A method for treating coal chemical salt-containing wastewater

Abstract

The application relates to the technical field of wastewater discharge, and particularly discloses a coal chemical salt-containing wastewater treatment method. The coal chemical salt-containing wastewater treatment method provided by the application comprises the following specific steps: pretreatment, advanced oxidation treatment and biochemical treatment. The advanced oxidation treatment step is as follows: concentrated water enters a Fenton reaction tank, the pH value is adjusted to 2.8-3.2, then hydrogen peroxide and ferrous salt spermidine are added in sequence, and the reaction time is 3-5 hours. The biochemical treatment step is as follows: effluent enters a biochemical unit, salt-tolerant bacterial agents and microbial growth promoters are added, and the treatment time is 72-120 hours. The microbial growth promoters comprise calcium salt, spermidine, sodium fatty acid methyl ester sulfonate, inorganic phosphoric acid substances and organic phosphonic acid substances. By using the above treatment method provided by the application, the content of impurities such as COD, ammonia nitrogen and TDS in coal chemical high-salt wastewater can be effectively removed, and excellent wastewater treatment effect is achieved.

Description

Technical Field

[0001] This application relates to the technical field of wastewater discharge, specifically to a method for treating saline wastewater from coal chemical industry. Background Technology

[0002] Wastewater discharge from coal chemical industries is a crucial research topic in the field of industrial wastewater treatment. With the rapid development of the coal chemical industry, wastewater discharge problems have become increasingly prominent, posing a severe challenge to environmental protection and sustainable development. Currently, research on coal chemical wastewater discharge mainly focuses on wastewater treatment technologies, zero-discharge technologies, and resource utilization.

[0003] Coal chemical wastewater is complex in composition, containing high concentrations of organic matter, heavy metal ions, and other pollutants, making it difficult to treat. Traditional wastewater treatment methods, such as physical, chemical, and biological methods, have limitations in treating coal chemical wastewater. Therefore, researchers are constantly exploring new wastewater treatment technologies, such as biofilm reactors and advanced oxidation technologies, to improve the efficiency and applicability of wastewater treatment.

[0004] Zero-discharge wastewater technologies: To achieve zero discharge of coal chemical wastewater, researchers are dedicated to developing efficient zero-discharge technologies. These technologies typically include pretreatment, membrane concentration, and evaporation crystallization steps to maximize the treatment and reuse of various components in the wastewater. However, due to the complexity of the composition of coal chemical wastewater and limitations in treatment technologies, the practical application effectiveness of zero-discharge technologies still needs further improvement.

[0005] Resource utilization: Coal chemical wastewater contains many valuable components, such as salts and organic matter. Through proper treatment and recycling, these components can be utilized as resources, reducing wastewater treatment costs and promoting resource recycling. Currently, resource utilization has become one of the important research directions in the field of coal chemical wastewater treatment.

[0006] Despite some progress in research on coal chemical wastewater discharge, the following problems remain: High treatment costs: The treatment of coal chemical wastewater requires a large amount of energy and chemical reagents, resulting in high treatment costs. This limits the widespread application and promotion of wastewater treatment technologies. Low treatment efficiency: Due to the complexity of the composition of coal chemical wastewater, traditional wastewater treatment methods often fail to achieve ideal treatment results. Although the development and application of new technologies have improved, further optimization and improvement are still needed. Technical bottlenecks: Zero-discharge technology for coal chemical wastewater still faces technical bottlenecks in practical applications, such as membrane fouling and evaporator scaling, affecting the stability and reliability of the technology. Low resource utilization: Currently, the recovery rate of valuable components in coal chemical wastewater is low, resulting in a large waste of resources. How to improve resource utilization and achieve wastewater reduction, resource recovery, and harmlessness remains an urgent problem to be solved.

[0007] In summary, while research on coal chemical wastewater discharge has yielded some results, it still faces numerous challenges and problems. In the future, further research efforts are needed to explore more efficient, economical, and environmentally friendly wastewater treatment technologies. Summary of the Invention

[0008] To address the aforementioned technical problems, this application provides a method for treating saline wastewater from coal chemical industry.

[0009] This application provides a method for treating saline wastewater from coal chemical industry, specifically including the following steps in sequence: pretreatment, advanced oxidation treatment, biochemical treatment, and posttreatment; The specific steps of the advanced oxidation treatment are as follows: the pretreated concentrated water enters the Fenton reactor, the pH value is adjusted to 2.8-3.2, and then hydrogen peroxide, ferrous salt, and spermine with a final concentration of 120-180 mg / L, 5-15 mg / L are added in sequence, and the reaction time is 3-5 hours. The specific steps of the biochemical treatment are as follows: the effluent from the advanced oxidation treatment enters the biochemical unit, salt-tolerant bacteria agent and microbial growth promoter are added, and the treatment time is 72-120 hours. The dosage of the salt-tolerant bacterial agent is 20-50 mg / L relative to the solid-liquid ratio of the wastewater treated per hour. The dosage of the microbial growth promoter is 2-12 mg / L relative to the solid-liquid ratio of the wastewater treated per hour; The microbial growth promoter specifically comprises the following components in parts by weight: 15-20 parts calcium salt, 4-8 parts spermidine, 4-8 parts sodium fatty acid methyl ester sulfonate, 1-4 parts inorganic phosphate, and 0.1-0.5 parts organic phosphonic acid.

[0010] Using the treatment method provided in this application, coal chemical saline wastewater is subjected to pretreatment, advanced oxidation treatment, biochemical treatment, and posttreatment steps in sequence. By controlling the type and dosage of salt-tolerant bacteria and microbial growth promoters in the biochemical treatment process, the content of impurities such as COD, ammonia nitrogen, TDS, and nitrate ions in high-salt coal chemical wastewater can be effectively removed, achieving excellent wastewater treatment results.

[0011] The inventive concept of the microbial growth promoter in this application lies in the significant impact of calcium ions on microbial growth. In wastewater treatment, appropriate amounts of calcium ions can promote microbial metabolic activity and enhance their wastewater treatment capacity; calcium salts can also regulate the pH of wastewater, providing a suitable growth environment for microorganisms. Spermine can enhance the stress resistance of microorganisms, helping them survive and reproduce in the harsh environment of wastewater treatment; it can also act as a signaling factor, enhancing the expression of antioxidant enzyme-related genes, thereby increasing the content of antioxidant enzymes within microbial cells, enhancing their ability to scavenge reactive oxygen species, and alleviating oxidative damage to the cell membrane under stress; furthermore, spermine can bind to antioxidant enzymes, directly increasing enzyme activity and further enhancing the antioxidant capacity of microorganisms. In wastewater treatment, the addition of sodium methyl ester sulfonate can enhance the activity of microorganisms in the wastewater treatment system, allowing it to be rapidly decomposed and utilized by microorganisms, thereby improving their metabolic rate and treatment efficiency. Inorganic phosphate can directly provide phosphorus sources for microorganisms, promoting their normal growth and metabolism; organophosphonic acids can release phosphorus through microbial decomposition for their utilization; appropriate amounts of phosphorus can promote microbial activity and enhance their ability to degrade organic pollutants. The addition of inorganic phosphate and organophosphonic acids can increase the ATP content within microbial cells, thereby improving their energy levels and metabolic activity; the addition of inorganic phosphate and organophosphonic acids can enhance system stability, improve the resistance of microorganisms to adverse conditions, and ensure the continuous and stable operation of wastewater treatment. By precisely designing the dosage of each raw material component as a microbial growth promoter, the treatment effect of salt-tolerant bacteria on wastewater can be effectively improved.

[0012] Preferably, the specific steps of the pretreatment are as follows: saline wastewater from coal chemical industry enters the reaction zone of a high-density clarifier, calcium hydroxide is added to adjust the pH value to 10.5-11.0, then sodium carbonate with a final concentration of 1.8-2.2 g / L, PFS coagulant with a final concentration of 8-12 mg / L, and PAM coagulant aid with a final concentration of 0.7-1.5 mg / L are added. After sufficient coagulation, the water enters the clarifier for sedimentation. Finally, hydrochloric acid is added at the outlet of the clarifier to adjust the pH to about 7. The water is then filtered to remove suspended solids and colloidal particles.

[0013] Preferably, after the advanced oxidation treatment, the COD content in the water is ≤1100mg / L, the TDS content is ≤5000mg / L, the ammonia nitrogen content is ≤350mg / L, and the nitrate ion content is ≤400mg / L.

[0014] Preferably, the dosage of the salt-tolerant bacterial agent is 30-40 mg / L relative to the solid-liquid ratio of the wastewater treated per hour; the dosage of the microbial growth promoter is 4-10 mg / L relative to the solid-liquid ratio of the wastewater treated per hour. Preferably, the salt-tolerant bacterial agent is selected from one or more of Bacillus licheniformis, Bacillus subtilis, Bacillus coagulans, and Bacillus pasteurellis.

[0015] Preferably, the salt-tolerant bacterial agent is composed of a mixture of Bacillus licheniformis and Bacillus coagulans with a live bacteria count ratio of 1-3:0.2-0.8; the live bacteria count of the salt-tolerant bacterial agent is ≥6 billion / g.

[0016] Furthermore, the salt-tolerant bacterial agent is composed of a mixture of Bacillus licheniformis and Bacillus coagulans with a live bacteria count ratio of 1.5-2.5:0.4-0.6; the live bacteria count of the salt-tolerant bacterial agent is ≥6 billion / g.

[0017] Preferably, the calcium salt is selected from one or more of calcium acetate, calcium propionate, calcium chloride, calcium nitrate, calcium sulfate, superphosphate, calcium citrate, calcium gluconate, and calcium amino acids.

[0018] Preferably, the inorganic phosphate is selected from one or more of sodium tripolyphosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, and sodium hexametaphosphate.

[0019] Preferably, the organophosphonic acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, 2-hydroxyphosphonoacetic acid, polyaminopolyether methylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid.

[0020] Preferably, the microbial growth promoter specifically comprises the following components in parts by weight: 16-19 parts by weight of superphosphate, 5-7 parts by weight of spermidine, 5-7 parts by weight of sodium methyl ester sulfonate of fatty acids, 2-3 parts by weight of sodium pyrophosphate, and 0.2-0.4 parts by weight of ethylenediaminetetramethylenephosphonic acid. In summary, the technical solution of this application has the following effects: Using the treatment method provided in this application, coal chemical saline wastewater is subjected to pretreatment, advanced oxidation treatment, and biochemical treatment in sequence. By controlling the type and dosage of salt-tolerant bacteria and microbial growth promoters in the biochemical treatment process, the content of impurities such as COD, ammonia nitrogen, TDS, and nitrate ions in high-salt coal chemical wastewater can be effectively removed, achieving excellent wastewater treatment results. Detailed Implementation

[0021] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application. Example

[0022] Examples 1-6 Examples 1-6 provide a method for treating saline wastewater from coal chemical industry.

[0023] The difference between the above embodiments lies in the type of salt-tolerant bacterial agent used in the biochemical treatment step, as shown below.

[0024] In Example 1: Bacillus licheniformis and Bacillus coagulans were taken at a viable count ratio of 2:0.5 and then cultured in the same LB medium for 36 hours at a fermentation temperature of 35-37°C. After the culture was completed, a seed culture was obtained. The seed culture was then inoculated at a rate of 10% into a 100L culture tank containing LB medium and fermented for 36 hours at a fermentation temperature of 32-37°C until the bacterial count density under microscopic examination reached more than 100. The culture was ended when the spore production rate reached more than 99%, and a salt-tolerant bacterial agent with a viable count of approximately 6.5 billion / g was obtained.

[0025] In Example 2: Bacillus licheniformis and Bacillus coagulans were taken at a live bacteria ratio of 1:0.8 and then cultured in the same LB medium for 36 hours at a fermentation temperature of 35-37°C. After the culture was completed, a seed culture was obtained. The seed culture was then inoculated at a rate of 10% into a 100L culture tank containing LB medium and fermented for 36 hours at a fermentation temperature of 32-37°C until the bacterial count density under microscopic examination reached more than 100. The culture was ended when the spore production rate reached more than 99%, and a salt-tolerant bacterial agent with a live bacteria count of approximately 6.5 billion / g was obtained.

[0026] In Example 3: Bacillus licheniformis and Bacillus coagulans were taken at a viable count ratio of 3:0.2 and then cultured in the same LB medium for 36 hours at a fermentation temperature of 35-37°C. After the culture was completed, a seed culture was obtained. The seed culture was then inoculated at a rate of 10% into a 100L culture tank containing LB medium and fermented for 36 hours at a fermentation temperature of 32-37°C until the bacterial count density under microscopic examination reached more than 100. When the spore production rate reached more than 99%, the culture was terminated, and a salt-tolerant bacterial agent with a viable count of approximately 6.5 billion / g was obtained.

[0027] In Example 4: Bacillus licheniformis and Bacillus coagulans were taken at a viable count ratio of 0.5:2 and then cultured in the same LB medium for 36 hours at a fermentation temperature of 35-37°C. After the culture was completed, a seed culture was obtained. The seed culture was then inoculated at a rate of 10% into a 100L culture tank containing LB medium and fermented for 36 hours at a fermentation temperature of 32-37°C until the bacterial count density under microscopic examination reached more than 100. The culture was ended when the spore production rate reached more than 99%, and a salt-tolerant bacterial agent with a viable count of approximately 6.5 billion / g was obtained.

[0028] In Example 5: Bacillus licheniformis and Bacillus subtilis were taken at a viable count ratio of 2:0.5 and then cultured in the same LB medium for 36 hours at a fermentation temperature of 35-37°C. After the culture was completed, a seed culture was obtained. The seed culture was then inoculated at a rate of 10% into a 100L culture tank containing LB medium and fermented for 36 hours at a fermentation temperature of 32-37°C until the bacterial count density under microscopic examination reached more than 100. The culture was ended when the spore production rate reached more than 99%, and a salt-tolerant bacterial agent with a viable count of approximately 6.5 billion / g was obtained.

[0029] In Example 6: Bacillus pasteurellii and Bacillus subtilis were taken at a viable count ratio of 2:0.5 and then cultured in the same LB medium for 36 hours at a fermentation temperature of 35-37°C. After the culture was completed, a seed culture was obtained. The seed culture was then inoculated at a rate of 10% into a 100L culture tank containing LB medium and fermented for 36 hours at a fermentation temperature of 32-37°C until the bacterial count density under microscopic examination reached more than 100. The culture was ended when the spore production rate reached more than 99%, and a salt-tolerant bacterial agent with a viable count of approximately 6.5 billion / g was obtained.

[0030] The method for treating saline wastewater from coal chemical industry in the above embodiments specifically includes the following steps in sequence: The average concentrations of various pollutants in the high-salt wastewater from coal chemical industry are as follows: COD 5721 mg / L, total hardness (calculated as CaCO3) 1235 mg / L, total alkalinity (calculated as CaCO3) 815 mg / L, TDS 6598 mg / L, ammonia nitrogen content 398 mg / L, and pH value 8.

[0031] (1) Pretreatment: High-salt wastewater from coal chemical industry enters the reaction zone of the high-density clarifier. Calcium hydroxide is added to adjust the pH to 10.5-11.0. Sodium carbonate (final concentration 2.0 g / L), PFS coagulant (final concentration 10 mg / L), and PAM coagulant aid (final concentration 1 mg / L) are added. After thorough coagulation, the wastewater enters the clarifier for sedimentation. Finally, hydrochloric acid is added at the clarifier outlet to adjust the pH to around 7. The effluent is then filtered to remove suspended solids and colloidal particles.

[0032] (2) Advanced oxidation treatment: The pretreated concentrate enters the Fenton reactor, the pH is adjusted to 2.8-3.2, and then hydrogen peroxide, ferrous salt, and spermine with a final concentration of 160 mg / L, 10 mg / L, and 0.4 mg / L are added in sequence. The reaction time is 4 hours. After Fenton oxidation, the COD content in the water is 1058 mg / L, the TDS content is 4857 mg / L, the ammonia nitrogen content is 302 mg / L, and the nitrate ion content is 367 mg / L.

[0033] (3) Biochemical Treatment: The effluent from the advanced oxidation treatment enters the biochemical unit. Before influent, activated sludge is inoculated into the biofilter of the biochemical unit at a sludge concentration of 4000 mg / L for startup. The conditions are: temperature 27℃, pH 7.5, and dissolved oxygen concentration 1.0 mg / L. Salt-tolerant bacteria are added to the filter at a rate of 35 mg / L per hour of wastewater treated, and microbial growth promoters are added at a rate of 7 mg / L per hour of wastewater treated to remove COD and nitrate. The total hydraulic retention time for biochemical treatment is 96 h. The microbial growth promoter consists of the following components by weight: 17 parts superphosphate, 6 parts spermidine, 6 parts sodium fatty acid methyl ester sulfonate, 2.5 parts sodium pyrophosphate, and 0.3 parts ethylenediaminetetramethylenephosphonic acid.

[0034] (4) Post-treatment: The effluent from the biological treatment enters the high-density clarifier. Sodium hydroxide is added in the reaction zone of the clarifier to maintain the pH value at around 11.5. Sodium carbonate with a final concentration of 2.0 g / L, PFS coagulant with a final concentration of 40 mg / L, and PAM coagulant aid with a final concentration of 4 mg / L are added. After thorough coagulation, the effluent enters the clarifier for sedimentation. Finally, hydrochloric acid is added at the outlet of the clarifier to adjust the pH to around 7. Then, suspended solids and colloidal particles in the water are removed by a filter to control the turbidity of the wastewater to ≤3 NTU. The wastewater then enters an ultrafiltration device with an operating pressure of 0.05 MPa. After ultrafiltration treatment, the final wastewater indicators are hardness ≤50 mg / L, COD ≤65 mg / L, and turbidity ≤1 NTU.

[0035] Examples 7-11 Examples 7-11 provide a method for treating saline wastewater from coal chemical industry.

[0036] The difference between the above embodiments and Embodiment 1 is that the types of microbial growth promoters are different, as detailed below.

[0037] In Example 7: The microbial growth promoter is composed of the following components in parts by weight: 17 parts calcium propionate, 6 parts spermidine, 6 parts sodium fatty acid methyl ester sulfonate, 2.5 parts sodium hexametaphosphate, and 0.3 parts diethylenetriaminepentamethylphosphonic acid.

[0038] In Example 8, the microbial growth promoter is composed of the following components in parts by weight: 17 parts calcium gluconate, 6 parts spermidine, 6 parts sodium fatty acid methyl ester sulfonate, 2.5 parts sodium hexametaphosphate, and 0.3 parts aminotrimethylene phosphonic acid.

[0039] In Example 9: The microbial growth promoter is composed of the following components in parts by weight: 15 parts by weight of superphosphate, 8 parts by weight of spermidine, 4 parts by weight of sodium fatty acid methyl ester sulfonate, 1 part by weight of sodium pyrophosphate, and 0.5 parts by weight of ethylenediaminetetramethylenephosphonic acid.

[0040] In Example 10: The microbial growth promoter is composed of the following components in parts by weight: 16 parts by weight of superphosphate, 7 parts by weight of spermidine, 5 parts by weight of sodium fatty acid methyl ester sulfonate, 2 parts by weight of sodium pyrophosphate, and 0.4 parts by weight of ethylenediaminetetramethylenephosphonic acid.

[0041] In Example 11: The microbial growth promoter is composed of the following components in parts by weight: 19 parts by weight of superphosphate, 5 parts by weight of spermidine, 7 parts by weight of sodium fatty acid methyl ester sulfonate, 3 parts by weight of sodium pyrophosphate, and 0.2 parts by weight of ethylenediaminetetramethylenephosphonic acid.

[0042] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0043] Examples 12-15 Examples 12-15 provide a method for treating saline wastewater from coal chemical industry.

[0044] The difference between the above embodiments and Embodiment 1 is that the dosage of salt-tolerant bacteria agent and microbial growth promoter are different, as detailed below.

[0045] In Example 12: the dosage of salt-tolerant bacteria agent and the solid-liquid ratio of the wastewater treated per hour were 20 mg / L; the dosage of microbial growth promoter and the solid-liquid ratio of the wastewater treated per hour were 12 mg / L.

[0046] In Example 13: the dosage of salt-tolerant bacteria agent and the solid-liquid ratio of the wastewater treated per hour were 50 mg / L; the dosage of microbial growth promoter and the solid-liquid ratio of the wastewater treated per hour were 2 mg / L.

[0047] In Example 14: the dosage of salt-tolerant bacteria agent and the solid-liquid ratio of the wastewater treated per hour were 30 mg / L; the dosage of microbial growth promoter and the solid-liquid ratio of the wastewater treated per hour were 4 mg / L.

[0048] In Example 15: the dosage of salt-tolerant bacteria agent and the solid-liquid ratio of the wastewater treated per hour were 40 mg / L; the dosage of microbial growth promoter and the solid-liquid ratio of the wastewater treated per hour were 10 mg / L.

[0049] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0050] Comparative Example Comparative Examples 1-3 Comparative Examples 1-3 each provide a method for treating saline wastewater from coal chemical industry.

[0051] The differences between the above comparative examples and Example 1 are as follows.

[0052] In Comparative Example 1, the microbial growth promoter consisted of the following components in parts by weight: 17 parts by weight of calcium propionate, 2.5 parts by weight of sodium hexametaphosphate, and 0.3 parts by weight of diethylenetriaminepentamethylphosphonic acid.

[0053] In Comparative Example 2: the microbial growth promoter consisted of the following components in parts by weight: 30 parts calcium propionate, 2 parts spermidine, 10 parts sodium fatty acid methyl ester sulfonate, 0.5 parts sodium hexametaphosphate, and 1 part diethylenetriaminepentamethylphosphonic acid.

[0054] In Comparative Example 3: the dosage of salt-tolerant bacteria agent and the solid-liquid ratio of the wastewater treated per hour were 60 mg / L; the dosage of microbial growth promoter and the solid-liquid ratio of the wastewater treated per hour were 1 mg / L.

[0055] All other process parameters in the above comparative examples are the same as those in Example 1.

[0056] Performance testing The influent water quality of the biological treatment unit (i.e., the effluent water quality of the advanced oxidation treatment) is as follows: COD content is 1058 mg / L, TDS content is 4857 mg / L, ammonia nitrogen content is 302 mg / L, and nitrate ion content is 367 mg / L.

[0057] The effluent from step (4) of the examples and comparative examples after being treated by the biofilter of the biochemical unit was specifically tested to evaluate the wastewater treatment.

[0058] Test results: As shown in Table 1 Table 1. Wastewater treatment test results in the examples and comparative examples. Based on Table 1, and by comparing the test results of the examples and comparative examples, it can be seen that by using the treatment method provided in this application to sequentially perform pretreatment, advanced oxidation treatment, and biochemical treatment steps on saline wastewater from coal chemical industry, and by controlling the types and amounts of salt-tolerant bacteria agents and microbial growth promoters in the biochemical treatment process, the content of impurities such as COD, ammonia nitrogen, TDS, and nitrate ions in high-salt wastewater from coal chemical industry can be effectively removed, achieving excellent wastewater treatment results.

[0059] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for treating saline wastewater from coal chemical industry, characterized in that, Specifically, the process includes the following steps in sequence: pretreatment, advanced oxidation treatment, biochemical treatment, and posttreatment; The specific steps of the advanced oxidation treatment are as follows: the pretreated concentrated water enters the Fenton reactor, the pH value is adjusted to 2.8-3.2, and then hydrogen peroxide, ferrous salt, and spermine with a final concentration of 120-180 mg / L, 5-15 mg / L are added in sequence, and the reaction time is 3-5 hours. After the advanced oxidation treatment, the COD content in the water is ≤1100mg / L, the TDS content is ≤5000mg / L, the ammonia nitrogen content is ≤350mg / L, and the nitrate ion content is ≤400mg / L; The specific steps of the biochemical treatment are as follows: the effluent from the advanced oxidation treatment enters the biochemical unit, salt-tolerant bacteria agent and microbial growth promoter are added, and the treatment time is 72-120 hours. The dosage of the salt-tolerant bacterial agent is 20-50 mg / L relative to the solid-liquid ratio of the wastewater treated per hour. The dosage of the microbial growth promoter is 2-12 mg / L relative to the solid-liquid ratio of the wastewater treated per hour. The salt-tolerant bacterial agent is composed of a mixture of Bacillus licheniformis and Bacillus coagulans with a viable count ratio of 1-3:0.2-0.8; the viable count of the salt-tolerant bacterial agent is ≥6 billion / g. The microbial growth promoter specifically comprises the following components in parts by weight: 15-20 parts calcium salt, 4-8 parts spermidine, 4-8 parts sodium fatty acid methyl ester sulfonate, 1-4 parts inorganic phosphate, and 0.1-0.5 parts organic phosphonic acid.

2. The method for treating saline wastewater from coal chemical industry according to claim 1, characterized in that, The specific steps of the pretreatment are as follows: saline wastewater from coal chemical industry enters the reaction zone of the high-density clarifier, calcium hydroxide is added to adjust the pH value to 10.5-11.0, then sodium carbonate with a final concentration of 1.8-2.2 g / L, PFS coagulant with a final concentration of 8-12 mg / L, and PAM coagulant aid with a final concentration of 0.7-1.5 mg / L are added. After sufficient coagulation, the water enters the clarifier for sedimentation. Finally, hydrochloric acid is added at the outlet of the clarifier to adjust the pH to about 7. The water is then filtered to remove suspended solids and colloidal particles.

3. The method for treating saline wastewater from coal chemical industry according to claim 1, characterized in that, The dosage of the salt-tolerant bacterial agent is 30-40 mg / L relative to the solid-liquid ratio of the wastewater treated per hour; the dosage of the microbial growth promoter is 4-10 mg / L relative to the solid-liquid ratio of the wastewater treated per hour.

4. The method for treating saline wastewater from coal chemical industry according to claim 1, characterized in that, The calcium salt is selected from one or more of calcium acetate, calcium propionate, calcium chloride, calcium nitrate, calcium sulfate, superphosphate, calcium citrate, calcium gluconate, and amino acid calcium.

5. The method for treating saline wastewater from coal chemical industry according to claim 1, characterized in that, The inorganic phosphate is selected from one or more of sodium tripolyphosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, and sodium hexametaphosphate.

6. The method for treating saline wastewater from coal chemical industry according to claim 1, characterized in that, The organophosphonic acid is selected from one or more of the following: hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, ethylenediaminetetramethylene phosphonic acid, 2-hydroxyphosphonoacetic acid, polyaminopolyether methylene phosphonic acid, and diethylenetriaminepentamethylene phosphonic acid.

7. The method for treating saline wastewater from coal chemical industry according to claim 1, characterized in that, The microbial growth promoter specifically comprises the following components in parts by weight: 16-19 parts by weight of superphosphate, 5-7 parts by weight of spermidine, 5-7 parts by weight of sodium fatty acid methyl ester sulfonate, 2-3 parts by weight of sodium pyrophosphate, and 0.2-0.4 parts by weight of ethylenediaminetetramethylenephosphonic acid.

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