A circulating cross-flow type anaerobic system

Abstract

The application discloses a circulating cross-flow type cascade anaerobic system, which comprises a reaction unit, an external circulation unit and an internal circulation unit; the reaction unit comprises a first-stage anaerobic reactor, a second-stage anaerobic reactor and a buffer pool which are sequentially connected in communication; the first-stage anaerobic reactor is filled with a filler carrier and is provided with a water inlet and an external circulation port; the water inlet flow is smaller than the water inlet flow of the external circulation port; the external circulation unit comprises an external circulation pipe and an external circulation pump; the external circulation pipe is connected with the buffer pool and the external circulation port; and the external circulation pump is arranged in the external circulation pipe; the internal circulation unit comprises an internal circulation pipe and an internal circulation pump; the two ends of the internal circulation pipe are connected with the top and the bottom of the second-stage anaerobic reactor respectively; and the internal circulation pump is arranged in the internal circulation pipe. The scheme improves the impact load capacity of the reactor, enables the system to maintain a stable anaerobic environment and a pure anaerobic bacterial population, realizes efficient fluidization of the filler in the anaerobic fluidized bed reactor, improves the treatment efficiency and reduces the energy consumption.

Description

Technical Field

[0001] This invention relates to the field of anaerobic reactor technology, and more specifically to a circulating cross-flow cascade anaerobic system. Background Technology

[0002] Industries such as petrochemicals, coal chemicals, coking, food processing, and pharmaceuticals generate large amounts of high-concentration organic wastewater, which contains various organic and inorganic pollutants. Currently, the pretreatment methods for high-concentration, recalcitrant organic wastewater include physical, chemical, and biological methods. Physical and chemical methods primarily target suspended solids, oils, inorganic pollutants, and non-dissolved organic pollutants. For dissolved organic pollutants, which constitute the majority of the wastewater, advanced oxidation, wet oxidation, and centrifugal extraction can also be used, but these methods are expensive. Biological methods, especially anaerobic biological methods, remain the most widely used pretreatment approach.

[0003] CN212504208U discloses an anaerobic reactor in which wastewater flows along the water flow direction through the main reaction zone, sludge settling zone and anaerobic biological packing zone to the overflow device at the upper rear end of the reactor body, and is finally discharged through the drain outlet. Through the distribution of horizontal and vertical space, the internal space of the anaerobic reactor is effectively utilized.

[0004] However, when treating high-concentration and toxic recalcitrant organic wastewater, this type of anaerobic reactor suffers from severe degradation efficiency due to the excessively high organic pollution load and the inhibitory effect of toxic substances on microorganisms. This makes it impossible to guarantee the effluent treatment effect and significantly increases wastewater treatment costs. Furthermore, because high-concentration recalcitrant wastewater has a complex composition and requires different hydraulic retention times for different pollutants, using a single-stage anaerobic reactor may result in some pollutants remaining untreated, leading to effluent quality deterioration and increased pressure on subsequent treatment systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a circulating cross-flow cascade anaerobic system to solve the technical problem that in the existing anaerobic reactors, when treating high-concentration and toxic difficult-to-treat organic wastewater, the degradation efficiency of pollutants is severely affected due to the excessively high organic pollution load and the inhibitory effect of toxic substances on microorganisms, thus failing to guarantee the effluent treatment effect of the system.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] This invention provides a circulating cross-flow cascade anaerobic system, comprising:

[0008] The reaction unit includes a primary anaerobic reactor, a secondary anaerobic reactor, and a buffer tank connected in sequence. The primary anaerobic reactor is filled with a packing carrier and has an inlet and an external circulation port. The inlet flow rate is less than the external circulation port flow rate.

[0009] An external circulation unit includes an external circulation pipe and an external circulation pump. The external circulation pipe connects the buffer pool and the external circulation port, and the external circulation pump is located in the external circulation pipe.

[0010] The internal circulation unit includes an internal circulation pipe and an internal circulation pump. The two ends of the internal circulation pipe are respectively connected to the top and bottom of the secondary anaerobic reactor, and the internal circulation pump is located in the internal circulation pipe.

[0011] In some embodiments, the reaction unit further includes a water inlet pipe that extends from the water inlet into the primary anaerobic reactor and has multiple water inlet channels at its top.

[0012] The external circulation port includes multiple external circulation branch ports, and the external circulation pipe includes an external circulation main pipe and multiple external circulation branch pipes. One end of the external circulation main pipe is connected to the buffer pool, and the other end is connected to multiple external circulation branch pipes. The multiple external circulation branch pipes extend into the primary anaerobic reactor from the multiple external circulation branch ports, and at least one external circulation branch pipe is located below the inlet pipe. The external circulation pump is located on the external circulation main pipe.

[0013] In some embodiments, the external circulation branch pipe is provided with a plurality of circulation outlet holes on both sides in the vertical direction; and / or,

[0014] The multiple external circulation branch pipes are arranged at intervals along the vertical direction. Correspondingly, the multiple external circulation branch pipes are arranged at intervals along the vertical direction, and the water inlet pipe is located between two adjacent external circulation branch pipes at the bottom.

[0015] In some embodiments, the inlet flow rate is Q1, and the outlet flow rate is Q2, satisfying Q2 / Q1≥10.

[0016] In some embodiments, the reaction unit further includes a first connecting pipe, one end of which is connected to the top of the primary anaerobic reactor and the other end of which is connected to the bottom of the secondary anaerobic reactor;

[0017] The connection point between the first connecting pipe and the primary anaerobic reactor is located above the external circulation port and the water inlet.

[0018] In some embodiments, the internal circulation pipe includes an internal circulation main pipe and a plurality of internal circulation branch pipes. One end of the internal circulation main pipe is connected to the top of the secondary anaerobic reactor, and the other end is connected to the plurality of internal circulation branch pipes. The plurality of internal circulation branch pipes are respectively connected to the bottom of the secondary anaerobic reactor, and the connection points with the secondary anaerobic reactor are arranged at intervals in the vertical direction. The internal circulation pump is located on the internal circulation main pipe.

[0019] In some embodiments, the connection between the first connecting pipe and the secondary anaerobic reactor is located between two adjacent internal circulation branch pipes at the bottom.

[0020] In some embodiments, the first connecting pipe portion extends into the secondary anaerobic reactor, and the top of the portion extending into the secondary anaerobic reactor is provided with a first water outlet channel.

[0021] Each of the internal circulation branch pipes extends into the secondary anaerobic reactor, and the top of the portion extending into the secondary anaerobic reactor is provided with a second outlet channel.

[0022] In some embodiments, the reaction unit further includes a second connecting pipe, one end of which is connected to the top of the secondary anaerobic reactor and the other end of which is connected to the buffer tank, and the connection point between the second connecting pipe and the secondary anaerobic reactor is located above the internal circulation pipe.

[0023] Specifically, the upward velocity of the water flow entering the primary anaerobic reactor from the inlet is V1, satisfying V1 > 5 m / h; the upward velocity of the water flow entering the primary anaerobic reactor from the external circulation port is V2, satisfying 0.25 m / s ≤ V2 ≤ 0.30 m / s; the upward velocity of the water flow entering the secondary anaerobic reactor from the first connecting pipe is V3, satisfying V3 > 0.5 m / h; and the upward velocity of the water flow entering the secondary anaerobic reactor from the internal circulation pipe is V4, satisfying 0.15 m / s ≤ V4 ≤ 0.30 m / s.

[0024] In some embodiments, the water flow rate from the primary anaerobic reactor to the secondary anaerobic reactor is Q3, and the water flow rate from the internal circulation pipe to the secondary anaerobic reactor is Q4, satisfying Q4 / Q3≥5.

[0025] Compared with existing technologies, the circulating cross-flow cascade anaerobic system provided by this invention uses a two-stage circulating cross-flow anaerobic reaction system as the main body, combined with high-performance packing carriers, efficient and uniform water distribution, and large-flow circulation, to improve the reactor's resistance to shock loads. This allows the system to maintain a stable anaerobic environment and pure anaerobic bacteria, and achieves efficient fluidization of the packing material within the anaerobic fluidized bed reactor. Specifically, the COD removal rate of the first-stage anaerobic reactor can reach 75%–80%, the COD removal rate of the second-stage anaerobic reactor can reach 55%–65%, and the total COD removal rate can reach 89%–93%. Furthermore, the system has no complex treatment process units, making it simple and efficient. Through cascade circulating reflux treatment technology, the anaerobic sludge undergoes enhanced cultivation of dominant specific bacteria, improving treatment efficiency and reducing the footprint by 10%–30%. In addition, the first-stage anaerobic reactor achieves a sludge-film symbiotic synergistic treatment effect, while the hydraulic cross-flow formed by the influent and external circulation achieves packing fluidization, eliminating the need for a power stirring device and reducing energy consumption by 10%–20%.

[0026] This allows for the use of a cascade anaerobic reactor as a pretreatment unit, reducing the content of toxic and harmful substances entering the system. By recirculating the system effluent back to the front end, the content of toxic and harmful substances is reduced while preventing the introduction of dissolved oxygen into the anaerobic reactor, thus ensuring the stability of the anaerobic environment. Furthermore, the sludge separated by the system is recirculated back to the front end, preventing the introduction of other microbial populations and ensuring the purity of the microbial community within the anaerobic reactor. The first-stage reactor can treat relatively easy-to-treat pollutants, and combined with the second-stage reactor, it can handle more difficult-to-treat pollutants, ensuring the system consistently meets standards. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a circulating cross-flow cascade anaerobic system provided in an embodiment of the present invention;

[0028] Figure 2 yes Figure 1 A schematic diagram of the intermediate-stage anaerobic reactor and its packing carrier;

[0029] Figure 3 yes Figure 2 Schematic diagram of a first-stage anaerobic reactor;

[0030] Figure 4 yes Figure 1 Schematic diagram of a secondary anaerobic reactor;

[0031] Figure 5 yes Figure 3 Enlarged diagram of point A in the middle.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Primary anaerobic reactor; 11. Inlet; 12. External circulation port; 121. External circulation branch port; 2. Secondary anaerobic reactor; 3. Buffer tank; 4. Packing carrier; 5. External circulation pipe; 51. External circulation pump; 52. External circulation main pipe; 53. External circulation branch pipe; 6. Internal circulation pipe; 61. Internal circulation pump; 62. Internal circulation main pipe; 63. Internal circulation branch pipe; 7. Inlet pipe; 71. Inlet lift pump; 8. First connecting pipe; 81. Inclined end face; 9. Second connecting pipe. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] To address the technical problem that existing anaerobic reactors, when treating high-concentration and toxic recalcitrant organic wastewater, suffer from excessively high organic pollution loads and the inhibitory effect of toxic substances on microorganisms, severely impacting pollutant degradation efficiency and failing to guarantee the system's effluent treatment effect, this invention provides a circulating cross-flow cascade anaerobic system. This system reduces the content of toxic and harmful substances entering the system without introducing dissolved oxygen into the anaerobic reactor, ensuring the stability of the anaerobic environment and achieving high treatment efficiency.

[0036] Please see Figures 1 to 4 , Figures 1 to 4 This is a schematic diagram of a circulating cross-flow cascade anaerobic system according to an embodiment of the present invention. The circulating cross-flow cascade anaerobic system includes a reaction unit, an external circulation unit, and an internal circulation unit. The reaction unit includes a primary anaerobic reactor 1, a secondary anaerobic reactor 2, and a buffer tank 3 connected in sequence. The primary anaerobic reactor 1 is filled with a packing carrier 4 and has an inlet 11 and an external circulation port 12. The inlet flow rate of the inlet 11 is less than the inlet flow rate of the external circulation port 12. The external circulation unit includes an external circulation pipe 5 and an external circulation pump 51. The external circulation pipe 5 is connected to the buffer tank 3 and the external circulation port 12. The external circulation pump 51 is located in the external circulation pipe 5. The internal circulation unit includes an internal circulation pipe 6 and an internal circulation pump 61. The two ends of the internal circulation pipe 6 are respectively connected to the top and bottom of the secondary anaerobic reactor 2. The internal circulation pump 61 is located in the internal circulation pipe 6.

[0037] The circulating cross-flow cascade anaerobic system provided by this invention uses a two-stage circulating cross-flow anaerobic reactor system as its main component, combined with high-performance packing material carrier 4, efficient and uniform water distribution, and a large-flow circulation system. This improves the reactor's resistance to shock loads, enabling the system to maintain a stable anaerobic environment and pure anaerobic bacteria, and achieving efficient fluidization of the packing material within the anaerobic fluidized bed reactor. Specifically, the COD (chemical oxygen demand) removal rate of the first-stage anaerobic reactor 1 can reach 75%–80%, the COD removal rate of the second-stage anaerobic reactor 2 can reach 55%–65%, and the total COD removal rate can reach 89%–93%. Furthermore, the system has no complex treatment process units, making it simple and efficient. Through cascade circulating reflux treatment technology, the anaerobic sludge undergoes enhanced cultivation of dominant specific bacteria, improving treatment efficiency and reducing the footprint by 10%–30%. In addition, the first-stage anaerobic reactor 1 achieves a sludge-film symbiotic synergistic treatment effect, while utilizing the hydraulic cross-flow formed by the influent and external circulation to achieve packing fluidization, eliminating the need for a power stirring device and reducing energy consumption by 10%–20%.

[0038] This allows for the use of a cascade anaerobic reactor as a pretreatment unit, reducing the content of toxic and harmful substances entering the system. By recirculating the system effluent back to the front end, the content of toxic and harmful substances is reduced while preventing the introduction of dissolved oxygen into the anaerobic reactor, thus ensuring the stability of the anaerobic environment. Furthermore, the sludge separated by the system is recirculated back to the front end, preventing the introduction of other microbial populations and ensuring the purity of the microbial community within the anaerobic reactor. The first-stage reactor can treat relatively easy-to-treat pollutants, and combined with the second-stage reactor, it can handle more difficult-to-treat pollutants, ensuring the system consistently meets standards.

[0039] In one embodiment, please refer to Figure 2 and Figure 3 The reaction unit also includes an inlet pipe 7, which extends into the primary anaerobic reactor 1 from the inlet 11, and has multiple inlet channels at its top; the external circulation port 12 includes multiple external circulation branch ports 121, and the external circulation pipe 5 includes an external circulation main pipe 52 and multiple external circulation branch pipes 53. One end of the external circulation main pipe 52 is connected to the buffer tank 3, and the other end is connected to multiple external circulation branch pipes 53. The multiple external circulation branch pipes 53 extend into the primary anaerobic reactor 1 from the multiple external circulation branch ports 121, and at least one external circulation branch pipe 53 is located below the inlet pipe 7. The external circulation pump 51 is located in the external circulation main pipe 52.

[0040] In this embodiment, the inlet pipe 7 of the primary anaerobic reactor 1 is placed above the external circulation branch pipe 53, so that the inlet water in the primary anaerobic reactor 1 can be uniformly mixed with the external circulation water. At the same time, multiple external circulation branch pipes 53 are set to improve the stirring capacity. It should be noted that in this scheme, the inlet pipe 7 and the external circulation branch pipes 53 are respectively arranged in a ring, allowing water to enter the primary anaerobic reactor 1 at multiple points in a ring.

[0041] In one embodiment, the external circulation branch pipe 53 is provided with multiple circulation outlet holes on both sides in the vertical direction; the multiple external circulation branch pipes 53 are arranged at intervals in the vertical direction, and the water inlet pipe 7 is located between two adjacent external circulation branch pipes 53 at the bottom.

[0042] In this scheme, water outlet holes are provided on the upper and lower sides of the external circulation branch pipe 53, so that the upper and lower sides of the external circulation branch pipe 53 can be fully stirred; at the same time, the water inlet pipe 7 is placed between the two external circulation branch pipes 53 at the bottom, and multiple external circulation branch pipes 53 are arranged at intervals in the vertical direction, so that the upper external circulation water can enter in layers, and at the same time, the external circulation water and the inlet water can be fully contacted and mixed in the reactor.

[0043] In one embodiment, the inlet flow rate of inlet 11 is Q1, and the inlet flow rate of external circulation port 12 is Q2, satisfying Q2 / Q1≥10. Furthermore, the flow rate from primary anaerobic reactor 1 to secondary anaerobic reactor 2 is Q3, and the flow rate from internal circulation pipe 6 to secondary anaerobic reactor 2 is Q4, satisfying Q4 / Q3≥5.

[0044] In this embodiment, the hydraulic jet of the upper external circulating water can ensure that the packing carrier 4 in the primary anaerobic reactor 1 is in a fluidized state. Specifically, the ratio of external circulating water to influent flow rate in the primary anaerobic reactor 1 is controlled at not less than 10:1; and the ratio of internal circulating water to influent flow rate in the secondary anaerobic reactor 2 is controlled at not less than 5:1. This allows for high-flow circulation inside and outside the system, improving the reactor's resistance to shock loads and enabling the system to maintain a stable anaerobic environment and pure anaerobic bacteria.

[0045] Furthermore, in this scheme, the packing material carrier 4 serves as the attachment carrier for microbial growth. The packing material should be selected to be durable, have a large specific surface area, be easily fluidized, possess good biocompatibility and chemical stability, and have a reasonable pore size distribution. Specifically, this packing material facilitates microbial attachment but has no adsorption effect on pollutants, preventing the accumulation of toxic substances on the packing material and the formation of localized high-concentration areas, which would be detrimental to microbial biofilm formation. The primary anaerobic reactor 1 adopts a fluidized bed configuration.

[0046] In one embodiment, the reaction unit further includes a first connecting pipe 8, one end of which is connected to the top of the primary anaerobic reactor 1 and the other end of which is connected to the bottom of the secondary anaerobic reactor 2; wherein the connection between the first connecting pipe 8 and the primary anaerobic reactor 1 is located above the external circulation port 12 and the water inlet 11.

[0047] In this embodiment, the first-stage anaerobic reactor 1 and the second-stage anaerobic reactor 2 are connected by the first connecting pipe 8, and the first connecting pipe 8 is set as described above so that the solution after initial treatment at the top of the first-stage anaerobic reactor 1 can flow downstream to the second-stage anaerobic reactor 2.

[0048] It should be noted that you should refer to [link / reference]. Figure 5 In one embodiment, the end of the first connecting pipe 8 connected to the primary anaerobic reactor 1 has an inclined end face 81. This inclined end face 81 is inclined from bottom to top toward the middle of the primary anaerobic reactor 1, and its lower end is located at the side wall of the primary anaerobic reactor 1. By adopting the above-mentioned special design to prevent packing loss and collision at the inlet end of the first connecting pipe 8, the packing is prevented from being lost with the effluent, and the obstruction of packing flow and wear of the packing caused by traditional screen types are avoided.

[0049] In one embodiment, the internal circulation pipe 6 includes an internal circulation main pipe 62 and a plurality of internal circulation branch pipes 63. One end of the internal circulation main pipe 62 is connected to the top of the secondary anaerobic reactor 2, and the other end is connected to the plurality of internal circulation branch pipes 63. The plurality of internal circulation branch pipes 63 are respectively connected to the bottom of the secondary anaerobic reactor 2, and the connection points with the secondary anaerobic reactor 2 are arranged at intervals in the vertical direction. The internal circulation pump 61 is located on the internal circulation main pipe 62.

[0050] In this embodiment, multiple internal circulation branch pipes 63 are also installed within the secondary anaerobic reactor 2 to improve the mixing uniformity of the influent and circulating solution within the secondary anaerobic reactor 2. It should be noted that in this design, the portion of the first connecting pipe 8 within the secondary anaerobic reactor 2 is arranged in a ring shape and employs a multi-point uniform water inlet method; similarly, each internal circulation branch pipe 63 is also arranged in a ring shape within the secondary anaerobic reactor 2 and employs a multi-point uniform water inlet method. It should also be noted that in one embodiment, the outlet channels on opposite sides of the external circulation branch pipe 53 and the internal circulation branch pipe 63 face towards the center of the corresponding reactor to further improve the stirring capacity.

[0051] In one embodiment, the connection between the first connecting pipe 8 and the secondary anaerobic reactor 2 is located between two adjacent internal circulation branch pipes 63 at the bottom.

[0052] In this embodiment, the effluent from the secondary anaerobic reactor 2 is recirculated back into the secondary circulating cross-flow anaerobic reactor. The internal circulating water enters the secondary anaerobic reactor 2 using a layered multi-point water inlet method, and the bottommost external circulating water inlet pipe 7 is located below the first internal connecting pipe 8, so that the circulating water and the inlet water can be fully contacted and mixed in the reactor. Furthermore, the upper internal circulating water enters in layers, which fully ensures that the internal circulating water and the inlet water are evenly mixed.

[0053] In one embodiment, a portion of the first connecting pipe 8 extends into the secondary anaerobic reactor 2, and the top of the portion extending into the secondary anaerobic reactor 2 is provided with a first water outlet channel; a portion of each internal circulation branch pipe 63 extends into the secondary anaerobic reactor 2, and the top of the portion extending into the secondary anaerobic reactor 2 is provided with a second water outlet channel.

[0054] In this embodiment, the outlets of the first connecting pipe 8 and the internal circulation branch pipe 63 are both located at their respective tops to extend the flow path of the output solution and enable it to be fully mixed with the subsequent solution, thereby improving the processing efficiency.

[0055] In one embodiment, the reaction unit further includes a second connecting pipe 9, one end of which is connected to the top of the secondary anaerobic reactor 2, and the other end is connected to the buffer tank 3. The connection point between the second connecting pipe 9 and the secondary anaerobic reactor 2 is located above the inner circulation pipe 6. The upward velocity of the water flow entering the primary anaerobic reactor 1 from the inlet 11 is V1, satisfying V1 > 5 m / h; the upward velocity of the water flow entering the primary anaerobic reactor 1 from the outer circulation port 12 is V2, satisfying 0.25 m / s ≤ V2 ≤ 0.30 m / s; the upward velocity of the water flow entering the secondary anaerobic reactor 2 from the first connecting pipe 8 is V3, satisfying V3 > 0.5 m / h; and the upward velocity of the water flow entering the secondary anaerobic reactor 2 from the inner circulation pipe 6 is V4, satisfying 0.15 m / s ≤ V4 ≤ 0.30 m / s.

[0056] In this embodiment, the flow rates of the influent and external circulating water in the primary anaerobic reactor 1 are set as described above to ensure the packing material remains in a fluidized state. Simultaneously, the flow rates of the influent and internal circulating water in the secondary anaerobic reactor 2 are set as described above to ensure sufficient contact and mixing between the influent and the sludge.

[0057] In addition, exhaust ports are provided at the top of the primary anaerobic reactor 1 and the secondary anaerobic reactor 2.

[0058] To better understand this invention, the following is combined with... Figures 1 to 5 The technical solution of the present invention will be described in detail below:

[0059] In one embodiment, the influent water quality is determined by COD. cr The design parameters are 20000~60000mg / L, pH=2~4, conductivity=20000~30000μS / cm, total nitrogen<1mg / L, total phosphorus<0.5mg / L, total phenol=500~1000mg / L, cyanide=20~100mg / L, and sulfide=50~500mg / L. To meet the emission standards for subsequent conventional processes such as activated sludge and biofilm treatment, each unit is set as follows.

[0060] The inlet pipe 7 of the first-stage anaerobic reactor 1 is arranged in a single layer and in a ring shape. The ring water distribution pipe is uniformly provided with flow holes. The number of layers of water distribution pipe and the number of flow holes are determined according to the upward flow velocity of the reactor. The upward flow velocity is >5m / h.

[0061] Primary Anaerobic Reactor 1: Primary anaerobic reactor 1 adopts a fluidized bed configuration, filled with packing material 4. The fluidization state of the packing material is ensured by the hydraulic cross-flow formed by the influent and external circulating influent. The packing material should be resistant to wear, have a large specific surface area, be easily fluidized, possess good biocompatibility and chemical stability, and have a reasonable pore size distribution. Specifically, this packing material facilitates microbial attachment but has no adsorption effect on pollutants.

[0062] External circulation pipe 5 of primary anaerobic reactor 1: The external circulation pipe 5 is arranged in layers within the primary anaerobic reactor 1. Each layer is arranged in a ring. Flow holes are evenly arranged on the ring water distribution pipe. The number of layers of water distribution pipe and the number of flow holes are determined according to the reactor height and the flow velocity at the orifice. The flow velocity at the orifice is 0.25~0.30m / s. The ratio of external circulation water flow rate to inlet water flow rate is not less than 10:1.

[0063] The internal circulation pipe 6 of the secondary anaerobic reactor 2 is arranged in layers within the secondary anaerobic reactor 2. Each layer is arranged in a ring shape. Flow holes are evenly distributed on the ring water distribution pipe. The number of layers of water distribution pipe and the number of flow holes are determined according to the reactor height and the flow velocity at the orifice. The flow velocity at the orifice is 0.15 to 0.20 m / s. The ratio of internal circulation water flow rate to inlet water flow rate is not less than 5:1.

[0064] The workflow is as follows:

[0065] 1. Inlet water of primary anaerobic reactor 1: Wastewater enters the primary anaerobic reactor 1 evenly through the inlet pipe 7 to react and remove pollutants from the wastewater. The inlet water system of primary anaerobic reactor 1 includes an inlet lift pump 71 and an inlet pipe 7. The inlet lift pump 71 is installed on the inlet pipe 7.

[0066] 2. Primary Anaerobic Reactor 1: Wastewater is reacted in the primary anaerobic reactor 1. The primary anaerobic reactor 1 adopts a fluidized bed form and is filled with packing material carrier 4 for microbial attachment and growth, forming a mud-film symbiotic anaerobic biological treatment system, through which microorganisms degrade pollutants in wastewater.

[0067] 3. Effluent from primary anaerobic reactor 1: After the wastewater is reacted in primary anaerobic reactor 1, it enters secondary anaerobic reactor 2 evenly through the first connecting pipe 8.

[0068] 4. Secondary anaerobic reactor 2: Wastewater is reacted in the secondary anaerobic reactor 2, and pollutants in the wastewater are further removed through microbial degradation within the secondary anaerobic reactor 2;

[0069] 5. Effluent from the secondary anaerobic reactor 2: After the wastewater is reacted in the secondary anaerobic reactor 2, it enters the buffer tank 3 and the subsequent treatment system through the second connecting pipe 9.

[0070] 6. External circulation unit: The effluent from the secondary anaerobic reactor 2 enters the primary anaerobic fluidized bed reactor through the external circulation unit, where it is fully combined and uniformly mixed with the influent of the primary anaerobic fluidized bed reactor, thereby reducing the concentration of pollutants in the anaerobic fluidized bed reactor. The external circulation unit includes an external circulation pump 51 and an external circulation pipe 5.

[0071] 7. Internal circulation unit: An internal circulation unit is set in the secondary anaerobic reactor 2 to realize internal circulation inside the secondary anaerobic reactor 2, so that the effluent and influent are fully and evenly mixed, reducing the pollutant concentration in the secondary anaerobic reactor 2. The internal circulation is realized by the internal circulation pump 61.

[0072] Therefore, this scheme adopts a circulating cross-flow cascade anaerobic reactor system, with a two-stage circulating cross-flow anaerobic reactor system as the main body, combined with high-performance packing material carrier 4, efficient and uniform water distribution, and large flow circulation inside and outside the system, to improve the reactor's resistance to shock loads, so that the system can maintain a stable anaerobic environment and pure anaerobic bacteria, and achieve efficient fluidization of the packing material in the anaerobic fluidized bed reactor, without causing biofilm detachment of the carrier due to hydraulic shear.

[0073] This solution addresses issues such as the impact of high-pollution-load influent on the reactor, the inhibition of microbial activity by toxic substances, the introduction of dissolved oxygen through activated sludge recirculation, and the detachment of carrier biofilm caused by excessive hydraulic or mechanical agitation. It is of great significance for improving the pretreatment efficiency of high-concentration, recalcitrant organic wastewater, reducing the difficulty of subsequent treatment units, enhancing the stability of system treatment effects, and reducing system investment and treatment costs.

[0074] Based on the above embodiments, this solution has the following advantages:

[0075] (1) High treatment efficiency: The COD removal rate of the primary anaerobic reactor 1 can reach 75% to 80%, the COD removal rate of the secondary anaerobic reactor 2 can reach 55% to 65%, and the total COD removal rate can reach 89% to 93%.

[0076] (2) The system is simple: there are no complex processing units in the system, making it simple and efficient.

[0077] (3) Reduced footprint: The anaerobic sludge was enhanced with dominant specific bacteria through cascade circulation reflux treatment technology, which improved treatment efficiency and reduced the footprint by 10% to 30%.

[0078] (4) Low energy consumption: The synergistic treatment effect of mud film symbiosis is formed in the first-stage anaerobic reactor 1. At the same time, the fluidization of the packing is achieved by using the hydraulic cross flow formed by the influent, without the need for a power stirring device, which reduces energy consumption by 10% to 20%.

[0079] (5) Cost-effective: The system greatly extends the hydraulic retention time of recalcitrant dissolved organic matter, thereby reducing the residence time of the anaerobic reactor and saving investment.

[0080] (6) Low operating cost: The coupled treatment process using high-performance packing material is adopted, and the effluent is returned to the front end of the system in large flow rate, which reduces the pollution load, saves reactor volume, and reduces operating cost.

[0081] (7) Good stability: The use of a cascade anaerobic reactor as a pretreatment unit reduces the content of toxic and harmful substances entering the system. Simultaneously, the system effluent is recirculated back to the front end, further reducing the content of toxic and harmful substances while preventing the introduction of dissolved oxygen into the anaerobic reactor, thus ensuring the stability of the anaerobic environment. The sludge separated by the system is recirculated back to the front end, preventing the introduction of other microbial populations and ensuring the purity of the microbial population within the anaerobic reactor. The cascade anaerobic reactor, with its primary reactor capable of treating relatively easy-to-treat pollutants and combined with secondary reactors, can handle more difficult-to-treat pollutants, ensuring the system consistently meets standards.

[0082] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A circulating cross-flow cascade anaerobic system, characterized in that, include: The reaction unit includes a primary anaerobic reactor, a secondary anaerobic reactor, and a buffer tank connected in sequence. The primary anaerobic reactor is filled with a packing carrier and has an inlet and an external circulation outlet. The inlet flow rate is less than the external circulation outlet flow rate, and the inlet flow rate is less than the external circulation outlet flow rate Q2 / Q1≥10. The flow rate from the primary anaerobic reactor to the secondary anaerobic reactor is Q3. An external circulation unit includes an external circulation pipe and an external circulation pump. The external circulation pipe connects the buffer pool and the external circulation port, and the external circulation pump is located in the external circulation pipe. and The internal circulation unit includes an internal circulation pipe and an internal circulation pump. The two ends of the internal circulation pipe are respectively connected to the top and bottom of the secondary anaerobic reactor. The internal circulation pump is located in the internal circulation pipe. The water flow rate of the internal circulation pipe to the secondary anaerobic reactor is Q4, which satisfies Q4 / Q3≥5. The reaction unit further includes a first connecting pipe, one end of which is connected to the top of the primary anaerobic reactor and the other end of which is connected to the bottom of the secondary anaerobic reactor; wherein, the connection point between the first connecting pipe and the primary anaerobic reactor is located above the external circulation port and the water inlet; the end of the first connecting pipe connected to the primary anaerobic reactor has an inclined end face, which is inclined from bottom to top toward the middle of the primary anaerobic reactor, and the lower end is located at the side wall of the primary anaerobic reactor.

2. The circulating cross-flow cascade anaerobic system according to claim 1, characterized in that, The reaction unit also includes a water inlet pipe, which extends from the water inlet into the primary anaerobic reactor and has multiple water inlet channels at its top. The external circulation port includes multiple external circulation branch ports, and the external circulation pipe includes an external circulation main pipe and multiple external circulation branch pipes. One end of the external circulation main pipe is connected to the buffer pool, and the other end is connected to multiple external circulation branch pipes. The multiple external circulation branch pipes extend into the primary anaerobic reactor from the multiple external circulation branch ports, and at least one external circulation branch pipe is located below the inlet pipe. The external circulation pump is located on the external circulation main pipe.

3. The circulating cross-flow cascade anaerobic system according to claim 2, characterized in that, The external circulation branch pipe has multiple circulation outlet holes on both sides in the vertical direction; and / or, The multiple external circulation branch pipes are arranged at intervals along the vertical direction. Correspondingly, the multiple external circulation branch pipes are arranged at intervals along the vertical direction, and the water inlet pipe is located between two adjacent external circulation branch pipes at the bottom.

4. The circulating cross-flow cascade anaerobic system according to claim 1, characterized in that, The internal circulation pipe includes an internal circulation main pipe and multiple internal circulation branch pipes. One end of the internal circulation main pipe is connected to the top of the secondary anaerobic reactor, and the other end is connected to multiple internal circulation branch pipes. The multiple internal circulation branch pipes are respectively connected to the bottom of the secondary anaerobic reactor, and the connection points with the secondary anaerobic reactor are arranged at intervals in the vertical direction. The internal circulation pump is located on the internal circulation main pipe.

5. The circulating cross-flow cascade anaerobic system according to claim 4, characterized in that, The connection point between the first connecting pipe and the secondary anaerobic reactor is located between two adjacent internal circulation branch pipes at the bottom.

6. The circulating cross-flow cascade anaerobic system according to claim 5, characterized in that, The first connecting pipe extends into the secondary anaerobic reactor, and the top of the portion extending into the secondary anaerobic reactor is provided with a first water outlet channel. Each of the internal circulation branch pipes extends into the secondary anaerobic reactor, and the top of the portion extending into the secondary anaerobic reactor is provided with a second outlet channel.

7. The circulating cross-flow cascade anaerobic system according to claim 1, characterized in that, The reaction unit further includes a second connecting pipe, one end of which is connected to the top of the secondary anaerobic reactor and the other end is connected to the buffer tank, and the connection point between the second connecting pipe and the secondary anaerobic reactor is located above the internal circulation pipe. Specifically, the upward velocity of the water flow entering the primary anaerobic reactor from the inlet is V1, satisfying V1 > 5 m / h; the upward velocity of the water flow entering the primary anaerobic reactor from the external circulation port is V2, satisfying 0.25 m / s ≤ V2 ≤ 0.30 m / s; the upward velocity of the water flow entering the secondary anaerobic reactor from the first connecting pipe is V3, satisfying V3 > 0.5 m / h; and the upward velocity of the water flow entering the secondary anaerobic reactor from the internal circulation pipe is V4, satisfying 0.15 m / s ≤ V4 ≤ 0.30 m / s.

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