Preparation method and application of a composite core for cultivating anaerobic granular sludge

Abstract

The present invention relates to a preparation method and application of a composite core for culturing anaerobic granular sludge. The preparation method is as follows: An embedding agent, humic acid, and bone powder are mixed to form a composite; A crosslinking agent is added to the composite for crosslinking to form a complex; The complex is added to a ferric chloride solution, and then sodium borohydride is added and stirred to obtain a combination of bone powder, humic acid, and nano-zero-valent iron, which is washed to neutrality to obtain a composite core of bone powder, humic acid, and nano-zero-valent iron. The present invention also provides an application of the composite core for culturing anaerobic granular sludge in the treatment of refractory wastewater and sewage. Through the adsorption of humic acid and the strong reducibility of nano-zero-valent iron, efficient degradation of pollutants is achieved. The bone powder releases various trace elements and a large amount of calcium, which promotes the biological metabolism of pollutants, accelerates the formation rate of anaerobic granular sludge, improves the crystal nucleus strength, enhances the metabolic activity and stability, and extends the service life.

Description

Technical Field

[0001] The present invention relates to a method for preparing a composite core for culturing anaerobic granular sludge and its application, belonging to the field of sewage treatment. Technical Background

[0002] At present, it takes a long time to cultivate anaerobic granular sludge in a UASB reactor, at least two or three months, and up to half a year or even longer. Moreover, the cultivated granular sludge has poor sedimentation performance, low methane production activity, and is loose and fragile, failing to meet the requirements of wastewater treatment, and even causing sludge loss and unable to achieve the requirements of wastewater treatment. There are many factors affecting the formation of granular sludge: organic load, hydraulic retention time, liquid upward flow rate, temperature in the reactor, pH, addition of different polymers and ions, etc. At present, the traditional treatment methods mainly explore the conditions for accelerating the formation of granular sludge by optimizing the above-mentioned factors affecting the formation, changing the organic load in the UASB, hydraulic retention time, adding a single polymer or ion, etc.

[0003] The method of forming the inner core of granular sludge by sludge granulation has the advantages of reducing the formation time of granular sludge, being able to form a large amount of granular sludge, and having a certain wastewater treatment capacity, etc. However, current research has found that: the cost required for the granules formed by sludge granulation is relatively large, the stability of sludge granules is poor, and they are easily slowly degraded by their own microorganisms, and cannot stably treat wastewater for a long time. Therefore, a new method for forming granular sludge needs to be proposed to improve the performance of granular sludge.

[0004] After retrieving relevant patents on sludge granulation, the results are as follows: There is a patent reporting a method for preparing a sludge aggregate to promote the rapid formation of aerobic granular sludge, patent number CN108675440A. This method concentrates activated sludge, mixes it with a cationic polymer, and forms a sludge aggregate through pH adjustment to promote the rapid formation of aerobic granular sludge. Although this method can promote the formation of aerobic granular sludge to a certain extent, the preparation method of the sludge aggregate is cumbersome and the aggregation efficiency is difficult to control. At the same time, the aerobic granular sludge prepared is essentially different from anaerobic granular sludge. Patent number CN104876332A. This patent uses zero-valent iron to promote the formation of anaerobic granular sludge and strengthen the enrichment of reductive dechlorination bacteria. The formed anaerobic granular sludge with dechlorination performance can be used to degrade chlorinated hydrocarbon wastewater. In this patent, the role of zero-valent iron is only as a sub-core, and the reducibility of zero-valent iron is very weak, and it has no beneficial effect on the degradation of chlorinated hydrocarbons. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method and application of a composite core for anaerobic granular sludge cultivation, in order to rapidly cultivate anaerobic granular sludge, improve the stability of anaerobic granular sludge, improve the degradation efficiency of pollutants, and overcome the disadvantage of being slowly degraded by its own microorganisms. Through the adsorption of humic acid, the contact between granular sludge and pollutants is promoted. The strong reducibility of nano zero-valent iron is used to destroy the molecular structure of macromolecular pollutants, converting pollutants into small molecular organic substances that are easy to metabolize biologically. Further, the high-efficiency electron transfer ability of humic acid promotes the metabolism of macromolecular pollutants and small molecular organic substances by microorganisms, thereby achieving the efficient degradation of pollutants. The bone powder in the composite core of bone powder, humic acid and nano zero-valent iron can release a variety of trace elements and a large amount of calcium, which not only promotes the biological metabolism of pollutants, but also can accelerate the formation rate of anaerobic granular sludge, improve the crystal nucleus strength, enhance the metabolic activity and stability of anaerobic granular sludge, and extend the service life of anaerobic granular sludge.

[0006] To achieve the above object, the present invention provides a preparation method of a composite core for cultivating anaerobic granular sludge, as follows:

[0007] Step (1): Mix an embedding agent, humic acid and bone powder powder to form a composite;

[0008] Step (2): Add a cross-linking agent to the composite in step (1) for cross-linking to form a complex;

[0009] Step (3): Add the complex in step (2) into a ferric chloride solution, then add sodium borohydride and stir to obtain a combination of bone powder, humic acid and nano zero-valent iron;

[0010] Step (4): Wash the combination of bone powder, humic acid and nano zero-valent iron in step (3) with distilled water 3-5 times until neutral to obtain a composite core of bone powder, humic acid and nano zero-valent iron;

[0011] The embedding agent in step (1) includes polyvinyl alcohol, sodium alginate and silicon dioxide.

[0012] Preferably, the mass ratio of the embedding agent, bone powder, humic acid, and ferric chloride is 100:(20-50):(0.2-0.5):(0.5-3), the concentration of ferric chloride in the ferric chloride solution is 0.5-3%, the molar ratio of sodium borohydride to Fe in the ferric chloride solution is (3-5):1, and the particle size of the bone powder powder is less than 0.2 mm. 3+ Preferably, the embedding agent is prepared by mixing and dissolving polyvinyl alcohol and sodium alginate in water, and then adding silicon dioxide and humic acid to obtain an embedding material containing humic acid.

[0013] Preferably, the embedding agent is prepared by mixing and dissolving polyvinyl alcohol and sodium alginate in water, and then adding silicon dioxide and humic acid to obtain an embedding material containing humic acid.

[0014] Preferably, the concentrations of the components in the humic acid-containing embedding material are as follows: polyvinyl alcohol is 6-12%, sodium alginate is 1-3%, silicon dioxide is 0.8-2.5%, and humic acid is 0.2-0.5%.

[0015] Preferably, the crosslinking agent in step (ii) is a saturated boric acid solution containing calcium chloride, and the concentration of calcium chloride in the saturated boric acid solution containing calcium chloride is 1-5%.

[0016] Preferably, the crosslinking time is 12-24 h and the temperature is 2-6 °C.

[0017] Preferably, step (iii) is carried out under a nitrogen atmosphere.

[0018] Preferably, the bone powder, humic acid and nano-zero valent iron combination prepared in step (iii) is washed to neutrality to obtain a composite core of bone powder, humic acid and nano-zero valent iron.

[0019] Preferably, the mass ratio of the embedding agent, bone powder, humic acid, and ferric chloride is 100:30:0.3:1.5.

[0020] The present invention also provides an application for culturing an anaerobic granular sludge composite core, and the composite core prepared by the present invention is applied in the treatment of refractory wastewater and sewage, such as coal gasification wastewater, coking wastewater, TA wastewater, etc.

[0021] Beneficial effects:

[0022] 1. The bone powder in the composite core provided by the present invention can provide trace elements for microorganisms, and contains a large amount of calcium to strengthen the crystal nucleus strength of the sludge. Through the slow release effect of humic acid, the matching of the persistence of zero valent iron reduction and the growth cycle of anaerobic microorganisms is achieved.

[0023] 2. In the present invention, humic acid can adsorb pollutants to provide nutrients for microorganisms, play the role of a bicarbonate buffer, and improve the activity of microorganisms.

[0024] 3. In the present invention, nano-zero valent iron can act on toxic pollutants, reduce the toxicity during the formation of granular sludge, provide an anaerobic environment, and produce hydrogen by corrosion to provide an electron donor for microorganisms, thereby improving the activity of methanogenic microorganisms.

[0025] 4. The combination of nano-zero valent iron and humic acid in the composite core provided by the present invention has a better bioelectron transfer efficiency, which has a significant promoting effect on the formation, growth and stability of anaerobic granular sludge, resulting in a short formation time, low energy consumption and high efficiency of granular sludge.

[0026] 5. In the present invention, through the coordination reaction of chemical groups in embedding agents such as sodium alginate with calcium ions in the crosslinking agent, an insoluble hydrogel sphere is formed, enabling humic acid, bone meal, nano zero-valent iron, and other embedding materials to quickly combine to form small spheres, providing a core for anaerobic granular sludge, facilitating the attachment of microorganisms, and accelerating the formation of granular sludge. Detailed implementation manners

[0027] The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the protection scope of the present invention. Specific embodiment 1

[0029] The bone meal was ground into powder for standby; 6 g of polyvinyl alcohol, 1.2 g of sodium alginate, and 1 g of silicon dioxide were taken, added with water and heated to 30 °C and dissolved in 100 ml. 20 g of bone meal and 0.2 g of humic acid were added and stirred evenly to prepare a composite. The composite was dropped into a saturated boric acid solution containing 2% calcium chloride, crosslinked at 6 °C in the dark for 12 h, and then washed 3 times with distilled water to obtain a bone meal and humic acid embedding body composite. The bone meal and humic acid embedding body composite was added to 200 ml of 1 w / t% ferric chloride solution, and 40 ml of 0.72 M NaBH4 was added under a nitrogen atmosphere to in-situ synthesize nano zero-valent iron loaded on the embedding structure, forming a combination of bone meal, humic acid, and nano zero-valent iron. After washing 3 times with distilled water, a composite core of bone meal, humic acid, and nano zero-valent iron was finally obtained and stored under anaerobic conditions. Specific embodiment 2

[0031] The bone meal was ground into powder for standby; 8 g of polyvinyl alcohol, 1.6 g of sodium alginate, and 1.5 g of silicon dioxide were taken, added with water and heated to 40 °C and dissolved in 100 ml. 30 g of bone meal and 0.3 g of humic acid were added and stirred evenly to prepare a composite. The composite was dropped into a saturated boric acid solution containing 3.5% calcium chloride, crosslinked at 4 °C in the dark for 18 h, and then washed 3 times with distilled water to obtain a bone meal and humic acid embedding body composite. The bone meal and humic acid embedding body composite was added to 200 ml of 1.5 w / t% ferric chloride solution, and 50 ml of 0.72 M NaBH4 was added under a nitrogen atmosphere to in-situ synthesize nano zero-valent iron loaded on the embedding structure, forming a combination of bone meal, humic acid, and nano zero-valent iron. After washing 3 times with distilled water, a composite core of bone meal, humic acid, and nano zero-valent iron was finally obtained and stored under anaerobic conditions. Specific embodiment 3

[0033] Grind bone meal into powder for later use; take 10 g of polyvinyl alcohol, 2.5 g of sodium alginate, 2 g of silicon dioxide, add water and heat to 35 °C to dissolve in 100 ml, add 35 g of bone meal, 0.4 g of humic acid, stir evenly to prepare a composite. Drop the composite into a saturated boric acid solution containing 4% calcium chloride, crosslink at 4 °C in the dark for 24 h, then wash 3 times with distilled water to obtain a bone meal and humic acid embedded body composite. Add the bone meal and humic acid embedded body composite to 200 ml of 2.5 w / t% iron chloride solution, and add 70 ml of 0.72 M NaBH4 in a nitrogen atmosphere to in-situ synthesize nano zero-valent iron loaded on the embedding structure, forming a combination of bone meal, humic acid and nano zero-valent iron. Wash 3 times with distilled water, and finally obtain a composite core of bone meal, humic acid and nano zero-valent iron, and store it under anaerobic conditions. Specific Example 4

[0035] Grind bone meal into powder for later use; take 12 g of polyvinyl alcohol, 2 g of sodium alginate, 1.2 g of silicon dioxide, add water and heat to 50 °C to dissolve in 100 ml, add 40 g of bone meal, 0.5 g of humic acid, stir evenly to prepare a composite. Drop the composite into a saturated boric acid solution containing 5% calcium chloride, crosslink at 4 °C in the dark for 24 h, then wash 3 times with distilled water to obtain a bone meal and humic acid embedded body composite. Add the bone meal and humic acid embedded body composite to 200 ml of 2 w / t% iron chloride solution, and add 60 ml of  0.72 M NaBH4 in a nitrogen atmosphere to in-situ synthesize nano zero-valent iron loaded on the embedding structure, forming a combination of bone meal, humic acid and nano zero-valent iron. Wash 3 times with distilled water, and finally obtain a composite core of bone meal, humic acid and nano zero-valent iron, and store it under anaerobic conditions.

[0036] Through the above preparation process, taking TA wastewater as the treatment object, the performance parameters of anaerobic granular sludge cultured with the composite core of bone meal, humic acid and nano zero-valent iron in the above different examples and the treatment effect on pollutants are compared with the anaerobic granular sludge formed without using the composite core of bone meal, humic acid and nano zero-valent iron (i.e., ordinary anaerobic granular sludge) as shown in Table 1:

[0037] Table 1 Comparison of performance parameters of different anaerobic granular sludges and treatment effect on pollutants

[0038]

[0039] The composite cores prepared by the above 4 implementation schemes are compared with the degradation effect of TA wastewater by culturing granular sludge by conventional methods. The results show that: by the method of preparing the composite core for pollutant removal, its COD and TA removal rates are high, the forming time of granular sludge is short, and the sedimentation rate of granular sludge is fast, and its effects are all stronger than those of ordinary anaerobic granular sludge.

Claims

1. A method for preparing anaerobic granular sludge composite nuclei, characterized in that: The preparation method is as follows: Step (1): mixing the embedding agent, humic acid and bone powder to form a composite; Step (2): adding a cross-linking agent to the complex of step (1) to cross-link to form a complex; Step (3): adding the complex described in step (2) to the ferric chloride solution, then adding sodium borohydride and stirring to obtain a combination of bone powder, humic acid and nano-zero-valent iron; Step (4): washing the bone powder, humic acid and nano-zero-valent iron combination described in step (3) until neutral to obtain a composite core of bone powder, humic acid and nano-zero-valent iron; The embedding agent in step (1) comprises polyvinyl alcohol, sodium alginate and silicon dioxide; the mass ratio of the embedding agent, bone powder, humic acid and ferric chloride is 100: (20-50): (0.2-0.5): (0.5-3), the concentration of ferric chloride in the ferric chloride solution is 0.5-3%, the sodium borohydride and the Fe in the ferric chloride solution are 0.5-3%, and the Fe in the ferric chloride solution is 0.5-3%. 3+ The molar ratio of the bone meal is (3-5):1, and the particle size of the bone meal powder is less than 0.2 mm.

2. The method for culturing anaerobic granular sludge composite nuclei according to claim 1, characterized in that: The embedding agent is prepared by mixing and dissolving polyvinyl alcohol and sodium alginate in water, and then adding silicon dioxide and humic acid to obtain the embedding agent containing humic acid.

3. The method for culturing anaerobic granular sludge composite nuclei according to claim 2, characterized in that: The concentrations of the components in the embedding agent containing humic acid are: 6-12% of polyvinyl alcohol, 1-3% of sodium alginate, 0.8-2.5% of silicon dioxide, and 0.2-0.5% of humic acid.

4. The method for culturing anaerobic granular sludge composite nuclei according to claim 1, characterized in that: The cross-linking agent in the step (ii) is a saturated boric acid solution containing calcium chloride, and the concentration of calcium chloride in the saturated boric acid solution containing calcium chloride is 1-5%.

5. The method for culturing anaerobic granular sludge composite nuclei according to claim 1 or 4, characterized in that: The cross-linking time is 12-24h and the temperature is 2-6°C.

6. The method for culturing anaerobic granular sludge composite nuclei according to claim 1, characterized in that: The step (3) is carried out under a nitrogen environment.

7. The method for culturing anaerobic granular sludge composite nuclei according to claim 1, characterized in that: The mass ratio of the embedding agent, bone powder, humic acid and ferric chloride is 100:30:0.3:1.

5.

8. A use for culturing anaerobic granular sludge composite nuclei according to any one of claims 1 to 7, characterized in that: The invention relates to an application of the composite nucleus for cultivating anaerobic granular sludge in the treatment of difficult-to-degrade wastewater and sewage.

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