Printing and dyeing wastewater treatment system integrating micro-aerobic hydrolytic acidification and biological contact oxidation

Abstract

The invention discloses a printing and dyeing wastewater treatment system integrating micro-aerobic hydrolytic acidification and biological contact oxidation, relates to the technical field of printing and dyeing wastewater treatment, and solves the problems that aeration pipes in an existing sewage treatment device are mostly placed at the bottom of an aeration device, aeration efficiency is reduced, and although the specific surface area of filler is large, the aeration efficiency is low. However, the filler is actually subjected to biological contact oxidation treatment on the sewage section in a point contact manner, so that the treatment effect is limited. A printing and dyeing wastewater treatment system integrating micro-aerobic hydrolytic acidification and biological contact oxidation comprises an L-shaped frame, a biological contact oxidation pond is installed on the inner side of the L-shaped frame, suspended filler and a rotating shaft are arranged on the inner side of the biological contact oxidation pond, and a plurality of rotating paddles are evenly installed on the two sides of the outer surface of the rotating shaft. The wastewater treatment effect is good, impurities in the wastewater can be cleaned, then micro-aerobic hydrolytic acidification is performed, and the aeration efficiency is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printing and dyeing wastewater treatment, in particular to a printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation. BACKGROUND

[0002] With the rapid development of China's economy, the textile industry has become one of the important pillar industries in the national economy and people's livelihood. Printing and dyeing wastewater contains a large amount of residual dyes, surfactants, heavy metals and printing and dyeing auxiliaries and other pollutants, which need to be treated by micro-aerobic hydrolysis acidification and biological contact oxidation.

[0003] Biological contact oxidation is a submerged biological membrane method, that is, biological fillers are suspended in the biological reaction tank, microorganism membranes grow on the fillers, and aeration heads (tubes) are installed below the fillers and supply oxygen to the microorganisms on the fillers and the activated sludge in the wastewater. The oxygenated wastewater submerges all the fillers and flows through the fillers at a certain flow rate. The wastewater and the biological membrane are in extensive contact, and under the metabolism of the microorganisms on the biological membrane, the organic pollutants in the wastewater are removed, and the wastewater is purified.

[0004] However, the aeration pipes in the existing wastewater treatment devices are mostly placed at the bottom of the aeration device, and the wastewater and oxygen are mixed by the upward floating of the bubbles. This way, the bubbles directly float upward, which leads to insufficient contact between the bubbles and the wastewater, reducing the aeration efficiency. Although the specific surface area of the fillers is large, the biological membranes are mostly covered on the surface of the fiber bundles, so the effective treatment area of the fillers is only the outer surface. When the wastewater flows vertically upward through the filler layer in the tank, the fillers actually contact the wastewater in a point contact manner for biological contact oxidation treatment, thus limiting the treatment effect. Therefore, it does not meet the existing needs, and for this purpose, we propose a printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation. SUMMARY

[0005] The present application aims to provide a printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation, to solve the problems in the prior art, such as the aeration pipes in the existing wastewater treatment devices being mostly placed at the bottom of the aeration device, the wastewater and oxygen being mixed by the upward floating of the bubbles, the bubbles directly floating upward leading to insufficient contact between the bubbles and the wastewater, reducing the aeration efficiency, and although the specific surface area of the fillers is large, the biological membranes are mostly covered on the surface of the fiber bundles, so the effective treatment area of the fillers is only the outer surface, and when the wastewater flows vertically upward through the filler layer in the tank, the fillers actually contact the wastewater in a point contact manner for biological contact oxidation treatment, thus limiting the treatment effect.

[0006] In order to achieve the above object, the present application provides the following technical scheme: a printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation, comprising an L-shaped frame, a biological contact oxidation tank is installed on the inner side of the L-shaped frame, a suspension filler and a rotating shaft are arranged on the inner side of the biological contact oxidation tank, a plurality of rotating paddles are uniformly installed on the outer surface of the rotating shaft, an annular groove is arranged above the inner wall of the biological contact oxidation tank, an annular guide rail is arranged on the inner side of the annular groove, a sliding block is sleeved on the outer surface of the annular guide rail, an arc block is installed on the front end surface of the sliding block, a spray head is installed on the lower end surface of the arc block, a top plate is installed on the upper end surface of the L-shaped frame, a forward and reverse motor is installed in front of the upper end surface of the top plate, a filter hydrolysis box is installed behind the forward and reverse motor, a liquid pump is installed on the upper end surface of the filter hydrolysis box, one end of the liquid pump is connected with a liquid inlet pipe, a through groove is arranged above the rear end surface of the filter hydrolysis box, a filter mechanism is movably arranged on the inner side of the through groove, a blower is installed below the rear end surface of the filter hydrolysis box, a partition plate is installed below the filter mechanism, an automatic stirring mechanism is arranged below the partition plate, and an aeration disc is installed on the lower end surface of the partition plate and the bottom surface of the filter hydrolysis box.

[0007] Preferably, the suspension filler is a honeycomb porous structure, the output end of the forward and reverse motor is fixedly connected with the upper end surface of the rotating shaft through a shaft coupling, the lower end surface of the rotating shaft is rotatably connected with the bottom surface of the biological contact oxidation tank through a bearing, and the upper end surface of the biological contact oxidation tank is provided with a groove.

[0008] Preferably, the length of the rotating paddle gradually decreases from top to bottom, the annular guide rail is fixedly connected with the inner wall of the annular groove through four supporting rods, the rear end surface of the sliding block is provided with a clamping groove, and the supporting rods penetrate through the clamping groove.

[0009] Preferably, the arc block is fixedly connected with the rotating shaft through a connecting plate, the bottom of the filter hydrolysis box is connected with the spray head through a connecting pipe, and the connecting pipe is a telescopic hose.

[0010] Preferably, the automatic stirring mechanism comprises a cross rod, a plurality of rotating leaves are uniformly installed on the outer surface of the cross rod, the two ends of the cross rod are rotatably connected with the inner surface of the filter hydrolysis box through short shafts, and the rotating leaves are made of foam plates.

[0011] Preferably, the other end of the liquid pump is connected with the inside of the filter hydrolysis box through a water inlet pipe, through holes are penetratingly arranged on the two sides of the upper end surface of the partition plate, the blower is connected with the aeration disc through an aeration pipe.

[0012] Preferably, the filter mechanism comprises a drawer, vertical grooves are arranged on the two sides of the upper end surface of the drawer, a first sieve plate is arranged on the upper end surface of the vertical groove, and a second sieve plate is arranged above the first sieve plate.

[0013] Preferably, the first screen plate and the second screen plate are movably connected by connecting rods, four corners of the outer surface of the second screen plate and the first screen plate are provided with round holes, and the connecting rods can be inserted into the inner side of the round holes.

[0014] Preferably, the second screen plate has a larger screen hole diameter than the first screen plate, the inner wall of the through groove is provided with a strip-shaped groove on both sides, the outer surface of the drawer is provided with a strip-shaped plate on both sides, the strip-shaped plate can be clamped into the inner side of the drawer, and the rear end surface of the drawer is provided with a handle.

[0015] Preferably, one side of the lower end surface of the biological contact oxidation tank is provided with a drain pipe, the inner side of the drain pipe is provided with an electromagnetic valve, and the upper end of the drain pipe extends into the inside of the biological contact oxidation tank.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1、The filter hydrolysis box, the filtering mechanism, the automatic stirring mechanism and the aerator plate are arranged, the printing and dyeing wastewater to be treated is added into the inside of the filter hydrolysis box through the liquid inlet pipe, the wastewater is filtered through the second screen plate first, the larger impurities are filtered, the smaller impurities are filtered through the first screen plate, and then the wastewater is filtered through the through hole and enters the lower side of the partition plate, the rotating blade is made of a foam plate, the foam plate is light in weight, the rotating blade can rotate when the wastewater flows downward through the through hole or when the bubbles float upward, the bubbles in the wastewater are stirred, the residence time of the bubbles in the wastewater is increased, the aeration efficiency is improved, the filtering mechanism can be pulled out from the inner side of the through groove through the handle, the impurities above the first screen plate and the second screen plate can be cleaned, the impurities in the wastewater can be cleaned, the wastewater is subjected to micro-aerobic hydrolysis acidification, and the aeration efficiency is high.

[0018] 2、The forward and reverse motor, the rotating paddle, the rotating shaft, the sliding block and the spray head are arranged, the switch of the forward and reverse motor is turned on, the rotating shaft is driven to rotate through the work of the forward and reverse motor, the rotating paddle and the sliding block are driven to rotate, the wastewater filtered and subjected to micro-aerobic hydrolysis acidification can be sprayed in the biological contact oxidation tank through the spray head rotating back and forth with the rotating shaft as the center, the wastewater in the biological contact oxidation tank is stirred, the process of the biofilm on the surface of the filler is accelerated, the growth, thickening and falling of the biofilm are accelerated, the suspension characteristics of the filler are ensured, the recycling of the suspended filler is ensured, meanwhile, the suspended filler has a honeycomb porous structure and a larger specific area, and the wastewater treatment effect is good. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structural schematic view of the whole front surface of the present application.

[0020] Figure 2The local structure diagram of the annular groove of the present application;

[0021] Figure 3 The main sectional view of the present application as a whole;

[0022] Figure 4 The main sectional view of the filter hydrolysis box of the present application;

[0023] Figure 5 The structure diagram of the turning blade of the present application;

[0024] Figure 6 The structure diagram of the filtering mechanism of the present application;

[0025] Figure 7 The structure diagram of the back of the present application as a whole.

[0026] In the figure: 1, L-shaped frame; 2, top plate; 3, filter hydrolysis box; 4, liquid inlet pipe; 5, liquid pump; 6, forward and reverse motor; 7, biological contact oxidation pool; 8, drainage pipe; 9, rotating shaft; 10, rotating paddle; 11, filtering mechanism; 1101, drawer; 1102, strip plate; 1103, vertical groove; 1104, first sieve plate; 1105, connecting rod; 1106, second sieve plate; 12, partition plate; 13, through hole; 14, automatic stirring mechanism; 1401, turning blade; 1402, cross bar; 15, suspended filler; 16, annular guide rail; 17, annular groove; 18, sliding block; 19, connecting pipe; 20, spray head; 21, groove; 22, arc block; 23, through groove; 24, air blower; 25, aeration disc. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application.

[0028] The liquid pump 5 (model IS200-150-400), the forward and reverse motor 6 (model 68KTYZ) and the air blower 24 (model 2HB810-7AH27) mentioned in the present application can be obtained from the market or private customization.

[0029] Please refer to Figures 1 to 7The application provides a printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation, which comprises an L-shaped frame 1, a biological contact oxidation tank 7 is arranged on the inner side of the L-shaped frame 1, a suspension filler 15 and a rotating shaft 9 are arranged on the inner side of the biological contact oxidation tank 7, a plurality of rotating paddles 10 are uniformly arranged on the outer surface of the rotating shaft 9, an annular groove 17 is arranged on the upper inner wall of the biological contact oxidation tank 7, an annular guide rail 16 is arranged on the inner side of the annular groove 17, a sliding block 18 is sleeved on the outer surface of the annular guide rail 16, an arc-shaped block 22 is arranged on the front end surface of the sliding block 18, a nozzle 20 is arranged on the lower end surface of the arc-shaped block 22, a top plate 2 is arranged on the upper end surface of the L-shaped frame 1, a forward and reverse motor 6 is arranged on the front of the upper end surface of the top plate 2, a filter hydrolysis box 3 is arranged on the rear of the forward and reverse motor 6, a liquid pump 5 is arranged on the upper end surface of the filter hydrolysis box 3, one end of the liquid pump 5 is connected with a liquid inlet pipe 4, a through groove 23 is arranged on the upper end surface of the rear of the filter hydrolysis box 3, a filter mechanism 11 is movably arranged on the inner side of the through groove 23, a blower 24 is arranged on the lower side of the rear of the filter hydrolysis box 3, a partition plate 12 is arranged on the lower side of the filter mechanism 11, an automatic stirring mechanism 14 is arranged on the lower side of the partition plate 12, and an aeration disc 25 is arranged on the lower end surface of the partition plate 12 and the bottom surface of the filter hydrolysis box 3.

[0030] The suspension filler 15 is in a honeycomb porous structure, the output end of the forward and reverse motor 6 is fixedly connected with the upper end surface of the rotating shaft 9 through a shaft coupling, the lower end surface of the rotating shaft 9 is rotatably connected with the bottom surface of the biological contact oxidation tank 7 through a bearing, the upper end surface of the biological contact oxidation tank 7 is provided with a groove 21, the suspension filler 15 is in a honeycomb porous structure and has a larger specific area, the wastewater treatment effect is good, and the forward and reverse motor 6 can drive the rotating shaft 9 to rotate, thereby improving the stability of the rotating shaft 9.

[0031] The length of the rotating paddle 10 gradually decreases from top to bottom, the annular guide rail 16 is fixedly connected with the inner wall of the annular groove 17 through four supporting rods, the rear end surface of the sliding block 18 is provided with a clamping groove, and the supporting rods penetrate through the clamping groove, so that the rotating paddle 10 cannot touch the inner wall of the biological contact oxidation tank 7, and the stability of the annular guide rail 16 on the inner side of the annular groove 17 is improved, and the movement of the sliding block 18 is not affected.

[0032] The arc-shaped block 22 is fixedly connected with the rotating shaft 9 through a connecting plate, the bottom of the filter hydrolysis box 3 is connected with the nozzle 20 through a connecting pipe 19, the connecting pipe 19 is a telescopic hose, the rotating shaft 9 can drive the arc-shaped block 22 to rotate around the rotating shaft 9, the filtered wastewater can be sprayed out through the nozzle 20 through the connecting pipe 19, and the connecting pipe 19 can be telescoped.

[0033] The automatic stirring mechanism 14 comprises a crossbar 1402, a plurality of rotating leaves 1401 are uniformly arranged on the outer surface of the crossbar 1402, the two ends of the crossbar 1402 are rotatably connected with the inner surface of the filter hydrolysis box 3 through short shafts, and the rotating leaves 1401 are made of foam plates, the foam plates are light in weight, and the rotating leaves 1401 can rotate when the wastewater flows through the through hole 13 or when the bubbles float up, so that the bubbles in the wastewater are stirred, the residence time of the bubbles in the wastewater is increased, and the aeration efficiency is improved.

[0034] The other end of the liquid pump 5 is connected with the inside of the filter hydrolysis box 3 through a water inlet pipe, the two sides of the upper end surface of the partition plate 12 are provided with through holes 13, the air blower 24 is connected with the aeration disc 25 through an aeration pipe, and the aeration disc 25 can be aerated when the air blower 24 works.

[0035] The filter mechanism 11 comprises a drawer 1101, the two sides of the upper end surface of the drawer 1101 are provided with vertical grooves 1103, the upper end surface of each vertical groove 1103 is provided with a first sieve plate 1104, and the upper side of the first sieve plate 1104 is provided with a second sieve plate 1106.

[0036] The first sieve plate 1104 and the second sieve plate 1106 are movably connected through a connecting rod 1105, the four end corners of the outer surface of the second sieve plate 1106 and the first sieve plate 1104 are provided with circular holes, the connecting rod 1105 can be inserted into the inner side of the circular hole, the first sieve plate 1104 and the second sieve plate 1106 can be separated, and the impurities between the first sieve plate 1104 and the second sieve plate 1106 can be cleaned.

[0037] The screen hole diameter of the second sieve plate 1106 is greater than that of the first sieve plate 1104, the two sides of the inner wall of the through groove 23 are provided with strip grooves, the two sides of the outer surface of the drawer 1101 are provided with strip plates 1102, the strip plates 1102 can be clamped into the inner side of the drawer 1101, and a handle is arranged on the rear end surface of the drawer 1101, so that the drawer 1101 can be pulled out from the inner side of the through groove 23 through the handle.

[0038] The lower end surface of the biological contact oxidation tank 7 is provided with a drain pipe 8 on one side, the inner side of the drain pipe 8 is provided with an electromagnetic valve, and the upper end of the drain pipe 8 extends to the inside of the biological contact oxidation tank 7, so that the treated wastewater can be discharged.

[0039] The integrated micro-aerobic hydrolysis acidification and biological contact oxidation printing and dyeing wastewater treatment system, when in use, through the filter hydrolysis box 3, the filter mechanism 11, the automatic stirring mechanism 14 and the aeration disc 25, the printing and dyeing wastewater to be treated is added into the inside of the filter hydrolysis box 3 through the liquid inlet pipe 4, the wastewater is filtered through the second sieve plate 1106 first, the larger impurities are filtered, then the first sieve plate 1104 is passed through, the smaller impurities are filtered, then the through hole 13 is passed through to the below of the partition plate 12, the rotating blade 1401 is made of a foam plate, the foam plate is lighter in weight, when the wastewater flows down through the through hole 13 or when the bubbles float up, the rotating blade 1401 can rotate, the bubbles in the sewage are stirred, the residence time of the bubbles in the sewage is increased, the aeration efficiency is improved, meanwhile, the filter mechanism 11 can be pulled out from the inside of the through slot 23 through the handle, the impurities above the first sieve plate 1104 and the second sieve plate 1106 can be cleaned, through the setting of the forward and reverse motor 6, the rotating paddle 10, the rotating shaft 9, the sliding block 18 and the spray head 20, the switch of the forward and reverse motor 6 is opened, the forward and reverse motor 6 works to drive the rotating shaft 9 to rotate, thereby driving the rotating paddle 10 and the sliding block 18 to rotate, the wastewater filtered and micro-aerobically hydrolyzed can pass through the spray head 20 rotating back and forth with the rotating shaft 9 as the center to be sprayed in the biological contact oxidation tank 7, the treatment effect is improved, the sewage in the biological contact oxidation tank 7 is stirred, the biofilm on the surface of the filler is accelerated to form, grow, thicken and fall off, the suspension characteristics of the filler are ensured, thereby the recycling of the suspended filler is ensured, meanwhile, the suspended filler 15 adopts a honeycomb porous structure, has a larger specific area, the wastewater treatment effect of the present application is good, the impurities in the wastewater can be cleaned, then the micro-aerobic hydrolysis acidification is carried out, the aeration efficiency is high.

[0040] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments but can be implemented in other embodiments without departing from the scope of the application. The scope of the application is defined by the appended claims rather than by the description of the exemplary embodiments above and therefore all changes and modifications that come within the meaning and range of equivalents of the claims are to be embraced by the application. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

Claims

1. A printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation, comprising an L-shaped frame (1), characterized in that: A biological contact oxidation tank (7) is installed on the inner side of the L-shaped frame (1), a suspended filler (15) and a rotating shaft (9) are provided on the inner side of the biological contact oxidation tank (7), a plurality of rotating paddles (10) are evenly installed on both sides of the outer surface of the rotating shaft (9), an annular groove (17) is provided above the inner wall of the biological contact oxidation tank (7), an annular guide rail (16) is provided on the inner side of the annular groove (17), a slider (18) is sleeved on the outer surface of the annular guide rail (16), an arc block (22) is installed on the front end surface of the slider (18), a nozzle (20) is installed on the lower end surface of the arc block (22), a top plate (2) is installed on the upper end surface of the L-shaped frame (1), and the front end surface of the upper end surface of the top plate (2) is provided. A forward and reverse motor (6) is installed, a filtering and hydrolysis box (3) is installed behind the forward and reverse motor (6), a liquid pump (5) is installed on the upper end surface of the filtering and hydrolysis box (3), one end of the liquid pump (5) is connected to a liquid inlet pipe (4), a through groove (23) is provided above the rear end surface of the filtering and hydrolysis box (3), a filtering mechanism (11) is movably provided inside the through groove (23), a blower (24) is installed below the rear end surface of the filtering and hydrolysis box (3), a partition (12) is installed below the filtering mechanism (11), an automatic stirring mechanism (14) is provided below the partition (12), and an aeration disk (25) is installed on the lower end surface of the partition (12) and the bottom surface of the filtering and hydrolysis box (3).

2. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1 is characterized in that: The suspended filler (15) is a honeycomb porous structure. The output end of the forward and reverse motor (6) is fixedly connected to the upper end surface of the rotating shaft (9) through a coupling. The lower end surface of the rotating shaft (9) is rotatably connected to the bottom surface of the biological contact oxidation tank (7) through a bearing. The upper end surface of the biological contact oxidation tank (7) is provided with a groove (21).

3. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1 is characterized in that: The length of the rotating paddle (10) decreases from top to bottom, the annular guide rail (16) is fixedly connected to the inner wall of the annular groove (17) through four support rods, the rear end surface of the slider (18) is provided with a card slot, and the support rod passes through the card slot.

4. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1, characterized in that: The arc block (22) is fixedly connected to the rotating shaft (9) via a connecting plate, and the bottom of the filtering and hydrolysis box (3) is connected to the nozzle (20) via a connecting pipe (19), and the connecting pipe (19) is a retractable hose.

5. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1 is characterized in that: The automatic stirring mechanism (14) includes a cross bar (1402), and a plurality of rotating blades (1401) are evenly installed on the outer surface of the cross bar (1402). The two ends of the cross bar (1402) are rotatably connected to the inner surface of the filtration and hydrolysis box (3) through a short shaft, and the rotating blades (1401) are made of foam boards.

6. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1, characterized in that: The other end of the liquid pump (5) is connected to the interior of the filtration and hydrolysis box (3) through a water inlet pipe, through holes (13) are provided on both sides of the upper end surface of the partition (12), and the blower (24) is connected to the aeration plate (25) through an aeration pipe.

7. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1, characterized in that: The filtering mechanism (11) comprises a drawer (1101), vertical grooves (1103) are provided on both sides of the upper end surface of the drawer (1101), a first sieve plate (1104) is provided on the upper end surface of the vertical groove (1103), and a second sieve plate (1106) is provided above the first sieve plate (1104).

8. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 7, characterized in that: The first sieve plate (1104) and the second sieve plate (1106) are movably connected via a connecting rod (1105). Circular holes are provided at four end corners on opposite sides of the outer surfaces of the second sieve plate (1106) and the first sieve plate (1104), and the connecting rod (1105) can be inserted into the inner side of the circular holes.

9. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 8, characterized in that: The aperture of the sieve holes of the second sieve plate (1106) is larger than the aperture of the sieve holes of the first sieve plate (1104), strip grooves are provided on both sides of the inner wall of the through groove (23), and strip plates (1102) are installed on both sides of the outer surface of the drawer (1101), and the strip plates (1102) can be stuck into the inner side of the drawer (1101), and a handle is installed on the rear end face of the drawer (1101).

10. The printing and dyeing wastewater treatment system integrating micro-aerobic hydrolysis acidification and biological contact oxidation according to claim 1, characterized in that: A drain pipe (8) is installed on one side of the lower end surface of the biological contact oxidation tank (7), a solenoid valve is installed on the inner side of the drain pipe (8), and the upper end of the drain pipe (8) extends to the interior of the biological contact oxidation tank (7).

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