An efficient sewage flocculation and sedimentation process

Abstract

The present invention discloses an efficient sewage flocculation and sedimentation process, which comprises the following steps: mixing sewage with coagulant 1 for coagulation treatment, then adding coagulant 2 for flocculation treatment, then standing still, collecting sludge, and discharging treated water; wherein, coagulant 1 is at least one of polyferric sulfate and polyaluminum chloride; and coagulant 2 is modified bentonite. The present invention can greatly improve the sewage flocculation effect and reduce the water content in the sludge through the design of coagulants 1 and 2 and the flocculation process.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a high-efficiency sewage flocculation and precipitation process. Background Art

[0002] The treatment of water eutrophication has become a difficult problem faced by environmental protection. Phosphorus element is one of the main factors leading to water eutrophication. Water treatment is an important measure to remove phosphorus element from sewage, and phosphorus removal is particularly important in sewage treatment.

[0003] Flocculants are commonly used phosphorus-removing substances, but currently the phosphorus removal rate of existing flocculants is relatively low, and it is necessary to improve their phosphorus removal effect. In addition, a large amount of sludge will be generated after flocculation. The special floc structure of the sludge makes the water in it difficult to remove, and a large amount of chemicals and energy are often required. The water content of the sludge after flocculation with existing flocculants is relatively high, and it is necessary to reduce the water content of the sludge. Summary of the Invention

[0004] Based on the technical problems existing in the background art, the present invention proposes a high-efficiency sewage flocculation and precipitation process. The present invention can greatly improve the sewage flocculation effect and reduce the water content in the sludge through the design of coagulants 1 and 2 and the flocculation process.

[0005] The present invention proposes a high-efficiency sewage flocculation and precipitation process, which includes the following steps: mixing sewage with coagulant 1 for coagulation treatment, then adding coagulant 2 for flocculation treatment, then standing still, collecting sludge, and discharging treated water; wherein, coagulant 1 is at least one of polyferric sulfate and polyaluminum chloride; coagulant 2 is modified bentonite.

[0006] Preferably, in the preparation process of modified bentonite, mixing cationic polyacrylamide intercalated modified bentonite with graphene oxide dispersion liquid for reaction, and freeze-drying to obtain an intermediate material; mixing the intermediate material with ferric chloride and ferrous sulfate, heating, adjusting the pH, carrying out heat preservation reaction, and carrying out solid-liquid separation to obtain modified bentonite.

[0007] The above-mentioned cationic polyacrylamide intercalated modified bentonite can be purchased from the market or prepared by conventional methods in the art. Its preparation method can be: mixing an aqueous solution of cationic polyacrylamide with cetyltrimethylammonium bromide organobentonite, heating for reaction, and carrying out solid-liquid separation to obtain cationic polyacrylamide intercalated modified bentonite.

[0008] The present invention selects cationic polyacrylamide intercalated modified bentonite to react with graphene oxide, and after freeze-drying, the cationic polyacrylamide and graphene oxide cooperate with each other to form a porous sponge-like structure, and the bentonite is evenly distributed in the sponge. Then, it reacts with ferric chloride and ferrous sulfate to reduce the graphene oxide, and nano-ferroferric oxide is evenly distributed on the surface of the porous sponge-like substance. This specific structure, on the one hand, the porous sponge-like structure endows the modified bentonite with a higher specific surface area and higher adsorption performance, and the reduced graphene oxide and cationic polyacrylamide intercalated modified bentonite cooperate with each other. Through the mutual cooperation of multiple effects such as electro-neutralization, bridging effect, and adsorption effect, the flocculation effect can be greatly improved, and the removal effects of COD Cr , BOD5, SS, and P can be improved; on the other hand, the nano-ferroferric oxide, bentonite, and reduced graphene oxide cooperate with each other, which can reduce the water content in the sludge and reduce the difficulty of sludge dewatering in the later stage; and the specific structure of the modified bentonite can accelerate the speed of flocculation precipitation.

[0009] In addition, the present invention selects polyferric sulfate or polyaluminum chloride to first coagulate with the sewage, and then flocculate with the modified bentonite, which can further improve the flocculation effect and accelerate the flocculation precipitation.

[0010] Preferably, in the preparation process of the modified bentonite, the reaction is carried out at 110-120 °C for 4-5 h, and the intermediate material is obtained by freeze-drying.

[0011] Preferably, in the preparation process of the modified bentonite, the weight ratio of the cationic polyacrylamide intercalated modified bentonite to graphene oxide is 12-14:1.

[0012] Preferably, in the preparation process of the modified bentonite, the temperature is raised to 50-55 °C.

[0013] Preferably, in the preparation process of the modified bentonite, the pH is adjusted to 9.5-10. Preferably, ammonia water is used to adjust the pH to 9.5-10.

[0014] Preferably, in the preparation process of the modified bentonite, the reaction is carried out under insulation for 1-1.5 h.

[0015] Preferably, in the preparation process of the modified bentonite, the weight ratio of the intermediate material to ferric chloride and ferric sulfate is 0.12-0.14:1:1.35-1.45.

[0016] Preferably, 1.3-1.5 g of coagulant 1 is added to each liter of sewage.

[0017] Preferably, 1.5-2 g of coagulant 2 is added to each liter of sewage.

[0018] Preferably, the coagulation treatment is carried out by stirring at a speed of 100-200 r / min for 3-5 min.

[0019] Preferably, stir and flocculate for 8 - 10 min at a speed of 40 - 50 r / min.

[0020] Preferably, let it stand for 20 - 30 min.

[0021] Selecting appropriate addition amounts and stirring speeds can further improve the flocculation effect.

[0022] Preferably, the treated water discharged is successively subjected to denitrification, deodorization, and disinfection treatments, and is discharged after passing the inspection.

[0023] After detection, when the COD, NH3-N, TN, and TP of the effluent meet the "Discharge Standards for Main Water Pollutants from Urban Sewage Treatment Plants" (DB33 / 2169 - 2018) in Zhejiang Province, and other indicators (such as BOD5, SS) meet the first-class A standard, it can be discharged.

[0024] Preferably, the sewage first undergoes grit removal and A2O treatment, and then is mixed evenly with coagulant 1.

[0025] The above-mentioned A2O, also known as AAO, is the abbreviation of the first letters of Anaerobic - Anoxic - Oxic in English (anaerobic - anoxic - aerobic), and is a commonly used secondary sewage treatment process with the function of synchronous nitrogen and phosphorus removal, and can be used for secondary sewage treatment or tertiary sewage treatment.

[0026] In the sewage after grit removal and A2O treatment, COD Cr is 45 - 55 mg / L, BOD5 is 8 - 12 mg / L, SS is 15 - 25 mg / L, TN is 10 - 14 mg / L, NH3-N is 1 - 2 mg / L, TP is 0.8 - 1.5 mg / L, and pH is 6 - 9.

[0027] Beneficial effects:

[0028] The porous sponge-like modified bentonite of the present invention, on the one hand, has a higher specific surface area and higher adsorption performance, and through the mutual cooperation of multiple actions such as electro-neutralization, bridging action, and adsorption action, can greatly improve its flocculation effect and improve COD Cr、 Removal effects of BOD5, SS and P; on the other hand, the nano-ferroferric oxide, bentonite and reduced graphene oxide in the modified bentonite cooperate with each other, which can reduce the water content in the sludge and the difficulty of sludge dewatering in the later stage; and the specific structure of the modified bentonite can accelerate the speed of flocculation precipitation. In addition, the present invention selects ferric sulfate or polyaluminum chloride to coagulate with the sewage first, and then flocculate with the modified bentonite, which can further improve the flocculation effect and accelerate the flocculation precipitation. Through the design of coagulants 1 and 2 and the flocculation process, the present invention can greatly improve the sewage flocculation effect and reduce the water content in the sludge. Detailed implementation manners

[0029] Next, the technical solutions of the present invention will be described in detail through specific examples.

[0030] Example 1

[0031] A high-efficiency sewage flocculation precipitation process includes the following steps: The sewage is first subjected to sand sedimentation treatment through a coarse grid, a fine grid, and a vortex grit chamber, then subjected to A2O treatment, and then, according to the dosage of adding 1.3 g of coagulant 1 per liter of sewage, the sewage is mixed with coagulant 1 and stirred for 3 min at a speed of 200 r / min for coagulation treatment. Then, according to the dosage of adding 2 g of coagulant 2 per liter of sewage, coagulant 2 is added, and the mixture is stirred for 10 min at a speed of 40 r / min for flocculation treatment. Then, it is allowed to stand for 20 min, the sludge is collected, and the treated water is discharged; then the treated water is successively subjected to denitrification, deodorization, and disinfection treatments, and is discharged after passing the detection;

[0032] Among them, coagulant 1 is at least one of ferric sulfate and polyaluminum chloride; coagulant 2 is modified bentonite;

[0033] In the preparation process of the modified bentonite, 0.14 g of cationic polyacrylamide intercalated modified bentonite is added to the aqueous dispersion containing 0.01 g of graphene oxide, stirred and mixed evenly, reacted at 110 °C for 5 h, and freeze-dried at -10 °C to obtain an intermediate material; 0.14 g of the intermediate material is evenly dispersed in water, and then added to the aqueous solution containing 1 g of ferric chloride and 1.45 g of ferrous sulfate, stirred and mixed evenly, heated to 55 °C, quickly adjusted to pH = 9.5 with ammonia water, kept warm and reacted for 1.5 h, filtered, washed with water, dried under reduced pressure at 40 °C, and ground to obtain the modified bentonite.

[0034] Example 2

[0035] An efficient sewage flocculation and sedimentation process, comprising the following steps: First, the sewage is subjected to sand sedimentation treatment through a coarse grid, a fine grid, and a vortex grit chamber, then treated by A2O, and then, according to the dosage of adding 1.5 g of coagulant 1 per liter of sewage, the sewage and coagulant 1 are mixed evenly, and stirred for coagulation treatment at a speed of 100 r / min for 5 min. Then, coagulant 2 is added according to the dosage of adding 1.5 g of coagulant 2 per liter of sewage, and stirred for flocculation treatment at a speed of 50 r / min for 8 min. Then, it is allowed to stand for 30 min, the sludge is collected, and the treated water is discharged. Then, the treated water is successively subjected to denitrification, deodorization, and disinfection treatment, and discharged after passing the test.

[0036] Among them, coagulant 1 is at least one of polyferric sulfate and polyaluminum chloride; coagulant 2 is modified bentonite.

[0037] In the preparation process of modified bentonite, 0.12 g of cationic polyacrylamide intercalated modified bentonite is added to an aqueous dispersion containing 0.01 g of graphene oxide, stirred and mixed evenly, reacted at 120 °C for 4 h, and freeze-dried at -10 °C to obtain an intermediate material. 0.12 g of the intermediate material is evenly dispersed in water, and then added to an aqueous solution containing 1 g of ferric chloride and 1.35 g of ferrous sulfate, stirred and mixed evenly, heated to 50 °C, quickly adjusted to pH = 10 with ammonia water, kept warm and reacted for 1 h, filtered, washed with water, dried under reduced pressure at 40 °C, and ground to obtain modified bentonite.

[0038] Example 3

[0039] An efficient sewage flocculation and sedimentation process, comprising the following steps: First, the sewage is subjected to sand sedimentation treatment through a coarse grid, a fine grid, and a vortex grit chamber, then treated by A2O, and then, according to the dosage of adding 1.4 g of coagulant 1 per liter of sewage, the sewage and coagulant 1 are mixed evenly, and stirred for coagulation treatment at a speed of 150 r / min for 4 min. Then, coagulant 2 is added according to the dosage of adding 1.8 g of coagulant 2 per liter of sewage, and stirred for flocculation treatment at a speed of 45 r / min for 9 min. Then, it is allowed to stand for 20 min, the sludge is collected, and the treated water is discharged. Then, the treated water is successively subjected to denitrification, deodorization, and disinfection treatment, and discharged after passing the test.

[0040] Among them, coagulant 1 is at least one of polyferric sulfate and polyaluminum chloride; coagulant 2 is modified bentonite.

[0041] In the preparation process of the modified bentonite, 0.13 g of cationic polyacrylamide intercalated modified bentonite was added to the aqueous dispersion containing 0.01 g of graphene oxide, stirred and mixed evenly, reacted at 115 °C for 4.5 h, and freeze-dried at -10 °C to obtain an intermediate material; 0.13 g of the intermediate material was evenly dispersed in water, and then added to the aqueous solution containing 1 g of ferric chloride and 1.4 g of ferrous sulfate, stirred and mixed evenly, heated to 55 °C, quickly adjusted the pH to 9.5 with ammonia water, kept the temperature for reaction for 1.5 h, filtered, washed with water, dried under reduced pressure at 40 °C, and ground to obtain the modified bentonite.

[0042] Comparative Example 1

[0043] A sewage flocculation and sedimentation process, wherein the modified bentonite is the intermediate material of Example 3, and the others are the same as in Example 3.

[0044] Comparative Example 2

[0045] A sewage flocculation and sedimentation process, wherein the modified bentonite is the intermediate material of Example 3, and "cationic polyacrylamide intercalated modified bentonite" is replaced with "sodium-based bentonite", and the others are the same as in Example 3.

[0046] Comparative Example 3

[0047] A sewage flocculation and sedimentation process, wherein graphene oxide is not added during the preparation of the modified bentonite, and the others are the same as in Example 3.

[0048] Comparative Example 4

[0049] A sewage flocculation and sedimentation process, wherein the coagulant 2 is cationic polyacrylamide intercalated modified bentonite, and the others are the same as in Example 3.

[0050] The sewage in Examples 1-3 and Comparative Examples 1-4 above was subjected to sand sedimentation treatment through a coarse grid, a fine grid, and a vortex grit chamber, and then the same sewage after A2O treatment, and the COD in the sewage Cr was 50.3 mg / L, BOD5 was 10.2 mg / L, SS was 20.0 mg / L, TN was 12.1 mg / L, NH3-N was 1.56 mg / L, TP was 1.03 mg / L, and pH was 6.5.

[0051] The processes of Examples 1-3 and Comparative Examples 1-4 were used to treat the same amount of sewage, and then the water quality of the discharged water of each group was detected, and the water content in the sludge of each group was detected. The detection results are shown in Table 1.

[0052] The detection method for the water content was as follows: The sludge was wrapped with a filter cloth and then filtered by a filter press, and the weight M1 of the sludge after filtration was weighed. Then, the sludge after filtration was dried at 100 °C for 3 h, and the weight M2 of the dried sludge was weighed. The water content = (M1 - M2) / M1 * 100%.

[0053] Table 1 Test Results

[0054]

[0055]

[0056] It can be seen from Table 1 that the process of the present invention has a good phosphorus removal effect and the water content of the sludge is relatively low.

[0057] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. An efficient sewage flocculation and sedimentation process, characterized in that, It includes the following steps: mixing sewage with coagulant 1, performing coagulation treatment, then adding coagulant 2, performing flocculation treatment, then standing still, collecting sludge, and discharging treated water; wherein, coagulant 1 is at least one of polyferric sulfate and polyaluminum chloride; coagulant 2 is modified bentonite; In the preparation process of modified bentonite, uniformly mixing cationic polyacrylamide intercalated modified bentonite and graphene oxide dispersion liquid, reacting, and freeze-drying to obtain an intermediate material; uniformly mixing the intermediate material with ferric chloride and ferrous sulfate, heating up, adjusting the pH, performing heat preservation reaction, and performing solid-liquid separation to obtain modified bentonite; In the modified bentonite, cationic polyacrylamide and graphene oxide cooperate with each other to form a porous sponge-like shape, and make bentonite evenly distributed in the sponge, and nano-ferroferric oxide is evenly distributed on the surface of the porous sponge-like substance; In the preparation process of modified bentonite, reacting at 110 - 120 °C for 4 - 5 h, and freeze-drying to obtain an intermediate material; In the preparation process of modified bentonite, the weight ratio of cationic polyacrylamide intercalated modified bentonite to graphene oxide is 12 - 14:1; In the preparation process of modified bentonite, heating up to 50 - 55 °C; In the preparation process of modified bentonite, adjusting the pH to 9.5 - 10; In the preparation process of modified bentonite, performing heat preservation reaction for 1 - 1.5 h; In the preparation process of modified bentonite, the weight ratio of the intermediate material to ferric chloride and ferrous sulfate is 0.12 - 0.14:1:1.35 - 1.45; Add 1.3 - 1.5 g of coagulant 1 to each liter of sewage; Add 1.5 - 2 g of coagulant 2 to each liter of sewage; Stirring for coagulation treatment at a speed of 100 - 200 r / min for 3 - 5 min; Stirring for flocculation treatment at a speed of 40 - 50 r / min for 8 - 10 min.

2. The high-efficiency sewage flocculation and sedimentation process according to claim 1, characterized in that Stand still for 20 - 30 min.

3. The high-efficiency sewage flocculation and sedimentation process according to claim 1 or 2, characterized in that, The discharged treated water is successively subjected to denitrification, deodorization, and disinfection treatment, and is discharged after passing the detection.

4. The efficient sewage flocculation and sedimentation process according to claim 1 or 2, characterized in that: The sewage first undergoes grit removal and A2O treatment, and then is mixed with coagulant 1.

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