WO2013002447A1

WO2013002447A1 - Method and apparatus for purifying waste water

Info

Publication number: WO2013002447A1
Application number: PCT/KR2011/005281
Authority: WO
Inventors: 김현배; 윤희철; 남해욱; 고주형; 오재일; 최영화; 박재웅; 임윤대
Original assignee: 블루그린링크(주); 주식회사 포스코건설
Priority date: 2011-06-27
Filing date: 2011-07-19
Publication date: 2013-01-03

Abstract

The present invention allows obtainment of filtered water having a superior water quality while requiring a short time for removing a plug, by disclosing a method for purifying waste water comprising: a plug formation step of forming the plug by inserting a material for forming a plug in waste water and mixing same in a mixing tub (100); a cyclone separation step of separating the waste water comprising the plug into waste water including a high-density plug and waste water including a low-density plug by means of a hydro cyclone (200); and a rising separation step of separating the waste water comprising the low-density plug into the low-density plug and filtered water by means of a rising separation tub (300).

Description

Sewage Purification Method and Purification Device

The present invention relates to the field of environmental technology, and more particularly, to a method and apparatus for purification of sewage.

Non-point source and confluent sewage sediment contaminants are mainly introduced into the purification device with rainwater in rainy weather, and the amount is so large that overload occurs frequently, and because of this, they are discharged to the river without being treated. Is required.

Conventionally, as one of the purification methods, a method of purifying sewage by adding flocculant or the like to sewage to form a floc and removing only the floc has been studied.

However, the conventional techniques have used a method of forming and flocculating only a high density floc or a method of forming and floating only a low density floc floating in water, all of which take a long time to remove the floc. , The water quality of the purified water was not good.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a sewage purification method and a purification device to obtain a purified water of excellent quality while taking a short time to remove the floc.

In order to solve the above problems, the present invention is a floc forming step of injecting the material for forming the flocculation into the sewage, by stirring by a stirring tank 100 to form a floc; A cyclone separation step of separating the sewage including the floc into a sewage including the high density floc and the low density floc by the hydrocyclone 200; It provides a sewage purification method comprising; a sewage separation step of separating the sewage containing the low density floc by the flotation separation tank 300, the low density floe and the purified water.

The floc forming material preferably includes a metal salt flocculant and a polymer flocculent aid.

It is preferable that the said floc forming material further contains micro sand.

A flocculation step of collecting the high density flocks generated in the cyclone separation step and the low density flocks generated in the flotation separation step; It is preferable to further include a; micro sand recovery step of recovering the micro sand by crushing the floc.

The micro sand recovery step is preferably performed by the in-line mixer 400.

In the floc forming step, it is preferable to stir the wastewater and the floc forming material at a high speed (240 to 360 RPM) in the stirring tank 100 so that bubbles are impregnated in the low density floc.

The present invention is a sewage purification apparatus for implementing the sewage purification method, the stirring tank (100) for the floc forming step; The hydrocyclone (200) for the cyclone separation step; Presents together with a sewage purification apparatus comprising ;; the flotation separation tank 300 for the flotation separation step.

The present invention is a sewage purification apparatus for implementing the sewage purification method, the stirring tank (100) for the floc forming step; The hydrocyclone (200) for the cyclone separation step; The floating separation tank 300 for the floating separation step; Presenting together the sewage treatment apparatus including; in-line mixer 400 for the micro sand recovery step.

It is an object of the present invention to provide a sewage purification method and a purification device which can obtain purified water of excellent quality while taking a short time to remove the floc.

Figure 1 below shows an embodiment of the present invention,

1 is a process chart of the purification method.

Figure 2 is a schematic diagram of the formation of the floc by the flocculant.

Figure 3 is a schematic diagram of the process of increasing the floc by the polymer.

Figure 4 is a schematic diagram of the process of increasing the density of the floc by the micro sand.

5 is a step-by-step photograph of the weighted aggregation reaction.

6,7 are schematics of two types of floc destruction.

8,9 are photographs of the bubble impregnation floes by cavitation.

10 is an exploded perspective view of a hydrocyclone in which the separation section is enlarged.

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

As shown in Figure 1 below, the sewage purification method according to the present invention is basically constituted by the following process.

The floc forming material is thrown into the sewage, and it is stirred by the stirring tank 100 to form a floc.

The sewage containing the floc is separated by the hydrocyclone 200 into sewage containing the high density floc and the low density floc, and the high density floc is screened out.

The sewage containing the low density floc is separated into the low density floc and the purified water by the flotation separation tank 300, the low density floc is screened out, and the purified water is discharged to the outside.

That is, a conventional method of forming a floc by removing the floc forming material into the sewage and removing the floc as in the prior art is formed by dividing the floc into a high density floc and a low density floc, among which the high density floc is formed in the hydrocyclone 200. Separation, low density flocs are separated by a separate float separation tank (300).

Therefore, the purification process is much faster than the conventional, there is an effect that can be obtained purified water of excellent quality.

Hereinafter, specific principles and examples of the purification method according to the present invention will be described.

The floc forming material introduced into the sewage for the formation of the floc preferably includes a metal salt flocculant and a polymer flocculent aid, and more preferably a micro sand.

In the case of using such a flocculation material, a high density floc and a low density floc can be obtained more smoothly and stably by a ballasted flocculation reaction.

Typical colloidal particles found in sewage have a negative surface charge.

Because of their size, the colloidal particles have a much smaller attraction force than the electrical repulsive force, causing them to float or have very low precipitation rates.

In this state, Brownian motion caused by the constant thermal collision of colloidal particles with relatively small water molecules surrounding between particles hinders the precipitation of the particles.

For this reason, colloidal particles are difficult to remove by precipitation for a suitable time so that these particles can be removed by chemical methods using chemical flocculants and coagulants.

Aggregation is a process in which colloidal particles become unstable as the particle size increases due to the collision of particles.

Agglomeration reactions are often unstable, and many side reactions occur with other substances, depending on the sewage characteristics that change seasonally or daily.

Coagulants are chemicals added to destabilize colloidal particles in sewage to form flocs.

When the colloidal particles of the electrically stable sewage are injected with a coagulant to form a cation of the metal to make an unstable state to minimize the repulsive force between the particles, the particles agglomerate with each other and form a floc (FIG. 2).

Weighted agglomeration is a method of increasing the settling rate by binding a dense particle to the floc using the crosslinking role of the polymer to produce a floe with a high density and size.

Coagulant adjuvant, such as a polymer injected for the weighted coagulation reaction, is like a bundle of thread and has a large number of polar groups, which are combined with the suspended particles and also cause coagulation by adsorption between the flocks bound to the suspended particles. .

This action also acts on the electrostatic bonds and hydrogen bonds in the process of the adsorption activator of the polymer that is present in the form of a loop in the aqueous solution to the surface of the particles (Fig. 3).

The flocs formed using only flocculants are very small in size and have low bonding strength.

When a coagulant aid polymer is added, the polymer binds to the floc and causes additional condensation with the other floc, which is called a double bond by a crosslinking role.

This polymer crosslinking not only reduces the settling time by forming larger flocs, but also makes it possible to bond with other particles, allowing them to bind with relatively dense and large particles such as micro sands ( 4).

Figure 5 shows the change in the size of the floc according to the actual drug injection, (a) is a colloidal state, (b) is the production state of the micro floc, (c) the micro sand injection state, (d) the weight of the flocculation floc It's about creation.

Micro sand used in the purification method according to the present invention has a particle size distribution of 75 ~ 150㎛, it is possible to produce a high density of floc good binding force.

The micro sand has a high density when it is 150 μm or more, but lacks the binding force during centrifugation due to the mass difference, and when the micro sand is less than 75 μm, the micro sand has a high binding force, but the density of the formed flocs is relatively small.

The characteristics of the floc are greatly influenced by the forming environment such as the stirring strength and the stirring method.

Stirring strength is expressed as the product of the rate gradient G and the stirring time t. If the G value is high, the number of collisions between particles increases, thereby increasing the reaction rate and the growth rate of the floc.

Even with the same agitation strength, the characteristics of the flocs vary depending on the speed gradient and the agitation time. The reason for this can be found in the principle that flocs are generated.

In the flocculation process, binding and breaking occur repeatedly during collisions.

The form of floc destruction is explained in two ways.

One is surface erosion, which means that the shear force acts on the outside of the floc to reduce the size of particles falling off the floc surface, which is caused by the collision of the floc with the inner wall and the impeller during agitation (FIG. 6).

The second is large-scale fragmentation, which is caused by splitting of several flocks of similar size by the tensile force generated outside the floc, which occurs when the flocs grow to a size that is difficult to maintain binding during stirring (FIG. 7).

At high agitation strength, the number of floc collisions increases to increase the growth rate, but the impact strength and shear force exerted on the outside increase, and the flow velocity increases to increase the tensile force acting on the flocs, which reduces the maximum growth limit. The bonds and breaks are repeated quickly and a dense floc is formed.

When the agitation strength is low, the number of collisions decreases, so that the growth rate is slow. However, the impact strength, shear force, and tensile force decrease, which increases the maximum limit growth size and tends to form flocs with low density of loose bonds.

For this reason, a weak stirring strength takes a long reaction time and produces a floc with a large limit growth size and a low density and strength.

These flocs are dissociated by hydrocyclone rotational impact due to their low density and strength.

On the other hand, the stronger the stirring strength, the shorter the reaction time and the smaller the limit growth size, but the higher density and strength of the floc is produced.

According to the present invention, a flotation capable of high-speed separation in a hydrocyclone and a high-speed flotation in a floating separation tank by the stirring strength difference is made.

Due to the high speed rotation of the impeller, the surface of the object moving at high speed in the liquid drops the liquid pressure, which creates vapors or bubbles in the liquid where the pressure is lower than the saturated vapor pressure of the liquid. It is called.

In the present invention, the stirring speed was increased to 240 to 360 RPM.

In the high-speed weighted agglomeration reactor (stirrer), bubbles generated by the cavitation by the high-speed rotation are impregnated with fine bubbles between the high density floes generated as shown in FIGS. 8 and 9.

In the above process, high pressure is maintained at a pressure of 3 to 5 bar for high-speed operation in the hydrocyclone, and the high-strength floc is first removed from the hydrocyclone, and then naturally decompressed in the flotation tank and impregnated with fine bubbles. Together, the low density flocks are floated and removed.

This compression may be made by a driving pump 10 or the like installed between the stirring vessel 100 and the hydrocyclone 200 (FIG. 1).

Hydrocyclone 200 is a sedimentation type separator with no mechanical drive at all by solid-liquid separation technology that separates particles by accelerating the settling speed of the particles by centrifugal force (FIG. 10).

Hydrocyclone is widely used in various industries because of its simple design, low cost, easy operation and low maintenance cost.

Due to the rotational force of the fluid, high specific gravity material is discharged through the lower outlet and low specific gravity material is separated through the upper outlet.Solid solid particles contained in the fluid can be separated only when the specific gravity is different from the specific gravity of the fluid. Since the kinetic properties of the solid particles contained in the fluid vary depending on the size, shape, density, and concentration of the particles, they are not well used for the separation of flocs with small size, low density, low concentration and unstable shape.

In the present invention, by introducing a weighted agglomeration reaction, a floc with high size and density and excellent bonding strength can be produced, which enables separation using a hydrocyclone, and a hydrocyclone having a relatively long residence time in a separation section (corn section). The advantage of this method is that it can be separated even with a relatively small density difference.

The general hydrocyclone is composed of a cylindrical section (conical section) and a combined form (conical section).

Suspended particles in the fluid flow tangentially through the inlet located at the top of the cylinder.

The tangential inflow initiates a strong rotational force from the inside, which causes strong vortex movements inside, resulting in centrifugal forces that accelerate the movement of the particles towards the outer wall, causing the particles to move downward spirally through the cylinder and cone. do.

Particles in the internal strong vortex motion are subject to gravity, centrifugal force, and drag force, which are less than the other two forces.

The fluid containing the fine fraction travels to the center of the hydrocyclone under the influence of drag and forms a strong upward flow from it, which is discharged through the outlet pipe in the upper middle, which is called the overflow pipe or vortex finder. .

The large fraction (coarse fraction) is governed by the centrifugal force acting in the circumferential direction, preventing the particles from flowing inward, which causes the particles moving into the inner wall to collide with the inner wall, losing the inertia force and flowing along the wall of the cone. Separated and discharged through the bottom outlet as a slurry or porridge state.

This part is called an underflow orifice or apex.

In the case of increasing the length of the cylinder to increase the flow velocity and increase the centrifugal force, the advantage of having a high separation efficiency even at a small density difference by increasing the residence time under high centrifugal force is added (FIG. 10).

Specifically, in the case of applying the hydrocyclone 200 of the purge trap method, since the flow rate flowing out to the top can be increased to 90% or more, it is more preferable (Fig. 10).

Flotation separation is one of the unit operations used to separate solid particles from a liquid. A pressure flotation separation method in which fine air is introduced into a liquid to cause particles to float and separation occurs, and a liquid containing a liquid by vacuuming the container. There is a decompression flotation method that bubbles up air dissolved in the air and separates floating.

When the resulting bubbles stick to the particulate material, they can float on the water due to the buoyancy caused by the large amount of bubbles.

Flotation separation is better than sedimentation because it can completely remove small, light particles that settle slowly in a short time.

Currently, the flotation separation used in many sewage and water treatment processes is mostly using air as a flotation accelerator.

Pressurized flotation separation method using air bubble has dissolved air flotation separation method and air flotation separation, and removal efficiency can be improved by adding various chemical additives.

Dissolved air floating separation method is a method of generating air bubbles by removing the pressure after injecting air under the condition that the sewage has a pressure, and air floating separation method is a process of giving up under atmospheric pressure to air into the sewage through a rotating impeller or diffuser. It is a method of floating airborne substances by forming air bubbles by injecting directly.

Floating separation tank in the present invention, unlike conventional methods, there is no separate air injection or decompression of the container.

Fine bubbles formed in the high-speed weighted agglomeration reactor (stirrer bath) are impregnated in the floc and floated at high speed by natural decompression occurring during transfer from the hydrocyclone to the flotation separation tank.

The flocks flowing into the flotation separation tank from the stirring tank are mostly low density flocs in which the high density flocs are first separated and removed from the hydrocyclone in the previous stage, which is advantageous for flotation separation.

Most of these flocks impregnate microbubbles inside the flocs.

In addition to the bubbles impregnated with the floc, air dissolved in the treated water expands to generate a large amount of bubbles, which causes the flotation to float very fast.

On the other hand, it is preferable to collect the high-density flocks generated in the cyclone separation step and the low-density flocks generated in the flotation separation step in a separate collecting container 20, and then crush these flocks and recover and reuse the micro sands (FIG. 1).

In order to reduce the bubbles of the low-density floe generated in the flotation separation tank 200, it may be agitated at a low speed in the collecting container 20 (Fig. 1).

In the case of high density flocs produced in agitating tanks, hydrocyclones alone are difficult to break / separate, as in the Actiflo process.

In order to recover and reuse the micro sand from the high-density high-strength floc, an additional in-line mixer 400 was used to cause vortex inside the pipe and increase the contact area to accelerate the fracture of the floc (FIG. 1).

In-line mixer consists of a series of mixing elements fixed in the pipeline, and the process of continuous flow splitting, redirection, and recombination is repeated when the fluid to be mixed is passed through the pipeline, and the continuous mixing of the fluids is mixed. Used for manipulation.

The floc and micro sand destroyed by the in-line mixer are separated by the difference in density in the hydrocyclone. Low-density flocs are sent to the top and sent to the sludge treatment process, and micro sands are separated to the bottom and fed to a high-speed weighted agglomeration reactor for reuse.

The mixture of the floc and the micro sand crushed by the in-line mixer 400 may be separated again from the second hydro cyclone 30 to remove the floc and transfer the micro sand to the stirring tank for reuse (FIG. 1).

Since the above has been described only with respect to some of the preferred embodiments that can be implemented by the present invention, the scope of the present invention, as is well known, should not be construed as limited to the above embodiments, the present invention described above It will be said that both the technical idea and the technical idea which together with the base are included in the scope of the present invention.

Claims

A floc forming step of inserting a floc forming material into sewage and stirring the agitation tank to form a floc;

A cyclone separation step of separating the sewage including the floc into a sewage including the high density floc and the low density floc by the hydrocyclone 200;

Floating separation step of separating the sewage containing the low density floc into the low density floc and purified water by the flotation separation tank 300;

Sewage purification method comprising.
The method of claim 1,

The floc forming material comprises a metal salt flocculant and a polymer flocculent aid.
The method of claim 2,

The floc forming material further comprises a micro sand.
The method of claim 3,

A flocculation step of collecting the high density flocks generated in the cyclone separation step and the low density flocks generated in the flotation separation step;

A micro sand recovery step of recovering the micro sand by crushing the floc;

Sewage purification method further comprising.
The method of claim 4, wherein

The micro sand recovery step

Sewage purification method characterized in that performed by the in-line mixer (400).
The method of claim 1,

The floc forming step

Sewage purification method characterized in that for stirring the sewage and the floc forming material at a high speed (240 ~ 360 RPM) in the stirring tank (100) so that bubbles are impregnated in the low density floc.
The method of claim 1,

The hydrocyclone 200 is a waste water purification method characterized in that the fuzzy trap method.
A sewage purification apparatus for implementing the sewage purification method of any one of claims 1 to 4,

The stirring tank 100 for the floc forming step;

The hydrocyclone (200) for the cyclone separation step;

The flotation separation tank 300 for the flotation separation step;

Sewage purifier included.
A sewage purification apparatus for implementing the sewage purification method of claim 5,

The stirring tank 100 for the floc forming step;

The hydrocyclone (200) for the cyclone separation step;

The floating separation tank 300 for the floating separation step;

In-line mixer 400 for the micro sand recovery step;

Sewage purifier included.