A slow-release membrane for sewage treatment and its preparation method

Abstract

The present invention relates to a slow-release membrane for sewage treatment and a preparation method thereof. The present invention provides a slow-release membrane for sewage treatment, which uses gelatin, sodium alginate and polyvinyl alcohol as raw materials and adopts a sol-gel method to coat a porous membrane on the outside of the slow-release filler, which can slowly and stably release the bacteria loaded on the internal slow-release filler, can effectively and long-term treat sewage, and the membrane material is environmentally friendly and can be naturally degraded, avoiding the problem of secondary pollution caused by the slow-release membrane material during use.

Description

Technical Field

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

[0002] Currently, common sewage treatment methods include the activated sludge method, the biofilm method, the oxidation ditch process, etc. Although the above methods can effectively remove organic matter, nitrogen, phosphorus and other nutrients in sewage. However, the above methods all require the construction of large-scale equipment, and the upfront infrastructure investment is relatively large.

[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 dosing of granular substances. However, it is found in practical applications that although adding the water treatment agent to polluted water can remove nitrogen and phosphorus pollutants, it is difficult to effectively purify sewage for a long time. The prior art CN 113999836 B discloses a biological bactericide, which is a multi-shell type particle structure. By using a biodegradable plastic as the shell layer material, the time-sharing release of each group of microorganisms is realized. Although the above form extends the effective duration of the bactericide to a certain extent, the use of polylactic acid and polyhydroxyalkanoates as biodegradable materials has slow decomposition, and the small molecular fragments of polylactic acid after degradation will still form aggregated particles in water, causing secondary pollution of the water body. Therefore, how to achieve long-term and effective purification of sewage by the water treatment agent and avoid secondary pollution is an urgent problem to be solved. Summary of the Invention

[0004] Based on the above technical problems to be solved, the present invention provides a slow-release membrane. Using gelatin, sodium alginate and polyvinyl alcohol as raw materials, a porous membrane is wrapped outside the slow-release filler by the sol-gel method, which can slowly and stably release the bacteria loaded on the internal slow-release filler, can effectively and long-term treat sewage, and the membrane material is environmentally friendly and can be naturally degraded, avoiding the problem of secondary pollution caused by the slow-release membrane material during use.

[0005] To achieve the above object, the present invention provides the following technical solution: Using gelatin, sodium alginate and polyvinyl alcohol as raw materials, and wrapping them outside the slow-release filler by the sol-gel method;

[0006] The slow-release filler by weight includes the following substances: 30-50 parts of the functional flora carrier, 20-30 parts of lignin, 1-5 parts of kaolin, 20-30 parts of agar, and 10-20 parts of the binder; the functional flora carrier is a carrier attached with nitrifying bacteria and polyphosphate-accumulating bacteria.

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

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

[0009] A preparation method of the slow-release membrane for sewage treatment is as follows.

[0010] S1: Inoculate nitrifying bacteria and polyphosphate-accumulating bacteria on the carrier to obtain a functional flora carrier, where the mass fraction of nitrifying bacteria in the functional flora carrier is 3-8%, and the mass fraction of polyphosphate-accumulating bacteria is 5-10%;

[0011] S2: Mix the functional flora carrier, lignin, kaolin, and agar in proportion, add a binder, mix evenly, and dry at room temperature. Obtain a slow-release filler containing functional flora;

[0012] S3: Prepare an aqueous solution of gelatin, sodium alginate, and polyvinyl alcohol, stir at 30-50 °C for 1 h, and then perform vacuum degassing treatment to obtain a mixed sol;

[0013] S4: Add the slow-release filler to the sol at a mass fraction of 10-20%, stir evenly, add a crosslinking agent of 1% mass fraction of Na2SO4, continue to stir for 1 h, stand at room temperature for aging for 48 h, filter, and freeze-dry to obtain a slow-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 by the technical solution provided by the present invention at least include:

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

[0018] 2. The sustained-release membrane prepared by the present invention can form a cross-linked network porous structure, which can slowly and stably release the bacteria loaded on the internal sustained-release filler. The inside of the sustained-release membrane is rich in hydroxyl and carboxyl functional groups, which can form hydrogen bond interactions with the functional groups in the sustained-release filler, facilitating the assembly of the internal sustained-release filler.

[0019] 3. The carrier in the sustained-release filler of the present invention provides a carbon source for the growth of bacteria. A network skeleton structure can be formed between lignin and agar, and the two have good biocompatibility, little toxicity to functional bacteria, reducing the film-forming time, and can stably release the bacteria in the filler for a long time. While serving as a filler, kaolin has certain adhesion properties and can provide trace elements such as Fe and Al for the growth of bacteria. 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. Specific Embodiments

[0020] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below. In the following examples and comparative examples, the same nitrifying bacteria and polyphosphate-accumulating bacteria are used. Among them, the nitrifying bacteria are a mixed colony including nitrate bacteria and nitrite bacteria, and the polyphosphate-accumulating bacteria are a mixed colony including polyphosphate-accumulating bacteria of the genus Pseudomonas, polyphosphate-accumulating bacteria of the genus Pseudomonas, and polyphosphate-accumulating bacteria of the genus Acinetobacter.

[0021] Example 1

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

[0023] S2: Mix 40 parts of the 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. Obtain a sustained-release filler containing functional bacteria;

[0024] S3: Prepare an aqueous solution of gelatin, sodium alginate and polyvinyl alcohol. After stirring at 30 °C for 1 h, perform vacuum degassing treatment 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 the sustained-release filler to the sol at a mass fraction of 10%, stir well, add a cross-linking agent of 1% mass fraction of Na2SO4, continue to stir for 1 h, stand and age at room temperature for 48 h, filter, and freeze-dry to obtain a sustained-release membrane.

[0026] Example 2

[0027] S1: Inoculate nitrifying bacteria and polyphosphate-accumulating bacteria onto a carrier to obtain a functional flora carrier, where the mass fraction of nitrifying bacteria in the functional flora carrier is 8% and the mass fraction of polyphosphate-accumulating bacteria is 10%;

[0028] S2: Mix 30 parts of the functional flora carrier, 30 parts of lignin, 5 parts of kaolin, and 30 parts of agar proportionally and uniformly, then add 20 parts of chitosan binder, mix uniformly and dry at room temperature. Obtain a slow-release filler containing the functional flora;

[0029] S3: Prepare an aqueous solution of gelatin, sodium alginate, and polyvinyl alcohol. After stirring at 30 °C for 1 h and then performing vacuum degassing treatment, obtain a mixed sol; where 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 the slow-release filler to the sol at a mass fraction of 20%, stir evenly, add a crosslinking agent of 1% mass fraction of Na2SO4, continue stirring for 1 h, stand and age at room temperature for 48 h, filter, and freeze-dry to obtain a slow-release membrane.

[0031] Example 3

[0032] S1: Inoculate nitrifying bacteria and polyphosphate-accumulating bacteria onto a carrier to obtain a functional flora carrier, where the mass fraction of nitrifying bacteria in the functional flora carrier is 3% and the mass fraction of polyphosphate-accumulating bacteria is 5%;

[0033] S2: Mix 30 parts of the functional flora carrier, 50 parts of lignin, 5 parts of kaolin, and 30 parts of agar proportionally and uniformly, then add 20 parts of chitosan binder, mix uniformly and dry at room temperature. Obtain a slow-release filler containing the functional flora;

[0034] S3: Prepare an aqueous solution of gelatin, sodium alginate, and polyvinyl alcohol. After stirring at 30 °C for 1 h and then performing vacuum degassing treatment, obtain a mixed sol; where 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 the slow-release filler to the sol at a mass fraction of 10%, stir evenly, add a crosslinking agent of 1% mass fraction of Na2SO4, continue stirring for 1 h, stand and age at room temperature for 48 h, filter, and freeze-dry to obtain a slow-release membrane.

[0036] Comparative Example

[0037] S1: Inoculate nitrifying bacteria and polyphosphate-accumulating bacteria onto a carrier to obtain a functional flora carrier, where the mass fraction of nitrifying bacteria in the functional flora carrier is 3% and the mass fraction of polyphosphate-accumulating bacteria is 5%;

[0038] S2: Mix the functional flora carrier, lignin, kaolin, and agar evenly in proportion, then add a chitosan binder, mix well, and dry at room temperature to obtain a slow-release filler containing the functional flora.

[0039] Performance evaluation

[0040] Put the slow-release membrane of the above embodiment and the slow-release filler of the comparative example into equal volumes of wastewater, add 10 g per liter of wastewater, and calculate the time required for the total nitrogen and total phosphorus removal rates in the wastewater to reach 90% and 95%.

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

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

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

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

[0045] As can be seen from Tables 1 and 2, the uncoated slow-release filler cannot effectively purify sewage for a long time, and the total nitrogen and total phosphorus removal rates of the sewage are only 90%; Examples 1-3 of the present application can play a role for a long time during the sewage treatment process, have a high removal effect on the total nitrogen and total phosphorus in the sewage, and can reach 95%.

[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a slow-release membrane for sewage treatment, characterized in that, The specific steps are as follows: S1: Inoculate nitrifying bacteria and polyphosphate-accumulating bacteria on a carrier to obtain a functional flora carrier. The carrier is starch granules. The mass fraction of nitrifying bacteria in the functional flora carrier is 3-8%, and the mass fraction of polyphosphate-accumulating bacteria is 5-10%. S2: Mix the functional flora carrier with lignin, kaolin, and agar in proportion, add a binder after mixing evenly, and dry at room temperature to obtain a slow-release filler containing the functional flora. S3: Prepare an aqueous solution of gelatin, sodium alginate, and polyvinyl alcohol. Stir for 1 h at 30-50 °C, and then perform vacuum defoaming treatment to obtain a mixed sol. S4: Add the slow-release filler to the sol at a mass fraction of 10-20%, stir evenly, add a cross-linking agent of 1% mass fraction of Na2SO4, continue to stir for 1 h, stand at room temperature for aging for 48 h, filter, and freeze-dry to obtain a slow-release membrane. The slow-release filler by weight includes the following substances: 30-50 parts of the functional flora carrier, 20-30 parts of lignin, 1-5 parts of kaolin, 20-30 parts of agar, and 10-20 parts of the binder; the binder is chitosan or chitin.

2. The preparation method of the slow-release membrane for sewage treatment according to claim 1, wherein, The nitrifying bacteria are one or more of nitrate bacteria and nitrite bacteria, and the polyphosphate-accumulating bacteria are one or more of polyphosphate-accumulating bacteria of the genus Monomonas, polyphosphate-accumulating bacteria of the genus Pseudomonas, or polyphosphate-accumulating bacteria of the genus Acinetobacter.

3. The preparation method of the slow-release membrane for sewage treatment according to claim 1, characterized in that, The mass fraction of nitrifying bacteria in the functional flora carrier is 3-8%, and the mass fraction of polyphosphate-accumulating bacteria is 5-10%; the average particle size of the carrier is 0.5-1 μm.

4. The preparation method of the slow-release membrane for sewage treatment according to claim 1, characterized in that: The mass fraction of polyvinyl alcohol is 2-3%, the mass fraction of gelatin is 5-10%, and the mass fraction of sodium alginate is 5-10%.