JPH08290184A - Septic tank - Google Patents

Abstract

PURPOSE: To provide a septic tank which is a small sized, membrane separation type septic tank and enables advanced treatment of sewage and also, can deal with short time inflow of the sewage. CONSTITUTION: This septic tank has two treating vessel, i.e., an anaerobic filter bed chamber 2 (the first vessel) and an aerobic activated sludge chamber 5 (the second vessel) provided with an air diffusing pipe 8, both of which are separated from each other by a partition wall 10, wherein a part of the treated water from the aerobic activated sludge chamber 5 is returned to the anaerobic filter bed chamber 2 and treated there. The aerobic activated sludge chamber 5 is provided in its inside with a membrane separation device 7 for separating a clarified liquid from the activated sludge liquid and discharging it and separated from the anaerobic chamber 2 by a partition wall 10 through the bottom of which the liquid in the chamber 5 can communicate with the chamber 2. Also, in the activated sludge chamber 5, a settling chamber 6 provided with a return pipe 9 that extends in the upper part of the chamber 5 and is used for returning a supernatant liquid to the anaerobic filter bed chamber 2 is placed. Further, an overflow pipe 4 extending from the lower part of the filter bed 3 of the anaerobic filter bed chamber 2 to the upper part of the aerobic activated sludge chamber 5 is placed so that the level of the outlet of the pipe 4 is equal to that of the suction port of the return pipe 9. Also, the chamber 5 is provided with an emergency outlet 12 at a higher level than that of the suction port of the return pipe 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a septic tank, and more particularly to a small household septic tank for treating sewage discharged from a toilet, washroom, bath, kitchen or the like at home.

[0002]

2. Description of the Related Art Household septic tanks that treat sewage discharged from household toilets, washrooms, baths, kitchens, etc., have traditionally been easy to maintain and maintain a high sludge concentration in the tank. A fixed bed type, which can be relatively small in size, is generally used. Most of the fixed bed type septic tank is composed of an anaerobic filter bed room, an aerobic activated sludge room, a sedimentation room and a disinfection room. Usually, a part of the supernatant water of the precipitation room is returned to the anaerobic filter bed room for treatment. Therefore, it is also called a circulation type.

In this type of septic tank, the organic matter in the wastewater introduced into the anaerobic filter bed is anaerobically decomposed (methane fermentation, etc.).
Receive. Further, nitrate ions in the water returned from the precipitation chamber are denitrified. Next, organic matter is oxidatively decomposed and ammonia is nitrified in the aerobic activated sludge chamber. And
Sludge and supernatant water are separated in the settling chamber, and part of the supernatant water is returned to the anaerobic filter bed chamber, and also sent to the disinfection chamber where it is sterilized with chlorine or the like and discharged. In recent years, a membrane separation type septic tank equipped with a membrane separation device in the aerobic activated sludge chamber instead of the sedimentation chamber and returning a part of the membrane filtrate to the aerobic activated sludge chamber has no effect even if sewage flows in in a short time. Considering that there is little risk of treated sewage flowing out, there is no need to adjust the flow rate, and it is expected that the tank will be smaller (water production technology: Volume 20, No. 2, No. 65-6
Page 8, 1994, JP-A-61-120694 and JP-A-2-71896).

[0004]

However, in the above-mentioned membrane separation type septic tank, when the filtration capacity is deteriorated due to deterioration of the membrane or clogging of the membrane, there is a risk that the water level in the septic tank rises and overflows. When returning the aerobic treated water to the anaerobic treatment chamber for the purpose of denitrification, returning the membrane separation filtrate,
Since it is necessary to carry out membrane filtration of a liquid which is several times the amount of inflowing wastewater, the load on the membrane separation device is large and an excessive membrane area is required. An object of the present invention is to provide a septic tank which solves the above-mentioned problems while utilizing the advantages of the membrane separation type septic tank, that is, a small-sized septic tank capable of highly treating sewage and capable of withstanding a short-time inflow of sewage.

[0005]

The septic tank of the present invention is divided into two parts, that is, an anaerobic filter bed chamber (first tank) and an aerobic activated sludge chamber (second tank) having an air diffuser, which are partitioned by a partition wall. It is a septic tank that has a tank treatment tank, and a part of the treated water in the aerobic activated sludge chamber is returned to the anaerobic filter bed chamber for treatment and is clarified from the activated sludge liquid in the aerobic activated sludge chamber. A membrane separation device for membrane separation and discharge of the liquid, and the liquid in the aerobic activated sludge chamber is partitioned by a partition that can communicate at the bottom, and a return pipe for returning the supernatant liquid to the anaerobic filter chamber at the top. It is a septic tank provided with a settling separation chamber.

In addition to the above structure, the septic tank of the present invention further comprises an overflow pipe from the lower part of the filter bed of the anaerobic filter bed to the upper part of the aerobic activated sludge room and a return pipe at the outlet position thereof. The septic tank is provided so as to be at the same height as the suction port, and the settling separation chamber is provided with an emergency discharge port at a level higher than the level of the return pipe suction port.

The main body of the septic tank of the present invention is made of FRP, SMC or the like, and at least an anaerobic filter bed chamber (first tank) divided by a partition wall and an aerobic activated sludge chamber (2
It has two tanks. The solid matter of the sewage flowing into the anaerobic filter bed chamber of the first tank is captured by the filter bed, and most of the organic matter of the sewage water is decomposed by the action of anaerobic bacteria living in the filter bed.

In the aerobic activated sludge chamber having an air diffuser which is the second tank of the septic tank of the present invention, a sedimentation separation chamber is provided together with the membrane separation device. As the membrane separation device used here,
Although there are flat membrane separators having flat membranes, hollow fiber membrane separators having hollow fiber membranes, etc., it is preferable from the viewpoints of membrane clogging and intermembrane clogging due to sludge, etc., and their ease of removal. ,
It is a flat membrane separation device. Various materials such as plastic, ceramic, and metal are used as the material of the film. The above-mentioned membrane separation device usually comprises a unit (this is referred to as a membrane module) including a membrane, a support thereof, a water collecting portion and the like, and an auxiliary device (pump etc.) thereof. In the present invention, one or two or more membrane modules, preferably one or two flat membrane modules are immersed vertically in the liquid of the aerobic activated sludge chamber in a state of standing vertically and sucked by a pump. While being treated and filtered. The membrane filtrate (clarified liquid) is not returned to the anaerobic filter chamber, but is then sent to the disinfection chamber, sterilized with chlorine or the like, and discharged.

The sedimentation separation chamber provided in the aerobic activated sludge chamber is
Partition (partition wall) whose bottom communicates with a part of the aerobic activated sludge chamber
It can be made by partitioning with. Since the flow of the liquid due to aeration and agitation is blocked by the partition in the sedimentation separation chamber, sludge separation by gravity sedimentation occurs. The supernatant of the solid-liquid interface (sludge interface) formed by sedimentation here is forcibly returned to the anaerobic chamber through a return pipe, for example, an air lift return pipe.

The air diffuser arranged in the aerobic activated sludge chamber is provided between the membrane module and the partition wall and at a position located below the membrane module. In addition to the purpose of aeration and agitation, this has the function of forcibly removing solids deposited on the film surface.

In a membrane separation type septic tank, it is generally said that untreated water is not discharged even if sewage flows in for a short period of time. However, deterioration of filtration capacity due to clogging of the membrane and the resulting water level. There is concern about a rise. Therefore, in the septic tank of the present invention, from the lower part of the anaerobic filter bed chamber to the upper part of the aerobic activated sludge chamber, an overflow pipe is provided so that its outlet position is at the same height as the return pipe suction port, and sedimentation separation is performed. The room will be equipped with an emergency outlet at a level higher than the level of the return pipe inlet (or overflow pipe outlet). The volume between the return pipe suction port (or the overflow pipe outlet) and the emergency discharge port is used as an empty volume for flow rate adjustment to prepare for the decrease in filtration capacity due to membrane clogging and the resulting rise in water level. .

By adjusting the level of the suction port of the return pipe, the concentration of activated sludge in the aerobic activated sludge chamber can be adjusted from several thousands ppm to several tens of thousands ppm. The excess sludge captured and accumulated on the filter bed of the anaerobic filter bed chamber 2 or the excess sludge accumulated in the aerobic activated sludge room is drawn out about once a year, and the sludge is properly managed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1 showing a schematic structure (longitudinal section) of a septic tank of the present invention. The septic tank of the present invention has an anaerobic filter bed chamber 2 and an aerobic activated sludge chamber 5 which are partitioned by a partition wall 10. The sewage that has entered the anaerobic filter bed chamber 2 passes through the filter bed 3 in a downward flow, and is guided from the lower part of the filter bed to the upper part of the aerobic activated sludge chamber 5 by an overflow pipe 4.

In the aerobic activated sludge chamber 5, one flat membrane module 7 (or a plurality of two or more flat membrane modules) is immersed vertically in the liquid. Between the flat membrane module 7 and the partition wall 10 and near the lower portion of the flat membrane module 7, an air diffuser 8
Is provided. The air diffuser 8 serves not only for aerobic conditions in the aerobic activated sludge chamber by supplying air, but also for cleaning the membrane surface by the air lift of the air fed under pressure. Since the amount of filtered water by the flat membrane module is proportional to the flow velocity through the membrane surface, the flat membrane module 7 is set so that the activated sludge liquid becomes a swirl flow while aerating while securing the oxygen amount necessary for aerobic activated sludge treatment. Deploy.

The flat sheet membrane module is sucked by the suction pump 11 to reduce the pressure to obtain membrane filtered water. The membrane-filtered water obtained is sterilized with chlorine or the like and then discharged.

A settling separation chamber 6 which is partitioned by a partition which can communicate at the bottom is provided in one stroke in the aerobic activated sludge chamber 5. Here, sludge flocs in the activated sludge liquid spontaneously settle, and a transparent supernatant layer is formed above the activated sludge flocs interface. Therefore, the supernatant liquid above the solid-liquid interface (sludge interface) formed by sedimentation is the air blower 13 While being blown with air, the water is pumped by an air lift and returned to the anaerobic filter bed chamber 2 through a return pipe. Nitrate ions in the returned aerobic activated sludge treated water are reduced and denitrified to nitrogen gas by the action of anaerobic bacteria living in the filter bed of the anaerobic filter chamber.

The suction port of the return pipe is provided at the same level as the flow control water level setting lowest level 15. Assuming the uppermost level 16 for setting the flow rate control water level, an outlet (for emergency) 12 is provided at this level to prepare for a decrease in the amount of permeated water due to clogging of the membrane. The anaerobic filter bed room 2, the aerobic activated sludge room 5 and the sedimentation separation room 6 are partitioned by partition walls or partitions at a level higher than the highest level 16 for setting the flow control water level, so that the sewage in each room is free. Only the supernatant water of the settling / separating chamber 6 is discharged even in an emergency, such as when the amount of permeated water is reduced due to clogging of the membrane without being mixed.

[0018]

The septic tank of the present invention is small in size, can highly treat sewage, and can withstand a short time inflow of sewage. Also,
Since the load on the membrane separation device is reduced, there are few operational troubles due to deterioration of the membrane filtration capacity over time.

[Brief description of drawings]

FIG. 1 is a diagram (longitudinal sectional view) showing a schematic configuration of a septic tank of the present invention.

[Explanation of symbols]

1: Main body of septic tank 2: Anaerobic filter bed 3: Filter bed 4: Overflow pipe 5: Aerobic activated sludge chamber 6: Sedimentation separation chamber 7: Flat membrane module 8: Air diffusion pipe 9: Return pipe 10: Partition wall 11: Suction Pump 12: Outlet for emergency 13: Air blower 14: Partition 15: Flow control water level setting lowest level 16: Flow control water level setting highest level

Claims (2)

[Claims] 1. An aerobic filter having a anaerobic filter bed chamber (first tank) and an aerobic activated sludge chamber (second tank) provided with an air diffuser, which are separated from each other by partition walls. A part of the treated water in the activated sludge chamber is a septic tank that is returned to the anaerobic filter bed chamber for treatment, and a membrane for separating the clarified liquid from the activated sludge liquid and discharging it in the aerobic activated sludge chamber. The separation device and the liquid in the aerobic activated sludge chamber are partitioned by a partition that can communicate at the bottom, and a sedimentation separation chamber with a return pipe for returning the supernatant to the anaerobic filter bed chamber is provided at the top. Septic tank. 2. An aerobic filter bed chamber (first tank) and an aerobic activated sludge chamber (second tank) provided with air diffusers, which are separated from each other by partition walls, and have two treatment tanks, and the aerobic gas is provided. A part of the treated water in the activated sludge chamber is a septic tank that is returned to the anaerobic filter bed chamber for treatment, and a membrane for separating the clarified liquid from the activated sludge liquid and discharging it in the aerobic activated sludge chamber. The separation device and the liquid in the aerobic activated sludge chamber are partitioned by a partition that can communicate at the bottom, and a sedimentation separation chamber with a return pipe for returning the supernatant to the anaerobic filter bed chamber is provided at the top. Further, an overflow pipe is provided from the filter bed lower part of the anaerobic filter bed chamber to the aerobic activated sludge chamber upper part so that its outlet position is at the same height as the return pipe suction port, and , A septic tank equipped with an emergency discharge port at a level higher than the level of the return pipe suction port in the sedimentation separation chamber