WO2021102484A1

WO2021102484A1 - Biological treatment apparatus, carrier capturing device for biological treatment apparatus, water treatment method and method of modifying biological treatment apparatus

Info

Publication number: WO2021102484A1
Application number: PCT/VN2020/000010
Authority: WO
Inventors: Nghiep DO BANG CONG; Hop NGUYEN VAN; Hiroaki Meguro
Original assignee: Organo (Vietnam) Co., Ltd.
Priority date: 2019-11-21
Filing date: 2020-11-20
Publication date: 2021-05-27
Also published as: TW202128570A

Abstract

The present invention aims at providing a biological treatment apparatus that can limit the number of carriers that adhere to a screen. Biological treatment apparatus (2) has bioreactor (2A) in which carriers flows, wherein the carriers immobilize microbes for biological treatment of water to be treated, partition wall (18) that is provided in bioreactor (2A), wherein partition wall (18) separates bioreactor (2A) into first region (19) that includes supply portion (22) for the water to be treated and second region (20) that is in communication with first region (19) at the lower part of bioreactor (2A), wherein exit portion (25) for treated water that has been treated by bioreactor (2A) is only formed in the upper part of second region (20). The apparatus further comprises carrier capturing device (26) having screen (27) that is provided at exit portion (25), wherein, screen (27) prevents the carriers from flowing out of bioreactor (2A).

Description

Title of Invention: BIOLOGICAL TREATMENT APPARATUS, CARRIER CAPTURING DEVICE FOR BIOLOGICAL TREATMENT APPARATUS, WATER TREATMENT METHOD AND METHOD OF MODIFYING BIOLOGICAL TREATMENT APPARATUS

Background of Invention

Technical Field

The present invention relates to a biological treatment apparatus, a carrier capturing device for the biological treatment apparatus, a water treatment method and a method of modifying a biological treatment apparatus.

Background Art

A water treatment system is known that performs a biological treatment that uses microbes, such as anaerobic bacteria and aerobic bacteria, that are immobilized by carriers in the form of gel or fiver. Organic matter that is contained in water to be treated that is supplied to a bio reactor are decomposed by the microbes. The carriers that immobilize the microbes flow in the bio reactor. A screen is provided at the exit portion of the bioreactor in order to prevent the carriers from flowing out. JP3668358B discloses a bioreactor having an exit portion and a screen that is provided at the exit portion. The exit portion protrudes from the main portion of the bioreactor toward the exit.

Summary of Invention

In the bioreactor that is disclosed in JP3668358B, the water contact portion of the screen generally faces the main portion, and the water in the main portion, as well as the carriers that are included in the water, generally horizontally flow into the exit portion. Most of the carriers that flow into the exit portion reach the screen and are captured by the screen. Thus, a large number of carriers adhere to the screen, and the screen requires periodical cleaning.

The present invention aims at providing a biological treatment apparatus that can limit the number of carriers that adhere to a screen.

A biological treatment apparatus of the present comprises: a bioreactor in which carriers flows, wherein the carriers immobilize microbes for biological treatment of water to be treated; a partition wall that is provided in the bioreactor, wherein the partition wall separates the bioreactor into a first region that includes a supply portion for the water to be treated and a second region that is in communication with the first region at a lower part of the bioreactor, wherein an exit portion for treated water that has been treated by the bioreactor is only formed in an upper part of the second region. The apparatus further comprises a carrier capturing device having a screen that is provided at the exit portion and that prevents the carriers from flowing Out of the bioreactor.

According to the present invention, the bioreactor is separated into the first region and the second region by the partition wall. The second region is in communication with the first region at the lower part of the bioreactor, and the exit portion of the treated water is only formed at the upper part of second region. The second region extends vertically. The carriers that enter the second region flow downward by gravity and the number of the carriers that reach the screen is limited. Thus, according to the present invention, the number of the carriers that adhere to the screen can be limited.

The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.

Brief Description of Drawings

Figure 1 is a sectional view of the water treatment system according to an embodiment of the present invention;

Figure 2 is a partial perspective view of the biological treatment apparatus of the water treatment system shown in Fig. 1;

Figure 3 is a partial sectional view of the biological treatment apparatus shown in Fig. 2; Figure 4 is a partial plan view of the biological treatment apparatus taken along line A-A in Fig. 3;

Figure 5 is an enlarged view of portion B in Fig. 3; and Figure 6 is a partial perspective view of the screen.

Description of Embodiments

An embodiment of a biological treatment apparatus according to the present invention will be described with reference to the drawings. The biological treatment apparatus is used as a part of a water treatment system. First, an exemplary arrangement of a water treatment system that includes biological treatment apparatus 2 will be described. Fig. 1 schematically illustrates the arrangement of water treatment system 1. Water treatment system 1 includes biological treatment apparatus 2 and sedimentation tank 3, Biological treatment apparatus 2 consists of denitrification treatment tank 2A (a first bioreactor) and aerobic treatment tank 2B (a second bioreactor). Denitrification treatment tank 2A is connected to supply line L1 for water to be treated and to recirculation line L2 that is provided with recirculation pump 5. The water to be treated is supplied to denitrification treatment tank 2A through supply line L1. A denitrification ; treatment or an anaerobic treatment is conducted in denitrification treatment tank 2A. In the denitrification treatment, in an environment where no oxygen is present in water, organic matter is decomposed into nitrogen, carbonic acid gas and water by the activity in which nitric acid in the water to be treated is used for the respiration of microbes that consumes organic matter. In the anaerobic treatment, in an environment where no dissolved oxygen or no oxygen in nitrous acid (NO^2-) or nitric acid (NO^3-) is present in water, organic matter is decomposed into methane gas, carbonic acid gas and water by microbes. The water that has been treated by denitrification treatment tank 2A (treated water) is sent to aerobic treatment tank 2B, where the aerobic treatment is carried out. Aerobic treatment tank 2B includes aeration device 55. Air is supplied to aerobic treatment tank 2B by aeration device 55 and the remaining organic matter is decomposed into carbonic acid gas and water by microbes. The water that has been treated by aerobic treatment tank 2B is sent to sedimentation tank 3, where microbe sludge is separated from the treated water. A part or the entire part of the microbe sludge is returned to denitrification treatment tank 2A through recirculation line L2 by recirculation pump 5. In the following description, the water that includes the microbe sludge and that is returned to denitrification treatment tank 2A through recirculation line L2, as well as the water to be treated that is supplied from supply line L1, are referred to as “water to be treated".

Next, the arrangement of biological treatment apparatus 2 will be described with reference to Figs. 2-6. Fig. 2 is a partial perspective view of biological treatment apparatus 2 of water treatment system 1 shown in Fig. 1 , wherein third sidewall 15 is omitted, Fig. 3 is a sectional view of denitrification treatment tank 2A of biological treatment apparatus 2 shown in Fig. 2. Fig. 4 is a plan view of denitrification treatment tank 2A of biological treatment apparatus 2 taken along line A-A in Fig. 3. Fig. 5 is an enlarged view of portion B in Fig. 3. Fig. 6 is a partial perspective view of screen 27. In the following descriptions, width direction W refers to a direction parallel to first and second sidewalls 13,14 of denitrification tank 2A. Denitrification tank 2A houses water to be treated, as well as carriers to which microbes (anaerobic microbes) are immobilized. Denitrification tank 2A is a container made of reinforced concrete having base plate 12 that forms bottom 12A of both denitrification tank 2A and aerobic treatment tank 2B, four side walls 13-16 that are connected to base plate 12 and to top plate 17. The sidewall of denitrification tank 2A on the side of the exit is referred to as first sidewall 13, the sidewall of denitrification tank 2A on the side of the inlet that is opposite to first sidewall 13 is referred to as second sidewall 14, and the sidewalls of both denitrification tank 2A and aerobic treatment tank 2B that are perpendicular to first and second sidewalls 13, 14 are referred to as third and fourth sidewalls 15, 16.

Denitrification tank 2A has partition wall 18. Denitrification tank 2A is separated into first region 19 and second region 20 by partition wall 18. First region 19 is a region mainly for the denitrification treatment of the water to be treated. First region 19 accommodates supply portion 22 for the water to be treated and agitators 23. Supply portion 22 for the water to be treated consists of supply line L1 and recirculation line L2. The positions, number and specification of agitators 23 are determined based on general selecting criteria that allow the carriers in denitrification tank 2A to be well agitated. Denitrification tank 2A does not have any aeration device that supplies air because it conducts an oxygen free or anaerobic treatment. First region 19 is covered with top plate 17 in order to prevent as much amount of oxygen as possible from entering. Top plate 17 has opening 17Ato allow supply line L1 and recirculation line L2 to pass through. Partition plate 18 extends downward from top plate 17, and the bottom end thereof is apart from bottom 12A of denitrification tank 2A. Accordingly, first region 19 and second region 20 are in communication with each other at communication portion 21 that is located in the lower part of denitrification tank 2A. Partition plate 18 is formed of reinforced concrete, but may also be formed of a metal plate. Examples of the metal plate include, for example, a stainless steel plate and a steel plate lined with stainless steel.

Supply line L1 and recirculation line L2 are arranged on the inlet side of denitrification tank 2A, that is, near second sidewall 14. Liquid supply line L1 and recirculation line L2 are arranged on both sides of the center line of second sidewall 14 with regard to width direction W and are arranged substantially symmetrically with regard to the center line. For this reason, the water to be treated that is supplied from supply line L1 and recirculation line L2 flows toward second region 20 in a direction substantially perpendicular to second sidewall 14. A plurality of supply ports 24 is formed on the side surfaces of supply line L1 and recirculation line L2. Supply ports 24 are open to denitrification tank 2A and supply the water to be treated to denitrification tank 2A. Supply ports 24 face second sidewall 14 and discharge the water to be treated toward second sidewall 14. The water to be treated collides against second sidewall 14, then turns in the opposite direction to flow toward second region 2. Accordingly, the water to be treated is not significantly biased in first region 19, and the carriers can efficiently flow in first region 19 due to the velocity of the water to be treated and by agitators 23.

Biased flow can be further limited in first region 19 by providing first baffle plate 51. The shape, arrangement and so on of first baffle plate 51 are not limited as long as the biased flow can be further limited in first region 19. In the present embodiment, as shown in Figs. 3 and 4, first baffle plate 51 is a wall similar to partition wall 18 that is provided downstream of supply line L1 and recirculation line L2. If first baffle plate 51 is not provided, then the water to be treated that is supplied from the upper portion of supply line L1 and recirculation line L2 does not uniformly flow toward communication portion 21 next to second region 20 over the entire region of first region 19. This causes biased flow near the upper portion of partition wall 18 of first region 19, and the biased flow may in turn deliver the carriers to the screen. By providing first baffle plate 51 , the water to be treated that is supplied to first region 19 is made uniform over the entire region of first region 19 by passing through first baffle plate 51, so that the biased flow can be limited near the upper portion of partition wall 18.

Second region 20 is a region that includes exit portion 25 of the water that has been treated by denitrification tank 2A (treated water), and the volume of second region 20 is smaller than the volume of first region 19. Second region 20 is defined by first sidewall 13, third sidewall 15, fourth sidewall 16 and partition wall 18. Top plate 17 is not provided in second region 20. Exit portion 25 of the treated water is only formed at the upper part of second region 20, more precisely, on top surface 13A of first sidewall 13. Top surface 13A of first sidewall 13 is a horizonal plane that is lower than the top surfaces of third sidewall 15, fourth sidewall 16 and partition wail 18, and allows the treated water that flows into second region 20 to flow into aerobic treatment tank 2B over top surface 13A of first sidewall 13.

Carrier capturing device 26 that prevents the carriers from flowing out of denitrification tank 2A is provided at exit portion 25, more precisely, on top surface 13A of first sidewall 13. Carrier capturing device 26 consists of screen 27 and support portion 28, and support portion 28 is supported on top surface 13A of first sidewall 13. Screen 27 is formed of a wire screen. As shown in Figs. 5, 6, screen 27 consists of a plurality of wire rods 29 and a plurality of support rods 30. Wire rods 29 are arranged at intervals and in parallel to each other. Support rods 30 extend in the direction perpendicular to wire rods 29 and are arranged at intervals in parallel to each other. The interval of support rods- 30 is larger than the interval of wire rods 29. Each wire rod 29 has an inverted triangle section having wider surface 29A and narrower surface 29B, and narrower surface 29B is fixed to support rods 30. The gap between adjacent wider surfaces 29A is sized to allow the treated water to pass through and to be sufficiently smaller than the average diameter of the carriers. Support rods 30 are fixed to support portion 28. Support portion 28 is made of a metallic plate and is fixed to top surface 13A of first sidewall 13 by means of bolts (not illustrated). Screen 27 is arranged such that wider surface 29A is positioned on the upstream side with regard to the flow direction of the treated water (depicted by the arrow in Fig. 6) and narrower surface 29B is positioned on the downstream side with regard to the flow direction of the treated water. The treated water passes through the gap between wider surfaces 29A of wire rods 29, and the carriers that are contained in the treated water are captured by wider surface 29A or by the gap between wider surfaces 29A. The arrangement of screen 27 is not limited to the wire screen, and any screen may be used as long as it can allow the treated water to pass through and can capture the carriers. For example, a punching metal having many small holes may be used as screen 27.

As shown in Fig.5, screen 27 is preferably inclined relative to vertical direction V. Specifically, screen 27 intersects with support portion 28 at angles other than 90 degrees. The water contact area of screen 27 can be increased by inclining screen 27. Screen 27 may be inclined toward second region 20 or toward the opposite side of second region 20 (the side of aerobic treatment tank 2B). The former is more preferable because the carriers that adhere to screen 27 fall into second region 20.

Carrier capturing device 26 may be provided with washing device 31 on the side of screen 27 opposite to second region 20 (on the side of aerobic treatment tank 2B). Washing device 31 injects washing liquid to screen 27. Washing device 31 includes pipe 32 for supplying the washing liquid. Pipe 32 extends in width direction W of screen 27 along substantially the entire width of screen 27. Pipe 32 has many nozzles 33 for injecting the washing liquid on a side thereof that faces screen 27. As described later, the number of the carriers that adhere to screen 27 is limited, but it is difficult to completely prevent the carriers from adhering to screen 27. Therefore, it is desirable to periodically remove the carriers that adhere to screen 27. The washing liquid is preferably water or air. Washing device 31 may be provided on the side of second region 20 or may be provided both on the side of second region 20 and on the side opposite to second region 20.

Next, referring to Fig. 3, the steps of the- method of the water treatment using biological treatment apparatus 2, or the operation of biological treatment apparatus 2, especially of denitrification treatment tank 2A, will be described. As described above, the water to be treated that is supplied to first region 19 of denitrification tank 2A is subjected to oxygen free or anaerobic treatment by the microbes that are immobilized on carriers C while the water to be treated flows toward second region 20 in first region 19. The treated water flows into second region 20 through communication portion 21 between first region 19 and second region 2. The treated water flows upward in second region 20, and carriers C also flow upward in second region 20, accompanied by the upward flow of the treated water. However, since the specific weight of carriers C is larger than the specific weight of the treated water, most carriers C flow downward or sediment due to gravity without reaching exit portion 25. in the region between communication portion 21 and the lower part of second region 20, due to the flow that is caused by the treated water that flows into second region 20, and due to the flow that is caused by agitators 23, the flow of the treated water and carriers C toward exit portion 25 is considered to coexist with the flow of carriers C that flow downward in second region 20 and then return to first region 19. Most of carriers C that enter second region 20 are considered to flow upward first in second region 20, then to flow downward and return to first region 1. Due to the flow of the treated water from communication portion 21 back to first region 19, carriers C are prevented from accumulating on bottom 12A of second region 20 or in communication portion 21.

The treated water reaches exit portion 25 of second region 20 and then overflows top surface 13A of first sidewall 13. The treated water passes through screen 27 to flow from denitrification tank 2A into aerobic treatment tank 2B. Most of carriers C in first region 19 stay in first region 19 due to the flow caused by agitators 23. A part of carriers C flows into second region 20 due to the flow from sidewall 14 to sidewall 13, but then sediment in second region 20 because the specific weight of carriers C is larger than the specific weight of the water. However, some of carriers C that flow into second region 20 may reach exit portion 25 of second region 20 without sedimenting. Carriers C that reach exit portion 25 of second region 20 are captured by screen 27 that is provided on top surface 13A of first sidewall 13 and are prevented from flowing out of denitrification treatment tank 2A.

Space D between partition wall 18 and bottom 12A of denitrification tank 2A is preferably set within a predetermined range. If space D is too small, then a sufficient amount of water cannot be supplied to second region 20 due to large pressure loss at communication portion 21. The predetermined range is preferably set, for example, such that the area that is calculated as a product of space D and the dimension of denitrification treatment tank 2A in width direction W is larger than the sectional area of second region 20. In addition, when biological treatment apparatus 2 is out of operation, there is no flow of the water. Thus, carriers C, which have a large specific weight, flow downward and accumulate on the bottom of first region 19. If space D is small, then carriers C that accumulate on bottom 12A may clog communication portion 21. If biological treatment apparatus 2 is restarted in this state, the carriers that clog communication portion 21 are pushed out toward second region 20. As a result, a large number of the carriers may reach screen 27 and may clog screen 27, Accordingly, space D is preferably larger than the thickness of the carrier layer that accumulates on the bottom when biological treatment apparatus 2 is out of operation. By doing so, a flow pass is secured above the carriers that accumulate on the bottom at communication portion 21 and allows the water in first region 19 to flow above the carriers into second region 20,

The thickness of the carrier layer that accumulates on bottom 12A of denitrification tank 2A depends on the filling rate of the carriers. The filling rate means the ratio of the volume of the carriers to the volume of the water that is held in denitrification tank 2A. Since denitrification tank 2A is substantially rectangular parallelepiped-shaped, the filling rate generally corresponds to the ratio of space D between partition wall 18 and bottom 12A of denitrification tank 2A to vertical distance H between top surface 13A of first sidewall 13 and bottom 12A of denitrification tank 2A. Accordingly, it is preferable that space D between partition wall 18 and bottom 12A of denitrification tank 2A is larger than the product of vertical distance H between top surface 13A of first sidewall 13 and bottom 12A of denitrification tank 2A and the filling rate of the carriers. The filling rate varies depending on the water quality etc. of the water to be treated. However, the filling rate rarely exceeds 40% and it is almost impossible for the filling rate to exceed 50%. Accordingly, in practice, space D does not need to be equal to or more than half of vertical distance H between top surface 13A of first sidewall 13 and bottom 12A of denitrification tank 2A, In other words, space D may be less than half of vertical distance H between top surface 13A of first sidewall 13 and bottom 12A of denitrification tank 2A.

As described above, in order to allow the carriers to sediment regardless of the upward flow of the treated water in second region 20, it is desirable that velocity V of the treated water in second region 20 be at least smaller than the sedimentation velocity of the carriers. The sedimentation velocity can be determined In advance based on the characteristics of the treated water and on the type of the carriers. Velocity V of the treated water in second region 20 is determined based on the flow rate of the water to be treated that is supplied to denitrification tank 2A (in other words, the flow rate of the treated water that is supplied to second region 20) and the sectional area of second region 20. In order to ensure that the carriers sediment, it is desirable that velocity V of the treated water in second region 20 is determined by taking into consideration a safety factor. The safety factor is desirably selected from a range of about 1.2- 2.0. In other words, it is desirable that velocity V of the treated water in second region 20 be 0.5-0.8 times the sedimentation velocity of the carriers. When the amount of water that is treated by biological treatment apparatus 2 in unit time is given, the sectional area of second region 20 is desirably determined such that velocity V of the treated water in second region 20 becomes a predetermined value.

The flow of the water that overflows first sidewall 13 from second region 20 depends on the flow rate that is stipulated by supply line L1 and recirculation line L2. However, as mentioned above, the biased flow that is caused by agitators 23 may reach the upper portion of second region 20 together with the carriers, and the carriers may adhere to the screen. By providing second buffer plate 52, it is possible to limit the biased flow that is caused by agitators 23, as well as the number of carriers C that reach carrier capturing device 26. The shape, arrangement and so on of second baffle plate 52 are not limited as long as the number of carriers C that reach carrier capturing device 26 can be limited. In the present embodiment, as shown in Figs. 3 and 4, second baffle plate 52 is a baffle plate that laterally protrudes from first side wall 13. Second baffle plate 52 limits the upward flow of the treated water in second region 20. As shown in Fig. 3, second baffle plate 52 is inclined downward. Due to this configuration, the carriers do not accumulate on the upper surface of second baffle plate 52 and allow the carriers that has once flown upward to fall or sediment along the upper surface of second baffle plate 52. Since the number of carriers C that reach carrier capturing device 26 can be limited by providing second baffle plate 52, screen 27 of carrier capturing device 26 can be downsized.

The present embodiment has the following advantages. As described above, the inlet of second region 20 (communication portion 21) is positioned at the lower part of denitrification tank 2A, and the exit of second region 20 is only provided at the upper part of second region 20. In other words, exit portion 25 or screen 27 is positioned above communication portion 21 and is provided at a position that cannot be directly seen from first region 19 in the horizontal direction. With this configuration, the treated water always flows upward immediately before flowing out of denitrification tank 2A, and the carriers are separated from the treated water. Since the number of the carriers that reach screen 27 is significantly reduced as compared to the number of the carriers that pass through communication portion 21, the water contact area of screen 27 can be reduced. In other words, since most of the carriers are separated from the treated water due to the configuration of the vertical flow pass of second region 20, screen 27 functions mainly as back-up. This leads to downsizing and cost down of screen 27. The frequency and/or the time required to wash screen 27 are also reduced.

In a conventional screen, most of the screen is submerged in denitrification tank 2A, and therefore, the method of washing the screen is limited. The washing can be easily conducted by draining denitrification tank 2A, but biological treatment apparatus 2 must be halted according to this method. In order to wash the submerged section during operation, a special device is required, and this leads to an increase of washing cost. In contrast, in the present embodiment, the washing can be easily conducted during operation and the washing cost also can be limited because screen 27 is provided where the treated water overflows. In addition, it is possible to expose almost the entire part of screen 27 without draining the tank just by stopping the supply of the water to be treated. This allows efficient washing. These advantages are especially significant for oxygen free or anaerobic treatment. As described above, an aeration device is generally provided for aerobic treatment, and screen 27 is constantly washed by the air that is injected from the aeration device. However, it is desirable in an oxygen free or anaerobic treatment that air not flow into denitrification tank 2A. Therefore, if screen 27 is washed by an aeration device, the efficiency of the treatment is reduced. In addition, considering that the efficiency with which oxygen dissolves increases as water depth increases, a screen having a submerged portion is disadvantageous. Thus, in the anaerobic treatment, the condition for aeration has to be mitigated as compared to the aerobic treatment, and the carriers tend to adhere to screen 27. In the present embodiment, such a problem in the anaerobic treatment can be easily solved because screen 27 can be easily washed. In addition, in the present embodiment, since first region 19 is separated from second region 20 by partition wall 18, air is less likely to flow into first region 19. Thus, in order to wash screen 27 by washing device 31 , air can be used -as the washing liquid.

The present invention has been described by an embodiment. However, the present invention is not limited to the present embodiment and may be modified in various manners depending on the types and concentration of objects that are to be removed. For example, water that is discharged from denitrification treatment tank 2A may be supplied to sedimentation tank 3 without providing aerobic treatment tank 2B. Carrier capturing device 26 having a similar arrangement may also be provided in aerobic treatment tank 2B. The carriers that immobilize aerobic bacteria are formed of a light material, such as sponge, and are less likely to sediment by gravity than the carriers for anaerobic microbes. However, the specific weight of carriers that contain water may be larger than the specific weight of the water, and the effect of the present invention may be obtained. Furthermore, in general, single partition wall 18 is sufficient to separate the carriers from the water, as in the present embodiment, but when the specific weight of the carriers is close to the specific weight of the water and the effect of separating the carriers by gravity is limited, another partition wall that arises from base plate 12 may be arranged upstream of partition wall 18.

The present invention may be applied to a method of modifying a biological treatment apparatus. For example, a biological treatment apparatus in which a large screen is provided on one side of a bioreactor may be modified into a biological treatment apparatus having the same arrangement as the present embodiment. The modification work may be conducted in the following steps. First,- the large screen is removed and then first sidewall 13 is provided. Partition plate 18 is provided in the bioreactor, and carrier capturing device 26 that includes small size screen 27 of the present embodiment is provided on top surface 13A of first sidewall 13. From the viewpoint of construction, partition wall 18 is preferably made of a metal plate.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims.

List of Reference Numerals 2 biological treatment apparatus 2A denitrification treatment tank (first bioreactor)

2B aerobic treatment tank (second bioreactoi)^·

12 base plate

13-16 first to fourth sidewalls 17 top plate 18 partition wall

19 first region

20 second region

21 communication portion

22 liquid supply portion 25 exit portion

26 carrier capturing device

27 screen

31 washing device

C carrier

Claims

1. A biological treatment apparatus comprising: a bioreactor in which carriers flows, wherein the carriers immobilize microbes for biological treatment of water to be treated; a partition wall that is provided in the bioreactor, wherein the partition wall separates the bioreactor into a first region that includes a supply portion for the water to be treated and a second region that is in communication with the first region at a lower part of the bioreactor, wherein an exit portion for treated water that has been treated by the bioreactor is only formed in an upper part of the second region, and a carrier capturing device having a screen that is provided at the exit portion and that prevents the carriers from flowing out of the bioreactor.

2 . The biological treatment apparatus according to claim 1, wherein the bioreactor has a first sidewall that faces the partition wall, wherein the second region is formed between the partition wall and the first sidewall, the treated water overflows the first sidewall to flow out of the bioreactor, and the carrier capturing device is provided on a top surface of the first sidewall.

3. The biological treatment apparatus according to claim 1 or 2, wherein the screen is inclined relative to a vertical direction.

4. The biological treatment apparatus according to any one of claims 1 to 3, wherein the carrier capturing device includes a washing device that injects washing liquid to the screen, wherein the washing device is provided on a side of the screen opposite to the second region.

5. The biological treatment apparatus according to any one of claims 1 to 4, wherein the microbes are anaerobic bacteria.

6. The biological treatment apparatus according to any one of claims 1 to 5, wherein the bioreactor has a second sidewall that is opposite to the first sidewall, wherein the supply portion is provided near the second sidewall, the supply portion has supply ports for the water to be treated that are open to the bioreactor, and the supply ports face the second sidewall.

7. A carrier capturing device for a biological treatment apparatus, wherein the biological treatment apparatus comprises a bioreactor in which carriers flows, wherein the carriers immobilize microbes for biological treatment of water to be treated, and a partition wall that is provided in the bioreactor, wherein the partition wall separates the bioreactor into a first region that includes a supply portion for the water to be treated and a second region that is in communication with the first region at a lower part of the bioreactor, wherein an exit portion for treated water that has been treated by the bioreactor is only formed in an upper part of the second region, wherein the carrier capturing device comprises a screen that is provided at the exit portion and that prevents the carriers from flowing out of the bioreactor.

8. The carrier capturing device according to claim 7, further comprising a washing device that injects washing liquid to the screen.

9 . A water treatment method using a biological treatment apparatus, the apparatus comprising a bioreactor in which carriers flows, wherein the carriers immobilize microbes for biological treatment of water to be treated, and a partition wall that is provided in the bioreactor, wherein the partition wall separates the bioreactor into a first region that includes a supply portion for the water to be treated and a second region that is in communication with the first region at a lower part of the bioreactor, wherein an exit portion for treated water that has been treated by the bioreactor is only formed in an upper part of the second region, the method comprising the steps of: supplying water to be treated to the first region in order to allow a part of the water to be treated to flow into the second region; and feeding the treated water through a screen, wherein the treated water flows out the second region through the exit portion, and the screen is provided at the exit portion and prevents the carriers from flowing out of the bioreactor. 10, A method of modifying a biological treatment apparatus, the apparatus comprising a bioreactor in which carriers flows, wherein the carriers immobilize microbes for biological treatment of water to be treated, the method comprising the steps of: providing a partition wall in the bioreactor, wherein the partition wall separates the bioreactor into a first region that includes a supply portion for the water to be treated and a second region that is in communication with the first region at a lower part of the bioreactor, wherein an exit portion for treated water that has been treated by the bioreactor Is only formed in an upper part of the second region, and providing a carrier capturing device having a screen that is provided at the exit portion and that prevents the carriers from flowing out of the bioreactor.