Membrane integrated treatment process for high-concentration chemical wastewater

Abstract

According to the technical scheme, the membrane integrated treatment process comprises the following steps: pretreating the high-concentration chemical wastewater from a collecting tank through a precision filter, removing large-particle impurities to obtain pretreated effluent, treating the pretreated effluent through a silicon carbide ultrafiltration membrane treatment device, and removing part of small particles to obtain silicon carbide membrane produced water, the wastewater passes through a ceramic nanofiltration membrane treatment device, ceramic nanofiltration clear liquid and concentrated liquid are obtained, the ceramic nanofiltration concentrated liquid is subjected to an extraction process, organic matter is recycled, remaining wastewater returns to a collection pool, the ceramic nanofiltration clear liquid is subjected to A2O integrated MABR membrane treatment, small-molecule chemical organic matter in the wastewater is degraded, and biochemical effluent is obtained. And finally, carrying out advanced treatment through an MBR membrane system in a high-concentration sludge system, wherein the effluent reaches the first-grade A emission standard. According to the membrane integrated treatment process for the high-concentration chemical wastewater, quality-divided treatment of the high-concentration chemical wastewater, recovery of high-concentration chemical organic matters and efficient treatment of the low-concentration chemical wastewater are realized, and stable and up-to-standard discharge of effluent is realized.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a membrane integrated treatment process for high-concentration chemical wastewater. Background Technology

[0002] High-concentration chemical wastewater is widely generated in the production processes of industries such as petrochemicals, pharmaceuticals, dyes, and coal chemicals. Its pollutants are complex and pose significant hazards. Major pollutants include aromatic compounds (such as phenol, nitrobenzene, and toluene), heterocyclic organic compounds (such as pyridine, quinoline, and imidazole), heavy metal ions (such as chromium, cadmium, nickel, and mercury), and high levels of salts (such as chloride, sodium, and sulfate ions). Some chemical wastewater also contains toxic components such as cyanide and sulfides. This type of wastewater is characterized by "high COD, high salinity, recalcitrant degradation, and strong toxicity." The pollutants often contain stable aromatic and heterocyclic structures, which are difficult to overcome with conventional treatment technologies, making this a key challenge in the field of chemical wastewater treatment.

[0003] Currently, some researchers have developed various technical approaches. For example, CN102557321A reported a low-cost method for achieving zero discharge of high-concentration wastewater, using a combination of "crystallization + membrane distillation + microwave catalytic combustion" to achieve zero discharge of high-concentration wastewater; CN206244574U reported a zero-discharge system for high-salt dyeing and printing wastewater. However, such technologies have drawbacks such as poor process stability and high operating costs. Some low-cost treatment processes, such as traditional biochemical treatment processes, are also difficult to meet the treatment needs of high-concentration chemical wastewater. For example, the conventional AAO process has poor tolerance to high-salt and highly toxic wastewater. High-salt and toxic components in the wastewater easily inhibit microbial activity, resulting in low pollutant treatment efficiency and failure to achieve stable and compliant discharge.

[0004] Therefore, there is an urgent need to develop a high-concentration chemical wastewater treatment process that is continuous and stable, has high treatment efficiency, and produces consistently compliant effluent, in order to help the chemical wastewater treatment industry solve its problems. Summary of the Invention

[0005] The purpose of this invention is to provide a membrane integrated treatment process for high-concentration chemical wastewater, which realizes the differentiated treatment of chemical wastewater, enables the resource recovery of pollutants in high-concentration chemical wastewater and the efficient treatment of low-concentration chemical wastewater, and ensures that the effluent meets the discharge standards.

[0006] The technical solution of this invention adopts a multi-stage membrane separation process to separate the organic phase and inorganic phase in high-concentration chemical wastewater. The organic phase is high-concentration chemical organic matter, and the inorganic phase is low-concentration chemical wastewater. The organic matter is extracted by an organic solvent extraction process, and the low-concentration chemical wastewater is treated by a composite membrane bioreactor using a biochemical treatment process and a membrane aeration process.

[0007] The specific process flow includes: First, high-concentration chemical wastewater from the collection tank undergoes pretreatment via a precision filter to remove large particles, colloids, and other impurities, yielding pretreated effluent; second, the pretreated effluent passes through a silicon carbide ultrafiltration membrane treatment device to remove some small particles, yielding silicon carbide membrane permeate; third, the silicon carbide permeate passes through a ceramic nanofiltration membrane treatment device to obtain ceramic nanofiltration clarified solution and ceramic nanofiltration concentrated solution. The ceramic nanofiltration concentrated solution undergoes an extraction process to recover organic matter, and the remaining wastewater is returned to the collection tank. The ceramic nanofiltration clarified solution undergoes A... 2 O-MABR treatment degrades small-molecule chemical organic matter in wastewater to obtain biochemical effluent; finally, the biochemical effluent undergoes further treatment in a high-concentration sludge system using an MBR membrane system, and the effluent meets the Class A discharge standard.

[0008] The filter element of the precision filter is made of PP cotton with a pore size of 5-10 μm. The silicon carbide microfiltration membrane has a pore size range of 0.05-0.1 μm, an operating temperature of 20-40 ℃, an operating pressure of 0.2-0.3 MPa, and a flux of 200-300 LMH. Among them, the ceramic nanofiltration membrane has a molecular weight cutoff of 200-1000 Da, an operating pressure of 1.5-2.5 MPa, and a temperature of 20-40 ℃; Among them, A 2 The HRT (hydraulic retention time) of the O-MABR system is 18-30 h, and the aeration pressure of the MABR operation is 0.03-0.05 MPa; The MBR membrane has a sludge concentration higher than 10,000 mg / L, a pore size range of 20-100 nm, and an operating negative pressure between -10 and -35 kPa.

[0009] The technical principle of this invention includes: a precision filter using PP cotton to adsorb and intercept particulate matter with a diameter greater than 5-10 μm in chemical wastewater; a silicon carbide microfiltration membrane to intercept small particulate matter with a diameter greater than 0.05-0.1 μm in chemical wastewater; and a ceramic nanofiltration membrane to intercept organic matter and colloidal substances with a diameter greater than 200-1000 Da in chemical wastewater, forming a concentrated nanofiltration solution and a clear nanofiltration solution. The organic matter in the concentrated nanofiltration solution is recovered through a solvent extraction process. The clear nanofiltration solution is subjected to an anaerobic-anoxic-aerobic membrane aeration process to enhance the biochemical treatment effect. The biochemical treatment effect is further enhanced in a high-concentration sludge system using an MBR membrane bioreactor process to ensure that the effluent meets the discharge quality standards.

[0010] Compared with the prior art, the present invention has significant advantages: The membrane integrated treatment process for high-concentration chemical wastewater of the present invention combines membrane separation processes with different pore sizes and materials, which solves the problems of complex composition, poor biodegradability and high technical difficulty of conventional process treatment of high-concentration chemical wastewater. Through physical separation technology, it realizes the separate treatment of high-concentration chemical wastewater, the recovery of high-concentration chemical organic matter, the efficient treatment of low-concentration chemical wastewater, and the stable discharge of effluent that meets the standards. Attached Figure Description

[0011] Figure 1 The flowchart of the membrane integrated treatment process for high-concentration chemical wastewater provided by the present invention is shown. Detailed Implementation

[0013] Compare with Example 1 The influent wastewater from a petrochemical plant, originating from a collection pond, has an influent COD of 22,000 mg / L, ammonia nitrogen of 800 mg / L, total phosphorus of 20 mg / L, salinity of 4.3%, and a BOD / COD ratio of 0.13. This wastewater is treated with an 8 μm precision filter to remove large particles, colloids, and other impurities, resulting in pretreated effluent. The pretreated effluent then undergoes A… 2 O-MABR treatment, with a hydraulic retention time of 24 h and an aeration pressure of 0.04 MPa, degrades small-molecule chemical organic matter in wastewater to obtain biological effluent. Finally, the biological effluent is subjected to further treatment by an MBR membrane system in a system with a sludge concentration higher than 14000 mg / L, using a membrane module with a pore size of 50 nm and an operating negative pressure of -20 kPa.

[0014] After treatment by this process, the final effluent quality is as follows: COD is 95 mg / L, ammonia nitrogen content is reduced to 12 mg / L, and total phosphorus content is 0.8 mg / L, which does not meet the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0015] Example 1 High-concentration wastewater from a biochemical company, collected in a collection pond, has the following influent characteristics: COD 25000 mg / L, ammonia nitrogen 750 mg / L, total phosphorus 25 mg / L, and an initial BOD / COD ratio of 0.12. The wastewater is first treated by a 5 μm precision filter to remove large particles, colloids, and other impurities, yielding pretreated effluent. Next, the pretreated effluent passes through a silicon carbide ultrafiltration membrane (0.05 μm pore size, initial operating temperature 20 °C, operating pressure 0.2 MPa, average operating flux 200 LMH) to remove some small particles, yielding silicon carbide membrane permeate. Finally, the silicon carbide permeate is treated by a ceramic nanofiltration membrane (200 Da molecular weight cutoff, 2.5 MPa, initial operating temperature 20 °C). At ℃, ceramic nanofiltration clarified solution and ceramic nanofiltration concentrated solution were obtained. The ceramic nanofiltration concentrated solution was subjected to carbon tetrachloride extraction to recover organic matter from the chemical wastewater, and the remaining wastewater was recycled to the collection tank; the ceramic nanofiltration clarified solution was subjected to A 2 O-MABR treatment, with a hydraulic retention time of 30 h and an aeration pressure of 0.05 MPa, degrades small-molecule chemical organic matter in chemical wastewater to obtain biochemical effluent. Finally, the biochemical effluent is further treated by an MBR membrane system in a sludge concentration of 12000 mg / L, using a membrane module with a pore size of 30 nm and an operating negative pressure of -30 kPa.

[0016] After treatment by this process, the final effluent quality is as follows: COD is 45 mg / L, ammonia nitrogen content is reduced to 4.6 mg / L, and total phosphorus content is 0.4 mg / L, meeting the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0017] Example 2 Wastewater from a dye chemical plant, collected in a collection pond, has the following influent characteristics: COD 21000 mg / L, ammonia nitrogen 820 mg / L, total phosphorus 22 mg / L, salinity 4.5%, and BOD / COD 0.13. The wastewater is first treated by a 10 μm precision filter to remove large particles, colloids, and other impurities, yielding pretreated effluent. Next, the pretreated effluent passes through a silicon carbide ultrafiltration membrane (0.1 μm pore size, initial operating temperature 35 ℃, operating pressure 0.3 MPa, average operating flux 300 LMH) to remove some small particles, yielding silicon carbide membrane permeate. Finally, the silicon carbide permeate is treated by a ceramic nanofiltration membrane (800 Da molecular weight cutoff, 1.5 MPa, initial operating temperature 35 ℃). At ℃, ceramic nanofiltration clarified solution and ceramic nanofiltration concentrated solution were obtained. The ceramic nanofiltration concentrated solution was used to recover organic matter from the chemical wastewater through carbon tetrachloride extraction, and the remaining wastewater was recycled to the collection tank; the ceramic nanofiltration clarified solution was processed through A 2 O-MABR treatment, with a hydraulic retention time of 18 h and an aeration pressure of 0.03 MPa, degrades small-molecule chemical organic matter in wastewater to obtain biological effluent. Finally, the biological effluent is subjected to further treatment by an MBR membrane system in a system with a sludge concentration higher than 13000 mg / L, using a membrane module with a pore size of 80 nm and an operating negative pressure of -10 kPa.

[0018] After treatment by this process, the final effluent quality is as follows: COD is 49 mg / L, ammonia nitrogen content is reduced to 4.7 mg / L, and total phosphorus content is 0.35 mg / L, meeting the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0019] Example 3 The influent wastewater from a petrochemical plant, originating from a collection tank, has an influent COD of 18000 mg / L, ammonia nitrogen content of 920 mg / L, total phosphorus content of 18 mg / L, salinity of 4.2%, and a BOD / COD ratio of 0.14. This wastewater is first treated with an 8 μm precision filter to remove large particles, colloids, and other impurities, yielding pretreated effluent. Next, the pretreated effluent passes through a silicon carbide ultrafiltration membrane (0.08 μm pore size, initial operating temperature 30 ℃, operating pressure 0.25 MPa, average operating flux 250 LMH) to remove some small particles, yielding silicon carbide membrane permeate. Finally, the silicon carbide permeate is treated with a ceramic nanofiltration membrane (500 Da molecular weight cutoff, operating pressure 2.0 kcal / kg). At an initial operating temperature of 30℃ and a pressure of MPa, ceramic nanofiltration clarified solution and ceramic nanofiltration concentrated solution are obtained. The ceramic nanofiltration concentrated solution is used to recover organic matter from the chemical wastewater through carbon tetrachloride extraction, and the remaining wastewater is recycled to a collection tank. The ceramic nanofiltration clarified solution is then processed by A… 2 O-MABR treatment, with a hydraulic retention time of 24 h and an aeration pressure of 0.04 MPa, degrades small-molecule chemical organic matter in wastewater to obtain biological effluent. Finally, the biological effluent is subjected to further treatment by an MBR membrane system in a system with a sludge concentration higher than 14000 mg / L, using a membrane module with a pore size of 50 nm and an operating negative pressure of -20 kPa.

[0020] After treatment by this process, the final effluent quality is as follows: COD is 42 mg / L, ammonia nitrogen content is reduced to 4.8 mg / L, and total phosphorus content is 0.3 mg / L, meeting the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0021] Table 1 Comparison of Processing Effects between Existing Technologies and the Invention Technology Table 1 Comparison of Processing Effects between Existing Technologies and the Invention Technology

Claims

1. A membrane integrated process for the treatment of high strength chemical wastewater, characterized by: The high-concentration chemical wastewater from the collection pool is first pretreated by a precision filter to remove large particles, colloids and other impurities in the chemical wastewater, to obtain pretreated effluent; Secondly, the pretreated effluent is treated by a silicon carbide ultrafiltration membrane treatment device to remove part of small particles in the chemical wastewater, to obtain silicon carbide membrane effluent; thirdly, the silicon carbide effluent is treated by a ceramic nanofiltration membrane treatment device to obtain ceramic nanofiltration clear liquid and ceramic nanofiltration concentrated liquid, the ceramic nanofiltration concentrated liquid is treated by a carbon tetrachloride extraction process to recover organic matters in the chemical wastewater, the remaining wastewater returns to the collecting pool, and the ceramic nanofiltration clear liquid is treated by an A 2 O integrated MABR membrane treatment to degrade small-molecule chemical organic matters in the chemical wastewater, to obtain biochemical effluent; finally, the biochemical effluent is treated by a high-concentration sludge system MBR membrane system for deep treatment, and the effluent reaches the first level A discharge standard.

2. The integrated membrane process for the treatment of high concentrated chemical wastewater as claimed in claim 1, wherein: The filter core material of the precision filter is PP cotton, and the pore size is 5-10 μm.

3. The integrated membrane process for the treatment of high concentrated chemical wastewater as claimed in claim 1, wherein: The pore size of the silicon carbide ultrafiltration membrane is 0.05-0.1 μm, the initial operation temperature is 20-40 ℃, the operation pressure is 0.2-0.3 MPa, and the average operation flux is 200-300 LMH.

4. The integrated membrane process for the treatment of high strength chemical wastewater as claimed in claim 1 wherein: The molecular weight cut-off of the ceramic nanofiltration membrane is 200-1000 Da, the operation pressure is 1.5-2.5 MPa, and the initial operation temperature is 20-40 ℃.

5. The process for integrated membrane treatment of high strength chemical wastewater as claimed in claim 1 wherein: The A 2 The HRT (Hydraulic Retention Time) of the O-MABR system is 18-30 h, and the operating aeration pressure of the MABR is 0.03-0.05 MPa.

6. The process for integrated membrane treatment of high strength chemical wastewater as claimed in claim 1 wherein: The sludge concentration of the MBR membrane system is higher than 10000 mg / L, the pore size of the MBR membrane ranges from 20 to 100 nm, and the operation negative pressure of the MBR membrane is between-10 kPa and-35 kPa.

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