High-efficiency short-process low-carbon-nitrogen-ratio autotrophic sewage treatment process

Abstract

The present application relates to a kind of high efficiency short process low carbon nitrogen ratio autotrophic sewage treatment process, belong to sewage denitrification processing technical field.The present application is based on nitrification aerobic granular sludge technology and other biological denitrification process synergistic autotrophic sewage treatment process, to biological adsorption+nitrification aerobic granular sludge+sulfur autotrophic denitrification forms without external carbon source addition, realizes the short process autotrophic sewage treatment process of ultra-low carbon nitrogen pollutant discharge.The biological adsorption / nitrification aerobic granular sludge / sulfur autotrophic denitrification short process low carbon nitrogen ratio autotrophic combined process constructed by the present application can achieve short process, reduce cost, save land, without carbon source addition, reduce sludge production and reduce the risk of secondary pollution etc.Advantages, effectively solve the problem of urban domestic sewage carbon source deficiency, effluent nitrate concentration does not reach standard.

Description

Technical Field

[0001] This invention relates to a high-efficiency, short-process, low-carbon-nitrogen-ratio autotrophic wastewater treatment technology, belonging to the field of wastewater denitrification technology. Background Technology

[0002] Currently, wastewater treatment plant discharge standards are becoming increasingly stringent. While most wastewater treatment plants in my country can meet or exceed the Class A discharge standard, to ensure effluent meets these standards, they typically add acetic acid and acetate to achieve the required total nitrogen levels. This increased chemical input raises operating costs. Wastewater treatment plants along rivers often face challenges such as low influent C / N ratios, heavy rainfall and long rainy seasons, lengthy process flows, and large amounts of influent sludge and sand, preventing them from meeting design standards and resulting in inefficient operations with high energy and chemical consumption. The increasing concentration of ammonia nitrogen in water bodies leads to eutrophication. Excessive nitrogen compounds cause a logarithmic growth of algae and microorganisms, reducing dissolved oxygen, poisoning fish, causing foul odors, and affecting the appearance and tourism value of water bodies, posing a significant challenge to water pollution control in my country. To address the issue of insufficient carbon sources affecting total inorganic nitrogen removal in water bodies, strategies that improve conventional processes to fully utilize existing carbon sources in wastewater can improve denitrification performance to some extent. However, based on traditional denitrification biochemical mechanisms and stoichiometry, this strategy has very limited effectiveness for low C / N wastewater. Furthermore, adding external carbon sources increases wastewater treatment operating costs. Therefore, it is necessary to select appropriate processes or modify the operating mode of wastewater treatment plants to enhance the treatment of low C / N wastewater. Thus, there is an urgent need to develop efficient, nitrogen-controlled, autotrophic, short-process wastewater treatment optimization processes for low C / N wastewater, achieving efficient and stable nitrogen control in low-carbon, short-process wastewater treatment. Summary of the Invention

[0003] [Technical Issues] This invention addresses the challenges posed by the low carbon and nitrogen content of influent to current wastewater treatment plants. Traditional biological denitrification technologies suffer from low denitrification efficiency, necessitate the addition of external carbon sources, and face the significant hurdle of meeting increasingly stringent effluent standards for urban wastewater treatment plants. Therefore, this invention proposes an autotrophic wastewater treatment process based on nitrifying aerobic granular sludge technology, synergistically integrating other biological denitrification processes. This short-process autotrophic wastewater treatment process, combining biological adsorption, nitrifying aerobic granular sludge, and sulfur autotrophic denitrification, achieves ultra-low carbon and nitrogen pollutant emissions without requiring external carbon source addition.

[0004] [Technical Solution] This invention provides a short-process autotrophic wastewater treatment process, the process of which is as follows: (1) The wastewater to be treated is fed into a biological adsorption tank inoculated with aerobic activated sludge for the first treatment, and then fed into a sedimentation tank for sludge sedimentation to obtain the effluent from the biological adsorption section sedimentation tank. (2) The effluent from the sedimentation tank of the biological adsorption section is fed into the acclimated and cultured nitrifying aerobic granular sludge system for a second treatment to obtain the effluent of nitrifying aerobic granular sludge; the acclimation and culture is carried out by acclimating and cultured nitrifying aerobic granular sludge using artificial simulated wastewater, and the water quality of the artificial simulated wastewater is as follows: carbon source is a mixed carbon source of CH3COONa and CH3CH2COONa, COD is 100-1000 mg / L, and NH4+ is 100-1000 mg / L. + -N concentrations are 30-50 mg / L, 20-30 mg / L KH₂PO₄, 30-40 mg / L K₂HPO₄, 90-100 mg / L MgSO₄, 70-80 mg / L CaCl₂, 5-15 mg / L EDTA, and 1-2 µg·L⁻¹. -1 FeCl3·6H2O, 0.1-0.2 µg·L -1 H3BO3, 0.02-0.04 µg·L -1 CuSO4·5H2O, 0.02-0.04 µg·L -1 KI, 0.1-0.2 µg·L -1 MnCl2·4H2O, 0.05-0.06 µg·L -1 ZnCl2, 0.1-0.2 µg·L -1 CoCl2·6H2O, 0.05-0.06 µg·L -1 Na2MoO4·2H2O; (3) The effluent from the obtained nitrified aerobic granular sludge is further fed into the sulfur autotrophic denitrification system for a third treatment to obtain treated effluent.

[0005] In one embodiment of the present invention, the COD of the wastewater to be treated in step (1) is 140~352 mg / L and the TN concentration is 29~43 mg / L.

[0006] In one embodiment of the present invention, the bottom of the biological adsorption tank in step (1) is equipped with an aeration head for aeration and oxygenation, and the dissolved oxygen range is controlled to be 0.5-1 mg / L. The hydraulic retention time of the biological adsorption section is 1 h, the sludge age is 2 d, the biomass is 4000-5000 mg / L, and a sedimentation tank is connected after the biological adsorption tank for sludge sedimentation. At the same time, a sludge return device is set up to ensure the biomass of the biological adsorption tank, and the sludge return ratio is 50%.

[0007] In one embodiment of the present invention, the acclimatization and cultivation process in step (2) includes: using aerobic granular sludge as inoculum sludge, gradually changing the influent conditions by simultaneously reducing the C:N ratio, and the acclimatization and cultivation conditions are divided into two stages: Phase I: Influent COD concentration decreased from 1000 mg / L to 100 mg / L, NH4+... + The -N concentration was decreased from 50 mg / L to 30 mg / L, and the treatment lasted for 40 days. Stage II, influent COD concentration is 0, NH4+ + The -N concentration was 30 mg / L, and the treatment lasted for 30 days.

[0008] In one embodiment of the present invention, the preparation process of the aerobic granular sludge in step (2) includes: Activated sludge from an aerobic tank was inoculated into an SBR reactor with an inoculation volume of 2 L and an MLSS concentration of 5.0 g / L. Artificially simulated synthetic wastewater was used as the influent, pumped into the reactor via a peristaltic pump at a flow rate of 900 ml. The experimental setup employed an SBR with an H / D ratio of 10:1. An aeration device was installed at the bottom of the reactor, and a rotor flow meter was used to control the aeration rate at 2 L / min during the aeration phase. A timer switch controlled the reactor's state at each stage. Each operating cycle included four processes: influent, aeration, settling, and effluent. The operating cycle lasted 4 hours, with an influent time of 5 min, an aeration time gradually increasing from 205 min to 215 min, a settling time gradually decreasing from 15 min to 5 min, and a effluent ratio of 60%. The reactor was cultured for 40 days. After d, fully granulated aerobic granular sludge was obtained; wherein, the artificially simulated synthetic wastewater included sodium acetate, sodium propionate, NH4Cl, K2HPO4, KH2PO4, MgSO4, CaCl2, EDTA and trace element concentrate, and the concentrations of NH3-N, COD and TP in the influent were 50, 1000 and 16 mg / L, respectively.

[0009] In one embodiment of the present invention, the second treatment in step (2) includes: the nitrifying aerobic granular sludge is operated in SBR mode, the inoculum sludge is the previously successfully acclimated nitrifying aerobic granular sludge, and the biomass of the inoculum sludge is 4000-5000 mg / L. The experimental device adopts an SBR with an H / D ratio of 10:1. An aeration device is set at the bottom of the reactor, and a rotor flow meter is used to control the aeration rate of 1.5 L / min during the aeration stage, with dissolved oxygen at 5-6 mg / L. A time-controlled switch is used to control the state of the reactor at each stage. Each operating cycle includes four processes: water influent, aeration, settling, and drainage. The operating cycle lasts for 4 hours, including 5 minutes of water influent, 205 minutes of aeration, 15 minutes of settling, 5 minutes of drainage, and the remaining time is for settling. The drainage ratio is 60%.

[0010] In one embodiment of the present invention, the sulfur autotrophic denitrification system in step (3) is a sulfur autotrophic denitrification filter with elemental sulfur as the packing material. The packing material has a particle size of 2-4 mm and a porosity of 40%-60%.

[0011] In one embodiment of the present invention, the treatment time of the sulfur autotrophic denitrification system in step (3) is 1-2 hours. Specifically, 1.5 hours may be selected.

[0012] In one embodiment of the present invention, the method specifically includes: (the process flow is shown in Figure 1). The inoculated sludge in the biosorption section is activated sludge from the aerobic tank of a wastewater treatment plant. The biosorption section is mainly used to remove most particulate organic matter, as well as some dissolved organic matter, total nitrogen, and total phosphorus. Aeration heads are installed at the bottom of the biosorption tank for aeration and oxygenation, controlling the dissolved oxygen range to 0.5-1 mg / L. The hydraulic retention time in the biosorption section is 1 h, the sludge age is 2 days, and the biomass is 4000-5000 mg / L. The biosorption tank is followed by a sedimentation tank for sludge settling. A sludge return device is also installed to ensure the biomass of the biosorption tank, with a sludge return ratio of 50%. The effluent from the biological adsorption sedimentation tank enters the nitrifying aerobic granular sludge reactor. The main function of the nitrifying aerobic granular sludge is to remove residual COD from the wastewater and completely oxidize residual ammonia nitrogen to nitrate nitrogen using heterotrophic bacteria. The nitrifying aerobic granular sludge operates in SBR mode, using previously acclimated nitrifying aerobic granular sludge with a biomass of 4000-5000 mg / L. The experimental setup uses an SBR with an H / D ratio of 10:1. An aeration device is installed at the bottom of the reactor, and a rotor flow meter is used to control the aeration rate during the aeration stage at 1.5 L / min, with dissolved oxygen at 5-6 mg / L. A timer switch controls the reactor's state at each stage. Each operating cycle includes four processes: influent, aeration, settling, and drainage. The operating cycle lasts for 4 hours, with 5 minutes of influent, 205 minutes of aeration, 15 minutes of settling, 5 minutes of drainage, and the remaining time for settling. The drainage ratio is 60%. The effluent from nitrifying aerobic granular sludge is pumped into a storage tank via a peristaltic pump to deplete oxygen, and then enters a sulfur autotrophic denitrification filter. Sulfur autotrophic denitrification primarily removes nitrate nitrogen, achieving the final denitrification goal. The sulfur autotrophic denitrification filter is cylindrical with an inner diameter of 10 cm. To prevent clogging, a gravel support layer is arranged at the bottom. The sulfur particles in the packing material have a diameter of 2-4 mm and a porosity of approximately 50%. The sulfur autotrophic denitrification hRT is 1.5 h. From bottom to top, the sulfur autotrophic denitrification filter can be divided into a water distribution layer, a deoxygenation layer, a reaction zone, and a clarification layer.

[0013] In one embodiment of the present invention, the test influent (sewage to be treated) is the effluent from the vortex grit chamber of a municipal sewage treatment plant, and its water quality index concentration range is shown below.

[0014]

[0015] Beneficial effects: This invention relates to a short-process, low-carbon-to-nitrogen ratio autotrophic combined process for constructing a biological adsorption / nitrification aerobic granular sludge / sulfur autotrophic denitrification process. This process offers advantages such as a short process flow, reduced costs, space saving, no need for carbon source addition, reduced sludge production, and reduced risk of secondary pollution. It effectively solves the problems of insufficient carbon source and substandard nitrate and nitrogen concentrations in urban domestic sewage. The effluent quality of this process consistently meets the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" DB32 / 4440. The 2022 Class A standard is met. This wastewater treatment process not only improves the total nitrogen removal rate but also enriches a large amount of particulate organic matter in the residual sludge of the biosorption stage, which is beneficial for subsequent anaerobic fermentation and acid production processes. Biosorption can retain most of the organic matter, which is conducive to the enrichment of nitrifying bacteria in the subsequent nitrification aerobic granular sludge system. The retention of heavy metals and antibiotics also helps protect the microorganisms in the nitrification aerobic granular sludge and sulfur autotrophic denitrification processes. Compared with the traditional A2 / O process, this invention's process has no sludge return system, nitrification and denitrification do not interfere with each other, and the system can operate stably. Attached Figure Description

[0016] Figure 1 This is a flow chart of a short-process autotrophic wastewater treatment process.

[0017] Figure 2 The effect of bio-adsorption on pollutant removal.

[0018] Figure 3 The pollutant removal efficiency during the acclimation stage of nitrifying aerobic granular sludge Figure 4 The effect of pollutant removal by nitrifying aerobic granular sludge.

[0019] Figure 5 The effect of sulfur autotrophic denitrification sludge on pollutant removal.

[0020] Figure 6 The pollutant removal efficiency of the short-process autotrophic wastewater treatment process. Detailed Implementation

[0021] Example 1: Operation of the biosorption section The inoculated sludge for the biological adsorption section was activated sludge from the aerobic tank of a wastewater treatment plant in Wuxi City (A 2 The activated sludge in the aerobic tank of the / O process is mainly used to remove most of the particulate organic matter, as well as some dissolved organic matter, total nitrogen, and total phosphorus. The bottom of the biological adsorption tank is equipped with aeration heads for aeration and oxygenation, and the dissolved oxygen range is controlled at 0.5-1 mg / L. The hydraulic retention time of the biological adsorption section is 1 h, the sludge age is 2 d, and the biomass is 4000-5000 mg / L. The biological adsorption tank is connected to a sedimentation tank for sludge sedimentation. At the same time, a sludge return device is set up to ensure the biomass of the biological adsorption tank. The sludge return ratio is 50%, and the effluent from the sedimentation tank of the biological adsorption section is obtained.

[0022] The treatment effect of the biological adsorption stage on actual domestic sewage (effluent from the vortex grit chamber of a sewage treatment plant in a certain town in Wuxi City) is as follows: Figure 2As shown, the biosorption process, through microbial flocculation and adsorption, can retain some suspended solids and adsorb recalcitrant organic matter. The actual domestic wastewater used in this invention exhibits COD fluctuating between 140 and 352 mg / L, and TN concentration ranging from 29 to 43 mg / L, classifying it as typical low C / N ratio wastewater. Studies have found that under the biosorption operating conditions of DO 0.5 mg / L and HRT = 1 h, it can achieve a COD removal rate of approximately 80% in the influent, with a CODss removal rate exceeding 90%. Simultaneously, it removes some dissolved COD, indicating that biosorption, with a relatively short HRT, can retain the majority of COD through microbial flocculation and adsorption, discharging it as excess sludge in the sedimentation tank. This excess sludge has a high organic content and potential for further recycling. The ammonia nitrogen in the effluent from the sedimentation tank of the biosorption stage is reduced by approximately 5 mg / L. Due to the short HRT, the removal rate of dissolved TN by biosorption is approximately 10%.

[0023] The residual sludge from the sedimentation tank in the biological adsorption section and the wastewater treatment plant A 2 A comparison was made between the sludge discharge from the secondary sedimentation tank of the / O process and the traditional A process. 2 The protein content of the residual sludge in the biological adsorption sedimentation tank, after removing a large amount of particulate organic matter, reached 41.84 mg / g, significantly higher than that of the sludge discharged from the secondary sedimentation tank of the sewage treatment plant (25.90 mg / g). However, the polysaccharide content of the sludge discharged from the biological adsorption sedimentation tank (31.34 mg / g) was lower than that of the sludge discharged from the secondary sedimentation tank of the sewage treatment plant (44.79 mg / g). At the same time, due to the anaerobic environment of the biological adsorption sedimentation tank, the humic acid content of the sludge was 15.73 mg / g, higher than that of the sludge discharged from the secondary sedimentation tank of the sewage treatment plant (11.17 mg / g). The C / N ratio of the sludge discharged from the biological adsorption sedimentation tank reached 17.80, indicating that the residual sludge in the adsorption section has better conditions for subsequent anaerobic fermentation compared to the sludge discharged from the secondary sedimentation tank of the sewage treatment plant.

[0024] Example 2: Operation of Nitrifying Aerobic Granular Sludge (1) Acclimation and cultivation of nitrifying aerobic granular sludge: The inoculum sludge was aerobic granular sludge with an inoculum volume of 2 L and an MLSS concentration of 5.0 g / L. Artificially prepared wastewater was used as the influent, and the artificially prepared wastewater was pumped into the reactor via a peristaltic pump. The experimental setup used an SBR with an H / D ratio of 10:1. An aeration device was installed at the bottom of the reactor, and a rotor flow meter was used to control the aeration rate at 1.5 L / min during the aeration stage. A timer switch was used to control the reactor's state at each stage. Each operating cycle included four processes: influent, aeration, settling, and drainage. The duration of each operating cycle was 240 min. Artificially simulated wastewater was used in the experiment. The influent water quality was as follows: the carbon source was a mixed carbon source (CH3COONa, CH3CH2COONa), and the COD gradually decreased from 1000 mg / L to 100 mg / L. NH4+ + -N was reduced from 50 mg / L to 30 mg / L, with the remaining concentrations being 29.25 mg / L KH₂PO₄, 37.41 mg / L K₂HPO₄, 97 mg / L MgSO₄, 75 mg / L CaCl₂, and 10 mg / L EDTA. Trace elements in the influent were determined using FeCl₃·6H₂O at a concentration of 1.5 µg·L⁻¹. -1 H3BO3 content is 0.15 µg·L -1 The concentration of CuSO4·5H2O is 0.03 µg·L. -1 KI is 0.03 µg·L -1 The concentration of MnCl2·4H2O is 0.12 µg·L. -1 ZnCl2 content was 0.058 µg·L⁻¹. -1 The concentration of CoCl2·6H2O is 0.15 µg·L. -1 The concentration of Na₂MoO₄·2H₂O is 0.06 µg·L⁻¹. -1 The above acclimatization and cultivation process used aerobic granular sludge as inoculum and gradually changed the influent conditions by simultaneously reducing the C:N ratio. The acclimatization and cultivation conditions are shown in Table 1.

[0025] The aerobic granular sludge involved was obtained through the following methods: Sludge was inoculated into the SBR reactor. The inoculated sludge was taken from the activated sludge in the aerobic tank of the A2 / O process in a wastewater treatment plant, with an inoculation volume of 2 L and a MLSS concentration of 5.0 g / L. The experimental influent was artificially simulated wastewater, which was pumped into the reactor via a peristaltic pump at a flow rate of 900 ml. The artificially simulated wastewater included sodium acetate, sodium propionate, NH4Cl, K2HPO4, KH2PO4, MgSO4, CaCl2, EDTA, and a trace element concentrate. The concentrations of NH3-N, COD, and TP in the influent were 50, 1000, and 16 mg / L, respectively. The experimental setup used an SBR with an H / D ratio of 10:1. An aeration device was installed at the bottom of the reactor, and a rotor flow meter was used to control the aeration rate during the oxygenation stage at 2 L / min. A time-controlled switch was used to control the reactor's state at each stage. Each operating cycle included four processes: influent, aeration, settling, and effluent. The operating cycle lasted for 4 hours, with influent time of 5 minutes, aeration time gradually increasing from the initial 205 minutes to 215 minutes, and settling time gradually decreasing from the initial 15 minutes to 5 minutes. The effluent ratio was 60%. After 40 days of reactor cultivation, fully granulated AGS was obtained, with sludge particle sizes ranging from 0.43 mm to 0.88 mm.

[0026] The artificially simulated synthetic wastewater involved is specifically: sodium acetate at a concentration of 357 mg·L⁻¹. -1 Sodium propionate is 1000 mg·L. -1 NH4Cl was 229 mg·L⁻¹ -1 The concentration of K2HPO4 was 44.8 mg·L⁻¹. -1 The concentration of KH2PO4 was 35.84 mg·L. -1 MgSO4 was 97 mg·L⁻¹ -1 The CaCl2 concentration was 75 mg·L⁻¹. -1 EDTA is 10 mg·L -1 1 ml of trace element concentrate. The trace element concentrate was prepared by adding FeCl3·6H2O to the influent at a concentration of 1.5 µg·L⁻¹. -1 H3BO3 content is 0.15 µg·L -1 The concentration of CuSO4·5H2O is 0.03 µg·L. -1 KI is 0.03 µg·L -1 The concentration of MnCl2·4H2O is 0.12 µg·L. -1 ZnCl2 content was 0.058 µg·L⁻¹. -1 The concentration of CoCl2·6H2O is 0.15 µg·L. -1 The concentration of Na₂MoO₄·2H₂O is 0.06 µg·L⁻¹. -1 .

[0027] Table 1. Conditions for changes in influent water quality

[0028] The removal efficiency of COD and ammonia nitrogen in the reactor is as follows: Figure 3 As shown, to prevent particle disintegration caused by drastic changes in the acclimation environment, COD and ammonia nitrogen were gradually reduced in the first stage until COD was completely removed and ammonia nitrogen reached 30 mg / L. Results showed that as the COD concentration gradually decreased from 1000 mg / L, the COD removal rate gradually decreased from 97.2% to 69.7% in the first stage, with the effluent COD remaining approximately 40 mg / L. In the second stage, the dissolved oxygen level in the reactor was maintained at 4–6 mg / L. The effluent was mainly composed of nitrite nitrogen. After approximately ten days of continuous operation, all ammonia nitrogen was converted to nitrate nitrogen, resulting in complete nitrification. The ammonia nitrogen removal rate reached over 90%, successfully acclimating a nitrifying aerobic granular sludge system capable of treating ammonia nitrogen.

[0029] (2) Treatment of urban domestic sewage by nitrifying aerobic granular sludge The effluent from the biological adsorption sedimentation tank was fed into the successfully acclimated nitrifying aerobic granular sludge system. The main function of the nitrifying aerobic granular sludge is to remove residual COD from the wastewater and completely oxidize residual ammonia nitrogen into nitrate nitrogen. The nitrifying aerobic granular sludge was operated in SBR mode. The inoculum sludge was the previously acclimated nitrifying aerobic granular sludge with a biomass of 4000-5000 mg / L. The experimental device adopted an SBR with an H / D ratio of 10:1. An aeration device was installed at the bottom of the reactor. A rotor flowmeter was used to control the aeration rate during the aeration stage at 1.5 L / min, and the dissolved oxygen at 5-6 mg / L. A timer switch was used to control the state of the reactor at each stage. Each operating cycle included four processes: influent, aeration, settling, and effluent. The operating cycle lasted for 4 hours, including 5 minutes of influent, 205 minutes of aeration, 15 minutes of settling, 5 minutes of effluent, and the remaining time for settling. The effluent ratio was 60%, resulting in the effluent from the nitrifying aerobic granular sludge system. The treatment effect of nitrifying aerobic granular sludge on the effluent from the biological adsorption stage is as follows: Figure 4 As shown, nitrifying aerobic granular sludge can achieve a 50% removal rate of residual COD in wastewater. The effluent from this stage meets the COD discharge standard DB32 / 4440-2022, indicating that the microbial community is relatively rich in the oligotrophic system, and some heterotrophic bacteria are still retained. Nitrifying aerobic granular sludge also improves the removal of NH4+ from urban domestic sewage. + The removal rate of NH4+ is as high as 90% or more, and complete nitrification can be achieved even when the dissolved oxygen is greater than 2 mg / L. + -N is converted to NO3 --N indicates that the addition of urban domestic sewage has little impact on the removal of pollutants by nitrifying aerobic granular sludge. This may be because most organic matter, suspended solids, and even some toxic and harmful substances such as heavy metal ions have already been removed in the biological adsorption stage, which provides good protection for the subsequent nitrifying aerobic granular sludge.

[0030] Example 3: Operation of sulfur autotrophic denitrification Sulfur autotrophic denitrification primarily removes nitrate nitrogen to achieve final nitrogen removal. The sulfur autotrophic denitrification filter is cylindrical with an inner diameter of 10 cm. To prevent clogging, a gravel support layer is placed at the bottom. The sulfur particles in the packing material have a diameter of 2-4 mm and a porosity of approximately 50%. The sulfur autotrophic denitrification hRT is 1.5 h. The effluent from the nitrifying aerobic granular sludge continues to be fed into the sulfur autotrophic filter for denitrification. The influent NO3... - -N fluctuated around 30 mg / L. The highest nitrate nitrogen in the effluent was 2.5 mg / L on day 2, while other test results were basically zero. The effluent NO2... - -N is below 0.5 mg / L, effluent NH4 + With a nitrogen concentration below 1.0 mg / L, the removal rate of total nitrogen (TN) can reach over 90% at an HRT of 1.5 h, and the total nitrogen in the effluent is stably below 10 mg / L. The total nitrogen in the effluent from the sulfur autotrophic denitrification process can meet the discharge standard of DB32 / 4440-2022, demonstrating a strong nitrogen removal effect.

[0031] Example 4: Treatment effect of short-process autotrophic wastewater treatment technology on urban domestic sewage Figure 6 To assess the overall COD and TN removal efficiency of this short-process autotrophic wastewater treatment technology, biological adsorption rapidly adsorbs, flocculates, and settles organic matter in the influent within a 1-hour h (HRT). Nitrification aerobic granular sludge further removes residual dissolved COD within a 4-hour h (HRT), resulting in a total effluent COD below 30 mg / L. TN removal relies on the close integration of three processes. While biological adsorption has limited effectiveness in removing ammonia nitrogen, it can remove most particulate TN. Subsequent ammonia nitrogen undergoes thorough nitrification in the nitrification aerobic granular sludge stage, followed by sulfur autotrophic denitrification using reduced sulfur as an electron donor within a 1.5-hour h (HRT), resulting in an effluent TN below 10 mg / L. The average dissolved COD in the influent is 240 mg / L, and the average COD in the effluent is 19.25 mg / L, with a COD removal rate as high as 92%. The average TN concentration in the influent is 38 mg / L, and the average TN concentration in the effluent is 4.5 mg / L, with a TN removal rate of up to 97%. This short-process autotrophic wastewater treatment process can achieve ultra-low carbon and nitrogen pollutant emissions within an HRT of 6.5 h.

[0032] Comparative Example 1: The short-process autotrophic process of this invention is compared with the AAO and SBR processes used in traditional wastewater treatment plants, and the comparison indicators are shown in Table 2. The hydraulic retention times of the AAO and SBR processes are long, exceeding 10 hours, and their treatment effects on low C / N ratio wastewater are difficult to consistently meet standards, requiring the addition of large amounts of carbon sources to achieve denitrification. The short-process autotrophic process, however, can achieve high carbon and nitrogen pollutant removal efficiency with a shorter hydraulic retention time. The proposed biological adsorption / nitrification aerobic granular sludge / sulfur autotrophic denitrification short-process low C / N ratio autotrophic combined process achieves a COD removal rate of 92%, a total nitrogen (TN) removal rate of 97%, and an ammonia nitrogen removal rate of 95% with a HRT of 6.5 hours. Under conditions of shorter hydraulic retention time and zero carbon source addition, the pollutant removal effect is significantly better than that of the AAO and SBR processes.

[0033] Table 2 Comparison of HRT and pollutant removal rates for different processes

[0034] Comparative Example 2: Referring to Example 3, the subsequent sulfur autotrophic denitrification process in the effluent of nitrifying aerobic granular sludge was replaced with other autotrophic nitrogen removal technologies. The corresponding nitrogen removal efficiency was measured.

[0035] The operation processes of other autotrophic nitrogen removal technologies are selected from: ① Anaerobic ammonia oxidation technology: An upflow anaerobic sludge blanket reactor (UASB) is used. The effective volume of the UASB is 8.8L, the inner diameter of the reaction zone is 10 cm, the height is 90 cm, and the height-to-diameter ratio is 9:1. An insulated zone is provided outside the reaction zone, and a circulating water bath pump is used to maintain the temperature of the reaction zone at around 35℃. A layer of black insulation cotton is wrapped around the entire reactor to reduce the impact of light on the anaerobic ammonia oxidizing bacteria. The effluent from the nitrifying aerobic granular sludge enters the reactor from the bottom through a peristaltic pump, and the effluent flows out from the overflow weir of the UASB.

[0036] ② Sulfur-iron autotrophic denitrification technology: The effluent from nitrifying aerobic granular sludge continues to flow into the sulfur-iron autotrophic denitrification filter for denitrification and nitrogen removal. Influent NO3... - -N fluctuates around 30 mg / L. The sulfur-iron autotrophic denitrification filter is cylindrical with an inner diameter of 10 cm. To prevent clogging, a gravel support layer is arranged at the bottom. The sulfur particles in the packing material have a diameter of 2-4 mm and a porosity of approximately 50%. Iron filings are wrapped in plastic balls with a diameter of 10 cm. The HRT of the sulfur-iron autotrophic denitrification filter is 3 h, and the sulfur-iron volume ratio is 7:1.

[0037] Results: Anaerobic ammonia oxidation technology has almost no denitrification effect on the effluent of nitrifying aerobic granular sludge. Anaerobic ammonia oxidation technology uses ammonia as an electron donor and nitrate or nitrite as an electron acceptor to convert ammonia into nitrogen gas for removal. Although it is an autotrophic denitrification technology, it is not compatible with nitrifying aerobic granular sludge technology.

[0038] Sulfur-iron autotrophic denitrification technology effluent nitrate nitrogen effluent NO3 - The average concentration of -N was 3.9 mg / L, and the removal rate of TN was only 75% at HRT=3 h, which is significantly weaker than the sulfur autotrophic denitrification technology used in this invention.

[0039] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A short-process autotrophic wastewater treatment process, characterized in that, The process includes the following steps: (1) The wastewater to be treated is fed into a biological adsorption tank inoculated with aerobic activated sludge for the first treatment, and then connected to a sedimentation tank for sludge sedimentation to obtain the effluent from the biological adsorption section sedimentation tank; the bottom of the biological adsorption tank is equipped with aeration heads for aeration and oxygenation, and the dissolved oxygen range is controlled at 0.5-1 mg / L. The hydraulic retention time of the biological adsorption section is 1 h, the sludge age is 2 days, and the biomass is 4000-5000 mg / L. The biological adsorption tank is connected to a sedimentation tank for sludge sedimentation. At the same time, a sludge return device is set up to ensure the biomass of the biological adsorption tank, and the sludge return ratio is 50%. (2) The effluent from the sedimentation tank of the biological adsorption section is fed into the acclimated and cultured nitrifying aerobic granular sludge system for a second treatment to obtain the effluent of nitrifying aerobic granular sludge; the acclimation and culture is carried out by acclimating and cultured nitrifying aerobic granular sludge using artificial simulated wastewater, and the water quality of the artificial simulated wastewater is as follows: carbon source is a mixed carbon source of CH3COONa and CH3CH2COONa, COD is 100-1000 mg / L, and NH4+ is 100-1000 mg / L. + -N concentrations are 30-50 mg / L, 20-30 mg / L KH₂PO₄, 30-40 mg / L K₂HPO₄, 90-100 mg / L MgSO₄, 70-80 mg / L CaCl₂, 5-15 mg / L EDTA, and 1-2 µg·L⁻¹. -1 FeCl3·6H2O, 0.1-0.2 µg·L -1 H3BO3, 0.02-0.04 µg·L -1 CuSO4·5H2O, 0.02-0.04 µg·L -1 KI, 0.1-0.2 µg·L -1 MnCl2·4H2O, 0.05-0.06 µg·L -1 ZnCl2, 0.1-0.2 µg·L -1 CoCl2·6H2O, 0.05-0.06 µg·L -1 Na2MoO4·2H2O; The acclimation and cultivation process includes: using aerobic granular sludge as inoculum, gradually changing the influent conditions by simultaneously reducing the C:N ratio; the acclimation and cultivation conditions are divided into two stages: Phase I: Influent COD concentration decreased from 1000 mg / L to 100 mg / L, NH4+... + The -N concentration was decreased from 50 mg / L to 30 mg / L, and the treatment lasted for 40 days. Stage II, influent COD concentration is 0, NH4+ + -N concentration was 30 mg / L, and treatment lasted for 30 days; (3) The effluent from the obtained nitrified aerobic granular sludge is further fed into the sulfur autotrophic denitrification system for a third treatment to obtain treated effluent; the sulfur autotrophic denitrification system is a sulfur autotrophic denitrification filter with elemental sulfur as the packing material.

2. The short-process autotrophic wastewater treatment process according to claim 1, characterized in that, The COD of the wastewater to be treated in step (1) is between 140 and 352 mg / L, and the TN concentration is between 29 and 43 mg / L.

3. The short-process autotrophic wastewater treatment process according to claim 1, characterized in that, The preparation process of the aerobic granular sludge in step (2) includes: Activated sludge from an aerobic tank was inoculated into an SBR reactor with an inoculation volume of 2 L and an MLSS concentration of 5.0 g / L. Artificially simulated synthetic wastewater was used as the influent, pumped into the reactor via a peristaltic pump at a flow rate of 900 ml. The experimental setup employed an SBR with an H / D ratio of 10:

1. An aeration device was installed at the bottom of the reactor, and a rotor flow meter was used to control the aeration rate at 2 L / min during the aeration phase. A timer switch controlled the reactor's state at each stage. Each operating cycle included four processes: influent, aeration, settling, and effluent. The operating cycle lasted 4 hours, with an influent time of 5 min, an aeration time gradually increasing from 205 min to 215 min, a settling time gradually decreasing from 15 min to 5 min, and a effluent ratio of 60%. The reactor was cultured for 40 days. After d, fully granulated aerobic granular sludge was obtained; wherein, the artificially simulated synthetic wastewater included sodium acetate, sodium propionate, NH4Cl, K2HPO4, KH2PO4, MgSO4, CaCl2, EDTA and trace element concentrate, and the concentrations of NH3-N, COD and TP in the influent were 50, 1000 and 16 mg / L, respectively.

4. The short-process autotrophic wastewater treatment process according to claim 1, characterized in that, The second treatment described in step (2) includes: the nitrified aerobic granular sludge is operated in SBR mode, the inoculated sludge is the previously successfully acclimated nitrified aerobic granular sludge, and the biomass of the inoculated sludge is 4000-5000 mg / L; the experimental device adopts an SBR with an H / D ratio of 10:1, an aeration device is set at the bottom of the reactor, and the aeration rate during the oxygenation stage is controlled by a rotor flow meter to be 1.5 L / min, and the dissolved oxygen is 5-6 mg / L; the state of each stage of the reactor is controlled by a time-controlled switch, and each operating cycle includes four processes: water inlet, aeration, settling, and drainage. The operating cycle lasts for 4 hours, including 5 minutes of water inlet, 205 minutes of aeration, 15 minutes of settling, 5 minutes of drainage, and the rest of the time is left to stand, with a drainage ratio of 60%.

5. The short-process autotrophic wastewater treatment process according to claim 1, characterized in that, The filler has a particle size of 2-4 mm and a porosity of 40%-60%.

6. The short-process autotrophic wastewater treatment process according to claim 1, characterized in that, The treatment time of the sulfur autotrophic denitrification system in step (3) is 1-2 h.

7. The short-process autotrophic wastewater treatment process according to claim 1, characterized in that, The treatment time of the sulfur autotrophic denitrification system in step (3) is 1.5 h.

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