Method for removing residual aluminum in water

Abstract

The invention relates to the technical field of water treatment and water environment restoration, and discloses a method for removing residual aluminum in water, which comprises the following steps: introducing effluent treated by an aluminum salt flocculant into a biological filter; the method comprises the following steps: immersing corbicula fluminea in a water body of a biological filter, and carrying out biological enrichment-filter feeding to obtain discharged flocs; the discharged floc is settled and then is subjected to solid-liquid separation. According to the method disclosed by the invention, residual aluminum clusters after being treated by the aluminum salt flocculant in water are converted into high-concentration, large-size and easily-settled flocculent aggregates by utilizing the filtering and feeding process of the corbicula fluminea, so that the residual aluminum in the water is efficiently removed and separated, the concentration of the residual aluminum in the water can be reduced by 80% within 24 hours, small-size trace pollutants in the water can be quickly removed, and the service life of the corbicula fluminea is prolonged. The method has the advantages of being good in residual aluminum removal effect, small in secondary pollution, environmentally friendly and the like, and the green development concept is met.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment and water environment restoration, and in particular to a method for removing residual aluminum in water. Background Art

[0002] The enhanced coagulation process, which mainly increases the dosage of aluminum salt flocculants, is an important way to efficiently remove pollutants from water bodies. As a secondary pollutant in water treatment and sudden water pollution control, the significant increase of residual aluminum in water plants and water bodies after sudden water pollution control has become an unavoidable problem. Residual aluminum has strong chemical activity and biological effectiveness, can be enriched in biological physiological tissues, and produce certain toxic effects, which is potentially harmful to water environment quality and human health.

[0003] The forms of aluminum in the water environment are complex and diverse, and the solubility and size of residual aluminum vary greatly. At present, methods such as changing the hydrolysis conditions of coagulants, optimizing the type and dosage of coagulants, and improving the water treatment process are usually used to reduce the residual aluminum content in the effluent of water plants and the water environment. However, after these methods are used, a large amount of aluminum remains in the water.

[0004] Therefore, how to provide a method for removing residual aluminum in water with good effect is an urgent problem to be solved by technicians in this field. Summary of the invention

[0005] In view of this, the present invention provides a method for removing residual aluminum in water to solve the problem of poor removal effect of existing methods for reducing residual aluminum in effluent from water plants.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for removing residual aluminum in water, comprising the following steps:

[0008] (1) Passing the effluent treated with aluminum salt flocculant into the biofilter;

[0009] (2) Submerging river clams in the water of a biological filter tank to obtain excrement flocs after biological enrichment and filtration;

[0010] (3) The excreted flocs are then separated into solid and liquid after sedimentation.

[0011] Preferably, the oxygen content of the water in step (2) is 6-15 mg / L, the pH value is 7-9, and the temperature is 10-25°C.

[0012] Preferably, the density of adding the river clams in step (2) is 10-50 kg / m 3 .

[0013] Preferably, the hydraulic retention time in the biofilter in step (2) is 4-10 hours.

[0014] Preferably, the pH value of the water in the sedimentation tank in step (3) is 7-9.

[0015] Preferably, the river clams in the hollow box in step (2) are replaced regularly, with a replacement period of 3-30 days.

[0016] Preferably, the method further comprises the following steps: passing the supernatant after the solid-liquid separation into a clean water tank, and purifying and domesticating the regularly replaced river clams in the clean water tank.

[0017] Preferably, the river clams are loaded in a hollow box, a weight is connected to the outer bottom of the hollow box, and a flow meter is provided on the side wall of the hollow box.

[0018] Preferably, a float is connected to the top of the outer side of the hollow box, and the other end of the float is connected to a valve frame, and the valve frame is fixed to the inner wall of the biofilter and is flush with the horizontal plane.

[0019] Preferably, a plurality of partitions are provided inside the hollow box from top to bottom, the hollow box is divided into a plurality of activity spaces by the plurality of partitions, and the clams are distributed in the plurality of activity spaces.

[0020] The present invention provides a method for removing residual aluminum in water. Compared with the prior art, the method has the following beneficial effects:

[0021] The present invention utilizes the filter feeding process of river clams to convert the dissolved and / or granular aluminum clusters remaining in the water after being treated with an aluminum salt flocculant into high-concentration, large-size, easily sedimentable flocculent aggregates, thereby achieving efficient removal and separation of residual aluminum in the water. The residual aluminum concentration in the water can be reduced by 80% within 24 hours, and small-size trace pollutants in the water can be quickly removed. The removal effect of residual aluminum is good, and the characteristics of low secondary pollution and environmental friendliness are met, which is in line with the concept of green development. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 It is a structural schematic diagram of the hollow box body of the present invention;

[0024] Figure 2This is a diagram showing the purification effect of river clams on AlCl3 coagulation effluent in the present invention;

[0025] Figure 3 This is a diagram showing the purification effect of river clams on PAC coagulation effluent in the present invention;

[0026] Figure 4 This is a graph showing the enrichment concentration of residual aluminum in the AlCl3 coagulation effluent by river clams in the present invention;

[0027] Figure 5 This is a graph showing the enrichment concentration of residual aluminum in PAC coagulation effluent by river clams in the present invention;

[0028] Figure 6 This is a graph showing the change in the removal rate of residual aluminum in the AlCl3 coagulation effluent by repeated use of river clams in the present invention;

[0029] Figure 7 This is a graph showing the change in the removal rate of residual aluminum in PAC coagulation effluent by repeated use of river clams in the present invention;

[0030] Figure 8 This is a graph showing the change in aluminum removal rate under different water temperatures, pH values, and dissolved oxygen content conditions in the present invention.

[0031] In the figure:

[0032] 1- float, 2- valve frame, 3- hollow box, 4- river clam, 5- weight, 6- flow meter. DETAILED DESCRIPTION

[0033] The present invention will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are only for illustrative purposes, and do not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise specified, the reagents and equipment used are all commercially available. If in the following examples, specific treatment conditions and treatment methods are not clearly described, then conditions and methods known in the art can be used to process.

[0034] The present invention provides a method for removing residual aluminum in water, comprising the following steps:

[0035] Step S100: passing the effluent treated with the aluminum salt flocculant into a biological filter.

[0036] In the present invention, the aluminum salt flocculant can be aluminum sulfate (Al2(SO4)3·18H2O), aluminum chloride (AlCl3), alum (Al2(SO4)3·K2SO4·2H2O), polyaluminum chloride (PAC), polyaluminum sulfate (PAS), polyaluminum chlorosulfide (PACS), etc., without special limitation.

[0037] Step S200: immerse river clams in water of a biological filter tank, and obtain excrement flocs after biological enrichment and filtration.

[0038] In this step, the river clams are domesticated river clams and are always immersed in the water during the treatment process. The gills of the river clams have a strong interception and filtration ability, which can filter the aluminum flocs remaining in the water and convert them into pseudo-fecal flocs (referred to as flocs) after a period of time and excrete them out of the body. After being excreted, the pseudo-fecal flocs are dispersed in the water.

[0039] It should be noted that river clams are freshwater benthic organisms that are cheap and easy to obtain. It is generally not considered to replace river clams with other shellfish aquatic organisms such as clams and scallops, because clams, scallops, etc. need to live in sea areas with large water flow and high salinity. The use environment of this application is a biological filter tank with small water flow and low salinity. In this environment, the mortality rate of other shellfish aquatic organisms will be very high. They are not ideal biological species and have great limitations.

[0040] In the present invention, the oxygen content of the water in the biofilter is preferably 6-15 mg / L, the pH value is preferably 7-9, and the temperature is preferably 10-25°C. The oxygen content of the water can be, for example, 6 mg / L, 8 mg / L, 10 mg / L, 12 mg / L, 13 mg / L, 15 mg / L, etc., the pH value can be, for example, 7, 7.5, 8, 8.5, 9, etc., and the temperature can be, for example, 10°C, 12°C, 14°C, 15°C, 20°C, 22°C, 24°C, 25°C, etc. The above conditions are suitable for the normal growth and life of river clams in the biofilter. If the water temperature is too low, the river clams stop feeding, affecting their interception and filtration capabilities. If the water temperature is too high, the mortality rate of river clams increases.

[0041] In the present invention, the density of adding river clams is preferably 10-50 kg / m 3 , for example 10kg / m 3 , 20kg / m 3 、30kg / m 3 , 40kg / m 3 , 50kg / m 3 The hydraulic retention time in the biological filter is preferably 4-10h, for example, it can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc. By limiting the density of clams and the hydraulic retention time, the survival rate of clams can be guaranteed and the removal effect of residual aluminum in the water can be ensured.

[0042] The present invention utilizes the filter feeding process of river clams to convert the residual dissolved and / or granular aluminum clusters (polymerized form of keegin-Al13) in water after being treated with aluminum salt flocculants into high-concentration, large-size, easily sedimentable flocculent aggregates, thereby achieving efficient removal and separation of residual aluminum in water.

[0043] In the present invention, river clams are preferably contained in a hollow box 3, and the material of the hollow box 3 is not particularly limited here, for example, it can be metal, wood, etc., and can be a regular shape or an irregular shape such as a net bag, and there is no special limitation on this. It should be noted that the pseudo-feces flocs discharged by river clams may adhere to the side walls and bottom of the hollow box 3. In order to avoid the long-term accumulation of flocs affecting the flow of water, the hollow box 3 is cleaned regularly.

[0044] In the present invention, the outer bottom of the hollow box 3 is preferably connected with a weight 5 to prevent the metal cage from shaking or falling due to the impact of water flow; the side wall of the hollow box 3 is preferably provided with a flow meter 6 for monitoring the water flow; the outer top of the hollow box 3 is preferably connected with a float 1, and the other end of the float 1 is connected to the valve frame 2, for example, it can be connected to the valve frame 2 through a nylon rope, and the valve frame 2 is fixed to the inner wall of the biofilter and flush with the horizontal plane. Through the relationship between the weight 5, the float 1, the valve frame 2 and the hollow box 3, the hollow box 3 can be immersed in the water body, and the immersion depth of the hollow box 3 can be adjusted by adjusting the height of the valve frame 2 in the hollow box 3.

[0045] In the present invention, river clams 4 are preferably cultured in a hollow box 3 by a hanging method. In order to achieve this culture method, the interior of the hollow box 3 is preferably provided with a plurality of partitions from top to bottom, and the hollow box 3 is divided into a plurality of activity spaces by the plurality of partitions, and the river clams 4 are distributed in the plurality of activity spaces. Preferably, the partition is a hollow partition, and the pseudo-fecal flocs produced by the river clams 4 are discharged through the hollow parts of the box and the partition.

[0046] Step S300: the excretion flocs are separated into solid and liquid after sedimentation.

[0047] In this step, the excreted flocs flow into the sedimentation tank with the water flow, and the water flow rate in the sedimentation tank slows down, causing the excreted flocs to settle in the sedimentation tank. The clear water after sedimentation enters the purification tank.

[0048] In the present invention, the pH value of the water in the sedimentation tank is preferably 7-9 to maintain the normal physiological activities of the river clams.

[0049] Step S400. The supernatant after the solid-liquid separation is passed into a clean water tank, and the regularly replaced river clams are purified and domesticated in the clean water tank.

[0050] In the present invention, the water temperature of the clear water pool is preferably maintained at 9-30°C, for example, it can be 9°C, 15°C, 20°C, 25°C, 30°C, etc., to ensure the normal physiological activities of river clams. The period of regular replacement of river clams is 3-30 days, preferably, 7-30 days, more preferably 7-15 days, for example, it can be 7 days, 9 days, 11 days, 13 days, 15 days, etc. The regular replacement is to regularly remove dead river clams to avoid pollution to the water environment. During the domestication period of river clams, bait is fed daily, and the bait can be the spirulina powder in the river clam diet. There is no special limitation on this, as long as the normal physiological activities of river clams can be maintained.

[0051] The technical solution of the present invention is explained below in conjunction with specific embodiments.

[0052] Example 1

[0053] Aluminum salt flocculant solutions with aluminum concentrations of 1 mg / L, 10 mg / L, and 50 mg / L were prepared using water after aeration for 24 hours. The types of aluminum salt flocculants were AlCl3 and PAC, respectively. Clams were placed in a 10L glass tank for a semi-static experiment. The volume of the solution in the tank was 5L. Ten domesticated healthy clams of similar size were added. The equivalent density of clam stocking was 34.07 kg / m 3 Before the experiment, the background value of aluminum concentration in river clams was determined. The experiment was conducted at 24°C and pH = 7. A small aeration device was used to maintain the oxygen content of the water at 10 mg / L. 5 mL of water samples were taken at 1, 2, 3, 5, 7, 12, and 24 hours to determine the residual aluminum content in the water samples. The results are shown in Figure 2 and Figure 3 ; After 24 hours, the survival rate of river clams was 90%.

[0054] The determination of residual aluminum content in water samples was carried out in accordance with the chrome azuro blue S spectrophotometric method specified in the "Standard Test Methods for Metal Indicators of Drinking Water" (GB / T5750.6-2006). In the pH range of 6.7-7.0, aluminum reacted with chrome azuro blue S in the presence of polyethylene glycol octylphenyl ether and cetylpyridinium bromide to form blue-green quaternary micelles, which were quantitatively determined by colorimetry.

[0055] Depend on Figure 2 and Figure 3 It can be seen that after 12 hours of coagulation treatment with river clam microorganisms, the removal rate of residual aluminum in the water sample can reach more than 80%.

[0056] Example 2

[0057] Aluminum salt flocculant solutions with aluminum concentrations of 1 mg / L, 10 mg / L, and 50 mg / L were prepared using water after 24 hours of aeration. The types of aluminum salt flocculants were AlCl3 and PAC, respectively. Clams were placed in a 10L glass tank for a semi-static experiment. The volume of the solution in the tank was 5L. Ten domesticated healthy clams of similar size were added, and the equivalent density of clam stocking was 30.56 kg / m 3 Before the experiment, the background value of aluminum concentration in river clams was determined. The experiment was conducted at 24°C and pH = 7. A small aeration device was used to maintain the oxygen content of the water at 10 mg / L. A river clam was taken out at 1, 2, 3, 4, 5, 6, and 7 days respectively. After the river clam shell was rinsed with deionized water, the shell and soft tissue of the river clam were quickly separated in an ice water bath, dried with filter paper, and then dried in a freeze dryer and weighed. Phosphate buffered saline was added at a ratio of weight (g): volume (mL) = 1:9, and placed in an ultrasonic cell crusher to make a homogenate. After dilution, the aluminum concentration was measured on the machine. The results are shown in Figure 4 and Figure 5 ; After 24 hours, the survival rate of river clams was 100%.

[0058] Depend on Figure 4 and Figure 5 It can be seen that river clams can effectively filter the residual aluminum flocs in the water, and within a certain period of time, as the action time of river clams increases, the effect of river clams on the adsorption of residual aluminum flocs in the water becomes better. Among them, after seven days of biological coagulation treatment, the enrichment concentration of residual aluminum in the AlCl3 coagulation effluent by river clams can reach 1100mg / kg; after five days of biological coagulation treatment, the enrichment concentration of residual aluminum in the PAV coagulation effluent by river clams can reach more than 1500mg / kg.

[0059] Example 3

[0060] Aluminum salt flocculant solution with an aluminum concentration of 1 mg / L was prepared using tap water after aeration for 24 hours. The types of aluminum salt flocculants were AlCl3 and PAC. Clams were placed in a 10L glass tank for a semi-static experiment. The volume of the solution in the tank was 5L. Ten domesticated healthy clams of similar size were added. The density of clam stocking was converted to 32.43 kg / m 3 Before the experiment, the background value of aluminum concentration in river clams was determined. The experiment was conducted at 24°C and pH = 7. A small aeration device was used to maintain the oxygen content of the water at 10 mg / L. The aluminum salt flocculant solution with the same volume and constant concentration was replaced every 12 hours. The experiment was repeated for 3 days. 5 mL of water samples were taken at 1, 3, 5, 7, 12, 24, 36, 48, 60, and 72 hours, and the residual aluminum content in the water samples was determined. The results are shown in Figure 6 and Figure 7 ; After 24 hours, the survival rate of river clams was 100%.

[0061] Depend on Figure 6 and Figure 7 It can be seen that after six consecutive replacements of the aluminum salt flocculant solution with constant volume concentration, the removal rate of residual aluminum in the water sample by the same group of river clams can reach more than 80%, and can reach up to 90%. The removal effect is good and the stability of the removal effect is good.

[0062] Comparative Example 1

[0063] Aluminum salt flocculant solution with an aluminum concentration of 1 mg / L was prepared using tap water after aeration for 24 hours. The types of aluminum salt flocculants were AlCl3 and PAC. Clams were placed in a 10L glass tank for a semi-static experiment. The volume of the solution in the tank was 5L. Ten domesticated healthy clams of similar size were added. The density of clam stocking was converted to 32.91 kg / m 3 , before the experiment, the background value of aluminum concentration in river clams was determined. The experiment was carried out at 30℃ and pH=7. A small aeration device was used to maintain the oxygen content of the water at 10mg / L. The aluminum salt flocculant solution with the same volume and constant concentration was replaced every 12 hours. The experiment was repeated for 3 days, and 5mL water samples were taken at 1, 3, 5, 7, 12, 24, 36, 48, 60, and 72 hours to determine the residual aluminum content in the water samples; after 24 hours, the survival rate of river clams was 50%.

[0064] Comparative Example 2

[0065] Comparative Example 2 is basically the same as Comparative Example 1, with the only difference being that the experiment was conducted at 24°C and pH=5, and a small aeration device was used to maintain the oxygen content of the water at 10 mg / L; and the survival rate of the river clams was 40% after 24 hours.

[0066] Comparative Example 3

[0067] Comparative Example 3 is basically the same as Example 1, with the only difference being that the experiment was conducted at 24°C and pH=7, and a nitrogen blowing device was used to remove part of the oxygen in the water so that the oxygen content of the water was maintained at 4 mg / L; after 24 hours, the survival rate of the river clams was 20%.

[0068] The residual aluminum content in the water samples was measured under the above experimental conditions. The results are shown in Figure 8 The measurement results showed that the aluminum removal rate decreased significantly after 12 hours, which was lower than the residual aluminum removal rate in the embodiment. Some river clams died, causing the water quality to deteriorate and the water to become turbid and odorous.

[0069] In summary, the method for removing residual aluminum in water of the present invention can effectively reduce the concentration of residual aluminum in water, realize the rapid removal of small-sized trace pollutants in water, and the removal effect is stable and has broad application prospects.

[0070] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for removing residual aluminum in water, characterized in that: The following steps are involved: (1) Passing the effluent treated with aluminum salt flocculant into the biofilter; (2) Submerging river clams in the water of a biological filter tank to obtain excrement flocs after biological enrichment and filtration; (3) The excreted flocs are then separated into solid and liquid after sedimentation.

2. The method for removing residual aluminum in water according to claim 1, characterized in that: The water in step (2) has an oxygen content of 6-15 mg / L, a pH value of 7-9, and a temperature of 10-25°C.

3. The method for removing residual aluminum in water according to claim 1, characterized in that: The density of adding the river clams in step (2) is 10-50 kg / m 3 .

4. The method for removing residual aluminum in water according to claim 1, characterized in that: The hydraulic retention time in the biofilter in step (2) is 4-10 hours.

5. The method for removing residual aluminum in water according to claim 1, characterized in that: The pH value of the water in the sedimentation tank in step (3) is 7-9.

6. The method for removing residual aluminum in water according to claim 1, characterized in that: The river clams described in step (2) are replaced regularly, with a replacement cycle of 3-30 days.

7. The method for removing residual aluminum in water according to claim 6, characterized in that: The following steps are also included: The supernatant after the solid-liquid separation is passed into a clean water tank, and the regularly replaced river clams are purified and domesticated in the clean water tank.

8. The method for removing residual aluminum in water according to any one of claims 1 to 7, characterized in that: The river clams are loaded in a hollow box, a weight is connected to the outer bottom of the hollow box, and a flow meter is arranged on the side wall of the hollow box.

9. The method for removing residual aluminum in water according to claim 8, characterized in that: A float is connected to the top of the outer side of the hollow box, and the other end of the float is connected to a valve frame. The valve frame is fixed to the inner wall of the biofilter and is flush with the horizontal plane.

10. The method for removing residual aluminum in water according to claim 8, characterized in that: A plurality of partitions are arranged inside the hollow box from top to bottom, and the hollow box is divided into a plurality of activity spaces by the plurality of partitions, and the clams are distributed in the plurality of activity spaces.

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