A method for strengthening the dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation

Abstract

The present application relates to sewage biological treatment technical field, specifically, it is a kind of based on carbon source regulation and control's mixed nutrition denitrification in the method of reinforcing that different reduction is ammonium.The method is mixed after wastewater and inoculation sludge, it is carried out to continuous water feeding sequencing batch treatment;In the process, with the reduction of initial chemical oxygen demand in wastewater, glucose is added as carbon source, and the total chemical oxygen demand in system is always maintained initial chemical oxygen demand.By adding glucose, carbon source regulation and control is realized, nitrate is preferentially converted to ammonium nitrogen, so as to improve the selectivity of nitrate dissimilatory reduction to ammonium reaction;The method can realize reaction path adjustment only by carbon source regulation and control, and it is simple to operate, easy to popularize and apply in actual wastewater treatment system, and provides a feasible technical approach for nitrogen resource utilization in wastewater treatment process.

Description

Technical Field

[0001] This invention relates to the field of wastewater biological treatment technology, and more specifically, to an enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation. Background Technology

[0002] In biological nitrogen removal processes in wastewater, traditional denitrification typically reduces nitrates to nitrogen gas to remove total nitrogen. However, this pathway leads to nitrogen resource loss and, under certain conditions, may be accompanied by the emission of intermediate products such as nitrous oxide. In contrast, dissimilatory reduction of nitrate to ammonium (DNRA) converts nitrates into ammonium nitrogen, allowing nitrogen to be retained in the system in a recyclable form. Therefore, it has application potential in nitrogen resource recovery, coupling with anaerobic ammonia oxidation, and low-carbon sustainable wastewater treatment.

[0003] Recent reviews and engineering studies have shown that DNRA and denitrification coexist in wastewater treatment systems, and the two directly compete for electron donors such as nitrates. Generally speaking, high organic carbon, limited nitrates, and strong reducing environments are more conducive to DNRA, but denitrification still often dominates in engineering systems, and stable induction and enhancement of DNRA are still difficult to achieve.

[0004] While existing technologies have recognized that factors such as C / N ratio, carbon source type, sulfides, sludge granulation, and hydraulic conditions affect the competition between DNRA and denitrification, the following shortcomings still exist: (1) Existing research focuses more on the promoting effect of high C / N conditions on DNRA, but lacks a systematic understanding of the role of carbon source type in DNRA pathway regulation. In particular, there is a lack of clear engineering regulation strategies based on carbon source type to achieve DNRA targeted enhancement, which leads to the carbon source selection still mainly relying on experience in practical applications.

[0005] (2) Research results on different carbon sources are not yet consistent; existing work suggests that fermentation carbon sources can change the competitive landscape between DNRA and denitrification, and different carbon sources can also reshape the metabolic patterns and microbial ecology in the reactor. However, there is still a lack of clear conclusions regarding the comparative patterns, applicable conditions and engineering replicability of representative carbon sources such as glucose, ethanol and acetic acid in mixed nutrient denitrification systems.

[0006] (3) Existing research mostly focuses on mechanism discussion or natural environment observation, and does not fully reveal the correspondence between "carbon source-path selection" in wastewater treatment reactors, making it difficult to provide a clear technical route for the stable enhancement and scale-up application of DNRA.

[0007] (4) Traditional research on external carbon sources mainly serves denitrification. In engineering, easily available carbon sources such as acetate are often preferred. However, this experience cannot be directly converted into a DNRA enhancement strategy. Instead, it may cause the target pathway to continue to favor denitrification.

[0008] Therefore, it is still necessary to propose a DNRA enhancement method for wastewater biological treatment processes, with carbon source type as the core control measure. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation.

[0010] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides an enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation. Wastewater and inoculated sludge are mixed and subjected to continuous influent sequencing batch treatment. During the treatment process, glucose is added as a carbon source as the initial chemical oxygen demand in the wastewater decreases, and the total chemical oxygen demand in the system is always maintained at the initial chemical oxygen demand.

[0011] Based on the above technical solution, the present invention can be further improved as follows.

[0012] Furthermore, during the treatment process, the nitrate dissimilatory reduction to ammonium pathway contributes more than or equal to 50% to the removal of nitrate nitrogen.

[0013] Furthermore, the initial chemical oxygen demand (COD) in the wastewater is 380-420 mg / L; the mass ratio of initial COD, nitrate nitrogen, and sulfide in the wastewater is 400:50:25.

[0014] Furthermore, the wastewater also contains 1007 mg / L of KH2PO4, 101 mg / L of MgSO4·7H2O, and 14.8 mg / L of NaOH.

[0015] Furthermore, the wastewater also includes a trace element solution, the amount of which is 4 mL / L. The composition of the trace element solution is: Na2-EDTA 50.0 g / L, ZnSO4·7H2O 2.2 g / L, CaCl2·2H2O 5.54 g / L, MnCl2·4H2O 5.06 g / L, FeSO4·7H2O 5.0 g / L, and (NH4)6Mo7O 24 ·4H2O 1.10 g / L, CuSO4·5H2O 1.57 g / L and CoCl2·6H2O 1.61 g / L.

[0016] Furthermore, the inoculated sludge is the return sludge from the secondary sedimentation tank of an urban wastewater treatment plant, the initial inoculation concentration of the inoculated sludge is 3000-4000 mg / L, and the pH value of the system after the wastewater and inoculated sludge are mixed is 7.05-7.15.

[0017] Furthermore, the continuous feed batch treatment includes multiple operating cycles, each of which includes a continuous feed and reaction stage, a sedimentation stage, and a drainage stage; after each operating cycle, the supernatant is discharged, and the remaining system continues to the next operating cycle.

[0018] Furthermore, the temperature of the continuous water influent batch treatment is 20-24℃; the duration of the continuous water influent and reaction stage is 580-620 minutes; the duration of the sedimentation stage is 45-50 minutes; and the duration of the drainage stage is 8-12 minutes.

[0019] Furthermore, during the continuous water intake and reaction phase, the system dilution rate is 0.024-0.26 h⁻¹. -1 .

[0020] Furthermore, the mass percentage of the supernatant discharged at the end of each operating cycle is 25%.

[0021] The beneficial effects of this invention are as follows: (1) The enhanced method of dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation of the present invention achieves carbon source regulation by adding glucose, so that nitrate is preferentially converted to ammonium nitrogen, thereby improving the selectivity of the dissimilatory reduction of nitrate to ammonium. (2) The enhanced method of dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation of the present invention can achieve reaction path adjustment by carbon source regulation alone. It is simple to operate and easy to promote and apply in actual sewage treatment systems. (3) The enhanced method of dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation of the present invention can improve the utilization efficiency of the reduction equivalent in the system, enhance the competitive advantage of functional bacteria that dissimilate nitrate to ammonium, and thus improve the conversion efficiency of nitrate to ammonium nitrogen. (4) The enhanced method of dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation of the present invention provides a feasible technical approach for the utilization of nitrogen resources in wastewater treatment. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the sequencing batch activated sludge reactor used in Embodiment 1 and Comparative Examples 1-2 of the present invention; Figure 2 This is a comparison chart of the contribution rates of denitrification and dissimilatory reduction to ammonium in Example 1 of the present invention; Figure 3 This is a comparison chart showing the contribution rates of denitrification and dissimilatory reduction to ammonium in Comparative Example 1 of the present invention; Figure 4 This is a comparison chart showing the contribution rates of denitrification and dissimilatory reduction to ammonium in Comparative Example 2 of the present invention. Detailed Implementation

[0023] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0024] The present invention relates to a carbon source-controlled mixed nutrient denitrification dissimilatory reduction to ammonium enhancement method, which involves mixing wastewater with inoculated sludge, adding glucose as a carbon source, and performing continuous influent sequencing batch treatment. During the treatment process, glucose is added as a carbon source as the initial chemical oxygen demand (COD) in the wastewater decreases, and the total chemical oxygen demand in the system is always maintained at the initial COD.

[0025] The present invention provides a carbon source-controlled method for enhancing dissimilatory reduction to ammonium in mixed nutrient denitrification. By selecting glucose as a specific carbon source, it can effectively control the competition between the dissimilatory reduction of nitrate to ammonium and the denitrification pathway in the reaction system under the same operating conditions, so that nitrate is preferentially converted to ammonium nitrogen, thereby significantly improving the selectivity of the dissimilatory reduction of nitrate to ammonium reaction.

[0026] This method does not require changes to the reactor structure or operation mode. It can achieve directional adjustment of the reaction path simply by controlling the type of carbon source. It is simple to operate, highly replicable in engineering, and easy to promote and apply in actual wastewater treatment systems.

[0027] This method retains nitrogen in the system as recyclable ammonium nitrogen, avoiding nitrogen resource loss and emissions of greenhouse gas intermediates such as nitrous oxide caused by traditional denitrification. It provides a feasible technical approach for nitrogen resource utilization in wastewater treatment, coupling with anaerobic ammonia oxidation processes, and low-carbon sustainable wastewater treatment. At the same time, it solves the problems in existing technologies such as the lack of a method for targeted regulation of the dissimilatory reduction of nitrate to ammonium in mixed nutrient denitrification systems based on carbon source type, the unclear law of nitrate dissimilatory reduction to ammonium enhancement under different carbon source conditions, and the lack of operable carbon source selection criteria in engineering applications.

[0028] When excessive glucose is added, causing the total chemical oxygen demand (TOD) in the system to exceed the initial TOD, it leads to excessively high carbon pollutant concentrations in the effluent and increases costs. Conversely, when insufficient glucose is added, causing the TOD to fall below the initial TOD, the system will reduce nitrates through denitrification instead of the DNRA pathway. For example, when COD / NO3... - When -N is 4-5, the DNRA reaction does not occur in the system, and nitrate is reduced to nitrogen gas through denitrification.

[0029] In the control method of the present invention, the reaction occurs in the continuous water intake stage of the continuous water intake batch treatment, and glucose is continuously added during the reaction process.

[0030] In the regulation method of the present invention, the contribution rate of the nitrate dissimilatory reduction to ammonium pathway to nitrate nitrogen removal is greater than or equal to 50% during the treatment process; glucose, as a fermentation carbon source, can improve the utilization efficiency of the reducing equivalent in the system, enhance the competitive advantage of the nitrate dissimilatory reduction to ammonium functional bacteria, and thus significantly improve the conversion efficiency of nitrate to ammonium nitrogen.

[0031] In the control method of this invention, the initial COD of the wastewater is 380-420 mg / L; the initial COD and nitrate nitrogen (NO3) are... - -N) and sulfides (S 2- The mass ratio of COD to NO3 is 400:50:25, and the initial COD is limited to 380-420 mg / L to ensure the COD / NO3 ratio of the system. - A sufficiently high -N value provides ample electron donors, which in turn makes the selection of the DNRA pathway more advantageous.

[0032] In the method of the present invention, the wastewater also includes 1007 mg / L of KH2PO4, 101 mg / L of MgSO4·7H2O and 14.8 mg / L of NaOH.

[0033] Furthermore, the wastewater also includes a trace element solution, with an addition volume of 4 mL / L. The composition of the trace element solution is: Na2-EDTA 50.0 g / L, ZnSO4·7H2O 2.2 g / L, CaCl2·2H2O 5.54 g / L, MnCl2·4H2O 5.06 g / L, FeSO4·7H2O 5.0 g / L, and (NH4)6Mo7O 24 ·4H2O 1.10 g / L, CuSO4·5H2O 1.57 g / L and CoCl2·6H2O 1.61 g / L.

[0034] The inoculation sludge used in this invention is the return sludge from the secondary sedimentation tank of an urban wastewater treatment plant. The initial inoculation concentration of the inoculation sludge is 3000-4000 mg / L, and the pH value of the system after the wastewater and inoculation sludge are mixed is 7.05-7.15.

[0035] The sludge returned from the secondary sedimentation tank of urban wastewater treatment plants is rich in microbial communities with multiple functions such as nitrification, denitrification, and organic matter degradation. These include nitrifying bacteria, denitrifying bacteria, and facultative anaerobic bacteria that can dissimilate nitrate to ammonium. Therefore, it has high microbial diversity and strong adaptability, and can be directly used as inoculum sludge for the start-up and operation of bioreactors without additional cultivation and acclimatization. This can shorten the start-up cycle of the reactor and reduce operating costs.

[0036] In the method of the present invention, the continuous feed batch treatment includes multiple operating cycles. Each operating cycle includes a continuous feed and reaction stage, a sedimentation stage, and a drainage stage. After each operating cycle, the supernatant is discharged, and the remaining system continues to the next operating cycle.

[0037] Preferably, the temperature for continuous water influent batch treatment is 20-24℃; the duration of the continuous water influent and reaction stage is 580-620 minutes, the sedimentation stage is 45-50 minutes, and the drainage stage is 8-12 minutes.

[0038] Preferably, during the continuous water intake and reaction stages, the system dilution rate is 0.024-0.26 h⁻¹. -1 .

[0039] Preferably, the mass percentage of supernatant discharged after each operating cycle is 25%.

[0040] The effects of the present invention will be illustrated below through specific embodiments and comparative examples.

[0041] Example 1 This embodiment uses glucose as a carbon source to directionally regulate the DNRA pathway in a mixed nutrient denitrification system. The sequencing batch reactor (SBR) used is as follows: Figure 1 As shown.

[0042] The specific processing procedure in this embodiment is as follows: (1) Prepare simulated wastewater with the following water composition: nitrate nitrogen (NO3) - -N) 50 mg / L, Chemical Oxygen Demand (COD) 400 mg / L, Sulfides (S 2- 25 mg / L.

[0043] Macro-element and micro-element solutions were added to the simulated wastewater. The macro-element solutions included 1007 mg / L KH2PO4, 101 mg / L MgSO4·7H2O, and 14.8 mg / L NaOH. The micro-element solution was added at a concentration of 4 mL / L. The simulated wastewater was sterilized before use, and an inert gas was introduced to remove dissolved oxygen.

[0044] (2) Using the sludge returned from the secondary sedimentation tank of a municipal wastewater treatment plant in Beijing as inoculum sludge, the inoculum sludge was added as follows: Figure 1 In the sequencing batch bioreactor shown, the initial sludge concentration was controlled at 3000–4000 mg / L; the temperature was controlled at 22℃, the pH at 7.1, and the stirring speed at 150 rpm during the reaction.

[0045] The reactor operates in a continuous feed sequencing batch reactor (SBR) mode. Each operating cycle includes a 600-minute continuous feed and reaction phase, a 45-minute sedimentation phase, and a 10-minute drainage phase. Water is continuously fed in at a flow rate of 25 mL / h via an influent pump to maintain the system dilution rate at 0.025 h⁻¹. -1 The drainage ratio is 25%.

[0046] (3) Under the above operating conditions, glucose was added to the reaction system as a carbon source, and the total COD of the system was controlled at 400 mg / L according to COD metering. After the system was running stably, the nitrogen conversion in the reaction system was detected.

[0047] like Figure 2 As shown, the detection results indicate that the DNRA pathway affects NO3-. - The contribution rate of -N removal is approximately 76.8%.

[0048] Comparative Example 1 This comparative example uses ethanol as a carbon source to directionally regulate the DNRA pathway in a mixed nutrient denitrification system, and the specific process is exactly the same as in Example 1. After the system is running stably, the nitrogen conversion in the reaction system is monitored.

[0049] like Figure 3 As shown, the detection results indicate that the DNRA pathway affects NO3-. - The contribution of -N removal is approximately 29.3%.

[0050] Comparative Example 2 This comparative example uses acetic acid as a carbon source to directionally regulate the DNRA pathway in a mixed nutrient denitrification system, and the specific process is exactly the same as in Example 1. After the system is running stably, the nitrogen conversion in the reaction system is monitored.

[0051] like Figure 4 As shown, the detection results indicate that the DNRA pathway affects NO3-. - The contribution of -N removal is approximately 37.3%.

[0052] Comparing the detection results of Example 1 and Comparative Examples 1-2, it can be found that, under the same reactor structure, operating mode, and water quality conditions, the contribution rate of the DNRA reaction differs significantly under different carbon source conditions. The results indicate that, under the same COD conditions, the contribution rate of DNRA in the glucose system is significantly higher than that in the ethanol and acetic acid systems, suggesting that the type of carbon source has a significant regulatory effect on the reaction pathway.

[0053] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation, characterized in that, Wastewater and inoculated sludge are mixed and then subjected to continuous influent sequencing batch treatment. During the treatment process, glucose is added as a carbon source as the initial chemical oxygen demand in the wastewater decreases, and the total chemical oxygen demand in the system is always maintained at the initial chemical oxygen demand.

2. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 1, characterized in that, In the aforementioned process, the nitrate dissimilatory reduction to ammonium pathway contributes more than or equal to 50% to the removal of nitrate nitrogen.

3. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 1, characterized in that, The initial chemical oxygen demand (COD) in the wastewater is 380-420 mg / L; the mass ratio of initial COD, nitrate nitrogen, and sulfide in the wastewater is 400:50:

25.

4. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 3, characterized in that, The wastewater also contains 1007 mg / L of KH2PO4, 101 mg / L of MgSO4·7H2O, and 14.8 mg / L of NaOH.

5. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 4, characterized in that, The wastewater also includes a trace element solution, which is added at a concentration of 4 mL / L. The trace element solution comprises: Na2-EDTA 50.0 g / L, ZnSO4·7H2O 2.2 g / L, CaCl2·2H2O 5.54 g / L, MnCl2·4H2O 5.06 g / L, FeSO4·7H2O 5.0 g / L, and (NH4)6Mo7O 24 ·4H2O 1.10 g / L, CuSO4·5H2O 1.57 g / L and CoCl2·6H2O 1.61 g / L.

6. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 3, characterized in that, The inoculated sludge is the return sludge from the secondary sedimentation tank of an urban wastewater treatment plant. The initial inoculation concentration of the inoculated sludge is 3000-4000 mg / L, and the pH value of the system after the wastewater and inoculated sludge are mixed is 7.05-7.

15.

7. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to any one of claims 1-6, characterized in that, The continuous feed batch treatment includes multiple operating cycles, each of which includes a continuous feed and reaction stage, a sedimentation stage, and a drainage stage; after each operating cycle, the supernatant is discharged, and the remaining system continues to the next operating cycle.

8. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 7, characterized in that, The temperature of the continuous water influent batch treatment is 20-24℃; the duration of the continuous water influent and reaction stage is 580-620 minutes; the duration of the sedimentation stage is 45-50 minutes; and the duration of the drainage stage is 8-12 minutes.

9. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 8, characterized in that, During the continuous water intake and reaction phase, the system dilution rate is 0.024-0.26 h⁻¹. -1 .

10. The enhanced method for dissimilatory reduction to ammonium in mixed nutrient denitrification based on carbon source regulation according to claim 7, characterized in that, The mass percentage of supernatant discharged at the end of each operating cycle is 25%.

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