JP6382742B2 - Natural flow sewer pipe - Google Patents

Description

  Embodiments described herein relate generally to a natural flow sewer pipe.

  In the sewage flowing through the pipe of the sewage pipe, two phenomena occur: consumption of dissolved oxygen due to the action of aerobic microorganisms and increase in dissolved oxygen due to dissolution of oxygen from the air into the sewage. Of the two phenomena described above, when the consumption rate of dissolved oxygen exceeds the increase rate, the amount of dissolved oxygen in the sewage decreases (so-called anaerobic progress).

Anaerobic in the pipeline causes, for example, the following problems.
First, sulfate-reducing bacteria present in sewage reduce sulfate ions using organic matter as a hydrogen donor to produce hydrogen sulfide gas in the sewage. When hydrogen sulfide gas is released into the air, it causes a bad odor and the like. Further, when the hydrogen sulfide gas released into the air is oxidized into sulfuric acid by the action of sulfur-oxidizing bacteria, it may cause corrosion of concrete or the like.
Secondly, methane gas is generated in the sewage by the action of the methanogen present in the sewage. Methane gas is sent to a sewage treatment plant in a state dissolved in sewage, and then released to the atmosphere in a sedimentation basin or reaction tank. Since methane gas has a greenhouse effect about 21 times that of carbon dioxide, it is released into the atmosphere, which causes global warming.

By the way, the above-described sewage pipes are roughly classified into a pressure-feed sewage pipe that circulates sewage in the pipe line by a pressure-feed pump and a natural-flow sewage pipe that circulates sewage in the pipe line by its own weight. Among these, the natural flow-down sewage pipe has a gas phase portion in which a gas such as air is present in the pipe line, so that the above-described anaerobic generation is less likely to occur compared to the pressure-feed sewage pipe.
However, even in a natural flow-down sewage pipe, when the length of the pipe to the sewage treatment plant is long, the consumption rate of dissolved oxygen exceeds the increase speed, and anaerobization may progress.

JP 2013-119717 A Japanese Patent Laid-Open No. 9-268636 Japanese Patent Laid-Open No. 9-268637

  The problem to be solved by the present invention is to provide a natural flow-down sewage pipe that can suppress anaerobic formation.

The natural flow type sewer pipe of the embodiment has a pipe line and an overflow dam. Sewage flows through the pipeline. The overflow dam protrudes upward from the inner peripheral surface of the pipe, and causes the sewage to overflow downstream. The surface facing the upstream side of the overflow weir has a guide portion that extends upward as it goes downstream. Concavities and convexities are formed in the guide portion.

Sectional drawing of the sewer pipe in embodiment. II arrow line view of FIG. Sectional drawing of the sewer pipe in the other structure of embodiment.

Hereinafter, a natural flow type sewer pipe (hereinafter, simply referred to as a sewer pipe) of an embodiment will be described with reference to the drawings.
As shown in FIG. 1, the sewage pipe 1 is embedded in the ground or the like and constitutes a part of a sewage pipe network 10 that connects, for example, between adjacent relay pump stations or between a relay pump station and a sewage treatment plant. . The sewage pipe 1 of this embodiment is installed in the downward slope part extended toward the downstream from the upstream in the distribution direction of the sewage W among the sewage pipe networks 10, and distribute | circulates the sewage W with dead weight.

  As shown in FIGS. 1 and 2, the sewage pipe 1 includes a pipeline 11 through which sewage W such as rainwater and sewage flows. The pipe line 11 has a cylindrical shape made of concrete, hard vinyl chloride, or the like, and sewage W flows along the axial direction thereof. A plurality of pipe lines 11 are connected via unillustrated joints to constitute the above-described sewer network 10.

  The diameter of the pipe line 11 is designed so that the maximum sewage flow rate can flow in a full pipe. Therefore, in a normal state, the space located above the liquid level of the sewage W in the pipe line 11 becomes the gas phase part 12 where a gas such as air exists. For example, the pipe 11 has a diameter of about 1000 mm to 3000 mm and a length of about 2.4 m when made of concrete, and has a diameter of about 100 mm to 1000 mm and a length of 4 when made of hard vinyl chloride. About 0.0m.

  On the inner peripheral surface of the pipeline 11, an overflow weir 21 is provided projecting upward so that the sewage W overflows toward the downstream side. The overflow weir 21 has a semicircular shape covering the lower half of the pipeline 11 in a front view as viewed from the flow direction, and is integrally formed with the pipeline 11. Further, as shown in FIG. 1, the overflow weir 21 has a triangular shape in a longitudinal sectional view along the flow direction. Specifically, the overflow weir 21 includes a downstream end surface 22 facing the downstream side, an upstream end surface 23 facing the upstream side, and a top portion 24 connecting the upper end portions of the downstream end surface 22 and the upstream end surface 23. ,have.

  The downstream end surface 22 rises perpendicularly from the inner peripheral surface of the conduit 11 toward the top 24 of the overflow weir 21 with respect to the inner peripheral surface of the conduit 11. That is, the downstream end face 22 extends perpendicular to the flow direction of the sewage W.

The upstream end surface 23 includes a guide portion 31 that extends upward as it goes downstream, and a connection portion 32 that connects the guide portion 31 and the top portion 24 of the overflow weir 21.
The guide portion 31 is an inclined surface that extends with an inclination to the inner peripheral surface of the pipe line 11. In the illustrated example, the height at the downstream end of the guide portion 31 is about half of the height of the overflow weir 21 (top 24). Note that the design of the gradient of the guide portion 31 can be changed as appropriate.
The connecting portion 32 extends perpendicularly to the inner peripheral surface of the pipe line 11 from the downstream end portion of the guide portion 31 toward the top portion 24.

In the sewage pipe 1 described above, the sewage W circulates in the pipe line 11 toward the downstream side by its own weight and reaches the overflow weir 21. The sewage W is blocked when the water level is lower than the height of the overflow weir 21 (the distance from the inner peripheral surface of the conduit 11 to the top 24), and the water level is set to the height of the overflow weir 21. When it reaches, it passes over the overflow weir 21 and circulates in the pipeline 11 toward the downstream side.
Here, in the process in which the sewage W gets over the overflow weir 21, the sewage W and the air are agitated and the sewage W is aerated by entraining the air in the gas phase portion 12. Thereby, the oxygen melt | dissolution from the gaseous-phase part 12 in the sewage W is accelerated | stimulated, and anaerobic is suppressed. As a result, generation of hydrogen sulfide gas and generation of methane gas can be suppressed.

As described above, in the present embodiment, by providing the overflow weir 21 in the pipe line 11, the sewage W can be aerated when the sewage W gets over the overflow weir 21. In this case, since a part of the sewage pipe network 10 is replaced with the sewage pipe 1 of the present embodiment, anaerobic generation can be suppressed, so that cost reduction and energy saving can be achieved as compared with the case where power such as an aeration pump is used. Can do.
In particular, in this embodiment, since the guide portion 31 is formed on the upstream end face 23 of the overflow weir 21, it becomes easy to guide the sewage W toward the top 24 of the overflow weir 21. Therefore, it can suppress that solid (for example, a fallen leaf, a piece of wood, etc.) stays in the upstream of overflow overflow weir 21. On the other hand, since the downstream end face 22 of the overflow weir 21 is formed perpendicular to the inner peripheral surface of the pipe line 11, it is possible to ensure a difference in height when the sewage W crosses the overflow weir 21, effectively Aeration is possible.

  In the above-described embodiment, the configuration in which the top portion 24 and the guide portion 31 are connected by the connection portion 32 on the upstream end surface 23 of the overflow weir 21 has been described, but the configuration is not limited thereto. For example, as shown in FIG. 3, the guide portion 31 may be formed so as to be continuous with the top portion 24 of the overflow weir 21. In this case, since the entire upstream end surface 23 of the overflow weir 21 is configured by an inclined surface, no step is formed between the top 24 of the overflow weir 21 and the guide portion 31. Therefore, it is possible to reliably suppress the retention of the solid on the upstream side of the overflow weir 21.

In the above-described embodiment, the configuration in which the guide portion 31 is formed on the inclined surface has been described, but the configuration is not limited thereto. For example, it may be formed in a staircase shape or the like that gradually rises upward as it goes downstream.
In the embodiment described above, the case where one overflow dam 21 is formed in the pipe line 11 is described. However, the present invention is not limited to this, and a plurality of overflow dams 21 may be formed at intervals in the flow direction. Absent.
In the above-described embodiment, the configuration in which the pipe line 11 and the overflow weir 21 are integrally formed has been described. However, the present invention is not limited thereto, and the pipe line 11 and the overflow weir 21 may be formed separately. .

  In addition, a configuration in which unevenness (dimple) is formed on the guide portion 31 may be adopted. In this case, in the process in which the sewage W circulates on the guide portion 31, the sewage W is aerated by disturbing the flow of the sewage W, so that anaerobic generation can be more reliably suppressed.

Further, in the above-described embodiment, the configuration in which the pipe line 11 extends downward as it goes downstream is not limited to this. If the sewage W is configured to flow by its own weight, the extending direction of the pipe line 11 can be appropriately changed in design.
Further, in the above-described embodiment, the overflow weir 21 (downstream end face 22 and connecting portion 32) is perpendicular to the inner peripheral surface of the pipe line 11 in the pipe line 11 that extends downward toward the downstream side. Although the extended structure was demonstrated, it is not restricted to this. For example, in the pipe line 11 that extends downward as it goes downstream, the overflow weir 21 may extend along the direction of gravity. In other words, the overflow weir 21 may be configured to extend upward regardless of the extending direction of the pipeline 11.

According to at least one embodiment described above, the overflow weir is provided so as to project upward from the inner peripheral surface of the pipe, and the surface facing the upstream side of the overflow weir faces the downstream side. Accordingly, the sewage can be aerated when the sewage passes over the overflow weir. In this case, anaerobicization can be suppressed by replacing a part of the sewer network with the sewer pipe of this embodiment, so that cost and energy saving can be achieved as compared with the case where power such as an aeration pump is used. .
In particular, since the guide portion is formed on the upstream end face of the overflow weir, it becomes easy to guide the sewage toward the top of the overflow weir. Therefore, it can suppress that solid (for example, a fallen leaf, a piece of wood, etc.) stays in the upstream of an overflow dam.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Sewage pipe, 11 ... Pipe line, 21 ... Overflow weir, 31 ... Guide part

Claims (2)

A pipeline through which sewage flows,
An overflow weir that protrudes upward from the inner peripheral surface of the pipe and overflows the sewage downstream,
The surface facing the upstream side of the overflow weir has a guide portion that extends upward as it goes downstream ,
The guide part is formed with irregularities,
Natural downflow sewer pipe. The guide portion is connected to the top of the overflow weir,
The natural flow type sewer pipe according to claim 1.

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