A low carbon-nitrogen ratio sewage treatment system

Abstract

The present invention belongs to the technical field of sewage treatment, and specifically relates to a low-carbon-nitrogen ratio sewage treatment system. The system includes a biochemical treatment unit and a tailwater lifting unit. The two anoxic zones of the biochemical treatment unit are internally provided with a plurality of support rods, and a suspended shell is vertically suspended in a string on the support rods of the two anoxic zones. The suspended shell is filled with a first autotrophic denitrification filler and a carrier; the tailwater lifting unit includes a water distribution zone, a tailwater lifting zone, and a water outlet zone; the tailwater lifting zone is internally filled with a second autotrophic denitrification filler and limestone. Using the sewage treatment system of the present invention to treat low-carbon-nitrogen ratio sewage can significantly improve the denitrification efficiency and denitrification performance of the sewage, and has low operating costs and stable effects.

Description

Technical Field

[0001] The present invention belongs to a sewage treatment system, and in particular relates to a low carbon-nitrogen ratio sewage treatment system. Background Art

[0002] Currently, with the continuous advancement of urbanization, the demand for small-scale centralized treatment of domestic sewage in villages and towns is becoming increasingly higher. The treatment of low carbon-nitrogen ratio sewage is of great significance.

[0003] At present, biological denitrification technologies include heterotrophic denitrification and autotrophic denitrification technologies. The key to heterotrophic denitrification technology is the addition of carbon sources. Adequate organic carbon sources such as methanol, sodium acetate, glucose, etc. are commonly used carbon source types. Heterotrophic denitrification has the advantages of fast reaction rate and high removal efficiency, but its disadvantages cannot be ignored. When the carbon source is insufficient, it will lead to the accumulation of by-products during the reaction process and cannot effectively remove nitrogen from the water; and excessive addition of carbon source will increase the COD of the effluent, causing secondary pollution and increasing operating costs. Autotrophic denitrification technology does not require the addition of carbon sources and has the advantages of low sludge production and low operating costs. Among them, sulfur autotrophic denitrification technology is an effective method for treating nitrate and nitrite polluted water bodies, especially for wastewater with a low carbon-nitrogen ratio. However, in actual application, there are problems such as low denitrification efficiency and unstable effects of autotrophic denitrification.

[0004] There is a need in this field to develop a stable, efficient, and low-cost low-carbon-nitrogen ratio sewage treatment system. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a low carbon-nitrogen ratio sewage treatment system, which adopts sulfur autotrophic denitrification technology as the core. It not only has high treatment efficiency, but also has stable effluent, no secondary pollution problem, and low operating costs.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A low carbon-nitrogen ratio sewage treatment system comprises a biochemical treatment unit, wherein the biochemical treatment unit comprises an anaerobic zone, a first anoxic zone, a first aerobic zone, a second anoxic zone, a second aerobic zone and a sedimentation effluent zone connected in sequence; wherein a plurality of support rods are provided inside the two anoxic zones, and a suspended shell filled with a first autotrophic denitrification filler and a carrier is vertically suspended in a string on the support rods of the two anoxic zones (14); the support rods are welded to angle irons on the inner wall of the equipment, or directly welded to the inner wall of the equipment.

[0008] The tailwater lifting unit includes a water distribution area, a tailwater lifting area and a water outlet area connected in sequence; the tailwater lifting area is provided with a second autotrophic denitrification filler layer and a limestone layer from bottom to top;

[0009] The sedimentation outlet area of ​​the biochemical treatment unit is connected to the water distribution area of ​​the tailwater lifting unit through an outlet pipe;

[0010] Preferably, the distance between adjacent support rods is 5 to 10 cm, and the center distance between adjacent suspended shells is 5 to 15 cm.

[0011] Preferably, the volume ratio of the first autotrophic denitrification filler to the carrier is 5:1 to 1:1.

[0012] Preferably, the carrier is any one or more combinations of a biological carrier or a slow-release carbon source. The autotrophic denitrification active ingredients of the first and second autotrophic denitrification filler layers include any one or more combinations of elemental sulfur, sulfide, sulfur-iron sulfide, and thiosulfate. The equivalent diameter of the first autotrophic denitrification filler is 3-10 mm. The equivalent diameter of the filler in the second autotrophic denitrification filler layer is 2-10 cm, and the equivalent diameter of the limestone in the limestone layer is 5-15 cm. The biological carrier includes MBBR filler, polyurethane sponge filler, volcanic rock filler, etc. The slow-release carbon source includes natural slow-release carbon sources, synthetic slow-release carbon sources, and modified slow-release carbon sources. Natural slow-release carbon sources such as corn cob slow-release carbon source, crop straw slow-release carbon source, sawdust slow-release carbon source, etc.; artificially synthesized and modified slow-release carbon sources such as acid-base modified crop slow-release carbon source, polycaprolactone (PCL) / starch blend slow-release carbon source, polybutylene succinate (PBS) / polylactic acid (PLA) blend slow-release carbon source, etc.

[0013] Preferably, an aeration device is provided at the bottom of the first anoxic zone and the second anoxic zone, and intermittent aeration is adopted as the aeration method.

[0014] Preferably, the hydraulic retention time of the first anoxic zone and the second anoxic zone is 1 to 3 hours and 0.5 to 2.5 hours respectively, and the denitrification volume load is 0.6 to 1 kg NO3-N / (m 3 Filler·d);

[0015] Preferably, an aeration device is provided at the bottom of the first and second aerobic zones, and braided biological fillers are provided inside. The braided biological fillers are suspended and filled inside the first and second aerobic zones, and the aeration device adopts continuous aeration.

[0016] Preferably, the tailwater lifting zone includes lifting zone 1, lifting zone 2, and lifting zone 3 connected in sequence.

[0017] Limestone provides alkalinity for the sulfur autotrophic denitrification reaction. Due to its large particle size, its corresponding volume is also large. At the same time, in order to ensure that the effective components in the second autotrophic denitrification filler can be fully utilized and sulfur autotrophic denitrification occurs, it is preferred that the volume ratio of the second autotrophic denitrification filler to the limestone is 15:1 to 5:1, the filling rate is 50% to 80%, and the filling height is 0.5 to 1.6 m.

[0018] It is preferred that the hydraulic retention time can be shortened when the effective components in the filler of the second autotrophic denitrification filler layer are easily soluble substances such as sulfide and thiosulfate. When the effective components are insoluble substances such as sulfur element, sulfur-iron sulfide, etc., in order to ensure thorough denitrification, the hydraulic retention time can be appropriately extended. The preferred hydraulic retention time is 0.5d to 3d. Since the water flow mode in the tailwater lifting area is a downward-upward vertical flow, the hydraulic load is high and it is filled with fillers. Therefore, the hydraulic and pollutant reduction loads increase. The preferred surface hydraulic load is 0.5 to 1.5m 3 / (m 2 ·d).

[0019] Preferably, the water distribution area is connected to the tailwater lifting area through an opening on one side wall, and is connected to a plurality of water distribution pipes; the lifting area 1 is connected to the lifting area 2 through an opening on the lower side wall, and is connected to a plurality of water collecting pipes; the lifting area 2 is connected to the lifting area 3 through an opening on one side wall, and is connected to a plurality of water distribution pipes; the lifting area 3 is connected to the water outlet area through an opening on the lower side wall, and is connected to a plurality of water collecting pipes; the water outlet area is connected to a retractable water outlet pipe; the water flow mode of the sequentially connected lifting area 1, lifting area 2, lifting area 3, and water outlet area is downward vertical flow, upward vertical flow, horizontal flow, and downward vertical flow, and the water flows through the side wall holes;

[0020] The outlet area is connected to a retractable outlet pipe. By extending the outlet pipe, the overall water level height of the tailwater lifting area can be adjusted, which can extend the hydraulic retention time to a certain extent. By shortening the outlet pipe, the water level height can be lowered, and the hydraulic retention time is shortened accordingly.

[0021] Preferably, the wall of the water distribution pipe is provided with a plurality of holes, the holes being staggered upwards at 45° to opposite sides, with a hole spacing of 30 to 50 cm and a hole diameter of 10 to 50 mm, with the hole diameter increasing sequentially with the radial direction of the water flow. The holes in the water distribution pipe being staggered upwards at 45° to opposite sides can prevent larger impurities in the water from blocking the holes downwards. With the holes being staggered upwards, impurities flow backwards with the water flow, and even if the last hole is blocked, the effect on water distribution uniformity is minimal. Due to hydraulic losses, a consistent hole diameter in the water distribution pipe may result in more water being distributed in the front section and less in the back section. Therefore, the hole diameter of the water distribution pipe is set to increase sequentially with the direction of water flow to reduce the unevenness of water distribution.

[0022] Preferably, the water collection pipe wall is perforated with multiple holes, opened at a 45° angle downward to the opposite sides, with a spacing of 30-50 cm and a uniform hole diameter of 10-50 mm. The water collection pipe is located below the packing. If the holes are opened upward, finer packing will clog the water collection holes, resulting in poor water flow in lift zones 2 and 3. Opening the holes downward reduces the possibility of clogging with fine packing. Since the water collection pipe is submerged, a consistent hole diameter ensures uniform water collection.

[0023] Preferably, the sedimentation outlet area is provided with an inclined tube packing layer, wherein the inclined tube packing comprises a hexagonal honeycomb packing made of polypropylene, ethylene propylene copolymer, polyvinyl chloride or the like, and is filled in the sedimentation outlet area.

[0024] In the technical solution of the present invention, by setting autotrophic denitrification fillers and carriers in the anoxic zone, the microbial load is greatly increased, forming a large number of sulfur autotrophic denitrification microenvironments, which can stably and efficiently remove nitrogen from sewage; and the denitrification denitrification fillers are set by hanging suspended balls, which is completely different from the traditional stacking form. During operation, there is no need for backwashing, which greatly reduces the operating cost and difficulty of operation and maintenance. The tailwater lifting unit uses autotrophic denitrification fillers to further enhance the autotrophic denitrification effect, and uses cheap limestone to provide the alkalinity required for the reaction; the water distribution pipe opening method of the tailwater lifting unit reduces the unevenness of water distribution and effectively prevents the problem of water inlet blockage. The entire tailwater lifting unit does not require operation and maintenance all year round, which greatly reduces the operation and maintenance costs, and has a high total nitrogen removal efficiency.

[0025] This technical solution realizes autotrophic denitrification and can remove nitrogen from sewage without adding a carbon source. It has a significant effect on the treatment of low carbon-nitrogen ratio sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the sewage treatment system of the present invention.

[0027] Figure 2 Schematic diagram of the biochemical treatment unit structure of the sewage treatment system.

[0028] Figure 3 This is a schematic diagram of the tailwater lifting unit structure of the sewage treatment system.

[0029] Figure 4 Schematic diagram of the suspended shell structure filled with autotrophic denitrification filler and carrier.

[0030] Figure 5 Schematic diagram of the water distribution pipe structure.

[0031] Figure 6 Schematic diagram of the water collecting pipe structure. DETAILED DESCRIPTION

[0032] The present invention is further explained below by means of specific examples:

[0033] See also Figure 1-6 A low carbon-nitrogen ratio sewage treatment system includes a biochemical treatment unit 1 and a tailwater lifting unit 2; the biochemical treatment unit 1 includes an anaerobic zone 11, a first anoxic zone 12, a first aerobic zone 13, a second anoxic zone 14, a second aerobic zone 15, and a sedimentation outlet zone 16 connected in sequence; the tailwater lifting unit 2 includes a water distribution zone 21, a tailwater lifting zone 22, and a water outlet zone 23 connected in sequence; the tailwater lifting zone 22 includes a lifting zone 1 221, a lifting zone 222, and a lifting zone 3 223;

[0034] The second anoxic zone 14 is equipped with multiple support rods 19 welded to the inner wall of the device. The suspended housing 144 is vertically suspended in a string from the multiple support rods 19 provided within the second anoxic zone 14. The first autotrophic denitrification filler 141 and the biological carrier 142 are loaded into the suspended housing 144 in a volume ratio of 5:1. The biological carrier is a polyurethane sponge filler. The first autotrophic denitrification filler is sulfide with an equivalent diameter of 3 to 10 mm.

[0035] The spacing between adjacent support rods 19 is 5 to 10 cm, and the center spacing between adjacent suspension shells 144 is 5 to 15 cm. The suspension shells are suspended in such a way that the anoxic zone filler will not be clogged, so there is no need to backwash the denitrification filler.

[0036] An aeration device 17 is provided at the bottom of the first anoxic zone 12 and the second anoxic zone 14. The aeration device 17 is connected to the aeration pipeline and the aeration pump or fan. Intermittent aeration is adopted to ensure that the dissolved oxygen concentration is within the anoxic range while saving energy.

[0037] The hydraulic retention time of the first anoxic zone 12 is 1 to 3 hours, the hydraulic retention time of the second anoxic zone 14 is 0.5 to 2.5 hours, and the volumetric load of the denitrification filler in the second anoxic zone 14 is 0.6 to 1 kg NO3-N / m 3 d. The volumetric load of this denitrification filler is significantly higher than the reference value recommended by industry technical specifications. This is because the first autotrophic denitrification filler installed in the anoxic zone itself contains alkalinity components, which can provide the alkalinity required for the autotrophic denitrification process, while the biological carrier 142 or slow-release carbon source 143 can provide a larger microbial load, resulting in extremely high denitrification efficiency in the anoxic zone.

[0038] The bottom of the first and second aerobic zones 13 and 15 are provided with an aeration device 17, which is provided with a braided biofiller 18. The braided biofiller is suspended and filled in the first and second aerobic zones. The aeration device 17 adopts continuous aeration.

[0039] The sedimentation outlet area 16 is internally provided with an oblique tube packing layer 161, and the oblique tube packing is a hexagonal honeycomb packing made of polypropylene, ethylene propylene copolymer, polyvinyl chloride and the like, which is filled in the sedimentation outlet area to precipitate the effluent from the two aerobic zones 15. The sedimentation outlet area 16 is connected to the outlet pipe, and the outlet pipe is connected to the water distribution area 21. The water distribution area 21 is connected to the tail water lifting area 22 through an opening on one side wall and is connected to a plurality of water distribution pipes 211. The lifting area 1 221 is connected to the lifting area 2 222 through an opening on the lower side wall and is connected to a plurality of water collecting pipes 212. Similarly, the lifting area 222 is connected to the lifting area 3 223 through an opening on one side wall and is connected to a plurality of water distribution pipes 211. The lifting area 3 223 is connected to the outlet area 23 through an opening on the lower side wall and is connected to a plurality of water collecting pipes 212. The outlet area 23 is connected to a retractable outlet pipe 231, which can adjust the water level of the tail water lifting area 22.

[0040] The wall of the water distribution pipe 211 is provided with a plurality of holes, which are staggered at 45° upwards and on opposite sides, with a hole spacing of 50 cm and a hole diameter of 50 mm. The hole diameter increases with the radial direction of the water flow to reduce the unevenness of water distribution.

[0041] The wall of the water collecting pipe 212 is provided with a plurality of holes, which are opened at a downward angle of 45 degrees to the opposite sides, with a hole spacing of 50 cm and a hole diameter of 50 mm. The hole diameter is uniform, and the downward opening method prevents the water collecting holes from being blocked by the second autotrophic denitrification filler and the limestone 225 and impurities contained in the sewage.

[0042] The tailwater lifting zone 22 is provided with a second autotrophic denitrification filler layer 224 and a limestone layer 225, arranged from bottom to top. The volume ratio of the filler in the second autotrophic denitrification filler layer 224 to the limestone in the limestone layer 225 is 15:1. The limestone has an equivalent diameter of 5 to 15 cm, a fill rate of 50%, and a fill height of 1 to 1.5 m. The limestone provides the alkalinity required for the sulfur autotrophic denitrification process. The second autotrophic denitrification filler is sulfide, with an equivalent diameter of 2 to 10 cm.

[0043] The data results before and after sewage treatment using the system of Example 1 are shown in Table 1:

[0044] Table 1

[0045]

[0046] Note: In the table, “TN removal rate of effluent from biochemical treatment unit” is TN value of effluent from biochemical treatment unit / TN value of influent × 100%; “TN removal rate of effluent from tailwater lifting unit” is TN value of effluent from tailwater lifting unit / TN value of effluent from biochemical treatment unit × 100%.

[0047] Example 2

[0048] The rest is the same as Example 1, except that the first autotrophic denitrification filler and the carrier (the carrier is a mixture of a biological carrier 142 and a slow-release carbon source 143 in an equal volume ratio) are loaded into the suspended shell 144 in a volume ratio of 1:1. The biological carrier is a polyurethane sponge filler, and the slow-release carbon source is a corn cob slow-release carbon source. The first autotrophic denitrification filler is a mixture of sulfide and sulfur-iron sulfide in an equal volume ratio, and the equivalent diameter is 3 to 10 mm. In addition to providing a place for microorganisms to live, the slow-release carbon source 143 can also provide a carbon source, so that an autotrophic-heterotrophic synergistic denitrification environment is formed in the two anoxic zones 14, thereby achieving a higher TN removal rate.

[0049] The holes in the distribution pipe 211 are staggered upwards at 45 degrees, with a hole spacing of 30 cm and a hole diameter of 10 mm. The holes in the collection pipe 212 are staggered downwards at 45 degrees, with a hole spacing of 30 cm and a hole diameter of 10 mm.

[0050] The tailwater lifting zone 22 is provided with a second autotrophic denitrification filler layer 224 and a limestone layer 225 from bottom to top. The volume ratio of the second autotrophic denitrification filler to the limestone is 5:1, and the filling rate is 80%. The second autotrophic denitrification filler is a mixture of sulfide and sulfur-iron sulfide in an equal volume ratio, with an equivalent diameter of 2 to 10 cm.

[0051] The data results before and after sewage treatment using the system in Example 2 are shown in Table 2:

[0052] Table 2

[0053]

[0054] Note: In the table, “TN removal rate of effluent from biochemical treatment unit” is TN value of effluent from biochemical treatment unit / TN value of influent × 100%; “TN removal rate of effluent from tailwater lifting unit” is TN value of effluent from tailwater lifting unit / TN value of effluent from biochemical treatment unit × 100%.

Claims

1. A low carbon-nitrogen ratio sewage treatment system, characterized in that: include: The biochemical treatment unit (1) includes an anaerobic zone (11), a first anoxic zone (12), a first aerobic zone (13), a second anoxic zone (14), a second aerobic zone (15), and a sedimentation effluent zone (16) connected in sequence; A plurality of support rods (19) are provided inside the two anoxic zones (14), and a suspension shell (144) is vertically suspended in a string on the support rods (19) of the two anoxic zones (14), and the suspension shell (144) is filled with a first autotrophic denitrification filler (141) and a carrier; the tail water lifting unit (2) comprises a water distribution area (21), a tail water lifting area (22) and a water outlet area (23) connected in sequence; the tail water lifting area (22) is provided with a second autotrophic denitrification filler layer (224) and a limestone layer (225) from bottom to top; the sedimentation outlet area (16) of the biochemical treatment unit (1) is connected to the water distribution area (21) of the tail water lifting unit (2) through an outlet pipe; the carrier is a biological carrier (142) or a slow-release carbon source (143) ); the autotrophic denitrification active ingredients of the fillers of the first autotrophic denitrification filler (141) and the second autotrophic denitrification filler layer (224) include any one or more combinations of sulfur, sulfur-iron sulfide, and thiosulfate, and the equivalent diameter of the first autotrophic denitrification filler (141) is 3-10 mm; the filler equivalent diameter of the second autotrophic denitrification filler layer (224) is 2-10 cm, and the equivalent diameter of the limestone is 5-15 cm; the volume ratio of the first autotrophic denitrification filler (141) to the carrier is 5:1-1:1; the spacing between adjacent support rods (19) is 5-10 cm, and the center spacing between adjacent suspended shells (144) is 5-15 cm.

2. The low carbon-nitrogen ratio sewage treatment system according to claim 1, characterized in that: The bottom of the first anoxic zone (12) and the second anoxic zone (14) are provided with an aeration device (17), and the aeration method adopts intermittent aeration; the hydraulic retention time of the first anoxic zone (12) and the second anoxic zone (14) are 1~3h and 0.5~2.5h respectively, and the denitrification volume load is 0.6~1kg NO3-N / (m 3 Filler·d).

3. The low carbon-nitrogen ratio sewage treatment system according to claim 1, characterized in that: The first aerobic zone (13) and the second aerobic zone (15) are provided with braided biological fillers (18) inside, and an aeration device (17) is provided at the bottom.

4. The low carbon-nitrogen ratio sewage treatment system according to claim 1, characterized in that: The tailwater lifting zone (22) includes a lifting zone 1 (221), a lifting zone 2 (222), and a lifting zone 3 (223) connected in sequence. The volume ratio of the filler in the second autotrophic denitrification filler layer (224) and the limestone in the limestone layer (225) filled in the tailwater lifting zone (22) is 15:1 to 5:1, the filling rate is 50% to 80%, the filling height is 0.5 to 1.6 m, the hydraulic retention time is 0.5 d to 3 d, and the surface hydraulic load is 0.5 to 1.5 m. 3 / (m 2 ·d).

5. The low carbon-nitrogen ratio sewage treatment system according to claim 4, characterized in that: The water distribution area (21) and the tailwater lifting area (22) are connected to a hole on the wall on one side and are connected to a plurality of water distribution pipes (211); the lifting area 1 (221) and the lifting area 2 (222) are connected to a hole on the wall below one side and are connected to a plurality of water collecting pipes (212); the lifting area 2 (222) and the lifting area 3 (223) are connected to a hole on the wall on one side and are connected to a plurality of water distribution pipes (211); the lifting area 3 (223) and the water outlet area (23) are connected to a hole on the wall below one side and are connected to a plurality of water collecting pipes (212); and the water outlet area (23) is connected to a retractable water outlet pipe (231).

6. The low carbon-nitrogen ratio sewage treatment system according to claim 5, characterized in that: The water distribution pipe (211) has a plurality of holes on its wall, which are opened in an upward 45° staggered manner on opposite sides, with a hole spacing of 30-50 cm and a hole diameter of 10 mm-50 mm, and the hole diameter increases in sequence with the radial direction of the water flow.

7. The low carbon-nitrogen ratio sewage treatment system according to claim 6, characterized in that: The wall of the water collecting pipe (212) is provided with a plurality of holes, which are opened at a downward angle of 45° to the opposite side, with a hole spacing of 30 to 50 cm and a hole diameter of 10 mm to 50 mm, and the hole diameters are uniform.

8. The low carbon-nitrogen ratio sewage treatment system according to claim 1, characterized in that: An inclined tube packing layer (161) is provided inside the sedimentation outlet area (16).

Images