WO2015030381A1

WO2015030381A1 - Partition-type floatation apparatus using fine bubbles

Info

Publication number: WO2015030381A1
Application number: PCT/KR2014/007160
Authority: WO
Inventors: Kwang Hee Lee
Original assignee: Gyeongju-Si,Gyeongsangbuk-Do
Priority date: 2013-08-27
Filing date: 2014-08-04
Publication date: 2015-03-05
Also published as: KR101362858B1

Abstract

Disclosed is a partition-type floatation apparatus including a reaction chamber (110) and a bubble generating unit (120). The reaction chamber (110) is connected to a sewage inflow pipe (111) and has a treated water discharge hole 112. Within the reaction chamber (110), lower partition walls (113) extending upward from the bottom and upper partition walls (114) extending from the top are alternately installed to form a plurality of bubble reaction zones (115) therebetween in each of which suspended solids are floated and removed. The bubble generating unit (120) generates fine bubbles (B) having a micrometer or nanometer size and injects the generated fine bubbles (B) into the sewage (10) supplied to the inside of the reaction chamber (110) using the sewage supply pipe (111) and a bubble supply pipe (121) or using a bubble sprayer module (165) installed within at least one of the reaction zones (115).

Description

PARTITION-TYPE FLOATATION APPARATUS USING FINE BUBBLES

The present invention relates to a partition-type floatation apparatus, and more particularly to a partition-type floatation apparatus which purifies sewage by removing suspended solids floated by fine bubbles using a structure having multistage partition walls installed in a flow direction.

Generally, Combined Sewer Overflows (CSOs) which enter a sewage treatment plant during rainy times contain adulterations and highly concentrated Suspended Solids (SS), causing shock loading to the sewage treatment plant followed by oligotrophication after the rain stops. CSOs are one of the factors that obstruct normal operation of the sewage treatment plant. The most critical problem of the CSOs is hydraulic loading to a water treatment plant. That is, CSOs may cause shock loading to a biological reactor and bulking in a final settling basin, leading to effluent containing a large amount of SS which exceeds the water quality standards.

In order to solve this problem, developed is a floatation apparatus which purifies sewage in a manner of injecting micro bubbles into a basin to which sewage is supplied, in order to cause SS and chemical sludge (Al+PO₄ ^-3 →AlPO₄) to adhere to the fine bubbles and float to the surface of sewage, and skimming the floated organic particles and chemical sludge.

However, conventional floatation apparatuses equipped with a single basin have the disadvantage that organic particles and chemical sludge, which are not adsorbed onto micro bubbles, still remain in treated water and flow out along with the treated water.

Documents of Related Art

(Patent Document 1) Korean Patent Application Publication No. 2012-0138025 (December 24, 2012; titled "Flotation Apparatus")

Accordingly, the present invention has been made keeping in mind the above concerns occurring in the related art, and the present invention is intended to propose a partition-type floatation apparatus using fine bubbles, which removes introduced particles of suspended solids while maintaining a bubble-saturated state by limiting temporary flow-out of fine bubbles in a stepwise manner by using a structure having partition walls installed in multiple stages in a flow direction of sewage, thereby purifying sewage in a short time and minimizing discharge of suspended solids contained in treated water.

In order to accomplish the above objects, according to one aspect, there is provided a partition-type floatation apparatus including: a reaction chamber 110 having a first side end connected to a sewage inflow pipe 111 through which sewage 10 containing suspended solids is supplied to an inside of the reaction chamber 110, a second side end in which a treated water discharge hole 112 for discharging treated water of the sewage 10 is formed, and a lower partition wall 113 and an upper partition wall 114 which are alternately installed to form a plurality of bubble reaction zones 115 in each of which the suspended solids are floated and removed, the lower partition wall 113 extending upward from a lower end of the reaction chamber, the upper partition wall 114 extending downward from an upper end of the reaction chamber; and a bubble generating unit 120 which generates fine bubbles B having a micrometer or nanometer size and injects the generated fine bubbles B into the sewage 10 supplied to the inside of the reaction chamber by communicating with the sewage supply pipe 111 and a bubble supply pipe 121 or by communicating with a bubble sprayer module 165 installed within at least one of the plurality of bubble reaction zones 115.

The partition-type floatation apparatus may further include a floating sludge discharging unit 130 installed above the reaction chamber 110 in order to remove floating sludge S1, which is floated to the surface of the sewage in each of the bubble reaction zones 115 by the fine bubbles B, by skimming the floating sludge S1 by rotating a rotation chain 132 to which a plurality of skimmers 131 is coupled.

A bottom surface of each of the bubble reaction zones 115 may be provided with a drain 116 for draining settled sludge S2 therethrough, wherein the drain 116 may be connected to a settled sludge discharge pipe 118 having a settled sludge discharge hole 118a at an end thereof so that the settled sludge S2 is discharged outside through the settled sludge discharge hole 118a.

The bottom surface 117 of each of the bubble reaction zones 115 may be an inclined surface which is down slopped with respect to the drain 116 so that the settled sludge S2 collects at the drain 116.

The bubble generating unit 120 may be installed on the bubble supply pipe 121, a first end of which is connected to an inside of any one bubble reaction zone 115c and a second end of which is connected to the sewage inflow pipe 111, wherein the bubble generating unit 120 generates fine bubbles B using the sewage 10 supplied from the bubble reaction zone 115c and supplies the fine bubbles B to the inside of the reaction chamber by injecting the sewage 10 containing the generated fine bubbles B into the sewage inflow pipe 111.

An end portion of the sewage inflow pipe 111 may penetrate and externally extend up to an inside of a first-stage bubble reaction zone 115a in order to supply the sewage 10 to the inside of the first-stage bubble reaction zone 115a, wherein the end portion of the sewage inflow pipe 111 is provided with a branched pipe 160 with a plurality of branch tubes, and wherein ends of the branch tubes are equipped with respective spray nozzles 161 configured to spray-inject the sewage 10 and the fine bubbles B into the inside of the first bubble reaction zone 115a through the sewage inflow pipe 111.

A plurality of anti-turbulence plates 162 may be arranged, in parallel with each other and in a direction in which the sewage 10 and the fine bubbles B are sprayed, in front of the respective spray nozzles 161 and may be distanced from respective ejection holes by a predetermined distance.

The floating sludge discharging unit 130 may include:

rotation rollers

133, 134 which are arranged, in parallel with each other in a horizontal direction, at an upper portion of a first side end of the first-stage bubble reaction zone 115a and an upper portion of a second side end of a last-stage bubble reaction zone 115c, respectively; the rotation chain 132 which is stretched between the

rotation rollers

133, 134 while engaging with the

rotation rollers

133, 134 in a rotatable manner and which has a circumferential surface to which the plurality of skimmers 131 extending outward from the circumferential surface are coupled; and a driving motor which offers rotational force to the

rotation rollers

133, 134, wherein a floating sludge discharge hole 119 is formed in an upper portion of the reaction chamber 110 and at the same height as the skimmers 131, and wherein the floating sludge S1, which is floated to the surface of the sewage in the bubble reaction zones 115, is guided to the floating sludge discharge hole 119 by the respective skimmers 131, which are rotated along the rotation chain 132 by the

rotation rollers

133, 134, and discharged outside.

A level controlling weir 140 may be installed at the second side end of the reaction chamber in which the treated water discharge hole 112 is formed, the level controlling weir 140 controlling a level of the sewage 10 supplied to the inside of the reaction chamber 110 by discharging the sewage 10 outside through the treated water discharge hole 112.

The level controlling weir 140 may include: a level controlling plate 141 which is a plate extending in a widthwise direction W and has a first end which is rotatably coupled to an external wall 110a of the second side end of the reaction chamber 110, in a position lower than the treated water discharge hole 112; a driving shaft 142 which is coupled to a second end of the level controlling plate 141 and rotates the second end of the level controlling plate 141 with respect to the first end of the level controlling plate 141; and a control motor 143 which offers a driving force to the driving shaft 142, wherein the level of the sewage 10 is controlled in a way of rotating the second end of the level controlling plate 141 according to a drive of the control motor 143.

A branched supply pipe 122 for supplying the fine bubbles B to the bubble sprayer module 165 may be installed on the bubble supply pipe 121, wherein a first end of the branched supply pipe 122 is connected to a first side of the bubble supply pipe 121 and a second end of the branched supply pipe 122 is connected to the bubble sprayer module 165 so that the fine bubbles B generated by the bubble generating unit 120 are supplied to the bubble sprayer module 165.

The branched supply pipe 122 may be inserted in each of the bubble reaction chambers 115 and arranged to extend in a widthwise direction of each bubble reaction zone, wherein more than one bubble sprayer module 165 is coupled to the branched supply pipe 122 and arranged at intervals in a longitudinal direction of the branched supply pipe so that uniform fine bubbles B are supplied to the entire area of the bubble reaction zone 115.

The bubble sprayer module 165 may be arranged such that a middle portion thereof is coupled to the bubble supply pipe 122, and respective side portions thereof are provided with a plurality of discharge holes 166 for discharging the fine bubbles B supplied from the middle portion, wherein the side portions with the discharge holes 166 are tapered toward respective ends thereof.

The bubble reaction zones 115 may be formed by the lower partition wall 113 and the upper partition wall 114 which are alternately arranged within the reaction chamber 110, wherein a retention time of the fine bubbles B for which the fine bubbles stay underwater within each of the bubble reaction zones 115 is adjusted according to a vertical length of the upper partition wall 114.

The partition-type floatation apparatus has the following advantages.

First, by using the structure having multistage partition walls installed in a flow direction of sewage, since particles of suspended solids are removed in a manner of temporarily limiting flow-out of bubbles in a stepwise manner while maintaining a bubble-saturated state, it is possible to purify sewage in a short time and minimize discharge of suspended solids which are flown out along with stream of treated water.

Second, by using a structure having multistage partition walls installed within a single reaction chamber, floating particles of suspended solids can be removed in a stepwise manner. Therefore, it is possible to reduce a required site area for installation of a reaction chamber while minimizing flow-out of suspended solids attributable to a short flow.

Third, since the bottom of each of the bubble reaction zones which are formed by dividing the inside space of the reaction chamber with partition walls is equipped with a drain for draining settled sludge which is settled within each bubble reaction chamber; the settled sludge which cannot be floated by fine bubbles can be easily discharged outside.

Fourth, since the bottom surface of each bubble reaction zone is down sloped with respect to the drain by a certain angle so that the settled sludge can be naturally guided to the drain; it is unnecessary to use a suction device to discharge the settled sludge.

Fifth, since the bubble generating unit generates fine bubbles and injects the generated fine bubbles into the sewage supplied to the inside of the reaction chamber, and the bubble generating unit is arranged to generate the fine bubbles using the sewage supplied from the last-stage bubble reaction zone; it is unnecessary to use an additional supply-water supply unit and an additional water supply pipe for supplying water, which would be used to generate the fine bubbles. For this reason, the structure of the floatation apparatus is simplified.

Sixth, since the branched pipe with a plurality of branch tubes is installed at an end of the sewage inflow pipe through which sewage is supplied to the inside of the reaction chamber, and since spray nozzles for spray-injecting the sewage and fine bubbles, supplied through the sewage inflow pipe, into the first-stage bubble reaction zone are installed at ends of respective branch tubes; it is possible to supply uniform fine bubbles to the entire area within the bubble reaction zones, thereby ensuring a stable reaction environment within the zones.

Seventh, since the anti-turbulence plates are arranged parallel to each other and perpendicular to a spray direction in which the sewage and fine bubbles are sprayed, and since the anti-turbulence plates are located in front of respective spray nozzles while being distanced from spray holes, it is possible to create a stable reaction environment between organic particles and fine bubbles by using the injection pressure of the sewage and fine bubbles within the bubble reaction zone.

Eighth, because of the installation of the level controlling weir that is disposed at the second side end of the reaction chamber and controls the level of sewage supplied to the inside of the reaction chamber by discharging the sewage through the treated water discharge hole, the concentration and thickness of floating sludge which is floated to the surface of the sewage in each bubble reaction zone can be controlled so that the floating sludge can be thickened.

Ninth, since the bubble reaction zones are formed by alternately installing the lower partition walls and the upper partition walls within the reaction chamber, and since the retention time of fine bubbles for which the fine bubbles can stay underwater in each bubble reaction zone can be adjusted according to the vertical lengths of the upper partition walls extending downward from the upper end of the reaction chamber; treated water with stable purification quality can be obtained.

FIG. 1 is a side view illustrating the overall construction of a partition-type floatation apparatus according to a preferred embodiment of the present invention;

FIG. 2 is a side view illustrating an operation principle which controls the thickness and concentration of floating sludge by controlling the level of sewage using a level controlling weir, according to the preferred embodiment of the present invention;

FIG. 3 is a plan view illustrating an operation principle which treats sewage in a manner of sequentially passing sewage and micro bubbles, supplied to a reaction chamber, through bubble reaction zones and discharging treated water, according to the preferred embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating another form of a spray nozzle according to the preferred embodiment of the present invention;

FIG. 5 is a plan view illustrating the construction of a branched supply pipe and a bubble sprayer module according to the preferred embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating a surface adsorption phenomenon in which micro bubbles are adsorbed onto the surface of organic particles, according to the preferred embodiment of the present invention; and

FIG. 7 is a schematic diagram illustrating dissolving and oxidizing effects of fine bubbles according to the preferred embodiment of the present invention.

Hereinbelow, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Specific structural and functional descriptions of embodiments of the present invention disclosed herein are only for illustrative purposes of the preferred embodiments of the present invention, and the present description is not intended to represent all of the technical spirit of the present invention. On the contrary, the present invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments that may be included within the spirit and scope of the present invention as defined by the appended claims.

Before describing embodiments of the present invention, some terms used hereinafter will be defined as follows. "Sewage" 10 means wastewater to be treated, such as crude sewage, industrial waste water, leachate, night soil wastewater, livestock wastewater, and includes CSOs. Accordingly, "suspended solids" contained in the sewage 10 mentioned below means various pollutants, which can be removed through the flotation of micro bubbles, including chemical sludge and high concentration organics as wells as adulterations which are present in a large amount in rain water.

"A partition-type floatation apparatus using fine bubbles according to a preferred embodiment of the present invention" (hereinafter, referred to as "partition-type floatation apparatus 100") is a purification apparatus that removes particles of suspended solids which are floated by bubbles while maintaining a bubble-saturated state by temporarily limiting flow-out of bubbles in a stepwise manner by using multistage partition walls arranged in a flow direction of the sewage 10, thereby enabling rapid purification and minimizing the concentration of suspended solids remaining in treated water. As illustrated in FIGS. 1 to 3, the apparatus includes a reaction chamber 10, a bubble generating unit 120, and a floating sludge discharging unit 130.

The reaction chamber 110 is a reaction zone in which suspended solids in the sewage 10 are floated and removed while the sewage 10 and fine bubbles B are being supplied to the reaction zone. As illustrated in the drawings, the reaction chamber has an inside space in which flotation is performed. A sewage inflow pipe 111 for supplying the sewage 10 containing suspended solids to the inside space is connected to a first side end of the reaction chamber, and a treated water discharge hole 112 is formed in a second side end of the reaction chamber. Within the inside space, lower partition walls 113 extending upward from a lower end of the inside space and upper partition walls 114 extending downward from an upper end of the inside space are alternately arranged, forming a plurality of bubble reaction zones 115 for floating and removing the suspended solids.

In the drawings, three

bubble reaction zones

115a, 115b, 115c are formed by three

lower partition walls

113a, 113b, 113c and three

upper partition walls

114a, 114b, 114c which are alternately arranged in a flow direction of the sewage 10 within the reaction chamber 110. However, the present invention is not limited to the illustrated structure and number. That is, there may be two bubble reaction zones 115, or four or more bubble reaction zones 115 according to conditions such as purification efficiency, the concentration of suspended solids contained in the sewage 10, and the volume of supplied fine bubbles B.

With reference to the drawings, an upper portion of the reaction chamber 110 is open so that the floating sludge discharging unit 130 can be installed above the reaction chamber 110. However, since stench is likely to linger around the reaction chamber, the upper portion of the reaction chamber may be covered by a cover which is in the form of covering over each of the floating sludge discharging units 130 installed above the respective bubble reaction zones 115.

The sewage 10 supplied through the sewage inflow pipe 111 is likely to contain suspended solids having a large size which cannot be floated by the fine bubbles B. In this case, these large suspended solids may settle with time so that they are not discharged outside. For this reason, the partition-type floatation apparatus 100 according to the preferred embodiment of the present invention may have a drain 116 in the bottom of each bubble reaction zone 115 for the purpose of draining settled sludge S2. An end of the drain 116 is connected to a settled sludge discharge pipe 118 which has a settled sludge discharge hole 118a at an end thereof, so that the settled sludge S2 can be discharged outside through the settled sludge discharge hole 118a. In this case, a control valve 118c for controlling the amount of the settled sludge S2 to be discharged may be installed on the settled sludge discharge pipe 118 through which the settled sludge S2 is discharged. With this structure, it is possible to discharge the settled sludge S2 produced from the suspended solids which are too large to be floated by the fine bubbles B.

In addition, with reference to FIG. 1, it is preferable that a bottom surface 117 of each bubble reaction zone 115 be down sloped with respect to the drain 116 by a certain angle so that the settled sludge S2 collects at the drain 116. Because of the inclined bottom surface, the settled sludge S2 on the bottom surface 117 can be easily discharged outside. Furthermore, it is not necessary to use a suction device for discharging the settled sludge S2 because the settled sludge S2 is naturally guided to the drain due to the inclination of the bottom surface 117.

In addition, the discharge pipe 118 may be provided with a sewage discharge hole 118b for discharging the sewage 10 through the settled sludge discharge hole 118a in order to evacuate each bubble reaction zone 115 as necessary.

The bubble generating unit 120 is a means for generating fine bubbles B having a micrometer or nanometer size and injecting the fine bubbles B into the sewage 10 supplied to the reaction chamber 110. The bubble generating unit 120 communicates with the sewage inflow pipe 111 and a bubble supply pipe 121 to inject the generated fine bubbles B into the sewage 10 in the reaction chamber 110.

As illustrated in FIGS. 1 and 3, a first end of the bubble generating unit 120 communicates with the inside of any one of the bubble reaction zones 115 and a second end of the bubble generating unit is disposed in a portion of the bubble supply pipe 121 which communicates with the sewage inflow pipe 111. The bubble generating unit 120 generates the fine bubbles B using the sewage 10 supplied from the bubble reaction zone 115 communicating with the bubble supply pipe 121. The bubble generating unit 120 injects the fine bubbles B into the inside space of the reaction chamber 110 by supplying the sewage 10 containing the generated fine bubbles B to the sewage inflow pipe 111.

Since the fine bubbles B are supplied by the bubble supply pipe 121 and the bubble generating unit 121, an additional supply-water supply unit and an additional water supply pipeline for supplying water, which is used to generate the fine bubbles B, are unnecessary. For this reason, the structure of the apparatus can be simplified. Furthermore, since a last-stage bubble reaction zone 115c and the bubble supply pipe 121 are connected to each other as illustrated in FIG. 1 and since treated water, which is free of organic particles and which is lastly purified through a third-stage bubble reaction zone 115c, can be used as the supply water which is used to generate the fine bubbles B, there is an advantage that an additional filter for removing organic particles contained in the sewage supplied to the bubble generating unit 121 is unnecessary.

In addition, as illustrated in FIG. 1, the end of the sewage inflow pipe 111 externally extends up to the inside of a first-stage reaction bubble zone 115a disposed in a first stage, through a first side end of the first-stage bubble reaction zone 115a, so that the sewage 10 can be supplied to the inside of the first-stage bubble reaction zone 115a. In addition, as illustrated in FIG. 3, the end of the sewage inflow pipe 111 is equipped with a branched pipe 160 having a plurality of branch tubes, and an end of each branch tube is equipped with an spray nozzle 161 in order to spray-inject the sewage 10 and the fine bubbles B, which are supplied through the sewage inflow pipe 111, into the inside of the first-stage bubble reaction zone 115a.

Although the drawings illustrate the structure in which the branched pipe 160 has four branch tubes and in which the sewage 10 containing the fine bubbles B is supplied to the inside of the bubble reaction zone 115a through the four spray nozzles 161, the present invention is not limited to the illustrated structure. Five or more spray nozzles 161 may be arranged according the size of the reaction chamber 110 in a widthwise direction W. By using the combination of the branched pipe 160 and the spray nozzle 161, uniform fine bubbles B can be supplied to the entire area within each bubble reaction zone 115 so that stable reaction between the fine bubbles B and organic particles can be ensured.

In addition, as illustrated in an enlarged view at the right side of FIG. 3, anti-turbulence plates 162 are preferably arranged parallel to each other and perpendicular to a spray direction in which the sewage 10 and the fine bubbles B are sprayed. The anti-turbulence plates 162 may be arranged in front of the spray nozzles 161 and distanced from spray holes by a predetermined length. The anti-turbulence plates 162 increase the injection pressure of the sewage 10 and the fine bubbles B within the bubble reaction zone s115, thereby ensuring uniform reaction between organic particles and the fine bubbles B.

The spray nozzles 161 may be configured to spray the fine bubbles while preventing turbulent flow even without using the anti-turbulence plates 162. To this end, as illustrated in FIG. 4, a plurality of spray holes 164 for diffusing fine bubbles B is arranged at intervals along the circumferential surface of the end of the spray nozzle 161, and the portion, in which the spray holes 164 are formed, are tapered toward an outer end in order to stably diffuse the fine bubbles B.

The bubble generating unit 120 according to the preferred embodiment of the present invention may spray-inject fine bubbles B generated by the bubble generating unit 120 into the first-stage bubble reaction zone 115a using the combination of the bubble supply pipe 121, the branched pipe 160, and the spray nozzles 161, or using a bubble sprayer module 165 installed in one or more bubble reaction zones selected from among second and third-stage

bubble reaction zones

115b and 115c.

For this, as illustrated in FIG. 5, a branched supply pipe 122 for supplying the fine bubbles B to the bubble sprayer module 165 is installed in the bubble supply pipe 121. A first end of the branched supply pipe 122 is connected to a first side of the bubble supply pipe 121 and a second end of the branched supply pipe is connected to the bubble sprayer module 165, so that the fine bubbles B generated by the bubble generating unit 120 are supplied to the bubble sprayer module 165.

The branched supply pipe 122 is inserted in each bubble reaction zone 115 and extends along the widthwise direction of the bubble reaction zone. One or more bubble sprayer modules 165 is coupled to the branched supply pipe 122 and arranged at regular intervals in a longitudinal direction of the branched supply pipe 122. With this structure, uniform fine bubbles B can be supplied to the inside of the bubble reaction zone 115.

As illustrated in an enlarged view of FIG. 5, the bubble sprayer module 165 is arranged such that a middle portion thereof is connected to the branched supply pipe 122, and respective side portions thereof are provided with a plurality of discharge holes 166 to discharge the fine bubbles B supplied from the middle portion. The side portions provided with the discharge holes 166 are tapered toward respective ends thereof.

With use of the combination of the branched supply pipe 122 and the bubble sprayer module 165, it is possible to supply uniform fine bubbles B to the entire inside area of each of the

bubble reaction zones

115b, 115b, causing a stable reaction between the fine bubbles B and suspended solids.

FIG. 6 illustrates a surface adsorption phenomenon in which the fine bubbles B are adsorbed onto the surface of organic particles, and FIG. 7 illustrates dissolving and oxidizing effects of the fine bubbles B.

With reference to FIGS. 6 and 7, the use of fine bubbles B for the treatment of suspended solids contained in the sewage 10 has many advantages. First, a retention time (floatation time) is shorter compared to a conventional sedimentation method (i.e. a settling time). Therefore, it has good responsiveness to a sharp increase in the quantity of water to be treated, it reduces a required site area for a treatment plant, and it uses a relatively small amount of coagulant compared with a sedimentation method because small sizes of suspended solids are enough to achieve a good floatation effect while the sedimentation method is required to use a large amount of coagulant to form large suspended solids (SS) for rapid sedimentation. On the other hand, the flotation method using fine bubbles B uses fine bubbles with sizes of micrometers or nanometers which are 50 micro meters or smaller than milli bubbles used for conventional air floatation methods. Since the micro or nano bubbles have excellent surface adsorption effects, the likelihood of adsorption between particles of suspended solids and bubbles is high. For this reason, particles of suspended solids with a size of 52 mm can be removed without using a coagulant. However, in order to secure far cleaner quality of treated water, it is necessary to use a small amount of coagulant. Accordingly, the amount of coagulant used for the flotation method using fine bubbles is substantially smaller than that for conventional air flotation methods.

Second, a rising speed of fine bubbles B underwater is about 13 mm/min. Accordingly, fine bubbles stay underwater for 15 minutes (at a minimum) to 1 hour (at a maximum). That is, since a contact time while particles of suspended solids and bubbles are in contact with each other is long, flotation efficiency improves.

Third, since the fine bubbles B have a large surface area, they have a high oxygen dissolution rate. Accordingly, after a floatation process, remaining fine bubbles B are completely dissolved in water, supersaturating treated water with Dissolved Oxygen (DO) so that DO-supersaturated water can be discharged. When this supersaturated treated water is discharged to a water system, influence of treated water on aquatic ecosystems is minimized.

Fourth, the fine bubbles B generate OH⁺ groups using a bubble crushing effect, thereby having deodorization and disinfection effects. Accordingly, the fine bubbles reduce stench from treated water or floating sludge and disinfect colon bacillus present in CSOs.

On the other hand, the floating sludge discharging unit 130 is a means for removing floating sludge S1, floated to the surface of sewage by the fine bubbles B within the open reaction chamber 110, by discharging the floating sludge S1 outside. The floating sludge discharging unit 130 is disposed above the open reaction chamber 110, and skims and discharges the floating sludge S1, floated to the surface by the fine bubbles B within each bubble reaction zone 115, by rotating a rotation chain with an outer surface to which a plurality of skimmers 131 are coupled.

Here, as illustrated in FIG. 1, the floating sludge discharging unit 130 includes

rotation rollers

133, 134, the rotation chain 132, and a driving motor (not shown). The rotation rollers are horizontally arranged at an upper portion of a first side end of the first-stage bubble reaction zone 115a disposed in a first stage and at an upper portion of a second side end of the third-stage bubble reaction zone 115c disposed in a last stage, respectively. The rotation chain 132 is stretched between the

rotation rollers

133, 134 and engages with the rotation rollers in a rotatable manner. The plurality of skimmers 131 extending outward from the circumferential surface of the rotation chain are coupled to the rotation chain. The driving roller offers rotational force to the

rotation rollers

133, 134.

The floating sludge discharging unit 130 is installed at the same height as the skimmers 131 and is disposed above the reaction chamber 110. As the skimmers 131 revolve around the

rotation rollers

133, 134 along the rotation chain 132, the floating sludge S1 floated to the surface in each bubble reaction zone 115 is skimmed and guided to the direction of the floating sludge discharging unit 130 so as to be discharged outside.

At the second side end of the reaction chamber 110 in which the treated water discharge hole 112 is formed, a level controlling weir 140 for controlling the level of the sewage 10 supplied to the reaction chamber 10 is installed in order to discharge the sewage 10 through the treated water discharge hole 112.

The level controlling weir 140 includes a level controlling plate 141, a driving shaft 142, and a control motor 143. The level controlling plate 141 takes the form of a plate extending in the widthwise direction W as illustrated in FIGS. 2 and 3 and is horizontally arranged. A first end of the level controlling plate is rotatably coupled to a portion of an external wall 11a of the second side end of the reaction chamber 110, in a position under the treated water discharge hole 112. The driving shaft 142 is coupled to a second end of the level controlling plate 141 and rotates the second end of the level controlling plate with respect to the first end of the level controlling plate. The control motor 143 sends driving force to the driving shaft 142.

The level of the sewage 10 is controlled in a manner that: the second end of the level controlling plate 141 is rotated according to the drive of the control motor 143 and lowered to a position which is lower than a current water level; and the sewage 10 is discharged through the treated water discharge hole 112. Since the level controlling weir 140 has this structure, the concentration and thickness of the floating sludge S1 at an upper end of each bubble reaction zone 115 can be controlled so that the floating sludge S1 can be adequately thickened.

Specifically, the function of the level controlling weir 140 is to finely adjust the level of the sewage 10 within the partition-type floatation apparatus 100. This function maintains a proper condition of a layer of the floating sludge S1 and variably adjusts the level of the sewage according to the quality of treated water, in order to enable stable operation of the partition-type floatation apparatus 100. The level controlling weir 140 is a curtain-type weir, and this weir operates by comparing a signal from a water gauge (not shown) with a level value which is input in advance. The level controlling weir 140 not only simply controls the level of the sewage but also appropriately controls the concentration of the floating sludge S1 by adjusting the floating sludge S1, causing the floating sludge S1 to be thickened. As illustrated in (a) of FIG. 2, when the level controlling plate 141 of the level controlling weir 140 is lowered to or below a predetermined level, the thickness of the layer of the floating sludge S1 increases. When the layer of the floating sludge S1 is excessively thick, the quality of treated water is deteriorated. In this case, as illustrated in (b) of FIG. 2, the level controlling plate 141 of the level controlling weir 140 is increased, so that the amount of overflow of the floating sludge S1 increases and the level of the sewage water 10 rises to a predetermined level or above. In this way, by decreasing the thickness of the layer of the floating sludge S1, it is possible to prevent suspended solids from flowing out. The level controlling weir 140 appropriately controls the level of sewage according to characteristics of inflow water and operation conditions, thereby maintaining optimum processing conditions.

The respective bubble reaction zones 115 are formed by dividing the inside space of the reaction chamber 110 with lower partition walls 113 and upper partition walls 114 which are alternately arranged within the reaction chamber 110. The retention time of the fine bubbles B for which the fine bubbles B stay underwater in each bubble reaction zone 115 is adjusted according to a vertical length of the upper partition wall 114. That is, by adjusting the vertical lengths (i.e., lengths of portions which overlap each lower partition wall 113) of a first upper partition wall 114a, a second upper partition wall 114b, and a third upper partition wall 114c which divide an upper space, it is possible to control the retention time for which the fine bubbles B and the sewage 10 stay underwater within each of the

bubble reaction zones

115a, 1115b, 115c.

For example, within the first-stage bubble reaction zone 115a, the length of the first upper partition wall 114a is set such that the retention time of the fine bubbles B in water is 5 minutes. That is, flotation is performed in a condition that the fine bubbles B are confined by the first upper partition wall 114a and retained in a highly dense and supersaturated state so that strong adsorption between the fine bubbles B and suspended solids occurs, and oxidation decomposition occurs. Within the second-stage bubble reaction zone 115b, floatation is performed by secondary adsorption between the fine bubbles B transferred from the first-stage bubble reaction zone 115a and suspended solids. The retention time for the second-stage bubble reaction zone 115b is set to 10 minutes. That is, the length of the second upper partition wall 114b is set to increase the retention time in order to increase efficiency of flotation of suspended solids which are not removed by the first-stage bubble reaction zone 115a.

Within the third-stage bubble reaction zone 115c, the length of the third upper partition wall 114c is set so that the retention time becomes 15 minutes in consideration of the rising speed of fine suspended solids. This ensures stable treatment of finally treated water. The treated water which has undergone the third-stage bubble reaction zone 115c is discharged to the treated water discharge hole 112 via the level controlling weir 140. The retention times for the respective

bubble reaction zones

115a, 115b, 115c are appropriately adjusted and adequately set according to the amount of supplied fine bubbles B and the concentration of suspended solids contained in the sewage 10.

By using the structures and functions of the partition-type floatation apparatus 100 according to the preferred embodiment of the present invention described above, temporary flow-out of fine bubbles B is restricted by partition walls installed in a flow direction of the sewage 10 in multiple stages so that floated suspended solids are removed while a bubble-saturated state is maintained. This enables purification in a short time and minimizes suspended solids discharged in treated water.

In addition, since it is possible to treat floated suspended solids in a stepwise manner by using a structure in which partial walls are installed within a single reaction chamber 110, it is possible to minimize flow-out of suspended solids attributable to a short flow and to save a required site area for installation.

Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Reference Signs List

10: Sewage

100: Partition-type floatation apparatus

110: Reaction chamber

111: Sewage inflow pipe

112: Treated water discharge hole

113: Lower partition wall

114: Upper partition wall

115: Bubble reaction zone

120: Bubble generating unit

121: Bubble supply pipe

1130: Floating sludge discharging unit

131: Skimmer

132: Rotation chain

133, 134: Rotation roller

140: Level controlling weir

141: Level controlling plate

142: Driving shaft

143: Control motor

160: Branched pipe

161: Spray nozzle

S1: Floating sludge

S2: Settled sludge

B: Fine bubbles

Claims

A partition-type floatation apparatus comprising: a reaction chamber (110) having: a first side end connected to a sewage inflow pipe (111) through which sewage (10) containing suspended solids is supplied to an inside of the reaction chamber (110); a second side end in which a treated water discharge hole 112 for discharging treated water of the sewage (10) is formed; and a lower partition wall (113) and an upper partition wall (114) which are alternately installed to form a plurality of bubble reaction zones (115) in each of which the suspended solids are floated and removed, the lower partition wall (113) extending upward from a lower end of the reaction chamber, the upper partition wall (114) extending downward from an upper end of the reaction chamber; and a bubble generating unit (120) which generates fine bubbles (B) having a micrometer or nanometer size and injects the generated fine bubbles (B) into the sewage (10) supplied to the inside of the reaction chamber by communicating with the sewage supply pipe (111) and a bubble supply pipe (121) or by communicating with a bubble sprayer module (165) installed within at least one of the plurality of bubble reaction zones (115).
The partition-type floatation apparatus according to claim 1, further comprising: a floating sludge discharging unit (130) installed above the reaction chamber (110) in order to remove floating sludge (S1), which is floated to the surface of the sewage in each of the bubble reaction zones (115) by the fine bubbles (B), by skimming the floating sludge (S1) by rotating a rotation chain (132) to which a plurality of skimmers (131) is coupled.
The partition-type floatation apparatus according to claim 2, wherein a bottom surface of each of the bubble reaction zones (115) is provided with a drain (116) for draining settled sludge (S2) therethrough, and wherein the drain (116) is connected to a settled sludge discharge pipe (118) having a settled sludge discharge hole (118a) at an end thereof so that the settled sludge (S2) is discharged outside through the settled sludge discharge hole (118a).
The partition-type floatation apparatus according to claim 3, wherein the bottom surface (117) of each of the bubble reaction zones (115) is an inclined surface which is down slopped with respect to the drain (116) so that the settled sludge (S2) collects at the drain (116).
The partition-type floatation apparatus according to claim 1, wherein the bubble generating unit (120) is installed on the bubble supply pipe (121), a first end of which is connected to an inside of any one bubble reaction zone (115c) and a second end of which is connected to the sewage inflow pipe (111), and wherein the bubble generating unit (120) generates fine bubbles (B) using the sewage (10) supplied from the bubble reaction zone (115c) and supplies the fine bubbles (B) to the inside of the reaction chamber by injecting the sewage (10) containing the generated fine bubbles (B) into the sewage inflow pipe (111).
The partition-type floatation apparatus according to claim 5, wherein an end portion of the sewage inflow pipe (111) penetrates and externally extends up to an inside of a first-stage bubble reaction zone (115a) in order to supply the sewage (10) to the inside of the first-stage bubble reaction zone (115a), wherein the end portion of the sewage inflow pipe (111) is provided with a branched pipe (160) with a plurality of branch tubes, and wherein ends of the branch tubes are equipped with respective spray nozzles (161) configured to spray-inject the sewage (10) and the fine bubbles (B) into the inside of the first bubble reaction zone (115a) through the sewage inflow pipe (111).
The partition-type floatation apparatus according to claim 6, wherein a plurality of anti-turbulence plates (162) are arranged, in parallel with each other and in a direction in which the sewage (10) and the fine bubbles (B) are sprayed, in front of the respective spray nozzles (161) and are distanced from respective ejection holes by predetermined distance.
The partition-type floatation apparatus according to claim 2, wherein the floating sludge discharging unit (130) includes:

rotation rollers (133, 134) which are arranged, in parallel with each other in a horizontal direction, at an upper portion of a first side end of the first-stage bubble reaction zone (115a) and an upper portion of a second side end of a last-stage bubble reaction zone (115c), respectively;

the rotation chain (132) which is stretched between the rotation rollers (133, 134) while engaging with the rotation rollers (133, 134) in a rotatable manner and which has a circumferential surface to which the plurality of skimmers (131) extending outward from the circumferential surface are coupled; and

a driving motor which offers rotational force to the rotation rollers (133, 134),

wherein a floating sludge discharge hole (119) is formed in an upper portion of the reaction chamber (110) and at the same height as the skimmers (131), and wherein the floating sludge (S1), which is floated to the surface of the sewage in the bubble reaction zones (115), is guided to the floating sludge discharge hole (119) by the respective skimmers (131), which are rotated along the rotation chain (132) by the rotation rollers (133, 134), and discharged outside.
The partition-type floatation apparatus according to claim 1, wherein a level controlling weir (140) is installed at the second side end of the reaction chamber in which the treated water discharge hole (112) is formed, the level controlling weir (140) controlling a level of the sewage (10) supplied to the inside of the reaction chamber (110) by discharging the sewage (10) outside through the treated water discharge hole (112).
The partition-type floatation apparatus according to claim 9, wherein the level controlling weir (140) comprises:

a level controlling plate (141) which is a plate extending in a widthwise direction (W) and has a first end which is rotatably coupled to an external wall (110a) of the second side end of the reaction chamber (110), in a position lower than the treated water discharge hole (112);

a driving shaft (142) which is coupled to a second end of the level controlling plate (141) and rotates the second end of the level controlling plate (141) with respect to the first end of the level controlling plate (141); and

a control motor (143) which offers a driving force to the driving shaft (142),

wherein the level of the sewage (10) is controlled by rotating the second end of the level controlling plate (141) according to a drive of the control motor (143).
The partition-type floatation apparatus according to claim 1, wherein a branched supply pipe (122) for supplying the fine bubbles (B) to the bubble sprayer module (165) is installed on the bubble supply pipe (121), and wherein a first end of the branched supply pipe (122) is connected to a first side of the bubble supply pipe (121) and a second end of the branched supply pipe (122) is connected to the bubble sprayer module (165) so that the fine bubbles (B) generated by the bubble generating unit (120) are supplied to the bubble sprayer module (165).
The partition-type floatation apparatus according to claim 11, wherein the branched supply pipe (122) is inserted in each of the bubble reaction chambers (115) and arranged to extend in a widthwise direction of each bubble reaction zone, and wherein more than one bubble sprayer module (165) is coupled to the branched supply pipe (122) and arranged at intervals in a longitudinal direction of the branched supply pipe so that uniform fine bubbles (B) are supplied to the entire area of the bubble reaction zone (115).
The partition-type floatation apparatus according to claim 12, wherein the bubble sprayer module (165) is arranged such that a middle portion thereof is coupled to the bubble supply pipe (122), and respective side portions thereof are provided with a plurality of discharge holes (166) for discharging the fine bubbles (B) supplied from the middle portion, and wherein the side portions with the discharge holes (166) are tapered toward respective ends thereof.
The partition-type floatation apparatus according to any one of claims 1 to 12, wherein the bubble reaction zones (115) are formed by the lower partition wall (113) and the upper partition wall (114) which are alternately arranged within the reaction chamber (110), and wherein a retention time of the fine bubbles (B) for which the fine bubbles stay underwater within each of the bubble reaction zones (115) is adjusted according to a vertical length of the upper partition wall (114).