Circulating cross-flow cascade anaerobic system

Abstract

The invention discloses a circulating cross-flow cascade anaerobic system which comprises a reaction unit, an outer circulating unit and an inner circulating unit, the reaction unit comprises a first-stage anaerobic reactor, a second-stage anaerobic reactor and a buffer tank which are sequentially communicated, the first-stage anaerobic reactor is filled with a filler carrier and is provided with a water inlet and an outer circulation port, and the water inlet flow of the water inlet is smaller than that of the outer circulation port; the outer circulation unit comprises an outer circulation pipe and an outer circulation pump, the outer circulation pipe is communicated with the buffer pool and the outer circulation port, and the outer circulation pump is arranged on the outer circulation pipe; the internal circulation unit comprises an internal circulation pipe and an internal circulation pump, two ends of the internal circulation pipe are respectively communicated with the top and the bottom of the secondary anaerobic reactor, and the internal circulation pump is arranged in the internal circulation pipe. According to the scheme, the impact load resistance of the reactor is improved, a stable anaerobic environment and pure anaerobic flora can be kept in the system, efficient fluidization of the filler in the anaerobic fluidized bed reactor is realized, the treatment efficiency is improved, and the energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of anaerobic reactors, and in particular to a circulating cross-flow cascade anaerobic system. Background Art

[0002] The production processes of industries such as petrochemicals, coal chemicals, coking, food processing, and medicine will produce a large amount of high-concentration organic wastewater, which contains various organic and inorganic characteristic pollutants. At present, the methods used for the pretreatment of high-concentration difficult-to-degrade organic wastewater are physical, chemical, and biological. Physical and chemical methods are mainly aimed at suspended matter, oils, inorganic pollutants, and non-dissolved organic pollutants. For soluble organic pollutants that account for the main components, they can also be treated by advanced oxidation, wet oxidation, and centrifugal extraction. However, the investment and treatment costs are expensive. Biological methods, especially anaerobic biological methods, are still the most widely used pretreatment methods.

[0003] Publication No. CN212504208U discloses an anaerobic reactor, in which wastewater flows along the direction of water flow through the main reaction zone, the sludge settling zone and the anaerobic biological filler zone to reach the overflow at the upper rear end of the reactor outer body, and is finally discharged through the drain port. Through the allocation of lateral and vertical space, the space inside the anaerobic reactor is effectively utilized.

[0004] However, when this type of anaerobic reactor is used to treat high-concentration and toxic difficult-to-treat organic wastewater, the degradation efficiency of pollutants is seriously affected due to the excessive organic pollution load and the inhibitory effect of toxic substances on microorganisms. The system effluent treatment effect cannot be guaranteed, and the cost of wastewater treatment will be greatly increased. At the same time, due to the complex composition of high-concentration difficult-to-degrade wastewater and the different hydraulic retention times required to treat different pollutants, when using a single-stage anaerobic reactor, some pollutants may not be degraded, causing the effluent water quality to deteriorate and increasing the pressure on the subsequent treatment system. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and propose a circulating cross-flow cascade anaerobic system to solve the technical problem that when the anaerobic reactor in the prior art treats high-concentration and toxic difficult-to-treat organic wastewater, the degradation efficiency of pollutants is seriously affected due to the excessive organic pollution load and the inhibitory effect of toxic substances on microorganisms, and the system effluent treatment effect cannot be guaranteed.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: The present invention provides a circulating cross-flow cascade anaerobic system, comprising: The reaction unit comprises a primary anaerobic reactor, a secondary anaerobic reactor and a buffer tank which are connected in sequence, wherein the primary anaerobic reactor is filled with a filler carrier and has a water inlet and an external circulation port, wherein the water inlet flow rate is smaller than the water inlet flow rate of the external circulation port; an external circulation unit, comprising an external circulation pipe and an external circulation pump, wherein the external circulation pipe is connected to the buffer pool and the external circulation port, and the external circulation pump is arranged on the external circulation pipe; and The internal circulation unit comprises an internal circulation pipe and an internal circulation pump. The two ends of the internal circulation pipe are respectively connected to the top and the bottom of the secondary anaerobic reactor. The internal circulation pump is arranged on the internal circulation pipe.

[0007] In some embodiments, the reaction unit further comprises a water inlet pipe, the water inlet pipe extends from the water inlet into the primary anaerobic reactor, and a plurality of water inlet channels are arranged on the top of the water inlet pipe; The external circulation port includes a plurality of external circulation branch ports, and the external circulation pipe includes an external circulation main pipe and a plurality of external circulation branch pipes. One end of the external circulation main pipe is connected to the buffer tank, and the other end is connected to the plurality of external circulation branch pipes. The plurality of external circulation branch pipes extend into the primary anaerobic reactor from the plurality of external circulation branch ports respectively, and at least one of the external circulation branch pipes is located below the water inlet pipe, wherein the external circulation pump is arranged on the external circulation main pipe.

[0008] In some embodiments, the outer circulation branch pipe is provided with a plurality of circulation water outlet holes on both sides in the vertical direction; and / or, The plurality of outer circulation branch pipes are arranged at intervals along the vertical direction. Correspondingly, the plurality of outer circulation branch pipes are arranged at intervals along the vertical direction, and the water inlet pipe is located between two adjacent outer circulation branch pipes at the bottom.

[0009] In some embodiments, the water inlet flow rate of the water inlet is Q1, and the water inlet flow rate of the external circulation port is Q2, satisfying Q2 / Q1≥10.

[0010] In some embodiments, the reaction unit further comprises 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.

[0011] In some embodiments, 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 spaced apart in the vertical direction, and the internal circulation pump is arranged on the internal circulation main pipe.

[0012] In some embodiments, the connection point between the first connecting pipe and the secondary anaerobic reactor is located between two adjacent inner circulation branch pipes at the bottom.

[0013] In some embodiments, the first connecting pipe partially extends into the secondary anaerobic reactor, and a first water outlet channel is provided on the top of the portion extending into the secondary anaerobic reactor; A portion of each of the internal circulation branch pipes extends into the secondary anaerobic reactor, and a second water outlet channel is provided on the top of the portion extending into the secondary anaerobic reactor.

[0014] In some embodiments, the reaction unit further comprises 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 inner circulation pipe; Among them, the rising speed of water flow input into the primary anaerobic reactor from the water inlet is V1, which satisfies V1>5m / h, the rising speed of water flow input into the primary anaerobic reactor from the external circulation port is V2, which satisfies 0.25m / s≤V2≤0.30m / s, the rising speed of water flow input into the secondary anaerobic reactor from the first connecting pipe is V3, which satisfies V3>0.5m / h, and the rising speed of water flow input into the secondary anaerobic reactor from the internal circulation pipe is V4, which satisfies 0.15m / s≤V4≤0.30m / s.

[0015] 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.

[0016] Compared with the prior art, the circulating cross-flow cascade anaerobic system provided by the present invention is based on a two-stage circulating cross-flow anaerobic reaction system, combined with filling high-performance filler carriers, efficient and uniform water distribution, and large-flow circulation of the system, to improve the reactor's ability to resist shock loads, so that the system can maintain a stable anaerobic environment and pure anaerobic bacteria, and achieve efficient fluidization of fillers in the anaerobic fluidized bed reactor. Specifically, the COD removal rate of the primary anaerobic reactor can reach 75% to 80%, the COD removal rate of the secondary anaerobic reactor can reach 55% to 65%, and the total COD removal rate can reach 89% to 93%; and there are no complex treatment process units in the system, which is simple and efficient; and through the cascade circulation reflux treatment technology, the anaerobic sludge is subjected to enhanced cultivation of dominant specialized bacteria, which improves the treatment efficiency and reduces the floor space by 10% to 30%; in addition, the effect of mud film symbiotic synergistic treatment is formed in the primary anaerobic reactor, and the hydraulic cross-flow is formed by the inlet water and the external circulation to achieve filler fluidization, without the need for a power stirring device, reducing the energy consumption by 10% to 20%.

[0017] Therefore, the cascade anaerobic reactor can be used as a pre-treatment unit to reduce the content of toxic and harmful substances entering the system. The system effluent is returned to the front end to reduce the content of toxic and harmful substances entering the system. At the same time, dissolved oxygen is not introduced into the anaerobic reactor, ensuring the stability of the anaerobic environment. The sludge separated by the system is returned to the front end, and no microbial populations with other characteristics are introduced, ensuring the purity of the microbial population in the anaerobic reactor. The first-stage reactor can handle relatively easy-to-handle pollutants, and combined with the secondary reactor, it can deal with more difficult-to-handle pollutants, ensuring that the system is stable and meets the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of a circulating cross-flow cascade anaerobic system provided by an embodiment of the present invention; Figure 2 yes Figure 1 Schematic diagram of the middle-stage anaerobic reactor and filler carrier; Figure 3 yes Figure 2 Schematic diagram of the middle-stage anaerobic reactor; Figure 4 yes Figure 1 Schematic diagram of the secondary anaerobic reactor; Figure 5 yes Figure 3 A magnified schematic diagram of center A.

[0019] Description of reference numerals: 1. Primary anaerobic reactor; 11. Water inlet; 12. External circulation port; 121. External circulation branch port; 2. Secondary anaerobic reactor; 3. Buffer tank; 4. Filling 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. Water inlet pipe; 71. Water inlet lift pump; 8. First connecting pipe; 81. Inclined end face; 9. Second connecting pipe. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] In order to solve the technical problem that when the anaerobic reactor in the prior art treats high-concentration and toxic difficult-to-treat organic wastewater, the degradation efficiency of pollutants is seriously affected due to the excessive organic pollution load and the inhibitory effect of toxic substances on microorganisms, and the water treatment effect of the system cannot be guaranteed, the present invention provides a circulating cross-flow cascade anaerobic system, which can reduce the content of toxic and harmful substances entering the system without introducing dissolved oxygen into the anaerobic reactor, thereby ensuring the stability of the anaerobic environment and high treatment efficiency.

[0022] See also Figures 1 to 4 , Figures 1 to 4 Schematic diagram of the structure of a circulating cross-flow cascade anaerobic system in 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 filler carrier 4, and has a water inlet 11 and an external circulation port 12, the water inlet flow rate of the water inlet 11 is less than the water 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, and the external circulation pump 51 is arranged on 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 the bottom of the secondary anaerobic reactor 2, and the internal circulation pump 61 is arranged on the internal circulation pipe 6.

[0023] In the circulating cross-flow cascade anaerobic system provided by the present invention, a two-stage circulating cross-flow anaerobic reaction system is used as the main body, combined with filling high-performance filler carriers 4, efficient and uniform water distribution and system large flow circulation, the reactor's anti-shock load capacity is improved, so that a stable anaerobic environment and pure anaerobic bacteria can be maintained in the system, and efficient fluidization of fillers in the anaerobic fluidized bed reactor is achieved. Specifically, the COD (chemical oxygen demand) 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%; and there are no complex treatment process units in the system, which is simple and efficient; and through the cascade circulation reflux treatment technology, the anaerobic sludge is subjected to enhanced cultivation of dominant specialized bacteria, which improves the treatment efficiency and reduces the occupied area by 10% to 30%; in addition, the effect of mud film symbiotic synergistic treatment is formed in the primary anaerobic reactor 1, and the hydraulic cross-flow is formed by the inlet water and the external circulation to achieve filler fluidization, without the need for a power stirring device, reducing the energy consumption by 10% to 20%.

[0024] Therefore, the cascade anaerobic reactor can be used as a pre-treatment unit to reduce the content of toxic and harmful substances entering the system. The system effluent is returned to the front end to reduce the content of toxic and harmful substances entering the system. At the same time, dissolved oxygen is not introduced into the anaerobic reactor, ensuring the stability of the anaerobic environment. The sludge separated by the system is returned to the front end, and no microbial populations with other characteristics are introduced, ensuring the purity of the microbial population in the anaerobic reactor. The first-stage reactor can handle relatively easy-to-handle pollutants, and combined with the secondary reactor, it can deal with more difficult-to-handle pollutants, ensuring that the system is stable and meets the standards.

[0025] In one embodiment, see Figure 2 and Figure 3 The reaction unit also includes a water inlet pipe 7, which extends from the water inlet 11 into the primary anaerobic reactor 1, and a plurality of water inlet channels are arranged on the top of the water inlet pipe 7; the external circulation port 12 includes a plurality of external circulation branch ports 121, the external circulation pipe 5 includes an external circulation main pipe 52 and a plurality of 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 the plurality of external circulation branch pipes 53, the plurality of external circulation branch pipes 53 extend from the plurality of external circulation branch ports 121 into the primary anaerobic reactor 1, and at least one external circulation branch pipe 53 is located below the water inlet pipe 7, wherein the external circulation pump 51 is arranged on the external circulation main pipe 52.

[0026] In this embodiment, the water inlet pipe 7 in the primary anaerobic reactor 1 is placed above the external circulation branch pipe 53, so that the water in the primary anaerobic reactor 1 can be evenly mixed with the external circulation water. At the same time, multiple external circulation branch pipes 53 are provided to improve the stirring capacity. It should be noted that in this solution, the water inlet pipe 7 and the external circulation branch pipe 53 are respectively arranged in a ring shape, and water is fed into the primary anaerobic reactor 1 at multiple points in a ring shape.

[0027] In one embodiment, the external circulation branch pipe 53 is provided with a plurality of circulation water outlet holes on both sides in the vertical direction; the plurality of external circulation branch pipes 53 are arranged at intervals in the vertical direction, and correspondingly, the plurality of 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.

[0028] In this solution, water outlet holes are respectively 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 spaced apart 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 are fully contacted and mixed in the reactor.

[0029] In one embodiment, the water flow rate of the water inlet 11 is Q1, and the water flow rate of the external circulation port 12 is Q2, satisfying Q2 / Q1≥10. The water flow rate from the primary anaerobic reactor 1 to the secondary anaerobic reactor 2 is Q3, and the water flow rate from the internal circulation pipe 6 to the secondary anaerobic reactor 2 is Q4, satisfying Q4 / Q3≥5.

[0030] In this embodiment, the filler carrier 4 in the first-level anaerobic reactor 1 can be fully ensured to be in a fluidized state through the hydraulic jet of the upper external circulating water. Specifically, the flow rate ratio of the external circulating water to the inlet water in the first-level anaerobic reactor 1 is controlled to be no less than 10:1; and the flow rate ratio of the internal circulation to the inlet water in the secondary anaerobic reactor 2 is controlled to be no less than 5:1, so that a large flow rate circulates inside and outside the system, the reactor's ability to resist shock loads is improved, and a stable anaerobic environment and pure anaerobic bacteria can be maintained in the system.

[0031] In addition, in this solution, the filler carrier 4 is used as an attachment carrier for the growth of microorganisms. The filler should be selected to be not easy to wear, have a large specific surface area, be easy to fluidize, have good biophilicity and chemical stability, and have a reasonable pore size distribution. In particular, the filler is easy for microorganisms to attach but has no adsorption effect on pollutants, preventing toxic substances from being enriched on the filler and forming a local high concentration area, which is not conducive to microbial biofilm. The primary anaerobic reactor 1 adopts a fluidized bed form.

[0032] In one embodiment, the reaction unit further includes a first connecting pipe 8, one end of which is connected to the top of the first anaerobic reactor 1, and the other end of which is connected to the bottom of the second anaerobic reactor 2; wherein the connection point between the first connecting pipe 8 and the first anaerobic reactor 1 is located above the external circulation port 12 and the water inlet 11.

[0033] In this embodiment, the primary anaerobic reactor 1 and the secondary anaerobic reactor 2 are connected by the first connecting pipe 8, and the first connecting pipe 8 is arranged as above so that the solution after the initial treatment at the top of the primary anaerobic reactor 1 can flow downstream to the secondary anaerobic reactor 2.

[0034] Please note that Figure 5 In one embodiment, the end of the first connecting pipe 8 connected to the primary anaerobic reactor 1 has an inclined end surface 81, which is inclined from bottom to top toward the middle of the primary anaerobic reactor 1, and the lower end is located at the side wall of the primary anaerobic reactor 1. The inlet end of the first connecting pipe 8 adopts the above-mentioned special design to prevent the loss and collision of fillers, which not only prevents the fillers from being lost with the effluent, but also avoids the obstruction of the flow of fillers and the wear of fillers by the traditional screen type.

[0035] In one embodiment, the internal circulation pipe 6 includes an internal circulation main pipe 62 and multiple 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 multiple internal circulation branch pipes 63. The multiple 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 arranged on the internal circulation main pipe 62.

[0036] In this embodiment, a plurality of internal circulation branches 63 are also arranged in the secondary anaerobic reactor 2 to improve the mixing uniformity of the influent and the circulating solution in the secondary anaerobic reactor 2. It should be noted that in this solution, the portion of the first connecting pipe 8 located in the secondary anaerobic reactor 2 is arranged in a ring shape, and a multi-point uniform water inlet method is adopted; similarly, each internal circulation branch 63 is also arranged in a ring shape in the secondary anaerobic reactor 2, and a multi-point uniform water inlet method is adopted. It should be noted that, in one embodiment, the outlet channels on the two opposite sides of the external circulation branch 53 and the internal circulation branch 63 are oriented toward the middle of the corresponding reactor to further improve the stirring capacity.

[0037] In one embodiment, the connection point between the first connecting pipe 8 and the secondary anaerobic reactor 2 is located between two adjacent inner circulation branch pipes 63 at the bottom.

[0038] In this embodiment, the effluent from the secondary anaerobic reactor 2 is circulated again to the secondary circulating cross-flow anaerobic reactor. The internal circulating water enters the secondary anaerobic reactor 2 in a layered multi-point water inlet manner, and the outer circulating water inlet pipe 7 at the bottom layer is located below the first connecting pipe 8 therein, so that the circulating water and the incoming water are fully contacted and mixed in the reactor, and the upper internal circulating water enters in layers, fully ensuring that the internal circulating water and the incoming water are evenly mixed.

[0039] In one embodiment, a portion of the first connecting pipe 8 extends into the secondary anaerobic reactor 2, and a first water outlet channel is provided on the top of the portion extending into the secondary anaerobic reactor 2; a portion of each internal circulation branch pipe 63 extends into the secondary anaerobic reactor 2, and a second water outlet channel is provided on the top of the portion extending into the secondary anaerobic reactor 2.

[0040] In this embodiment, the water outlets of the first connecting pipe 8 and the inner circulation branch pipe 63 are both arranged 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.

[0041] In one embodiment, the reaction unit further comprises a second connecting pipe 9, one end of which is connected to the top of the secondary anaerobic reactor 2, and the other end of which is connected to the buffer tank 3, and the connection point between the second connecting pipe 9 and the secondary anaerobic reactor 2 is located above the inner circulation pipe 6; wherein, the rising velocity of the water flow input into the primary anaerobic reactor 1 from the water inlet 11 is V1, satisfying V1>5m / h, the rising velocity of the water flow input into the primary anaerobic reactor 1 from the external circulation port 12 is V2, satisfying 0.25m / s≤V2≤0.30m / s, the rising velocity of the water flow input into the secondary anaerobic reactor 2 from the first connecting pipe 8 is V3, satisfying V3>0.5m / h, and the rising velocity of the water flow input into the secondary anaerobic reactor 2 from the inner circulation pipe 6 is V4, satisfying 0.15m / s≤V4≤0.30m / s.

[0042] In this embodiment, the flow rates of the inlet water and the external circulating water in the primary anaerobic reactor 1 are set as above to facilitate the filler to maintain a fluidized state. At the same time, the flow rates of the inlet water and the internal circulating water in the secondary anaerobic reactor 2 are set as above to facilitate the inlet water and the sludge to fully contact and mix.

[0043] In addition, exhaust ports are provided at the tops of the primary anaerobic reactor 1 and the secondary anaerobic reactor 2 .

[0044] In order to better understand the present invention, the following Figures 1 to 5 The technical solution of the present invention is described in detail: In one embodiment, the influent water quality is measured by COD cr =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, sulfide=50~500mg / L are designed. In order to meet the emission standards that can be entered into subsequent conventional process treatments such as activated sludge method and biofilm method, each unit is set as follows.

[0045] Water inlet pipe 7 of primary anaerobic reactor 1: The water inlet pipe 7 is arranged in a single layer in the primary anaerobic reactor 1, and is arranged in a ring shape. Flow holes are evenly arranged on the ring-shaped water distribution pipe. The number of layers of the water distribution pipe and the number of flow holes are determined according to the rising flow velocity of the reactor. The rising flow velocity is greater than 5m / h.

[0046] The primary anaerobic reactor 1: The primary anaerobic reactor 1 adopts a fluidized bed form, in which a filler carrier 4 is filled, and the fluidization state of the filler is ensured by hydraulic cross-flow formed by the influent and the external circulating influent; the filler should be not easy to wear, have a large specific surface area, be easy to fluidize, have good biophilicity and chemical stability, and have a reasonable pore size distribution. In particular, the filler is easy for microorganisms to attach but has no adsorption effect on pollutants.

[0047] External circulation pipe 5 of primary anaerobic reactor 1: The external circulation pipe 5 is arranged in layers in the primary anaerobic reactor 1, and the single layer is arranged in a ring. Flow holes are evenly arranged on the ring-shaped water distribution pipe. The number of layers and flow holes of the water distribution pipe are determined according to the reactor height and the orifice flow rate. The orifice flow rate is 0.25-0.30m / s; the ratio of the external circulation water flow rate to the inlet water flow rate is not less than 10:1.

[0048] Internal circulation pipe 6 of secondary anaerobic reactor 2: The internal circulation pipe 6 is arranged in layers in the secondary anaerobic reactor 2, with a single layer arranged in a ring. Flow holes are evenly arranged on the annular water distribution pipe. The number of layers of the water distribution pipe and the number of flow holes are determined according to the reactor height and the orifice flow rate. The orifice flow rate is 0.15-0.20 m / s; the ratio of the internal circulation water flow rate to the inlet water flow rate is not less than 5:1.

[0049] The workflow is as follows: 1. Water inlet of the primary anaerobic reactor 1: wastewater passes through the water inlet pipe 7 of the primary anaerobic reactor 1 and enters the primary anaerobic reactor 1 evenly for reaction to remove pollutants in the wastewater. The water inlet system of the primary anaerobic reactor 1 includes a water inlet lift pump 71 and a water inlet pipe 7. The water inlet lift pump 71 is arranged on the water inlet pipe 7; 2. Primary anaerobic reactor 1: The wastewater reacts in the primary anaerobic reactor 1. The primary anaerobic reactor 1 adopts a fluidized bed form. The reactor is filled with a filler carrier 4 for microorganisms to attach and grow, forming an anaerobic biological treatment system of mud film symbiosis, and the pollutants in the wastewater are degraded by microorganisms; 3. Effluent from the primary anaerobic reactor 1: After the wastewater reacts in the primary anaerobic reactor 1, it evenly enters the secondary anaerobic reactor 2 through the first connecting pipe 8; 4. Secondary anaerobic reactor 2: The wastewater reacts in the secondary anaerobic reactor 2, and the pollutants in the wastewater are further removed through the degradation of microorganisms in the secondary anaerobic reactor 2; 5. Effluent from the secondary anaerobic reactor 2: After the wastewater reacts in the secondary anaerobic reactor 2, it enters the buffer pool 3 and the subsequent treatment system through the second connecting pipe 9; 6. External circulation unit: the effluent of the secondary anaerobic reactor 2 enters the primary anaerobic fluidized bed reactor through the external circulation unit, and is fully combined and uniformly mixed with the influent of the primary anaerobic fluidized bed reactor to reduce 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; 7. Internal circulation unit: An internal circulation unit is provided in the secondary anaerobic reactor 2 to realize internal circulation inside the secondary anaerobic reactor 2 , so that the effluent and the influent are fully and evenly mixed to reduce the pollutant concentration in the secondary anaerobic reactor 2 . The internal circulation is realized by an internal circulation pump 61 .

[0050] Thus, this scheme adopts a circulating cross-flow cascade anaerobic reaction system, with a two-stage circulating cross-flow anaerobic reaction system as the main body, combined with filling high-performance filler carrier 4, efficient and uniform water distribution, and large flow circulation inside and outside the system, to improve the reactor's ability to resist shock loads, so that the system can maintain a stable anaerobic environment and pure anaerobic flora, and achieve efficient fluidization of fillers in the anaerobic fluidized bed reactor, and the biofilm of the carrier will not fall off due to hydraulic shearing.

[0051] It solves the problems of the impact of high-pollution-load influent on the reactor, the inhibition of microbial activity by toxic substances, the introduction of dissolved oxygen by activated sludge return, and the shedding of carrier biofilm due to excessive hydraulic or mechanical stirring. It is of great significance to improve the treatment efficiency of high-concentration difficult-to-degrade organic wastewater pretreatment, reduce the treatment difficulty of subsequent treatment units, enhance the stability of system treatment effects, and reduce system investment and treatment costs.

[0052] Based on the above embodiments, this solution has the following advantages: (1) High treatment efficiency: The COD removal rate of the first-stage anaerobic reactor 1 can reach 75% to 80%, the COD removal rate of the second-stage anaerobic reactor 2 can reach 55% to 65%, and the total COD removal rate can reach 89% to 93%.

[0053] (2) Simple system: There are no complex processing units in the system, which is simple and efficient.

[0054] (3) Reduced floor space: Through the cascade circulation reflow treatment technology, the dominant specialized bacteria of anaerobic sludge are cultured in an enhanced manner, which improves the treatment efficiency and reduces the floor space by 10% to 30%.

[0055] (4) Low energy consumption: A mud film symbiotic synergistic treatment effect is formed in the primary anaerobic reactor 1. At the same time, hydraulic cross flow is formed by the incoming water to achieve filler fluidization. No power stirring device is required, which reduces energy consumption by 10% to 20%.

[0056] (5) Low investment: The system greatly prolongs the hydraulic retention time of difficult-to-degrade soluble organic matter, thereby reducing the residence time of the anaerobic reactor and saving investment.

[0057] (6) Low operating costs: A coupling treatment process using high-performance fillers as carriers is adopted, and a large flow of effluent is returned to the front end of the system, reducing pollution load, saving reactor volume, and reducing operating costs.

[0058] (7) Good stability: The cascade anaerobic reactor is used as the pre-treatment unit to reduce the content of toxic and harmful substances entering the system. At the same time, the system effluent is returned to the front end to reduce the content of toxic and harmful substances entering the system. Dissolved oxygen is not introduced into the anaerobic reactor, ensuring the stability of the anaerobic environment. The sludge separated by the system is returned to the front end, and no microbial populations with other characteristics are introduced, ensuring the purity of the microbial population in the anaerobic reactor. The cascade anaerobic reactor, the first reactor can treat relatively easy-to-treat pollutants, and combined with the secondary reactor, it can deal with pollutants that are more difficult to treat, ensuring that the system is stable and meets the standards.

[0059] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A circulating cross-flow cascade anaerobic system, characterized in that: include: The reaction unit comprises a primary anaerobic reactor, a secondary anaerobic reactor and a buffer tank which are connected in sequence, wherein the primary anaerobic reactor is filled with a filler carrier and has a water inlet and an external circulation port, and the water inlet flow rate of the water inlet is smaller than the water inlet flow rate of the external circulation port; An external circulation unit, comprising an external circulation pipe and an external circulation pump, wherein the external circulation pipe is connected with the buffer pool and the external circulation port, and the external circulation pump is arranged on the external circulation pipe; and The internal circulation unit comprises an internal circulation pipe and an internal circulation pump. The two ends of the internal circulation pipe are respectively connected to the top and the bottom of the secondary anaerobic reactor. The internal circulation pump is arranged on the internal circulation pipe.

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

3. The circulating cross-flow cascade anaerobic system according to claim 2, characterized in that: The outer circulation branch pipe is provided with a plurality of circulation water outlet holes on both sides in the vertical direction; and / or, The plurality of external circulation branch pipes are arranged at intervals along the vertical direction. Correspondingly, the plurality of 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 water inlet flow rate of the water inlet is Q1, and the water inlet flow rate of the external circulation port is Q2, satisfying Q2 / Q1≥10.

5. The circulating cross-flow cascade anaerobic system according to claim 1, characterized in that: The reaction unit further comprises a first connecting pipe, one end of which is connected to the top of the first anaerobic reactor, and the other end of which is connected to the bottom of the second 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.

6. The circulating cross-flow cascade anaerobic system according to claim 5, 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 connecting points with the secondary anaerobic reactor are arranged at intervals in the vertical direction. The internal circulation pump is arranged on the internal circulation main pipe.

7. The circulating cross-flow cascade anaerobic system according to claim 6, characterized in that: The connection point between the first connecting pipe and the secondary anaerobic reactor is located between two adjacent inner circulation branch pipes at the bottom.

8. The circulating cross-flow cascade anaerobic system according to claim 7, characterized in that: The first connecting pipe part extends into the secondary anaerobic reactor, and a first water outlet channel is provided on the top of the part extending into the secondary anaerobic reactor; A portion of each of the inner circulation branch pipes extends into the secondary anaerobic reactor, and a second water outlet channel is provided on the top of the portion extending into the secondary anaerobic reactor.

9. The circulating cross-flow cascade anaerobic system according to claim 5, 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 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 inner circulation pipe; Among them, the rising speed of water flow input into the primary anaerobic reactor from the water inlet is V1, which satisfies V1>5m / h, the rising speed of water flow input into the primary anaerobic reactor from the external circulation port is V2, which satisfies 0.25m / s≤V2≤0.30m / s, the rising speed of water flow input into the secondary anaerobic reactor from the first connecting pipe is V3, which satisfies V3>0.5m / h, and the rising speed of water flow input into the secondary anaerobic reactor from the internal circulation pipe is V4, which satisfies 0.15m / s≤V4≤0.30m / s.

10. The circulating cross-flow cascade anaerobic system according to claim 1, characterized in that: 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.

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