A new biofilm treatment method for xanthate contamination of flotation wastewater

Abstract

The invention discloses a novel biofilm treatment method for xanthate pollution in flotation wastewater, comprising the following steps: using tailings pond sediments taken from heavy metal mine pollution sites, using selective culture medium to screen and enrich xanthate degradation functional bacteria therefrom, and performing subculture; injecting xanthate functional degradation bacteria into a membrane aeration biofilm reaction system, using mineral processing wastewater containing xanthate as a matrix, passing oxygen-containing gas, and culturing biofilm; when the xanthate concentration in the system effluent of the membrane aeration biofilm reaction system drops below 1.0 mg / L, the enrichment of biofilm is completed; based on the xanthate degradation efficiency of the biofilm under different environmental parameters, determining the optimal operation strategy for the membrane aeration bioreactor system; and based on the optimal operation strategy, passing mineral processing wastewater for in-situ biological treatment, and returning the treated reused water to the mineral processing workshop for reuse. The method is green, environmentally friendly, and economical, does not generate secondary pollution, and efficiently and completely treats xanthate.

Description

Technical Field

[0001] The invention relates to the field of water treatment, in particular to a novel biofilm treatment method for xanthate-contaminated flotation wastewater. Background Art

[0002] In the flotation capture process of heavy metal sulfide ores, a large amount of flotation reagent (xanthate) is often required. Xanthate has the characteristics of carcinogenicity, teratogenicity and high toxicity at low concentrations. For example, when the concentration in water exceeds 50 ug / L, it will produce odor. When it exceeds 180 ug / L, it can cause a large number of deaths of fry in the yolk sac exhaustion period. When it exceeds 320 ug / L, it can induce deformities in loach embryos. If it is not properly treated, discharging it into natural water bodies may pose a serious threat to organisms and ecosystems. Therefore, the discharge concentration of xanthate in the mine wastewater treatment process is required to be relatively high. In order to protect the ecological environment of mines, the removal of xanthate in mineral processing wastewater is imminent.

[0003] At present, physical or chemical methods need to add a large amount of chemical reagents (such as sodium hypochlorite, Fenton reagent, iron sulfate, etc.) to the mineral processing wastewater, which is easy to produce carbon disulfide and cause secondary pollution, and the operation is cumbersome and costly. The biological method is widely used in the removal of various organic pollutants because of its advantages such as low cost and low energy consumption. Existing applications are based on traditional biological methods such as biological contact oxidation method and SBR method, which use a single strain of bacteria to biodegrade xanthate, but there is a high concentration of xanthate with strong toxicity to organisms, resulting in poor treatment effect (see Hu Xuewei, Hu Yuanwei, Zuo Xiaolin. A biological treatment process for flotation wastewater [P]. Yunnan Province: CN105800796B, 2019-04-09.). In addition, substances such as carbon disulfide and alcohols that are easy to cause secondary pollution are easily produced during the treatment process, which have not been paid attention to and studied. Furthermore, some researchers have used the selected xanthate-degrading bacteria and added a slow-release carbon source for ex situ biological treatment (see Wang Li, Tang Honghu, Ji Bin, et al. A combined treatment method for mineral processing wastewater containing xanthate residues [P]. Hunan: CN107487952A, 2017-12-19.), but the treatment speed is slow and cannot meet the needs of large-scale mineral processing wastewater treatment and reuse in actual mines. In addition, the existing biological treatment process generally uses aeration technology, which greatly increases the treatment energy consumption and treatment cost. Therefore, the development of a new green and efficient biological treatment method for xanthate flotation wastewater is a long-term demand in the field of mineral processing wastewater treatment.

[0004] Membrane aerated biofilm reactor is an emerging wastewater treatment technology based on electron donor and acceptor back diffusion. Compared with traditional aeration, membrane aerated biofilm reactor can achieve bubble-free aeration, high gas utilization efficiency, and minimize air pollution caused by the diffusion of volatile organic compounds (see Gong W, Fan A, Zhang H, et al. Cowmanure anaerobic fermentation effluent treatment by oxygen-based membraneaerated biofilm reactor[J]. Chemical Engineering Journal, 2020, 3(95): 511-524.). Secondly, studies have shown that the heterogeneous mass transfer characteristics in membrane aerated biofilm reactor can achieve a unique microbial community structure on the membrane surface, increase biomass while reducing the inhibitory effect on the toxicity of organic pollutants (see Zheng CW, Luo YH, Long X, et al. The structure of biodegradable surfactants shaped themicrobial community, antimicrobial resistance, and potential for horizontalgene transfer[J]. Water Research, 2023, 23(6): 119-944.). Finally, membrane aerated biofilm reactors have been widely used to remove refractory organic compounds from wastewater, such as quaternary ammonium compounds (QACs) and CTAB (see Gong W, Fan A, Zhang H, et al. Cow manure anaerobic fermentation effluent treatment by oxygen-based membrane aerated biofilm reactor [J]. Chemical Engineering Journal, 2020, 3 (95): 511-524.). At present, there is no research on the method of regulating the gas mass transfer efficiency in the membrane aerated biofilm reactor to cultivate functional bacteria that can efficiently degrade xanthate in the mineral processing wastewater, thereby achieving efficient and complete treatment of xanthate in the mineral processing wastewater. Summary of the invention

[0005] In view of the problems of the prior art that the complete biodegradation of xanthate cannot be achieved, secondary pollution is generated, and the treatment cost is high, the present application provides a novel biofilm treatment method for xanthate contamination of flotation wastewater. The method firstly adopts a biological treatment method to reduce the difficulty of cultivation and implementation cost of biological treatment; secondly, the energy consumption and treatment cost are greatly saved in the process of bubble-free aeration, and the gaseous pollutants will not be released into the atmosphere during the treatment process to cause more difficult to treat secondary pollution; thirdly, the special heterogeneous mass transfer structure of the membrane aeration biofilm reactor improves the activity of xanthate functional degradation bacteria, while reducing the toxic effect of xanthate on microorganisms, and realizing efficient biodegradation of xanthate.

[0006] To achieve the above-mentioned purpose, one aspect of the present invention is to provide a biofilm treatment method for xanthate contamination of flotation wastewater, comprising the following steps: (a) using tailings pond sediments taken from heavy metal mine contamination sites, screening and enriching xanthate-degrading functional bacteria therefrom using a selective culture medium, and subculturing the xanthate-degrading functional bacteria; (b) after the subculture is completed, injecting the xanthate-degrading functional bacteria into a membrane aerated biofilm reaction system, using the mineral processing wastewater containing xanthate as a matrix, introducing oxygen-containing gas, and culturing the biofilm; (c) after the concentrations of potassium amyl xanthate, potassium butyl xanthate, and potassium isopropyl xanthate in the system effluent of the membrane aerated biofilm reaction system are all reduced to 1.0 (d) determining the optimal operation strategy for the membrane aeration bioreactor system based on the xanthate degradation efficiency of the biofilm under different environmental parameters; and (e) based on the optimal operation strategy, placing the membrane aeration bioreactor system in the heavy metal mine contaminated site, introducing mineral processing wastewater for in-situ biological treatment, and returning the treated reused water to the mineral processing workshop for reuse.

[0007] In a possible implementation of the method of the present invention, the selective culture medium comprises: 200-500 mg / L of one or more of potassium amyl xanthate, potassium butyl xanthate, potassium isopropyl xanthate, 53.04 g / L of KH2PO4, 106.10 g / L of K2HPO4, 36.20 g / L of NaCl, 3.00 g / L of MgCl2·6H2O, 1.00 g / L of CaCl2·2H2O, 2.20 g / L of FeCl2, 0.14 g / L of ZnCl2 and 1 mL of trace element stock solution.

[0008] In a possible implementation of the method of the present invention, the trace element stock solution includes: 0.14 g / L ZnCl2, 0.20 g / L MnCl2·4H2O, 0.06 g / L H3BO3, 0.48 g / L CoCl2·6H2O, 0.48 g / L Na2MoO4, 0.09 g / L CuCl2·2H2O, 0.12 g / L NiCl2·6H2O, 0.17 g / L Na2WO4·2H2O and 0.13 g / L Na2SeO4·5H2O.

[0009] In a possible implementation of the method of the present invention, the oxygen-containing gas is pure oxygen, air or a mixture of the two.

[0010] In a possible implementation of the method of the present invention, the environmental parameters include: a hydraulic retention time of 6 to 24 h, an oxygen-containing gas partial pressure of 3 to 10 psig, and a xanthate concentration of 100 to 200 mg / L in the mineral processing wastewater.

[0011] In a possible implementation of the method of the present invention, the optimal operating condition is a correlation between hydraulic retention time, oxygen-containing gas pressure and xanthate concentration obtained by combining experiments and relevant theoretical calculations.

[0012] In a possible implementation of the method of the present invention, the pH of the mineral processing wastewater is adjusted to 5.5 to 9.5 before being introduced into the membrane aeration biofilm reactor in step (e).

[0013] In a possible implementation of the method of the present invention, the xanthate concentration in the ore dressing wastewater in the step (e) is 100-300 mg / L, and the xanthate type is an alkyl group containing 2 to 5 carbon atoms.

[0014] In a possible implementation of the method of the present invention, the xanthate-degrading functional bacteria include Flavobacterium, Sediminibacterium and Mesorhizobium One or more of .

[0015] Another aspect of the present invention is to provide the use of any of the above methods in removing xanthate, a refractory organic flotation agent, from mineral processing wastewater in heavy metal mining areas.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) Green, environmentally friendly and economical: The aeration membrane technology is used to cultivate the biofilm formed by xanthate-degrading functional bacteria, which greatly saves energy consumption and processing costs during the bubble-free aeration process.

[0018] (2) No secondary pollution: During the treatment process of this system, the gaseous pollutant CS2 will not be released into the atmosphere to cause secondary pollution that is more difficult to treat.

[0019] (3) Efficient and complete treatment: The special heterogeneous mass transfer structure of the membrane aerated biofilm reactor improves the activity of xanthate degradation and bacteria degradation, while reducing the toxicity of xanthate to microorganisms, achieving efficient biodegradation of xanthate and controlling the xanthate in the effluent to below 1.0 mg / L.

[0020] The above contents of the present application will be more concise and understandable in the following description of multiple embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings of the present application will be provided below. These drawings are only for embodying the present application in a more intuitive form. They are exemplary and are not intended to limit the scope of the present application.

[0022] Figure 1 It is a structural schematic diagram of the membrane aeration biofilm reaction system of the present invention;

[0023] Figure 2 A standard curve of potassium amyl xanthate in one embodiment of the method of the present invention;

[0024] Figure 3 A standard curve of potassium butyl xanthate in one embodiment of the method of the present invention;

[0025] Figure 4 A standard curve of potassium isopropyl xanthate in one embodiment of the method of the present invention;

[0026] Figure 5 This is a diagram showing the degradation effect of three xanthates by biofilm in one embodiment of the method of the present invention;

[0027] Figure 6 A graph showing the effect of xanthate degradation under different hydraulic retention time conditions in one embodiment of the method of the present invention;

[0028] Figure 7 A graph showing the effect of xanthate degradation under different oxygen pressure conditions in one embodiment of the method of the present invention;

[0029] Figure 8 A graph showing the change in xanthate degradation effect under different substrate concentration conditions in one embodiment of the method of the present invention;

[0030] Fig. 9 A graph showing changes in carbon disulfide concentration during a batch experiment in one embodiment of the method of the present invention; and

[0031] Fig.10This is a relative abundance diagram of xanthate-degrading functional bacteria in the biofilm of the membrane aeration biofilm reaction system in one embodiment of the present invention. DETAILED DESCRIPTION

[0032] To make the present application easier to understand, the present application is further described below in conjunction with specific examples. The experimental methods described in this application are all conventional methods unless otherwise specified; the materials described are all commercially available unless otherwise specified. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application. If there is any inconsistency, the meaning described in this specification or the meaning derived from the contents recorded in this specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0033] In order to accurately describe the technical contents in this application and to accurately understand the present invention, the following explanations or definitions are given for the words and terms used in this specification before describing the specific implementation methods.

[0034] The words "one embodiment" or "an embodiment" as used in this specification means that a particular feature, step, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily all refer to the same embodiment, but may refer to the same embodiment. In addition, in one or more embodiments, the particular features, steps, or characteristics can be combined in any suitable manner, as will be apparent to one of ordinary skill in the art from this application.

[0035] In view of the many problems and challenges of the prior art, the inventors of the present invention have discovered a method for effectively treating xanthate pollution in flotation wastewater by inoculating selectively screened and cultured xanthate-degrading functional bacteria in a membrane aeration biofilm reactor. The principle of the present invention is as follows. During the aerobic biodegradation process of xanthate, many intermediates are produced, such as carbon disulfide (CS2), xanthogenic acid (ROCS2H), sulfide ions (S 2- ) and alcohol substances, etc., will have a certain degree of negative impact on the ecological environment. The method of the present invention first selectively screens and cultivates xanthate-degrading functional bacteria, and then inoculates the cultivated xanthate-degrading functional bacteria into a membrane aerated biofilm reactor to form a biofilm, which can oxidize and degrade xanthate into SO4 2- , CO2 and H2O, reducing the generation of gaseous pollutants such as CS2, while greatly reducing aeration costs and energy consumption. The chemical formula of the reaction between the biofilm of xanthate-degrading functional bacteria and xanthate includes:

[0036]

[0037]

[0038]

[0039] The novel biofilm treatment method for xanthate contamination of flotation wastewater of the present invention comprises the step (a) of using tailings pond sediments taken from a heavy metal mine contaminated site, screening and enriching xanthate-degrading functional bacteria therefrom using a selective culture medium, and subculturing the xanthate-degrading functional bacteria. In some embodiments of the method of the present invention, three locations of the heavy metal mine contaminated site are sampled as tailings pond sediments, and the xanthate concentration, COD, heavy metals and other indicators in the sampled sediments are detected. If xanthate contamination is found at all three sampling points, the xanthate-degrading functional bacteria are cultured using the culture medium. In some embodiments of the method of the present invention, the selective culture medium comprises: 200-500 mg / L of one or more of potassium amyl xanthate, potassium butyl xanthate, potassium isopropyl xanthate, 53.04 g / L of KH2PO4, 106.10 g / L of K2HPO4, 36.20 g / L of NaCl, 3.00 g / L of MgCl2·6H2O, 1.00 g / L of CaCl2·2H2O, 2.20 g / L of FeCl2, 0.14 g / L of ZnCl2 and 1 mL of trace element stock solution. In some embodiments of the method of the present invention, the trace element stock solution includes: 0.14 g / L ZnCl2, 0.20 g / L MnCl2·4H2O, 0.06 g / L H3BO3, 0.48 g / L CoCl2·6H2O, 0.48 g / L Na2MoO4, 0.09 g / L CuCl2·2H2O, 0.12 g / L NiCl2·6H2O, 0.17 g / L Na2WO4·2H2O and 0.13 g / L Na2SeO4·5H2O. In some embodiments of the method of the present invention, xanthate functional bacteria are cultured by adding xanthate of different gradient concentrations (200 mg / L, 500 mg / L), and the xanthate concentration is detected every 12 hours. It can be completely degraded within 72 hours, and the xanthate concentration drops below 1 mg / L, and the passage is completed. In some embodiments of the present invention, xanthate degrading functional bacteria include Flavobacterium, Sediminibacterium and Mesorhizobium One or more of. It is understandable that the xanthate functional degradation bacteria of the present invention are selectively screened and cultured from tailings pond sediments, so the xanthate functional bacteria screened and cultured from tailings pond sediments in different regions or even at different times may have certain changes in composition and proportion of each component. However, such changes will not substantially affect the ability of the bacteria to degrade xanthate.

[0040] The novel biofilm treatment method for xanthate contamination of flotation wastewater of the present invention comprises the following steps: (b) after the passage is completed, the xanthate functional degradation bacteria are injected into a membrane aeration biofilm reaction system, the mineral processing wastewater containing xanthate is used as a matrix, oxygen-containing gas is introduced, and biofilm is cultivated. The membrane aeration biofilm reaction system used in the novel biofilm treatment method for xanthate contamination of flotation wastewater of the present invention is as follows: Figure 1 As shown, it includes the following components: (1) a reaction system body, (2) an aeration pump, and (3) a vent membrane assembly. In some embodiments of the method of the present invention, the permeable membrane assembly (3) is placed in the reaction system, and then the system is inoculated with xanthate functional degradation bacteria that have been screened and cultured, and the inoculated reaction system is sunk into the mineral processing wastewater, and pure oxygen, air or a combination thereof is introduced into the membrane through (2) an oxygen generator / aeration pump to ensure that a small amount of bubbles overflow from the membrane pores until a biofilm is formed on the vent membrane; finally, the enrichment degree of the biofilm is evaluated by testing the xanthate content in the effluent of the system. In some embodiments of the method of the present invention, the xanthate concentration of the mineral processing wastewater in step (b) is 200 mg / L, the oxygen pressure is 10 psig, and the hydraulic retention time is 12 h. In some embodiments of the method of the present invention, the duration of step (b) is 60 days. It is understandable that the duration of step (b) is affected by many factors, including but not limited to the xanthate concentration of the mineral processing wastewater, the oxygen pressure on the surface of the aeration membrane assembly, the hydraulic retention time, the temperature and other factors that can affect the growth of xanthate functional degrading bacteria into biofilms.

[0041] The novel biofilm treatment method for xanthate contamination of flotation wastewater of the present invention comprises step (c) when the concentrations of potassium amyl xanthate, potassium butyl xanthate and potassium isopropyl xanthate in the system effluent of the membrane aeration biofilm reaction system are all reduced to below 1.0 mg / L, the enrichment of the biofilm is completed.

[0042] The novel biofilm treatment method for xanthate contamination of flotation wastewater of the present invention comprises step (d): determining the optimal operation strategy for the membrane aeration bioreactor system based on the xanthate degradation efficiency of the biofilm under different environmental parameters. In some embodiments of the present invention, the different environmental parameters include: a hydraulic retention time of 6 to 24 h, an oxygen-containing gas partial pressure of 3 to 10 psig, and a xanthate concentration of 100 to 200 mg / L in the beneficiation wastewater. In some embodiments of the present invention, the concentration change of carbon disulfide produced during the biodegradation process is detected by batch experiments to evaluate the xanthate degradation efficiency. In some embodiments of the present invention, the optimal operating condition is the correlation between the hydraulic retention time, the oxygen-containing gas pressure, and the xanthate concentration obtained by combining experiments with relevant theoretical calculations.

[0043] The novel biofilm treatment method for xanthate contamination of flotation wastewater of the present invention comprises step (e): Based on the optimal operation strategy, the membrane aeration bioreactor system is placed in the heavy metal mine contaminated site, and the ore dressing wastewater is introduced for in-situ biological treatment, and the treated recycled water is returned to the ore dressing workshop for reuse. In some embodiments of the method of the present invention, the pH of the ore dressing wastewater is adjusted to 5.5-9.5 before being introduced into the membrane aeration biofilm reactor in step (e). In some embodiments of the present invention, the xanthate concentration in the ore dressing wastewater in step (e) is 100-300 mg / L, and the xanthate type is an alkyl group containing 2-5 carbon atoms.

[0044] The various aspects of the present invention are further described below in conjunction with a specific embodiment of the method of the present invention. Example

[0045] A novel biofilm treatment method for xanthate flotation wastewater comprises the following specific steps:

[0046] (a) The tailings pond sediments were taken from a heavy metal mine contaminated area, and the culture medium composition was KH2PO4 53.04 mg / L, K2HPO4 106.14 mg / L, NaCl 36.24 mg / L, MgCl2·6H2O 3.045 mg / L, CaCl2·2H2O1.029 mg / L, FeCl2 2.224 mg / L, ZnCl2 0.136 mg / L and trace elements. Two groups of different xanthate concentrations (200 mg / L, 500 mg / L) were set as culture matrix, and three different xanthate parallel experiments were set up in each group. 100 mL of culture medium solution and 10 mL of sample were added to 250 mL conical flasks respectively, and the samples were shaken and cultured in a constant temperature oscillator at 30°C and 120 r / min. The changes in bacterial solution and COD (chemical oxygen demand) were observed once a week until strains with strong degradation ability and stable activity against xanthate were screened and cultivated. When the xanthate concentration can be reduced to below 1 mg / L within 72 hours, the screening and cultivation are completed. The final bacterial solution is used as inoculum for standby use. At this time, the inoculum of mixed microorganisms is injected into the membrane aerated biofilm reactor. Figure 2-4 The standard curves of the selective culture medium containing potassium amyl xanthate (PAX), potassium butyl xanthate (KBX) and potassium isopropyl xanthate (PIX) in the method of the present invention are shown in sequence. The concentrations of the three xanthates are 0.1-30 mg / L, and the zero tube is used as a blank. The absorbance value is measured at a wavelength of 310 nm using a quartz cuvette in an ultraviolet spectrophotometer. Figure 2-4 It can be seen that the R2 values ​​of the standard curves of the three xanthates, PAX, KBX and PIX, are all over 0.99, proving that the detection is accurate.

[0047] (b) The selected xanthate functional bacteria were injected into the membrane aerated biofilm reactor. The mineral processing wastewater containing xanthate was used as the matrix, and oxygen-containing gas was introduced to cultivate the biofilm. The mineral processing wastewater contained PAX, KBX and PIX at a concentration of 200 mg / L. The culture medium components were the same as above. The hydraulic retention time of the membrane aerated biofilm reaction system was 6 h, and the oxygen pressure was 10 psig.

[0048] (c) Continue to observe the biofilm enrichment on the reactor until the COD drops below 60 mg / L and the xanthate concentration drops below 1 mg / L, which is considered to be the completion of biofilm enrichment. Before exploring the optimal operation strategy of the membrane aeration bioreactor system, the xanthate tolerance and degradation capacity of the enriched biofilm are also evaluated. According to the investigation of xanthate concentration at the mineral processing site, the actual concentration of xanthate in the mineral processing wastewater is about 100 mg / L. Therefore, the matrix concentrations of PAX, KBX, and PIX are set to 100 mg / L, respectively, and the culture medium components are the same as above. Three groups of membrane aeration biofilm reaction systems were operated continuously for 30 days under the conditions of a hydraulic retention time of 6 h and an oxygen pressure of 6 psig. Figure 5 As shown, it was found that the effluent concentration of the three structures of xanthate could reach below 2.0 mg / L, and the removal rate was above 98%.

[0049] (d) By adjusting different hydraulic retention time, air pressure and xanthate concentration conditions, the optimal operation strategy of the membrane aeration bioreactor system was explored to achieve the best degradation effect of xanthate. Figure 6 The graph showing the change of xanthate degradation effect under different hydraulic retention time conditions is shown. By setting different hydraulic retention times of 6 h, 12 h, and 18 h, the substrate concentration of PAX is set to 100 mg / L, and the culture medium composition is the same as above. In order to explore the effect of the membrane aerated biofilm reaction system on the degradation efficiency of PAX with the same substrate concentration, it can be seen that with the increase of hydraulic retention time, the effluent xanthate concentration gradually decreases. When the hydraulic retention time is extended to 18 h, the effluent xanthate concentration is less than 0.5 mg / L. Figure 7 The graph showing the change of xanthate degradation effect under different oxygen pressure conditions is shown. By setting different oxygen pressures of 3 psig and 6 psig, the COD and xanthate concentrations of PAX effluent with the same substrate concentration were tested for one week. The substrate concentration was set to 100 mg / L PAX, and the culture medium composition was the same as above. It can be seen that with the increase of gas pressure, the xanthate concentration in the effluent gradually decreased. When the gas pressure rose to 6psig, the xanthate concentration in the effluent was less than 0.5 mg / L. Figure 8The graph showing the change of xanthate degradation effect under different substrate concentration conditions is shown. By setting different concentrations of influent xanthate concentrations (100 mg / L, 200 mg / L), the culture medium composition is the same as above. The system was operated continuously for 30 days under the conditions of hydraulic retention time (HRT) of 12h and oxygen pressure of 6 psig to explore the effect of membrane aeration biofilm reaction system on the degradation efficiency of different substrate concentrations, and the effluent xanthate concentration and COD were tested. The xanthate with a substrate concentration of 100 mg / L can be reduced to below 0.5 mg / L within 24h, and the COD concentration can be reduced to below 30 mg / L; the xanthate with a substrate concentration of 200 mg / L can be reduced to below 1 mg / L within 24h.

[0050] The oxygen pressure and oxygen demand during biodegradation are calculated using the following formula:

[0051]

[0052] According to the reaction formula, 1.8 g of oxygen is required to treat 1 g of sodium amyl xanthate. Therefore, assuming that the hydraulic retention time is 6 hours and the influent sodium amyl xanthate concentration is 100 mg / L, the maximum oxygen consumption required per day for a 36 ml laboratory microreactor is 26 mg. Since the membrane area of ​​the micro membrane reactor is 1.06*10 -2 m 2 Therefore, the oxygen flux per unit membrane area is at least 2450 mg-O 2 •m -2 •d -1 (77 mmole-O2•m -2 •d -1 ) corresponds to a minimum oxygen pressure of 1.5 psig or 0.1 standard atmosphere.

[0053] From the above, it is determined that the optimal operation strategy of the membrane aeration bioreactor system of this embodiment includes: hydraulic retention time of 12 hours, oxygen pressure of 6 psig, and substrate concentration of 100 mg / L.

[0054] (e) According to the above optimal operation strategy, the membrane aeration bioreactor system is placed in a heavy metal mine contaminated site, and the mineral processing wastewater is introduced for in-situ biological treatment. The treated recycled water is returned to the mineral processing workshop for reuse. Among them, sequential batch experiments were carried out simultaneously in two membrane aeration biofilm reactors, and the PAX concentration, COD concentration and the concentration of the harmful intermediate CS2 generated in each period were detected. The headspace volatile gas was repeatedly extracted with a syringe, and the CS2 concentration was detected by gas chromatograph using manual injection. Fig. 9As shown, potassium amyl xanthate degraded rapidly within 30 minutes and degraded to below 1 mg / L within 4 hours, accompanied by the production of CS2; CS2 gradually decreased within six hours and gradually converted into sulfate ions.

[0055] In addition, the biological samples at each stage of the suspension, inoculated reactor, and membrane aeration biofilm reaction system were sequenced and analyzed. The abundance of sulfur-oxidizing bacteria in the suspension was lower than that in the biofilm, while the abundance of sulfur-oxidizing bacteria in the suspension was Pseudomonas The abundance is high, which may be due to the high toxicity of xanthate, which leads to high toxicity resistance. Pseudomonas Large amount of enrichment; on biofilm Pseudomonas The abundance gradually decreased, and Zoogloea The abundance of Zoogloea gradually increased. Zoogloea is tolerant to toxins in the natural environment and has the ability to adapt to new environments. It maintains a stable dominant position in the microbial community and the species diversity of the community gradually increases. The biofilm structure is more resistant to toxicity. A variety of thiosulfate and sulfur oxidation-related bacteria were screened from the biofilm of the membrane aeration biofilm reaction system. Flavobacterium It has been shown to be an aerobic heterotrophic bacterium known to oxidize thiosulfate using thiosulfate dehydrogenase; Sediminibacterium It is beneficial to the degradation and removal of organic carbon under aerobic conditions and plays an important role in the sulfur oxidation process; Mesorhizobium It is a new type of sulfur-oxidizing rhizobium that has been found to oxidize thiosulfate and elemental sulfur to perform chemical rock autotrophic growth. Fig.10 The relative abundance of xanthate-degrading functional bacteria in the biofilm of the membrane aerated biofilm reaction system is shown.

[0056] The above are only preferred embodiments of the present application and the technical principles used. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present application. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the concept of the present application, all of which belong to the scope of protection of the present application.

Claims

1. A biofilm treatment method for flotation wastewater contaminated by xanthate, comprising the following steps: (a) using tailings pond sediments taken from heavy metal mine contaminated areas, screening and enriching xanthate-degrading functional bacteria therefrom using a selective culture medium, and subculturing the xanthate-degrading functional bacteria; (b) after the subculture is completed, the xanthate-degrading functional bacteria are injected into a membrane aeration biofilm reaction system, the flotation wastewater containing xanthate is used as a matrix, oxygen-containing gas is introduced, and biofilm is cultured; (c) When the concentrations of potassium amyl xanthate, potassium butyl xanthate, and potassium isopropyl xanthate in the effluent of the membrane aeration biofilm reaction system all drop below 1.0 mg / L, the biofilm enrichment is completed; (d) determining an optimal operation strategy for the membrane aerated biofilm reaction system based on the xanthate degradation efficiency of the biofilm under different environmental parameters; The different environmental parameters include: a hydraulic retention time of 6 to 24 hours, an oxygen-containing gas partial pressure of 3 to 10 psig, and a flotation wastewater xanthate concentration of 100 to 200 mg / L; The optimal operating conditions are the correlation between hydraulic retention time, oxygen-containing gas partial pressure and xanthate concentration obtained by combining experiments and relevant theoretical calculations; as well as (e) Based on the optimal operation strategy, the membrane aeration biofilm reaction system is placed in the heavy metal mine contaminated area, and flotation wastewater is introduced for in-situ biological treatment, and the treated reused water is returned to the ore dressing workshop for reuse; The membrane aeration biofilm reaction system comprises the following components: (1) a reaction system body, (2) an aeration pump, and (3) an aeration membrane assembly. The (3) aeration membrane assembly is placed in the reaction system. Then, the system is inoculated with xanthate-degrading functional bacteria that have been screened and cultured. The inoculated reaction system is sunk into flotation wastewater. Pure oxygen, air or a combination thereof is introduced into the membrane through the (2) aeration pump to ensure that a small amount of bubbles overflow from the membrane pores until a biofilm is formed on the aeration membrane. Finally, the enrichment degree of the biofilm is evaluated by testing the xanthate content in the effluent of the system.

2. The method according to claim 1, characterized in that The selective culture medium comprises: 200-500 mg / L of one or more of potassium amyl xanthate, potassium butyl xanthate, potassium isopropyl xanthate, 53.04 g / L of KH2PO4, 106.10 g / L of K2HPO4, 36.20 g / L of NaCl, 3.00 g / L of MgCl2·6H2O, 1.00 g / L of CaCl2·2H2O, 2.20 g / L of FeCl2, 0.14 g / L of ZnCl2 and 1 mL of trace element stock solution.

3. The method according to claim 2, characterized in that The trace element stock solution includes: 0.14 g / L ZnCl2, 0.20 g / L MnCl2·4H2O, 0.06 g / L H3BO3, 0.48 g / L CoCl2·6H2O, 0.48 g / L Na2MoO4, 0.09 g / L CuCl2·2H2O, 0.12 g / L NiCl2·6H2O, 0.17 g / L Na2WO4·2H2O and 0.13 g / L Na2SeO4·5H2O.

4. The method according to claim 1, characterized in that: The oxygen-containing gas is pure oxygen, air or a mixture of the two.

5. The method according to claim 1, characterized in that: Before being introduced into the membrane aeration biofilm reaction system in step (e), the pH of the flotation wastewater is adjusted to 5.5 to 9.

5.

6. The method according to claim 1, characterized in that The xanthate concentration in the flotation wastewater in the step (e) is 100-300 mg / L, and the xanthate type is an alkyl group containing 2 to 5 carbon atoms.

7. The method according to claim 1, characterized in that The xanthochloride-degrading functional bacteria include Flavobacterium, Sediminibacterium and Mesorhizobium One or more of .

8. Use of the method according to any one of claims 1 to 7 in removing xanthate, a refractory organic flotation agent, from mineral processing wastewater in heavy metal mining areas.

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