Acid mine pollution treatment method based on microbial regulation and control

Abstract

The invention discloses an acid mine pollution treatment method based on microbial regulation and control, and belongs to the technical field of environmental protection engineering, and the acid mine pollution treatment method comprises the following steps: S1, screening and domesticating acid-resistant and heavy metal-resistant functional microbial communities; s2, constructing a sectional bioreactor, and filling the sectional bioreactor with a corresponding composite biological carrier; s3, inoculating the functional microbial community obtained by domestication in the step S1 into the sectional reactor constructed in the step S2, and carrying out biofilm culturing in simulated AMD; and S4, introducing AMD to be treated into the reaction system in the step S3, and regulating and controlling microbial activity through pH gradient regulation and dynamic supply of electron donors to realize heavy metal precipitation and water quality remediation. According to the method, closed-loop treatment of sulfate reduction, heavy metal precipitation and acid neutralization is achieved through the synergistic effect of microbial regulation and control and the functionalized biological carrier, and the problems of efficiency, cost and secondary pollution of traditional AMD treatment are solved.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection engineering technology, specifically relating to a method for treating acid mine pollution based on microbial regulation. Background Technology

[0002] Acid mine drainage (AMD) is a serious environmental pollution problem resulting from mining activities. It originates from the oxidation of sulfide minerals (such as pyrite FeS2) in mine waste rock or tailings under the influence of oxidation, water leaching, and microorganisms. This process releases large amounts of sulfuric acid (H2SO4), resulting in extremely acidic drainage (pH often below 3.0) and high sulfate concentrations (SO42-). 2- (Up to several thousand mg / L) and rich in various dissolved heavy metal ions (such as Fe) 2+ Cu 2+ Zn 2 + Al 3+ (etc.). Direct discharge of untreated AMD will cause devastating damage to surrounding water and soil ecosystems and seriously threaten human health.

[0003] Currently, the main methods for treating AMD include chemical neutralization and biological methods. Chemical neutralization is the most widely used traditional method, which involves adding alkaline substances (such as lime CaO or limestone CaCO3) to neutralize the acidity, causing heavy metals to precipitate as hydroxides or carbonates. This method is simple, reacts rapidly, and can quickly raise the pH to neutral and remove most heavy metals (such as Fe and Al); however, it requires the continuous addition of large amounts of alkaline agents (e.g., treating 1 ton of AMD requires approximately 0.5 to 1.0 tons of lime), resulting in high operating costs; the generated calcium salt sludge (such as CaSO4 and CaCO3) contains heavy metals, is difficult to dispose of safely, and easily causes secondary pollution; and excessive agents can easily lead to scaling and reactor blockage, among other significant drawbacks.

[0004] In contrast, the biological method uses sulfate-reducing bacteria (SRBs) as its core, utilizing SRBs (such as the genus *Desulfovibrio*) to convert sulfate (SO4) into sulfur dioxide. 2- ) is reduced to sulfide (S 2-), forming insoluble sulfides (such as CuS and ZnS) precipitates with heavy metal ions. This biological treatment method is environmentally friendly and has low operating costs, relying on microbial metabolism to reduce the consumption of chemical agents; heavy metals precipitate in the form of sulfides, and the amount of sludge is only 1 / 3 to 1 / 2 of that of chemical methods, with less sludge production and heavy metals precipitating in a more stable sulfide form (with potential for resource recovery). However, some problems still exist in the practical application of existing technologies, such as: poor environmental adaptability, the activity of conventional microorganisms decreases significantly under extremely low pH (<3) and high heavy metal concentrations, making stable operation difficult; a single reactor is difficult to maintain microbial activity and is easily affected by insufficient carbon source, electron donor competition (such as methanogens), and fluctuations in redox potential (ORP); H2S is easily released into the atmosphere, forming toxic gases and causing secondary acidification.

[0005] Therefore, it is crucial to develop an efficient, stable, low-cost, and environmentally friendly AMD governance technology. Summary of the Invention

[0006] In view of this, the present invention provides a method for the treatment of acid mine pollution based on microbial regulation. This method achieves closed-loop treatment of sulfate reduction, heavy metal precipitation and acid neutralization through the synergistic effect of microbial regulation and functionalized biological carriers, thus solving the problems of efficiency, cost and secondary pollution in traditional AMD treatment.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for treating acidic mine drainage based on microbial regulation, comprising the following steps:

[0009] S1. Screening and domestication of functional microbial communities: Screening and domesticating acid-resistant and heavy metal-resistant functional microbial communities;

[0010] S2. Construction of composite biological carrier reaction system: Construct a segmented bioreactor, which is divided into a front acid production zone, a middle reduction zone and a rear sulfur oxidation zone, and fill the corresponding composite biological carrier in each functional zone.

[0011] S3. Microbial inoculation and biofilm culture: The functional microbial community obtained from domestication in step S1 is inoculated into the segmented reactor constructed in step S2 and cultured in a simulated AMD to allow the microorganisms to form a stable biofilm on the surface and in the pores of the carrier.

[0012] S4. AMD Treatment and Microbial Activity Regulation: The AMD wastewater to be treated is introduced into the reaction system in step S3. Microbial activity is regulated by pH gradient control and dynamic supply of electron donors to achieve heavy metal precipitation and water quality remediation.

[0013] Preferably, in step S1, the functional microbial community includes one or a combination of acidophilic heterotrophic bacteria, sulfate-reducing bacteria (SRB), iron-reducing bacteria (IRB), and sulfur-oxidizing bacteria (TB); the functional microbial community is active under conditions of pH 2.0–4.0 and total heavy metal concentration of 500–2500 mg / L.

[0014] Preferably, the acidophilic heterotrophic bacteria are Lactobacillus acidophilus, the sulfate-reducing bacteria (SRB) are Desulfovibrio desulfuricans, the iron-reducing bacteria (IRB) are Geobacter metallireducens, and the sulfur-oxidizing bacteria (TB) are Thiobacillus thiooxidans.

[0015] Preferably, in step S2, the volume ratio of each zone in the bioreactor is 30% for the front acid-producing zone, 50% for the middle reduction zone, and 20% for the rear sulfur oxidation zone.

[0016] Preferably, the composite biological carrier in the front acid-producing zone comprises, by mass percentage: 81.5% matrix material, 15% calcium lactate microspheres, 3% calcite, and 0.5% humic acid; the matrix material is composed of ceramsite, zeolite, and activated carbon mixed in a mass ratio of 7:2:1.

[0017] Preferably, the composite biological carrier in the intermediate reduction zone comprises, by mass percentage: 74.5% matrix material, 15% calcium lactate microspheres, 5% apatite, 3% calcite, 2% zero-valent iron, and 0.5% magnetic particles; the matrix material is composed of ceramsite, zeolite, and activated carbon mixed in a mass ratio of 7:2:1.

[0018] Preferably, the composite biological carrier in the downstream sulfur oxidation zone comprises, by mass percentage: 91.85% matrix material, 5% apatite, 3% calcite, 0.1% vitamin B12, and 0.05% thiamine; the matrix material is composed of ceramsite, zeolite, and activated carbon mixed in a mass ratio of 5:12:3.

[0019] Preferably, the particle size of the calcium lactate microspheres is 50–100 μm.

[0020] Preferably, in step S3, the functional microbial community is divided into 1×10 9The biofilm was inoculated onto the carrier surface at a concentration of CFU / mL; artificial AMD at pH 2.5 was used for biofilm culture at a flow rate of 0.5–1.0 BV / d, with a hydraulic retention time (HRT) of 48 h; micro-aeration was implemented in the first acid-producing zone to control the dissolved oxygen (DO) at 0.5–1.0 mg / L, while the middle reduction zone and the final sulfur oxidation zone were kept in an anaerobic to microaerobic environment until a stable biofilm with a thickness ≥200 μm was formed.

[0021] Preferably, in step S4, the dynamic supply of the electron donor is based on the influent chemical oxygen demand / sulfate ratio (COD / SO4). 2- Feedback adjustment is performed based on online monitoring results of oxidation-reduction potential (ORP) and pH.

[0022] Preferably, in step S4, the pH gradient control involves setting up a neutralization zone at the reactor front end, using calcite and apatite to maintain the influent pH at 3.5–4.0; the target range for the ORP guidance is -200 mV to -100 mV (vs. SHE), and the influent COD / SO4 ratio is... 2- The ratio is ≥0.5.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention achieves efficient, stable, low-cost, and environmentally friendly synergistic treatment of acid mine wastewater (AMD) through the integration of multi-species synergistic metabolic closed-loop, segmented reactor design, and functionalized biological carriers. The details are as follows:

[0025] (1) This invention constructs a complete closed loop from “organic matter degradation → sulfate reduction / heavy metal precipitation → sulfide oxidation”, which solves the problems of traditional biological methods such as simple metabolism, easy imbalance and secondary pollution.

[0026] (i) Carbon source relay of acid-producing bacteria (e.g., Lactobacillus acidophilus) → SRB / IRB: Introducing acid-producing heterotrophic bacteria such as Lactobacillus acidophilus at the front end effectively converts recalcitrant complex organic matter into simple organic acids such as lactic acid, providing a stable and controllable endogenous electron donor for SRBs (e.g., Desulfovibrio desulfuricans) in the mid-stage reduction zone. This avoids the problem of "carbon source excess" caused by adding easily degradable carbon sources (e.g., acetic acid), significantly suppresses competition from methanogens and other miscellaneous bacteria, ensures the dominant position and high efficiency of the sulfate reduction reaction, and also realizes the resource utilization of waste.

[0027] (ii) Synergistic reduction and precipitation of SRB and IRB: In the middle stage, desulfovibrio desulfuricans utilize lactic acid provided by acid-producing bacteria or H2 produced by zero-valent iron (nZVI) as electron donors to reduce high concentrations of sulfate (SO42-).2- ) Reduced to sulfide (S 2- Simultaneously, iron-reducing bacteria (IRBs) such as Geobacter metallireducens reduce Fe... 3+ Reduced to Fe 2+ S 2- with Fe 2+ FeS precipitate is formed, while Cu 2+ Zn 2+ Heavy metal ions also interact with S 2- The combination forms sulfides with extremely low solubility (such as CuS and ZnS), achieving a heavy metal removal rate of >95%. The synergistic effect of SRB and IRB achieves a synergistic enhancement of sulfate reduction and heavy metal removal, and the generated sulfide sludge has stable chemical properties.

[0028] (iii) Terminal treatment of H2S by sulfur-oxidizing bacteria: The entire segmented bioreactor of this invention (including the front, middle, and rear sections) is a closed container system, and all connections (such as pipe interfaces and sampling ports) are designed to be sealed. Most of the H2S generated in the middle reduction zone will dissolve in the treated water, forming HS- or H2S(aq). The water containing dissolved H2S flows continuously from the middle reduction zone into the rear sulfur oxidation zone under the drive of pumps or gravity. In the rear sulfur oxidation zone, Thiobacillus thiooxidans will decompose any remaining H2S or S that may be generated. 2- Oxidized to elemental sulfur (S) 0 This process completely eliminates the risks of foul odor, toxicity, and secondary acidification caused by H2S emission; it also converts sulfur into recyclable elemental sulfur, realizing the recycling of sulfur resources and making the entire biological treatment process truly "closed-loop" and environmentally friendly.

[0029] (2) The present invention adopts a segmented reactor design of “front-end acid production zone - middle-end reduction zone - rear-end sulfur oxidation zone” and fills it with a suitable composite biological carrier to achieve the zoning optimization of microbial function.

[0030] (i) The pre-treatment acid-producing zone (30%) primarily functions to hydrolyze and acidify complex organic matter, providing a stable carbon source for the intermediate SRB treatment; it also provides initial pH buffering. Its carriers include calcium lactate microspheres (slow-release carbon source), calcite (providing alkalinity and raising the pH to 3.5–4.0), and humic acid (promoting microbial attachment); the matrix material (ceramsite / zeolite / activated carbon = 7:2:1) provides a high specific surface area and porous structure, promoting the attachment of acid-producing bacteria. This achieves in-situ, stable, and controllable carbon source supply, avoiding external addition; the mineral matrix initially neutralizes the acidity, reducing the treatment load on the intermediate stage; micro-aeration (DO 0.5–1.0 mg / L) promotes the attachment of acid-producing bacteria, ensuring a continuous carbon source supply.

[0031] (ii) The intermediate reduction zone (accounting for 50%) contains calcium lactate microspheres (the main carbon source), zero-valent iron (nZVI) (which acts as an alternative electron donor, maintaining the reducing environment through H2 production), and apatite (which adsorbs phosphates and co-precipitates heavy metals, such as Fe). 3+ The system utilizes calcite (to maintain alkalinity) and magnetic particles (to facilitate sludge separation). The dual electron donor (lactic acid + H2) design at this stage enhances the system's robustness under carbon source fluctuations, ensuring SRB maintains high activity (ORP maintained at -200 to -100 mV) even under extreme conditions. The synergistic effect of the mineral matrix strengthens pH buffering and heavy metal stabilization. The magnetic particles provide the physical basis for the rapid and efficient separation of heavy metal-containing sludge (recovery rate >85%), simplifying the resource recovery process.

[0032] (iii) The subsequent sulfur oxidation zone (accounting for 20%) is primarily supported by inert materials with high specific surface area, containing apatite and calcite (to maintain alkalinity and adsorption), and growth factors such as vitamin B12 and thiamine are added to promote the growth of sulfur-oxidizing bacteria. The matrix material (ceramsite / zeolite / activated carbon = 5:12:3) optimizes mass transfer and adhesion performance. This stage ensures the complete oxidation of H2S, achieving harmless emissions. The micro-oxygen environment design avoids competition with SRB for electron donors, maintaining the metabolic balance of the entire system. The addition of growth factors enhances the activity of sulfur-oxidizing bacteria, ensuring the stability of the closed loop.

[0033] In summary, this invention solves the problems of single function and easy secondary pollution of traditional biological methods by multi-species synergistic metabolic closed loop; by matching segmented reactors with functional biological carriers, it realizes the zonal optimization of microbial functions, and ultimately achieves comprehensive benefits such as efficient removal of pollutants (heavy metals >95%), significant reduction in operating costs, and resource utilization of sludge reduction, providing a scientific, efficient and sustainable innovative solution for AMD treatment. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of the acid mine pollution control method based on microbial regulation according to the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0037] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0038] This invention provides a method for treating acid mine pollution based on microbial regulation, comprising the following steps:

[0039] S1. Screening and domestication of functional microbial communities:

[0040] Screening and acclimation of complex functional microbial communities capable of tolerating strong acids and high concentrations of heavy metals; such communities include, but are not limited to, the following microorganisms: acidophilic heterotrophic bacteria, such as *Lactobacillus acidophilus*, for degrading complex organic matter to produce acid; sulfate-reducing bacteria (SRBs), such as *Desulfovibrio desulfuricans*, for reducing sulfate to produce sulfides; and iron-reducing bacteria (IRBs), such as *Geobacter metallireducens*, for reducing iron. 3+ It also synergistically precipitates heavy metals; sulfur-oxidizing bacteria (TB), such as Thiobacillus thiooxidans, are used to oxidize H2S into elemental sulfur, avoiding secondary pollution.

[0041] The above-mentioned strains or their mixed bacterial communities were subjected to gradient acclimatization in a simulated AMD environment with pH 2.0–4.0 and total heavy metal concentration of 500–2500 mg / L. The acidity and heavy metal concentration were gradually increased to screen out stable functional microbial communities with high activity and strong adaptability.

[0042] S2. Construction of the composite biological carrier reaction system:

[0043] A segmented bioreactor was constructed, which was divided into three functional zones along the water flow direction. The volume ratio of each zone was as follows: the acid production zone in the front section accounted for 30% of the total reactor volume, the reduction zone in the middle section accounted for 50% of the total reactor volume, and the sulfur oxidation zone in the rear section accounted for 20% of the total reactor volume.

[0044] Among them, the composite biological carrier matched in the front acid-producing zone: by mass percentage, the matrix material is 79.5-81.5%, calcium lactate microspheres are 15-20%, calcite is 0.5-3%, and humic acid is 0-0.5%. The matrix material is a mixture of ceramsite, zeolite, and activated carbon in a mass ratio of 7:2:1.

[0045] The composite biological carrier matched in the mid-section reduction zone: by mass percentage, the matrix material is 70-74.5%, calcium lactate microspheres are 15-20%, apatite is 5-10%, calcite is 3%, zero-valent iron (nZVI) is 2%, and magnetic particles are 0-0.5%. The matrix material is a mixture of ceramsite, zeolite, and activated carbon in a mass ratio of 7:2:1.

[0046] The composite biological carrier matched in the later sulfur oxidation zone: by mass percentage, the matrix material is 91.85%, apatite is 5%, calcite is 3%, vitamin B12 is 0.1%, and thiamine is 0.05%; the matrix material is a mixture of ceramsite, zeolite, and activated carbon in a mass ratio of 5:12:3 to optimize mass transfer and the attachment of sulfur-oxidizing bacteria.

[0047] S3. Microbial inoculation and biofilm culture:

[0048] The functional microbial community obtained from domestication in step S1 is used at a rate of 1×10⁻⁶. 9 The CFU / mL concentration was inoculated into the segmented reactor constructed in step S2; subsequently, artificial simulated AMD (with its ionic composition prepared according to the actual AMD water quality) at pH 2.5 was continuously introduced into the reactor at a flow rate of 0.5–1.0 BV / d for biofilm culture, and the hydraulic retention time (HRT) was controlled at 48 h.

[0049] In the initial acid-producing zone, micro-aeration was implemented to maintain the dissolved oxygen (DO) concentration at 0.5–1.0 mg / L to promote the attachment and growth of aerobic / facultative bacteria such as acidophilic heterotrophs. The middle reduction zone and the final sulfur oxidation zone maintained an anaerobic to microaerobic environment to meet the growth requirements of SRB, IRB, and TB. Cultivation continued until a stable and dense biofilm with a thickness ≥200 μm was formed on the carrier surface and within the pores of each reaction zone.

[0050] S4.AMD treatment and regulation of microbial activity:

[0051] The actual acid mine drainage (AMD) wastewater to be treated is introduced into the reaction system in step S3 where a stable biofilm has already formed. The activity of microorganisms in each functional zone is regulated through the following strategies:

[0052] pH gradient control: Calcite and apatite in the carrier are used as neutralizing agents at the front end of the reactor. The alkalinity is released slowly through their dissolution, raising the pH of the influent from ≤2.5 and stabilizing it in the suitable range of 3.5 to 4.0, thus creating a favorable growth environment for microorganisms in the middle and later stages.

[0053] Dynamic electron donor supply: based on the influent chemical oxygen demand / sulfate ratio (COD / SO4). 2-The online monitoring results of oxidation-reduction potential (ORP) and pH are used for feedback adjustment. The target range for ORP is set at -200mV to -100mV (vs. SHE) to ensure a strongly reducing environment in the intermediate reduction zone to activate SRB; and to ensure the influent COD / SO4 ratio is within acceptable limits. 2- The ratio should be ≥0.5 to provide sufficient electron donors.

[0054] When the ORP is detected to be higher than -100mV (indicating insufficient electron donor), the release rate of calcium lactate microspheres can be automatically increased or the dosage of nZVI can be adjusted; when the H2S concentration is too high, the electron donor supply can be appropriately reduced to avoid over-reduction.

[0055] Through the above regulation, the bioreduction of sulfate and the removal of heavy metal ions (such as Cu) are achieved. 2+ Zn 2+ Fe 3+ The process involves precipitation removal of H2S, in-situ oxidation and resource recovery, and avoidance of secondary pollution. Ultimately, it achieves efficient, stable, low-cost, and environmentally friendly comprehensive treatment of acidic mine drainage.

[0056] The following is in conjunction with the appendix Figure 1 The technical solution of the present invention will be further explained through specific embodiments:

[0057] Example 1

[0058] This example demonstrates the operation of a laboratory-scale AMD governance system.

[0059] S1. Screening and domestication of functional microbial communities:

[0060] Samples were collected from sediment near a drainage outlet of an acidic mine and enriched using a simulated AMD-based culture medium (containing Fe). 2+ 1000mg / L, SO4 2- 3000 mg / L, Cu 2+ 50mg / L, Zn 2+The culture was prepared at 80 mg / L, pH 2.5. After inoculation, the pH was gradually decreased (from 4.0 to 2.0) and the heavy metal concentration was gradually increased (from 500 mg / L to 2000 mg / L) for an 8-week gradient acclimatization period. The resulting functional microbial community included: *Lactobacillus acidophilus*, *Desulfovibrio desulfuricans*, *Geobacter metallireducens*, and *Thiobacillus thiooxidans*. These four bacteria were mixed at a cell density ratio of 1:1:1:1 to obtain the functional microbial community. Testing showed that under conditions of pH 3.0 and a total heavy metal concentration of 1500 mg / L, the sulfate reduction rate of *SRB* remained at 65% of its initial activity, and the iron reduction efficiency of *IRB* reached 92%.

[0061] S2. Construction of the composite biological carrier reaction system:

[0062] Construct a columnar segmented bioreactor with a total effective volume of 10L, with the volumes of each section allocated in a 3:5:2 ratio:

[0063] The first acid-producing zone (3L) is filled with a matching composite biological carrier, which consists of 81.5% matrix material (ceramsite:zeolite:activated carbon = 7:2:1), 15% calcium lactate microspheres, 3% calcite powder and 0.5% humic acid by mass percentage.

[0064] Mid-section reduction zone (5L): filled with a matching composite biological carrier, which by mass percentage consists of 74.5% matrix material (ceramsite:zeolite:activated carbon = 7:2:1), 15% calcium lactate microspheres, 5% apatite powder, 3% calcite powder, 2% nano zero-valent iron (nZVI) and 0.5% Fe3O4 magnetic particles.

[0065] The downstream sulfur oxidation zone (2L) is filled with a matching composite biological carrier C, which consists of 91.85% matrix material (ceramsite:zeolite:activated carbon = 5:12:3), 5% apatite powder, 3% calcite powder, 0.1% vitamin B12 and 0.05% thiamine by mass percentage.

[0066] S3. Microbial inoculation and biofilm culture:

[0067] The functional microbial community obtained in S1 was adjusted to a concentration of 1×10⁻⁶. 9 CFU / mL was evenly sprayed onto each segment of the carrier. Subsequently, artificially prepared simulated AMD (pH 2.5, major ion concentration: Fe) was used. 2+ 1200 mg / L, SO42- 3500 mg / L, Cu 2+ 60mg / L, Zn 2+ The culture medium was 100 mg / L, and water was continuously added at a flow rate of 0.8 BV / d (i.e., 8 L / d), with the HRT controlled at 48 h.

[0068] The acid-producing zone at the front end uses micro-pore aeration heads for micro-aeration to control DO at 0.8 mg / L.

[0069] The middle and rear sections were maintained in an anaerobic to microaerobic environment by nitrogen purging. After 60 days of culture, samples were taken for testing. Visible biofilms were formed on the surface of each section of the carrier. The biofilm thickness was measured by laser confocal microscopy (CLSM) to be approximately 220 μm in the front section, 250 μm in the middle section, and 210 μm in the rear section. The average thickness of the biofilms exceeded 200 μm, forming a stable biofilm system.

[0070] S4.AMD treatment and regulation of microbial activity:

[0071] The actual AMD wastewater (pH 2.3, Fe) discharged from a certain mine 2+ 1150 mg / L, SO4 2- 3200mg / L, Cu 2+ 55mg / L, Zn 2+ A 95 mg / L solution was introduced into the pre-coated reaction system for continuous treatment. The system operating parameters are as follows:

[0072] pH gradient control: The pH of the influent is raised to 3.8 before entering the middle stage by the action of calcite and apatite in the front-end carrier.

[0073] Dynamic electronic donor supply: Online pH, ORP, and COD sensors are installed, with the ORP control target set at -150mV (range -200 to -100mV), and the influent COD / SO4... 2- The ratio is controlled to be ≥0.5; when the ORP monitoring value is >-100mV, the system automatically fine-tunes (such as slightly increasing water flow disturbance to promote nZVI corrosion or adjusting microsphere release) to ensure that the ORP falls back to the target range, thereby achieving heavy metal precipitation and water quality restoration.

[0074] Performance test:

[0075] To verify the operational effectiveness described in Example 1, a 120-day period of system stability monitoring was conducted. This verified the removal efficiency of the method of the present invention for pH, heavy metals, and sulfates, its H2S control capability, and the yield and resource utilization potential of sludge when treating actual AMD.

[0076] Testing plan: Starting from the stable operation period of the system (after day 30), the main water quality indicators will be tested once a week, and the biofilm and sludge characteristics will be tested once every 30 days. pH, ORP and DO will be monitored online throughout the process.

[0077] Sampling points: inlet, front outlet, middle outlet, final outlet, and air outlet (rear exhaust pipe).

[0078] Sample preparation: After the water sample is filtered through a 0.45μm filter membrane, it is stored according to the requirements of the test items (e.g., heavy metal samples are acidified with nitric acid until pH<2, and COD samples are refrigerated at 4℃).

[0079] (1) The water quality index test data are shown in Table 1 (13 tests were conducted from day 30 to 120, and the average value was taken).

[0080] Table 1

[0081]

[0082] (2) H2S control effect test

[0083] Liquid phase H2S: Samples were taken from the outlets of the middle and rear sections of the reactor. The H2S concentration in the middle section outlet was 1.0-1.5 mg / L, and the H2S concentration in the rear section outlet was <0.1 mg / L (methylene blue method), indicating that H2S was effectively converted in the rear section.

[0084] Gas-phase H2S: Continuous monitoring was conducted at the final exhaust port (downstream) of the reactor using a portable H2S gas detector. The H2S concentration at the exhaust port remained below 1.0 mg / m³ for 120 days. 3 (Detection limit 0.5 mg / m³) 3 ), and there was no rotten egg smell at the scene.

[0085] (3) Sludge Characteristics and Resource Utilization Testing (Days 30, 60, 90, and 120): Sludge production: Sludge was collected daily from the sedimentation tank, and its volume and weight were measured. The average wet sludge production over 120 days was 0.11 ± 0.02 kg / m³. 3 AMD (moisture content approximately 70%). During the same period, the average sludge production of the lime neutralization treatment system at this mine was 0.34 ± 0.05 kg / m³. 3 AMD. This indicates that the amount of biological sludge produced in this embodiment is approximately 32% of that produced by the chemical method (i.e., 0.11 / 0.34), or approximately 1 / 3.

[0086] (4) Magnetic separation efficiency: Take 100g (wet weight) of mid-section sludge sample on day 120, place it in a beaker, apply an external magnet (magnetic field strength 0.5T), let it stand for 10min, transfer the sludge adsorbed by the magnet to another container and weigh it; the mass of sludge adsorbed by the magnetic particles is 86.5g, and the recovery rate is 86.5 / 100=86.5%, which is greater than 85%.

[0087] (5) CuS recovery by flotation: Flotation tests were conducted on the enriched sludge (containing approximately 18% Cu) after magnetic separation. Butyl xanthate was used as the collector and pine oil as the frother. Flotation was carried out under pH 6-8 conditions. Concentrate and tailings were obtained after flotation, dried, weighed, and Cu content was determined by ICP-OES. The Cu content in the concentrate was 88.7%, and the Cu flotation recovery rate was 81.5%.

[0088] In summary, through a systematic testing period of 120 days, this embodiment achieved significant treatment results: excellent effluent quality, a stable pH value increase to 6.8-7.2, and low levels of heavy metals (Cu). 2+ Zn 2+ The removal rates of Fe and Fe were both over 95%, and the sulfate removal rate reached 85%; the H2S risk was effectively controlled, with the outlet concentration below 1 mg / m³. 3 Furthermore, the absence of any noticeable odor confirms that the sulfur-oxidizing bacteria in the later stage successfully converted sulfides into elemental sulfur, achieving harmlessness. The sludge reduction effect is outstanding, with the biological sludge production being approximately one-third of that of the traditional chemical method. Simultaneously, the recovery rate of sludge containing heavy metals exceeds 85% through magnetic separation technology. Further flotation treatment can yield CuS-rich aggregates with a purity higher than 88%, and the copper recovery rate exceeds 80%, demonstrating good economic and environmental benefits.

[0089] Example 2

[0090] This example illustrates the treatment of high-concentration heavy metal AMD.

[0091] S1. Screening and domestication of functional microbial communities:

[0092] Samples were collected from the sediment at the target mine site for high-intensity tolerance acclimatization. Artificially simulated AMD was used as the basal culture medium (initial composition: Fe). 2+ 800 mg / L, SO4 2- 3000 mg / L, Cu 2+ 80mg / L, Zn 2+ 100mg / L, Mn 2+ 40mg / L,Al 3+ 120 mg / L, pH 3.0), after inoculation, the total heavy metal concentration was gradually increased and the pH was gradually decreased, with the total heavy metal concentration being increased in stages from 800 mg / L to 2500 mg / L (of which Cu2+ Up to 400 mg / L, Zn 2+ Up to 500 mg / L, Fe 2+ The medium concentration was increased to 1600 mg / L, and the pH was gradually decreased from 3.0 to 2.0. The acclimatization period was 12 weeks, during which the culture medium was changed regularly and microbial activity was monitored. The final functional microbial community included: Lactobacillus acidophilus, Desulfovibrio desulfuricans, Geobacter metallireducens, and Thiobacillus thiooxidans. Tests showed that under conditions of pH 2.2 and a total heavy metal concentration of 2200 mg / L, the sulfate reduction rate of SRB remained at 58% of its initial activity, and the iron reduction efficiency of IRB reached 89%, indicating its extremely strong tolerance.

[0093] S2. Construction of the composite biological carrier reaction system:

[0094] Construct a columnar segmented bioreactor with a total effective volume of 15L, with the volumes of each section allocated in a 3:5:2 ratio:

[0095] The front acid-producing zone (4.5L) is filled with a matching composite biological carrier, which consists of 81.5% matrix material (ceramsite:zeolite:activated carbon = 7:2:1), 15% calcium lactate microspheres, 3% calcite powder and 0.5% humic acid by mass percentage.

[0096] Mid-section reduction zone (7.5L): filled with a matching composite biological carrier, which consists of 70.5% matrix material (ceramsite:zeolite:activated carbon = 7:2:1), 15% calcium lactate microspheres, 9% apatite powder, 3% calcite powder, 2% nano zero-valent iron (nZVI) and 0.5% Fe3O4 magnetic particles by mass percentage.

[0097] The downstream sulfur oxidation zone (3L) is filled with a matching composite biological carrier C, which consists of 91.85% matrix material (ceramsite:zeolite:activated carbon = 5:12:3), 5% apatite powder, 3% calcite powder, 0.1% vitamin B12 and 0.05% thiamine by mass percentage.

[0098] S3. Microbial inoculation and biofilm culture:

[0099] The functional microbial community obtained in S1 was adjusted to a concentration of 1×10⁻⁶. 9 CFU / mL, evenly inoculated onto the surface of each segment of the carrier; artificial AMD (major ion concentration: Fe) was simulated at pH 2.2.2+ 1600 mg / L, SO4 2- 4000 mg / L, Cu 2+ 400mg / L, Zn 2+ The culture was carried out with 500 mg / L of water for biofilm formation, with continuous water influent at a flow rate of 0.6 BV / d and HRT controlled at 48 h.

[0100] The acid-producing zone at the front end uses micro-pore aeration heads for micro-aeration to control DO at 0.7 mg / L.

[0101] The middle and rear sections were maintained in a strictly anaerobic to microaerobic environment by nitrogen purging. After 90 days of culture, samples were taken for testing. Visible biofilms were formed on the surface of each section of the carrier. The biofilm thickness was measured by laser confocal microscopy (CLSM) and was approximately 215 μm in the front section, 265 μm in the middle section, and 205 μm in the rear section. The average thickness of the biofilms was over 200 μm, forming a stable biofilm system.

[0102] S4.AMD treatment and regulation of microbial activity:

[0103] The mine actually discharged high-concentration AMD wastewater (pH 2.1, Fe) 2+ 1780 mg / L, SO4 2- 4200mg / L, Cu 2+ 380mg / L, Zn 2+ 490mg / L,Al 3+ A 150 mg / L solution was introduced into the pre-coated reaction system for continuous treatment. The system operating parameters are as follows:

[0104] pH gradient control: The pH of the influent is raised to 3.7 before entering the middle stage by the action of calcite and apatite in the front-end carrier.

[0105] Dynamic electronic donor supply: Online pH, ORP, and COD sensors are installed, with the ORP control target set to -200 to -100 mV, and the influent COD / SO4... 2- The ratio is controlled to be ≥0.5; when the ORP monitoring value is >-100mV, the system automatically fine-tunes (such as slightly increasing water flow disturbance to promote nZVI corrosion or adjusting microsphere release) to ensure that the ORP falls back to the target range, thereby achieving heavy metal precipitation and water quality restoration.

[0106] Performance test:

[0107] After the system completes the biofilm formation, it enters a stable operation period, and the effectiveness is evaluated from day 91 to day 150.

[0108] Water quality indicators: Samples were taken and tested once a week (7 days) at the final outlet, for a total of 9 tests;

[0109] H2S concentration: Continuous online monitoring is performed at the final outlet, and manual calibration and comparison are performed once a week.

[0110] Sampling points: water inlet, final water outlet (after treatment in the downstream sulfur oxidation zone), and final air outlet (rear exhaust pipe).

[0111] Sample preparation: After filtering the water sample through a 0.45μm filter membrane, it was stored according to the requirements of the test items (heavy metals were acidified with HNO3 to pH<2, and other items were refrigerated at 4℃).

[0112] (1) Water quality index test data are shown in Table 2. From day 91 to 150, a total of 9 tests were conducted, and the average value was taken.

[0113] Table 2

[0114]

[0115] (2) H2S control effect test

[0116] Online monitoring of gaseous H2S: An online H2S gas analyzer (electrochemical sensor) was used to continuously monitor the H2S concentration at the outlet. During the 150-day monitoring period, the H2S concentration at the outlet remained consistently below 1.0 mg / m³. 3 (Detection limit is 0.5 mg / m³) 3 (), for the vast majority of the time below 0.8 mg / m² 3 During operation, there was no "rotten egg" odor around the reactor, which confirmed that H2S was effectively controlled by sensory evidence.

[0117] Liquid phase H2S verification: Samples were taken at the intermediate and final effluent outlets and detected using the methylene blue spectrophotometric method (HJ482-2009). The H2S concentration in the intermediate effluent was 1.0-1.8 mg / L (due to SRB activity), while the H2S concentration in the final effluent was <0.1 mg / L, confirming that the sulfur-oxidizing bacteria (TB) in the downstream section efficiently oxidize H2S to elemental sulfur.

[0118] Example 3

[0119] This example describes the treatment of acidic mine drainage under low-temperature conditions.

[0120] S1. Screening and domestication of functional microbial communities:

[0121] Samples were collected from low-temperature mining environments, and cold-resistant microbial communities were enriched and cultured. A simulated AMD-based culture medium (containing Fe) was used as the basal medium. 2+ 1000mg / L, SO4 2- 3000 mg / L, Cu 2+ 50mg / L, Zn 2+The bacteria were inoculated at 80 mg / L (pH 2.5), and then gradually acclimatized to 4°C. The resulting functional microbial community included: *Lactobacillus acidophilus*, *Desulfovibrio desulfuricans*, *Geobacter metallireducens*, and *Thiobacillus thiooxidans*. Tests showed that under conditions of pH 3.0, a total heavy metal concentration of 1500 mg / L, and a temperature of 4°C, the sulfate reduction rate of SRB remained at 60% of its initial activity, and the iron reduction efficiency of IRB reached 90%.

[0122] S2. Construction of the composite biological carrier reaction system:

[0123] Construct a columnar segmented bioreactor with a total effective volume of 10L, with the volumes of each section allocated in a 3:5:2 ratio:

[0124] The first acid-producing zone (3L) is filled with a matching composite biological carrier, which consists of 81.5% matrix material (ceramsite:zeolite:activated carbon = 7:2:1), 15% gelatin-encapsulated calcium lactate microspheres, 3% calcite powder and 0.5% humic acid by mass percentage.

[0125] Mid-section reduction zone (5L): filled with a matching composite biological carrier, which by mass percentage consists of 74.5% matrix material (ceramsite:zeolite:activated carbon = 7:2:1), 15% calcium lactate microspheres, 5% apatite powder, 3% calcite powder, 2% nano zero-valent iron (nZVI) and 0.5% Fe3O4 magnetic particles.

[0126] The downstream sulfur oxidation zone (2L) is filled with a matching composite biological carrier C, which consists of 91.85% matrix material (ceramsite:zeolite:activated carbon = 5:12:3), 5% apatite powder, 3% calcite powder, 0.1% vitamin B12 and 0.05% thiamine by mass percentage.

[0127] S3. Microbial inoculation and biofilm culture:

[0128] The functional microbial community obtained in S1 was adjusted to a concentration of 1×10⁻⁶. 9 CFU / mL was evenly sprayed onto each segment of the carrier. Subsequently, artificially prepared simulated AMD (pH 2.5, major ion concentration: Fe) was used. 2+ 1200 mg / L, SO4 2- 3500 mg / L, Cu 2+ 60mg / L, Zn 2+The culture medium was 100 mg / L, and water was continuously added at a flow rate of 0.8 BV / d. The heating time (HRT) was controlled at 48 h. The experiment was conducted in a constant temperature incubator at 4 °C.

[0129] The acid-producing zone at the front end uses micro-pore aeration heads for micro-aeration to control DO at 0.8 mg / L.

[0130] The middle and rear sections were maintained in an anaerobic to microaerobic environment by nitrogen purging. After 90 days of culture, samples were taken for testing. Visible biofilms were formed on the surface of each section of the carrier. The biofilm thickness was measured by laser confocal microscopy (CLSM) and was approximately 210 μm in the front section, 240 μm in the middle section, and 200 μm in the rear section. The average thickness of the biofilms was over 200 μm, forming a stable biofilm system.

[0131] S4.AMD treatment and regulation of microbial activity:

[0132] The actual AMD wastewater (pH 2.3, Fe) discharged from a certain mine 2+ 1150 mg / L, SO4 2- 3200mg / L, Cu 2+ 55mg / L, Zn 2+ A 95 mg / L solution was introduced into the pre-coated reaction system for continuous treatment. The system operating parameters are as follows:

[0133] pH gradient control: The pH of the influent is raised to 3.8 before entering the middle stage by the action of calcite and apatite in the front-end carrier.

[0134] Dynamic electronic donor supply: Online pH, ORP, and COD sensors are installed, with the ORP control target set at -150mV (range -200 to -100mV), and the influent COD / SO4... 2- The ratio is controlled to be ≥0.5; when the ORP monitoring value is >-100mV, the system automatically fine-tunes (such as slightly increasing water flow disturbance to promote nZVI corrosion or adjusting microsphere release) to ensure that the ORP falls back to the target range, thereby achieving heavy metal precipitation and water quality restoration.

[0135] Performance test:

[0136] After the system completes the biofilm formation, it enters a stable operation period, and the effectiveness is evaluated from day 91 to day 120.

[0137] Water quality indicators: Samples were taken and tested once a week (7 days) at the final outlet, for a total of 5 tests;

[0138] H2S concentration: Continuous online monitoring is performed at the final outlet, and manual calibration and comparison are performed once a week.

[0139] Sampling points: water inlet, final water outlet (after treatment in the downstream sulfur oxidation zone), and final air outlet (rear exhaust pipe).

[0140] Sample preparation: After filtering the water sample through a 0.45μm filter membrane, it was stored according to the requirements of the test items (heavy metals were acidified with HNO3 to pH<2, and other items were refrigerated at 4℃).

[0141] (1) The water quality index test data are shown in Table 3. From day 91 to 120, a total of 5 tests were conducted, and the average value was taken.

[0142] Table 3

[0143]

[0144] (2) H2S control effect test

[0145] Online monitoring of gaseous H2S: An online H2S gas analyzer (electrochemical sensor) was used to continuously monitor the H2S concentration at the outlet. During the 120-day monitoring period, the H2S concentration at the outlet remained consistently below 1.0 mg / m³. 3 (Detection limit is 0.5 mg / m³) 3 During operation, there was no "rotten egg" odor around the reactor, which confirmed that H2S was effectively controlled by sensory evidence.

[0146] Validation of H2S in liquid phase: Samples were taken from the intermediate and final effluent outlets and detected using the methylene blue spectrophotometric method (HJ482-2009). The H2S concentration in the intermediate effluent was 1.2-1.6 mg / L, while the H2S concentration in the final effluent was <0.1 mg / L, confirming that the sulfur-oxidizing bacteria (TB) in the downstream section efficiently oxidize H2S to elemental sulfur.

[0147] In summary, through a 120-day systematic testing, the operational performance of this embodiment under low-temperature conditions was as follows: the effluent water quality consistently met standards; at a low temperature of 4℃, the system was still able to stably raise the pH to 6.8-7.2, and the Cu... 2+ (>96%), Zn 2+ Highly efficient and stable removal of Fe (>95%), Fe (94%), and sulfate (>80%) was achieved; H2S risk was effectively controlled, with the outlet concentration below 1 mg / m³. 3 Furthermore, the absence of any noticeable odor confirms that the sulfur-oxidizing bacteria in the later stage successfully converted the sulfides into elemental sulfur, thus rendering them harmless.

[0148] The above provides a detailed description of a microbial-regulated method for the remediation of acidic mine pollution disclosed in this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of these embodiments are merely illustrative of the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A method for treating acidic mine drainage based on microbial regulation, characterized in that, Includes the following steps: S1. Screening and domestication of functional microbial communities: Screening and domesticating acid-resistant and heavy metal-resistant functional microbial communities; S2. Construction of composite biological carrier reaction system: Construct a segmented bioreactor, which is divided into a front acid production zone, a middle reduction zone and a rear sulfur oxidation zone, and fill the corresponding composite biological carrier in each functional zone. S3. Microbial inoculation and biofilm culture: The functional microbial community obtained from domestication in step S1 is inoculated into the segmented reactor constructed in step S2 and cultured in a simulated AMD to allow the microorganisms to form a stable biofilm on the surface and in the pores of the carrier. S4. AMD Treatment and Microbial Activity Regulation: The AMD wastewater to be treated is introduced into the reaction system in step S3. Microbial activity is regulated by pH gradient control and dynamic supply of electron donors to achieve heavy metal precipitation and water quality remediation.

2. The method for treating acidic mine drainage based on microbial regulation according to claim 1, characterized in that, In step S1, the functional microbial community includes one or a combination of acidophilic heterotrophic bacteria, sulfate-reducing bacteria (SRB), iron-reducing bacteria (IRB), and sulfur-oxidizing bacteria (TB). The functional microbial community is active under conditions of pH 2.0–4.0 and total heavy metal concentration of 500–2500 mg / L.

3. The method for treating acidic mine drainage based on microbial regulation according to claim 2, characterized in that, The acidophilic heterotrophic bacteria are Lactobacillus acidophilus, the sulfate-reducing bacteria (SRB) are Desulfovibrio desulfuricans, the iron-reducing bacteria (IRB) are Geobacter metallireducens, and the sulfur-oxidizing bacteria (TB) are Thiobacillus thiooxidans.

4. The method for treating acidic mine drainage based on microbial regulation according to claim 1, characterized in that, In step S2, the volume ratio of each zone in the bioreactor is 30% for the front acid production zone, 50% for the middle reduction zone, and 20% for the rear sulfur oxidation zone.

5. The method for treating acidic mine drainage based on microbial regulation according to claim 4, characterized in that, The composite biological carrier in the front acid-producing zone comprises, by mass percentage: 79.5-81.5% matrix material, 15-20% calcium lactate microspheres, 0.5-3% calcite, and 0-0.5% humic acid; the matrix material is a mixture of ceramsite, zeolite, and activated carbon in a mass ratio of 7:2:

1.

6. The method for treating acidic mine drainage based on microbial regulation according to claim 4, characterized in that, The composite biological carrier in the middle reduction zone comprises, by mass percentage: 70-74.5% matrix material, 15-20% calcium lactate microspheres, 5-10% apatite, 3% calcite, 2% zero-valent iron, and 0-0.5% magnetic particles; the matrix material is a mixture of ceramsite, zeolite, and activated carbon in a mass ratio of 7:2:

1.

7. The method for treating acidic mine drainage based on microbial regulation according to claim 4, characterized in that, The composite biological carrier in the downstream sulfur oxidation zone comprises, by mass percentage: 91.85% matrix material, 5% apatite, 3% calcite, 0.1% vitamin B12, and 0.05% thiamine; the matrix material is composed of ceramsite, zeolite, and activated carbon mixed in a mass ratio of 5:12:

3.

8. The method for treating acidic mine drainage based on microbial regulation according to claim 1, characterized in that, In step S3, the functional microbial community is divided into 1×10 9 The culture medium was inoculated onto the carrier surface at a concentration of CFU / mL; artificial AMD at pH 2.5 was used for biofilm culture at a flow rate of 0.5–1.0 BV / d, with a HRT of 48 h; micro-aeration was implemented in the first acid-producing zone to control DO at 0.5–1.0 mg / L, while the middle reduction zone and the last sulfur oxidation zone were kept in an anaerobic to microaerobic environment until a stable biofilm with a thickness ≥200 μm was formed.

9. The method for treating acidic mine drainage based on microbial regulation according to claim 1, characterized in that, In step S4, the dynamic supply of electron donors is adjusted based on feedback from online monitoring results of the influent chemical oxygen demand / sulfate ratio (COD / SO42-), oxidation-reduction potential (ORP), and pH.

10. The method for treating acidic mine drainage based on microbial regulation according to claim 1, characterized in that, In step S4, the pH gradient control involves setting up a neutralization zone at the front end of the reactor and using calcite and apatite to maintain the influent pH at 3.5–4.0; the target range for the ORP guidance is -200 mV to -100 mV (vs. SHE), and the influent COD / SO42- ratio is ≥0.5.

Images