KR20010048042A - Water purifying method and apparatus using dissolved air flotation method - Google Patents

Abstract

PURPOSE: A method for purifying water using dissolved air flotation is provided to remove suspended solid, algae, VOC (volatile organic compound), and odor with smaller site area in comparison with conventional sedimentation tank. CONSTITUTION: The method mainly consists of a dissolved air flotation tank (40) installed with an inlet (66) which is set at the lower part of first wall thereof and an outlet (66) which is set at the upper part of opposite of first wall; a compressed water injector (42a, 42b) which is installed between partition walls through which a compressed water supplier (58) is connected to a compressed water supplying pipe (62); a sludge removal device installed with rollers (48a, s8b), a chain (70a, 70b) by which sludge is collected for discharging sludge (52) into a sludge discharge pipe (54).

Description

Water treatment method using dissolved air flotation method and water treatment method using the same {WATER PURIFYING METHOD AND APPARATUS USING DISSOLVED AIR FLOTATION METHOD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water purifier, and more particularly, to an improved water treatment apparatus using a dissolved air flotation (DAF) and a water treatment method employing the same.

1 shows a water treatment process of a water purification plant using a sedimentation basin according to the conventional gravity sedimentation principle. Referring to the drawing, raw water (surface water) spouted from the water intake source 10 through the landing well 12 passes through the rapid mixing paper 14 and the slow mixing paper 16 in order to undergo condensation of contaminants.

Surface water used for drinking water supply contains various contaminants such as suspended substances such as suspended solids and colloids, chromaticity, THM precursors, and microorganisms including algae. In order to destabilize these, remove color, etc., the rapid mixing paper 14 accelerates the reaction of the flocculant with a stirrer while adding a flocculant such as aluminum sulfate or iron sulfate. Contaminants are adsorbed to the hydrates produced by the flocculant hydration, producing small micro flocs. The water that has undergone the condensation process of the pollutants in the rapid mixing paper is first sent to the slow mixing paper 16 to stay in the flocculating paper for about 20-30 minutes. The agitation strength of each blended paper, which is usually divided into three rows, is reduced to undergo a flocculation process to produce a small micro floc into a macro floc having good sedimentation properties.

The sedimentation is the next step to remove the flocs thus produced by the coagulation process in water. Existing sedimentation processes mostly take the form of rectangular gravitational sedimentation (CGS). That is, the mass of contaminants turned into flocs by the previous coagulation process has a higher specific gravity than water and sinks to the bottom surface of the load battery 18 by the action of gravity. By discharging the flocks that have settled to the bottom, a significant amount of contaminants contained in the water are removed, while relatively clear water that accumulates at the top of the settling basin 18 is sent to the sand filter 20 to be removed in advance. Finally filter out contaminants that have not been found. The water passing through the sand filter paper 20 is disinfected in the disinfecting paper 22 and then supplied to each household 24.

One of the main features of this conventional water treatment process is that the sedimentation basin 18 is subject to gravity settling. Such sedimentation basin has a problem that although the system is simple, it requires a large site and is uneconomical. This is because the flocculated flocs contained in the water flowing into the sedimentation basin 18 have to be settled for a long time of about 3 to 4 hours until gravity settles to the desired level. This is because the area of the sedimentation basin 18 is inevitably large for production.

In addition, the removal efficiency of suspended solids, algae, volatile organic substances (VOCs), taste, odor-causing substances, etc. is low, and the adaptability to water quality changes during the flooding period is low. In addition, because the sedimentation is good to produce a good flocculation flocculation there is a burden to precisely control the operation of the flocculation process.

The low treatment efficiency of the sedimentation basin puts a large load on the sand filter, which is a post-treatment process, which causes the consumption of purified water, waste of power, and reduction of treatment capacity due to backwashing of the sand filter. In the case of the Nakdong River basin, which uses the conventional method, the sand filter is backwashed at least five times a day.

As a result, the water purification process using the sedimentation basin according to the conventional gravity sedimentation method repeats a vicious cycle of producing treated water of low quality due to the low treatment efficiency and high cost.

In order to solve the above conventional problems, the present invention can replace the existing sedimentation basin, using a dissolved air flotation (DAF) that can significantly improve the installation area is significantly reduced water treatment efficiency It is a first object to provide an improved water treatment apparatus.

It is also a second object of the present invention to provide an improved water treatment method that can improve the water treatment efficiency by employing an improved water treatment apparatus.

1 shows a water treatment process of a water purification plant using a sedimentation basin according to the conventional gravity sedimentation principle.

2 shows a water treatment process using the water treatment apparatus according to the present invention.

Figure 3 shows the planar configuration of the water treatment apparatus according to the present invention and the configuration of the system related thereto.

<Description of the symbols for the main parts of the drawings>

30: Slow Mixed Paper 40: DAF Group

42a, 42b: compressed water jet 44a, 44b, 44c, 44d: guide bulkhead

46: motor 48a, 48b: roller

50: scraping edge 52: flocculant contaminant (flock)

54: discharge pipe 56: feedback pipe

58: air dissolved tank (compressed water supply)

60: air compressor 62: compressed water supply pipe

64: compressed air supply pipe 66: inlet

68: outlet

In order to achieve the first object, an inlet through which contaminant treatment water is added by adding a flocculant and having undergone contaminant flocculation is formed along a lower edge of the first side wall, and is treated at an upper side of the opposite side wall of the first side wall. A rectangular water tank in which a water discharge port is formed, and a sludge discharge port is formed in an upper portion of the third side wall; One or more compressed water ejectors installed on the bottom surface of the water tank along the inlet and configured to mix the mixture of compressed air and water with the contaminated contaminants and to rise above the water surface; Compressed water supply means for making a mixture of the compressed air and water and supplying it to the compressed water ejector; And a sludge removal means for scraping the sludge of the contaminant floating on the water surface in the tank and sending it out of the sludge discharge port.

Preferably, the water treatment apparatus further includes a plurality of guide partitions for inducing the flow of the flocculated treated water so that the flocculated treated water introduced through the inlet is repeatedly raised and lowered. In this case, the compressed water ejector is preferably located on the bottom surface of the region where the flocculated water rises.

The tanks are attached to each other while sharing the side wall with the slow mixing paper for coagulating the contaminants contained in the flocculation water by using the flocculant through the inlet, the inlet is connected to the tank and the slow It is formed by being installed away from the common bottom surface of the mixed paper.

On the other hand, in order to achieve the second object, by adding a contaminant flocculant to the raw water secured from the intake source through the impregnating well, the flocculation sludge by post-treatment of the contaminated flocculation water after the contaminant flocculation treatment in the rapid and slow mixing A water treatment method for removing water, comprising the steps of: making compressed air using an air compressor; Feeding back a portion of the purified water and mixing the compressed air with the compressed air produced in the air compressor to store compressed water in an air dissolved tank; While flowing the flocculated water into the lower part of the dissolved air flotation tank, the compressed water stored in the air dissolved tank is ejected through a compressed water ejector installed near the bottom of the dissolved air flotation tank to flow the flocculated water. Elevating towards the surface; And scraping up the contaminant sludge that has risen on the surface of the dissolved air flotation tank by the ejection of the compressed water, and removing the contaminant sludge from the dissolved air flotation tank. Provided is a water treatment method for removing using a method.

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

First, the principle of dissolved air injury will be briefly described. In relation to the dissolution of air in water, the following relation is generally established.

KH = [air] / P air

Where K _H is Henry's Constant, P _air is the pressure of air, and [air] is the concentration of air in the water.

If we transform the above expression,

[Air] = K _H * P _air

And the amount of air in the water increases as P _air increases. Where K _H is inversely proportional to temperature as the experimental constant.

This principle can be applied to dissolved air flotation. In other words, pressurized compressed air is mixed with water to make compressed water, and then the compressed water is sprayed from the bottom of the tank containing water, and the pressure of air saturated in the compressed water is reduced, creating a large number of bubbles. do. This bubble enhances the coagulation of the various contaminants in the water in the tank, and at the same time raises the flocculated contaminant flocs onto the water surface by the addition of the flocculant. As a result, contaminant sludge rises above the surface.

A side view of the water treatment apparatus using the dissolved air floating principle is shown in FIG. 2 showing the water treatment process using the water treatment apparatus according to the present invention. According to Fig. 2, the water treatment apparatus of the present invention comprises a DAF tank 40 and its accessories. This water treatment apparatus is used in place of the conventional sedimentation basin 18 of FIG. 1 to perform water treatment. 3 shows a water treatment apparatus centering on the planar configuration of the DAF tank 40 according to the present invention.

Referring to the accompanying drawings, the configuration of the water treatment apparatus according to the present invention will be described in more detail. The DAF tank has a rectangular water tank 40. An inlet 66 through which the coagulated water flows is formed along a lower edge of the first side wall of the water tank 40, and an outlet 68 of the treated water is formed at an upper side of the opposite side wall of the first side wall.

The water tank 40 is attached to each other while sharing the side wall with the slow mixing paper 30, the inlet 66 is formed by installing the side wall spaced apart from the common bottom surface of the water tank 40 and slow mixing paper 30. . The flocculation treated water, which primarily performed the flocculation treatment of the contaminants contained in the flocculation water using the flocculant in the quick blending paper 14 and the slow blending paper 30, is formed from the inlet (30). 66 is introduced into the water tank (40).

In the vicinity of the bottom surface of the water tank 40, the compressed water ejectors 42a and 42b are installed long to cross the flow direction of the water to strongly inject the compressed water. Although two compressed water ejectors 42a and 42b are illustrated in the figure, the actual number of installations may be appropriately determined in consideration of the size of the water tank and the water treatment capacity. Compressed water ejectors (42a, 42b) is made of a cylindrical column or a hexahedral column formed with a plurality of holes in a row on the upper surface. In addition, the compressed water ejectors 42a and 42b are provided through a compressed water supply pipe 62 so that compressed water can be supplied from an air dissolved tank that stores the dissolved air installed outside the water tank 40, that is, the compressed water supply 58. It is connected to the compressed water supply (58).

The compressed water supplier 58 receives compressed air from the air compressor 60 for compressing the air at high pressure through the compressed air supply pipe 64. At the same time, the compressed water supply unit 58 receives a part of the treated water through a pipe 56 connected to the discharge pipe 54 of the treated water connected to the outlet 68 of the water tank 40. Then, the compressed air and the fed back treated water are mixed to produce compressed water containing the compressed air, that is, compressed water, and at the same time, the compressed air supply pipe 64 carries a mixture of compressed air and the treated water through the compressed water ejector 42a, 42b).

The water tank 40 includes a plurality of guide partitions 44a, 44b, 44c for inducing the flow of the flocculated treated water so that the flocculated treated water introduced from the slow mixing paper 30 through the inlet 66 is repeated to rise and fall. 44d) is installed. The first compressed water ejector 42a and the second compressed water jet between the first guide partition 44a and the side wall toward the inlet 66 of the water tank and between the second guide partition 44b and the third guide partition 44c. Each group 42b is installed. Each guide partition wall is installed so as to connect the side wall of the tank parallel to the running direction of the flocculation water, the first and third guide partitions (44a, 44c) is installed lower than the water surface so that the flocculation water passes over the self, The second and fourth guide partition walls 44b and 44d are installed at a predetermined height away from the bottom surface of the water tank so that the flocculated water flows out below the porcelain.

On the other hand, the sludge removal means for scraping out the contaminant sludge 52 which floats on the water surface of the tank 40 to be discharged out of the tank 40 through the sludge discharge port (not shown) of the tank 40 is required. To this end, a pair of rotatable rollers 48a and 48b are installed at the upper sidewalls of the inlet 66 and the outlet 68 of the water tank 40. Then, a pair of chains 70a and 70b are wound around both of the pair of rollers 48a and 48b for rotational power transmission. One or more skimming blades 50 for scraping out the contaminant sludge 52 which floats on the surface of water while moving in conjunction with the movement of the chains 70a and 70b to be discharged out through the sludge outlets. ). The motor 46 is also connected to the roller 48a to rotate the roller 48b.

Hereinafter, a water treatment process performed using the water treatment apparatus according to the present invention will be described in detail.

The pretreatment of the DAF tank 40 according to the present invention, that is, the water treatment process up to the slow mixing paper 30, follows the conventional method. That is, the raw water obtained from the water intake source 10 through the impingement 12 is collected in the rapid mixing paper 14, and then a coagulant such as aluminum sulfate (Al ₂ SO ₄ ) is added and the agitator is operated to add the coagulant to the raw water. Allow for rapid flocculation of contaminants. The agglomerated treatment water thus treated is delivered to the DAF tank 40 through the inlet port 66 from the bottom of the slow mixing paper 30. Here, in the flocculation treatment water flowing into the DAF tank 40, a large amount of contaminants are suspended in a colloidal state in which a large amount of contaminants are flocculated by a prior process made in the rapid mixing paper 14 and the slow mixing paper 30.

On the other hand, the compressed water supply unit 58 receives a part of the treated water through the feedback pipe 56 and at the same time receives the compressed air of about 3 to 6 atm from the air compressor 60, and mixes the two to compress the compressed water Make Then, the compressed water is supplied to the compressed water ejectors 42a and 42b provided on the bottom surface of the water tank 40. According to the experiment, it was confirmed that the recycling rate of the treated water used to produce the compressed water should be about 5 to 10.

Water containing compressed air (compressed water), which had been under high pressure until reaching the compressed water ejectors 42a and 42b, is strongly ejected toward the water through the compressed water ejectors 42a and 42b to experience a rapid pressure drop. In this process, the air dissolved in the compressed water is precipitated in the water, generating an infinite number of fine bubbles.

The generated bubbles float the aggregated contaminant colloids 52 remaining in the flocculated water in the water tank 40 onto the water surface. The rising force of the compressed water is discharged through the conduit 54 connected to the discharge port 68 while repeatedly raising and lowering the flow of the flocculated water flowing into the water tank 40 together with gravity.

On the other hand, the contaminant sludge 52 floating on the water surface of the DAF tank 40 is scraped repeatedly while the scraping blade 50 moves on the water surface to the sludge collection tank (not shown) through the sludge discharge port. Discharge it. This movement of the scraping blade 50 is ensured by the linear movement of the chains 70a and 70b by driving the motor 46 to rotate the rollers 48a and 48b. Although the drawing shows that one scratching blade 50 is installed for convenience, it may be effective to use a plurality of scratching blades 50 because it may settle again if left for a long time without quickly scraping contaminant sludge on the water surface. .

The treated water treated in the DAF tank 40 is moved to the sand filter paper 20. The sand filter paper 20 removes contaminants remaining in the treated water more completely by passing the treated water through a filtering layer made of sand or the like. Then, the disinfectant paper 22 is supplied to each home through the disinfectant treatment.

Table 1 below compares the treatment efficiency between a water treatment system (DAF system) using a DAF tank according to the present invention and a gravity settling system (CGS system), which is a general water treatment system in Korea.

Raw water CGS system DAF system Dissolved Oxygen Growth Rate (mg / L) 6.3 6.95 9.56 10.3 51.7 KMnO ₄ removal rate (mg / L) 12.5 9.1 4.7 27.2 62.4 Detergent Retention Rate (mg / L) 0.08 0.033 0.005 58.5 93.8 Turbidity (NTU) 2.6 0.89 0.44 65.8 83.1 UV ₂₅₄ 0.244 0.102 0.069 58.2 71.7

For reference, KMnO ₄ removal rate is an evaluation index for measuring the indirect amount of organic matter in water oxidized by KMnO ₄ oxidizer, and UV ₂₅₄ is a unit indicating the amount of organic material absorbing ultraviolet rays having a wavelength of 254 nm indirectly. It is an evaluation index indicating the amount of organic matter.

As can be seen from the above table, for all five evaluation indexes, it was confirmed that the water purification apparatus (DAF system) according to the present invention had a superior water purification capability compared to the conventional gravity sedimentation system (CGS system). Can be.

When the water treatment apparatus according to the present invention is used as a substitute for the sedimentation basin of the existing water treatment plant having low treatment efficiency, the following effects can be obtained. First, the DAF system can be installed with one tenth of the area of the conventional sedimentation basin, thus reducing the construction cost to 1/4 to 1/5. Second, the coagulation reaction of pollutants is enhanced by the partial output of compressed water and the efficiency of forced injury of colloid is high, so that the removal efficiency of suspended matter, algae, volatile organic matter, taste, and odorous substances is improved. Third, it is possible to produce a certain quality drinking water even in the water quality change during the flooding period. Fourth, it can reduce the load of the sand filter paper, which is the post-treatment process, to maintain the actual treatment capacity of the basic equipment and improve the overall treatment quality.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (7)

A rectangular water tank in which an inflow port into which the flocculation water has undergone the contaminant flocculation treatment is added along a lower edge of the first side wall, and an outlet of the treated water is formed at an upper side of the opposite side wall of the first side wall; One or more compressed water ejectors installed on the bottom surface of the water tank along the inlet, for ejecting a mixture of compressed air and water in the water direction to raise the aggregated contaminants onto the water surface; Compressed water supply means for making a mixture of the compressed air and water and supplying it to the compressed water ejector; And And a sludge removing means for scraping the sludge of the contaminants floating on the water surface in the tank and sending it out of the tank. According to claim 1, The flocculation process water flowing through the inlet is further provided with a plurality of guide partitions for inducing the flow of the flocculation treatment water to repeat the rising and falling, the compressed water ejector is the flocculation treatment water rises Water purification apparatus, characterized in that located on the bottom surface of the area. The compressor of claim 1, wherein the compressed water supply means comprises: an air compressor for compressing air; And a compressed water supplier receiving a part of the treated water and receiving compressed air from the air compressor and mixing the mixed water and supplying a mixture of the compressed air and water to the compressed water ejector through a supply pipe. Processing unit. According to claim 1, The sludge removing means comprises a pair of rollers each rotatably installed on both side walls on the water surface of the tank; Chains wound at both ends of the pair of rollers; One or more scraping blades fixed to the chain for scraping off contaminant sludge that floats on the water while moving in conjunction with the movement of the chain and sending them out of the tank; And a motor that rotates the roller to enable sludge removal of the scraping blade. The water tank of claim 1, wherein the water tanks are attached to each other while sharing a sidewall with slow mixing paper for coagulating contaminants contained in the coagulated water using the coagulant through the inlet, and the inlet is connected to the sidewall. The water treatment apparatus characterized in that it is formed by installing a spaced apart from the common bottom surface of the water tank and the slow mixing paper. In the purified water treatment method for the post-treatment of the contaminated flocculant after the contaminant flocculation treatment is added to the raw water obtained from the water intake through the impregnating well, Making compressed air using an air compressor; Feeding back a portion of the purified water and mixing the compressed air with the compressed air produced in the air compressor to store compressed water in an air dissolved tank; The condensed treated water is introduced into the lower part of the dissolved air flotation tank, and the compressed water stored in the air dissolved tank is ejected toward the water surface through a compressed water ejector installed near the bottom of the dissolved air flotation tank. Performing at least one or more elevations of the flow towards the surface; And Scraping contaminant sludge that has risen on the surface of the dissolved air flotation tank by the ejection of the compressed water, and removing the sludge from the outside of the dissolved air flotation tank, And a flocculating sludge removing step of removing the flocculated contaminants of the flocculated water using a dissolved air flotation method. The water treatment method according to claim 6, further comprising a sand filtration process for filtering the contaminants remaining in the treated water by introducing the treated water purified by the flocculation sludge removal process into a sand filter. .