A method for regulating denitrifying functional bacteria in a micro-aerobic sludge bed and the micro-aerobic sludge bed

Abstract

The present invention relates to a method for regulating the denitrifying functional flora of a micro-aerobic sludge bed and a micro-aerobic sludge bed, belonging to the technical field of sewage treatment. It solves the technical problems that using commercial-grade nano zero-valent iron to regulate the flora is expensive and flammable, and it is difficult to control the release of iron ions when adding sponge iron. The solution is as follows: In the startup stage, zero-valent iron green-synthesized from agricultural waste is added to the micro-aerobic sludge bed to regulate the denitrifying functional flora of the micro-aerobic sludge bed. The micro-aerobic sludge bed includes a reactor, and packing balls are placed in the reactor. The packing balls include an outer shell and a content located inside the outer shell; the content is loaded with zero-valent iron green-synthesized from agricultural waste. The present invention synthesizes zero-valent iron through the extract of agricultural waste, reducing the pollution risk in the preparation process and the preparation cost. It avoids the disadvantages of commercial-grade nano zero-valent iron such as lack of stability and difficulty in separating from the purified medium, reduces particle aggregation, and improves the effectiveness of zero-valent iron.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a method for regulating denitrifying functional bacteria in a micro-aerobic sludge bed and a micro-aerobic sludge bed. Background Art

[0002] Achieving energy conservation and consumption reduction in sewage treatment plants themselves is an important measure. As an energy-intensive industry, the electricity consumption of sewage treatment plants accounts for 60% - 70% of the total energy consumption, and the removal of nitrogen is a key and difficult content in sewage treatment. Most sewage treatment plants in China adopt aerobic activated sludge method as the core treatment method, and its aeration system has extremely high energy consumption. The micro-aerobic denitrification process has been extensively studied and applied because it only requires extremely low dissolved oxygen. However, in the micro-aerobic denitrification process, microorganisms grow slowly, the start-up time is long, the content of functional bacteria is low, and the denitrification efficiency needs to be improved.

[0003] Iron can enhance the activity of denitrifying microorganisms. Zero-valent iron can improve the activities of two nitrifying enzymes, ammonia monooxygenase and nitrite oxidase of nitrifying bacteria, promote the denitrification ability of iron-type denitrifying bacteria and hydrogen autotrophic denitrifying bacteria, and promote the synthesis of heme in the cells of anaerobic ammonia-oxidizing bacteria. Therefore, adding zero-valent iron to the micro-aerobic biological denitrification process can improve the denitrification efficiency. However, due to the magnetic property and extremely high reducibility of zero-valent iron, it is prone to aggregation, precipitation, and oxidation, so it is difficult to control its position and state in the reactor.

[0004] Currently, there are roughly the following ways to add zero-valent iron: directly adding nano- or micro-scale zero-valent iron into water, or directly adding sponge iron. However, commercial nano zero-valent iron is expensive and flammable, and directly adding sponge iron has a large dosage and it is difficult to control the release of iron ions. Therefore, it is difficult to achieve the promoting effect of zero-valent iron at the optimal concentration on denitrifying microorganisms. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art, and provide a method for regulating denitrifying functional bacteria in a micro-aerobic sludge bed and a micro-aerobic sludge bed, which solves the technical problems such as the high price and flammability of using commercial nano zero-valent iron to regulate bacteria and the difficulty in controlling the release of iron ions by adding sponge iron.

[0006] To solve the above problems, the technical solution of the present invention is: a method for regulating denitrifying functional bacteria in a micro-aerobic sludge bed. In the startup stage, zero-valent iron green-synthesized from agricultural waste is added to the micro-aerobic sludge bed to regulate the denitrifying functional bacteria in the micro-aerobic sludge bed; for wastewater with a carbon-nitrogen ratio lower than 3 and an ammonia nitrogen concentration lower than 100 mg / L, zero-valent iron green-synthesized with a content of hydroxyl and carboxyl groups greater than 60% is added.

[0007] Optionally, for wastewater with a carbon-nitrogen ratio greater than or equal to 3 and an ammonia-nitrogen concentration higher than 100 mg / L, green synthesized zero-valent iron with a concentration of hydroxyl and carboxyl groups less than 30% is added.

[0008] With the above settings, due to the different types and contents of extracts from different raw material waste crops, the green synthesized zero-valent iron varies in terms of structure, elemental contents such as iron content, stability, and removal efficiency, and also has different effects on micro-aerobic activated sludge. Therefore, based on the different effects of zero-valent iron synthesized from extracts of different crops on micro-aerobic activated sludge, this difference is utilized to enrich and cultivate different functional bacterial communities, enabling different denitrifying functional bacterial communities to have relatively fixed ecological niches in the micro-aerobic sludge bed for treating wastewater with different water qualities. This increases the abundance of functional bacterial communities in different ecological niches, strengthens the cooperation between the bacterial communities, and enhances the denitrification efficiency in the micro-aerobic sludge bed. According to the water quality characteristics, different types of green synthesized zero-valent iron are flexibly added to achieve the regulation of denitrifying functional bacterial communities in the micro-aerobic sludge bed suitable for different water qualities.

[0009] Optionally, the agricultural waste includes one of winery dregs, persimmon peels, banana peels, and pomelo peels.

[0010] Optionally, the preparation steps of zero-valent iron green synthesized from agricultural waste include:

[0011] Step 1, extract reducing substances: After crushing the agricultural waste, it is mixed with water in a ratio of agricultural waste: water = 20g - 50g: 1L and heated under a water bath condition of 50°C - 80°C to prepare a polyphenol solution with reducing properties.

[0012] Step 2, mixing reaction: A liquid containing 0.05mol / L - 0.2mol / L of Fe 3+ or Fe 2+ is mixed with the same volume of the polyphenol solution, and Fe 3+ and Fe 2+ are reduced to zero-valent iron by the reducing property of the polyphenol solution, thereby generating nano zero-valent iron.

[0013] Optionally, the filler balls are immersed in the prepared zero-valent iron solution, taken out, and suspended in the micro-aerobic sludge bed for use.

[0014] Another object of the present invention is to provide a micro-aerobic sludge bed, which includes a reactor. Filler balls are placed in the reactor. The filler balls include an outer shell and a content located inside the outer shell; the content is made of a porous and water-absorbing material, and the content is loaded with the above-mentioned zero-valent iron green synthesized from agricultural waste.

[0015] Optionally, the reactor is provided with a sewage inlet, a sludge taking port, a water taking port, and a water outlet; the water outlet is connected to a reflux pool.

[0016] Optionally, a water outlet pipe for discharging a part of the fully aerated return water is provided on the return flow pool, the water outlet pipe is connected to the sewage inlet through a pipeline, and a return pump is arranged on the pipeline.

[0017] Optionally, there are several packing balls, and the several packing balls are suspended in the reactor through connecting ropes, and adjacent packing balls are connected through connecting ropes.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. The zero-valent iron green synthesized from agricultural waste can efficiently remove pollutants such as nitrate in sewage, and improve the pollutant removal efficiency of the effluent.

[0020] 2. The green synthesized zero-valent iron has higher environmental protection, economy, efficiency and stability, and has good biocompatibility with the activated sludge in the micro-aerobic sludge bed.

[0021] 3. The working principle of a method for regulating the denitrifying functional flora in the micro-aerobic sludge bed of the present invention is as follows: Since the types and concentrations of reducing substances extracted from different agricultural wastes are different, the green synthesized zero-valent iron has different crystal forms, different hydroxyl and carboxyl contents, as well as different particle sizes, specific surface areas and surface charges. Therefore, the effects on the functional microorganisms in the activated sludge are different, and different functional microorganisms are suitable for treating different water qualities. Therefore, the present invention realizes the enrichment of suitable functional flora for different water qualities by immersing the water-absorbing sponge or polyurethane in the zero-valent iron filler ball into zero-valent iron with different structures.

[0022] 4. The present invention synthesizes zero-valent iron through the extract of agricultural waste. Since the use of traditional reducing agents such as toxic hydroborides and hydrazines is avoided, the pollution risk in the preparation process is reduced, and a green and environmentally friendly preparation process is realized. At the same time, the preparation cost is reduced. In addition, the green synthesized nano zero-valent iron has low toxicity and good biocompatibility, avoiding some disadvantages of commercial nano zero-valent iron itself, such as lack of stability and difficulty in separating from the purified medium, reducing particle aggregation, and improving the effectiveness of zero-valent iron. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the zero-valent iron-upflow sludge bed micro-aerobic denitrification process in Example 4;

[0024] Figure 2 It is a sectional view of the zero-valent iron-upflow sludge bed micro-aerobic denitrification process in Example 4;

[0025] Figure 3 It is a schematic connection diagram of the reactor and the return flow pool in Example 4.

[0026] Reference numerals: 1, reactor; 11, sewage inlet; 12, sludge extraction port; 13, water intake; 14, water outlet; 2, packing ball; 21, outer shell; 22, content; 3, reflux tank; 31, outlet pipe; 4, reflux pump; 41, pipeline; 5, connecting rope. Detailed implementation mode

[0027] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0028] Embodiment 1: This embodiment provides a method for regulating the denitrifying functional bacteria in a micro-aerobic sludge bed. In the startup stage, zero-valent iron green-synthesized from agricultural waste is added to the micro-aerobic sludge bed to regulate the denitrifying functional bacteria in the micro-aerobic sludge bed.

[0029] In this embodiment, 40 g of grape seed waste is taken and added to 1 L of water. It is heated at 70 °C for 2 hours. After filtration, a 0.2 M ferric chloride solution is added to the supernatant. After the solution reacts and turns black, the packing ball is immersed in the solution for 3 minutes, and then the packing ball loaded with zero-valent iron solution is hung in the reactor.

[0030] The influent is wastewater with a COD concentration of 70 mg / L, a carbon-nitrogen ratio of 2, and an ammonia-nitrogen concentration of 35 mg / L. The influent pump pumps the wastewater into the reactor from the reactor inlet. The wastewater flows through the reactor and the packing ball loaded with zero-valent iron. The zero-valent iron promotes the microbial activity to complete the metabolism of microorganisms, thereby achieving the purpose of wastewater treatment. The treated water flows into the reflux tank from the reactor outlet. After the effluent is fully aerated in the reflux tank, the reflux pump returns part of the fully aerated return water and the influent to the reactor from the reactor inlet for oxygen supply, and the remaining water is discharged. The discharged water has a COD concentration of 20 mg / L, an ammonia-nitrogen concentration of 3 mg / L, and a TN concentration of 10 mg / L.

[0031] The zero-valent iron promotes the biological activity of micro-aerobic microorganisms, and at the same time, the zero-valent iron packing provides a place for the micro-aerobic microorganisms to attach and grow, thereby accelerating the removal of pollutants in the wastewater.

[0032] In the startup stage, zero-valent iron green-synthesized from agricultural waste is added to the micro-aerobic sludge bed. When treating wastewater with a carbon-nitrogen ratio lower than 3 and an ammonia-nitrogen concentration lower than 100 mg / L, green-synthesized zero-valent iron with more hydroxyl and carboxyl groups is added, which effectively alleviates the problem of sludge bulking when treating wastewater with a low carbon-nitrogen ratio and a low ammonia-nitrogen concentration, increases the sludge particle size, and the hydroxyl groups of the green-synthesized zero-valent iron can interact with the phospholipid molecules in the cell membrane, resulting in changes in the arrangement of phospholipid molecules, thereby affecting the permeability and fluidity of the cell membrane, increasing the content of iron ions outside the cell membrane entering the cell, and increasing the abundance and activity of autotrophic bacteria.

[0033] Example 2: This example provides a method for regulating the denitrifying functional bacteria in a micro-aerobic sludge bed. A wastewater experiment with a carbon-nitrogen ratio of 3 and an ammonia-nitrogen concentration higher than 100 mg / L was carried out in the same micro-aerobic sludge bed as in Example 1. Take 50 g of pomelo peel waste, add it to 1 L of water, heat it at 70 °C for 2 hours, filter it, add 0.1 M ferric chloride solution to the supernatant. After the solution reacts and turns black, immerse the packing balls into the solution for 3 minutes, and then hang the packing balls loaded with zero-valent iron solution into the reactor.

[0034] Change the influent conditions to wastewater with a COD concentration of 330 mg / L, a carbon-nitrogen ratio of 3, and an ammonia-nitrogen concentration of 110 mg / L. The influent pump pumps the wastewater from the influent port of the reactor into the reactor, flowing through the reactor and the packing balls loaded with zero-valent iron. The zero-valent iron promotes the microbial activity to complete the metabolism of microorganisms so as to achieve the purpose of wastewater treatment. The treated water flows into the reflux pool from the effluent port. After the effluent is fully aerated in the reflux pool, part of the fully aerated return water and the influent are pumped back into the reactor from the influent port by the reflux pump for oxygen supply, and the remaining water is discharged. The discharged water has a COD concentration of 30 mg / L, an ammonia-nitrogen concentration of 4.2 mg / L, and a TN concentration of 12 mg / L.

[0035] The zero-valent iron promotes the biological activity of micro-aerobic microorganisms, and at the same time, the zero-valent iron packing provides a place for the micro-aerobic microorganisms to attach and grow, thereby accelerating the removal of pollutants in the wastewater.

[0036] In the startup stage, zero-valent iron green synthesized from agricultural waste is added to the micro-aerobic sludge bed. When treating wastewater with a carbon-nitrogen ratio of 3 and an ammonia-nitrogen concentration higher than 100 mg / L, since the carbon-nitrogen ratio meets the requirements of heterotrophic denitrification and the denitrification effect is good, the main problem in this micro-aerobic sludge bed is the problem that the sludge is prone to expand under micro-aerobic conditions. In this example, the polyphenol content in pomelo peel is less, and the zero-valent iron synthesized carries fewer hydroxyl and carboxyl groups. However, pomelo peel contains various minerals and trace elements such as calcium, magnesium, phosphorus, zinc, copper, and manganese. Adding zero-valent iron synthesized from pomelo peel can not only provide trace elements for the activated sludge, but also effectively alleviate the problem that the sludge is prone to expand under micro-aerobic conditions and increase the removal efficiency.

[0037] Example 3: This example provides a method for regulating the denitrifying functional bacteria in a micro-aerobic sludge bed. A wastewater experiment with a carbon-nitrogen ratio greater than 3 and an ammonia-nitrogen concentration higher than 100 mg / L was carried out in the same micro-aerobic sludge bed as in Example 1. Take 40 g of pomelo peel waste, add it to 1 L of water, heat it at 80 °C for 2 hours, filter it, add 0.1 M ferric chloride solution to the supernatant. After the solution reacts and turns black, immerse the packing balls into the solution for 3 minutes, and then hang the packing balls loaded with zero-valent iron solution into the reactor.

[0038] Change the influent conditions to wastewater with a COD concentration of 385 mg / L, a carbon-nitrogen ratio of 3.5, and an ammonia-nitrogen concentration of 110 mg / L. The influent pump pumps the sewage from the influent port into the reactor, where it flows through the micro-aerobic sludge bed and the zero-valent iron packing balls. The zero-valent iron promotes the microbial activity to complete the metabolism of the microorganisms, thereby achieving the purpose of sewage treatment. The treated water flows into the reflux pool from the effluent port. After sufficient aeration in the reflux pool, a part of the fully aerated return water and the influent are pumped back into the reactor from the influent port by the reflux pump for oxygen supply, and the remaining water is discharged. The discharged water has a COD concentration of 37 mg / L, an ammonia-nitrogen concentration of 3.7 mg / L, and a TN concentration of 10.2 mg / L.

[0039] Example 4: As Figures 1 - 3 shown, this example provides a micro-aerobic sludge bed, including a reactor 1, in which packing balls 2 are placed. The packing balls 2 include a shell 21 and a content 22 located inside the shell 21; the content 22 is made of a porous and water-absorbent material, and the content 22 is loaded with zero-valent iron green-synthesized from agricultural waste described in any one of Examples 1-3.

[0040] In a micro-aerobic sludge bed of this example, the reactor 1 is provided with a sewage influent port 11, a sludge sampling port 12, a water sampling port 13, and an effluent port 14; the effluent port 14 is connected to the reflux pool 3.

[0041] In a micro-aerobic sludge bed of this example, the reflux pool 3 is provided with an outlet pipe 31 for the outflow of a part of the fully aerated return water. The outlet pipe 31 is connected to the sewage influent port 11 through a pipeline 41, and a reflux pump 4 is provided on the pipeline 41.

[0042] In a micro-aerobic sludge bed of this example, there are several packing balls 2. The several packing balls 2 are suspended in the reactor 1 by connecting ropes 5, and adjacent packing balls 2 are connected by connecting ropes 5.

[0043] In a micro-aerobic sludge bed of this example, the diameter of the reactor 1 is 10 cm and the height is 50 cm.

[0044] In a micro-aerobic sludge bed of this example, the shell 21 is made of plastic material, and the content 22 is sponge or polyurethane, etc., and its porous property is used to load zero-valent iron.

Claims

1. A method for regulating the denitrifying functional flora in a micro-aerobic sludge bed, characterized in that, In the startup stage, zero-valent iron green synthesized from agricultural waste is added to the micro-aerobic sludge bed to regulate the nitrogen-removing functional flora in the micro-aerobic sludge bed; for wastewater with a carbon-nitrogen ratio lower than 3 and an ammonia-nitrogen concentration lower than 100 mg / L, zero-valent iron green synthesized with a content of hydroxyl and carboxyl groups greater than 60% is added.

2. A method for regulating the denitrifying functional flora in a micro-aerobic sludge bed, characterized in that, In the startup stage, zero-valent iron green synthesized from agricultural waste is added to the micro-aerobic sludge bed to regulate the nitrogen-removing functional flora in the micro-aerobic sludge bed; for wastewater with a carbon-nitrogen ratio greater than or equal to 3 and an ammonia-nitrogen concentration higher than 100 mg / L, zero-valent iron green synthesized with a content of hydroxyl and carboxyl groups less than 30% is added.

3. A method for regulating the denitrifying functional flora in a micro-aerobic sludge bed according to claim 1 or 2, characterized in that The agricultural waste mentioned above includes one of winery lees, persimmon peels, banana peels, and pomelo peels.

4. A method for regulating the denitrifying functional flora in a micro-aerobic sludge bed according to claim 1 or 2, characterized in that The preparation steps of zero-valent iron green synthesized from agricultural waste include: Step 1, extracting reducing substances: After crushing the agricultural waste, it is mixed with water at a ratio of agricultural waste: water = 20 g - 50 g: 1 L, and heated under a water bath condition of 50 °C - 80 °C to prepare a polyphenol solution with reducibility; Step 2, Mixing reaction: Mix a liquid containing 0.05 mol / L - 0.2 mol / L of Fe 3+ or Fe 2+ with a polyphenol solution of the same volume. Through the reducing property of the polyphenol solution, Fe 3+ and Fe 2+ are reduced to zero-valent iron, thereby generating nano zero-valent iron.

5. A method for regulating the denitrifying functional flora in a micro-aerobic sludge bed according to claim 4, characterized in that, The packing balls are immersed in the prepared zero-valent iron solution, taken out, and suspended in the micro-aerobic sludge bed for use.

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