CN111807629A

CN111807629A - Zero-discharge treatment method and system for coking ammonia distillation wastewater

Info

Publication number: CN111807629A
Application number: CN202010693558.8A
Authority: CN
Inventors: 邹宗海; 郝欣欣; 臧彦强; 赵峰; 冯建辉; 张金富; 王东恩
Original assignee: Shandong Ruihai Environmental Technology Co ltd
Current assignee: Shandong Ruihai Environmental Technology Co ltd
Priority date: 2020-07-17
Filing date: 2020-07-17
Publication date: 2020-10-23

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a zero-discharge treatment method and system for coking ammonia distillation wastewater. The invention relates to a zero discharge treatment method of coking ammonia distillation wastewater, which is characterized in that the coking ammonia distillation wastewater is sequentially subjected to ozone pre-oxidation, air flotation, electrocatalytic oxidation, an A/O biochemical process, precipitation, flocculation, ozone catalytic oxidation, an aeration biological filter tank process, ultrafiltration membrane filtration, nanofiltration membrane filtration and reverse osmosis membrane treatment; the hydraulic retention time of electrocatalytic oxidation is 10-60min, and the anode plateIs a lead-rhenium coated electrode, the cathode is a graphite carbon electrode, the distance between the polar plates is 3-10 cm, and the current density is 5-20mA/cm². The treatment method disclosed by the invention is low in treatment cost, realizes advanced treatment, realizes resource utilization of the treated coking ammonia distillation wastewater, and really realizes zero emission; meanwhile, the invention provides a coking ammonia distillation wastewater zero-discharge treatment system which is convenient and fast to operate.

Description

Zero-discharge treatment method and system for coking ammonia distillation wastewater

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to a zero-discharge treatment method and system for coking ammonia distillation wastewater.

Background

The coking wastewater is industrial wastewater containing volatile phenol, polycyclic aromatic hydrocarbon, oxygen, sulfur, nitrogen and other heterocyclic compounds generated in the processes of coking and coal gas high-temperature dry distillation, purification and byproduct recovery, and is industrial organic wastewater which has high CODcr, high phenol value and high ammonia nitrogen and is difficult to treat. Its main sources are three: the residual ammonia water is the wastewater generated in the coal carbonization and coal gas cooling, the water amount of the residual ammonia water accounts for more than half of the total amount of the coking wastewater, and the residual ammonia water is the main source of the coking wastewater; secondly, the waste water produced in the coal gas purification process, such as final cold water of coal gas, crude benzene separation water and the like; and the third is the waste water produced in the refining process of tar, crude benzene and other places. Coking wastewater is industrial wastewater containing a large amount of refractory organic pollutants, has complex components, contains a large amount of toxic and harmful substances such as phenol, cyanogen, benzene, ammonia nitrogen and the like, and causes serious pollution to the environment due to the coking wastewater which is discharged in an overproof way. The coking wastewater has the characteristics of large change of water quality and water quantity, complex components, high content of organic matters, particularly refractory organic matters, high ammonia nitrogen concentration and the like.

Nitrogen-containing compounds are organic substances with a large number of waste water and quite complex composition in a coking plant. Mass spectrometry has identified quinolines and certain alkyl substituents, suspected of being carcinogens. Aromatic hydrocarbons and aromatic amines and the like have similarly many biologically active substances. The phthalic acid vinegar is another carcinogen in the wastewater, wherein dimethyl phthalate and diisooctyl phthalate are also pollutants preferentially detected by the United states environmental protection agency. In conclusion, the coking wastewater has complex components and various pollutants, and a plurality of pollutants are biologically active substances with carcinogenic and carcinogenic activities. For this kind of phenol cyanide waste water, direct discharge is not allowed by the country. Therefore, most coking enterprises recycle the wastewater after treatment.

The recycling precondition of the treated coking wastewater is to meet the standard, and then whether other treatment processes are adopted is considered according to the requirement of recycled water. Regarding the index of reuse water, coke plants of steel and iron integrated enterprises, coal and coke integrated enterprises and independent coke plants are distinguished, and coke plants adopting wet quenching or dry quenching are also distinguished. In order to realize zero discharge of the coking wastewater, corresponding treatment processes are required to be adopted for different recycling users according to enterprise properties, so that the coking wastewater resources after treatment are reasonably utilized to the maximum extent.

The coking wastewater after treatment can be recycled in a coking plant and can also be used in a turbid circulating water system of the iron and steel enterprises. Thus, the wastewater treatment needs to reach the first grade standard of GBl3456-92 discharge Standard of pollutants for the Steel industry.

Secondly, the coking wastewater after treatment can be sent to a coal washing plant besides a coking plant and used as coal washing supplementary water, and the coking wastewater also needs to reach the primary standard in GB8978-1996 Integrated wastewater discharge Standard.

Thirdly, if the independent coking plant adopts a wet quenching process, the treated coking wastewater can reach the first-level standard in GB8978-1996 Integrated wastewater discharge Standard.

If a dry coke quenching process is adopted in the independent coking plant, the environmental protection department does not allow the dry coke quenching process to be discharged, and only the ammonia distillation wastewater is not consumed by the coking plant even if other water quantities are not considered. A deep treatment process must be employed.

Zero discharge is required, only the coking plant consumes the coking wastewater after treatment, and an advanced treatment process is needed to be adopted, so that the advanced treatment produced water is used for producing clean circulating water make-up water.

The existing treatment process flow of the coking ammonia distillation wastewater is mainly air floatation-A/O biochemistry, and the COD of the effluent is 200-500 mg/L. The reason for the poor treatment effect of the process is as follows:

(1) the coking wastewater contains phenols and cyanogen substances which have toxic inhibition effect on microorganisms, so that the removal efficiency of a biochemical system is not high;

(2) the coking wastewater contains organic matters which are difficult to biodegrade, and the index requirements are difficult to reach by biochemical treatment alone.

In conclusion, the coking ammonia distillation wastewater only adopts biochemical treatment and is difficult to reach the discharge or recycling standard. Most coking enterprises are located in northwest areas with water shortage and drought, and the national environmental protection policy gradually cancels the wet quenching process, so that the zero discharge of ammonia distillation wastewater becomes the only outlet of the coking enterprises.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a zero-emission treatment method for coking ammonia distillation wastewater, which has low treatment cost and realizes advanced treatment, so that the treated coking ammonia distillation wastewater is recycled, and zero emission is really realized; meanwhile, the invention provides a coking ammonia distillation wastewater zero-discharge treatment system which is convenient and fast to operate.

The invention relates to a zero discharge treatment method of coking ammonia distillation wastewater, which is characterized in that the coking ammonia distillation wastewater is sequentially subjected to ozone pre-oxidation, air flotation, electrocatalytic oxidation, an A/O biochemical process, precipitation, flocculation, ozone catalytic oxidation, an aeration biological filter tank process, ultrafiltration membrane filtration, nanofiltration membrane filtration and reverse osmosis membrane treatment; discharging sludge obtained by the air flotation and flocculation process to the residual sludge; the A/O biochemical process is divided into an anoxic biological tank and an aerobic biological tank, and effluent of the aerobic biological tank flows back to the anoxic biological tank; returning sludge in the sedimentation tank to the anoxic biological tank; and (3) evaporating the solutions obtained by filtering the nanofiltration membrane and the reverse osmosis membrane respectively, and recovering the obtained solid salt.

Preferably, in the ozone pre-oxidation process, the adding concentration of ozone is 50-100mg/L, the adding mode of ozone is jet flow, and the oxidation time is 30-60 min.

The process oxidizes phenols in the wastewater into meta-phenol and para-phenol, and the meta-phenol and the para-phenol form coal tar floating on the water surface by utilizing the characteristic of low solubility of the meta-phenol and the para-phenol in the wastewater; the biological toxic substances such as sulfide, cyanide and the like in the wastewater are oxidized to form elemental sulfur and harmless organic matters, so that the biodegradability of the wastewater is improved; the strong oxidizing property of ozone on the organic matters containing unsaturated bonds is utilized to oxidize the unsaturated aromatic organic matters in the wastewater, so that the biodegradability of the wastewater is further improved; the content of dissolved oxygen in the wastewater is improved, and favorable conditions are provided for the subsequent process.

Preferably, in the air floatation process, the hydraulic retention time is 20-40min, the volume ratio of air to water is 500:1, the concentration of the added polyaluminium chloride is 50-100mg/L, and the concentration of the added cationic polyacrylamide is 3-6 mg/L.

The process utilizes the flocculation and air flotation effects to remove original suspended matters and colloids in the wastewater; coal tar and elemental sulfur generated in the ozone pre-oxidation process section are removed.

Preferably, the hydraulic retention time of the electrocatalytic oxidation is 10-60min, the anode plate is a lead-rhenium coated electrode, the cathode is a graphite carbon electrode, the distance between the electrode plates is 3-10 cm, and the current density is 5-20mA/cm²。

The process utilizes a large amount of oxygen dissolved in water in an ozone process section to produce hydrogen peroxide near a cathode to further oxidize the wastewater, and the premise that the cathode generates hydrogen peroxide in the electrolysis process is that a large amount of dissolved oxygen exists in the water; under the action of a direct current electric field, macromolecular organic matters in the wastewater are oxidized into micromolecular organic matters by utilizing the catalytic action of a lead-rhenium electrode, so that the biodegradability of the wastewater is further improved; the method has the advantages that the electrocatalysis is utilized to oxidize chloride ions in the wastewater into chlorine, the chlorine is dissolved in water to produce hypochlorous acid, and the hypochlorous acid can oxidize ammonia nitrogen in the wastewater into nitrogen, so that the total nitrogen load of a subsequent biochemical process is reduced, and the stable operation of a biochemical system is ensured; the electrolysis accelerates the decomposition of residual ozone in the wastewater, and avoids the influence on the stability of the subsequent biochemical process (the ozone has toxic action on microorganisms) caused by the overlarge ozone content in the wastewater.

Preferably, the hydraulic retention time of the A/O biochemical process is 50-100 hours, and the dissolved oxygen in the anoxic biological tank is controlled below 0.5 mg/L; the dissolved oxygen of the aerobic biological tank is controlled to be 2-4mg/L, and the sludge concentration is controlled to be 4000-6000 mg/L.

The process utilizes the decomposition effect of carbonized microorganisms to reduce the content of organic matters in the sewage; removing nitrogen-containing substances in the wastewater by using a nitrification-denitrification reaction; and removing part of total phosphorus by discharging residual sludge.

Preferably, the surface load of the sedimentation tank in the sedimentation process is 0.6-1.0m³/(m²H) effecting a sludge-water separation by the process.

Preferably, the adding concentration of a flocculating agent PAC in the flocculation process is 25-100mg/L, the adding concentration of a coagulant aid PAM is 3-8mg/L, and the settling time is 3 hours.

The process removes suspended substances and colloids in water; the oxidant dosage and the backwashing frequency of the subsequent ozone catalytic oxidation process are reduced.

Preferably, in the catalytic ozonation process, the adding concentration of ozone is 50-200mg/L, the adding mode of ozone is jet flow, and the hydraulic retention time is 30-120 min.

The process has the advantages that the ozone oxidizes and decomposes organic matters in water under the action of the catalyst, so that the content of COD (chemical oxygen demand) in the wastewater is reduced, and the service life of membrane equipment in the subsequent process is prolonged; the oxidation of the ozone on organic matters is utilized, the biodegradability of the wastewater is improved, good operation conditions are provided for subsequent biochemistry, and the operation cost of the whole process is reduced; the ozone catalyst is a heterogeneous solid catalyst, the effective component is in the form of transition metal oxide, and the carrier is porous oxide of silicon and aluminum.

Preferably, the hydraulic retention time of the biological aerated filter process is 2-3 hours, and the biological filter material is volcanic rock or ceramsite.

The process utilizes a biochemical method to further reduce the content of organic matters and nitrogenous substances in the wastewater and ensure the stable operation of the subsequent process.

Preferably, the ultrafiltration membrane adopts a polyvinylidene fluoride flat ultrafiltration membrane for filtration, and the water permeability of the membrane is 0.5-5.0m³/(m²D), operating pressure of 0.1-0.5MPa, molecular weight cut-off of 100 kDa.

The process reduces the content of suspended matters in the wastewater and ensures the stable operation of the subsequent membrane process.

Preferably, the pore diameter of the nano-filtration membrane is 1nm, and the operating pressure is 5.0-30 bar.

The process intercepts nano-scale substances, and is generally used for intercepting bivalent and above ions and most organic matters; concentrating divalent salt in the wastewater by 3-8 times; and (3) feeding the nanofiltration membrane concentrated solution into an evaporator for evaporation, recycling the condensate, and selling the solid salt which is sodium sulfate containing crystal water and can be used as an industrial byproduct.

Preferably, the operating pressure of the reverse osmosis membrane process is 2-10 MPa; the water permeability of the membrane is 0.1-2.5m³/(m²D) thickness of 100-.

The process can effectively remove dissolved salts, colloids, microorganisms, organic matters and the like in water; and (3) feeding the reverse osmosis membrane concentrated solution into an evaporator for evaporation, recycling the condensed liquid, and selling the solid salt containing sodium chloride as an industrial byproduct.

The zero discharge treatment system for the coking ammonia distillation wastewater comprises an ozone pre-oxidation tank, an air floatation device, an electrocatalytic oxidation device, an A/O biochemical process device, a sedimentation tank, a flocculation sedimentation tank, an ozone catalytic oxidation device, an aeration biological filter tank, an ultrafiltration membrane device, a nanofiltration membrane device and a reverse osmosis membrane device which are sequentially connected; the A/O biochemical process device is divided into an anoxic biological tank and an aerobic biological tank, and a return pipeline is arranged between the aerobic biological tank and the anoxic biological tank; a sludge return pipeline is arranged between the sedimentation tank and the anoxic biological tank; the air flotation device and the bottom of the flocculation sedimentation tank are respectively connected with the residual sludge; the nanofiltration membrane device and the reverse osmosis membrane device are respectively connected with the first evaporator and the second evaporator.

Preferably, the ozone pre-oxidation tank is connected with a first ozone input pipeline and a coking ammonia distillation wastewater input pipeline.

Preferably, the air flotation device is connected with the first PAC and PAM input pipeline.

Preferably, the aerobic biological tank is provided with a compressed air input pipeline.

Preferably, the flocculation sedimentation tank is connected with a second PAC and PAM input pipeline.

Preferably, the ozone catalytic oxidation device is provided with a second ozone input pipeline.

Preferably, the first evaporator and the second evaporator are respectively provided with a first condensate return pipeline and a second condensate return pipeline, and the first condensate return pipeline and the second condensate return pipeline are connected with the water outlet.

Preferably, a crystal water-containing sodium sulfate solid salt discharge pipeline is arranged at the bottom of the first evaporator; and a discharge pipeline for solid salt containing sodium chloride is arranged at the bottom of the second evaporator.

Compared with the prior art, the invention has the following beneficial effects:

1. the wastewater treated by the method can meet the recycling requirement, and directly enters a circulating cooling water system, and the generated solid salt can be recycled or sold as an industrial byproduct, so that the resource utilization of the coking ammonia distillation wastewater is realized.

2. The method adopts the ozone pre-oxidation, air flotation and electrocatalytic oxidation processes to pre-treat the coking ammonia distillation wastewater, and firstly, the coal tar can be removed to the maximum extent, so that the stability of the subsequent process is ensured; secondly, substances which have toxic and harmful effects on microorganisms, such as phenolics, sulfides, cyanides, unsaturated aromatics and the like are removed through oxidation, the biodegradability of the wastewater is improved, the stability and the treatment load of a biochemical process are ensured, and the subsequent biochemical process can exert the maximum efficiency.

3. The invention adopts flocculation precipitation, ozone catalytic oxidation and an aeration biological filter tank process to carry out advanced treatment on the coking ammonia distillation wastewater, further removes organic matters which are difficult to degrade biologically, ensures the stable operation of the subsequent membrane process, leads the effluent to pass through an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane and an evaporation process, can recycle the condensate, leads the effluent to meet the recycling requirement, sells solid salt as industrial byproducts, and realizes the zero discharge treatment of the coking ammonia distillation wastewater.

4. The method has low treatment cost, the solid salt generated by the process can be sold as an industrial byproduct, the whole process is stable to operate, the service life of the equipment is long, the efficiency of the biochemical process is maximized, and the treatment cost is reduced to the minimum on the premise of ensuring the treatment effect.

5. The system is convenient to operate, and all devices are flexibly connected and convenient to maintain.

Drawings

FIG. 1 is a process flow diagram according to the present invention;

FIG. 2 is a schematic diagram of the system architecture of the present invention;

in the figure, 1, a first ozone input pipeline, 2, a coking ammonia distillation wastewater input pipeline, 3, a first PAC and PAM input pipeline, 4, an air flotation device, 5, a return pipeline, 6, a compressed air input pipeline, 7, a second PAC and PAM input pipeline, 8, a second ozone input pipeline, 9, an ozone catalytic oxidation device, 10, an ultrafiltration membrane device, 11, a first evaporator, 12, a crystal water-containing sodium sulfate solid salt discharge pipeline, 13, a first condensate return pipeline, 14, a second condensate return pipeline, 15 and a sodium chloride-containing solid salt discharge pipeline; 16. a second evaporator, 17, a reverse osmosis membrane device, 18, a nanofiltration membrane device, 19, an aeration biological filter, 20, a flocculation sedimentation tank, 21, a sedimentation tank, 22, a sludge return pipeline, 23, an aerobic biological tank, 24, a residual sludge position, 25, an anoxic biological tank, 26, an electrocatalytic oxidation device, 27 and an ozone pre-oxidation tank.

Detailed Description

The system used in the examples, as shown in FIG. 1:

the ozone pre-oxidation tank 27, the air flotation device 4, the electrocatalytic oxidation device 26, the A/O biochemical process device, the sedimentation tank 21, the flocculation sedimentation tank 20, the ozone catalytic oxidation device 9, the biological aerated filter 19, the ultrafiltration membrane device 10, the nanofiltration membrane device 18 and the reverse osmosis membrane device 17 are sequentially connected; the A/O biochemical process device is divided into an anoxic biological tank 25 and an aerobic biological tank 23, and a return pipeline 5 is arranged between the aerobic biological tank 23 and the anoxic biological tank 25; a sludge return pipeline 22 is arranged between the sedimentation tank 21 and the anoxic biological tank 25; the air flotation device 4 and the bottom of the flocculation sedimentation tank 20 are respectively connected with a residual sludge position 24; the nanofiltration membrane device 18 and the reverse osmosis membrane device 17 are respectively connected with the first evaporator 11 and the second evaporator 16.

The ozone pre-oxidation tank 27 is connected with the first ozone input pipeline 1 and the coking ammonia distillation wastewater input pipeline 2.

The air flotation device 4 is connected with a first PAC and PAM input pipeline 3.

The aerobic biological tank 23 is provided with a compressed air input pipeline 6.

The flocculation sedimentation tank 20 is connected with a second PAC and PAM input pipeline 7.

The ozone catalytic oxidation device 9 is provided with a second ozone input pipeline 8.

The first evaporator 11 and the second evaporator 16 are respectively provided with a first condensate return pipeline 13 and a second condensate return pipeline 14, and the first condensate return pipeline 13 and the second condensate return pipeline 14 are connected with the water outlet.

A crystal water-containing sodium sulfate solid salt discharge pipeline 12 is arranged at the bottom of the first evaporator 11; the bottom of the second evaporator 16 is provided with a discharge line 15 for solid salt containing sodium chloride.

Example 1

Ammonia distillation wastewater of a certain coking plant: COD is 4000mg/L, volatile phenol is 400mg/L, cyanide is 15mg/L, sulfide is 75mg/L, and ammonia nitrogen is 1100 mg/L.

The treatment method provided by the invention is adopted for treatment:

adding 50mg/L ozone into wastewater to be treated, and then feeding the wastewater into an ozone pre-oxidation tank, wherein the pre-oxidation time is 30 minutes;

adding 50mg/L of polymeric aluminum and 3mg/L of cationic polyacrylamide into ozone pre-oxidation effluent, and then entering air flotation, wherein the retention time of air flotation water power is 20 minutes, and the volume ratio of air to water is 500: 1;

the air-floated effluent enters an electrocatalytic oxidation unit for oxidation for 10 minutes, and the current density between the polar plates is 5.0mA/cm²The distance between the polar plates is 10 cm;

the effluent of the electrocatalytic oxidation enters an anoxic/aerobic biological tank, the sludge concentration is kept to be 4000mg/L, the hydraulic retention time is 50 hours, nitrate in the water in the anoxic biological tank is converted into nitrogen to overflow by denitrifying bacteria under the anoxic condition, the dissolved oxygen in the anoxic biological tank is controlled to be below 0.5mg/L, the effluent of the anoxic biological tank enters the aerobic biological tank, the dissolved oxygen in the aerobic biological tank is 2mg/L, and partial organic matters and ammonia nitrogen in the water are decomposed into CO by aerobic microorganisms₂、H₂O、NO₃ ^2-The effluent part of the aerobic biological tank reflows to the anoxic biological tank according to 100 percent of reflow ratio to remove NO₃ ^2-The effluent of the aerobic biological tank enters a sedimentation tank for mud-water separation, the sludge at the bottom returns to the anoxic biological tank, the supernatant enters a flocculation sedimentation tank for removing suspended matters and colloids in the water, 25mg/L of flocculant and 3mg/L of coagulant aid are added, and the sedimentation time is 3 hours;

after flocculation and precipitation, the effluent enters an ozone catalytic oxidation unit for oxidation for 30 minutes, and the ozone adding concentration is 50 mg/L;

the effluent of the catalytic ozonation enters an aeration biological filter for 2 hours to further reduce the content of organic matters and nitrogen-containing substances in the wastewater, and the biological filter material is volcanic rock;

the effluent of the aeration biological filter tank firstly enters an ultrafiltration membrane filtration process to reduce the content of suspended matters in water so as to ensure that the subsequent membrane process stably operates, the operating pressure is 0.1MPa, and the water permeability of the membrane is 0.5m³/(m²D), adopting a polyvinylidene fluoride flat ultrafiltration membrane, wherein the intercepted molecular mass is 100 kDa;

filtering water by the ultrafiltration membrane, allowing the filtered water to enter a nanofiltration membrane, wherein the pore diameter of a micropore of the nanofiltration membrane is 1nm, the operating pressure is 5.0bar, evaporating the generated concentrated solution, using solid salt as sodium sulfate containing crystal water, and recycling the condensate;

filtered water of the nanofiltration membrane enters a reverse osmosis membrane, and the technological operating pressure of the reverse osmosis membrane is 2 MPa; the water permeability of the membrane is 0.1m³/(m²D) the thickness is 100 mu m, substances such as dissolved salts, colloids, microorganisms, organic matters and the like in the water are removed, the generated concentrated solution is evaporated, solid salt contains sodium chloride, the condensate is recycled, and the zero emission of the coking wastewater is realized by the whole process.

COD of the effluent is 57mg/L, volatile phenol is 0mg/L, cyanide is 0mg/L, sulfide is 0.5mg/L, ammonia nitrogen is 0.2mg/L, and treatment cost is 15 yuan/m³。

Example 2

Ammonia distillation wastewater of a certain coking plant: COD is 6000mg/L, volatile phenol is 840mg/L, cyanide is 30mg/L, sulfide is 120mg/L, ammonia nitrogen is 1500 mg/L.

The treatment method provided by the invention is adopted for treatment:

adding 80mg/L ozone into wastewater to be treated, and then feeding the wastewater into an ozone pre-oxidation tank, wherein the pre-oxidation time is 45 minutes;

adding 70mg/L of polymeric aluminum and 5mg/L of cationic polyacrylamide into ozone pre-oxidation effluent, and then entering air flotation, wherein the hydraulic retention time of the air flotation is 30 minutes, and the volume ratio of air to water is 500: 1;

the air-floated effluent enters an electrocatalytic oxidation unit for oxidation for 40 minutes, and the current density between the polar plates is 15mA/cm²The distance between the polar plates is 6 cm;

the effluent of the electrocatalytic oxidation enters an anoxic/aerobic biological tank, the sludge concentration is kept to be 5000mg/L, the hydraulic retention time is 80 hours, nitrate in the water in the anoxic biological tank is converted into nitrogen to overflow by denitrifying bacteria under the anoxic condition, the dissolved oxygen in the anoxic biological tank is controlled to be below 0.5mg/L, the effluent of the anoxic biological tank enters the aerobic biological tank, the dissolved oxygen in the aerobic biological tank is 3mg/L, and partial organic matters and ammonia nitrogen in the water are decomposed into CO by aerobic microorganisms₂、H₂O、NO₃ ^2-The effluent part of the aerobic biological tank reflows to the anoxic biological tank according to the reflow ratio of 250 percent to remove NO₃ ^2-The effluent of the aerobic biological tank enters a sedimentation tank for mud-water separation, the sludge at the bottom returns to the anoxic biological tank, the supernatant enters a flocculation sedimentation tank for removing suspended matters and colloids in the water, 65mg/L of flocculating agent and 5mg/L of coagulant aid are added, and the sedimentation time is 3 hours;

after flocculation and precipitation, the effluent enters an ozone catalytic oxidation unit for oxidation for 80 minutes, and the ozone adding concentration is 130 mg/L;

the effluent of the catalytic ozonation enters an aeration biological filter for 2.5 hours to further reduce the content of organic matters and nitrogen-containing substances in the wastewater, and the biological filter material is ceramsite;

the effluent of the aeration biological filter tank firstly enters an ultrafiltration membrane filtration process to reduce the content of suspended matters in water so as to ensure that the subsequent membrane process stably operates, the operating pressure is 0.3MPa, and the water permeability of the membrane is 3.0m³/(m²D), adopting a polyvinylidene fluoride flat ultrafiltration membrane, wherein the intercepted molecular mass is 100 kDa;

filtering water by the ultrafiltration membrane, allowing the filtered water to enter a nanofiltration membrane, wherein the micropore aperture of the nanofiltration membrane is 1nm, the operating pressure is 20bar, the generated concentrated solution is subjected to evaporation treatment, solid salt is sodium sulfate containing crystal water, and the condensate is recycled;

filtered water of the nanofiltration membrane enters a reverse osmosis membrane, and the technological operating pressure of the reverse osmosis membrane is 5 MPa; the water permeability of the membrane is 2.5m³/(m²D) the thickness is 150 mu m, substances such as dissolved salts, colloids, microorganisms, organic matters and the like in the water are removed, the generated concentrated solution is evaporated, solid salt contains sodium chloride, the condensate is recycled, and the whole process realizes zero emission of the coking wastewater.

The COD of the effluent is 41mg/L, the volatile phenol is 0mg/L, the cyanide is 0mg/L, the sulfide is 0.3mg/L, the ammonia nitrogen is 0.2mg/L, and the treatment cost is 17 yuan/m³。

Example 3

Ammonia distillation wastewater of a certain coking company: COD is 8000mg/L, volatile phenol is 1100mg/L, cyanide is 40mg/L, sulfide is 150mg/L, ammonia nitrogen is 2000 mg/L.

The treatment method provided by the invention is adopted for treatment: adding 100mg/L ozone into wastewater to be treated, and then feeding the wastewater into an ozone pre-oxidation tank, wherein the pre-oxidation time is 60 minutes;

adding 100mg/L of polymeric aluminum and 6mg/L of cationic polyacrylamide into ozone pre-oxidation effluent, and then entering air flotation, wherein the retention time of air flotation water power is 40 minutes, and the volume ratio of air to water is 500: 1;

the air-floated effluent enters an electrocatalytic oxidation unit for oxidation for 60 minutes, and the current density between the polar plates is 20mA/cm²The distance between the polar plates is 3 cm;

the effluent of the electrocatalytic oxidation enters an anoxic/aerobic biological tank, the sludge concentration is kept to be about 6000mg/L, the hydraulic retention time is 100 hours, nitrate in the water in the anoxic biological tank is converted into nitrogen to overflow under the anoxic condition, the dissolved oxygen in the anoxic biological tank is controlled to be below 0.5mg/L, the effluent of the anoxic biological tank enters the aerobic biological tank, the dissolved oxygen in the aerobic biological tank is 4mg/L, and partial organic matters and ammonia nitrogen in the water are decomposed into CO by aerobic microorganisms₂、H₂O、NO₃ ^2-The effluent part of the aerobic biological tank reflows to the anoxic biological tank according to the reflow ratio of 400 percent to remove NO₃ ^2-The effluent of the aerobic biological tank enters a sedimentation tank for mud-water separation, the sludge at the bottom returns to the anoxic biological tank, the supernatant enters a flocculation sedimentation tank for removing suspended matters and colloids in the water, 100mg/L of flocculating agent and 8mg/L of coagulant aid are added, and the sedimentation time is 3 hours;

after flocculation and precipitation, the effluent enters an ozone catalytic oxidation unit for oxidation for 120 minutes, and the ozone adding concentration is 200 mg/L;

the effluent of the catalytic oxidation of ozone enters an aeration biological filter for 3 hours to further reduce the content of organic matters and nitrogen-containing substances in the wastewater, and the biological filter material is volcanic rock;

the effluent of the aeration biological filter tank firstly enters an ultrafiltration membrane filtration process to reduce the content of suspended matters in water so as to ensure that the subsequent membrane process stably operates, the operating pressure is 0.5MPa, and the water permeability of the membrane is 5.0m³/(m²D), adopting a polyvinylidene fluoride flat ultrafiltration membrane, wherein the intercepted molecular mass is 100 kDa;

filtering water by the ultrafiltration membrane, allowing the filtered water to enter a nanofiltration membrane, wherein the micropore aperture of the nanofiltration membrane is 1nm, the operating pressure is 30bar, the generated concentrated solution is subjected to evaporation treatment, solid salt is sodium sulfate containing crystal water, and the condensate is recycled;

filtered water of the nanofiltration membrane enters a reverse osmosis membrane, and the technological operating pressure of the reverse osmosis membrane is 10 MPa; the water permeability of the membrane is 1.5m³/(m²D) the thickness is 200 mu m, substances such as dissolved salts, colloids, microorganisms, organic matters and the like in the water are removed, the generated concentrated solution is evaporated, solid salt contains sodium chloride, the condensate is recycled, and the zero emission of the coking wastewater is realized by the whole process.

The COD of the effluent is 35mg/L, the volatile phenol is 0mg/L, the cyanide is 0mg/L, the sulfide is 0.2mg/L, the ammonia nitrogen is 0.5mg/L, and the treatment cost is 18 yuan/m³。

Of course, the foregoing is only a preferred embodiment of the invention and should not be taken as limiting the scope of the embodiments of the invention. The present invention is not limited to the above examples, and equivalent changes and modifications made by those skilled in the art within the spirit and scope of the present invention should be construed as being included in the scope of the present invention.

Claims

1. A zero discharge treatment method for coking ammonia distillation wastewater is characterized in that: the coking ammonia distillation wastewater is sequentially subjected to ozone pre-oxidation, air flotation, electrocatalytic oxidation, A/O biochemical process, precipitation, flocculation, ozone catalytic oxidation, aeration biological filter tank process, ultrafiltration membrane filtration, nanofiltration membrane filtration and reverse osmosis membrane treatment;

the hydraulic retention time of electrocatalytic oxidation is 10-60min, the anode plate is a lead-rhenium coated electrode, the cathode is a graphite carbon electrode, the distance between the electrode plates is 3-10 cm, and the current density is 5-20mA/cm²。

2. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: in the ozone pre-oxidation process, the adding concentration of ozone is 50-100mg/L, the adding mode of ozone is jet flow, and the oxidation time is 30-60 min;

in the catalytic ozonation process, the adding concentration of ozone is 50-200mg/L, the adding mode of ozone is jet flow, and the hydraulic retention time is 30-120 min.

3. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: the retention time of air floatation water power is 20-40min, the volume ratio of air to water is 500:1, the concentration of the added polymeric aluminum is 50-100mg/L, and the concentration of the added cationic polyacrylamide is 3-6 mg/L.

4. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: the hydraulic retention time of the A/O biochemical process is 50-100 hours, and the dissolved oxygen in the anoxic biological tank is controlled below 0.5 mg/L; the dissolved oxygen of the aerobic biological tank is controlled to be 2-4mg/L, and the sludge concentration is controlled to be 4000-6000 mg/L.

5. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: the surface load of the sedimentation tank in the sedimentation process is 0.6-1.0m³/(m²H); in the flocculation process, the adding concentration of a flocculating agent PAC is 25-100mg/L, the adding concentration of a coagulant aid PAM is 3-8mg/L, and the settling time isWas 3 hours.

6. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: the hydraulic retention time of the aeration biological filter tank process is 2-3 hours, and the biological filter material is volcanic rock or ceramsite.

7. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: the ultrafiltration membrane adopts polyvinylidene fluoride flat ultrafiltration membrane, and the water permeability of the membrane is 0.5-5.0m³/(m²D), the operating pressure is between 0.1 and 0.5MPa, the molecular mass cut-off is 100 kDa; the pore diameter of the nano-filtration membrane is 1nm, and the operating pressure is 5.0-30 bar.

8. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: the operating pressure of the reverse osmosis membrane process is 2-10 MPa; the water permeability of the membrane is 0.1-2.5m³/(m²D) thickness of 100-.

9. The coking ammonia distillation wastewater zero emission treatment method according to claim 1, characterized in that: discharging sludge obtained by the air flotation and flocculation process to the residual sludge; the A/O biochemical process is divided into an anoxic biological tank and an aerobic biological tank, and effluent of the aerobic biological tank flows back to the anoxic biological tank; returning sludge in the sedimentation tank to the anoxic biological tank; and (3) evaporating the solutions obtained by filtering the nanofiltration membrane and the reverse osmosis membrane respectively, and recovering the obtained solid salt.

10. The zero discharge treatment system for the coking ammonia distillation wastewater of any one of claims 1 to 9 is characterized in that: the device comprises an ozone pre-oxidation tank (27), an air floatation device (4), an electrocatalytic oxidation device (26), an A/O biochemical process device, a sedimentation tank (21), a flocculation sedimentation tank (20), an ozone catalytic oxidation device (9), an aeration biological filter (19), an ultrafiltration membrane device (10), a nanofiltration membrane device (18) and a reverse osmosis membrane device (17) which are sequentially connected; the A/O biochemical process device is divided into an anoxic biological tank (25) and an aerobic biological tank (23), and a return pipeline (5) is arranged between the aerobic biological tank (23) and the anoxic biological tank (25); a sludge return pipeline (22) is arranged between the sedimentation tank (21) and the anoxic biological tank (25); the air flotation device (4) and the bottom of the flocculation sedimentation tank (20) are respectively connected with a residual sludge position (24); the nanofiltration membrane device (18) and the reverse osmosis membrane device (17) are respectively connected with the first evaporator (11) and the second evaporator (16).