WO2005068380A1

WO2005068380A1 - A-sbr apparatus for removing nitrogen and phosphorous in sewage/waste water

Info

Publication number: WO2005068380A1
Application number: PCT/KR2005/000122
Authority: WO
Inventors: Myung-Sun Lee; Jong-Gun Kim
Original assignee: Water Mod Inc.
Priority date: 2004-01-16
Filing date: 2005-01-14
Publication date: 2005-07-28
Also published as: KR100453479B1

Abstract

The present invention relates to an A-SBR apparatus for removing nitrogen and phosphorus in sewage/waste water, comprising subjecting sewage/waste water to advanced treatment, and, more specifically, comprising: a first step of screening impurities from inflow water; a second step of flow stabilizing for controlling flow rate and water quality of the inflow water that passed through the first step; a third step of A-SBR reaction for removing organic materials, nitrogen and phosphorus contained in the inflow water by subjecting the inflow water that passed through the second step to periodically repeated anaerobic, aerobic and anoxic conditions; a fourth step of filtration for removing suspended material and phosphorus remaining in the treated water that passed through the third step; and a fifth step of sterilizing, disinfecting, and removing color from the treated water subject to filtration during the fourth step.

Description

[DESCRIPTION] [Invention Title]

A-SBR APPARATUS FOR REMOVING NITROGEN AND PHOSPHOROUS IN SEWAGE/WASTE WATER

[Technical Field]

The present invention relates to an A-SBR apparatus for removing nitrogen and phosphorus from sewage/waste water, and more particularly to an A-SBR apparatus for removing nitrogen and phosphorus from sewage/waste water, which includes a flow equalization tank installed at the front of an A-SBR reactor, a clarified supernatant liquid discharge equipment installed in the A-SBR reactor, and an up flow filtration equipment and a photocatalyst device installed at the rear of the A-SBR reactor.

[Background Art] At present, an activated sludge process, which is widely used in most of the national wastewater treatment plants, can provide stable water quality of discharged water in terms of treatment of organic and suspended materials, but still requires an additional advanced treatment facility to facilitate efficient removal of nitrogen and phosphorus. Biological treatment processes developed hitherto may be broadly divided into continuous flow processes and batch flow processes. As the most economical processes to remove nitrogen or phosphorus, from among continuous flow processes, mention may be made of an anaerobic/anoxic/aerobic (A²/O) process, a Bardenpho process and the Virginia Initiative Plant (VIP) process. The A /0 process is an improved version of a conventional A/O process and involves an anaerobic tank, an anoxic tank and an aerobic tank, and consists of an internal recycle for removing nitrate and a sludge recycle. The anaerobic tank releases phosphorus such that microorganisms ingest excess phosphorus in the aerobic tank, while the anoxic tank serves to denitrify nitrate. This process is easily applicable when the conventional wastewater plant is modified to the advanced treatment process, but suffers from disadvantages in that, due to nitrate present in the recycle sludge, release of phosphorus is inhibited under the anaerobic conditions, thus resulting in a decreased removal efficiency of phosphorus and, further, a slight drop in the removal efficiency of nitrogen and phosphorus in the winter, as water temperature lowers. Meanwhile, the Bardenpho process involves an anaerobic tank, an anoxic tank, an aerobic tank, an anoxic tank and an aerobic tank in this order. The anaerobic tank, anoxic tank, and aerobic tank, positioned at the front of the plant, remove organic materials, nitrogen and phosphorus, the rear anoxic tank removes untreated nitrate through a denitrifϊcation process, and the last aerobic tank removes nitrogen gas remaining in the wastewater and prevents elution of phosphorus in the final settling basin. This process benefits from relatively high removal efficiency of nitrogen compared to other biological processes for removing nitrogen and has a relatively long retention time compared to the A²/0 process, thus providing high oxidizing capability of organic carbons. However, this process suffers from the disadvantage that when the concentration of organic materials in inflow raw water is low, or in winter when water temperature drops, removal efficiency of nitrogen and phosphorus is reduced accordingly. Additionally, the VIP (Virginia Initiative Plant) process is a modified version of the conventional activated sludge process and involves an anaerobic tank, an anoxic tank and an aerobic tank, and consists of an internal recycle for removing nitrate (nitrifier recycle), and an internal recycle from the anoxic tank to anaerobic tank and sludge recycle from a settling basin. This process is advantageous in that since some of the organic materials contained in inflow water are decomposed in the anaerobic tank by anaerobic decomposition the process oxygen demand is reduced, treatment efficiency is more stable than in the A /O process, the process is economical due to the small reactor size, and the process is easily achieved by the conversion of conventional wastewater treatment facilities into advanced treatment process. However, such process also has disadvantages such as high maintenance costs due to the prolonged use of a pump for the internal recycle, and reduction of nitrogen and phosphorus removal efficiency in the winter when the water temperature is low. The above-mentioned A /O (Anaerobic/Anoxic/Aerobic) process,

Bardenpho process and VIP (Virginia Initiative Plant) process are suitable for conditions in which wastewater control systems are well organized, but are not suitable for conditions in which inflow water has a low BOD/TN ratio due to low propagation of wastewater management systems. Therefore, considering characteristics of national wastewater treatment plants having low concentration of organic materials necessary for removing nitrogen and phosphorus, such continuous flow processes are unsuitable. Meanwhile, among continuous processes and batch processes, batch processes are broadly divided into an intermittent feed type, representatively a SBR process and a continuous feed type, based on feed type. A conventional SBR process is a process in which inflow of sewage/waste water and outflow of treated water occur in a single reactor according to the predetermined time sequencing and each unit process is continuously performed. At this time, the process is progressed in the order of filling process, reaction, settling process, drawing process and idling process. This process is advantageous in that it is possible to remove nitrogen and phosphorus by controlling reaction conditions, all the processes are performed in a single reactor, thus leading to flexibility in controlling a separate settling basin and filamentous fungi, and facilities are simple and thus operation is convenient. However, an adaptation period of microorganisms in inflow water is required due to the absence of a sludge recycle, and thus a mean hydraulic retention time in the SBR reactor is long, i.e., 15 to 24 hours, and a large area is necessary to install and operate the wastewater treatment plant. In most other processes, aside from the above-mentioned processes, balanced removal of nitrogen and phosphorus is difficult to obtain, or the processes are only applicable to small scale sewage/waste water treatment plants.

[Disclosure] [Technical Solution]

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an A-SBR apparatus for removing nitrogen and phosphorus from sewage/waste water, which includes a flow equalization tank installed at the front of an A-SBR reactor, a clarified supernatant liquid discharge equipment installed in the A- SBR reactor, an upflow filtration equipment and a photocatalyst device installed at the rear of the A-SBR apparatus.

[Description of the Drawings]

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a diagram illustrating a sewage/waste water treatment system in accordance with the present invention; Fig. 2 is a detailed view of a medium/large-size clarified supernatant liquid discharge equipment in accordance with the present invention; and Fig. 3 is a detailed view of a medium/small-size clarified supernatant liquid discharge equipment in accordance with the present invention.

[Best Mode]

The preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. Fig. 1 is a diagram illustrating a sewage/waste water treatment system in accordance with the present invention, Fig. 2 is a detailed view of a medium/large-size clarified supernatant liquid discharge equipment in accordance with the present invention, and Fig. 3 is a detailed view of a medium/small-size clarified supernatant liquid discharge equipment in accordance with the present invention. Firstly, the initial screening step involves removal of impurities from inflow water and serves to protect equipment in subsequent processes. In this step, the inflow water, i.e., sewage/waste water is introduced through an inlet into a screen tank 1, and impurities in sewage/waste water are removed through a screen installed in the screen tank 1 and then transferred to next stage. Next, a second step of controlling flow rate is a step for stabilizing flow rate and water quality of the inflow water. In this step, the inflow water, from which impurities were removed in the screen tank 1, is introduced through a first line, LI, into a flow equalizing tank 2, thus the flow rate to be treated in the next process is controlled. Then, a third step of A-SBR reaction is a step of removing organic materials, nitrogen and phosphorus contained in the inflow water by periodically repeating anaerobic, aerobic and anoxic conditions. In this step, the inflow water stabilized in the flow equalizing tank 2 is first introduced via a second line, L2 into an A-SBR pre-reactor 3-1, then is spontaneously transferred to an A-SBR main reactor 3-2, and thus organic materials, nitrogen and phosphorus are removed from the inflow water by periodically repeating anaerobic, aerobic and anoxic conditions. Specifically referring to reaction steps occurring in the A-SBR main reactor 3-2, the reaction steps consist of an anaerobic agitation step, a first aerobic step, an anoxic agitation step, a second aerobic step, a settling step, and a discharging step. First, in the anaerobic agitation step, the inflow water, i.e., sewage/waste water is introduced through the flow equalizing tank 2, then via the second line, L2, into the A-SBR pre-reactor 3-1, thus elevating the water level in the reactor 3-1. Then, the inflow water is spontaneously transferred to the A-SBR main reactor 3-2 wherein the inflow water and sedimented sludge are mixed by agitation, organic nitrogen in the inflow water is converted into ammonia, nitrogen is removed through a denitrification reaction, and phosphorus accumulated in microbial body is released. Thereafter, in the first aerobic step, aerobic bacteria convert organic materials into the form of biomass (C₅H7O₂N) or C0₂ followed by removal, in the A-SBR main reactor 3-2. Decomposed ammonia nitrogen and released phosphorus in the anaerobic agitation step are subjected to nitrification and excess uptake of phosphorus. This reaction may be expressed as follows: Organic materials (CHON) + 0₂ + nutrients → C₅H₇O₂N + C0₂ +

NH₃ + products

Next, in the anoxic agitation step, nitrified liquid and settled sludge are mixed by agitation in the A-SBR main reactor 3-2, and as denitrification bacteria activated in the sludge activation tank are gradually activated, denitrification is initiated and at the same time, dephosphorization bacteria propagate. In order to increase denitrification efficiency, high activity sludge, which was predominantly activated by denitrification bacteria in a microorganism activation tank 7, is transferred through a fourth line, L4, to the A-SBR reactor 3. At this time, less than 0.5 to 1 ppm of dissolved oxygen is present in the microorganism activation tank 7, and thus the microorganism activation tank 7 is maintained under facultative anaerobic conditions. Therefore, denitrification bacteria, for example, Pseudomonas, Micrococcus, Achromobactor and Bacillus become the dominant species. In addition, cohesive force of sludge may be reinforced by adding an activated sludge promoter containing loess, Si0₂, Fe₂0₃ or powdered activated charcoal as components to the microorganism activation tank 7. Further, when operating the present system in winter, the lowered temperature leads to deterioration of denitrification efficiency. Therefore, it is possible to increase denitrification efficiency by transferring larger amounts of high activity sludge than in summer in which temperature is high to the A-SBR reactor 3. Next, in the second aerobic step, the remaining nitrogen gas is released through oxygen aeration such that solid-liquid separation is smoothly performed in the A-SBR main reactor 3-2, and release of phosphorus by microorganisms is inhibited. Next, in the settlement step, oxygen aeration in the A-SBR main reactor 3-2 is stopped, and activated sludge is sedimented by gravity thus resulting in separation of sludge and clarified supernatant liquid. Next, in the discharge step, the clarified supernatant liquid is discharged through a third line, L3, by the clarified supernatant liquid discharge equipment 3-4. At this time, a large part of sludge is transferred through a ninth line, L9, to a sludge reservoir 8, and then is discarded via a discharge line, L10, and some of sludge is cultivated into high activity sludge for denitrification in the microorganism activation tank 7 which is then transferred through a fourth line, L4, to the A-SBR reactor 3 for the anoxic agitation step. This step takes 6 hours per cycle and is repeated four times during a day. Next, the fourth filtration step serves to remove suspended material and phosphorus remaining in the treated water after passing through the third step. In this step, the treated water, discharged through the third line, L3, from the clarified supernatant liquid discharge equipment 3-4, is transferred to an upflow filtration equipment 4, and in order to achieve higher water quality of effluent, an appropriate amount of alum (A1₂(S0 )₃), NaOH and polymer is transferred from a liquid chemical tank 4-1 through a fifth line, L5 to the upflow filtration equipment 4. Then, the filtrate water thus treated is transferred to a filtrate water tank 4-2 through a sixth line, L6. Next, a fifth step of disinfection serves to sterilize, disinfect, and remove color from the filtrate water. In this step, the treated water stored in the filtrate water tank 4-2 is transferred through a seventh line, L7, to a photocatalyst device 5 which in turn generates OH radicals having strong oxidizing power to remove colors of the treated water and to sterilize and disinfect pathogenic bacteria contained therein, and then the treated water is transferred to and stored in a reclaimed water reservoir 6 through an eighth line, L8, thus generating reclaimed water from the treated water. Fig. 2 shows a detailed view of clarified supernatant liquid discharge equipment 3-4 used when the treated water is discharged from the A-SBR reaction step, upon performing a sewage/waste water treatment system in accordance with the present invention. This clarified supernatant liquid discharge equipment 3-4 is used in a medium/large-size sequencing batch reactor. A plurality of guide rails 10 are arranged in parallel and vertically erected in the reactor 3-2, and a buoy 21 is slidably penetrated through the guide rails 10. A discharge tank 18 having a sealably partitioned discharge chamber 17 is attached to the buoy 21 at the inner surface thereof. Therefore, when the buoy 21 moves vertically along the guide rails 10, the discharge tank 18 also moves vertically together with the buoy 21. Further, the discharge tank 18 has a plurality of discharge ports 15, and an inlet 12 arranged at a predetermined space relative to the discharge ports 15, formed at the bottom thereof. One end of each of a plurality of flexible pipes 11 is oil tight connected to the discharge ports 15 such that the inside of the discharge chamber 17 communicates with the flexible tubes 11, the other ends of the respective flexible pipes 11 are, respectively, oil tight connected with one end of each of a plurality of transfer pipes 19, the other ends of which ^■ communicate with an effluent tank 3-3. An open-and-shut plate 13 is connected to the inlet 12 at the bottom of the discharge tank 18, such that the plate 13 is connected to a switching device 40 so as to selectively open and close the inlet 12. The switching device 40 includes a double acting cylinder 41, a directional control valve 44 controlling the double acting cylinder 41, a regulator 45 connected to the directional control valve 44 and supplying a predetermined pressure to the directional control valve 44, and a compressed oil source 46 connected to the regulator 45. At this time, the directional control valve 44 of the switching device 40 is connected to a controller 60, and thus the inlet 12 is maintained at the present state, open or closed by the open-and-shut plate 13 in response to the control of the controller 60. Therefore, when the open-and-shut plate 13 is open, the discharge chamber 17 communicates with the clarified supernatant liquid in the reactor 3-2. Conversely, when the open-and-shut plate 13 is closed, there is no communication between the discharge chamber 17 and the clarified supernatant liquid in the reactor 3-2. The controller 60 is connected to a plurality of position sensors arranged at a predetermined space in the reactor 3-2 in order to detect water level of the liquid to be treated stored in the reactor 3-2. Among a plurality of position sensors, the position sensor SI detects acceptable maximum water level of the liquid to be treated, the position sensor S2 detects maximum water level of the clarified supernatant liquid in which the clarified supernatant liquid is distributed, when the liquid to be treated has acceptable maximum water level, and the position sensor S3 detects minimum water level of the clarified supernatant liquid in which the clarified supernatant liquid is distributed, when the liquid to be treated has acceptable maximum water level, and then transmits the detection values to the controller 60 which in turn determines a position of the directional control valve 44 of the switching device 40. Fig. 3 shows clarified supernatant liquid discharge equipment employed in a medium/small-size sequential batch reactor, as another embodiment of the clarified supernatant liquid discharge equipment 3-4. Unlike the clarified supernatant liquid discharge equipment employed in a medium/large-size sequential batch reactor, in this clarified supernatant liquid discharge equipment, a pump 80 for discharging clarified supernatant liquid of the liquid to be treated in the reactor is arranged in the effluent tank 3-3. A valve, VI is disposed at the other end of the flexible pipe 11 and is oil tight connected to the one end of the transfer pipe 19, the other end of which is connected to an inlet of the pump 80. As a result, the discharge chamber 17 communicates with the pump 80 through a discharge port 15, the flexible pipe 11, the transfer pipe 19 and the valve VI . In addition, a pan check valve, V2 is disposed at the inlet 12.

Accordingly, when the discharge chamber 17 is under the predetermined negative pressure by the action of the pump 40, the pan check valve, V2 is opened and the discharge chamber 17 communicates with the clarified supernatant liquid in the reactor 3-2. In contrast, when the pump 80 is in inactive mode, the pan check valve, V2 is closed and thus the discharge chamber 17 is not in communication with the clarified supernatant liquid in the reactor 3-2. At this time, the pump 80 is connected to a pump controller 90, and operation and shut down thereof are controlled by control of the pump controller 90. As described above, in accordance with the present invention, in the anoxic agitation step, high activity sludge activated in the microorganism activation tank is transferred to the A-SBR reactor and induces proliferation of denitrification bacteria which in turn efficiently remove nitrogen; and, in the discharge step, sludge which took excess phosphorus in the aerobic step is removed, thus being capable of achieving balanced removal of nitrogen and phosphorus even in sewage/waste water having a low concentration of organic material and nitrogen and also realizing high treatment efficiency. In addition, owing to division of the A-SBR reactor into the A-SBR pre-reactor and A-SBR main reactor, the adaptation period of microorganisms in inflow water is reduced by the fluidized filter medium and high activity sludge in the A-SBR pre-reactor and thereby a mean hydraulic retention time in the SBR reactor is shortened and an area necessary for installing and operating the water treatment plant is reduced. Further, in accordance with the present invention, installation of an upflow filtration equipment and photocatalyst device at the rear position of the A-SBR reactor may provide effective removal of suspended materials and phosphorus remaining in the treated water, sterilization and disinfection of pathogenic bacteria and color removal, and complete decomposition of recalcitrant or non-biodegradable endocrine disrupting chemicals, thus the treated water being recycled as reclaimed water. Although the preferred embodiments of the present invention have been disclosed 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.

Claims

[CLAIMS]

[Claim 1] An A-SBR apparatus for removing nitrogen and phosphorus in sewage/waste water, comprising: a screen tank for removing impurities and suspended materials contained in inflow water; a flow equalization tank for controlling flow rate and water quality of the inflow water that passed through the screen tank; an A-SBR reactor for decomposing organic materials and removing nitrogen and phosphorus in the inflow water that passed through the flow equalization tank, and including an A-SBR pre-reactor, an A-SBR main reactor and an effluent tank; a clarified supernatant liquid discharge equipment for discharging clarified supernatant liquid that passed through the A-SBR reactor; an upflow filtration equipment for removing suspended materials and phosphorus in the clarified supernatant liquid that passed through the A- SBR reactor; a liquid chemical tank for transferring alum, NaOH and polymer to the upflow filtration equipment; a photocatalyst device for sterilizing and disinfecting the treated water that passed through the upflow filtration equipment; a reclaimed water reservoir for storing the treated water that passed through the photocatalyst device; a microorganism activation tank for improving activity and denitrification efficiency of microorganisms in the A-SBR reactor; and a sludge reservoir for treating surplus sludge produced in the A-SBR reactor.