Acid mine wastewater treatment process and system

Abstract

A process and system for treating acid mine wastewater, belonging to the field of wastewater treatment. The treatment process comprises the following steps: in a regulating tank, regulating the water quality and water quantity of the acid mine wastewater to be treated; in an aeration tank, aerating the effluent of the regulating tank, so that the first part of the metal elements in the effluent of the regulating tank reacts into metal oxides; in a sedimentation tank, removing the metal oxides produced by the effluent of the aeration tank through precipitation; and removing at least part of the second part of the metal elements in the effluent of the sedimentation tank through a permeable reaction wall. The treatment process can effectively treat acid mine wastewater, achieve low operating costs, and also has the advantages of high efficiency, ecological protection, and stable effluent.

Description

Technical Field

[0001] The present application relates to the field of wastewater treatment, and in particular, to a process and system for treating acidic mine wastewater. Background Art

[0002] During the mining process, coal mines, metal mines, etc. will leave behind a lot of slag, pits and caves. After the mine is closed, the pits or caves will overflow with yellow wastewater due to long-term water accumulation, and this yellow wastewater is mine wastewater. This wastewater has the characteristics of low pH (strong acidity) and high content of characteristic pollutants - iron and heavy metals. If mine wastewater is allowed to flow indiscriminately, it will cause pollution to downstream rivers, lakes and farmland, and endanger the safety of surrounding residents.

[0003] At present, the main methods for treating acid mine wastewater include physical treatment, chemical treatment, physical and chemical treatment, biological method and mineral method. Among them, alkali neutralization precipitation method is the most widely used. However, alkali neutralization precipitation method has the following problems:

[0004] The initial construction investment is large;

[0005] The equipment corrodes quickly during operation;

[0006] High operating costs, such as high energy consumption, labor costs, and drug consumption;

[0007] The scope of application is small and the treatment effect on difficult-to-precipitate heavy metal wastewater is poor.

[0008] In order to solve the problems encountered in the existing acid mine drainage treatment process, it is urgent to develop a new process for treating acid mine drainage. Summary of the invention

[0009] In order to improve or even solve at least one of the above-mentioned problems, the present application proposes a process and system for treating acidic mine wastewater.

[0010] This application is implemented as follows:

[0011] In a first aspect, an embodiment of the present application provides an acid mine drainage treatment process, which includes the following steps: in a regulating tank, regulating the water quality and water quantity of the acid mine drainage to be treated; in an aeration tank, aerating the effluent from the regulating tank to react the first part of the metal elements in the effluent from the regulating tank into metal oxides; in a sedimentation tank, removing the metal oxides produced by sedimentation in the effluent from the aeration tank; and removing at least part of the second part of the metal elements in the effluent from the sedimentation tank through a permeable reaction wall.

[0012] In other examples of the first aspect, the treatment process includes the step of discharging the effluent from the permeable reaction wall into a receiving water body.

[0013] In other examples of the first aspect, the treatment process includes the following steps: allowing the precipitate containing metal oxides in the sedimentation tank to stand in a sludge storage tank, and after a selected period of time, discharging the sludge and returning the supernatant to the regulating tank.

[0014] In other examples of the first aspect, in each step, the wastewater is transported by gravity flow.

[0015] In some other examples of the first aspect, there are a plurality of permeable reaction walls, and each permeable reaction wall is used to process a different element in at least a portion of the second portion of metal elements.

[0016] In other examples of the first aspect, all of the permeable reaction walls sequentially treat the sedimentation tank effluent to remove at least a portion of the second portion of metal elements.

[0017] In other examples of the first aspect, the permeable reaction wall removes the second portion of the metal elements through the reaction filler provided.

[0018] In other examples of the first aspect, the reactive filler in each permeable reactive wall includes one or more.

[0019] In other examples of the first aspect, the treatment process also includes one or more of the following limitations: the dissolved oxygen concentration in the aeration tank is above 3 mg / L, the hydraulic retention time is 4 hours; the surface load of the reaction filler is 5m 3 / (m 2 h) to 9m 3 / (m 2 h); the treatment time of sedimentation tank effluent through the permeable reaction wall is at least 3 hours.

[0020] In a second aspect, an embodiment of the present application provides an acidic wastewater treatment system for implementing the above-mentioned acidic mine wastewater treatment process, which includes: an equalization tank for receiving raw water containing acidic mine wastewater to be treated and adjusting the water quality and water quantity of the raw water; an aeration tank connected to the equalization tank, for receiving the effluent from the equalization tank and generating metal oxides through dissolved oxygen reaction; a sedimentation tank connected to the aeration tank, for receiving the effluent from the aeration tank; a permeable reaction wall connected to the sedimentation tank, for receiving and treating the effluent from the sedimentation tank; a sludge temporary storage tank connected to both the equalization tank and the sedimentation tank, for receiving the sludge discharged from the sedimentation tank, and discharging the bottom sludge after the sludge has been allowed to stand and returning the supernatant to the equalization tank.

[0021] The wastewater treatment process exemplified in this application solves the problem of acid mine wastewater treatment process being difficult to maintain stable treatment that meets standards, and has the characteristics of low operating costs, high treatment efficiency, stable effluent that meets standards, and ecological, economical and environmentally friendly.

[0022] First, the process controls the quality and quantity of incoming water so that the subsequent process steps can continue to treat wastewater normally. The subsequent process steps treat the wastewater differently according to different functional units, thereby removing different objects to be treated in the wastewater, so that the wastewater is treated efficiently and the process discharge is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the flow of wastewater in the acid mine drainage treatment process provided for the example of this application;

[0025] Figure 2 A schematic diagram of the structure of the acid mine drainage treatment system provided for the example of this application;

[0026] Figure 3 A schematic diagram of the structure of a carrier frame for fixing reactive fillers in a permeable reactive wall in an acid mine drainage treatment system provided as an example of the present application.

[0027] Icons: 101-permeable reaction wall; 1011-carrier frame; 201-regulating tank; 202-aeration tank; 203-sedimentation tank; 204-sludge storage tank. DETAILED DESCRIPTION

[0028] In this application, all embodiments, implementation methods and features of this application can be combined with each other without contradiction or conflict. In this application, conventional equipment, devices, components, etc. can be purchased commercially or made according to the contents disclosed in this application. In this application, in order to highlight the key points of this application, some conventional operations and equipment, devices, and components are omitted or simply described.

[0029] In view of the problems existing in the existing process of treating acid mine wastewater by adding alkali and precipitation, the inventors of this application proposed a new process ( Figure 1 The wastewater flow in the treatment process is shown) for treating acid mine drainage. By implementing this new process, it is expected that one or more advantages and improvements in terms of cost, efficiency, effluent stability, effluent compliance rate, ecological protection, etc. can be achieved when treating wastewater.

[0030] Acid mine drainage is a special type of industrial wastewater produced during the mining process. Its main characteristics are: low pH and acidic; high Fe and Mn content and yellowish brown color; generally contains special heavy metals such as Cd and Ni according to the properties of the ore.

[0031] The traditional process generally adopts the alkali neutralization precipitation method, which has problems such as severe equipment corrosion, large amount of reagents, large amount of sludge generated, difficult operation and maintenance, etc., which leads to high operating costs of the system based on this method, and it cannot operate normally and stably, and the stable compliance rate of effluent is low.

[0032] This application mainly designs solutions for indicators such as heavy metal ions and pH of acid mine wastewater, so that the system effluent meets the requirements of the corresponding wastewater discharge standards, such as the "Coal Industry Pollutant Emission Standard" (GB20426-2006). The process of this application can achieve advantages in at least the following aspects: on the one hand, it makes full use of gravity energy, solar energy, etc., reduces the use of equipment, and achieves the purpose of energy saving and consumption reduction; on the other hand, it develops reactive fillers for characteristic pollutants in wastewater, and regularly maintains them, which greatly reduces the later operating costs.

[0033] In general, the process mainly includes a number of process units that will be described in detail later, and each process unit has a relatively independent function (which can also be selectively coordinated as needed) to achieve corresponding treatment operations on wastewater. In the example, the process units mainly include a unit for regulating the water quality and water quantity of raw water, a unit for aeration treatment, a unit for precipitation, and a unit for osmotic reaction. Furthermore, the process unit can also be set up as needed to match the unit for precipitation to perform sediment treatment.

[0034] Raw water mainly refers to acidic wastewater discharged from mines. In other examples, raw water can also be water that has undergone a preliminary simple treatment of the aforementioned acidic wastewater. The "preliminary simple treatment" can be, for example, dilution with water, removal of solid impurities (such as stones, firewood, metals, etc.), or other common treatments.

[0035] Generally, the above-mentioned process units can be implemented near the mine to treat the wastewater nearby. Alternatively, the process units are selected to be implemented in appropriate areas, and the mine wastewater is transported and treated by transportation equipment (liquid transport vehicles, etc.). It should be pointed out that although the treatment process is described using acid mine drainage as an example in this application, it is not intended to limit the process of this application to only be applied to acid mine drainage. It should be understood that the process in the example can be used for wastewater with the same or similar composition as acid mine drainage, or other wastewater that has been treated to have a composition or characteristics close to that of acid mine drainage.

[0036] In order to implement the above process, the inventors have proposed an acid mine wastewater treatment system. Figure 2 , the acid wastewater treatment system includes: a regulating tank 201, an aeration tank 202, a sedimentation tank 203, a permeable reaction wall 101 and a sludge temporary storage tank 204. The entire system is implemented to treat wastewater, so the wastewater is transported between each tank through a pipe or a ditch; accordingly, each tank can be connected by the aforementioned pipe or ditch. The transportation of wastewater between each pool or treatment unit can be achieved by self-flow under the action of gravity, or it can also be transported by a water pump. The transportation of wastewater by equipment such as a water pump requires the supply of electricity. Therefore, based on energy consumption considerations, gravity self-flow can be selected. However, gravity self-flow needs to consider the spatial position layout of each pool, so it may be necessary to design the corresponding structure and functionality of each pool. For example, according to the self-flow direction of the fluid from high to low under the action of gravity, the regulating tank, aeration tank, sedimentation tank, and permeable reaction wall are sequentially configured with their respective outlet heights arranged and laid out from high to low. That is, through the design and control of the liquid level elevation of each process unit, the entire process flow can utilize the gravity flow of wastewater into each process unit, thereby reducing operating costs.

[0037] Functionally speaking, each treatment pool has at least the following functions and effects.

[0038] The regulating tank is used to receive raw water containing acid mine drainage to be treated. The raw water is regulated in quality and quantity in the regulating tank, and after meeting the required requirements, it is transported to the subsequent tank. As a structure for regulating the inlet and outlet flow, the regulating tank can enable the pipelines and other equipment to work normally without being affected by the peak flow, valley flow or concentration changes of the wastewater. As a structure for regulating water quality, the regulating tank can also regulate the water quality of the sewage, such as the pH value and water temperature of the sewage, to meet the working needs of the subsequent process units.

[0039] The effluent (mainly overflow) from the regulating tank is transported to the aeration tank, and the metal oxides are generated by the dissolved oxygen reaction in the aeration tank. Aeration pipes or stirring devices are provided in the aeration tank to form a certain concentration of dissolved oxygen in the wastewater in the aeration pipes. Some impurities in the wastewater (mainly metal substances, such as metal ions) can react with the dissolved oxygen in the water to form solid substances (such as metal oxides) and be separated from the water.

[0040] The aeration tube directly delivers oxygen or air to the water body in a dispersed manner. During the contact between oxygen and water, the oxygen dissolves in the water body through mass transfer and becomes dissolved oxygen. Therefore, an air pump is also provided for the aeration tube to supply air. The aeration tube is a hollow pipe with multiple air holes on the wall to disperse the delivered gas in the water body. The aeration method can also be achieved by using waterfall aeration or solar aeration devices to effectively reduce electrical energy.

[0041] The stirring device can rapidly and violently stir the water in the aeration tank so that the air contacts the water, thereby fully and quickly dissolving the oxygen in the water. The stirring device can be realized by connecting an impeller to a motor. The impeller provides rotational power through the motor to stir the water. For the method of increasing the dissolved oxygen in the water by the stirring device, the concentration of dissolved oxygen in the water can be adjusted by adjusting the speed or intensity of the stirring. Generally, the speed of the motor is changed by adjusting the power of the motor. In other examples, the motor can be equipped with a gearbox to control its output speed. Accordingly, the motor is connected to the gearbox, and the gearbox is connected to the impeller. That is, the output shaft of the motor is connected to the input end of the gearbox (which can be connected through a transmission shaft), and the output end of the gearbox is connected to the impeller. The impeller with adjustable speed makes the dissolved oxygen content in the water meet the requirements of partial oxidation of metal ions in the wastewater and maintain the dissolved oxygen level in the pool.

[0042] Furthermore, in order to reduce the demand and consumption of external electricity, the stirring device can also be equipped with a power supply. The power supply generates electricity through wind energy or solar energy, thereby supplying power to the electrical equipment. In an alternative example, the power supply includes a solar power generation panel and a bracket connected by a connecting device. Furthermore, the solar power generation panel can also be rotated by a steering gear provided in the connecting device. Thus, the solar power generation panel can be rotated according to the local lighting conditions and the sunlight, so as to receive more sunlight for power generation.

[0043] The effluent from the aeration tank is transported to the sedimentation tank. The wastewater in the sedimentation tank is left to stand, and through sedimentation (solids settle from the liquid due to density differences, thereby separating; or chemical reagents can be used to solidify and precipitate the substances to be removed from the liquid through flocculation through reaction), the metal oxides in the aeration tank settle to the bottom of the sedimentation tank, while the upper water can be transported downstream for corresponding treatment. After long-term use of the sedimentation tank, the solid substances such as metal oxides accumulated at the bottom of the sedimentation tank will occupy the effective volume of the sedimentation tank and hinder the normal use of the sedimentation tank. Therefore, as needed, at the appropriate time, the "sludge" settled at the bottom of the sedimentation tank is discharged to reserve sedimentation space for the sewage in the aeration tank.

[0044] Corresponding to the sedimentation tank, in the example, the acidic wastewater treatment system includes a sludge storage tank. It is used to receive the sludge discharged from the sedimentation tank. Similar to the sedimentation tank, the sludge discharged from the sedimentation tank (which can be achieved by a sludge pump) is left to stand in the sludge storage tank, and will also settle accordingly to achieve stratification - the bottom sludge at the bottom and the supernatant at the upper layer. Among them, the bottom sludge discharge can be reduced, dried, etc., and the supernatant can be discharged or refluxed to the aforementioned regulating tank to regulate the raw water. Accordingly, the sludge storage tank can be connected to the regulating tank, and can also be connected to the sedimentation tank.

[0045] The permeable reaction wall is used to receive and process the effluent from the sedimentation tank. The permeable reaction wall can filter the wastewater through osmosis to separate the impurities (water-soluble, such as ions, etc.; or water-insoluble, such as macromolecular biological metabolites, etc.) from the water. The permeable reaction wall can also remove selected substances from the wastewater through reaction.

[0046] Considering that the components and substances in wastewater are relatively complex, a permeable reaction wall with a single function may not be easy to remove the aforementioned substances. Accordingly, it can be considered to set up multiple permeable reaction walls or optimize and improve the functions of the permeable reaction walls. For example, there are multiple functional units in the permeable reaction wall that can play a role of penetration and reaction, and they are adaptively combined. In the example of the present application, it is chosen to coordinately optimize and improve the number and function of the permeable reaction walls. For example, the permeable reaction wall includes a primary permeable reaction wall and a secondary permeable reaction wall, and the inlet of the primary permeable reaction wall is connected to the sedimentation tank, and the outlet of the primary permeable reaction wall is connected to the inlet of the secondary permeable reaction wall. See. Figure 3 , each permeable reaction wall 101 is also built with a reaction filler. The reaction filler can react with specific components in the water body through active substances. Therefore, the permeable reaction wall generally includes a wall body and a reaction filler fixed inside it, wherein the reaction filler can be fixed in the wall body through a metal frame and a carrier frame 1011. Based on optimization considerations, the reaction filler is implemented in a replaceable manner. For example, the metal frame and the carrier frame as a whole are replaced.

[0047] The reaction filler in this process is a non-toxic, harmless and environmentally friendly material. It is reusable and can undergo a series of physical and chemical reactions with wastewater to achieve the purpose of removing heavy metal ions. The reaction filler can be determined through experimental research and development according to the types and characteristics of heavy metals in the wastewater, and its quantity / type can be one or several selected ratios. For example, three types of reaction fillers are provided in the example. The elements of the first reaction filler are Mn (manganese), Si (silicon), Fe (iron), S (sulfur), Mg (magnesium), and O (oxygen), and its reaction mechanism is redox, electrostatic adsorption, and complex reaction; the elements of the second reaction filler are Mn (manganese), Fe (iron), Al (aluminum), O (oxygen), and H (hydrogen), and its reaction mechanism is catalytic oxidation, interception filtration, and neutralization; the elements of the third reaction filler are Si (silicon), Fe (iron), Al (aluminum), and O (oxygen), and its reaction mechanism is potential adsorption, catalytic oxidation, and interception filtration.

[0048] In addition, in order to distribute the wastewater, the water inlet and outlet of the primary permeable reaction wall and the secondary permeable reaction wall are both provided with water distribution troughs, so that the water distribution troughs are evenly distributed in each permeable reaction wall, so that the infiltration and reaction can occur more efficiently. Considering the simplification of the system and the convenience of construction, the water outlet of the primary permeable reaction wall and the water inlet of the secondary permeable reaction wall share the water distribution trough. The water distribution trough can be implemented in a variety of ways. As an example, the water distribution trough can be selected as a perforated flower wall structure or a perforated pipe flower wall structure, wherein the perforations are square holes of 50mm×50mm, and the diameter of the perforated pipe is 50mm.

[0049] Based on the aforementioned system, an acid mine drainage treatment process can be explained by the following description.

[0050] (1) The acid mine wastewater that needs to be treated is led to the regulating tank through pipelines to adjust the water quality and quantity of the raw water.

[0051] (2) The effluent from the regulating tank is lifted to the aeration tank by gravity or pump to fully oxidize the metal ions such as iron and manganese in the wastewater. The aeration tank is generally divided into two compartments, and the dissolved oxygen concentration in the tank is generally controlled at above 3 mg / L, with a hydraulic retention time of 4 hours.

[0052] (3) The effluent from the aeration tank flows into the sedimentation tank by gravity, and the metal oxides produced are removed through sedimentation treatment to ensure the water quality requirements of the first-level permeable reaction wall. It is generally divided into 2 compartments with a surface load of 5 to 9 m 3 / (m 2 h).

[0053] (4) The effluent from the sedimentation tank flows by gravity into the first-level permeable reaction wall, which is filled with process reaction fillers. After the wastewater comes into contact with the reaction fillers, neutralization and adsorption occur to remove certain metal ions in the wastewater. It is generally divided into two compartments, and the reaction time is controlled to be at least 3 hours.

[0054] (5) The effluent from the primary permeable reaction wall flows by gravity into the secondary permeable reaction wall, which is filled with process reaction fillers. After the wastewater comes into contact with the reaction fillers, oxidation and filtration occur to further remove metal ions in the wastewater. It is generally divided into two compartments, and the reaction time is controlled to be at least 4 hours.

[0055] (6) The effluent from the secondary permeable reaction wall is discharged into the receiving water body through pipes.

[0056] (7) The sludge temporary storage tank is mainly used to store the sludge discharged from the sedimentation tank regularly. The supernatant is returned to the equalization tank and the sludge is transported out for disposal regularly.

[0057] Example 1

[0058] The main excessive factors of water gushing out of a closed abandoned mine in Hunan Province were iron, manganese, pH and chromaticity.

[0059] In response to the above-mentioned mine water inrush, the Figure 1 The process flow shown is for wastewater treatment.

[0060] Designed treatment capacity is 150m 3 / d, the designed influent pH is 3.0, the total iron concentration is 400 mg / L, and the manganese concentration is 4.5 mg / L.

[0061] The total iron in the effluent complies with the "Coal Industry Pollutant Emission Standard" (GB20426-2006), which is 7 mg / L;

[0062] The effluent pH and manganese comply with the "Comprehensive Sewage Discharge Standard" (GB8978-1996), that is, the pH is 6-9 and the manganese concentration is 2 mg / L.

[0063] The dimensions of the main process units are as follows:

[0064] Regulating tank: 5.0m×4.7m×2.5m;

[0065] Aeration tank 8.2m×3.0m×2.5m;

[0066] Sedimentation tank 8.2m×3.0m×2.5m;

[0067] The first-level permeable reaction wall is 8.2m×4.0m×2.5m;

[0068] Secondary permeable reactive wall 8.2m×4.0m×2.5m;

[0069] The sludge storage tank is 5.0m×3.3m×2.5m.

[0070] Main equipment: Solar aerator with oxygenation capacity of 3-8m 3 / h, 2 units; submersible pump Q = 10m 3 / h, H=15m, N=1.5kW, 2 units.

[0071] The process reaction fillers mainly include filler 1, filler 2 and filler 3, and the ratio thereof is 2:5:3.

[0072] The project investment was about 1.964 million yuan, and it was put into operation in July 2018. It operates stably and reliably, the effluent quality meets the discharge standards, and the operating cost is about 1.02 yuan per ton of water.

[0073] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for treating acidic mine wastewater, characterized in that: The treatment process comprises the following steps: In the regulating tank, the water quality and quantity of the acid mine wastewater to be treated are regulated; In the aeration tank, aeration is performed on the effluent from the regulating tank, so that the first part of the metal elements in the effluent from the regulating tank reacts into metal oxides; the dissolved oxygen concentration in the aeration tank is above 3 mg / L, and the hydraulic retention time is 4 hours; in the sedimentation tank, the effluent from the aeration tank is precipitated to remove the generated metal oxides; The effluent from the sedimentation tank is passed through a permeable reaction wall to remove at least part of the second part of the metal elements, wherein the permeable reaction wall removes the second part of the metal elements through a set reaction filler, wherein each of the permeable reaction walls includes one or more reaction fillers, and the surface load of the reaction filler is 5m 3 / (m 2 h) to 9m 3 / (m 2 h); the treatment time of the effluent from the sedimentation tank through the permeable reaction wall is at least 3 hours; the elements of the first reaction filler are Mn, Si, Fe, S, Mg, and O, and its reaction mechanism is redox, electrostatic adsorption, and complex reaction; the elements of the second reaction filler are Mn, Fe, Al, O, and H, and its reaction mechanism is catalytic oxidation, interception filtration, and neutralization; the elements of the third reaction filler are Si, Fe, Al, and O, and its reaction mechanism is potential adsorption, catalytic oxidation, and interception filtration.

2. The acid mine drainage treatment process according to claim 1, characterized in that: The treatment process comprises the following steps: The effluent from the permeable reaction wall is discharged into the receiving water body.

3. The acid mine drainage treatment process according to claim 1 or 2, characterized in that: The treatment process comprises the following steps: The precipitate containing metal oxides in the sedimentation tank is placed in a sludge temporary storage tank. After a selected period of time, the sludge is discharged and the supernatant is returned to the regulating tank.

4. The acid mine drainage treatment process according to claim 3, characterized in that: In each step, wastewater is transported by gravity flow.

5. The acid mine drainage treatment process according to claim 1, characterized in that: There are a plurality of permeable reaction walls, and each permeable reaction wall is used to process a different element in at least a portion of the second portion of metal elements.

6. The acid mine drainage treatment process according to claim 5, characterized in that: All of the permeable reaction walls sequentially treat the sedimentation tank effluent to remove at least a portion of the second portion of metal elements.

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