Device and method for treating municipal low carbon-nitrogen ratio sewage by SLOAO process

Abstract

The application belongs to the technical field of sewage biological treatment, and discloses a device and method for treating urban low-carbon-nitrogen-ratio sewage by using SLOAO process, wherein a sewage inlet is arranged at the bottom of the water inlet side of the first low-oxygen-oxygen tank, the sewage inlet is connected with the water inlet pipe through a pipeline, a first water outlet is arranged at the water outlet side of the first low-oxygen-oxygen tank, the first water outlet is communicated with an anoxic tank, a second water outlet is further arranged at the water outlet side of the anoxic tank, the second water outlet is communicated with a second oxygen tank, the water outlet side of the second oxygen tank is connected with a sedimentation tank, a sewage inlet of the anoxic tank is further arranged at the bottom of the anoxic tank, the sewage inlet of the anoxic tank is also connected with the water inlet pipe through a pipeline, stirring devices are arranged in the first low-oxygen-oxygen tank and the anoxic tank, an aeration pipe is arranged at the bottom of the first low-oxygen-oxygen tank and the second oxygen tank, the aeration pipe is connected with a blower, and the stirring devices and the blower are electrically connected with a control assembly respectively.

Description

Technical Field

[0001] This application belongs to the field of wastewater biological treatment technology, specifically relating to an apparatus and method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process. Background Technology

[0002] With the rapid development of my country's economy and the acceleration of urbanization, the discharge of domestic and industrial wastewater has been increasing year by year, and water shortage and pollution problems have become increasingly serious. my country has also imposed stricter requirements on the control of pollutants such as nitrogen and phosphorus. Therefore, efficient wastewater treatment has become an environmental problem that the industry urgently needs to solve. Due to urban development, changes in residents' water use habits, and problems with municipal pipe networks, wastewater treatment plant influent generally exhibits a low C / N ratio. Theoretical research suggests that in practical applications, a C / N ratio of above 4.00 is generally required to meet the requirements of microbial denitrification. When treating wastewater with a low C / N ratio, ensuring efficient removal of total nitrogen is challenging, but the removal of total phosphorus (TP) can be achieved through advanced treatment with chemical dosing.

[0003] Currently, wastewater treatment plants widely employ the activated sludge process, relying on microorganisms to remove pollutants such as organic matter, nitrogen, and phosphorus. However, traditional nitrification / denitrification processes, such as the AAO process (a commonly used secondary wastewater treatment process), suffer from high aeration energy consumption, low utilization rate of raw wastewater carbon sources, large external carbon source dosage, and high energy consumption of return pumps when treating low C / N wastewater, leading to high wastewater treatment costs. Therefore, reducing energy and chemical consumption in wastewater treatment while ensuring efficient nitrogen removal, and achieving carbon reduction and efficiency improvement, is a research hotspot in the wastewater treatment industry.

[0004] In summary, the existing technologies have the following problems: (1) Traditional biological treatment processes do not make full use of the carbon source in the original sewage and cannot meet the carbon source requirements of different bacterial groups; (2) Sewage treatment plants need to add additional carbon sources when treating low C / N sewage, which increases the consumption of reagents; (3) The setting of pre-denitrification makes the denitrification efficiency dependent on the size of the internal reflux ratio, which increases the energy consumption of the reflux pump and increases the cost of sewage treatment.

[0005] Therefore, developing a novel wastewater treatment process with high efficiency in nitrogen removal is an important aspect of current research on low C / N wastewater treatment technologies. Summary of the Invention

[0006] The purpose of this application is to address the problems of the prior art by providing an apparatus and method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process.

[0007] To solve the technical problem, the technical solution of this application is: a device for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process, comprising a first hypoxic-aerobic tank, an anoxic tank, a second aerobic tank, and a sedimentation tank connected in sequence, as well as a control component. A wastewater inlet is provided at the bottom of the inlet side of the first hypoxic-aerobic tank, connected to an inlet pipe via a pipeline. A first outlet is provided on the outlet side of the first hypoxic-aerobic tank, communicating with the anoxic tank. A second outlet is also provided on the outlet side of the anoxic tank. The first outlet is connected to the second aerobic tank, and the outlet side of the second aerobic tank is connected to the sedimentation tank. The plane where the first outlet and the second outlet are located is higher than the plane where the sewage inlet is located. The bottom of the anoxic tank is also provided with an anoxic tank sewage inlet, which is also connected to the inlet pipe through a pipe. Both the first low-oxygen aerobic tank and the anoxic tank are equipped with a stirring device. Both the first low-oxygen aerobic tank and the second aerobic tank are equipped with aeration pipes at the bottom. The aeration pipes are connected to a blower. The stirring device and the blower are electrically connected to the control component.

[0008] The dissolved oxygen concentration in the first low-oxygen aerobic tank is 0.5–0.9 mg / L, and the dissolved oxygen concentration in the second aerobic tank is 1.5–2 mg / L. The first low-oxygen aerobic tank is inoculated with activated sludge, which causes the cumulative nitrite nitrogen rate in the wastewater entering from the wastewater inlet to reach 50% or more, achieving short-cut nitrification acclimation. The wastewater after short-cut nitrification is mixed with another part of the wastewater entering the anoxic tank from the wastewater inlet, and short-cut denitrification and phosphorus release by polyphosphate-accumulating bacteria are carried out. After the reaction, the wastewater is transported to the second aerobic tank for phosphorus uptake and organic matter removal, and then transported to the sedimentation tank to obtain the treated water.

[0009] Preferably, both the wastewater inlet and the wastewater inlet of the anoxic pool are connected to the inlet pipe via an inlet pump, and the inlet pump is electrically connected to the control component.

[0010] Preferably, the bottom of the sedimentation tank is connected to the sludge return port at the bottom of the first low-oxygen aerobic tank via a pipe, and a sludge return pump is installed on the pipe, which is electrically connected to the control component.

[0011] Preferably, a method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process, comprising the following steps:

[0012] Step 1: Sludge inoculation and acclimatization; Inoculate activated sludge into the first low-oxygen aerobic tank to acclimate the activated sludge, control the dissolved oxygen concentration in the first low-oxygen aerobic tank to 0.5-0.9 mg / L, and at the same time make the nitrite accumulation rate reach 50% or more to achieve short-cut nitrification acclimatization.

[0013] Step 2: Calculate the inlet diversion ratio r based on the inlet parameters of the inlet pipe, and transport the sewage to the first low-oxygen aerobic tank and the anoxic tank respectively through the inlet pipe according to the inlet diversion ratio r.

[0014] Step 3: A portion of the wastewater undergoes short-cut nitrification in the first low-oxygen aerobic tank, and then enters the anoxic tank;

[0015] Step 4: The wastewater after the short-cut nitrification reaction is mixed with another part of the wastewater transported to the anoxic tank through the inlet pipe to carry out the short-cut denitrification reaction and the phosphorus release process by polyphosphate-accumulating bacteria.

[0016] Step 5: The wastewater after the reaction in Step 4 is transported to the second aerobic tank, where the dissolved oxygen concentration is controlled at 1.5-2 mg / L to carry out phosphorus uptake and organic matter removal. Then it is transported to the sedimentation tank to obtain the treated water.

[0017] Preferably, step 1 specifically involves: taking activated sludge from a conventional process and inoculating it into the first low-oxygen aerobic tank, aerating it for 1 day to activate the activity of the activated sludge, controlling the dissolved oxygen concentration in the first low-oxygen aerobic tank to be 0.5–0.9 mg / L, and the hydraulic retention time to be 2–4 h, and continuously monitoring the nitrite nitrogen concentration in the effluent of the first low-oxygen aerobic tank. When the cumulative nitrite nitrogen rate reaches 50% or more, the short-cut nitrification acclimatization is considered to be complete.

[0018] Preferably, the influent flow ratio r in step 2 is calculated as follows: the influent flow ratio r refers to the proportion of wastewater entering the first low-oxygen aerobic tank to the total influent volume in the influent pipe, and the formula for calculating the influent flow ratio r is:

[0019]

[0020] In the formula:

[0021] —— ;

[0022] —Influent NH3-N concentration, mg / L;

[0023] —— ;

[0024] ——

[0025] —The organic matter removal rate of the first low-oxygen aerobic tank;

[0026] The formula for calculating the organic matter removal rate of the first low-oxygen aerobic tank is as follows:

[0027]

[0028] In the formula:

[0029] —— ℃;

[0030] —— ;

[0031] —— ;

[0032] ——

[0033] —— ;

[0034] —— d -1 ;

[0035] —Hydraulic retention time (h) in the first low-oxygen aerobic tank;

[0036] —Sludge concentration, mg / L;

[0037] —MLVSS / MLSS;

[0038] —Influent COD concentration, mg / L.

[0039] Preferably, step 3 specifically involves: after calculating the influent flow ratio r, the wastewater is transported to the first low-oxygen aerobic tank through the influent pipe to undergo short-cut nitrification to generate nitrite. The first low-oxygen aerobic tank is equipped with a stirring device. The dissolved oxygen concentration in the wastewater is controlled at 0.5–0.9 mg / L by a rotor flow meter, the hydraulic retention time is controlled at 2–4 h, the sludge concentration is maintained at 3000–5000 mg / L, and some organic matter is removed. The wastewater after the reaction enters the anoxic tank.

[0040] Preferably, step 4 specifically involves: the effluent from the first low-oxygen aerobic tank is transported to the bottom of the anoxic tank, while an anoxic tank wastewater inlet is provided at the bottom of the anoxic tank. Based on the inflow-to-outflow ratio r, another portion of wastewater is directly transported to the anoxic tank through the inlet pipe. A stirring device is installed in the anoxic tank, the hydraulic retention time is controlled at 3-5 hours, and the sludge concentration is maintained at 3000-5000 mg / L. Microorganisms in the anoxic tank utilize the remaining organic matter from the reaction in the first low-oxygen aerobic tank and the organic matter entering the wastewater through the wastewater inlet of the anoxic tank as electron donors. The nitrite nitrogen generated in the reaction in the first low-oxygen aerobic tank serves as an electron acceptor for short-range denitrification, while phosphorus release by polyphosphate-accumulating bacteria also occurs. The wastewater after the reaction in the anoxic tank enters the second aerobic tank.

[0041] Preferably, step 5 specifically involves: the effluent from the anoxic tank being transported to the bottom of the second aerobic tank, where an aeration pipe is installed at the bottom; the dissolved oxygen concentration in the water is controlled at 1.5–2 mg / L by a rotor flow meter; the hydraulic retention time is controlled at 2–4 h; and the sludge concentration is maintained at 3000–5000 mg / L. In the second aerobic tank, microorganisms perform deep removal of organic matter and nitrogen and complete the phosphorus uptake process by polyphosphate-accumulating bacteria. After the reaction, the wastewater enters the sedimentation tank.

[0042] Preferably, the sedimentation tank is equipped with a sludge return system, with the sludge return ratio controlled at 70% to 100%, and the sludge is returned to the bottom of the first low-oxygen aerobic tank through the sludge return port.

[0043] Compared with the prior art, the advantages of this application are:

[0044] (1) This application provides an apparatus and method for treating urban low carbon-nitrogen ratio wastewater using the SLOAO process. It has high denitrification efficiency, low aeration energy consumption, no internal backflow, and the carbon source can be added at zero or low levels. This significantly improves the denitrification efficiency of low carbon-nitrogen wastewater, reduces energy consumption during wastewater treatment, reduces overall wastewater treatment costs, and improves treatment efficiency and economic benefits.

[0045] (2) The method of this application allows a portion of the wastewater to undergo short-cut nitrification in the first low-oxygen aerobic tank. The nitrite generated by the reaction directly enters the anoxic tank and undergoes short-cut denitrification with another portion of the wastewater. This eliminates the step of nitrification liquid recirculation in the traditional process, abandons the setting of pre-denitrification in the traditional denitrification process, and reduces the energy consumption of the internal recirculation pump.

[0046] (3) This application proposes to divert the sewage influent and determines the influent diversion ratio calculation method in combination with the influent water quality, making full use of the carbon source in the original sewage, meeting the carbon source requirements of different spatial bacterial communities, and achieving low / zero carbon source addition;

[0047] (4) The first low-oxygen aerobic tank of this application achieves short-cut nitrification under low dissolved oxygen conditions, reduces the aeration volume and the carbon source demand in the denitrification process, and achieves efficient nitrogen removal;

[0048] (5) The sludge of this application is returned to the first low-oxygen aerobic tank, which activates the sludge activity and enhances the reproduction of the dominant bacteria of short-cut nitrification and denitrification. The application of short-cut nitrification and denitrification in the SLOAO process of this application reduces the reaction time of wastewater in the biological tank, that is, reduces its hydraulic retention time. Compared with the conventional AAO process, it reduces the size of the structure and the floor area. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the structure of a device for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process, as described in this application.

[0050] Figure 2 The NO in the effluent from the first low-oxygen aerobic tank of Embodiment 1 of this application is x - -N variation graph;

[0051] Figure 3 This is a graph showing the comparison of the concentrations of various pollutants in the effluent of Example 1 of this application;

[0052] Figure 4 The NO in the effluent from the first low-oxygen aerobic tank in Embodiment 2 of this application is... x - -N variation graph;

[0053] Figure 5 This is a graph showing the comparison of the concentrations of various pollutants in the effluent of Example 2 of this application.

[0054] Explanation of reference numerals in the attached figures:

[0055] 1. First low-oxygen aerobic tank; 2. Anoxic tank; 3. Second aerobic tank; 4. Stirring device; 5. First outlet; 6. Inlet pump; 7. Sewage inlet; 8. Aeration pipe; 9. Blower; 10. Sludge return outlet; 11. Sewage inlet of anoxic tank; 12. Sludge return pump; 13. Sedimentation tank; 14. Second outlet; 15. Inlet pipe. Detailed Implementation

[0056] The present application is described in detail below with reference to the accompanying drawings and specific embodiments, but the present application is not limited to these embodiments. The present application covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present application. To provide the public with a thorough understanding of the present application, specific details are described in detail in the following embodiments, but those skilled in the art will fully understand the present application even without these detailed descriptions.

[0057] like Figure 1As shown, this application discloses a device for treating urban low-carbon-nitrogen ratio wastewater using the SLOAO process. The SLOAO process, or SplitLow-oxygen Oxic-Anoxia-Oxic process, includes a first low-oxygen aerobic tank 1, an anoxic tank 2, a second aerobic tank 3, and a sedimentation tank 13 connected in sequence, as well as control components. A wastewater inlet 7 is located at the bottom of the inlet side of the first low-oxygen aerobic tank 1, connected to an inlet pipe 15 via a pipeline. A first outlet 5 is located on the outlet side of the first low-oxygen aerobic tank 1, communicating with the anoxic tank 2. A second outlet 14 is also located on the outlet side of the anoxic tank 2, communicating with the second... The aerobic tank 3 is connected, and the outlet side of the second aerobic tank 3 is connected to the sedimentation tank 13. The plane where the first outlet 5 and the second outlet 14 are located is higher than the plane where the sewage inlet 7 is located. The bottom of the anoxic tank 2 is also provided with an anoxic tank sewage inlet 11, which is also connected to the inlet pipe 15 through a pipe. Both the first low-oxygen aerobic tank 1 and the anoxic tank 2 are provided with a stirring device 4. Both the bottom of the first low-oxygen aerobic tank 1 and the second aerobic tank 3 are provided with an aeration pipe 8, which is connected to a blower 9. The stirring device 4 and the blower 9 are electrically connected to the control component respectively.

[0058] The dissolved oxygen concentration in the first low-oxygen aerobic tank 1 is 0.5–0.9 mg / L, and the dissolved oxygen concentration in the second aerobic tank 3 is 1.5–2 mg / L. The first low-oxygen aerobic tank 1 is inoculated with activated sludge, which causes the nitrite nitrogen accumulation rate in the wastewater entering from the wastewater inlet 7 to reach 50% or more, thus achieving short-cut nitrification acclimation. The wastewater after short-cut nitrification is mixed with another part of the wastewater entering from the anoxic tank wastewater inlet 11 to carry out short-cut denitrification and phosphorus release by polyphosphate-accumulating bacteria. After the reaction, the wastewater is transported to the second aerobic tank 3 for phosphorus uptake and organic matter removal, and then transported to the sedimentation tank 13 to obtain the treated water.

[0059] Preferably, both the sewage inlet 7 and the anoxic tank sewage inlet 11 are connected to the inlet pipe 15 via the inlet pump 6, and the inlet pump 6 is electrically connected to the control component.

[0060] Preferably, the bottom of the sedimentation tank 13 is connected to the sludge return port 10 at the bottom of the first low-oxygen aerobic tank 1 via a pipe, and a sludge return pump 12 is installed on the pipe, which is electrically connected to the control component.

[0061] Preferably, a method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process, comprising the following steps:

[0062] Step 1: Sludge inoculation and acclimatization; Inoculate activated sludge into the first low-oxygen aerobic tank 1 to acclimatize the activated sludge, control the dissolved oxygen concentration in the first low-oxygen aerobic tank 1 to be 0.5-0.9 mg / L, and at the same time make the nitrite nitrogen accumulation rate reach 50% or more to achieve short-cut nitrification acclimatization.

[0063] Step 2: Calculate the inlet diversion ratio r based on the inlet parameters of the inlet pipe 15, and transport the sewage to the first low-oxygen aerobic tank 1 and the anoxic tank 2 through the inlet pipe 15 according to the inlet diversion ratio r.

[0064] Step 3: A portion of the wastewater undergoes short-cut nitrification in the first low-oxygen aerobic tank 1, and then enters the anoxic tank 2;

[0065] Step 4: The wastewater after short-cut nitrification is mixed with another part of the wastewater transported to the anoxic tank 2 through the inlet pipe 15 to carry out short-cut denitrification and phosphorus release by polyphosphate-accumulating bacteria.

[0066] Step 5: The wastewater after the reaction in Step 4 is transported to the second aerobic tank 3, and the dissolved oxygen concentration in the second aerobic tank 3 is controlled at 1.5-2 mg / L to carry out phosphorus absorption and organic matter removal. Then it is transported to the sedimentation tank 13 to obtain the treated water.

[0067] Preferably, step 1 specifically involves: taking activated sludge from the traditional process and inoculating it into the first low-oxygen aerobic tank 1, aerating it for 1 day to activate the activity of the activated sludge, controlling the dissolved oxygen concentration in the first low-oxygen aerobic tank 1 to be 0.5-0.9 mg / L, and the hydraulic retention time to be 2-4 h, and continuously monitoring the nitrite nitrogen concentration in the effluent of the first low-oxygen aerobic tank 1. When the cumulative nitrite nitrogen rate reaches 50% or more, the short-cut nitrification acclimatization is considered to be completed.

[0068] Preferably, the influent flow ratio r in step 2 is calculated as follows: the influent flow ratio r refers to the proportion of wastewater entering the first low-oxygen aerobic tank 1 to the total influent volume of the influent pipe 15, and the formula for calculating the influent flow ratio r is:

[0069]

[0070] In the formula:

[0071] —— ;

[0072] —Influent NH3-N concentration, mg / L;

[0073] —— ;

[0074] ——

[0075] —The organic matter removal rate of the first low-oxygen aerobic tank;

[0076] The formula for calculating the organic matter removal rate of the first low-oxygen aerobic tank is as follows:

[0077]

[0078] In the formula:

[0079] —— ℃;

[0080] —— ;

[0081] —— ;

[0082] ——

[0083] —— ;

[0084] —— d -1 ;

[0085] —Hydraulic retention time (h) in the first low-oxygen aerobic tank;

[0086] —Sludge concentration, mg / L;

[0087] —MLVSS / MLSS;

[0088] —Influent COD concentration, mg / L.

[0089] Preferably, step 3 specifically involves: after calculating the influent flow ratio r, the wastewater is transported to the first low-oxygen aerobic tank 1 through the influent pipe 15 to undergo short-cut nitrification to generate nitrite nitrogen. The first low-oxygen aerobic tank 1 is equipped with a stirring device 4. The dissolved oxygen concentration in the wastewater is controlled at 0.5-0.9 mg / L by a rotor flow meter, the hydraulic retention time is controlled at 2-4 h, the sludge concentration is maintained at 3000-5000 mg / L, and some organic matter is removed. The wastewater after the reaction enters the anoxic tank 2.

[0090] Preferably, step 4 specifically involves: the effluent from the first low-oxygen aerobic tank 1 being transported to the bottom of the anoxic tank 2, while the bottom of the anoxic tank 2 is equipped with an anoxic tank wastewater inlet 11. Based on the inflow-to-outflow ratio r, another portion of wastewater is directly transported to the anoxic tank 2 through the inlet pipe 15. The anoxic tank 2 is equipped with a stirring device 4, the hydraulic retention time is controlled at 3-5 hours, and the sludge concentration is maintained at 3000-5000 mg / L. Microorganisms in the anoxic tank 2 utilize the remaining organic matter from the reaction in the first low-oxygen aerobic tank 1 and the organic matter entering the wastewater through the anoxic tank wastewater inlet 11 as electron donors. The reaction in the first low-oxygen aerobic tank 1 generates nitrite nitrogen, which acts as an electron acceptor for short-range denitrification. At the same time, a phosphorus release process by polyphosphate-accumulating bacteria occurs. The wastewater after the reaction in the anoxic tank 2 enters the second aerobic tank 3.

[0091] Preferably, step 5 specifically involves: the effluent from the anoxic tank 2 being transported to the bottom of the second aerobic tank 3, where an aeration pipe 8 is installed at the bottom; the dissolved oxygen concentration in the water is controlled at 1.5–2 mg / L by a rotor flow meter; the hydraulic retention time is controlled at 2–4 h; and the sludge concentration is maintained at 3000–5000 mg / L. In the second aerobic tank 3, microorganisms perform deep removal of organic matter and nitrogen and complete the phosphorus uptake process by polyphosphate-accumulating bacteria. After the reaction, the wastewater enters the sedimentation tank 13.

[0092] Preferably, the sedimentation tank 13 is equipped with a sludge return system, with the sludge return ratio controlled at 70% to 100%, and the sludge is returned to the bottom of the first low-oxygen aerobic tank 1 through the sludge return port 10.

[0093] Example 1

[0094] This embodiment includes the following steps:

[0095] Step 1: Sludge Inoculation: The sludge inoculated during the short-cut nitrification acclimatization stage was activated sludge from a traditional water treatment process, taken from a wastewater treatment plant's return sludge. After impurities were removed by sieving through a 2mm screen, it was added to the SLOAO reactor. The sludge concentration in the reactor after inoculation was 4000 mg / L. During the acclimatization stage, the reactor influent was artificially prepared, with COD, NH3-N, TN, and TP at 400 mg / L, 45 mg / L, 50 mg / L, and 7 mg / L, respectively. The dissolved oxygen concentration in the first low-aerobic aerobic tank 1 was controlled at 0.7 mg / L, and the hydraulic retention time was 3 hours. After continuous monitoring, short-cut nitrification acclimatization was achieved on day 28, with the cumulative nitrite nitrogen rate in the effluent from the first low-aerobic aerobic tank 1 reaching 61%.

[0096] Step 2: Take the wastewater after effluent from the grit chamber of the actual wastewater treatment plant. The wastewater has a BOD5 / COD ratio of 0.56, a BOD5 / TN ratio of 2.95~3.82, and COD, NH3-N, TN, and TP of 220~280 mg / L, 37.9~48.1 mg / L, 41.3~52.9 mg / L, and 4.8~7 mg / L, respectively. The organic matter removal rate of the first low-oxygen aerobic tank 1 is calculated to be 51%, the influent flow ratio r is 0.69~0.81, and the influent flow ratio is taken as 0.75. The sludge return ratio is 80%.

[0097] Step 3: According to the influent flow ratio r, the wastewater is fed into the first low-oxygen aerobic tank 1 for short-cut nitrification, and then enters the anoxic tank 2.

[0098] Step 4: The wastewater from the anoxic tank 2 and the inlet pipe 15 is mixed to carry out a short-cut denitrification reaction and phosphorus release process by polyphosphate-accumulating bacteria.

[0099] The wastewater after the reaction in steps 5 and 4 is transported to the second aerobic tank 3, where the dissolved oxygen concentration is controlled at 1.5-2 mg / L to carry out phosphorus uptake and organic matter removal. Then it is transported to the sedimentation tank 13 to obtain the treated water.

[0100] like Figure 2 As shown, NAR is NO2. - -N cumulative rate, NO2 in the effluent of the first low-oxygen aerobic tank 1 - The average cumulative rate of -N was 50.6%, indicating that partial short-cut nitrification was successfully achieved in the first low-oxygen aerobic tank 1; Figure 3 As shown, after the actual wastewater underwent a stable SLOAO process and continuous reaction for 20 days, the average COD concentration of the sedimentation tank effluent without the addition of external carbon sources was 23.96 mg / L, the average NH3-N concentration was 0.183 mg / L, the average TN concentration was 8.29 mg / L, meeting the Class IV discharge standard for wastewater treatment plants, and the average TP concentration was 0.82 mg / L.

[0101] Example 2

[0102] Actual campus domestic sewage was collected. After pretreatment, the sewage had a BOD5 / COD ratio of 0.47, a BOD5 / TN ratio of 2.42-3.19, and COD, NH3-N, TN, and TP of 276.80-403.37 mg / L, 41.05-52.14 mg / L, 49.51-59.81 mg / L, and 4.97-6.14 mg / L, respectively. The influent flow ratio r was 0.80.

[0103] like Figure 4 As shown, the NO2 in the effluent from the first low-oxygen aerobic tank 1 -The average cumulative rate of -N was 56%, indicating that partial short-cut nitrification was successfully achieved in the first low-oxygen aerobic tank 1; Figure 5 As shown, after the actual wastewater underwent continuous reaction for 36 days in the SLOAO process with stable sludge acclimatization in step 1, the average COD concentration of the sedimentation tank effluent was 24.68 mg / L, the average NH3-N concentration was 0.247 mg / L, the average TN concentration was 10.82 mg / L, meeting the Class A standard (GB18918-2002) of the pollutant discharge standards for urban wastewater treatment plants, and the average TP concentration was 0.95 mg / L.

[0104] This application provides a device for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process, referred to as the SLOAO process. The core of this process is short-cut nitrification and denitrification, with separate wastewater influent. The SLOAO process, along the direction of water flow, includes a first low-oxygen aerobic tank 1, an anoxic tank 2, and a second aerobic tank 3. The device also includes a sedimentation tank 13 and a sludge return system.

[0105] This application provides an apparatus and method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process. It features high denitrification efficiency, low aeration energy consumption, no internal backflow, and no need for additional carbon source addition, significantly reducing energy consumption during wastewater treatment, lowering overall wastewater treatment costs, and improving treatment efficiency and economic benefits.

[0106] The method described in this application allows a portion of the wastewater to undergo short-cut nitrification in the first low-oxygen aerobic tank. The nitrite produced by the reaction directly enters the anoxic tank to undergo short-cut denitrification with another portion of the wastewater. This eliminates the step of nitrification liquor recirculation in traditional processes, abandons the setting of pre-denitrification in traditional denitrification, and reduces the energy consumption of the recirculation pump.

[0107] This application proposes to divert wastewater influent, clearly calculate the influent diversion ratio, make full use of the carbon source in the original wastewater, meet the carbon source requirements of different spatial bacterial communities, and achieve low / zero carbon source addition.

[0108] The first low-oxygen aerobic tank of this application achieves short-cut nitrification under low dissolved oxygen conditions, reducing the aeration volume and carbon source demand in the denitrification process, thereby achieving efficient nitrogen removal.

[0109] The sludge returned to the first low-oxygen aerobic tank can quickly activate the sludge activity and enhance the removal effect of pollutants.

[0110] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

[0111] Many other changes and modifications can be made without departing from the concept and scope of this application. It should be understood that this application is not limited to the specific embodiments, and the scope of this application is defined by the appended claims.

Claims

1. A method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process, characterized in that, Wastewater treatment using the SLOAO process for treating urban wastewater with a low carbon-to-nitrogen ratio includes the following steps: Step 1: Sludge inoculation and acclimatization; Inoculate activated sludge into the first low-oxygen aerobic tank (1) to acclimatize the activated sludge, control the dissolved oxygen concentration in the first low-oxygen aerobic tank (1) to be 0.5-0.9 mg / L, and at the same time make the nitrite nitrogen accumulation rate reach 50% or more to achieve short-cut nitrification acclimatization. Step 2: Calculate the inlet diversion ratio r based on the inlet parameters of the inlet pipe (15), and transport the sewage to the first low-oxygen aerobic tank (1) and the anoxic tank (2) respectively through the inlet pipe (15) according to the inlet diversion ratio r. The influent flow ratio r in step 2 is calculated as follows: the influent flow ratio r refers to the proportion of wastewater entering the first low-oxygen aerobic tank (1) to the total influent volume of the influent pipe (15). The formula for calculating the influent flow ratio r is: In the formula: —— ； —Influent NH3-N concentration, mg / L; —— ； —— —The organic matter removal rate of the first low-oxygen aerobic tank; The formula for calculating the organic matter removal rate of the first low-oxygen aerobic tank is as follows: In the formula: —— ，℃； —— ； —— ； —— —— ； —— ，d -1 ； —Hydraulic retention time (h) in the first low-oxygen aerobic tank; —Sludge concentration, mg / L; ——MLVSS / MLSS; —Influent COD concentration, mg / L; Step 3: A portion of the wastewater undergoes short-cut nitrification in the first low-oxygen aerobic tank (1) and then enters the anoxic tank (2). Step 4: The wastewater after short-cut nitrification is mixed with another part of the wastewater transported to the anoxic tank (2) through the inlet pipe (15) to carry out short-cut denitrification and phosphorus release by polyphosphate-accumulating bacteria. Step 5: The wastewater after the reaction in Step 4 is transported to the second aerobic tank (3), and the dissolved oxygen concentration in the second aerobic tank (3) is controlled to be 1.5-2 mg / L to carry out phosphorus absorption and organic matter removal. Then it is transported to the sedimentation tank (13) to obtain the treated water. The SLOAO process for treating urban low-carbon-nitrogen ratio wastewater includes a first hypoxic-aerobic tank (1), an anoxic tank (2), a second aerobic tank (3), and a sedimentation tank (13) connected in sequence, as well as a control component. The first hypoxic-aerobic tank (1) has a wastewater inlet (7) at the bottom of its inlet side, which is connected to an inlet pipe (15) via a pipeline. The first hypoxic-aerobic tank (1) has a first outlet (5) on its outlet side, which is connected to the anoxic tank (2). The anoxic tank (2) also has a second outlet (14) on its outlet side, which is connected to the second aerobic tank (3). 3) The effluent side is connected to the sedimentation tank (13). The plane where the first effluent outlet (5) and the second effluent outlet (14) are located is higher than the plane where the sewage inlet (7) is located. The bottom of the anoxic tank (2) is also provided with an anoxic tank sewage inlet (11). The anoxic tank sewage inlet (11) is also connected to the inlet pipe (15) through a pipe. The first low-oxygen aerobic tank (1) and the anoxic tank (2) are both provided with a stirring device (4). The bottom of the first low-oxygen aerobic tank (1) and the second aerobic tank (3) are both provided with an aeration pipe (8). The aeration pipe (8) is connected to a blower (9). The stirring device (4) and the blower (9) are electrically connected to the control component respectively. The dissolved oxygen concentration in the first low-oxygen aerobic tank (1) is 0.5-0.9 mg / L, and the dissolved oxygen concentration in the second aerobic tank (3) is 1.5-2 mg / L. The first low-oxygen aerobic tank (1) is inoculated with activated sludge. The activated sludge makes the cumulative nitrite nitrogen rate in the part of the sewage entering from the sewage inlet (7) reach 50% or more, realizing short-cut nitrification. The sewage after short-cut nitrification reaction is mixed with another part of the sewage entering the anoxic tank (2) from the sewage inlet (11) of the anoxic tank to carry out short-cut denitrification reaction and phosphorus release process by polyphosphate-accumulating bacteria. After the reaction, the sewage is transported to the second aerobic tank (3) for phosphorus absorption process and organic matter removal, and then transported to the sedimentation tank (13) to obtain the treated water.

2. The method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that: The wastewater inlet (7) and the wastewater inlet (11) of the anoxic pool are both connected to the inlet pipe (15) via the inlet pump (6), and the inlet pump (6) is electrically connected to the control component.

3. The method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that: The bottom of the sedimentation tank (13) is connected to the sludge return port (10) at the bottom of the first low-oxygen aerobic tank (1) via a pipe. A sludge return pump (12) is installed on the pipe and is electrically connected to the control component.

4. The method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that, Step 1 specifically involves: taking activated sludge from the traditional process and inoculating it into the first low-oxygen aerobic tank (1), aerating it for 1 day to activate the activity of the activated sludge, controlling the dissolved oxygen concentration in the first low-oxygen aerobic tank (1) to be 0.5-0.9 mg / L, and the hydraulic retention time to be 2-4 h, continuously monitoring the nitrite nitrogen concentration in the effluent of the first low-oxygen aerobic tank (1), and when the cumulative nitrite nitrogen rate reaches 50% or more, the short-cut nitrification acclimatization is considered to be completed.

5. The method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that, Step 3 is as follows: After calculating the influent flow ratio r, the sewage is transported to the first low-oxygen aerobic tank (1) through the influent pipe (15) to carry out short-range nitrification reaction to generate nitrite nitrogen. The first low-oxygen aerobic tank (1) is equipped with a stirring device (4). The dissolved oxygen concentration in the sewage is controlled at 0.5 to 0.9 mg / L by a rotor flow meter, the hydraulic retention time is controlled at 2 to 4 hours, the sludge concentration is maintained at 3000 to 5000 mg / L, some organic matter is removed, and the sewage after reaction enters the anoxic tank (2).

6. The method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that, Step 4 is as follows: the effluent from the first low-oxygen aerobic tank (1) is transported to the bottom of the anoxic tank (2), and the bottom of the anoxic tank (2) is equipped with an anoxic tank sewage inlet (11). According to the inlet flow ratio r, another part of the sewage is directly transported to the anoxic tank (2) through the inlet pipe (15). The anoxic tank (2) is equipped with a stirring device (4), the hydraulic retention time is controlled at 3-5 hours, and the sludge concentration is maintained at 3000-5000 mg / L. The microorganisms in the anoxic tank (2) use the organic matter remaining from the reaction of the first low-oxygen aerobic tank (1) and the organic matter entering the sewage through the anoxic tank sewage inlet (11) as electron donors. The nitrite nitrogen generated by the reaction of the first low-oxygen aerobic tank (1) is used as an electron acceptor to carry out short-range denitrification reaction, and at the same time, the phosphorus release process of polyphosphate bacteria is carried out. The sewage after the reaction of the anoxic tank (2) enters the second aerobic tank (3).

7. The method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that, Step 5 specifically involves: the effluent from the anoxic tank (2) is transported to the bottom of the second aerobic tank (3), and an aeration pipe (8) is installed at the bottom of the second aerobic tank (3). The dissolved oxygen concentration in the water is controlled at 1.5-2 mg / L by a rotor flow meter, the hydraulic retention time is controlled at 2-4 h, and the sludge concentration is maintained at 3000-5000 mg / L. The microorganisms in the second aerobic tank (3) perform deep removal of organic matter and nitrogen and complete the phosphorus uptake process by polyphosphate-accumulating bacteria. After the reaction, the wastewater enters the sedimentation tank (13).

8. A method for treating urban wastewater with a low carbon-to-nitrogen ratio using the SLOAO process according to claim 1, characterized in that, The sedimentation tank (13) is equipped with a sludge return system, and the sludge return ratio is controlled at 70% to 100%. The sludge is returned to the bottom of the first low-oxygen aerobic tank (1) through the sludge return port (10).

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