JPS5929085A - Solid-liquid separator in water treatment plant - Google Patents

Abstract

PURPOSE:To provide a titled device which has adequate floating performance without decreasing the treatment performance of an aeration tank, by providing a circulation pump and a gas supply device in the midway of a supply conduit for the treated water of a solid-liquid sepn. tank arriving at the deep part of the aeration tank provided through the flow passage for the liquid mixture of the aeration tank. CONSTITUTION:A circulation conduit 6 for the treated water of a solid-liquid sepn. tank 2 arriving at the deep part of an aeration tank 1 is provided through the flow passage for the liquid mixture of the tank 1. The conduit 6 arrives at prescribed depth along the flow passage (ascending flow passage) 5 of the vessel 1, ascends again along the passage 5 and is conducted to the solid-liquid sepn. tank so that the treated water in the tank 2 circulates in the conduit 6. A circulation pump 7 and a gas supply device 8 exist in the midway of the conduit 6. The device 8 is used to supply the gas to be dissolved in the liquid under circulation. A defoaming device 9 which removes coarse foam is provided in the midway of the conduit 6 and a saturation tank 10 in the deepest part of the conduit 6 in the tank 1, respectively. The amt. of the gas dissolved in the treated water in the tank 2 is improved by the above-mentioned constitution, whereby the floating capacity for the activated sludge by fine foam is adequately obtd.

Description

[Detailed description of the invention] The present invention relates to a solid-liquid separation device in water treatment equipment.

A vertical aeration layer is used to internally circulate sewage and factory wastewater and perform microbial treatment while providing aeration, and a solidification layer is used to separate the liquid treated in this vertical aeration tank into activated sludge and treated water. Water treatment equipment equipped with a liquid separation device is known. Conventionally, as one form of this type of equipment, the liquid treated in the aeration tank overflows from the upper part of the tank to the solid-liquid separator, and the solid-liquid separator separates this by attaching fine bubbles in the liquid to the activated sludge. In some cases, a method is adopted in which the waste is separated by flotation and recovered. This type of flotation separation occurs when dissolved gases dissolved in a liquid under pressure in a deep aeration tank precipitate out as fine bubbles when returned to atmospheric pressure, which adhere to the sludge and exert buoyancy. It takes advantage of this fact. However, in the above method in which treated water overflows from the top of the aeration tank to the solid-liquid separator, a considerable amount of the dissolved gas in the liquid turns into air bubbles during the process of the liquid rising inside the tank and reaching the top of the tank. , the amount of microbubbles in the overflowing liquid is not sufficient for flotation separation. In order to ensure a sufficient amount of microbubbles, a high flow rate (usually 1m/
It is possible to extract the liquid within a few seconds (seconds or more) and send it to the solid-liquid separation tank, but increasing the flow rate of the ascending flow path itself in order to obtain the above-mentioned high flow rate requires excessive operating power, which is uneconomical. In addition, there is a problem that the device becomes complicated if the speed is partially increased for extraction.

The present invention aims to solve the above-mentioned conventional problems and propose a solid-liquid separator that can obtain appropriate flotation performance without causing a decrease in the processing performance of the aeration tank.

For this reason, the present invention provides a circulation conduit for the solid-liquid separation tank treated water that reaches the deep part of the layer through the mixed liquid channel of the aeration tank, and a circulation pump and a circulation conduit for supplying gas to the circulation conduit in the middle of this circulation conduit. This system is equipped with a gas supply device, and utilizes the deep flow of the aeration tank to place the solid-liquid separation tank treated water under pressure, increasing the amount of dissolved gas, and using this as pressurized water together with the aeration tank effluent. By placing the barrel in the solid-liquid separation tank, a sufficient amount of fine bubbles is ensured in the solid-liquid separation tank, and appropriate sludge flotation performance can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which (1) is a vertical aeration tank, (2) is a flotation type solid-liquid separation tank, and (3) is the head tank of the aeration tank, ( 4) is a descending flow path, (
5) is an upward flow path.

The apparatus of the present invention has a circulation conduit (6) for the solid-liquid separation tank treated water that reaches the deep part of the aeration tank (1) through the mixed liquid flow path of the tank. In order to increase the microbubbles in the solid-liquid separation tank treated water, the present invention places the treated water at a high water depth and puts it under pressure so that a large amount of gas can be dissolved therein. For this purpose, the mixed liquid flow path of the aeration tank (1) is used for the piping of the circulation conduit (6).

That is, the circulation conduit (6) led from the solid-liquid separation tank (2) reaches a predetermined depth along the flow path (5) (increasing flow path in this example) of the aeration tank (1), and then returns to the flow path. (5) and is led to the solid-liquid separation tank (2).
The treated water of step 2) can be circulated within this circulation conduit (6).

A circulation pump (7) and a gas supply device (8) are interposed in the middle of the circulation conduit (6).

This gas supply device (8) supplies gas to be dissolved in the liquid during circulation, and for example, a compressor, blower, or ejector is used.

In addition, in this embodiment, a defoaming device (9) is installed in the middle of the circulation conduit (6) on the inlet side of the solid-liquid separation tank, and a saturation tank (10) is installed at the deepest part of the circulation conduit (6) in the aeration tank (1). are provided for each. The defoaming device (9) is provided to remove coarse bubbles because if coarse bubbles exist in the pressurized water, the bubbles will coalesce and the amount of fine bubbles that adhere to the sludge will decrease, which will have a negative effect on flotation performance. It will be done. This device (9) is, for example,
It consists of a box and a bubble removal tube attached to the top of the box. In addition, the saturation tank (10) is installed when it is desired to obtain pressurized water containing a larger amount of dissolved gas, and the saturation tank (10) is installed when it is desired to obtain pressurized water containing a larger amount of dissolved gas. By giving time, the gas is dissolved to near saturation concentration. The saturation tank (10) may be of any suitable type, such as one with a hollow interior or one with a suitable flow path formed therein.

Figure 2 shows another embodiment, in which the defoaming device (9) is large-sized, the treated water is circulated in the circulation conduit (6), and the degassing device (9) It is possible to supply pressurized treated water to the solid-liquid separation tank (2) in the same amount as the solid-liquid separation tank (2).

According to the above device, the circulation conduit (
The treated water circulated through 6) is guided to a high water depth together with the gas supplied by the gas supply device (8). The gas is dissolved in the liquid under high water pressure, and the treated water with a large amount of gas dissolved in this way is sent to the solid-liquid separation tank (2).
will be returned to. In this example, coarse air bubbles that do not dissolve in the liquid are removed by the defoaming device (9) on the inlet side.

According to the apparatus of the present invention described above, it is possible to increase the amount of gas dissolved in the treated water in the solid-liquid separation tank and to appropriately obtain activated sludge flotation performance due to fine bubbles. This has the advantage that it can be achieved with reasonable equipment that utilizes deep flow channels.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. FIG. 2 is an explanatory diagram partially showing another embodiment of the present invention. In the figure, (1) is an aeration tank, (2) is a solid-liquid separator,
(4) (5) indicates the flow path, (6) indicates the circulation conduit, and (8) indicates the gas supply device.■

Claims (1)

[Claims] In a solid-liquid separator that uses a flotation separation method and is configured so that liquid flows from the upper part of the aeration tank by overflow, circulation of the solid-liquid separation tank treated water reaches the deep part of the tank through the mixed liquid flow path of the aeration tank. 1. A solid-liquid separation device for a water treatment system, characterized in that a conduit is provided, and a circulation pump and a gas supply device for supplying gas into the circulation conduit are interposed in the middle of the circulation conduit.