Multi-membrane combined double-circulation bioreactor, multi-membrane combined double-circulation biological treatment system and low carbon-nitrogen ratio organic wastewater treatment method

Abstract

The present invention provides a multi-membrane combined double circulation bioreactor, a multi-membrane combined double circulation biological treatment system and a low carbon-nitrogen ratio organic wastewater treatment method, which belongs to the technical field of wastewater treatment. The multi-membrane combined double circulation bioreactor provided by the present invention has a reasonable structure and can realize double internal circulation. When the low carbon-nitrogen ratio organic wastewater is treated by the multi-membrane combined double circulation biological treatment system based on the multi-membrane combined double circulation bioreactor, no carbon source and phosphorus removal agent are added, and no deep treatment unit is added; at the same time, under the conditions of low energy consumption and low residual sludge production, stable and efficient nitrogen removal and phosphorus removal effects can be achieved; in addition, the amount of suspended sludge and the transmembrane pressure difference can be reduced during the treatment process, the decline of membrane flux can be delayed, the service life and working cycle of the membrane can be extended, and the investment and operation and maintenance costs of the treatment system can be saved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a multi-membrane combined double-circulation bioreactor, a multi-membrane combined double-circulation biological treatment system and a method for treating low-carbon-nitrogen ratio organic wastewater. Background Art

[0002] Domestic sewage treatment in towns and villages is one of the current focuses of water pollution control. Its treatment projects are characterized by geographical dispersion, small scale, and lack of funds and operation and management personnel. The membrane-bioreactor (MBR) treatment technology, which combines biological treatment technology with membrane separation technology, has the advantages of small footprint, high treatment efficiency, and good effluent quality, avoiding the problems of large footprint, inconvenient operation and management, and high energy consumption per ton of water treatment caused by the application of traditional urban sewage treatment plant treatment processes. However, when the traditional activated sludge MBR process treats low carbon-nitrogen ratio (C / N) organic wastewater with a certain ammonia nitrogen and total phosphorus content, due to the low C / N (usually 2 to 16), it is easy to have problems such as poor biological denitrification and phosphorus removal, and substandard effluent total nitrogen and total phosphorus. It is usually necessary to add carbon sources and phosphorus removal agents (such as polyaluminium chloride, abbreviated as PAC), and even increase deep treatment to meet the GB18918-2002 Class A standard.

[0003] Compared with conventional biological treatment, the total aeration demand of MBR process in actual operation increases by about 50%, because in addition to the oxygenated aeration required for microbial growth and reproduction, the aeration airflow needs to be used to continuously flush the membrane with a certain intensity, which consumes a lot of energy. In addition, the sludge concentration in the membrane pool is high, the transmembrane pressure difference increases and the membrane flux decreases quickly, which affects the service life and working cycle of the membrane, increasing the investment and maintenance cost of the membrane. At the same time, the residual sludge output of this process is large, which increases the difficulty of sludge treatment. These shortcomings have seriously hindered the promotion and application of MBR process in the field of township domestic sewage treatment. Summary of the invention

[0004] The object of the present invention is to provide a multi-membrane combined double circulation bioreactor, a multi-membrane combined double circulation biological treatment system and a method for treating low carbon-nitrogen ratio organic wastewater. The multi-membrane combined double circulation bioreactor provided by the present invention has a reasonable structure and can realize double internal circulation. When the low carbon-nitrogen ratio organic wastewater is treated by the multi-membrane combined double circulation biological treatment system based on the multi-membrane combined double circulation bioreactor, no carbon source and phosphorus removal agent are added, the residual sludge output is low, and stable and efficient nitrogen removal and phosphorus removal effects can be achieved.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a multi-membrane combined double circulation bioreactor, comprising a multi-membrane combined biofilm reaction zone and a microfiltration membrane filtration zone; the multi-membrane combined biofilm reaction zone comprises a suspended filler biofilm reaction zone, an iron-sulfur-stone coupling filler denitrification reaction zone and an iron-based filler enhanced phosphorus removal zone, which are sequentially connected;

[0007] A water distribution device 16 is provided on the top of the suspended filler biofilm reaction zone, and a first aeration device 121 is provided at the bottom of the suspended filler biofilm reaction zone. The first aeration device 121 is connected to the air pump 06 via a first air inlet electric valve 71; the suspended filler biofilm reaction zone is filled with biofilm suspended filler 111;

[0008] A first guide plate 131 is arranged between the iron-sulfur-stone coupled filler denitrification reaction zone and the suspended filler biofilm reaction zone, a filler filter 17 is arranged at the bottom of the first guide plate 131, and the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone is connected to the bottom of the suspended filler biofilm reaction zone through the filler filter 17; a second aeration device 122 is arranged at the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone, and the second aeration device 122 is connected to the air pump 06 via the second air intake electric valve 72; the iron-sulfur-stone coupled filler denitrification reaction zone is filled with iron-sulfur-stone coupled filler 112;

[0009] A second guide plate 132 is provided between the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone are connected through the top of the second guide plate 132; the iron-based filler enhanced dephosphorization zone is filled with iron-based filler 113;

[0010] A third guide plate 133 is arranged between the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone, the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone are connected through the top of the third guide plate 133, and at the same time, the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone are connected through the bottom of the third guide plate 133; an immersed microfiltration membrane assembly 14 is arranged in the microfiltration membrane filtration zone, and the water outlet of the immersed microfiltration membrane assembly 14 is connected to the water collection device 15; a third aeration device 123 is arranged at the bottom of the microfiltration membrane filtration zone, and the third aeration device 123 is connected to the air pump 06 via the third air inlet electric valve 73; a reflux pump 042 is arranged at the bottom of the microfiltration membrane filtration zone, and the water outlet of the reflux pump 042 is connected to a pipeline extending to the suspended filler biofilm reaction zone.

[0011] Preferably, a first water level float switch 21 is provided on the top of the suspended filler biofilm reaction zone.

[0012] Preferably, the biofilm suspension filler 111 is spherical, including a filling inner material and an outer shell covering the surface of the filling inner material, the filling inner material is polyurethane sponge, polyvinyl alcohol or polyester, and the outer shell is made of polyethylene, polypropylene or polycarbonate.

[0013] Preferably, the iron-sulfur-stone coupling filler 112 includes a sulfur-stone coupling filler and an iron-based filler; the sulfur-stone coupling filler is a mixed filler of sulfur elemental particles and limestone particles, and the mass ratio of the sulfur elemental particles to the limestone particles is (2-3):1;

[0014] The iron-sulfur-stone coupled filler denitrification reaction zone is filled with the iron-based filler and the sulfur-stone coupled filler in sequence from bottom to top.

[0015] Preferably, the submerged microfiltration membrane assembly 14 is an submerged membrane-bioreactor assembly, the material of the microfiltration membrane in the submerged microfiltration membrane assembly 14 includes hydrophilically modified polypropylene, hydrophilically modified polytetrafluoroethylene or hydrophilically modified polyvinylidene fluoride, and the average pore size of the microfiltration membrane is 0.1-0.2 μm.

[0016] The present invention provides a multi-membrane combined dual circulation biological treatment system, comprising a slag removal device, a lifting pump 041, a multi-membrane combined dual circulation bioreactor 05, a self-priming pump 10 and an ultraviolet disinfector 08 connected in sequence; the multi-membrane combined dual circulation bioreactor 05 is the multi-membrane combined dual circulation bioreactor described in the above technical scheme, the lifting pump 041 is connected to the water distribution device 16 in the multi-membrane combined dual circulation bioreactor 05, and the self-priming pump 10 is connected to the water collection device 15 in the multi-membrane combined dual circulation bioreactor 05.

[0017] Preferably, the slag removal device comprises a grille 01, a second water level float switch 22 and a grid 03 which are arranged in sequence; the aperture of the grid 03 is ≤2 mm.

[0018] Preferably, the ultraviolet sterilizer 08 is connected to a glass rotor flowmeter 09 .

[0019] Preferably, the number of the multi-membrane combined dual circulation bioreactors 05 in the multi-membrane combined dual circulation biological treatment system is one or two sets. When there are two sets of the multi-membrane combined dual circulation bioreactors 05, they are arranged in parallel.

[0020] The present invention provides a method for treating low carbon-nitrogen ratio organic wastewater by using the multi-membrane combined double-circulation biological treatment system described in the above technical solution, comprising the following steps:

[0021] (I) transporting low carbon-nitrogen ratio organic wastewater to a slag removal device for slag removal treatment to obtain slag removal wastewater; the carbon-nitrogen ratio of the low carbon-nitrogen ratio organic wastewater is 2 to 16;

[0022] (II) The deslagging wastewater is transported to the multi-membrane combined dual-circulation bioreactor 05 via a lift pump 041, and is biologically treated in the suspended filler biofilm reaction zone, the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced phosphorus removal zone in sequence to obtain biologically treated wastewater;

[0023] The biologically treated wastewater enters the microfiltration membrane filtration zone, and part of the biologically treated wastewater is refluxed to the iron-based filler enhanced phosphorus removal zone through the top of the third guide plate 133 under the action of the aeration airflow formed by the third aeration device 123 to form a first internal circulation, and the biologically treated wastewater undergoing the first internal circulation accounts for 50-70% of the total biologically treated wastewater inflow; at the same time, part of the biologically treated wastewater is refluxed to the suspended filler biofilm reaction zone through the reflux pump 042 to form a second internal circulation, and the biologically treated wastewater undergoing the second internal circulation accounts for 5-15% of the total biologically treated wastewater inflow; the wastewater in the microfiltration membrane filtration zone is intercepted and treated by the immersed microfiltration membrane assembly 14 to obtain biologically purified water;

[0024] (III) the biologically purified water is transported to the ultraviolet disinfector 08 by the self-priming pump 10 for disinfection and then discharged after meeting the standards;

[0025] During the operation of the multi-membrane combined dual-circulation biological treatment system, the first air intake electric valve 71, the second air intake electric valve 72 and the third air intake electric valve 73 are started intermittently.

[0026] The present invention provides a multi-membrane combined double circulation bioreactor. The multi-membrane combined double circulation bioreactor provided by the present invention has a reasonable structure and can realize double internal circulation. When the multi-membrane combined double circulation biological treatment system based on the multi-membrane combined double circulation bioreactor is used to treat low carbon-nitrogen ratio organic wastewater, no carbon source and phosphorus removal agent are added, and no deep treatment unit is added; at the same time, under the conditions of low energy consumption and low residual sludge output, stable and efficient nitrogen removal and phosphorus removal effects can be achieved; in addition, the amount of suspended sludge and transmembrane pressure difference during the treatment process can be reduced, the decline of membrane flux can be delayed, the service life and working cycle of the membrane can be extended, and the investment and operation and maintenance costs of the treatment system can be saved. Compared with the simple membrane-bioreactor technology, the technical solution provided by the present invention can reduce the oxygenation energy consumption by about 50%, the transmembrane pressure difference can be maintained at a low level, the membrane flux of the microfiltration membrane is stable and good, the service life and working cycle of the membrane are extended, thereby reducing the investment and operation and maintenance costs of the system; the residual sludge output is very small, and there is no need to set up a sludge treatment device separately, and the suspended sludge concentration of the system is reduced by 80-90%; the total nitrogen and total phosphorus removal effect is stable and efficient. Therefore, the present invention has obvious advantages in treating medium and small-scale low-concentration and low-carbon-nitrogen ratio wastewater with higher discharge requirements or requiring reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1It is a schematic diagram of the structure of the multi-membrane combined double circulation bioreactor in the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of the multi-membrane combined double-circulation biological treatment system of the present invention;

[0029] Figure 3 Another structural schematic diagram of the multi-membrane combined double-circulation biological treatment system of the present invention;

[0030] Among them, 01 is a grille; 21 is a first water level float switch; 22 is a second water level float switch; 03 is a grid; 041 is a lift pump; 042 is a reflux pump; 05 is a multi-membrane combined dual-circulation bioreactor; 06 is an air pump; 71 is a first air intake electric valve; 72 is a second air intake electric valve; 73 is a third air intake electric valve; 08 is an ultraviolet disinfector; 09 is a glass rotor flowmeter; 10 is a self-priming pump; 111 is a biofilm suspended filler; 112 is an iron-sulfur-stone coupling filler; 113 is an iron-based filler in an iron-based filler enhanced phosphorus removal zone; 121 is a first aeration device; 122 is a second aeration device; 123 is a third aeration device; 131 is a first guide plate; 132 is a second guide plate; 133 is a third guide plate; 14 is an immersed microfiltration membrane assembly; 15 is a water collection device; 16 is a water distribution device; 17 is a filler filter. DETAILED DESCRIPTION

[0031] The present invention provides a multi-membrane combined double circulation bioreactor, comprising a multi-membrane combined biofilm reaction zone and a microfiltration membrane filtration zone; the multi-membrane combined biofilm reaction zone comprises a suspended filler biofilm reaction zone, an iron-sulfur-stone coupling filler denitrification reaction zone and an iron-based filler enhanced phosphorus removal zone, which are sequentially connected;

[0032] A water distribution device 16 is provided on the top of the suspended filler biofilm reaction zone, and a first aeration device 121 is provided at the bottom of the suspended filler biofilm reaction zone. The first aeration device 121 is connected to the air pump 06 via a first air inlet electric valve 71; the suspended filler biofilm reaction zone is filled with biofilm suspended filler 111;

[0033] A first guide plate 131 is arranged between the iron-sulfur-stone coupled filler denitrification reaction zone and the suspended filler biofilm reaction zone, a filler filter 17 is arranged at the bottom of the first guide plate 131, and the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone is connected to the bottom of the suspended filler biofilm reaction zone through the filler filter 17; a second aeration device 122 is arranged at the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone, and the second aeration device 122 is connected to the air pump 06 via the second air intake electric valve 72; the iron-sulfur-stone coupled filler denitrification reaction zone is filled with iron-sulfur-stone coupled filler 112;

[0034] A second guide plate 132 is provided between the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone are connected through the top of the second guide plate 132; the iron-based filler enhanced dephosphorization zone is filled with iron-based filler 113;

[0035] A third guide plate 133 is arranged between the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone, the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone are connected through the top of the third guide plate 133, and at the same time, the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone are connected through the bottom of the third guide plate 133; an immersed microfiltration membrane assembly 14 is arranged in the microfiltration membrane filtration zone, and the water outlet of the immersed microfiltration membrane assembly 14 is connected to the water collection device 15; a third aeration device 123 is arranged at the bottom of the microfiltration membrane filtration zone, and the third aeration device 123 is connected to the air pump 06 via the third air inlet electric valve 73; a reflux pump 042 is arranged at the bottom of the microfiltration membrane filtration zone, and the water outlet of the reflux pump 042 is connected to a pipeline extending to the suspended filler biofilm reaction zone.

[0036] The multi-membrane combined double-circulation bioreactor provided by the present invention comprises a multi-membrane combined biofilm reaction zone, and the multi-membrane combined biofilm reaction zone comprises a suspended filler biofilm reaction zone, an iron-sulfur-stone coupled filler denitrification reaction zone, and an iron-based filler enhanced phosphorus removal zone, which are sequentially connected. In the present invention, the wastewater to be treated undergoes organic degradation and efficient denitrification and phosphorus removal reactions in the multi-membrane combined biofilm reaction zone, wherein the path through which the wastewater to be treated passes is the suspended filler biofilm reaction zone, the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced phosphorus removal zone, in sequence.

[0037] In the present invention, a water distribution device 16 is provided on the top of the suspended filler biofilm reaction zone to allow the wastewater to be treated to evenly enter the suspended filler biofilm reaction zone.

[0038] In the present invention, a first aeration device 121 is provided at the bottom of the suspended filler biofilm reaction zone, and the first aeration device 121 is connected to the air pump 06 via the first air inlet electric valve 71; the first aeration device 121 provides oxygenation through the air pump 06 to form an aerated airflow. The present invention can control the aeration condition of the first aeration device 121 by intermittently opening the first air inlet electric valve 71, and alternately form an anaerobic-anoxic-aerobic environment in the suspended filler biofilm reaction zone to complete the preliminary aerobic nitrification phosphorus absorption, anoxic denitrification reaction and anaerobic phosphorus release reaction of microorganisms, and at the same time cooperate with the sulfur autotrophic denitrification effect of the subsequent iron-sulfur-stone coupled filler denitrification reaction zone and the iron-enhanced phosphorus removal effect of the iron-based filler enhanced phosphorus removal zone to achieve efficient deep denitrification and phosphorus removal effects.

[0039] In the present invention, the suspended filler biofilm reaction zone is filled with a biofilm suspended filler 111, and the biofilm suspended filler 111 is preferably spherical, including a filling inner material and an outer shell coated on the surface of the filling inner material, and the filling inner material is preferably polyurethane sponge, polyvinyl alcohol or polyester, and the material of the outer shell preferably includes polyethylene, polypropylene or polycarbonate. In the present invention, the particle size of the biofilm suspended filler is preferably 5 to 10 cm, and the thickness of the outer shell is preferably 0.3 to 0.5 mm. The filling inner material of the biofilm suspended filler in the present invention has a large specific surface area, and the outer shell material has good erosion resistance and anti-aging properties.

[0040] As an embodiment of the present invention, a first water level float switch 21 is provided on the top of the suspended filler biofilm reaction zone for controlling the water level.

[0041] In the present invention, a first guide plate 131 is arranged between the iron-sulfur-stone coupled filler denitrification reaction zone and the suspended filler biofilm reaction zone, and a filler filter 17 is arranged at the bottom of the first guide plate 131. The bottom of the iron-sulfur-stone coupled filler denitrification reaction zone and the bottom of the suspended filler biofilm reaction zone are connected through the filler filter 17; the pore size of the filler filter 17 is preferably 3 to 5 cm, and the filler filter 17 can prevent the biofilm suspended filler from entering the iron-sulfur-stone coupled filler denitrification reaction zone.

[0042] In the present invention, a second aeration device 122 is provided at the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone, and the second aeration device 122 is connected to the air pump 06 via the second air intake electric valve 72; the second aeration device 122 provides oxygenation through the air pump 06 to form an aeration airflow. The present invention can intermittently open the second air intake electric valve 72 to control the aeration airflow generated by the second aeration device 122 to clean up the aged biofilm and particulate matter generated during the operation, thereby ensuring the smooth flow of the iron-sulfur-stone coupled filler denitrification reaction zone, and facilitating the stable and efficient sulfur autotrophic denitrification reaction.

[0043] In the present invention, the iron-sulfur-stone coupled filler denitrification reaction zone is filled with iron-sulfur-stone coupled filler 112, and the iron-sulfur-stone coupled filler 112 preferably includes sulfur-stone coupled filler and iron-based filler; the sulfur-stone coupled filler is preferably a mixed filler of sulfur element particles and limestone particles, and the mass ratio of the sulfur element particles to the limestone particles is preferably (2-3):1; the particle size of the sulfur element particles is preferably 6-10 mm, and the particle size of the limestone particles is preferably 10-15 mm. In the present invention, the iron-based filler is preferably iron shavings or other iron-containing waste slag; the iron-based filler is preferably loaded in a modular loading manner to facilitate replacement and avoid short-circuiting. In the present invention, the iron-based filler and sulfur-stone coupled filler are preferably filled in the denitrification reaction zone of the iron-sulfur-stone coupled filler from bottom to top. In the present invention, in the iron-sulfur-stone coupled filler denitrification reaction zone, wastewater flows through the iron-based filler and the sulfur-stone coupled filler in sequence, and the iron-based filler is sacrificed to play a deoxidation role to ensure an anoxic denitrification environment for sulfur autotrophic denitrification. The iron-based filler releases H in the sulfur autotrophic denitrification reaction. + After dissolution of Fe 2+ , in sulfur, Fe 2+ And under the action of sulfur autotrophic denitrifying bacteria, NO 3- Converted to N2.

[0044] In the present invention, a second guide plate 132 is provided between the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone are connected through the top of the second guide plate 132. In the present invention, the iron-based filler enhanced dephosphorization zone is filled with iron-based filler 113, and the optional range of the types of the iron-based filler 113 is preferably consistent with the optional range of the iron-based filler filled in the iron-sulfur-stone coupled filler denitrification reaction zone, which will not be repeated here.

[0045] The multi-membrane combined double-circulation bioreactor provided by the present invention includes a microfiltration membrane filtration zone, a third guide plate 133 is arranged between the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone, the microfiltration membrane filtration zone is connected to the iron-based filler enhanced phosphorus removal zone through the top of the third guide plate 133, and the microfiltration membrane filtration zone is connected to the iron-based filler enhanced phosphorus removal zone through the bottom of the third guide plate 133. In the present invention, an immersed microfiltration membrane assembly 14 is arranged in the microfiltration membrane filtration zone, which is used to intercept the biofilm and particulate matter that fall off during operation, and return them to the suspended filler biofilm reaction zone through the reflux pump 042. As an embodiment of the present invention, the immersed microfiltration membrane assembly 14 is an immersed membrane-bioreactor assembly, and the material of the microfiltration membrane in the immersed microfiltration membrane assembly 14 preferably includes hydrophilic modified polypropylene, hydrophilic modified polytetrafluoroethylene or hydrophilic modified polyvinylidene fluoride, and the average pore size of the microfiltration membrane is preferably 0.1-0.2 μm. The present invention has no special limitation on the hydrophilic modification reagent used for the hydrophilic modified polypropylene, hydrophilic modified polytetrafluoroethylene and hydrophilic modified polyvinylidene fluoride. Any hydrophilic modification reagent familiar to those skilled in the art can be used. Specifically, non-ionic surfactants or lipid organic substances and other hydrophilic modification agents can be used for modification. The modification method can specifically be blending modification.

[0046] In the present invention, the water outlet of the submerged microfiltration membrane assembly 14 is connected to a water collecting device 15, and the water collecting device 15 is used to collect wastewater treated by the multi-membrane combined double-circulation bioreactor.

[0047] In the present invention, a third aeration device 123 is provided at the bottom of the microfiltration membrane filtration zone, and the third aeration device 123 is connected to the air pump 06 via the third air inlet electric valve 73. In the present invention, during the actual operation, the sewage in the iron-based filler enhanced phosphorus removal zone enters the microfiltration membrane filtration zone through the bottom of the third guide plate 133, and the third aeration device 123 provides oxygenation through the air pump 06, thereby forming an aeration airflow. Under the action of the aeration airflow, the wastewater in the microfiltration membrane filtration zone rises and returns to the iron-based filler enhanced phosphorus removal zone from the top of the third guide plate 133 to form a first internal circulation; the present invention can control the aeration airflow generated by the third aeration device 123 by intermittently opening the third air inlet electric valve 73, and at the same time cooperate with the action of the third guide plate 133 to make part of the wastewater in the microfiltration membrane filtration zone intermittently form the first internal circulation in the microfiltration membrane filtration zone and between the iron-based filler enhanced phosphorus removal zone to enhance phosphorus removal; specifically, the iron-based filler releases H in the sulfur self-oxygen denitrification reaction. + After dissolution of Fe 2+ , part of Fe 2+ It forms chemical precipitation with phosphorus and strengthens the adsorption of extracellular polymers (EPS) to remove phosphorus. 2+The subsequent second internal circulation flows through the suspended filler biofilm reaction zone to the iron-sulfur-stone coupling filler denitrification reaction zone to strengthen the sulfur autotrophic denitrification reaction. At the same time, the aeration airflow generated by the third aeration device 123 can also flush the immersed microfiltration membrane assembly 14, delaying the clogging of the immersed microfiltration membrane assembly 14; and Fe 2+ It can make the filter cake layer on the surface of the microfiltration membrane looser and delay the clogging of the microfiltration membrane.

[0048] In the present invention, a reflux pump 042 is provided at the bottom of the microfiltration membrane filtration zone, and the outlet of the reflux pump 042 is connected to a pipeline extending to the suspended filler biofilm reaction zone, so that part of the wastewater in the microfiltration membrane filtration zone can be refluxed to the suspended filler biofilm reaction zone to form a second internal circulation. Specifically, the H + , Fe 2+ 、NO 3- and NO 2- The reflux pump 042 returns to the suspended multi-membrane combined biofilm reaction area, and NO 2- Conventional denitrification was carried out in the anoxic layer of the suspended multi-membrane combined biofilm reaction zone. + Promoting CO3 removal in the denitrification reaction zone of iron-sulfur-stone coupled packing 2- The dissolution of Fe 2+ 、NO 3- With dissolved CO3 2- Sulfur autotrophic denitrification reaction occurs to achieve efficient nitrogen removal. The second internal circulation cooperates with the first internal circulation in the present invention to enhance mass transfer and enhance nitrogen and phosphorus removal.

[0049] The structural schematic diagram of the multi-membrane combined double circulation bioreactor provided by the present invention is as follows Figure 1 As shown, it includes a first water level float switch 21, a reflux pump 042, an air pump 06, a first air intake electric valve 71, a second air intake electric valve 72, a third air intake electric valve 73, a biofilm suspension filler 111, an iron-sulfur-stone coupling filler 112, an iron-based filler 113, a first aeration device 121, a second aeration device 122, a third aeration device 123, a first guide plate 131, a second guide plate 132, a third guide plate 133, an immersed microfiltration membrane assembly 14, a water collection device 15, a water distribution device 16 and a filler filter 17. The multi-membrane combined double-circulation bioreactor provided by the present invention is used to treat low carbon-nitrogen ratio organic wastewater, and the residual sludge output is very small, and there is no need to set up a separate sludge treatment device. The sludge accumulated at the bottom of the multi-membrane combined double-circulation bioreactor can be cleaned once every six months or one year.

[0050] The present invention provides a multi-membrane combined dual circulation biological treatment system, comprising a slag removal device, a lifting pump 041, a multi-membrane combined dual circulation bioreactor 05, a self-priming pump 10 and an ultraviolet disinfector 08 connected in sequence; the multi-membrane combined dual circulation bioreactor 05 is the multi-membrane combined dual circulation bioreactor described in the above technical scheme, the lifting pump 041 is connected to the water distribution device 16 in the multi-membrane combined dual circulation bioreactor 05, and the self-priming pump 10 is connected to the water collection device 15 in the multi-membrane combined dual circulation bioreactor 05.

[0051] The multi-membrane combined double-circulation biological treatment system provided by the present invention includes a slag removal device for removing large-particle impurities in wastewater to avoid clogging of subsequent equipment. As an embodiment of the present invention, Figure 2 As shown, the slag removal device includes a grid 01, a second water level float switch 22 and a partition 03 which are arranged in sequence; the aperture of the grid 01 is preferably ≤10mm, and the aperture of the partition 03 is preferably ≤2mm.

[0052] The multi-membrane combined dual-circulation biological treatment system provided by the present invention includes a lifting pump 041, which is connected to the slag removal device, specifically connected to one end of the slag removal device where a partition screen 03 is provided; the lifting pump 041 is used to lift the wastewater passing through the partition screen 03 to the multi-membrane combined dual-circulation biological reactor 05 for treatment.

[0053] The multi-membrane combined dual circulation biological treatment system provided by the present invention comprises a multi-membrane combined dual circulation biological reactor 05, and the multi-membrane combined dual circulation biological reactor 05 is the multi-membrane combined dual circulation biological reactor described in the above technical solution, and its structure is not described in detail. In the present invention, the water distribution device 16 in the multi-membrane combined dual circulation biological reactor 05 is connected to the lifting pump 041.

[0054] As an embodiment of the present invention, the number of multi-membrane combined dual-circulation bioreactors 05 in the multi-membrane combined dual-circulation biological treatment system is one or two sets. When the multi-membrane combined dual-circulation bioreactors 05 are two sets, they are arranged in parallel (such as Figure 3 As shown, the air pump 06 is not shown).

[0055] The multi-membrane combined dual circulation biological treatment system provided by the present invention includes a self-priming pump 10, which is connected to a water collecting device 15 in the multi-membrane combined dual circulation bioreactor 05. The self-priming pump 10 is used to transport the treated wastewater in the multi-membrane combined dual circulation bioreactor 05 to a subsequent ultraviolet sterilizer 08 for treatment.

[0056] The multi-membrane combined double-circulation biological treatment system provided by the present invention comprises an ultraviolet sterilizer 08 , which is connected to a self-priming pump 10 and is used to disinfect the wastewater treated in the multi-membrane combined double-circulation biological reactor 05 .

[0057] As an embodiment of the present invention, Figure 2 As shown, the ultraviolet sterilizer 08 is connected to a glass rotor flowmeter 9, and the glass rotor flowmeter 9 is used to measure the water flow rate and flow rate.

[0058] As an embodiment of the present invention, the multi-membrane combined dual-circulation biological treatment system adopts a programmable controller and a touch screen intelligent control, and has a remote communication and control interface, which can realize remote control, and specifically an automatic electric control cabinet can be used.

[0059] Aiming at the characteristics of low carbon-nitrogen ratio organic wastewater treatment projects, the present invention organically combines membrane-bioreactor technology, biological contact oxidation technology, sulfur self-oxygen denitrification technology, iron-enhanced biological phosphorus removal technology, and intermittent aeration method, and utilizes a circulating pump and a unique double internal circulation structure to form an efficient and energy-saving multi-membrane combined double internal circulation biological reaction system, so as to achieve the purposes of reducing reactor volume, saving floor space, reducing energy consumption, reducing residual sludge, and efficiently removing nitrogen and phosphorus.

[0060] The present invention provides a method for treating low carbon-nitrogen ratio organic wastewater by using the multi-membrane combined double-circulation biological treatment system described in the above technical solution, comprising the following steps:

[0061] (I) transporting low carbon-nitrogen ratio organic wastewater to a slag removal device for slag removal treatment to obtain slag removal wastewater; the carbon-nitrogen ratio of the low carbon-nitrogen ratio organic wastewater is 2 to 16;

[0062] (II) The deslagging wastewater is transported to the multi-membrane combined dual-circulation bioreactor 05 via a lift pump 041, and is biologically treated in the suspended filler biofilm reaction zone, the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced phosphorus removal zone in sequence to obtain biologically treated wastewater;

[0063] The biologically treated wastewater enters the microfiltration membrane filtration zone, and part of the biologically treated wastewater is refluxed to the iron-based filler enhanced phosphorus removal zone through the top of the third guide plate 133 under the action of the aeration airflow formed by the third aeration device 123 to form a first internal circulation, and the biologically treated wastewater undergoing the first internal circulation accounts for 50-70% of the total biologically treated wastewater inflow; at the same time, part of the biologically treated wastewater is refluxed to the suspended filler biofilm reaction zone through the reflux pump 042 to form a second internal circulation, and the biologically treated wastewater undergoing the second internal circulation accounts for 5-15% of the total biologically treated wastewater inflow; the wastewater in the microfiltration membrane filtration zone is intercepted and treated by the immersed microfiltration membrane assembly 14 to obtain biologically purified water;

[0064] (III) the biologically purified water is transported to the ultraviolet disinfector 08 by the self-priming pump 10 for disinfection and then discharged after meeting the standards;

[0065] During the operation of the multi-membrane combined dual-circulation biological treatment system, the first air intake electric valve 71, the second air intake electric valve 72 and the third air intake electric valve 73 are started intermittently.

[0066] The present invention transports low carbon-nitrogen ratio organic wastewater to a slag removal device for slag removal treatment to obtain slag removal wastewater; the carbon-nitrogen ratio of the low carbon-nitrogen ratio organic wastewater is 2 to 16. In the present invention, the carbon-nitrogen ratio of the low carbon-nitrogen ratio organic wastewater is 2 to 16, preferably 4 to 15; the present invention has no special limitation on the source of the low carbon-nitrogen ratio organic wastewater, and domestic wastewater or hospital sewage can be used.

[0067] After obtaining the deslagging wastewater, the deslagging wastewater of the present invention is transported to the multi-membrane combined double-circulation bioreactor 05 through the lifting pump 041, and is biologically treated in the suspended filler biofilm reaction zone, the iron-sulfur-stone coupled filler denitrification reaction zone and the iron-based filler enhanced phosphorus removal zone in sequence to obtain biologically treated wastewater. In the present invention, during the biological treatment process, the operating conditions preferably include: the filling rate of the biofilm suspended filler in the suspended filler biofilm reaction zone is 30-50%, the hydraulic retention time is 3-10h, and during aeration, DO is controlled to be ≥2mg / L; the hydraulic retention time of the iron-sulfur-stone coupled filler denitrification reaction zone is 2-8h, and DO is controlled to be <0.5mg / L; the hydraulic retention time of the iron-based filler enhanced phosphorus removal zone is 2-8h; and the sludge settling ratio of the microfiltration membrane filtration zone is controlled to be 10-25%.

[0068] After obtaining the biological treatment wastewater, the present invention allows the biological treatment wastewater to enter the microfiltration membrane filtration area, and part of the biological treatment wastewater is refluxed to the iron-based filler enhanced phosphorus removal area through the top of the third guide plate 133 under the action of the aeration airflow formed by the third aeration device 123 to form a first internal circulation, and the biological treatment wastewater undergoing the first internal circulation accounts for 50-70% of the total water intake of the biological treatment wastewater; at the same time, part of the biological treatment wastewater is refluxed to the suspended filler biofilm reaction area through the reflux pump 042 to form a second internal circulation, and the biological treatment wastewater undergoing the second internal circulation accounts for 5-15% of the total water intake of the biological treatment wastewater; the wastewater in the microfiltration membrane filtration area is intercepted and treated by the immersed microfiltration membrane assembly 14 to obtain biological purified water. In the present invention, the air-water ratio of the aeration airflow of the first internal circulation is preferably not more than 10:1; the immersed microfiltration membrane assembly 14 used for the interception treatment is preferably opened intermittently, and more preferably, the water discharge is suspended for 0.5-2 minutes every 6-10 minutes of operation.

[0069] After obtaining the biologically purified water, the present invention transports the biologically purified water to the ultraviolet disinfector 08 through the self-priming pump 10 for disinfection and then discharges it to the outside after reaching the standard. The present invention has no special limitation on the disinfection, and a disinfection method well known to those skilled in the art can be used.

[0070] When domestic wastewater is discharged using the method provided by the present invention, the effluent water quality is far superior to the Class A standard of the Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB18918-2002); when hospital sewage is discharged using the method provided by the present invention, the effluent water quality is far superior to the Water Pollutant Discharge Standard for Medical Institutions (GB18466-2005).

[0071] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0072] Example 1

[0073] The multi-membrane combined double-circulation biological treatment system provided by the present invention is used to treat domestic wastewater, and the treated water volume is 100m 3 / d; The processing method includes the following steps:

[0074] The sewage (with a carbon-nitrogen ratio of 4.4) from the collection tank of a county sewage treatment plant is removed by a 10mm grid 01 and a 2mm grid 03, and then lifted to a multi-membrane combined dual-circulation bioreactor 05 by a lifting pump 041, and then evenly distributed in the multi-membrane combined biofilm reaction zone by a water distribution device 16. The wastewater flows through the suspended filler biofilm reaction zone, the iron-sulfur-stone coupling filler denitrification reaction zone and the iron-based filler enhanced phosphorus removal zone in turn for biological treatment to obtain biologically treated wastewater; specifically, the filling inner material of the biofilm suspended filler in the suspended filler biofilm reaction zone is polyurethane sponge, the outer shell is polyethylene, the outer shell thickness is 0.4mm, the particle size of the biofilm suspended filler is 5cm, the filling rate is 30%, and the hydraulic retention time of the reaction zone is 4h; by intermittently starting the first air inlet electric valve 71 and then controlling the aeration airflow formed by the first aeration device 121, an anaerobic-anoxic-aerobic environment is alternately formed in the suspended filler biofilm reaction zone, and microbial aerobic nitrification, anoxic denitrification and and anaerobic phosphorus removal. During aeration, DO is controlled to be ≥ 2 mg / L. After that, the wastewater enters the iron-sulfur-stone coupling filler denitrification reaction zone and the iron-based filler enhanced phosphorus removal zone for efficient deep denitrification and phosphorus removal. The fillers in the iron-sulfur-stone coupling filler denitrification reaction zone are iron shavings, sulfur and limestone, respectively. The height of the iron shavings filler is 0.5m, the particle size of the sulfur is 6-10mm, the particle size of the limestone is 10-15mm, and the mass ratio of the sulfur and limestone is 3:1. The water in the reaction zone is The hydraulic retention time is 2.5h, and DO is controlled to be less than 0.5mg / L; the aeration airflow formed by the second aeration device 122 is controlled by intermittently starting the second air inlet electric valve 72 to clean the aged biofilm and particulate matter generated during the operation, and the cleaning cycle is once every 30 days; the iron-based filler in the iron-based filler enhanced phosphorus removal area is also iron shavings, and the height of the iron shavings filler is 1.5m. The hydraulic retention time of this area is 3h; the sludge settling ratio of the microfiltration membrane filtration area is controlled to be 10-25%;

[0075] The biological treatment wastewater enters the microfiltration membrane filtration area, and the aeration airflow formed by the second aeration device 123 is controlled by intermittently starting the third air inlet electric valve 73. Under the action of the aeration airflow formed by the third aeration device 123, part of the biological treatment wastewater forms a first internal circulation between the microfiltration membrane filtration area and the iron-based filler enhanced phosphorus removal area. The air-water ratio of the first internal circulation aeration airflow is (8-9): 1; at the same time, part of the biological treatment wastewater is refluxed to the suspended filler biofilm reaction area through the reflux pump 042 to form a second internal circulation; the wastewater in the microfiltration membrane filtration area is immersed in the water. The immersion microfiltration membrane assembly 14 is used for treatment, and the detached biofilm and particulate matter are retained to obtain biologically purified water, wherein the immersion microfiltration membrane assembly 14 is made of hydrophilic modified polytetrafluoroethylene, and the average pore size of the microfiltration membrane is 0.1-0.2 μm. It is intermittently opened, and the water discharge is suspended for 0.5 minutes every 8 minutes of operation; the detached biofilm and particulate matter are returned to the suspended filler biofilm reaction zone through the reflux pump 042, and part of the biofilm is digested by the metazoans living in the biofilm system, and the remaining biofilm is decomposed by the anaerobic microorganisms in the inner layer of the biofilm growing on the suspended filler;

[0076] The biologically purified water is transported to the ultraviolet disinfector 08 by the self-priming pump 10 for disinfection and then discharged after meeting the standards.

[0077] The above method was run continuously for half a year without any residual sludge being discharged.

[0078] After testing, the effluent after disinfection treatment meets the Level A standard of "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB18918-2002). The specific data are shown in Table 2.

[0079] This embodiment adopts intermittent aeration, and the aeration volume is designed only according to the maximum value of the microfiltration membrane air flushing and the biological reaction gas demand. The total gas-water ratio between the microfiltration membrane filtration area and the suspended filler biofilm reaction area does not exceed 10:1; a simple membrane-bioreactor is used to treat similar domestic sewage, and the total gas-water ratio exceeds 15:1.

[0080] Due to the low concentration of suspended sludge in the multi-membrane combined double-circulation bioreactor 05, the transmembrane pressure difference of the microfiltration membrane does not exceed 1.5m, and the membrane flux is stable at 15-20L / m 2 h, the same type of microfiltration membrane is used in conventional membrane-bioreactor system, the transmembrane pressure difference exceeds 2m, and the membrane flux is generally 12-15L / m after stabilization 2 ·h.

[0081] Table 1 Main equipment used in Example 1 (total installed power 5kW)

[0082]

[0083] Table 2 Treatment effect of Example 1

[0084]

[0085] As shown in Table 2, the effluent COD cr The concentrations of TN and TP were 20.1 mg / L, 6.0 mg / L and 0.3 mg / L respectively, and the removal rates were 87.46%, 83.65% and 91.18% respectively. The effluent quality was far better than the Level A standard of Pollutant Discharge Standard for Municipal Wastewater Treatment Plants (GB18918-2002).

[0086] Example 2

[0087] The multi-membrane combined double-circulation biological treatment system provided by the present invention is used to treat hospital sewage, with a treatment water volume of 30m 3 / d; The processing method includes the following steps:

[0088] The sewage discharged into a township hospital into a water collection tank (with a carbon-nitrogen ratio of 14.25) is removed by a 10mm grid 01 and a 2mm grid 03, and then lifted to a multi-membrane combined dual-circulation bioreactor 05 by a lifting pump 041, and then evenly distributed in the multi-membrane combined biofilm reaction zone by a water distribution device 16. The wastewater flows through the suspended filler biofilm reaction zone, the iron-sulfur-stone coupling filler denitrification reaction zone and the iron-based filler enhanced phosphorus removal zone in turn for biological treatment to obtain biologically treated wastewater; specifically, the filling inner material of the biofilm suspended filler in the suspended filler biofilm reaction zone is polyurethane sponge, the outer shell is polyethylene, the outer shell thickness is 0.4mm, the particle size of the biofilm suspended filler is 5cm, the filling rate is 50%, and the hydraulic retention time of the reaction zone is 6h; the first air inlet electric valve 71 is intermittently started to control the aeration airflow formed by the first aeration device 121, so that an anaerobic-anoxic-aerobic environment is alternately formed in the suspended filler biofilm reaction zone. During aeration, DO is controlled to be ≥2mg / L, and the initial The first step is to carry out microbial aerobic nitrification, anoxic denitrification and anaerobic phosphorus removal. After that, the wastewater enters the iron-sulfur-stone coupling filler denitrification reaction zone and the iron-based filler enhanced phosphorus removal zone for efficient deep denitrification and phosphorus removal. The fillers in the iron-sulfur-stone coupling filler denitrification reaction zone are iron shavings, sulfur and limestone. The height of the iron shavings filler is 0.5m, the particle size of the sulfur is 6-10mm, the particle size of the limestone is 10-15mm, and the mass ratio of elemental sulfur to limestone is 3:1. The water in the reaction zone is 200 μm high and 100 μm high. The hydraulic retention time is 3.5h, and DO is controlled to be less than 0.5mg / L; the aeration airflow formed by the second aeration device 122 is controlled by intermittently starting the second air inlet electric valve 72 to clean the aged biofilm and particulate matter generated during the operation, and the cleaning cycle is once every 15 days; the iron-based filler in the iron-based filler enhanced phosphorus removal area is also iron shavings, and the height of the iron shavings filler is 1.2m. The hydraulic retention time of this area is 4h; the sludge settling ratio of the microfiltration membrane filtration area is controlled to be 10-25%;

[0089] The biological treatment wastewater enters the microfiltration membrane filtration area, and the aeration airflow formed by the second aeration device 123 is controlled by intermittently starting the third air inlet electric valve 73. Under the action of the aeration airflow formed by the third aeration device 123, part of the biological treatment wastewater forms a first internal circulation between the microfiltration membrane filtration area and the iron-based filler enhanced phosphorus removal area. The air-water ratio of the first internal circulation aeration airflow is (8-9):1; at the same time, part of the biological treatment wastewater is refluxed to the suspended filler biofilm reaction area through the reflux pump 042 to form a second internal circulation; the wastewater in the microfiltration membrane filtration area is The detached biofilm and particulate matter are intercepted by the immersed microfiltration membrane assembly 14 to obtain biologically purified water, wherein the detached microfiltration membrane assembly 14 (made of hydrophilic modified polypropylene, with an average pore size of the microfiltration membrane of 0.1-0.2 μm) is intermittently opened, and the water discharge is suspended for 1 minute after every 8 minutes of operation; the detached biofilm and particulate matter are returned to the suspended filler biofilm reaction zone through the reflux pump 042, and part of the biofilm is digested by the metazoans living in the biofilm system, and the remaining biofilm is decomposed by the anaerobic microorganisms in the inner layer of the biofilm growing on the suspended filler;

[0090] The biologically purified water is transported to the ultraviolet disinfector 08 by the self-priming pump 10 for disinfection and then discharged after meeting the standards.

[0091] The above method was run continuously for half a year without any residual sludge being discharged.

[0092] After testing, the treated effluent meets the water pollutant discharge standard for medical institutions (GB18466-2005). The specific data are shown in Table 4.

[0093] This embodiment adopts intermittent aeration, and the aeration volume is designed only according to the maximum value of the microfiltration membrane air flushing and the biological reaction gas demand. The total gas-water ratio between the microfiltration membrane filtration area and the suspended filler biofilm reaction area does not exceed 15:1; a simple membrane-bioreactor is used to treat similar hospital sewage, and the total gas-water ratio exceeds 20:1.

[0094] Due to the low concentration of suspended sludge in the multi-membrane combined double-circulation bioreactor 05, the transmembrane pressure difference of the microfiltration membrane does not exceed 1.5m, and the membrane flux is stable at 15-20L / m 2 h, the same type of microfiltration membrane is used in conventional membrane-bioreactor system, the transmembrane pressure difference exceeds 2m, and the membrane flux is generally 12-15L / m after stabilization 2 ·h.

[0095] Table 3 Main equipment used in Example 2 (total installed power 3.2kW)

[0096]

[0097]

[0098] Table 4 Treatment effect of Example 2

[0099]

[0100] It can be seen from Table 4 that the effluent COD cr The concentrations of TN and TP were 20.2 mg / L, 7.3 mg / L and 0.4 mg / L, respectively, and the removal rates were 96.71%, 83.06% and 91.11%, respectively. The effluent quality was much better than the Discharge Standard for Water Pollutants from Medical Institutions (GB18466-2005).

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multi-membrane combined double-circulation bioreactor, characterized in that: It includes a multi-membrane combined biofilm reaction zone and a microfiltration membrane filtration zone; the multi-membrane combined biofilm reaction zone includes a suspended filler biofilm reaction zone, an iron-sulfur-stone coupling filler denitrification reaction zone and an iron-based filler enhanced phosphorus removal zone which are connected in sequence; A water distribution device (16) is arranged at the top of the suspended filler biofilm reaction zone, a first aeration device (121) is arranged at the bottom of the suspended filler biofilm reaction zone, and the first aeration device (121) is connected to the air pump (06) via a first air inlet electric valve (71); the suspended filler biofilm reaction zone is filled with biofilm suspended filler (111); A first guide plate (131) is arranged between the iron-sulfur-stone coupled filler denitrification reaction zone and the suspended filler biofilm reaction zone, a filler filter (17) is arranged at the bottom of the first guide plate (131), and the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone is connected to the bottom of the suspended filler biofilm reaction zone through the filler filter (17); a second aeration device (122) is arranged at the bottom of the iron-sulfur-stone coupled filler denitrification reaction zone, and the second aeration device (122) is connected to the air pump (06) via a second air intake electric valve (72); the iron-sulfur-stone coupled filler denitrification reaction zone is filled with iron-sulfur-stone coupled filler (112); A second guide plate (132) is provided between the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone, and the iron-based filler enhanced dephosphorization zone and the iron-sulfur-stone coupled filler denitrification reaction zone are connected through the top of the second guide plate (132); the iron-based filler enhanced dephosphorization zone is filled with iron-based fillers (113); A third guide plate (133) is arranged between the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone, the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone are connected through the top of the third guide plate (133), and at the same time, the microfiltration membrane filtration zone and the iron-based filler enhanced phosphorus removal zone are connected through the bottom of the third guide plate (133); an immersed microfiltration membrane assembly (14) is arranged in the microfiltration membrane filtration zone, and the water outlet of the immersed microfiltration membrane assembly (14) is connected to a water collection device (15); a third aeration device (123) is arranged at the bottom of the microfiltration membrane filtration zone, and the third aeration device (123) is connected to an air pump (06) via a third air inlet electric valve (73); a reflux pump (042) is arranged at the bottom of the microfiltration membrane filtration zone, and the water outlet of the reflux pump (042) is connected to a pipeline extending to a suspended filler biofilm reaction zone.

2. The multi-membrane combined dual circulation bioreactor according to claim 1, characterized in that: A first water level float switch (21) is arranged on the top of the suspended filler biofilm reaction zone.

3. The multi-membrane combined dual circulation bioreactor according to claim 1, characterized in that: The biofilm suspension filler (111) is spherical, and comprises a filling inner material and an outer shell covering the surface of the filling inner material. The filling inner material is polyurethane sponge, polyvinyl alcohol or polyester, and the outer shell is made of polyethylene, polypropylene or polycarbonate.

4. The multi-membrane combined dual circulation bioreactor according to claim 1, characterized in that: The iron-sulfur-stone coupling filler (112) comprises a sulfur-stone coupling filler and an iron-based filler; the sulfur-stone coupling filler is a mixed filler of sulfur particles and limestone particles, and the mass ratio of the sulfur particles to the limestone particles is (2-3):1; The iron-sulfur-stone coupled filler denitrification reaction zone is filled with the iron-based filler and the sulfur-stone coupled filler in sequence from bottom to top.

5. The multi-membrane combined dual circulation bioreactor according to claim 1, characterized in that: The immersed microfiltration membrane assembly (14) is an immersed membrane-bioreactor assembly. The material of the microfiltration membrane in the immersed microfiltration membrane assembly (14) includes hydrophilically modified polypropylene, hydrophilically modified polytetrafluoroethylene or hydrophilically modified polyvinylidene fluoride. The average pore size of the microfiltration membrane is 0.1-0.2 μm.

6. A multi-membrane combined double-circulation biological treatment system, characterized in that: It comprises a slag removal device, a lifting pump (041), a multi-membrane combined dual circulation bioreactor (05), a self-priming pump (10) and an ultraviolet disinfector (08) which are connected in sequence; the multi-membrane combined dual circulation bioreactor (05) is the multi-membrane combined dual circulation bioreactor according to any one of claims 1 to 5, the lifting pump (041) is connected to a water distribution device (16) in the multi-membrane combined dual circulation bioreactor (05), and the self-priming pump (10) is connected to a water collection device (15) in the multi-membrane combined dual circulation bioreactor (05).

7. The multi-membrane combined double-circulation biological treatment system according to claim 6 is characterized in that: The slag removal device comprises a grille (01), a second water level float switch (22) and a grid (03) which are arranged in sequence; the aperture of the grid (03) is ≤2 mm.

8. The multi-membrane combined double-circulation biological treatment system according to claim 6 is characterized in that: The ultraviolet sterilizer (08) is connected to a glass rotor flowmeter (09).

9. The multi-membrane combined double-circulation biological treatment system according to claim 6, characterized in that: The number of the multi-membrane combined dual circulation bioreactors (05) in the multi-membrane combined dual circulation biological treatment system is one or two sets. When there are two sets of the multi-membrane combined dual circulation bioreactors (05), they are arranged in parallel.

10. A method for treating low carbon-nitrogen ratio organic wastewater using the multi-membrane combined double-circulation biological treatment system according to any one of claims 6 to 9, comprising the following steps: (I) transporting low carbon-nitrogen ratio organic wastewater to a slag removal device for slag removal treatment to obtain slag removal wastewater; the carbon-nitrogen ratio of the low carbon-nitrogen ratio organic wastewater is 2 to 16; (II) the deslagging wastewater is transported to a multi-membrane combined dual-circulation bioreactor (05) via a lift pump (041), and is subjected to biological treatment in a suspended filler biofilm reaction zone, an iron-sulfur-stone coupled filler denitrification reaction zone, and an iron-based filler enhanced phosphorus removal zone in sequence to obtain biologically treated wastewater; The biologically treated wastewater enters the microfiltration membrane filtration zone, and part of the biologically treated wastewater is refluxed to the iron-based filler enhanced phosphorus removal zone through the top of the third guide plate (133) under the action of the aeration airflow formed by the third aeration device (123) to form a first internal circulation, and the biologically treated wastewater undergoing the first internal circulation accounts for 50-70% of the total biologically treated wastewater inflow; at the same time, part of the biologically treated wastewater is refluxed to the suspended filler biofilm reaction zone through the reflux pump (042) to form a second internal circulation, and the biologically treated wastewater undergoing the second internal circulation accounts for 5-15% of the total biologically treated wastewater inflow; the wastewater in the microfiltration membrane filtration zone is intercepted and treated by an immersed microfiltration membrane assembly (14) to obtain biologically purified water; (III) the biologically purified water is transported to the ultraviolet disinfector (08) through a self-priming pump (10) for disinfection and then discharged after meeting the standards; Wherein, during the operation of the multi-membrane combined dual-circulation biological treatment system, the first air intake electric valve (71), the second air intake electric valve (72) and the third air intake electric valve (73) are started intermittently.

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