A method for immobilizing oxidation bacteria and its application

Abstract

The present invention provides a method for immobilizing oxidation bacteria and its application, belonging to the technical field of water pollution treatment. The method for immobilizing oxidation bacteria provided by the present invention comprises the following steps: mixing an oxidation bacteria liquid with a modified 9K liquid medium, adjusting the pH to 2-5 to obtain a bacterial mixture, mixing the biological ceramsite with the bacterial mixture to obtain a reaction solution, and regarding that the film formation of this batch is completed when the oxidation-reduction potential reaches above 550 mV; taking out the ceramsite and the reaction solution, re-adding the modified 9K liquid medium for culture, and repeating this operation until the time when the oxidation-reduction potential of each batch reaches above 550 mV remains at a stable level for at least 2-3 consecutive times, then the film formation immobilization is completed. The present invention for the first time uses biological ceramsite as a film formation carrier to form a film on oxidation bacteria, forming an oxidation film with high efficiency, which can rapidly oxidize and remove iron and manganese in wastewater in a short time.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution treatment, and particularly relates to a method for immobilizing oxidation bacteria and its application. Background Art

[0002] Heavy metal wastewater has a wide range of sources, mainly including industries such as mining and metallurgy, chemical engineering, leather making, printing and dyeing, machinery manufacturing, electronics, and instrumentation. Since heavy metals cannot be degraded in the environment, they will participate in the food chain cycle and ultimately accumulate in organisms, posing great harm to the ecological environment and human health. At present, the main methods for treating heavy metal wastewater include chemical precipitation, ion exchange, electrodialysis, adsorption method, constructed wetland method, etc. However, each method is used in a specific environment and still has problems such as large consumption of chemicals in the chemical precipitation method, large amount of sediment, difficult subsequent treatment, complex operation and management; poor stability and universality in ion exchange, electrodialysis, activated carbon adsorption, etc., and high operation costs; large land area occupied by the constructed wetland method, long treatment cycle, and the useful metals in the wastewater cannot be recovered. In recent years, it has been found that in nature, specific dominant bacterial strains can be screened and separated, and then through their own physiological and biochemical reactions or the interaction between their metabolites and metal ions, the purpose of efficient wastewater treatment can be achieved. Therefore, due to its low cost, high treatment efficiency, less secondary pollution and environmental friendliness, the biological method has gradually become a key research direction in the field of wastewater treatment.

[0003] In industrial or actual technical applications, compared with free suspended cells, immobilized microorganisms have many advantages. For example, immobilized organisms can improve the properties of organisms, such as improving the stability and mechanical strength of organisms, being easy to control the particle size and shape, not being easily blocked in a continuous reactor with high load, being easy for solid-liquid separation, simplifying the treatment process, and being easy to regenerate and reuse without being damaged. However, there are few reports on the removal of iron and manganese in mine wastewater by immobilized iron and manganese oxidation bacteria, and the existing immobilization processes have the defect of low wastewater treatment speed. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for immobilizing oxidation bacteria. When the biofilm-carrying ceramsite prepared by the method of the present invention is used to treat wastewater, it can significantly remove iron and manganese in the wastewater on the basis of high-flow wastewater injection, greatly improving the removal speed of iron and manganese in mine wastewater.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for immobilizing oxidation bacteria, comprising the following steps: mixing the oxidation bacteria liquid with a modified 9K liquid medium, adjusting the pH to 2-5 to obtain a bacterial mixture, mixing the biological ceramsite with the bacterial mixture to obtain a reaction solution, and when the oxidation-reduction potential reaches above 550 mV, it is regarded as the completion of the first batch of film hanging; taking out the ceramsite and the reaction solution, adding the modified 9K liquid medium again for cultivation, repeating this operation until the time when the oxidation-reduction potential of each batch reaches above 550 mV remains stable for at least 2-3 consecutive times, then the film hanging immobilization is completed; the concentration of Fe 2+ in the modified 9K liquid medium is 0.5 g / L - 1 g / L.

[0007] Preferably, the diameter of the biological ceramsite is 3-5 mm.

[0008] Preferably, the biological ceramsite is the pretreated biological ceramsite, and the pretreatment method comprises the following steps: soaking the cleaned biological ceramsite in an acidic solution to obtain the pretreated biological ceramsite.

[0009] Preferably, the volume ratio of the bacteria liquid to the modified 9K liquid medium is 1:9 - 3:7; the volume ratio of the taken-out reaction solution to the re-added modified 9K liquid medium is 1:9 - 3:7.

[0010] The present invention also provides a film-hanging biological ceramsite prepared by the above method.

[0011] The present invention also provides an application of the above method or the above film-hanging biological ceramsite in removing iron and / or manganese in wastewater.

[0012] The present invention also provides a method for removing iron and / or manganese in wastewater, comprising the following steps: placing the above film-hanging biological ceramsite in a filter column as a filter layer, injecting the wastewater into the filter column for filtration, and the flow rate of the wastewater injection is 8.2 L / h according to the inner diameter of the filter column of 50 mm.

[0013] Preferably, the concentration of iron in the wastewater is 0 - 1000 mg / L, and / or the concentration of manganese is 0 - 100 mg / L.

[0014] Preferably, the thickness of the filter layer is 2 / 3 of the height of the filter column, and before injecting the wastewater, the pH value of the wastewater is adjusted to above 7.5.

[0015] Preferably, when filtering with a filter column, the aeration position is opposite to the liquid inlet position.

[0016] The beneficial effects of the present invention:

[0017] For the first time, the present invention uses biological ceramsite as a carrier for film formation, forms an oxidation film with high efficiency by culturing oxidation bacteria on it, and can quickly oxidize and remove iron and manganese in wastewater in a short time in cooperation with an aeration device. The present invention places the mature ceramsite that has achieved the fastest oxidation rate through continuous film formation in a filter column, greatly accelerating the start-up time of the reaction column and improving the removal efficiency of iron and manganese in mine wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. is a schematic diagram of the wastewater treatment device of the present invention, where 1 is a filter column, 2 is biological ceramsite, 3 is a sampling port, 4 is a filter plate, 5 is an aeration device, 6 is an air pump, 7 is a valve, 8 is a funnel, 9 is a peristaltic pump, 10 is a liquid inlet tank, and 11 is a tail liquid tank;

[0019] Figure 2 FIG. is a comparison chart of the oxidation rates of bacteria immobilized by film formation in different batches;

[0020] Figure 3 is for Fe 2+ and Mn 2+ FIG. shows the test results of the limiting flow rate for the removal effects of iron and manganese in simulated wastewater with concentrations of 50 mg / L and 20 mg / L respectively;

[0021] Figure 4 is for Fe 2+ and Mn 2+ FIG. shows the test results of the limiting flow rate for the removal effects of iron and manganese in simulated wastewater with concentrations of 200 mg / L and 20 mg / L respectively;

[0022] Figure 5 is for Fe 2+ and Mn 2+ FIG. shows the test results of the limiting flow rate for the removal effects of iron and manganese in simulated wastewater with concentrations of 500 mg / L and 20 mg / L respectively; DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention provides a method for immobilizing oxidation bacteria, which includes the following steps: mixing the oxidation bacteria liquid with a modified 9K liquid medium, adjusting the pH to 2-5 to obtain a bacterial mixture, mixing the biological ceramsite with the bacterial mixture to obtain a reaction solution, and when the oxidation-reduction potential reaches above 550 mV, it is considered that the film formation of the first batch is completed; taking out the ceramsite and the reaction solution, adding the modified 9K liquid medium again for culturing, and repeating this operation until the time when the oxidation-reduction potential reaches above 550 mV in each batch remains stable for at least 2-3 consecutive times, then the film formation and immobilization are completed; the concentration of Fe 2+ in the modified 9K liquid medium is 0.5 g / L - 1 g / L.

[0024] In the present invention, the oxidation bacteria are preferably iron and manganese oxidation bacteria, more preferably Thiobacillus ferrooxidans. There is no special limitation on the specific source of the oxidation bacteria in the present invention. In the present invention, the improved 9K liquid culture medium reagent preferably consists of (NH4)2SO4, K2HPO4, KCl, MgSO4, Ca(NO3)2 and Fe 2+ components. The volume ratio of the oxidation bacteria liquid to the improved 9K liquid culture medium is preferably 1:9 to 3:7, more preferably 2:8. There is no special limitation on the specific concentration of the oxidation bacteria liquid in the present invention. There is no special limitation on the specific reagent for adjusting the pH value in the present invention. Preferably, the pH is adjusted to 3-4. There is no special limitation on the specific source of the biological ceramsite in the present invention. In the present invention, the diameter of the biological ceramsite is preferably 3-5 mm, more preferably 4 mm. The biological ceramsite is preferably the pretreated biological ceramsite. The pretreatment method preferably includes the following steps: soaking the cleaned biological ceramsite in an acidic solution to obtain the pretreated biological ceramsite. There is no special limitation on the specific type of the acidic solution in the present invention. The pH value of the acidic solution is preferably 2-5, more preferably 3-4. There is no special limitation on the cleaning method of the biological ceramsite in the present invention. The biological ceramsite and the pretreatment method selected in the present invention can shorten the biofilm formation time of the bacteria, enhance the bacteria immobilization effect, and significantly improve the oxidation rate and stability of iron and manganese ions in the wastewater. There is no special limitation on the specific compound type of adding Fe 2+ in the improved 9K liquid culture medium. In the specific embodiment of the present invention, the source of Fe 2+ is FeSO4·7H2O. In the present invention, the culture is preferably shaking culture, and the culture conditions are preferably 25°C and 170 r / min. There is no special limitation on the specific detection method of the oxidation-reduction potential in the present invention. Any conventional oxidation-reduction potential detection method in the art can be used. After the first batch of biofilm formation is completed, the ceramsite and the reaction solution are taken out. Here, the taken-out reaction solution is preferably a part of the reaction solution. After taking out the reaction solution, the improved 9K liquid culture medium is added again for culture. The volume ratio of the taken-out reaction solution to the re-added improved 9K liquid culture medium is preferably 1:9 to 3:7, more preferably 2:8. Repeating this operation refers to repeating the steps of taking out the ceramsite and the reaction solution and adding the improved 9K liquid culture medium again for culture until the time when the oxidation-reduction potential of each batch reaches more than 550 mV remains stable for at least 2-3 consecutive times, which indicates that the biofilm immobilization step is completed. The immobilization method provided by the present invention can make the oxidation bacteria evenly distributed and maintain a high bacterial population density, avoid the loss of free iron and manganese oxidation bacteria due to hydraulic shock. In addition, the secondary minerals produced by the oxidation bacteria will adhere to the surface of the ceramsite, reduce the precipitation and accumulation of minerals, and further improve the stability and mechanical strength of the reaction system.

[0025] The present invention also provides a biofilm-carrying ceramsite prepared by the above method, and the application of the above method or the biofilm-carrying ceramsite in removing iron and / or manganese in wastewater. In the present invention, the wastewater includes mine wastewater.

[0026] The present invention also provides a method for removing iron and / or manganese in wastewater, comprising the following steps: placing the above biofilm-carrying ceramsite in a filter column as a filter layer, and injecting the wastewater into the filter column for filtration, wherein the flow rate of the wastewater injection is 8.2 L / h or less according to the inner diameter of the filter column of 50 mm.

[0027] The present invention has no special requirements for the material of the filter column, and the filter column is used to simulate the filter tank in actual production. The present invention places the mature ceramsite that has reached the fastest oxidation rate after continuous biofilm formation in the filter column, which greatly shortens the start-up time of the reaction column. When using the method of the present invention to remove iron and / or manganese in wastewater, the preferred operation mode is that the aeration position is opposite to the liquid inlet position, that is, if aeration is carried out at the top, the liquid enters from the bottom and exits from the top, and if aeration is carried out at the bottom, the liquid enters from the top and exits from the bottom. When using the method of the present invention to remove iron and / or manganese in wastewater, the preferred device diagram is as Figure 1 shown. If the steam and water flow in the same direction (upward flow with bottom aeration), the aeration disturbance will weaken the physical interception ability of the filter layer, resulting in the ineffective interception of iron and manganese oxides and causing the iron and manganese concentrations to exceed the standard. Finally, the present invention selects the operation mode of bottom aeration, liquid inlet from the top and liquid outlet from the bottom, which further ensures that iron and manganese in the wastewater can be rapidly oxidized and removed in a short time.

[0028] In the present invention, the concentration of iron in the wastewater is preferably 0 - 1000 mg / L, more preferably 50 - 500 mg / L, and the concentration of manganese is preferably 0 - 100 mg / L, more preferably 0 - 20 mg / L. In the present invention, the thickness of the filter layer is preferably 2 / 3 of the height of the filter column. The defined filter layer thickness in the present invention helps to improve the removal effect of manganese in the wastewater. Before injecting the wastewater, it is preferred to adjust the pH value of the wastewater to 5.5 - 8.5, and more preferably to adjust the pH value of the wastewater to above 7.5.

[0029] In the present invention, the flow rate of the wastewater injection is 2.3 L / h - 8.2 L / h based on the inner diameter of the filter column being 50 mm. If the inner diameter of the filter column or filter tank is higher than 50 mm, it indicates that the flow rate of the wastewater inlet will also increase accordingly. Since in actual industrial applications, the faster the treatment speed, the higher the economic benefits. Therefore, the method of the present invention not only ensures the removal efficiency but also achieves the technical effect of significantly improving the speed of treating wastewater. When using the method of the present invention to remove iron and manganese from wastewater, the adjustment of the flow rate should be gradually and slowly adjusted, the flow rate span should not be too large, and after the flow rate is increased, it should be operated stably for a period of time. Excessive changes in the flow rate will cause the oxidized bacteria fixed on the ceramsite and the free oxidized bacteria to be washed away by the water flow, thus affecting the removal efficiency. In the present invention, the flow rate adjustment preferably starts from a flow rate of 2.3 L / h, and is adjusted to the next flow rate every 0.5 h. The span of the two-stage flow rate is preferably 0.6 - 0.9 L / h.

[0030] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0031] In the following embodiments, unless otherwise specified, all are conventional methods.

[0032] In the following embodiments, the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.

[0033] Example 1

[0034] Biological ceramsite pretreatment: Weigh 1000 g of biological ceramsite with a diameter of 3 - 5 mm, and place it in an ultrasonic cleaning tank with a power P = 1.5 W / cm 2 , a frequency F = 26 KHz, and a water temperature of 30 °C for 3 h, and then soak it in a solution with a pH = 2.0 for 12 h to enable the biological ceramsite to adapt to the acidic reaction conditions.

[0035] Bacterial continuous film-forming test: Take 2 500 mL conical flasks, add 20 mL of Thiobacillus ferrooxidans bacterial solution and 180 mL of modified 9K liquid medium (the composition of the modified 9K liquid medium is shown in Table 1), and adjust the pH of the system to 2.0 with 1:1 H2SO4 to obtain a bacterial mixture. Mix the pretreated biological ceramsite with the bacterial mixture to obtain a reaction solution, and place it in a shaker at 25 °C and 170 r / min for constant-temperature oscillation culture. During the film-forming period, samples are taken regularly to measure the pH value and Eh value of the solution. When the redox potential reaches above 550 mV, it is considered that the film-forming of this batch is completed. Take out the ceramsite and 10% of the reaction solution, and re-add the modified 9K liquid medium (ensure that the volume ratio of the taken-out reaction solution to the re-added modified 9K liquid medium is 1:9), and repeat this operation until the time when the redox potential of each batch reaches above 550 mV (Fe in the solution 2+If the stable level is maintained for three consecutive batches of biological oxidation time, the bio-ceramsite film-forming test is considered completed.

[0036] Take the group without adding ceramsite as the blank group and compare it with the above bio-ceramsite group.

[0037] Table 1 Composition of Modified 9K Medium

[0038]

[0039] Compare the oxidation rates under different batches, and the results are as Figure 2 shown. It can be seen from Figure 2 that as the number of film-forming times increases, the change rate of Eh in the solution accelerates accordingly. That is, the time for the potential in the solution to reach above 550 mV is shortened from about 48 h in the first film-forming to about 11 h in the eighth film-forming, indicating that adding a bio-ceramsite carrier can significantly accelerate its oxidation rate. The co-oxidation rate of bacteria in the film and free bacteria on the bio-ceramsite is about 3 times that of free bacteria.

[0040] Example 2

[0041] Bio-ceramsite pretreatment: Weigh a certain amount of bio-ceramsite with a diameter of 3 - 5 mm, put it into an ultrasonic cleaning tank with a power P = 1.5 W / cm 2 , a frequency F = 26 KHz, and a water temperature of 30 °C for 3 h, and then soak it in a solution with pH = 2.0 for 12 h to make the bio-ceramsite adapt to acidic reaction conditions.

[0042] Bacterial continuous film-forming test: Take 2 250 mL conical flasks, add 20 mL of Thiobacillus ferrooxidans bacterial solution and 180 mL of modified 9K liquid medium (the composition of the modified 9K liquid medium is shown in Table 2), and adjust the pH of the system to 2.0 with 1:1 H2SO4 to obtain a bacterial mixture. Mix the pretreated bio-ceramsite with the bacterial mixture to obtain a reaction solution, and place it in a shaker at 25 °C and 170 r / min for constant-temperature oscillation culture. During the film-forming period, regularly sample to measure the pH value and Eh value of the solution. When the oxidation-reduction potential reaches above 550 mV, this batch of film-forming is considered completed. Take out the ceramsite and 20% of the reaction solution, and re-add the modified 9K liquid medium (ensure that the volume ratio of the taken-out reaction solution to the re-added modified 9K liquid medium is 1:9), and repeat this operation until the time for the oxidation-reduction potential to reach above 550 mV in each batch (F e2+ in the solution, biological oxidation time) is maintained at a stable level for two consecutive batches, then the bio-ceramsite film-forming test is considered completed.

[0043] Take the group without adding ceramsite as the blank group and compare it with the above bio-ceramsite group.

[0044] Table 2 Composition of Modified 9K Medium

[0045]

[0046] Example 3

[0047] The biofilm-carrying ceramsite obtained in Example 1 was filled in an acrylic filter column to simulate the filter tank in actual production. The filter column was 800 mm high and 50 mm in inner diameter. The biofilm-carrying ceramsite was used as the filter layer with a thickness of 533 mm. The effective liquid volume of the reactor was about 500 mL. The test device was as shown in Figure 1 . The reaction column was continuously operated at an aeration rate of 38 L / min, a pH value of 5.5, and room temperature.

[0048] The simulated wastewater was prepared by adding FeSO4·7H2O and MnSO4 to the 9K medium described in Table 1, where the Fe 2+ concentration was added at 50 mg / L and the Mn 2+ concentration was uniformly added at 20 mg / L. The pH value of the simulated wastewater was adjusted to 5.5 with lime milk. The test device started to operate at a flow rate of 2.3 L / h and was adjusted to the next flow rate every 0.5 h (the flow rate gradient was set as 2.3, 3.1, 3.8, 4.5, 5.4, 6.2, 6.9, 7.5 L / h). After the flow rate was stably operated for 0.5 h, the water sample was taken out, and the influent pH value, effluent pH value, and temperature were recorded during the process. The effluent solution was filtered through a 0.1-μm microporous filter membrane, 10 ml of the filtrate was taken, and the total Fe and Mn concentrations in the tail liquid were analyzed by flame atomic absorption spectrometry. The results are shown in Table 3 and Figure 3 .

[0049] Table 3 Experimental results of the limiting flow rate for the removal of iron and manganese in the simulated wastewater with Fe 2+ and Mn 2+ concentrations of 50 mg / L and 20 mg / L respectively

[0050]

[0051]

[0052] From the data in Table 3 and Figure 3 , it can be seen that the oxidation rate of Fe 2+ by the biofilm-carrying ceramsite reaction column of the present invention is excellent in the whole stage from a flow rate of 2.3 L / h to 7.5 L / h. The effluent iron concentration is below 0.4 mg / L, and the iron removal rate is as high as over 99.2%. The effluent manganese concentration starts to increase significantly at a flow rate of 4.5 L / h and reaches a peak value of 1.58 mg / L at 5.4 L / h. However, the overall manganese removal effect is good. The average effluent manganese concentration is 0.882 mg / L, and the manganese removal rate can reach over 92%.

[0053] Example 4

[0054] The difference from Example 3 is that Fe 2+ is added at a concentration of 200 mg / L, and the flow rate gradient is increased to 8.2 L / h after 7.5 L / h described in Example 3, and the rest are the same as Example 3. The results are shown in Table 4 and Figure 4 as follows.

[0055] Table 4 Removal efficiency of iron and manganese in simulated wastewater with Fe 2+ and Mn 2+ at concentrations of 200 mg / L and 20 mg / L respectively - Results of the limiting flow rate test

[0056]

[0057] From the data in Table 4 and Figure 4 it can be seen that for the biofilm - loaded biological ceramsite reaction column of the present invention, the oxidation rate of Fe 2+ is good throughout the entire stage with a flow rate ranging from 2.3 L / h to 8.2 L / h. The average effluent iron concentration is 0.201 mg / L, the peak value is 0.398 mg / L, and the iron removal rate is as high as over 99.8%; the effluent manganese concentration increases within a small range as the flow rate increases, and the overall removal effect is good. The average effluent manganese concentration is 0.587 mg / L, the peak value is 0.838 mg / L, and the manganese removal rate can reach over 95.8%.

[0058] Example 5

[0059] The difference from Example 3 is that Fe 2+ is added at a concentration of 500 mg / L, and the flow rate gradient is increased to 8.2 L / h after 7.5 L / h described in Example 3, and the rest are the same as Example 3. The results are shown in Table 5 and Figure 5 as follows.

[0060] Table 5 Removal efficiency of iron and manganese in simulated wastewater with Fe 2+ and Mn 2+ at concentrations of 500 mg / L and 20 mg / L respectively - Results of the limiting flow rate test

[0061]

[0062] From the data in Table 5 and Figure 5 it can be seen that the biofilm - loaded biological ceramsite reaction column of the present invention shows abnormal performance at a flow rate of 2.3 L / h. At this flow rate, the effluent iron and manganese concentrations are both at peak values, which may be because the device has not yet been stably operated and the microorganisms in the biological filter layer have not adapted to the new concentration environment. At other flow rates, the iron and manganese oxidation and removal effects are good. The average effluent iron and manganese concentrations are 0.306 mg / L and 0.499 mg / L respectively, and the iron and manganese removal rates can reach 99.8% and over 95.8% respectively.

[0063] Example 6

[0064] It is different from Example 3 in that Fe 2+ is added at a concentration of 1000 mg / L, and the flow rate gradient is set to not contain 7.5 L / h described in Example 3, and the rest are the same as in Example 3. The results are shown in Table 6. Table 6 shows the Fe 2+ and Mn 2+ Results of the ultimate flow rate test for the removal of iron and manganese in simulated wastewater with concentrations of 1000 mg / L and 20 mg / L respectively

[0065]

[0066]

[0067] It can be seen from the data in Table 6 that with the increase of the flow rate in the bio-ceramsite reaction column with attached film of the present invention, the iron and manganese concentrations in the effluent are not satisfactory. This may be because the stable operation time of the device is too short, and the microorganisms in the filter layer cannot process iron and manganese ions at this concentration in a short time. It may also be because the addition amount of the alkaline reagent is not enough, and the average effluent pH value is only about 5.62, and the oxidized iron and manganese ions cannot be completely precipitated.

[0068] Example 7

[0069] Removal effect of iron and manganese in real wastewater in the bio-ceramsite reaction column with attached film of the present invention at different flow rates

[0070] The total Fe and Mn concentrations in the real wastewater measured by flame atomic absorption spectrometry are 131.85 mg / L and 5.895 mg / L respectively. The specific test process is the same as in Example 3, except that real wastewater is used instead of the simulated wastewater in Example 3, and the flow rate of 8.2 L / h is added, and the rest are the same as in Example 3. The results are shown in Table 7.

[0071] Table 7 Results of the ultimate flow rate test for the removal of iron and manganese in real wastewater

[0072]

[0073] It can be seen from the data in Table 7 that the bio-ceramsite reaction column with attached film of the present invention shows good performance in the oxidation and removal of iron at various flow rates. The average effluent iron concentration is 0.379 mg / L, and the peak value is the effluent iron concentration at the maximum flow rate of 8.2 L / h, which is 0.866 mg / L, and the iron removal rate can reach more than 99.3%. However, at the initial flow rate of 2.3 L / h, the phenomenon that the manganese concentration in the effluent is higher than that in the influent appears. This may be because during the influent process in the upper part of the filter layer, the high-valent manganese oxide originally attached to the bio-ceramsite directly contacts the high-concentration Fe 2+ and the high-concentration Fe 2+ reduces it and dissolves out Mn2+ , with the increase of the flow rate and the continuous operation of the reaction column, the manganese concentration in the effluent gradually stabilizes. Except for the initial abnormal data, the average manganese removal rate is 95.18%.

[0074] It can be seen from the test results of treating simulated wastewater and real wastewater at different concentrations in Examples 3 to 7 that the effluent concentration of manganese is basically greater than that of iron. This is because under neutral reaction conditions, Fe 2+ can be rapidly oxidized by dissolved oxygen and bacteria, while Mn 2+ can hardly be oxidized by dissolved oxygen and can only be oxidized under the catalysis of extracellular enzymes of bacteria. In addition, the difference in redox potential between Mn 2+ and the Fe 2+ system is as high as 0.4V, which makes Fe 2+ be preferentially oxidized in the filter column. Therefore, the presence of Fe 2+ will delay the oxidation process of Mn 2+ .

[0075] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for removing iron and manganese from wastewater, characterized in that, The method includes the following steps: placing the biofilm-carrying ceramsite in a filter column as a filter layer, injecting wastewater into the filter column for filtration, and the flow rate of the wastewater injection is 8.2 L / h or less based on the inner diameter of the filter column being 50 mm; the concentration of iron in the wastewater is 50 - 1000 mg / L, and the concentration of manganese is 20 - 100 mg / L; the thickness of the filter layer is 2 / 3 of the height of the filter column, and before injecting the wastewater, adjust the pH value of the wastewater to above 7.5; The preparation method of the biofilm-carrying ceramsite includes the following steps: Mix the oxidized bacterial liquid with the modified 9K liquid medium, adjust the pH to 2-5 to obtain a bacterial mixture, mix the biofilm-carrying ceramsite with the bacterial mixture to obtain a reaction solution. When the oxidation-reduction potential reaches above 550 mV, it is regarded as the completion of the first batch of biofilm formation; Take out the ceramsite and the reaction solution, add the modified 9K liquid medium again for cultivation, and repeat this operation until the time when the oxidation-reduction potential of each batch reaches above 550 mV remains at a stable level for at least 2-3 consecutive times, then the biofilm immobilization is completed; The concentration of Fe 2+ in the modified 9K liquid medium is 0.5 g / L - 1 g / L; the biofilm-carrying ceramsite is the pretreated biofilm-carrying ceramsite, and the pretreatment method includes the following steps: soaking the cleaned biofilm-carrying ceramsite in an acidic solution to obtain the pretreated biofilm-carrying ceramsite; the volume ratio of the iron-oxidizing bacteria liquid to the modified 9K liquid medium is 1:9 to 3:7; the volume ratio of the taken-out reaction liquid to the re-added modified 9K liquid medium is 1:9 to 3:7; the iron-oxidizing bacteria is Thiobacillus ferrooxidans; the pH value of the acidic solution is 2 - 5.

2. The method according to claim 1, wherein the diameter of the biofilm-carrying ceramsite is 3 - 5 mm.

3. The method according to claim 1, wherein When using the filter column for filtration, the aeration position is opposite to the liquid inlet position.

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