Short-cut nitrification-denitrification + multi-stage aeration + fixed biofilm activated sludge combined process

Abstract

This invention relates to a combined process of short-cut nitrification-denitrification + multi-stage AO + fixed biofilm activated sludge. The treatment system includes a pretreatment unit, a pre-denitrification unit, a short-cut nitrification unit, a post-denitrification unit, an aeration unit, a separation unit, and a magnetic separation phosphorus removal unit connected in sequence. The short-cut nitrification unit is connected to the pre-denitrification unit via a first return pipe; the aeration unit is connected to the post-denitrification unit via a second return pipe; the separation unit is connected to the pre-denitrification unit via a sludge return pipe; and biological packing is installed in the short-cut nitrification unit and the aeration unit. The treatment system of this invention utilizes a multi-stage AO framework of "pre-denitrification + short-cut nitrification + post-denitrification + deep aeration," core-coupled with IFAS and short-cut nitrification-denitrification technology, and supplemented by magnetic separation phosphorus removal at the end, to achieve simultaneous and efficient nitrogen and phosphorus removal from high-ammonia nitrogen wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a biological nitrogen and phosphorus removal system and process for wastewater with high ammonia nitrogen, high organic matter, and low carbon-to-nitrogen ratio, which is particularly suitable for the treatment of difficult-to-treat industrial organic wastewater such as train sewage, aquaculture wastewater, and landfill leachate. Background Technology

[0002] Train wastewater is a typical type of high-concentration, high-ammonia-nitrogen, low-carbon-nitrogen-ratio organic wastewater. It is characterized by extremely high concentrations of chemical oxygen demand (COD), suspended solids (SS), ammonia nitrogen (NH3-N), and total phosphorus (TP), with significant fluctuations in water quality and quantity. Traditional activated sludge processes for treating this type of wastewater face several bottlenecks: nitrification requires high oxygen levels, denitrification requires large amounts of external carbon sources, resulting in high energy consumption; sludge production is high, leading to expensive treatment costs; and the system has weak resistance to shock loads, making it difficult to consistently meet increasingly stringent emission standards for nitrogen and phosphorus levels in the effluent.

[0003] CN108928992A discloses a biological nitrogen removal system and method that combines nitrification and denitrification. The system includes: a pretreatment device, a nitrification reactor, an intermediate water tank, a denitrification reactor, an external carbon source addition device, a sedimentation and filtration device, and an aeration device. The pretreatment device is sequentially connected to the nitrification reactor, the intermediate water tank, the denitrification reactor, and the sedimentation and filtration device; the external carbon source addition device is connected to the front end of the denitrification reactor; an aeration device is installed inside the nitrification reactor; a carrier for embedded nitrifying bacteria is added to the nitrification reactor; and a carrier for embedded denitrifying bacteria is added to the denitrification reactor.

[0004] CN111233280A discloses a denitrification biological nitrogen removal system, including a coagulant mixing tank, a carbon source mixing tank, an activated sludge mixing tank, and a denitrification deep bed filter. The coagulant mixing tank and the carbon source mixing tank are connected by a first pipeline, the carbon source mixing tank and the denitrification deep bed filter are connected by a second pipeline, and the activated sludge mixing tank and the denitrification deep bed filter are connected by a third pipeline.

[0005] Short-cut nitrification-denitrification technology can control ammonia nitrogen oxidation to nitrite (NO2). -The process involves a stage where nitrite is directly denitrified, theoretically saving approximately 25% of aeration energy and 40% of organic carbon source. However, this process operates under demanding conditions (such as extremely high requirements for dissolved oxygen (DO), temperature, pH, and sludge settling time), making it difficult to maintain long-term stability in practical engineering. Multi-stage AO (anoxic / aerobic) processes can achieve graded utilization of carbon sources and in-depth nitrogen removal, while IFAS (fixed biofilm-activated sludge) processes, by combining suspended activated sludge and attached biofilm in the same reactor, can significantly increase biomass, enhance system stability, and improve treatment efficiency. How to organically couple these advanced processes and solve the high phosphorus removal problem is key to treating sewage effluent. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a combined process of short-cut nitrification-denitrification + multi-stage AO + fixed biofilm activated sludge. The treatment system of this invention utilizes a multi-stage AO framework of "pre-denitrification + short-cut nitrification + post-denitrification + deep aeration," core-coupled with IFAS and short-cut nitrification-denitrification technology, and supplemented by magnetic separation for phosphorus removal at the end, achieving simultaneous and efficient nitrogen and phosphorus removal from high-ammonia nitrogen wastewater.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a wastewater treatment system for short-cut nitrification-denitrification coupled with multi-stage AO-IFAS, wherein the wastewater treatment system comprises a pretreatment unit, a pre-denitrification unit, a short-cut nitrification unit, a post-denitrification unit, an aeration unit, a separation unit, and a magnetic separation phosphorus removal unit connected in sequence.

[0009] The short-cut nitrification unit is connected to the pre-denitrification unit via a first return pipe; the aeration unit is connected to the post-denitrification unit via a second return pipe; and the separation unit is connected to the pre-denitrification unit via a sludge return pipe.

[0010] The short-range nitrification unit and aeration unit are equipped with biological packing material.

[0011] The treatment system of this invention utilizes a multi-stage AO framework of "pre-denitrification + short-cut nitrification + post-denitrification + deep aeration," core-coupled with IFAS and short-cut nitrification-denitrification technology, and supplemented by magnetic separation for phosphorus removal at the end, achieving simultaneous and efficient nitrogen and phosphorus removal from high-ammonia nitrogen wastewater. The integrated process of this invention has a high degree of modularity, making it particularly suitable for applications in space-constrained environments such as railway stations and mobile treatment vehicles. The treatment system of this invention has the following advantages:

[0012] 1) High-efficiency nitrogen removal using short-cut nitrification-denitrification: Through micro-oxygen control, NH4+ is removed. + -N oxidation stops at NO2.- -N, with NO2 - -N acts as an electron acceptor, omitting NO2. - -N to NO3 - The oxidation process of -N saves the external carbon source required for the denitrification process; the acidity produced by nitrification can be partially neutralized by the alkalinity produced by denitrification; the treatment process of this invention can shorten the hydraulic retention time, reduce the reactor volume and floor space; and at the same time reduce the gas supply by about 25%, thus reducing energy consumption.

[0013] 2) Enhanced biofilm through multi-stage AO coupled IFAS: A certain amount of packing material is added to the aeration tank to form a biofilm. The packing material usually has a high specific surface area and good adhesion. The microorganisms on the packing material can use the organic matter in the wastewater for growth and metabolism, thereby converting the organic matter in the wastewater into harmless substances such as inorganic salts and carbon dioxide.

[0014] 3) Magnetic flocculation for high-efficiency phosphorus removal and magnetic powder recovery: By adding magnetic powder with an appropriate specific gravity, it is combined with pollutants to enhance the coagulation and flocculation effect, resulting in denser and more compact flocs, thereby achieving high-speed sedimentation and high-efficiency removal of total phosphorus (TP) in the effluent. The matching drum collector enables magnetic powder recovery and reduces operating costs.

[0015] As a preferred technical solution of the present invention, the pretreatment unit includes a pre-separation device and a primary sedimentation adjustment device.

[0016] The pre-separation device includes any one of a bar screen, a filter, or a sieve; the primary sedimentation adjustment device includes a primary sedimentation adjustment tank.

[0017] As a preferred embodiment of the present invention, the magnetic separation phosphorus removal unit includes a coagulation reactor, a magnetic separation device, and a magnetic seed recovery device connected in sequence.

[0018] The coagulation reactor is equipped with magnetic seed dosing equipment and coagulant dosing equipment.

[0019] As a preferred embodiment of the present invention, the short-range nitration unit is equipped with a carbon source addition device.

[0020] Preferably, the separation unit includes a gravity sedimentation tank or a membrane separation assembly.

[0021] Preferably, the biological packing material includes suspended packing material or fixed packing material.

[0022] Secondly, the present invention provides a method for treating wastewater from sewage collection using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS system, wherein the wastewater treatment method uses the wastewater treatment system described in the first aspect.

[0023] As a preferred technical solution of the present invention, the method for treating sewage collection wastewater includes the following steps:

[0024] (1) After passing through the pretreatment unit, the wastewater from the collection of feces enters the pre-denitrification unit and is mixed with the first reflux liquid from the short-cut nitrification unit and the sludge reflux liquid from the separation unit for denitrification treatment;

[0025] (2) The effluent from the pre-denitrification unit enters the short-cut nitrification unit for nitrification treatment;

[0026] (3) The effluent from the short-cut nitrification unit enters the post-denitrification unit and is mixed with the second reflux liquid from the aeration unit for deep denitrification treatment;

[0027] (4) The effluent from the post-denitrification unit enters the aeration unit for aeration treatment;

[0028] (5) The effluent from the aeration unit enters the separation unit for mud-water separation to obtain supernatant and sludge; part of the sludge enters the pre-denitrification unit through the sludge return pipe.

[0029] (6) The supernatant of the separation unit enters the magnetic separation phosphorus removal unit for phosphorus removal treatment.

[0030] The treatment method of this invention first removes large particulate impurities through a pretreatment unit, then enters a pre-denitrification tank where it is mixed with the first internal return liquid from the short-cut nitrification tank and the sludge return liquid from the sludge-water separation unit. Here, the organic carbon source in the raw water is used to neutralize the nitrite nitrogen (NO2) in the return liquid. - -N) and some nitrate nitrogen (NO3) - -N) is denitrified into nitrogen gas, achieving pre-nitrogen removal and saving carbon source;

[0031] Subsequently, in the short-cut nitrification unit, by precisely controlling the dissolved oxygen concentration, pH, temperature, and sludge age of the nitrification treatment, ammonia-oxidizing bacteria (AOB) are selectively enriched while the activity of nitrite-oxidizing bacteria (NOB) is inhibited, thus reducing most of the ammonia nitrogen (NH4+) to nitrogen. + -N is efficiently and stably oxidized to nitrite (NO2). - This achieves short-cut nitrification; the biofilm growing on the biological packing material in the tank enhances the retention of nitrifying bacteria and improves system stability.

[0032] The mixed liquor from short-cut nitrification enters the post-denitrification tank: a small amount of supplementary carbon source is added here to remove the nitrite (NO2) produced by short-cut nitrification. - ) and residual nitrates (NO3) in the reflux liquid of the deep aeration unit. -The effluent is completely reduced to nitrogen gas, completing deep denitrification. The post-denitrification effluent then enters the aeration unit: through efficient aeration, residual ammonia nitrogen and organic matter are further oxidized, stabilizing water quality. This unit also contains biological packing material to form an aerobic biofilm, enhancing the nitrification effect.

[0033] The effluent from the aeration unit enters the separation unit for sludge-water separation. The supernatant enters the subsequent phosphorus removal unit, while most of the sludge is returned to the pre-denitrification tank to maintain the system's sludge concentration. The supernatant from the separation unit enters the magnetic separation phosphorus removal unit. By adding magnetic seeds and coagulants, phosphates and coagulants form flocs with the magnetic seeds as the core. Subsequently, a high-gradient magnetic separator rapidly separates and adsorbs the phosphorus-containing flocs, ensuring that the total phosphorus (TP) in the effluent meets discharge standards. The separated magnetic seeds are regenerated and reused after being recycled.

[0034] The treatment method of this invention significantly reduces the aeration energy consumption in the nitrification stage and the carbon source addition in the denitrification stage through a "short-cut nitrification-denitrification" pathway, resulting in low operating costs and achieving highly efficient and energy-saving nitrogen removal. The "multi-stage AO+IFAS" structure creates a rich anoxic / aerobic environment and a diverse microbial community. The IFAS process significantly increases the total biomass and the number of nitrifying / denitrifying bacteria in the system, especially enhancing the stability of short-cut nitrification and the system's resistance to shock loads, ensuring excellent effluent quality under high ammonia nitrogen loads, resulting in high and stable treatment efficiency. The terminal uses magnetic separation phosphorus removal technology, which has the advantages of fast settling speed, small footprint, high phosphorus removal efficiency (up to 95% or more), and stable operation, effectively addressing the high phosphorus problem in sewage wastewater and ensuring stable effluent TP compliance. The raw water carbon source is preferentially used for pre-denitrification, with only a small amount of carbon source supplementation required for post-denitrification, achieving efficient cascade utilization of carbon sources and conforming to the low-carbon treatment concept.

[0035] As a preferred technical solution of the present invention, the control conditions for the nitrification treatment in step (2) include dissolved oxygen concentration, pH, temperature and sludge age.

[0036] Preferably, the dissolved oxygen concentration is 0.3-1.0 mg / L, such as 0.3 mg / L, 0.4 mg / L, 0.5 mg / L, 0.6 mg / L, 0.7 mg / L, 0.8 mg / L, 0.9 mg / L, 1.0 mg / L, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] Preferably, the pH is 7.5-8.5, such as 7.5, 7.7, 7.9, 8.1, 8.3, 8.5, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0038] Preferably, the temperature is 25-35℃, such as 25℃, 27℃, 29℃, 31℃, 33℃, 35℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the sludge age is longer than that of nitrite-oxidizing bacteria but shorter than that of ammonia-oxidizing bacteria.

[0040] As a preferred technical solution of the present invention, a carbon source is added to the post-denitrification unit described in step (3) to perform deep denitrification treatment.

[0041] Preferably, the carbon source comprises any one or a combination of at least two of sodium acetate, methanol, or glucose, with typical but non-limiting examples of such combinations being sodium acetate and methanol, sodium acetate and glucose, and methanol and glucose.

[0042] As a preferred technical solution of the present invention, the reflux ratio of the first reflux liquid in step (1) is 100-300%, such as 100%, 150%, 200%, 250%, 300%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the reflux ratio of the sludge reflux liquid in step (1) is 50-100%, such as 50%, 60%, 70%, 80%, 90%, 100%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] Preferably, the reflux ratio of the second reflux liquid in step (3) is 50-150%, such as 50%, 60%, 70%, 80%, 90%, 100%, 120%, 140%, 150%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] As a preferred technical solution of the present invention, magnetic seeds and coagulants are added to the magnetic separation and phosphorus removal unit in step (6) to carry out phosphorus removal treatment.

[0046] Preferably, the magnetic seed comprises magnetite (Fe3O4) magnetic particles.

[0047] Preferably, the coagulant comprises polyaluminum chloride or aluminum sulfate.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) Short-cut nitrification-denitrification high-efficiency nitrogen removal: through micro-oxygen control, NH4 + -N oxidation stops at NO2. - -N, with NO2 --N acts as an electron acceptor, omitting NO2. - -N to NO3 - The oxidation process of -N saves the external carbon source required for the denitrification process; the acidity produced by nitrification can be partially neutralized by the alkalinity produced by denitrification; the treatment process of this invention can shorten the hydraulic retention time, reduce the reactor volume and floor space; and at the same time reduce the gas supply by about 25%, thus reducing energy consumption.

[0050] (2) Multi-stage AO coupled IFAS biofilm enhancement: A certain amount of packing material is added to the aeration tank to form a biofilm. The packing material usually has a high specific surface area and good adhesion. The microorganisms on the packing material can use the organic matter in the wastewater for growth and metabolism, thereby converting the organic matter in the wastewater into harmless substances such as inorganic salts and carbon dioxide;

[0051] (3) Magnetic flocculation for efficient phosphorus removal and magnetic powder recovery: By adding magnetic powder with appropriate specific gravity, it is combined with pollutants to enhance the coagulation and flocculation effect, making the generated flocs denser and stronger, thereby achieving high-speed sedimentation and efficient removal of TP. The matching drum collector is used to realize magnetic powder recovery and reduce operating costs.

[0052] (4) High-efficiency and energy-saving denitrification: Through the “short-cut nitrification-denitrification” pathway, the aeration energy consumption in the nitrification stage and the carbon source addition in the denitrification stage are significantly reduced, resulting in low operating costs;

[0053] (5) High and stable treatment efficiency: The "multi-stage AO+IFAS" structure creates a rich anoxic / aerobic environment and a diverse microbial community. The IFAS process significantly increases the total biomass of the system and the number of nitrifying / denitrifying bacteria, especially enhancing the stability of short-cut nitrification and the system's resistance to shock loads, ensuring excellent effluent quality under high ammonia nitrogen loads;

[0054] (6) Deep phosphorus removal guarantee: The terminal adopts magnetic separation phosphorus removal technology, which has the advantages of fast settling speed, small footprint, high phosphorus removal efficiency (up to 95% or more) and stable operation. It can effectively deal with the high phosphorus problem of sewage and ensure that the total phosphorus TP in the effluent meets the standard.

[0055] (7) tiered utilization of carbon source: the raw water carbon source is preferentially used for pre-denitrification, and only a small amount of carbon source needs to be added for post-denitrification, which realizes the efficient tiered utilization of carbon source and is in line with the concept of low-carbon treatment.

[0056] (8) Compact process: The integrated process of the present invention has a high degree of modularity, making it particularly suitable for applications in places with limited space, such as railway stations and mobile processing vehicles. Attached Figure Description

[0057] Figure 1This is a schematic diagram of a short-cut nitrification-denitrification coupled multi-stage AO-IFAS wastewater treatment system provided by the present invention. Detailed Implementation

[0058] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0059] Example 1

[0060] This embodiment provides a wastewater treatment system for short-cut nitrification-denitrification coupled with multi-stage AO-IFAS. The wastewater treatment system includes a pretreatment unit, a pre-denitrification unit, a short-cut nitrification unit, a post-denitrification unit, an aeration unit, a separation unit, and a magnetic separation phosphorus removal unit connected in sequence.

[0061] The short-cut nitrification unit is connected to the pre-denitrification unit via a first return pipe; the aeration unit is connected to the post-denitrification unit via a second return pipe; and the separation unit is connected to the pre-denitrification unit via a sludge return pipe.

[0062] The short-range nitrification unit and the aeration unit are equipped with biological packing material; the biological packing material is a suspended packing material.

[0063] The pretreatment unit includes a pre-separation device and a primary sedimentation conditioning device; the pre-separation device is a bar screen; the primary sedimentation conditioning device is a primary sedimentation conditioning tank; the magnetic separation phosphorus removal unit includes a coagulation reactor, a magnetic separation device, and a magnetic seed recovery device connected in sequence; the coagulation reactor is equipped with a magnetic seed addition device and a coagulant addition device; the short-cut nitrification unit is equipped with a carbon source addition device; the separation unit is a gravity sedimentation tank.

[0064] Example 2

[0065] This embodiment provides a wastewater treatment system for short-cut nitrification-denitrification coupled with multi-stage AO-IFAS. The wastewater treatment system includes a pretreatment unit, a pre-denitrification unit, a short-cut nitrification unit, a post-denitrification unit, an aeration unit, a separation unit, and a magnetic separation phosphorus removal unit connected in sequence.

[0066] The short-cut nitrification unit is connected to the pre-denitrification unit via a first return pipe; the aeration unit is connected to the post-denitrification unit via a second return pipe; and the separation unit is connected to the pre-denitrification unit via a sludge return pipe.

[0067] The short-range nitrification unit and the aeration unit are equipped with biological packing material; the biological packing material is a fixed packing material.

[0068] The pretreatment unit includes a pre-separation device and a primary sedimentation conditioning device; the pre-separation device is a filter; the primary sedimentation conditioning device is a primary sedimentation conditioning tank; the magnetic separation phosphorus removal unit includes a coagulation reactor, a magnetic separation device, and a magnetic seed recovery device connected in sequence; the coagulation reactor is equipped with a magnetic seed addition device and a coagulant addition device; the short-cut nitrification unit is equipped with a carbon source addition device; the separation unit is a membrane separation component.

[0069] Comparative Example 1

[0070] This comparative example provides a short-cut nitrification-denitrification coupled multi-stage AO-IFAS wastewater treatment system. The difference from Example 1 is that the aeration unit is not connected to the post-denitrification unit through the second return pipe, but all other aspects are the same as Example 1.

[0071] Comparative Example 2

[0072] This comparative example provides a wastewater treatment system for sewage collection that uses short-cut nitrification-denitrification coupled with multi-stage AO-IFAS. The difference from Example 1 is that the post-denitrification unit is omitted. That is, the sewage collection wastewater treatment system includes a pretreatment unit, a pre-denitrification unit, a short-cut nitrification unit, an aeration unit, a separation unit, and a magnetic separation phosphorus removal unit connected in sequence. Everything else is the same as in Example 1.

[0073] Comparative Example 3

[0074] This comparative example provides a wastewater treatment system for sewage collection with short-cut nitrification-denitrification coupled with multi-stage AO-IFAS. The difference from Example 1 is that the short-cut nitrification unit and the aeration unit do not have biological packing material. All other aspects are the same as in Example 1.

[0075] Application Example 1

[0076] This application example provides a method for treating sewage collection wastewater using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS, wherein the sewage collection wastewater treatment method uses the sewage collection wastewater treatment system described in Example 1;

[0077] The chemical oxygen demand (COD) content in the wastewater is 1000-5000 ppm, the suspended solids content is 500-2000 ppm, the ammonia nitrogen (NH3-N) content is 1000-2000 ppm, and the total phosphorus (TP) content is 50-200 ppm.

[0078] The method for treating fecal wastewater includes the following steps:

[0079] (1) After passing through the pretreatment unit, the wastewater from the sewage collection enters the pre-denitrification unit, where it is mixed with the first reflux liquid from the short-cut nitrification unit and the sludge reflux liquid from the separation unit for denitrification treatment; the reflux ratio of the first reflux liquid is 100%; the reflux ratio of the sludge reflux liquid is 50%.

[0080] (2) The effluent from the pre-denitrification unit enters the short-cut nitrification unit for nitrification treatment; the nitrification treatment controls the dissolved oxygen concentration to be 0.3 mg / L, the pH to be 7.5, the temperature to be 25°C, and the sludge age to be longer than that of nitrite oxidizing bacteria but shorter than that of ammonia oxidizing bacteria.

[0081] (3) The effluent from the short-cut nitrification unit enters the post-denitrification unit, is mixed with the second reflux liquid from the aeration unit, and sodium acetate is added for deep denitrification treatment; the reflux ratio of the second reflux liquid is 50%;

[0082] (4) The effluent from the post-denitrification unit enters the aeration unit for aeration treatment;

[0083] (5) The effluent from the aeration unit enters the separation unit for mud-water separation to obtain supernatant and sludge; part of the sludge enters the pre-denitrification unit through the sludge return pipe.

[0084] (6) The supernatant of the separation unit enters the magnetic separation phosphorus removal unit, and magnetic particles of iron oxide and polyaluminum chloride are added for phosphorus removal treatment.

[0085] Application Example 2

[0086] This application example provides a method for treating sewage collection wastewater using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS, wherein the sewage collection wastewater treatment method uses the sewage collection wastewater treatment system described in Example 1;

[0087] The method for treating fecal wastewater includes the following steps:

[0088] (1) After passing through the pretreatment unit, the wastewater from the sewage collection enters the pre-denitrification unit, where it is mixed with the first reflux liquid from the short-cut nitrification unit and the sludge reflux liquid from the separation unit for denitrification treatment; the reflux ratio of the first reflux liquid is 200%; the reflux ratio of the sludge reflux liquid is 80%.

[0089] (2) The effluent from the pre-denitrification unit enters the short-cut nitrification unit for nitrification treatment; the nitrification treatment controls the dissolved oxygen concentration to be 0.5 mg / L, the pH to be 8, the temperature to be 30°C, and the sludge age to be longer than that of nitrite oxidizing bacteria but shorter than that of ammonia oxidizing bacteria.

[0090] (3) The effluent from the short-cut nitrification unit enters the post-denitrification unit, is mixed with the second reflux liquid from the aeration unit, and methanol is added for deep denitrification treatment; the reflux ratio of the second reflux liquid is 100%;

[0091] (4) The effluent from the post-denitrification unit enters the aeration unit for aeration treatment;

[0092] (5) The effluent from the aeration unit enters the separation unit for mud-water separation to obtain supernatant and sludge; part of the sludge enters the pre-denitrification unit through the sludge return pipe.

[0093] (6) The supernatant of the separation unit enters the magnetic separation phosphorus removal unit, and magnetic particles of iron oxide and aluminum sulfate are added for phosphorus removal treatment.

[0094] Application Example 3

[0095] This application example provides a method for treating sewage collection wastewater using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS, wherein the sewage collection wastewater treatment method uses the sewage collection wastewater treatment system described in Example 1;

[0096] The method for treating fecal wastewater includes the following steps:

[0097] (1) After passing through the pretreatment unit, the wastewater from the sewage collection enters the pre-denitrification unit, where it is mixed with the first reflux liquid from the short-cut nitrification unit and the sludge reflux liquid from the separation unit for denitrification treatment; the reflux ratio of the first reflux liquid is 300%; the reflux ratio of the sludge reflux liquid is 100%.

[0098] (2) The effluent from the pre-denitrification unit enters the short-cut nitrification unit for nitrification treatment; the nitrification treatment controls the dissolved oxygen concentration to be 1 mg / L, the pH to be 8.5, the temperature to be 35°C, and the sludge age to be longer than that of nitrite oxidizing bacteria but shorter than that of ammonia oxidizing bacteria.

[0099] (3) The effluent from the short-cut nitrification unit enters the post-denitrification unit, is mixed with the second reflux liquid from the aeration unit, and glucose is added for deep denitrification treatment; the reflux ratio of the second reflux liquid is 150%;

[0100] (4) The effluent from the post-denitrification unit enters the aeration unit for aeration treatment;

[0101] (5) The effluent from the aeration unit enters the separation unit for mud-water separation to obtain supernatant and sludge; part of the sludge enters the pre-denitrification unit through the sludge return pipe.

[0102] (6) The supernatant of the separation unit enters the magnetic separation phosphorus removal unit, and magnetic particles of iron oxide and aluminum sulfate are added for phosphorus removal treatment.

[0103] Application Example 4

[0104] This application example provides a method for treating wastewater from sewage collection using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS. The wastewater treatment method uses the sewage collection wastewater treatment system described in Example 2, and all other aspects are the same as in Application Example 1.

[0105] Comparative Application Example 1

[0106] This comparative application example provides a method for treating wastewater from sewage collection using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS. The wastewater treatment method uses the wastewater treatment system described in Comparative Example 1, and all other aspects are the same as in Application Example 1.

[0107] Comparative Application Example 2

[0108] This comparative application example provides a method for treating wastewater from sewage collection using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS. The wastewater treatment method uses the sewage collection wastewater treatment system described in Comparative Example 2, and all other aspects are the same as in Application Example 1.

[0109] Comparative Application Example 3

[0110] This comparative application example provides a method for treating wastewater from sewage collection using a short-cut nitrification-denitrification coupled multi-stage AO-IFAS. The wastewater treatment method uses the sewage treatment system described in Comparative Example 3, and all other aspects are the same as in Application Example 1.

[0111] Performance testing

[0112] The COD, ammonia nitrogen, total nitrogen, and total phosphorus contents of the treated wastewater in Application Examples 1-4 and Comparative Application Examples 1-3 were tested. The test results are shown in Table 1.

[0113]

[0114] The test results show that:

[0115] (1) As can be seen from Application Examples 1 to 4, the present invention uses a multi-stage AO framework of "pre-denitrification + short-cut nitrification + post-denitrification + deep aeration", with IFAS and short-cut nitrification-denitrification technology coupled at the core, and magnetic separation for phosphorus removal at the end, which can reduce the total phosphorus content and ammonia nitrogen content of train wastewater.

[0116] (2) By comparing Application Example 1 with Comparative Application Examples 1-3, it can be seen that in Comparative Application Example 1, the aeration unit is not connected to the post-denitrification unit through the second return pipe, which means that the nitrates remaining in the aeration unit cannot be completely reduced to nitrogen, resulting in a high nitrite nitrogen content in the final effluent; in Comparative Application Example 2, the post-denitrification unit is omitted, which means that the nitrites produced by short-cut nitrification cannot be removed, thus greatly increasing the nitrite nitrogen content in the effluent; in Comparative Application Example 3, the short-cut nitrification unit and the aeration unit are not equipped with biological packing, which means that the organic matter in the wastewater cannot be fully removed, which reduces the stability of short-cut nitrification and the system's resistance to shock loads, resulting in a high nitrite nitrogen content in the effluent.

[0117] In summary, this invention provides a combined process of short-cut nitrification-denitrification + multi-stage AO + fixed biofilm activated sludge. The treatment system of this invention utilizes a multi-stage AO framework of "pre-denitrification + short-cut nitrification + post-denitrification + deep aeration," core-coupled with IFAS and short-cut nitrification-denitrification technology, and supplemented by magnetic separation for phosphorus removal at the end, achieving simultaneous and efficient nitrogen and phosphorus removal from high-ammonia nitrogen wastewater. The integrated process of this invention has a high degree of modularity, making it particularly suitable for applications in space-constrained environments such as railway stations and mobile treatment vehicles.

[0118] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A short-cut nitrification-denitrification coupled multi-stage AO-IFAS wastewater treatment system, characterized in that, The wastewater treatment system includes a pretreatment unit, a pre-denitrification unit, a short-cut nitrification unit, a post-denitrification unit, an aeration unit, a separation unit, and a magnetic separation phosphorus removal unit connected in sequence. The short-cut nitrification unit is connected to the pre-denitrification unit via a first return pipe; the aeration unit is connected to the post-denitrification unit via a second return pipe; and the separation unit is connected to the pre-denitrification unit via a sludge return pipe. The short-range nitrification unit and aeration unit are equipped with biological packing material.

2. The wastewater treatment system according to claim 1, characterized in that, The pretreatment unit includes a pre-separation device and a primary sedimentation adjustment device; The pre-separation device includes any one of a bar screen, a filter, or a sieve; the primary sedimentation adjustment device includes a primary sedimentation adjustment tank.

3. The wastewater treatment system according to claim 1 or 2, characterized in that, The magnetic separation phosphorus removal unit includes a coagulation reactor, a magnetic separation device, and a magnetic seed recovery device connected in sequence. The coagulation reactor is equipped with magnetic seed dosing equipment and coagulant dosing equipment.

4. The wastewater treatment system according to any one of claims 1-3, characterized in that, The short-range nitration unit is equipped with a carbon source addition device; Preferably, the separation unit includes a gravity sedimentation tank or a membrane separation module; Preferably, the biological packing material includes suspended packing material or fixed packing material.

5. A method for treating sewage wastewater using short-cut nitrification-denitrification coupled with multi-stage AO-IFAS, characterized in that, The method for treating wastewater from fecal collection is carried out using the wastewater treatment system described in any one of claims 1-4.

6. The method for treating fecal wastewater according to claim 5, characterized in that, The method for treating fecal wastewater includes the following steps: (1) After passing through the pretreatment unit, the wastewater from the collection of feces enters the pre-denitrification unit and is mixed with the first reflux liquid from the short-cut nitrification unit and the sludge reflux liquid from the separation unit for denitrification treatment; (2) The effluent from the pre-denitrification unit enters the short-cut nitrification unit for nitrification treatment; (3) The effluent from the short-cut nitrification unit enters the post-denitrification unit and is mixed with the second reflux liquid from the aeration unit for deep denitrification treatment; (4) The effluent from the post-denitrification unit enters the aeration unit for aeration treatment; (5) The effluent from the aeration unit enters the separation unit for mud-water separation to obtain supernatant and sludge; part of the sludge enters the pre-denitrification unit through the sludge return pipe. (6) The supernatant of the separation unit enters the magnetic separation phosphorus removal unit for phosphorus removal treatment.

7. The method for treating fecal wastewater according to claim 5 or 6, characterized in that, The control conditions for nitrification treatment in step (2) include dissolved oxygen concentration, pH, temperature and sludge age; Preferably, the dissolved oxygen concentration is 0.3-1.0 mg / L; the pH is 7.5-8.5; the temperature is 25-35℃; and the sludge age is longer than that of nitrite-oxidizing bacteria but shorter than that of ammonia-oxidizing bacteria.

8. The method for treating fecal wastewater according to any one of claims 5-7, characterized in that, Add a carbon source to the post-denitrification unit described in step (3) to perform deep denitrification treatment; Preferably, the carbon source includes any one or a combination of at least two of sodium acetate, methanol, or glucose.

9. The method for treating fecal wastewater according to any one of claims 5-8, characterized in that, Step (1) The reflux ratio of the first reflux liquid is 100-300%; Preferably, the reflux ratio of the sludge return liquid in step (1) is 50-100%; Preferably, in step (3), the reflux ratio of the second reflux liquid is 50-150%.

10. The method for treating fecal wastewater according to any one of claims 5-9, characterized in that, Magnetic seeds and coagulants are added to the magnetic separation and phosphorus removal unit described in step (6) to carry out phosphorus removal treatment; Preferably, the magnetic seeds comprise magnetic particles of iron oxide (Fe3O4); Preferably, the coagulant comprises polyaluminum chloride or aluminum sulfate.

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