Double-biological-membrane sewage treatment process for deep nitrogen and phosphorus removal coupled sludge reduction

Abstract

The invention discloses a double-biological-membrane sewage treatment process for deep nitrogen and phosphorus removal coupled sludge reduction, and belongs to the technical field of sewage treatment. The process is composed of an anoxic biofilm reaction tank, an aerobic biofilm reaction tank and an iron autotrophic denitrification biofilter, and efficient nitrogen and phosphorus removal is performed on sewage through the double-biofilm sewage treatment process. Nitrogen and phosphorus removal and sludge in-situ reduction are mainly carried out in the front-end biological membrane reaction tank, and deep nitrogen and phosphorus removal is mainly carried out in the iron autotrophic denitrification biological filter tank. And the residual sludge is predded by using a protozoon / metazoon food chain of the aerobic biological membrane reaction tank, so that the effect of zero generation of the residual sludge is achieved. The concentration of iron ions is changed by adjusting the reflux ratio of iron-ion-containing reflux liquid generated by the iron autotrophic denitrification biofilter, so that the number and community structures of micro-organisms are effectively controlled, the control on sludge predation is further achieved, and the sludge reduction effect is improved. The process is obvious in effect, can stably operate for a long time and is suitable for engineering application.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment and sludge treatment technology, and specifically to a sewage process for deep nitrogen and phosphorus removal coupled with in-situ sludge reduction. Background Art

[0002] Due to the advancement of urbanization and the needs of economic development, the amount of sewage generated and treated in cities has increased significantly in recent years. At the same time, the requirements for sewage discharge standards and the control of treatment by-products have become increasingly stringent. Many sewage treatment plants are faced with the challenge of upgrading sewage treatment standards. The low carbon-nitrogen ratio of municipal sewage is also unfavorable for activated sludge treatment. At the same time, the amount of sludge generated during sewage treatment using the activated sludge process is large, and as the water volume increases, the production of excess sludge also shows an upward trend. The treatment of this excess sludge has disadvantages such as high cost, imperfect technology, and the risk of secondary pollution.

[0003] In order to meet the increasingly stringent discharge standards for municipal sewage and reduce the amount of residual sludge generated during the treatment process, researchers have proposed many solutions. Patent No. CN202410752286.2 uses a biological treatment process for treating low C / N wastewater by integrating anaerobic and aerobic treatment processes, effectively improving the removal efficiency of nitrogen and phosphorus in low C / N wastewater. However, this process has a post-treatment process and still requires the construction of additional operating units and increased operating costs. Patent No. CN201711429308.8 uses a biofilm-enhanced denitrification treatment process, which uses biological fillers to further optimize the microecological environment and can achieve better denitrification effects. However, this process still has the problem of residual sludge treatment. Patent No. CN201810999406.3 uses a plug-flow coupled sewage treatment device and uses fixed metazoan carrier fillers. However, this device still requires the additional addition of dephosphorization drugs and regular sludge discharge, and the residual sludge problem has not been completely solved. The present invention does not require the addition of additional sludge treatment equipment and additional external carbon sources. In response to the current situation of low C / N ratio of municipal sewage and the fact that a large amount of excess sludge is generated by the existing activated sludge method, a double biofilm sewage treatment process is applied to achieve deep denitrification and phosphorus removal of sewage while significantly reducing the generation of excess sludge to meet the needs of today's sewage treatment plants. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, in order to achieve efficient denitrification and phosphorus removal for sewage and achieve the effect of in-situ sludge reduction, the present invention designs a double biofilm sewage treatment process with deep denitrification and phosphorus removal coupled with sludge reduction. The sewage treatment process structure is as shown in the attached figure. Figure 1The process flow is as follows: the effluent from the primary sedimentation tank 1 flows through a lift pump 2 into the anoxic biofilm reactor 3, where it then flows into the aerobic biofilm reactor 4. The tailwater, having been treated in the front-end biofilm reactor, flows into the ferrotrophic denitrification biofilter 5. The effluent from the aerobic biofilm reactor flows back to the anoxic biofilm reactor via reflux device 6 via reflux liquid 1. A portion of the effluent from the ferrotrophic denitrification biofilter flows back to the anoxic biofilm reactor via reflux device 7 via reflux liquid 2.

[0005] The process unit consists of an anoxic biofilm reactor, an aerobic biofilm reactor, and an iron autotrophic denitrification filter. The front end consists of the anoxic and aerobic biofilm reactors. The anoxic biofilm reactor primarily performs denitrification, while the aerobic biofilm reactor primarily performs nitrification to remove ammonia nitrogen from the wastewater. It also provides a favorable growth environment for protozoa and metazoans, preying on excess sludge produced by the system and achieving in-situ sludge reduction. The back end of the process is an iron autotrophic denitrification biofilter, whose packing is covered with a biofilm formed by iron autotrophic denitrifying bacteria, which deeply denitrifies and removes phosphorus from the front-end tailwater. Reflux 1 primarily refluxes nitrification liquid, returning the nitrate- and nitrite-containing water produced by the aerobic biofilm reactor to the anoxic biofilm reactor for denitrification. The reflux liquid 2 is mainly used to reflux water containing iron ions. The reflux liquid 2 is returned to the front-end biofilm reaction tank, further improving the denitrification capacity of the front-end biofilm reaction tank by promoting electron transfer; at the same time, iron ions have a certain control effect on protozoa / metazoa. Iron ions can control the number and community structure of microorganisms, and avoid damage to the functional bacteria of the aerobic biofilm reaction tank; at the same time, it can also regulate the sludge predation ability of protozoa / metazoa and control the sludge reduction performance of the process.

[0006] This invention utilizes a dual-biofilm wastewater treatment process that combines deep nitrogen and phosphorus removal with sludge reduction. Its technical requirements include the use of fixed bio-bed fillers in both the anoxic and aerobic bio-film reactors. The optimal solution is a fixed bio-bed filler assembled from MBR curtain fabrics and placed in both the anoxic and aerobic bio-film reactors. The fill ratio of the bio-bed carrier should range from 20% to 80%, with an optimal fill ratio of 60% to 80%. The filler for the ferrotrophic denitrification biofilter is mixed directly with particles. A mixture of limestone, siderite, and magnetite is uniformly mixed and filled into the ferrotrophic denitrification biofilter. The optimal biofilter filler is a mixture of limestone, siderite, and magnetite of equal particle size, mixed and filled in a volume ratio of 1:2:1 (V / V / V). The aerobic biofilm reaction tank is continuously aerated to ensure that the dissolved oxygen in the aerobic biofilm reaction tank is controlled between 1-5 mg / L; the power of the lifting pump is adjusted to ensure that the hydraulic retention time of the aerobic biofilm reaction tank and the anoxic biofilm reaction tank is controlled between 12-24 hours; the operating parameters of the reflux device are controlled so that the reflux ratio of reflux liquid 1 is controlled between 60-120%, and the reflux ratio of reflux liquid 2 is controlled between 60-100%.

[0007] The technical principle of the present invention is as follows: in terms of treating pollutants in sewage water bodies, the present invention applies a double biofilm sewage treatment process and finds that the sewage treatment process has a deep removal ability for water pollutants. The rear-end iron autotrophic denitrification biological filter can not only enhance the denitrification and phosphorus removal capabilities of the entire system, but also enable sewage to achieve deep denitrification and phosphorus removal; at the same time, the iron ions contained in the reflux 2 will enrich the electron transfer mode between microbial species, promote the electron transfer rate of microorganisms, and greatly improve the activity of the denitrifying bacteria in the front-end biofilm reaction tank, especially the denitrifying bacteria activity of the anoxic biofilm reaction tank, while enriching the denitrifying bacteria in the anoxic biofilm reaction tank and the nitrifying bacteria in the aerobic biofilm reaction tank, thereby improving the treatment performance of the biofilm reactor. By controlling the reflux ratio of the reflux 2, the system can regulate the denitrification capacity of the biofilm reaction tank, especially the denitrification capacity of the anoxic biofilm reaction tank.

[0008] In terms of excess sludge reduction, the present invention applies a dual biofilm system, which greatly reduces the generation of excess sludge from the root, and at the same time inoculates protozoa / metazoa in the aerobic biofilm reaction tank, so that the excess sludge generated by the dual biofilm system is completely preyed upon. In this system, the present invention reveals the regulatory effect of iron ions on protozoa / metazoa in the front-end aerobic biofilm reaction tank. Since iron ions have a certain control and regulatory effect on microorganisms, the iron ions contained in the reflux liquid 2 will also control the number and community structure of microorganisms. Iron ions will cause the microorganism community to evolve, and protozoa such as ciliates and metazoans such as nematodes and rotifers that have strong adaptability to iron ions will gradually become dominant populations, thereby achieving the stable operation of the excess sludge predation system. By controlling the reflux ratio of the reflux liquid 2 in the system, the sludge reduction capacity of the system can be further regulated.

[0009] The iron ion concentration within the front-end biofilm reactor plays a significant role in regulating the process's denitrification and sludge reduction capabilities. During this process, the reflux ratio of reflux 2 should be controlled to minimize excessive iron ion concentration within the biofilm reactor. The reflux ratio should be maintained between 60% and 100% to ensure that the iron ion concentration positively impacts the biofilm reactor.

[0010] Specific process implementation steps:

[0011] Step 1: Fixed bio-bed filler is loaded into the anoxic and aerobic biofilm reactors at a filling ratio of 20%–80%. Iron ore filler is evenly mixed and used as a biofilm composite carrier, which is then loaded into the ferruginous autotrophic denitrification biofilter. Primary sedimentation tank wastewater is continuously introduced into the dual biofilm treatment process. Exogenous activated sludge is inoculated into the anoxic and aerobic biofilm reactors to form biofilms. Autotrophic denitrifying bacteria are inoculated into the ferruginous autotrophic denitrification filter to form biofilms. Once biofilm formation is successful, the dual biofilm system is constructed according to the process diagram.

[0012] Step 2: Start lift pump 2, reflux device 6, and reflux device 7. The effluent from primary clarifier 1 flows through lift pump 2 into anoxic biofilm reactor 3. The effluent then flows into aerobic biofilm reactor 4. The tailwater, treated in the front-end biofilm reactor, flows into ferrotrophic denitrification biofilter 5. The effluent from the aerobic biofilm reactor flows back into the anoxic biofilm reactor via reflux device 6, via reflux liquid 1. A portion of the effluent from the ferrotrophic denitrification biofilter flows back into the anoxic biofilm reactor via reflux liquid 2, via reflux device 7. Water treated in this dual biofilm process is discharged in compliance with standards.

[0013] Step 3: Determine the optimal filling rate of the fixed-bed biofilm carrier of the anoxic biofilm reactor and the aerobic biofilm reactor, the optimal hydraulic retention time, the dissolved oxygen concentration of the aerobic biofilm reactor, the optimal filling ratio of the composite filler of the iron autotrophic denitrification filter, and the optimal reflux ratio of reflux liquid 1 to reflux liquid 2 based on the specific conditions on site, and continue to treat municipal sewage efficiently and continuously after the commissioning is completed.

[0014] Based on the above technical solution, compared with the existing known technology, it has the following effects:

[0015] This dual-biofilm process deeply removes nitrogen and phosphorus from municipal wastewater, effectively reducing its turbidity and demonstrating strong pollutant treatment capabilities. Furthermore, the dual-biofilm system maintains improved pollutant treatment capacity while maintaining low sludge production, ensuring the system's long-term operational potential.

[0016] Through micro-biological predation technology, a food chain / food web mainly composed of residual sludge and protozoa / metazoa is formed in the aerobic biofilm reaction tank, which greatly improves the in-situ sludge reduction capacity of the double biofilm sewage treatment process. It can achieve long-term non-sludge discharge operations and no secondary pollution problems, reducing the sludge treatment cost in actual applications and the difficulty of long-term operation.

[0017] The return of reflux liquid 2 improves the denitrification performance of the anoxic and aerobic biofilm reactors, particularly the denitrification performance of the anoxic biofilm reactor. It also controls and regulates the protozoa and metazoa in the aerobic biofilm reactor, creating a dynamic balance between sludge growth and microbial predation.

[0018] This method is simple to operate, safe and economical, suitable for practical engineering applications, and worthy of wide promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process principle of the present invention.

[0020] Notes on the accompanying figures: 1-primary sedimentation tank; 2-lifting pump; 3-anoxic biofilm reaction tank; 4-aerobic biofilm reaction tank; 5-ferroautotrophic denitrification biological filter; 6-reflux liquid 1 reflux device; 7-reflux liquid 2 reflux device.

[0021] Figure 2This is a performance diagram of inlet and outlet water pollutant removal under the conditions of anoxic biofilm reaction tank and aerobic biofilm reaction tank MBR curtain fabric filling rate of 60%, internal reflux ratio of 100%, hydraulic retention time of 16h, dissolved oxygen concentration of aerobic reaction tank of 4mg / L, limestone, siderite and magnetite composite filler with a filling ratio of 1:2:1 (V / V / V), optimal reflux ratio of reflux liquid 1 of 100%, and optimal reflux ratio of reflux liquid 2 of 60% during the implementation of the present invention.

[0022] Figure 3 This is a diagram of sludge reduction under the conditions of anoxic biofilm reaction tank and aerobic biofilm reaction tank MBR curtain fabric filling rate of 60%, internal reflux ratio of 100%, hydraulic retention time of 16h, dissolved oxygen concentration of aerobic reaction tank of 4mg / L, limestone, siderite and magnetite composite filler with a filling ratio of 1:2:1 (V / V / V), optimal reflux ratio of reflux liquid 1 of 100%, and optimal reflux ratio of reflux liquid 2 of 60% during the implementation of the present invention.

[0023] Figure 4 This is a performance diagram of inlet and outlet water pollutant removal under the conditions of anoxic biofilm reaction tank and aerobic biofilm reaction tank MBR curtain fabric filling rate of 60%, internal reflux ratio of 100%, hydraulic retention time of 16h, dissolved oxygen concentration of aerobic reaction tank of 4mg / L, limestone, siderite and magnetite composite filler with a filling ratio of 1:2:1 (V / V / V), optimal reflux ratio of reflux liquid 1 of 100%, and optimal reflux ratio of reflux liquid 2 of 80% during the implementation of the present invention.

[0024] Figure 5 This is a diagram of sludge reduction under the conditions of anoxic biofilm reaction tank and aerobic biofilm reaction tank MBR curtain fabric filling rate of 60%, internal reflux ratio of 100%, hydraulic retention time of 16h, dissolved oxygen concentration of aerobic reaction tank of 4mg / L, limestone, siderite and magnetite composite filler with a filling ratio of 1:2:1 (V / V / V), optimal reflux ratio of reflux liquid 1 of 100%, and optimal reflux ratio of reflux liquid 2 of 80% during the implementation of the present invention.

[0025] Figure 6 This is a performance diagram for removing pollutants from inlet and outlet water under the following conditions: a filling rate of 60% for the MBR curtain fabric of the anoxic biofilm reaction tank and the aerobic biofilm reaction tank, an internal reflux ratio of 100%, a hydraulic retention time of 16 h, a dissolved oxygen concentration of 4 mg / L in the aerobic reaction tank, a composite filler of limestone, siderite and magnetite with a filling ratio of 1:2:1 (V / V / V), an optimal reflux ratio of 100% for the reflux liquid 1, and an optimal reflux ratio of 100% for the reflux liquid 2 during the implementation of the present invention.

[0026] Figure 7This figure shows the sludge reduction situation under the conditions of the MBR curtain fabric filling rate of the anoxic biofilm reaction tank and the aerobic biofilm reaction tank in the implementation process of the present invention being 60%, the internal reflux ratio being 100%, the hydraulic retention time being 16h, the dissolved oxygen concentration in the aerobic reaction tank being 4mg / L, the limestone, siderite and magnetite composite filler being used with a filling ratio of 1:2:1 (V / V / V), the optimal reflux ratio of reflux liquid 1 being 100%, and the optimal reflux ratio of reflux liquid 2 being 100%. DETAILED DESCRIPTION

[0027] Example 1: Improving the system's pollutant removal capacity and sludge reduction effect under the condition of a reflux ratio of 60% for reflux liquid 2

[0028] Step (1) A fixed biobed carrier composed of MBR curtain fabrics is assembled into an anoxic biofilm reactor and an aerobic biofilm reactor at a filling rate of 60%. An iron ore filler is formed by mixing limestone, siderite, and magnetite in a volume ratio of 1:2:1 (V / V / V) and then filled into the iron autotrophic denitrification biofilter;

[0029] Step (2) starts the dual biofilm treatment process based on step (1), exogenously inoculates activated sludge in the anoxic biofilm reaction tank and the aerobic biofilm reaction tank for biofilm formation; adds the activated sludge to the biofilm reaction tank, turns on the stirring device of the anoxic tank and the aeration device of the aerobic zone, and makes the inside of the biofilm reaction tank in a circulating flow state by a circulating water pump, and performs carrier biofilm formation, and the circulation time is 24 hours; adds the autotrophic denitrifying bacteria liquid to the iron autotrophic denitrification biofilter, controls the rising flow rate of the bacteria liquid in the filter to 0.0300 m / s to perform carrier biofilm formation, and the biofilter biofilm formation time is 24 hours;

[0030] Step (3) is based on step (2) and connects an aerobic biofilm reaction tank, an anoxic biofilm reaction tank and an iron autotrophic denitrification biofilter according to a process flow chart to continuously treat municipal sewage. The lifting pump is adjusted so that the hydraulic retention time of the biofilm reaction tank is 16 hours, the internal circulation water pump is adjusted so that the internal reflux ratio is 100%, and the aeration pump is adjusted so that the dissolved oxygen concentration of the aerobic reaction tank is 4 mg / L. The reflux water pump is adjusted to adjust the reflux ratio of reflux liquid 1 to 100% and the reflux water pump is adjusted to adjust the reflux ratio of reflux liquid 2 to 60%. The system is operated stably for 25 days under these conditions, and the COD, ammonia nitrogen, total nitrogen and phosphate concentrations of the inlet and outlet water of the system are detected every day. At the same time, the sludge condition before and after the operation of the system is measured.

[0031] Example 2: Improving the system's pollutant removal capacity and sludge reduction effect under the condition of a reflux ratio of 80% for reflux liquid 2

[0032] Step (1) A fixed biobed carrier composed of MBR curtain fabrics is assembled into an anoxic biofilm reactor and an aerobic biofilm reactor at a filling rate of 60%. An iron ore filler is formed by mixing limestone, siderite, and magnetite in a volume ratio of 1:2:1 (V / V / V) and then filled into the iron autotrophic denitrification biofilter;

[0033] Step (2) starts the dual biofilm treatment process based on step (1), exogenously inoculates activated sludge in the anoxic biofilm reaction tank and the aerobic biofilm reaction tank for biofilm formation; adds the activated sludge to the biofilm reaction tank, turns on the stirring device of the anoxic tank and the aeration device of the aerobic zone, and makes the inside of the biofilm reaction tank in a circulating flow state by a circulating water pump, and performs carrier biofilm formation, and the circulation time is 24 hours; adds the autotrophic denitrifying bacteria liquid to the iron autotrophic denitrification biofilter, controls the rising flow rate of the bacteria liquid in the filter to 0.0300 m / s to perform carrier biofilm formation, and the biofilter biofilm formation time is 24 hours;

[0034] Step (3) is based on step (2) and connects an aerobic biofilm reaction tank, an anoxic biofilm reaction tank and an iron autotrophic denitrification biofilter according to a process flow chart to continuously treat municipal sewage. The lifting pump is adjusted so that the hydraulic retention time of the biofilm reaction tank is 16 hours, the internal circulation water pump is adjusted so that the internal reflux ratio is 100%, and the aeration pump is adjusted so that the dissolved oxygen concentration of the aerobic reaction tank is 4 mg / L. The reflux water pump is adjusted to adjust the reflux ratio of reflux liquid 1 to 100% and the reflux water pump is adjusted to adjust the reflux ratio of reflux liquid 2 to 80%. The system is operated stably for 25 days under these conditions, and the COD, ammonia nitrogen, total nitrogen and phosphate concentrations of the inlet and outlet water of the system are detected every day. At the same time, the sludge condition before and after the operation of the system is measured.

[0035] Example 3: Improving the system's pollutant removal capacity and sludge reduction effect under the condition of a 100% reflux ratio of the iron ion reflux liquid

[0036] Step (1) A fixed biobed carrier composed of MBR curtain fabrics is assembled into an anoxic biofilm reactor and an aerobic biofilm reactor at a filling rate of 60%. An iron ore filler is formed by mixing limestone, siderite, and magnetite in a volume ratio of 1:2:1 (V / V / V) and then filled into the iron autotrophic denitrification biofilter;

[0037] Step (2) starts the dual biofilm treatment process based on step (1), exogenously inoculates activated sludge in the anoxic biofilm reaction tank and the aerobic biofilm reaction tank for biofilm formation; adds the activated sludge to the biofilm reaction tank, turns on the stirring device of the anoxic tank and the aeration device of the aerobic zone, and makes the inside of the biofilm reaction tank in a circulating flow state by a circulating water pump, and performs carrier biofilm formation, and the circulation time is 24 hours; adds the autotrophic denitrifying bacteria liquid to the iron autotrophic denitrification biofilter, controls the rising flow rate of the bacteria liquid in the filter to 0.0300 m / s to perform carrier biofilm formation, and the biofilter biofilm formation time is 24 hours;

[0038] Step (3) is based on step (2) and connects an aerobic biofilm reaction tank, an anoxic biofilm reaction tank and an iron autotrophic denitrification biofilter according to a process flow chart to continuously treat municipal sewage. The lifting pump is adjusted so that the hydraulic retention time of the biofilm reaction tank is 16 hours, the internal circulation water pump is adjusted so that the internal reflux ratio is 100%, and the aeration pump is adjusted so that the dissolved oxygen concentration of the aerobic reaction tank is 4 mg / L. The reflux water pump is adjusted to adjust the reflux ratio of reflux liquid 1 to 100% and the reflux water pump is adjusted to adjust the reflux ratio of reflux liquid 2 to 100%. The system is operated stably for 25 days respectively, and the COD, ammonia nitrogen, total nitrogen and phosphate concentrations of the inlet and outlet water of the system are detected every day, and the sludge condition before and after the operation of the system is measured.

[0039] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. This description is not restrictive. What is shown in the accompanying drawings is only one of the embodiments of the present invention and is not intended to limit the present invention.

Claims

1. A double biofilm wastewater treatment process for deep nitrogen and phosphorus removal coupled with sludge reduction, characterized in that: The effluent from the primary sedimentation tank enters the anoxic biofilm reaction tank through a lifting pump, and then flows into the aerobic biofilm reaction tank. The tail water treated in the front-end biofilm reaction tank flows into the iron autotrophic denitrification biofilter; the effluent from the aerobic biofilm reaction tank is returned to the anoxic biofilm reaction tank by reflux liquid 1, and part of the effluent from the iron autotrophic denitrification biofilter is returned to the anoxic biofilm reaction tank by reflux liquid 2; The carriers of the anoxic biofilm reaction tank and the aerobic biofilm reaction tank are fixed bio-bed fillers, which are filled at a filling ratio of 20%-80%; The iron autotrophic denitrification biofilter is constructed by filling the iron ore composite filler, which is a mixture of limestone, siderite and magnetite in a volume ratio of 1:2:1; The dissolved oxygen range of the aerobic biofilm reaction tank is between 1-5 mg / L; the hydraulic retention time of the aerobic biofilm reaction tank and the anoxic biofilm reaction tank is controlled between 12-24 h, the reflux ratio of the reflux liquid 1 is controlled between 60-120%, and the reflux ratio of the reflux liquid 2 is controlled between 60-100%.

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