Slow-release membrane for sewage treatment and preparation method thereof

Abstract

The invention relates to a slow-release membrane for sewage treatment and a preparation method thereof, and provides the slow-release membrane for sewage treatment, which is characterized in that gelatin, sodium alginate and polyvinyl alcohol are used as raw materials, a layer of porous membrane is coated outside a slow-release filler by adopting a sol-gel method, and flora loaded on the internal slow-release filler can be slowly and stably released; and the membrane material is environment-friendly and can be naturally degraded, so that the problem of secondary pollution caused by a slow-release membrane material during use is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a slow-release membrane for sewage treatment and a preparation method thereof. Background Art

[0002] Currently, commonly used sewage treatment methods include activated sludge process, biofilm process, oxidation ditch process, etc. Although the above methods can effectively remove organic matter and nutrients such as nitrogen and phosphorus in sewage, they all require the construction of large-scale equipment and large initial infrastructure investment.

[0003] The granular water treatment agent containing bacteria is a water treatment product that combines the advantages of microbial technology and physical form. By fixing the microbial flora on the carrier particles, the treatment agent not only has the efficient degradation and conversion ability of microorganisms, but also has the good dispersibility, stability and easy addition characteristics of granular substances. However, it is found in practical applications that although adding water treatment agents to polluted water bodies can remove nitrogen and phosphorus pollutants, it is difficult to effectively purify sewage for a long time. Prior art CN 113999836 B discloses a biological bacterial agent, which is a multi-shell particle structure. By using degradable plastic as a shell material, the time-sharing release of each group of microorganisms is achieved. Although the above form prolongs the effective duration of the bacterial agent to a certain extent, it uses polylactic acid and polyhydroxyalkanoate as degradable materials. It has slow decomposition, and the degraded polylactic acid small molecule fragments will still form agglomerated particles in the water, causing secondary pollution of the water body. Therefore, how to achieve long-term effective purification of sewage by water treatment agents and avoid secondary pollution is a problem to be solved. Summary of the invention

[0004] Based on the above-mentioned technical problems to be solved, the present invention provides a sustained-release membrane, which uses gelatin, sodium alginate and polyvinyl alcohol as raw materials, and adopts a sol-gel method to wrap a layer of porous membrane on the outside of the sustained-release filler. The membrane can slowly and stably release the bacterial flora loaded on the internal sustained-release filler, and can effectively and long-term treat sewage. The membrane material is environmentally friendly and can undergo natural degradation, thus avoiding the problem of secondary pollution caused by the sustained-release membrane material during use.

[0005] To achieve the above object, the present invention provides the following technical solution: gelatin, sodium alginate and polyvinyl alcohol are used as raw materials and wrapped on the outside of the sustained-release filler by a sol-gel method;

[0006] The sustained-release filler comprises the following substances in weight: 30-50 parts of a functional bacterial community carrier, 20-30 parts of lignin, 1-5 parts of kaolin, 20-30 parts of agar, and 10-20 parts of a binder; the functional bacterial community carrier is a carrier to which nitrifying bacteria and polyphosphate bacteria are attached.

[0007] The nitrifying bacteria are one or more of nitrate bacteria and nitrite bacteria, and the polyphosphate bacteria are one or more of Phomonas polyphosphate bacteria, Pseudomonas polyphosphate bacteria or Acinetobacter polyphosphate bacteria.

[0008] The mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3-8%, and the mass fraction of polyphosphate bacteria is 5-10%; the carrier is starch particles with an average particle size of 0.5-1 μm.

[0009] A method for preparing the sustained-release membrane for sewage treatment, comprising the following specific steps:

[0010] S1: Inoculating nitrifying bacteria and polyphosphate bacteria on a carrier to obtain a functional bacterial community carrier, wherein the mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3-8%, and the mass fraction of polyphosphate bacteria is 5-10%;

[0011] S2: The functional bacteria carrier is mixed with lignin, kaolin, and agar in proportion, and then a binder is added, and the mixture is dried at room temperature to obtain a sustained-release filler containing functional bacteria;

[0012] S3: preparing an aqueous solution of gelatin, sodium alginate and polyvinyl alcohol, stirring at 30-50°C for 1 hour, and performing vacuum degassing to obtain a mixed sol;

[0013] S4: Add 10-20% of the sustained-release filler to the sol at a mass fraction, stir evenly, add 1% of the Na2SO4 cross-linking agent at a mass fraction, continue stirring for 1 hour, age at room temperature for 48 hours, filter, and freeze-dry to obtain a sustained-release membrane.

[0014] The mass fraction of the polyvinyl alcohol is 2-3%, the mass fraction of the gelatin is 5-10%, and the mass fraction of the sodium alginate is 5-10%.

[0015] The binder is chitosan or chitin.

[0016] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0017] 1. The present invention uses gelatin, sodium alginate and polyvinyl alcohol as raw materials, and adopts the sol-gel method to wrap a layer of porous membrane on the outside of the sustained-release filler, which can slowly and stably release the bacterial flora loaded on the internal sustained-release filler, and can effectively and long-term treat sewage. At the same time, a protective layer can be formed on the outside of the filler, avoiding the direct impact of different water quality conditions on the bacterial flora during sewage treatment, extending the use time, and the sustained-release membrane material is environmentally friendly and can be naturally degraded, avoiding the problem of secondary pollution caused by the sustained-release membrane material during use.

[0018] 2. The sustained-release membrane prepared by the present invention can form a cross-linked mesh porous structure, which can slowly and stably release the bacterial flora loaded on the internal sustained-release filler. The interior of the sustained-release membrane is rich in hydroxyl and carboxyl functional groups, which can form hydrogen bonds with the functional groups in the sustained-release filler, which is beneficial to the assembly of the internal sustained-release filler.

[0019] 3. The carrier in the slow-release filler of the present invention provides a carbon source for the growth of the flora, and a network skeleton structure can be formed between lignin and agar. Both have good bioaffinity, low toxicity to functional flora, reduced biofilm time, and can stably release the flora in the filler for a long time. While serving as a filler, kaolin has certain adhesive properties and can provide trace elements such as Fe and Al for flora production. In addition, agar has certain water absorption, and the hydroxyl hydrophilic groups in lignin can combine with water molecules, avoiding the problem of water absorption and swelling of the carrier and kaolin during storage. DETAILED DESCRIPTION

[0020] To make the purpose, technical scheme and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail. In the following examples and comparative examples, identical nitrifying bacteria and polyphosphate bacteria are used, wherein the nitrifying bacteria are mixed colonies comprising nitrate bacteria and nitrite bacteria, and the polyphosphate bacteria are mixed colonies comprising Pseudomonas polyphosphate bacteria, Pseudomonas polyphosphate bacteria and Acinetobacter polyphosphate bacteria.

[0021] Example 1

[0022] S1: Inoculate nitrifying bacteria and polyphosphate bacteria on a carrier to obtain a functional bacterial community carrier, wherein the mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3%, and the mass fraction of polyphosphate bacteria is 5%;

[0023] S2: Mix 40 parts of functional bacteria carrier, 20 parts of lignin, 1 part of kaolin, and 20 parts of agar in proportion, add 10 parts of chitosan binder, mix well, and dry at room temperature to obtain a sustained-release filler containing functional bacteria;

[0024] S3: Prepare an aqueous solution of gelatin, sodium alginate and polyvinyl alcohol, stir at 30°C for 1 hour, and perform vacuum degassing to obtain a mixed sol; wherein the mass fraction of polyvinyl alcohol is 2%, the mass fraction of gelatin is 5%, and the mass fraction of sodium alginate is 5%.

[0025] S4: Add 10% by mass of the sustained-release filler to the sol, stir evenly, add 1% by mass of the Na2SO4 cross-linking agent, continue stirring for 1 hour, age at room temperature for 48 hours, filter, and freeze-dry to obtain a sustained-release membrane.

[0026] Example 2

[0027] S1: Inoculate nitrifying bacteria and polyphosphate bacteria on a carrier to obtain a functional bacterial community carrier, wherein the mass fraction of nitrifying bacteria in the functional bacterial community carrier is 8%, and the mass fraction of polyphosphate bacteria is 10%;

[0028] S2: Mix 30 parts of functional bacteria carrier, 30 parts of lignin, 5 parts of kaolin, and 30 parts of agar in proportion, add 20 parts of chitosan binder, mix well, and dry at room temperature to obtain a sustained-release filler containing functional bacteria;

[0029] S3: Prepare an aqueous solution of gelatin, sodium alginate and polyvinyl alcohol, stir at 30°C for 1 hour, and perform vacuum degassing to obtain a mixed sol; wherein the mass fraction of polyvinyl alcohol is 3%, the mass fraction of gelatin is 10%, and the mass fraction of sodium alginate is 10%.

[0030] S4: Add 20% of the sustained-release filler to the sol at a mass fraction, stir evenly, then add 1% of the Na2SO4 cross-linking agent at a mass fraction, continue stirring for 1 hour, age at room temperature for 48 hours, filter, and freeze-dry to obtain a sustained-release membrane.

[0031] Example 3

[0032] S1: Inoculate nitrifying bacteria and polyphosphate bacteria on a carrier to obtain a functional bacterial community carrier, wherein the mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3%, and the mass fraction of polyphosphate bacteria is 5%;

[0033] S2: Mix 30 parts of functional bacteria carrier, 50 parts of lignin, 5 parts of kaolin, and 30 parts of agar in proportion, add 20 parts of chitosan binder, mix well, and dry at room temperature to obtain a sustained-release filler containing functional bacteria;

[0034] S3: Prepare an aqueous solution of gelatin, sodium alginate and polyvinyl alcohol, stir at 30°C for 1 hour, and perform vacuum degassing to obtain a mixed sol; wherein the mass fraction of polyvinyl alcohol is 3%, the mass fraction of gelatin is 8%, and the mass fraction of sodium alginate is 8%.

[0035] S4: Add 10% by mass of the sustained-release filler to the sol, stir evenly, add 1% by mass of the Na2SO4 cross-linking agent, continue stirring for 1 hour, age at room temperature for 48 hours, filter, and freeze-dry to obtain a sustained-release membrane.

[0036] Comparative Example

[0037] S1: Inoculate nitrifying bacteria and polyphosphate bacteria on a carrier to obtain a functional bacterial community carrier, wherein the mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3%, and the mass fraction of polyphosphate bacteria is 5%;

[0038] S2: The functional bacteria carrier is mixed with lignin, kaolin, and agar in proportion, and then chitosan binder is added, and the mixture is dried at room temperature to obtain a sustained-release filler containing functional bacteria;

[0039] Performance Evaluation

[0040] The sustained-release membrane of the above embodiment and the sustained-release filler of the comparative example were added into an equal volume of wastewater, 10 g was added per liter of wastewater, and the time required for the removal rates of total nitrogen and total phosphorus in the wastewater to reach 90% and 95% was calculated.

[0041] Table 1 Time required for total nitrogen and total phosphorus removal rates to reach 90%

[0042] Total nitrogen (hours) Total phosphorus (hours) Example 1 36 40 Example 2 33 38 Example 3 39 41 Comparative Example 22 24

[0043] Table 2 Time required for total nitrogen and total phosphorus removal rates to reach 95%

[0044] Total nitrogen (hours) Total phosphorus (hours) Example 1 65 73 Example 2 68 77 Example 3 66 74 Comparative Example —— ——

[0045] It can be seen from Tables 1 and 2 that unwrapped slow-release fillers cannot effectively purify sewage for a long time, and the removal rate of total nitrogen and total phosphorus in sewage is only 90%; Examples 1-3 of the present application can exert their effectiveness for a long time in the sewage treatment process, and have a high efficiency removal effect of total nitrogen and total phosphorus in sewage, which can reach 95%.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A sustained-release membrane for sewage treatment, characterized in that: Gelatin, sodium alginate and polyvinyl alcohol are used as raw materials and are coated on the outside of the sustained-release filler by the sol-gel method; The sustained-release filler comprises the following substances in weight: 30-50 parts of a functional bacterial community carrier, 20-30 parts of lignin, 1-5 parts of kaolin, 20-30 parts of agar, and 10-20 parts of a binder; the functional bacterial community carrier is a carrier to which nitrifying bacteria and polyphosphate bacteria are attached.

2. The sustained-release membrane for sewage treatment according to claim 1, characterized in that: The nitrifying bacteria are one or more of nitrate bacteria and nitrite bacteria, and the polyphosphate bacteria are one or more of Phomonas polyphosphate bacteria, Pseudomonas polyphosphate bacteria or Acinetobacter polyphosphate bacteria.

3. The sustained-release membrane for sewage treatment according to claim 1, characterized in that: The mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3-8%, and the mass fraction of polyphosphate bacteria is 5-10%; the carrier is starch particles with an average particle size of 0.5-1 μm.

4. A method for preparing a sustained-release membrane for sewage treatment according to claim 3, characterized in that: The specific steps are: S1: Inoculating nitrifying bacteria and polyphosphate bacteria on a carrier to obtain a functional bacterial community carrier, wherein the mass fraction of nitrifying bacteria in the functional bacterial community carrier is 3-8%, and the mass fraction of polyphosphate bacteria is 5-10%; S2: The functional bacteria carrier is mixed with lignin, kaolin, and agar in proportion, and then a binder is added. After mixing, the mixture is dried at room temperature to obtain a sustained-release filler containing functional bacteria; S3: preparing an aqueous solution of gelatin, sodium alginate and polyvinyl alcohol, stirring at 30-50°C for 1 hour, and performing vacuum degassing to obtain a mixed sol; S4: Add 10-20% of the sustained-release filler to the sol at a mass fraction, stir evenly, add 1% of the Na2SO4 cross-linking agent at a mass fraction, continue stirring for 1 hour, age at room temperature for 48 hours, filter, and freeze-dry to obtain a sustained-release membrane.

5. The method for preparing the sustained-release film according to claim 4, characterized in that: The mass fraction of the polyvinyl alcohol is 2-3%, the mass fraction of the gelatin is 5-10%, and the mass fraction of the sodium alginate is 5-10%.

6. The method for preparing the sustained-release membrane according to claim 4, characterized in that: The binder is chitosan or chitin.