Method for treating heavy metal polluted water body through microorganism induced precipitation

Abstract

The invention relates to the technical field of environmental pollution treatment, and provides a method for treating a heavy metal polluted water body through microorganism induced precipitation, which comprises the following steps: S1, screening a microorganism strain with the capability of efficiently inducing calcium carbonate precipitation from a polluted water body or soil; s2, optimizing culture conditions, including a carbon source, a nitrogen source, pH and temperature, of the strain through a single factor experiment and a response surface method to obtain a high-activity functional strain; s3, inoculating the bacterial suspension in the step S2 into wastewater containing heavy metal ions; s4, bicarbonate or carbonate is added into a reaction system in S3, and carbonate ions are provided; s5, adjusting the pH value of the solution in S4 to 7.0-8.5, and controlling the reaction temperature to be 25-35 DEG C; and S6, forming of calcium carbonate precipitates is induced through a stirring reaction, the reaction time is 2-24 hours, and fixation and removal of the heavy metal ions are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental pollution treatment, and specifically, to a method for treating heavy metal-polluted water bodies by microbial-induced precipitation. Background Art

[0002] With the rapid development of industrialization and urbanization, the problem of heavy metal pollution in water bodies has become increasingly serious, posing a great threat to the ecosystem and human health. Although traditional chemical treatment methods (such as chemical precipitation, ion exchange, and membrane separation) can remove heavy metals to a certain extent, they have problems such as high cost, complex operation, and easy generation of secondary pollution. In recent years, microbial technology has gradually become a research hotspot in the field of pollution treatment due to its advantages of high efficiency, environmental protection, and sustainability.

[0003] Microbial-induced calcium carbonate precipitation (MICP) is an emerging bioengineering technology, and its core lies in the formation of calcium carbonate precipitation induced by specific microorganisms (such as Bacillus) under specific conditions; however, the existing technology still has deficiencies in the following aspects:

[0004] First, the selection and optimization of microbial strains are insufficient, resulting in limited treatment efficiency;

[0005] Second, the optimization of reaction conditions (such as pH, temperature, carbon source, etc.) is not systematic enough, affecting the treatment effect;

[0006] Third, the lack of in-depth research on the heavy metal fixation mechanism limits the further popularization of the technology;

[0007] In view of the above problems, the present invention proposes a method for treating heavy metal pollution in water bodies based on the microbial-induced calcium carbonate precipitation technology. By screening high-efficiency strains, optimizing reaction conditions, and deeply analyzing the action mechanism, the removal efficiency of heavy metals and the process stability are significantly improved. Summary of the Invention

[0008] The present invention proposes a method for treating heavy metal-polluted water bodies by microbial-induced precipitation, which solves the problem of limited treatment efficiency caused by insufficient selection and optimization of microbial strains in the prior art.

[0009] The technical solution of the present invention is as follows: A method for treating heavy metal-polluted water bodies by microbial-induced precipitation, comprising the following steps:

[0010] S1: Screen microbial strains with high-efficiency calcium carbonate precipitation induction ability from polluted water bodies or soils;

[0011] S2: Optimize the culture conditions of the strains, including carbon source, nitrogen source, pH, and temperature, through single-factor experiments and response surface methods to obtain highly active functional strains;

[0012] S3: Inoculate the bacterial suspension in S2 into the wastewater containing heavy metal ions;

[0013] S4: Add bicarbonate or carbonate to the reaction system in S3 to provide carbonate ions;

[0014] S5: Adjust the pH of the solution in S4 to 7.0 - 8.5, and control the reaction temperature at 25 - 35 °C;

[0015] S6: Induce the formation of calcium carbonate precipitation through stirring reaction, with the reaction time being 2 - 24 hours, to achieve the fixation and removal of heavy metal ions.

[0016] Preferably, the microbial strain is a strain of the genus Bacillus.

[0017] Preferably, in S1, the specific implementation process for screening the strain of the genus Bacillus is as follows:

[0018] (1). Make a suspension of the polluted water body or soil sample through pretreatment, and then perform separation and purification to obtain multiple different strains;

[0019] (2). Inoculate the above - mentioned multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake - flask experiment, which is the heat - resistant spore of Bacillus.

[0020] Preferably, in S2, the specific implementation process for optimizing the culture conditions of the strain of the genus Bacillus through single - factor experiments is as follows:

[0021] (1). Divide the basal medium into 5 groups of conical flasks, set different pH gradients for each group, with the pH values being 5.0, 6.0, 7.0, 8.0, and 9.0 respectively. Inoculate equal amounts of the bacterial solution of the strain of the genus Bacillus into the 5 groups of media, keep other conditions unchanged, and by measuring the growth data (OD600 value) of the strain of the genus Bacillus, the OD600 value in the medium with a pH of 7.0 is the largest;

[0022] (2). Divide the carbon - source - free basal medium into four groups, add equal amounts of glucose, sucrose, starch, and glycerol as carbon sources to each group respectively, and set the carbon - source - free basal medium as the control group. Inoculate equal amounts of the bacterial solution of the strain of the genus Bacillus into the 5 groups of media, and by measuring the growth data (OD600 value) of the strain of the genus Bacillus, the OD600 value in the medium with glucose as the carbon source is the largest;

[0023] (3) Divide the nitrogen-free basal medium into four groups, and add equal amounts of beef extract, peptone, yeast extract, and urea to each group as nitrogen sources. Set the nitrogen-free basal medium as the control group. Inoculate the five groups of media with an equal amount of the bacterial solution of the Bacillus genus. By measuring the growth data (OD600 value) of the Bacillus genus, the OD600 value in the medium with beef extract as the nitrogen source is the largest;

[0024] (4) Dispense the basal medium into four groups of conical flasks, and set different temperature gradients for each group, with the temperatures being 20°C, 30°C, 40°C, 50°C, and 60°C. Inoculate the five groups of media with an equal amount of the bacterial solution of the Bacillus genus. By measuring the growth data (OD600 value) of the Bacillus genus, the OD600 value in the medium at 30°C is the largest.

[0025] Preferably, in S2, the specific implementation process of optimizing the culture conditions of the Bacillus genus by the response surface method is as follows:

[0026] (1) According to the results of the single-factor experiment, select 3 - 5 factors that have a significant impact on the response value;

[0027] (2) Design the experiment using Central Composite Design (CCD), and generate an experimental plan table through software;

[0028] (3) Prepare the medium according to the conditions of the design table, culture the Bacillus genus, measure the OD600 value, repeat each experimental point 3 times, and take the average value;

[0029] (4) Calculate and predict the optimal culture conditions of the Bacillus genus through a mathematical model: the carbon source is glucose (1.0%), the nitrogen source is beef extract (0.3%), the pH is 7.2, and the temperature is 30°C.

[0030] Preferably, in S4, the concentration of the bicarbonate or carbonate is 0.1 - 1.0 mol / L.

[0031] Preferably, in S6, after the formation of calcium carbonate precipitation is induced by stirring the reaction, the precipitate needs to be separated by filtration and centrifugation to complete the removal of heavy metal ions.

[0032] Preferably, in S6, the heavy metal ions include lead ions (Pb 2+ ), cadmium ions (Cd 2+ ), arsenic ions (As 3+ / As 5+ ), and mercury ions (Hg 2+ ).

[0033] The working principle and beneficial effects of the present invention are as follows:

[0034] (1) The present invention significantly improves the removal efficiency of heavy metals by screening and optimizing specific functional strains, and the removal rates of heavy metal ions such as lead, cadmium, and arsenic can reach over 95%.

[0035] (2) The reaction conditions of the present invention are mild, the cost is low, no complex chemical reagents need to be added, and it has good economic and environmental protection performance.

[0036] (3) Through the chemical-biological synergistic effect of the present invention, the heavy metals fixed in the calcium carbonate crystals are not easily released, improving the stability of pollution treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0038] Figure 1 It is a flow chart of a method for treating heavy metal-polluted water by microbial-induced precipitation of the present invention;

[0039] Figure 2 It is a comparison chart of the removal efficiency of lead ions by different strains of the present invention;

[0040] Figure 3 It is a schematic diagram of the influence of pH on the formation of calcium carbonate precipitation of the present invention;

[0041] Figure 4 It is a curve graph of the influence of temperature on the removal rate of cadmium ions of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0043] The present invention provides a method for treating heavy metal-polluted water by microbial-induced precipitation, which includes the following steps:

[0044] S1: Screen microbial strains with high-efficiency ability to induce calcium carbonate precipitation from polluted water or soil. The specific implementation process is as follows:

[0045] (1) Make a suspension of the polluted water or soil sample through pretreatment, and then separate and purify to obtain multiple different strains;

[0046] (2) Inoculate the above-mentioned multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the most calcium carbonate precipitation induced through a shake flask experiment, which is the Bacillus thermophilus spore;

[0047] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methodology, including carbon source, nitrogen source, pH, and temperature, to obtain highly active functional strains.

[0048] S3: Inoculate the bacterial suspension in S2 into the wastewater containing heavy metal ions.

[0049] S4: Add 0.1 - 1.0 mol / L bicarbonate or carbonate into the reaction system in S3 to provide carbonate ions.

[0050] S5: Adjust the pH of the solution in S4 to 7.0 - 8.5 and control the reaction temperature at 25 - 35 °C.

[0051] S6: Induce the formation of calcium carbonate precipitation through stirring reaction for 2 - 24 hours, and separate the precipitate by filtration and centrifugation to achieve the immobilization and removal of heavy metal ions.

[0052] The present invention significantly improves the removal efficiency of heavy metals by screening and optimizing specific functional strains. The removal rates of heavy metal ions such as lead, cadmium, and arsenic can reach over 95%. The reaction conditions are mild, the cost is low, no complex chemical reagents need to be added, and it has good economic efficiency and environmental protection. Through the synergistic effect of chemistry and biology, the heavy metals fixed in calcium carbonate crystals are not easily released, improving the stability of pollution treatment.

[0053] Furthermore, the microbial strain is a strain of the genus Bacillus.

[0054] Furthermore, in S2, the specific implementation process of optimizing the culture conditions of the strain of the genus Bacillus through single-factor experiments is as follows:

[0055] (1). Dispense the basal medium into 5 groups of conical flasks, set different pH gradients for each group, with pH values of 5.0, 6.0, 7.0, 8.0, and 9.0 respectively. Inoculate equal amounts of the bacterial solution of the strain of the genus Bacillus into the 5 groups of media, keep other conditions unchanged. By measuring the growth data (OD600 value) of the strain of the genus Bacillus, the OD600 value in the medium with a pH of 7.0 is the largest.

[0056] (2). Divide the carbon-source-free basal medium into four groups, add equal amounts of glucose, sucrose, starch, and glycerol as carbon sources to each group respectively, and set the carbon-source-free basal medium as the control group. Inoculate equal amounts of the bacterial solution of the strain of the genus Bacillus into the 5 groups of media. By measuring the growth data (OD600 value) of the strain of the genus Bacillus, the OD600 value in the medium with glucose as the carbon source is the largest.

[0057] (3) Divide the nitrogen-free basal medium into four groups, and add equal amounts of beef extract, peptone, yeast extract, and urea to each group as nitrogen sources, and set the nitrogen-free basal medium as the control group. Inoculate the same amount of bacterial liquid of Bacillus species in the 5 groups of media. By measuring the growth data (OD600 value) of Bacillus species, the OD600 value in the medium with beef extract as the nitrogen source is the largest;

[0058] (4) Dispense the basal medium into 4 groups of conical flasks, and set different temperature gradients for each group. The temperatures are 20°C, 30°C, 40°C, 50°C, and 60°C. Inoculate the same amount of bacterial liquid of Bacillus species in the 5 groups of media. By measuring the growth data (OD600 value) of Bacillus species, the OD600 value in the medium at 30°C is the largest.

[0059] Further, in S2, the specific implementation process of optimizing the culture conditions of Bacillus species by the response surface method is as follows:

[0060] (1) According to the results of the single-factor experiment, select 3 - 5 factors that have a significant impact on the response value;

[0061] (2) Design the experiment using Central Composite Design (CCD), and generate an experimental plan table through software;

[0062] (3) Prepare the medium according to the conditions of the design table, culture Bacillus species, measure the OD600 value, repeat each experimental point 3 times, and take the average value;

[0063] (4) Calculate and predict the optimal culture conditions of Bacillus species through a mathematical model: the carbon source is glucose (1.0%), the nitrogen source is beef extract (0.3%), the pH is 7.2, and the temperature is 30°C.

[0064] Further, in S6, the heavy metal ions include lead ions (Pb 2+ ), cadmium ions (Cd 2+ ), arsenic ions (As 3+ / As 5 + ), and mercury ions (Hg 2+ ).

[0065] Example 1:

[0066] This example proposes a method for treating heavy metal - contaminated water by microbial - induced precipitation, including the following steps:

[0067] S1: Screen microbial strains with high - efficiency calcium carbonate precipitation - inducing ability from polluted water or soil. The specific implementation process is as follows:

[0068] (1) Prepare a suspension from the polluted water body or soil sample through pretreatment, and then perform separation and purification to obtain multiple different strains of bacteria;

[0069] (2) Inoculate the above-mentioned multiple different strains of bacteria into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake flask experiment, which is the thermophilic spore of Bacillus;

[0070] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methods, including carbon source, nitrogen source, pH, and temperature, to obtain a highly active functional strain;

[0071] S3: Inoculate the bacterial suspension in S2 into wastewater containing lead ions (Pb 2+ , with an initial concentration of 100 mg / L);

[0072] S4: Add 0.5 mol / L of KHCO3 to the reaction system in S3 to provide carbonate ions;

[0073] S5: Adjust the pH of the solution in S4 to 7.0 and control the reaction temperature at 25 °C;

[0074] S6: Induce the formation of calcium carbonate precipitation through stirring reaction. The reaction time is 6 hours, and the precipitate is separated by filtration and centrifugation to achieve the fixation and removal of lead ions.

[0075] Example 2:

[0076] This example proposes a method for treating heavy metal-polluted water bodies by microbial-induced precipitation, including the following steps:

[0077] S1: Screen microbial strains with high-efficiency calcium carbonate precipitation induction ability from polluted water bodies or soils. The specific implementation process is as follows:

[0078] (1) Prepare a suspension from the polluted water body or soil sample through pretreatment, and then perform separation and purification to obtain multiple different strains of bacteria;

[0079] (2) Inoculate the above-mentioned multiple different strains of bacteria into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake flask experiment, which is the thermophilic spore of Bacillus;

[0080] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methods, including carbon source, nitrogen source, pH, and temperature, to obtain a highly active functional strain;

[0081] S3: Inoculate the bacterial suspension in S2 into wastewater containing lead ions (Pb 2+ , with an initial concentration of 100 mg / L);

[0082] S4: Add 0.5 mol / L of KHCO3 to the reaction system in S3 to provide carbonate ions;

[0083] S5: Adjust the pH of the solution in S4 to 7.5 and control the reaction temperature at 25 °C;

[0084] S6: Induce the formation of calcium carbonate precipitate through stirring reaction for 6 hours, and separate the precipitate by filtration and centrifugation to achieve the fixation and removal of lead ions.

[0085] Example 3:

[0086] This example presents a method for treating heavy metal-polluted water by microbial-induced precipitation, including the following steps:

[0087] S1: Screen microbial strains with high efficiency in inducing calcium carbonate precipitation from polluted water or soil. The specific implementation process is as follows:

[0088] (1). Make a suspension of the polluted water or soil sample through pretreatment, and then separate and purify it to obtain multiple different strains;

[0089] (2). Inoculate the above-mentioned multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake flask experiment, which is the Bacillus thermophilus spore;

[0090] S2: Optimize the culture conditions of the strain, including carbon source, nitrogen source, pH, and temperature, through single-factor experiments and response surface methodology to obtain highly active functional strains;

[0091] S3: Inoculate the bacterial suspension in S2 into the wastewater containing lead ions (Pb 2+ , with an initial concentration of 100 mg / L);

[0092] S4: Add 0.5 mol / L of KHCO3 to the reaction system in S3 to provide carbonate ions;

[0093] S5: Adjust the pH of the solution in S4 to 8.0 and control the reaction temperature at 25 °C;

[0094] S6: Induce the formation of calcium carbonate precipitate through stirring reaction for 6 hours, and separate the precipitate by filtration and centrifugation to achieve the fixation and removal of lead ions.

[0095] Example 4:

[0096] This example presents a method for treating heavy metal-polluted water by microbial-induced precipitation, including the following steps:

[0097] S1: Screen microbial strains with high-efficiency calcium carbonate precipitation induction ability from polluted water bodies or soil. The specific implementation process is as follows:

[0098] (1) Make the polluted water body or soil sample into a suspension through pretreatment, and then separate and purify it to obtain multiple different strains;

[0099] (2) Inoculate the above multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the most calcium carbonate precipitation induced through a shake flask experiment. This strain is the Bacillus thermophilic spore;

[0100] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methodology, including carbon source, nitrogen source, pH, and temperature, to obtain highly active functional strains;

[0101] S3: Inoculate the bacterial suspension in S2 into wastewater containing lead ions (Pb 2+ , with an initial concentration of 100 mg / L);

[0102] S4: Add 0.5 mol / L of KHCO3 to the reaction system in S3 to provide carbonate ions;

[0103] S5: Adjust the pH of the solution in S4 to 8.5 and control the reaction temperature at 25 °C;

[0104] S6: Induce the formation of calcium carbonate precipitation through stirring reaction. The reaction time is 6 hours. Separate the precipitate through filtration and centrifugation to achieve the fixation and removal of lead ions.

[0105] Example 5:

[0106] This example proposes a method for treating heavy metal-polluted water bodies by microbial-induced precipitation, including the following steps:

[0107] S1: Screen microbial strains with high-efficiency calcium carbonate precipitation induction ability from polluted water bodies or soil. The specific implementation process is as follows:

[0108] (1) Make the polluted water body or soil sample into a suspension through pretreatment, and then separate and purify it to obtain multiple different strains;

[0109] (2) Inoculate the above multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the most calcium carbonate precipitation induced through a shake flask experiment. This strain is the Bacillus thermophilic spore;

[0110] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methodology, including carbon source, nitrogen source, pH, and temperature, to obtain highly active functional strains;

[0111] S3: Inoculate the bacterial suspension in S2 into wastewater containing cadmium ions (Cd2+ , into the wastewater with an initial concentration of 50 mg / L;

[0112] S4: Add 0.8 mol / L of NaHCO3 to the reaction system in S3 to provide carbonate ions;

[0113] S5: Adjust the pH of the solution in S4 to 7.5 and control the reaction temperature at 25 °C;

[0114] S6: Induce the formation of calcium carbonate precipitation through stirring reaction for 12 hours, and separate the precipitate by filtration and centrifugation to achieve the fixation and removal of cadmium ions.

[0115] Example Six:

[0116] This example presents a method for treating heavy metal-polluted water bodies by microbial-induced precipitation, including the following steps:

[0117] S1: Screen microbial strains with high efficiency in inducing calcium carbonate precipitation from polluted water bodies or soil. The specific implementation process is as follows:

[0118] (1). Make the polluted water body or soil sample into a suspension through pretreatment, and then separate and purify it to obtain multiple different strains;

[0119] (2). Inoculate the above multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake flask experiment, which is the Bacillus thermophilus spore;

[0120] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methods, including carbon source, nitrogen source, pH, and temperature, to obtain highly active functional strains;

[0121] S3: Inoculate the bacterial suspension in S2 into the wastewater containing cadmium ions (Cd 2+ , with an initial concentration of 50 mg / L);

[0122] S4: Add 0.8 mol / L of NaHCO3 to the reaction system in S3 to provide carbonate ions;

[0123] S5: Adjust the pH of the solution in S4 to 7.5 and control the reaction temperature at 30 °C;

[0124] S6: Induce the formation of calcium carbonate precipitation through stirring reaction for 12 hours, and separate the precipitate by filtration and centrifugation to achieve the fixation and removal of cadmium ions.

[0125] Example Seven:

[0126] This example presents a method for treating heavy metal-polluted water bodies by microbial-induced precipitation, including the following steps:

[0127] S1: Screen microbial strains with high-efficiency ability to induce calcium carbonate precipitation from polluted water bodies or soils. The specific implementation process is as follows:

[0128] (1). Make the polluted water body or soil sample into a suspension through pretreatment, and then separate and purify it to obtain multiple different strains;

[0129] (2). Inoculate the above-mentioned multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake flask experiment, which is the thermophilic spore of Bacillus;

[0130] S2: Optimize the culture conditions of the strain through single-factor experiments and response surface methods, including carbon source, nitrogen source, pH, and temperature, to obtain highly active functional strains;

[0131] S3: Inoculate the bacterial suspension in S2 into the wastewater containing cadmium ions (Cd 2+ , with an initial concentration of 50 mg / L);

[0132] S4: Add 0.8 mol / L of NaHCO3 to the reaction system in S3 to provide carbonate ions;

[0133] S5: Adjust the pH of the solution in S4 to 7.5 and control the reaction temperature at 35 °C;

[0134] S6: Induce the formation of calcium carbonate precipitation through stirring reaction. The reaction time is 12 hours, and the precipitate is separated by filtration and centrifugation to achieve the fixation and removal of cadmium ions.

[0135] Comparative Example 1:

[0136] This comparative example proposes a method for treating heavy metal-polluted water bodies by microbial-induced precipitation. The specific steps are basically the same as those in Example 1, and the only difference is that: the strain screened from the polluted water body or soil is Bacillus megaterium;

[0137] Comparative Example 2:

[0138] This comparative example proposes a method for treating heavy metal-polluted water bodies by microbial-induced precipitation. The specific steps are basically the same as those in Example 1, and the only difference is that: the strain screened from the polluted water body or soil is Bacillus subtilis.

[0139] Experimental Example 1:

[0140] This experimental example determines the residual concentration of lead ions in Example 1, Comparative Example 1, and Comparative Example 2, and calculates the removal efficiency of lead ions according to the following formula, so as to judge the removal efficiency of different strains on lead ions:

[0141]

[0142] It can be seen from Figure 1 that under the same conditions, the heat-resistant spores of Bacillus have the highest removal efficiency for lead ions, thus achieving the maximum removal of lead ions and improving the effect of treating heavy metals in sewage.

[0143] Experimental Example Two:

[0144] In this experimental example, by measuring the sedimentation amount of calcium carbonate in Example One, Example Two, Example Three and Example Four, the influence of different pH values on the formation of calcium carbonate precipitation was judged, and the measurement results are Figure 3 shown as follows;

[0145] It can be seen from Figure 2 that under the condition of the same other conditions and a reaction pH of 8.0, the amount of calcium carbonate precipitation is the largest, which indicates that the removal effect on lead ions is the best under this pH condition, and the removal effect of metal ions in sewage can be further optimized.

[0146] Experimental Example Three:

[0147] In this experimental example, by measuring the residual concentration of cadmium ions in Example Five, Example Six and Example Seven, and calculating the removal efficiency of cadmium ions according to the following formula, the influence of different temperatures on the removal rate of cadmium ions was judged:

[0148]

[0149] It can be seen from Figure 3 that under the condition of the same other conditions and a temperature of 30 °C, the removal rate of cadmium ions is the largest, which indicates that the removal effect on cadmium ions is the best under this temperature condition, and the removal effect of metal ions in sewage can be further optimized.

[0150] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for treating heavy metal - contaminated water bodies by microbial - induced precipitation, characterized in that, It includes the following steps: S1: Screen microbial strains with high-efficiency calcium carbonate precipitation induction ability from polluted water bodies or soils; S2: Optimize the culture conditions of the strains through single-factor experiments and response surface methodology, including carbon source, nitrogen source, pH, and temperature, to obtain highly active functional strains; S3: Inoculate the bacterial suspension in S2 into the wastewater containing heavy metal ions; S4: Add bicarbonate or carbonate in the reaction system of S3 to provide carbonate ions; S5: Adjust the pH of the solution in S4 to 7.0 - 8.5 and control the reaction temperature at 25 - 35 °C; S6: Induce the formation of calcium carbonate precipitation through stirring reaction, with the reaction time being 2 - 24 hours, to achieve the fixation and removal of heavy metal ions.

2. The method for treating heavy metal-polluted water body by microbial induced precipitation according to claim 1, characterized in that, The microbial strains are strains of the genus Bacillus.

3. The method for treating heavy metal-polluted water body by microbial-induced precipitation according to claim 2, characterized in that, In S1, the specific implementation process for screening the strains of the genus Bacillus is as follows: (1). Make the polluted water body or soil sample into a suspension through pretreatment, and then conduct separation and purification to obtain multiple different strains; (2). Inoculate the above multiple different strains into a liquid medium containing a calcium source and a substrate, and obtain the strain with the largest amount of induced calcium carbonate precipitation through a shake flask experiment, which is the heat-resistant spore of Bacillus.

4. A method for treating heavy metal contaminated water body by microbial induced precipitation according to claim 1, characterized in that, In S2, the specific implementation process for optimizing the culture conditions of the strains of the genus Bacillus through single-factor experiments is as follows: (1). Divide the basal medium into 5 groups of conical flasks, each group set with different pH gradients, with pH values being 5.0, 6.0, 7.0, 8.0, and 9.0 respectively. Inoculate the bacterial suspensions of the strains of the genus Bacillus in equal amounts into the 5 groups of media, with other conditions unchanged. By measuring the growth data (OD600 value) of the strains of the genus Bacillus, the OD600 value in the medium with a pH of 7.0 is the largest; (2). Divide the carbon-source-free basal medium into four groups, and add equal amounts of glucose, sucrose, starch, and glycerol as carbon sources to each group respectively, and set the carbon-source-free basal medium as the control group. Inoculate the bacterial suspensions of the strains of the genus Bacillus in equal amounts into the 5 groups of media. By measuring the growth data (OD600 value) of the strains of the genus Bacillus, the OD600 value in the medium with glucose as the carbon source is the largest; (3). Divide the nitrogen-source-free basal medium into four groups, and add equal amounts of beef extract, peptone, yeast extract, and urea as nitrogen sources to each group respectively, and set the nitrogen-source-free basal medium as the control group. Inoculate the bacterial suspensions of the strains of the genus Bacillus in equal amounts into the 5 groups of media. By measuring the growth data (OD600 value) of the strains of the genus Bacillus, the OD600 value in the medium with beef extract as the nitrogen source is the largest; (4). Divide the basal medium into 4 groups of conical flasks, each group set with different temperature gradients, with temperatures being 20 °C, 30 °C, 40 °C, 50 °C, and 60 °C respectively. Inoculate the bacterial suspensions of the strains of the genus Bacillus in equal amounts into the 5 groups of media. By measuring the growth data (OD600 value) of the strains of the genus Bacillus, the OD600 value in the medium with a temperature of 30 °C is the largest.

5. A method for treating heavy metal contaminated water body by microbial induced precipitation according to claim 4, characterized in that, In S2, the specific implementation process for optimizing the culture conditions of the strains of the genus Bacillus through response surface methodology is as follows: (1) Select 3 - 5 factors that have a significant impact on the response value according to the results of single - factor experiments. (2) Design the experiment using Central Composite Design (CCD) and generate an experimental plan table through software. (3) Prepare the culture medium according to the conditions in the design table, culture the Bacillus species, measure the OD600 value, repeat each experimental point 3 times, and take the average value. (4) Calculate and predict the optimal culture conditions for the Bacillus species through a mathematical model: the carbon source is glucose (1.0%), the nitrogen source is beef extract (0.3%), the pH is 7.2, and the temperature is 30 °C.

6. The method for treating heavy metal contaminated water body by microbial induced precipitation according to claim 1, characterized in that, In S4, the concentration of the bicarbonate or carbonate is 0.1 - 1.0 mol / L.

7. A method for treating heavy metal-polluted water body by microbial induced precipitation according to claim 1, characterized in that, In S6, after the stirring reaction induces the formation of calcium carbonate precipitation, the precipitate needs to be separated by filtration and centrifugation to complete the removal of heavy metal ions.

8. A method for treating heavy metal contaminated water body by microbial induced precipitation according to claim 1, characterized in that, In S6, the heavy metal ions include lead ions (Pb²⁺), cadmium ions (Cd²⁺), arsenic ions (As³⁺ / As 5 ⁺), and mercury ions (Hg²⁺).

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