Method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation

Abstract

The invention relates to the field of wastewater treatment, and discloses a method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation, which comprises the following steps: firstly, introducing nitrogen-containing wastewater into an Anammox reactor, inoculating granular sludge taken from a secondary sedimentation tank of a sewage treatment plant into the Anammox reactor, carrying out anaerobic ammonia oxidation reaction, controlling hydraulic retention time, and carrying out anaerobic ammonia oxidation treatment on the sludge; the method comprises the following steps: pumping effluent and sulfur source inlet water into an sDNRA reactor together, inoculating ordered batch sDNRA sludge into the sDNRA reactor, performing DNRA action under sulfide driving in a stirring state, and controlling hydraulic retention time to realize automatic effluent. According to the method disclosed by the invention, a carbon source does not need to be added, byproducts generated along with complex carbon metabolism can be effectively reduced, the cost can be effectively reduced while secondary pollution is avoided, the total nitrogen removal rate of the system can be successfully improved, and the generation of greenhouse gas N2O is reduced.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and particularly to a method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonium oxidation. Background Art

[0002] Anaerobic ammonium oxidation (Anammox) has developed rapidly due to its advantages such as low cost, high load, and no N2O generation. However, since about 12% of nitrite is converted into nitrate nitrogen in the Anammox reaction, the theoretical maximum value of the total nitrogen removal rate of the system is 88%. Therefore, how to further improve the total nitrogen removal rate of the anaerobic ammonium oxidation process is an important scientific problem that needs to be solved urgently for the popularization and application of this process. In recent years, researchers have been committed to studying the coupled processes of Anammox to improve the total nitrogen removal rate, such as the short-cut denitrification-anaerobic ammonium oxidation combined process, the simultaneous denitrification-anaerobic ammonium oxidation process, and the simultaneous nitrification-denitrification-anaerobic ammonium oxidation process. However, since the short-cut denitrification process requires an external carbon source and generates N2O, and the short-cut nitrification process requires strict control of the dissolved oxygen concentration to inhibit the proliferation of nitrite-oxidizing bacteria, a new type of autotrophic coupled process is urgently needed.

[0003] In the past decade, due to the development of stable isotope technology, people have gradually distinguished the dissimilatory reduction of nitrate to ammonium (DNRA) from denitrification. Under anaerobic conditions, for every 1 mol of nitrate reduced, DNRA transfers 3 more electrons than denitrification, and the synthesized biomass is twice that of denitrification. The final reduction product of the DNRA reaction is NH4 + , without involving the emission of N2O, and NH4 + is more easily utilized by plants and other microorganisms. In full-scale sewage treatment plants with simultaneous short-cut nitrification, anaerobic ammonium oxidation, and denitrification, the typical functional genes of DNRA ( nrfA ) are significantly increased compared with denitrification. In addition, the coexistence of anaerobic ammonium oxidation bacteria and DNRA bacteria has been found in natural habitats, and the sulfide-driven DNRA (sDNRA) is beneficial to anaerobic ammonium oxidation. sDNRA uses sulfide as an electron donor and nitrate as an electron acceptor for the reaction, which is a key process connecting the sulfur and nitrogen cycles and occupies a unique position in both natural habitats and wastewater. However, due to the harsh conditions for enriching autotrophic DNRA, difficult start-up, unstable reactor performance, and difficulty in distinguishing the contribution of the denitrification process to nitrate reduction, it has become a bottleneck problem restricting the research on sulfur autotrophic DNRA. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonium oxidation, which does not require carbon source addition, can effectively reduce the by-products generated by complex carbon metabolism, avoid secondary pollution, effectively reduce costs, and can successfully improve the total nitrogen removal rate of the system and reduce the generation of greenhouse gas N2O.

[0005] To achieve the above object, the technical solution of the present invention is as follows: A method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonium oxidation, comprising the following steps: First, the nitrogen-containing wastewater is introduced into an Anammox reactor, which is inoculated with granular sludge taken from the secondary sedimentation tank of a sewage treatment plant. Anaerobic ammonium oxidation reaction is carried out here, and the hydraulic retention time is controlled. The effluent and the sulfur source influent are jointly pumped into an sDNRA reactor, which is inoculated with sequential batch sDNRA sludge. Under stirring, DNRA driven by sulfide is carried out, and the hydraulic retention time is controlled to achieve automatic effluent.

[0006] In the above solution, the granular sludge taken from the secondary sedimentation tank of the sewage treatment plant and the sequential batch sDNRA sludge are respectively washed several times with tap water until clear, and then a phosphate buffer solution with pH = 7.2 is added to seal the sludge and let it stand overnight. The next day, the granular sludge taken from the secondary sedimentation tank of the sewage treatment plant and the sequential batch sDNRA sludge are respectively transferred to the Anammox reactor and the sDNRA reactor.

[0007] In the above solution, the composition of each liter of the sulfur source influent is as follows: 0.46 g of Na2S·9H2O, 2.00 g of KH2PO4, 0.20 g of NaHCO3, 0.03 g of CaCl2, 0.20 g of MgCl2, and 1.00 mL of trace elements.

[0008] In a further technical solution, the composition of each liter of the trace elements is as follows: 20.00 g of EDTA-2Na, 2.20 g of ZnSO4·7H2O, 0.03 g of H3BO3, 0.20 g of Na2MoO4·2H2O, 0.02 g of MnCl2·4H2O, 0.02 g of NiCl2·6H2O, 0.02 g of FeSO4·7H2O, 1.57 g of CuSO4·5H2O, and 1.61 g of CoCl2·6H2O.

[0009] In the above solution, the hydraulic retention time in both reactors is 24 h.

[0010] In the above solution, the sDNRA reactor is sealed with a rubber gasket and wrapped with tinfoil to run in the dark.

[0011] In the above solution, the pH in the Anammox reactor and the sDNRA reactor is controlled at 7.5 ± 0.1, and the temperature is maintained at 23 ± 1°C.

[0012] In the above solution, the Anammox reactor is an upflow anaerobic sludge bed or a membrane bioreactor, and the sDNRA reactor is a sequencing batch reactor or a sequencing batch biofilm reactor.

[0013] Through the above technical solution, a method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation provided by the present invention has the following beneficial effects: 1. In the present invention, the coupling of sDNRA (sulfur autotrophic dissimilatory nitrate reduction to ammonia) and Anammox (anaerobic ammonia oxidation) breaks through the theoretical limit of the total nitrogen removal rate of Anammox, and improves the total nitrogen removal efficiency from 88% to 99%; 2. In the present invention, sulfur-oxidizing bacteria are simultaneously enriched to oxidize S 2- to S 0 and SO4 2- , effectively weakening the toxic effect of S 2- on Anammox bacteria; 3. The method of the present invention has a low construction cost, does not require external carbon sources, has low energy consumption, can effectively reduce the by-products generated by complex carbon metabolism, avoid secondary pollution, effectively reduce costs, and can successfully improve the total nitrogen removal rate of the system, reduce the generation of greenhouse gas N2O. It is an efficient and carbon-neutral friendly wastewater treatment technology and is convenient for engineering applications. Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0015] Figure 1 It is a schematic diagram of a wastewater treatment system using an Anammox reactor and an sDNRA reactor in combination disclosed in the embodiments of the present invention; Figure 2 It is the nitrogen and sulfur removal performance during the long-term operation of the reactor; Figure 3 It is the potential DNRA, denitrification, and SRAO rates in the sDNRA reactor of the reactor on the 220th day; Figure 4 It is the change in the relative abundance of the main functional genes of nitrogen metabolism in mRNA at two time nodes during the inoculation period and after domestication in the Anammox reactor; Figure 5 It is the change in the relative abundance of the main functional genes of nitrogen metabolism in mRNA at two time nodes during the inoculation period and after domestication in the sDNRA reactor.

[0016] In the figure, 1. Anammox reactor; 2. sDNRA reactor; 3. Mechanical agitator; 4. Artificial simulated wastewater; 5. Sulfur source inlet water; 6. Membrane assembly. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0018] The present invention provides a method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonium oxidation, which uses a wastewater treatment system in which an Anammox reactor 1 and an sDNRA reactor 2 are combined. Figure 1 shown.

[0019] The first step is to inoculate sludge: The inoculum sludge for the anammox reactor was obtained from granular sludge in the secondary sedimentation tank of a wastewater treatment plant, while the inoculum sludge for the sDNRA reactor was obtained from sequencing batch reactor sDNRA sludge that had been operating in the laboratory for over 300 days. Each reactor was washed several times with tap water until clarified, then sealed with a defined volume of phosphate buffer solution (pH = 7.2, 0.2 M) and allowed to stand overnight. The next day, the granular sludge from the secondary sedimentation tank of the wastewater treatment plant and the sequencing batch reactor sDNRA sludge were transferred to an upflow anaerobic sludge blanket (the anammox reactor) and a sequencing batch biofilm reactor (the sDNRA reactor), respectively.

[0020] The second step is to prepare artificial simulated nitrogen-containing wastewater: The composition of artificial simulated wastewater per liter is as follows: 0.20g NH4Cl, 0.22g NaNO2, 0.03g CaCl2 2H2O, 0.12g MgSO4 7H2O, 0.03g KH2PO4, 0.50g KHCO3 and 1mL trace element solution.

[0021] The trace element composition per liter is as follows: 20.00 g EDTA-2Na, 0.43 g ZnSO₄·7H₂O, 0.99 g MnCl₂·4H₂O, 0.24 g CoCl₂·6H₂O, 0.19 g NiCl₂·6H₂O, 0.25 g CuSO₄·5H₂O, 0.22 g Na₂MoO₄·2H₂O, and 0.01 g H₃BO₃. After preparation, the artificial simulated wastewater was aerated with pure nitrogen (99.9%) for at least 20 min.

[0022] Step 3: Anammox and sDNRA: like Figure 1As shown in the figure, the prepared artificial simulated wastewater 4 is introduced into the Anammox reactor 1 from the bottom of the Anammox reactor 1. The rotation speed of the peristaltic pump is adjusted to control the effluent flow rate, and the hydraulic retention time is controlled to be 24 h. The effluent and the sulfur source influent 5 are continuously pumped into the sDNRA reactor 2 from 1 / 4 of the top of the sDNRA reactor 2. The flow rates of the two influent streams are kept consistent. A mechanical stirrer 3 is installed at the top of the sDNRA reactor 2 to promote the mixing of the substrate and microorganisms in the reactor. The hydraulic retention time is controlled at 24 h, and a membrane module 6 is installed at the outlet to prevent sludge loss, and a time controller is used to achieve automatic effluent of the system. The sDNRA reactor is sealed with a rubber pad and wrapped with tin foil to operate in the dark. The rotation speed of the peristaltic pump is adjusted to control the effluent flow rate, and HCl or NaOH is pumped in using an online pH meter to control the pH to be maintained at 7.5 ± 0.1, and the temperature is maintained at 23 ± 1°C.

[0023] The composition of each liter of the sulfur source influent is as follows: 0.46 g of Na2S·9H2O, 2.00 g of KH2PO4, 0.20 g of NaHCO3, 0.03 g of CaCl2, 0.20 g of MgCl2, and 1.00 mL of trace elements. The composition of each liter of the trace elements is as follows: 20.00 g of EDTA-2Na, 2.20 g of ZnSO4·7H2O, 0.03 g of H3BO3, 0.20 g of Na2MoO4·2H2O, 0.02 g of MnCl2·4H2O, 0.02 g of NiCl2·6H2O, 0.02 g of FeSO4·7H2O, 1.57 g of CuSO4·5H2O, and 1.61 g of CoCl2·6H2O. After the sulfur source influent is prepared, it is aerated with pure nitrogen (99.9%) for more than 20 min.

[0024] During the operation of the reactor, parameters such as the ammonia conversion performance, functional gene abundance, Anammox / DNRA, and denitrification potential rate of Anammox and sDNRA are continuously monitored. The concentrations of NO3 - -N, NO2 - -N, NH4 + -N, S 2- -S, and SO4 2- -S in the reactor are monitored using an ultraviolet spectrophotometer and an ion chromatograph, respectively. The determination of the potential rates of sDNRA and denitrification is achieved through 15 N isotopes. The abundances and expression effects of the main functional genes of Anammox and DNRA after inoculation and acclimation are determined.

[0025] It can be seen from Figure 2 that during the stable operation stage, the total nitrogen (TN) removal rate is 99% ± 1% (182 - 220).

[0026] As Figure 3 shown, during the stable operation stage, isotope tests were conducted on sDNRA sludge, and the potential rates of DNRA, denitrification, and SRAO were found to be 2.41 ± 0.57 μmol / (L·h), 0.17 ± 0.08 μmol / (L·h), and 0.09 ± 0.02 μmol / (L·h), respectively. The potential rate of DNRA was more than 14 times that of the denitrification process, demonstrating that the DNRA process dominated during this stage and was accompanied by the SRAO process.

[0027] As Figure 4 and Figure 5 shown, inoculated and acclimated Anammox and sDNRA sludge (on the 0th and 300th days of operation) were selected for mRNA relative abundance analysis. The abundances and expressions of Anammox functional genes and DNRA functional genes were determined by qPCR and RT-qPCR techniques. Anammox functional genes include Anammox genes ( hao , hdh and hzs ), nitrate reduction genes ( narG and nirS ), ammonia assimilation genes ( glnA ), sulfur oxidation genes ( soxB ), and sulfur reduction genes ( dsrB ). DNRA functional genes include ammonia assimilation ( glnA ), nitrate reduction genes ( narG and nirS ), DNRA functional genes ( nirB , nrfA , nrfH ), sulfur oxidation genes ( soxB ), and Thiobacillus thioparus representative genes (Thi). The results showed that in the sDNRA reactor, sox B was upregulated 589.49-fold (fold change), and nir B responsible for DNRA was upregulated 19.25-fold (fold change); in the Anammox reactor, the expression levels of genes hao and Anhzs responsible for regulating the Anammox process were both upregulated, by 40.04 and 2.14-fold (fold change) respectively in the samples on the 220th day of operation.

[0028] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation, characterized in that, It includes the following steps: The nitrogen-containing wastewater is first introduced into the Anammox reactor. The Anammox reactor is inoculated with granular sludge taken from the secondary sedimentation tank of a sewage treatment plant. Anaerobic ammonium oxidation reaction is carried out here. The hydraulic retention time is controlled. The effluent and the sulfur source influent are jointly pumped into the sDNRA reactor. The sDNRA reactor is inoculated with sequencing batch sDNRA sludge. The DNRA driven by sulfide is carried out under stirring conditions. The hydraulic retention time is controlled to achieve automatic effluent.

2. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation according to claim 1, wherein The granular sludge taken from the secondary sedimentation tank of the sewage treatment plant and the sequencing batch sDNRA sludge are each washed several times with tap water until clear, and then a phosphate buffer solution with pH = 7.2 is added. The sludge is sealed and left standing overnight. The next day, the granular sludge from the secondary sedimentation tank of the sewage treatment plant and the sequencing batch sDNRA sludge are respectively transferred to the Anammox reactor and the sDNRA reactor.

3. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation according to claim 1, wherein, The composition of each liter of the sulfur source influent is as follows: 0.46 g of Na2S·9H2O, 2.00 g of KH2PO4, 0.20 g of NaHCO3, 0.03 g of CaCl2, 0.20 g of MgCl2, 1.00 mL of trace elements.

4. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation according to claim 3, characterized in that, The composition of each liter of the trace elements is as follows: 20.00 g of EDTA-2Na, 2.20 g of ZnSO4·7H2O, 0.03 g of H3BO3, 0.20 g of Na2MoO4·2H2O, 0.02 g of MnCl2·4H2O, 0.02 g of NiCl2·6H2O, 0.02 g of FeSO4·7H2O, 1.57 g of CuSO4·5H2O, 1.61 g of CoCl2·6H2O.

5. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation according to claim 1, wherein The hydraulic retention time in both reactors is 24 h.

6. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonium oxidation according to claim 1, wherein The sDNRA reactor is sealed with a rubber gasket and wrapped with tinfoil to operate in the dark.

7. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation according to claim 1, wherein The pH in the Anammox reactor and the sDNRA reactor is controlled at 7.5 ± 0.1, and the temperature is maintained at 23 ± 1 °C.

8. The method for treating nitrogen-containing wastewater based on sulfur autotrophic DNRA and anaerobic ammonia oxidation according to claim 1, characterized in that The Anammox reactor is an upflow anaerobic sludge bed or a membrane bioreactor, and the sDNRA reactor is a sequencing batch reactor or a sequencing batch biofilm reactor.

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