In-situ pumping and injecting microbial remediation method for acid uranium mining groundwater

Abstract

The present application relates to sewage remediation technical field, particularly to a kind of in-situ microbial pumping and injection remediation method of acid uranium mining groundwater.The method provided by the present application has the following advantages:1) the present application uses contaminated raw water to culture sulfate-reducing bacteria into bacterial solution, and continuously injects bacterial solution into the area to be repaired, and supplements new culture medium, so as to realize the continuous pumping and injection of bacterial solution, by reasonably controlling the continuous pumping and injection ratio (15%, 20% pumping and injection alternately), increase the reproduction and expansion rate of functional microorganisms, enhance the self-reproduction and repair effect of in-situ microorganisms, realize the efficient removal of iron, uranium and sulfate, reduce the degree of water pollution;2) low cost: sulfate-reducing bacteria is a kind of biological catalyst that can self-reproduce, by suitable pumping and injection ratio, in-situ biological sustainable remediation effect can be realized, and the cost of groundwater pumping and treatment is reduced;3) environmentally friendly: sulfate-reducing bacteria is non-toxic and harmless to the environment, and will not cause secondary pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage remediation, in particular to an in-situ microbial pumping and injection remediation method for acid uranium mining groundwater. BACKGROUND

[0002] The acid uranium mining groundwater contains a large amount of sulfate and hexavalent uranium ions, which seriously affect the water environment and endanger the ecological system. The traditional water treatment method is generally to pump the groundwater out for surface biological disposal, including chemical precipitation: using chemical reagents (such as calcium hydroxide and sodium hydroxide) to react with sulfate to form insoluble precipitates; chemical reduction: using chemical reducing agents (such as sodium sulfide) to reduce hexavalent uranium to insoluble tetravalent uranium. However, the traditional water treatment method has poor effect on treating acid uranium mining groundwater, is easy to block and has high cost. SUMMARY

[0003] In order to solve the above problems, the present application provides an in-situ pumping and injection microbial remediation method for acid uranium mining groundwater. The remediation method provided by the present application not only has good effect on treating acid uranium mining groundwater, can efficiently remove uranium and sulfate, but also has low cost, is non-toxic and harmless to the environment, and will not cause secondary pollution.

[0004] In order to achieve the above purpose, the present application provides the following technical scheme:

[0005] The present application provides an in-situ microbial pumping and injection remediation method for acid uranium mining groundwater, comprising the following steps:

[0006] Sulfate-reducing bacteria are inoculated into a device containing culture medium for cultivation to obtain a bacterial solution; the culture medium comprises a carbon source, a nitrogen source and contaminated raw water; the contaminated raw water is contaminated raw water in an acid uranium mine underground;

[0007] A part of the bacterial solution in the device is injected into the acid uranium mine groundwater to be remediated in a continuous feeding and discharging mode, and new culture medium is supplemented in the device; the volume of the new culture medium is the same as that of the part of the bacterial solution; every 10-15 days is an operation cycle, and in the odd-numbered operation cycle, the total volume of the part of the bacterial solution added per day is 15% of the total volume of the bacterial solution in the device, and in the even-numbered operation cycle, the total volume of the part of the bacterial solution added per day is 20% of the total volume of the bacterial solution in the device.

[0008] Preferably, the mass ratio of the contaminated raw water, the carbon source and the nitrogen source is 10000:10-20:0.5-2.

[0009] Preferably, the carbon source comprises sodium lactate, and the nitrogen source comprises peptone.

[0010] Preferably, the contaminated raw water is pretreated before the culture medium is prepared, the pretreatment including filtering and adjusting the pH value to 4-7.5; the filter mesh aperture of the filtering is 5 μm.

[0011] Preferably, the sulfate-reducing bacteria include Desulfovibrio desulfuricans subsp. Desulfuricans ATCC 7757.

[0012] Preferably, the temperature of the culture is 20-25 ℃, the pH value is 5-6, and the rotating speed is 100-150 rpm.

[0013] Preferably, the OD value of the bacterial solution is 2-2.5. 600

[0014] Preferably, the part of the bacterial solution is pretreated before being added into the acid uranium mine groundwater to be repaired, the pretreatment including diluting the part of the bacterial solution with the contaminated raw water so that the OD value of the part of the bacterial solution is 2-2.5. 600

[0015] Preferably, in the continuous feeding and discharging mode, the temperature in the device is 20-25 ℃, the pH value is 5-6, and the rotating speed is 100-150 rpm.

[0016] Preferably, in the continuous feeding and discharging mode, the part of the bacterial solution in the device flows out at a constant speed, and new culture medium is fed in at a constant speed.

[0017] Advantages:

[0018] The in-situ microbial pumping and injection repair method provided by the application has the following advantages:

[0019] 1) The sulfate-reducing bacteria are cultured into a bacterial solution by using the contaminated raw water, and the bacterial solution is continuously injected into the area to be repaired and new culture medium is supplemented, so that the continuous pumping and injection of the bacterial solution is realized, the reproduction and expansion rate of the functional microorganisms is increased by reasonably controlling the continuous pumping and injection ratio (15% and 20% are alternately pumped and injected), the self-reproduction and repair effect of the in-situ microorganisms is enhanced, and the iron, uranium and sulfate can be efficiently removed, thereby reducing the pollution degree of the water body.

[0020] 2) Low cost: the sulfate-reducing bacteria are a kind of biological catalyst that can self-reproduce, and the in-situ biological sustainable repair effect can be realized by the suitable pumping and injection ratio, thereby reducing the cost of the groundwater pumping and treatment.

[0021] 3) Environment-friendly: the sulfate-reducing bacteria are non-toxic and harmless to the environment and will not cause secondary pollution. BRIEF DESCRIPTION OF DRAWINGS ​​

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments.

[0023] Figure 1 A schematic diagram of the continuous pumping and injection system of the present application. DETAILED DESCRIPTION

[0024] The present application provides an in-situ microbial pumping and injection remediation method for acid uranium mining groundwater, comprising the following steps:

[0025] Sulfate-reducing bacteria are inoculated into a device containing a culture medium, cultured, and a bacterial solution is obtained; the culture medium comprises a carbon source, a nitrogen source and contaminated raw water; the contaminated raw water is contaminated raw water from an acid uranium mine underground;

[0026] In a continuous feeding and discharging mode, part of the bacterial solution in the device is injected into the acid uranium mine groundwater to be remediated, and new culture medium is supplemented into the device at the same time; the volume of the new culture medium supplemented is the same as the volume of the part of the bacterial solution; every 10-15 days is one operation cycle, in the odd-numbered operation cycle, the total volume of the part of the bacterial solution added every day is 15% of the total volume of the bacterial solution in the device, and in the even-numbered operation cycle, the total volume of the part of the bacterial solution added every day is 20% of the total volume of the bacterial solution in the device.

[0027] As shown in Figure 1 The present application preferably extracts contaminated raw water from acid uranium mine groundwater, which is treated by a continuous pumping and injection system, and is sequentially injected into the contaminated area of the underground aquifer through a filter, a buffer regulator, a culture medium batching tank, a microbial culture tank and a liquid injection mixing tank. In the present application, the filter preferably uses a filter bag with a pore size of 5 μm to trap large particles in the groundwater; the buffer regulator preferably contains an alkaline solution, and the alkaline solution is preferably a sodium hydroxide solution; the buffer regulator can preferably maintain the pH value of the extracted contaminated raw water at 4-7.5, further preferably at 4-6, and more preferably at 4-5. By maintaining the pH value of the contaminated raw water at 4-7.5, the present application can effectively and stably control the pH value and avoid the influence of acidity fluctuation on the growth activity of the microorganisms in the rear end.

[0028] The dosing tank can supplement nitrogen source and carbon source at a constant speed, and mix with the contaminated raw water to obtain a culture medium for culturing sulfate-reducing bacteria. In the present application, the mass ratio of the contaminated raw water, the carbon source and the nitrogen source is preferably 10000:10-20:0.5-2, further preferably 10000:15-20:1-2, and more preferably 10000:20:1. The carbon source preferably comprises sodium lactate, and the nitrogen source preferably comprises peptone. The sulfate-reducing bacteria preferably comprise Desulfovibrio desulfuricansubsp. ATCC7757, which is preferably purchased from Ningbo Mingzhou Biotechnology Co., Ltd.

[0029] The sulfate-reducing bacteria are preferably activated to obtain a seed liquid.

[0030] After obtaining the seed liquid and the culture medium, the culture medium is preferably pumped into a microbial culture tank at a certain flow rate controlled by a flow meter, and then the seed liquid is inoculated, cultured, and a bacterial liquid is obtained. In the present application, the inoculation amount of the seed liquid is preferably 0.1% (v / v); the culture temperature is preferably 20-25°C, further preferably 23-25°C, and more preferably 25°C; the pH value of the culture is 5-6, further preferably 5.5-6, and more preferably 6; the rotation speed of the culture is 100-150 rpm, further preferably 100-125 rpm, and more preferably 100 rpm; and the OD 600 value of the bacterial liquid is preferably 2-2.5, further preferably 2-2.2, and more preferably 2.

[0031] After obtaining the bacterial liquid, the bacterial liquid in the microbial culture tank is preferably pumped into a liquid injection mixing tank at a certain flow rate controlled by a flow meter, and the contaminated raw water is used to dilute the part of the bacterial liquid, so that the OD 600 value of the part of the bacterial liquid is 2-2.5, further preferably 2-2.2, and more preferably 2. By controlling the OD 600 value of the injected bacterial liquid to be 2-2.5, a high enough bacterial concentration can be ensured to resist adverse external conditions, and a low sludge age can also increase the growth rate of microorganisms, promote the expansion of the bacterial agent, and in addition, a suitable concentration of the bacterial liquid can prevent the blockage of the underground sandstone aquifer.

[0032] This invention employs a continuous feeding and discharging mode, injecting a portion of the bacterial solution from the device into the groundwater of the acidic uranium mine to be remediated, while simultaneously replenishing the device with new culture medium; the volume of the new culture medium replenished is the same as the volume of the portion of bacterial solution; each operating cycle is 10 to 15 days, preferably 10 days; in odd-numbered operating cycles, the total volume of the portion of bacterial solution added each day is 15% of the total volume of bacterial solution in the device, and in even-numbered operating cycles, the total volume of the portion of bacterial solution added each day is 20% of the total volume of bacterial solution in the device.

[0033] In the continuous feeding and discharging mode of the present invention, a portion of the bacterial solution in the device preferably flows out at a uniform rate, and new culture medium is preferably added at a uniform rate, with the outflow and inflow rates preferably being the same.

[0034] The remediation effect of acidic uranium mining groundwater is positively correlated with the biomass of injected sulfate-reducing bacteria. Factors influencing the injected biomass are mainly determined by the injection volume and bacterial concentration. Traditional injection methods generally employ a single-injection model, while this invention introduces a continuous culture-injection model, which is innovative in the field of groundwater pollution treatment. Through systematic experiments and tests, this invention has determined the optimal hydraulic retention time and bacterial solution extraction ratio. This continuous culture-injection technology is unique and innovative in in-situ remediation of groundwater pollution, achieving the highest microbial remediation efficiency. By rationally controlling the continuous extraction ratio (15% and 20% alternating extraction), this invention increases the reproduction and expansion rate of functional microorganisms, enhances the self-proliferation and remediation function of in-situ microorganisms, and can achieve efficient removal of iron, uranium, and sulfate, reducing the degree of water pollution.

[0035] To further illustrate the present invention, the following detailed description of an in-situ microbial injection remediation method for acidic uranium mining groundwater, provided by the present invention, is provided in conjunction with the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] In August 2023, trials were conducted at Factory 737 in Yili, Xinjiang, as detailed below:

[0038] like Figure 1 As shown, contaminated raw water is extracted from groundwater in an acidic uranium mine, treated by a continuous injection system, and then sequentially passed through a filter, buffer regulator, culture medium preparation tank, microbial culture tank, and injection mixing tank before being reinjected into the contaminated area of ​​the aquifer. The extracted contaminated raw water has a pH of 3.5–5.5, a temperature range of 10–16℃, a sulfate concentration of 900–2500 mg / L, a uranium concentration of 0.1–0.5 mg / L, and an iron ion concentration of 50–150 mg / L.

[0039] The filter adopts a filter bag with a pore size of 5 μm; the buffer regulator is a sodium hydroxide solution, which maintains the pH value of the extracted contaminated raw water at 4.0±0.1.

[0040] The ingredient tank supplements constant-speed protein peptone and sodium lactate and stirs the contaminated raw water to obtain a culture medium for culturing sulfate-reducing bacteria; the mass ratio of the contaminated raw water, sodium lactate and protein peptone is 10000:20:1; the sulfate-reducing bacteria is Desulfovibrio desulfuricansubsp. ATCC 7757.

[0041] The dry powder of the sulfate-reducing bacteria is inoculated into 10 mL postgate liquid medium after high-temperature sterilization and nitrogen stripping, and the culture conditions (25℃, pH 6.0, lightless anaerobic) are controlled to activate the culture to obtain a primary seed liquid, which is inoculated into a microbial culture tank at a rate of 10% (v / v) to obtain a functional bacteria agent (i.e. the seed liquid inoculated into the microbial culture tank).

[0042] The seed liquid is inoculated into the microbial culture tank after the culture medium is pumped into the microbial culture tank at a certain flow rate controlled by a flow meter, and the culture is carried out to obtain a bacteria liquid with an OD 600 value of 2. The inoculation amount of the seed liquid is 0.1% (v / v); the culture temperature is 25℃, the pH value is 6.0, and the rotation speed is 100 rpm.

[0043] The bacteria liquid in the microbial culture tank is pumped into a liquid injection mixing tank at a certain flow rate controlled by a flow meter, and the contaminated raw water is used to dilute the bacteria liquid to make the OD 600 value of the bacteria liquid be 2.

[0044] In a continuous feeding and discharging mode, part of the bacteria liquid in the microbial culture tank is added into the acidic uranium mine groundwater, and an equal volume of new culture medium is supplemented into the microbial culture tank; every 10 days is a running cycle, and in the odd running cycles, the volume of the part of the bacteria liquid added every day is 15% of the total volume of the bacteria liquid in the device, and in the even running cycles, the volume of the part of the bacteria liquid added every day is 20% of the total volume of the bacteria liquid in the device.

[0045] Comparative Example 1

[0046] A method similar to Example 1, the only difference is that 90% of the volume of the bacteria liquid in the culture tank is extracted every 7 days to be added into the acidic uranium mine groundwater, and the culture medium mixed with raw water is supplemented into the culture tank.

[0047] Comparative Example 2

[0048] A method similar to Example 1, the only difference is that the volume of the part of the bacteria liquid added every day is 15% of the total volume of the bacteria liquid in the device in all running cycles.

[0049] Comparative Example 3

[0050] A method similar to Example 1, except that the volume of the portion of the sludge liquid added each day was 20% of the total volume of the sludge liquid in the device for all of the operating periods.

[0051] Comparative Example 4

[0052] A method similar to Example 1, except that the volume of the portion of the sludge liquid added each day was 25% of the total volume of the sludge liquid in the device for all of the operating periods.

[0053] Comparative Example 5

[0054] A method similar to Example 1, except that the volume of the portion of the sludge liquid added each day was 25% of the total volume of the sludge liquid in the device for even-numbered operating periods.

[0055] Comparative Example 6

[0056] A method similar to Comparative Example 5, except that each 15 days was an operating period.

[0057] Comparative Example 7

[0058] A method similar to Example 1, except that each 15 days was an operating period.

[0059] Test Example

[0060] The cumulative amount of sludge liquid added over 45 days was detected for the different methods of Example 1 and Comparative Examples 1 to 7. The method for detecting the dry cell weight of the sludge liquid was as follows: the sludge liquid was suction filtered through a 0.22 μm filter membrane, dried in an oven at 105°C, and then cooled, the difference between the weight of the filter paper before and after was the sludge concentration (mlss), the filter paper was placed in a muffle furnace at 500°C for 2 hours, and the difference between the weight before and after was the dry ash content, and the dry cell weight was equal to the sludge concentration minus the dry ash, i.e. the mixed liquid volatile suspended solid concentration (mlvss). The cumulative amount of sludge liquid added was equal to the dry cell weight of the sludge liquid added each day multiplied by the volume of the sludge liquid added on that day. The results of the detection are shown in Table 1.

[0061] Table 1 Cumulative amount of sludge liquid added over 45 days (g VSS)

[0062]

[0063] From Table 1, it can be seen that the cumulative injection amount of bacteria is the lowest when 90% of the bacteria in the culture tank is injected every 7 days, and the in-situ bioremediation effect is limited. When the daily injection ratio of bacteria to tank is increased from 20% to 25%, the sludge concentration in the culture tank is greatly reduced, the daily biomass increment is significantly reduced, and the total injection amount of bacteria is reduced within 45 days. When the daily injection ratio of bacteria to tank is reduced from 20% to 15%, the sludge concentration in the culture tank is continuously increased, the substrate utilization rate is greatly increased, and carbon source and sulfate need to be continuously added for substrate replenishment. However, when the daily injection amount is maintained at 15%, the hydrogen sulfide content is continuously increased, which inhibits the growth of functional microorganisms, and the total injection amount of bacteria is reduced within 45 days. By maintaining the bacterial concentration (OD value of 2) and adopting an intermittent injection ratio of 15% and 20% every 10 days, the problem of hydrogen sulfide accumulation can be effectively alleviated, the injection amount of bacteria can be increased, the total injection amount of bacteria within 45 days can be increased, and the in-situ groundwater bioremediation can be facilitated.

[0064] In summary, the intermittent injection ratio of 15% and 20% every 10 days is the best, the injection amount of biomass within 45 days is the largest, and the in-situ groundwater bioremediation is facilitated.

[0065] Although the above embodiments have been described in detail, they are only part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the above embodiments without creativity, which are within the protection scope of the present application.

Claims

1. A method for in-situ microbial injection remediation of acidic uranium mining groundwater, characterized in that, Includes the following steps: Sulfate-reducing bacteria are inoculated into a device containing a culture medium and cultured to obtain a bacterial solution; the culture medium includes a carbon source, a nitrogen source, and contaminated raw water; the contaminated raw water is contaminated raw water from underground acidic uranium mines; A continuous feeding and discharging method is adopted, in which part of the bacterial solution in the device is injected into the groundwater of the acidic uranium mine to be remediated, and new culture medium is added to the device at the same time; the volume of the new culture medium added is the same as the volume of the partial bacterial solution; each operating cycle is 10 to 15 days. In the odd-numbered operating cycles, the total volume of the partial bacterial solution added each day is 15% of the total volume of the bacterial solution in the device, and in the even-numbered operating cycles, the total volume of the partial bacterial solution added each day is 20% of the total volume of the bacterial solution in the device.

2. The in-situ microbial injection remediation method according to claim 1, characterized in that, The mass ratio of the polluted raw water, carbon source, and nitrogen source is 10000:10-20:0.5-2.

3. The in-situ microbial injection remediation method according to claim 1 or 2, characterized in that, The carbon source includes sodium lactate, and the nitrogen source includes peptone.

4. The in-situ microbial injection remediation method according to claim 1 or 2, characterized in that, The contaminated raw water is pretreated before the culture medium is prepared. The pretreatment includes filtration and pH adjustment to 4-7.

5. The filter screen has a pore size of 5 μm.

5. The in-situ microbial injection remediation method according to claim 1, characterized in that, The sulfate-reducing bacteria include *Desulfovibrio desulfuricans* subsp. *Desulfuricans* ATCC 7757.

6. The in-situ microbial injection remediation method according to claim 1, characterized in that, The culture temperature is 20–25°C, the pH value is 5–6, and the rotation speed is 100–150 rpm.

7. The in-situ microbial injection remediation method according to claim 1, characterized in that, The OD of the bacterial solution 600 The value is 2 to 2.

5.

8. The in-situ microbial injection remediation method according to claim 1, characterized in that, Before adding a portion of the bacterial solution to the acidic uranium mine groundwater to be remediated, the bacterial solution undergoes pretreatment. This pretreatment includes diluting the bacterial solution with the contaminated raw water to reduce the OD value of the bacterial solution. 600 The value is 2 to 2.

5.

9. The in-situ microbial injection remediation method according to claim 1, characterized in that, In the continuous feeding and discharging mode, the temperature in the device is 20-25°C, the pH value is 5-6, and the rotation speed is 100-150 rpm.

10. The in-situ microbial injection remediation method according to claim 1 or 9, characterized in that, In the continuous feeding and discharging mode, a portion of the bacterial solution in the device flows out at a constant speed, and new culture medium is added at a constant speed.

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