JP2002086146A - Device for preventing generation of scum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for preventing generation of scum by which clear supernatant water can be obtained without causing new scum. SOLUTION: The device for preventing generation of scum is constituted of a precipitator (A), a scum removing device (B) which sucks and degasses the scum floating in waste water in the precipitator and discharges the scum inside the precipitator when the precipitation is internally filled with the waste water and an agitating device (C) for dispersing precipitates of the waste water accumulated at a bottom part of the precipitator. The device for preventing generation of scum is distinguished by that the agitating device (C) stops operating only during a period when the waste water flows-in or flows-out of the precipitator (A) and the scum removing device (B) is operated at least during a period when the agitating device (C) stops operating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for preventing generation of scum in a wastewater treatment process.

[0002]

2. Description of the Related Art A large amount of scum is generated on the water surface of a sedimentation tank in a wastewater treatment step such as a septic tank treatment step or a sewage treatment step. When scum is generated, the scum is mixed into the supernatant water of the sedimentation tank and deteriorates the quality of the treated water. Conventionally, a float type scum skimmer comprising a combination of a sedimentation tank / coagulation tank main body and a pipe for sucking and transferring sludge has been used as such a scum removal device (for example, Japanese Patent Application Laid-Open No. 3-296).
No. 403).

[0003]

However, in a float type scum skimmer generally used, the purpose is to generate scum once, suck the scum, and discharge the sludge out of the sedimentation tank. As a result, there is a problem that a water flow is generated in a direction in which the sediment is raised, and a new scum is induced. Furthermore, since the float type scum skimmer is too large for a small processing tank such as a small purification tank, there is no appropriate scum countermeasure at present. It is an object of the present invention to provide a scum generation preventing device capable of obtaining clear supernatant water without inducing new scum.

[0004]

According to the first aspect of the present invention,
A sedimentation tank (A), a scum removing device (B) for suctioning and degassing scum floating in the wastewater in the sedimentation tank when the sedimentation tank is filled with wastewater, and discharging the scum into the sedimentation tank; A scum generation preventing device comprising a stirrer (C) for dispersing a sediment of the wastewater deposited on the bottom of the sedimentation tank,
The scum generation preventing device causes the stirrer (C) to stop operating only during a period during which drainage flows into or out of the sedimentation tank (A), and the scum removal device (B)
This is a scum generation preventing device that is operated at least during a period when the operation of the stirring device (C) is stopped.

[0005] The sedimentation tank (A) is a tank for temporarily storing wastewater containing sediment components, and is not particularly limited as long as it has this function. The entrance and exit of the wastewater is not particularly limited as long as it is installed at a height enough to store the wastewater.However, in order to ensure the clarity of the supernatant water, it should flow into the center well of the surface of the sedimentation tank. It is more preferable to make it.

The scum removal device (B) sucks scum floating on the drainage surface and degass the scum,
The scum is turned into a solid precipitate by raising the scum specific gravity and simultaneously guiding the scum into the wastewater in the sedimentation tank and discharging it.

[0007] As a specific means of the scum removing device (B), for example, a suction port is provided on the water surface, and only the water surface layer is selectively sucked by the suction means to remove the suspended sediment to the sucked scum. A method in which the wastewater is guided to the bottom of the drainage by a transportation means such as a pipe while being subjected to a gas treatment, discharged, and settled.

[0008] The scum precipitated by the treatment of the scum removing device (B) is a solid substance generally called sludge, and is physically compacted during the sedimentation. On the other hand, since the solid matter is sludge containing a large amount of microorganisms, gas produced by respiration or metabolism adheres to the surroundings as fine bubbles. Alternatively, the sludge to which air bubbles have adhered may flow in the aeration treatment step or the like in the previous step. In this way, the sludge-based sediment that has been compacted while adhering fine air bubbles eventually forms flocs of various sizes. Such a floc has a specific gravity reduced by air bubbles, and floats due to a slight change in the environment such as a water flow and a water temperature.

The stirrer (C) disperses the sediment deposited on the bottom of the sedimentation tank (A), thereby crushing and stirring the flocs and removing bubbles adhering to the flocs which cause re-floating. . Such means are not particularly limited, a mechanical stirring device having a blade,
A diffuser type device (air bubble type) and the like can be mentioned.

The scum generation preventing device of the present invention is arranged such that the agitating device (C) stops operating only during a period during which drainage flows into or out of the sedimentation tank (A), and the scum removing device (B). Is operated at least during a period when the stirring device (C) is stopped. The stirrer (C) stops operation during the period when water enters and exits the sedimentation tank (A), thereby preventing the occurrence of the scum and preventing the supernatant water from mixing with the sediment. Further, the scum removing device (B) may be placed so as to be operated at least during a period when the stirring device (C) is stopped, and may be continuously operated at the same time as the operation of the stirring device (C). .

The means for controlling the scum removal device (B) and the stirring device (C) can be achieved by a timer programmed to operate or stop at regular intervals. The inflow time of the wastewater can be known at the stage of designing the wastewater treatment device. Thus, at the predicted raw water inflow time, a period can be programmed to shut down the stirrer.

According to a second aspect of the present invention, as the scum removing device (B), a scum floating on the water surface is sucked by using an air lift pump, so that air, water and scum pass through the inside of the pipe. When they collide with each other, the scum is crushed and degassed to make it easy to reprecipitate, and then it is easier to discharge the scum into the sedimentation tank. In addition, a blower (blower) can be used as power for the air lift pump,
It is preferable as a small wastewater treatment device such as a small septic tank or a simple and inexpensive device.

As a specific form of the scum removing device (B), a slit-shaped opening formed in the side surface of the pipe end is divided into a scum suction port arranged near the water surface, and a plurality of branches are provided. It is particularly preferable that the scum discharge port submerged in the vicinity of the water surface of the settling tank and the scum conveyance pipe connecting the suction port and the discharge port use an air lift pump as a suction force.

According to a third aspect of the present invention, the stirrer (C) uses a diffuser for generating bubbles in water, and the bubbles adhering to the flocs causing scum are removed by the agitating force of the diffuser. It degass and crushes massive flocks. A blower (blower) can be used as power for the agitating device using the air diffuser, and it is preferable as a small wastewater treatment device such as a small septic tank or a simple and inexpensive device.

(Operation) The scum generation preventing apparatus of the present invention uses the sedimentation tank (A) to reduce a certain amount of wastewater that has flowed in.
At the same time as storing, the amount of water corresponding to the wastewater that has flowed in over a certain amount is allowed to flow out (overflow).

The scum removing device (B) has its suction port installed on the water surface, sucks the floating sediment on the water surface, crushes the scum, degass and re-precipitates the scum, thereby reducing the generation of scum. To prevent.

The stirrer (C) stirs the sediment during operation, crushes the sediment compacted and solidified into a large lump larger than the palm of a hand, and at the same time causes air bubbles adhering to the flocs of the sediment to cause floating. Is deaerated by aeration or mechanical agitation, ie, scum is prevented from forming in the bottom sedimentation zone.

Also, the operation of the agitator (C) is stopped only during the period when the wastewater enters and exits the sedimentation tank (A), so that no sediment is mixed into the supernatant water. Can overflow (overflow). In addition, by operating the agitator (C) only during a period when no wastewater enters or exits the sedimentation tank (A), scum can be prevented by the above mechanism.

FIG. 1 is a partial cross-sectional view showing a scum generation preventing device of the present invention in which a scum removing device (B) and an aeration device as a stirring device (C) are attached to a sedimentation tank (A).
Is a partial plan view and a partial cross-sectional view in which the scum removing device (B) is attached to the sedimentation tank (A) and the flow directions of air and water are indicated by dashed arrows, and FIG. FIG. 4 is a partial cross-sectional view showing a state in which the aeration device is attached to the sedimentation tank to diffuse air, FIG. 4 is a schematic diagram of the scum removal device, and FIG. FIG.

As shown in FIG. 1, a scum generation preventing device 1
Is a settling tank 10, a scum removing device 12, and a stirring device 1
4 The scum generation preventing device 1 is attached to a sedimentation tank 10 that performs a sedimentation step. The sedimentation tank 10 has a hopper shape and produces a sediment 15 at the bottom. The sediment 15 is an accumulation of slime, and is generally composed of microorganisms generally called sludge and residues of wastewater treatment. These sludges form flocs and have fine bubbles inside and outside. The size varies from a fine floc of 1 mm or less to a giant floc of 100 mm or more, and each can re-emerge as scum. The settling tank 10 is usually provided with an overflow pipe 11 so that the supernatant water 16 flows out when the raw water flows in.

As shown in FIG. 2, a plurality of the same scum removing devices 12 are attached, and the direction of the plurality of discharge ports 122 is such that a swirling flow as shown by a dashed arrow in the plan view is generated on the surface of the sedimentation tank. The scum is sucked through the suction port 121 without emitting a dead water area. As shown in the vertical cross-sectional view of FIG. 2, a vertical flow of water is not generated in the sedimentation tank, and a water flow is generated only in the pipe of the scum removing device.

The scum removal device is shown in more detail in FIG. The air supplied from the blower is first supplied to the scum transfer pipe 1 constituting the air lift pump of the scum removal device 12.
23 flows in from the lower part. Due to the principle of the air lift pump, an upward water flow is generated inside the scum conveyance pipe 123, thereby sucking the scum from the suction port 121.
The sucked scum is degassed while being transported in the tube, and is crushed and discharged toward the discharge port 122. The released scum quickly re-sediments due to crushing and degassing.

As shown in FIG. 3, a stirrer (using a diffuser) 14 winds up the sediment with a diffuser bubble 18 and stirs it to crush and degas the compacted and settled sludge. At this time, the precipitate and the supernatant water become a solid-liquid mixture 17, and the solid is re-precipitated when the stirring device 14 is stopped.

The scum generation preventing device was operated according to time charts A to E shown in FIG. In A, the scum removing device was operated continuously, and the air diffuser was operated intermittently from 2:00 to 3:00. B was operated alternately so that the air diffuser was operated from 2:00 to 3:00 and the scum removing device was operated at all times except 2:00 to 3:00. In C, only the scum removing device was operated continuously, and the air diffuser was stopped. D shuts off the scum remover and operates the diffuser intermittently from 2 to 3 o'clock. In E, both the scum removing device and the air diffusing device were stopped. F installed a float type scum skimmer and performed intermittent operation every hour.

In a hopper-type settling tank of 200 liters, 5000 milligrams of activated sludge per liter was arbitrarily introduced from 6:00 to 24:00 at a rate of 150 liters per day. At this time, it was examined whether or not supernatant water containing about 100 milligrams of sludge per liter could be obtained by overflow when activated sludge was introduced. The experimental period was two weeks, and the settled sludge was appropriately extracted so that supernatant water could be continuously taken. The results are shown in Table 1.

[0026]

[Table 1] As is evident from the results in Table 1, the contaminant concentration of the supernatant water in A and B is very low as compared with other values.

[0027]

The scum generation preventive device of the present invention breaks down, by stirring, flocculent sedimentation and flocculation which causes scum during the time when water does not enter and exit the sedimentation tank, and simultaneously removes floc from and inside the floc which causes floating. Adhered air bubbles can be removed, while floating flocs are removed on the water surface and re-precipitated, so that clear supernatant water can be constantly obtained. Furthermore, if an air diffuser is used as the agitator, it can be designed to be more compact than a conventional float scum skimmer.

Further, by using the specified scum removing device and the stirring device according to the second and third aspects, it is possible to make the device easily and compactly by processing a ready-made PVC pipe, so that the device is inexpensive and simple. This is suitable for a small processing tank used for a small purification tank or the like. Also, unlike the float type scum skimmer, the scum removing device is not a method of removing scum out of the sedimentation tank system, but a method of eliminating the cause of scum in the sedimentation tank system. It does not generate any upward water flow and does not induce new scum.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view illustrating an embodiment of a scum generation preventing device according to the present invention.

FIG. 2 is a partial plan view and a partial cross-sectional view illustrating a flow of water in a scum removing device in the scum generation preventing device.

FIG. 3 is a partial cross-sectional view illustrating an embodiment of an air diffusion device in the scum generation preventing device.

FIG. 4 is a schematic diagram of a scum removal device in the scum generation prevention device.

FIG. 5 is a time chart illustrating an operation state of the scum removal device and the air diffuser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scum generation prevention apparatus 10 Precipitation tank 11 Overflow pipe 12 Scum removal apparatus 121 Suction port 122 Outlet port 123 Scum transport pipe 14 Stirrer 15 Precipitate 16 Supernatant water 17 Solid-liquid mixture 18 Spray air bubbles

Claims (3)

[Claims] (1) When a wastewater is filled in the settling tank, the scum floating in the wastewater in the settling tank is suctioned and degassed and discharged into the settling tank. A scum removal device, and (C) a scum generation prevention device comprising a stirring device for dispersing the sediment of the wastewater deposited on the bottom of the sedimentation tank, wherein the scum generation prevention device is provided in the sedimentation tank (A). The stirrer (C) is deactivated only during the period during which the wastewater flows in or out, and the scum removal device (B) is operated at least during the period in which the stirrer (C) is deactivated. A scum generation preventing device characterized in that: 2. The scum removal device (B) utilizes an air lift pump.
A scum generation prevention device as described in the above. 3. The scum generation preventing device according to claim 1, wherein the stirring device (C) uses an aeration device for generating bubbles in water.