Method for enhancing denitrification performance of iron autotrophic denitrification biofilter by utilizing immobilized biochar

Abstract

The invention discloses a method for enhancing denitrification performance of an iron autotrophic denitrification biological filter by utilizing immobilized biochar, and relates to the technical field of biological sewage treatment. An iron autotrophic denitrification biofilter is adopted, and immobilized biochar is prepared from biochar, a sodium alginate aqueous solution and sponge filler and is added into a filter reactor, so that the electron transfer rate in the reactor is increased, and the purpose of improving the denitrification efficiency is achieved. The method achieves the purpose of efficiently treating nitrate sewage, has the advantages of economy and high efficiency, and has important significance for optimizing and regulating an iron autotrophic denitrification nitrogen removal technology.

Description

Technical Field

[0001] The invention belongs to the technical field of biological sewage treatment, and in particular relates to a method for enhancing the denitrification performance of an iron autotrophic denitrification biological filter by utilizing immobilized biochar. Background Art

[0002] Nitrogen pollution is one of the major problems of the world's water environment. China's current nitrogen emissions to water bodies are about 14.5 million tons per year. The sources of nitrogen pollution mainly include natural sources and human sources, among which human sources are the main source of nitrogen pollution, mainly including the large-scale use of pesticides and fertilizers, and the discharge of domestic sewage and industrial wastewater. In addition, the release of sediment will also cause secondary pollution to water bodies. The increasing nitrogen pollution in water will not only lead to eutrophication of water bodies, affect aquatic organisms, and destroy the balance of water ecology; it will also threaten human health and cause the "three-cause" hazards of teratogenicity, carcinogenicity, and mutagenicity.

[0003] According to the basic principles, wastewater denitrification can be divided into three categories: physical, chemical and biological. The physical method is to use physical separation to remove nitrogen, mainly including adsorption, reverse osmosis, electrodialysis and ion exchange; the chemical method is to use chemical reducing agents to remove nitrogen, mainly including electrochemical reduction and catalytic reduction; the biological method is to reduce nitrogen in the water body into gaseous nitrogen compounds (mainly N2) through the nitrification and denitrification of microorganisms, and the main processes include denitrifying biological filter (DNBF), moving bed biofilm reactor (MBBR) and artificial wetland method. Since biological denitrification can generally meet water quality requirements, is inexpensive, and the secondary pollution generated is easy to handle, biological denitrification is currently a hot research field.

[0004] In the process of biological denitrification, denitrification has gradually become a key factor affecting sewage denitrification. According to the different electron donors, biological denitrification can be divided into heterotrophic denitrification and autotrophic denitrification. Heterotrophic denitrification refers to the process in which microorganisms convert nitrate nitrogen into nitrogen gas under anaerobic or anoxic conditions, and the electron donor is provided by the carbon source. For low carbon-nitrogen ratio sewage, it is necessary to supplement the carbon source as an electron donor to ensure the normal progress of the denitrification reaction, but at present, no efficient and cheap carbon source has been found, which not only increases the operating cost but also may affect the denitrification process and cause secondary pollution. Autotrophic denitrification refers to the process in which microorganisms use inorganic substances (H2, Fe, S, etc.) as electron donors and inorganic carbon as a carbon source to reduce nitrate nitrogen to nitrogen gas. Autotrophic denitrification is an effective way to solve the contradiction between supply and demand of electron donors in the biological denitrification process of low C / N sewage. Compared with heterotrophic denitrification, autotrophic denitrification does not require an external carbon source, has low sludge production and low operating costs, so it has received widespread attention. Iron-type autotrophic denitrification has the advantages of being non-toxic, harmless, cheap, easily available, and having high treatment efficiency, and has broader development prospects and research and development potential. Summary of the invention

[0005] In order to solve the problems of high cost and high risk of secondary pollution of existing heterotrophic denitrification, the present invention proposes a method for enhancing the denitrification performance of an iron autotrophic denitrification biological filter by using immobilized biochar based on autotrophic denitrification. By adding immobilized biochar filler into the biological filter, the denitrification efficiency is improved, and the accumulation of ammonium nitrogen and nitrite nitrogen is reduced, thereby achieving efficient treatment of nitrate wastewater, which has the advantages of being economical, efficient, non-toxic and harmless.

[0006] A method for enhancing the denitrification performance of an iron autotrophic denitrification biofilter using immobilized biochar, comprising the following steps:

[0007] Step 1, preparing immobilized biochar;

[0008] First, the biochar was ground and sieved (40 meshes), 30 g of the biochar was added to a sodium alginate aqueous solution (2%), and the mixture was evenly mixed using a magnetic stirrer to obtain a mixed solution.

[0009] Then, a sponge filler is added to the mixed solution, and the mixture is continuously mixed to make the biochar adhere to the sponge filler; the mixed sponge filler is added to a calcium chloride solution (4%) to form immobilized biochar.

[0010] Finally, the immobilized biochar was soaked in calcium chloride solution (0.4%) and stored at 4% before use.

[0011] Step 2: Use organic glass as raw material to process the main part of the experimental device reactor and construct an iron autotrophic denitrification biofilter reactor.

[0012] The structure and working principle of the autotrophic denitrification biofilter reactor are as follows: the artificially configured wastewater in the inlet pool passes through the inlet pipe and the peristaltic pump to the inlet at the bottom of the reactor and enters the reactor. Microbial communities, iron, sponge fillers and immobilized biochar are distributed in the reactor, and the microbial communities, iron, sponge fillers and immobilized biochar are evenly mixed. Sampling ports are left on the reactor body and the top side. The treated effluent flows through the sampling port through the outlet pipe and is discharged into the effluent pool. An air outlet is left at the top of the reactor, and the air outlet is connected to a gas collection bag.

[0013] One end of the water inlet pipe is connected to the water inlet pool, and the other end is connected to the peristaltic pump. One end of the water inlet pipe is connected to the peristaltic pump, and the other end is connected to the water inlet of the reactor.

[0014] Step 3, domesticating the anaerobic microorganisms in the autotrophic denitrification biofilter reactor;

[0015] Activated sludge was added to the reactor, the sludge mixed liquor suspended solid concentration MLSS = 5000 mg / L, the anaerobic sludge composition and concentration were NaNO3 = 0.273 g / L, KH2PO4 = 0.5 g / L, NaHCO3 = 1.1655 g / L, CaCl2·2H2O = 0.4 g / L, MgSO4·7H2O = 0.4 g / L, C / N = 4;

[0016] The activated sludge is washed with water and then added to the reactor through the water inlet tank. The volume of the activated sludge added accounts for 2 / 5 of the reactor.

[0017] After cultivation and domestication, when the nitrate treatment efficiency reaches more than 60%, the cultivation and domestication of anaerobic microorganisms is completed.

[0018] After acclimation, anaerobic microorganisms aggregate on the surface of immobilized biochar to form a biofilm.

[0019] Step 4, treating wastewater in a reactor to which immobilized biochar is added;

[0020] Firstly, nitrate wastewater (45 mg / L) enters the anaerobic reactor from the inlet tank through the inlet pipe and the inlet pipe under the action of the peristaltic pump.

[0021] Then, in the anaerobic reactor, the immobilized biochar promotes the iron autotrophic denitrification process under the joint action of microorganisms, iron and immobilized biochar. In the reactor, the iron, microorganisms, sponge filler and immobilized biochar are uniformly mixed.

[0022] Finally, after the reaction is completed in the anaerobic reactor, the wastewater flows into the outlet pool through the outlet pipe, completing the denitrification of nitrate wastewater.

[0023] The denitrification efficiency of nitrate wastewater reaches over 86%, and the reaction cycle is 1 day.

[0024] The present invention utilizes biochar to enhance the denitrification performance of the iron autotrophic denitrification biofilter, and has the advantages of:

[0025] (1) The present invention does not require the addition of an external organic carbon source during the anaerobic denitrification process of wastewater, thereby avoiding secondary pollution and reducing operating costs.

[0026] (2) The immobilized biochar filler prepared by the present invention has the characteristic of improving the electron shuttling ability in the reactor, which can improve the denitrification efficiency, is economical and efficient, has low cost and a simple method.

[0027] (3) In the iron autotrophic denitrification process of the present invention, the sludge output is small, thus saving the sludge disposal cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1A structural diagram of the iron autotrophic denitrification biofilter reactor used in the process of the present invention;

[0029] Figure 2 The nitrate nitrogen concentration and denitrification efficiency of the inlet and outlet water of the iron autotrophic denitrification biological filter in the embodiment of the present invention are shown.

[0030] Figure 3 The immobilized biochar according to the embodiment of the present invention and its morphological characteristics before and after the reaction. Figure 3 a is the prepared immobilized biochar; Figure 3 b shows the morphological characteristics of immobilized biochar; Figure 3 c is the morphological characteristics of the immobilized biochar after the reaction.

[0031] In the figure: 1-water inlet pool, 2-water inlet pipe, 3-peristaltic pump, 4-water inlet pipe, 5-sponge filler, 6-sampling port, 7-air outlet, 8-air collecting bag, 9-sampling port / water outlet, 10-water outlet, 11-water outlet pool, 12-anaerobic reactor, 13-microorganisms, 14-iron element, 15-immobilized biochar filler. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] The present invention provides a process for enhancing the denitrification performance of an iron autotrophic denitrification biological filter by using immobilized biochar

[0034] An iron autotrophic denitrification biological filter was adopted. By adding immobilized biochar filler, the electron transfer rate in the reactor was accelerated, the denitrification efficiency was significantly improved, and the efficient treatment of nitrate wastewater was achieved. It has the advantages of economy and efficiency, and is of great significance for optimizing and regulating iron autotrophic denitrification technology.

[0035] This method is divided into the following steps:

[0036] Step 1: Preparation of immobilized biochar: Prepare immobilized biochar. Grind and sieve the biochar (40 mesh), take 30g of biochar and add it to the sodium alginate aqueous solution (2%), and use a magnetic stirrer to mix evenly. Then add the sponge filler and continue to mix evenly so that the biochar adheres to the sponge filler, and then add the mixed sponge filler to the calcium chloride solution (4%) to form immobilized biochar. Finally, soak the immobilized biochar in the calcium chloride solution (0.4%) and store it at 4% before use.

[0037] Step 2: domestication stage: This method of using immobilized biochar to enhance the denitrification performance of the iron autotrophic denitrification biofilter uses an anaerobic biofilter reactor 12 that is an iron autotrophic denitrification biofilter. Activated sludge 13 is added to the reactor 12. The activated sludge is taken from the A2 / O process anoxic tank of the Shahe Reclaimed Water Plant in Changping District, Beijing. The sludge MLSS is 5000 mg / L. After washing, it is added to the reactor 12. The volume of the activated sludge added accounts for 2 / 5 of the reactor volume. The composition and concentration of the anaerobic sludge are NaNO3=0.273g / L, KH2PO4=0.5g / L, NaHCO3=1.1655g / L, CaCl2·2H2O=0.4g / L, MgSO4·7H2O=0.4g / L, C / N=4, and the nitrate treatment efficiency after cultivation and domestication reaches more than 60%.

[0038] Step 3: Reactor startup: The entire reaction process of the iron autotrophic denitrification anaerobic reactor used is as follows: Nitrate wastewater enters the reactor from the water inlet pool 1 through the peristaltic pump 3. One end of the water inlet pipe 2 is connected to the water inlet pool 1, and the other end is connected to the peristaltic pump 3. One end of the water inlet pipe 4 is connected to the peristaltic pump 3, and the other end is connected to the water inlet of the reactor. In the anaerobic reactor 12, the iron autotrophic denitrification process strengthened by the immobilized biochar 15 is completed under the joint action of the microbial community 13, the iron element 14, and the immobilized biochar 15. The gas collection bag 8 is connected to the air outlet 7. The sampling ports are 6 and 9. After the reaction cycle is completed, the effluent flows into the water pool 11 through the outlet pipe 10. The effective volume of the reactor is about 500ml, and a total of 3 anaerobic reactors are set up. Iron powder 14 is added to the anaerobic reactor 12 as an electron donor, and 5g of iron source is added. About 200ml of the microbial community 13 after cultivation and domestication is added, accounting for 2 / 5 of the reactor volume.

[0039] Step 4: Intensification stage: Add the prepared immobilized biochar into the anaerobic reactor 12 and operate the reactor.

[0040] The results show that:

[0041] The process is designed to have an influent nitrate nitrogen concentration of 45 mg / L. Figure 2 It can be seen that the average concentration of nitrate nitrogen in the reactor in the first stage with the addition of iron powder was 37.71 mg / L, the concentration of nitrate nitrogen in the effluent was 7.26 mg / L, and the removal rate was 80.63%. The average concentration of nitrate nitrogen in the second stage was 42.27 mg / L. After adding immobilized biochar filler 15, the average concentration of nitrate nitrogen in the effluent was 5.56 mg / L, and the removal rate was 86.84%. In addition, after adding immobilized biochar filler, the reaction cycle was shortened from 2 days to 1 day.

[0042] The immobilized biochar used in the present invention is Figure 3 As shown, Figure 3a is the prepared immobilized biochar. Figure 3 As can be seen in b, the immobilized biochar of preparation number has a layered structure and a relatively smooth surface; Figure 3 c shows a SEM change of the immobilized biochar before and after the reaction. It can be seen from the figure that a large number of microorganisms are gathered on the surface of the immobilized biochar after the reaction.

Claims

1. A method for enhancing the denitrification performance of an iron autotrophic denitrification biofilter using immobilized biochar, characterized in that: The specific steps are as follows: Step 1, preparing immobilized biochar; First, the biochar was ground and sieved, and 30 g of the biochar was added to a 2% sodium alginate aqueous solution and mixed evenly using a magnetic stirrer to obtain a mixed solution; Then, a sponge filler is added to the mixed solution and the mixture is continued to be mixed evenly so that the biochar adheres to the sponge filler; the mixed sponge filler is added to a 4% calcium chloride solution to form immobilized biochar; Finally, the immobilized biochar was soaked in 0.4% calcium chloride solution and stored at 4% before use; Step 2: using organic glass as raw material to process the main part of the experimental device reactor to construct an iron autotrophic denitrification biofilter reactor; The structure and working principle of the autotrophic denitrification biofilter reactor are as follows: the artificially configured wastewater in the inlet pool reaches the inlet at the bottom of the reactor through the inlet pipe and the peristaltic pump and enters the reactor; microbial communities, elemental iron and immobilized biochar are distributed in the reactor, and the microbial communities, elemental iron and immobilized biochar are evenly mixed; sampling ports are reserved on the reactor body and the top side; the treated effluent flows through the sampling port through the effluent pipe and is discharged into the effluent pool; A gas outlet hole is left at the top of the reactor, and the gas outlet hole is connected to a gas collection bag; Step 3, domesticating the anaerobic microorganisms in the autotrophic denitrification biofilter reactor; Activated sludge was added to the reactor, the sludge mixed liquor suspended solid concentration MLSS = 5000 mg / L, the anaerobic sludge composition and concentration were NaNO3 = 0.273 g / L, KH2PO4 = 0.5 g / L, NaHCO3 = 1.1655 g / L, CaCl2·2H2O = 0.4 g / L, MgSO4·7H2O = 0.4 g / L, C / N = 4; The activated sludge is washed with water and then added to the reactor through the water inlet tank, and the volume of the activated sludge added accounts for 2 / 5 of the reactor; After cultivation and domestication, when the nitrate treatment efficiency reaches more than 60%, the cultivation and domestication of anaerobic microorganisms is completed; Step 4, treating wastewater in a reactor to which immobilized biochar is added; First, 45 mg / L nitrate wastewater enters the anaerobic reactor from the inlet tank through the inlet pipe and the inlet pipe under the action of the peristaltic pump; Then, in the anaerobic reactor, the immobilized biochar promotes the iron autotrophic denitrification process under the joint action of microorganisms, elemental iron and immobilized biochar; Finally, after the reaction is completed in the anaerobic reactor, the wastewater flows into the outlet pool through the outlet pipe, completing the denitrification of nitrate wastewater.

2. The method of enhancing the denitrification performance of an iron autotrophic denitrification biological filter using immobilized biochar according to claim 1, characterized in that: The grinding fineness of the biochar screened was 40 mesh.

3. The method of enhancing the denitrification performance of an iron autotrophic denitrification biofilter using immobilized biochar according to claim 1, characterized in that: The water inlet process of the reactor water inlet end is as follows: one end of the first water inlet pipe is connected to the water inlet pool, and the other end is connected to the peristaltic pump; one end of the second water inlet pipe is connected to the peristaltic pump, and the other end is connected to the reactor water inlet.

4. The method of enhancing the denitrification performance of an iron autotrophic denitrification biofilter using immobilized biochar according to claim 1, characterized in that: After acclimation, anaerobic microorganisms aggregate on the surface of immobilized biochar to form a biofilm.

5. A biofilter for strengthening iron autotrophic denitrification using immobilized biochar, characterized in that: The denitrification efficiency of nitrate wastewater reaches over 86%, and the reaction cycle is 1 day.

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