A method for coupling and modifying a biofilm carrier

Abstract

The present invention discloses a method for coupling and modifying a biofilm carrier, which specifically includes: dissolving the industrial waste ferrous sulfate heptahydrate of titanium dioxide in water, adding a commercially available biofilm carrier filler and mixing evenly with the ferrous sulfate solution, acidifying the mixed solution with concentrated sulfuric acid, and then adding industrial aluminum sulfate; heating and stirring under the condition of a water bath at 50°C - 80°C, adding concentrated nitric acid for oxidation while stirring, and carrying out a polymerization reaction for 30 - 60 minutes; then adding a stabilizer, separating the biofilm carrier from the polyferric sulfate after standing for a period of time to obtain a modified biofilm carrier and a polyferric sulfate coagulant respectively. The method of the present invention realizes the modification of the biofilm carrier without affecting the preparation of the polyferric sulfate coagulant, and has the advantages of low cost, simple operation, easy industrial popularization, etc.

Description

Technical Field

[0001] The present invention relates to a method for coupling and modifying a biofilm carrier, belonging to the technical field of environmental protection. Background Art

[0002] The biofilm method is widely used in sewage treatment. It refers to a method of sewage biological treatment using microorganisms (i.e., biofilm) attached and grown on the surface of certain solids, ultimately achieving the purpose of purifying sewage. Compared with the activated sludge method, the biofilm method has a series of remarkable advantages such as high biomass, strong impact load resistance, stable operation, and small floor area.

[0003] The biofilm carrier is a key material for the biofilm method. Its performance such as structural shape, density, surface roughness, hydrophilic and hydrophobic properties directly relates to the ease of film formation on the carrier, the amount of biomass in the reactor, and the efficiency of sewage treatment. However, traditional carriers mostly use polyethylene and polypropylene, and the bioaffinity of the carrier material is poor, resulting in problems such as slow film formation speed of the biofilm carrier, low activity of the attached biofilm, and poor water treatment effect, leading to a relatively slow start-up of the biofilm process. Therefore, how to improve the hydrophilic and hydrophobic properties and bioaffinity of the filler has become a research hotspot in recent years.

[0004] In current research on surface charge modification of biofilm carriers, generally, the hydrophilicity of the biofilm carrier surface is first changed by a strong oxidant, and then the modified biofilm carrier is placed in a solution of FeCl3 and left standing or evaporated to dryness, so that iron ions are loaded onto the surface of the biofilm carrier to improve the hydrophilic and hydrophobic properties and bioaffinity of the biofilm carrier. However, these methods usually consume a large amount of oxidant and FeCl3 solution, and the cost is very high, which is the main obstacle to their industrial application. In addition, the iron loaded onto the surface of the biofilm carrier can only exist in the form of Fe 3+ or low-polymerized ions after being re-wetted into the sewage, and the low potential results in too low microbial affinity of the carrier filler, having defects such as a long film formation cycle and low microbial growth. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a method for coupling and modifying a biofilm carrier, which adds the modification of the biofilm carrier to the preparation process of the inorganic polymer coagulant polyferric sulfate (PFS). Without affecting the structural performance of PFS, it realizes the hydrophilic modification and load charge modification of the biofilm carrier filler, reduces the preparation cost of the biofilm carrier, shortens the film formation cycle of the carrier, increases the microbial growth, and improves the sewage treatment effect.

[0006] Specifically, a method for coupling and modifying a biofilm carrier includes:

[0007] (1) Take 550 parts of ferrous sulfate heptahydrate and dissolve it in water;

[0008] (2) Add the biofilm carrier and mix it evenly with ferrous sulfate heptahydrate by stirring;

[0009] (3) Add 73 - 83 parts of concentrated sulfuric acid with a mass fraction of 98% for acidification;

[0010] (4) Add 60 - 70 parts of industrial aluminum sulfate to the acidified mixture, stir evenly and dilute with a small amount of water;

[0011] (5) Place the reaction vessel in a water bath, add 49 - 56 parts of oxidant while stirring, heat at 50°C - 80°C for 30 - 60 minutes, and stir slowly at the same time;

[0012] (6) Add 18 - 56 parts of stabilizing agent phosphoric acid;

[0013] (7) According to the reaction requirement, add sodium hydroxide or carbonic acid to control the basicity of the coagulant product to 8% - 16%;

[0014] (8) Let it stand for 12 - 24 hours;

[0015] (9) Through solid - liquid separation, obtain the coagulant liquid product and the modified biofilm carrier filler respectively. After testing, the pH value of the coagulant liquid product with a mass concentration of 1% is 2.0 - 2.7.

[0016] In the present invention, the material of the biofilm carrier is high - density polyethylene (HDPE), polypropylene (PP) or polyurethane (PU), and the shape is cylinder, cube, cascade ring, sheet, polyhedral hollow sphere, etc.

[0017] The oxidant in the present invention is selected from concentrated nitric acid, sodium chlorate, potassium chlorate or sodium hypochlorite, and preferably concentrated nitric acid.

[0018] In the present invention, the biofilm carrier should be able to be completely submerged in the ferrous sulfate heptahydrate solution.

[0019] In step (9) of solid - liquid separation, the modified biofilm carrier filler is rinsed, and then used after natural drying or drying at a temperature below 80°C.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] (1) Compared with the liquid - phase oxidation - iron ion loading method, the method of the present invention does not need to add additional oxidant or iron ion, and the relative cost is almost zero, greatly reducing the modification cost of the biofilm carrier filler, and having good prospects for popularization and application.

[0022] (2) Since the PFS reaction process itself includes multiple reaction steps such as heating, concentrated sulfuric acid, and oxidation by strong oxidants, these substances can themselves achieve the oxidation modification of the biofilm carrier filler, improving the hydrophilicity of the carrier filler; at the same time, there are a large number of polymeric iron ions in the reaction system itself, and the polymeric iron ions can be loaded onto the oxygen-containing functional groups on the surface of the carrier filler, improving the hydrophilicity and microbial affinity of the modified biofilm carrier filler.

[0023] (3) The method of the present invention is improved on the basis of the PFS preparation process. The biofilm fillers are all inert substances and do not affect the quality of the PFS product. Therefore, there is no need to add additional reaction equipment, and it is easy to promote.

[0024] (4) When the iron ions are loaded onto the biofilm carrier filler, a polymerization reaction has already occurred. After the iron on the surface of the biofilm carrier is re-wetted into the sewage, it mostly exists in the form of polymeric iron ions, improving the microbial affinity of the biofilm carrier filler. Specific Embodiments

[0025] The present invention will be further described below in conjunction with embodiments. Example 1

[0026] (1) Place 550 grams of ferrous sulfate heptahydrate in a beaker, add about 100 ml of water and stir evenly; add HDPE cylindrical fillers with a length of 10 mm and a diameter of 25 mm to completely immerse them in the ferrous sulfate heptahydrate solution, and drop 40 ml of concentrated sulfuric acid (mass fraction 98%); add 60 g of industrial aluminum sulfate and a small amount of distilled water to the acidified mixture and stir evenly at a low speed.

[0027] (2) Place the above liquid in a water bath at a temperature of 80 °C and heat it. While heating and stirring, drop 40 ml of concentrated nitric acid for oxidation and stir slowly for about 60 min; introduce 10 ml of phosphoric acid as a stabilizer during the reaction process. After stirring is completed, take out the product and let it stand and cure for 24 h.

[0028] (3) Use tweezers to take out the modified HDPE carrier, rinse it with clean water, and let it dry naturally. The remaining coagulant can be used directly. Measure the pH value of the 1% mass concentration coagulant liquid product to be 2.0 - 2.7.

[0029] (4) Experiments found that taking domestic sewage as the treatment object, the total phosphorus removal rate of the coagulant is 93.24%, and the COD removal rate is 87.16%. The method of the present invention does not affect the quality of the coagulant product.

[0030] (5) Experiments found that compared with the unmodified filler, the film-forming time of the modified filler was shortened by 29.75%, the film-forming amount was increased by 59.62%, and the COD removal rate was increased by 14.83%. Example 2

[0031] (1) Place 550 grams of ferrous sulfate heptahydrate in a beaker, add about 100 ml of water and stir evenly; add PP multi-faceted hollow sphere fillers with a length of 10 mm and a diameter of 25 mm to completely immerse them in the ferrous sulfate heptahydrate solution, and dropwise add 40 ml of concentrated sulfuric acid; add 60 g of industrial aluminum sulfate and a small amount of distilled water to the acidified mixture, and stir slowly and evenly.

[0032] (2) Place the above liquid in a water bath at a temperature of 50 °C and heat it. While heating and stirring, dropwise add 40 ml of concentrated nitric acid for oxidation, and stir slowly for about 30 min; introduce 10 ml of phosphoric acid as a stabilizer during the reaction process. After the stirring is completed, take out the product and let it stand for ripening for 24 h.

[0033] (3) Use tweezers to take out the modified PP carrier, rinse it with clean water, and dry it below 80 °C. The remaining coagulant can be used directly. Measure the pH value of the 1% mass concentration coagulant liquid product to be 2.0 - 2.7.

[0034] (4) Experiments found that when treating domestic sewage, the total phosphorus removal rate of the coagulant was 79.44%, and the COD removal rate was 62.69%.

[0035] (5) Experiments found that compared with the unmodified filler, the film-forming time of the modified filler was shortened by 9.23%, the film-forming amount was increased by 18.49%, and the COD removal rate was increased by 6.24%. Example 3

[0036] (1) Place 550 grams of ferrous sulfate heptahydrate in a beaker, add about 100 ml of water and stir evenly; add PP cylindrical fillers with a length of 10 mm and a diameter of 25 mm to completely immerse them in the ferrous sulfate heptahydrate solution, and dropwise add 40 ml of concentrated sulfuric acid; add 60 g of industrial aluminum sulfate and a small amount of distilled water to the acidified mixture, and stir slowly and evenly.

[0037] (2) Place the above liquid in a water bath at a temperature of 70 °C and heat it. While heating and stirring, dropwise add 35 ml of concentrated nitric acid for oxidation, and stir slowly for about 60 min; introduce 10 ml of phosphoric acid as a stabilizer during the reaction process. After the liquid is uniform, add 20 ml of sodium hydroxide with a concentration of 2 mol / L to adjust the basicity. After the stirring is completed, take out the product and let it stand for ripening for 18 h.

[0038] (3) Use tweezers to take out the modified PP carrier, rinse it with clean water, and let it dry naturally. The remaining coagulant can be used directly. Measure the pH value of the 1% mass concentration coagulant liquid product to be 2.0 - 2.7.

[0039] (4)It was found in the experiment that when domestic sewage was used as the treatment object, the total phosphorus removal rate of the coagulant was 95.53%, and the COD removal rate was 85.66%.

[0040] (5)It was found in the experiment that compared with the unmodified packing, the film-forming time of the modified packing was shortened by 32.34%, the film-forming amount was increased by 48.75%, and the COD removal rate was increased by 11.64%. Example 4

[0041] (1)Put 550 grams of ferrous sulfate heptahydrate into a beaker, add about 100 ml of water and stir evenly; add a PU sponge with a side length of 2 cm to make it completely immersed in the ferrous sulfate heptahydrate solution, and drop 45 ml of concentrated sulfuric acid; add 70 g of industrial aluminum sulfate and a small amount of distilled water to the acidified mixture, and stir slowly and evenly.

[0042] (2)Put the above liquid into a water bath at 80 °C and heat it. While heating and stirring, drop 35 ml of concentrated nitric acid for oxidation, and stir slowly for about 45 min; introduce 30 ml of phosphoric acid as a stabilizer during the reaction. After the liquid is uniform, add 40 ml of sodium carbonate with a concentration of 2 mol / L to adjust the degree of alkalinity. After stirring is completed, take out the product and let it stand for aging for 12 h.

[0043] (3)Use tweezers to take out the modified PU carrier, rinse it with clean water, and dry it naturally. The remaining coagulant can be used directly. The pH value of the liquid product of the coagulant with a mass concentration of 1% was measured to be 2.0 - 2.7.

[0044] (4)It was found in the experiment that when domestic sewage was used as the treatment object, the total phosphorus removal rate of the coagulant was 95.82%, and the COD removal rate was 84.50%.

[0045] (5)It was found in the experiment that compared with the unmodified packing, the film-forming time of the modified packing was shortened by 22.78%, the film-forming amount was increased by 37.65%, and the COD removal rate was increased by 10.25%.

[0046] The contact angles of the modified biofilm carrier packings prepared in Examples 1 - 3 were measured using a static contact angle measuring instrument, and the zeta potential was measured using a Malvern Zetasizer Nano-ZS90 potential analyzer. The results are shown in Table 1 below.

[0047] Table 1

[0048]

[0049] The test results show that the hydrophilicity of the carrier packing has been improved, and the zeta potential has changed to a positive value.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for coupling and modifying a biofilm carrier, characterized in that The specific steps are as follows: (1) Take 550 parts of ferrous sulfate heptahydrate and dissolve it in water; (2) Add a biofilm carrier and mix the biofilm carrier and ferrous sulfate heptahydrate evenly by stirring; (3) Add concentrated sulfuric acid with a mass fraction of 98% for acidification; (4) Add 60 - 70 parts of industrial aluminum sulfate to the acidified mixture, stir evenly and dilute with a small amount of water; (5) Place the reaction vessel in a water bath, add an oxidant while stirring, heat at 50°C - 80°C for 30 - 60 minutes, and stir slowly at the same time; (6) Add the stabilizer phosphoric acid; (7) According to the reaction requirements, add sodium hydroxide or sodium carbonate to control the basicity of the coagulant product to be 8% - 16%; (8) Let it stand for 12 - 24 hours; (9) Through solid - liquid separation, a liquid coagulant product and a modified biofilm carrier filler are obtained respectively.

2. The biofilm carrier coupling modification method according to claim 1, characterized in that The material of the biofilm carrier described in step (2) is high - density polyethylene, polypropylene or polyurethane, and the shape is a cylinder, cube, ladder ring, sheet, or multi - faceted hollow sphere.

3. The biofilm carrier coupling modification method according to claim 1, characterized in that, The oxidant described in step (5) is selected from concentrated nitric acid, sodium chlorate, potassium chlorate or sodium hypochlorite.

4. A method for coupling and modifying a biofilm carrier according to claim 1, characterized in that, In step (2), the biofilm carrier should be able to be completely submerged in the ferrous sulfate heptahydrate solution.

5. A method for coupling and modifying a biofilm carrier according to claim 1, characterized in that, In step (9), for solid - liquid separation, rinse the modified biofilm carrier filler and use it after natural drying or drying at a temperature below 80°C.

6. The biofilm carrier coupling modification method according to claim 1, wherein, Measure that the pH value of the liquid coagulant product with a mass concentration of 1% is 2.0 - 2.7.

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