A method for strengthening double short-cut anaerobic ammonia oxidation of municipal sewage by means of intermittent aeration and segmented water feeding

Abstract

The application discloses a method for strengthening double short-cut anaerobic ammonia oxidation of municipal sewage by means of intermittent aeration and segmented water feeding, and belongs to the field of sewage biological treatment. The double short-cut anaerobic ammonia oxidation is a biological denitrification process dominated by short-cut nitrification, short-cut denitrification and anaerobic ammonia oxidation reaction. The method is characterized in that the double short-cut anaerobic ammonia oxidation process is operated by means of intermittent aeration AOAOAOA, is used for maintaining stable operation of the short-cut nitrification, and provides a stable substrate source for the anaerobic ammonia oxidation bacteria; segmented water feeding is used, 4 / 5 of raw water is pumped into the SBR (Sequencing Batch Reactor) reactor, internal carbon sources are stored under anaerobic conditions, and the remaining 1 / 5 of raw water is pumped into the second aerobic end of the intermittent aeration, so that the COD in the raw water is directly used by the denitrifying bacteria. The method solves the problems of unstable short-cut nitrification, high demand for carbon sources of the short-cut denitrification, long time consumption of the internal source denitrification and the like in the double short-cut anaerobic ammonia oxidation process.

Description

TECHNICAL FIELD

[0001] The application discloses a method for strengthening double short-cut anaerobic ammonia oxidation of municipal sewage by means of intermittent aeration and segmented water feeding, and belongs to the wastewater treatment field. BACKGROUND

[0002] Traditional nitrification-denitrification nitrogen removal technology is difficult to meet the increasingly stringent nitrogen removal standards due to the limitation of limited carbon source in raw water. In addition, the nitrification-denitrification process requires huge aeration energy consumption and carbon source consumption, so that the traditional wastewater treatment becomes a high-energy-consumption process.

[0003] The autotrophic denitrification technology represented by anaerobic ammonia oxidation has been widely concerned due to its advantages of saving aeration energy consumption and not requiring additional carbon source. However, in the system for treating low C / N ratio municipal sewage, anaerobic ammonia oxidation bacteria grow slowly, are difficult to retain, and the denitrification contribution rate is difficult to improve. At present, the substrate nitrite required for the anaerobic ammonia oxidation reaction can be obtained mainly through short-cut nitrification and short-cut denitrification. The short-cut nitrification, short-cut denitrification and anaerobic ammonia oxidation are coupled, that is, the double short-cut anaerobic ammonia oxidation technology. Compared with the widely studied PNA technology, the addition of short-cut denitrification makes a small amount of nitrate produced in the nitrification reaction in the aerobic section and the anaerobic ammonia oxidation reaction in the anoxic section be directly reduced to nitrite for the anaerobic ammonia oxidation bacteria to utilize, so that the maximum denitrification efficiency of the anaerobic ammonia oxidation technology can be effectively improved.

[0004] The nitrification reaction is controlled in the short-cut nitrification stage, and about 60% of the aeration energy consumption can be saved. However, for low C / N ratio municipal sewage, the stable short-cut nitrification is difficult to maintain, and the NOB is difficult to inhibit. In the PNA integrated process, the short-cut nitrification is maintained through intermittent aeration, which is an important strategy for inhibiting the NOB. In addition, through intermittent aeration, the nitrite concentration in the system can be controlled to be at a low level, and the inhibition of high-concentration nitrite on functional bacteria in the system is reduced.

[0005] Under the AOA operation mode of anaerobic-aerobic-anoxic, nitrogen removal mainly relies on the endogenous denitrification in the post-anoxic section, the carbon source in the raw water can be fully utilized, and the AOA operation mode has advantages of saving carbon source, saving energy and reducing consumption, and is suitable for advanced denitrification of low C / N ratio domestic sewage. However, the existing endogenous denitrification process still has problems of insufficient internal carbon source storage capacity, long time consumption of internal carbon source utilization, and low denitrification efficiency, and needs to be further optimized. Through segmented water feeding, a part of the raw water COD is stored as internal carbon source, and another part of the raw water is directly supplemented to the anoxic section, so that the denitrifying bacteria directly utilize the raw water COD for denitrification in the anoxic section, the raw water carbon source is fully utilized, the anoxic reaction time is effectively shortened, and the system denitrification efficiency is improved.

[0006] Based on the problems and challenges in mainstream urban sewage treatment, the present application takes double short-cut anaerobic ammonia oxidation process as the main part, makes the COD in raw water be fully utilized through internal source conversion and external source absorption by means of segmented water feeding technology, overcomes the problem of long time consumption of internal source denitrification, maintains the stability of short-cut nitrification through intermittent aeration, controls the nitrite concentration of the system at a low level, reduces the toxic effect on microorganisms caused by high nitrite concentration in the anoxic section, provides a more suitable living environment for anaerobic ammonia oxidation bacteria, and improves the contribution rate of anaerobic ammonia oxidation denitrification. The present application provides a stable and efficient new technology for deep denitrification of urban sewage, promotes the popularization and application of double short-cut anaerobic ammonia oxidation process in sewage treatment. The present research provides necessary theoretical basis and technical support for deep treatment of urban sewage and energy saving and consumption reduction, and has important research significance and application value. SUMMARY

[0007] The present application provides a method for strengthening double short-cut anaerobic ammonia oxidation of urban sewage by means of intermittent aeration and segmented water feeding. The double short-cut anaerobic ammonia oxidation process is operated by means of intermittent aeration AOAOAOA, which is used to maintain stable operation of short-cut nitrification and provide stable substrate source for anaerobic ammonia oxidation bacteria. The segmented water feeding is used to pump 4 / 5 of raw water into the SBR reactor to store internal carbon source under anaerobic conditions, and the remaining 1 / 5 of raw water is pumped into the second aerobic end of intermittent aeration, so that the COD in raw water is directly utilized by denitrifying bacteria. The last aerobic-anoxic section of intermittent aeration is set to control the total nitrogen in effluent at a low level by controlling the aerobic and anoxic time. This method solves the problems of unstable short-cut nitrification, high demand for carbon source of short-cut denitrification, low contribution rate of anaerobic ammonia oxidation denitrification, and long time consumption of internal source denitrification in double short-cut anaerobic ammonia oxidation process, and provides a new idea for the treatment of low C / N ratio urban sewage.

[0008] The purpose of the present application is realized by the following technical solutions:

[0009] A method for strengthening double short-cut anaerobic ammonia oxidation of urban sewage by means of intermittent aeration and segmented water feeding, characterized in that it comprises the following steps:

[0010] 1) Inoculate short-cut nitrification floc sludge to SBR reactor with effective volume of 10 L, keep sludge concentration at 3000-4000 mg / L, gradually reduce sludge settling time from 30 min to 5 min according to the setting of 5 min reduction per 5 days, and do not actively discharge sludge. Hydraulic retention time is 20 h, drainage ratio is 50%, operate two cycles per day, and do not control temperature. Operate each cycle according to anaerobic-aerobic-anoxic (AOA) mode, domesticate and enrich endogenous denitrifying bacteria, anaerobic for 2 h, aerobic for 2-3 h, and anoxic for 5-6 h. Keep dissolved oxygen at 0.5-2 mg / L during aerobic stage. Raw water is domestic sewage, ammonia nitrogen concentration is 55-65 mg / L, and COD / TIN ratio is 2-3. When the system operates for more than 30 d, ammonia nitrogen at the end of aerobic stage is less than 5 mg / L, nitrite accumulation rate is greater than 90%, effluent nitrite is 10-15 mg / L, and total nitrogen removal rate is 70%-80%, which indicates that the short-cut nitrification-endogenous denitrification system is successfully started up.

[0011] After the short-cut nitrification-endogenous denitrification system is successfully started up, inoculate anaerobic ammonia oxidation granular sludge and short-cut denitrification floc sludge to the reactor, so that the MLVSS ratio of short-cut nitrification floc sludge, anaerobic ammonia oxidation granular sludge and short-cut denitrification floc sludge in the reactor is 3:1:1. Keep sludge concentration at 3000-4000 mg / L, keep sludge settling time at 5 min, and do not actively discharge sludge. Hydraulic retention time is 15 h, drainage ratio is 50%, operate three cycles per day, one cycle lasts for 7.5 h, and do not control temperature. Operate each cycle according to anaerobic-aerobic-anoxic-aerobic-anoxic-aerobic-anoxic (AOAOAOA) mode, time is 1.5 h, 30 min, 30 min, 30 min, 3 h, 30 min and 1 h respectively. Keep dissolved oxygen concentration at 0.5-2 mg / L during aerobic stage. Raw water is domestic sewage, ammonia nitrogen concentration is 55-65 mg / L, and COD / TIN ratio is 2-3. Pump 4 / 5 of raw water into the SBR reactor first, and pump the remaining 1 / 5 of raw water at the end of the second intermittent aeration. When the system operates for more than 90 d, detect that nitrite accumulation rate during aerobic stage is greater than 93%, anaerobic ammonia oxidation denitrification contribution rate during anoxic stage is 55%-60%, effluent ammonia nitrogen concentration is less than 5 mg / L, nitrite concentration is less than 5 mg / L, and nitrate concentration is less than 1 mg / L, and total nitrogen removal rate is greater than 85%, which indicates that the urban sewage double short-cut anaerobic ammonia oxidation process strengthened by intermittent aeration and segmented water feeding is successfully started up and stably operated.

[0012] 3) System stable operation process, a typical cycle is: first, 4 / 5 of the raw water is pumped into the SBR reactor, after 2h anaerobic stirring, the biologically available COD in the raw water is stored as microbial internal carbon source; then 30min aerobic aeration, short nitrification bacteria convert 30% ± 3% of ammonia nitrogen in the influent into nitrite, then 30min anoxic stirring, a total of 15% ~ 20% of total nitrogen is removed; then 30min aerobic aeration, through short nitrification reaction, 30% ± 3% of ammonia nitrogen in the influent is converted into nitrite, and then 1 / 5 of the remaining raw water is pumped in at the end of the aerobic stage, followed by 3h anoxic stirring, a total of 50% ~ 55% of total nitrogen is removed. Then 30min aerobic aeration and 1h anoxic stirring, 20% ~ 25% of total nitrogen is removed. The total nitrogen removal rate of the system is maintained above 85%.

[0013] The present application provides a method for strengthening urban sewage double short nitrification and anaerobic ammonia oxidation by using intermittent aeration and segmented water.

[0014] 1) The present application constructs a double short nitrification and anaerobic ammonia oxidation process, reduces the aeration energy consumption required in the biological denitrification process through short nitrification, reduces the amount of carbon source required in the anoxic stage through short denitrification, and reduces the amount of carbon source required in the anoxic stage through anaerobic ammonia oxidation autotrophic denitrification.

[0015] 2) The present application strengthens the stability of short nitrification in the system by intermittent aeration, so that the nitrite accumulation rate in the aerobic stage of the system is greater than 90%.

[0016] 3) The present application uses intermittent aeration to keep the nitrite concentration in the system less than 15mg / L, reduces the toxic effects of high concentration nitrite on microorganisms, and provides suitable environment for multi-pathway denitrification by adjusting the anoxic stage time after aeration.

[0017] 4) The present application uses segmented water to reduce the loss of COD in the aerobic stage by storing internal carbon source in the anaerobic stage, inhibit the reproduction of aerobic heterotrophic bacteria, and supplement external carbon source for anoxic denitrification by re-feeding at the end of the aerobic stage, so that suitable carbon source conditions are provided for short denitrification bacteria, multi-pathway denitrification in the anoxic stage becomes possible, the carbon source in the raw water is fully utilized, and the reaction time required for nitrogen removal in the anoxic stage is shortened.

[0018] 5) The present application uses segmented water to promote short denitrification bacteria to reduce the small amount of nitrate produced by aerobic nitrification and anaerobic ammonia oxidation to nitrite for anaerobic ammonia oxidation by re-feeding external carbon source, which can improve the efficiency of anaerobic ammonia oxidation denitrification and reduce the demand for carbon source for denitrification.

[0019] 6) The present application adopts 5min sedimentation time, enriches microorganisms with good sedimentation performance, improves the proportion of granular sludge in the system, is conducive to the retention of anammox bacteria in the system, and improves the nitrogen removal contribution of anammox bacteria in the treatment of low C / N ratio municipal wastewater.

[0020] 7) The present application is simple to operate, flexible and stable to run, and is suitable for the treatment of low C / N ratio municipal wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 To utilize the intermittent aeration and step feed mode to strengthen the system operation mode of the double short-cut anammox process of municipal wastewater.

[0022] Figure 2 To utilize the intermittent aeration and step feed mode to strengthen the nitrogen and COD changes of the double short-cut anammox process of municipal wastewater in a typical cycle. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0024] First, inoculate short-cut nitrification floc sludge in the SBR reactor, keep the sludge concentration at 3000-4000mg / L, gradually reduce the sludge settling time from 30min to 5min by setting a decrease of 5min every 5 days, and do not actively discharge sludge. The hydraulic retention time is 20h, the drainage ratio is 50%, two cycles are run every day, and the temperature is not controlled. Each cycle is run according to the anoxic-aerobic-anoxic AOA mode, domesticates and enriches endogenous denitrifying bacteria, anoxic for 2h, aerobic for 2-3h, and anoxic for 5-6h. The dissolved oxygen in the aerobic section is kept at 0.5-2mg / L. The raw water is domestic wastewater, the ammonia nitrogen concentration is 55-65mg / L, and the COD / TIN ratio is 2-3. When the system runs for more than 30d, the ammonia nitrogen at the end of the aerobic stage is less than 5mg / L, the nitrite accumulation rate is greater than 90%, the effluent nitrite is 10-15mg / L, and the total nitrogen removal rate is 70%-80%, indicating that the short-cut nitrification-endogenous denitrification system is successfully started.

[0025] After successful startup of the short-cut nitrification-endogenous denitrification system, anaerobic ammonia oxidation granular sludge and short-cut denitrification flocculent sludge are inoculated into the reactor, maintaining an MLVSS ratio of 3:1:1 for short-cut nitrification flocculent sludge, anaerobic ammonia oxidation granular sludge, and short-cut denitrification flocculent sludge. The sludge concentration is maintained at 3000–4000 mg / L, and the sludge settling time is maintained at 5 min; no active sludge discharge is performed. The hydraulic retention time is 15 h, the effluent ratio is 50%, and the system operates for three cycles per day, with each cycle lasting 7.5 h. Temperature is not controlled. Each cycle operates in an anaerobic-aerobic-anoxic-aerobic-anoxic-aerobic-anoxic (AOAOAOA) pattern, with durations of 1.5 h, 30 min, 30 min, 30 min, 3 h, 30 min, and 1 h, respectively. The dissolved oxygen concentration in the aerobic phase is controlled at 0.5–2 mg / L. The raw water was domestic sewage with an ammonia nitrogen concentration of 55–65 mg / L and a COD / TIN ratio of 2–3. A staged influent process was used, with 4 / 5 of the raw water pumped into the SBR reactor first, and the remaining 1 / 5 pumped into the second aerobic stage during intermittent aeration. After more than 90 days of system operation, the nitrite accumulation rate in the aerobic stage was greater than 93%, the anaerobic ammonia oxidation nitrogen removal contribution rate in the anoxic stage was 55%–60%, and the effluent ammonia nitrogen concentration was less than 5 mg / L, nitrite concentration less than 5 mg / L, nitrate nitrogen concentration less than 1 mg / L, and total nitrogen removal rate greater than 85%. This indicates that the enhanced dual-short-cut anaerobic ammonia oxidation process for urban sewage, utilizing intermittent aeration and staged influent, was successfully started up and is operating stably.

[0026] During stable system operation, a typical cycle is as follows: First, 4 / 5 of the raw water is pumped into the SBR reactor. After 2 hours of anaerobic stirring, the bioavailable COD in the raw water is stored as a carbon source for the microorganisms. Then, 30 minutes of aerobic aeration is performed, during which short-cut nitrifying bacteria convert 30% ± 3% of the ammonia nitrogen in the influent into nitrite. Following this, 30 minutes of anoxic stirring removes 15%–20% of the total nitrogen. Another 30 minutes of aerobic aeration is then performed, converting another 30% ± 3% of the ammonia nitrogen in the influent into nitrite through short-cut nitrification. At the end of the aerobic cycle, the remaining 1 / 5 of the raw water is pumped in, followed by 3 hours of anoxic stirring, removing 50%–55% of the total nitrogen. Finally, 30 minutes of aerobic aeration and 1 hour of anoxic stirring remove 20%–25% of the total nitrogen. The system's total nitrogen removal rate remains above 85%.

[0027] The foregoing has provided a detailed description of a method for enhancing dual-short-cut anaerobic ammonium oxidation of urban sewage using intermittent aeration and segmented water inlet, and specific examples have been used to illustrate the principle and implementation of the invention. The above description of the specific examples is only for the purpose of helping to understand the method and core idea of ​​the invention; for those skilled in the art, there will be changes in the specific implementation based on the idea of ​​the invention, therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A method for enhancing dual-short-cut anaerobic ammonium oxidation of urban wastewater using intermittent aeration and segmented influent, characterized in that: 1) Inoculate the SBR reactor with short-cut nitrification flocculent sludge, maintaining the sludge concentration at 3000-4000 mg / L. Gradually reduce the sludge settling time from 30 min to 5 min every 5 days, without actively discharging sludge. The hydraulic retention time is 20 h, the effluent ratio is 50%, and the system operates for two cycles per day without temperature control. Each cycle follows an anaerobic-aerobic-anoxic (AOA) mode to acclimate and enrich endogenous denitrifying bacteria: 2 h anaerobic, 2-3 h aerobic, and 5-6 h anoxic. The dissolved oxygen in the aerobic stage is maintained at 0.5-2 mg / L. The raw water is municipal wastewater with an ammonia nitrogen concentration of 55-65 mg / L and a COD / TIN ratio of 2-3. When the system has been running for more than 30 days, the ammonia nitrogen at the end of the aerobic stage is less than 5 mg / L, the nitrite accumulation rate is greater than 90%, the effluent nitrite is 10-15 mg / L, and the total nitrogen removal rate is 70%-80%, indicating that the short-cut nitrification-endogenous denitrification system has been successfully started up. 2) After successful startup of the short-cut nitrification-endogenous denitrification system, anaerobic ammonia oxidation granular sludge and short-cut denitrification flocculent sludge are inoculated into the reactor to achieve an MLVSS ratio of 3:1:

1. The sludge concentration is maintained at 3000~4000 mg / L, the sludge settling time is maintained at 5 min, and no active sludge discharge is performed. The hydraulic retention time is 15 h, the effluent ratio is 50%, and the system operates for three cycles per day, with each cycle lasting 7.5 h. Temperature is not controlled. Each cycle operates in an anaerobic-aerobic-anoxic-aerobic-anoxic-aerobic-anoxic pattern, with durations of 1.5 h, 30 min, 30 min, 30 min, 3 h, and 30 min respectively. In 1 hour; the dissolved oxygen concentration in the aerobic stage was controlled at 0.5~2 mg / L; the raw water was urban sewage with an ammonia nitrogen concentration of 55~65 mg / L and a COD / TIN ratio of 2~3; using segmented influent, 4 / 5 of the raw water was first pumped into the SBR reactor, and the remaining 1 / 5 of the raw water was pumped into the second aerobic stage during intermittent aeration; after the system had been running for more than 90 days, the nitrite accumulation rate in the aerobic stage was found to be greater than 93%, the anaerobic ammonia oxidation denitrification contribution rate in the anoxic stage was 55%~60%, the effluent ammonia nitrogen concentration was less than 5 mg / L, the nitrite concentration was less than 5 mg / L, the nitrate nitrogen concentration was less than 1 mg / L, and the total nitrogen removal rate was greater than 85%, indicating that the urban sewage dual short-cut anaerobic ammonia oxidation process enhanced by intermittent aeration and segmented influent was successfully started up and operated stably; 3) During stable system operation, a typical cycle is as follows: First, 4 / 5 of the raw water is pumped into the SBR reactor. After 2 hours of anaerobic stirring, the bioavailable COD in the raw water is stored as a carbon source for the microorganisms. Then, 30 minutes of aerobic aeration is performed, and short-cut nitrifying bacteria convert 30%±3% of the ammonia nitrogen in the influent into nitrite. After 30 minutes of anoxic stirring, a total of 15%~20% of the total nitrogen is removed. Then, 30 minutes of aerobic aeration is performed again, and 30%±3% of the ammonia nitrogen in the influent is converted into nitrite through short-cut nitrification. At the end of the aerobic process, the remaining 1 / 5 of the raw water is pumped in, followed by 3 hours of anoxic stirring, which removes a total of 50%~55% of the total nitrogen. Then, 30 minutes of aerobic aeration and 1 hour of anoxic stirring are performed, which removes 20%~25% of the total nitrogen. The total nitrogen removal rate of the system is maintained above 85%.

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