CN113683263A

CN113683263A - Small watershed non-point source pollution control system

Info

Publication number: CN113683263A
Application number: CN202110993596.XA
Authority: CN
Inventors: 方昊; 崔益斌; 丁程成; 陈捷; 钱进
Original assignee: Nanjing University of Information Science and Technology; Hohai University HHU; Nanjing Institute of Environmental Sciences MEE
Current assignee: Jiangsu Senmai Environmental Protection Technology Group Co ltd
Priority date: 2021-08-27
Filing date: 2021-08-27
Publication date: 2021-11-23
Anticipated expiration: 2041-08-27
Also published as: CN113683263B

Abstract

The invention discloses a small watershed non-point source pollution control system, which comprises a floating platform and a water suction pump, wherein a precipitation filtering area is arranged on the top surface of the floating platform, an aquatic plant area is arranged at the outer ring position of the precipitation filtering area, the water suction pump is used for pumping water in a river to the precipitation filtering area for precipitation filtering, the water after precipitation filtering flows to the aquatic plant area for purification and finally flows back to the river, biological fillers are suspended on the bottom surface of the floating platform, a plurality of telescopic supporting pieces are arranged at the same time, each telescopic supporting piece comprises a fixed seat, a plurality of insertion rods arranged at the bottom of the fixed seat, and a telescopic rod rotatably connected to the top of the fixed seat, each insertion rod is used for being inserted into the bottom of the river, and the telescopic rod is used for being connected with the floating platform. The system can be stably arranged in a river in a small watershed, can reduce impact influence of water flow, can always float in sleep along with water level change, stably plays a role, realizes pollution control through means of precipitation filtration, plant absorption, biological purification, oxygen enrichment and the like, and has a remarkable effect.

Description

Small watershed non-point source pollution control system

Technical Field

The invention relates to the technical field of non-point source pollution treatment, in particular to a small watershed non-point source pollution control system.

Background

Non-point source pollution is also called non-point source pollution, mainly comprises soil silt particles, nutrient substances such as nitrogen and phosphorus, pesticides, various atmospheric particulates and the like, and enters water, soil or atmospheric environment in the modes of surface runoff, soil erosion, farmland drainage and the like. The method has the characteristics of randomness, universality, hysteresis, fuzziness, latency and the like, and increases the difficulty of corresponding research, treatment and management policy making.

Aiming at non-point source pollution of small watershed, the effective control measure is to carry out biological purification by an ecological floating island at present. The floating island is positioned to play a role stably because the flow velocity of water flow of a river in a small watershed is generally high and the water level is changed frequently, and the floating island is directly inserted into the river bottom through the inserted link in a commonly used fixing mode at present, but the inserted link is easily pulled up and loses the fixing effect under the impact of water flow after the floating island is fixed, and the floating island cannot lift along with the water level after the floating island is fixed, so that the control effect is influenced.

Disclosure of Invention

The invention aims to provide a small watershed non-point source pollution control system, which solves the defects of the existing small watershed non-point source pollution control floating island system in the implementation process.

The invention realizes the purpose through the following technical scheme:

the utility model provides a small watershed non-point source pollution control system, includes floating platform and suction pump, floating platform's top surface is equipped with the sediment filtering area, the outer lane position of sediment filtering area is equipped with the aquatic plant district, the suction pump is used for extracting the water in the river to sediment filtering area and deposits the filtration, and the water flows to the aquatic plant district in to purify after the sediment filters, at last backward flow to in the river, floating platform's bottom surface has hung biofilm carrier, is equipped with a plurality of flexible support piece simultaneously, flexible support piece includes the fixing base to and locate a plurality of inserted bars of fixing base bottom to and rotatable connection in the telescopic link at fixing base top, the inserted bar is used for inserting the river bottom, the telescopic link is used for connecting floating platform.

The improved telescopic rod is characterized in that the fixing seat is provided with a plurality of elastic pieces, one end of each elastic piece is connected with the fixing seat, and the other end of each elastic piece is connected with the side wall of the telescopic rod and used for buffering and supporting the telescopic rod.

The improved structure of the water filter is characterized in that the sedimentation filter area consists of a sedimentation tank and a filter tank positioned outside the sedimentation tank, a water body in the sedimentation tank overflows into the filter tank, a composite filter layer is arranged in the filter tank and used for filtering, the composite filter layer consists of a hard filter layer positioned on the upper part and a soft filter layer positioned on the lower part, and a water outlet is formed in the outer side wall of the filter tank.

The floating platform is further improved in that the floating platform is circular, and the sedimentation tank, the filtering tank and the aquatic plant area are arranged on the floating platform from inside to outside in concentric circles.

The further improvement is that a fixed pipe is vertically arranged on the floating platform, a movable pipe is movably arranged in the fixed pipe, the water suction pump is arranged at the bottom end of the movable pipe and communicated with the movable pipe, the top of the fixed pipe is provided with a pulley, the outer part of the fixed pipe is movably provided with a lifting cylinder, the lifting cylinder is connected with the movable tube after bypassing the pulley through a pull rope, the bottom end of the lifting cylinder is made of a magnetic material, and is provided with a through opening, the bottom of the filtering tank is provided with an extrusion plate, the extrusion plate is connected with a transmission piece, the transmission part penetrates through the composite filter layer upwards and then is vertically connected with the wall of the sedimentation tank in a sliding manner, a transmission wheel and a sealing cover are respectively arranged in the sedimentation tank through a vertical rod, one side of the driving wheel is meshed with the driving part, the other side of the driving wheel is meshed with the outer wall of the lifting cylinder, the sealing cover is made of a magnetic material, and the sealing cover extends into the lifting cylinder and corresponds to the vertical position of the through hole;

the pulling force of the water suction pump and the movable pipe on the pull rope is greater than the pulling force of the lifting cylinder on the pull rope, the lifting cylinder gradually rises under the action of the difference of the pulling force, so that the position of a through hole is blocked and sucked by the sealing cover, at the moment, the water body sucked by the water suction pump is conveyed by the movable pipe and the fixed pipe to fall into the lifting cylinder for storage, when the water storage in the lifting cylinder is higher than the maximum critical amount, the lifting cylinder is separated from the sealing cover and falls, the lifting cylinder falls to drive the driving wheel to rotate, and further drive the driving part and the extrusion plate to rise, the extrusion plate extrudes the composite filter layer above, so that the water body remained in the soft filter layer flows upwards, thereby playing a role in back-flushing and cleaning on the hard filter layer, the through hole position is opened in the falling process of the lifting cylinder, the water body in the lifting cylinder is discharged, when the water storage in the lifting cylinder is lower than the minimum critical amount, the pulling force of the water suction pump and the pull rope by the movable pipe is greater than the lifting cylinder on the pull rope, the lifting cylinder is pulled to gradually rise after being decelerated and stopped, meanwhile, the extrusion plate is driven to recover to the bottom position, and then the process is repeated, so that the composite filter layer is periodically back-flushed and cleaned.

The further improvement is that the top end of the fixed tube is provided with an outward turning edge.

The improved structure is characterized in that the through opening and the sealing cover are correspondingly provided with a plurality of parts, and the driving wheel and the transmission part are correspondingly provided with a plurality of parts.

The further improvement lies in that the vertical rod for installing the sealing cover extends into the lifting cylinder from the through opening, the size of the sealing cover is larger than that of the through opening, and a sealing rubber layer is arranged on the bottom surface of the sealing cover.

The further improvement lies in that when the lifting cylinder falls to the lowest position, the bottom end of the lifting cylinder is higher than the water level in the sedimentation tank.

The invention has the beneficial effects that:

(1) the system can be stably arranged in a river in a small watershed, can reduce impact influence of water flow, can always float in sleep along with water level change, stably plays a role, realizes pollution control through means of precipitation filtration, plant absorption, biological purification, oxygen enrichment and the like, and has a remarkable effect.

(2) When the system filters water, the back flushing cleaning of the filter layer can be automatically carried out at certain intervals, so that impurity particles are prevented from blocking the filter layer, the long-term effectiveness of the system is ensured, the back flushing cleaning process only utilizes the gravity action of components in the system and the water, a power source is not required to be additionally provided, and the effects of saving energy and simplifying control are achieved.

Drawings

FIG. 1 is a schematic cross-sectional view of the elevator shaft of the present invention at the highest position;

FIG. 2 is an enlarged view of portion A of FIG. 1;

FIG. 3 is a schematic cross-sectional view of the elevator shaft of the present invention at the lowest point;

FIG. 4 is a top view of the present invention;

in the figure: 1. a floating platform; 2. a water suction pump; 3. an aquatic plant area; 4. biological fillers; 5. a fixed seat; 6. inserting a rod; 7. a telescopic rod; 8. an elastic member; 9. a sedimentation tank; 10. a filtration tank; 11. a hard filter layer; 12. a soft filter layer; 13. a water outlet; 14. a fixed tube; 15. a movable tube; 16. a pulley; 17. a lifting cylinder; 18. pulling a rope; 19. a port; 20. a pressing plate; 21. a transmission member; 22. a vertical rod; 23. a driving wheel; 24. a sealing cover; 25. and (5) turning the edges outwards.

Detailed Description

The present application will now be described in further detail with reference to the drawings, it should be noted that the following detailed description is given for illustrative purposes only and is not to be construed as limiting the scope of the present application, as those skilled in the art will be able to make numerous insubstantial modifications and adaptations to the present application based on the above disclosure.

Referring to fig. 1 to 4, a small watershed non-point source pollution control system comprises a floating platform 1 and a water suction pump 2, wherein a sedimentation filtering area is arranged on the top surface of the floating platform 1, the sedimentation filtering area is composed of a sedimentation tank 9 and a filtering tank 10 positioned outside the sedimentation tank 9, a water body in the sedimentation tank 9 overflows into the filtering tank 10, an aquatic plant area 3 is arranged at the outer ring position of the sedimentation filtering area, the water suction pump 2 is used for pumping the water body in a river to the sedimentation filtering area for sedimentation filtering, the water body flows into the aquatic plant area 3 for purification after sedimentation filtering, and finally flows back into the river, biological fillers 4 are suspended on the bottom surface of the floating platform 1, and a plurality of telescopic supports are arranged simultaneously, each telescopic support comprises a fixed seat 5, a plurality of inserted rods 6 arranged at the bottom of the fixed seat 5, and a telescopic rod 7 rotatably connected to the top of the fixed seat 5, the inserted rods 6 are used for being inserted into the bottom of the river, the telescopic rod 7 is used for connecting the floating platform 1.

In the process of water body suction and backflow, the effect of increasing the dissolved concentration of oxygen can be achieved; the biological filler 4 extends into the water body to purify the water body by microorganisms, and the root system and the leaves and the stems of the aquatic plant region 3 can be used for purifying the water body and simultaneously can increase the aesthetic property.

In the invention, the fixed seat 5 is provided with a plurality of elastic pieces 8, one end of each elastic piece 8 is connected with the fixed seat 5, and the other end of each elastic piece 8 is connected with the side wall of the telescopic rod 7 and is used for buffering and supporting the telescopic rod 7. When meetting rivers and assaulting, rivers can drive telescopic link 7 to rotate to the impact force of flotation platform 1 and telescopic link 7, compression elastic component 8, thereby played the cushioning effect, make the impact force reduce the influence of inserted bar 6 inserted position, can effectively avoid inserted bar 6 to extract the phenomenon, in addition, when the water level changes, the automatic flexible regulation of accessible telescopic link 7 makes flotation platform 1 be the surface of water floating state all the time, guarantee the long-term steady operation of system.

In the invention, a composite filter layer is arranged in the filtering tank 10 for filtering, the composite filter layer is composed of a hard filter layer 11 positioned at the upper part and a soft filter layer 12 positioned at the lower part, and a water outlet 13 is arranged on the outer side wall of the filtering tank 10. The hard filter layer 11 may be a metal filter net, such as a stainless steel wire net, or an inorganic fiber filter layer, which is not easily compressed and deformed. The soft filter layer 12 may be made of sponge material, has soft property, can store a certain amount of water, and can be compressed. The composite filter layer consisting of the hard filter layer 11 and the soft filter layer 12 has good filtering effect and cannot collapse and deform due to the accumulation of a large amount of impurities on the top.

In the invention, the floating platform 1 is circular, and the sedimentation tank 9, the filtering tank 10 and the aquatic plant area 3 are concentrically arranged on the floating platform 1 from inside to outside. Namely, the sedimentation tank 9 is circular, and the filtering tank 10 and the aquatic plant area 3 are circular, so that the whole structure is compact and attractive, and the requirement of a water body flowing path is met. Of course, the floating platform 1 may be designed in other configurations.

In the operation process, the sedimentation tank 9 is used for depositing larger granule impurity particles or rubbish, and the filtering tank 10 then filters less impurity particles, because tiny impurity is more in the polluted water body, causes compound filter layer to block up easily, especially silt blocks up the 11 meshes of stereoplasm filtering layer on top surface, directly can cause the unable infiltration of large tracts of land wire side to filter. It is therefore necessary to clean the filter screens once in a short time, which is obviously cumbersome.

Therefore, the corresponding structure of the filtering process is further optimized, and the method specifically comprises the following steps: a fixed pipe 14 is vertically arranged on the floating platform 1, a movable pipe 15 is movably arranged in the fixed pipe 14, the fixed pipe 14 and the movable pipe 15 can slide relatively, meanwhile, the sliding surface keeps better water tightness, a water suction pump 2 is arranged at the bottom end of the movable pipe 15 and is communicated with the movable pipe 15, a pulley 16 is arranged at the top of the fixed pipe 14, a lifting cylinder 17 is movably arranged outside the fixed pipe 14, the lifting cylinder 17 is connected with the movable pipe 15 after bypassing the pulley 16 through a pull rope 18, so that the linkage between the lifting cylinder 17 and the movable pipe 15 is realized, the bottom end of the lifting cylinder 17 is made of a hydrophilic material, such as iron and alloy thereof, nickel and alloy thereof, and is provided with a through hole 19, an extrusion plate 20 is arranged at the bottom of the filter tank 10, a transmission piece 21 is connected on the extrusion plate 20, the transmission piece 21 vertically slides and is connected with the tank wall of the sedimentation tank 9 after upwards passing through a composite filter layer, a transmission wheel 23 and a sealing cover 24 are respectively arranged in the sedimentation tank 9 through a vertical rod 22, one side of the driving wheel 23 is meshed with the driving piece 21 (provided with a corresponding rack), the other side of the driving wheel is meshed with the outer wall of the lifting cylinder 17 (provided with a corresponding rack), the sealing cover 24 is made of magnetic materials, such as neodymium iron boron magnet, samarium cobalt magnet and the like, and the sealing cover 24 extends into the lifting cylinder 17 and corresponds to the vertical position of the through hole 19;

when water body filtration is carried out, the pulling force of the water suction pump 2 and the movable pipe 15 to the pulling rope 18 (after water body buoyancy is overcome) is greater than the pulling force of the lifting cylinder 17 to the pulling rope 18, so that if no water body is stored in the lifting cylinder 17, the lifting cylinder 17 can gradually rise under the action of a pulling force difference, in the rising process, the water body sucked by the water suction pump 2 is conveyed by the movable pipe 15 and the fixed pipe 14, but is directly discharged into the sedimentation tank 9 through the through opening 19 until the water body continues to rise, so that the position of the through opening 19 is blocked and sucked by the sealing cover 24, at the moment, the water body sucked by the water suction pump 2 is conveyed by the movable pipe 15 and the fixed pipe 14 to fall into the lifting cylinder 17 for storage, and the state is shown in fig. 1; when the water storage in the lifting cylinder 17 is higher than the maximum critical amount, the lifting cylinder 17 and the sealing cover 24 are separated instantly and fall rapidly, the lifting cylinder 17 falls to drive the driving wheel 23 to rotate, thereby driving the transmission member 21 and the extrusion plate 20 to rise, the extrusion plate 20 extrudes the upper composite filter layer, so that the water body remained in the soft filter layer 12 flows upwards, thereby playing a role in back flushing and cleaning the hard filter layer 11, opening 19 is opened when the lifting cylinder 17 falls down, the water in the lifting cylinder 17 is discharged, and the state is shown in figure 3, when the internal water storage body of the lifting cylinder 17 is lower than the minimum critical amount, the pulling force of the water suction pump 2 and the movable pipe 15 to the pulling rope 18 is larger than the pulling force of the lifting cylinder 17 to the pulling rope 18, the lifting cylinder 17 is pulled to gradually rise after being decelerated and stopped, meanwhile, the extrusion plate 20 is driven to recover to the bottom position, and then the process is repeated, so that the composite filter layer is periodically back-flushed and cleaned.

In addition, in the periodic back flushing cleaning process of the composite filter layer, the water suction pump 2 can move up and down along with the periodic back flushing cleaning process, so that water bodies with different depths can be sucked, and the efficiency and the effect of comprehensive control are improved.

In order to satisfy the above-mentioned tension requirement for the pulling rope 18, it is necessary to adjust the weight of the structure during construction. For example, in order to satisfy that the pulling force of the water suction pump 2 and the movable pipe 15 to the pulling rope 18 (after overcoming the buoyancy of the water body) is greater than the pulling force of the lifting cylinder 17 itself to the pulling rope 18, the counterweight adjustment can be performed on the water suction pump 2 and the lifting cylinder 17, and the specific adjustment mode is selected at will. In addition, neglecting the friction resistance factor, the above-mentioned maximum critical amount refers to the amount of the stored water body when the total weight of the lifting cylinder 17 and the stored water body is equal to the sum of the attraction force of the sealing cover 24 to the lifting cylinder 17, the pulling force of the suction pump 2 and the movable pipe 15 to the pulling rope 18, and the gravity of the transmission member 21 and the extrusion plate 20; the minimum critical amount refers to the amount of the stored water body when the total weight of the lifting cylinder 17 and the stored water body is equal to the sum of the pulling force of the water suction pump 2 and the movable pipe 15 on the pulling rope 18, the gravity of the transmission member 21 and the extrusion plate 20, and the rebounding force of the soft filter layer 12.

In the invention, the top end of the fixed pipe 14 is formed with the outward turning edge 25, and the edge of the outward turning edge 25 is positioned above the lifting cylinder 17, thus being beneficial to the falling and collection of the water body.

In the present invention, there are several corresponding openings 19 and sealing covers 24, for example, four openings may be shown in fig. 4, and several corresponding transmission wheels 23 and transmission members 21 may be shown in fig. 4, for example, four openings may be shown. In addition, the vertical rod 22 provided with the sealing cover 24 extends into the lifting cylinder 17 from the through hole 19, the size of the sealing cover 24 is larger than that of the through hole 19, the sealing cover 24 can be aligned with the through hole 19 and forms a barrier in the lifting process of the lifting cylinder 17, sealing is completed, the lifting cylinder 17 is prevented from continuously lifting, and a sealing rubber layer is arranged on the bottom surface of the sealing cover 24, so that sealing performance is improved.

In the present invention, when the lifting cylinder 17 falls to the lowest position, i.e. the position shown in fig. 3, the height of the bottom end of the lifting cylinder 17 is still higher than the height of the water level in the sedimentation tank 9, so that the influence of the water in the sedimentation tank 9 on the sufficient falling of the lifting cylinder 17 can be avoided.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A small watershed non-point source pollution control system comprises a floating platform (1) and a water suction pump (2), and is characterized in that a precipitation filtering area is arranged on the top surface of the floating platform (1), an aquatic plant area (3) is arranged at the outer ring position of the precipitation filtering area, the water suction pump (2) is used for pumping water in a river to the precipitation filtering area for precipitation filtering, the water flows into the aquatic plant area (3) for purification after precipitation filtering, and finally flows back to the river, biological fillers (4) are suspended on the bottom surface of the floating platform (1), a plurality of telescopic support members are arranged at the same time, each telescopic support member comprises a fixed seat (5), a plurality of insertion rods (6) arranged at the bottom of the fixed seat (5), and telescopic rods (7) rotatably connected to the top of the fixed seat (5), and the insertion rods (6) are used for being inserted into the bottom of the river, the telescopic rod (7) is used for connecting the floating platform (1).

2. The small watershed non-point source pollution control system according to claim 1, wherein the fixing base (5) is provided with a plurality of elastic members (8), one end of each elastic member (8) is connected with the fixing base (5), and the other end of each elastic member is connected with the side wall of the telescopic rod (7) and used for buffering and supporting the telescopic rod (7).

3. The small watershed non-point source pollution control system according to claim 1, wherein the sedimentation filter zone comprises a sedimentation tank (9) and a filter tank (10) located outside the sedimentation tank (9), a water body in the sedimentation tank (9) overflows into the filter tank (10), a composite filter layer is arranged inside the filter tank (10) for filtering, the composite filter layer comprises a hard filter layer (11) located at the upper part and a soft filter layer (12) located at the lower part, and a water outlet (13) is formed in the outer side wall of the filter tank (10).

4. A small watershed non-point source pollution control system according to claim 3, characterized in that the floating platform (1) is circular, and the sedimentation tank (9), the filtration tank (10) and the aquatic plant area (3) are arranged on the floating platform (1) from inside to outside in concentric circles.

5. The small watershed non-point source pollution control system according to claim 3, wherein a fixed pipe (14) is vertically arranged on the floating platform (1), a movable pipe (15) is movably arranged in the fixed pipe (14), the water suction pump (2) is installed at the bottom end of the movable pipe (15) and communicated with the movable pipe (15), a pulley (16) is arranged at the top of the fixed pipe (14), a lifting cylinder (17) is movably arranged outside the fixed pipe (14), the lifting cylinder (17) bypasses the pulley (16) through a pull rope (18) and then is connected with the movable pipe (15), the bottom end of the lifting cylinder (17) is made of a hydrophilic material and is provided with a through hole (19), a squeezing plate (20) is arranged at the bottom of the filter tank (10), a transmission member (21) is connected onto the squeezing plate (20), and the transmission member (21) passes through the composite filter layer upwards and then is connected with the wall of the sedimentation tank (9) in a vertical sliding manner, a driving wheel (23) and a sealing cover (24) are respectively installed in the sedimentation tank (9) through a vertical rod (22), one side of the driving wheel (23) is meshed with the driving piece (21), the other side of the driving wheel is meshed with the outer wall of the lifting cylinder (17), the sealing cover (24) is made of a magnetic material, and the sealing cover (24) extends into the lifting cylinder (17) and corresponds to the vertical position of the through hole (19);

the pulling force of the water suction pump (2) and the movable pipe (15) to the pulling rope (18) is larger than the pulling force of the lifting cylinder (17) to the pulling rope (18), the lifting cylinder (17) gradually rises under the action of the pulling force difference, so that the position of the through hole (19) is blocked and sucked by the sealing cover (24), at the moment, the water body sucked by the water suction pump (2) is conveyed by the movable pipe (15) and the fixed pipe (14) to fall into the lifting cylinder (17) for storage, when the stored water body in the lifting cylinder (17) is higher than the maximum critical amount, the lifting cylinder (17) and the sealing cover (24) are separated and fall, the lifting cylinder (17) falls to drive the driving wheel (23) to rotate, and then the driving piece (21) and the extrusion plate (20) are driven to rise, the extrusion plate (20) extrudes the upper composite filter layer, so that the water body reserved in the soft filter layer (12) flows upwards, and the hard filter layer (11) is backflushed and cleaned, opening (19) position is opened in the whereabouts in-process of a lift section of thick bamboo (17), and the water in a lift section of thick bamboo (17) is discharged, when a lift section of thick bamboo (17) memory water storage body is less than minimum critical volume, the pulling force of water sucking pump (2) and movable tube (15) to stay cord (18) is greater than a lift section of thick bamboo (17) to the pulling force of stay cord (18), is pulled after a lift section of thick bamboo (17) slows down and stops and is risen gradually, drives stripper plate (20) to resume to the bottom position simultaneously, then repeats above-mentioned process, makes compound filter layer obtain periodic recoil clearance.

6. A small watershed area-source pollution control system according to claim 5, wherein the top end of the fixed pipe (14) is formed with an upturned edge (25).

7. A small-area non-point source pollution control system according to claim 5, wherein there are a plurality of said ports (19) and said sealing caps (24), and a plurality of said driving wheels (23) and said driving members (21).

8. A small watershed non-point source pollution control system as claimed in claim 5, characterized in that the vertical rod (22) for installing the sealing cover (24) extends into the lifting cylinder (17) from the through hole (19), the size of the sealing cover (24) is larger than that of the through hole (19), and a sealing rubber layer is arranged on the bottom surface of the sealing cover (24).

9. The small watershed non-point source pollution control system as claimed in claim 5, wherein when the lifting cylinder (17) falls to the lowest position, the height of the bottom end of the lifting cylinder (17) is higher than the height of the water level in the sedimentation tank (9).