In-situ remediation method for water body polluted by rare earth / manganese ore mining

Abstract

The invention relates to an in-situ remediation method for a water body polluted by rare earth / manganese ore mining, which comprises the following steps: domesticating and screening microalgae through the polluted water body, and treating sewage by adopting the screened dominant microalgae. A microalgae floating bed containing screened and propagated microalgae and a slow-release phosphorus source is suspended on the water surface, the microalgae floating bed is a microalgae bioreactor, and only water can pass through the microalgae floating bed, so that the microalgae continuously perform material exchange with the water body in the microalgae floating bed, ammonia nitrogen in the sewage is assimilated and removed, the pH of the sewage is increased, and the sewage treatment effect is improved. The acidic sewage is gradually converted into a neutral water body, the pollution degree of the water body is relieved, and the water body is repaired; the microalgae are kept in the microalgae floating bed, so that the microalgae cannot pollute a water body, and the microalgae can be taken out from the microalgae floating bed after growing to a certain amount. According to the method, the surface illumination of the polluted water body is fully utilized, other substances are not needed except the slow-release phosphorus source, and the method is low in technical cost and free of pollution.

Description

Technical Field

[0001] The invention relates to the field of water body restoration, in particular to an in-situ restoration method for surrounding water bodies during rare earth / manganese ore mining. Background Art

[0002] Rare earth elements (REE) are the general term for the 15 lanthanide elements and two elements, scandium and yttrium, in the periodic table. Rare earth elements play an important role in military, aviation, metallurgy, agriculture and other fields, and are valuable strategic resources. At the same time, my country is the world's largest exporter of rare earth resources, and China's rare earth reserves account for 57.7% of the world's reserves. In southern China, such as Ganzhou City, Jiangxi Province, rare earth mines are mainly ion adsorption heavy rare earth mines. There is already a set of mature mining processes for this type of rare earth mine, among which sulfate in-situ leaching is a simple and commonly used method. This method injects a high-concentration ammonium sulfate solution into the rock layer containing rare earth elements through an infiltration well, dissolves the rare earth ions in the mountain into the ammonium sulfate solution through ion exchange, and then drills a hole at the bottom of the mountain to collect the ammonium sulfate solution with dissolved rare earth ions, and then adds oxalic acid and other chemical reagents to precipitate and collect the rare earth ions. After the rare earth mining is completed, a large amount of ammonium sulfate still remains in the abandoned mines and the surrounding groundwater, and then flows out with rainwater, causing pollution to small lakes and reservoirs around the mining area.

[0003] Manganese ore is a very important strategic mineral resource, especially rich manganese ore and high-quality manganese ore resources, which have been listed as scarce minerals in China. The distribution of manganese ore resources in my country is uneven. As of the end of 2010, 23 provinces and cities have found manganese ore, mainly distributed in the southern region. In modern industry, manganese and its compounds are used in various fields of the national economy. Among them, the steel industry is the most important field, with manganese accounting for 90% to 95%, mainly as a deoxidizer and desulfurizer in the process of iron and steelmaking, and used to make alloys. The remaining 10% to 5% of manganese is used in other industrial fields, such as the chemical industry (manufacturing various manganese salts), light industry (for batteries, matches, printing paint, soap making, etc.), building materials industry (colorants and decolorants for glass and ceramics), national defense industry, electronics industry, as well as environmental protection and agriculture and animal husbandry. The vast majority of manganese ores in my country are poor ores and must be processed by mineral processing. However, since most manganese ores are fine-grained or micro-grained, and contain a considerable amount of high-phosphate ores, high-iron ores, and co-existing (associated) beneficial metals, it is very difficult to process the ore. The commonly used manganese ore beneficiation methods in my country are mechanical selection (including ore washing, screening, gravity selection, strong magnetic separation and flotation), as well as pyrometallurgical enrichment and chemical beneficiation. However, the outflowing beneficiation wastewater will cause huge pollution to the water bodies around the mines. Summary of the invention

[0004] In view of the above-mentioned water bodies polluted by mining, the present invention provides a microalgae bioremediation technology to carry out in-situ remediation treatment. The main characteristics of the water bodies polluted by rare earth mining are: low pH value, high NH 4 + -N, the main characteristics of water bodies polluted by manganese mining: low pH value, high NH 4 + -N and high content of Mn 2+ .

[0005] An in-situ remediation method for water bodies contaminated by rare earth / manganese ore mining comprises the following steps:

[0006] (1) Screening of specific microalgae: Select microalgae from natural water bodies, use the polluted water to be treated for domestication and screening, obtain specific microalgae, and then expand them; the microalgae are screened and domesticated from the malignant water to be treated. For example, the specific microalgae in this application is obtained from the rare earth tail water produced by the Ganzhou rare earth mine after three years of domestication. It has good acid resistance and can also quickly remove high concentrations of ammonia nitrogen in the water.

[0007] (2) Preparation of microalgae floating bed: using a material that is permeable to water but impermeable to microalgae to make a container with an open top, the container can float on the water surface;

[0008] (3) In-situ remediation of polluted water bodies: Several microalgae floating beds are suspended in polluted water bodies for water remediation. The container is open and located above the water surface of the polluted water body. Screened and expanded microalgae and slow-release phosphorus sources are placed in the container. The total amount of microalgae added is about 500-1000 mg / L, and the amount of phosphorus source added is 0.5-1.25 g / m 3 (The rate of assimilation of ammonia nitrogen by microalgae is 2 mg / L*d -1 The most suitable nitrogen-phosphorus ratio for microalgae is 16:1, and the phosphorus concentration in fluorapatite and its concentration in water are used to calculate the result.

[0009] (4) Recovery and reuse of microalgae: After the polluted water body is restored to normal indicators, the microalgae floating bed is removed from the water body and the microalgae in it are recovered and recycled.

[0010] The phosphorus source is phosphate rock powder, the main components of which are: fluoroapatite (containing 10% to 35% phosphorus pentoxide, with low solubility in water)

[0011] The microalgae floating bed is a three-dimensional frame lined with filament geotextile, and a circle of foam plates or a number of suspended balls are added in the middle of the height direction of the outer side of the frame. Water can freely pass through the filament geotextile, but microalgae cannot pass through the filament geotextile;

[0012] The microalgae floating bed is made of filament geotextile to form a cloth bag with an open top, and a supporting three-dimensional frame is arranged inside or outside the cloth bag. The microalgae floating bed is used as a bioreactor to provide a place for the growth and development of microalgae and to remove pollutants in water during biological treatment.

[0013] The main body of the microalgae floating bed has a rectangular shape or a cylindrical shape, and the water entry depth of the microalgae floating bed is 400mm-600mm.

[0014] The microalgae floating bed is rectangular, with a length, width and height of 3000mm, 1000mm and 800mm respectively (the length can be adjusted appropriately according to the specific water conditions). A circle of suspended foam plates or suspended balls is added 300mm below the top, and the foam plates are 40mm-60mm wide and 40mm-60mm thick.

[0015] The arrangement of the microalgae floating bed is 1 per 20-30m2 of water area. 2 .

[0016] The polluted water body is a rare earth mineral polluted water body, and the specific microalgae are mainly mixed algae such as Chlorella and Scenedesmus.

[0017] The polluted water body is a manganese ore polluted water body, and the specific microalgae are mixed algae mainly composed of Chlorella vulgaris.

[0018] The present invention tames and screens microalgae by polluting water bodies, and uses the screened superior microalgae for sewage treatment. The present invention specially designs a microalgae floating bed, and suspends the microalgae floating bed containing microalgae and a phosphorus source on the water surface. The microalgae floating bed becomes a bioreactor for the microalgae. Since the filament geotextile can only allow water to pass through, the microalgae continuously exchange and treat the sewage in the microalgae floating bed until the sewage is restored to normal, while the microalgae cannot pass through the filament geotextile and remain in the filament geotextile. The microalgae will not pollute the water body, and the microalgae floating bed can be taken out after the restoration is completed.

[0019] The main advantages of using microalgae biotreatment technology to treat water bodies polluted by mineral mining are:

[0020] 1) Microalgae can complete the restoration of polluted water bodies on their own, without the need for other organisms, and only requires the addition of phosphorus sources. Microalgae can use their own assimilation function to absorb ammonia nitrogen, and at the same time increase the pH in the water. The extracellular polymers they secrete also have the function of absorbing heavy metals. The main mechanism is that microalgae assimilate ammonia nitrogen through their own glutamine-glutamate conversion. At the same time, microalgae can absorb bicarbonate ions and carbon dioxide in the water as carbon sources and release oxygen, thereby increasing the pH value of the water body. Its absorption of metal ions mainly depends on the secreted extracellular polymers (EPS). EPS contains a large number of groups such as hydroxyl, carboxyl, and amino groups that can adsorb metal ions. Its main adsorption pathways are ion exchange, complexation / chelation, and electrostatic attraction.

[0021] 2) After the sewage is repaired, the microalgae can be removed without remaining in the water. The microalgae grow and reproduce in the microalgae floating bed and absorb pollutants in the water. Therefore, after the water body is repaired, the microalgae floating bed can be removed without causing secondary pollution to the water body.

[0022] 3) Microalgae can improve water quality while repairing water bodies: the photosynthesis of microalgae can fix carbon dioxide in the water and release oxygen, increase the concentration of dissolved oxygen in the water, and provide a good living environment for the subsequent growth of organisms.

[0023] 4) The added value of microalgae can be reused as a resource: After water restoration, microalgae can be reused as a resource, such as biological feed, farmland fertilizer, etc.

[0024] 5) Microalgae bioremediation technology is low-cost and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the microalgae floating bed in the present invention (rectangular type),

[0026] Figure 2 Schematic diagram of the microalgae floating bed of the present invention (cylindrical type), wherein the reference numerals are as follows: 1-frame, 2-suspended foam plate. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the embodiments and drawings.

[0028] Microalgae floating bed design:

[0029] like Figure 1As shown, the microalgae floating bed is a rectangular parallelepiped, and its main body is a rectangular parallelepiped frame 1, and its length, width and height are respectively: 3000mm, 1000mm, and 800mm (which can be adjusted according to the size of the water area and the degree of pollution in the water). A circle of suspended foam board 2 is added at a distance of 300mm from the top, and the thickness of the foam board is about 50mm and the width is 50mm. A filament geotextile is arranged inside the rectangular parallelepiped frame, and the top is open to provide a place for microalgae to attach and water quality exchange and repair. The design of the microalgae floating bed is about 500mm deep. This depth can make the microalgae fully contact with the water body, and at the same time, sunlight can also irradiate the microalgae to photosynthesize the microalgae. If the water body is relatively turbid or there are more suspended matter in the water that affects the light irradiation, the depth of the reactor into the water can be appropriately reduced (the shape of the device is not limited to a rectangular parallelepiped. Since the microalgae in the device continuously repairs the water body, the concentration of pollutants inside and outside the device produces a concentration difference, that is, the pollutants diffuse from the outside to the inside, and the contact area of ​​its diffusion is also relatively important, so the shape of the device is not limited to a rectangular parallelepiped). The main framework of the microalgae floating bed is a three-dimensional frame built with corrosion-resistant materials (such as stainless steel) and a filament geotextile lining (water can flow freely, but the biological materials in the device will not penetrate into the water body).

[0030] Layout of microalgae floating beds: The polluted waters can be divided into grid-type areas. One microalgae floating bed can repair about 25m 2 Water bodies. The screened and expanded microalgae can be directly added to the water body for repair when they reach a certain concentration. At the same time, a slow-release phosphorus source (such as phosphate rock powder, the main component of which is fluoroapatite) should be appropriately added to ensure the normal operation of the microalgae. Phosphate rock powder is a solid mineral that can slowly release phosphorus sources and does not need to be added continuously.

[0031] The microalgae floating bed of the present invention can also be cylindrical. Figure 2 The cylindrical frame 1 has a diameter of 1000 mm (which can be adjusted according to the size of the water area and the degree of pollution in the water). A circle of suspended foam board 2 is added 300 mm below the top, and the foam board is about 50 mm thick and 50 mm wide. Filament geotextile is arranged inside the cylindrical frame, with an open top, to provide a place for microalgae to attach and water quality exchange and repair. The rest is the same as the above three-dimensional type.

[0032] Likewise, the above-mentioned suspended foam panels can be replaced with suspended balls to allow the microalgae floating bed to float on the water surface.

[0033] Embodiment 1:

[0034] A polluted lake near a rare earth mine in Longnan City, Ganzhou, has a low pH value and high NH 4 + -N, so that the lake's ecological environment is bad and almost no higher aquatic organisms survive, and the water is clear. In addition, due to the lake's low pH value and high NH4 + -N, which means it cannot be directly used for drinking or irrigation, and it needs to be treated when it rains to prevent overflow water from polluting farmland and water bodies below the mountain. This is not only a waste of water resources, but also has a serious impact on the surrounding environment. In response to this situation, microalgae restoration technology is used to restore the water body, and the repaired water area is about 260m 2 , the water depth is about 2.5-3m.

[0035] Repair steps:

[0036] Step a) Detection of water indicators: Take water samples around the Ganzhou rare earth mine for indicator detection

[0037] Step b) domestication and expansion of microalgae: the content of microalgae added is different for different water bodies of different sizes, and the algae species added to water bodies of different water quality are also different. Therefore, algae species should be domesticated before repairing the water body: the microalgae taken out from the water body itself is added to the water body to be repaired to allow it to grow and develop freely. After a period of time, the surviving microalgae are screened out, and then the screened algae species are expanded and cultured. After laboratory screening and domestication, the obtained microalgae are mainly specific Chlorella and Scenedesmus mixed algae. Because they also have good sedimentation performance, they are called co-flocculation microalgae.

[0038] Step c) Layout of microalgae floating bed: The area of ​​polluted water to be treated is approximately 260m 2 , arrange 10 microalgae floating beds.

[0039] Step d) Water body restoration: Add the expanded algae into the arranged restoration device, and continuously monitor the water quality and the growth of the algae (the concentration of the supplementary phosphorus source is about 0.5g / m 3 ), the water temperature condition is the actual regional water temperature. The initial inoculation amount of microalgae is about 500mg / L, and the restoration time is 3 months

[0040] Step e) recycling and reuse of microalgae: when the water body is restored to normal indicators, the microalgae floating bed can be taken out of the water body and the microalgae therein can be recycled and reused.

[0041] Main indicators before water restoration:

[0042]

[0043] Main indicators after water restoration:

[0044]

[0045] After microalgae restoration, the ammonia nitrogen and nitrate nitrogen in the water body reached the discharge standards, and the water body reached the surface water Class IV standard.

[0046] Example 2

[0047] The mining wastewater generated by manganese mining in a certain area of ​​Guizhou has caused serious pollution to the surrounding water bodies, making the water bodies around the mining area acidic and containing high levels of ammonia nitrogen and manganese ions. It cannot be directly discharged or used for farmland irrigation, resulting in a huge waste of water resources. Microalgae bioremediation technology was used to make it usable. The repaired water surface is about 210m 2 , the water depth is about 3-3.5m.

[0048] Repair steps:

[0049] Step a) Detection of water indicators: Take small water samples around the Guilin Manganese Mine in Guangxi for indicator detection

[0050] Step b) domestication and expansion of microalgae: the content of microalgae added is different for different water bodies of different sizes, and the algae species added to water bodies of different water quality are also different. Therefore, algae species should be domesticated before repairing the water body: microalgae taken from the water body itself (freshwater lake) are added to the water body to be repaired and allowed to grow and develop freely. After a period of time, the surviving algae are screened and then the screened algae species are expanded and cultured. After laboratory screening and domestication, the obtained microalgae are mostly Chlorella.

[0051] Step c) Layout of microalgae floating bed: The area of ​​polluted water to be treated is approximately 210m 2 , arranged 9 microalgae floating beds.

[0052] Step d) Water body restoration: Add the expanded algae into the arranged restoration device, and continuously monitor the water quality and the growth of the algae (the concentration of the supplementary phosphorus source is about 1g / m 3 ), the water temperature condition is the actual regional water temperature. The initial inoculation amount of microalgae is about 700 mg / L, and the restoration time is 12 months.

[0053] Step e) recycling and reuse of microalgae: when the water body is restored to normal indicators, the microalgae floating bed can be taken out of the water body and the microalgae therein can be recycled and reused.

[0054] Main indicators before water restoration:

[0055]

[0056] Main indicators after water restoration:

[0057]

[0058] After the polluted water body was restored by microalgae, its ammonia nitrogen and manganese concentrations reached the discharge standards, and the water body reached the surface water Class IV standard.

Claims

1. An in-situ remediation method for water bodies contaminated by rare earth / manganese ore mining, comprising the following steps: (1) Screening of specific microalgae: Select microalgae from natural water bodies, use the polluted water to be treated for domestication and screening, obtain specific microalgae, and then expand them; microalgae are screened from the malignant water to be treated, domesticated, (2) Preparation of microalgae floating bed: using a material that is permeable to water but impermeable to microalgae to make a container with an open top, the container can float on the water surface; (3) In-situ remediation of polluted water bodies: Several microalgae floating beds are suspended in polluted water bodies for water remediation. The container is open and located above the water surface of the polluted water body. Screened and expanded microalgae and slow-release phosphorus sources are placed in the container. The total amount of microalgae added is about 500-1000 mg / L, and the concentration of supplementary phosphorus source is about 0.5-1.25 g / m 3 . (4) Recovery and reuse of microalgae: After the polluted water body is restored to normal indicators, the microalgae floating bed is removed from the water body and the microalgae in it are recovered and recycled.

2. The method according to claim 1, wherein the phosphorus source is phosphate rock powder.

3. According to the method of claim 1, the microalgae floating bed is a three-dimensional frame lined with filament geotextile, and a circle of foam boards or a number of suspended balls are added in the middle position of the height direction of the outside of the frame.

4. The method according to claim 3, wherein the main body of the microalgae floating bed is in a rectangular or cylindrical shape, and the water depth of the microalgae floating bed is 400mm-600mm.

5. The method according to claim 4, wherein the microalgae floating bed is arranged in a water area of ​​1 / 20-30m 2 .

6. According to the method of claim 5, the microalgae floating bed is in a rectangular shape, with a length, width and height of 3000mm, 1000mm and 800mm respectively, and a circle of suspended foam plates or suspended balls is added at a distance of 300mm below the top of the microalgae floating bed, and the width of the foam plates is 40mm-60mm and the thickness is 40mm-60mm.

7. The method according to claim 1, wherein the polluted water body is a rare earth mineral polluted water body, and the specific microalgae are mixed algae mainly composed of Chlorella and Scenedesmus.

8. The method according to claim 1, wherein the polluted water body is a manganese ore polluted water body, and the specific microalgae is a mixed algae mainly composed of Chlorella vulgaris.

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