Method for treating coal chemical sewage into earth surface III-type water

Abstract

The invention relates to the technical field of sewage treatment, in particular to a method for treating coal chemical sewage into earth surface III-type water, and a regeneration treatment process comprises the following steps: sequentially treating the sewage through an adjusting tank, a two-stage AO biochemical system, coagulation air floatation, filtration through a gravity valveless filter tank, a powdered activated carbon membrane bioreactor and a quick-acting denitrification system, and then discharging. According to the method disclosed by the invention, the combination of processes can ensure that discharged sewage continuously and stably reaches the standard, particularly pollutants such as COD (Chemical Oxygen Demand), total nitrogen, total phosphorus and the like which are difficult to biodegrade continuously and stably reach the standard, and the treatment cost is lower than that of a traditional process.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method for treating coal chemical sewage into surface Class III water. Background Art

[0002] Coal chemical wastewater is wastewater generated during coal processing and chemical industry. Its main sources include coal coking, coal gasification, coal-to-oil and other processes. Coal chemical wastewater has a large volume of water and has high indicators such as COD, ammonia nitrogen, sulfide, cyanide, and low pH value. In terms of COD, the COD of coal chemical wastewater can be as high as 1000mg / L or more, exceeding the provisions of the comprehensive sewage discharge standard of about 500mg / L. High COD mainly comes from the primary cooling wastewater in the coal coking process, which contains many organic substances that are difficult to biodegrade. In terms of ammonia nitrogen, the ammonia nitrogen content is about 100-500mg / L, which is also significantly higher than the limit of about 100mg / L of the sewage discharge standard. This is because ammonium salts are used as solvents or inhibitors in both coal-to-gas and coal-to-oil processes, which eventually enter the wastewater. In addition, coal chemical wastewater also contains toxic and harmful components such as hydrogen sulfide, cyanide, and phenol. In addition to the excessive main pollutant indicators, coal chemical wastewater presents acidic characteristics, and the pH value is generally below 6. This is mainly because raw coal and most intermediate products are acidic and can release H+ in aqueous solution. In addition, inorganic acids such as hydrochloric acid are often added as detergents or catalysts in the process, which eventually enter the wastewater and reduce the pH value.

[0003] At present, coal chemical wastewater treatment is mainly carried out by traditional treatment technologies, such as "physical and chemical + biochemical", "physical and chemical + adsorption", "adsorption + biochemical" and other treatment methods, or advanced oxidation or RO membrane and other processes. With the continuous development of the coal chemical industry, water pollution is becoming increasingly serious. As a country with a severe shortage of water resources, it is very necessary for my country to strictly control the excessive discharge of sewage and the recycling of sewage. Summary of the invention

[0004] The purpose of the present invention is to provide a method for treating coal chemical wastewater to surface Class III water, which can ensure that the discharged wastewater continuously and stably meets the standards, especially the continuously and stably meets the standards of pollutants such as difficult-to-biodegrade COD, total nitrogen, total phosphorus, etc., and the treatment cost is lower than that of traditional processes.

[0005] The scheme adopted by the present invention to achieve the purpose is: a method for treating coal chemical wastewater to surface Class III water, comprising the following steps:

[0006] Step 1: The wastewater discharged by the coal chemical enterprise is collected through the pipe network and enters the mixing tank of the regeneration plant and the mechanical screen for separation to remove the larger suspended matter, and then enters the regulating tank for homogenization and equalization;

[0007] Step 2: The sewage in the regulating tank is transported to the flotation device, and coagulants are added to remove most of the SS and animal and vegetable oils in the sewage, while reducing some COD, BOD, ammonia nitrogen, and total nitrogen indicators;

[0008] Step 3: The effluent from the flotation device enters the two-stage AO biochemical system to remove most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, and suspended matter indicators in the sewage through the microorganisms in the activated sludge, and the addition of carbon source increases the rate of denitrification reaction and strengthens the denitrification effect of the anoxic tank;

[0009] Step 4: The effluent from the two-stage AO biochemical system enters the coagulation flotation tank, where SS and total phosphorus pollutants in the sewage are further removed by adding coagulants and flotation.

[0010] Step 5: The effluent from the coagulation flotation tank is further filtered by a gravity valveless filter and then flows to the powdered activated carbon membrane bioreactor system, where the powdered activated carbon is used to adsorb and remove the difficult-to-biodegrade COD in the sewage, and the saturated powdered activated carbon is separated and adsorbed by an immersed ultrafiltration membrane;

[0011] Step 6: The effluent from the powdered activated carbon membrane bioreactor system is transported to the rapid denitrification system, where the macromolecular denitrification resin is used to adsorb and remove nitrate nitrogen from the sewage to ensure that the total nitrogen meets the discharge standards;

[0012] Step 7: The effluent from the rapid denitrification system is added with disinfectant in the effluent disinfection tank and then reaches Class III surface discharge standards.

[0013] Preferably, in step 2, the coagulants are PAC and PAM, the dosage of PAC is 60-250 mg / L of dry powder, the alumina content of PAC is ≥28%, the dosage of PAM is 8-15 mg / L, and PAM is anionic.

[0014] Preferably, in step three, the two-stage AO biochemical system comprises a pre-denitrification tank, an aerobic tank 1, an anoxic tank, an aerobic tank 2 and a sedimentation tank which are connected in sequence, and the process parameters of the two-stage AO biochemical system are as follows: the residence time of the pre-denitrification tank is 7-12h; the residence time of the aerobic tank 1 is 13-20h; the residence time of the anoxic tank is 2-6h; the residence time of the aerobic tank 2 is 2-4h; the DO index of the anoxic tank is ≤0.5mg / L, and the DO index of the aerobic tank is >2mg / L.

[0015] Preferably, in step three, the carbon source is methanol, and the equivalent ratio of methanol to COD is 1g methanol: 1.5g COD.

[0016] Make full use of cheap carbon source methanol for denitrification and reduce treatment costs.

[0017] Preferably, in step 4, the coagulants are PAC and PAM, the dosage of PAC is 10-30 mg / L of dry powder, the alumina content of PAC is ≥28%, the dosage of PAM is 2-5 mg / L, and PAM is selected to be anionic.

[0018] Preferably, in the step five, the powdered activated carbon process parameters are selected as follows: size is 100 mesh, methylene blue value is greater than 12, iodine value is greater than 800, ash content is ≤8%, the ratio of activated carbon dosage to influent water volume is 100-300 mg / L, and the activated carbon concentration in the powdered activated carbon membrane bioreactor system is 2500-4500 mg / L.

[0019] Preferably, in step five, the average flux of the submerged ultrafiltration membrane during process operation is 10-20 L / ㎡.h, and the gas-water ratio during operation is 10-15:1.

[0020] Preferably, in step six, the adsorption saturated resin is reused after regeneration, the regenerated waste liquid enters the denitrification tank through the collection tank for denitrification, and the effluent is returned to the front-end regulating tank and then processed through the above step two until it meets the discharge standards.

[0021] Preferably, the saturated adsorption resin is regenerated using a sodium chloride aqueous solution with a mass percentage of 5% to 8%.

[0022] Preferably, in step seven, the disinfectant is sodium hypochlorite, and the dosage of available chlorine in sodium hypochlorite is 6-40 mg / L.

[0023] The present invention has the following advantages and beneficial effects:

[0024] The method of the present invention uses a combination of processes to ensure that the discharged sewage continuously and stably meets the standards, especially the continuously and stably meets the standards of pollutants such as difficult-to-biodegrade COD, total nitrogen, total phosphorus, etc., and the treatment cost is lower than that of traditional processes.

[0025] The deep treatment of the present invention uses a CUF system (activated carbon membrane bioreactor system) to remove most of the difficult-to-degrade or non-degradable organic matter, toxic and harmful substances, heavy metal ions, etc.

[0026] The deep treatment of the present invention uses the CUF system to make the indicators such as COD, ammonia nitrogen, and suspended matter in the effluent meet the surface water discharge standard of Class III.

[0027] The present invention uses a quick-acting denitrification system to ensure that the total nitrogen index of the effluent water can stably meet the surface water discharge standard of Class III. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a process flow chart of the present invention;

[0029] Figure 2 A system diagram for implementing the process of the present invention;

[0030] 1. Screen machine, 2. Equalization tank, 3. Flotation machine, 4. Pre-denitrification tank, 5. Aerobic tank 1, 6. Anoxic tank, 7. Aerobic tank 2, 8. Sedimentation tank, 9. Coagulation flotation tank, 10. Gravity valveless filter, 11. CUF system, 12. Quick-acting denitrification system, 13. Clean water disinfection tank, 14. Sludge tank, 15. Sludge dewatering system. DETAILED DESCRIPTION

[0031] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0032] Example 1

[0033] Figure 1 As shown, the present invention provides a process for treating coal chemical wastewater to Class III surface water. The regeneration treatment process includes sequentially passing through a regulating tank, a two-stage AO biochemical system, coagulation flotation, gravity valveless filter filtration, a powdered activated carbon membrane bioreactor (CUF), and a rapid denitrification system for treatment and then discharge, and includes the following steps:

[0034] Step 1: The wastewater discharged by the coal chemical enterprise is collected through the pipeline network and enters the mixing tank of the regeneration plant and the mechanical screen for separation to remove larger suspended matter, and then enters the regulating tank for homogenization and equalization.

[0035] Step 2: The sewage in the regulating tank is quantitatively transported to the flotation machine by a pump, and PAC and PAM are added to remove most of the pollutants such as SS, animal and vegetable oils in the sewage, and at the same time reduce some pollutant indicators such as COD, BOD, ammonia nitrogen, total phosphorus, and total nitrogen. The dosage of PAC is 60-250mg / L of dry powder, and the alumina content of PAC is ≥28%. The dosage of PAM is 8-15mg / L, and PAM is selected as anionic type.

[0036] Step 3: The effluent from the flotation machine enters the two-stage AO biochemical system, and most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, suspended matter and other pollutant indicators in the sewage are removed by microorganisms in the activated sludge. After this step, the COD index in the coal chemical wastewater can be reduced to below 50mg / L, with a typical value of 30mg / L, the BOD index can be reduced to below 15mg / L, with a typical value of 8mg / L, the ammonia nitrogen index can be reduced to below 1mg / L, with a typical value of 0.5mg / L, the total nitrogen index can be reduced to below 30mg / L, with a typical value of 20mg / L, and the total phosphorus index can be reduced to below 3mg / L, with a typical value of 1mg / L. The operating parameters of the biochemical system are: residence time of the pre-denitrification tank: 9h; residence time of aerobic tank 1: 15h; residence time of anoxic tank: 4h; residence time of aerobic tank 2: 2.9h; DO index of anoxic tank ≤0.5mg / L, with a typical value of 0.3mg / L L, aerobic pool DO index > 2mg / L typical value is 2.5mg / L, sludge yield: 0.6kgSS / kgBOD5; biochemical system BOD load: 0.0737kgBOD5 / kgMLSS.d; biochemical system NH3-N load: 0.0112kgNH3-N / kgMLSS.d; biochemical system TN load: 0.023kgTN / kgMLSS.d; sludge return ratio: 52%, maximum 100%; mixed liquor return ratio: maximum 400%; sludge age: 18d; sludge concentration; 5000mg / L; gas-water ratio 8.1:1; SVI = 60%. By adding methanol as a carbon source in the pre-denitrification tank and the anoxic tank, the rate of denitrification reaction is increased and the denitrification effect of the anoxic tank is enhanced. The COD equivalent of methanol is 1g methanol = 1.5gCOD. Adding cheap and high-quality methanol is convenient for saving reagent costs.

[0037] Step 4: The effluent from the two-stage AO biochemical system enters the coagulation and flotation tank. Through the addition of PAC, PAM agents and flotation, SS and total phosphorus pollutants in the sewage are further removed. In this step, the dosage of PAC is 10-30 mg / L of dry powder, and the alumina content of PAC is ≥28%. The dosage of PAM is 2-5 mg / L, and PAM is anionic. This step uses the coagulation effect of PAC to combine with inorganic phosphorus elements in water, which can reduce the total phosphorus index in coal chemical wastewater to below 0.2 mg / L, and the typical value is 0.1 mg / L.

[0038] Step 5: The effluent from the coagulation and flotation process flows by gravity to the powdered activated carbon membrane bioreactor system. The powdered activated carbon is used to adsorb and remove the difficult-to-biodegrade COD in the sewage. The saturated powdered activated carbon is separated and adsorbed by an immersed ultrafiltration membrane. After this step, the COD index in the coal chemical wastewater can be reduced to below 20 mg / L, and the typical value is 12 mg / L. The suspended particle phosphorus in step 4 is removed by separation to stabilize the total phosphorus to 0.05 mg / L. The process parameters of powdered activated carbon are selected; 100 mesh, methylene blue value>12, iodine value>800, ash content ≤8%. The ratio of activated carbon dosage to influent water volume is 100-300 mg / L, and the activated carbon concentration in the bioreactor pool is 2500-4500 mg / L. According to the changes in the incoming water quality, increasing the activated carbon concentration is beneficial to the anti-shock load of the pool body and the attachment of microorganisms. After the activated carbon adsorption is saturated, it can be discharged to the biological pool according to demand and follow the residual sludge discharge system.

[0039] The submerged ultrafiltration membrane in the above-mentioned carbon membrane bioreactor is composed of multiple groups of membranes and stainless steel frames, aeration systems, and water inlet and outlet systems. The parameters of the membrane assembly are 550㎡ per group, the average flux during process operation is 15L / ㎡.h, and the gas-water ratio during operation is 10-15:1. It is mainly used for gas disturbance to wash away the activated carbon on the membrane surface. The above-mentioned submerged ultrafiltration membrane produces water for 8 minutes, backwashes for 2 minutes, and adds 100-500mg / L of effective chlorine sodium hypochlorite and 0.5% sodium citrate for online chemical washing to restore flux.

[0040] Step 6. The effluent from the powdered activated carbon membrane bioreactor system is pumped to a rapid denitrification tank, where macromolecular denitrification resin is used to adsorb and remove nitrate nitrogen from the sewage to ensure that total nitrogen meets discharge standards. The total nitrogen value in the water entering the denitrification tank ranges from 1 to 30 mg / L, and the total nitrogen value after adsorption by targeted macroporous denitrification resin is below 1 mg / L. The typical operating conditions are an inlet total nitrogen concentration of 20 mg / L and an outlet total nitrogen concentration of 1 mg / L. The single tank operation time is 20 hours, and regeneration and cleaning are performed after adsorption saturation.

[0041] The above-mentioned quick-acting denitrification tank operation mode: To ensure the stable operation of the upstream and downstream processes, there must be 2 or more quick-acting denitrification tubes in operation within a 24-hour cycle, and the other 1 is in the process of regeneration, cleaning, and waiting. The resin regeneration takes about 3h to 6h, and the typical operation cycle is as follows:

[0042] 1) Run for 20 hours;

[0043] 2) Small backwash for 15 minutes, flow rate 15m / h, let the resin layer stand for 10 minutes and then fall off to clean the suspended matter on the upper layer;

[0044] 3) Regeneration of sodium chloride aqueous solution for 60 min, flow rate 3 m / h, concentration of sodium chloride aqueous solution 5%-8%, countercurrent regeneration to restore the resin adsorption capacity;

[0045] 4) Replace for 60 minutes at a flow rate of 4 m / h, and use clean water to countercurrently push out the brine in the resin layer;

[0046] 5) Positive flushing for 30 minutes, flow rate 15m / h, flush out the replacement regeneration liquid in the resin layer until the nitrate ion in the effluent is less than 1mg / L. Then enter the static and operation. The above operation process time can be adjusted according to the process requirements, mainly adjusting the regeneration and replacement time.

[0047] The saturated resin in this step is regenerated with the above-mentioned salt water concentration and reused. The regenerated waste liquid enters the denitrification tank through the collection tank for denitrification and denitrification. The effluent is returned to the front-end regulating tank and then treated through the above-mentioned step 2 until it meets the discharge standards.

[0048] Step 7. The effluent from the rapid denitrification system is disinfected in the effluent disinfection tank with sodium hypochlorite and reaches the surface Class III discharge standard. The residence time in the disinfection tank is not less than 0.5h, and the dosage of sodium hypochlorite effective chlorine is 6-40mg / L.

[0049] like Figure 2 As shown, the system for implementing the method of this embodiment includes a pretreatment system (including a mechanical grille 1, a regulating tank 2, and a flotation machine 3), a secondary biochemical treatment system (including a pre-denitrification tank 4, an aerobic tank 15, an anoxic tank 6, an aerobic tank 27, and a sedimentation tank 8), a deep treatment system (including a coagulation flotation tank 9, a gravity valveless filter 10, a powdered activated carbon membrane bioreactor system CUF system 11, a quick-acting denitrification system 12, and a disinfection tank 13); wherein the powdered activated carbon membrane bioreactor reactor includes (carbon distribution system, blower, dosing system, MB membrane assembly, water production system, backwash system), the quick-acting denitrification system includes (denitrification lifting pump, denitrification tank, regeneration agent tank, regeneration liquid collection tank, denitrification tank, denitrification and denitrification MBR tank and water production tank), a sludge tank 14 and a sludge dewatering system 15.

[0050] Example 2

[0051] The method of Example 1 was used to treat the wastewater of a coal chemical production enterprise with the original process of wastewater treatment (the original process was: mechanical grid + two-stage regulation + hydrolysis tank + two-stage aerobic + anoxic tank + three-stage aerobic + sedimentation tank + coagulation flotation tank + gravity valveless filter + clear water tank) of the enterprise, and the data are shown in Table 1:

[0052] Table 1

[0053]

[0054]

[0055] It can be seen from the data in the table that the sewage discharged after being treated by the process of the present invention has been improved from the Class A standard in the original "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB18918-2002) to the Class III standard for surface water in the "Surface Water Environmental Quality Standard" (GB 3838-2002).

[0056] Example 3

[0057] The process of Example 1, conventional secondary treatment biochemical process (conventional two-stage biochemical process; grid, regulating pretreatment + coagulation primary sedimentation tank + AAO biological pool + secondary sedimentation tank + coagulation sedimentation tank + denitrification filter + disinfection tank; wherein the excessive ammonia nitrogen and total nitrogen cannot reach the standard in the AAO biological pool process, and the actual operation of the process is COD influent 1460mg / L, effluent value 22mg / L, and removal rate 98.49%. Total nitrogen influent 168mg / L, effluent value 69.2mg / L, removal rate 58.80%. Ammonia nitrogen influent 73.1mg / L, effluent value 1.67mg / L, removal rate 97.71%. Total phosphorus influent 1.74mg / L, effluent value 0.0 5mg / L, removal rate 97.13%. ) and reverse osmosis membrane treatment process (grid, adjustment pretreatment + coagulation flotation + AAO biological pool + coagulation sedimentation tank + ultrafiltration nanofiltration double membrane, in the actual operation of this process, COD influent 1493mg / L, effluent value 13mg / L, removal rate 99.13%. Total nitrogen influent 171mg / L, effluent value 3.2mg / L, removal rate 98.12%. Ammonia nitrogen influent 75mg / L, effluent value 0.9mg / L, removal rate 98.8%. Total phosphorus influent 1.68mg / L, effluent value 0.05mg / L, removal rate 97.02%.) treated the wastewater of a coal chemical production enterprise with the same water quality, and the data are shown in Table 2:

[0058] Table 2

[0059]

[0060]

[0061] It can be seen from the data in Table 2 that compared with conventional treatment processes, the present invention can be treated to a higher standard, and compared with advanced oxidation or reverse osmosis membrane treatment processes, it has the advantages of low cost and no concentrated water waste.

[0062] Comprehensive process comparison shows that the combined process of the present invention has better treatment effect, lower investment cost, lower operating cost, more stable operation and stronger applicability than traditional processes and other processes in the treatment of coal chemical wastewater.

[0063] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A method for treating coal chemical wastewater to Class III surface water, characterized in that: The following steps are involved: Step 1: The wastewater discharged by the coal chemical enterprise is collected through the pipe network and enters the mixing tank of the regeneration plant and the mechanical screen for separation to remove the larger suspended matter, and then enters the regulating tank for homogenization and equalization; Step 2: The sewage in the regulating tank is transported to the flotation device, and coagulants are added to remove most of the SS and animal and vegetable oils in the sewage, while reducing some COD, BOD, ammonia nitrogen, and total nitrogen indicators; Step 3: The effluent from the flotation device enters the two-stage AO biochemical system to remove most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, and suspended matter indicators in the sewage through the microorganisms in the activated sludge, and the addition of carbon source increases the rate of denitrification reaction and strengthens the denitrification effect of the anoxic tank; Step 4: The effluent from the two-stage AO biochemical system enters the coagulation flotation tank, where SS and total phosphorus pollutants in the sewage are further removed by adding coagulants and flotation. Step 5: The effluent from the coagulation flotation tank is further filtered by a gravity valveless filter and then flows to the powdered activated carbon membrane bioreactor system, where the powdered activated carbon is used to adsorb and remove the difficult-to-biodegrade COD in the sewage, and the saturated powdered activated carbon is separated and adsorbed by an immersed ultrafiltration membrane; Step 6: The effluent from the powdered activated carbon membrane bioreactor system is transported to the rapid denitrification system, where the macromolecular denitrification resin is used to adsorb and remove nitrate nitrogen from the sewage to ensure that the total nitrogen meets the discharge standards; Step 7: The effluent from the rapid denitrification system is fed through the effluent disinfection tank and then added with disinfectant to meet the Class III surface discharge standards.

2. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step 2, the coagulants are PAC and PAM, the dosage of PAC is 60-250 mg / L of dry powder, the alumina content of PAC is ≥28%, the dosage of PAM is 8-15 mg / L, and PAM is anionic.

3. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step 3, the two-stage AO biochemical system includes a pre-denitrification tank, an aerobic tank 1, an anoxic tank, an aerobic tank 2 and a sedimentation tank which are connected in sequence. The process parameters of the two-stage AO biochemical system are as follows: the residence time of the pre-denitrification tank is 7-12h; the residence time of the aerobic tank 1 is 13-20h; the residence time of the anoxic tank is 2-6h; the residence time of the aerobic tank 2 is 2-4h; the DO index of the anoxic tank is ≤0.5mg / L, and the DO index of the aerobic tank is >2mg / L.

4. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step 3, the carbon source is methanol, and the equivalent ratio of methanol to COD is 1g methanol: 1.5g COD.

5. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step 4, the coagulants are PAC and PAM, the dosage of PAC is 10-30 mg / L of dry powder, the alumina content of PAC is ≥28%, the dosage of PAM is 2-5 mg / L, and PAM is selected to be anionic.

6. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step five, the process parameters of powdered activated carbon are selected; the size is 100 mesh, the methylene blue value is greater than 12, the iodine value is greater than 800, the ash content is ≤8%, the ratio of activated carbon dosage to influent water volume is 100-300 mg / L, and the activated carbon concentration in the powdered activated carbon membrane bioreactor system is 2500-4500 mg / L.

7. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step 5, the average flux of the immersed ultrafiltration membrane during process operation is 10-20 L / ㎡.h, and the gas-water ratio during operation is 10-15:

1.

8. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In the step six, the adsorption saturated resin is regenerated and reused, the regenerated waste liquid enters the denitrification tank through the collection tank for denitrification, and the effluent is returned to the front-end regulating tank and then treated through the above step two until it meets the discharge standards.

9. The method for treating coal chemical wastewater to Class III surface water according to claim 8, characterized in that: The saturated adsorption resin is regenerated by using a sodium chloride aqueous solution with a mass percentage of 5% to 8%.

10. The method for treating coal chemical wastewater to Class III surface water according to claim 1, characterized in that: In step seven, the disinfectant is sodium hypochlorite, and the dosage of effective chlorine in sodium hypochlorite is 6-40 mg / L.

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