JPS6350077B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a batch-type sewage treatment device that can effectively discharge and remove scum.

[Conventional technology]

Conventionally, in batch-type activated sludge treatment equipment that performs aeration, precipitation, and discharge of supernatant liquid in one tank, the precipitated supernatant liquid is discharged after the sedimentation process, but at this time, scum remains in the treatment tank. are often emerging. The supernatant liquid is discharged by a supernatant liquid discharge means that moves up and down above the liquid surface. At this time, the scum is usually removed by a scum baffle surrounding the overflow pipe of the supernatant liquid discharge means. Prevents contamination. However, with conventional systems, when the scum bathful descends to the water surface, the scum inside the scum bathtubule inevitably flows into the overflow pipe of the supernatant liquid discharge means and is discharged, and it is difficult to separate and remove the scum. There was a problem that I couldn't do it. Another problem was that it was difficult to create an independent scum discharge mechanism because the water level in the tank changed.

[Summary of the invention]

This invention has been made in order to solve the above-mentioned problems.The aeration device that performs aeration by spouting a gas-liquid mixture during the aeration process sprays out only the liquid for a predetermined period of time after the discharge process is completed, thereby eliminating the above-mentioned discharge. A sewage circulation flow is generated in the horizontal return direction in the treatment tank whose water level has decreased during the process, and this circulation flow removes scum from the wastewater using a skimmer installed near the average water level above the low water level in the treatment tank. It is an object of the present invention to provide a sewage treatment device that can effectively eliminate the scum by advecting the scum in the direction of the scum and flowing it into the skimmer.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the batch type activated sludge treatment tank 1 includes a supernatant liquid discharge means 2, a skimmer 3 for scum discharge, and aeration is performed by jetting out a bubble mixture during the aeration process. An aeration device (jet aerator) 4 is arranged to jet out only the liquid for a predetermined period of time after the discharge process is completed. As shown in FIG. 2, the supernatant liquid discharge means 2 is for discharging the supernatant liquid during the discharge process following the precipitation process, and is supported so as to be movable up and down about a shaft pipe 5. It consists of a discharge pipe 6, an overflow pipe 7 attached to the free end of the discharge pipe 6 and having an overflow port 7a, and a float 8. Therefore, when the overflow pipe 7 is descending from the high water level (HWL) in the treatment tank 1 to the low water level (LWL), the supernatant liquid in the treatment tank 1 is discharged from the overflow of the supernatant liquid discharge means 2. It flows into the overflow pipe 7 from the flow port 7a, and is discharged to the outside through the shaft pipe 5. Further, in a state where the overflow pipe 7 is rotated and displaced by a rotation means (not shown) so that it is at a position higher than the high water level liquid level, the liquid in the processing tank 1 is not discharged. Here, the skimmer 3 for scum discharge is operated near the average water level in the treatment tank 1, more specifically at the second
In the figure, a scum outlet 3a is arranged horizontally in the direction across the treatment tank 1 near the mean water level (MWL) above the low water level (LWL), and has a scum discharge port 3a that opens at the mean water level above the low water level. are doing. In addition, the above skimmer 3 is a low water level (LWL)
mean water level (MWL) between and high water level (HWL)
It can be installed anywhere as long as it is nearby. The skimmer 3 includes, as shown in FIG.
A scum discharge valve 9 is connected which is opened only at a predetermined time after the discharge process is completed. The aeration device 4 generates a circulating flow in the direction of the arrow (reflux direction) in the treatment tank 1 by spouting only liquid, and performs aeration by jetting out a gas-liquid mixture during the aeration process, and is a circulation pump. 10 and
It is composed of an aeration blower 11 which is controlled by switching, and achieves a sufficient stirring and mixing effect with a small amount of power by ejecting the gas-liquid mixture, that is, by shearing the jet flow and entraining the surrounding flow. Here, in the aeration step, both the circulation pump 10 and the aeration blower 11 are operated to blow out the gas-liquid mixture. However, since gas-liquid mixing is not required when the scum is advected in the direction of the skimmer 3 during a predetermined period of time after the discharge process is completed, only the circulation pump 10 is operated to generate only the circulation flow in the direction of the arrow. Even if you set this predetermined time with a timer,
It may also be set using the water level in the tank. Next, the operation of this invention will be explained. Inside the treatment tank 1, there is an aeration process in which the inflowing wastewater is aerated while generating a circulating flow in the direction of the arrow by ejecting the gas-liquid mixture from the aeration device 4, and the other process is to aerate the inflowing wastewater by stopping the air blowing and removing the liquid from the liquid. The operation of 1 cycle consisting of the precipitation step of precipitating the activated sludge and the discharge step of lowering the supernatant liquid discharge means 2 and discharging the supernatant liquid is repeated, and the activated sludge is continuously or optionally supplied from the inlet 1a. The inflowing sewage is mixed with activated sludge and treated. Further, the sludge in the treatment tank 1 is extracted at an appropriate time. Here, when the discharge process is completed, the liquid level is low and new sewage flows in from the inlet 1a. At almost the same time, only the circulation pump 10 of the aeration device 4 is activated, and only the liquid is ejected to generate a circulation flow, and by this circulation flow,
The scum is advected in the direction of the arrow in FIG. 1 and collected near the scum discharge port 3a of the skimmer 3 as shown in FIG. The water level in the treatment tank 1 gradually rises due to the inflowing wastewater, and when the liquid level in the tank reaches around the average water level above the low water level, a control device (not shown) is activated. Thus, the controlled scum discharge valve 9 changes from the closed state to the open state, and the scum is discharged to the outside of the treatment tank 1 together with the inflowing sewage. In this case, until the liquid level reaches around the average water level,
The scum is circulated within the treatment tank 1 by a circulation flow caused by only the liquid ejected from the aeration device 4. Therefore, by checking the time it takes for the water level to reach the vicinity of the average water level from a low water level and delaying it by setting a timer, it is possible to reduce the time during which the scum circulates within the processing tank 1. After a predetermined period of time (for example, about 3 to 5 minutes) has elapsed, the scum discharge valve 9 is closed, scum discharge is completed, and a new aeration process is started. The scum discharge valve 9 may be opened by a signal when the supernatant liquid discharge means 2 reaches a low water level and the downward movement of the supernatant liquid discharge means 2 is stopped. In this way, detection near the average water level is not necessary. Further, the scum may not be discharged every time, but may be discharged as needed.

【Effect of the invention】

As described above, according to the present invention, by generating a liquid circulation flow in the treatment tank by liquid jetting from the aeration device after the discharge process is completed, the scum is transferred toward the skimmer by this liquid circulation flow. The scum can be smoothly discharged from the skimmer, which has the excellent effect of effectively and reliably removing scum from a batch type activated sludge treatment tank where the water level fluctuates.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view thereof. 1... Batch type activated sludge treatment tank, 2... Supernatant liquid discharge means, 3... Skimmer, 4... Aeration device.

Claims (1)

[Claims] 1. A batch-type activated sludge treatment tank that repeats an aeration process, a precipitation process, and a discharge process, a supernatant liquid discharge means that is arranged vertically movably within this treatment tank and discharges a supernatant liquid during the above-mentioned discharge process, and the above-mentioned treatment A skimmer is installed near the average water level above the low water level in the tank and is opened for a predetermined period of time after the discharge process, and a skimmer is placed in the treatment tank to mix gas and liquid during the aeration process. In addition to aeration by jetting out the liquid, the scum in the liquid in the tank is removed by ejecting only the liquid over a predetermined period of time after the completion of the discharge process to generate a circulating flow in the horizontal reflux direction within the treatment tank. and an aeration device that advects water toward the skimmer.