JPS598436B2 - Flotation separation method for solids contained in sewage sludge, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved flotation separation method in which solids contained in sewage sludge and the like are floated and separated using fine air bubbles of uniform particle size.

Conventionally, in this type of solid flotation separation method, treated water saturated with air under pressure is injected together with sewage sludge into a flotation tank, and dissolved air is precipitated by rapidly reducing the pressure in the separation tank. This causes fine bubbles to be generated, and the solid matter in the sludge in the tank is attached to the bubbles and floated together with the bubbles to be separated.

However, this method uses air dissolved in water, so there is a limit to the amount of bubbles, and it also requires a high-pressure tank, compressor, high-pressure pump, etc. to bring the air and water into contact under high pressure.

In addition, if the dispersed air flotation method uses a perforated plate or rotary blade to generate a large amount of air bubbles, coarse air bubbles are likely to be generated, which reduces the amount of sludge adhering and flotation, and also causes turbulence to cause floating floss. It has drawbacks such as easy settling and difficulty in removal after flotation.

In view of this, the present invention is designed to uniformly form bubble particles in the separation tank in a fine and uniform manner so that solids in sewage can be effectively floated and separated without causing turbulence in the separation tank. , will be explained below based on the illustrated embodiment.

In the figure, 1 is a flotation separation tank, into which sewage sludge, etc. is supplied through a supply pipe 2, and at the bottom of the tank there is also a sludge pipe 3 for discharging settled solids. A floss scraper 4 for scraping and discharging floating solids is installed at the top.

Furthermore, this separation tank 1 has a solid matter discharge tank 5 for discharging floating solid matter scraped by the floss scraper 4 to the outside of the tank.
A drainage tank 6 is provided adjacent to the scraper 4 and on the side opposite to the sewage sludge supply side of this separation tank and in communication with the lower part of the solids discharge tank, and the solids are floated and separated. Water overflows from the weir γ and is drained outside the tank.

In addition, when sewage sludge, etc. is injected into the separation tank, the bubble water containing finely divided air bubbles is mixed with the sewage sludge and supplied to the separation tank. Manufactured.

That is, the in-line mixer 1 is installed adjacent to the coarse foam separation tank 8 so as to absorb water from the upper part of the tank 8, which is conductive at the upper part of the tank and partitioned at the lower part by a partition plate 9.
0 is provided, and the treated water absorbed from the tank 8 is subjected to a large shearing force by the turbine and stator within this in-line mixer.

At this time, the air sucked in at the same time as the treated water is pulverized and supplied to the lower part of the coarse bubble separation tank 8 together with the treated water, and the large bubbles in these bubbles have a higher floating speed than fine bubbles and are discharged into the tank 8. The large bubbles will rise to the water surface in a short time and disappear, but the fine bubbles will float in the tank.

These fine bubbles, especially the bubbles of 0.1X or less required for flotation separation of solids, have a slow flotation speed of 100 mm/mil@, so the amount of them that floats to the water surface and disappears is extremely small.

These microbubbles are suspended in the treated water and flow down over the partition plate 9 to the chamber on the opposite side from which they were discharged from the in-line mixer, and then flow through the bubbly water supply pipe 11 connected to the lower part of the bubbly water discharge chamber B. The sewage sludge is supplied into the sewage sludge supply pipe 2, mixed with sewage sludge, and then supplied to the separation tank.

In this separation tank 7, solid matter in the sewage sludge adheres to uniform fine bubbles, floats to the water surface, separates, and is discharged as froth, similar to conventional flotation separation.

In addition, as a method for forming uniform fine bubbles, instead of using an in-line mixer, aerated water may be produced using an external air self-priming mechanical diffuser 12 in a coarse bubble separation tank as shown in FIG. .

Furthermore, it is possible to remove coarse bubbles using a hydrocyclone, and to generate bubbles, the process consists of an air introduction device and a mixing device that atomizes the introduced air, and the water in the bubble water storage tank is circulated. It is also possible to increase the amount of fine bubbles and eliminate coarse bubbles.

Reference numeral 13 denotes a wastewater supply pipe for supplying wastewater from the wastewater tank 6 into the coarse bubble separation tank 8 using a pump P.

Therefore, in the pressure flotation method, in which treated water saturated with air is injected into a flotation tank under pressure and dissolved air is precipitated and turned into bubbles, the injection of high-pressure water creates turbulence, which disturbs the hardened froth and creates bubbles. Solids may be difficult to adhere to and may settle.

In addition, in order to float 1 kg of solid matter in sludge, approximately 15
t of air is required, and the amount of water required to dissolve 15 t of air is o. Approximately 57 If is required.

In other words, when treating one volume of sludge with a solid concentration of 1%, it is 150 tons.
However, in the present invention, the treated water is uniform and contains a large amount of fine bubbles in advance, and this is used as sewage sludge. Since the mixture is mixed and fed into the flotation separation tank, turbulence is less likely to occur in the tank, and since the air bubbles are uniformly fine particles, adhesion of air bubbles and solids is promoted, making it efficient. Capable of flotation separation, compared to the dissolved air precipitation method which has a limit on the amount of bubbles generated, it is possible to inject as many fine bubbles as necessary after removing coarse bubbles in advance, and it is easier to use high pressure tanks, high head pumps, etc. than conventional methods. This method has advantages such as eliminating the need for a simple device and low running costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing one embodiment of the present invention, and FIG. 2 is a diagram of a different embodiment of the microbubble generator. 1...flotation separation tank, 2...supply pipe, 3
...Sludge removal pipe, 4...Scum scraping machine, 5
...Solid discharge tank, 6...Drainage tank, 7
...Weir, 8... Coarse bubble separation tank, 9.
..... Partition plate, 10 ..... In-line mixer, 11 ..... Aerated water supply pipe, 12 ..... Air diffuser, 13 ..... Drainage supply pipe , P...
Pump, B...Bubble water discharge chamber.

Claims (1)

[Claims] 1. In a device that floats and separates solids contained in sewage sludge, etc. by generating fine bubbles in a separation tank, the coarse bubbles generated by the bubble generator are used to utilize the difference in floating speed between the coarse bubbles and the fine bubbles. After removing the bubbly water, which contains a large amount of microbubbles with a substantially uniform particle size, the mixture is mixed with sewage sludge, etc., and then injected into a flotation tank. A flotation separation method for solids contained in sewage sludge, etc.