JPH0127920Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a so-called deep shaft type water treatment equipment. 2. Description of the Related Art A so-called deep shaft type water treatment facility is known as a device for biologically treating and purifying sewage and industrial wastewater. This equipment has 50 to 150
It has a vertical aeration tank (deep shaft) with a depth of m. It is equipped with an air system, and the mixed liquid (wastewater plus activated sludge) is circulated from the downward flow path to the upward flow path for biological treatment. In addition, this type of equipment has a solid-liquid separator, and the treated liquid is sent to this solid-liquid separator, where the liquid is separated into treated water and activated sludge, and only the activated sludge is transferred to the vertical type. It is designed to be sent back to the aeration tank.
By the way, in such equipment, air is blown into the liquid by the aeration device, so a large amount of foam is generated at the top of the aeration tank, and if left untreated, it can overflow outside the tank and cause circulation pollution. be. In addition, air is blown into the raw water receiving tank, sludge storage tank, etc. attached to the equipment to prevent rot.
These tanks also have the same foaming problem as above. Conventionally, as a countermeasure against this problem, foaming is eliminated by spraying water at the foaming location, but with this method, it is necessary to install a spray device at each foaming location, and the treated water itself is used for watering. The drawback is that it requires a large amount of water, about 20%. In addition, in an aeration tank in which the head tank is a closed type and back pressure is generated in the head tank by gas,
For example, as seen in JP-A No. 56-85282, a closed pressurized water tank with a gas vent at the top is provided, and a ventilation pipe connected to the top of the head tank is guided into the pressurized water tank, and its tip is connected to the top of the head tank. The vent conduit is located at a predetermined depth in the pressurized water tank, and gas is released from the vent conduit only when the back pressure in the head tank exceeds a predetermined level. However, even with this equipment, the bubbles generated in the head tank are only guided into the pressurizing water tank through the ventilation pipe, and a large amount of foaming occurs in the pressurizing water tank, and unless water is sprinkled, the bubbles will overflow from the gas vent. I'll wash it away. The present invention was devised to solve these conventional difficulties, and is a system that can properly defoamer foam generated in vertical aeration tanks, etc., without requiring special water for defoaming. Its purpose is to provide. For this reason, the present invention adopts a configuration in which defoaming can be performed using a mixing tank for mixing wastewater and sludge returned from the solid-liquid separation tank, and the wastewater flowing into the mixing tank. Its basic feature is that the upper part of the tank where bubbles are to be generated is sealed, and a foam outlet pipe is guided from the upper part of the tank into the mixing tank, and the waste water inflows from the tip of the foam outlet pipe and the upper part of the tank. A perforated plate is disposed between the tank and the tank to sprinkle wastewater falling from the wastewater inlet onto the water surface in the tank. The present invention will be explained in detail below. Among water treatment facilities equipped with vertical aeration tanks, equipment equipped with a mixing tank that mixes wastewater (raw water) sent from outside the system with returned sludge separated in a solid-liquid separation tank and sent back is known. However, the major feature of the present invention is that the mixing tank is heated to eliminate foam. Figures 1 and 2 show an embodiment of the present invention, in which 1 is a vertical aeration tank, 2 is a solid-liquid separation tank, 3 is a mixing tank, 4 is a water tank for pressurization, and 5 is a vertical aeration tank. 6 is also an upward flow path, and 7 is an upper head tank. The downward flow path 5 and the upward flow path 6 communicate with the lower end of the tank and the head tank 7. Further, 8 is an outflow conduit led from the middle of the ascending channel 6 to the solid-liquid separation tank 2, and 9 is an outflow conduit led from the mixing tank 3 into the ascending channel 6, and the end thereof rises in a U-shape at the bottom of the ascending channel. It is an inflow conduit. Furthermore, 10 is a floating sludge scraping device, 11 is a groove for discharging the scraped activated sludge, and in this embodiment, wastewater is supplied into the groove 11 from outside the system through a conduit 12, and a conduit 13 The sludge is sent to the mixing tank 3 together with the returned sludge through the sludge. Further, in order to maintain a constant back pressure in the closed type head tank 7, the pressurizing water tank 4 is provided, and a ventilation conduit 14 is led into the pressurizing water tank 4 from the upper part of the head tank 7, and its tip is connected to the inside of the tank. It is located at a predetermined depth. In the above configuration, the pressurizing water tank 4 has its upper part sealed, and the foam outlet pipe 15 is led into the mixing tank 3 from the upper part of the sealed tank, so that the pressurizing water tank 4 is connected to the mixing tank 3. It is designed to send out the bubbles that are generated. It is preferable that the tip of the foam outlet pipe 15 is positioned so as not to reach the water surface in the mixing tank. The conduit 13 is connected to the mixing tank 3 at a position above the tip of the foam outlet pipe;
A perforated plate 17 is disposed between the wastewater inlet 16 position and the foam outlet pipe tip position, and the wastewater inlet 1
The wastewater (including returned sludge) falling from the tank can be sprayed onto the water surface in the tank. It goes without saying that both the wastewater inlet 16 and the perforated plate 17 should be located above the water surface in the mixing tank 3. In this embodiment, the perforated plate 17 is attached to the inner wall of the mixing tank 3 so as to cover the entire inside of the mixing tank 3, and the bubble outlet pipe 15 extends downward through the perforated plate 17. Furthermore, in this embodiment, a defoaming device 18 is auxiliary disposed above the perforated plate 17, so that water can be sprinkled when the defoaming effect of the waste water is not sufficient. As this defoaming device 18, an appropriate device such as a spray nozzle or a perforated plate similar to that described above can be used. To explain what else is shown in the drawings, 19
is a bottom circulation conduit installed between the lower part of the solid-liquid separation tank 2 and the mixing tank 3, and the activated sludge settled by the scraping device (not shown) installed at the lower part of the solid-liquid separation tank 2 is scraped up and then collected at the bottom. It is returned to the mixing tank 3 via the circulation conduit 19. In addition, 20 is a discharge groove for treated water from which sludge has been separated, and 21 is aeration in the end of the inflow conduit 9 that rises in a U-shape in the downward flow path 5 and the upward flow path 6 of the vertical aeration tank. This is an air diffuser that performs The scraping device 10 is composed of sprocket wheels 22, 22, an endless chain 23, and scraping elements 24 attached at intervals to the endless chain. Note that, although the above-described embodiments show the case where the present invention is applied to equipment having a pressurized water tank, it goes without saying that the embodiments of the present invention are not limited thereto. That is, regardless of the presence or absence of the pressurizing water tank 4, the foam outlet pipe can be led directly from the head tank 7 to the mixing tank 3. In addition, as mentioned above, in addition to the vertical aeration tank and pressurized water tank, there are other tanks in water treatment equipment that may cause foaming, such as sludge storage tanks and raw water receiving tanks, and these should also be sealed at the top. From there, the foam outlet pipe can be led to the mixing tank 3. As a preferred embodiment of the present invention, it is possible to adopt a configuration in which all the tanks that require water sprinkling are of a closed structure, and the foam outlet pipe 15 is led from these to the mixing tank 3. Foaming countermeasures in water treatment can be limited to the mixing tank only. Next, the operation of the present invention will be explained. In the equipment shown in FIGS. 1 and 2, the air diffuser 2
1 supplies air as an oxygen source for oxidative decomposition of wastewater into the tank, and the ascending flow path 6

[Inflow conduit] An airlift pump is formed at the top by aeration inside the pipe, and wastewater (mixed liquid) is oxidized and decomposed by activated sludge while repeatedly rising and falling in the aeration tank. Wastewater from outside the system flows into the groove 11, and further flows into the mixing tank 3 through the conduit 13 together with the return sludge discharged into this groove from the solid-liquid separation tank 2. Furthermore, the air is drawn into the inflow conduit 9 due to the air lift effect caused by the air diffused from the air diffuser 21, and flows into the ascending channel 6. A large amount of air from aeration is dissolved in the liquid descending through the descending channel 5 due to its hydrostatic pressure, and a portion of this liquid ascends the outflow conduit 8 as a treated liquid and is discharged into the solid-liquid separation tank 2. Served.
As shown in the figure, this treated liquid is extracted from the deep part of the ascending channel where there is still a large amount of dissolved gas in the liquid, and the dissolved gas in the liquid is mainly precipitated as microbubbles in the solid-liquid separation tank 2. , adheres to activated sludge and causes it to float. The floated activated sludge is scraped up by the scraping device 10 and discharged into the groove 11. Further, as described above, the sludge that does not float and settles to the bottom of the solid-liquid separation tank is scraped up by the lower scraping device and returned to the mixing tank 3 through the bottom circulation guide 19. During the process described above, a predetermined back pressure is applied to the head tank 7 by the water in the pressurizing water tank 4, and only when the back pressure in the head tank exceeds a predetermined level is water released into the head tank 7. Ru.
The bubbles accumulated in the pressurizing water tank 4 are led to the mixing tank side through the foam outlet pipe 15 and are discharged to the water surface in the tank. Wastewater mixed with return sludge flows in from the wastewater inflow section 16 above the water surface, and as this wastewater passes through the perforated plate 17, it is sprayed onto the water surface.
Defoaming is performed. Moreover, if the defoaming by this waste water is not sufficient, water is separately sprinkled from the defoaming device 18 at the top. In addition, it goes without saying that when the present invention is applied to other tanks, appropriate defoaming will be performed in the same way, especially for all tanks that require water sprinkling for water treatment. When the present invention is applied, there is an additional advantage that the foaming countermeasure is limited to only one mixing tank, and the foaming countermeasure can be implemented rationally and economically for the entire water treatment facility. According to the present invention described above, the upper part of the tank where bubbles are to be generated is sealed, and the foam outlet pipe is led into the mixing tank from the upper part of the tank, and the tip position of the bubble outlet pipe in the mixing tank and its upper part are A perforated plate was installed between the wastewater inlet and the wastewater inlet to sprinkle the wastewater that falls from the wastewater inlet on the water surface in the tank, so that bubbles generated in the vertical aeration tank can be removed by special watering. There is an advantage that foaming can be appropriately eliminated using the wastewater flowing into the system without having to do so, and that foaming countermeasures in water treatment equipment can be taken rationally and economically.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is an overall explanatory view, and FIG. 2 is a partially enlarged explanatory view of the mixing tank in FIG. 1. In the figure, 1 is a vertical aeration tank, 2 is a solid-liquid separation tank, 3 is a mixing tank, 4 is a pressurizing water tank, 15 is a foam outlet pipe, 16 is a wastewater inlet, and 17 is a perforated plate.

Claims (1)

[Scope of utility model registration request] In a water treatment device that has a mixing tank for mixing wastewater and sludge returned from a solid-liquid separation tank, and is configured to supply the mixed liquid in the tank to a vertical aeration tank, there is a problem in which foam should be generated. While sealing the top of the tank,
A foam outlet pipe is led into the mixing tank from the top of the tank, and between the tip of the foam outlet pipe in the mixing tank and the wastewater inlet position above it, wastewater falling from the wastewater inlet is guided into the tank. A water treatment device equipped with a vertical aeration tank characterized by a perforated plate for sprinkling water on the water surface.