Anaerobic biological sedimentation tank and method for treating highway bridge runoff crossing sensitive water body

Abstract

The invention discloses an anaerobic biological sedimentation tank and method for treating highway bridge runoff crossing sensitive water. The sedimentation tank is sequentially provided with an oil separation, trash holding and sand setting area, a primary anaerobic biological area and a secondary anaerobic biological area along the runoff direction. A plurality of biological filler net hanging devices are fixedly arranged between the walls of the primary anaerobic biological treatment area and the secondary anaerobic biological treatment area, and backflow partition walls are arranged in the primary anaerobic biological treatment area and the secondary anaerobic biological treatment area. The anaerobic biological hanging net device is additionally arranged in the settling pond, and the trash holding net and the oil separation baffle are arranged, so that multiple effects of intercepting suspended solids, settling mud and sand, isolating oil pollution, purifying initial rainwater and the like are realized, the discharged water quality is improved, and the influence on the ecological environment of a sensitive water body is reduced. In practical application, the anaerobic biological sedimentation tank and the grass planting shallow disc ditch are combined for application, natural grassland and planting soil have the capability of absorbing, storing and purifying rainwater, the quality of tail water of the sedimentation tank is improved, and the ecological environment safety of sensitive water is protected.

Description

Technical Field

[0001] This invention relates to the field of highway bridge engineering technology, specifically to a high-efficiency sedimentation tank equipment and combined process application method for treating oil tanker leaks and initial rainwater runoff pollution on highway bridges, which combines oil separation, pollution interception, sand settling, and anaerobic biological treatment. Background Technology

[0002] During the construction and operation of highways, it is inevitable to build numerous bridges that cross sensitive water bodies (such as rivers, wetland nature reserves, etc.) with high water function zones, including drinking water sources. Bridge surface runoff can form due to rainfall, snowmelt, or sudden hazardous material leaks. Bridge surface runoff is typically caused by rainwater or snowmelt carrying pollutants from vehicle exhaust deposits, mud adhering to vehicle frames, particles from worn tires, and leaked oil from vehicles operating under poor conditions. In special circumstances, bridge surface runoff can even be from sudden hazardous chemical leaks. Bridge surface runoff is characterized by its suddenness and uncertainty, and its complex pollutant composition (mainly COD, SS, oils, surfactants, heavy metals, and other inorganic salts); furthermore, highways are often far from cities and lack supporting stormwater and sewage pipe networks and facilities, making management relatively difficult. If allowed to discharge locally, bridge surface runoff will cause serious drinking water source pollution problems across sensitive water bodies.

[0003] Traditional bridge sedimentation tanks typically only collect bridge runoff and lack treatment capabilities, or even oil separation capabilities. In the event of an oil tanker leak, the oily waste liquid must be removed from the sedimentation tank by tanker truck for centralized treatment, increasing operating and treatment costs. During rainfall, rainwater may carry residual oily waste liquid out of the sedimentation tank and into water bodies. Traditional sedimentation tanks cannot effectively treat and decompose oil tanker leaks and initial rainwater runoff pollution; the discharge of pollutants into sensitive water bodies can harm public health and damage the ecological environment. Therefore, this invention proposes an anaerobic biological sedimentation tank and method for treating runoff from highway bridges crossing sensitive water bodies, as well as an application method combining it with a grass-covered shallow ditch process. Summary of the Invention

[0004] The purpose of this invention is to provide an anaerobic biological sedimentation tank and its application method for treating runoff from highway bridges crossing sensitive water bodies, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An anaerobic biological sedimentation tank for treating runoff from highway bridges crossing sensitive water bodies is provided. The anaerobic biological sedimentation tank is enclosed by sedimentation tank walls and includes an oil-water separation and sedimentation zone, a primary anaerobic biological zone, and a secondary anaerobic biological zone arranged sequentially along the water flow direction. The anaerobic biological sedimentation tank is combined with a grass-covered shallow ditch for water treatment.

[0007] A water inlet pipe system is installed on the rear wall of the oil-water separation, sludge removal, and sedimentation zone; a vent pipe system is located below the front wall of the oil-water separation, sludge removal, and sedimentation zone; a sludge-blocking net is vertically installed in the front section of the interior of the oil-water separation, sludge removal, and sedimentation zone, and an oil-water separating baffle is vertically installed in the rear section; and suspended biological packing balls are placed on the liquid surface behind the sludge-blocking net.

[0008] A drainage pipe system is installed on the oil-water barrier-anaerobic biological zone partition wall between the oil-water barrier and sedimentation zone and the primary anaerobic biological zone.

[0009] The primary anaerobic biological zone has backflow partitions perpendicular to the water flow direction installed on the front and rear walls respectively, and a biological packing mesh device is fixedly installed between the front and rear walls of the primary anaerobic biological zone.

[0010] A water passage hole is provided below the anaerobic biological zone partition wall between the primary anaerobic biological zone and the secondary anaerobic biological zone.

[0011] The secondary anaerobic biological zone is equipped with a biological packing mesh device fixedly installed between its front and rear walls; the secondary anaerobic biological zone has return flow partitions perpendicular to the water flow direction on its front and rear walls; the secondary anaerobic biological zone has a venting pipe system and an overflow pipe system on its right wall; the secondary anaerobic biological zone has an outlet pipe system on its front wall; the secondary anaerobic biological zone is connected to the grassed shallow ditch through the outlet pipe system.

[0012] The tops of the oil-water separator, sedimentation zone, primary anaerobic biological zone, and secondary anaerobic biological zone are equipped with prefabricated covers.

[0013] Furthermore, the water inlet pipe system consists of a water inlet pipe and a waterproof pipe sleeve. The waterproof pipe sleeve is fixedly installed on the rear wall of the oil-water separator and sedimentation zone. The water inlet pipe is fitted inside the waterproof pipe sleeve, and the water outlet direction of the water inlet pipe is downward.

[0014] Furthermore, the drainage pipe system consists of a drainage pipe and a waterproof sleeve for the drainage pipe. The waterproof sleeve is fixedly installed on the wall between the oil-water separator and sedimentation zone and the primary anaerobic biological zone. The vertical drain pipe is fitted inside the waterproof sleeve.

[0015] Furthermore, the venting pipe system consists of a venting pipe, a waterproof sleeve for the venting pipe, and a venting pipe valve. The waterproof sleeve is fixedly installed at the lower part of the front wall of the oil-water separator and sedimentation zone and at the lower part of the right wall of the secondary anaerobic biological zone. The venting pipe is fitted inside the waterproof sleeve, and a venting pipe valve is fixedly installed on the venting pipe.

[0016] Furthermore, the water outlet system consists of a water outlet pipe, a waterproof sleeve for the water outlet pipe, and a water outlet pipe valve; the waterproof sleeve for the water outlet pipe is fixedly installed on the front wall of the secondary anaerobic biological zone, and the water outlet pipe is fitted inside the waterproof sleeve for the water outlet pipe; a water outlet pipe valve is fixedly installed on the water outlet pipe.

[0017] Furthermore, the biological packing netting device consists of a netting rope, bolt clips, and a biological packing rope; the netting rope is fixedly installed by the bolt clips, and the biological packing rope is bound to the netting rope, with the microorganism attached to the biological packing rope being Clostridium butyricum.

[0018] Furthermore, the outer shell of the suspended biological filler ball is filled with biological filler, and the microorganism in the biological filler is Clostridium butyricum.

[0019] Furthermore, the overflow pipe system consists of an overflow pipe and an overflow pipe waterproof sleeve; the overflow pipe waterproof sleeve is installed on the right wall of the secondary anaerobic biological zone, and the overflow pipe is fitted inside the overflow pipe waterproof sleeve.

[0020] Furthermore, the present invention also includes a maintenance manhole, which is located at the top of the primary anaerobic biological zone and the secondary anaerobic biological zone, and is covered by a cover plate with a handle.

[0021] Furthermore, a vent cap is provided on the prefabricated cover plate.

[0022] Furthermore, pebbles are provided at the connection between the grassed shallow ditch and the outlet pipe system. From top to bottom, the grassed shallow ditch consists of turf, planting soil, gravel, and permeable geotextile. The grassed shallow ditch removes suspended solids, nutrients, and other pollutants through sedimentation, filtration, and biological processes, effectively purifying rainwater and improving the effluent quality of this invention.

[0023] Furthermore, the grass-covered shallow ditch has a trapezoidal profile, with its lowest point 10-30 cm lower than the surrounding ground level, and is surrounded by permeable geotextile. The grass-covered shallow ditch can slow runoff, promote rainwater infiltration, reduce peak flow, delay discharge, and mitigate the impact on sensitive water bodies; it is also ecologically friendly, has landscaping functions, and is easy to construct and maintain.

[0024] Furthermore, the debris-blocking net installed in the oil-water separation and sedimentation zone can intercept suspended pollutants such as leaves and garbage in the bridge surface runoff, preventing blockage of drainage pipes and ensuring smooth water flow. Larger particles such as silt, impurities, and tire debris in the bridge surface runoff will slowly settle at the bottom of the oil-water separation and sedimentation zone.

[0025] Furthermore, the oil-water separating baffle in the oil-water separating and sedimentation zone can separate water and oil, and the drainage pipe in the oil-water separating and sedimentation zone further deepens the isolation of oil pollution, preventing oil pollutants from being discharged into natural water bodies.

[0026] Furthermore, the suspended biological packing balls placed in the oil-water separation and sedimentation zone can adsorb and degrade oil pollutants leaked from the tanker truck, reducing pollution to the aquatic environment.

[0027] Furthermore, the biological packing material of the netting device in the primary and secondary anaerobic biological zones can effectively remove pollutants from the initial rainwater on the highway bridge surface, reducing the pollution of sensitive water bodies by the effluent.

[0028] Furthermore, the reflux partitions set in the primary and secondary anaerobic biological zones increase the contact time between the bridge surface runoff and the biological packing material, thereby improving the pollutant removal efficiency.

[0029] Furthermore, the reflux partitions set in the primary and secondary anaerobic biological zones increase the contact time between the bridge surface runoff and the biological packing material, thereby improving the pollutant removal efficiency.

[0030] Furthermore, the effluent from the anaerobic biological sedimentation tank flows into a grassy shallow ditch, utilizing the filtering, infiltration, and delaying discharge time functions of the grassland to further optimize the quality of the discharged water and reduce the pollution load on sensitive water bodies.

[0031] A method for treating sensitive water bodies crossed by highway bridge runoff using the above-mentioned anaerobic biological sedimentation tank includes the following steps:

[0032] In normal use, the vent valve is normally closed, and the outlet valve is normally open;

[0033] When rainfall occurs, the runoff from the highway bridge surface flows into the oil-water separation and sedimentation zone through the inlet pipe. The zone is equipped with a vertically installed screen along the water flow direction to intercept floating and suspended debris carried in the runoff, preventing blockage of the drainage pipe. The outlet of the inlet pipe faces downwards to avoid direct impact of the runoff on the screen, thus mitigating the impact force. Oil-water separators installed vertically along the water flow within the zone separate water and oil. Oil, being lighter than water, floats on the surface and is blocked by the separators. When the runoff from the highway bridge surface consists only of rainwater, the rainwater flows through the drain pipe below the separators and enters the primary anaerobic biological zone.

[0034] When a tanker truck leaks oil onto a highway bridge, the runoff mixed with oil pollution first passes through a debris barrier, then is separated from the water by an oil-water separator, and finally undergoes deep separation of the oil pollution through a drainage pipe, preventing the oil from flowing into the primary anaerobic biological zone. Suspended biological packing balls added to the oil-water separator and sedimentation zone can provide preliminary treatment of the hazardous chemicals leaked from the tanker truck. Subsequently, an oil suction truck removes the leaked oil for centralized treatment. Clostridium butyricum has an adsorption and degradation effect on phenol in petroleum products and a bond-breaking effect on long-chain alkanes, cycloalkanes, and aromatic hydrocarbons. The debris barrier and oil-water separator in the oil-water separator and sedimentation zone are a certain distance from the bottom of the pool, allowing sludge and sediment in the bridge runoff to slowly settle at the bottom, gradually reducing the turbidity of the runoff.

[0035] The runoff from the highway bridge surface passes through an oil-water separation and sedimentation zone. After oil-water separation by baffles, most of the runoff flowing into the primary anaerobic biological treatment zone is rainwater. An anaerobic biological packing mesh device is installed inside the primary anaerobic biological treatment zone. The runoff and several anaerobic microorganisms gradually form a biofilm on the anaerobic biological packing mesh, treating and degrading the pollutants in the runoff. Clostridium butyricum has a high potential for degrading nitrogen and heavy metal pollutants in the initial rainwater. A return flow barrier in the primary anaerobic biological treatment zone guides the water flow, reduces short-circuiting, and prolongs the contact time between the runoff and the biological packing, enhancing the treatment effect. The runoff treated by the anaerobic biological packing mesh device flows into the secondary anaerobic biological treatment zone through water passages.

[0036] The bridge surface runoff passes through an oil-water separation and sedimentation zone and a primary anaerobic biological treatment zone before finally flowing into a secondary anaerobic biological treatment zone. While most pollutants in the highway bridge surface runoff are removed through these zones, they still do not meet the discharge standards of sensitive water bodies with high water quality requirements. The secondary anaerobic biological treatment zone is equipped with anaerobic biological packing mesh devices to further treat and degrade the bridge surface runoff. The return flow barriers in the secondary anaerobic biological treatment zone reduce short-circuiting, prolong the contact time between the bridge surface runoff and the biological packing, and improve treatment efficiency. The treated bridge surface runoff is then discharged into natural water bodies through an outlet pipe.

[0037] This invention removes pollutants from tanker leaks and initial rainwater at the source. The grass-planted shallow ditch can ecologically degrade and improve the quality and efficiency of the tailwater. The combination of this invention and the grass-planted shallow ditch fully leverages the advantages of each to protect the ecological environment of sensitive water bodies.

[0038] In the event of heavy or torrential rain, due to the limited size of this invention, it cannot withstand the instantaneous excess rainwater runoff, and the excess bridge surface runoff is discharged through the overflow pipe.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. This invention uses a debris-blocking net to intercept suspended pollutants such as leaves and garbage in road bridge runoff, preventing blockage of the drainage pipe and ensuring smooth water flow. When an oil tanker leaks from a road bridge, the oil-separating baffle installed in this invention can separate water and oil into layers, and the drainage pipe further separates the water and oil, preventing oil pollutants from entering natural water bodies.

[0041] 2. The suspended biological packing balls added in this invention can adsorb and degrade oil pollutants leaked from tank trucks. The biological packing mainly consists of anaerobic dominant bacteria that adsorb and degrade oil pollutants. After treatment, the runoff from highway bridge surfaces can be discharged, which can reduce pollution to sensitive water bodies, protect the aquatic ecological environment, and improve the ability to deal with sudden tank truck leakage accidents.

[0042] 3. This invention incorporates a hanging net biological packing device, where anaerobic microorganisms form a biofilm on the packing material. This biofilm efficiently decomposes organic pollutants without the need for aeration, resulting in low maintenance costs, resistance to shock loads, strong adaptability to fluctuations in water quality and quantity, and the ability to survive at low temperatures (10℃~30℃). This invention also increases the contact time between bridge runoff and the biological packing material through a return flow partition, thereby improving pollutant removal efficiency and achieving water quality standards for discharge into sensitive water bodies.

[0043] 4. This invention utilizes gravity flow throughout the entire process, consumes no electricity, and is energy-saving and efficient. Compared with traditional initial rainwater sedimentation tanks for highway bridges, it can not only settle sediment but also treat and degrade bridge surface runoff, improve the quality of discharged water, and protect sensitive water bodies.

[0044] 5. The combined process of this invention can efficiently purify initial rainwater, replenish groundwater, improve the quality of discharged water, protect the ecological environment, and is easy to construct and maintain, and beautifies the landscape. Attached Figure Description

[0045] Figure 1 This is a planar schematic diagram I of the present invention.

[0046] Figure 2 This is a planar schematic diagram II of the present invention.

[0047] Figure 3 This is a schematic diagram of the top cover plate of the present invention.

[0048] Figure 4 for Figure 2 Schematic diagram of section 1-1 (oil-blocking, pollution-blocking, and sand-sedimentation zone).

[0049] Figure 5 for Figure 2 Schematic diagram of section 2-2 (primary biological anaerobic zone).

[0050] Figure 6 for Figure 2 Schematic diagram of section 3-3 (secondary biological anaerobic zone).

[0051] Figure 7 for Figure 2 Schematic diagram of section 4-4 in the figure.

[0052] Figure 8 for Figure 2 Schematic diagram of section 5-5 in the figure.

[0053] Figure 9 for Figure 2 Schematic diagram of section 6-6 in the figure.

[0054] Figure 10 This is a schematic diagram of the combined process of the present invention.

[0055] Figure 11 This is a cross-sectional view of the shallow ditch for planting grass according to the present invention.

[0056] Figure 12 This is a schematic diagram of the structure of a suspended biological packing ball.

[0057] The components in the diagram are as follows:

[0058] 1. Oil-water separator and sedimentation zone; 2. Primary anaerobic biological zone; 3. Secondary anaerobic biological zone; 4. Sedimentation tank wall; 4. Front wall 401; Rear wall 402; Left wall 403; Right wall 404; Oil-water separator-anaerobic biological zone partition wall 405; Anaerobic biological zone partition wall 406; Inlet pipe system; 5. Inlet pipe 501; Inlet pipe waterproof sleeve 502; Spill screen; 6. Oil-water separator baffle; 7. Drainage pipe system; 8. Drain pipe 801; Drain pipe waterproof sleeve 802; Vent pipe system; 9. Vent pipe 901; Vent pipe waterproof sleeve 902; Valve 903; Maintenance steps; 10. Suspended biological packing balls; 11. Outer shell; 1101. Adsorption and degradation of oil pollution. Anaerobic biological packing material 1102, anaerobic biological packing material netting device 12, netting rope 1201, anaerobic biological packing material rope 1202, return partition wall 13, water passage hole 14, overflow pipe system 15, overflow pipe 1501, overflow pipe waterproof sleeve 1502, ladder 16, water outlet pipe system 17, water outlet pipe 1701, water outlet pipe waterproof sleeve 1702, valve 1703, sedimentation tank top cover system 18, prefabricated cover plate 1801, cover plate handle 1802, maintenance manhole 1803, vent cap 19, grassed shallow ditch 20, pebbles 2001, turf 2002, planting soil 2003, crushed stone 2004, permeable geotextile 2005. Detailed Implementation

[0059] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all embodiments obtained by those with common skills in the art without creative effort are within the scope of protection of the present invention.

[0060] Example 1

[0061] like Figures 1-12 As shown, this embodiment provides an anaerobic biological sedimentation tank for treating runoff from highway bridges crossing sensitive water bodies. The anaerobic biological sedimentation tank is enclosed by a sedimentation tank wall 4, and internally includes an oil-water separation and sedimentation zone 1, a primary anaerobic biological zone 2, and a secondary anaerobic biological zone 3 arranged sequentially along the water flow direction. In this embodiment, the sedimentation tank top cover system 18 includes a prefabricated cover plate 1801. The anaerobic biological sedimentation tank is combined with a grass-covered shallow ditch 20 for water treatment. An inlet pipe system 5 is installed on the rear wall 402 of the oil-water separation and sedimentation zone 1. A venting pipe system 9 is located at the lower corner of the front wall 401; a grease trap 6 is vertically installed at the front section of the oil-water barrier and sedimentation zone 1, and an oil-water baffle 7 is vertically installed at the rear section, with suspended biological packing balls 11 placed on the liquid surface behind the grease trap 6; a drainage pipe system 8 is installed on the oil-water barrier-anaerobic biological zone partition wall 405; in this embodiment, the oil-water barrier and sedimentation zone is separated from the primary anaerobic biological zone by the oil-water barrier-anaerobic biological zone partition wall 405, and the primary anaerobic biological zone is separated from the secondary anaerobic biological zone by the anaerobic biological zone partition wall 406;

[0062] The primary anaerobic biological zone 2 has two return flow partitions 13, one perpendicular to the water flow direction, installed on the front wall 401 and the other on the rear wall 402. A biological packing mesh device 12 is fixedly installed between the front wall 401 and the rear wall 402 of the primary anaerobic biological zone 2. A water passage hole 14 is provided below the anaerobic biological zone partition wall 406. The secondary anaerobic biological zone 3 also has a biological packing mesh device 12 fixedly installed between the front wall 401 and the rear wall 402. The primary anaerobic biological zone 2 has backflow partitions 13 perpendicular to the water flow direction on its front wall 401 and rear wall 402; the secondary anaerobic biological zone 3 has a venting pipe system 9 and an overflow pipe system 15 on its right wall 404; the secondary anaerobic biological zone 3 has an outlet pipe system 17 on its front wall 401; the secondary anaerobic biological zone 3 is connected to the grassed shallow ditch 20 through the outlet pipe system 17; the tops of the oil-water separating and sedimentation zone 1, the primary anaerobic biological zone 2, and the secondary anaerobic biological zone 3 are equipped with prefabricated cover plates 1801. The grassed shallow ditch 20 has pebbles 2001 at the connection point with the outlet pipe system 17, and from top to bottom, the grassed shallow ditch 20 consists of turf 2002, planting soil 2003, gravel 2004, and permeable geotextile 2005. The grass-planted shallow ditch 20 has a trapezoidal profile, with the lowest point elevation being 10-30cm lower than the surrounding ground elevation, and the perimeter is wrapped with permeable geotextile 2005.

[0063] like Figure 1 and Figure 2 As shown, this embodiment also includes a maintenance manhole 1803, which is located at the top of the primary anaerobic biological zone 2 and the secondary anaerobic biological zone 3. A cover plate is placed over the manhole, and the cover plate has a handle 1802. A vent cap 19 is provided on the prefabricated cover plate 1801. Figure 4 As shown, the oil-water separator and sedimentation zone 1 has maintenance steps 10 fixedly installed on the inner sides of its rear wall 402 and left wall 403; as Figure 7 As shown, the primary anaerobic biological zone 2 has maintenance steps 10 fixedly installed on the inner side of its front wall 401. In the secondary anaerobic biological zone 3, maintenance steps 10 are fixedly installed on the inner side of the right wall 404, and a ladder 16 is fixedly installed on the outer side of the right wall 404.

[0064] The biological packing netting device 12 consists of a netting rope 1201, bolt clips 1202, and a biological packing rope 1203. The netting rope 1201 is fixedly installed by the bolt clips 1202, and the biological packing rope 1203 is bound to the netting rope 1201. The microorganism attached to the biological packing rope 1203 is Clostridium butyricum, with the number CICC 23847, purchased from the China Industrial Microbiological Culture Collection Center. The outer shell 1101 of the suspended biological packing ball 11 is filled with biological packing 1102. The microorganism in the biological packing 1102 is Clostridium butyricum, with the number CICC 23847, purchased from the China Industrial Microbiological Culture Collection Center.

[0065] It should be noted that the water inlet pipe system 5 consists of a water inlet pipe 501 and a waterproof pipe sleeve 502. The waterproof pipe sleeve 502 is fixedly installed on the rear wall 402 of the oil-water separator and sedimentation zone 1. The water inlet pipe 501 is fitted inside the waterproof pipe sleeve 502, and the water outlet direction of the water inlet pipe 501 is downward.

[0066] It should be noted that the drainage pipe system 8 consists of a drainage pipe 801 and a drainage pipe waterproof sleeve 802. The pipe waterproof sleeve 802 is fixedly installed on the wall between the oil-water separator and sedimentation zone 1 and the primary anaerobic biological zone 2. The drainage pipe riser 801 is fitted inside the drainage pipe waterproof sleeve 802.

[0067] It should be noted that the venting pipe system 9 consists of a venting pipe 901, a venting pipe waterproof sleeve 902, and a venting pipe valve 903. The pipe waterproof sleeve 902 is fixedly installed at the lower corner of the front wall 401 of the oil-water separator and sedimentation zone 1 and at the lower corner of the right wall 404 of the secondary anaerobic biological zone 3. The venting pipe 901 is fitted inside the pipe waterproof sleeve 902, and the venting pipe valve 903 is fixedly installed on the venting pipe 901.

[0068] It should be noted that the water outlet pipe system 17 consists of a water outlet pipe 1701, a water outlet pipe waterproof sleeve 1702, and a water outlet pipe valve 1703; the water outlet pipe waterproof sleeve 1702 is fixedly installed on the front wall 401 of the secondary anaerobic biological zone 3, and the water outlet pipe 1701 is fitted inside the water outlet pipe waterproof sleeve 1702; the water outlet pipe valve 1703 is fixedly installed on the water outlet pipe 1701.

[0069] It should be noted that the overflow pipe system 15 consists of an overflow pipe 1501 and an overflow pipe waterproof sleeve 1502; the overflow pipe waterproof sleeve 1502 is installed on the right wall 404 of the secondary anaerobic biological zone 3, and the overflow pipe 1501 is fitted inside the overflow pipe waterproof sleeve 1502.

[0070] Parameter description of the present invention:

[0071] 1. Dimensions in the drawings are in millimeters.

[0072] 2. The walls of this invention are all reinforced concrete structures. The relevant foundations, walls, reinforcement, etc. should be calculated and determined by structural designers. The dimensions in this drawing are for reference only.

[0073] 3. H1 and H2 in the figure are determined according to the burial depth of the inlet pipe. The effective water depth of this invention is 2000 mm. The packing height of the anaerobic biological packing rope 1202 in the primary anaerobic biological zone 2 and the secondary anaerobic biological zone 3 is 1500 mm, and the hydraulic retention time is 6-8 hours.

[0074] 4. According to the data: The volume of a small oil tanker is generally 5~10 m³. 3 Medium-sized oil tankers have a volume of 14-25 m³. 3 Large semi-trailer tankers are 20-40 m long. 3 .

[0075] 5. The initial rainwater collection volume can be calculated using the following formula:

[0076] V=10DFψβ

[0077] Where: V – effective volume (m³) 3 );

[0078] D – Storage capacity (mm), calculated based on rainfall, can be taken as 4 mm to 8 mm;

[0079] F – Catchment area (hm²) 2 ) ;

[0080] ψ – runoff coefficient;

[0081] β – Safety factor, which can be taken as 1.1~1.5.

[0082] 6. The effective volume of the oil-water separation and sedimentation zone 1 is based on the type of oil tanker trucks passing over the highway bridge. The volumes of the primary anaerobic biological zone 2 and the secondary anaerobic biological zone 3 are the maximum values ​​of the oil tanker truck and the initial rainwater collection volume. The specific dimensions of this invention are calculated and determined by the designer.

[0083] 7. The debris barrier 6 is made of plastic, and the mesh spacing should be 25 mm to 40 mm.

[0084] 8. The oil baffle 7 is made of 304 stainless steel, making it sturdy and robust.

[0085] 9. The ventilation cap 19 is made of plastic, and its outlet is covered with an 18-mesh steel wire mesh to prevent foreign objects from entering.

[0086] 10. The microorganisms on the suspended biological packing ball 11 and the anaerobic biological packing rope 1202 are Clostridium butyricum.

[0087] 11. The precast cover plate 1801 is made of concrete. The maintenance manhole 1803 can be made of concrete or cast iron. The ladder 16 is made of steel.

[0088] 12. To prevent pipe leakage and protect the pipe, a waterproof sleeve 502 for the inlet pipe, a waterproof sleeve 802 for the drain pipe, a waterproof sleeve 902 for the vent pipe, a waterproof sleeve 1502 for the overflow pipe, and a waterproof sleeve 1702 for the outlet pipe are fixedly installed on the wall 4 of this invention.

[0089] 13. When the present invention is buried underground, the elevation of the precast cover plate 1801 of the present invention should be 20cm higher than the outdoor ground elevation to prevent unauthorized personnel from entering the sedimentation tank area; the ladder 16 is eliminated, and the precast cover plate 1801 can be directly accessed from the outdoor ground for maintenance.

[0090] The following is an application method for anaerobic biological sedimentation tanks used to treat runoff from highway bridges crossing sensitive water bodies:

[0091] The application methods of this invention are divided into the following three types:

[0092] Application Method 1: In the event of rainfall or oil tanker leakage, the operating procedure of this invention is as follows:

[0093] In daily use, the vent valve 903 is normally closed, and the outlet valve 1703 is normally open. During rainfall, the road surface runoff flows into the oil-water separation and sedimentation zone 1 through the inlet pipe 501. The oil-water separation and sedimentation zone 1 is vertically installed with a debris screen 6 along the water flow direction to intercept floating and suspended debris carried in the runoff, preventing blockage of the drainage pipe. The outlet of the inlet pipe 501 faces downwards to prevent the runoff from directly impacting the debris screen 6, thus mitigating the impact force. The oil-water separation baffle 7, installed vertically along the water flow within the oil-water separation and sedimentation zone 1, separates water and oil. Oil, being lighter than water, floats on the surface and is blocked by the baffle 7, preventing it from flowing out. When the road surface runoff consists only of rainwater, the rainwater flows under the baffle 7 and into the drainage pipe 801, entering the primary anaerobic biological zone 2. When a tanker truck leaks oil onto a highway bridge, the runoff mixed with oil pollution first passes through the debris barrier 6, then is separated from the water by the oil-water separator 7, and finally undergoes deep separation of the oil pollution through the drainage pipe 801, preventing the oil from flowing into the primary anaerobic biological zone 2. The suspended biological packing balls 11 added to the oil-water separator and sedimentation zone 1 can provide preliminary treatment for the hazardous chemicals leaked from the tanker truck. Subsequently, the leaked oil is sucked away by an oil suction truck for centralized treatment. Clostridium butyricum has an adsorption and degradation effect on phenol in petroleum hydrocarbons and a bond-breaking effect on long-chain alkanes, cycloalkanes, and aromatic hydrocarbons. The debris barrier 6 and the oil-water separator 7 in the oil-water separator and sedimentation zone 1 are a certain distance from the bottom of the pool, allowing sludge and sediment in the bridge runoff to slowly settle at the bottom, gradually reducing the turbidity of the runoff.

[0094] A vent cap 19 is fixedly installed on the prefabricated cover plate 1801 of the present invention. It is used to balance the internal and external air pressure, ensure smooth drainage, and discharge harmful gases.

[0095] The road bridge runoff passes through the oil-water separation and sedimentation zone 1, where it undergoes oil-water separation via the oil-water baffle 7. The majority of the runoff flowing into the primary anaerobic biological treatment zone 2 is rainwater. The primary anaerobic biological treatment zone 2 is equipped with an anaerobic biological packing mesh device 12. The runoff and several anaerobic microorganisms gradually form a biofilm on the anaerobic biological packing rope 1202, treating and degrading the pollutants in the runoff. Clostridium butyricum has a high potential for degrading nitrogen and heavy metal pollutants in the initial rainwater. The return flow baffle 13 in the primary anaerobic biological treatment zone 2 guides the water flow, reduces short-circuiting, and prolongs the contact time between the runoff and the biological packing, enhancing the treatment effect. The runoff treated by the anaerobic biological packing mesh device 12 flows into the secondary anaerobic biological treatment zone 3 through the water passage 14.

[0096] The bridge surface runoff passes through the oil-water separation and sedimentation zone 1, the primary anaerobic biological treatment zone 2, and finally flows into the secondary anaerobic biological treatment zone 3. While most pollutants in the highway bridge surface runoff are removed through the oil-water separation and sedimentation zone 1 and the primary anaerobic biological treatment zone 2, they still do not meet the discharge standards of sensitive water bodies with high water quality requirements. The secondary anaerobic biological treatment zone 2 is equipped with an anaerobic biological packing mesh device 12 to further treat and degrade the bridge surface runoff pollutants. The return flow baffle 13 in the secondary anaerobic biological treatment zone 2 reduces short-circuiting, prolongs the contact time between the bridge surface runoff and the biological packing, and improves treatment efficiency. The treated bridge surface runoff is discharged into natural water bodies through the effluent pipe 1701.

[0097] When heavy rain or torrential rain occurs, the present invention, due to its limited size, cannot withstand the instantaneous excess rainwater runoff, and the excess bridge deck runoff is discharged through the overflow pipe 1501.

[0098] Application Method 2: This invention (anaerobic biological sedimentation tank) + 20-meter grass-covered shallow ditch combination process

[0099] The effluent pipe 1701 of this invention (anaerobic biological sedimentation tank) is connected to a grass-covered shallow ditch 20, into which the effluent is discharged. The grass-covered shallow ditch 20 is 1 m wide, with pebbles 2001 laid at the front end for hydraulic energy dissipation. The grass-covered shallow ditch 20 has a trapezoidal cross-section, with its lowest point elevation 10-30 cm lower than the surrounding ground elevation. From top to bottom, it consists of: turf 2002, 15-25 cm thick planting soil 2003, 10 cm thick gravel 2004, and a permeable geotextile 2005 wrapped around the outermost layer.

[0100] The grass-planted shallow ditch 20 process can effectively purify rainwater by removing pollutants such as suspended solids and nutrients through sedimentation, filtration and biological action, thereby improving the effluent quality of the invention; it slows down runoff, reduces peak flow, delays discharge, and reduces the impact on sensitive water bodies; it promotes rainwater infiltration and replenishes groundwater; at the same time, it is ecological and environmentally friendly, has a landscaping function, and is easy to construct and maintain.

[0101] The combined process of this invention and the grass-planted shallow ditch 20 fully leverages the advantages of each. This invention removes pollutants from oil tanker leaks and initial rainwater at the source, while the grass-planted shallow ditch 20 further improves the quality of the wastewater by utilizing its ecological degradation, economic and aesthetic advantages, thus protecting the ecological environment of sensitive water bodies.

[0102] Application Method 3: When this invention requires maintenance and cleaning, it should be done in good weather:

[0103] Maintenance personnel open the prefabricated cover 1801 of the oil-water separator and sedimentation zone 1 using the cover handle 1802, and use dredging tools to clean up the garbage, suspended biological packing balls, and remaining oil from the water surface. The oil is then collected in a collector. The valve 903 fixedly installed on the drain pipe 901 is opened, and a vacuum truck is used to remove the wastewater and sludge from the tank. Maintenance personnel can also open the prefabricated cover 1801 or the maintenance manhole 1803 using the cover handle 1802. After the manhole has been open for a period of time, maintenance personnel can use the maintenance steps 10 to enter the oil-water separator and sedimentation zone 1, the primary anaerobic biological zone 2, and the secondary anaerobic biological zone 3. When the invention is above ground, maintenance personnel use the ladder 16 to access the sedimentation tank for maintenance.

[0104] Example 2

[0105] Anaerobic biological sedimentation tanks are used for the degradation of nitrate nitrogen concentrations in water bodies:

[0106] At nitrate nitrogen concentrations of 50 mg / L, 100 mg / L, and 150 mg / L, the removal rates of nitrate nitrogen by *Clostridium butyricum* in the anaerobic biological sedimentation tank were 98.56%, 92.24%, and 80.79%, respectively; the removal rates of total nitrogen were 91.54%, 80.47%, and 65.39%, respectively; the removal rates of phenol were 75.21%, 72.57%, and 73.16%, respectively; and the removal rates of TOC were 93.12%, 89.64%, and 74.25%, respectively. The increase in nitrate nitrogen concentration had little effect on the phenol removal rate, which may be due to the relatively independent phenol metabolic pathway of *Clostridium butyricum* and its degradation mechanism, which is mainly based on cometabolism.

[0107] Table 1. Effects of different nitrate nitrogen concentrations on pollutant degradation

[0108]

[0109] Example 3

[0110] Anaerobic biological sedimentation tanks are used for the degradation of phenol in water bodies with different concentrations:

[0111] At phenol concentrations of 5 mg / L, 10 mg / L, and 15 mg / L, the removal rates of nitrate nitrogen by *Clostridium butyricum* in the anaerobic biological sedimentation tank were 98.69%, 98.58%, and 82.70%, respectively; the removal rates of total nitrogen were 93.03%, 91.50%, and 70.67%, respectively; the removal rates of phenol were 75.26%, 52.60%, and 29.45%, respectively; and the removal rates of total organic carbon (TOC) were 92.29%, 86.36%, and 80.87%, respectively. Increased phenol concentration led to an increase in TOC in the anaerobic biological sedimentation tank, and simultaneously increased the pollutant treatment load on *Clostridium butyricum*. Therefore, with increasing phenol concentration, the removal rates of nitrate nitrogen, total nitrogen, phenol, and TOC decreased accordingly.

[0112] Table 2. Effects of different phenol concentrations on pollutant degradation

[0113]

[0114] Example 4

[0115] Anaerobic biological sedimentation tanks are used for the degradation of water bodies with different hydraulic retention times (HRT):

[0116] At HRTs of 6 h, 8 h, and 10 h, the removal rates of nitrate nitrogen by Clostridium butyricum in the anaerobic biological sedimentation tank were 95.02%, 98.54%, and 99.02%, respectively; the removal rates of total nitrogen were 89.41%, 93.67%, and 93.43%, respectively; the removal rates of phenol were 63.12%, 74.88%, and 78.24%, respectively; and the removal rates of TOC were 90.70%, 92.64%, and 93.10%, respectively. Extending the HRT increases the contact reaction time between Clostridium butyricum and pollutants in the anaerobic sedimentation tank, thus further facilitating the removal of nitrate nitrogen, total nitrogen, phenol, and TOC.

[0117] Table 3. Effects of different HRTs on pollutant degradation

[0118]

[0119] This invention can efficiently degrade and remove oil pollution from tanker truck leaks and pollutants in initial rainwater runoff, solving the problem of environmental pollution caused by untreated bridge runoff being directly discharged into sensitive water bodies, and achieving the goal of protecting the aquatic ecological environment.

[0120] Although embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An anaerobic biological sedimentation tank for treating runoff from highway bridges crossing sensitive water bodies, characterized in that: The anaerobic biological sedimentation tank is enclosed by sedimentation tank walls (4), and includes an oil-water separation and sedimentation zone (1), a primary anaerobic biological zone (2), and a secondary anaerobic biological zone (3) arranged sequentially along the water flow direction; the anaerobic biological sedimentation tank is combined with grass-covered shallow ditch (20) for water treatment. A water inlet pipe system (5) is installed on the rear wall (402) of the oil-water separator and sedimentation zone (1); a vent pipe system (9) is installed below the front wall (401) of the oil-water separator and sedimentation zone (1); a sludge net (6) is vertically installed in the front part of the interior of the oil-water separator and sedimentation zone (1), an oil-water baffle (7) is vertically installed in the rear part, and a suspended biological packing ball (11) is placed on the liquid surface behind the sludge net (6). A drainage pipe system (8) is installed on the oil-water barrier-anaerobic biological zone partition wall (405) between the oil-water barrier and sedimentation zone (1) and the primary anaerobic biological zone (2). The primary anaerobic biological zone (2) has a return flow partition wall (13) perpendicular to the water flow direction on the front wall (401) and the rear wall (402) respectively. The primary anaerobic biological zone (2) has a biological packing netting device (12) fixedly installed between its front wall (401) and rear wall (402). A water passage hole (14) is provided below the anaerobic biological zone partition wall (406) between the primary anaerobic biological zone (2) and the secondary anaerobic biological zone (3). The secondary anaerobic biological zone (3) has a biological packing mesh device (12) fixedly installed between its front wall (401) and rear wall (402); the secondary anaerobic biological zone (2) has a return flow partition wall (13) perpendicular to the water flow direction on its front wall (401) and rear wall (402); the secondary anaerobic biological zone (3) has a vent pipe system (9) and an overflow pipe system (15) on its right wall (404); the secondary anaerobic biological zone (3) has an outlet pipe system (17) on its front wall (401); the secondary anaerobic biological zone (3) is connected to the grass-planted shallow ditch (20) through the outlet pipe system (17); The top of the oil-water separation and sedimentation zone (1), the primary anaerobic biological zone (2), and the secondary anaerobic biological zone (3) are equipped with prefabricated cover plates (1801).

2. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: The water inlet pipe system (5) consists of a water inlet pipe (501) and a waterproof pipe sleeve (502). The waterproof pipe sleeve (502) is fixedly installed on the rear wall (402) of the oil-water separator and sedimentation area (1). The water inlet pipe (501) is fitted inside the waterproof pipe sleeve (502), and the water outlet direction of the water inlet pipe (501) is downward. The drainage pipe system (8) consists of a drainage pipe (801) and a drainage pipe waterproof sleeve (802). The pipe waterproof sleeve (802) is fixedly installed on the wall between the oil-water separator and sedimentation zone (1) and the primary anaerobic biological zone (2). The drainage pipe riser (801) is fitted inside the drainage pipe waterproof sleeve (802). The venting pipe system (9) consists of a venting pipe (901), a venting pipe waterproof sleeve (902), and a venting pipe valve (903). The pipe waterproof sleeve (902) is fixedly installed below the front wall (401) of the oil-water separator and sedimentation zone (1) and below the right wall (404) of the secondary anaerobic biological zone (3). The venting pipe (901) is fitted inside the pipe waterproof sleeve (902), and the venting pipe valve (903) is fixedly installed on the venting pipe (901). The water outlet pipe system (17) consists of a water outlet pipe (1701), a water outlet pipe waterproof sleeve (1702), and a water outlet pipe valve (1703). The water outlet pipe waterproof sleeve (1702) is fixedly installed on the front wall (401) of the secondary anaerobic biological zone (3), and the water outlet pipe (1701) is fitted inside the water outlet pipe waterproof sleeve (1702). A water outlet pipe valve (1703) is fixedly installed on the water outlet pipe (1701).

3. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: The biological packing netting device (12) consists of a netting rope (1201), bolt clips (1202), and a biological packing rope (1203). The netting rope (1201) is fixedly installed by the bolt clips (1202), and the biological packing rope (1203) is bound to the netting rope (1201). The microorganism attached to the biological packing rope (1203) is Clostridium butyricum.

4. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: The outer shell (1101) of the suspended biological filler ball (11) is filled with biological filler (1102), and the microorganism of the biological filler (1102) is Clostridium butyricum.

5. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: The overflow pipe system (15) consists of an overflow pipe (1501) and an overflow pipe waterproof sleeve (1502); the overflow pipe waterproof sleeve (1502) is installed on the right wall (404) of the secondary anaerobic biological zone (3), and the overflow pipe (1501) is fitted inside the overflow pipe waterproof sleeve (1502).

6. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: It also includes a maintenance manhole (1803), which is located on the top of the primary anaerobic biological zone (2) and the secondary anaerobic biological zone (3), and is covered by a cover plate with a cover plate handle (1802).

7. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: A vent cap (19) is provided on the prefabricated cover plate (1801).

8. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 1, characterized in that: The grass-planting shallow ditch (20) is connected to the water outlet pipe system (17) with pebbles (2001). The grass-planting shallow ditch (20) consists of turf (2002), planting soil (2003), gravel (2004) and permeable geotextile (2005) from top to bottom.

9. The anaerobic biological sedimentation tank for treating sensitive water bodies crossed by highway bridge runoff as described in claim 8, characterized in that: The grass-planted shallow ditch (20) has a trapezoidal profile, with the lowest point elevation 10-30 cm lower than the surrounding ground elevation, and the perimeter is wrapped with permeable geotextile (2005).

10. A method for treating sensitive water bodies crossed by highway bridge runoff using the anaerobic biological sedimentation tank according to any one of claims 1 to 9, characterized in that, Includes the following steps: In daily use, the venting pipe valve (903) is normally closed, and the outlet pipe valve (1703) is normally open; When rainfall occurs, the runoff from the highway bridge surface flows into the oil-water separation and sedimentation zone (1) through the inlet pipe (501). The oil-water separation and sedimentation zone (1) is equipped with a vertically installed screen (6) along the direction of water flow to intercept floating and suspended matter carried in the bridge surface runoff, thus preventing blockage of the drainage pipe. The outlet of the inlet pipe (501) faces downwards, which can prevent the runoff from directly impacting the screen (6) and reduce the impact force. The oil-water separation baffle (7) installed vertically along the water flow in the oil-water separation and sedimentation zone (1) can separate water and oil. The oil is lighter than water and floats on the upper layer of water. It is blocked by the oil-water separation baffle (7) and cannot flow out. When the runoff from the highway bridge surface is only rainwater, the rainwater runoff flows through the drain pipe (801) from below the oil-water separation baffle (7) and enters the primary anaerobic biological zone (2). When a tanker truck leaks oil on a highway bridge, the runoff mixed with oil pollution first passes through the debris barrier (6), then is separated by the oil-water baffle (7), and then the oil pollution is further separated by the drainage pipe (801) to prevent the oil pollution from flowing into the primary anaerobic biological zone (2); the suspended biological packing balls (11) added to the oil-water barrier sedimentation zone (1) can perform preliminary treatment on the dangerous chemical substances leaked from the tanker truck, and then the oil pollution is sucked away by the oil suction truck for centralized treatment; Clostridium butyricum has an adsorption and degradation effect on phenol in petroleum products, and has a bond-breaking effect on long-chain alkanes, cycloalkanes, aromatic hydrocarbons, etc.; the grease trap (6) and grease trap (7) of the oil-water barrier and sedimentation zone (1) are a certain distance away from the bottom of the pool, and the mud and sand in the bridge surface runoff will slowly settle at the bottom of the pool, and the turbidity of the runoff will gradually decrease. The bridge surface runoff passes through the oil-water separation and sedimentation zone (1), and the bridge surface runoff is separated into oil and water by the oil-water separation baffle (7). Most of the bridge surface runoff flowing into the primary anaerobic biological treatment zone (2) is rainwater runoff. The primary anaerobic biological treatment zone (2) is equipped with an anaerobic biological packing netting device (12). The bridge surface runoff and a number of anaerobic microorganisms will gradually form a biofilm on the anaerobic biological packing rope (1202) to treat and degrade the bridge surface runoff pollution. Clostridium butyricum has a high potential for efficient degradation of nitrogen and heavy metal pollutants in the initial rainwater. The return flow partition (13) set in the primary anaerobic biological treatment zone (2) guides the water flow, reduces short-circuiting, prolongs the contact time between the bridge surface runoff and the biological packing, and enhances the treatment effect. The bridge surface runoff treated by the anaerobic biological packing netting device (12) flows into the secondary anaerobic biological treatment zone (3) through the water passage (14). The bridge surface runoff passes through the oil-water separation and sedimentation zone (1) and the primary anaerobic biological zone (2), and finally flows into the secondary anaerobic biological treatment zone (3). Most of the pollutants in the highway bridge surface runoff are removed through the oil-water separation and sedimentation zone (1) and the primary anaerobic biological zone (2), but they still do not meet the discharge standards of sensitive water bodies with high water quality requirements. The secondary anaerobic biological treatment zone (2) is equipped with an anaerobic biological packing mesh device (12) to further treat and degrade the bridge surface runoff pollution. The return flow partition wall (13) set in the secondary anaerobic biological treatment zone (2) reduces short-circuiting, prolongs the contact time between the bridge surface runoff and the biological packing, and improves the treatment efficiency. The treated bridge surface runoff is discharged into natural water bodies through the outlet pipe (1701). When heavy rain or torrential rain occurs, the anaerobic biological sedimentation tank, due to its limited volume, cannot withstand the instantaneous excess rainwater runoff, and the excess bridge surface runoff is discharged through the overflow pipe (1501).

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