JPH0852486A - Sludge returning method for anaerobic waste water treatment - Google Patents

Abstract

PURPOSE:To reactivate sludge and to efficiently execute waste water treatment of sewage by returning the treated water obtd. by an aeration treatment in an aeration tank to a settling chamber, recovering the settled sludge deposited therein and the suspended sludge in the intermediate part of the settling chamber and returning the sludge to the aeration tank. CONSTITUTION:The sewage 30 sent to the aeration tank 2 is aerated together with aerobic microorganisms by an aeration blower 10. The generated sludge 1 and treated water 18 are sent to the settling chamber 3 by flowing over the aeration tank 2 in a mixed state. The sludge and the treated water are separated to the settled sludge 16 and the settled and treated water 19. The intermediate sludge 17 in the settling chamber of the low concn. suspended in the intermediate part of the settling chamber 3 is sucked by an intermediate part sludge return pump 14 through a vertically movable intermediate part sludge withdrawal pipe 15 and the settled sludge 16 is sucked by a sludge return pump 7 and both sludge are returned again to the aeration tank 2. The returned intermediate part sludge in the settling chamber and the settled sludge 16 include the aerobic bacteria and are, therefore, activated again in the aeration tank 2 and are again subjected as the active sludge of the aerobic waste water treatment to the waste water treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerobic wastewater treatment method, and more particularly to a sludge for aerobic wastewater treatment which can improve the efficiency of wastewater treatment by collecting sludge floating in the middle part of a sedimentation tank. Regarding the return method.

[0002]

2. Description of the Related Art Generally, aerobic wastewater treatment, which treats wastewater using activated sludge, utilizes the self-cleaning action of a river. Since the river water is in wide contact with air, a lot of oxygen is dissolved in the water, and when polluted organic matter flows in, aerobic microorganisms rapidly grow and decompose the polluted organic matter. When the polluted organic matter disappears, the microorganisms die, and the carcasses are eaten by the remaining microorganisms (polluted organic matter is consumed and reduced as an energy source while moving from one organism to another), and the river becomes clear again. If you continue to aerate sewage containing polluted organic matter by applying such a principle, many aerobic microorganisms grow,
Proliferated microorganisms usually form a mass (floc) of a fraction of a few mm to a few mm including solid substances in water. If this is transferred to the next tank and left to stand, clear water (treated water) is obtained in the upper part, and flocs accumulate in the lower layer to form a mud. If this mud is collected and added to the next sewage, the number of microorganisms will further increase, and as a result, the rate of absorbing polluted organic substances will be further increased. This sludge rich in microorganisms is activated sludge, and this system is a sewage treatment method called an activated sludge method or an aerobic wastewater treatment method.
As a conventional sewage treatment method, for example, one shown in FIG. 2 is known. From the upstream side, the aeration tank (2), the precipitation tank (3), the coagulation reaction tank (4),
Four treatment tanks of a coagulation sedimentation tank (5) are sequentially connected, and sewage is treated through these tanks. First, the aeration tank (2)
Then, the aerobic blower (10) mixes and stirs the aerobic microorganisms in the premises and the sewage (30) to supply oxygen necessary for the aerobic microorganisms, and at the same time, the nutrients contained in the sewage are activated sludge, that is, aerobic. Decomposes by microorganisms. The sludge (1) generated at this time and the treated water (18) are sent as a mixed solution from the aeration tank (2) to the precipitation tank (3) through the water supply pipe 2a. The mixed solution is again separated into settling sludge (16) and settling water (19). Settled sludge (16)
Is collected and concentrated in the center of the bottom of the settling tank (3) by the settling tank stirrer (11), and returned to the aeration tank (2) via the return pipe 7a by the sludge return pump (7) to obtain effective aerobic microorganisms. As a group, the sludge concentration and treatment capacity in the aeration tank (2) are maintained. In addition, the remaining settled sludge (16) other than the amount of sludge that maintains the treatment capacity is sent to the sludge dewatering machine (9) by the dewatering machine feed pump (8) as excess sludge, dehydrated and disposed of. .

On the other hand, treated water (1) generated in the settling tank (3)
9) is sent to the flocculation reaction tank (4), where chemicals such as polyaluminium chloride and a polymer flocculant are injected, and the flocculation reaction is performed while gently stirring by the flocculation reaction tank stirrer (12). The solution is sent to the coagulation sedimentation tank (5). And
In this coagulating sedimentation tank 5, coagulated sludge (20) and coagulated treated water (2
1), and only the coagulated water (21) of the supernatant water is discharged out of the system through the coagulated water tank (6). The coagulation sludge (20) collected at the bottom of the coagulation sedimentation tank (5) is collected at the center of the bottom by the coagulation sedimentation tank agitator (13), and sent to the sludge dehydrator (9) by the dehydrator mud pump (8). Then
It is dehydrated and disposed of.

As described above, the settled sludge (16) accumulated in the bottom of the settling tank (3) is a group of aerobic microorganisms and has a relatively large specific gravity. Therefore, the sludge return pump (7),
By returning to the aeration tank (2) through the water supply pipe 2a, it is reactivated and is effectively used for aerobic wastewater treatment.

[0005]

However, in the above-mentioned conventional aerobic wastewater treatment, since only the sludge at the bottom of the settling tank is extracted and returned to the aeration tank (2), the settling tank (3) Settling water (19) and settling sludge (1
The sludge (17) in the middle part of the sedimentation tank floating near the boundary of 6) cannot be pulled out. This settling tank middle part sludge (1
Since 7) has a smaller specific gravity than the above settling sludge (16), even if it is returned from the settling tank (3) to the aeration tank (2) by the sludge returning pump (7), it remains floating in the middle part of the settling tank. Then, since it is not returned to the aeration tank (2) again, it floats in a half-dead state without being activated, and eventually decays. Therefore, the sludge in which the non-activated microorganisms floating in the middle part are in a semi-dead state is thickly accumulated in the middle part as the operation continues, and when it accumulates near the water surface of the settling tank,
It overflowed from the settling tank together with the treated water, which deteriorated the quality of the treated water and was one of the factors that lowered the efficiency of the entire wastewater treatment.

Further, the higher the treatment capacity in the aeration tank (2) and the sedimentation tank (3), the smaller the particles of suspended matter contained in the treated water for precipitation (19), and the smaller the quantity, so the appearance is compared. It is sent in a clean state.

However, in the flocculation reaction tank (4), particles of suspended matter in the precipitation-treated water (19) are small,
When the amount of suspended solids is small in quantity, a cohesive sludge (20) that is light and has a poor sedimentation property is formed, so that the coagulation-sedimentation effect is deteriorated.

The present invention has been made in view of such circumstances, and an object thereof is to reactivate sludge floating in an intermediate portion of a sedimentation tank which has not been reused conventionally. It is to provide a method for efficiently treating wastewater drainage. Another object is to provide a method for forming a coagulated sludge (20) having a good sedimentation property by utilizing the intermediate sludge (17) of the sedimentation tank.

[0009]

[Means for Solving the Problems] In the aerobic wastewater treatment for treating sewage with activated sludge, the sewage obtained by aerating the sewage with an aeration tank (2) is a settling tank. Liquid is sent to (3), and settled sludge (16) and settling water (1
9) Settling sludge accumulated at the bottom of the settling tank and sedimentation tank middle section sludge floating in the middle part in the step of separating and separating into (17)
Is recovered and returned to the aeration tank (2) by a sludge returning method for aerobic wastewater treatment. In addition, in the aerobic wastewater treatment for treating wastewater with activated sludge, the treated water obtained by aeration treatment of the wastewater in the aeration tank (2) is sent to the sedimentation tank (3), and the sedimentation sludge ( Aerobic wastewater that collects sludge (17) in the intermediate part of the sedimentation tank that floats in the middle part of the sedimentation tank and sends it to the coagulation reaction tank (4) in the step of sedimentation separation into 16) and treated water (19) Achieved by the sludge return method of treatment. Furthermore, in aerobic wastewater treatment in which sewage is treated with activated sludge, the treated water obtained by aeration treatment of the sewage in an aeration tank is sent to a settling tank, where it is separated into settling sludge and settling treated water. In the step of, the settled sludge accumulated on the bottom of the settling tank and the sludge of the settling tank intermediate part floating in the middle part of the settling tank are respectively collected and returned to the aeration tank,
It is also achieved by a sludge returning method for aerobic wastewater treatment, characterized in that a part of the sludge in the intermediate part of the settling tank floating in the intermediate part of the settling tank is sent to the coagulation reaction tank.

That is, the sludge returning method for aerobic wastewater treatment according to the present invention is characterized in that the sludge (17) in the middle part of the settling tank (3) floating in the middle part is reactivated for wastewater treatment. This is an effective method, and by mixing the sludge (17) in the middle part of the sedimentation tank with the treated water (19),
This is due to the method of forming coagulated sludge with good sedimentation properties.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an overall explanatory view of the wastewater treatment sludge returning method of the present invention. In the figure, the same numbers are assigned to the same devices and equipment as those of the conventional technique, and the description thereof will be omitted. FIG.
First, the sewage (3) sent to the aeration tank (2)
0) is aerated with aerobic microorganisms by an aeration blower (10). The sludge (1) treated water (18) generated at this time overflows from the aeration tank (2) in a mixed state and is sent to the settling tank (3) to be settled sludge (16) and settling treated water (19). And separated. At this time, the sludge (17) having a low concentration that floats in the middle of the settling tank (3) is transferred by the intermediate sludge return pump (14) through the vertically movable intermediate sludge drawing pipe (15). Aspirate and return to the aeration tank (2) again. Since the returned sludge (17) in the middle part of the sedimentation tank contains aerobic microorganisms, the sludge (17) is reactivated in the aeration tank (2) and is used again as wastewater treatment as activated sludge for aerobic wastewater treatment. Therefore, it is possible to prevent the spoiled sludge, which keeps floating in the intermediate layer, from being carried over from the settling tank, and the efficiency of wastewater treatment can be improved. In addition, it is desirable that the middle sludge extraction pipe (15) is appropriately moved up and down according to the amount of the settling water (19) flowing into the settling tank (3). Moreover, you may make it provide several intermediate | middle sludge extraction piping (15). This is because the return flow rate can be adjusted more easily by providing a plurality.

Further, the intermediate sludge return pump (1
It is more preferable to install an intermediate sludge disposal pipe (22) for feeding liquid to the coagulation reaction tank (4) in addition to 5). That is, by providing this intermediate sludge disposal pipe (22), the sedimentation treated water (19) is mixed with the intermediate sludge of the sedimentation tank (17) to form the core of the agglutination reaction, and the agglomerated sludge (20) having a large specific gravity. ) Can be formed, it can be efficiently precipitated at the bottom of the coagulating sedimentation tank (5). Therefore, since this coagulated sludge (20) is sent to the sludge dewatering machine (9) by the dehydrator feed pump (8) and is disposed of by dehydration treatment disposal, the sludge (16) is removed from the coagulating sedimentation tank (5). It can be processed continuously without overflowing. The intermediate sludge disposal pipe (22) is connected to the intermediate sludge return pump (14).
The intermediate sludge extraction pipe (15) and the intermediate sludge discard pipe (22) may be branched via a pipe, or a pipe dedicated to the intermediate sludge discard pipe (22) and one or more pumps. A book may be provided. Also, 1
A plurality of intermediate sludge disposal pipes (22) may be branched from one pump.

[0013]

As described above, according to the sludge returning method of the aerobic wastewater treatment of the present invention, the conventional sedimentation tank (3) continues to float in the middle portion and decomposes and overflows from the upper portion to improve the wastewater treatment efficiency. The sludge (17) in the middle part of the settling tank, which caused the deterioration,
Since it is returned to the aeration tank (2) for use, the sludge can be activated again. Therefore, it is possible to improve the treatment efficiency in continuously treating a wastewater with aerobic wastewater.

Further, the sludge (17) in the middle part of the sedimentation tank is returned to the coagulation reaction tank (4) and mixed in an appropriate amount with the precipitation-treated water (19), thereby forming the core of the coagulation reaction and having a large specific gravity. 20) can be formed and the aggregation effect can be improved. Therefore, the surface area load of the coagulation sedimentation tank (5) can be increased, and the coagulation sedimentation tank (5) can be made into a compact facility.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a wastewater treatment system according to an embodiment of the present invention.

FIG. 2 is a conventional wastewater treatment system diagram.

[Explanation of symbols]

 1 Sludge 2 Aeration Tank 3 Precipitation Tank 4 Coagulation Reaction Tank 5 Coagulation Sedimentation Tank 6 Coagulation Treatment Water Tank 7 Sludge Return Pump 8 Dehydrator Mud Pump 9 Sludge Dewaterer 10 Aeration Blower 11 Sedimentation Tank Stirrer 12 Coagulation Reaction Tank Stirrer 13 Coagulation Sedimentation Tank Stirrer 14 Intermediate sludge return pump 15 Intermediate sludge extraction pipe 16 Settled sludge 17 Settling tank intermediate sludge 18 Treated water 19 Precipitated treated water 20 Coagulated sludge 21 Flocculated treated water 22 Intermediate sludge waste pipe 30 Sewage

Claims (3)

[Claims] 1. In aerobic wastewater treatment for treating wastewater with activated sludge, treated water obtained by aeration treatment of the wastewater in an aeration tank is sent to a settling tank to obtain a settling sludge and a settling treated water. The sedimentation sludge that accumulates at the bottom of the sedimentation tank in the process of sedimentation separation into
A sludge returning method for aerobic wastewater treatment, characterized in that sludge floating in the middle of the settling tank is collected and returned to the aeration tank. 2. In the aerobic wastewater treatment for treating sewage with activated sludge, the treated water obtained by aerating the sewage in an aeration tank is sent to a settling tank to obtain a settling sludge and a settling treated water. A sludge returning method for aerobic wastewater treatment, which comprises collecting sludge in the middle part of the sedimentation tank in the step of separating and separating in the sedimentation tank, and sending the sludge to the coagulation reaction tank. 3. In the aerobic wastewater treatment for treating sewage with activated sludge, the treated water obtained by aerating the sewage in an aeration tank is sent to a settling tank to obtain a settling sludge and a settling treated water. The sedimentation sludge that accumulates at the bottom of the sedimentation tank in the process of sedimentation separation into
Collecting the sludge in the middle part of the settling tank in the middle part of the settling tank and returning it to the aeration tank, and sending a part of the sludge in the middle part of the settling tank in the middle part of the settling tank to the coagulation reaction tank A method for returning sludge for aerobic wastewater treatment, which is characterized by: