Efficient sludge dewatering method based on biological flocculant

Abstract

The invention relates to the technical field of sludge dewatering, in particular to an efficient sludge dewatering method based on a biological flocculant. According to the sludge dewatering method, the municipal excess sludge is flocculated and concentrated by adopting a biological flocculant, the concentrated sludge is subjected to filter pressing dewatering, the biological flocculant comprises glycoprotein, mucopolysaccharide, carboxymethylcellulose, calcium chloride and sludge incineration residue micro powder in the process, and the sludge is dewatered by high-speed stirring and aeration in the flocculation process. According to the present invention, the flocculant and the sludge can be rapidly and uniformly mixed, and the deposition of the calcium ions can be promoted so as to make the deposited calcium ions and the sludge incineration residue micro-powder form the core in the sludge floc during the subsequent low-speed stirring process, such that the subsequent sludge dehydration can be promoted.

Description

Technical Field

[0001] The invention relates to the technical field of sludge dehydration, and in particular to a method for efficiently dehydrating sludge based on a biological flocculant. Background Art

[0002] Sludge contains a large amount of nutrients that can be used by plants, such as nitrogen, carbon, potassium, humus, and trace elements such as zinc, copper, and iron, which can be used as resources. However, sludge also contains a large number of pathogens, parasites (eggs), and heavy metals such as copper, aluminum, zinc, chromium, and mercury, as well as polychlorinated biphenyls, dioxins, radioactive elements and other toxic and harmful substances that are difficult to degrade. If not effectively treated, the toxic and harmful substances in the sludge will contaminate the soil and water, causing serious pollution and damage to the environment.

[0003] Existing sludge treatment methods include drying, incineration, pyrolysis, fermentation, etc. Before treatment, the sludge needs to be dehydrated. The existing methods use PAC and PAM for flocculation, and then use dehydration equipment for dehydration. However, traditional PAM monomers have certain toxicity and can easily cause water pollution. At the same time, due to the presence of a large amount of extracellular polymers EPS between sludge cells, high-pressure belt machines and plate and frame filter presses are often required to achieve better treatment effects during dehydration, which has high energy consumption.

[0004] Therefore, developing a more energy-saving and environmentally friendly sludge dewatering process route is a technical problem that needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for efficiently dehydrating sludge based on a biological flocculant to solve the problems that traditional PAM flocculants have monomer residual toxicity, are easy to enrich and cause water pollution, and have high energy consumption for dehydration after flocculation, which is not conducive to energy conservation and treatment cost reduction.

[0006] To achieve the above object, the present invention adopts the following technical solution: a method for efficient sludge dehydration based on biological flocculants, comprising the following steps:

[0007] S1. Introduce the municipal surplus sludge into the sludge conditioning tank, and adjust the pH in the conditioning tank to weak alkaline under stirring conditions;

[0008] S2. Add bioflocculant to the conditioning tank under high-speed stirring and aeration conditions, fully stir and mix, and then stir at a low speed until obvious alum flowers are produced in the conditioning tank, and let it stand to obtain concentrated sludge;

[0009] S3, transporting the concentrated sludge in S2 to a sludge dehydration device for dehydration, thereby completing the sludge dehydration process of the present invention.

[0010] Furthermore, in the S1, the stirring intensity is 30-60 r / min, and the pH in the conditioning tank is controlled at 8-9.

[0011] Furthermore, in the S2, the stirring intensity of the high stirring is 60-120 r / min; the aeration gas is air, and the ventilation volume is 3-5 m 3 Air / (m 3 mud·h); the stirring intensity of low-speed stirring is 30~60r / min.

[0012] Furthermore, in the S2, the added amount of the biological flocculant is 100-200 kg / t of absolute dry sludge.

[0013] Furthermore, in the S2, the bioflocculant includes 10-20 parts of glycoprotein, 40-60 parts of mucopolysaccharide, 30-50 parts of cellulose, 1-5 parts of calcium chloride and 1-10 parts of micropowder.

[0014] Furthermore, the sources of the glycoprotein, mucopolysaccharide and protein include yam, cactus, cassava, potato, bovine submandibular gland and gastropod mucus.

[0015] Furthermore, the cellulose is carboxymethyl cellulose.

[0016] Furthermore, the micro powder includes sludge incineration residue micro powder with a particle size of 50 to 100 μm.

[0017] Furthermore, in said S3, the dehydration equipment comprises a common belt filter press, and the filtration is performed once or multiple times.

[0018] Furthermore, the moisture content of the sludge after the first filtration by the ordinary belt filter press can be reduced to below 83%, and the moisture content of the sludge after the second filtration can be reduced to below 60%.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention adopts biological flocculants, which are safe and harmless, can effectively avoid the problem of monomer residual toxicity existing in traditional PAM flocculants, and is more environmentally friendly;

[0021] 2. The method of the present invention forms micronuclei in floc sludge, which can play the role of a skeleton in the subsequent sludge dehydration process, which is conducive to the efficient dehydration of the sludge. After two dehydrations using an ordinary belt machine, the water content in the sludge can be reduced to below 60%, and has broad application prospects. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0023] The principle of the present invention is:

[0024] During the operation of the method of the present invention, the pH of the conditioning tank is adjusted to weak alkalinity, and after the flocculant is added, aeration and stirring are used to mix the sludge. During the process, on the one hand, the flocculant and the sludge can be quickly mixed, and on the other hand, the carbon dioxide in the air will be fixed in the water body under alkaline conditions and deposited with calcium ions, thereby generating fine crystal nuclei. The crystal nuclei can simultaneously promote the deposition of ammonia nitrogen, magnesium ions and phosphate in the water body, and continue to grow, and also react with the micropowder to form larger particles.

[0025] When the high-speed stirring stops, the sludge flocculates and forms floc sludge under the condition of low-speed stirring. Since the stirring does not stop, the small particles formed in the sewage are adsorbed by the sludge flocs and thus deposited in the concentrated sludge. In the subsequent dehydration process, it plays the role of aggregate support and mechanical grinding, and effectively promotes sludge dehydration.

[0026] Example 1

[0027] The bioflocculant of the present invention can be obtained by taking 15 parts of yam glycoprotein, 50 parts of bovine submandibular gland mucopolysaccharide, 40 parts of carboxymethyl cellulose, 3 parts of calcium chloride and 5 parts of sludge incineration residue powder and mixing them evenly.

[0028] Example 2

[0029] Taking the residual sludge in the secondary sedimentation tank of a municipal sewage treatment plant as an example, the water content was found to be 99.1%.

[0030] Take about 10m of the remaining sludge 3 It is then introduced into the sludge conditioning tank. At a stirring intensity of 50 r / min, sodium hydroxide solution is added into the conditioning tank to adjust the pH of the sludge to 8-9.

[0031] 100r / min stirring intensity and 4m 3 Air / (m 3 Under the condition of 15 kg of the biological flocculant of the embodiment, aeration and stirring were continued for 15 min after the addition.

[0032] At this time, stop aeration and stir at a low speed at a stirring intensity of 40r / min until obvious alum flowers can be seen in the water body. At this time, stop stirring and let it stand and concentrate for 30 to 60 minutes until the sludge flocs are completely precipitated.

[0033] The concentrated sludge is pumped from the bottom of the conditioning tank to the sludge dewatering machine. In this embodiment, the sludge dewatering machine uses an ordinary belt filter press, and filtration is performed in the ordinary belt filter press. After the first filtration, it is measured that the water content in the sludge is 82.6%. After the second filtration, the water content in the sludge is 58.9%.

[0034] Comparative Example 1

[0035] In this comparative example, PAC+PAM was used to flocculate the residual sludge.

[0036] Take about 10m3 of excess sludge from the same batch as Example 2 3 , 100r / min stirring intensity and 4m 3 Air / (m 3 Under the condition of mud·h), 5kg PAC and 10kg PAM were added to the conditioning tank. After the addition, aeration and stirring were continued for 15 minutes.

[0037] After stirring and mixing, stop stirring and let it stand and concentrate for 30 to 60 minutes until the sludge flocs are completely precipitated.

[0038] The concentrated sludge is pumped from the bottom of the conditioning tank to the sludge dewatering machine. In this comparative example, the same ordinary belt filter press as in Example 2 is selected. After the first filtration, the water content of the sludge is 86.7%, and after the second filtration, the water content of the sludge is 71.8%.

[0039] It can be seen that the filter pressing effect of using traditional flocculants to treat sludge is obviously inferior to that of the biological flocculant and the treatment method used in the present invention.

[0040] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A method for efficient sludge dehydration based on biological flocculants, characterized in that: The following steps are involved: S1. Introduce the municipal surplus sludge into the sludge conditioning tank, and adjust the pH in the conditioning tank to weak alkaline under stirring conditions; S2. Add bioflocculant to the conditioning tank under high-speed stirring and aeration conditions, fully stir and mix, and then stir at a low speed until obvious alum flowers are produced in the conditioning tank, and let it stand to obtain concentrated sludge; S3, transporting the concentrated sludge in S2 to a sludge dehydration device for dehydration, thereby completing the sludge dehydration process of the present invention.

2. The method for efficient sludge dehydration based on biological flocculants according to claim 1, characterized in that: In the S1, the stirring intensity is 30-60 r / min, and the pH in the conditioning tank is controlled at 8-9.

3. The method for efficient sludge dehydration based on biological flocculants according to claim 1, characterized in that: In the S2, the stirring intensity of the high stirring is 60-120 r / min; the aeration gas is air, and the ventilation volume is 3-5 m 3 Air / (m 3 mud·h); the stirring intensity of low-speed stirring is 30~60r / min.

4. The method for efficient sludge dehydration based on biological flocculants according to claim 1, characterized in that: In the S2, the added amount of the biological flocculant is 100-200 kg / t of absolutely dry sludge.

5. The method for efficient sludge dehydration based on biological flocculants according to claim 1, characterized in that: In the S2, the bioflocculant includes 10-20 parts of glycoprotein, 40-60 parts of mucopolysaccharide, 30-50 parts of cellulose, 1-5 parts of calcium chloride and 1-10 parts of micropowder.

6. The sludge deodorization treatment process based on biological flocculants according to claim 5 is characterized by: The sources of the glycoprotein, mucopolysaccharide and protein include yam, cactus, cassava, potato, bovine submandibular gland and gastropod mucus.

7. The sludge deodorization treatment process based on biological flocculants according to claim 5 is characterized by: The cellulose is carboxymethyl cellulose.

8. The method for efficient sludge dehydration based on biological flocculants according to claim 5, characterized in that: The micro powder includes sludge incineration residue micro powder, and the particle size is 50-100 μm.

9. The method for efficient sludge dehydration based on biological flocculants according to claim 1, characterized in that: In the above-mentioned S3, the dehydration equipment includes a common belt filter press, and the number of filtration is one or more times.

10. The method for efficient sludge dehydration based on biological flocculants according to claim 9, characterized in that: The water content of the sludge can be reduced to below 83% after the first filtration by the ordinary belt filter press, and the water content of the sludge can be reduced to below 60% after the second filtration.