CN109205960B - High-salt-content organic wastewater treatment system and method - Google Patents
High-salt-content organic wastewater treatment system and method Download PDFInfo
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- CN109205960B CN109205960B CN201811326177.5A CN201811326177A CN109205960B CN 109205960 B CN109205960 B CN 109205960B CN 201811326177 A CN201811326177 A CN 201811326177A CN 109205960 B CN109205960 B CN 109205960B
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Images
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/048—Purification of waste water by evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
- C02F1/32—Treatment of water, waste water, or sewage by irradiation with ultraviolet light
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
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- Life Sciences & Earth Sciences (AREA)
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- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Physical Water Treatments (AREA)
- Treatment Of Water By Ion Exchange (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
The invention discloses a system and a method for treating high-salt organic wastewater, which comprises an AOPs pretreatment system, an FO concentration system, a concentration crystallization system and a crude salt washing system; the high-salt organic wastewater enters an FO concentration system after being subjected to heat exchange by an AOPs pretreatment system, refined brine or electrolyzed light brine enters a concentration crystallization system after being concentrated by a communicated FO device, the wastewater after passing through the concentration crystallization system obtains crystallized salt and condensed water, a microorganism treatment tank of a condensed water biochemical treatment system is used for treating organic matters, and the effluent is recycled; the crystallized salt entering the crude salt washing system sequentially enters two communicated washing chambers for dissolution and purification; washing the crystallized salt with refined saturated salt solution to obtain pure crystallized salt for reuse. The invention can realize zero discharge of high-salt organic wastewater treatment, and efficiently utilize water resources and salt resources.
Description
Technical Field
The invention relates to the field of industrial wastewater treatment, in particular to a high-salt-content organic wastewater treatment system and method.
Background
The high-salt organic wastewater contains a large amount of soluble salt besides organic pollutants,such as Cl-、Na+、SO4 2-、Ca2+And the like. Such waste water has poor biodegradability and is difficult to treat directly by microbiological methods.
At present, some enterprises adopt membrane separation technologies such as reverse osmosis to concentrate and desalt high-salt organic wastewater, but suspended matters and organic matters in the wastewater can pollute and easily block up membrane materials, the separation effect of the membrane is reduced, and even the service life of the membrane is shortened. Therefore, the wastewater needs to be pretreated before entering the reverse osmosis membrane separation device. The reverse osmosis membrane separation device is used for treating the organic wastewater with high salt content, and the discharged concentrated water is still difficult to treat due to the high salt and organic matter content. If the concentrated water is evaporated and crystallized, the salt evaporated and crystallized can not be reused because of containing various impurities, and can only be treated as solid waste or even dangerous waste, thus not only increasing the economic burden of enterprises, but also causing secondary pollution to the environment. The zero emission of the treatment of the organic wastewater with high salt content can not be realized only by adopting membrane separation technologies such as reverse osmosis and the like.
Disclosure of Invention
In order to solve the above defects in the prior art, the present invention aims to provide a system and a method for treating high-salt organic wastewater, which achieve "zero emission" of high-salt organic wastewater treatment by degrading organic pollutants in the wastewater and separating water from soluble salt substances, so as to efficiently utilize water resources and salt resources and achieve the purpose of environmental protection.
The invention is realized by the following technical scheme.
A method for treating high-salt organic wastewater comprises the following steps:
1) the method comprises the following steps of (1) enabling high-salt-content organic wastewater to enter a plate heat exchanger for heat exchange treatment, and heating the wastewater to 65-75 ℃;
2) sending the heat-exchanged high-salt-content organic wastewater into an oxidation reactor of an AOPs pretreatment system, introducing an oxidant according to the proportion of 1.5-5 times of the COD value in the wastewater, and controlling the wavelength, the reaction temperature and the time of an ultraviolet lamp to obtain pretreated wastewater;
3) cooling the pretreated wastewater through a heat exchanger, maintaining the temperature at 20-40 ℃, sending the pretreated wastewater into an FO concentration system through a concentration pump, and adding an extraction solution according to the proportion of 180-360 g/L; membrane concentration is carried out through an FO membrane component, and pretreated wastewater is concentrated to 1/3-1/5 of the amount of a raw material;
4) cooling the concentrated wastewater to 20-40 ℃ through a plate heat exchanger, and sending the wastewater into an FO concentration crystallization system; the draw solution is diluted in the FO device and then returns to the brine extraction plant salt well injection well;
5) before the wastewater enters a concentration crystallization system, the wastewater enters an evaporator after heat exchange through a heat exchanger to obtain crystallized salt and condensed water, the condensed water is heated and then sent to a biochemical treatment system, and the crystallized salt is sent to a crude salt washing system;
6) the condensed water entering the biochemical treatment system is used for treating organic matters through microbial flora, the COD and ammonia nitrogen of the wastewater are controlled, and the effluent of the biochemical treatment system returns to the production system to replace the production water;
7) the crystallized salt entering the crude salt washing system enters a first washing chamber, is immersed in an organic solvent, and is stirred to fully dissolve organic impurities in the salt; the organic solvent flows out of the first washing chamber and then enters a rectifying tower for purification, and gaseous light component ammonia nitrogen and organic impurities separated by rectification are sent to a treatment device; the organic solvent is purified and then returns to the washing chamber again;
8) and (3) feeding the crystallized salt washed by the first washing chamber into a second washing chamber, washing the crystallized salt by refined saturated salt water, feeding the washed saturated salt water into a salt water refining process again, and reusing the pure crystallized salt.
With respect to the above technical solutions, the present invention has a further preferable solution:
preferably, in the step 1), hydrochloric acid with the volume fraction of 25-35% is used for adjusting the pH value of the high-salt organic wastewater to 4-8, and the wastewater is heated through steam with the pressure of 0.3-0.8 MPa.
Preferably, in the step 2), at least one ultraviolet lamp with a dominant wavelength of 150-400 nm is arranged in the oxidation reactor, the reaction temperature is 30-80 ℃, and the reaction time is controlled within 30-90 min.
Preferably, in step 2), the oxidant is O3Or H2O2。
Preferably, in step 3), the FO membrane module is made of one of cellulose triacetate, polybenzimidazole, polyacrylonitrile polyethersulfone or polyethersulfone.
Preferably, in the step 3), the drawing solution is high-concentration brine entering the electrolytic bath or weak brine electrolyzed by the electrolytic bath;
the concentration of the high-concentration inlet tank brine is 260-360 g/L; the concentration of the electrolyzed dilute brine is 180-280 g/L.
Preferably, the weak brine is chemically dechlorinated by vacuum dechlorination or sodium sulfite to ensure that the weak brine is free of free chlorine.
Preferably, in the step 4), the concentration crystallization mode is one of MVR crystallization, freezing crystallization and MVR crystallization, membrane distillation and multi-effect evaporation; when the concentration of the waste water after FO concentration is high or close to saturation, the concentration crystallization system, the crude salt washing system and the biochemical treatment system can be omitted.
Preferably, in step 7), the condensed water of the biochemical treatment system is used for treating organic matters through an activated sludge method, a biological contact oxidation method, a membrane biological reaction method or an anaerobic biological treatment method.
Preferably, in the step 7), the organic solvent is one or a mixture of toluene, carbon tetrachloride, hexane and xylene, the washing temperature is 35-45 ℃, and the crystalline salt is immersed in the organic solvent for 1-4 hours; the organic solvent enters a rectifying tower for purification at the temperature of 75-85 ℃.
The invention further provides a high-salt organic wastewater treatment system, which comprises an AOPs pretreatment system, an FO concentration system, a concentration crystallization system and a crude salt washing system; the AOPs pretreatment system is communicated with a heat exchanger, and is communicated with an FO concentration system through the heat exchanger; the FO concentration system comprises an FO device, and the FO device is communicated with a salt well injection well, a refined salt water tank and an electrolytic tank; the FO device is communicated with a concentration and crystallization system, the concentration and crystallization system is respectively communicated with a microbial treatment pool of a biochemical treatment system and a concentration and crystallization device, and the concentration and crystallization device is connected with two stages of washing chambers which are sequentially communicated with a crude salt washing system; the first washing chamber of the two-stage washing chambers is communicated with an adsorption device, and the second washing chamber is communicated with a refined saturated salt water device and a crystallized salt storage tank.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
1. the invention can realize zero emission of the high-salt organic wastewater treatment, and efficiently utilize water resources and salt resources; the obtained evaporation condensate water has good water quality and can be reused in a production system; the washed crystalline salt can also be reused.
2. The FO process of the invention utilizes the electrolyzed light salt brine or refined salt brine as the FO drawing solution, concentration and regeneration of the drawing solution are not needed, and the salt brine is recycled without wasting materials.
3. The process flow provided by the invention is simple in design and easy to realize, and can be particularly combined with chlor-alkali and related enterprises.
4. The invention can not introduce secondary pollution, and only water and CO are obtained after the oxidant reacts2The organic detergent is recovered by rectification without producing pollutants.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention:
FIG. 1 is a general flow chart of the treatment of organic wastewater with high salt content;
FIG. 2 is a flow diagram of a FO concentration system;
FIG. 3 is a flow diagram of a crude salt wash system;
FIG. 4 is a flow chart of wastewater treatment in example 1;
FIG. 5 flow diagram of wastewater treatment in example 2;
FIG. 6 flow chart of wastewater treatment in example 3.
Detailed Description
The present invention will now be described in detail with reference to the drawings and specific embodiments, wherein the exemplary embodiments and descriptions of the present invention are provided to explain the present invention without limiting the invention thereto.
The invention relates to a method for advanced treatment of high-salt organic wastewater, which can effectively utilize the treated water resource and salt resource.
As shown in fig. 1, the system for treating organic wastewater with high salt content provided by the present invention is divided into five subsystems, namely an AOPs pretreatment system, an FO concentration system, a concentration and crystallization system, a biochemical treatment system and a crude salt washing system. Wherein: the AOPs pretreatment system is communicated with a heat exchanger, and is communicated with the FO concentration system through the heat exchanger; the FO concentration system comprises an FO device, and the FO device is communicated with a salt well injection well, a refined salt water tank and an electrolytic tank; the FO device is communicated with a concentration and crystallization system, the concentration and crystallization system is respectively communicated with a microbial treatment pool of a biochemical treatment system and a concentration and crystallization device, and the concentration and crystallization device is connected with two stages of washing chambers which are sequentially communicated with a crude salt washing system; the first washing chamber of the two-stage washing chambers is communicated with an adsorption device, and the second washing chamber is communicated with a refined saturated salt water device and a crystallized salt storage tank.
Specifically, the method comprises the following steps:
(1) AOPs pretreatment system
The AOPs pretreatment system of the invention adopts an oxidant + oxidation reactor form. The core equipment of the oxidation reactor is ultraviolet lamps with dominant wavelength of 150-400 nm, and the number of the ultraviolet lamps is one or more.
(2) FO concentration system
The electrolytic cell communicated with the FO concentration system FO device adopts any type of electrolytic cell in the chlor-alkali industry or the sewage treatment industry. Any type of FO membrane may be used for the FO device.
(3) Concentration and crystallization system
The concentration crystallization system adopts one or more of multi-effect evaporation, MVR and freezing crystallization.
(4) Crude salt washing system
A first washing chamber and a second washing chamber are employed. In the first step, the crude salt is washed with an organic detergent to remove most of the organic impurities in the salt. And the second step is to wash the crude salt after the first step washing by using saturated refined salt water to remove the residual organic detergent in the salt. The obtained refined salt is reused and can be used for dissolving salt for chlor-alkali enterprises.
(5) Biochemical treatment system
The condensed water is sent into a biochemical treatment system and then is reused in a production system.
The biochemical treatment system adopts one or more technology coupling process methods of activated sludge, biological contact oxidation, a membrane bioreactor, anaerobic biological treatment and the like.
The invention provides a method for treating high-salt-content organic wastewater, which comprises the following steps:
1) adjusting the pH value of the high-salt-content organic wastewater to 4-8 by using hydrochloric acid with the volume fraction of 25-35%, heating the wastewater by using steam with the pressure of 0.3-0.8 MPa, allowing the high-salt-content organic wastewater to flow through an oxidation reactor at a certain speed, allowing the high-salt-content organic wastewater to enter a plate heat exchanger for heat exchange treatment, and heating the wastewater to 65-75 ℃.
2) Sending the heat-exchanged high-salt-content organic wastewater into an oxidation reactor of an AOPs pretreatment system, and introducing an oxidant O at a constant speed according to the proportion of 1.5-5 times of the COD value in the wastewater3Or H2O2(H2O2Calculated by 100 percent), controlling the wavelength of the ultraviolet lamp to be 150-400 nm, the reaction temperature to be 30-80 ℃ and the reaction time to be 30-90 min, and obtaining the pretreated wastewater.
3) And (3) cooling the pretreated wastewater through a plate heat exchanger, maintaining the temperature at 5-40 ℃, sending the pretreated wastewater into an FO concentration system through a concentration pump under normal pressure, then adding an extraction solution, performing membrane concentration through an FO membrane component, and concentrating the pretreated wastewater into 1/3-1/5 of the amount of the raw liquid.
Wherein, the drawing liquid is brine water entering the cell from a brine extraction plant salt well to a high-concentration electrolytic cell or dilute brine water electrolyzed by the electrolytic cell; the process of the drawing liquid treatment is to send the diluted drawing liquid into a salt well injection well to generate new brine, or to add new salt into the diluted drawing liquid to improve the concentration of the new brine. The concentration of the high-concentration entering-tank brine is 260-360 g/L, and the concentration of the electrolyzed light brine is 180-280 g/L; the light brine is dechlorinated by vacuum or sodium sulfite chemistry to ensure that the light brine is free of free chlorine.
Wherein, the FO membrane material that FO membrane module adopted is one in triacetylcellulose, polybenzimidazole, polyacrylonitrile polyethersulfone or polyethersulfone.
4) And cooling the concentrated wastewater to 20-40 ℃ through a heat exchanger, sending the concentrated wastewater into an FO concentration crystallization system, and selecting one of MVR crystallization, freezing crystallization and MVR crystallization, membrane distillation and multi-effect evaporation in a concentration crystallization mode. The draw solution is diluted in the FO device and then returns to the brine extraction plant salt well injection well.
5) Before the wastewater enters the concentration and crystallization system, the wastewater enters the evaporator after heat exchange through the plate heat exchanger, soluble salt in the wastewater is crystallized and separated out, crystallized salt is sent to the crude salt washing system, and condensed water is sent to the biochemical treatment system after being heated.
The concentration crystallization system is one or more of multi-effect evaporation, MVR and freezing crystallization. When the concentration crystallization system adopts multi-effect evaporation or MVR, the evaporation temperature is controlled to be 80-100 ℃, the pressure in the evaporator is controlled to be 20-100 kpa (a), and crystallized slurry flowing out of the evaporator is centrifugally dehydrated to obtain crystallized crude salt. The condensed water discharged from the evaporator exchanges heat with the waste water before entering the evaporator, and then enters a biochemical treatment system.
When the concentration crystallization system adopts a freezing crystallization method, the cold source adopts frozen salt water, and the waste water is repeatedly cooled by the circulating pump, so that the temperature of the waste water is maintained at-10-0 ℃.
6) The condensed water entering the biochemical treatment system is used for treating organic matters through microbial flora, the biochemical treatment system adopts one or more technology coupling process methods of activated sludge, biological contact oxidation, a membrane bioreactor, anaerobic biological treatment and the like to control COD (chemical oxygen demand) and ammonia nitrogen of the wastewater, and the effluent of the biochemical treatment system returns to the production system to replace production water for use.
7) And (4) entering a crude salt washing system to remove organic impurities in the crystallized crude salt, and recycling the crystallized salt after washing.
The crude salt washing system is divided into two parts, wherein in the first step, organic detergent is used for washing crude salt, and most of organic impurities in the salt are removed; the organic washing agent is one or a mixture of toluene, carbon tetrachloride, hexane and xylene. And the second step is to wash the crude salt after the first step washing by using saturated refined salt water to remove the residual organic detergent in the salt. The obtained refined salt is reused and can be used for dissolving salt for chlor-alkali enterprises.
The crystal salt enters a first washing chamber, the crystal salt is immersed in an organic solvent, and the crystal salt is immersed in the organic solvent for 1-4 hours at the temperature of 30-50 ℃; stirring to fully dissolve organic impurities in the salt; the organic solvent flows out of the first washing chamber and then enters a rectifying tower for purification, and the purification temperature of the organic solvent entering the rectifying tower is 75-85 ℃; sending the gaseous light component ammonia nitrogen and the organic impurities separated by rectification to a treatment device; the organic solvent is purified and then returned to the washing chamber again.
The organic detergent is insoluble in crystalline salt and has good solubility in most organic substances. After the first step of cleaning, the organic detergent is purified and recycled by rectification.
8) And (3) feeding the crystallized salt into a second washing chamber after washing in the first washing chamber, and washing the crystallized salt by adopting refined saturated salt water, wherein the washing temperature in the second step is respectively maintained at 40-80 ℃, and the washing time is 0.5-2 hours. The washed saturated salt water is sent to the brine refining process again, and the pure crystal salt is reused.
The present invention is not limited to the five subsystems described above, wherein the concentration of wastewater after FO concentration is high or near saturation, and the concentration crystallization system, crude salt washing system, and biochemical treatment system may be omitted; the concentration and crystallization system is used for further increasing the concentration multiple of the FO concentration system, and can directly produce refined salt for direct use again.
The principle of the invention is as follows:
(1) the generation of OH is accelerated in the oxidation reactor, and the organic matters which are difficult to degrade are gradually degraded into micromolecular organic matters with good biochemical property, even into CO2. And (2) allowing the high-salt-content organic wastewater to flow through one to three ultraviolet reactors connected in series, adding an oxidant at a constant speed before the wastewater enters the ultraviolet reactors, and maintaining the reaction temperature at 30-80 ℃. Ultraviolet irradiation can not only accelerate the oxidant to generate more OH, but also induce the organic matters to be in an excited state, so that pollutants are more easily oxidized and degraded. The AOPs pretreatment system ensures degradation of refractory organic impurities in wastewater, effectively improves biodegradability and enables BOD5The value of/COD is above 0.5.
(2) FO can effectively reduce the waste water treatment capacity in the concentration and crystallization process, greatly reduce the operation load of the concentration and crystallization process, and the inside of a virtual frame in figure 2 is divided into an FO concentration system. The temperature of the electrolyzed weak brine or high-concentration salt water entering the electrolytic cell used as the drawing liquid is controlled to be 25-40 ℃ before entering the FO device, and the drawing liquid forms cross flow with the wastewater after entering the FO device. The concentrated wastewater is sent to a concentration crystallization system through a pump; the draw solution is diluted and sent to a salt well injection well or a certain amount of new salt is added, so that new salt water is generated and becomes high-concentration salt water entering the tank again, and the salt water can be used as the draw solution again. Or the new brine is refined and then sent into an electrolytic bath for caustic soda production, and the discharged electrolyzed light brine (free chlorine removal) is used as the draw solution again. Therefore, the FO drawing liquid does not need to be concentrated and regenerated, and the technical bottleneck that the FO is difficult to industrialize is ingeniously avoided.
(3) When the salt in the wastewater is mainly soluble salt (such as NaCl) with the solubility of which is less influenced by the temperature, the concentration and crystallization system generally adopts multi-effect evaporation or MVR technology, and the evaporator is generally selected to be a forced circulation evaporator. The condensed water discharged from the evaporator is close to the evaporation temperature, and exchanges heat with the wastewater before entering the evaporator, so that the temperature of the wastewater is close to the evaporation temperature, and the load of evaporation crystallization is effectively reduced.
Soluble salts (e.g. NaSO) in which the solubility of the salts in the wastewater is significantly affected by temperature4) When the concentration crystallization system is mainly used, a freezing crystallization method is generally selected. Repeatedly exchanging heat between the frozen brine and the concentrated waste water of FO, and maintaining the temperature at-10-0 ℃ to obtain more than 90% of NaSO4Etc. to NaSO4·10H2And separating out the O crystals, and drying and discharging the O crystals out of the system through a centrifugal machine.
(4) After pretreatment of AOPs, part of small molecular organic impurities remained in the wastewater enter into crystallized salt along with the crystallization process, and part of small molecular organic impurities are 'left' in condensed water. Crude salts doped with organic impurities are difficult to reuse. Organic impurities were removed by means of a crude salt process, the washing process being shown in FIG. 3. The crude salt wash is divided into two steps, the first step being carried out in a first washing chamber and the second step being carried out in a second washing chamber. And feeding the crude salt into a first washing chamber, stirring to ensure that the crude salt is fully contacted with the organic detergent, and removing impurities by utilizing the solubility difference of the organic impurities and the salt in an organic solvent to dissolve the organic impurities in the organic detergent. The organic detergent dissolved with the organic impurities is pumped into a rectifying tower for separation, and the organic detergent is purified and then reused in the first washing chamber. And (4) sending the separated organic impurities into an activated carbon or resin adsorption device for collection. After the first washing step is finished, the crystallized salt contains an organic detergent, the crystallized salt is sent to a second washing chamber for second washing, the crystallized salt is washed by saturated refined brine, the organic detergent is removed from the crystallized salt, and the washed saturated brine returns to brine refining. The washed refined salt can be reused.
(5) The condensed water discharged from the concentration and crystallization system is sent to a biochemical treatment system to further improve the water quality. The condensed water can then be reused in the production system.
The invention is further illustrated by the following specific examples.
Example 1
The quality of hydrazine hydrate wastewater produced by a certain enterprise is shown in table 1, and the embodiment selects an AOPs pretreatment system, an FO concentration system, a concentration crystallization system, a crude salt washing system and a biochemical treatment system.
As shown in fig. 4, the method comprises the steps of:
(1) adjusting the pH value of hydrazine hydrate wastewater with pH value of 12 to 4 by using hydrochloric acid (volume fraction of 31 percent), and controlling the flow rate of the hydrazine hydrate wastewater to be 40m3The wastewater enters a plate heat exchanger for h, and is heated and controlled at 65 ℃ by 0.4MPa steam.
(2) And (4) sending the waste water into an AOPs pretreatment system after heat exchange. The AOPs pretreatment system adopts a UV oxidation reactor, wherein the wavelength of ultraviolet lamps is 400nm, and the number of the ultraviolet lamps in the device is 3. Introducing oxidant according to the proportion of 1.5 times of COD value in the wastewater, wherein the oxidant is 30% H2O2Solution of H2O2Adding the solution into the wastewater at a constant speed of 510kg/h by an oxidant filler before the wastewater enters an oxidation reactor, reacting at 50 ℃ for 30min to obtain pretreated wastewater, and discharging the wastewater out of an AOPs system after passing through an UV oxidation reactor.
(3) The waste water discharged by the AOPs pretreatment system is cooled by a plate heat exchanger, the temperature is maintained at 35 ℃, and the waste water is sent into an FO concentration system by a concentration pump. The module form of the FO membrane used in the FO concentrator is hollow fiber; wherein the FO membrane is made of cellulose triacetate; the drawing solution is dilute brine which is discharged in the caustic soda preparation process of the Wuddylara 5-generation ion membrane electrolytic cell after electrolysis in an electrolytic cell, the concentration of the dilute brine is 225g/L, the temperature is 75 ℃, the dilute brine is firstly subjected to vacuum dechlorination or chemical dechlorination by sodium sulfite, and the dilute brine is ensured not to contain free chlorine. The electrolyzed light brine is diluted in the FO device and then returns to the brine well injection well of the brine production plant.
(4) Cooling the concentrated waste water to 25 ℃ by a plate heat exchanger at a temperature of 60m3And/h is sent to an FO concentration device, and the waste water is concentrated into 1/2 of the original liquid amount and then enters a concentration crystallization system at 20t/h through a pump.
(5) Before entering the evaporator, the waste water exchanges heat through the plate heat exchanger, the heat source is condensed water discharged by the evaporator, and the temperature is about 80 ℃.
MVR crystallization is selected in the concentration crystallization mode of the embodiment, and the initial heat source is 0.6-0.7 MPa of raw steam. The evaporator is a forced circulation evaporator, the internal pressure of the evaporator is 70KPa (a), and the compressor adopts a high-efficiency centrifugal fan. 5.3t/h of crystal salt and 14.7t/h of condensed water are obtained. The condensed water is sent into a biochemical treatment system after heating the wastewater. The crystallized salt is sent to a crude salt washing system.
(6) Condensed water is sent into a biochemical treatment system through a condensed water pump, the biochemical treatment mode is an activated sludge method, COD (chemical oxygen demand) of wastewater is controlled below 50mg/L, ammonia nitrogen is controlled below 3mg/L, and effluent of the biochemical treatment system returns to a hydrazine hydrate production system to replace production water for use.
(7) The temperature of the crystal salt fed into the first washing chamber of the crude salt washing system is maintained at 45 ℃, and the organic washing solvent is toluene which is 5m3And/h into the first washing chamber. The crystalline salt was immersed in toluene for 1h and stirred to dissolve the organic impurities in the salt well in toluene. In this example toluene was present at 5m3The gas-state light components (ammonia nitrogen and organic impurities) separated by rectification are sent to an activated carbon adsorption device matched with a PVC production device. After purification of the toluene, the mixture is again purified by 5m3And/h is returned to the first washing chamber.
(8) The crystallized salt after toluene washing is sent to a second washing chamber, the washing temperature of the second step is respectively maintained at 40 ℃, and the refined saturated salt water is 10m3Speed of washing for 1h, washingThe saturated brine is sent to the brine refining process again, and the clean NaCl crystallized salt is used for salt dissolving.
TABLE 1 quality of hydrazine hydrate wastewater before and after treatment of a certain enterprise
| Serial number | Index name | Unit of | Before treatment | After treatment |
| 1 | pH | - | 12 | 6～9 |
| 2 | NaCl | mg/L | 130000 | 300 |
| 3 | COD | mg/L | 500 | 50 |
| 4 | Ammonia nitrogen | mg/L | 86 | 3 |
Example 2
The water quality of the wastewater after mercury removal in the production process of calcium carbide PVC in a certain plant is shown in Table 2. In this example, the AOPs pretreatment system, the FO concentration system, the concentration and crystallization system, and the crude salt washing system were selected. The wastewater treatment scheme is shown in FIG. 5. The method comprises the following steps:
(1) the pH value of the wastewater is 8, the wastewater enters a plate heat exchanger at 5t/h, the wastewater is heated and maintained at 75 ℃ through 0.3MPa steam, and the wastewater enters an AOPs pretreatment system after being heated.
(2) The pretreatment system for AOPs in this example employs a UV oxidation reactor, in which the wavelength of UV lamps is 180nm and the number of UV lamps in the apparatus is 2. Introducing an oxidant according to the proportion of 5 times of the COD value in the wastewater, wherein the oxidant is 30% H2O2Solution of H2O2(30%) solution is added into the wastewater at a constant speed of 20kg/h through an oxidant filler before the wastewater enters an oxidation reactor, the reaction temperature is 30 ℃ and the reaction time is 90min, and the wastewater is discharged out of the AOPs system after passing through the UV oxidation reactor.
(3) Waste water discharged by AOPs pretreatment is cooled and maintained at 5 ℃ through a plate heat exchanger, and is sent into an FO concentration system through a membrane concentration pump, the assembly form of an FO membrane of the FO device is hollow fiber, and the FO membrane is made of polyacrylonitrile polyether sulfone. The drawing liquid is refined brine entering the electrolytic bath by an electrolytic bath, the concentration of the brine is 310g/L, the temperature is 75 ℃, and the content of free chlorine in the refined brine is ensured to be 0.
(4) Cooling the refined brine to 40 deg.C by heat exchanger at 10m3The/h is sent to the FO concentration unit. The refined brine is diluted and then returns to the brine refining process again. And (4) after the wastewater is concentrated by about 3 times, discharging the wastewater out of the FO concentration system and entering a membrane concentration liquid tank.
(5) Concentrated waste water from the FO unit was fed to the concentration and crystallization system at 1.7 t/h. Before the wastewater enters the concentration and crystallization system, the wastewater enters the evaporator after heat exchange through the plate heat exchanger, soluble salt in the wastewater is crystallized and separated out, crystallized salt is sent to the crude salt washing system, and condensed water is sent to the biochemical treatment system after being heated.
In this embodiment, the concentration crystallization system employs a freezing crystallization + MVR crystallization method. The concentrated wastewater and the refrigerating unit frozen brine of the plant are repeatedly subjected to heat exchange and temperature reduction to-8 to-3 ℃ through a freezing circulating pump, so that Na in the wastewater is reduced2SO4Crystallizing and separating out mirabilite in the form of mirabilite, and selling the mirabilite for the outside. And the residual wastewater exchanges heat with condensed water at 90 ℃ discharged by an MVR device and then enters an MVR evaporator to obtain NaCl crystalline salt at 0.2t/h and condensed water at 1.0 t/h. The condensed water is used for the calcium carbide method PVC production process after heat exchange. The evaporator is a forced circulation evaporator, the evaporation temperature is controlled at 100 ℃, the internal pressure of the evaporator is 43KPa (a), and the pressure can reach 100KPa (a), and a Roots blower is selected as a compressor.
(6) The condensed water entering the biochemical treatment system is treated by the microbial flora to treat organic matters, the biochemical treatment system adopts a biological contact oxidation method to treat, the COD and ammonia nitrogen of the wastewater are controlled, and the effluent of the biochemical treatment system returns to the production system to replace the production water for use.
(7) The method comprises the following steps that (1) crystalline salt enters a crude salt washing system, the crystalline salt enters a first washing chamber, the crystalline salt is immersed in an organic solvent, and the crystalline salt is immersed in the organic solvent for 4 hours at the temperature of 50 ℃; stirring to fully dissolve organic impurities in the salt; the organic detergent is selected from carbon tetrachloride and xylene mixed solution of which the thickness is 1m3The flow out of the first washing chamber at a speed of/h enters a rectifying tower, and the purification temperature is maintained at 75 ℃. After rectification and purification, the concentration is 1m again3And/h is returned to the first washing chamber. The light components (organic impurities) of the gas are sent to a resin adsorption device, and the resin is sent to a nearby thermal power plant to be burnt as fuel after the resin is adsorbed and saturated.
(8) Feeding the crystallized salt washed with the mixed solution of carbon tetrachloride and xylene into a second washing chamber, and refining the saturated salt solution to 2m3The speed temperature of the/h is 80 ℃ for 2 h. The washed saturated brine is sent to a brine refining process, and clean crystal salt is used for dissolving salt. The process flow is shown in figure 5.
TABLE 2 comparison of water quality before and after wastewater treatment
| Serial number | Index name | Unit of | Before treatment | After treatment |
| 1 | pH | - | 7～9 | 7～9 |
| 2 | NaCl | mg/L | 36253 | 6.1 |
| 3 | Na2SO4 | mg/L | 121440 | 5.8 |
| 4 | COD | mg/L | 700 | 41 |
| 5 | Ammonia nitrogen | mg/L | 3.97 | 0.108 |
Example 3
The water quality of diphenylmethane diisocyanate (MDI) wastewater produced by a certain polyurethane enterprise is shown in Table 3. In this embodiment, only the AOPs pretreatment system and the FO concentration system are used. The wastewater treatment scheme is shown in FIG. 6. The method comprises the following steps:
(1) adjusting the pH value of MDI wastewater to 6 by using high-purity hydrochloric acid (31%), raising the temperature of the wastewater to 70 ℃ by using a plate heat exchanger, heating and then entering an AOPs pretreatment system.
(2) MDI wastewater with the particle size of 10m3And h, entering an AOPs pretreatment system, wherein the AOPs pretreatment system adopts a UV oxidation reactor, the wavelength of ultraviolet lamps is 150nm, and the number of the ultraviolet lamps in the equipment is 2. The temperature of the UV reactor is maintained at 80 ℃, the reaction time is 60min, an oxidant is introduced according to the proportion of 3 times of the COD value in the wastewater, the oxidant selects ozone, and the ozone is prepared by an ozone generator by taking the oxygen as a gas source. Ozone was continuously passed into the UV oxidation reactor.
(3) Waste water discharged by the AOPs pretreatment system is cooled to 40 ℃ through a cooler and then is sent into an FO device, the FO membrane of the FO device is in a flat plate membrane module form, and the FO membrane is made of polybenzimidazole. The drawing liquid is high-concentration saline water with the concentration of 360g/L, and the content of free chlorine in the refined saline water is ensured to be 0.
(4) The brine was cooled to 20 ℃ by a heat exchanger at 16m3The/h is sent to the FO concentration unit. Concentrating and crystallizing mode selection membrane distillation; and (3) measuring the concentration of the high-concentration brine after dilution, adding a certain amount of NaCl new salt according to the concentration condition, preparing the high-concentration brine again into 350-360 g/L, and returning the high-concentration brine to the FO concentration device. The FO concentration system in this example concentrates MDI waste water by about 1.5 times. After concentration, the salt concentration of the wastewater reaches 255g/L, 88Kg/h of NaC is addedThe new salt is prepared into 350-360 g/L high-concentration brine solution which is used as the drawing solution. The process flow is shown in figure 6.
TABLE 3 comparison of water quality before and after wastewater treatment
| Serial number | Index name | Unit of | Before treatment | After treatment |
| 1 | pH | - | 12 | 7.6 |
| 2 | NaCl | g/L | 170 | 25 |
| 3 | COD | mg/L | 40 | 2.7 |
| 4 | Ammonia nitrogen | ppm | 4 | - |
| 5 | Aniline | ppm | 3 | - |
| 6 | Diamines | ppm | 1 | - |
As can be seen from the above examples, the NaCl content in the water quality obtained from the high-salt organic wastewater treated by the method is not more than 300 mg/L; the COD value is not more than 50 mg/L. Therefore, the method is a good method for treating the organic wastewater, and is worthy of popularization and application.
The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.
Claims (9)
1. The method for treating the high-salt-content organic wastewater is characterized by comprising the following steps of:
1) the method comprises the following steps of (1) enabling high-salt-content organic wastewater to enter a plate heat exchanger for heat exchange treatment, and heating the wastewater to 65-75 ℃;
2) sending the heat-exchanged high-salt-content organic wastewater into an oxidation reactor of an AOPs pretreatment system, introducing an oxidant according to the proportion of 1.5-5 times of the COD value in the wastewater, and controlling the wavelength, the reaction temperature and the time of an ultraviolet lamp to obtain pretreated wastewater;
3) cooling the pretreated wastewater through a heat exchanger, maintaining the temperature at 20-40 ℃, sending the pretreated wastewater into an FO concentration system through a concentration pump, and adding an extraction solution according to the proportion of 180-360 g/L; the drawing liquid is high-concentration electrolytic bath inlet brine or weak brine electrolyzed by an electrolytic bath; the concentration of the saline water entering the high-concentration electrolytic cell is 260-360 g/L; the concentration of the dilute brine after electrolysis in the electrolytic cell is 180-280 g/L; membrane concentration is carried out through an FO membrane component, and pretreated wastewater is concentrated to 1/3-1/5 of the amount of a raw material;
4) cooling the concentrated wastewater to 20-40 ℃ through a plate heat exchanger, and sending the wastewater into an FO concentration crystallization system; diluting the draw solution in the FO device and then returning the dilute draw solution to a brine extraction plant salt well injection well or adding new salt for refining;
5) before entering a concentration crystallization system, the wastewater enters an evaporator after heat exchange through a plate heat exchanger to obtain crystallized salt and condensed water, the condensed water is heated and then sent to a biochemical treatment system, and the crystallized salt is sent to a crude salt washing system;
when the salt in the wastewater is mainly soluble salt with the solubility less influenced by the temperature, the concentration and crystallization system adopts a multi-effect evaporation or MVR technology, and the evaporator selects a forced circulation evaporator; condensed water discharged by the evaporator is close to the evaporation temperature, and exchanges heat with the wastewater before entering the evaporator, so that the temperature of the wastewater is close to the evaporation temperature, and the load of evaporation crystallization is effectively reduced;
when the salt in the wastewater is mainly soluble salt with the solubility obviously influenced by the temperature, a freezing crystallization method is adopted in a concentration crystallization system, the frozen salt water and the FO concentrated wastewater exchange heat repeatedly, more than 90% of the soluble salt is converted into soluble salt with crystallization water to be crystallized and separated out when the temperature is maintained at-10-0 ℃, and the soluble salt is dried by a centrifuge and discharged out of the system;
6) the condensed water entering the biochemical treatment system is used for treating organic matters through microbial flora, the COD and ammonia nitrogen of the wastewater are controlled, and the effluent of the biochemical treatment system returns to the production system to replace the production water;
7) the crystallized salt entering the crude salt washing system enters a first washing chamber, is immersed in an organic solvent, and is stirred to fully dissolve organic impurities in the salt; the organic solvent flows out of the first washing chamber and then enters a rectifying tower for purification, and gaseous light component ammonia nitrogen and organic impurities separated by rectification are sent to a treatment device; the organic solvent is purified and then returns to the washing chamber again;
8) and (3) feeding the crystallized salt washed by the first washing chamber into a second washing chamber, washing the crystallized salt by refined saturated salt water, feeding the washed saturated salt water into a salt water refining process again, and reusing the pure crystallized salt.
2. The method for treating the organic wastewater with high salt content according to claim 1, wherein in the step 1), hydrochloric acid with a volume fraction of 25-35% is used for adjusting the pH value of the organic wastewater with high salt content of 4-8, and the wastewater is heated by steam with a pressure of 0.3-0.8 MPa.
3. The method for treating high-salinity organic wastewater according to claim 1, wherein in the step 2), at least one ultraviolet lamp with a main wavelength of 150-400 nm is arranged in the oxidation reactor, the reaction temperature is 30-80 ℃, and the reaction time is controlled to be 30-90 min; the oxidant is O3Or H2O2。
4. The method for treating high-salinity organic wastewater according to claim 1, characterized in that in the step 3), the FO membrane module is made of one of cellulose triacetate, polybenzimidazole, polyacrylonitrile polyethersulfone or polyethersulfone.
5. The method as claimed in claim 1, wherein the weak brine is dechlorinated by vacuum or sodium sulfite chemical method to ensure that it contains no free chlorine.
6. The method for treating the organic wastewater with high salt content according to claim 1, wherein in the step 4), the concentration crystallization mode is one of MVR crystallization, freezing crystallization and MVR crystallization, membrane distillation and multi-effect evaporation; when the waste water concentration after FO concentration is close to saturation, the concentration crystallization system, the crude salt washing system and the biochemical treatment system are omitted.
7. The method for treating organic wastewater with high salt content according to claim 1, wherein in step 7), the condensed water of the biochemical treatment system is used for treating organic matters through an activated sludge process, a biological contact oxidation process, a membrane biological reaction process or an anaerobic biological treatment process.
8. The method for treating high-salinity organic wastewater according to claim 1, wherein in the step 7), the organic solvent is one or more of toluene, carbon tetrachloride, hexane and xylene; the washing temperature is 35-45 ℃, and the crystalline salt is immersed in the organic solvent for 1-4 hours; the organic solvent enters a rectifying tower for purification at the temperature of 75-85 ℃.
9. A high salinity organic wastewater treatment system used in the method of any one of claims 1 to 8, which is characterized by comprising an AOPs pretreatment system, an FO concentration system, a concentration crystallization system and a crude salt washing system; the AOPs pretreatment system is communicated with a heat exchanger, and is communicated with an FO concentration system through the heat exchanger; the FO concentration system comprises an FO device, and the FO device is communicated with a salt well injection well, a refined salt water tank and an electrolytic tank; the FO device is communicated with a concentration and crystallization system, the concentration and crystallization system is respectively communicated with a microbial treatment pool of a biochemical treatment system and a concentration and crystallization device, and the concentration and crystallization device is connected with two stages of washing chambers which are sequentially communicated with a crude salt washing system; the first washing chamber of the two-stage washing chambers is communicated with an adsorption device, and the second washing chamber is communicated with a refined saturated salt water device and a crystallized salt storage tank.
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