Suspended filler as well as preparation and use methods thereof

Abstract

The invention relates to the technical field of municipal sewage treatment and industrial wastewater treatment, in particular to suspended filler and a preparation and use method thereof. The suspended filler is prepared from the following components in parts by weight: 90 to 92 weight percent of high-density polyethylene, 4 to 5 weight percent of zeolite, 3.5 to 4 weight percent of activated carbon and 0.5 to 1 weight percent of talcum powder. The characteristics that zeolite and activated carbon are rough and porous are utilized, the surface characteristics of the filler are improved, the surface roughness and hydrophilicity are improved, and conditions are created for rapid attachment growth of microorganisms. According to the micro-tooth and hexagonal honeycomb design in the suspended filler disclosed by the invention, the surface area of the suspended filler is increased while the wear of the filler is avoided and the overall stability is improved, the formation of a good turbulent flow state is facilitated, and the contact efficiency of pollutants and microorganisms and the updating frequency of a biological membrane are improved. Each filler forms a relatively independent ecological system, so that the impact resistance of the system to environmental changes such as water quality and temperature is improved.

Description

Technical Field

[0001] The invention relates to the technical field of municipal sewage treatment and industrial wastewater treatment, and in particular to a suspended filler and a preparation and use method thereof. Background Art

[0002] With the continuous improvement of effluent standards and sewage collection rates in various regions, the demand for upgrading and expanding sewage treatment projects has become increasingly prominent. However, on the one hand, the traditional upgrading and expansion process has problems such as high requirements for project expansion land, tight reserved land, difficulty in land acquisition and demolition, and great financial pressure. On the other hand, the pollutant energy consumption of sewage treatment projects remains high, and the energy consumption is high and the cost is high. At the same time, the problem of handling and disposing of a large amount of activated sludge generated by sewage treatment has become an operational dilemma and even an operational bottleneck for sewage treatment projects, which needs to be solved urgently.

[0003] Moving-bed biofilm reactor is a membrane bioreactor that uses suspended fillers as biofilm carriers. Since the first productive sewage treatment plant based on KMT-MBBR process was established in STEINSHOLT, Norway in the 1990s, MBBR wastewater treatment process with suspended fillers as the core has been applied worldwide and has gradually developed into a simple, flexible and compact sewage treatment process. It can effectively utilize existing sewage treatment units such as A2O and improved AO for in-situ expansion and transformation, and has good process mosaic characteristics.

[0004] MBBR can improve the biological abundance in the unit reactor, improve the utilization rate of carbon sources, improve the efficiency of pollutant removal, strengthen the denitrification effect of the system, and reduce the output of activated sludge. In the MBBR reactor, the density of the filler is close to that of water. During aeration, it is completely mixed with water, and the environment for microbial growth is gas, liquid, and solid. The collision and shearing effect of the carrier in the water makes the air bubbles smaller and increases the utilization rate of oxygen. In addition, each carrier has different biological species inside and outside, with some anaerobic or facultative aerobic bacteria growing inside and good bacteria growing outside. In this way, each carrier is a microreactor, allowing nitrification and denitrification reactions to exist at the same time, thereby improving the treatment effect. However, the suspended filler, which is the core of this process technology, still has some problems to be solved, such as deficiencies in hydrophilicity, bioaffinity, and mechanical strength, which need to be further improved and enhanced. Summary of the invention

[0005] The present invention aims to solve the practical problems of suspended fillers in moving bed biofilm reactors in project applications, and proposes a suspended filler, a preparation and use method, which can effectively improve the mechanical properties, surface electrical properties and biological affinity of the suspended filler, and use the filler for in-situ expansion and transformation of sewage treatment units such as A2O and improved AO, thereby realizing non-stop water transformation of the project, effectively shortening the biofilm formation time of the suspended filler, improving the biofilm formation efficiency, enhancing the mechanical properties of the suspended filler, reducing the loss during operation and maintenance, extending the service life and reducing the operating cost.

[0006] A suspension filler is prepared from the following components in parts by weight: 90-92 wt% of high-density polyethylene, 4-5 wt% of zeolite, 3.5-4 wt% of activated carbon, and 0.5-1 wt% of talc.

[0007] Specifically, the amount of talc added is adjusted according to the density of high-density polyethylene in the raw material so that the density of the suspended filler is 0.97±0.01% g / cm³.

[0008] A suspension filler, the preparation method of which is as follows: Step 1: crushing the zeolite and activated carbon to a particle size between 10-75 μm; Step 2: stirring and mixing high-density polyethylene, crushed zeolite, and crushed activated carbon at a temperature not higher than 200° C. and completing granulation; Step 3: Shaping: the outer layer of the suspended filler is made into a cylindrical structure with a standard circular cross-section. The outer surface of the cylinder is a smooth surface without protrusions. The internal structure of the suspended filler is provided with micro-toothed protrusions along the height direction of the cylinder on the inside of the cylinder. The internal structure is composed of stable multi-layer six-sided honeycomb holes, which are arranged outward in sequence with the six-sided honeycomb holes as the center. The arrangement level of the honeycomb holes is set according to the size of the suspended seasoning, and micro-toothed protrusions are set on the walls of the six-sided honeycomb holes along the height direction of the cylinder.

[0009] A suspended filler, the use method of which is as follows: Step 1: The sewage enters the anaerobic zone, the anoxic zone, and the aerobic zone in sequence; suspended fillers are added to one or more reactors in the anaerobic zone, the anoxic zone, and the aerobic zone; Step 2: The anaerobic and anoxic zones are mechanically stirred and pushed by agitators. The aeration in the aerobic zone is aerated by the aeration plate at the bottom to fluidize and move the filler. A filler interception grid is added at the outlet of the reactor. The suspended filler moves freely under the action of the swirling and turning of the water flow in the reactor and refluxes at the interception grid.

[0010] Beneficial effects of the present invention: Adding appropriate amounts of zeolite, activated carbon and talc to high-density polyethylene and completing the granulation and molding of smooth side fillers at an appropriate temperature can effectively improve their mechanical properties and toughness, effectively extend the service life of suspended fillers, and reduce wear and tear between each other during transportation, use and maintenance, as well as wear and tear on other equipment and structures in the working environment.

[0011] Taking advantage of the rough and porous characteristics of zeolite and activated carbon, the surface properties of the filler are improved, the surface roughness and hydrophilicity are improved, and conditions are created for the rapid attachment and growth of microorganisms. It can accelerate the initial adhesion of macromolecules (proteins, polysaccharides) on the filler surface, planktonic cell adsorption, bacterial cell adsorption, cell-cell signaling molecule expression, cell proliferation, and produce more EPS to complete the "binding" of the initial biofilm, thereby achieving rapid startup of the system.

[0012] It provides a larger space for microorganisms to attach and grow. By increasing the total amount of microorganisms in a single suspended filler, the total content of microorganisms per unit space can be increased. On the one hand, the system's efficiency in removing pollutants in the water can be improved. On the other hand, since a richer microbial community can be formed inside a single suspended filler, a more complex micro-ecosystem with a longer food chain can be formed, the sludge generated inside the system can be more decomposed and consumed, which can reduce the generation of residual sludge in the system.

[0013] The micro-teeth + hexagonal honeycomb design inside the suspended filler not only avoids filler wear and improves overall stability, but also increases its surface area, helps to form a good turbulent state, improves the contact efficiency between pollutants and microorganisms, and the frequency of biofilm renewal.

[0014] The present invention has good mechanical properties, mechanical strength, stability, biofilm adhesion, and moderate specific gravity. It is suspended in water by the stirring and driving effect of a submersible stirrer and a membrane-type microporous aeration disk. Each filler forms a relatively independent ecosystem, which improves the system's ability to resist impacts of environmental changes such as water quality and temperature. At the same time, the whole system swirls with the flow of water, continuously exchanging matter and energy with the external water body, so that the biofilm is always maintained in a high activity state, and the pollutants in the water body are efficiently purified.

[0015] It can be embedded in the anaerobic zone, anoxic zone, and aerobic zone of the original sewage treatment project in conjunction with the MBBR process, and operated under different conditions according to the different characteristics of the original chemical treatment of the project, providing more options for the in-situ expansion and transformation of existing sewage treatment projects. The operating parameters such as the reflow ratio, aeration volume, and hydraulic retention time can be adjusted according to the load, operating conditions, and system improvement, and different functional requirements can be achieved through flexible adjustment of the operating mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1This is a cross-sectional view of the first size of the suspension filler of the present invention.

[0017] Figure 2 This is a cross-sectional view of a second size of the suspension filler of the present invention.

[0018] Figure 3 This is a perspective view of a first size of the suspension filler of the present invention.

[0019] Figure 4 This is a perspective view of a second size of the suspension filler of the present invention.

[0020] Figure 5 The present invention is a flow chart of adding the suspended filler into the anaerobic zone.

[0021] Figure 6 The present invention is a flow chart of adding the suspended filler into the anoxic zone.

[0022] Figure 7 The present invention is a flow chart of adding the suspended filler into the aerobic zone.

[0023] Figure 8 The present invention is a flow chart of the preparation method of the suspension filler.

[0024] Fig. 9 The present invention is a flow chart of the method for using the suspension filler. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Example

[0026] A suspension filler is prepared from the following components in parts by weight: 90-92 wt% of high-density polyethylene, 4-5 wt% of zeolite, 3.5-4 wt% of activated carbon, and 0.5-1 wt% of talc.

[0027] Zeolite is composed of silicate minerals, and its basic skeleton is composed of silicon-oxygen tetrahedron or aluminum-oxygen tetrahedron. Both silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron can be connected to each other through oxygen atoms at the top of the tetrahedron. Two adjacent tetrahedrons are also connected through oxygen atoms. At the nanometer scale, its molecular chain structure presents a polyhedral framework microstructure. Because it contains regular voids at the molecular scale, it has a negative Poisson's ratio. Therefore, it has special mechanical properties and undergoes lateral contraction (expansion) under uniaxial pressure (tension). It has more advantages than other materials in terms of shear bearing capacity, fracture resistance, energy absorption and indentation resistance. Adding this negative Poisson's ratio material to the suspended filler will effectively improve the shear modulus, fracture resistance and toughness of the suspended filler during operation, reduce its loss during operation and maintenance, extend its service life and reduce operating costs.

[0028] Zeolite has a large specific surface area, uniform pores, and adsorption properties for liquids and some gases. Adding an appropriate amount of zeolite can increase the specific surface area of ​​the suspended filler, improve the surface roughness, increase the microbial attachment points, and increase the adsorption properties of the suspended filler.

[0029] Activated carbon has a rich pore structure, with the characteristics of large specific surface area, high adsorption capacity and good stability. The diameter range of micropores and mesopores of activated carbon is usually between 2-50nm, which can form an internal microenvironment. At the same time, due to the large number of hydrophilic polar functional groups such as hydroxyl and carboxyl groups on the surface of activated carbon, the hydrophilicity of the surface of activated carbon is improved; adding an appropriate amount of activated carbon to the suspended filler so that it can work together with zeolite can improve the surface roughness of the suspended filler while utilizing its adsorption performance and hydrophilicity. In the early stage of system startup, more cell recognition sites are provided for the differentiation and reproduction of microbial cells, so that bacteria can adhere to the surface of the suspended filler more quickly and stably in the constantly disturbed water body, adjust their gene expression, and secrete a large amount of EPS while growing and reproducing to prevent being washed down by the water flow, and more firmly adhere to the filler to better complete the initial startup of the moving bed bioreactor.

[0030] The suspended filler has good corrosion resistance and a large specific surface area of ​​780-960m2 / m3 to ensure the rapid growth of biofilm.

[0031] Furthermore, the amount of talcum powder added is appropriately adjusted according to the density of high-density polyethylene in the raw material, so that the density of the suspended filler is 0.97±0.01% g / cm³, so that it can be suspended in the target water body and maintain a good fluidized state. Example

[0032] A method for preparing a suspended filler: Step 1: crushing the zeolite and activated carbon to a particle size between 10-75 μm; Step 2: High-density polyethylene, crushed zeolite, and crushed activated carbon are stirred, mixed, and granulated at a temperature not higher than 200° C., so that the high-density polyethylene maintains good crystallinity and mechanical properties after molding; Step 3: Shaping: the outer layer of the suspended filler is made into a cylindrical structure with a standard circular cross section. The outer surface of the cylinder is a smooth surface without protrusions to reduce the scratching and wear of the suspended filler on the surrounding fillers, flow generators, agitators and reactor tank walls during transportation, supply, actual operation or maintenance. The internal structure of the suspended filler is provided with micro-toothed protrusions along the height direction of the cylinder. The internal structure is composed of stable multi-layer six-sided honeycomb holes, which are arranged outward in sequence with the six-sided honeycomb holes as the center. The arrangement level of the honeycomb holes is set according to the size of the suspended seasoning, and the six-sided honeycomb hole walls are provided with micro-toothed protrusions along the height direction of the cylinder. See Figure 1-Figure 4 .

[0033] Furthermore, the wall thickness of the floating filler is 0.3mm±0.01 and the diameter can be 25mm ( Figure 1 , Figure 3 ) or 35mm ( Figure 2 , Figure 4 ), or adjust the size of the floating filler according to the actual application. The height of the floating filler is 1 / 2 of the diameter of the floating filler. Example

[0034] A method for using a suspended filler: Step 1: The sewage enters the anaerobic zone, the anoxic zone, and the aerobic zone in sequence; suspended fillers are added to one or more reactors in the anaerobic zone, the anoxic zone, and the aerobic zone; Step 2: The anaerobic zone and the anoxic zone rely on agitators for mechanical stirring and flow propagation. The aerobic zone is aerated through the aeration plate at the bottom to fluidize and move the filler. To prevent the filler from flowing out with the water, a filler interception grid is added at the outlet of the reactor. The suspended filler moves freely under the action of the swirling and turning of the water flow in the reactor, and flows back at the interception grid.

[0035] Furthermore, the suspended filler is added in the anaerobic zone: The test shows that after adding 30% suspended filler by volume into the anaerobic zone, the anaerobic hydrolysis and acidification effect is significantly improved after 14 days, and the phosphorus removal efficiency of the system is significantly improved; because the anaerobic pool is mainly for polyphosphate bacteria (PAOs) to release phosphorus, PAOs obtain energy by decomposing polyphosphates in the body. Under the enhanced hydrolysis, the difficult-to-degrade substances in the water, especially the high-molecular organic matter that cannot be directly used by microorganisms, are decomposed into short-chain small molecular products. Under the enhanced acidification, the soluble organic matter is more converted by acidifying bacteria into end products mainly composed of volatile fatty acids (including volatile fatty acids, alcohols, lactic acid, carbon dioxide, ammonia, etc.), which can be dissolved in water and are more easily used by microorganisms. Providing more high-quality carbon sources that are easily absorbed and utilized for PAOs in the anaerobic zone, on the one hand, promotes the enhanced phosphorus release of PAOs, opens up space for enhanced phosphorus absorption in subsequent processes, and improves the phosphorus removal rate; on the other hand, due to the formation of a stable and constantly growing biofilm in the independent suspended filler, the abundance, quantity and activity of anaerobic microorganisms in the anaerobic zone are increased. The emergence of facultative anaerobes can also play a certain protective role for strict anaerobic bacteria. Therefore, on the basis of full release of internal carbon sources, the addition of suspended fillers effectively improves the biodegradability and reaction efficiency of the system, creates a more suitable reaction environment for subsequent biochemical processes, and also provides a basis for reducing the generation of residual sludge in the system. Furthermore, the suspended filler is added in the anoxic zone: The experiment shows that by adding 30% suspended filler by volume into the anoxic zone, the denitrification efficiency of the system is significantly improved after 18 days. The system is switched from a single-sludge system to a double-sludge system with mud-film symbiosis. The biomass is significantly increased and the concentration of activated sludge is more than doubled compared with before the addition. Under this condition, the denitrifying bacteria with a longer sludge age are enriched, and the abundance, quantity and activity of the bacteria are improved. The nitrate brought in by the internal reflow is converted into nitrogen gas through biological denitrification and escapes into the atmosphere, thereby improving the denitrification efficiency of the system and achieving the purpose of denitrification.

[0036] Furthermore, the suspended filler is added in the aerobic zone: The test shows that after adding 30% of the volume ratio of suspended fillers in the aerobic zone, the nitrification efficiency of the system is improved after 15 days, and the COD removal capacity and denitrification effect are significantly improved. The addition of suspended fillers, under the action of the bottom microporous aeration plate and the inlet and outlet water flow, forms a unity of a completely mixed flow state and an overall plug flow state. On the one hand, when the suspended fillers are added to the aerobic zone, the biofilm attached and grown on the fillers has good mass transfer properties, forming a local hypoxic microenvironment inside the biofilm and an aerobic environment outside, which solves the competition for dissolved oxygen and carbon sources among autotrophic nitrifying bacteria, heterotrophic denitrifying bacteria and heterotrophic bacteria, and can also provide a good growth environment for microorganisms of different types and functions, and can survive longer generation cycles of bacteria (such as bell worms, nematodes, paramecium and other protozoa), so that a rich microbial community and a complex micro-ecosystem are formed in the biofilm, achieving deep removal of organic pollutants; on the other hand, the suspended fillers are turned over in the pool body. Shearing will further break up the tiny bubbles overflowing from the aeration disk, increase contact with the water flow, achieve more adequate oxygenation and oxygen utilization, and strengthen the growth of chemoautotrophic nitrifying bacteria. It also has the dual characteristics of anaerobic and aerobic, thereby improving the system's denitrification capacity and enhancing the TN removal effect. At the same time, the longer food chain allows more activated sludge to be decomposed and consumed by microorganisms in the system, resulting in less residual sludge. Since the floc particles formed after the biofilm falls off have better density and larger particle size, the residual sludge discharged from the system has better sedimentation performance, reducing the difficulty of subsequent sludge treatment.

[0037] Furthermore, there are multiple modes for adding suspended fillers, such as: adding only to the anaerobic zone, or adding only to the anoxic zone, or adding only to the aerobic zone, or adding to the anaerobic zone and the anoxic zone, or adding to the anaerobic zone and the aerobic zone, or adding to the anoxic zone and the aerobic zone, or adding to the anaerobic zone, the anoxic zone, and the aerobic zone at the same time; on the one hand, the dosage of the suspended filler in each delivery area can be adjusted (controlled between 20% and 55%, too small an dosage will not significantly improve the system treatment effect, and too large an dosage will affect the fluidization effect of the filler), and on the other hand, the operating parameters such as the reflux ratio, aeration volume, and hydraulic retention time can be adjusted according to the water impact load, operating conditions, and system improvement. Through flexible adjustment of the operating mode, different functional requirements can be achieved.

[0038] Furthermore, according to the inlet and outlet water quality requirements of the sewage treatment project and future operational needs, steel partitions are used to divide different functional areas. Through refined optimization and allocation, the addition position and amount of the suspended filler of the present invention are further adjusted in the refined subdivided areas, and the operating parameters in each refined subdivided area are adjusted. Through further adjustment of the operating mode, multi-mode adjustable operation of the biochemical system is achieved, the stability of the process operation is enhanced, and the goal of energy saving and consumption reduction is further achieved while ensuring that the effluent water quality meets the standards.

[0039] This embodiment is applied to the A2O treatment system of a sewage treatment plant, and the influent water quality is shown in Table 1 below.

[0040] Influent water quality parameters of a sewage treatment plant

[0041] Table 1

[0042] As described above, adding 30% of the suspended filler of the present invention in different reaction zones can significantly improve the biochemical effect and denitrification rate of the sewage treatment system, and form a biofilm system with different advantages according to the different distribution of pollutants in the water, so that the removal of various pollutants is more targeted and efficient, while improving the system's denitrification and phosphorus removal capabilities, enhancing the ability to resist water inlet shock loads, and improving the stability of system operation; overall, the median value of the nitrification rate increase in the above three working modes is 12.2%, and the median value of the denitrification rate increase is 13.9%. Without adding an external carbon source, COD≤40mg / L, TN≤17mg / L, TP≤0.5mg / L; COD≤40mg / L, TN≤16mg / L, TP≤0.6mg / L; COD≤40mg / L, TN≤15mg / L, TP≤0.55mg / L can be achieved respectively.

[0043] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A suspension filler, prepared from the following components in parts by weight: 90-92 wt% high-density polyethylene, 4-5 wt% zeolite, 3.5-4 wt% activated carbon, and 0.5-1 wt% talc.

2. A suspension filler according to claim 1, characterized in that: The amount of talc added was adjusted according to the density of high-density polyethylene in the raw material so that the density of the suspended filler was 0.97±0.01% g / cm³.

3. A suspension filler according to claim 1-2, wherein the preparation method is as follows: Step 1: crushing the zeolite and activated carbon to a particle size between 10-75 μm; Step 2: stirring and mixing high-density polyethylene, crushed zeolite, and crushed activated carbon at a temperature not higher than 200° C. and completing granulation; Step 3: Shaping: the outer layer of the suspended filler is made into a cylindrical structure with a standard circular cross-section. The outer surface of the cylinder is a smooth surface without protrusions. The internal structure of the suspended filler is provided with micro-toothed protrusions along the height direction of the cylinder on the inside of the cylinder. The internal structure is composed of stable multi-layer six-sided honeycomb holes, which are arranged outward in sequence with the six-sided honeycomb holes as the center. The arrangement level of the honeycomb holes is set according to the size of the suspended seasoning, and micro-toothed protrusions are set on the walls of the six-sided honeycomb holes along the height direction of the cylinder.

4. The method for preparing a suspended filler according to claim 3, characterized in that: The wall thickness of the floating filler is 0.3mm±0.01, and the diameter is 25mm or 35mm. The size specifications of the floating filler are adjusted according to the actual application. The height of the floating filler is 1 / 2 of the diameter of the floating filler.

5. A suspension filler according to claim 1-2, wherein the method of using the suspension filler is as follows: Step 1: The sewage enters the anaerobic reaction zone, the anoxic reaction zone, and the aerobic reaction zone in sequence; suspended fillers are added to one or more reactors in the anaerobic reaction zone, the anoxic reaction zone, and the aerobic reaction zone; Step 2: The anaerobic and anoxic zones are mechanically stirred and pushed by agitators. The aeration in the aerobic zone is aerated by the aeration plate at the bottom to fluidize and move the filler. A filler interception grid is added at the outlet of the reactor. The suspended filler moves freely under the action of the swirling and turning of the water flow in the reactor and refluxes at the interception grid.

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