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

Abstract

The invention 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.The composite filler is prepared from, by mass, 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 and 5-10 parts of ferric hydroxide. The modified sodium alginate containing the nitrifying bacteria is prepared by carrying out composite crosslinking modification on polyurethane and nano silicon dioxide and then inoculating the modified sodium alginate with the nitrifying bacteria, and the modified montmorillonite is ammonium polymethacrylate modified montmorillonite. The problems that a composite filler in an existing bioretention facility is poor in nitrogen and phosphorus removal effect, and secondary pollution is serious are solved.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a composite filler for controlling urban non-point source pollution and a preparation method thereof. Background Art

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

[0003] As point source pollution is effectively managed, non-point source pollution caused by initial rainwater has received increasing attention. As a new concept for rainwater treatment, low-impact development technology has been widely adopted because it can effectively reduce the environmental burden. For the treatment of initial rainwater non-point source pollution, three strategies are usually adopted: source control, process control and terminal control. Specific measures include but are not limited to bioretention facilities, overflow storage tanks, artificial wetlands, etc.

[0004] Most runoff treatment facilities, represented by bioretention facilities, have the function of removing suspended pollutants, but are not very effective in removing nitrogen and phosphorus. The core of bioretention facilities is the use of a composite filler that must have high water retention and good adsorption properties.

[0005] Currently, there are mainly the following types of composite fillers:

[0006] 1. Based on humus soil: Although it can provide good growth conditions, the nutrients inside it are easily lost to the water body with runoff, causing secondary pollution, and the permeability is relatively poor.

[0007] 2. Peat-based: Peat has excellent water retention and nutrient retention capabilities, but as a non-renewable resource, its exploitation is strictly restricted.

[0008] 3. Based on sand: Sand 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. Based on planting soil: Planting soil also has the problem of nutrient loss and poor permeability to water.

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

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

[0012] The purpose of the present invention is to solve the problem that the composite fillers in existing bioretention facilities have poor removal effects on nitrogen and phosphorus and serious secondary pollution, and to provide a composite filler for urban non-point source pollution control and a preparation method thereof.

[0013] In order to achieve the above-mentioned purpose, the 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 a binder. The modified sodium alginate containing nitrifying bacteria is a modified sodium alginate that is cross-linked and modified with polyurethane and nano-silicon dioxide and then inoculated with nitrifying bacteria, and the modified montmorillonite is a montmorillonite modified with ammonium polymethacrylate.

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

[0015] The present invention also discloses a method for preparing the composite filler for controlling urban non-point source pollution, comprising the following steps:

[0016] S1, washing ceramsite and quartz sand with deionized water, drying, and preparing a binder solution with a mass concentration of 4-6%;

[0017] S2, evenly stirring ceramsite, quartz sand, modified sodium alginate containing nitrifying bacteria, sodium persulfate, modified montmorillonite, zeolite, and ferric hydroxide, spraying a binder solution while mixing, to form a preliminarily mixed composite filler;

[0018] S3, granulating the preliminarily mixed composite filler, standing it for curing in a ventilated environment, and drying it to obtain the composite filler.

[0019] In step S2, the method for preparing modified sodium alginate containing nitrifying bacteria comprises the following steps:

[0020] A1, mix the sodium alginate solution, the polyurethane solution and the dispersed nano-silicon dioxide, heat to 40-50°C while stirring, and continue stirring for 1-2 hours;

[0021] A2, adding pentosaldehyde to carry out cross-linking reaction, maintaining the reaction at 50-60°C for 1-2 hours, standing for 24 hours, and drying to obtain modified sodium alginate;

[0022] A3, enriching the whole-process nitrifying bacteria through sludge, inoculating the modified sodium alginate with the whole-process nitrifying bacteria, and obtaining the modified sodium alginate containing nitrifying bacteria.

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

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

[0025] In the step S2, the preparation method of the modified montmorillonite is as follows: montmorillonite is mixed with ammonium polymethacrylate solution, fully stirred, reacted at room temperature for 2-4 hours, and dried to obtain the modified montmorillonite.

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

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

[0028] In the step S3, the composite filler is granulated into a particle size of 4 mm to 6 mm.

[0029] The invention enhances the microstructural stability of sodium alginate by means of the high surface area of ​​nano-silicon dioxide, and at the same time, the introduction of polyurethane significantly improves the mechanical strength and durability of sodium alginate, thereby determining the overall stability of the modified sodium alginate and the adhesion performance of nitrifying bacteria; pentose aldehyde is used as a cross-linking agent to form a three-dimensional network structure of the modified material, further enhancing the strength and hydrolysis resistance of the material, and at the same time improving its ability to immobilize nitrifying bacteria; by inoculating nitrifying bacteria, the microenvironment on the surface of the material is optimized, thereby affecting the activity of the nitrifying bacteria and the ammonia nitrogen removal efficiency; the microbial adhesion ability of the modified sodium alginate is significantly enhanced, the mechanical stability and durability of the prepared filler are improved, the long-term sewage treatment capacity is ensured, the ammonia nitrogen removal efficiency is improved, and the biodegradation ability is enhanced.

[0030] In the modified montmorillonite, ammonium polymethacrylate acts as a cationic polymer and undergoes ion exchange reaction with the surface of montmorillonite, thereby enhancing the cation exchange capacity of montmorillonite and its adsorption capacity for phosphate. During the modification process, uniform dispersion ensures sufficient contact between ammonium polymethacrylate and montmorillonite, while appropriate drying conditions can avoid polymer degradation and ensure the stability of adsorption performance. The adsorption performance of modified montmorillonite for phosphate and heavy metal ions is significantly enhanced, and the chemical stability of the prepared filler is improved, making it suitable for complex water quality environments. At the same time, the modified montmorillonite enhances the synergistic adsorption effect with other components (such as sodium alginate and zeolite). In terms of synergistic adsorption of phosphate and heavy metal ions, the composite adsorption capacity is significantly enhanced by increasing the cation exchange capacity and porous structure. The biodegradation mechanism provided by the modified sodium alginate is combined with the physical adsorption of the modified montmorillonite and zeolite and the chemical precipitation of iron hydroxide to form a multi-level pollutant removal mechanism.

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

[0032] 1. The composite filler can effectively remove ammonia nitrogen, phosphates and other pollutants in the water through the synergistic effect of different components, achieving excellent water purification effects. In particular, the biocompatibility of modified sodium alginate and the activity of nitrifying bacteria enable the filler to form a biofilm when treating water bodies, enhance the ability to convert ammonia nitrogen, and promote ecological circulation. In addition, the composite modification of polyurethane and nano-silica not only improves the mechanical strength and durability of sodium alginate, reduces the degradation of the filler during long-term use, ensures its long-lasting working performance, but also improves the physical and chemical stability of the filler. The addition of modified montmorillonite and iron hydroxide further enhances the adsorption capacity of the filler in removing heavy metals and nutrients, which helps to further improve water quality. This composite filler uses degradable materials and natural ingredients, which is fully in line with the concept of green environmental protection and is very suitable for the control of urban non-point source pollution;

[0033] 2. Modified sodium alginate materials show excellent water treatment potential through enhanced physical properties, biocompatibility, improved nitrification capacity and good environmental adaptability. After modification, the material not only has higher strength and toughness, and can withstand greater physical impact and long-term immersion during water treatment, thus extending its service life, but also provides a high-quality attachment surface for the growth of nitrifying bacteria, promotes the formation of stable biofilms, and enhances bacterial activity and survival rates. The inoculated full-process nitrifying bacteria can effectively grow on modified sodium alginate, efficiently converting ammonia nitrogen into nitrite and nitrate, achieving natural purification of water bodies and removal of nutrients, significantly improving water quality. In addition, the structural stability and biocompatibility of modified sodium alginate ensure its good performance under different water quality conditions, making it particularly suitable for the control of urban non-point source pollution.

[0034] 3. The modified montmorillonite not only has stronger cation exchange capacity and anion adsorption capacity, which can effectively remove heavy metals, phosphorus and other pollutants in water bodies, but also improves its surface hydrophilicity and dispersibility due to the introduction of ammonium polymethacrylate, which is beneficial to its application in water treatment and soil remediation. DETAILED DESCRIPTION

[0035] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with embodiments.

[0036] Example 1

[0037] The specific preparation of the composite filler in this embodiment includes the following steps:

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

[0039] A1, 15 kg of sodium alginate solution, 5 kg of polyurethane solution and 5 kg of dispersed nano-silicon dioxide were mixed, heated to 40°C under stirring, and stirred for 2 hours;

[0040] A2, adding 1 kg of pentosaldehyde for cross-linking reaction, maintaining the reaction at 50°C for 2 hours, standing for 24 hours, and drying to obtain modified sodium alginate;

[0041] A3, enriching the complete nitrifying bacteria through sludge, first diluting the sludge containing the complete nitrifying bacteria with clean water to 3500 mg / L, and then pouring it into the modified sodium alginate for several times to obtain the modified sodium alginate containing nitrifying bacteria.

[0042] 2. Preparation of modified montmorillonite

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

[0044] 3. Preparation of composite fillers:

[0045] S1, 35 kg of ceramsite and 25 kg of quartz sand are washed with deionized water, dried, and a binder solution with a mass concentration of 4% is prepared;

[0046] S2, 30kg ceramsite, 20kg quartz sand, 5kg modified sodium alginate containing nitrifying bacteria, 1kg sodium persulfate, 5kg modified montmorillonite, 5kg zeolite, and 5kg ferric hydroxide are uniformly stirred, and 36L of binder solution is sprayed while mixing to form a preliminarily mixed composite filler;

[0047] S3, granulating the preliminarily mixed composite filler into a granule with a particle size of 4 mm, standing and curing in a ventilated environment, and drying to obtain the composite filler.

[0048] Example 2

[0049] The specific preparation of the composite filler in this embodiment includes the following steps:

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

[0051] A1, 17 kg of sodium alginate solution, 5.5 kg of polyurethane solution and 5.5 kg of dispersed nano-silicon dioxide were mixed, heated to 45°C under stirring, and stirred for 1.5 hours;

[0052] A2, adding 1.5 kg of pentose aldehyde for cross-linking reaction, maintaining the reaction at 55°C for 1.5 hours, standing for 24 hours, and drying to obtain modified sodium alginate;

[0053] A3, enriching the complete nitrifying bacteria through sludge, first diluting the sludge containing the complete nitrifying bacteria with clean water to 4000 mg / L, and then pouring it into the modified sodium alginate several times to obtain the 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 ammonium polymethacrylate solution, stirred thoroughly, reacted at room temperature for 3 h, and dried to obtain modified montmorillonite.

[0056] 3. Preparation of composite fillers:

[0057] S1, washing 40kg of ceramsite and 30kg of quartz sand with deionized water, drying, and preparing a binder solution with a mass concentration of 5%;

[0058] S2, 35 kg of ceramsite, 25 kg of quartz sand, 7.5 kg of modified sodium alginate containing nitrifying bacteria, 2 kg of sodium persulfate, 10 kg of modified montmorillonite, 10 kg of zeolite, and 7.5 kg of ferric hydroxide are uniformly stirred, and 50 L of binder solution is sprayed while mixing to form a preliminarily mixed composite filler;

[0059] S3, granulating the preliminarily mixed composite filler into a granule with a particle size of 5 mm, standing and curing in a ventilated environment, and drying to obtain the composite filler.

[0060] Example 3

[0061] The specific preparation of the composite filler in this embodiment includes the following steps:

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

[0063] A1, 18 kg of sodium alginate solution, 6 kg of polyurethane solution and 6 kg of dispersed nano-silicon dioxide were mixed, heated to 50°C under stirring, and stirred for 1 hour;

[0064] A2, adding 2 kg of pentosaldehyde for cross-linking reaction, maintaining the reaction at 60°C for 1 hour, standing for 24 hours, and drying to obtain modified sodium alginate;

[0065] A3, enriching the full-process nitrifying bacteria through sludge, first diluting the sludge containing the full-process nitrifying bacteria with clean water to 4500 mg / L, and then pouring it into the modified sodium alginate for multiple times to obtain the modified sodium alginate containing nitrifying bacteria.

[0066] 2. Preparation of modified montmorillonite

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

[0068] 3. Preparation of composite fillers:

[0069] S1, washing 45 kg of ceramsite and 35 kg of quartz sand with deionized water, drying, and preparing a binder solution with a mass concentration of 6%;

[0070] S2, 40kg ceramsite, 30kg quartz sand, 10kg modified sodium alginate containing nitrifying bacteria, 3kg sodium persulfate, 15kg modified montmorillonite, 15kg zeolite, and 10kg ferric hydroxide are uniformly stirred, and 63L of binder solution is sprayed while mixing to form a preliminarily mixed composite filler;

[0071] S3, granulating the preliminarily mixed composite filler into a granule with a particle size of 6 mm, standing and curing in a ventilated environment, and drying 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 by ordinary montmorillonite.

[0076] The individual components in the composite filler and the composite fillers of Examples 1-3 are mixed with ammonia nitrogen, phosphate and heavy metal ions (such as Pb 2+ 、Cd 2+ ) was used to treat the simulated wastewater. The pollutant removal rate data are shown in Table 1

[0077] Table 1 Removal rates of pollutants in simulated wastewater by individual components of the composite filler and the composite fillers of Examples 1-3

[0078]

[0079] The composite filler of Example 2 significantly improves the removal rate of all pollutants, especially the removal rate of ammonia nitrogen reaches 95%, and the removal rate of phosphate and heavy metals also reaches more than 85%, showing a significant synergistic effect.

[0080] Comparative Example 1 and Examples 1-3 were subjected to mechanical strength tests and nitrifying bacteria attachment rate tests, and the data are shown in Table 2.

[0081] Table 2 Mechanical strength test results and nitrifying bacteria attachment rate test results of Comparative Example 1 and Examples 1-3

[0082]

[0083] The mechanical properties of the filler of Example 2 are significantly higher than those of the filler of Comparative Example 1, indicating that the composite cross-linking of polyurethane and nano-silicon dioxide can enhance strength. The number and attachment rate of attached bacteria of the filler of Example 2 are significantly higher than those of the filler of Comparative Example 1, indicating that the modification improves the surface affinity and biocompatibility.

[0084] Comparative Example 2 and Examples 1-3 were subjected to lead ion adsorption experiments. The data are shown in Table 3.

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

[0086]

[0087] The filler of Example 2 is significantly better than the filler of Comparative Example 2 in terms of lead ion adsorption, and the removal rate is increased by 26%, indicating that the modification effect of ammonium polymethacrylate is significant.

[0088] The composite fillers prepared in Examples 1-3 and Comparative Examples 1-2 were respectively used in 5 bioretention facilities to filter and purify rainwater runoff, and then discharged into rainwater pipes after purification.

[0089] Table 4 Water treatment effects of the composite fillers prepared in Examples 1-3 and Comparative Examples 1-2 in 5 bioretention facilities

[0090]

[0091] By comparing the comparative example 1 with the example 2, it can be found that the removal rate of ammonia nitrogen is significantly improved by adding the modified sodium alginate containing nitrifying bacteria in the example 2. This shows that the modified sodium alginate not only provides an excellent growth environment for nitrifying bacteria and promotes the formation of biofilm, but also strengthens the conversion process of ammonia nitrogen into nitrite and nitrate, thereby achieving a more efficient ammonia nitrogen removal effect.

[0092] From the comparison between Comparative Example 2 and Example 2, it can be seen that after adding modified montmorillonite in Example 2, the efficiency of phosphorus removal and ammonia nitrogen removal is significantly improved. Modified montmorillonite not only effectively captures and fixes phosphorus and nitrogen compounds in water bodies through enhanced cation exchange capacity and adsorption capacity for anions, but also promotes the removal of pollutants, showing its important role in water purification. This finding emphasizes the potential of modified montmorillonite in improving the overall efficiency of water treatment systems, especially in comprehensively solving ammonia nitrogen and phosphorus pollution problems.

[0093] The above description is only a preferred embodiment of the present invention, which is only illustrative and not restrictive of the present invention. Those skilled in the art understand that many changes, modifications, and even equivalences may be made to the present invention within the spirit and scope defined by the claims of the present invention, but all of them will fall within the scope of protection of the present invention.

Claims

1. A composite filler for urban non-point source pollution control, characterized in that: The invention comprises the following raw materials in parts by mass: 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 a binder. The modified sodium alginate containing nitrifying bacteria is a modified sodium alginate which is cross-linked and modified with polyurethane and nano-silicon dioxide and then inoculated with nitrifying bacteria. The modified montmorillonite is a montmorillonite modified with ammonium polymethacrylate.

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

3. A method for preparing a composite filler for urban non-point source pollution control as claimed in claim 1 or 2, characterized in that: The following steps are involved: S1, washing ceramsite and quartz sand with deionized water, drying, and preparing a binder solution with a mass concentration of 4-6%; S2, evenly stirring ceramsite, quartz sand, modified sodium alginate containing nitrifying bacteria, sodium persulfate, modified montmorillonite, zeolite, and ferric hydroxide, spraying a binder solution while mixing, to form a preliminarily mixed composite filler; S3, granulating the preliminarily mixed composite filler, allowing it to stand and solidify in a ventilated environment, and drying it to obtain the composite filler.

4. The method for preparing a composite filler for controlling urban non-point source pollution according to claim 3, characterized in that: In step S2, the method for preparing modified sodium alginate containing nitrifying bacteria comprises the following steps: A1, mix the sodium alginate solution, the polyurethane solution and the dispersed nano-silicon dioxide, heat to 40-50°C while stirring, and continue stirring for 1-2 hours; A2, adding pentosaldehyde to carry out cross-linking reaction, maintaining the reaction at 50-60°C for 1-2 hours, standing for 24 hours, and drying to obtain modified sodium alginate; A3, enriching the whole-process nitrifying bacteria through sludge, inoculating the modified sodium alginate with the whole-process nitrifying bacteria, and obtaining the modified sodium alginate containing nitrifying bacteria.

5. The method for preparing a composite filler for controlling urban non-point source pollution according to claim 4, characterized in that: In the step A1, the mass ratio of sodium alginate, polyurethane solution and nano-silicon dioxide is 3:1:

1.

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

7. The method for preparing a composite filler for controlling urban non-point source pollution according to claim 3, characterized in that: In step S2, the preparation method of modified montmorillonite is as follows: montmorillonite is mixed with ammonium polymethacrylate solution, fully stirred, reacted at room temperature for 2-4 hours, and dried to obtain modified montmorillonite.

8. The method for preparing a composite filler for controlling urban non-point source pollution according to claim 7, characterized in that: The dosage of the ammonium polymethacrylate solution is 5-10% of the mass of the montmorillonite.

9. The method for preparing a composite filler for controlling urban non-point source pollution according to claim 3, characterized in that: In the step S2, the particle size of the zeolite is 3 mm to 5 mm.

10. The method for preparing a composite filler for controlling urban non-point source pollution according to claim 3, characterized in that: In the step S3, the composite filler is granulated into a particle size of 4 mm to 6 mm.

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