PH12012000114A1

PH12012000114A1 - Advanced wasted-water treatment apparatus having function for removing phosphorus

Info

Publication number: PH12012000114A1
Application number: PH12012000114A
Authority: PH
Inventors: Cho Sang Su; Lee Byoung Ro; Lee Yong Woon; Lee Byong Hee; Seo Jae Sik
Original assignee: Daejin Environment Industry; Dae Ho Environmental Technology Co Ltd
Priority date: 2011-08-31
Filing date: 2012-05-17
Publication date: 2014-11-10
Also published as: KR101122745B1

Abstract

The advanced waste water treatment apparatus having a function of removing phosphorus is disclosed. The advanced waste water treatment apparatus may treat simultaneously organic matters, nitrogen, and phosphorus within wasted water in a membrane bio-reactor manner, efficiently improve removal efficiency of the phosphorus through electrolysis, and continuously discharge treated water even through a solid-liquid separation function of a membrane is not performed.

Description

v ADVANCED WASTED-WATER TREATMENT APPARATUS HAVING

FUNCTION FOR REMOVING PHOSPHORUS

I. Field

Embodiments relate to an advanced waste water treatment apparatus, and more particularly, to an advanced waste water treatment apparatus which treats organic matters, nitrogen, and phosphorus within sewage and/or wasted water in a membrane bio-reactor manner at the same time, efficiently improves removal efficiency of phosphorus through electrolysis, and continuously discharges treated water even though a solid-liquid separation function of a membrane is not performed. 2. Description of the Related Art

[0001]

An advanced waste water treatment apparatus using a membrane bio-reactor (hereinafter, referred to as “MBR”) is advantageous in that the area required for installation is small and an automatic operation thereof is easy. In addition, since the advanced waste water treatment apparatus does not comprises a separate settling tank, limitations such as sludge bulking, etc. can be fundamentally solved. Thus, the advanced waste water treatment apparatus utilizing the MBR has been widely utilized for small-scale waste water treatment institutions. ]

[0002]

In particular, since the quality of treated water can be adjusted, as necessary, according to selection of membrane, the advanced waste water treatment apparatus employing the MBR has been widely used for small-scale water purification institutions to keep pace with political consideration with respect to the recent water i reuse.

[0003]

The advanced waste water treatment apparatus using the MBR has a disadvantage in terms of removal efficiency of phosphorous because a generation rate of surplus sludge is significant less when compared to an existing method, and it is accepted as an advantage of a MBR system. Thus, an advanced MBR system which makes up for a limitation in terms of the removal efficiency of phosphorus and removes nitrogen and phosphorus at the same time is required.

[0004]

In typical MBR methods in which a separation membrane is immersed in an activated sludge aeration tank, an anaerobic or anoxic tank is disposed at a front side of the activated sludge aeration tank, and an aerobic reaction tank in which a membrane is immersed is disposed at a rear side of the activated sludge aeration tank.

Also, most of the typical MBR methods use a process similar to an A2/O process that is a conventional advanced waste water treatment technology as a fundamental process to apply a membrane. This process has a limitation in which organic matters within inflow water is lost by dissolved oxygen within sludge due to excessive sludge ; return up to 2~6Q, and thus removal efficiency of nitrogen and phosphorus is reduced.

[0005]

Also, the process using the separation membrane has the other limitation in : which a cake layer is accumulated on a surface of the membrane as filtering time elapses to significantly reduce a permeate flow rate. The transmittance of a membrane is reduced by a concentration polarization phenomenon in which a solute in the vicinity of the membrane is increased in concentration to reduce transmittance as an osmotic pressure is increased and a separation membrane fouling phenomenon in which a solute is absorbed or deposited on a surface of the membrane or within the membrane to reduce transmittance.

[0006]

The concentration polarization phenomenon does not affect property of the separation membrane itself and depends on a hydraulic state of the surface of the membrane. However, since materials are accumulated or absorbed on the surface of the membrane, the fouling of the membrane may cause a change in the property of the separation membrane to reduce the transmittance. The concentration polarization phenomenon reduces an effective pressure for transmittance in the surface of the membrane, but does not permanently change materials and transmittance of the membrane. Thus, the methods for minimizing the concentration polarization phenomenon in the light of the hydrodynamic viewpoint by means of development the various shapes of the membrane module have been studied.

[0007]

However, the fouling of the membrane may permanently reduce the transmittance of the membrane when pollutants are strongly attached and accumulated on the surface of the membrane according to properties of inflow water. Also, the separation membrane may be changed in property so that a solid-liquid separation function of the separation membrane cannot be performed. :

[0008]

Environmental water quality standards as water quality improvement measures : of a public water area in which water is quickly polluted in recent years are gradually ] tightened. Thus, it may be important to remove nutrient (e.g., nitrogen, phosphorus, [ etc.) as well as organic matters to improve water quality in a final discharge water : area. In particular, nitrogen or phosphorus component in water may serve as i pollutants in itself to reduce valuation of water resource. In addition, nitrogen or phosphorus component may be used as nutrient required for algal growth to further cause water pollution.

[0009]

In almost conventional water treatment processes, a biological or chemical treatment process may be performed to remove phosphorus. However, in case of middle or small-scale water purification institutions, it is difficult to stably perform the phosphorus removal process due to a complicated operation thereof and a rapid change of a load of inflow water. Also, a generation rate of chemical sludge may be increased. Thus, remarkable development of process which can satisfy the tightened water quality standards is being urgently needed.

SUMMARY

[0010]

An aspect of the present invention provides an advanced waste water treatment apparatus which can continuously discharge treated water even though a solid-liquid separation function of a separation membrane is not performed due to pollution of the separation membrane disposed in a membrane bio-reactor (MBR) tank and reduce ; energy consumption by maximally using a dissolved oxygen (DO) concentration consumed in the MBR tank.

[0011] ]

Another aspect of the present invention provides an advanced waste water treatment apparatus which can treat phosphorus, which is not biologically treated, by ] means of the electrolysis to maximally reduce a concentration of the phosphorus of discharged water and is not affected by external change factors. -4- 1

[0012]

In order to achieve the above objects, the advanced waste water treatment apparatus according to the present invention comprises an intermittent reaction tank into which water to be treated and activated sludge are introduced, the intermittent reaction tank comprising an intermittent aeration means; a membrane bio-reactor (MBR) tank into which a mixture is introduced from the intermittent reaction tank, the

MBR tank comprising a treated water discharging means for discharging treated water through a separation membrane which removes remaining organic matters of the introduced mixture and separates water and sludge from each other, and the MBR tank further comprising an aeration means; a transition tank into which the activated sludge is introduced from the MBR tank, the transition tank reducing dissolved oxygen (DO) of the activated sludge to promote denitrification; a treated water circulation part circulating some of the treated water discharged from the MBR tank into the intermittent reaction tank and the MBR tank; an electrolysis part comprising an electrolysis tank through which the treated water circulated by the treated water circulation part passes and an electrode module which electrolyzes the treated water introduced into the electrolysis tank to produce ferrum iron or aluminum ions, thereby reducing phosphorus content of the treated water discharged from the MBR tank; and an internal return means for returning the activated sludge from one of the MBR tank ; and the transition tank into the intermittent reaction tank according to an aeration or j nonaeration condition within the intermittent reaction tank.

[0013]

In the advanced waste water treatment apparatus of the present invention, the internal return means may comprise a first internal return unit for returning the activated sludge from the MBR tank into the intermittent reaction tank when the intermittent aeration means is operated; and a second internal return unit and a / supernatant discharging unit returning the activated sludge from the transition tank 1 into the intermittent reaction tank when the intermittent aeration means is not ’ operated.

[0014]

Here, the second internal return unit and the supernatant discharging unit halt a return of the activated sludge and discharging supernatant in the transition tank to the outside when a solid-liquid separation function of the separation membrane is not performed.

[0015]

In addition, the first internal return unit may comprise a first return line connecting the MBR tank and the transition tank, and a first transfer pump disposed on the first return line to transfer the activated sludge within the MBR tank into the intermittent reaction tank, and the second internal return unit and the supernatant discharging unit comprises a cylindrical elevation pipe vertically movably disposed in the transition tank, the elevation pipe having suction holes arranged in a line from one side of an upper portion thereof to the other side and being spaced from each other; an elevation part for moving vertically the elevation pipe; a discharge line connected to the elevation pipe; a second transfer pump disposed on the discharge line to transfer the supernatant or the activated sludge to the outside through the elevation pipe; a second return line branched from the discharge line and connected to the intermittent reaction tank to transfer the activated sludge; a treated water discharge line branched from the discharge line to discharge the supernatant; and a three-way valve disposed at a branched point between the second transfer line and the treated water discharge line. ]

Preferably, the second internal return unit and the supernatant discharging unit ) further comprises a suspended solid inflow prevention means for preventing suspended solids floating on an upper portion of the transition tank from being introduced into the elevation pipe when the supernatant is discharged.

[0017]

In addition, the suspended solid inflow prevention means may comprise rod-shaped support bars vertically disposed between the suction holes and guide collar disposed on each of both edges of the obstruction cover and extended in a direction of the support bars.

Preferably, the guide collar is extended in an arc shape to guide the flow of the supernatant into the suction holes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]

The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain principles of the present disclosure. In the drawings:

[0019]

FIG. 1 is a block diagram illustrating a structure of an advanced waste water treatment apparatus according to one embodiment of the present invention;

[0020]

Te

FIG. 2 is a schematic view of the advanced waste water treatment apparatus - shown in FIG. 1;

[0021]

FIG. 3 is a partially cut-away perspective view of a transition tank of the advanced waste water treatment apparatus in FIG. 1;

[0022]

FIG. 4 is a perspective view of an essential part of a transition tank employed in the advanced waste water treatment apparatus according to another embodiment of the present invention;

[0023]

FIG. 5 is a cross-sectional view of FIG. 4; and

[0024]

FIG. 6 is a cross-sectional view of an essential part of a transition tank employed in the advanced waste water treatment apparatus according to yet another embodiment of the present invention.

DETAILED DESCRIPTION

[0025]

Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. : Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. 1

[0026]

Hereinafter, an advanced waste water treatment apparatus having a function ; for removing phosphorus according to preferred embodiments will be described in detail with reference to the accompanying drawings.

[0027]

Referring to FIGS. 1 to 3, an advanced waste water treatment apparatus according to one embodiment of the present invention includes an intermittent reaction tank 10, a membrane bio-reactor (hereinafter, referred to as “MBR?”) tank 20, a transition tank 30, a treated water circulation part, an electrolysis part 100, and an internal return means.

[0028]

Sewage water or waste water which is an object to be treated is passed through a well pretreatment apparatus, i.e., a screen, a grit tank, a first settling tank, a flow rate adjustment tank and the like, and then introduced into the intermittent reaction tank 10 through an inflow water line 7. A pump 6 is disposed within the flow rate adjustment tank 5 to forcibly move the water to be treated into the intermittent ration tank 10 through the inflow water line 7. Also, activated sludge returns from the

MBR tank 20 or the transition tank 30 by the internal return unit and is introduced into the intermittent reaction tank 10.

[0029] J

A mixture in which the water to be treated and the activated sludge are mixed is converted into an aerobic condition or nonaeration (anoxic) condition according to whether aeration exists in the intermittent reaction tank 10 and then nitrification and ] denitrification reactions are performed. ]

[0030]

An intermittent aeration unit for creating aeration or nonaeration conditions is disposed in the intermittent reaction tank 10. An air blower 11 for injecting air into the intermittent reaction tank 10 is provided as the intermittent aeration unit. An air diffuser 13 connected to the air blower 11 is disposed at a lower portion of the intermittent reaction tank 10. Also, a solenoid valve, a motorized valve and a timer which change a time interval for supplying air from the air blower 11 into the air diffuser 13 may be provided. Also, a stirrer 15 for mixing the water to be treated and the activated sludge is disposed within the intermittent reaction tank 10.

[0031]

In the intermittent reaction tank 10, excessive intake of phosphorus due to microorganisms and an oxidation reaction in which ammonical nitrogen is converted into nitrite nitrogen occur in the aeration condition, i.e., the aerobic condition. On the other hand, in the intermittent reaction tank 10, nitrite nitrogen is reduced into nitrogen gas by microorganisms relating to denitrification in the nonaeration condition, 1.e., the anoxic state to remove nitrogen. Through the above-described method, the aeration condition and the nonaeration condition may be alternately repeated to induce the excessive intake of the phosphorus, the nitrification, and the denitrification, thereby effectively removing the nitrogen and phosphorus.

[0032]

The intermittent aeration is intermittently performed in the intermittent reaction tank 10 at a predetermined period for about 45 minutes of an aeration time and about 75 minutes of a nonaeration time. Here, it may be possible to adjust the aeration time and the nonaeration time according to a biological oxygen demand (BOD) concentration of the inflowed water to be treated. _10- i

[0033]

The MBR tank 20 is disposed on a rear portion of the intermittent reaction tank 10. When the mixture within the intermittent reaction tank 10 reaches a predetermined water level, the mixture is gravity-flowed into the MBR tank 20 through a connection pipe 19. The mixture is continuously introduced from the intermittent reaction tank 10 into the MBR tank 20.

A separation membrane 21 for removing remaining organic matters of the introduced mixture and separating water from sludge is disposed in the MBR tank 20.

Preferably, the separation membrane 21 may be a digestion membrane. The MBR tank 20 includes a treated-water discharging means for discharging the treated-water separated through the separation membrane 21 and an aeration means.

[0034]

The treated-water discharging means includes a suction pump 22 for sucking the treated-water using a suction force and a suction line 23 connecting the suction pump 22 to the separation membrane 21 to transmit the suction force of the suction pump 22 into the separation membrane 21.

[0035]

Also, the aeration means for creating the aerobic condition within the MBR tank 20 includes an air blower 25 and an air diffuser 27 connected to the air blower 25 and disposed under the separation membrane 21. The aerobic condition is created in the MBR tank 20 by the aeration means to allow the nitrification reaction to be ] performed. Also, the sludge attached to the separation membrane 21 is separated from the separation membrane 21 by a shear force generated by colliding air bubbles i generated by the air diffuser 27 with the separation membrane 21. d

[0036]

S11 -

It is preferable that the activated sludge within the MBR tank 20, i.e., mixed ’ liquor suspended solid (MLSS) may have a microorganism concentration of 5,000 mg/0 to 10,000 mg/l.

The transition tank 30 is disposed on a rear end of the MBR tank 20. The activated sludge within the MBR tank 20 is gravity-flowed into the transition tank 30 through the connection pipe 29. The activated sludge continuously flows into the transition tank 30. The transition tank 30 reduces dissolved oxygen (DO) of the activated sludge to promote denitrification.

[0037]

A stirrer 31 for providing a gas stripping time to reduce the dissolved oxygen of the introduced activated sludge and making sludge characteristics uniform is disposed within the transition tank 30. :

[0038]

The internal return means returns the activated sludge from one of the MBR tank 20 and the transition tank 30 into the intermittent reaction tank 10 according to the aeration or nonaeration condition within the intermittent reaction tank 10.

[0039]

For example, the internal return means includes a first internal return unit and a second internal return unit and a supernatant-discharging unit.

[0040]

When the intermittent aeration means of the intermittent reaction tank 10 is operated, the internal return unit returns the activated sludge from the MBR tank 20 into the intermittent reaction tank 10. The first internal return unit includes a first return line 90 connecting the MBR tank 20 and the transition tank 30 and a first ]

transfer pump 91 disposed on the first return line 90 to transfer the activated sludge ) within the MBR tank 20 into the intermittent reaction tank 10.

[0041]

In the aeration condition within the intermittent reaction tank 10, i.e., in a state where the air blower 11 of the intermittent aeration means is operated to generate the aeration in the intermittent reaction tank 10, the activated sludge within the MBR tank 20 having a high dissolved oxygen concentration is introduced into the intermittent reaction tank 10 through the first internal return unit. Thus, an operation time of the air blower for creating the aeration condition of the intermittent reaction tank 10 may be reduced to reduce energy consumption.

[0042]

Also, when the intermittent aeration means is not operated, i.e., in a state where the air blower 11 of the intermittent aeration means is not operated so that the inside of the intermittent reaction tank 10 is in the nonaeration state, the second internal return unit and the supernatant discharging unit returns the activated sludge from the transition tank 30 into the intermittent reaction tank 10. Also, when, due to } a pollution of the separation membrane 21, the solid-liquid separation function is not : performed, the second internal return unit and the supernatant discharging unit stops the return of the activated sludge and then discharge the supernatant to an outside.

[0043]

As described above, the activated sludge within the transition tank 30 is returned usually into the intermittent reaction tank 10 through the second internal 1 return unit and the supernatant discharging part e part. In an emergency in which the solid-liquid separation function of the separation membrane 21 is not performed, 3 however, the supernatant in the transition tank 30 may be discharged so that waste 3 water can be treated continuously water without halting the operation of the apparatus. ’ Also, ferrum or aluminum ions produced by electrolysis may be bonded to phosphate ions and the bonded ions are sunken naturally, thereby improving the solid-liquid separation function in the transition tank 30. Thus, the supernatant discharged from the transition tank 30 may sufficiently satisfy the water quality standards.

[0044]

The second internal return unit and the supernatant discharging unit includes a cylindrical elevation pipe 50 vertically movably disposed on the transition tank 10 and having suction holes 52 arranged in a line from one side of an upper portion thereof up to the other side and spaced from each other, an elevation part 40 vertically moving the elevation pipe 50, a discharge line 60 connected to the elevation pipe 50, a second transfer pump 61 disposed on the discharge line 60 to transfer the supernatant or the activated sludge to the outside through the elevation pipe 50, a second return line 95 branched from the discharge line 60 and connected to the intermittent reaction tank 10 to transfer the activated sludge, a treated water discharge line 63 branched from the discharge line 60 to discharge the supernatant, and a three-way valve 65 disposed at a branched point between the second transfer line 95 and the treated water discharge line 63.

[0045]

The elevation pipe 50 is vertically movably disposed within the transition tank 30 in upward/downward directions. The plurality of suction holes 52 are formed on the upper portion of the elevation pipe 50 from a left side to a right side. The suction holes 52 are arranged at regular intervals. Each of the suction holes 52 may have a circular or rectangular shape.

[0046] _14- !

Coupling members 54, each of which having a square shape, are disposed at ) both sides of the elevation pipe 20. A screw hole is formed in and passed vertically through each coupling member 54. A first guide bar 45 and a second guide bar 47, which will be described below, are screw-coupled to the coupling members 54 through screw holes, respectively.

[0047]

The first and second guide bars 45 and 47 are vertically disposed on both sides of the inside of the transition tank 30 toward the elevation part 40, respectively. A spiral part is formed on an outer circumference surface of each of the first and second guide bars 45 and 47. Lower ends of the first and second guide bars 45 and 47 are rotatably supported to a bottom of the transition tank 30, and upper ends are rotatably supported to a fixed panel 39 disposed at an upper portion of the transition tank 30.

First and second bevel gears 46 and 48 are disposed on upper portions of the first and second guide bars 45 and 47, respectively. A driving bar 42 including third and fourth bevel gears 43 and 44 mounted on both ends thereof is disposed on the first and : second guide bars 45 and 47 to transmit simultaneously a driving force to the first and J second guide bars 45 and 47. The third and fourth bevel gears 43 and 44 disposed on the driving bar 42 are meshed with the first and second bevel gears 46 and 48, respectively. A driving motor 41 is disposed on the fixed panel 39 on which the third bevel gear 43 is mounted. The driving motor 41 is connected to the driving bar 42 to rotate the driving bar 42.

[0048]

Due to the above-described structure of the elevation part 40, the elevation pipe 50 discharges the supernatant from an upper portion of the transition tank 30 or discharges the activated sludge from a lower portion of the transition tank 30 while being vertically moved.

[0049]

The discharge line 60 is connected to the elevation pipe 50 and extended to an outside of the transition tank 30 to transfer the supernatant or the sludge introduced into the elevation pipe 50 to the outside. The discharge line 60 should have a length enough to allow the elevation pipe 50 to be vertically moved within the transition tank 30. Preferably, the discharge line 60 may be a flexible hose.

[0050]

The supernatant or the activated sludge is discharged from the transition tank 30 through the second transfer pump 61 disposed on the discharge line 60. Here, the supernatant or the activated sludge is discharged into the second transfer line 95 or the treated water discharge line 63 by the three-way valve 65. For example, in a case where the supernatant is discharged, the three-way valve 65 connects the discharge line 60 and a flow passage of the treated water discharge line 63. Also, in a case where the activated sludge is discharged, the three-way valve 65 connects the discharge line 60 and a flow passage of the second transfer line 95. Undoubtedly, the switching of the flow passage of the three-way valve 65 may be controlled by a typical control unit.

[0051]

In a case where the supernatant is discharged through the second internal return unit and the supernatant discharging unit, power is applied to the driving motor 41] to rotate the first and second guide bars 45 and 47, thereby moving the elevation pipe 50 upward. In a state where the elevation pipe 50 is located at the upper portion of the transition tank 30, for example, in a state where the elevation pipe is immersed into a water surface by a depth of 0.5 m to 2 m, the second transfer pump 61 is operated. As the second transfer pump 61 is operated, the supernatant is introduced into the elevation pipe 50 through the suction holes 52.

[0052]

At this time, it is preferable to provide a suspended solid inflow prevention means for preventing the suspended solids floating on the upper portion of the transition tank 30 from being introduced into the elevation pipe 50. In another embodiment of the present invention, therefore, the second internal return unit and the supernatant discharging unit include the suspended solid inflow prevention unit.

[0053]

Referring to FIGS. 4 and 35, a plurality of suction holes 53 are formed on the an elevation pipe 50 at regular intervals. The suction holes 53 are arranged in a line from one side to the other side of the elevation pipe 50. In one example shown in the drawing, each of the suction holes 53 has a rectangular shape.

[0054] :

Support bars 71 and an obstruction cover 75 are provided as the suspended solid inflow prevention means. :

[0055]

Each of the plurality of support bars 71 is disposed between two suction holes 53, and the plurality of support bars are vertically disposed. Each of the support bars 71 has arod shape. The arc-shaped obstruction cover 75 is coupled to upper portions of the support bars 75. Thus, the obstruction cover 75 is spaced a predetermined distance upward from an outer circumference surface of the elevation pipe 50. This ] obstruction cover 75 covers an upper side of the elevation pipe 50 to block the suction holes from an upper side.

[0056]

The obstruction cover 75 prevents a flow of supernatant introduced into the suction holes 53 from being formed above the suction holes 53 to effectively prevent suspended solids floating on a water surface from being introduced into the suction holes 53.

[0057]

In addition to the obstruction cover 75, as shown in FIG. 6, the suspended solid inflow prevention means further includes a guide blade collar 77. The guide collar 77 prevents a swirl from being formed on an inside the obstruction cover 75 and induces a flow of the supernatant into the suction holes 53. The guide collars 77 are formed on both side edges of the obstruction cover 75 and extended in a direction of the support bars 71. Here, the guide collar 77 may extend in an arc shape so as to allow the inflow of the supernatant introduced into the suction holes 53 to be formed ] on both side surfaces of the suction holes 53. Ends of the extended guide collar 77 may adjacent to the suction holes 53 to easily guide the flow of the supernatant into the suction holes 53.

[0058]

Referring again to FIGS. 1 to 3, the above-described internal return means may include a separate control unit for selectively operating the first internal return unit and the second internal return unit and the supernatant discharging unit. For example, when the control unit controls and operates the air blower 11 of the intermittent aeration unit, the control unit applies a power to the first transfer pump 91 of the first internal return unit to operate the first transfer pump 91. And, when the air blower 11 is not operated, the control unit operates the second transfer pump 61 of the second internal return unit and the supernatant discharging unit. As such control unit, a conventional computer such as a microprocessor, various driving circuits and an input/output unit may be used.

[0059]

On the other hand, the treated water circulation part circulates some of the treated water discharged from the MBR tank 20 into the intermittent reaction tank 10 and the MBR tank 20.

[0060]

For example, the treated water circulation part includes a treated water discharge line 80 connected to an outlet of the suction pump 22 to discharge the treated water separated through the separation membrane 21, a first circulation line 81 branched from the treated water discharge line 80 and connected to an electrolysis tank 101, a second circulation line 83 connected to the electrolysis tank 101 and extended to the intermittent reaction tank 10 and a third circulation line 85 connected to the electrolysis tank 101 and extended to the MBR tank 20. ]

[0061] ;

The electrolysis part 100 electrolyzes the treated water circulated by the 1 treated water circulation part. As described above, some (about 2% to 3% of the total volume of the treated water) of the treated water separated by the separation membrane 21 passes through the electrolysis tank 101 through the first circulation line 81. ]

[0062]

The electrolysis part 100 includes the electrolysis tank 101 connected to the first circulation line 81 and an electrode module (not shown) disposed in the ] electrolysis tank 101 to electrolyze the treated water passing through the electrolysis tank 101. When power is applied to the electrode module, ferrum or aluminum ions } produced at an anode are introduced into the intermittent reaction tank 10 and the

MBR tank 20 through the second and third circulation lines 83 and 85 together with the treated water. Ferrum or aluminum ions are bonded to phosphate ions contained in water to be treated to treat phosphorus. Thus, phosphorus in the treated water discharged from the MBR tank 20 to the outside may be effectively reduced through the electrolysis part 100.

[0063]

Although not shown, the electrode module has a typical structure, i.e., includes a pair of electrodes constituted by an anode and a cathode. The anode is formed of an iron or aluminum material. Ferrum or aluminum ions produced at the anode are bonded to and reacted with phosphate ions (PO4>) to product metal salt shape such as ferric phosphate (FePO,) or aluminum phosphate (AIPO,), thereby treating phosphorus .

[0064]

Phosphorus contained in the water to be treated is existed as phosphate ions j (PO4>) by sufficient oxygen. Phosphate ions are bonded to ferrum or aluminum ions produced at the anode during the electrolysis to form insoluble phosphates as follows.

[0065]

Fe** + PO — FePOu(s), Al3*" + PO, — AIPO4(s) : [0066]

Here, a titanium electrode coated with platinum (Pt) may be used as the cathode. Hydrogen is produced at the cathode to reduce nitrate (NO;’) nitrogen and nitrite (NO, nitrogen into gaseous nitrogen (N,). Thus, nitrogen, nitrite nitrogen and phosphorus may be removed simultaneously through the electrolysis.

[0067]

As described above, since the phosphorus is additionally removed by the electrolysis, overall efficiency of the waste water treatment apparatus may be improved. Also, since the phosphorus is removed by the method which is not affected by external change factors, phosphorus removal efficiency may be constantly maintained. Also, since treated water in which a solid and liquid are separated from each other through the separation membrane is electrolyzed, formation of scale on a surface of the electrode may be minimized to improve electrolysis efficiency.

[0068]

EMBODIMENTS

[0069]

The treated water finally discharged through the advanced waste water treatment apparatus has high water treatment effects as shown in below Tables 1 and 2 ]

[0070]

When the aerobic reaction tank was operated for 45 minutes in an aeration state and for 75 minutes in a nonaeration state and the waste water was treated for total hydraulic retention time (HRT) of 7.5 hours including the HRT of the intermittent reaction tank of 2.9 hours, the HRT of the MBR tank of 3.1 hours and the

HRT of the transition tank of 1.5 hours, a concentration of the treated water discharged through the separation membrane is shown in below Table 1. J

[Table 1] - 0

Items Inflowed water Treated water Removal rate (%)

SRT=2245

BOD(mg/L) | 46.2~353.6(119.8) 1.0

CODMy(mg/L) | 22.0~377.4(79.9) 5.8

SS(mg/L) 50.0~1480.0(218.5) 1.9

T-N(mg/L) 8.632~78.95(23.5) 8.6

T-P(mg/L) 1.665~11.228(3.7) 0.152

[0071]

Also, assuming that a solid-liquid function was not performed due to pollution of the separation membrane, supernatant within the transition tank was examined below.

[0072]

The aerobic reaction tank was operated for 45 minutes in the aeration state and for 75 minutes in the nonaeration state and the waste water was treated for total hydraulic retention time (HRT) of 9.0 hours including the HRT of the intermittent ] reaction tank of 2.9 hours, the HRT of the MBR tank of 3.1 hours and the HRT of the transition tank of 3.0 hours, a concentration of the discharged supernatant is shown in below Table 2. [Table 2] :

Items Inflowed water Removal rate (%) ;

SRT=22445

BODmg) | 795131501053

CODumg) | 57.0-108.0(320)

Sng) | 72515630007)

TNL) | 2054942568024)

T-P(mg/L) 2.546~4.598(3.692) 1.238 {

} [0073]

In Tables 1 and 2, each of values in parentheses in the item of the inflowed water represents a mean value.

[0074]

As described above, even though the solid-liquid separation function of the separation membrane is not performed due to the pollution of the separation membrane in the MBR tank, the supernatant in the transition tank may be discharged through the second internal return unit and the supernatant discharging unit disposed in the transition tank. Also, since ferrum or aluminum ion produced by the electrolysis may be bonded to the phosphate ions and then naturally sunken, the solid-liquid separation function in the transition tank is improved. Thus, a water quality of the supernatant discharged from the transition tank may be enhanced.

[0075]

Also, the activated sludge may internally and selectively return from one of the MBR tank and the transition tank into the intermittent reaction tank according to ] the aeration or nonaeration condition within the intermittent reaction tank. Thus, the activated sludge having a high DO concentration may be introduced from the MBR i tank into the intermittent reaction tank to reduce energy.

[0076] ;

Also, since phosphorus is additionally removed by the electrolysis, the overall ; efficiency of the waste water treatment apparatus may be improved. Also, the ] phosphorus is removed by the method which is not affected by external change i elements, and so the phosphorus removal efficiency may be constantly maintained and 1 the total concentration of phosphorus of the discharged water may meet the water quality standards.

[0077]

Exemplary embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as set forth in the following claims.

Claims

WHAT IS CLAIMED IS

1. An advanced waste water treatment apparatus, comprising: an intermittent reaction tank into which water to be treated and activated sludge are introduced, the intermittent reaction tank comprising an intermittent aeration means; a membrane bio-reactor (MBR) tank into which a mixture is introduced from the intermittent reaction tank, the MBR tank comprising a treated water discharging means for discharging treated water through a separation membrane which removes remaining organic matters of the introduced mixture and separates water and sludge from each other, and the MBR tank further comprising an aeration means; a transition tank into which the activated sludge is introduced from the MBR tank, the transition tank reducing dissolved oxygen (DO) of the activated sludge to promote denitrification; a treated water circulation part circulating some of the treated water discharged from the MBR tank into the intermittent reaction tank and the MBR tank; 1 an electrolysis part comprising an electrolysis tank through which the treated water circulated by the treated water circulation part passes and an electrode module which electrolyzes the treated water introduced into the electrolysis tank to produce ferrum iron or aluminum ions, thereby reducing phosphorus content of the treated . water discharged from the MBR tank; and ; an internal return means for returning the activated sludge from one of the MBR ] tank and the transition tank into the intermittent reaction tank according to an aeration i or nonaeration condition within the intermittent reaction tank. _25- :

.

2. The advanced waste water treatment apparatus as claimed in claim 1, wherein the internal return means comprises: a first internal return unit for returning the activated sludge from the MBR tank into the intermittent reaction tank when the intermittent aeration means is operated, and a second internal return unit and a supernatant discharging unit returning the activated sludge from the transition tank into the intermittent reaction tank when the intermittent aeration means is not operated, the second internal return unit and the supernatant discharging unit stopping a return of the activated sludge and discharging supernatant in the transition tank to the outside when a solid-liquid separation function of the separation membrane is not performed.

3. The advanced waste water treatment apparatus as claimed in claim 2, wherein the first internal return unit comprises a first return line connecting the MBR tank and the transition tank, and a first transfer pump disposed on the first return line to transfer the activated sludge within the MBR tank into the intermittent reaction tank, and the second internal return unit and the supernatant discharging unit comprises a cylindrical elevation pipe vertically movably disposed in the transition tank, the elevation pipe having suction holes arranged in a line from one side of an upper portion thereof to the other side and being spaced from each other; an elevation part for moving vertically the elevation pipe; a discharge line connected to the elevation pipe; a second transfer pump disposed on the discharge line to transfer the supernatant or the activated sludge to the outside through the elevation pipe; a second return line branched from the discharge line and connected to the intermittent reaction tank to transfer the activated sludge; a treated water discharge line branched from the discharge line to discharge the supernatant; and a three-way valve disposed at a branched point between the second transfer line and the treated water discharge line. i

4. The advanced waste water treatment apparatus as claimed in claim 3, wherein the second internal return unit and the supernatant discharging unit further comprises a suspended solid inflow prevention means for preventing suspended solids floating on an upper portion of the transition tank from being introduced into the elevation pipe when the supernatant is discharged.

5. The advanced waste water treatment apparatus as claimed in claim 4, wherein the suspended solid inflow prevention means comprises rod-shaped support bars vertically disposed between the suction holes; an obstruction cover coupled upper portions of the support bars so as to let an outer circumference surface of the elevation space apart thereform and covering the suction holes to prevent a flow of the supernatant introduced in the suction holes from being formed above the suction holes; and a guide collar disposed on each of both edges of the obstruction cover and extended in a direction of the support bars.

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0. The advanced waste water treatment apparatus as claimed in claim 4, wherein the guide collar is extended in an arc shape to guide the flow of the supernatant into the suction holes.