CN204675951U - A kind of acidic mine waste water treatment system - Google Patents

Abstract

The utility model discloses an acid mine wastewater treatment system, which comprises limestone ditches, sedimentation tanks and subsurface composting wetlands arranged according to the direction of water flow, and the subsurface composting wetlands include anaerobic pools (2) and limestone beds (5); The anaerobic pond (2) is filled with compost (3), the anaerobic pond (2) is separated from the limestone bed (5) and the bottom of the anaerobic pond (2) communicates with the limestone bed (5), and the limestone bed (5) The top is covered with an organic substrate layer (6), and wetland plants (7) are planted on the organic substrate layer (6). The processing system has the advantages of simple structure, low construction cost, economical and effective, and simple maintenance.

Description

A kind of acid mine wastewater treatment system

technical field

The utility model relates to the purification technology of acid waste water, in particular to an acid mine waste water treatment system.

Background technique

South my country is rich in metal mineral resources, and the mining of metal mines leads to the generation of a large amount of acid mine wastewater (AMD). The pH of AMD is low and the content of heavy metals is high. Untreated AMD enters the surrounding water body, leading to ecological degradation of the water body and the spread of heavy metal pollution. Affected by this, the pH of farmland soil along the banks of AMD-polluted rivers and in irrigated areas decreases, and the content of heavy metals exceeds the standard, which reduces the output and quality of agricultural products and threatens human health. Remediation of AMD and its polluted water bodies is of great significance to the protection of the ecological environment and agricultural production.

In order to overcome the pollution problem of AMD, chemical neutralization technology is currently the most widely used acid wastewater treatment technology, but this treatment technology has the following technical defects: it needs to continuously add alkaline substances, the operation and maintenance costs are high, and a large amount of waste water is produced. sludge containing heavy metals.

"Passive" treatment technology has the characteristics of low operation and maintenance costs and environmental friendliness. Treatment of AMD is suitable for passive treatment techniques based on organic substrates such as composting wetlands. However, the traditional composting wetland is a surface flow wetland, and the traditional composting wetland has the following technical defects: acidic wastewater cannot fully contact with the organic matrix and alkaline substances at the bottom, and the removal efficiency of acidity and metals is low.

The vertical flow composting wetland solves the technical problems of the traditional composting wetland, but the vertical flow composting wetland has the following technical defects: high construction cost, clogging when dealing with AMD with high Fe and Al content, and requires professional maintenance.

Utility model content

The technical problem to be solved by the utility model is to provide an acid mine wastewater treatment system. The treatment system has simple structure, low construction cost, economical efficiency and simple maintenance.

The scheme that the utility model solves the problems of the technologies described above is as follows:

An acid mine wastewater treatment system, comprising limestone ditches, sedimentation tanks and subsurface composting wetlands arranged in the direction of water flow, the subsurface composting wetlands comprising anaerobic ponds (2) and limestone beds (5); the anaerobic ponds (2 ) is filled with compost (3), the anaerobic pond (2) is separated from the limestone bed (5) and the bottom of the anaerobic pond (2) communicates with the limestone bed (5), and the limestone bed (5) is covered with a layer of organic The substrate layer (6), wetland plants (7) are planted on the organic substrate layer (6).

The water inlet of the subsurface composting wetland is located at the top of the anaerobic pool (2), the outlet of the subsurface composting wetland is at the same height as the organic matrix layer (6), and the water level of the entire subsurface composting wetland is flush with the limestone bed.

The limestone trench is 0.2m-1m wide and 0.3m-1.0m deep, the length is determined by the hydraulic load, and the limestone particle size is 5cm-10cm. The aspect ratio of the sedimentation tank is 2 to 4, and the depth is 0.5m to 1m.

The subsurface composting wetland is 5m-8m long, 0.8m-1.2m deep, and the width is determined by the processing load. The volume of the anaerobic pond (2) accounts for 10% to 30% of the total volume of the subsurface composting wetland, and the compost (3) is plant waste composting.

The depth of the limestone bed (5) is 20cm-40cm greater than the depth of the anaerobic pond (2).

The organic matrix layer (6) is 10cm-20cm thick.

The wetland plants (7) are cattails, and Cd/Zn hyperaccumulator plants are interplanted to strengthen the removal of heavy metals Cd and Zn by the system.

The Cd/Zn hyperaccumulator plant is Sedum chinensis.

The treatment method of above-mentioned acid mine wastewater treatment system, comprises the steps:

(1) The acidic mine wastewater enters the limestone ditch for neutralization, promotes the oxidation and hydrolysis of Fe and Al, and realizes the preliminary purification of AMD. The residence time of the wastewater in the limestone ditch is 2 to 4 hours, and the acidic wastewater within 2 to 4 hours Neutralization is fast and efficient. When pH>5, the neutralization efficiency of acidic wastewater and limestone is greatly reduced, and the wastewater enters the sedimentation tank;

(2) The sedimentation tank separates the insoluble heavy metals in the wastewater. The residence time of the wastewater in the sedimentation tank is 1 to 3 hours, so that the metal sediments in the water can be settled and prevented from entering the subsurface composting wetland;

(3) Then the wastewater enters the anaerobic tank, where the wastewater flows vertically through the compost in the anaerobic tank, and the compost produces adsorption, ion exchange and organic complexation for heavy metals, and the anaerobic environment formed by compost degradation promotes the sulfuric acid reduction process of microorganisms, producing Alkalinity and precipitation of heavy metals in the form of sulfides;

(4) When the wastewater enters the limestone bed, the pH is further improved, and some metals are precipitated in the form of carbonates and hydroxides; the organic matrix layer and wetland plants on the surface of the limestone bed can adsorb and absorb heavy metals, further improving the quality of the effluent; The total residence time of wastewater in the anaerobic pond and limestone bed is 1.5d to 2.5d.

The composition of the organic matrix layer is peat soil and compost, wherein the volume of the compost accounts for 10-30%.

The utility model has the following advantages relative to the prior art:

The acid mine wastewater treatment system and the treatment method thereof of the utility model have low construction cost and simple maintenance, and can effectively reduce acidity and heavy metals in AMD. Limestone ditch pretreatment prevents low pH from adversely affecting microbial growth in anaerobic ponds and reduces metal treatment loads in composting wetlands. The compost is concentrated in the anaerobic pond at the front of the wetland, which makes the supplement or replacement of compost flexible and convenient, and the problem of clogging can also be solved by turning or loosening the compost in the anaerobic pond. The organic matrix layer on the surface of the limestone bed makes the limestone bed a sealed system and promotes the generation of alkalinity in the limestone bed. The subsurface design makes the root absorption of wetland plants and super-accumulator plants play a more direct and important role in improving the quality of effluent water. The treatment system can make the system run effectively for a long time through the replacement of compost, so as to economically and effectively ensure the safety of farmland irrigation water in mining areas.

Description of drawings

Fig. 1 is the flowchart of the acid mine wastewater treatment system of the present invention.

Fig. 2 is a cross-sectional structure diagram of the subsurface composting wetland of the present invention.

Fig. 3 is a graph showing pH detection value curves of water bodies in AMD raw material pools, limestone ditches, and subsurface composting wetlands.

Fig. 4 is a curve diagram of detected Zn content in water bodies in AMD raw material ponds, limestone ditches, and subsurface composting wetlands.

Fig. 5 is a curve diagram of Cd content detected values in water bodies in AMD raw material ponds, limestone ditches, and subsurface composting wetlands.

Fig. 6 is a graph of the detection value of Pb in water bodies in AMD raw material ponds, limestone ditches, and subsurface composting wetlands.

In Figure 3-Figure 6, the relative relationship of each curve is:

—■—AMD —▲—Limestone Ditch ———Subflow Composting Wetland

The square points indicate that the test water samples are taken from the AMD raw material pool,

The triangle points indicate that the test water samples were taken from limestone ditches,

The diamond points indicate that the water samples were taken from subsurface flow composting wetlands.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

A kind of acid mine wastewater treatment system, comprises limestone ditch, sedimentation tank and subsurface composting wetland arranged according to water flow direction, as shown in Figure 2, described subsurface composting wetland comprises anaerobic pond 2 and limestone bed 5; Said anaerobic pond 2 is filled with compost 3, the anaerobic pool 2 and the limestone bed 5 are separated from each other and the bottom of the anaerobic pool 2 communicates with the limestone bed 5, and the limestone bed 5 is covered with an organic matrix layer 6, and a wetland is planted on the organic matrix layer 6 plant7.

The water inlet 1 of the subsurface composting wetland is located at the top of the anaerobic pool 2, the outlet 8 of the subsurface composting wetland is at the same height as the organic matrix layer 6, and the water level of the entire subsurface composting wetland is flush with the limestone bed.

The limestone ditch is 0.6m wide and 0.6m deep, and the length is determined by the hydraulic load. The limestone particle size is 5cm-10cm. The sedimentation tank has an aspect ratio of 3 and a depth of 0.8m.

The subsurface composting wetland is 7m long and 1m deep, and the width is determined by the processing load. The volume of the anaerobic pool 2 accounts for 20% of the total volume of the subsurface composting wetland, and the composting pool 3 is plant waste composting.

The depth of the limestone bed 5 is 30 cm greater than that of the anaerobic pond 2 , and the limestone part of the limestone bed 5 extends below the compost 3 of the anaerobic pond 2 .

The organic matrix layer 6 is 15 cm thick.

The wetland plants 7 are cattails, and Sedum sedum is interplanted to strengthen the system's removal of heavy metals Cd and Zn.

The treatment method of above-mentioned acid mine wastewater treatment system, as shown in Figure 1, comprises the steps:

(1) The acid mine wastewater enters the limestone ditch for neutralization, promotes the oxidation and hydrolysis of Fe and Al, and realizes the preliminary purification of AMD. The residence time of the wastewater in the limestone ditch is 3 hours, and the neutralization of the acid wastewater within 3 hours is fast , Efficient, when the pH>5, the neutralization efficiency of acidic wastewater and limestone is greatly reduced, and the wastewater enters the sedimentation tank;

(2) The sedimentation tank separates the insoluble heavy metals in the wastewater. The residence time of the wastewater in the sedimentation tank is 2 hours, so that the metal sediments in the water can be settled and prevented from entering the subsurface composting wetland;

(3) Then the wastewater enters the anaerobic tank, where the wastewater flows vertically through the compost in the anaerobic tank, and the compost produces adsorption, ion exchange and organic complexation for heavy metals, and the anaerobic environment formed by compost degradation promotes the sulfuric acid reduction process of microorganisms, producing Alkalinity and precipitation of heavy metals in the form of sulfides;

(4) When the wastewater enters the limestone bed, the pH is further improved, and some metals are precipitated in the form of carbonates and hydroxides; the organic matrix layer and wetland plants on the surface of the limestone bed can adsorb and absorb heavy metals, further improving the quality of the effluent; The total residence time of wastewater in the anaerobic pond and limestone bed is 2 days.

The composition of the organic matrix layer is peat soil and compost, wherein the volume of compost accounts for 20%.

In order to confirm the treatment effect of the acid mine wastewater treatment system, the following simulation experiment 1 was carried out:

The limestone ditch is modeled with PVC pipes. The size of the PVC pipe is reduced in proportion. The PVC pipe is filled with limestone, and an elbow is installed at both ends of the PVC pipe. The other end of the elbow is vertically upward, so that the water can completely immerse the limestone in the pipe. One hole, used as water inlet and water outlet respectively.

The subsurface composting wetland was simulated and established with plastic boxes. The size of the plastic box is reduced in proportion, and a 15cm-long partition is set inside the box, and a 5cm-high gap is left at the lower end of the partition. The isolated small space is used as an anaerobic pond, and the bottom is filled with limestone to the lower end of the partition, and then filled with compost, and the filling height of the compost is 20cm. The space on the other side of the partition is filled with limestone, and a layer of organic substrate is laid on the surface of the limestone bed, on which cattails are planted and Sedum sedum is interplanted.

Use H ₂ SO ₄ to configure AMD wastewater, and its parameters are as follows: pH 3.3, 2mg/L Fe ²⁺ (FeSO ₄ ·7H ₂ O), 8mg/L Fe ³⁺ (Fe ₂ (SO ₄ ) ₃ ·xH ₂ O ), 25mg/L Zn(ZnSO ₄ ·7H ₂ O), 0.3mg/L Pb(Pb(NO ₃ ) ₂ ), 0.1mg/L Cd(CdCl ₂ ·0.5H ₂ O), 0.08mg/L Cu( CuSO ₄ ).

Simulated system operation: In a 1000L plastic box, 800L simulated AMD is prepared each time. AMD first enters the limestone ditch with a hydraulic retention time of 4 hours, then enters the subsurface composting wetland system with a hydraulic retention time of 35 hours, and is discharged after being treated by the subsurface composting wetland system.

The processing effect of the processing system on AMD is shown in Figure 3-Figure 6.

As shown in Figure 3:

The water sample of the AMD raw material pool has a pH of about 3.3.

The pH of the water sample in Limestone Ditch rose to about 6.3, but after 75 days, the pH of the effluent began to drop. After 128 days, the pH of the effluent dropped sharply, and the pH dropped to about 4.5. The reason is that metal oxides settle on the surface of limestone to form a layer of coating (Armoring), which reduces the dissolution rate of limestone. It can be effectively solved by increasing the slope of limestone ditch (>12%) or periodically flushing limestone. Membrane issues, keep the pH around 6.3.

In the water samples of the subsurface composting wetland, the pH value continued to rise slowly within 42 days, and after 42 days, the pH was basically stable at about 7, which was neutral water. Although the pH value of the water flowing from the limestone ditch was low after 128 days, the subsurface composting wetland has a strong acid buffering capacity and can still maintain the pH value of the effluent at about 7.

As shown in Figure 4,

In the water sample of the AMD raw material pool, the Zn content is about 24mg/L.

In the water samples of the limestone ditch, the Zn content was about 18 mg/L in the first 75 days, and about 21 mg/L after 75 days, because the Zn removal effect of the limestone ditch was affected by its acid neutralization ability.

In the water samples of subsurface composting wetland, before 75 days, the Zn content was below 2 mg/L, and after 75 days, the Zn content of the effluent fluctuated slightly, which was mainly affected by the increase of Zn content in the influent water (that is, the limestone ditch effluent).

As shown in Figure 5,

The water sample of the AMD raw material pool has a Cd content of about 105ug/L.

In the water samples of the limestone ditch, the Cd content dropped to about 28ug/L from 0 to 51 days, and rose to about 82ug/L after 51 days, because the removal effect of the limestone ditch was affected by its acid neutralization ability.

In the water samples of the subsurface composting wetland, the Cd in the effluent was 0.5-2.0ug/L in the first 22 days, and no Cd was detected thereafter (the detection limit was 0.1ug/L).

As shown in Figure 6,

The water sample of the AMD raw material pool has a Pb content of about 200ug/L.

In the water samples of the limestone ditch, the Pb content dropped to about 30ug/L from 0 to 128d, and rose to about 105ug/L after 128d, because the removal effect of the limestone ditch was affected by its acid neutralization ability.

No Pb was detected in the water samples of the subsurface composting wetland (detection limit 1.0ug/L).

In summary, the treatment system can effectively increase the pH of AMD, remove highly toxic heavy metals (Cd, Pb) in AMD, remove a high proportion of Zn, protect the aquatic ecological environment and soil environment, and promote agricultural production.

In order to further confirm the treatment effect of the acid mine wastewater treatment system, the following simulation experiment 2 was carried out:

The aerobic limestone ditch is 0.5m wide, 0.4m deep, and 6m long. The filling particle size in the ditch is 5cm limestone (porosity 42.6%), and the filling height is 0.3m. The residence time is about 4h.

The effluent from the limestone ditch enters the sedimentation tank, which is 1m long, 0.5m wide, 0.5m deep, and 0.4m deep, with a residence time of 2h. The effluent enters the subsurface composting wetland.

The subsurface composting wetland is 5m long, 2m wide and 1m deep. During construction, first lay a layer of 30cm thick limestone with a particle size of 5cm on the bottom of the wetland, and then place a partition 4 at a distance of 1m from the water inlet. The partition 4 is 2m long and 1m wide with sufficient toughness and strength. transparent plastic plate. After the dividing plate 4 is fixed, the front end space is filled with compost to form the anaerobic pool 2, and the rear end space is filled with limestone with a particle size of 5 cm to form the limestone bed 5. The thickness of the limestone bed 5 is 0.85m, and the height of the anaerobic pool compost 3 is substantially equal to the limestone bed 5 . The dividing plate 4 divides the whole wetland into two major parts, the anaerobic pool at the front and the limestone bed at the back, so that the water in the anaerobic pool can only flow downward through the compost, and then enter the limestone bed 5 at the back through the limestone layer at the bottom.

After the limestone bed 5 is built, a 15cm thick peat soil layer is spread on its surface to form an organic matrix layer 6, and then plant Cattail angustifolia in the organic matrix layer 6, and the planting density of Cattail angustifolia is 0.5m×0.5m.

After the system is completed, the acid mine wastewater is introduced into the system, the effective volume of the subsurface composting wetland is calculated as 40% of the total volume, and the hydraulic retention time is designed as 2d, so the hydraulic load of the system is 2.2m ³ /d.

Experimental results:

The parameters of the water samples in the AMD raw material pool are: pH 3.3, Zn 25mg/L, Cd 0.1mg/L, Pb 0.2mg/L.

After the system has been in operation for 3 months, the parameters of the water samples from the system outlet are as follows: pH>7, Cd, Zn, and Pb contents meet the standards for agricultural irrigation water (Zn 2mg/L, Cd 0.01mg/L, Pb 0.1mg/L L).

The above-mentioned embodiments are only preferred embodiments of the present utility model, and are not intended to limit the implementation scope of the present utility model. That is, all equivalent changes and modifications made according to the content of the utility model are covered by the scope of protection required by the claims of the utility model.

Claims (8)

1. an acid mine wastewater treatment system is characterized in that: comprise limestone ditch, settling tank and subsurface composting wetland arranged according to flow direction, described subsurface composting wetland comprises anaerobic pond (2) and limestone bed (5); Fill the compost (3) in the anaerobic pond (2), the anaerobic pond (2) is separated from the limestone bed (5) and the bottom of the anaerobic pond (2) communicates with the limestone bed (5), and the limestone bed (5) ) is covered with an organic matrix layer (6), and wetland plants (7) are planted on the organic matrix layer (6). 2. a kind of acid mine wastewater treatment system according to claim 1, is characterized in that: the water inlet of described subsurface composting wetland is positioned at the top of anaerobic pond (2), and the outlet of subsurface composting wetland and organic matrix layer ( 6) Located at the same height. 3. An acid mine wastewater treatment system according to claim 1, characterized in that: the limestone ditch is 0.2m-1m wide, 0.3m-1.0m deep, and the limestone particle size is 5cm-10cm. 4. The acid mine wastewater treatment system according to claim 1, characterized in that: the subsurface composting wetland is 5m to 8m long and 0.8m to 1.2m deep, and the volume of the anaerobic pool (2) occupies The proportion of the total volume is 10%-30%, and the compost (3) is plant waste compost. 5. An acid mine wastewater treatment system according to claim 1, characterized in that: the depth of the limestone bed (5) is 20cm-40cm greater than the depth of the anaerobic pond (2). 6. The acid mine wastewater treatment system according to claim 1, characterized in that: the organic matrix layer (6) is 10cm-20cm thick. 7. The acid mine wastewater treatment system according to claim 1, characterized in that: the wetland plants (7) are cattails, and Cd/Zn hyperaccumulator plants are interplanted. 8. The acid mine wastewater treatment system according to claim 7, characterized in that: the Cd/Zn hyperaccumulator plant is Sedum chinensis.