Organic arsenic polluted soil ex-situ leaching and wet detoxification coupling remediation system

Abstract

The utility model discloses an organic arsenic contaminated soil ex-situ leaching and wet detoxification coupling remediation system, which is characterized in that a slurry making roller, a screening machine, a dehydrator and an elution stirring tank are sequentially connected in series, external contaminated soil is communicated with the slurry making roller by virtue of a screening belt, and a coarse grain outlet and a fine grain muddy water outlet are formed in the screening machine; the elution stirring tank is provided with a supernatant outlet and a mixture outlet, the supernatant outlet is sequentially connected with a washing and dewatering tank, an adsorption and flocculation basin, a sludge temporary storage tank, a second filter press and an adjusting water tank in series, and a liquid outlet in the adsorption and flocculation basin is communicated with a liquid inlet in the adjusting water tank; and the mixture outlet is sequentially connected in series with the concentration precipitation equipment and the first filter press. When the device is used for repairing the polluted soil, the biological activity of the soil is not completely lost while the detoxification of the polluted soil is realized, the activity of the soil can be gradually recovered in the processes of composting and the like in the future, and backfilling or reutilization can be realized.

Description

Technical Field

[0001] The utility model relates to the technical field of contaminated soil treatment and restoration, and in particular to an ex situ leaching and wet detoxification coupling restoration system for organic arsenic contaminated soil. Background Art

[0002] At present, the commonly used methods in the remediation of heavy metal contaminated soil sites include soil solidification / stabilization, soil ex situ leaching, cement kiln co-disposal, barrier landfill and phytoremediation, among which soil ex situ leaching is widely used due to its advantages of good remediation effect, short remediation time and relatively low cost. The technical key of this soil leaching method is to select suitable elution reagents and optimal treatment process parameters so that heavy metal compounds can be resolved from the surface of soil particles, thereby achieving the purpose of remediation.

[0003] In practical applications, soil leaching is the most common method for treating chromium and its compounds, and there are also many studies on relative technical optimization and equipment optimization, such as the already disclosed CN114669591A, CN 110125164A, etc. However, there are few reports on the research of ex situ leaching and remediation of arsenic and its compounds, especially organic arsenic contaminated soil. In addition, based on the physicochemical properties of organic arsenic, it is difficult to dissolve in water. Conventional physical leaching cannot effectively transfer pollutants to the leaching solution, and special proportions of agents must be used for treatment, which makes the treatment more difficult. Furthermore, for some remediation methods, such as high-temperature pyrolysis, the biological properties of the treated soil are completely lost, and the target requirements for reuse after remediation cannot be met. Utility Model Content

[0004] In view of the shortcomings of the prior art, the utility model provides a coupled remediation system for ex situ leaching and wet detoxification of organic arsenic contaminated soil. The system combines the two major treatment methods of soil ex situ leaching and wet detoxification, and can separate organic arsenic and other pollutants in the soil from the soil through leaching and specific chemical means, reduce the arsenic content in the soil, achieve soil detoxification, and solve the problem of secondary pollution that may exist in single leaching. At the same time, the biological activity of the soil is restored through composting, etc., providing conditions for subsequent land reuse or backfilling.

[0005] The utility model adopts the following technical solutions:

[0006] A coupled remediation system for ex situ leaching and wet detoxification of organic arsenic contaminated soil comprises a pulping drum, a screening machine, a dewatering machine and an elution stirring tank, as well as a concentration sedimentation device, a first filter press, an elution water tank, an adsorption flocculation tank, a sludge temporary storage tank, a second filter press and a regulating water tank, which are sequentially arranged in series. The external contaminated soil is connected to the pulping drum by means of a screening belt. The screening machine is provided with a coarse particle outlet and a fine particle muddy water outlet, which are connected to the dewatering machine. The elution stirring tank is provided with an upper layer liquid outlet and a mixture outlet. The upper layer liquid outlet is sequentially arranged in series with the elution water tank, the adsorption flocculation tank, the sludge temporary storage tank, the second filter press and the regulating water tank. The liquid outlet on the adsorption flocculation tank is connected with the liquid inlet on the regulating water tank, and a mud cake outlet is also provided on the filter press. The mixture outlet is sequentially arranged in series with the concentration sedimentation device and the first filter press.

[0007] The system also includes a circulating water tank, industrial water, an eluting agent device, an oxidant device, a release agent device and a pH regulator device. The dehydrator, the concentration and precipitation equipment and the first filter press are all provided with liquid outlets, which are all connected to the liquid inlet on the circulating water tank. The pulping drum, the screening machine and the first filter press are all provided with liquid inlets, which are all connected to the liquid outlet on the circulating water tank.

[0008] The adsorption flocculation tank and the second filter press are both provided with liquid outlets, and are both connected with the liquid inlet on the regulating water tank; the elution stirring tank is provided with a liquid inlet, and is connected with the liquid outlet on the regulating water tank.

[0009] The elution agent device and the oxidant device are both connected to the elution stirring tank, the release agent device is connected to the adsorption flocculation tank, and the pH regulator device is connected to the regulating water tank.

[0010] The industrial water supply device is connected with the liquid inlets on the regulating water tank and the circulating water tank through pipelines respectively.

[0011] The regulating water tank and the circulating water tank are both provided with two water inlets, one for process circulating water and the other for industrial water. During operation, the total arsenic content of the circulating water is tested and it can be used only if it meets the reuse water standard. Otherwise, industrial water is introduced and the two water inlet pipes are switched with each other.

[0012] The elution stirring tank comprises two tanks connected in parallel, each of which has a high-efficiency stirrer inside, so that the contaminated soil, water and elution agent inside are vigorously mixed, so that the pollutants are effectively eluted.

[0013] A stirring device is arranged in the elution water tank.

[0014] The dehydrator is a device that dehydrates using the centrifugal or vibration principle.

[0015] The technical solution of the utility model has the following advantages:

[0016] A. The repair process system provided by the utility model is fully applicable to the repair and treatment of soil contaminated with organic arsenic. It can achieve detoxification of contaminated soil without completely losing the biological activity of the soil. Its activity can be gradually restored in the future composting process, and backfilling or reuse can be achieved. The entire repair system combines two major treatment methods, ex situ leaching and wet detoxification, with high efficiency, short time, simple operation and no secondary pollution.

[0017] B. Specifically, the use of the utility model remediation system for organic arsenic contaminated soil remediation has the following advantages:

[0018] ① Reduction: Pollutants are generally adsorbed on fine soil particles. Through screening and elution, the coarse particles are purified and separated, and pollutants such as organic arsenic are completely transferred to the liquid. Then, water treatment methods such as adsorption flocculation are used to enrich the pollutants in the final small amount of mud cake, effectively reducing the amount of contaminated soil to be treated and achieving reduction.

[0019] ② Detoxification: After soil leaching and screening, the elution process is used to transfer pollutants such as organic arsenic attached to fine soil particles to the liquid phase and carry out water treatment. Finally, it is compressed and dehydrated to form a small amount of contaminated mud cake, which is sent for thermal decomposition treatment.

[0020] ③ Strong applicability: It can remove most pollutants, such as heavy metals, semi-volatile organic compounds, and non-volatile organic compounds.

[0021] ④Excellent effect: One-stage screening in the pretreatment process can meet the elution effect. The elution object does not need to be screened at multiple levels. This process is different from the conventional leaching process. At the same time, the expansion of the eluted soil particle size range can improve the removal rate of organic arsenic in the entire soil. The remediation effect is stable and the cycle is short. In addition, the elution agent, flocculation release agent, and the rationalization of process operation parameters can all improve the removal rate of pollutants in the entire soil site.

[0022] ⑤ Reuse: The clean soil after elution treatment can be gradually restored to its activity through composting and other methods and can be reused.

[0023] ⑥ Resource conservation: Minimize the use of eluent during soil leaching, flexibly switch between recycled water and industrial water, and use recycled water as much as possible to save water.

[0024] ⑦ Equipment integration and modularization: The overall system is modularly designed to achieve minimum space usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the utility model, the drawings required for use in the specific implementation methods will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of the overall structure of the ex situ leaching and wet detoxification coupling remediation system for organic arsenic contaminated soil in the utility model;

[0027] Figure 2 This is the process flow chart of the coupled remediation of organic arsenic contaminated soil by ex situ leaching and wet detoxification.

[0028] The following are marked in the figure:

[0029] 1-contaminated soil; 2-screening belt; 3-pulping drum; 4-screening machine, 401-coarse particle outlet, 402-fine particle mud and water outlet; 5-dehydrator; 6-elution stirring tank, 601-upper layer liquid outlet, 602-mixture outlet; 7-concentration sedimentation equipment; 8-first filter press; 9-elution water tank; 10-adsorption flocculation tank; 11-sludge temporary storage tank; 12-second filter press, 1201-mud cake outlet; 13-regulating water tank; 14-circulating water tank; 15-industrial water supply device; 16-elution agent device; 17-oxidant device; 18-release agent device; 19-pH adjuster device; 20-coarse particle pile; 21-mud cake pile; 22-clean soil pile; 23-unqualified sewage. DETAILED DESCRIPTION

[0030] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] like Figure 1As shown, the utility model provides an ex situ leaching and wet detoxification coupled remediation system for organic arsenic contaminated soil, comprising a pulping drum 3, a screening machine 4, a dewatering machine 5 and an elution stirring tank 6 arranged in series, as well as a concentration sedimentation device 7, a first filter press 8, an elution water tank 9, an adsorption flocculation tank 10, a sludge temporary storage box 11, a second filter press 12 and a regulating water tank 13. The external contaminated soil 1 is connected to the pulping drum 3 by means of a screening belt 2. The screening machine 4 is provided with a coarse particle outlet 401 and a fine particle muddy water outlet 402, the fine particle muddy water outlet 402 is connected to the dehydrator 5, the elution stirring tank 6 is provided with an upper layer liquid outlet 601 and a mixture outlet 602, the upper layer liquid outlet 601 is sequentially connected in series with the elution water tank 9, the adsorption flocculation tank 10, the sludge temporary storage tank 11, the second filter press 12, and the regulating water tank 13, the liquid outlet on the adsorption flocculation tank 10 is connected with the liquid inlet on the regulating water tank 13, and the filter press 12 is also provided with a mud cake outlet 1201. The mixture outlet 602 is sequentially connected in series with the concentration sedimentation device 7 and the first filter press 8.

[0032] Furthermore, the system also includes a circulating water tank 14, an industrial water supply device 15, an eluting agent device 16, an oxidant device 17, a release agent device 18 and a pH regulator device 19. The dehydrator 5, the concentration sedimentation device 7 and the first filter press 8 are all provided with liquid outlets, which are all connected to the liquid inlet on the circulating water tank 14. The pulping drum 3, the screening machine 4 and the first filter press 8 are all provided with liquid inlets, which are all connected to the liquid outlet on the circulating water tank 14. The adsorption flocculation tank 10 and the second filter press 12 are all provided with liquid outlets, which are all connected to the liquid inlet on the regulating water tank 13, and the liquid outlet of the regulating water tank 13 is connected to the liquid inlet of the elution stirring tank 6. The elution agent device 16 and the oxidant device 17 are both connected to the elution stirring tank 6, the release agent device 18 is connected to the adsorption flocculation tank 10, and the pH adjuster device 19 is connected to the regulating water tank 13. The corresponding devices for providing elution agents, pH adjusters, oxidants, and release agents are all equipped with agent tanks and power transmission equipment.

[0033] The industrial water supply device 15 is connected to the liquid inlets on the regulating water tank 13 and the circulating water tank 14 through pipelines. The regulating water tank 13 and the circulating water tank 14 are both provided with two water inlets, one for the circulating water in the process and the other for industrial water. The total arsenic content of the circulating water is tested during operation. It can be used only if it meets the recycled water standard. Otherwise, industrial water is introduced and the two water inlet pipes are switched with each other.

[0034] The elution stirring tank 6 includes two tanks connected in parallel to ensure continuous operation. A stirrer is arranged inside each elution stirring tank 6 so that the polluted soil, water and elution agent inside are mixed violently, so that the pollutants are effectively eluted. A stirring device is also arranged inside the elution water tank 9.

[0035] like Figure 2As shown, the utility model also provides a specific method for coupling ex situ elution and wet detoxification remediation of organic arsenic contaminated soil using a remediation system, comprising the following steps:

[0036] S1. Slurry making: The contaminated soil 1 is transferred to the slurry making drum 3 by the screening belt 2, and a proper amount of water is added into the slurry making drum 3 through the liquid inlet on the slurry making drum 3. During the rolling process of the drum, the contaminated soil is broken up and the soil is crushed and mixed into a uniform slurry.

[0037] S2. Screening: The dispersed soil slurry is transferred to the screening machine 4 and screened by means of a pressurized nozzle using the principles of vibration and screening. The screened coarse particles (including wood blocks, gravel, metal residues, etc.) with a particle size greater than 5 mm are discharged from the coarse particle outlet 401 and collected and processed separately.

[0038] S3, dehydration: the fine-grained muddy water obtained by screening in step S2 enters the dehydrator 5 based on the centrifugal or vibration principle through the fine-grained muddy water outlet 402 for full dehydration. The dehydrated material has a higher solid content, which provides convenience for subsequent processing; the water generated by the dehydrator 5 is filtered through the filter and then pumped into the circulating water tank 14, and the water in the water tank is reused for the pulping drum 3 and the screening machine 4.

[0039] S4, elution: The dehydrated material is transferred to the screw feeder by a conveyor and sent to the elution stirring tank 6. The elution and rinsing are performed by adding elution agents and vigorous stirring to effectively separate the pollutants in the material from the soil solids. The solid-liquid mixture with a high water content after rinsing is discharged from the upper liquid outlet 601 to the elution water tank 9; a high-efficiency agitator is set inside the elution stirring tank to make the polluted soil, water and elution agents inside be vigorously mixed, so that the pollutants are effectively eluted; a single elution includes agent elution + rinsing. The specific operation is as follows:

[0040] S4-1. The material and the reagent are eluted and stirred to mix, so that most of the pollutants are complexed into the eluent, so as to achieve the purpose of separating the pollutants from the soil solids. After the elution is completed, precipitation is carried out, and the upper layer of liquid in the elution stirring tank 6 is discharged to the elution water tank 9 with a stirring device; the elution reagent added to the elution stirring tank 6 is composed of a surfactant mixture and vegetable oil. At the same time, in order to ensure the elution efficiency, water of a suitable temperature is used to mix with the elution reagent, and the water temperature matches the composition and ratio of the elution reagent.

[0041] S4-2, perform n rinses, where n≥2, and for each rinse, the elution stirring tank 6 needs to be closed, and the agitator inside it is used to vigorously stir to suspend the solid materials. After rinsing for a certain period of time, the precipitate is discharged to the concentration precipitation equipment 7; to ensure the best rinsing effect, the rinsing operating conditions are as follows: the rinsing water is adjusted to alkaline, and the rinsing water temperature is the same as the elution water temperature; during the rinsing process, an oxidant 30% H2O2 solution needs to be added during the second rinse.

[0042] S5, dehydration and filter pressing: the washed soil-water mixture is firstly passed through the concentration sedimentation equipment 7 to increase the solid content from the mixture outlet 602, and then the clean soil with high solid content is obtained by the pressure of the first filter press 8; in order to restore the natural characteristics of the soil, the washed soil is mixed with a compost mixture composed of urban sewage sludge and organic structural materials for composting treatment. The resulting soil-compost mixture can be used for greening and can be transported back to the extraction site for reuse; the water generated by dehydration passes through the filter and is pumped into the circulating water tank 14 to provide water for the pulping drum 3, the screening machine 4 and the first filter press 8.

[0043] S6, eluent adsorption flocculation: the solid-liquid mixture in the elution water tank 9 in step S4 is pumped into the adsorption flocculation tank 10, mixed with the release agent for stirring and flocculation, and when the flocculation is completed, the pollutants are integrated into the sludge floccules and enter the sedimentation tank, the supernatant is discharged to the regulating water tank 13 for reuse, and the sludge floccules are discharged into the sludge temporary storage tank 11; the added release agent is composed of activated carbon, bentonite, cationic active surfactant, ferric chloride and polyacrylamide in any proportion.

[0044] S7. Filter pressing and dehydration of sludge flocs: The sludge in the sludge temporary storage box 11 is pumped into the second filter press 12 for compression and dehydration, and the obtained mud cake is sent to the subsequent pyrolysis treatment through the mud cake outlet 1201.

[0045] S8, water for recycling during elution and wet detoxification: The water produced by dehydration of the concentration precipitation equipment 7 and the first filter press 8 is filtered by the filter and then pumped into the circulating water tank 14, which is used to provide water for the pulping drum 3, the screening machine 4 and the first filter press 8. The circulating water tank 14 is provided with two water inlets, one for the circulating water in the process and the other for industrial water. During the operation, the total arsenic content of the circulating water is tested and can only be used if it meets the standard for recycled water. Otherwise, industrial water is introduced and the two water inlets are switched.

[0046] S9, water recycled from adsorption flocculation and filter press: the water discharged from the adsorption flocculation tank 10 and the second filter press 12 is discharged to the regulating water tank 13 for temporary storage, and then recycled to the elution stirring tank 6; similarly, the total arsenic content is tested, and it can be used only when it meets the recycled water standard; the regulating water tank 13 is mainly used to adjust the water temperature and pH value to maintain the water quality at the best reaction conditions; the regulating water tank 13 is provided with an industrial water inlet pipeline, and when the recycled water does not meet the standard or the liquid level in the water tank is low, the water is replenished.

[0047] The repair process system provided by the utility model is fully applicable to the repair and treatment of organic arsenic contaminated soil. It can achieve detoxification of contaminated soil without completely losing the biological activity of the soil. Its activity can be gradually restored in the future composting process, and it can be backfilled or reused. The entire repair system combines two major treatment methods, ex situ leaching and wet detoxification, with high efficiency, short time, simple operation, and no secondary pollution. Specifically, the use of the repair system of the utility model for organic arsenic contaminated soil remediation has the following advantages:

[0048] ① Reduction: Pollutants are generally adsorbed on fine soil particles. Through screening and elution, the coarse particles are purified and separated, and pollutants such as organic arsenic are completely transferred to the liquid. Then, water treatment methods such as adsorption flocculation are used to enrich the pollutants in the final small amount of mud cake, effectively reducing the amount of contaminated soil to be treated and achieving reduction.

[0049] ② Detoxification: After soil leaching and screening, the elution process is used to transfer pollutants such as organic arsenic attached to fine soil particles to the liquid phase and carry out water treatment. Finally, it is compressed and dehydrated to form a small amount of contaminated mud cake, which is sent for thermal decomposition treatment.

[0050] ③ Strong applicability: It can remove most pollutants, such as heavy metals, semi-volatile organic compounds, and non-volatile organic compounds.

[0051] ④Excellent effect: One-stage screening in the pretreatment process can meet the elution effect. The elution object does not need to be screened at multiple levels. This process is different from the conventional leaching process. At the same time, the expansion of the eluted soil particle size range can improve the removal rate of organic arsenic in the entire soil. The remediation effect is stable and the cycle is short. In addition, the elution agent, flocculation release agent, and the rationalization of process operation parameters can all improve the removal rate of pollutants in the entire soil site.

[0052] ⑤ Reuse: The clean soil after elution treatment can be gradually restored to its activity through composting and other methods and can be reused.

[0053] ⑥ Resource conservation: Minimize the use of eluent during soil leaching, flexibly switch between recycled water and industrial water, and use recycled water as much as possible to save water.

[0054] ⑦ Equipment integration and modularization: The overall system is modularly designed to achieve minimum space usage requirements.

[0055] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the present utility model.

Claims

1. An ex situ leaching and wet detoxification coupled remediation system for organic arsenic contaminated soil, characterized in that: The invention comprises a pulping drum (3), a screening machine (4), a dewatering machine (5) and an elution stirring tank (6) which are sequentially connected in series, as well as a concentration sedimentation device (7), a first filter press (8), an elution water tank (9), an adsorption flocculation tank (10), a sludge temporary storage tank (11), a second filter press (12) and a regulating water tank (13); the external contaminated soil (1) is connected to the pulping drum (3) by means of a screening belt (2); the screening machine (4) is provided with a coarse particle outlet (401) and a fine particle muddy water outlet (402); the fine particle muddy water outlet (402) is connected to the dewatering machine (5); the elution stirring tank (6) is connected to the dewatering machine (5); the contaminated soil (1 ... The stirring tank (6) is provided with an upper liquid outlet (601) and a mixture outlet (602); the upper liquid outlet (601) is sequentially connected in series with the elution water tank (9), the adsorption flocculation tank (10), the sludge temporary storage tank (11), the second filter press (12), and the regulating water tank (13); the liquid outlet on the adsorption flocculation tank (10) is connected to the liquid inlet on the regulating water tank (13), and the filter press (12) is also provided with a mud cake outlet (1201); the mixture outlet (602) is sequentially connected in series with the concentration sedimentation equipment (7) and the first filter press (8).

2. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 1 is characterized in that: The system also includes a circulating water tank (14), an industrial water supply device (15), an eluting agent device (16), an oxidant device (17), a release agent device (18) and a pH regulator device (19). The dehydrator (5), the concentration and precipitation device (7) and the first filter press (8) are all provided with liquid outlets, which are all connected to the liquid inlet on the circulating water tank (14). The pulping drum (3), the screening machine (4) and the first filter press (8) are all provided with liquid inlets, which are all connected to the liquid outlet on the circulating water tank (14).

3. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 2 is characterized in that: The adsorption flocculation tank (10) and the second filter press (12) are both provided with liquid outlets, and are both connected to the liquid inlet on the regulating water tank (13); the elution stirring tank (6) is provided with a liquid inlet, and is connected to the liquid outlet on the regulating water tank (13).

4. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 3 is characterized in that: The elution agent device (16) and the oxidant device (17) are both connected to the elution stirring tank (6), the release agent device (18) is connected to the adsorption flocculation tank (10), and the pH regulator device (19) is connected to the regulating water tank (13).

5. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 4 is characterized in that: The industrial water supply device (15) is connected to the liquid inlets on the regulating water tank (13) and the circulating water tank (14) through pipelines.

6. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 5 is characterized in that: The regulating water tank (13) and the circulating water tank (14) are both provided with two water inlets, one for inletting circulating water during the process and the other for inletting industrial water. During operation, the total arsenic content of the circulating water is tested and can only be used if it meets the standards for recycled water. Otherwise, industrial water is introduced and the two water inlet pipes are switched with each other.

7. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 1 is characterized in that: The elution stirring tank (6) includes two tanks connected in parallel to ensure continuous operation of the system; a stirrer is arranged inside each of the elution stirring tanks (6) so that the contaminated soil, water and elution agent inside are vigorously mixed and the pollutants are effectively eluted.

8. The organic arsenic contaminated soil ex situ elution and wet detoxification coupled remediation system according to claim 1 is characterized in that: A stirring device is arranged in the elution water tank (9).

9. The organic arsenic contaminated soil ex situ leaching and wet detoxification coupled remediation system according to claim 1 is characterized in that: The dehydrator (5) is a device that dehydrates using the centrifugal or vibration principle.

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