JP3105519B2 - Sewage denitrification equipment - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a denitrification apparatus used for sewage treatment, and more particularly to a denitrification apparatus suitable for denitrification treatment of primary treatment water of domestic sewage.

[Prior art] Sewage contains various nitrogen compounds mainly composed of organic nitrogen and ammonia nitrogen. These nitrogen compounds cause eutrophication of rivers and lakes, and therefore need to be removed. is there.

Methods for removing nitrogen in sewage include (1) selective physicochemical treatment methods such as ammonia stripping method and ion exchange method, (2) biochemical treatment methods such as biological denitrification method, 3) A general physicochemical treatment such as a reverse osmosis method and an electrodialysis method has been proposed. Of these, the physicochemical treatment method of (3) is expensive, and the physicochemical treatment method of (1) is
Both are aimed at removing ammoniacal nitrogen,
Organic nitrogen can hardly be removed. On the contrary,
The biochemical treatment method (2), particularly the biological denitrification method,
Since organic nitrogen can be removed together with ammonia nitrogen,
In recent years, it has come into practical use in the field of various domestic wastewater treatments.

Biological denitrification involves the ultimate conversion of nitrogen compounds into nitrogen gas, utilizing microorganisms that live in nature and are involved in the nitrogen cycle. In this method, the reaction tank is divided into a nitrification tank and a denitrification tank, and organic nitrogen is oxidized to ammonia nitrogen by BOD oxidizing bacteria in the nitrification tank, and then nitrite is oxidized by obligately aerobic nitrite or nitrite. After being oxidized to nitrate nitrogen, nitrite and nitrate nitrogen are reduced with a anaerobic anaerobic denitrifying bacterium in a denitrification tank to form nitrogen gas, which is released into the atmosphere. At this time, a large amount of alkali for pH adjustment is required in the nitrification tank, and methanol is required in the denitrification tank. Therefore, in consideration of economy, the first and second denitrification tanks and the second denitrification tank are placed before and after the nitrification tank. And a method of circulating nitrification has also been proposed.

[Problems to be Solved by the Invention] However, the conventional biological denitrification method as described above has the following problems.

(1) Driving operation becomes very complicated.

(2) A vast site is required to install the processing equipment.

(3) The construction cost of the processing equipment is high.

(4) Sludge treatment is required and management is complicated.

(5) Addition of methanol causes a problem of toxicity.

(6) At low temperatures, processing efficiency decreases.

Therefore, the management becomes complicated and requires advanced management techniques, and although it is suitable for use in large-scale urine purification plants with skilled and dedicated managers, it is suitable for households, stores, public facilities, etc. Small-scale use in human waste septic tanks was not possible.

An object of the present invention is to solve the problems of the prior art,
Taking advantage of the superior features of biological denitrification, it is easy to operate, does not require special management, requires a small footprint, is low-cost, has no toxicity problems, and is less susceptible to cold and heat Another object of the present invention is to provide a denitrification apparatus suitable for small-scale sewage treatment.

[Means for Solving the Problems] The inventor of the present invention has conducted research on a sewage treatment system for many years, and as a result, buried a collecting pipe in a permeable soil, and obtained a BOD concentration from a treated water infiltration member provided above the collecting pipe. When the treated water is supplied into the soil and the treated water is infiltrated into the soil, a hydrodynamic gradient line is formed radially on the left and right of the collecting pipe, with oxidation above the gradient line and reduction on the lower side. It was found that the denitrification of the primary treated water was performed very efficiently, and the present invention was completed.

That is, according to the present invention, a space having a width of 60 cm to 4 m having an open upper portion is formed in the soil by the water-impermeable member, the space is filled with air-permeable soil, and a water collecting pipe is laid at the bottom. At the same time, a treated water infiltration member is provided above the water collection pipe, and an embankment is provided above the space over the outside of the impermeable member, and the sewage treated water supplied to the treated water infiltration member is supplied into the air permeable soil. A denitrification apparatus for sewage, characterized in that the sewage is denitrified by infiltrating into a wastewater and then discharged from the water collecting pipe.

[Operation] In the apparatus of the present invention, when the treated water is supplied to the treated water infiltrating member, the treated water infiltrates into the soil from the treated water infiltrating member, and as shown in FIG. The hydrodynamic gradient lines A and A ′ are formed. The upper side of this hydrodynamic gradient line becomes a capillary unsaturated water zone, the negative pressure of pore water in the soil is high, aerobic is maintained, nitrogen compounds in treated water are oxidized by aerobic bacteria, nitrite, nitrate Nitrogen. In particular,
The primary treated water supplied from the septic chamber has almost zero dissolved oxygen, but takes in oxygen very efficiently when infiltrating into the soil by siphon phenomenon and unsaturated flow from the treated water infiltration member be able to. Also, it is desirable to use, as the primary treated water, a water having a high BOD concentration and containing a large amount of organic matter which is a feed for soil microorganisms. With these, the respiratory action and metabolic activity of the microorganism can be activated, and the oxidation reaction can be promoted.

On the other hand, the lower side of the hydrodynamic gradient line becomes a capillary saturated water zone, and the negative pressure of pore water in the soil decreases over time, resulting in oxygen deficiency. Therefore, in this zone, nitrite and nitrate nitrogen generated by oxidation in the above-mentioned capillary unsaturated water zone are reduced by the ventilated anaerobic bacteria to become nitrogen gas.

Thus, oxidation and reduction can be performed continuously in one treatment tank.

In addition, in the upper part of the space formed by the impermeable member,
By embankment over the outside of the water-impermeable member, by communicating between the inside and the outside of the water-impermeable member, the inside of the water-impermeable member can be maintained at a negative pressure due to the siphon phenomenon, and is separated by the hydraulic gradient line. It is possible to form a capillary unsaturated water zone and a capillary saturated water zone. When the inside and the outside of the water-impermeable member are not communicated, the inside becomes a positive pressure, the whole inside becomes anaerobic, and it is difficult to form both the capillary unsaturated water zone and the capillary saturated water zone. . The embankment also serves to prevent rainwater from flowing into the apparatus by flowing rainwater as a surface flow.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic vertical sectional view showing an example of a sewage treatment system using the sewage denitrification apparatus of the present invention, and FIG. 2 is a transverse sectional view showing an example of the sewage denitrification apparatus of the present invention. 1 and 2, 1 is a sewage supply pipe, 2 is a first septic chamber,
Reference numeral 3 denotes a second septic chamber, 4 denotes a filtration chamber, 5 denotes a pump, and 6 denotes a pump chamber. Reference numeral 7 denotes a sewage denitrification apparatus of the present invention, which is an impermeable member 8 forming an open space in soil 9, air-permeable soil 10 filled in the space, and laid at the bottom of the space. Water collecting pipe 11, treated water infiltration member also provided above water collecting pipe 11.
12. An embankment 13 is formed on the upper part of the space, outside the water-impermeable member 8, that is, over the soil 9 side. 14 is a drainage storage tank. Note that the discharge end 11a of the water collecting pipe 11 is bent upward so as to have a constant hydrostatic head length in order to maintain predetermined hydraulic gradient lines A and A '.

Examples of the water-impermeable member 8 that forms a space having an open top in the soil 9 include a synthetic resin sheet, fiber-reinforced plastic, and reinforced concrete. The width W of the space formed by the water-impermeable member 8 needs to be 60 cm to 4 m, and particularly preferably 1 m to 3 m. When the width W of the space is out of the above range, the hydraulic gradient line
A and A 'are not formed, and as a result, oxidation and reduction cannot be continuously performed in one treatment tank, and the object of the present invention cannot be achieved.

Examples of the water collecting pipe 11 include a synthetic resin pipe having an appropriate number of water holes or a pipe formed by braiding a synthetic resin monofilament into a tubular shape and having a diameter of 5 to 10 mm and wrapped with a nonwoven fabric. Can be.

Further, the treated water infiltration member 12 may be any member as long as it can infiltrate the treated water into the soil in an unsaturated state, and any structure such as that shown in FIG. 3 is preferable. Used for In the treated water infiltration member 12 shown in FIG. 3, a tubular body 21 made of a water-absorbent sheet is used.
A plurality of wing pieces 22, 2 also made of a water-absorbent sheet on the side of
2 ′ is formed to protrude, and the bristle fibers 2
3, and a water permeable pipe 24 is provided at the center thereof. The outside of the lower surface of the tubular body 21 is covered with an impermeable sheet 25. As the water-absorbing sheet constituting the tubular body 21 and the wing pieces 22, 22 ', a polyester fiber nonwoven fabric having a thickness of about 1 to 10 mm is suitably used.

The embankment 13 provided over the soil 9 outside the water-impermeable member 8 above the space formed by the water-impermeable member 8 may be formed so as to have a thickness of usually 10 cm or more from the surface of the soil 9. In addition, the distance between the water collecting pipe 11 and the treated water infiltrating member 12 is usually sufficient if it is 20 to 30 cm.

Now, domestic sewage supplied via the sewage supply pipe 1 is separated into suspended matter, sediment and supernatant water in the first and second septic chambers 2 and 3, and the supernatant water is filtered out of the filtration chamber 4 And filtered. The high-BOD-concentration primary treated water thus treated is sent to the sewage denitrification device 7 by the pump 5 in the pump chamber 6. That is, the primary treated water is sent to the treated water infiltration member 12 by the pump 5 and is infiltrated into the soil 10 evenly in an unsaturated state.

In the soil 10, as shown in FIG. 2, parabolic hydrodynamic gradient lines A and A 'are formed on the left and right of the water collecting pipe 11, and the upper side of the hydrodynamic gradient lines A and A' is the capillary unsaturated water. It becomes a zone, and the negative pressure of pore water in the soil is high and aerobic is maintained. When the primary treated water with a high BOD concentration infiltrates the soil 10, it efficiently takes in oxygen, and in this zone, active oxidation by aerobic bacteria is performed, and organic and ammoniacal nitrogen in the primary treated water is oxidized. Nitrite and nitrate nitrogen.

The treated water that has been subjected to the oxidation treatment in this manner has a hydrodynamic gradient line A,
Infiltrate into the capillary saturated water zone (anaerobic zone) below A '
Nitrite and nitrate nitrogen generated by oxidation in the capillary unsaturated water zone are reduced by the ventilated anaerobic bacteria to become nitrogen gas.

Thus, the treated water subjected to the denitrification treatment is discharged from the water collecting pipe 11 to the drainage storage tank 14.

In addition, by communicating the inside and the outside of the water-impermeable member 8 with the embankment 13, the inside of the water-impermeable member 8 can be maintained at a negative pressure due to the siphon phenomenon, and separated by the hydrodynamic gradient lines A and A '. It is possible to form a capillary unsaturated water zone and a capillary mismatch water zone, and perform the oxidation treatment and the reduction treatment sequentially, but whether the discharge end 11a of the water collection pipe 11 is rotatable left and right. Alternatively, if the length of the still water is made variable by making it expandable and contractible, the position of the hydraulic gradient lines A and A 'is adjusted by adjusting the negative pressure difference between the inside and the outside of the water-impermeable member 8. This is desirable because it can be controlled to move up and down.

[Effects of the Invention] The effects of the present invention are as follows.

(1) It is possible to denitrify to 20 ppm or less with total nitrogen and 10 ppm or less with nitrate nitrogen, and the water after the denitrification treatment may be discharged into rivers as it is. It can also be used for watering and water.

(2) Since no driving device is used except for the pump for sending the treated water, no special operation is required and the equipment cost is low.

(3) The site for installing the processing equipment is small,
Moreover, since it is buried underground, it can be used for flower beds, vegetable gardens and the like.

(4) Sludge treatment is hardly necessary.

(5) There is no need to add methanol, and no toxicity problem occurs.

(6) Since the soil temperature is stable, it is hardly affected by the temperature.

Therefore, the sewage denitrification apparatus of the present invention is extremely suitable for treatment of domestic sewage such as night soil and gray water in homes, shops, public facilities, and the like, and is a very significant invention in preventing environmental pollution.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an example of a sewage treatment system using the sewage denitrification apparatus of the present invention, FIG. 2 is a transverse sectional view showing an example of the sewage denitrification apparatus of the present invention, and FIG. It is a cross-sectional view which shows an example of the treated water infiltration member used in this invention. 7 … sewage denitrification device 8… impervious member 9… soil 10… permeable soil 11… water collecting pipe 12… treated water infiltration member 13… embankment

Claims (3)

(57) [Claims] 1. A width in which an upper part is opened by a water-impermeable member.
A space of 60 cm to 4 m is formed in the soil, the space is filled with air-permeable soil, a water collection pipe is laid at the bottom, and a treated water infiltration member is provided above the water collection pipe, and the space is provided. In the upper part, embankment is performed over the outside of the water-impermeable member, and the sewage treatment water supplied to the treated water infiltration member is infiltrated into the permeable soil to be denitrified, and then discharged from the water collection pipe. Characterized sewage denitrification equipment. 2. The sewage denitrification apparatus according to claim 1, wherein the treated water infiltrating member is formed by projecting a plurality of wing pieces made of a water-absorbent sheet on a side surface of the tubular body of the water-absorbent sheet. 3. The sewage denitrification device according to claim 1, wherein the length of the hydrostatic head at the discharge end of said water collecting pipe can be changed.