A method for regulating the enrichment of denitrification functional bacteria in microaerobic sludge bed by zero-valent iron

Abstract

The present invention relates to a method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed by zero-valent iron, which belongs to the technical field of sewage treatment and solves the technical problems of insufficient carbon source in the existing treatment of low carbon-nitrogen ratio wastewater, resulting in a long startup cycle and poor denitrification capacity. The solution is: a method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed by zero-valent iron, in which different concentrations of green synthetic zero-valent iron are added in stages during the startup period of the microaerobic sludge bed treating wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration, so as to enrich different denitrification functional bacteria. On the 1st to 15th day of the startup period, 100-140 mmol / L of green synthesized zero-valent iron is added every 1-2 days; on the 16th to 30th day, 230-280 mmol / L of green synthesized zero-valent iron is added every 1-2 days; on the 31st to 45th day, 20-30 mmol / L of green synthesized zero-valent iron is added every 1-2 days; on the 46th to 55th day, 7-12 mmol / L of green synthesized zero-valent iron is added every 1-2 days. Compared with the prior art, the present invention has the advantages of enriching different denitrification functional bacteria in stages, improving nitrogen removal rate, shortening startup time, and being green and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed with zero-valent iron. Background Art

[0002] Microaerobic sludge bed is a static bed system that operates under the condition of dissolved oxygen less than 0.5mg / L. Due to the low oxygen demand, it has the characteristics of energy saving. Microaerobic biological treatment system allows a variety of functional bacteria with different physiological and ecological characteristics to grow and multiply in the same reaction system. These bacteria can effectively remove chemical oxygen demand (COD) through the metabolism of chemoheterotrophic bacteria, and have multiple denitrification mechanisms such as nitrification and denitrification, short-range nitrification and denitrification, anaerobic ammonia oxidation, and denitrification and polyphosphate. This diversity makes microaerobic biological treatment technology have great potential in biological denitrification efficiency. In addition, biological denitrification in a microaerobic environment significantly reduces the demand for organic carbon sources, which reduces the cost of adding external carbon sources when the carbon content of low-carbon wastewater is low. In addition, microaerobic biological treatment technology also has the advantages of low power consumption and low residual sludge production, which further reduces the treatment cost.

[0003] The low dissolved oxygen state of the microaerobic sludge bed allows aerobic bacteria, facultative bacteria and anaerobic bacteria to coexist in the same reaction device, forming sludge flocs with nitrifying bacteria on the outer layer and denitrifying bacteria on the inner layer. This special bacterial community structure is conducive to the collaboration of denitrifying bacteria with different functions. However, in large-scale applications, due to the low sludge production of microaerobic sludge bed technology, the source of seed sludge is relatively scarce. The full nitrification and denitrification process produces a large amount of sludge, but when the sludge of the full nitrification and denitrification process is used as seed sludge to start the microaerobic sludge bed to treat wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration, the sludge of the full nitrification and denitrification process contains a large number of nitrite oxidizing bacteria and heterotrophic denitrifying bacteria, which does not meet the sludge characteristics of multi-bacteria collaboration unique to the microaerobic sludge bed. Therefore, when treating wastewater with a low carbon-nitrogen ratio, there are shortcomings such as insufficient carbon source, long startup cycle, and the denitrification capacity needs to be improved. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art and solve the technical problems of long startup period and poor denitrification capacity caused by insufficient carbon source in the existing treatment of low carbon-nitrogen ratio wastewater, the present invention provides a method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed with zero-valent iron.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed by using zero-valent iron. In the start-up period of treating wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration in a microaerobic sludge bed, different concentrations of green synthesized zero-valent iron are added in stages to enrich different denitrification functional bacteria.

[0007] During the 1st to 15th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 100-140 mmol / L of green synthesized zero-valent iron is added every 1-2 days; during the 16th to 30th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 230-280 mmol / L of green synthesized zero-valent iron is added every 1-2 days; during the 31st to 45th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 20-30 mmol / L of green synthesized zero-valent iron is added every 1-2 days; during the 46th to 55th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 7-12 mmol / L of green synthesized zero-valent iron is added every 1-2 days.

[0008] Furthermore, the seed sludge used in the micro-aerobic sludge bed to treat wastewater with a low carbon-nitrogen ratio and ammonia nitrogen concentration is sludge from a full nitrification and denitrification process.

[0009] Furthermore, the micro-aerobic sludge bed is a static bed system, and the micro-aerobic sludge bed adopts a bubble-free aeration method.

[0010] Furthermore, the dissolved oxygen concentration of the microaerobic sludge bed is 0.1-0.5 mg / L, the suspended solids concentration of the mixed liquor in the microaerobic sludge bed is 4000-8000 mg / L, and the volatile suspended solids concentration of the mixed liquor in the microaerobic sludge bed is 2500-4500 mg / L.

[0011] Furthermore, the carbon-nitrogen ratio of the low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater is less than 3, and the ammonia nitrogen concentration is not more than 60 mg / L.

[0012] Furthermore, the green synthetic zero-valent iron preparation method is as follows: drying and crushing agricultural waste containing polyphenols and mixing it with water in a solid-liquid ratio of agricultural waste containing polyphenols: water = 20g-50g:1L, heating and leaching in a water bath at 50-80°C, centrifuging it in a centrifuge, taking the supernatant and filtering it to obtain a polyphenol extract; adding the polyphenol extract to a ferric chloride solution under nitrogen protection to obtain a zero-valent iron suspension, drying the zero-valent iron suspension under vacuum conditions and grinding it into powder to obtain green synthetic zero-valent iron.

[0013] Furthermore, the polyphenol-containing agricultural waste includes one of winery lees, persimmon peel, banana peel or grapefruit peel.

[0014] Furthermore, the rotation speed of the centrifuge is 7000-13000r / min.

[0015] Furthermore, the concentration of the ferric chloride solution is 0.05-0.2 mol / L.

[0016] The beneficial effects achieved by the present invention are:

[0017] According to the different sensitivity effects of the activity of denitrifying functional bacteria to green synthesized zero-valent iron, the present invention adds different concentrations of green synthesized zero-valent iron in stages during the start-up period of treating low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater in a microaerobic sludge bed, thereby enriching different types of denitrifying functional bacteria in stages: in the early start-up period of treating low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater in a microaerobic sludge bed, the iron is added according to the inhibitory concentration of iron on nitrite oxidizing bacteria and heterotrophic denitrifying bacteria; in the late start-up period of treating low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater in a microaerobic sludge bed, the iron is added according to the promoting concentration of iron on ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria;

[0018] Green synthetic zero-valent iron is selected because it contains a large number of active groups such as hydroxyl and carboxyl groups. Hydroxyl and carboxyl groups have reducing ability, which can further reduce nitrates in the micro-aerobic sludge bed to treat wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, ultimately improving the nitrogen removal rate of the micro-aerobic sludge bed to treat wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, and shortening the startup time;

[0019] The hydroxyl groups of green synthesized zero-valent iron can interact with the phospholipid molecules in the cell membrane of microorganisms in microaerobic activated sludge, causing changes in the arrangement of phospholipid molecules, thereby affecting the permeability and fluidity of the cell membrane, increasing the amount of iron ions outside the cell membrane entering the cell, and thus increasing the iron content in the microaerobic activated sludge; in addition, the carboxyl groups of green synthesized zero-valent iron can form coordination bonds with iron ions to form stable iron compounds.

[0020] Agricultural waste containing polyphenols is green and environmentally friendly, which reduces the pollution risk in the preparation process, realizes a green and environmentally friendly preparation process, and reduces the preparation cost.

[0021] Compared with the prior art, the present invention has the advantages of enriching different denitrification functional bacteria in stages, improving nitrogen removal rate, shortening start-up time, and being green and environmentally friendly. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Example

[0023] A method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed by using zero-valent iron, wherein different concentrations of green synthesized zero-valent iron are added in stages during the start-up period of the microaerobic sludge bed for treating wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration, so as to enrich different denitrification functional bacteria.

[0024] In this embodiment, the winery lees are dried and crushed and then mixed with water according to the solid-liquid ratio of winery lees: water = 40g:1L. The winery lees are green and environmentally friendly, reducing the pollution risk in the preparation process, realizing a green and environmentally friendly preparation process, and reducing the preparation cost. Heat extraction under 70°C water bath conditions, centrifuge and take the supernatant for suction filtration to obtain a polyphenol extract, the speed of the centrifuge is 10000r / min; the polyphenol extract is slowly added to a 0.1mol / L ferric chloride solution under nitrogen protection to obtain a zero-valent iron suspension; the zero-valent iron suspension is dried and ground into powder under vacuum conditions at 100°C to obtain green synthesized zero-valent iron.

[0025] In a micro-aerobic sludge bed with an effective volume of 5L, sludge from the full nitrification and denitrification process is added as seed sludge for micro-aerobic sludge bed treatment, and the suspended solids concentration of the mixed liquor in the micro-aerobic sludge bed is maintained at 5500mg / L, and the volatile suspended solids concentration of the mixed liquor is maintained at 3000mg / L; the micro-aerobic sludge bed is a static bed system, the hydraulic retention time is 24 hours, and a bubble-free reoxygenation method with aeration reflux and oxygen supply by an external aeration pump is adopted. The inlet water of the micro-aerobic sludge bed is distribution water, the carbon-nitrogen ratio of the wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration is 2, the COD concentration is 120mg / L, and the ammonia nitrogen concentration is 60mg / L.

[0026] During the 1st to 15th days of the start-up period of the micro-aerobic sludge bed for treating wastewater with a low carbon-nitrogen ratio and low ammonia-nitrogen concentration, i.e., stage 1, 130 mmol / L of green synthesized zero-valent iron was added every other day; during the 16th to 30th days of the start-up period of the micro-aerobic sludge bed for treating wastewater with a low carbon-nitrogen ratio and low ammonia-nitrogen concentration, i.e., stage 2, 260 mmol / L of green synthesized zero-valent iron was added every other day; during the 31st to 45th days of the start-up period of the micro-aerobic sludge bed for treating wastewater with a low carbon-nitrogen ratio and low ammonia-nitrogen concentration, i.e., stage 3, 25 mmol / L of green synthesized zero-valent iron was added every 1-2 days; during the 46th to 55th days of the start-up period of the micro-aerobic sludge bed for treating wastewater with a low carbon-nitrogen ratio and low ammonia-nitrogen concentration, i.e., stage 4, 10 mmol / L of green synthesized zero-valent iron was added every 1-2 days.

[0027] According to the results of previous studies, the sensitivity of green synthesized zero-valent iron to short-term exposure is in the order of ANAMMOX bacteria (5.11mmol / L) > AOB bacteria (16.2mmol / L) > NOB bacteria (24.3mmol / L) > heterotrophic denitrifying bacteria (51.4mmol / L). In the early stage of the start-up period of the microaerobic sludge bed treatment of low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater, iron is added according to the inhibitory concentration of nitrite oxidizing bacteria and heterotrophic denitrifying bacteria. In the late stage of the start-up period of the microaerobic sludge bed treatment of low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater, iron is added according to the promoting concentration of ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria.

[0028] The real-time fluorescence quantitative polymerase chain reaction was performed on the sludge of the whole nitrification and denitrification process before the start of the micro-aerobic sludge bed to treat the wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration and the initial sludge at the end of each stage. The results showed that the amoA gene copy number representing the number of AOB, the gene copy number representing the number of NOB, the gene copy number representing the number of ANAMMOX bacteria, and the gene copy number representing the number of heterotrophic denitrifiers in the sludge of the whole nitrification and denitrification process were 8.09×10 1 copies / ngDNA,7.42×10 1 copies / ngDNA, 1.51×10 3 copies / ngDNA, 1.26×10 1 copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 1 were 6.17×10 1 copies / ngDNA, 5.92×10 1 copies / ngDNA, 1.07×10 3 copies / ngDNA,0.99×10 1 copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 2 were 5.67×10 1 copies / ngDNA, 5.26×10 1 copies / ngDNA, 0.86×10 3 copies / ngDNA, 0.75×10 1 copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 3 were 9.66×10 1 copies / ngDNA,4.13×10 1 copies / ngDNA, 1.32×10 3 copies / ngDNA, 0.69×10 1copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 4 were 10.06×10 1 copies / ngDNA, 3.77×10 1 copies / ngDNA, 2.08×10 3 copies / ngDNA, 0.61×10 1 From the results, it can be clearly seen that the amoA gene copy number characterizing the number of AOB first decreases from stage 1 to stage 2, and continues to increase in stages 3 and 4, the gene copy number characterizing the number of NOB has been decreasing from stage 1 to stage 4, the gene copy number characterizing the number of ANAMMOX bacteria first decreases from stage 1 to stage 2, and continues to increase in stages 3 and 4, and the gene copy number characterizing the number of heterotrophic denitrifiers has been decreasing from stage 1 to stage 4. At the end of the culture, the gene copy number characterizing AOB and ANAMMOX is finally increased, and the gene copy number characterizing NOB and heterotrophic denitrifiers is suppressed, thereby satisfying the staged enrichment of denitrification functional bacteria of different functional types.

[0029] After the start-up of the microaerobic sludge bed for treating wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, the effluent ammonia nitrogen concentration and the effluent total nitrogen concentration of stage 1, stage 2, stage 3 and stage 4 were measured respectively. The effluent ammonia nitrogen concentration of stage 1, stage 2, stage 3 and stage 4 were 28 mg / L, 35 mg / L, 10 mg / L and 2 mg / L respectively, and the effluent total nitrogen concentration of stage 1, stage 2, stage 3 and stage 4 were 38 mg / L, 46 mg / L, 21 mg / L and 11 mg / L respectively. It can be seen that the final nitrogen removal rate increased significantly, which is mainly due to the fact that the green synthesized zero-valent iron contains a large number of active groups such as hydroxyl and carboxyl groups. The hydroxyl and carboxyl groups have reducing ability, which further reduce the nitrate of the microaerobic sludge bed for treating wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, and finally improve the nitrogen removal rate of the microaerobic sludge bed for treating wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration. In addition, compared with other micro-aerobic sludge beds that use sludge from the full nitrification and denitrification process as seed sludge to start treating wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration, the startup time is significantly shortened. Example

[0030] A method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed by using zero-valent iron, wherein different concentrations of green synthesized zero-valent iron are added in stages during the start-up period of the microaerobic sludge bed for treating wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration, so as to enrich different denitrification functional bacteria.

[0031] In this embodiment, the persimmon peel is dried and crushed and then mixed with water according to the solid-liquid ratio of persimmon peel: water = 30g: 1L. The persimmon peel is green and environmentally friendly, which reduces the pollution risk in the preparation process, realizes a green and environmentally friendly preparation process, and reduces the preparation cost. Heat and extract under 80°C water bath conditions, centrifuge and take the supernatant for suction filtration to obtain a polyphenol extract, the speed of the centrifuge is 10000r / min; the polyphenol extract is slowly added to a 0.2mol / L ferric chloride solution under nitrogen protection to obtain a zero-valent iron suspension; the zero-valent iron suspension is dried and ground into powder under vacuum conditions at 100°C to obtain green synthesized zero-valent iron.

[0032] In a micro-aerobic sludge bed with an effective volume of 5L, sludge from the full nitrification and denitrification process is added as seed sludge for micro-aerobic sludge bed treatment, and the suspended solids concentration of the mixed liquor in the micro-aerobic sludge bed is maintained at 4500mg / L, and the volatile suspended solids concentration of the mixed liquor is maintained at 2600mg / L; the micro-aerobic sludge bed is a static bed system, the hydraulic retention time is 24 hours, and a bubble-free reoxygenation method with aeration reflux and oxygen supply by an external aeration pump is adopted. The inlet water of the micro-aerobic sludge bed is distribution water, the carbon-nitrogen ratio of the wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration is 1, the COD concentration is 60mg / L, and the ammonia nitrogen concentration is 60mg / L.

[0033] During the 1st to 15th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, i.e., stage 1, 100 mmol / L of green synthesized zero-valent iron was added every 2 days; during the 16th to 30th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, i.e., stage 2, 240 mmol / L of green synthesized zero-valent iron was added every 2 days; during the 31st to 45th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, i.e., stage 3, 22 mmol / L of green synthesized zero-valent iron was added every 2 days; during the 46th to 55th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, i.e., stage 4, 8 mmol / L of green synthesized zero-valent iron was added every 1 day.

[0034] According to the results of previous studies, the sensitivity of green synthesized zero-valent iron to short-term exposure is in the order of ANAMMOX bacteria (5.11mmol / L) > AOB bacteria (16.2mmol / L) > NOB bacteria (24.3mmol / L) > heterotrophic denitrifying bacteria (51.4mmol / L). In the early stage of the start-up period of the microaerobic sludge bed treatment of low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater, iron is added according to the inhibitory concentration of nitrite oxidizing bacteria and heterotrophic denitrifying bacteria. In the late stage of the start-up period of the microaerobic sludge bed treatment of low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater, iron is added according to the promoting concentration of ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria.

[0035] The real-time fluorescence quantitative polymerase chain reaction was performed on the sludge of the whole nitrification and denitrification process before the start of the micro-aerobic sludge bed to treat the wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration and the initial sludge at the end of each stage. The results showed that the amoA gene copy number representing the number of AOB, the gene copy number representing the number of NOB, the gene copy number representing the number of ANAMMOX bacteria, and the gene copy number representing the number of heterotrophic denitrifiers in the sludge of the whole nitrification and denitrification process were 7.55×10 1 copies / ngDNA,7.01×10 1 copies / ngDNA, 1.36×10 3 copies / ngDNA,1.17×10 1 copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 1 were 6.03×10 1 copies / ngDNA,5.88×10 1 copies / ngDNA, 1.01×10 3 copies / ngDNA, 0.92×10 1 copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 2 were 5.54×10 1 copies / ngDNA,5.07×10 1 copies / ngDNA, 0.81×10 3 copies / ngDNA, 0.67×10 1 copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 3 were 9.98×10 1 copies / ngDNA, 4.24×10 1 copies / ngDNA, 1.47×10 3 copies / ngDNA, 0.62×10 1copies / ngDNA; the number of amoA gene copies representing the number of AOB, the number of NOB genes, the number of ANAMMOX genes, and the number of heterotrophic denitrifying bacteria in the initial sludge at the end of stage 4 were 10.23×10 1 copies / ngDNA, 3.45×10 1 copies / ngDNA,1.99×10 3 copies / ngDNA,0.58×10 1 From the results, it can be clearly seen that the amoA gene copy number characterizing the number of AOB first decreases from stage 1 to stage 2, and continues to increase in stages 3 and 4, the gene copy number characterizing the number of NOB has been decreasing from stage 1 to stage 4, the gene copy number characterizing the number of ANAMMOX bacteria first decreases from stage 1 to stage 2, and continues to increase in stages 3 and 4, and the gene copy number characterizing the number of heterotrophic denitrifiers has been decreasing from stage 1 to stage 4. At the end of the culture, the gene copy number characterizing AOB and ANAMMOX is finally increased, and the gene copy number characterizing NOB and heterotrophic denitrifiers is suppressed, thereby satisfying the staged enrichment of denitrification functional bacteria of different functional types.

[0036] After the start-up of the micro-aerobic sludge bed for treating wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, the effluent ammonia nitrogen concentration and the effluent total nitrogen concentration of stage 1, stage 2, stage 3 and stage 4 were measured respectively. The effluent ammonia nitrogen concentration of stage 1, stage 2, stage 3 and stage 4 were 24 mg / L, 31 mg / L, 9 mg / L and 1.8 mg / L respectively, and the effluent total nitrogen concentration of stage 1, stage 2, stage 3 and stage 4 were 31 mg / L, 42 mg / L, 20 mg / L and 10 mg / L respectively. It can be seen that the final nitrogen removal rate increased significantly, which is mainly due to the fact that the green synthesized zero-valent iron contains a large number of active groups such as hydroxyl and carboxyl groups. The hydroxyl and carboxyl groups have reducing ability, which further reduce the nitrate of the micro-aerobic sludge bed for treating wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, and finally improve the nitrogen removal rate of the micro-aerobic sludge bed for treating wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration. In addition, compared with other micro-aerobic sludge beds that use sludge from the full nitrification and denitrification process as seed sludge to start treating wastewater with a low carbon-nitrogen ratio and low ammonia nitrogen concentration, the startup time is significantly shortened.

[0037] The above describes in detail the implementation modes of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes. The implementation modes can still be changed within the knowledge scope of ordinary technicians in the field. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for regulating the enrichment of denitrification functional bacteria in a microaerobic sludge bed by zero-valent iron, characterized in that: During the start-up period of the micro-aerobic sludge bed to treat wastewater with low carbon-nitrogen ratio and low ammonia nitrogen concentration, different concentrations of green synthetic zero-valent iron are added in stages to enrich different denitrification functional bacteria. During the 1st to 15th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 100-140 mmol / L of green synthesized zero-valent iron is added every 1-2 days; during the 16th to 30th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 230-280 mmol / L of green synthesized zero-valent iron is added every 1-2 days; during the 31st to 45th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 20-30 mmol / L of green synthesized zero-valent iron is added every 1-2 days; during the 46th to 55th days of the start-up period of treating wastewater with low carbon-nitrogen ratio and low ammonia-nitrogen concentration in the microaerobic sludge bed, 7-12 mmol / L of green synthesized zero-valent iron is added every 1-2 days.

2. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 1, characterized in that: The seed sludge used in the micro-aerobic sludge bed to treat wastewater with a low carbon-nitrogen ratio and ammonia nitrogen concentration is sludge from a full-process nitrification and denitrification process.

3. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 1, characterized in that: The micro-aerobic sludge bed is a static bed system, and the micro-aerobic sludge bed adopts a bubble-free aeration method.

4. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 1, characterized in that: The dissolved oxygen concentration of the microaerobic sludge bed is 0.1-0.5 mg / L, the suspended solids concentration of the mixed liquor in the microaerobic sludge bed is 4000-8000 mg / L, and the volatile suspended solids concentration of the mixed liquor in the microaerobic sludge bed is 2500-4500 mg / L.

5. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 1, characterized in that: The carbon-nitrogen ratio of the low carbon-nitrogen ratio and low ammonia nitrogen concentration wastewater is less than 3, and the ammonia nitrogen concentration is not more than 60 mg / L.

6. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 1, characterized in that: The green synthetic zero-valent iron preparation method is as follows: drying and crushing agricultural waste containing polyphenols, mixing the mixture with water according to a solid-liquid ratio of agricultural waste containing polyphenols: water = 20g-50g:1L, heating and leaching in a water bath at 50-80°C, centrifuging in a centrifuge, and filtering the supernatant to obtain a polyphenol extract; The polyphenol extract is added to a ferric chloride solution under nitrogen protection to obtain a zero-valent iron suspension, and the zero-valent iron suspension is dried and ground into powder under vacuum conditions to obtain green synthesized zero-valent iron.

7. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 6, characterized in that: The polyphenol-containing agricultural waste includes one of winery lees, persimmon peels, banana peels or grapefruit peels.

8. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 6, characterized in that: The rotation speed of the centrifuge is 7000-13000r / min.

9. The method for enriching functional bacteria in a microaerobic sludge bed by regulating denitrification by zero-valent iron according to claim 6, characterized in that: The concentration of the ferric chloride solution is 0.05-0.2 mol / L.