Aerobic-anaerobic three-phase pulsed stepped influent wetland system

Abstract

The present invention provides an aerobic-anaerobic three-phase pulsed stepped water inlet wetland system. A water distribution structure and a stepped water inlet pipe are arranged at the top and side of the wetland system. An outlet is arranged at the bottom of the wetland system and is connected to a siphon drain pipe. The top of the siphon drain pipe is lower than the top height of the wetland system to form a pressure difference for periodic siphon drainage, so that the area of the wetland system above the L-shaped vent pipe on the siphon drain pipe is the upper aerobic zone, and the area below it is the lower anaerobic zone. The position of the L-shaped vent pipe can adjust the ratio of the two. The system provided by the present invention solves the problems of insufficient carbon source, poor reoxygenation effect, and high energy consumption in constructed wetlands. The stepped water inlet pipe is used to realize the redistribution of the influent carbon source and improve the carbon source utilization rate. The siphon drain pipe and the L-shaped vent pipe are used to adjust the height of the periodic siphon drainage, so that the upper aerobic zone is periodically in a gas-liquid-solid three-phase mixed state and the height is controllable to balance the redox environment of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, in particular to an aerobic-anaerobic three-phase pulsed stepped water inlet wetland system. Background Art

[0002] Although the total amount of fresh water resources in China is relatively large, accounting for 6% of the global water resources, the per capita water resources are scarce, only about 30% of the world average level. With the rapid development of social economy, problems such as water shortage and poor water environment have become increasingly prominent. Therefore, the efficient treatment of sewage and the reuse of water resources are the keys to ensuring the sound development of social economy.

[0003] At present, there are many kinds of water treatment processes in China, but the biological treatment method is still the main one. The current mainstream biological treatment methods can be divided into the activated sludge method and the biofilm method. Among them, as a kind of biofilm method, constructed wetland has unique ecological effects and is unique among many water treatment processes. Compared with traditional water treatment methods, constructed wetland has the advantages of low investment, low operating cost, low energy consumption, and low management level requirements. In recent years, it has been widely used to treat domestic sewage, industrial wastewater, storm runoff, eutrophic water bodies, etc.

[0004] A constructed wetland is an artificial water treatment ecosystem composed of media such as stones, sand, soil, and cinder in a certain proportion, with a closed bottom and selectively implanted aquatic vegetation. Its purification ability is the artificial enhancement of the natural purification process, including various effects such as microbial degradation, plant absorption, physical adsorption, and chemical precipitation. Among them, aerobic respiration of microorganisms is an important way for the wetland to remove organic pollutants (measured by chemical oxygen demand, COD) in sewage, and the nitrogen in sewage is mainly removed through the nitrification and denitrification processes of microorganisms in the alternating aerobic / anaerobic environment inside the constructed wetland.

[0005] At present, there are also several limiting factors in the actual engineering application of artificial wetlands. Numerous studies have shown that in traditional artificial wetlands, low dissolved oxygen levels and insufficient carbon sources are the main factors limiting the low denitrification efficiency of artificial wetlands. At present, artificial wetland oxygenation technology can be divided into artificial aeration technology and artificial enhanced atmospheric reoxygenation technology according to the reoxygenation pathway. Although artificial aeration is considered to be the most effective method of oxygenation, continuous aeration leads to a significant increase in operating costs; artificial enhanced atmospheric reoxygenation technology mainly includes waterfall oxygenation water inlet, tidal water inlet, setting of ventilation pipes, setting of wetland unsaturated layers, etc. Although the reoxygenation method of artificial enhanced atmospheric reoxygenation technology reduces the operating cost compared with artificial aeration, it still cannot avoid the loss of organic matter and unbalanced redox conditions caused by excessive reoxygenation, resulting in the inability to effectively remove nitrogen. In response to the problem of insufficient carbon source, researchers mainly add external carbon sources, such as soluble carbon sources, solid carbon sources, plant carbon sources, etc. However, the dosage of soluble carbon sources is difficult to control, and they are easily degraded by aerobic degradation in artificial wetlands, and cannot function for a long time; solid carbon sources need to be pre-buried in the artificial wetland matrix in advance, and the effect is stable, but it is difficult to replenish and the cost is expensive; plant carbon sources are cheap and easy to obtain, but the effect is unstable, easily disturbed, and will also increase the chromaticity of the effluent. It can be seen that the current technology cannot meet the needs of continuous and efficient reoxygenation and efficient and stable denitrification in large-scale economic applications of wetlands.

[0006] In summary, the existing technology lacks effective solutions to the problems of poor reoxygenation effect, high energy consumption, insufficient carbon source, low COD and nitrogen removal rates, and organic pollution blockage in artificial wetlands. Summary of the invention

[0007] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides an aerobic-anaerobic three-phase pulsed cascade water inlet wetland system, which realizes the redistribution of the carbon source of the inlet water through the water distribution pipe and the cascade water inlet pipe, thereby improving the utilization rate of the carbon source; the upper aerobic zone is periodically in a gas-liquid-solid three-phase mixed state through the siphon drainage pipe to periodically siphon the water, thereby improving the gas mass transfer rate and realizing efficient reoxygenation; the upper aerobic zone and the lower anaerobic zone are made to have an appropriate ratio through the L-shaped ventilation pipe, thereby creating a balanced redox environment and strengthening the removal of pollutants such as COD and nitrogen in the water.

[0008] The present invention provides the following technical solution: an aerobic-anaerobic three-phase pulsed stepped water inlet wetland system, the wetland system comprising a main functional layer, a water inlet layer located at the top of the main functional layer, a drainage layer located at the bottom of the main functional layer, a water inlet pipe connected with a plurality of water distribution pipes located at the upper part of the water inlet layer, an outlet pipe located in the drainage layer, a stepped water inlet pipe uniformly distributed in the main functional layer, and a siphon drainage pipe communicated with the outlet pipe. An L-shaped vent pipe is arranged on the siphon drainage pipe, and a plurality of uniformly parallel two-way joints are uniformly distributed on the siphon drainage pipe. The L-shaped vent pipe is communicated with the siphon drainage pipe through one of the two-way joints. The horizontal plane where the vent is located divides the main functional layer into an upper aerobic zone and a lower anaerobic zone; one end of the water distribution pipe is connected with the water inlet pipe and the other end is closed, and the plurality of water distribution pipes are parallel to each other; the water inlet pipe is connected with a variable frequency water pump, and the stepped water inlet pipe is connected with a general water pump, so that the water distribution pipe realizes pulsed water inlet;

[0009] The highest top of the siphon drainage pipe is lower than the top of the wetland system, so as to form a pressure difference for periodic siphon drainage;

[0010] The main functional layer is filled with small particle size fillers, and wetland plants are planted on the water inlet layer;

[0011] A plurality of water distribution pipes arranged at the top of the wetland system and the water inlet pipe connected with the plurality of water distribution pipes form a pulsed water distribution system.

[0012] Further, the height of the water inlet layer is 5 cm, and the height of the drainage layer is 10 cm.

[0013] Further, a pulsed water distribution system and a stepped water inlet pipe are respectively arranged at the top and side of the wetland system, and the water distribution volume of the pulsed water distribution system is greater than that of the stepped water inlet pipe.

[0014] Further, both the water inlet layer and the drainage layer are filled with large particle size fillers.

[0015] Further, the stepped water inlet pipe is arranged below 20 cm of the top of the wetland system and is uniformly distributed at intervals of 10 cm on the same vertical axis.

[0016] Further, a plurality of horizontal water distribution holes are arranged on the water distribution pipe, a plurality of horizontal water distribution holes are arranged on the stepped water inlet pipe, and the horizontal water distribution holes of two adjacent water distribution pipes are spaced apart in the horizontal direction.

[0017] Further, the siphon drainage pipe is of an inverted U-shaped structure. The first opening of the siphon drainage pipe is communicated with the outlet pipe, and the first opening is suspended to a position 5 cm lower than the outlet pipe. When siphon occurs, a continuous pressure difference is formed for siphon drainage.

[0018] Furthermore, the interval distance between the two-way connectors uniformly arranged on the siphon drainage pipe is 10 cm; the uppermost two-way connector is 20 cm away from the top of the wetland system, and the lowermost two-way connector is 10 cm away from the bottom of the wetland system; the L-shaped ventilation pipe can be connected to the siphon drainage pipe at any two-way connector through a screw sleeve.

[0019] Furthermore, the two-way connector does not coincide with the inverted U-shaped siphon drainage pipe on the vertical axial plane, and the L-shaped ventilation pipe does not coincide with the inverted U-shaped siphon drainage pipe on the vertical axial plane.

[0020] Furthermore, the height of the L-shaped ventilation pipe is equal to that of the wetland system.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. The wetland system provided by the present invention realizes the redistribution of influent carbon sources. Compared with traditional constructed wetlands, the water distribution structure and stepped inlet pipe adopted in the wetland inlet can introduce water step by step, avoiding excessive consumption of carbon sources in the aerobic zone, improving the utilization rate of carbon sources, providing necessary energy for subsequent denitrification and nitrogen removal in the constructed wetland system, and thus improving the nitrogen removal capacity of the wetland system. It solves the problems of insufficient carbon sources, poor reoxygenation effect, and high energy consumption in constructed wetlands. The redistribution of influent carbon sources is realized through the stepped inlet pipe to improve the utilization rate of carbon sources; the periodic siphon drainage height is adjusted through the siphon drainage pipe and the L-shaped ventilation pipe, so that the upper aerobic zone is periodically in a gas-liquid-solid three-phase mixed state and the height is controllable to balance the oxidation-reduction environment of the system.

[0023] 2. The pulse water distribution structure provided by the wetland system of the present invention can realize pulse water inlet through a variable-frequency water pump, enabling the water to be treated to be evenly distributed on the surface of the wetland system. Compared with the inlet water of traditional constructed wetlands, this water distribution method can prevent the blockage of the inlet pipe, optimize the water flow path, increase the contact area between the water body and the filler, and avoid the phenomenon of short circuit.

[0024] 3. The wetland system provided by the present invention realizes efficient atmospheric reoxygenation. Compared with traditional constructed wetlands, the siphon drainage height controller set at the outlet of the wetland system creates an oxygen mass transfer condition of gas-liquid-solid three-phase coexistence for the upper part of the wetland system, enhancing the gas mass transfer efficiency of the constructed wetland system, being beneficial to biological growth, and thus achieving a better water purification effect.

[0025] 4. The upper part of the wetland system provided by the present invention can reach a periodic state of submergence and evacuation through the siphon drainage pipe and the L-shaped ventilation pipe. Compared with traditional constructed wetlands, the alternating aerobic / anaerobic state in the upper part of this wetland system is conducive to the mineralization and degradation of intercepted organic matter, and thus effectively reduces the risk of organic blockage in the influent layer.

[0026] 5. The wetland system provided by the present invention can regulate the ratio of the upper aerobic zone to the lower anaerobic zone through the installation position of the L-shaped vent pipe, create a more balanced redox environment, and strengthen the removal of pollutants such as COD and nitrogen in water.

[0027] 6. The wetland plants planted on the surface of the wetland system provided by the present invention can not only play an auxiliary purification role, but also bring ornamental value to the entire wetland system from an aesthetic perspective. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be described in more detail below based on embodiments and with reference to the drawings. Among them:

[0029] Figure 1 is the front view of the wetland system provided by the present invention;

[0030] Figure 2 is the right view of the wetland system provided by the present invention;

[0031] Figure 3 is the top view of the wetland system provided by the present invention;

[0032] In the figure, 1: inlet pipe, 2: inlet layer, 3: main functional layer, 4: drainage layer, 5: small particle size filler, 6: stepped water distribution pipe, 7: outlet pipe, 8: anaerobic zone, 9: aerobic zone, 10: water distribution pipe, 11: large particle size filler, 12: L-shaped vent pipe, 13: siphon drainage pipe, 14: wetland plants, 15: two-way joint. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that the terms used here are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used here, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] As Figures 1-3As shown in the figure, the present invention provides an aerobic-anaerobic three-phase pulsed stepped water inlet wetland system. The wetland system includes a main functional layer 3, a water inlet layer 2 located at the top of the main functional layer 3, a drainage layer 4 located at the bottom of the main functional layer 3, a water inlet pipe 1 connected with a plurality of water distribution pipes 10 located above the water inlet layer 2, a water outlet pipe 7 located in the drainage layer 4, a stepped water inlet pipe 6 uniformly distributed in the main functional layer 3, and a siphon drainage pipe 13 communicated with the water outlet pipe 7. An L-shaped air vent pipe 12 is arranged on the siphon drainage pipe 13. A plurality of uniformly parallel two-way joints 15 are uniformly distributed on the siphon drainage pipe 13. The L-shaped air vent pipe 12 is communicated with the siphon drainage pipe 13 through a two-way joint 15. The horizontal plane where the air vent is located divides the main functional layer 3 into an upper aerobic zone 9 and a lower anaerobic zone 8. One end of the water distribution pipe 10 is connected with the water inlet pipe 1, and the other end is closed. A plurality of water distribution pipes 10 are parallel to each other. The water inlet pipe 1 is connected with a variable-frequency water pump, and the stepped water inlet pipe is connected with a general water pump, so that the water distribution pipe realizes pulsed water inlet.

[0036] The highest top of the siphon drainage pipe 13 is lower than the top of the wetland system, so as to form a pressure difference for periodic siphon drainage.

[0037] The main functional layer 3 is internally filled with small-sized fillers 5 with a particle size of 3 mm to 5 mm, and wetland plants 14 are planted on the water inlet layer 2.

[0038] A plurality of water distribution pipes 10 arranged at the top of the wetland system, and the water inlet pipe 1 connected with the plurality of water distribution pipes 10 form a pulsed water distribution system. A pulsed water distribution structure and a stepped water inlet pipe 6 are arranged at the top and side of the wetland system. The pulsed water distribution structure includes a water inlet pipe 1 and a water distribution pipe 10. The water distribution pipes 10 are parallel to each other, one end is connected with the water inlet pipe 1, and the other end is closed. The water distribution pipe and the stepped water inlet pipe are provided with a plurality of horizontal water distribution holes, and the water distribution holes of adjacent water distribution pipes are distributed at intervals to ensure the uniformity of subsequent pulsed water distribution on the surface of the wetland system.

[0039] The water outlet pipe 7 at the bottom of the wetland system is connected with the siphon drainage pipe 13 and the L-shaped air vent pipe 12. The siphon drainage pipe 13 and the L-shaped air vent pipe 12 can respectively realize the periodic drainage of the wetland system and the setting of the drainage height by using the principles of siphon and communicating vessel. Furthermore, the wetland substrate above the L-shaped air vent pipe 12 is continuously exposed to the gas phase for efficient reoxygenation, realizing efficient oxygen supply for the wetland and avoiding high-energy consumption aeration. Furthermore, an aerobic environment is formed above the L-shaped air vent pipe 12 and an anaerobic environment is formed below. The water to be treated flows through the aerobic zone that is periodically in the gas-liquid-solid three-phase mixture and the anaerobic zone that continuously maintains an anaerobic environment in sequence, providing necessary redox conditions for the biofilm on the filler surface to efficiently remove total nitrogen and achieving a better water purification effect.

[0040] Among them, the height of the water inlet layer 2 is 5 cm, and the height of the drainage layer 4 is 10 cm.

[0041] A pulsed water distribution system and a stepped water inlet pipe are respectively arranged at the top and side of the wetland system, and the water distribution volume of the pulsed water distribution system is greater than that of the stepped water inlet pipe.

[0042] Large-sized fillers 11 with a particle size of 5 mm to 8 mm are filled in both the water inlet layer 2 and the drainage layer 4. The drainage layer 4 and the water inlet layer 2 are made of large-sized ceramsite fillers 11 with a particle size of 5 mm to 8 mm to prevent the blockage of the drainage layer and the water inlet layer. The main functional layer 3 of the wetland system is made of small-sized ceramsite fillers 5 with a particle size of 3 mm to 5 mm to increase the specific surface area and carry more biofilms to achieve an efficient water purification effect.

[0043] Wetland plants 14 are arranged on the top of the wetland system. Arranging wetland plants on the top of the wetland system can play an auxiliary purification role.

[0044] The stepped water inlet pipe 6 is arranged below 20 cm of the top of the wetland system and is evenly distributed at intervals of 10 cm on the same vertical axis. A plurality of horizontal water distribution holes are arranged on the water distribution pipe 10, and a plurality of horizontal water distribution holes are arranged on the stepped water inlet pipe 6. The horizontal water distribution holes of two adjacent water distribution pipes 10 are distributed at intervals in the horizontal direction.

[0045] The siphon drain pipe 13 is of an inverted U-shaped structure. The first opening of the siphon drain pipe 13 is communicated with the outlet pipe 7, and the first opening is suspended to a position slightly lower than the outlet pipe 7 by 5 cm, so as to form a pressure difference for periodic siphon drainage. The siphon drain pipe 13 is of an inverted U-shaped structure. One end of the inverted U-shaped structure is communicated with the water outlet of the wetland system, and the other end is suspended to a position slightly lower than the water outlet of the wetland system; the uniform interval distance between the two-way connectors 15 on the siphon drain pipe 13 is 10 cm; the highest two-way connector 15 is 20 cm away from the top of the wetland system, and the lowest two-way connector 15 is 10 cm away from the bottom of the wetland system. The L-shaped air vent pipe 12 can be connected to the siphon drain pipe 13 at any two-way connector 15 through a screw sleeve to control the siphon drainage height, so as to control the ratio of the aerobic zone 9 to the anaerobic zone 8, create a more coordinated redox environment for the wetland system, and thus strengthen the removal of pollutants such as COD and nitrogen in the water body.

[0046] The two-way connector 15 does not coincide with the inverted U-shaped siphon drain pipe 13 in the vertical axis plane, and the L-shaped air vent pipe 12 does not coincide with the inverted U-shaped siphon drain pipe 13 in the vertical axis plane. The two-way connectors 15 are parallel to each other, and the vertical axis plane should not coincide with the inverted U-shaped drain pipe, so that the L-shaped air vent pipe 12 does not coincide with the inverted U-shaped drain pipe. The length of the L-shaped air vent pipe 12 is equal to the height of the wetland system to meet the control requirements of different siphon drainage heights.

[0047] Furthermore, the height of the L-shaped air vent pipe is equal to that of the wetland system.

[0048] Through the cooperation of the water distribution structure, the stepped water inlet pipe 6, the siphon drain pipe 13 and the L-shaped ventilation pipe 12, the present invention realizes intermittent water inlet and periodic drainage. A treatment cycle is defined from the end of one drainage to the end of the next siphon drainage. During one cycle, a part of the water to be treated first enters the wetland system water inlet layer 2 from top to bottom through the water distribution structure, and then enters the main functional layer 3 of the wetland system under the action of gravity. Then, another part of the water to be treated enters the main functional layer 3 of the wetland system through the stepped water inlet pipe and flows upward in the form of plug flow, so that the liquid level of the wetland system is higher than the top of the siphon drain pipe 13, realizing periodic siphon drainage. When the wetland system drains to the height of the bottom of the L-shaped ventilation pipe 12, the siphon is broken, and the next water treatment cycle begins.

[0049] Based on the above intermittent water inlet and periodic siphon drainage process, most of the water to be treated is in the aerobic zone of the wetland system above the bottom height of the L-shaped ventilation pipe 12, where a large amount of COD is consumed and part of the ammonia nitrogen is oxidized to nitrate nitrogen; then part of the water enters the main functional area 3 of the substrate system through the stepped water inlet pipe 6, supplementing the organic carbon source; in the lower anaerobic zone 8, the remaining COD and the supplemented organic carbon source are used as the carbon source for denitrifying bacteria to reduce nitrate, and the nitrate is reduced to nitrogen and discharged from the system.

[0050] The wetland system provided by the present invention overcomes the problems existing in the prior art, such as poor reoxygenation effect, high energy consumption, insufficient carbon source, low removal rates of COD and nitrogen, and organic fouling in traditional and improved constructed wetlands.

[0051] Although the present invention has been described with reference to the preferred embodiments, various modifications can be made to it and components therein can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. Aerobic-anaerobic three-phase pulsed stepped influent wetland system, characterized in that, The wetland system includes a main functional layer (3), a water inlet layer (2) located at the top of the main functional layer (3), a drainage layer (4) located at the bottom of the main functional layer (3), a water inlet pipe (1) connected with a plurality of water distribution pipes (10) located above the water inlet layer (2), a water outlet pipe (7) located in the drainage layer (4), a stepped water inlet pipe (6) evenly distributed in the main functional layer (3), and a siphon drainage pipe (13) communicated with the water outlet pipe (7). An L-shaped ventilation pipe (12) is arranged on the siphon drainage pipe (13). A plurality of two-way joints (15) evenly and parallelly distributed are evenly arranged on the siphon drainage pipe (13). The L-shaped ventilation pipe (12) is communicated with the siphon drainage pipe (13) through one of the two-way joints (15). The horizontal plane where the orifice of the L-shaped ventilation pipe (12) is located divides the main functional layer (3) into an aerobic zone (9) in the upper part and an anaerobic zone (8) in the lower part. One end of the water distribution pipe (10) is connected with the water inlet pipe (1), and the other end is closed. The plurality of water distribution pipes (10) are parallel to each other. The water inlet pipe (1) is connected with a variable-frequency water pump, and the stepped water inlet pipe is connected with a water pump. The highest top of the siphon drainage pipe (13) is lower than the top of the wetland system. Small-sized fillers (5) are filled inside the main functional layer (3), and wetland plants (14) are planted on the water inlet layer (2). A plurality of water distribution pipes (10) arranged at the top of the wetland system and the water inlet pipe (1) connected with the plurality of water distribution pipes (10) form a pulsed water distribution system. The siphon drainage pipe (13) is of an inverted U-shaped structure. The first opening of the siphon drainage pipe (13) is communicated with the water outlet pipe (7), and the first opening is suspended to be lower than the water outlet pipe (7). The interval distance between the two-way joints (15) evenly arranged on the siphon drainage pipe (13) is 10 cm. The highest two-way joint (15) is 20 cm away from the top of the wetland system, and the lowest two-way joint (15) is 10 cm away from the bottom of the wetland system. The two-way joint (15) does not coincide with the inverted U-shaped siphon drainage pipe (13) on the vertical axial plane, and the L-shaped ventilation pipe (12) does not coincide with the inverted U-shaped siphon drainage pipe (13) on the vertical axial plane. The height of the L-shaped ventilation pipe is equal to that of the wetland system.

2. The aerobic-anaerobic three-phase pulsed stepped influent wetland system according to claim 1, characterized in that, The height of the water inlet layer (2) is 5 cm, and the height of the drainage layer (4) is 10 cm.

3. The aerobic-anaerobic three-phase pulsed stepped influent wetland system according to claim 1, wherein, A pulsed water distribution system and a stepped water inlet pipe are respectively arranged at the top and side of the wetland system, and the water distribution volume of the pulsed water distribution system is greater than that of the stepped water inlet pipe.

4. The aerobic-anaerobic three-phase pulsed stepped influent wetland system according to claim 1, characterized in that, Large-sized fillers (11) are filled in both the water inlet layer (2) and the drainage layer (4).

5. The aerobic-anaerobic three-phase pulsed stepped influent wetland system according to claim 1, wherein The stepped water inlet pipe (6) is arranged below 20 cm of the top of the wetland system and is evenly distributed at intervals of 10 cm on the same vertical axis.

6. The aerobic-anaerobic three-phase pulsed stepped influent wetland system according to claim 1, characterized in that, A plurality of horizontal water distribution holes are arranged on the water distribution pipe (10), and a plurality of horizontal water distribution holes are arranged on the stepped water inlet pipe (6). The horizontal water distribution holes of two adjacent water distribution pipes (10) are spaced apart in the horizontal direction.

Images