Composite filler for urban non-point source pollution control and preparation method thereof

Abstract

The application relates to the technical field of water treatment, in particular to a composite filler for urban non-point source pollution control and a preparation method thereof, which comprises the following raw materials in mass fractions: 30-40 parts of ceramic granules, 20-30 parts of quartz sand, 5-10 parts of modified sodium alginate containing nitrifying bacteria, 1-3 parts of sodium persulfate, 5-15 parts of modified montmorillonite, 5-15 parts of zeolite, 5-10 parts of iron hydroxide, and 4-10 parts of a binder; the modified sodium alginate containing nitrifying bacteria is modified through polyurethane and nano silicon dioxide composite crosslinking, and then the modified sodium alginate is inoculated with nitrifying bacteria; the modified montmorillonite is polyammonium methacrylate modified montmorillonite, and the problems that the composite filler in the existing biological retention facilities has poor nitrogen and phosphorus removal effect and serious secondary pollution are solved.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a composite filler for urban non-point source pollution control and its preparation method. Background Technology

[0002] Urban non-point source pollution refers to a form of pollution caused by rainwater carrying dissolved or solid pollutants into water bodies from non-specific locations during rainfall. It is a type of water pollution relative to point source pollution, and is also known as urban non-point source pollution.

[0003] With point source pollution effectively managed, non-point source pollution caused by initial stormwater runoff is receiving increasing attention. Low Impact Development (LID) technologies, as a new approach to stormwater management, are widely adopted due to their ability to effectively reduce environmental burden. Three strategies are typically employed to address non-point source pollution from initial stormwater runoff: source control, process control, and end-of-pipe control. Specific measures include, but are not limited to, bioretention facilities, overflow storage tanks, and constructed wetlands.

[0004] Most runoff treatment facilities, such as bioretention facilities, can remove suspended pollutants, but their removal efficiency for nitrogen and phosphorus is poor. The core of bioretention facilities lies in the use of a composite packing material, which needs to have high water retention and good adsorption properties.

[0005] Currently, composite packings mainly fall into the following categories:

[0006] 1. Humus-based soil: Although it can provide good growing conditions, the nutrients inside it are easily lost to water bodies by runoff, causing secondary pollution, and its permeability is relatively poor.

[0007] 2. Based on peat: Peat has excellent water retention and nutrient retention capabilities, but as a non-renewable resource, its extraction is strictly limited.

[0008] 3. Based on sandy soil: Sandy soil has excellent permeability, but its water retention capacity is insufficient, which may limit the choice of plant species and thus affect the aesthetics of the landscape.

[0009] 4. Using planting soil as a base: Planting soil also suffers from nutrient loss and has poor water permeability.

[0010] Therefore, it is necessary to find a composite packing material that can fix phosphorus, adsorb and decompose ammonia nitrogen, and reduce secondary pollution.

[0011] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention

[0012] The purpose of this invention is to solve the problem that the composite packing material in existing bioretention facilities has poor removal efficiency for nitrogen and phosphorus and serious secondary pollution, and to provide a composite packing material for urban non-point source pollution control and its preparation method.

[0013] To achieve the above objectives, this invention discloses a composite filler for controlling urban non-point source pollution, comprising the following raw materials in parts by weight: 30-40 parts of ceramsite, 20-30 parts of quartz sand, 5-10 parts of modified sodium alginate containing nitrifying bacteria, 1-3 parts of sodium persulfate, 5-15 parts of modified montmorillonite, 5-15 parts of zeolite, 5-10 parts of ferric hydroxide, and 4-10 parts of binder. The modified sodium alginate containing nitrifying bacteria is a polyurethane and nano-silica composite cross-linked modified sodium alginate, which is then inoculated with nitrifying bacteria. The modified montmorillonite is polymethyl methacrylate modified montmorillonite.

[0014] The composite filler comprises the following raw materials in parts by weight: 35 parts ceramsite, 25 parts quartz sand, 7.5 parts modified sodium alginate containing nitrifying bacteria, 2 parts sodium persulfate, 10 parts modified montmorillonite, 10 parts zeolite, 7.5 parts ferric hydroxide, and 7 parts binder.

[0015] This invention also discloses a method for preparing the above-mentioned composite filler for urban non-point source pollution control, comprising the following steps:

[0016] S1. Wash the ceramsite and quartz sand with deionized water, dry them, and prepare a binder solution with a mass concentration of 4-6%.

[0017] S2, ceramsite, quartz sand, modified sodium alginate containing nitrifying bacteria, sodium persulfate, modified montmorillonite, zeolite, and ferric hydroxide are mixed evenly, and a binder solution is sprayed while mixing to form a pre-mixed composite filler.

[0018] S3 involves granulating the pre-mixed composite filler, allowing it to stand and solidify in a ventilated environment, and then drying it to obtain the composite filler.

[0019] In step S2, the preparation method of modified sodium alginate containing nitrifying bacteria includes the following steps:

[0020] A1. Mix sodium alginate solution, polyurethane solution and dispersed nano-silica, heat to 40-50℃ while stirring, and continue stirring for 1-2 hours.

[0021] A2, then add pentose aldehyde to carry out a cross-linking reaction, maintain the reaction at 50-60℃ for 1-2 hours, let stand for 24 hours, and dry to obtain modified sodium alginate;

[0022] A3, by enriching nitrifying bacteria in sludge, modified sodium alginate is inoculated with nitrifying bacteria to obtain modified sodium alginate containing nitrifying bacteria.

[0023] In step A1, the mass ratio of sodium alginate, polyurethane solution, and nano silica is 3:1:1.

[0024] In step A3, the specific inoculation process is as follows: the sludge containing nitrifying bacteria is diluted with clean water to 3500-4500 mg / L, and then the sludge is poured into modified sodium alginate in multiple batches.

[0025] In step S2, the modified montmorillonite is prepared as follows: montmorillonite is mixed with a polymethyl methacrylate solution, stirred thoroughly, reacted at room temperature for 2-4 hours, and dried to obtain the modified montmorillonite.

[0026] The amount of the polymethacrylate ammonium solution used is 5-10% of the mass of montmorillonite.

[0027] In step S2, the zeolite particle size is 3mm-5mm.

[0028] In step S3, the particle size of the composite filler is 4mm-6mm.

[0029] This invention enhances the microstructural stability of sodium alginate through the high surface area of ​​nano-silica. Simultaneously, the introduction of polyurethane significantly improves the mechanical strength and durability of sodium alginate, thus determining the overall stability of the modified sodium alginate and the adhesion performance of nitrifying bacteria. Pentofructaldehyde, as a crosslinking agent, enables the modified material to form a three-dimensional network structure, further enhancing the material's strength and hydrolysis resistance, while also improving its ability to immobilize nitrifying bacteria. Inoculation with nitrifying bacteria optimizes the microenvironment on the material surface, thereby affecting the activity of nitrifying bacteria and ammonia nitrogen removal efficiency. The modified sodium alginate exhibits significantly enhanced microbial adhesion, improving the mechanical stability and durability of the resulting packing material, ensuring long-term wastewater treatment capacity, increasing ammonia nitrogen removal efficiency, and enhancing biodegradability.

[0030] In modified montmorillonite, polymethyl methacrylate (PMMA) acts as a cationic polymer, undergoing an ion exchange reaction with the surface of montmorillonite. This enhances the cation exchange capacity and phosphate adsorption capacity of montmorillonite. During the modification process, uniform dispersion ensures sufficient contact between PMMA and montmorillonite, while appropriate drying conditions prevent polymer degradation and ensure stable adsorption performance. Modified montmorillonite significantly enhances the adsorption performance of phosphate and heavy metal ions, and the chemical stability of the prepared filler is improved, making it suitable for complex water quality environments. Furthermore, modified montmorillonite enhances the synergistic adsorption effect with other components (such as sodium alginate and zeolite). In the synergistic adsorption of phosphate and heavy metal ions, the composite adsorption capacity is significantly enhanced by improving the cation exchange capacity and porous structure. The biodegradation mechanism provided by modified sodium alginate, combined with the physical adsorption of modified montmorillonite and zeolite, and the chemical precipitation of ferric hydroxide, forms a multi-level pollutant removal mechanism.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. Composite packing materials, through the synergistic effect of different components, can effectively remove ammonia nitrogen, phosphate, and other pollutants from water, achieving excellent water purification results. In particular, the biocompatibility of modified sodium alginate and the activity of nitrifying bacteria enable the packing material to form a biofilm during water treatment, enhancing its ammonia nitrogen conversion capacity and promoting ecological cycling. Furthermore, the composite modification of polyurethane and nano-silica not only improves the mechanical strength and durability of sodium alginate, reducing the deterioration of the packing material during long-term use and ensuring its sustained performance, but also enhances the physical and chemical stability of the packing material. The addition of modified montmorillonite and ferric hydroxide further enhances the adsorption capacity of the packing material in removing heavy metals and nutrients, contributing to further improvement of water quality. This composite packing material uses biodegradable materials and natural components, fully complying with the concept of green environmental protection, and is very suitable for the treatment of urban non-point source pollution.

[0033] 2. Modified sodium alginate exhibits exceptional water treatment potential due to its enhanced physical properties, biocompatibility, improved nitrification capacity, and excellent environmental adaptability. After modification, this material not only possesses higher strength and toughness, enabling it to withstand greater physical impact and long-term immersion during water treatment, thus extending its service life, but also provides an excellent attachment surface for nitrifying bacteria, promoting the formation of a stable biofilm and enhancing bacterial activity and survival rate. Inoculated nitrifying bacteria can effectively grow on modified sodium alginate, efficiently converting ammonia nitrogen into nitrite and nitrate, achieving natural water purification and nutrient removal, and significantly improving water quality. Furthermore, the structural stability and biocompatibility of modified sodium alginate ensure its excellent performance under various water quality conditions, making it particularly suitable for the treatment of urban non-point source pollution.

[0034] 3. Modified montmorillonite not only has stronger cation exchange capacity and anion adsorption capacity, effectively removing pollutants such as heavy metals and phosphorus from water bodies, but also improves its surface hydrophilicity and dispersibility due to the introduction of ammonium polymethacrylate, which is beneficial for applications in water treatment and soil remediation. Detailed Implementation

[0035] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the embodiments.

[0036] Example 1

[0037] The composite filler in this embodiment is prepared by the following steps:

[0038] 1. Preparation of modified sodium alginate containing nitrifying bacteria:

[0039] A1. Mix 15 kg of sodium alginate solution, 5 kg of polyurethane solution and 5 kg of dispersed nano silica, heat to 40°C while stirring, and continue stirring for 2 hours.

[0040] A2, then add 1 kg of pentofructaldehyde to carry out the cross-linking reaction, maintain the reaction at 50℃ for 2 hours, let stand for 24 hours, and dry to obtain modified sodium alginate.

[0041] A3, through the enrichment of nitrifying bacteria throughout the entire process in sludge, firstly, the sludge containing nitrifying bacteria throughout the entire process is diluted with clean water to 3500mg / L, and then it is leached into modified sodium alginate in multiple batches to obtain modified sodium alginate containing nitrifying bacteria.

[0042] 2. Preparation of modified montmorillonite

[0043] 20 kg of montmorillonite was mixed with 1 kg of polymethyl methacrylate solution, stirred thoroughly, reacted at room temperature for 2 h, and dried to obtain modified montmorillonite.

[0044] 3. Preparation of composite fillers:

[0045] S1. Wash 35kg of ceramsite and 25kg of quartz sand with deionized water, dry them, and prepare a 4% (w / w) binder solution.

[0046] S2, mix 30kg of ceramsite, 20kg of quartz sand, 5kg of modified sodium alginate containing nitrifying bacteria, 1kg of sodium persulfate, 5kg of modified montmorillonite, 5kg of zeolite, and 5kg of ferric hydroxide evenly, and spray 36L of binder solution while mixing to form a pre-mixed composite filler.

[0047] S3. The pre-mixed composite filler is granulated to a particle size of 4mm, then allowed to stand and cure in a ventilated environment, and dried to obtain the composite filler.

[0048] Example 2

[0049] The composite filler in this embodiment is prepared by the following steps:

[0050] 1. Preparation of modified sodium alginate containing nitrifying bacteria:

[0051] A1. Mix 17 kg of sodium alginate solution, 5.5 kg of polyurethane solution and 5.5 kg of dispersed nano silica, heat to 45°C while stirring, and continue stirring for 1.5 hours.

[0052] A2, then add 1.5 kg of pentofructaldehyde to carry out the cross-linking reaction, maintain the reaction at 55℃ for 1.5 hours, let stand for 24 hours, and dry to obtain modified sodium alginate;

[0053] A3, through the enrichment of nitrifying bacteria throughout the process by sludge, first dilute the sludge containing nitrifying bacteria to 4000 mg / L with clean water, and then leach it into modified sodium alginate in multiple batches to obtain modified sodium alginate containing nitrifying bacteria.

[0054] 2. Preparation of modified montmorillonite

[0055] 22.5 kg of montmorillonite was mixed with 1.75 kg of polymethyl methacrylate solution, stirred thoroughly, reacted at room temperature for 3 h, and dried to obtain modified montmorillonite.

[0056] 3. Preparation of composite fillers:

[0057] S1. Wash 40kg of ceramsite and 30kg of quartz sand with deionized water, dry them, and prepare a 5% (w / w) binder solution.

[0058] S2, mix 35kg of ceramsite, 25kg of quartz sand, 7.5kg of modified sodium alginate containing nitrifying bacteria, 2kg of sodium persulfate, 10kg of modified montmorillonite, 10kg of zeolite, and 7.5kg of ferric hydroxide evenly, and spray 50L of binder solution while mixing to form a pre-mixed composite filler.

[0059] S3. The pre-mixed composite filler is granulated to a particle size of 5mm, then allowed to stand and cure in a ventilated environment, and dried to obtain the composite filler.

[0060] Example 3

[0061] The composite filler in this embodiment is prepared by the following steps:

[0062] 1. Preparation of modified sodium alginate containing nitrifying bacteria:

[0063] A1. Mix 18 kg of sodium alginate solution, 6 kg of polyurethane solution and 6 kg of dispersed nano silica, heat to 50°C while stirring, and continue stirring for 1 hour.

[0064] A2, then add 2 kg of pentofructaldehyde to carry out the cross-linking reaction, maintain the reaction at 60℃ for 1 hour, let stand for 24 hours, and dry to obtain modified sodium alginate.

[0065] A3, through the enrichment of nitrifying bacteria throughout the entire process in sludge, firstly, the sludge containing nitrifying bacteria throughout the entire process is diluted with clean water to 4500mg / L, and then it is leached into modified sodium alginate in multiple batches to obtain modified sodium alginate containing nitrifying bacteria.

[0066] 2. Preparation of modified montmorillonite

[0067] 25 kg of montmorillonite was mixed with 2.5 kg of polymethyl methacrylate solution, stirred thoroughly, reacted at room temperature for 4 h, and dried to obtain modified montmorillonite.

[0068] 3. Preparation of composite fillers:

[0069] S1. Wash 45kg of ceramsite and 35kg of quartz sand with deionized water, dry them, and prepare a 6% (w / w) binder solution.

[0070] S2, mix 40kg of ceramsite, 30kg of quartz sand, 10kg of modified sodium alginate containing nitrifying bacteria, 3kg of sodium persulfate, 15kg of modified montmorillonite, 15kg of zeolite, and 10kg of ferric hydroxide evenly, and spray 63L of binder solution while mixing to form a pre-mixed composite filler.

[0071] S3. The pre-mixed composite filler is granulated to a particle size of 6mm, then allowed to stand and cure in a ventilated environment, and dried to obtain the composite filler.

[0072] Comparative Example 1

[0073] The difference between this embodiment and Embodiment 2 is that the modified sodium alginate containing nitrifying bacteria is replaced with ordinary sodium alginate.

[0074] Comparative Example 2

[0075] The difference between this embodiment and Embodiment 2 is that the modified montmorillonite is replaced with ordinary montmorillonite.

[0076] The individual components of the composite packing and the composite packing of Examples 1-3 were compared with those containing ammonia nitrogen, phosphate and heavy metal ions (such as Pb). 2+ Cd 2+ The simulated wastewater was treated, and the pollutant removal rate data are shown in Table 1.

[0077] Table 1. Removal rates of individual components in the composite packing and the composite packings in Examples 1-3 for pollutants in simulated wastewater.

[0078]

[0079] The composite packing material in Example 2 significantly improved the removal rate of all pollutants, especially ammonia nitrogen removal rate reaching 95%, and phosphate and heavy metal removal rates reaching over 85%, showing a significant synergistic effect.

[0080] Mechanical strength and nitrifying bacteria adhesion rate tests were conducted on Comparative Example 1 and Examples 1-3, and the data are shown in Table 2.

[0081] Table 2. Results of mechanical strength test and nitrifying bacteria adhesion rate test for Comparative Example 1 and Examples 1-3

[0082]

[0083] The mechanical properties of the filler in Example 2 were significantly higher than those in Comparative Example 1, indicating that the composite crosslinking of polyurethane and nano-silica can enhance strength. The number and adhesion rate of attached bacteria in the filler in Example 2 were significantly higher than those in Comparative Example 1, indicating that the modification improved surface affinity and biocompatibility.

[0084] Lead ion adsorption experiments were conducted on Comparative Example 2 and Examples 1-3, and the data are shown in Table 3.

[0085] Table 3 Results of lead ion adsorption experiments in Comparative Example 2 and Examples 1-3

[0086]

[0087] The packing material in Example 2 was significantly better than that in Comparative Example 2 in terms of lead ion adsorption capacity, with a removal rate increase of 26%, indicating that the modification effect of polymethyl methacrylate was significant.

[0088] The composite packing materials prepared in Examples 1-3 and Comparative Examples 1-2 were applied in five bioretention facilities to filter and purify rainwater runoff, which was then discharged into rainwater pipes.

[0089] Table 4. Water treatment effects of the composite packing materials prepared in Examples 1-3 and Comparative Examples 1-2 in five bioretention facilities.

[0090]

[0091] Comparative analysis of Example 1 and Example 2 revealed that the addition of modified sodium alginate containing nitrifying bacteria in Example 2 significantly improved the ammonia nitrogen removal rate. This indicates that modified sodium alginate not only provides an excellent growth environment for nitrifying bacteria and promotes biofilm formation, but also enhances the conversion of ammonia nitrogen to nitrite and nitrate, thereby achieving a more efficient ammonia nitrogen removal effect.

[0092] The comparison between Comparative Example 2 and Example 2 shows that the addition of modified montmorillonite in Example 2 significantly improved the efficiency of phosphorus and ammonia nitrogen removal. Modified montmorillonite, through its enhanced cation exchange capacity and anion adsorption capacity, not only effectively captured and immobilized phosphorus and nitrogen compounds in the water but also promoted pollutant removal, demonstrating its important role in water purification. This finding highlights the potential of modified montmorillonite in improving the overall efficiency of water treatment systems, particularly in comprehensively addressing ammonia nitrogen and phosphorus pollution.

[0093] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A composite filler for controlling urban non-point source pollution, characterized in that, The raw materials include the following parts by weight: 30-40 parts ceramsite, 20-30 parts quartz sand, 5-10 parts modified sodium alginate containing nitrifying bacteria, 1-3 parts sodium persulfate, 5-15 parts modified montmorillonite, 5-15 parts zeolite, 5-10 parts ferric hydroxide, and 4-10 parts binder. The modified sodium alginate containing nitrifying bacteria is polyurethane and nano-silica composite cross-linked modified sodium alginate, and then inoculated with nitrifying bacteria. The modified montmorillonite is polymethyl methacrylate modified montmorillonite. The preparation method of the modified sodium alginate containing nitrifying bacteria includes the following steps: A1. Mix sodium alginate solution, polyurethane solution and dispersed nano-silica, heat to 40-50℃ while stirring, and continue stirring for 1-2 hours. A2, then add pentose aldehyde to carry out a cross-linking reaction, maintain the reaction at 50-60℃ for 1-2 hours, let stand for 24 hours, and dry to obtain modified sodium alginate; A3, by enriching nitrifying bacteria in sludge, and then inoculating modified sodium alginate with nitrifying bacteria, modified sodium alginate containing nitrifying bacteria is obtained.

2. The composite filler for urban non-point source pollution control as described in claim 1, characterized in that, The composite filler comprises the following raw materials in parts by weight: 35 parts ceramsite, 25 parts quartz sand, 7.5 parts modified sodium alginate containing nitrifying bacteria, 2 parts sodium persulfate, 10 parts modified montmorillonite, 10 parts zeolite, 7.5 parts ferric hydroxide, and 7 parts binder.

3. The composite filler for urban non-point source pollution control as described in claim 1, characterized in that, In step A1, the mass ratio of sodium alginate, polyurethane solution, and nano silica is 3:1:

1.

4. The composite filler for urban non-point source pollution control as described in claim 1, characterized in that, In step A3, the specific inoculation process is as follows: the sludge containing nitrifying bacteria is diluted with clean water to 3500-4500 mg / L, and then the sludge is poured into modified sodium alginate in multiple batches.

5. A method for preparing a composite filler for urban non-point source pollution control as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Wash the ceramsite and quartz sand with deionized water, dry them, and prepare a binder solution with a mass concentration of 4-6%. S2, ceramsite, quartz sand, modified sodium alginate containing nitrifying bacteria, sodium persulfate, modified montmorillonite, zeolite, and ferric hydroxide are mixed evenly, and a binder solution is sprayed while mixing to form a pre-mixed composite filler. S3 involves granulating the pre-mixed composite filler, allowing it to stand and solidify in a ventilated environment, and then drying it to obtain the composite filler.

6. The method for preparing a composite filler for urban non-point source pollution control as described in claim 5, characterized in that, In step S2, the preparation method of modified montmorillonite is as follows: montmorillonite is mixed with polymethyl methacrylate solution, stirred thoroughly, reacted at room temperature for 2-4 hours, and dried to obtain modified montmorillonite.

7. The method for preparing a composite filler for urban non-point source pollution control as described in claim 6, characterized in that, The amount of the polymethacrylate ammonium solution used is 5-10% of the mass of montmorillonite.

8. The method for preparing a composite filler for urban non-point source pollution control as described in claim 5, characterized in that, In step S2, the zeolite particle size is 3mm-5mm.

9. The method for preparing a composite filler for urban non-point source pollution control as described in claim 5, characterized in that, In step S3, the particle size of the composite filler is 4mm-6mm.

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