Wastewater treatment system for unstable influent

Abstract

The present application relates to sewage treatment system for unstable inflow, including regulating pool, intermediate control pool, biochemical treatment unit and post-treatment unit connected in sequence, and the unstable inflow sewage enters the regulating pool for homogeneous regulation; the intermediate control pool includes overflow area, water inlet area and water outlet area arranged in sequence, the water outlet pipe of the regulating pool is connected with the water inlet area, the bottom of the downstream side of the water inlet area is connected with the water outlet area, the overflow plate is arranged between the upstream side of the water inlet area and the overflow area, and the water outlet pipe of the overflow area is connected with the regulating pool for flow control of the water outlet of the regulating pool; the biochemical treatment unit includes anaerobic pool, primary anoxic pool, primary aerobic pool, secondary anoxic pool and secondary aerobic pool connected in sequence for biochemical treatment of the water outlet of the regulating pool; and the post-treatment unit includes sedimentation tank for mud-water separation of the water body after biochemical treatment to obtain product water.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a sewage treatment system for unstable inflow. BACKGROUND

[0002] In sewage treatment, unstable inflow includes two main factors of unstable inflow quantity and unstable inflow quality, for example, the problem of unstable inflow is common in rural sewage treatment. The unstable inflow quantity includes great changes in inflow quantity at different time of day and great fluctuations in inflow quantity in four seasons of a year, especially when it rains, rainwater often enters the pipe network, causing great changes in water quantity and water quality. The unstable inflow quality is due to the small population in rural areas, and the water quality at different time of day changes greatly, and at the same time, in summer, groundwater or rainwater often flows into the pipe network, also causing fluctuations in water quality.

[0003] The above unstable inflow brings difficulties to traditional sewage treatment equipment, and often causes adverse results such as out-of-standard effluent quality and loss of microorganisms in the system. SUMMARY

[0004] In view of the above problems, the application provides a sewage treatment system for unstable inflow, which comprises a regulating tank, an intermediate control tank, a biochemical treatment unit and a post-treatment unit connected in sequence, and the unstable inflow sewage enters the regulating tank for homogeneous regulation; the intermediate control tank comprises an overflow area, an inflow area and an outflow area arranged in sequence, the outflow pipe of the regulating tank is connected to the inflow area, the bottom of the downstream side of the inflow area is connected to the outflow area, an overflow plate is arranged between the upstream side of the inflow area and the overflow area, and the outflow pipe of the overflow area is connected to the regulating tank, for flow control of the outflow of the regulating tank.

[0005] The biochemical treatment unit comprises an anaerobic tank, a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank and a secondary aerobic tank connected in sequence, for biochemical treatment of the outflow of the regulating tank; and the post-treatment unit comprises a sedimentation tank, for mud-water separation of the water body after biochemical treatment, to obtain product water.

[0006] Optionally, the upstream side of the inflow area is provided with an overflow plate, and the downstream side is provided with an outflow hole plate, the top end of the overflow plate is lower than the top end of the outflow hole plate, and if the water quantity in the inflow area is too large, the water overflows through the overflow plate into the overflow area and returns to the regulating tank.

[0007] The lower part of the outflow hole plate is uniformly provided with a plurality of outflow holes for connecting the inflow area and the outflow area.

[0008] Optionally, a nitrification liquid reflux pipe is connected between the secondary aerobic tank and the primary anoxic tank, for refluxing the nitrification liquid of the aerobic tank to the anoxic tank; a sludge reflux pipe is connected between the sedimentation tank and the anaerobic tank, for returning part of the sludge obtained by sedimentation to the anaerobic tank to supplement the sludge quantity.

[0009] Optionally, a middle part of the anaerobic tank is provided with a flow guide mixing device, a lower part of the flow guide mixing device is connected with a water outlet pipe of the water outlet area, and a top part of the flow guide mixing device is connected with an outlet of the sludge return pipe, so as to mix the water inlet of the anaerobic tank with the returned sludge uniformly; a stirring device is arranged on an upstream side of the anaerobic tank, so as to continuously mix the sludge-water mixture flowing out of the flow guide mixing device with the water body in the anaerobic tank, and promote the anaerobic biochemical treatment.

[0010] Further optionally, the flow guide mixing device comprises a flow guide cylinder, a first stirring part and a second stirring part inside the flow guide cylinder, the water pipe of the water outlet area connected with the anaerobic tank is connected with a bottom part of the flow guide cylinder, and the outlet of the sludge return pipe is connected with a top part of the flow guide cylinder; the stirring paddle of the first stirring part is a continuous single helix stirring blade, which can continuously transport the sludge transported by the sludge return pipe downward in the flow guide cylinder;

[0011] A gas separation part and a second stirring part are sequentially arranged below the first stirring part, the sewage input into the bottom part of the flow guide cylinder is agitated by the second stirring part, so that the flow rate is increased, part of the oxygen-containing gas is separated out by the gas separation part, and then the water body continues to mix with the sludge upwardly;

[0012] The side wall of the flow guide cylinder is provided with an outflow port for outputting the mixed sewage and sludge.

[0013] Further optionally, the gas separation part comprises a conical separation cover and an exhaust pipe, the separation cover is small at the top and large at the bottom, and is in a conical shape, the separation cover is arranged concentrically with the flow guide cylinder, and a gap is formed between the bottom edge of the separation cover and the inner wall of the flow guide cylinder, so as to allow the sewage in the flow guide cylinder to pass through the separation cover;

[0014] The top part of the separation cover is connected with at least two exhaust pipes, the exhaust pipes pass out of the flow guide cylinder, extend along the outer wall of the flow guide cylinder to above the liquid surface of the anaerobic tank, and discharge the gas separated by the separation cover, and the exhaust pipes can be connected with the position for fixing the separation cover.

[0015] Further optionally, an expansion part is arranged between the gas separation part and the second stirring part, a diameter of the part of the flow guide cylinder corresponding to the expansion part is greater than the diameters of other parts of the flow guide cylinder, so that the inside of the expansion part expands outwardly;

[0016] The ratio of the inner diameter of the non-expansion part of the flow guide cylinder to the inner diameter of the expansion part is 1:(1.5-2), and the height of the expansion part accounts for 50-75% of the height of the part of the flow guide cylinder between the gas separation part and the second stirring part.

[0017] Optionally, a stirring device is arranged between the upstream side of the anaerobic tank and the flow guide cylinder, a stirring shaft of the stirring device is arranged vertically and the top part of the stirring shaft is connected with a third motor above the anaerobic tank, a plurality of mixing stirring pieces are arranged on the stirring shaft corresponding to the position of the outflow port, and the plurality of mixing stirring pieces are arranged uniformly along the circumferential direction of the stirring shaft;

[0018] The mixing stirring piece is a semispherical shape recessed towards the stirring shaft direction and hollow, the opening of the mixing stirring piece is a circular surface vertically through the ball center, and the opening of the mixing stirring piece faces away from the stirring shaft direction; the outflow port is between the highest point of the opening of the mixing stirring piece and the ball center.

[0019] Optionally, the outlet of the nitrification liquid reflux pipe is provided with a reducing pipe, the pipe diameter of the reducing pipe gradually decreases from top to bottom, the reducing pipe is inclined and inclined towards the downstream side of the first anoxic tank, and the reducing pipe is located at the bottom of the first anoxic tank.

[0020] The bottom of the downstream side of the first anoxic tank is provided with an inclined plate, which is beneficial to change the flow direction of the water body with pressure output by the reducing pipe, drive the water in the first anoxic tank to form a rotating state, and promote the contact between the sludge and the sewage.

[0021] Optionally, the post-processing unit comprises a first sedimentation tank, a coagulation tank and a second sedimentation tank connected in sequence, the bottom of the first sedimentation tank is provided with a gas stripping device, the gas stripping device is connected with the sludge reflux pipe, and the top of the second sedimentation tank discharges produced water. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a sewage treatment system for unstable influent;

[0023] Figure 2 It is a schematic diagram of a flow guide mixing device;

[0024] Figure 3 It is a schematic diagram of a stirring device in an anaerobic tank;

[0025] Figure 4 It is a schematic diagram of another flow guide mixing device of embodiment 1.

[0026] In the drawings, 1 is a regulating tank, 2 is an intermediate control tank, 3 is an overflow area, 4 is an influent area, 5 is an effluent area, 6 is an anaerobic tank, 7 is a first anoxic tank, 8 is a first aerobic tank, 9 is a second anoxic tank, 10 is a second aerobic tank, 11 is an effluent orifice plate, 12 is a nitrification liquid reflux pipe, 13 is a sludge reflux pipe, 14 is a flow guide cylinder, 15 is a first stirring part, 16 is a second stirring part, 17 is an outflow port, 18 is a separation cover, 19 is an exhaust pipe, 20 is a stirring shaft, 21 is a mixing stirring piece, 22 is an opening, 23 is a fourth motor, 24 is a connecting shaft, 25 is a reducing pipe, 26 is an inclined plate, 27 is a first aeration device, 28 is a second aeration device, 29 is a pre-sedimentation tank, 30 is a first sedimentation tank, 31 is a coagulation tank, 32 is a second sedimentation tank, and 33 is an expansion part. DETAILED DESCRIPTION

[0027] The embodiment provides a sewage treatment system for unstable influent, which comprises a regulating tank, an intermediate control tank, an anaerobic tank, a first anoxic tank, a first aerobic tank, a second anoxic tank, a second aerobic tank, an effluent orifice plate, a nitrification liquid reflux pipe, a sludge reflux pipe, a flow guide cylinder, a first stirring part, a second stirring part, an outflow port, a separation cover, an exhaust pipe, a stirring shaft, a mixing stirring piece, a fourth motor, a connecting shaft, a reducing pipe, an inclined plate, a first aeration device, a second aeration device, a pre-sedimentation tank, a first sedimentation tank, a coagulation tank, a second sedimentation tank, and an expansion part. Figures 1-3As shown, it comprises a regulating tank 1, an intermediate regulating tank 2, a biochemical treatment unit and a post-treatment unit connected in sequence, and the unstable raw sewage is homogenously regulated in the regulating tank 1; the intermediate regulating tank 2 comprises an overflow area 3, an inlet area 4 and an outlet area 5 arranged in sequence, the outlet pipe of the regulating tank 1 is connected to the inlet area 4, the bottom of the downstream side of the inlet area 4 is connected to the outlet area 5, an overflow plate is arranged between the upstream side of the inlet area 4 and the overflow area 3, and the outlet pipe of the overflow area 3 is connected to the regulating tank 1 for flow control of the outlet water of the regulating tank 1;

[0028] The biochemical treatment unit comprises an anaerobic tank 6, a primary anoxic tank 7, a primary aerobic tank 8, a secondary anoxic tank 9 and a secondary aerobic tank 10 connected in sequence for biochemical treatment of the outlet water of the regulating tank 1; and the post-treatment unit comprises a sedimentation tank for mud-water separation of the water body after biochemical treatment to obtain product water.

[0029] Optionally, a circulating stirrer and a sewage lifting pump are arranged in the regulating tank 1, the sewage lifting pump is connected to the outlet pipe of the regulating tank 1 and further connected to the inlet area 4 of the intermediate regulating tank 2.

[0030] If the unstable raw sewage is directly subjected to biochemical treatment, it will cause impact on the biochemical system, the treatment effect is poor when the water quantity is large, and the energy is wasted when the water quantity is small. The unstable raw sewage is buffered, mixed and homogenized in the regulating tank 1. The impeller of the circulating stirrer rotates horizontally to drive the raw sewage to flow downward rapidly, scour the bottom of the regulating tank 1 to prevent sludge deposition, and form a circulating stirring to homogenize the raw sewage.

[0031] Optionally, an overflow plate is arranged on the upstream side of the inlet area 4, and a water outlet hole plate 11 is arranged on the downstream side, the top end of the overflow plate is lower than the top end of the water outlet hole plate 11, and if the water quantity in the inlet area 4 is too large, the water will overflow through the overflow plate into the overflow area 3 and then return to the regulating tank 1.

[0032] The lower part of the water outlet hole plate 11 is uniformly provided with a plurality of water outlet holes for connecting the inlet area 4 and the outlet area 5.

[0033] The intermediate regulating tank 2 is used for controlling the quantity of the raw sewage entering the subsequent biochemical treatment unit. The overflow plate and the water outlet hole plate 11 divide the intermediate regulating tank 2 into three areas in sequence, i.e. the overflow area 3, the inlet area 4 and the outlet area 5. The raw sewage delivered by the sewage lifting pump first enters the inlet area 4 for buffering, then flows to the outlet area 5 through the water outlet holes on the water outlet hole plate 11, and then enters the anaerobic tank 6.

[0034] The diameter of the water outlet hole is 10-20 mm, and the number and diameter of the water outlet hole are determined according to the average water inflow. The pressure of the water outlet hole is from the difference between the liquid level of the inlet area 4 and the liquid level of the water outlet hole position, and the number, diameter and liquid level difference of the water outlet hole can be calculated according to the average water inflow. The overflow plate discharges the excess raw sewage in the inlet area 4 to the overflow area 3 and then returns to the regulating tank 1 in time.

[0035] Optionally, the secondary aerobic tank 10 is connected with the primary anoxic tank 7 through a nitrification liquid reflux pipe 12 for refluxing nitrification liquid from the aerobic tank to the anoxic tank; the sedimentation tank is connected with the anaerobic tank 6 through a sludge reflux pipe 13 for returning part of the sludge obtained through sedimentation to the anaerobic tank 6 to supplement the sludge amount.

[0036] Optionally, a middle part of the anaerobic tank 6 is provided with a flow guide mixing device, the lower part of the flow guide mixing device is connected with the water outlet pipe of the water outlet area 5, and the top part is connected with the outlet of the sludge reflux pipe 13, for mixing the water inflow of the anaerobic tank 6 with the refluxed sludge uniformly; the upstream side of the anaerobic tank 6 is provided with a stirring device for continuously mixing the sludge-water mixture output by the flow guide mixing device with the water body in the anaerobic tank 6 to promote the anaerobic biochemical treatment;

[0037] The top part of the downstream side of the anaerobic tank 6 is provided with a first connecting pipe for connecting the bottom part of the upstream side of the primary anoxic tank 7 to input the water body treated by the anaerobic tank 6 into the primary anoxic tank 7.

[0038] Further optionally, the flow guide mixing device comprises a flow guide cylinder 14, a first stirring part 15 and a second stirring part 16 inside the flow guide cylinder 14, the water pipe connecting the anaerobic tank 6 is connected with the bottom part of the flow guide cylinder 14, and the outlet of the sludge reflux pipe 13 is connected with the top part of the flow guide cylinder 14; the stirring paddle of the first stirring part 15 is a continuous single helix stirring blade, which can continuously transport the sludge transported by the sludge reflux pipe 13 downward in the flow guide cylinder 14;

[0039] The first stirring part 15 is sequentially provided with a gas separation part and a second stirring part 16 below, the sewage input into the bottom part of the flow guide cylinder 14 is agitated by the second stirring part 16, the flow rate is increased, part of the oxygen-containing gas is separated out through the gas separation part, and then the water body continues to mix with the sludge upwardly;

[0040] The side wall of the flow guide cylinder 14 is provided with an outflow port 17 for outputting the mixed sewage and sludge.

[0041] Further optionally, the flow guide cylinder 14 is in a whole cylindrical shape, the top part of the flow guide cylinder 14 is open and higher than the liquid surface of the anaerobic tank 6, the sludge reflux pipe 13 is used for inputting the refluxed sludge into the top part of the flow guide cylinder 14, and the bottom part of the flow guide cylinder 14 is located at the bottom part of the anaerobic tank 6;

[0042] The top part of the rotating shaft of the first stirring part 15 protrudes upwardly above the liquid surface of the anaerobic tank 6 and is connected with a first motor above the anaerobic tank 6 for driving the first stirring part 15 to rotate; the bottom part of the rotating shaft of the second stirring part 16 is connected downwardly with a second motor, and the second motor is arranged at the bottom part of the flow guide cylinder 14 for driving the second stirring part 16 to rotate.

[0043] Further, the gas separation part comprises a conical separation cover 18 and exhaust pipes 19. The separation cover 18 is conical, with the small end on top and the large end on the bottom. The separation cover 18 is concentric with the flow guide cylinder 14, and there is a gap between the bottom edge of the separation cover 18 and the inner wall of the flow guide cylinder 14, allowing the sewage in the flow guide cylinder 14 to pass through the separation cover 18.

[0044] The top of the separation cover 18 is connected to at least two exhaust pipes 19, which extend out of the flow guide cylinder 14 and along the outer wall of the flow guide cylinder to above the liquid surface of the anaerobic tank 6, to exhaust the gas separated by the separation cover 18. The exhaust pipes 19 can be connected to the position of the separation cover 18 to fix it.

[0045] Preferably, each exhaust pipe 19 is symmetrically installed with the center of the separation cover 18 as the center, which not only balances the distribution of exhaust, but also facilitates the stable installation of the separation cover 18.

[0046] Further, the second stirring part 16 comprises a plurality of uniformly distributed stirring blades, forming a conventional impeller. The impeller is horizontally arranged as a whole, providing stirring power for the sewage input from below.

[0047] The sewage from the effluent zone 5 is input into the bottom of the flow guide cylinder 14. Under the agitation of the second stirring part 16, the sewage flows upward. After passing through the second stirring part 16, the water flow speed increases and flows upward in a spiral. Under the condition of large flow speed and spiral agitation, it is beneficial to the discharge of gas in the sewage (which contains oxygen, which is not conducive to the biochemical reaction of the anaerobic tank 6). When the sewage reaches the separation cover 18, the separation cover 18 performs gas-liquid separation. The separated liquid continues to flow upward from the edge of the separation cover 18, and the separated gas is exhausted from the anaerobic tank 6 through the exhaust pipes 19. The water body rushing into the separation cover 18 is in a rotating upward shape, and the separation cover 18 is also a downward-opening conical shape, which is conducive to the continued rotation of the rising water body in the separation cover 18 and the gas-liquid separation. The separated gas also maintains a rotating shape, and the exhaust pipes 19 in each direction facilitate the intake of gas and the rapid exhaust of gas.

[0048] The sewage passing through the separation cover 18 continues to flow upward in a spiral rotating shape. The sludge return pipe 13 outputs the sludge mixture (sludge and water) to the spiral stirring blades of the first stirring part 15, which are input downward under the drive of the first stirring part 15. The rotation direction of the first stirring part 15 is opposite to that of the second stirring part 16. At the bottom of the first stirring part 15, the sludge flow and the sewage flow meet, forming more intense disturbance and promoting the mixing of sludge and water. By adjusting the rotation speed of the two stirring parts and the flow of sewage entering the flow guide cylinder 14, the sewage has a large kinetic energy and can rise to a position close to the top of the flow guide cylinder 14, but not overflow at the top of the flow guide cylinder 14, thereby enabling the sewage to mix with the sludge over a large part of the length of the first stirring part 15.

[0049] Optionally, along the length direction of the first stirring part 15, the sludge concentration gradually decreases from top to bottom, and the sludge is gradually and uniformly dispersed in the sewage, the height of the outflow port 17 corresponds to the height of the middle part of the first stirring part 15, the sludge concentration of the middle part of the first stirring part 15 is moderate, the mixing effect of the sewage and the sludge is good, and the sludge-water mixture is suitable to be discharged at this height;

[0050] The outflow port 17 faces the upstream side of the anaerobic tank 6, which is beneficial to the sludge-water mixture directly entering the area close to the upstream part of the anaerobic tank 6 and contacting and reacting with the anaerobic sludge.

[0051] The present application comprehensively considers the factors such as the settling property of the sludge and the rising flow rate of the sewage, under the stirring action of the first stirring part 15 and the flow and rotation action of the sewage rising from the rotating separation cover 18, the rising sewage is mixed with the descending sludge, the sludge concentration is higher in the area close to the top or upper part of the flow guide cylinder 14, and the mixing degree with the sewage from the intermediate regulating tank 2 is lower. In the area near the bottom of the first stirring part 15, most of it is sewage, and the sludge-water is in the initial mixing stage, and the rising sewage forms impact and lifting on the sludge. In the area near the middle part of the first stirring part 15, the mixing degree of the sewage and the sludge is good, and the outflow port 17 is arranged here to discharge the well-mixed sludge-water mixture into the anaerobic tank 6.

[0052] Optionally, a stirring device is arranged between the upstream side of the anaerobic tank 6 and the flow guide cylinder 14, the stirring shaft 20 of the stirring device is vertically arranged and the top is connected to the third motor above the anaerobic tank 6, a plurality of mixing stirring pieces 21 are arranged on the stirring shaft 20 corresponding to the position of the outflow port 17, and the plurality of mixing stirring pieces 21 are uniformly arranged along the circumference of the stirring shaft 20;

[0053] The mixing stirring piece 21 is a semispherical shape recessed towards the stirring shaft 20, and is hollow, the circular face of the opening 22 of the mixing stirring piece 21 is vertical and passes through the spherical center, and the opening 22 of the mixing stirring piece 21 faces away from the stirring shaft 20; the outflow port 17 is between the highest point of the opening of the mixing stirring piece 21 and the spherical center.

[0054] Further optionally, a hollow cavity is arranged on the stirring shaft 20, a plurality of fourth motors 23 are arranged in the hollow cavity, the number of the fourth motors 23 is equal to the number of the mixing stirring pieces 21, each fourth motor 23 is correspondingly connected to one mixing stirring piece 21 for driving the rotation of the mixing stirring piece 21, and the fourth motor is a micro motor.

[0055] Further optionally, the spherical vertex of the mixing stirring piece 21 is connected to the corresponding fourth motor in the hollow cavity through a connecting shaft 24, the vertex is on the horizontal circular face where the spherical center is located, the radius of the circular face is equal to the radius of the mixing stirring piece 21, the connecting shaft is horizontal and penetrates into the hollow cavity to connect the corresponding fourth motor;

[0056] All the spherical vertexes of the mixing stirrers 21 are at the same height.

[0057] The third motor drives all the mixing stirrers 21 to rotate horizontally through the stirring shaft 20, and the circular openings (vertical) of the mixing stirrers 21 are alternately faced to the outflow ports 17 of the draft tube 14. The mixing stirrers 21 are vertically placed semi-spherical (similar to bowl-shaped), and the sludge-water mixture discharged from the outflow ports 17 is still in a fast rotating state, and is impacted into the concave spherical surface of the mixing stirrers 21 along a tangential direction similar to the draft tube 14 (not a standard tangential direction, according to the respective rotating speeds of the first stirring part 15 and the second stirring part 16, the material flow direction of the outflow ports 17 is closer to the draft tube 14 or farther away from the draft tube 14 than the standard tangential direction), and the sludge-water mixture is spirally rotated along the inner wall of the spherical surface and radially diffused to the periphery of the spherical surface, and finally diffused from the mixing stirrers 21 and completely into the water body in the anaerobic tank 6. The cooperation of the draft tube 14 and the mixing stirrers 21 in the present application makes the sludge-water mixing effect good, and the sludge-water mixture is well mixed with the water body in the anaerobic tank 6.

[0058] The stirring shaft 20 below the mixing stirrers 21 can also be provided with conventional stirring paddles, and the form and number thereof are determined according to the actual situation of the anaerobic tank 6.

[0059] Optionally, the outlet of the nitrification liquid reflux pipe 12 is provided with a reducing pipe 25, the pipe diameter of the reducing pipe 25 gradually decreases from top to bottom, the reducing pipe 25 is inclined and inclined towards the downstream side of the first-stage anoxic tank 7, and the reducing pipe 25 is located at the bottom of the first-stage anoxic tank 7.

[0060] The bottom of the downstream side of the first-stage anoxic tank 7 is provided with an inclined plate 26, which is beneficial to change the flow direction of the water with pressure output by the reducing pipe 25, drive the water in the first-stage anoxic tank 7 to form a rotating state, and promote the contact between the sludge and the sewage.

[0061] The top of the downstream side of the first-stage anoxic tank 7 is provided with a second connecting pipe for connecting the bottom of the upstream side of the first-stage aerobic tank 8, and the water treated by the first-stage anoxic tank 7 is input into the first-stage aerobic tank 8.

[0062] The first-stage anoxic tank 7 provides an anoxic environment, and the water with high oxygen content of the nitrification liquid reflux pipe 12 and the water with low oxygen content of the anaerobic tank 6 enter the first-stage anoxic tank 7 at the same time to form a mixed liquid, and by adjusting the amount of nitrification liquid reflux water, the dissolved oxygen value of the mixed liquid is controlled to be 0.3-0.5 mg / L.

[0063] The application designs a reducing pipe 25, which is at an angle of 20-30 degrees with the horizontal plane, and the water outlet direction of the reducing pipe 25 is also at an angle of 20-30 degrees. The reducing pipe 25 can accelerate the water flow, and output high-speed water flow (large momentum), so as to form a negative pressure zone and a small water flow zone with strong rotation around the outlet of the reducing pipe 25. After biochemical reaction, the small nitrogen gas bubbles generated in the first stage anoxic tank 7 can quickly escape from the water body when they contact the water flow zone, and form large bubbles and quickly rise, so as to avoid nitrogen accumulation. In combination with the inclined plate 26, the inclined plate 26 faces the outlet of the reducing pipe 25, so that the water flow impacting the surface of the inclined plate 26 forms a water flow basically upward, and the water flow upwardly impacts the middle and upper part of the first stage anoxic tank 7, and under the action of gravity, the water flow flows downward again, and then forms a rotating state, so as to play a stirring role on the water body and sludge.

[0064] Optionally, the first stage aerobic tank 8 is provided with a first aeration device 27 at the bottom, and the first aeration device 27 is arranged close to the downstream side of the first stage aerobic tank 8, and the second connecting pipe is located at the upstream side of the first stage aerobic tank 8, so that the water inlet of the first stage aerobic tank 8 is upwardly pushed by the first aeration device 27, and then forms a circulation similar to that in the first stage anoxic tank 7.

[0065] The top of the downstream side of the first stage aerobic tank 8 is provided with a third connecting pipe for connecting the bottom of the upstream side of the second stage anoxic tank 9, so as to input the water body treated by the first stage aerobic tank 8 into the second stage anoxic tank 9.

[0066] Optionally, a circulation agitator is arranged in the second stage anoxic tank 9, so as to agitate the water body, prevent sludge deposition and uniformly mix the water body. The top end of the upper pipe of the circulation agitator is 400-500 mm away from the liquid surface, so as to prevent vortex suction of air. The top of the downstream side of the second stage anoxic tank 9 is communicated with the top of the second stage aerobic tank 10.

[0067] Optionally, the second stage aerobic tank 10 is provided with a second aeration device 28 at the bottom, and the second aeration device 28 is arranged close to the upstream side of the second stage aerobic tank 10.

[0068] The bottom of the downstream side of the second stage aerobic tank 10 is communicated with a pre-sedimentation tank 29, and the pre-sedimentation tank 29 is provided with a sewage lifting pump. The outlet of the sewage lifting pump is connected with a nitrification liquid return pipe 12. The top of the downstream side of the pre-sedimentation tank 29 is provided with a water outlet for communicating with a sedimentation tank.

[0069] The second aeration device 28 aerates upwardly to form a circulating flow, but the flow velocity of the water at the bottom of the downstream side of the secondary aerobic tank 10 is low, which is beneficial to the settlement of sludge and forms a concentrated sludge area. The pre-sedimentation tank 29 is connected to the bottom of the downstream side of the secondary aerobic tank 10, and the nitrification liquid in the secondary aerobic tank 10 is concentrated in the pre-sedimentation tank 29 and is returned to the primary anoxic tank 7 through the nitrification liquid return pipe 12. Meanwhile, the pre-sedimentation tank 29 can screen flocculable sludge, which contains a large number of beneficial bacteria in the process of nitrification in the aerobic tank and denitrification in the anoxic tank, to prevent the beneficial bacteria from entering the subsequent sedimentation tank. The flocculable sludge is settled at the bottom of the pre-sedimentation tank 29 and is returned through the nitrification liquid return pipe 12, and other loose sludge that is not easy to settle enters the sedimentation tank.

[0070] Optionally, the post-processing unit comprises a primary sedimentation tank 30, a coagulation tank 31 and a secondary sedimentation tank 32 connected in sequence, the bottom of the primary sedimentation tank is provided with a gas stripping device, and the gas stripping device is connected to the sludge return pipe 13; the primary sedimentation tank, the coagulation tank and the secondary sedimentation tank are conventional settings, and the top of the secondary sedimentation tank discharges the produced water.

[0071] The following example processes domestic sewage in a certain village in Henan Province, which has the characteristics of unstable inflow. The maximum instantaneous inflow occurs in the early, middle and late time periods, and the inflow is very small at night. The average inflow during the peak period is 10.6 m 3 / h, and the average inflow during the trough period is 1.5 m 3 / h, and the ratio of the two is about 7 times. Through the effective adjustment of the adjustment tank, the effluent flow is stably maintained at about 4.3 m 3 / h with little fluctuation, ensuring uniform effluent from the adjustment tank throughout the day. The effluent flow coefficient is maintained within 1.05, achieving the purpose of stable effluent flow from the adjustment tank. After adjustment by the adjustment tank, the effluent COD in the effluent area is stably maintained at about 106 mg / L, and the effluent concentration coefficient is maintained within 1.1.

[0072] The biochemical treatment parameters of the anaerobic tank are as follows: the inflow is stably maintained at 4.3 m 3 / h, the COD inflow concentration is 106 mg / L, the ammonia nitrogen inflow concentration is 23 mg / L, and the sludge concentration SV30 value of the anaerobic tank is 50% to 60%.

[0073] Example 1

[0074] This example provides a sewage treatment system for unstable inflow with all the above features. In addition, as shown in Figure 4 , an expansion part 33 is provided between the gas separation part and the second stirring part, the diameter of the part of the draft tube corresponding to the expansion part is greater than the diameter of other parts of the draft tube, so that the inside of the expansion part 33 expands outwardly;

[0075] The ratio of the inner diameter of the non-expanding part of the draft tube to the inner diameter of the expanding part is 1:1.5, and the height of the expanding part accounts for 50% of the height of the draft tube part between the gas separation part and the second stirring part.

[0076] The sewage passing through the second stirring part has a high rotation speed and flow rate, and the separation cover covers most of the cross section inside the draft tube, hindering the passage of the sewage. The present application designs an expanding part, so that the sewage has a survival space below the separation cover, avoiding a large amount of sewage directly impacting the separation cover. However, the expanding part will reduce the flow rate of the sewage, so the size of the expanding part is limited, so that the rotation speed and flow rate of the sewage do not decrease too much, and the flow resistance of the separation cover is not too prominent.

[0077] Example 2

[0078] The present embodiment provides a sewage treatment system for unstable inflow water, which is the same as example 1, except that the ratio of the inner diameter of the non-expanding part of the draft tube to the inner diameter of the expanding part is 1:2.

[0079] Example 3

[0080] The present embodiment provides a sewage treatment system for unstable inflow water, which is the same as example 1, except that the ratio of the inner diameter of the non-expanding part of the draft tube to the inner diameter of the expanding part is 1:2.1.

[0081] Example 4

[0082] The present embodiment provides a sewage treatment system for unstable inflow water, which is the same as example 1, except that the height of the expanding part accounts for 75% of the height of the draft tube part between the gas separation part and the second stirring part.

[0083] Example 5

[0084] The present embodiment provides a sewage treatment system for unstable inflow water, which is the same as example 1, except that the height of the expanding part accounts for 76% of the height of the draft tube part between the gas separation part and the second stirring part.

[0085] Example 6

[0086] The present embodiment provides a sewage treatment system for unstable inflow water, which is the same as example 1, except that no expanding part is provided.

[0087] Table 1 Comparison of anaerobic tank treatment effects of examples 1-6

[0088]

[0089]

[0090] From the above table, the setting of the expansion part is conducive to containing more sewage below the separation cover, avoiding the impact of the water flow on the separation cover, improving the gas-liquid separation efficiency, reducing the amount of oxygen carried by the sewage, and being beneficial to anaerobic biochemical treatment. The appropriate sewage flow rate also improves the mixing effect of the sewage and the sludge in the first stirring part, making the sewage and sludge more uniformly mixed.

Claims

1. A sewage treatment system for an unsteady water inflow, characterized in that The wastewater treatment device comprises a regulating tank, an intermediate regulating tank, a biochemical treatment unit and a post-treatment unit connected in sequence, and the unstable raw water is evenly regulated in the regulating tank; the intermediate regulating tank comprises overflow area, water inlet area and water outlet area arranged in sequence, the water outlet pipe of the regulating tank is connected to the water inlet area, the bottom of the downstream side of the water inlet area is connected to the water outlet area, the overflow plate is arranged between the upstream side of the water inlet area and the overflow area, the water outlet pipe of the overflow area is connected to the regulating tank, and the overflow plate is used for controlling the flow of the water outlet of the regulating tank; The biochemical treatment unit comprises an anaerobic tank, a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank connected in sequence, and the water outlet of the regulating tank is subjected to biochemical treatment; the post-treatment unit comprises a sedimentation tank, and the water body after biochemical treatment is subjected to mud-water separation to obtain product water; The second-stage aerobic tank is connected to the first-stage anoxic tank through a nitrification liquid reflux pipe, and the nitrification liquid of the aerobic tank is refluxed to the anoxic tank; The sedimentation tank is connected to the anaerobic tank through a sludge reflux pipe, and the sludge obtained by sedimentation is partially returned to the anaerobic tank to supplement the sludge amount; The middle part of the anaerobic tank is provided with a flow guide mixing device, the lower part of the flow guide mixing device is connected to the water outlet pipe of the water outlet area, and the top part of the flow guide mixing device is connected to the outlet of the sludge reflux pipe, so as to mix the water inlet of the anaerobic tank and the refluxed sludge uniformly; the upstream side of the anaerobic tank is provided with a stirring device, so as to continuously mix the sludge-water mixture output by the flow guide mixing device with the water body in the anaerobic tank, and promote anaerobic biochemical treatment; The flow guide mixing device comprises a flow guide cylinder and a first stirring part and a second stirring part in the flow guide cylinder, the water pipe of the water outlet area connected to the anaerobic tank is connected to the bottom of the flow guide cylinder, and the outlet of the sludge reflux pipe is connected to the top of the flow guide cylinder; the stirring paddle of the first stirring part is a continuous single helix stirring blade, which can continuously transport the sludge transported by the sludge reflux pipe downward in the flow guide cylinder; The lower part of the first stirring part is sequentially provided with a gas separation part and a second stirring part, the sewage input into the bottom of the flow guide cylinder is agitated by the second stirring part, the flow rate is increased, part of the oxygen-containing gas is separated out through the gas separation part, and then the water body continues to mix with the sludge upward; the side wall of the flow guide cylinder is provided with an outflow port for outputting the mixed sewage and sludge; The gas separation part comprises a conical separation cover and an exhaust pipe, the separation cover is small at the top and large at the bottom, and is conical, the separation cover is arranged concentrically with the flow guide cylinder, and the separation cover has a gap between the bottom edge and the inner wall of the flow guide cylinder, so as to allow the sewage in the flow guide cylinder to pass through the separation cover; The top of the separation cover is connected to at least two exhaust pipes, the exhaust pipes pass out of the flow guide cylinder, extend along the outer wall of the flow guide cylinder to above the liquid surface of the anaerobic tank, and discharge the gas separated by the separation cover, and the exhaust pipes can be connected to the position for fixing the separation cover; The upstream side of the anaerobic tank is provided with a stirring device between the flow guide cylinder, the stirring shaft of the stirring device is vertically arranged and connected to the third motor above the anaerobic tank at the top, the stirring shaft is provided with a plurality of mixing stirring pieces at the position corresponding to the outflow port, and the plurality of mixing stirring pieces are uniformly arranged along the circumference of the stirring shaft; The mixing stirring piece is a semispherical shape recessed toward the stirring shaft direction, and is hollow, the circular face of the opening of the mixing stirring piece is vertical and passes through the spherical center, the opening of the mixing stirring piece faces away from the stirring shaft direction; the outflow port is between the highest point of the opening of the mixing stirring piece and the spherical center.

2. The wastewater treatment system against unstable inflow according to claim 1, characterized by, The upstream side of the water inlet area is provided with an overflow plate, and the downstream side is provided with a water outlet hole plate, the top end of the overflow plate is lower than the top end of the water outlet hole plate, if the water quantity in the water inlet area is too large, the water will overflow to the overflow area through the overflow plate, and then return to the adjusting pool; the lower part of the water outlet hole plate is uniformly provided with a plurality of water outlet holes for connecting the water inlet area and the water outlet area.

3. The wastewater treatment system for unsteady influent according to claim 1, characterized by, The gas separation part and the second stirring part are provided with an expansion part, the diameter of the corresponding part of the draft tube is greater than the diameter of other parts of the draft tube, so that the inside of the expansion part expands outward; The ratio of the inner diameter of the non-expansion part of the draft tube to the inner diameter of the expansion part is 1:(1.5-2), and the height of the expansion part accounts for 50-75% of the height of the draft tube part between the gas separation part and the second stirring part.

4. The wastewater treatment system for unsteady influent according to claim 1, characterized by, The outlet of the nitration liquid reflux pipe is provided with a reducing pipe, the diameter of the reducing pipe gradually decreases from top to bottom, the reducing pipe is inclined, and inclines to the downstream side of the primary anoxic tank, the reducing pipe is at the bottom of the primary anoxic tank; The bottom of the downstream side of the primary anoxic tank is provided with an inclined plate, which is beneficial to change the flow direction of the water body with pressure output by the reducing pipe, drives the water in the primary anoxic tank to form a rotating state, and promotes the contact of sludge and sewage.

5. The wastewater treatment system for unsteady influent according to claim 1, wherein The post-processing unit comprises a primary sedimentation tank, a coagulation tank and a secondary sedimentation tank connected in sequence, the bottom of the primary sedimentation tank is provided with a gas lifting device, the gas lifting device is connected with a sludge reflux pipe, and the top of the secondary sedimentation tank discharges produced water.

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