozzles 65a and 65b, a pressure air valve 66, and a methanol injection valve 67 are provided. The pipe nozzles 65 a and 65 b connect the hollow portion of the perforated pipe 61 and the pressure air valve 66 or the methanol injection valve 67. The methanol injection valve 67 injects a methanol diluent for denitrification, leaches the methanol diluent from the hole 61 a of the perforated tube 61, and feeds it through the nonwoven fabric 62 to the water tank 7 together with the treated water. From one pressure air valve 66, fine particles irregularly deposited on the upper surface of the nonwoven fabric 62 are removed from the blower brought in from the outside with pressure air. The blower is not installed as a device.

The treated water is led from the water collecting cloth 63 of the water collecting apparatus 6 to the denitrification part at the lowermost layer of the storage frame 4 by the water guiding cloth bundle 64 which is a thin cloth bundle. The denitrification part is a water tank 7 surrounded by a side plate and a bottom plate.
As shown in FIG. 1, a partition plate 74 having a lower opening is provided at the inlet of the denitrification tank 72, and nitrified sewage is supplied from the lower part of the inflow tank 71. The outlet of the denitrification tank 72 is provided with a partition plate 75 in the direction opposite to the inlet side, and overflows from the upper part of the partition plate to the adjacent treatment water tank 73 and flows in. The reason for the overflow is that nitrogen gas generated by denitrification may adhere to soil particles in water and generate scum, and the purpose is to discharge this scum.
From the adjacent treated water tank 73, the water is drained out of the system by the submersible pump 76.

The denitrification tank 72 is charged with clay as SV (Slidege Volume) so as to be about 50 to 70%.
The clay to be added is obtained from easily available soil and is not special, so its particles are various. Coarse particles and particles with a high specific gravity are deposited and consolidated in the denitrification tank 72 as they are. In order to prevent this, the denitrification tank 7 is filled with a water retention material 8.

  As shown in FIG. 8, the water retaining material 8 uses a net-like short tube 81 similar to the mesh tube 51 used for the wedge material 5 and wrapped with a plurality of nonwoven fabrics 82. In order to lay this over the entire surface of the denitrification tank 72, a heavy weight 83 such as crushed stone is placed in the reticulated short pipe 81 so as not to rise. Consolidation occurs because water is removed from the bottom when soil particles are deposited. Therefore, if water is always contained in the nonwoven fabric 82, consolidation can be prevented and the denitrification tank 72 flows. Can be kept in the clay solution.

Since the denitrifying bacteria are attached to the clay particles, the nitrate nitrogen is reduced during the upward flow from the denitrification tank 72 inlet to the denitrification tank 72 outlet. In addition, the organic carbon source required by the denitrifying bacteria that are other vegetative bacteria is in a well-mixed state along with the nitrified treated water by injecting a methanol diluent into the perforated tube 61 from the methanol injection valve 67. It is supplied to the denitrification tank 72.
The amount of methanol to be injected is measured by measuring the residual nitric acid concentration in the treated water tank 73, grasping the required amount, and adjusting the amount of injection.
For the methanol dilution, install a dedicated tank outside and feed a fixed amount with a metering pump. Denitrified treated water may be used for dilution of methanol.

  The soil denitrification treatment apparatus 1 of the present invention in which the treated soil 4, the water spray device 3, the wedge material 5, the water collection device 6, the water retention material 8, clay, etc. are installed in the storage frame 2 and the denitrification tank 72 is shown in FIG. Thus, it becomes one unit. FIG. 10 shows a completed unit in which the treated soil 4 is packed. The side surface where the treated soil 4 is packed is exposed, and the wedge material 5 is embedded, so that the treated soil 4 does not collapse from the opening that is largely open to the side surface. Five of the side surfaces become surface soil and receive supply of air from the atmosphere. With respect to the nitrification ability by natural soil, in terms of area, the four sides are the ability to be the surface layer.

If the area of the unit is 1.5 m × 3.0 m, a processing capacity of about 2 m ³ / day per day is obtained. If a processing capacity of 10 m ³ / day per day is required, water will flow through 5 units simultaneously. Although six units are shown in FIG. 11, the main body that performs the denitrification treatment of sewage is natural soil. In these devices that use natural soil artificially, it is necessary to maintain an ecosystem that becomes a food chain of microorganisms in the soil. For this reason, one of the units needs to be operated by a method of pausing for a certain period as a spare.

Between the six units arranged in FIG. 11, as shown in FIGS. 9 and 10, gaps are provided in four directions with the width of the treated water tank protruding from the storage frame at the upper part of the treated water tank 73. This gap is a work area for attaching and removing the side plate for initial rolling when the initial soil is put into the processing frame, and becomes a space for exposing the side surface to the atmosphere after removing the side plate.
Since the lower part of the soil denitrification treatment apparatus 1 composed of a plurality of units is the water tank 7 of the inflow tank 71, the denitrification tank 72, and the treatment water tank 73, the treated water penetrates into the basement like an existing soil treatment apparatus. Since there is no leakage from the unit, it can be installed on the ground or buried underground.

Soil denitrification equipment storage frame overview Cross section of soil denitrification equipment Plan view of each stage of soil denitrification equipment Wedge material perspective view Plan view and cross-sectional view when installing wedge material (A) is a sectional view from the side of the water collecting device, (B) is a sectional view from the front of the water collecting device. Perspective view showing the formation of a lantern-shaped nonwoven fabric Side view of water retaining material Soil denitrification equipment internal parts assembly perspective view Soil denitrification equipment assembly perspective view after loading the soil The perspective view which shows the state which installed the several soil denitrification processing apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Soil denitrification processing device, 2 ... Housing frame, 21 ... Support material, 3 ... Sprinkling device, 31 ... Water injection pipe, 31a ... Water injection port, 32 ... Sha Water plate, 4 ... treated soil, 4a ... treated soil with reduced consolidation, 5 ... wedge material, 51 ... mesh tube, 52 ... flat plate, 6 ... water collecting device, 61 ... perforated tube, 61a ... hole, 61b ... plate, 62 ... non-woven fabric, 62a ... non-woven fabric crushed by the accumulation of soil particles, 63 ... water collecting cloth, 64 ... Water guide cloth bundle, 65a ... Nozzle for pipe, 65b ... Nozzle for pipe, 66 ... Pressure air valve, 67 ... Methanol injection valve, 7 ... Water tank, 71 ... Inflow tank 72 ... Denitrification tank, 73 ... Treated water tank, 74 ... Partition plate, 75 ... Partition plate, 76 ... Submersible pump 8 ... water-retaining material, the short tube 81 ... network, 82 ... nonwoven fabric, 83 ... weight

Claims (4)

The sandy soil or Ranaru treated soil contained within a frame side is opened, radial collapse and preventing the side, water-permeable, to enhance breathability, a flat plate as a ground anchor to the short tube of the mesh The supporting member fixed horizontally in the horizontal direction is embedded in the side surface of the treated soil horizontally and embedded in a plurality of stages, thereby exposing the side surface to the atmosphere and further receiving the earth pressure from the whole treated soil. the accommodating frame having a bottom by Rukoto stacked in a plurality of stages in the vertical direction increases the nitrification capacity of the treated soil and placed denitrification tank was charged clay directly below the housing frame and ammonium nitrogen in wastewater A soil denitrification treatment apparatus characterized in that it is a unit type that performs a series of treatment in the vertical direction from nitrification to denitrification. In order to prevent the treated soil from falling and to obtain uniform water flow, a water collecting pipe covered with a non-woven fabric is arranged over the entire bottom layer of the multi-stage storage frame. The soil denitrification treatment apparatus according to claim 1, further comprising a water baffle bundle for feeding treated water dripped from the nonwoven fabric of the water pipe to the denitrification tank.   The uppermost layer of the housing frame has a plurality of water spraying devices in which a plurality of net-like tubes are embedded in the treated soil, and a water blocking plate for preventing water leakage to the side surface is embedded around the periphery. The soil denitrification apparatus according to claim 1. In the denitrification tank, the outer surface of a net-like tube containing a weight of crushed stone or the like was covered with a non-woven fabric in order to prevent the clay for retaining the denitrifying bacteria from consolidating to the bottom. Fill the entire surface of the tank with water-retaining material, and also provide partition plates for the inflow and drainage parts, and provide an opening in the lower part of the inflow part partition plate, so that drainage flows upward from the upper part of the partition plate. The soil denitrification apparatus according to claim 1 , wherein the clay in the denitrification tank is fluidized and agitation or the like is not required, so that there is no solid-liquid separation in the precipitation tank .