WO2009119964A1

WO2009119964A1 - Advanced wastewater treatment apparatus with two-stage reactor

Info

Publication number: WO2009119964A1
Application number: PCT/KR2008/007429
Authority: WO
Inventors: Jin Hwan Oh; Kyu Chan Choi; Byeong Hyuk Choi; Jung Min Lee
Original assignee: Sam Chang Enterprise Co., Ltd.
Priority date: 2008-03-26
Filing date: 2008-12-16
Publication date: 2009-10-01
Also published as: KR20090102409A; KR100935914B1; CN101980971A

Abstract

An advanced wastewater treatment apparatus with a two-stage reactor is disclosed to maximize an efficiency of nutrient removal while the number of reactors is minimized. The advanced wastewater treatment apparatus includes a first reactor (30) supplied by the sewage from the initial precipitation reactor (20) to perform an anaerobic, anoxic and aerobic process in operation of an aeration agitator (90), a second reactor (40) supplied by the sewage from the first reactor (30) to perform an aerobic and anoxic process in the operation of the aeration agitator (90), an internal return duct (50) for returning the sewage nitrified by the second reactor (40) to the first reactor (30) and returning sludge formed by the second reactor (40) and the final precipitation reactor (60) to the first reactor (30) or the second reactor (40), and a controller (70) receiving a signal from sensors installed in the first and second reactors (30 and 40) and outputting driving signals to the aeration agitator (90).

Description

ADVANCED WASTEWATER TREATMENT APPARATUS WITH TWO-STAGE REACTOR

Technical Field

[1] The present invention relates to a system for controlling an advanced wastewater treatment apparatus capable of removing nutrients contained in sewage or wastewater, and more particularly, to an advanced wastewater treatment apparatus with a two-stage reactor which can maximize an efficiency of nutrient removal while the number of reactors is minimized. Background Art

[2] Various contaminants contained in sewage or wastewater are generally treated by an activated sludge method. Due to increase in environmental regulations, an advanced wastewater treatment method capable of removing heavy metals and various nutrients, such as nitrogen or phosphor, contained in the sewage or wastewater is recently developed.

[3] According to the activated sludge method, as shown in FIG. 1, the sewage that flows through a fine wedge bar screen or coarse screen of a grit remover 110 to remove sand is pumped by a pump 115, and then flows through an initial precipitation reactor 120, an aeration reactor 130 and a final precipitation reactor 140 before it is disinfected and discharged to rivers.

[4] The aeration reactor 130 lets the sewage to react with air which is introduced into the sewage flowing through the final precipitation reactor 120. The sewage is subjected to absorption, coagulation or oxidation during the aeration period, so that organics are converted into biological activated sludge, and the activated sludge reacted during a stay time is precipitated and separated in the final precipitation reactor 140.

[5] A lot of nutrients, such as nitrogen and phosphor, contained in the sewage which is discharged from the final precipitation reactor 140 after disinfection are discharged while being not removed by the activated sludge method. Since rivers or lakes are recently suffered from eutrophication due to the nutrients such as nitrogen and phosphor, the necessity to remove nitrogen or phosphor.

[6] In particular, even a small quantity of nitrogen and phosphor contained in the final precipitation reactor 140 induces propagation of waterweeds, as compared with other organics. The waterweeds consume oxygen existing in the water to lead fishes and shellfishes to die. In order to prevent the ill effect, an advanced wastewater treatment method (third treatment) is added to the present process.

[7] The advanced wastewater treatment method is a method to remove the nitrogen or phosphor contained in the water. In particular, in case of removing nitrogen, ammonia is oxidized into nitrate under aerobic conditions, or a nitrogen gas is reduced into air under anoxic reactor. In case of removing phosphor, anionic phosphate is added with a positive ion to form chemical precipitate, for example, biomass that absorbs the phosphor, otherwise the phosphor is added with metal salt to form precipitate, as a biological treatment process.

[8] As described above, microorganisms are involved to remove nitrogen or phosphor, and energy is needed for propagation and growing of microorganisms. Also, when nitrogen is removed, it is needed for oxygen in the aerobic process, for nitrite in the anoxic process, and for an energy source such as carbon dioxide in the anaerobic process, in accordance with the final electron receptor.

[9] In particular, since the simultaneous removal of nitrogen and phosphor cannot be performed by an activated sludge process, the anoxic process and the anaerobic process should be added. More specifically, as shown in FIG. 2, a multiple-stage reactor, such as two-stage reactor of anoxic and aerobic type, or four-stage reactor of anaerobic, anoxic, aerobic and anoxic type, is provided, otherwise a sequencing batch reactor, in which anoxic, anaerobic, aerobic, precipitation, and discharge processes are continuously performed, is applied to a single reactor.

[10] Therefore, since reactors having different features, such as an anoxic reactor, an anaerobic reactor, and an aerobic reactor, should be provided in the advanced wastewater treatment method to simultaneously remove nitrogen and phosphor, an exclusive area of the treatment apparatus is increased, and operation or maintenance expense is thus increased. Disclosure of Invention Technical Problem

[11] Accordingly, the present invention is directed to an advanced wastewater treatment apparatus that substantially obviates one or more problems due to limitations and disadvantages of the related art.

[12] One object of the present invention is to provide an advanced wastewater treatment apparatus with a two-stage reactor which can maximize an efficiency of nutrient removal while the number of reactors is minimized. Technical Solution

[13] In order to accomplish these objects, there is provided an advanced wastewater treatment apparatus supplied by sewage from a grit remover and an initial precipitation reactor to remove nutrients and discharging the sewage to a final precipitation reactor, the advanced wastewater treatment apparatus comprising: a first reactor supplied by the sewage from the initial precipitation reactor to perform an anaerobic, anoxic and aerobic process in operation of an aeration agitator; a second reactor supplied by the sewage from the first reactor to perform an aerobic and anoxic process in the operation of the aeration agitator; an internal return duct for returning the sewage nitrified by the second reactor to the first reactor and returning sludge formed by the second reactor and the final precipitation reactor to the first reactor or the second reactor; and a controller receiving a signal from sensors installed in the first and second reactors and outputting driving signals to the aeration agitator. [14]

Advantageous Effects

[15] According to the advanced wastewater treatment apparatus with the two-stage reactor to remove nutrients such as nitrogen or phosphor, the number of processes and working loading are reduced to improve its workability. Since an exclusive area of the treatment apparatus can be reduced, an installation cost or maintenance expense is thus decreased.

[16] Also, the anaerobic, anoxic and aerobic process is performed by any one of the first reactor or the second reactor, the sewage or wastewater can be treated at the optimum expenses. Brief Description of the Drawings

[17] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

[18] FIG. 1 is a view depicting a conventional wastewater treatment line;

[19] FIG. 2 is a view depicting a conventional advanced wastewater treatment method;

[20] FIG. 3 is a block diagram depicting an advanced wastewater treatment apparatus according to the present invention;

[21] FIG. 4 is a view schematically depicting the construction of an advanced wastewater treatment apparatus according to the present invention;

[22] FIG. 5 is a view depicting an aeration agitator of an advanced wastewater treatment apparatus according to the present invention; and

[23]

Best Mode for Carrying Out the Invention

[24] A preferred embodiment according to the present invention will now be explained with reference to the accompanying drawings.

[25] FIG. 3 is a block diagram depicting an advanced wastewater treatment apparatus according to the present invention, and FIG. 4 is a view schematically depicting the construction of an advanced wastewater treatment apparatus according to the present invention.

[26] The advanced wastewater treatment apparatus supplied by sewage from a grit remover and an initial precipitation reactor to remove nutrients and discharging the sewage to a final precipitation reactor 60, includes a first reactor 30 supplied by the sewage from the initial precipitation reactor 20 to perform an anaerobic, anoxic and aerobic process in operation of an aeration agitator 90; a second reactor 40 supplied by the sewage from the first reactor 30 to perform an aerobic and anoxic process in the operation of the aeration agitator 90; an internal return duct 50 for returning the sewage nitrified by the second reactor 40 to the first reactor 30 and returning sludge formed by the second reactor 40 and the final precipitation reactor 60 to the first reactor 30 or the second reactor 40; and a controller 70 receiving a signal from sensors installed in the first and second reactors 30 and 40 and outputting driving signals to the aeration agitator 90.

[27] The advanced wastewater treatment apparatus of the present invention treats the sewage by using the grit remover 10, the initial precipitation reactor 20, the first and second reactors 30 and 40, and the final precipitation reactor 60, in which an efficiency of nutrient removal is improved by using the first and second reactors 30 and 40 installed between the initial precipitation reactor 20 and the final precipitation reactor 60.

[28] The first reactor 30 continuously changes an oxygen supplying time of an intermittent aeration reactor of anaerobic, anoxic and aerobic state and a volume of sludge carried by the internal return duct in accordance with ammonium nitrogen of the sewage supplied from the initial precipitation reactor. The second reactor 40 removes organics and nutrients such as nitrogen or phosphor by maintaining a semi- aerobic state and aerobic state.

[29] The biological removal of nitrogen is mainly divided into three parts; first, nitrate assimilation of sludge performed in a biological process, in which 20 to 30% of the inflow water is removed by a conventional activated sludge method; secondly, nitrification and denitrification, in which oxygen is consumed by oxidizing reduced nitrogen into nitrate nitrogen, and oxidized nitrogen is reduced into a nitrogen gas; and finally, nitrogen intake using specific predominated microorganism. The process mostly used as the advanced wastewater treatment process is a process concurrently employing the nitrification and denitrification.

[30] The biological nitrification and denitrification consists of a nitrification reaction

(aerobic microorganism) performed under an aerobic condition and a denitrification reaction (optional microorganism) performed under an anoxic condition. In particular, a major microorganism species is autotrophic organism representative of Nitrosomonas sp. and Nitrobacter sp. It obtains growth energy by oxidizing inorganic nitrogen compound, and utilizes carbonate as a carbon source needed for synthesis of cell. [31] In this instance, the maximum growth speed of the ammonium nitrogen in the Ni- trobacter sp. is remarkably faster than that of Nitrosomonas sp. Accumulation of nitrite is not large, and it is considered a rate controlling step of oxidization from ammonium nitrogen to nitrogen. [32] Major factors of the nitrification are pH, dissolved oxygen, and organics. The optimum pH is 8 to 9, and the optimum dissolved oxygen is more 2ml/l. Alkali capable of neutralizing hydrogen ion which is generated from the ammonium nitrogen can be dissolved in the water, as Equation 1 below. [33] Equation 1

[34]

NH₄ ⁺ + i .83o₂ + 1.98HCO; » 0.021C₅H₇O₂ + 0.98N0; + 1.04H0 + 1.88H₂CO₃

[35] The biological denitrification reaction is to convert nitrate into NOx through reduction, and is concerned in various heterotrophs using nitrate as an electron acceptor and organics as an electron donor, as Equation 2 below.

[36] Equation 2

^[37] NH₃ ^" + i . ,83C//₃ OH + 0.24H₂ co₃ » o.o56c₅ H₇O₂N + 0.47N₂ + \ MH₂O + HCO;

[38] In this instance, COD of 3.7 g is consumed to denitrify the nitrite of 1 g. Also, and microorganism of 0.045 g is synthesized, and alkali of 3.57 is reduced. In case where dissolved oxygen is existed in the water, since the organic carbon source used as an electron donor is consumed, and the denitrification reaction is inhibited, it is important to maintain the nitrate in an anoxic state.

[39] As shown in FIGs. 2 and 3, the apparatus of the present invention is to return the sludge of IQ to 1.5Q to the first reactor 30 through the internal return duct 50, return the sludge of 0.5Q to IQ from the precipitation reactor 60, and use the organic carbon source supplied from the first reactor 30 as the denitrification source.

[40] Referring to FIG. 3, the apparatus of the present invention is adapted to selectively perform the step in which the sewage is returned from the second reactor 40 to the first reactor 30 and the sludge is returned from the precipitation reactor to the first reactor 30, and the step in which the sludge is returned from the final precipitation reactor 60 to the second reactor 40, when the sewage is supplied to the first reactor 30 from the initial precipitation reactor 20.

[41] More specifically, in the internal return duct 50, the first process means that the sewage is conveyed to the first reactor 30 and the sludge is returned to the first reactor 30 from the final precipitation 60, while the sewage is supplied to the first reactor 30, and the second process means that the sludge is returned to the second reactor 40 from the final precipitation reactor 60. [42] As shown in FIG. 4, preferably, sludge return flow meters 51 and 52, a sludge return pump 53, an internal return flow meter 54 and an internal return pump 55 are mounted in the internal return duct 50.

[43] In order to drive the first reactor 30 under an anoxic and semi-anaerobic state and the second reactor 40 under an aerobic and semi-aerobic state, ORP (Oxidation-Reduction Potential) sensors 31 and 41 and oxygen (DO) sensor 32 and 42 are respectively installed in the first and second reactors 30 and 40, and values of the ORP sensor and DO sensors are monitored by a controller in real time. The controller controls an operation time of the aeration agitator 90 in accordance with the operation signal of the controller 70.

[44] The previous step of the first reactor 30, i.e., the process of passing the sewage and wastewater of the grit remover 10 through a grit chamber and a screen and then the initial precipitation reactor 20, is well known in the art, and thus its detailed description will now be omitted herein.

[45] Also, the apparatus of the present invention can prevent the eutophication by using the first and second reactors 30 and 40, the internal return duct 50 for changing water paths of the first and second reactors 30 and 40 to independently or complementarily drive the first and second reactors, the aeration agitators 90 each mounted in the first and second reactors 30 and 40 to simultaneously perform the aeration and agitation, and a phosphor filter 80 driven by sensors installed in the first and second reactors 30 and 40 and a sensor for detecting quality of discharged water.

[46] More specifically, if the supplied sewage is identical to or similar to a designed volume, it proceeds to the first process, in which the first reactor 10 and the second reactor 20 are complementarily operated so that the supplied sewage is discharged to the final precipitation through the first reactor and the second reactor.

[47] In this process, the denitrification process is performed by returning the nitrate nitrified by the second reactor 40 to the first reactor 30 through the internal return duct 50. The return pumps 53 and 55 are driven by an inverter in order to achieve accurate return volume, and a flow meter measures the internal return volume in the first reactor.

[48] The first reactor 30 performs the anoxic, semi-anaerobic and anaerobic process using a blower, diffuser, and an agitator, and the second reactor 40 performs the aerobic and anoxic process by using an oxygen sensor (DO meter) and PLC in accordance with oxygen concentration and time control.

[49] The first reactor 30 is operated in the anoxic and semi-anaerobic state, while concentration of the dissolved oxygen is maintained in average 0.5mg/l. The second reactor 40 is operated in the aerobic and semi-aerobic state, while concentration of the dissolved oxygen is maintained in average 1.5 mg/1 or more. [50] In case of the denitrification reaction, while the first reactor performs the anoxic, semi-anaerobic and anaerobic process, the sewage nitrified by the second reactor is denitrified by the first reactor. In case of removing phosphor, the microorganism is alternatively exposed to the anaerobic state (the first reactor) and the aerobic state (the second reactor) to give stress to the microorganism. That is, the process of removing the phosphor is repeated by extremely changing environmental conditions which converts metabolic pathway of the microorganism to induce excess intake.

[51] Also, the sewage and wastewater is suffered from flow rate fluctuation of about 3Q during 4 seasons. If the quality and flow rate of the inflow water are reduced less than a set level, the first reactor and the second reactor are independently driven by the signal of the controller 70.

[52] This is determined by monitoring the inflow flow meter and the water quality of the inflow sewage, and the process is carried out by converting the inflow water using a motored gate valve or a motored valve. The inflow sewage is supplied to the first reactor or the second reactor, and then is subjected to the SBR process. In this instance, the respective reactors performs the advanced wastewater treatment process.

[53] The inflow process, the react process, the precipitation process, the discharge process, and the suspension process are performed in the SBR to increase a value of MLSS (Mixed Liquor Suspended Solid) and thus prolong SRT (Sludge Retention Time). Therefore, auto-oxidation of the sludge is progressed to remarkably reduce generation of sludge.

[54] It is not easy for the advanced wastewater treatment process to obtain outflow water at a level of swimmable water by simultaneously removing nitrogen and phosphor, except for a chemical method of putting chemicals into a biological reactor. Therefore, according to the present invention, the nitrogen is treated by using two-stage reactor of aeration and agitation, and the phosphor is indirectly removed. In particular, the system is adapted to discharge the outflow through the phosphor filter 80 if SS and T-P concentration exceeds a reference value.

[55] Although about 60% of T-P which is a reference of present sewage is removed (T-P of 8mg/l - 2 to 3 mg/1), it does not satisfy 0.5mg/l which is a reference of the swimmable water. The present invention utilizes the phosphor filter for the purpose of recycling of discharged water and resource recovery through recovery/recycling of phosphor contained in the discharged water.

[56] More specifically, by mounting the phosphor concentration sensor 85 in the discharge path of the final precipitation reactor 60 and installing the motored valve or gate valve in the discharge path, the discharge of the sewage is guided to the phosphor filter 80 in accordance with the signal of the controller 70 receiving the signal detected by the phosphor concentration sensor 85. [57] As shown in FIG. 3, the phosphor filter 80 is installed on a rear end of the advanced wastewater treatment apparatus to remove the phosphor by filtration and absorption. The phosphor filter 80 is made of a material having a filtration and absorption function to filter SS components and absorb the phosphor by passing the secondary discharged water through the phosphor filter to remove the T-P.

[58] In this instance, the phosphor filter 80 consists of a pre-filtering material of a synthetic resin made of fiber or polyurethane to filter the SS component contained in the discharged water, and a main filtering material of a hydrotacite- or zirconium- based absorption agent to absorb the phosphoric component.

[59] Accordingly, the advanced wastewater treatment apparatus according to the present invention monitors T-N and T-P in real time. If the removal of T-P is temporarily unstable, the outflow water duct is guided to the phosphor filter 80 immediately, so that the discharged water is constantly maintained at the highest level.

[60] Concentration of the DO (Dissolved Oxygen) monitored by the apparatus of the present invention is as follows (see Table 1). The first reactor 30 is operated in the anaerobic, anoxic, and semi-anaerobic state, while concentration of the dissolved oxygen is maintained in average 0.5mg/l. The second reactor 40 is operated in the aerobic and semi-aerobic state, while concentration of the dissolved oxygen is maintained in about 1.5 mg/1 or more.

[61] Another type of the operation of the apparatus according to the present invention is a control method using an oxygen sensor. The type of the first reactor 30 and the second reactor 40 which are driven by aeration and agitation is as follows (see Table T).

[62] The time of the aeration and agitation in the first reactor 30 and the agitation time and intensity have an effect on the water quality. The frequency per one hour has an effect on the water quality of the discharged water in accordance with temperature of the inflow water and operation conditions, but 3 to 6 alternative operations are performed. When the aerobic operation is converted into the anoxic and anaerobic operation, the time control can be achieved by concentration of ammonium nitrogen and nitrate.

[63] Table 1

[Table 1]

Concentration of DO in the respective reactors

[64] The second reactor 40 is operated in the aerobic and anoxic state, the nitrate is returned to the second reactor through the internal return duct to remove nitrogen or phosphor.

[65] Concentration of the DO is increased by supplying external air into the reactor to increase activity of microorganism, and the agitation is performed from a water level of the reactor to a bottom surface thereof. This is achieved by simultaneously operating the agitator and the aerator in the first reactor and the second reactor to smoothly dissolve the oxygen.

[66] The first reactor 30 and the second reactor 40 take a role of another reactor consisting of an anaerobic reactor, an anoxic reactor and an aerobic reactor in order to achieve the sufficient advanced wastewater treatment process.

[67] Table 2 [Table 2]

Concentration of DO obtained by alternately operating reactors

Anaerobic

[68] Meanwhile, there are the first method using a blower or diffuser and the second method using a surface aerator in order to supply air into the first and second reactors 30 and 40. Also, the first method of agitation utilizes an underwater mixer, and the second method utilizes a hydrofoil agitator.

[69] The apparatus of the present invention employs the aeration agitator 90 which can alternatively operate the surface aerator and the underwater mixer to temporarily perform the aeration and agitation and remarkably reduce maintenance and power expenses.

[70] As shown in FIG. 5, the aeration agitator 90 includes a driving unit for generating a driving force using a rotation shaft 92 which is driven by a driving motor 91, an operating unit for performing aeration and agitation by using an aeration impeller 93-1 and an agitation impeller 93-2 which are mounted around the rotation shaft 92, a diffusing unit for diffusing and guiding the sewage by using a guide plate 94 mounted around the rotation shaft 92, and a control unit for adjusting a direction and range of spray by using a spray angle adjuster 96 enclosing the guide plate 94.

[71] The spray angle adjuster 96 includes a guide vane 96-1, mounted on the guide plate

94 by a support post and a support plate, for forming a lateral flow path between the guide plate 94 and the guide vane 96-1, and a cylindrical body 96-2, coupled to a bottom surface of the guide vane 96- 1 , for forming a bottom flow path between the guide plate 94 and the cylindrical body 96-2.

[72] The cylindrical body 96-2 is provided on it lower end with an enlarged duct 96-3 for smoothly receiving the sewage to perform the aeration process. The guide plate 94 has an angular portion 94-1 for guiding flow of the sewage together with the cylindrical body 96-2.

[73] In this instance, the aeration agitator 90 diffuses the water in a circle pattern in the aeration process of the sewage, but the aeration is performed in a rectangular pattern by the guide vane 96- 1.

[74] Further, supposing the aeration and agitation are simultaneously performed by the aeration agitator 90, the alternative operation comprising the aerobic process is smoothly carried out.

[75] As shown in Table 3, the anaerobic reactor is not installed on the front end of the advanced wastewater treatment apparatus, the anaerobic, anoxic, and anaerobic process is performed in the first reactor 30, and the aerobic and anoxic process is performed in the second reactor 40. Therefore, it can reduce the installation area and maintenance expenses. Also, the advanced wastewater treatment can be performed only by using the first reactor and the second reactor, without installing the anaerobic reactor on the front end.

[76] The apparatus of the present invention includes an internal return duct for conveying the sludge between the first reactor, the second reactor and the final precipitation reactor in the process of performing the denitrification of the sewage nitrified by the second reactor.

[77] Table 3

[Table 3]

Process of advanced wastewater treatment in reactors

N - N

[78] The efficiency of the nitrification is increased and the SRT is extended by properly maintaining the SRT, smoothly performing the advanced wastewater treatment process and highly maintaining the MLSS (3~5000mg/L or more).

[79] Thus, auto-oxidation of the sludge is increased, and generation of the sludge is decreased. Since expenses required for sludge treatment is large in the whole wastewater treatment expenses, it is another advantage of the present invention.

[80] In case where a volume of the sewage supplied from the flow rate adjusting reactor or the initial precipitation reactor is abruptly changed or reduced, that is, a flow rate of 3 Q is changed at summer and winter or the flow rate is changed by external factors, the SBR is performed by supplying the sewage to any one of the first and second reactors using the motored valve or gate valve.

[81] In this instance, the advanced wastewater treatment process of anaerobic, anoxic and aerobic state is carried out, and the precipitation is earned out m the final precipitation reactor. The sewage supplied to the first reactor is guided to the second reactor at the time when the advanced wastewater treatment process is earned output, and the second reactor also performs the same advanced wastewater treatment process. At that time, the fluctuation of the flow rate is automatically converted into SBR by the inflow flow meter.

[82] That is, the first reactor and the second reactor are independently operated while performing the SBR.

[83] The apparatus of the present invention is characterized by selectively operating the first reactor and the second reactor by the internal return duct consisting of a line extending from the first reactor to the second reactor and a plurality of return lines for selectively supplying the sewage to the first reactor or the second reactor from the final precipitation reactor.

[84] In case of driving one reactor to provide against the fluctuation of flow rate in summer and winter, the sludge is selectively supplied to continuously maintain concentration of MLSS, thereby securing the highest water quality in the advanced wastewater treatment.

[85] In particular, Table 4 depicts the state where the first reactor 30 alternatively performs the anoxic, semi- anaerobic and anaerobic operation, and Table 5 depicts the state where the second reactor 40 alternatively performs the semi-aerobic and aerobic operation. The apparatus of the present invention can quickly increase the DO and perform the anaerobic, anoxic and aerobic operation and the aerobic and anoxic operation by using only one aeration agitator with the first reactor or the second reactor to simplify the advanced wastewater treatment process and reduce the operation expenses.

[86] Table 4 [Table 4]

Graph depicting alternating of first reactor

0400 1200 1600 2000 0000 04 )0 ca oo 1210 1600 2010 0)00

[87] The aeration agitator 90 includes the driving motor 91 , the rotating shaft having the aeration impeller 93-1 and the agitation impeller 93-2, and the guide vane 96-1 determining a spray direction, and repeats the aeration function and the agitation function in accordance with the rotating direction of the apparatus. [88] The water is uniformly sprayed in the circular or rectangular reactor by the guide vane 96-1 when the aeration agitator 90 aerates, so that a dead zone is minimized to improve a delivery rate of the oxygen.

[89] The agitation is smoothly performed even at an edge of the circular or rectangular reactor by the shape of the guide vane 96-1 when the aeration agitator 90 aerates. Therefore, the sludge is smoothly moved in the reactor to prevent aerobic storage of the sludge in the reactor. Also, the sludge is moved at the lowest speed so as to prevent its surface from coming in contact with oxygen.

[90] Table 5 [Table 5]

Graph depicting alternating operation of second reactor

[91] The apparatus of the present invention can control the alternative anaerobic, anoxic and aerobic operation of the first reactor and the alternative aerobic and anoxic operation of the second reactor by using the multi-functional aeration agitator. Although the apparatus of the present invention can employ a blower, a diffuser and an agitator, the aeration agitator is mostly suitable for the pilot test so as to perform the process.

[92] Since the aeration of the complex reactors employs the surface aeration manner, fine wastewater is discharged in the air at the aeration, which is caused by offensive odor. Therefore, in case of utilizing the complex reactors, the whole area of the reactors is covered by a cover to prevent scattering. [93] The water quality of the discharged water is constantly monitored in the advanced wastewater treatment process in order to secure the discharged water of swimmable water level and prevent autrophication of the lake. If the phosphor of proper level is not removed, the discharged water is guided to the phosphor filter 80 by the motored valve or gate valve, as shown in FIG. 3, to remove the phosphor.

[94] In case where the apparatus of the present invention is applied to a separate sewer, two biological reactors of 60m³ were constructed, and it was designed to treat 300 to 350m³/d. The operating conditions of the apparatus were as follows.

[95] Table 6 [Table 6] [Table ] Operating conditions of advanced wastewater treatment apparatus

[96] [97] Table 7

[Table 7]

[Table ]

Removal rate of nutrients (per season)

[98] According to Table 7, the removal efficiency of nitrogen was maintained at 60% or more, and the removal efficiency of phosphor was maintained about 50%, except for the winter. Most of nutrients are removed from the sewage.

[99] Table 8 [Table 8] [Table ] Removal rate of nutrients (in real time)

[100] Table 9 [Table 9]

Graph depicting removal rate of nutrients

(a)

mg/l Inflow Outflow

Order of analysis

(b)

Order of analysis

[101] Although the optimum efficiency is obtained by 6 operations during 8 HRTs when the advanced wastewater treatment apparatus is driven, this embodiment can secure the optimum water quality by performing the alternative operation 3 to 6 times per hour.

[102] According to Tables 8 and 9, As a result of performing the first process by using the advanced wastewater treatment apparatus, at least 70 to 80% of nitrogen or phosphor is removed from the sewage, and most of nutrients are removed from the sewage, thereby using the discharged water as swimmable water.

[103] The forgoing embodiment is merely exemplary and is not to be construed as limiting the present invention. The present teachings can be readily applied to other types of apparatus. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

Claims

[1] An advanced wastewater treatment apparatus supplied by sewage from a grit remover and an initial precipitation reactor to remove nutrients and discharging the sewage to a final precipitation reactor 60, the advanced wastewater treatment apparatus comprising: a first reactor 30 supplied by the sewage from the initial precipitation reactor 20 to perform an anaerobic, anoxic and aerobic process in operation of an aeration agitator 90; a second reactor 40 supplied by the sewage from the first reactor 30 to perform an aerobic and anoxic process in the operation of the aeration agitator 90; an internal return duct 50 for returning the sewage nitrified by the second reactor

40 to the first reactor 30 and returning sludge formed by the second reactor 40 and the final precipitation reactor 60 to the first reactor 30 or the second reactor

40; and a controller 70 receiving a signal from sensors installed in the first and second reactors 30 and 40 and outputting driving signals to the aeration agitator 90.

[2] The advanced wastewater treatment apparatus as claimed in claim 1 , wherein the aeration agitators 90 each installed in the first and second reactors 30 and 40 are alternatively operated in real time.

[3] The advanced wastewater treatment apparatus as claimed in claim 1, wherein the aeration agitators 90 each installed in the first and second reactors 30 and 40 are alternatively operated by time set of the first and second reactors.

[4] The advanced wastewater treatment apparatus as claimed in claim 1, wherein the final precipitation reactor 60 includes a phosphor filter for absorbing a phosphor component contained in the sewage.

[5] The advanced wastewater treatment apparatus as claimed in claim 1, wherein the final phosphor filter 80 consists of a pre-filtering material of a synthetic resin made of fiber or polyurethane to filter the SS component contained in the discharged water, and a main filtering material of a hydrotacite- or zirconium- based absorption agent to absorb the phosphoric component.

[6] The advanced wastewater treatment apparatus as claimed in claim 1 or 4, wherein the final precipitation reactor 60 includes a phosphor concentration sensor 85, installed in a discharge duct, for detecting concentration of phosphor contained in the sewage to output the signal to the phosphor filter 80.

[7] The advanced wastewater treatment apparatus as claimed in claim 1 or 4, wherein the final precipitation reactor 60 includes any one of a motored valve or a gate valve, installed in a discharge duct, for guiding a discharge direction of the sewage in an installation direction of the phosphor filter.

[8] The advanced wastewater treatment apparatus as claimed in claim 1, wherein the sensor is oxidization reduction potentiometers 31 and 41 provided in the first reactor 30.

[9] The advanced wastewater treatment apparatus as claimed in claim 1 , wherein the sensor is oxygen sensors 32 and 42 provided in the first reactor 30 or the second reactor 40.

[10] The advanced wastewater treatment apparatus as claimed in any one of claims 1,

8 and 9, wherein the controller 70 outputs an operation signal to the first reactor 30 and the second reactor 40 in response to a signal of the sensors 31 , 41 , 32 and 42.

[11] The advanced wastewater treatment apparatus as claimed in claim 1, wherein the aeration agitator 90 includes a driving unit for generating a driving force using a rotation shaft 92 which is driven by a driving motor 91, an operating unit for performing aeration and agitation by using an aeration impeller 93-1 and an agitation impeller 93-2 which are mounted around the rotation shaft 92, a diffusing unit for diffusing and guiding the sewage by using a guide plate 94 mounted around the rotation shaft 92, and a control unit for adjusting a direction and range of spray by using a spray angle adjuster 96 enclosing the guide plate 94.

[12] The advanced wastewater treatment apparatus as claimed in claim 11, wherein the spray angle adjuster 96 includes a guide vane 96- 1 , mounted on the guide plate 94 by a support post and a support plate, for forming a lateral flow path between the guide plate 94 and the guide vane 96-1, and a cylindrical body 96-2, coupled to a bottom surface of the guide vane 96- 1 , for forming a bottom flow path between the guide plate 94 and the cylindrical body 96-2.

[13] The advanced wastewater treatment apparatus as claimed in claim 11 or 12, wherein the cylindrical body 96-2 encloses a circumference of the aeration impeller 93-1.

[14] The advanced wastewater treatment apparatus as claimed in claim 11 or 12, wherein the cylindrical body 96-2 is provided on it lower end with an enlarged duct 96-3 for smoothly receiving the sewage to perform the aeration process.

[15] The advanced wastewater treatment apparatus as claimed in claim 11, wherein the guide plate 94 has an angular portion 94- 1 for guiding flow of the sewage together with the cylindrical body 96-2.

[16] The advanced wastewater treatment apparatus as claimed in claim 1, wherein the first reactor and second reactors 30 and 40 includes a cover for covering offensive odor which is resulted from discharge of the sewage.

[17] The advanced wastewater treatment apparatus as claimed in claim 1, wherein when the internal return duct 50 is opened or closed, the step in which the sewage is returned from the second reactor 40 to the first reactor 30 and the sludge is returned from the precipitation reactor to the first reactor 30, and the step in which the sludge is returned from the final precipitation reactor 60 to the second reactor 40, are independently or complementarily performed.

[18] The advanced wastewater treatment apparatus as claimed in claim 11 or 12, wherein the internal return duct 50 includes sludge return flow meters 51 and 52, a sludge return pump 53, an internal return flow meter 54 and an internal return pump 55, which are driven accordance with a signal of the controller 70.