JPS60225685A - Method and apparatus for floating treatment of sludge - Google Patents

Abstract

PURPOSE:To recover a high concn. sludge solid within a short time with good efficiency, by electrochemically performing the adsorption of air bubbles and the sludge solid while supplying said sludge solid to a separation tank from a reaction tank by dynamic water pressure. CONSTITUTION:An aqueous solution of a flocculant capable of being charged to charge corresponding to the characteristic of a sludge solid having to receive concn. treatment is sent to a mixing apparatus 6 along with air and mixed with air under stirring. Next, the resulting mixture is sent to a foaming tank 7 and stirred under atmospheric pressure to generate fine air bubbles and guided to a reaction tank 3 to be mixed with dirty water supplied by a sludge supply pump 2. At this time, the surfaces of fine air bubbles are electrochemically adsorbed with that of sludge solid particles to each other by the action of the flucculant and, because a gradually rising water level forms a water head pressure between said water level and that in a separation tank 11, said solid particles are flowed into the separation tank 11 and floated to the upper part in the separation tank 11 by the action of fine air bubbles. By this method, the concn. sludge solid is separated from lower clear water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sludge flotation treatment method and its apparatus, and more particularly to a treatment method and its apparatus characterized by a sludge flotation and concentration step.

Conventional Technology As is well known, sludge concentration techniques include sedimentation concentration, flotation concentration, and the like. The flotation concentration technology described above is generally considered to be able to provide more effective sludge concentration results than sedimentation concentration technology, and has recently been used in sludge treatment facilities, sewage treatment facilities, and the like.

However, conventional sludge flotation concentration technology is mostly a pressurized flotation concentration method or device. In other words, air is dissolved in circulating water under pressure, and in the process of sending the water to the bottom of the separation tank by a pump, it is returned to atmospheric pressure and introduced into the bottom of the separation tank together with the sludge to be concentrated. Because the adsorption form of sludge solids is physical, solids are absorbed by fine air bubbles.
According to many experiments, possible thickened sludge concentrations range from 4% to 5%.
%, and there is a limit to the concentration of sludge solids with higher concentrations. Also, since the water introduced into the separation tank is pressurized by the pump, circulation occurs within the separation tank and the sludge interface is disturbed, so increasing the thickness of the floss will reduce the sludge solid content recovery rate. There is a tendency. Furthermore, in order to achieve high concentration, the residence time in the separation tank is relatively long. Therefore, there are limits to effective concentration. Also, in general, floating floss is concentrated due to the consolidation effect from below, so it is said that the thicker the floss, the higher the concentration effect, but the area load of the pressurized flotation concentrator is Since the force that pushes the floating sludge to the water surface is weak, the sludge concentration does not increase even if the floss is thick. ■According to many experiments,
The area load of this device is 20Kg-D, S, /r
n' and h are the limits, and the problem to be solved by the invention.Therefore, the present invention is: 1. By strengthening the adsorption power of air bubbles and sludge solids, it is possible to set a sufficiently large air-solid ratio, and a high concentration of sludge solids can be obtained. The purpose of the present invention is to provide a method and device that can improve the sludge solid content recovery rate without causing disturbance of the sludge interface, and furthermore, It is an object of the present invention to provide a method and apparatus capable of achieving high concentration with a long residence time. Another object of the present invention is to provide a method and apparatus capable of better compacting sludge pushed up to the water surface by a large amount of air bubbles and concentrating highly concentrated sludge solids. and (1) to provide a device that can maintain a substantially constant sludge recovery rate regardless of the area load, and (3) to provide a device that occupies a small area for installation, is compact, and is easy to maintain and inspect.

Means and operation for solving the problems In order to achieve these objectives, microbubbles charged with an opposite charge to the charge outside the floating sludge of the present application are generated, and the microbubbles and polluted water are reacted to form sludge. Sludge solids and microbubbles are electrochemically adsorbed while coagulating solids, and then sent to a separation process using hydrodynamic pressure. In the separation process, sludge solids are floated and concentrated, and they are scraped off to remove pollution. The sludge flotation treatment device of the present application is configured to separate water into concentrated solids and bottom clear water, and the sludge flotation treatment device of the present application includes a mixing device for mixing an aqueous flocculant solution with foaming properties and air, and a mixing device for mixing these with air. It consists of a bubbling tank for generating fine bubbles through generated turbulent flow, and a flocculant supply pipe system that supplies fine bubbles charged to the opposite charge to the surface charge of the sludge solids to be treated, and a condensing agent supply pipe system. A polluted water supply pipe system consisting of a water supply pump is equipped with a stirring means to start coagulation of the sludge solids in the polluted water, and to electrochemically adsorb the coagulated sludge solids and fine bubbles. The reactor has a structure characterized in that the reaction scraping means is provided in series with the reaction tank, and a discharge system for clear water is connected to the lower part.

Example Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the figure, 1 indicates a sludge supply pipe, which is connected to a reaction tank 3 via a sludge feed pump 2.

On the other hand, a flocculant supply pipe system is connected to this reaction tank 3.

That is, the flocculant supply pipe system sequentially connects the flocculant aqueous solution tank 4, flocculant feed pump 5, mixing device 6, and foaming tank 7 from the second stream, and also connects the flocculant aqueous solution tank 4, flocculant feed pump 5, mixing device 6, and foaming tank 7 between the feed pump 5 and the foaming tank 7. The flocculant aqueous solution tank 4 is connected to an air supply pipe 9 that is fed by a blower 8, and the flocculant aqueous solution tank 4 contains sludge that has foaming properties and is to be concentrated in the foaming tank 7. It has a 0° twisted shape that produces microbubbles charged with an electric charge opposite to the electric charge on the surface of the solid object, and elements with the twist direction to the right or left are arranged alternately as right-handed elements and left-handed elements. , and is configured as a continuous mixing/stirring device which is fixed so as to form left and right double strands 906, respectively, and the foaming tank 7 further comprises a tank and a stirring means driven by an electric motor.

Now, the reaction tank 3 described in section 2 is composed of a stirring means driven by an electric motor, and is connected to the next-stage separation tank 11 via a pipe IO. In the separation tank 11, the tip of the pipe IO opens at the bottom, and a scraping means 17 is arranged near the upper water surface. This scraping means 12 includes, for example, several scraping devices in which a plurality of scraping blades are driven endlessly by an electric motor, arranged in a radial manner on the upper part of the tank, and further arranged around the circumferential edge of the tank part. A collection groove is formed in the shape of
Separate scraping blades are provided within the collection groove for circumferential movement.

After reacting the foam and sludge water to start coagulation of sludge solids and electrochemically adsorbing the sludge solids and fine bubbles, the water head in 1 reaction tank 3 is increased to send the foam to separation tank 11. The water level in the reaction tank 3 and the water level in the separation tank 11 are maintained at approximately the same level, and when polluted water, etc. is supplied to the reaction tank 3, , the water head of the rising water level corresponding to the supplied amount sends them to the separation tank 11, and the sludge solids and bottom clear water are sequentially separated and discharged from the separation tank 11 as described later. supply by the difference in water head,
That is, the supply by hydraulic pressure is carried out continuously. Now, to the separation tank ll, a sludge solids discharging pipe 14 having a feed pump 13 is connected in the middle corresponding to the position where the scraping means 12 is disposed, and a sludge solids discharging pipe 14 is connected to the lower part. A bottom clear water distribution pipe 15 is connected to the drain pipe 15, and the pipe 15 is continuously connected to the discharge pipe 15.

The water level adjustment device 16 has a vertically movable nozzle that can be adjusted vertically from the outside.The water level is determined by the position of the nozzle, so the water level in the separation tank 11 is adjusted based on this water level.

Further, the above-mentioned suspended solids filter has an endlessly driven mesh arranged inside the tank.

In this example, before introducing the separated bottom clear water to the discharge system, the secondary side of the feed pump 19 and the mixing device 6 are used to recover the flocculant mixed into the water. A recovery pipe 20 connects the primary side of the separation tank 11.
This figure shows an example in which a sludge return pipe 21 is connected between the bottom of the sludge supply pipe 1 and the sludge supply pipe 1.

Next, the operation of this embodiment will be explained.

If the solid sludge stored in the aqueous coagulant solution tank 4 has foaming properties and is to be concentrated and is organic, its surface is negatively charged, and if it is inorganic, it is positively charged. Therefore, depending on its properties, an aqueous flocculant solution is sent to the mixing device 6 by the feed pump 5 so that the surface of the bubbles generated in the next step and thereafter can be charged at an electric charge opposite to that of the surface of the sludge solids. In the process, the air sucked in by the blower is dissolved in the aqueous condensate solution and sent to the mixing device 6. In the mixing device 6, the flocculant aqueous solution and air are divided by the action of dividing the flow, reversing the flow to right-handed and left-handed twisting, and converting the flow from the center to the wall and from the wall to the center. The flocculant aqueous solution is better mixed and stirred, and fine air particles are uniformly mixed into the flocculant aqueous solution, which is then led to the primary foaming tank 7. In the foaming tank 7, a turbulent region is formed by stirring at normal pressure, and the shear force of the turbulent flow generates fine bubbles of about 300 to 500 millimicrons. The generated microbubbles are then led to the reaction tank 3, where they are mixed with polluted water sent by the sludge supply pump 2,
Due to the action of the coagulant, the sludge solid particles in the polluted water begin to coagulate, and since the surfaces of the micro bubbles and the surfaces of the sludge solid particles are electrically oppositely charged to each other, they electrochemically adsorb to each other. do. When the polluted water and the flocculant bubble liquid are supplied into the reaction tank 3, the water level in the reaction tank rises each time, and a water level difference occurs between the water level in the separation tank 11 and a water head pressure. The head pressure causes a flow from the reaction tank 3 to the separation tank 11, and the polluted water that starts coagulation and suspends the sludge solids to which fine bubbles are attached is sequentially guided to the separation tank 11. In the separation tank 11, the sludge solids that have aggregated and are captured by fine bubbles are collected in the separation tank 11.
When the sludge flows into the lower part of the tank 1, it is floated to the second part of the separation tank 11 by the action of the fine bubbles, and solid sludge is concentrated in the upper part of the separation tank 11, while water is separated in the lower part as bottom water.

Since the flow from the reaction tank 3 to the separation tank 11 described above is carried out by being pushed out by hydrodynamic pressure, no turbulence is generated in the separation tank 11, so that the liquid level in the separation tank 11 is not disturbed. do not have. Therefore, there is no effect of separating air bubbles from the floating sludge solids, and since the solids do not settle, the sludge solids float more reliably, and the concentrated sludge concentration can be increased.

Further, as mentioned above, the adsorption mode of the flocculated sludge solids and fine bubbles is strong because it is electrochemical adsorption, unlike physical adsorption such as a pressure flotation method. Therefore, the gas-solid ratio can be set sufficiently large, and sludge solids with a high concentration can be obtained. In addition, high concentration can be achieved by residence in the separation tank for a short time. Furthermore, a large amount of air bubbles generated in the foaming tank in the previous process and passed through the reaction tank are introduced into the separation tank, which effectively consolidates the sludge pushed up to the water surface as described above. The floating sludge is compressed and highly concentrated sludge solids can be separated.

Now, the sludge solids concentrated in the upper part of the separation tank 11 are collected by the scraping action of the scraping means 12, and sent by the pump 13 to be dewatered according to a conventional method. On the other hand, the separated bottom clear water at the bottom of the separation tank 11 is transferred to the separation tank water level adjustment device 1.
6, the suspended solids are sent to a suspended solids filter 17, where the contained suspended solids are removed, and then passed through a tank 18 to a pump 19.
is led to the exhaust system. A portion of the H is returned to the front of the mixing device 6 via the pipe 20, so that the flocculant contained therein can be reused.

In the above process, the flow from the reaction tank 3 into the separation tank 11 is caused by the head pressure based on the difference between the water level of the reaction tank and the water level of the separation tank 11. Separation tank l by changing the nozzle height of the device 16 from the outside
It can be adjusted as necessary by changing the water level.

As described in detail above, the first invention of the present application mixes an aqueous flocculant solution having foaming properties with air, and then stirs the mixture under atmospheric pressure to generate turbulent flow, thereby creating a turbulent flow on the surface of the sludge solids to be adsorbed. Microbubbles charged to the opposite charge are generated, and the microbubbles react with the polluted water to coagulate the sludge solids while electrochemically adsorbing the sludge solids and the microbubbles. A sludge flotation system characterized in that the sludge is sent to a separation process sequentially by water pressure, the sludge solids are floated and concentrated in the separation process, and the sludge is scraped off to separate the polluted water into concentrated solids and bottom clear water. The second invention of the present application is a mixing device for mixing an aqueous flocculant solution having a foaming property with air, and a foaming device for stirring these to generate fine bubbles through the generated turbulent flow. A flocculant supply pipe system consisting of a tank and supplying microbubbles charged with a charge opposite to that of the surface of the sludge solids to be treated, and a polluted water supply pipe system consisting of a polluted water feed pump are connected to each other by a stirring means. microbubbles that are connected to a reaction tank and flowed in by hydraulic pressure from the reaction tank to start coagulation of the sludge solids in the polluted water and to electrochemically adsorb the flocculated sludge solids and the microbubbles. It has a separation tank that floats and concentrates the sludge solids that adhere to it and separates the bottom clear water, and a scraping means is provided near the water surface area of the separation tank, and a bottom clear water discharge system is provided at the bottom. Because it is a sludge floating-I treatment device characterized by the fact that it is connected to the Since there are no restrictive conditions, the gas-solid ratio can be sufficiently increased and highly concentrated sludge solids can be concentrated.
In addition, since the feeding from the reaction tank to the separation tank is carried out by hydraulic pressure, there is no disturbance at the sludge interface, and there is no action to separate air bubbles that adhere to the sludge solids, so the sludge solid content recovery rate is greatly improved. In addition, it is possible to achieve a high concentration with a short residence time in the separation tank, and it is possible to better consolidate the sludge pushed onto the water surface by Mars bubbles, resulting in a high concentration of sludge solids. In addition, ■ the sludge recovery rate can be kept almost constant regardless of the area load, especially ■ compared to the conventional pressurized flotation method, there is no need for pressure pumps, pressure tanks, or pressure adjustment around the separation tank. Because there is no need to install incidental equipment such as a
Since the overall structure of the device is simple, it has various advantages in practical use, such as easy maintenance and inspection.

[Brief explanation of drawings]

The attached drawing is an apparatus system diagram showing an embodiment of the present invention, in which 1 is a polluted water supply pipe, 2 is a polluted water feed pump, 3 is a reaction tank, 4 is a coagulant aqueous solution tank, and 5 is a coagulant supply pipe. feeding pump,
6 is a mixing device, 7 is a foaming tank, 8 is a blower, 9 is an air supply pipe, 10 is a pipe, 11 is a separation tank, 12 is a scraping means, 13 is a feed pump, 14 is a sludge solids feed pipe , 15 is a bottom clear water discharge pipe, 16 is a separation tank water level adjustment device, 17 is a suspended solids filter, 18 is a storage tank, 19 is a feed pump, 20 is a recovery pipe, and 21 is a sludge return pipe.

Claims (1)

[Claims] ■ A turbulent flow is created by mixing an aqueous flocculant solution with foaming properties and air, and then stirring the mixture under atmospheric pressure, so that a charge opposite to that of the surface of the sludge solids to be adsorbed is created. Electrified microbubbles are generated, and the microbubbles and polluted water are reacted to coagulate the sludge solids, while the sludge solids and microbubbles are electrochemically adsorbed, which are sequentially subjected to a separation process using hydraulic pressure. A sludge flotation treatment characterized in that the sludge solids are concentrated and scraped to separate the sludge solids into the concentrated solids and the bottom clear water. Method. ■It consists of a mixing device for mixing an aqueous flocculant solution with foaming properties and air, and a foaming tank for stirring these and generating fine bubbles through the generated turbulence. A flocculant supply pipe system that supplies microbubbles charged with an opposite electric charge and a polluted water supply pipe system consisting of a polluted water feed pump are connected to each other by means of stirring means. At the same time, the flocculated sludge solids and fine air bubbles are connected to a reaction tank for electrochemical adsorption, and the fine air bubbles that flow in from the reaction tank by hydraulic pressure float and concentrate the sludge solids to which they adhere. It has a separation tank that separates clear water, and the water surface of the separation tank is