Sludge conditioner and its use in the treatment of organic biochemical sludge

Abstract

The application discloses a sludge conditioner, which comprises the following components in parts by weight: benzalkonium bromide 0.5-1 parts, sodium hexametaphosphate 0.5-1 parts, titanium modified tanninized chitosan 5-10 parts and water 88-95 parts. The application also discloses application of the sludge conditioner in treatment of organic biochemical sludge. The efficient sludge conditioner is obtained by compounding benzalkonium bromide, sodium hexametaphosphate and titanium modified tanninized chitosan, the conditioner has the advantages of small dosage, excellent settling performance, no secondary pollution and low water content of treated sludge.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of sludge conditioner, also relate to the application of above-mentioned sludge conditioner in the treatment of organic biochemical sludge. BACKGROUND

[0002] The sludge generated by sewage treatment plant is the collection of microbial agglutination formed by various microorganisms and adsorbed organic and inorganic matters, which has special colloidal structure and high hydrophilicity, resulting in large specific resistance value (the larger the specific resistance value, the worse the filtration performance of sludge, and the more difficult the dewatering), and poor dewatering performance. In order to destroy the colloidal structure of sludge and improve the dewatering performance of sludge, the sludge needs to be conditioned. The most widely used conditioning method in sewage treatment plant at present is chemical conditioning method, which neutralizes the charge of sludge colloidal particles by adding sludge chemical conditioner, thereby destroying the colloidal structure of sludge, reducing its affinity with water, reducing specific resistance, making it easy to concentrate and filter, thereby reducing the operation difficulty. The sludge conditioner currently mainly includes two categories of inorganic sludge conditioner (such as PAC, calcium salt) and organic sludge conditioner (such as PAM). Although the inorganic sludge conditioner has low cost, it has large addition amount (6-9wt‰ of sludge amount), large sludge yield (20-30wt% of absolute dry sludge), low conditioning efficiency, slow settling speed of sludge agglomerate after conditioning, poor resource utilization performance of sludge, and easy soil compaction and salinization during landfill; compared with the inorganic sludge conditioner, the organic flocculant has small addition amount, excellent settling performance, but low dewatering efficiency, and cannot effectively remove biological intracellular fluid, intercellular space water and extracellular polymer combined water, but only removes free water in sludge, and the moisture content of sludge can only be reduced to about 75-85%, at the same time, the conditioner is difficult to biodegrade, and acrylamide monomer and oligomer easily cause secondary pollution of the environment. SUMMARY

[0003] The present application aims to provide a sludge conditioner, which can effectively reduce the addition amount of the conditioner when used for treating organic biochemical sludge, and has excellent settling performance, high dewatering rate and low moisture content of treated sludge; and the present application also aims to provide the application of the above-mentioned sludge conditioner in treating organic biochemical sludge.

[0004] Technical solution: The sludge conditioner according to the present application comprises the following components in parts by weight: benzalkonium bromide (new jieerling) 0.5-1 part, sodium hexametaphosphate 0.5-1 part, titanium-modified tanninized chitosan 5-10 parts, and water 88-95 parts.

[0005] The titanium-modified tanninized chitosan is prepared by mixing TiO2 nanoparticles with tanninized chitosan solution, uniformly mixing, and then high-temperature calcining to obtain the titanium-modified tanninized chitosan.

[0006] The concentration of the tanninized chitosan solution is 0.05-0.2g / L; the concentration of TiO2 nanoparticles in the tanninized chitosan solution is 0.1-1.0g / L. The tanninized chitosan obtained after modification of tannin can greatly improve the solubility of chitosan in water, so that the tanninized chitosan solution can be obtained.

[0007] The high-temperature calcination temperature is 160-180℃, and the reaction time is 1-2h.

[0008] The tanninized chitosan is prepared by the following method:

[0009] (1) chitosan is dissolved in acetic acid, and then stirred uniformly to adjust the pH to 6-7;

[0010] (2) benzaldehyde is added dropwise into the solution of step (1) under high temperature for reaction; the benzaldehyde reacts with the amino group of chitosan to form Schiff base, and the generated Schiff base is stable in neutral environment, so that the amino group of chitosan is protected from reaction (not reacted with tannin); the Schiff base will be hydrolyzed rapidly in acidic environment to restore the free amino group;

[0011] (3) tannin is added into step (2) and mixed uniformly;

[0012] (4) glyoxal is added dropwise into the mixture of step (3) under high temperature for reaction; the glyoxal as a crosslinking agent can graft tannin to chitosan to modify it;

[0013] (5) the product after reaction is soaked in hydrochloric acid, and then dried to obtain the powder of tanninized chitosan.

[0014] In steps (2) and (4), the reaction temperature is 65-70℃, and the reaction time is 2-3h.

[0015] In step (3), the mass ratio of chitosan to tannin is 1:1.

[0016] In steps (2) and (4), the mass ratio of benzaldehyde to chitosan is 1.5-2:1; the mass ratio of glyoxal to chitosan is 1.5-2:1.

[0017] In step (5), the drying temperature is 45-50℃, and the drying time is 22-24h.

[0018] The reaction principle of chitosan and tannin for preparing tanninized chitosan is as follows:

[0019]

[0020] Reaction principle of tanninized chitosan and TiO2 to form titanium modified tanninized chitosan:

[0021]

[0022] The benzalkonium bromide in the sludge conditioner of the present application can change the permeability of the cell membrane, so as to denature the protein on the bacterial cell wall and cell membrane, realize the disintegration of the bacterial cell structure in the sludge by inhibiting the activity of the key enzyme in the bacteria, and then release the intracellular water in the sludge; the sodium hexametaphosphate can effectively destroy the structure of the extracellular polymeric substance (EPS) and release the bound water by the action mechanisms of chelation, change of ionic strength, promotion of hydrolysis, change of surface properties and physical destruction, so as to facilitate the subsequent treatment; the titanium modified tanninized chitosan is an amphoteric polymer compound (tanninized chitosan) synthesized by taking chitosan and tannin as main reaction raw materials, which can overcome the incomplete flocculation problem of chitosan as a sludge conditioner due to the too small molecular weight of chitosan on one hand, and introduce the polyphenol hydroxyl and carboxyl groups of tannin into the chitosan molecules on the other hand, so as to effectively improve the solubility of chitosan (referring to the solubility of chitosan in water, the improved solubility is more conducive to the dispersion of the sludge conditioner in the reaction system, so that various reactions in the system are more sufficient); in addition, the titanium salt is loaded on the tanninized chitosan, which can greatly improve the settling performance of the sludge conditioner.

[0023] Beneficial effects: Compared with the prior art, the present application has the following remarkable effects: the efficient sludge conditioner obtained by compounding benzalkonium bromide, sodium hexametaphosphate and titanium modified tanninized chitosan has the advantages of small dosage, excellent settling performance, no secondary pollution, low water content of the treated sludge, and the treated sludge can be calcined at high temperature to obtain TiO2 with high photocatalytic activity, thereby further reducing the treatment cost of solid waste. DETAILED DESCRIPTION

[0024] Example 1

[0025] The preparation method of the sludge conditioner of the present application comprises the following steps:

[0026] (1) Preparation of tanninized chitosan:

[0027] (1.1) 0.2g of chitosan is dissolved in 50mL of 0.5M acetic acid, and placed in a stirred tank for slow stirring at room temperature for 10-15min until uniform;

[0028] (1.2) To the solution of step (1.1), 30wt% sodium hydroxide was added to adjust the pH to 6-7 (by adjusting the pH to 6-7, on the one hand, chitosan can be dissolved in the system, not precipitated, on the other hand, chitosan can be more fully reacted with benzaldehyde); the temperature of the stirred tank was adjusted to 65-70℃, and 0.3g benzaldehyde was continuously added, and the reaction was carried out for 2-3h;

[0029] (1.3) The solution of step (1.2) was placed in a 45℃ oven, and the solid powder was obtained by drying, and the solid powder was dispersed in water again, and 0.2g tannin was added, and the mixture was slowly stirred at room temperature for 10-15min to be uniform;

[0030] (1.4) 0.3g glyoxal was added to the stirred tank, and the temperature of the stirred tank was adjusted to 65-70℃, and the reaction was carried out for 2-3h;

[0031] (1.5) The solution of step (1.4) was placed in a 45℃ oven, and the solid powder was obtained by drying, and then the solid powder was soaked in 5mL 30wt% hydrochloric acid for 5-8h, and the benzaldehyde reacted with chitosan was removed during the soaking process, and the amino group of chitosan was restored to free amino group;

[0032] (1.6) The solution of step (1.5) was placed in a 45℃ oven and dried for 24h to obtain a powdered tanninized chitosan;

[0033] (2) The tanninized chitosan was dissolved in water to obtain a tanninized chitosan solution with a concentration of 0.1g / L;

[0034] (3) The nano-TiO2 powder was added to the above-mentioned tanninized chitosan solution with a concentration of 0.1g / L, and ultrasonic dispersion was carried out for 30min, and then the mixture was placed in a muffle furnace and reacted at 170℃ for 1.5h to obtain a titanium-modified tanninized chitosan powder; wherein the concentration of nano-TiO2 powder in the tanninized chitosan solution was 0.5g / L;

[0035] (4) 8g titanium-modified tanninized chitosan, 1g benzalkonium chloride, 1g sodium hexametaphosphate and 90g water were sequentially placed in a stirred tank, and stirred at room temperature for 2-3h to obtain a high-efficiency sludge conditioner.

[0036] Example 2

[0037] The method for treating organic biochemical sludge by using the sludge conditioner prepared in Example 1 is as follows:

[0038] 1. Sludge conditioning

[0039] The pH of the raw sludge, the absolute dry sludge content, and the moisture content are determined, and the sludge conditioner is added according to the absolute dry sludge content. The rotation speed is 200-500 rpm, and the conditioning time is 3-5 min.

[0040] 2. Capillary suction time determination

[0041] The CST-2 capillary suction time determination instrument is currently used to measure the wetting time (in theory, the shorter the CST time, the better the hydrophobicity of the conditioned sludge, the better the separation effect of sludge and water in the filter pressing process, and the lower the moisture content of the formed sludge cake after dewatering). The dosage of the conditioner with the shortest CST time is selected for subsequent experiments.

[0042] 3. Plate and frame filter pressing

[0043] A small plate and frame filter press is selected for filter pressing. The 750B type polypropylene filter cloth (filtration accuracy 10 μm) is selected, and the parameters are set as follows: top pressure ≥ 20 MPa, feed air pressure 6-7 kg, feed time 2 h, diaphragm pressing pressure 1.5-2.0 MPa, and pressing time 1 h. The sludge is pressed.

[0044] 4. Parameter determination

[0045] The appearance of the dewatered sludge cake is observed. The plate frame needs to be filled (at least ≥ 50 g of absolute dry sludge), and the thickness of the sludge cake around the plate frame is uniform.

[0046] A rapid moisture meter is used to determine the absolute dry sludge content and the moisture content conversion of the sludge cake.

[0047] The filter pressing sludge feeding amount is recorded, and the feeding rate of the small-scale plate and frame filter press is calculated according to the absolute dry content of the raw sludge.

[0048] The water quality indicators of the treated organic biochemical sludge are shown in Table 1.

[0049] Table 1

[0050]

[0051] Comparative Example 1

[0052] Comparative Example 1 and Example 2 have basically the same treatment steps, with the only difference being that Comparative Example 1 uses a traditional inorganic conditioner, i.e. lime + ferric chloride (the lime is in solid form when added, it is not soluble in water, and the ferric chloride is first prepared into a 30 wt% solution before being added) to treat the organic biochemical sludge.

[0053] Parameter determination

[0054] The appearance of the dewatered sludge cake is observed. The plate frame needs to be filled (at least ≥ 50 g of absolute dry sludge), and the thickness of the sludge cake around the plate frame is uniform.

[0055] The absolute dry sludge content and water content conversion of the mud cake are determined by using a rapid moisture tester;

[0056] The pressure filtration mud input is recorded, and the feeding rate of the small test plate frame filter press is calculated according to the absolute dry content of the original sludge;

[0057] The corrosion ion concentration of the sludge filtrate is tested by using an inductively coupled plasma atomic emission spectrometry, including iron ions, chloride ions and chloride ions.

[0058] The water quality indicators of the treated organic biochemical sludge are shown in Table 2.

[0059] Table 2

[0060]

[0061] As can be seen from Tables 1-2, the dosing amount of the sludge conditioner of the present application is 6.1% of the traditional inorganic conditioner (the total dosing amount of ferric chloride and lime is 49.2wt% of the sludge solid content, and the dosing amount of the sludge conditioner of the present application is 3wt% of the sludge solid content). In addition, the dewatering effect of the sludge conditioner of the present application on the organic biochemical sludge and the absolute dry mud feeding rate are better than those of the traditional inorganic conditioner, the dewatering rate is reduced by 23.15%, the absolute dry mud feeding rate is increased by 34.33%, and the corrosion ion concentration of the sludge filtrate is reduced by 68.37%.

[0062] Comparative Example 2

[0063] Comparative Example 2 and Example 2 have basically the same treatment steps, the only difference is that the conditioner used in Comparative Example 2 is a traditional organic conditioner, i.e., PAM, for treating organic biochemical sludge.

[0064] Parameter determination

[0065] The appearance of the dewatered mud cake is observed, which needs to be filled with a plate frame (at least ≥50g of absolute dry sludge), and the thickness of the mud cake around is uniform;

[0066] The absolute dry sludge content and water content conversion of the mud cake are determined by using a rapid moisture tester;

[0067] The pressure filtration mud input is recorded, and the feeding rate of the small test plate frame filter press is calculated according to the absolute dry content of the original sludge;

[0068] The corrosion ion concentration of the sludge filtrate is tested by using an inductively coupled plasma atomic emission spectrometry, including iron ions, chloride ions and chloride ions.

[0069] The water quality indicators of the treated organic biochemical sludge are shown in Table 3:

[0070] Table 3

[0071]

[0072] As can be seen from Table 1 and Table 3, the addition amount of the sludge conditioner of the present application is 60% of the traditional organic conditioner, and in addition, compared with the traditional organic conditioner, the sludge conditioner of the present application reduces the dewatering rate of the organic biochemical sludge by 24.72%, and increases the absolute dry sludge feeding rate by 15.65%.

[0073] The sludge conditioner of the present application can reduce the water content of the treated sludge to below 55% by releasing the intracellular water and intercellular water of bacteria, releasing the EPS combined water by sodium hexametaphosphate, and adsorbing and dispersing the sludge particles by titanium modified tanninized chitosan, which is about 25% lower than the water content of the sludge after using the organic sludge conditioner, and does not have the risk of secondary pollution. At the same time, compared with the inorganic sludge conditioner, the sludge conditioner of the present application does not contain corrosive ions such as chloride ions, trivalent iron ions and aluminum ions, and will not increase the concentration of corrosive ions in the sludge filtrate, avoiding the problems of equipment corrosion, poor resource performance of dewatered sludge, soil compaction and salinization after landfill, etc.

[0074] Comparative Example 3

[0075] The preparation method of the sludge conditioner of Comparative Example 3 is basically the same as that of Example 1, except that the titanium modified tanninized chitosan is replaced by tanninized chitosan without titanium modification, and the specific steps are as follows:

[0076] (1) Preparation of tanninized chitosan:

[0077] (1.1) 0.2g of chitosan was dissolved in 50mL of 0.5M acetic acid, and placed in a stirred tank for slow stirring at room temperature for 10-15min until uniform;

[0078] (1.2) 30wt% sodium hydroxide was added to the solution of step (1.1), and the pH was adjusted to 6-7; the temperature of the stirred tank was adjusted to 65-70℃, and 0.3g of benzaldehyde was continuously added, and reacted for 2-3h;

[0079] (1.3) The solution of step (1.2) was placed in a 45℃ oven, and the solid powder was obtained by drying, and then dispersed in water, and 0.2g of tannin was added, and placed in a stirred tank for slow stirring at room temperature for 10-15min until uniform;

[0080] (1.4) 0.3g of glyoxal was added to the stirred tank, and the temperature of the stirred tank was adjusted to 65-70℃, and reacted for 2-3h;

[0081] (1.5) The solution of step (1.4) was placed in a 45℃ oven, and the solid powder was obtained by drying, and then soaked in 5mL of 30wt% hydrochloric acid for 5-8h;

[0082] (1.6) The solution of step (1.5) was placed in a 45°C oven and dried for 24h to obtain the tanninized chitosan in powder form;

[0083] (2) The tanninized chitosan was dissolved in water to obtain a tanninized chitosan solution with a concentration of 0.1g / L;

[0084] (3) 8g of the tanninized chitosan solution with a concentration of 0.1g / L, 1g of benzalkonium chloride, 1g of sodium hexametaphosphate and 90g of water were sequentially placed in a stirred tank, and stirred at room temperature for 2-3h to obtain the sludge conditioner.

[0085] Subsequently, the organic biochemical sludge was treated with the sludge conditioner of Comparative Example 3 in a manner basically the same as the treatment steps of Example 2.

[0086] Parameter determination

[0087] The appearance of the dewatered cake was observed, and the plate frame needed to be filled (at least ≥50g of absolute dry sludge), and the thickness of the cake around the plate frame was uniform;

[0088] A rapid moisture meter was used to determine the absolute dry sludge content and the water content conversion of the cake;

[0089] The pressure filtration sludge input was recorded, and the feed rate of the laboratory plate frame filter press was calculated according to the absolute dry content of the original sludge;

[0090] The inductively coupled plasma atomic emission spectrometry was used to test the corrosion ion concentration of the sludge filtrate, including iron ions, chloride ions and chloride ions.

[0091] The water quality indicators of the treated organic biochemical sludge are shown in Table 4:

[0092] Table 4

[0093]

[0094] As can be seen from Tables 1 and 4, compared with Example 1, the dosage of the sludge conditioner of Comparative Example 3 increased by 33.33%, the dewatering effect on the organic biochemical sludge decreased by 10%, and the absolute dry sludge feed rate decreased by 17.21%.

[0095] Comparative Example 4

[0096] The preparation method of the sludge conditioner of Comparative Example 4 was basically the same as that of Example 1, except that the titanium-modified tanninized chitosan was replaced by titanium-modified chitosan, and the specific steps were as follows:

[0097] (1) The chitosan was dispersed in water to obtain a chitosan dispersion with a concentration of 0.1g / L;

[0098] (2) The nano-TiO2 powder is added to the chitosan dispersion liquid, and after ultrasonic dispersion for 30 min, the mixture is placed in a muffle furnace for reaction at 170°C for 1.5 h to obtain titanium-modified chitosan powder; wherein the concentration of the nano-TiO2 powder in the chitosan dispersion liquid is 0.5 g / L;

[0099] (3) 8 g of titanium-modified chitosan, 1 g of benzalkonium bromide, 1 g of sodium hexametaphosphate, and 90 g of water are sequentially placed in a stirring kettle, and stirred at room temperature for 2-3 h to obtain a sludge conditioner.

[0100] Subsequently, the sludge conditioner of Comparative Example 4 is used to treat the organic biochemical sludge, and the treatment steps are basically the same as those of Example 2.

[0101] Parameter determination

[0102] The appearance of the dewatered cake is observed, and the plate frame needs to be filled (at least ≥ 50 g of absolute dry sludge), and the thickness of the cake around is uniform;

[0103] A rapid moisture meter is used to determine the absolute dry sludge content and the water content conversion of the cake.

[0104] The pressure filtration sludge input is recorded, and the feed rate of the laboratory plate frame filter press is calculated according to the absolute dry content of the original sludge.

[0105] The inductively coupled plasma atomic emission spectrometry is used to test the concentration of corrosive ions in the sludge filtrate, including iron ions, chloride ions, and chloride ions.

[0106] The water quality indicators of the treated organic biochemical sludge are shown in Table 5:

[0107] Table 5

[0108]

[0109] As can be seen from Tables 1 and 5, compared with Example 1, the dosage of the sludge conditioner of Comparative Example 4 is increased by 100%, the dewatering effect on the organic biochemical sludge is reduced by 13.33%, and the absolute dry sludge feed rate is increased by 8.79%.

[0110] The sludge conditioner of the application is added to the concentrated sludge, the new benzalkonium chloride in the medicament can release the intracellular water of bacteria in the sludge by changing the permeability of cell membrane, denaturing the protein on the bacterial cell wall and cell membrane, and can effectively weaken the adhesion between bacteria and EPS; the sodium hexametaphosphate in the medicament can effectively destroy the EPS structure and release the bound water by the action mechanisms of chelation, promoting polysaccharide and protein hydrolysis, changing the surface charge of EPS and physical destruction, and change the morphology of sludge flocs. Due to the existence of rich active amino and hydroxyl groups on the surface of chitosan, the chemical structure of chitosan can be changed by tannin amination of these free amino groups, and the chitosan is converted into tannin chitosan, which can effectively improve the solubility of chitosan, increase the number of active groups such as polyphenol hydroxyl and carboxyl on the molecular chain, and the generated polymer has a dendritic structure, disperses the flocculation groups, has a stronger adsorption and electric neutralization effect and adsorption bridging effect on the sludge, and at the same time, the titanium salt is loaded on the tannin chitosan, which can improve the settling performance of the cationic chitosan as a flocculant, and the sludge after flocculation and precipitation can obtain TiO2 with high photocatalytic activity after high-temperature calcination.

Claims

1. A sludge conditioner characterized by, The composition comprises the following components in parts by weight: benzalkonium bromide 0.5-1 part, sodium hexametaphosphate 0.5-1 part, titanium-modified tanninized chitosan 5-10 parts, and water 88-95 parts; The titanium-modified tanninized chitosan is prepared by mixing TiO2 nanoparticles with a tanninized chitosan solution, uniformly mixing, and calcining at high temperature to obtain the titanium-modified tanninized chitosan. The tanninized chitosan is prepared by the following method steps: (1) dissolving chitosan in acetic acid, uniformly stirring, and adjusting the pH to 6-7; (2) adding benzaldehyde dropwise into the solution of step (1) at high temperature to react; (3) dispersing the reacted product in water, adding tannin, and uniformly mixing; (4) adding glyoxal dropwise into the mixture of step (3) at high temperature to react; (5) soaking the reacted product in hydrochloric acid, drying after soaking to obtain tanninized chitosan.

2. The sludge conditioner of claim 1, wherein: The concentration of the tanninized chitosan solution is 0.05-0.2 g / L; the concentration of TiO2 nanoparticles in the tanninized chitosan solution is 0.1-1.0 g / L.

3. The sludge conditioner of claim 1, wherein: The high-temperature calcination temperature after mixing TiO2 nanoparticles with the tanninized chitosan solution is 160-180℃, and the reaction time is 1-2h.

4. The sludge conditioner of claim 1, wherein: In steps (2) and (4), the reaction temperature is 65-70℃, and the reaction time is 2-3h.

5. The sludge conditioner of claim 1, wherein: In step (3), the mass ratio of chitosan to tannin is 1:1-1.

5.

6. The sludge conditioner of claim 1, wherein: In steps (2) and (4), the mass ratio of benzaldehyde to chitosan is 1.5-2:1; the mass ratio of glyoxal to chitosan is 1.5-2:

1.

7. The sludge conditioner of claim 1, wherein: In step (5), the drying temperature is 45-50℃, and the drying time is 22-24h.

8. Use of the sludge conditioner of claim 1 in treating organic biochemical sludge.

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