JPH05293483A - Septic tank for sewage - Google Patents

Abstract

PURPOSE:To easily control the flow rate of an object liquid of treatment to be sent back to an anaerobic filtration bed, carry out stable biological treatment, and carry out the overhauling of a tank easily by installing an obstacle which cushions the impact of the liquid rising together with bubbles in the upper side of an air lift pipe. CONSTITUTION:A septic tank for sewage is composed by setting a contact aeration tank E downstream an anaerobic filtration bed tank N and a returning route Ap to send back the liquid in the tank from the lower part of the contact aeration tank E to the anaerobic filtration bed tank N wherein the returning route Ap is composed of an air lift pipe Aa and a returning route Ap which communicates with the air lift pipe Aa to lead the liquid in the tank to the anaerobic filtration bed tank N. In the upper part of the air lift pipe Aa, an obstacle 1 to cushion the impact of the liquid rising together with bubbles is installed. Consequently, the bubbles are dispersed as small bubbles and following it, unevenness of flow speed of the object liquid of treatment is eliminated and intermittent jetting to the upper side is suppressed. As a result, the water level at the upper part of the air lift pipe Aa is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a contact aeration tank downstream of an anaerobic filter bed tank, and provides a return path for returning the liquid in the tank from the lower part of the contact aeration tank to the anaerobic filter bed tank. The present invention relates to a septic tank including an air lift pipe and a return pipe connected to the upper part of the air lift pipe so as to guide the liquid in the tank to the anaerobic filter bed tank.

[0002]

2. Description of the Related Art Conventionally, a septic tank of this type
Biological treatment is carried out while naturally advancing from the anaerobic filter bed tank to the contact aeration tank, and a part of the liquid to be treated in the contact aeration tank is returned to the anaerobic filter bed tank via the return path to remove the sludge. In addition to circulating treatment of nitric acid and nitrification liquid, a settling tank is installed downstream of the contact aeration tank, and the solid content is allowed to settle in this settling tank. Was becoming.

The return path makes an air lift pipe rise from the bottom of the contact aeration tank, and forms an opening at the lower end of the air lift pipe for taking in the liquid in the tank,
An air supply pipe from an air supply device is connected in communication near the lower end, an open box is connected to the upper end of the air lift pipe, and excess water overflows from one end of the box into a contact aeration tank. A return pipe was provided for returning by allowing the return, and a return pipe for guiding the in-tank liquid to the anaerobic filter tank was connected to the other end of the box.

[0004]

However, in the above-mentioned configuration, the water level in the air lift pipe changes due to the air bubbles blown into the air lift pipe, and when the water level changes, the water pressure at the air supply pipe connection position has an effect. Fluctuations in the flow rate of the liquid to be treated that is returned to the anaerobic filter bed tank and the liquid to be treated that is returned to the contact aeration tank. Is large and it is difficult to adjust the flow rate of the liquid to be treated returned to the anaerobic filter bed tank. However, for example, when the flow rate of the liquid to be treated returned to the anaerobic filter bed tank is small, the amount of nitrifying solution and the amount of peeled sludge returned to the anaerobic filter bed tank are small, and the amount of oxygen to be returned is also small. The denitrification treatment for decomposing the nitrification solution proceeds, but the amount of denitrification treatment is insufficient and the concentration of sludge in the contact aeration tank tends to increase. Further, if the flow rate of the liquid to be treated returned to the anaerobic filter bed tank becomes too large, the amount of oxygen returned to the inside of the anaerobic filter bed tank also becomes large, and it becomes difficult to proceed with the anaerobic treatment or denitrification treatment itself. That is, the conventional septic tank has a drawback that it is difficult to perform the above-mentioned stable biological treatment. Therefore, an object of the present invention is to easily adjust the flow rate of the liquid to be treated returned to the anaerobic filter bed tank through the return passage,
It is to provide a septic tank that is easy to perform stable biological treatment.

[0005]

To achieve this object, a septic tank according to the present invention is characterized in that a contact aeration tank is provided downstream of an anaerobic filter bed tank, and a liquid inside the tank is introduced from the lower part of the contact aeration tank. In the septic tank comprising a return passage for returning the anaerobic filter bed tank to the anaerobic filter bed tank by communicating with an air lift tube and an upper part of the air lift tube. The upper part of the air lift pipe is provided with an obstacle for alleviating the impact of the liquid rising together with the bubbles, and the function and effect thereof are as follows.

[0006]

With the supply of air from the lower part of the air lift pipe, the liquid to be treated, which rises in the pipe together with the air bubbles, collides with an obstacle provided on the upper part of the air lift pipe, whereby the air bubbles become small bubbles. It is finely dispersed, and accordingly, the flow velocity of the liquid to be treated is eliminated, and intermittent ejection to the upper part is suppressed. As a result, the water level above the air lift pipe is stabilized.

[0007]

Therefore, the flow rate of the liquid to be treated returned to the anaerobic filter bed tank can be easily adjusted, and stable biological treatment can be easily performed. It is also easy to inspect the inside of the tank.

[0008]

EXAMPLES Examples of the present invention will be described below. As shown in FIG. 1, from the upstream side, an anaerobic filter bed tank N composed of an anaerobic filter bed tank first chamber N1 and an anaerobic filter bed tank second chamber N2, a contact aeration tank E, and a precipitation tank P are treated liquids to be treated. The septic tank is configured so as to flow in this order by natural advection.

The anaerobic filter bed tank N is provided with filter beds F1 and F2 for growing anaerobic microorganisms that anaerobically decompose organic substances in the water to be treated and fixing their biofilms. The contact aeration tank E is provided with a contact material C for fixing aerobic microorganisms that decompose organic matters remaining in the water to be treated and nitrify ammoniacal nitrogen, and generate a circulating flow of the water to be treated in the tank. At last, the aerobic microorganisms fixed on the contact material C are provided with an air diffuser D for well contacting the water to be treated containing the organic matter with the aerobic microorganisms and supplying the air that gives oxygen necessary for the aerobic microorganisms. .. Further, in order to prevent clogging due to excessive adhesion of biofilm or the like to the contact material C, a backwash pipe R for bubbling air to remove excess biofilm or the like as separation sludge is used as the contact material. It is provided below C, and the suspended sludge and BO in the contact aeration tank E are contacted by the above-mentioned sludge sludge.
In order to prevent the amount of D from increasing too much, the return passage A for returning the separated sludge to the anaerobic filter bed first chamber N1 is connected to the air lift pipe Aa and the upper part of the air lift pipe Aa so as to communicate with the liquid in the tank. Is provided with a return pipe Ap leading to the anaerobic filter bed tank N.

As shown in FIGS. 1 and 2, the air lift pipe Aa rises vertically from the bottom of the contact aeration tank E, and an opening Ai for taking in the liquid in the tank to the lower end of the air lift pipe Aa. And an air supply pipe S from an air supply device is communicatively connected near the lower end, an air lift pipe expanded portion A1 is formed above the air lift pipe Aa via a taper portion At, and the return is performed. The return pipe expanded portion A2 is also formed in the pipe, and the return pipe expanded portion A2 is connected to the air lift pipe expanded portion A1.

The air lift pipe expanded portion A1 is open to the upper portion, but a lid or the like having an air vent hole may be provided. A float 1 having a specific gravity of about 1.5 formed in a short cylindrical shape is provided as an obstacle for relaxing the impact of the liquid to be treated rising together with the air bubbles and reducing the fluctuation of the water level in the expanded diameter portion A1 of the air lift pipe. There is. The diameter of the float 1 is larger than the diameter of the lower part of the taper portion At of the air lift pipe and smaller than the diameter of the air lift pipe expanded portion A1, and the float 1 is pushed up by the upward flow of the liquid to be treated. The liquid to be treated is allowed to escape to the upper part through the gap around the. A notch 3 for returning surplus water to the contact aeration tank E is formed in the expanded diameter portion A2 of the return pipe, and only the liquid to be treated having a small amount of bubbles is allowed to pass through on the upstream side thereof to reduce the ripple of the liquid surface. A baffle plate 4 having an opening formed in the lower portion is provided, and an obstruction formed in the lower portion at the downstream side of the cutout portion 3 for allowing the liquid to be processed to pass therethrough with a small change in the transfer liquid amount. A plate 5 is provided.

The liquid to be treated from the contact aeration tank E is transferred from the bottom to the settling tank P, and the supernatant liquid of the settling tank P overflows and is guided to the disinfecting tank Q, where it is treated as a solid disinfectant. Each tank is formed so as to be discharged from the discharge port Z after being contacted and disinfected.

With the above structure, the flow rate of the liquid to be treated returned to the anaerobic filter bed N1 becomes stable and the flow rate can be easily adjusted, so that stable biological treatment can be performed.

[Other Embodiments] Obstacles for mitigating the impact of the liquid to be treated rising in the air lift pipe together with the bubbles to suppress the fluctuation of the water level are truncated cones, cylindrical caps,
A float having a shape other than the above-mentioned cylindrical shape may be used, such as a spherical shape or one in which a plurality of vertically running grooves are formed on the side surface of a truncated cone. Alternatively, a disk-shaped obstacle having a large number of holes in a lattice shape or a honeycomb shape may be fixedly provided in the air-lift pipe expanded portion or in the vicinity thereof. Alternatively, for example, a net may be formed below the expanded diameter portion of the air lift pipe, and a filling layer of pebbles or the like may be provided on the net.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a septic tank according to the present invention.

FIG. 2 is a vertical cross-sectional view of the main part of the return path.

[Explanation of symbols]

 E Contact aeration tank N Anaerobic filter bed tank A Return path Aa Air lift tube Ap Return tube 1 Obstacle

Front Page Continuation (72) Inventor Kazuyuki Honda, 1 Takamatsu, Kosai-cho, Koga-gun, Shiga Prefecture 1 Stock company, Kubota Plant (72) Inventor Katsumi Hamada, 1-share, Takamatsu, Koga-gun, Shiga Prefecture Kubota Company, Ltd. Inside the Shiga factory

Claims (1)

[Claims] 1. A contact aeration tank (E) is provided downstream of the anaerobic filter bed tank (N), and the liquid in the tank is returned to the anaerobic filter bed tank (N) from the contact aeration tank (E). The air return pipe (A) is connected to the air lift pipe (Aa) and the upper part of the air lift pipe (Aa) so that the liquid in the tank is guided to the anaerobic filter bed tank (N) (Ap). A septic tank provided with an obstacle (1) on the upper part of the air lift pipe (Aa) for absorbing the impact of the liquid rising together with the bubbles.