JPH0771672B2 - Small treatment septic tank - Google Patents

Description

TECHNICAL FIELD The present invention relates to a small treatment septic tank having 50 or less persons to be treated, and more particularly to a septic tank for purifying sewage using microorganisms.

[Conventional technology]

Conventionally, as a small septic tank with a processing target of 50 people or less,
Most of them are contact aeration systems.

An example of the schematic flow of this system is shown in FIG. As shown in this figure, the contact aeration type septic tank includes an anaerobic filter bed tank 100, a contact aeration tank 110, and a sedimentation tank 12 from the sewage inflow side.
0 and disinfection tank 130.

In this type of septic tank, the sewage is first anaerobic filter bed tank 10
Most of floating substances in the inflowing wastewater are separated and stored here. On the other hand, the treated water from which the suspended matter has been separated is transferred to the next contact aeration tank 110.

The contact aeration tank 110 is filled with a contact material having a corrugated plate shape, a honeycomb shape, a net-like elongated cylindrical shape, or the like. By aeration of the treated water in this tank 110, the treated water is treated by the action of microorganisms adhering to the surface of the contact material, and then transferred to the precipitation tank 120 where it is separated into supernatant water and precipitated sludge. .

The supernatant water is discharged after further disinfection, and the sludge settled in the settling tank 120 is transferred to the contact aeration tank 110 or the anaerobic filter bed tank 100.

[Problems to be Solved by the Invention]

However, in such a conventional contact aeration system, a settling tank 120 having a considerable capacity is required in the subsequent stage, and there is a problem in the system itself that the device itself cannot be made compact. There has also been a demand for downsizing of the device by improving the processing performance of a conventional contact aeration tank provided with a contact material such as a corrugated plate.

The present invention was devised in view of the above circumstances, and an object thereof is to provide a compact small-sized treatment septic tank having excellent treatment performance such as BOD removal rate.

[Means for Solving the Problems]

In order to solve the above problems, the present invention is a small treatment septic tank of 50 or less target persons of sewage treatment, a raw water tank having a filter bed to which anaerobic microorganisms are attached, and aerobic microorganisms are attached. A biofilm filtration tank having a biofilm filtration layer filled with a granular porous carrier, to which anaerobic biologically treated wastewater is supplied from the raw water tank through the raw water tank, and the biofilm filtration tank. From the treated water tank through which the aerobic biological treatment is released through the biological membrane filtration tank, and the treated water in the treated water tank is returned to the biological membrane filtration tank and flows backward in the biological membrane filtration layer. A backwashing pump that connects the biofilm filtration tank and the raw water tank to each other, and drains the sewage in the biofilm filtration tank that increases due to the treated water that has flowed back through the biofilm filtration layer to the raw water tank. It is characterized by having a drainage pipe.

[Action]

According to the small treatment septic tank, the anaerobic microorganisms attached to the filter bed of the raw water tank decompose and adsorb organic matter contained in wastewater such as domestic gray water, and further treat such anaerobic organisms. The sewage thus obtained is subjected to physical filtration by a granular porous carrier packed in a biological membrane filtration layer of organisms and aerobic biological treatment by aerobic microorganisms attached to the granular porous carrier, and organic matter and SS ( Inorganic suspended matter) is removed. Then, the backwash pump causes the treated water in the treated water tank to flow back into the biofilm filtration layer, and the organic substances and the proliferating microorganisms adhering and trapped in the biofilm filtration layer are separated from the porous carrier, and the biofilm filtration is performed. The layer is washed. Further, the backwash drainage used by the backwash pump for backwashing the inside of the biofilm filtration layer is returned to the raw water tank by the backwash drain pipe.

〔Example〕

A preferred embodiment of the present invention will be described in detail with reference to FIGS. 1 to 9.

Small treatment septic tank of the present invention (hereinafter simply referred to as septic tank)
Has a raw water tank R, a biofilm filtration tank S, and a treated water tank T, and is compactly integrated.

The raw water tank R is composed of a first raw water tank R ₁ and a second raw water tank R ₂ which are communicated with each other by a partition wall 1 having an opening 10 at a low water level (LWL), and which are partitioned from each other. Filter bed to remove organic matter and large rubber treated with anaerobic microorganisms
3a and 3b are provided, and spaces are provided below the filter beds 3a and 3b, respectively. The first raw water tank R ₁ is provided with an inflow port 5 for inflowing raw water which is sewage, and a water guiding pipe 7 having an opening at a lower side and a side face connected to the inflowing port 5, and an opening below the water guiding pipe 7. Directly below the filter bed and above the filter bed 3a is the water conduit 7.
The baffle plate 9 is provided in order not to concentrate the water flow in one place and to diffuse it to the surroundings so as not to agitate the water in the tank.

In addition, a partition wall 1 for partitioning the first raw water tank R ₁ and the second raw water tank R ₂
A cleaning cylinder 13 is provided that extends vertically below the filter bed 3 and opens there. The cleaning cylinder 13 is for inserting a nozzle of a cleaning pump (not shown) to the bottom of the cleaning cylinder 13 at the time of cleaning.

The second raw water tank R ₂ has an intermittent metering pump 15 just above the filter bed 3b.
The water intake port 17 of the intermittent metering pump 15 is opened downward through the one-way valve 19 into the upper surface of the filter bed 3b. The intermittent metering pump 15 is operated by a pump blower 23 connected to the pipe 11 via a solenoid valve 21. The second raw water tank R ₂
When the water level is low (low water level: LWL), the biofilm filtration tank S
No water is sent to, but only when there is more than this. Further, when the water level of the first raw water tank R ₁ becomes a high water level (HWL), a means (not shown) is provided to prevent inflow of sewage, but a means that cannot take this means allows this. Use a septic tank of a large size. Therefore, even if the amount of sewage flowing into the water conduit 7 increases or decreases, it is sent to the biofilm filtration tank S intermittently quantitatively via the pipe 25 rather than the overflow type by the intermittent metering pump 15, and a stable treatment is always performed. it can.

The biofilm filtration tank S is provided with a biofilm filtration layer 45, and a large number of granular porous carriers are filled in this filtration layer 45, which is optimal for adhering and proliferating microorganisms at a high concentration. It has a structure. In the biofilm filtration tank S, aerobic biological treatment and physical filtration are simultaneously performed, and mainly organic substances and SS are removed.

That is, the biological treatment is carried out by the microorganisms attached to the carrier packed in the biofilm filtration layer 45, and the physical filtration is carried out by the gap formed between the packed carrier particles and the adsorption on the wide biofilm surface. .

More specifically, the biofilm filtration tank S will be described in detail. In the biofilm filtration tank S, an opening 27 of the pipe 25 is provided above the partition wall 29 that separates the second raw water tank R ₂ from the biofilm filtration tank S. Further upward, the opening of the backwash drain pipe 31 through which the treated water increased and overflowed in the biofilm filtration tank S during the backwash is returned to the first raw water tank R ₁ .
33 is provided, and the other end is connected to the water conduit 7. An aeration / backwash pipe 37 connected to an aeration blower 35 shown in FIG. 2 is framed near the bottom, and many holes are provided in the framed part. Then, the loss 3 is provided above and below the frame portion of the aeration / backwash pipe 37 and above and below the opening 27 of the pipe 25.
9, 41 are provided, and a biofilm filtration layer 45 is formed by filling a large number of carriers 43 made of granular porous ceramics to which aerobic microorganisms are attached between them. This carrier 43 is 5-50
Since it is a spherical body with a diameter of 2 to 10 mm provided with micropores and is porous, it has a large specific surface area and a large pore volume, and has an optimal structure for adhering and proliferating microorganisms, and can keep organisms at a high concentration. Further, the specific gravity is close to 1, and the position is changed by a little flow and stirring is performed. That is, the backwash power may be extremely low. Specific materials for such a porous ceramics carrier 43 include, for example, zeolite, slag, anthracite, anti-fire stone, natural minerals, granular foam glass, CB filter, actinolite, and the like. Further, at the bottom of the biofilm filtration tank S, below the rustle 39, that is, below the biofilm filtration layer 45, the treated water purified by the biofilm filtration layer 45 is supplied to the treated water tank T, and vice versa. At the time of washing, a pipe 47 is provided for feeding back the treated water in the treated water tank T to the biofilm filtration tank S.

In the treated water tank T partitioned by the partition walls 49, 51, the other end of the pipe 47 extends to the bottom portion, and a backwash pump 53 for feeding back the treated water is attached thereto. An elbow pipe 55 is provided at an intermediate position of the pipe 47, and the treated water treated in the biofilm filtration tank S is discharged to the treated water tank T. Small chambers 57, 59, and 61 are provided to allow the treated water to overflow and convect, and the treated water is discharged from the discharge port 63 provided in the small chamber 61. A medicine cylinder 65 is provided in either one of the small chambers 59 and 61 to neutralize and sterilize the treated water treated with organic substances (see FIGS. 1, 2, 9).

Next, a method for treating sewage using such a septic tank will be described.

Explaining the case of a septic tank that is applied to treat sewage that is domestic miscellaneous wastewater, at home it is a washroom, cooking,
The amount of sewage flowing into the septic tank is not constant depending on the selection, use of the bath, etc., and the amount used. However, 7-8 in the morning
There is no sudden inflow in a short time, except for a few large peaks from 6 to 7 pm in the evening. Therefore, the size of the septic tank is such that this peak can be floated.

The sewage passes from the inflow port 5 through the water conduit 7, is spread by the baffle plate 9, is removed by the filter bed 3a, and is sent to the first raw water tank R ₁ of the raw water tank R. The raw water flows out from the side opening when the water level rises and reaches the middle of the water conduit 7. When the sewage passes through the filter bed 3a, anaerobic microorganisms are attached to the filter bed 3a, where organic substances are decomposed and adsorbed. The passed water raises the water level in the 2nd raw water tank R ₂ , and it is the same as the filter bed.
Organic substances are decomposed and adsorbed in 3b. After the water level exceeds the horizontal portion 20 of the suction pipe, the solenoid valve 21 is opened, and the pressure of the pump blower 23 operates the intermittent metering pump 15 through the pipe 11. By this intermittent metering pump 15, sewage is quantitatively sent to the biofilm filtration tank S regardless of the inflow amount. Therefore, when the inflow is large, the water level in the raw water tank R is high (H.
Rise within the line of (WL).

The water sent by the pipe 25 enters the biofilm filtration tank S through the opening 27 and passes through the biofilm filtration layer 45 in a downward flow. The biofilm filtration layer 45 is filled with a large number of carriers 43 made of spherical porous ceramics, and descends while being bent. By the way, at this time, the aeration blower 35 operates,
Air bubbles are blown out from the aeration / backwash pipe 37 framed at the bottom and rise. Since the bubbles rise in a curve while colliding with the carrier 43, the bubbles do not suddenly coarsen and the residence time becomes long, and a high oxygen utilization rate is obtained, so that high load operation is possible.

By countercurrently contacting raw water and air in the biofilm filtration layer 45 in this way, contact aeration is performed, high oxygen dissolution in sewage is attempted, and biodegradation function is enhanced to decompose organic substances and proliferate microorganisms. At the same time, it is purified more efficiently by the filtration action between the carrier particles and the adsorption on the wide surface of the biofilm to obtain treated water. Therefore, organic matter is adsorbed and captured by the biofilm filtration layer 45. Further, as will be described later, it is backwashed after a certain period of time elapses, so that it hardly precipitates on the bottom.

The treated water is sent to the treated water tank T from the opening of the elbow pipe 55 by the pipe 47. The water level of the treated water that has been sent therein rises and is discharged from the discharge port 63 through the small chambers 57, 59, 61. During this time, the treated water overflowing from the small chamber 57 is discharged by being neutralized and sterilized by the chemical injection from the chemical cylinder 65.

This discharge is due to the water supply by the intermittent metering pump 15.
The processing speed is set, and this setting is set by the processing capacity of the biofilm filtration layer 45 of the biofilm filtration tank S. Therefore, it is possible to always ensure stable treated water quality. As a result of the treatment of the sewage, organic substances and proliferating microorganisms are attached to the carrier 43 of the biofilm filtration layer 45, and before the backwash pump 53 is activated before the organic substances and the proliferating microorganisms are detached from the carrier 43, the inside of the treated water tank T is The treated water accumulated in the backflows through the pipe 47 and blows up from the bottom of the biofilm filtration layer S into the biofilm filtration layer 45.

By this upward flow, the proliferating microorganisms adhered and captured in the biofilm filtration layer 45 are removed together with the bubbles blown from the aeration blower 35 through the aeration / backwash pipe 37, and the backwash is performed. Floats in drainage. Here, the biofilm filtration layer 45 is a large number of carriers 43 of porous ceramics, and since the specific gravity is close to 1, the carriers 43 fly up and collide with each other, so that the trapped proliferating microorganisms are released. And will be washed.

Since the treated water in the treated water tank T is sent by the backwash pump 53, the water level in the biofilm filtration tank S rises and is guided by the backwash drainage pipe 31 from the upper opening 33 as backwash drainage together with the floating microorganisms. It is sent to the water pipe 7 and returned to the first raw water tank R ₁ . The backwash drainage passes through the filter bed 3 and is decomposed again by anaerobic microorganisms.

This backwashing is performed every predetermined time to wash the biofilm filtration layer 45, restore the decomposition and adsorption capacity, and return the proliferating microorganisms to the raw water tank R. From the cleaning cylinder 13 of the raw water tank R to the nozzle of the cleaning pump. Insert and periodically remove the grown sludge for treatment.

After this backwashing is completed, the inflow of sewage into the raw water tank R continues and normal purification processing is performed. In the case of domestic miscellaneous drainage as in this example, it is sufficient to backwash once a day at about 2:00 am.

The septic tank of the present invention can be applied to either so-called single treatment or combined treatment.

Next, specific examples will be shown below to describe the present invention in more detail.

Experimental Example 1 Raw water having an average BOD concentration of 240 mg / was treated in the present septic tank shown in FIG. 1, and the change in BOD concentration in each treatment tank was measured.

As a result, the average BOD concentration after the anaerobic treatment in the raw water tank R was 144.7 mg / average after the aerobic treatment in the biofilm filtration tank.
The BOD concentration was 12.0 mg /. As a result, it was confirmed that the BOD removal rate in the biofilm filtration tank was 91.7%, which was extremely high, and the final BOD concentration could be reduced to 20.0 mg / or less.

In this experiment, when the SS concentration was measured at the same time, the inflowing raw water SS concentration was 240 mg /, the average SS concentration after anaerobic treatment in the raw water tank R was 39.6 mg /, and the average SS concentration after aerobic treatment in the biofilm filtration tank. Was 11.0 mg /, and it was confirmed that SS was also sufficiently removed.

In addition, it was confirmed that it also had denitrification and dephosphorization effects.

Experimental Example 2 Using the septic tank of the present invention, the BOD-MLSS load and the BOD area load were obtained.

MLSS in the biofilm filtration tank was 6500 mg /
The OD-MLSS load required was 0.13 kg BOD / kg-MLSS-day. This value is less than half compared with the BOD-MLSS load of ordinary activated sludge.

When the BOD area load was determined from the specific surface area, the results shown in Table 1 on the next page were obtained.

From these results, it can be seen that the porous ceramics filled in the biofilm filtration tank has an optimal structure for microorganism attachment.

KL _a value according to the presence or absence of the filled carrier of Experimental Example 3 Biological membrane filtration tank (oxygen transfer efficiency) was measured.

There are two measurement points: an A point (upper part of the solution above the carrier when the carrier is filled) A point and an intermediate part (intermediate part of the carrier when the carrier is filled) B point of the biofilm filtration tank. Porous ceramics with an average diameter of 8 mm were used.

The measurement results are shown in Table 2 below.

This result, KL _a value 4-5 times by filling the porous ceramic biofilm filtration tank was obtained.

〔The invention's effect〕

 The effect of the present invention is clear from the above experimental results.

That is, a small processing septic tank of the present invention is provided with a biofilm filtration tank in which a large number of the porous support having a biological membrane filtration layer filled, this compound have a very high BOD removal performance and KL _a value On the contrary, the BOD-MLSS load is small.

Therefore, the size of the device can be greatly reduced with the improvement of the performance of the septic tank. And according to the present invention, the treated water obtained by backwashing the biofilm filtration layer is discharged to the raw water tank which is an anaerobic treatment tank, so that the treatment water returned from the treated water tank to the raw water tank through the biofilm filtration tank. Since the water is again anaerobically treated by passing through the filter bed of the raw water tank to which the anaerobic microorganisms are attached, this increases the BOD volume load in the biofilm filtration tank, and A high denitrification treatment capacity can be obtained by reducing the nitrite ions and nitrate ions remaining in the treated water. And, by such improvement of the processing capacity, the size of the septic tank can be reduced accordingly.

[Brief description of drawings]

Fig. 1 is an exploded view of a schematic constitution of the septic tank of the present invention, Fig. 2 is a schematic constitutional view similar to Fig. 1 in which the septic tanks are further disassembled, and Fig. 3 is an overall perspective view of the septic tank partially omitted. Fig. 4 is a perspective view of the biofilm filtration tank partially omitted, Fig. 5 is a plan view of the septic tank,
FIG. 6 is a sectional view taken along line VI-VI of FIG. 5, FIG. 7 is a schematic configuration diagram of a treated water tank, FIG. 8 is a schematic configuration diagram showing a biofilm filtration tank and a treated water tank that are arranged in parallel, and FIG. Perspective view of the main part of the aquarium,
FIG. 10 is a schematic flow diagram of a conventional contact aeration type septic tank. R (R ₁ , R ₂ ) ... Raw water tank, S ... Biofilm filtration tank, T ...
Treated water tank, 15 …… intermittent metering pump, 25 …… pipe, 31…
… Backwash drain pipe, 37 …… Aeration and backwash pipe, 45 ……
Biofilm filtration layer, 47 …… pipe, 53 …… backwash pump.

Front page continuation (72) Inventor Yasunobu Niimi 3-3-11 Nishi, Kunitachi, Tokyo (72) Inventor Noboru Akiyama 3-15-20 Tsurusenishi, Fujimi-shi, Saitama (72) Inventor Shigeru Ono Aichi 1-2-1, Chiyodabashi, Chikusa-ku, Nagoya, Japan (72) Inventor Toshiro Nagaya 518-10 Maeda-cho, Totsuka-ku, Yokohama-shi, Kanagawa (56) Reference JP-A-52-146966 (JP, A) 59-22229 (JP, A) JP 60-132696 (JP, A) JP 63-4899 (JP, A) JP 50-143343 (JP, A) JP 61-283395 (JP , A) JP 62-11596 (JP, A) JP 53-96261 (JP, A) JP 62-204896 (JP, A)

Claims (2)

[Claims] 1. A small-scale treatment septic tank having 50 or less target persons for sewage treatment, which comprises a raw water tank having a filter bed to which anaerobic microorganisms are attached, and a granular porous carrier to which aerobic microorganisms are attached. A biofilm filtration tank having a packed biofilm filtration layer, to which the anaerobic biologically treated wastewater is supplied from the raw water tank through the raw water tank, and the biofilm filtration tank from the biofilm filtration tank A treated water tank through which treated water that has undergone aerobic biological treatment is released, and a backwash pump that returns the treated water in the treated water tank to the biological membrane filtration tank and causes a reverse flow in the biological membrane filtration layer, A backwash drain pipe for connecting the biofilm filtration tank and the raw water tank to drain the wastewater in the biofilm filtration tank, which is increased by the treated water flowing back in the biofilm filtration layer, to the raw water tank. A small treatment septic tank that is characterized by 2. The small treatment septic tank according to claim 1, wherein the porous carrier is a porous ceramic carrier.