CN110981055A - Wastewater treatment method and wastewater treatment system - Google Patents
Wastewater treatment method and wastewater treatment system Download PDFInfo
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- CN110981055A CN110981055A CN201911213689.5A CN201911213689A CN110981055A CN 110981055 A CN110981055 A CN 110981055A CN 201911213689 A CN201911213689 A CN 201911213689A CN 110981055 A CN110981055 A CN 110981055A
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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
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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
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
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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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/046—Treatment of water, waste water, or sewage by heating by distillation or evaporation under vacuum produced by a barometric column
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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
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
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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
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
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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
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal 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
Abstract
The invention discloses a wastewater treatment method and a wastewater treatment system, under the condition that heavy metal substances are dissolved in water, the traditional chemical method is not adopted to add chemical substances to precipitate and separate out, but the whole process adopts a physical treatment method, water-insoluble substances in water are completely removed, then the heavy metal substances are extracted through evaporation and baking steps, solid waste finally obtained by a baking powder system is a compound containing high-purity chromium salt, nickel salt or other metal salts, and the substances can be directly recycled without landfill or discarding treatment, so that additional environmental pollution is avoided; the invention adopts a physical treatment mode, does not carry out chemical treatment, saves the step of chemical treatment, can save the use of a large amount of chemical reagents and obviously reduces the production cost; the secondary pollution of chemical reagents in the production process is reduced, and the method is more environment-friendly; heavy metals can be directly recycled, and the economic value is high.
Description
Technical Field
The invention relates to the field of wastewater treatment in the surface treatment industry, in particular to a wastewater treatment method and a wastewater treatment system.
Background
The surface treatment process refers to a process for decorating and protecting metal or nonmetal surfaces and acquiring certain new surface characteristics by using a chemical or electrochemical method, wherein the components of wastewater discharged in the processes of pre-plating treatment, metal layer plating, post-plating treatment and the like are complex, and main pollutants are generatedIs the pollution of various heavy metals, acid, alkali, surfactant, additive and organic matters, wherein harmful heavy metals are used as main pollutants, and Cu is used as some2+、Zn2+、Cr3+、Ni2+In the form of iso-cations, some are CrO4 2-、Cr2O7 2-、Cu(CN)4 3-、Cu(P2O7)2 6-In the form of plasma or complex ions. Heavy metals cannot be decomposed and can only be converted into their physical and chemical forms. If the treatment is improper, the heavy metal ions enter the environment by taking soil or water as a medium, which brings great harm to the environment and human health, for example, heavy metal accumulation of crops caused by heavy metal pollution of soil in certain areas; discharge of cyanide-containing waste water into rivers and lakes causes yield reduction and even mass death of fishery and the like.
At present, the treatment of waste water in the surface treatment industry is mainly that various waste water is treated according to the classification of chromium series, cyanogen series, acid-base, oil, phosphorus and the like, and then is comprehensively treated. The method has the advantages of complex flow, multiple operation links, high labor intensity, high operating cost and large amount of generated sludge. The most common method for chromium-series waste water is chemical reduction precipitation method, the basic principle of said method is that waste iron filings or ferrous sulfate are used as reducing agent, firstly, the hexavalent chromium is reduced into trivalent chromium, then the flocculating agent is added to make the trivalent chromium produce hydroxide precipitation, then the solid-liquid separation is implemented so as to attain the goal of removing chromium.
For example, chinese patent ZL201710983122.0 discloses a method for treating chromium-containing wastewater by chemical precipitation + membrane method, which comprises rinsing, chemical precipitation, reverse osmosis advanced treatment, and evaporation crystallization, wherein hexavalent chromium needs to be reduced to trivalent chromium in the chemical precipitation step, and a chemical reduction precipitation method is adopted, chromium ions are removed in this step, and the subsequent reverse osmosis advanced treatment, evaporation crystallization and other steps are only the treatment of the supernatant after precipitation, that is, only the treatment of other soluble salts, organic matters, colloids and microorganisms in the supernatant, in order to make the supernatant reach the discharge standard, and the chromium-containing solid sludge obtained by chemical reduction precipitation cannot be reused,it can only be discarded or landfilled, but chromium ion reversion may occur, which results in the final completion of treatment and even more serious pollution due to diffusion. In addition, after the chemical precipitation step, hexavalent chromium ions in the waste water are removed, and the salt content in the waste water is greatly increased, such as by using a sulfur dioxide reduction method, SO42-Can remain in the waste water in a large number, when the evaporation step, the waste water is slightly heated, and salinity is a large amount of immediately appearing, blocks up the pipeline of evaporimeter very easily, especially the pipeline of heat exchanger, can only shut down to demolish the washing behind the jam pipeline, seriously influences the treatment process. The present industrial waste water evaporation plant uses external heat exchanger to carry out the circulation heating more, waste water in the evaporating pot gets into the heat exchanger from external pipeline and heats the back rethread pipeline and returns the evaporating pot, because liquid has the temperature to run off in the pipeline of circulation heating, so evaporate the energy that the required concentration of waste water needs to be consumed high, in addition, in the chemical treatment step, probably because the reaction is insufficient, or partial trivalent chromium ion can reverse, therefore can remain hexavalent chromium ion in the waste water, because hexavalent chromium ion has stronger corrosivity, hexavalent chromium ion can seriously corrode the evaporimeter jar body during follow-up evaporation step, lead to the evaporimeter to take place to damage unable use. There are also existing evaporation devices that use MVR for evaporation, although energy-saving, the MVR algorithm is complex and the internal structure of the evaporation device is complex.
For example, the prior Chinese patent ZL201110449172.3 discloses a heavy metal wastewater treatment process, wherein wastewater is subjected to oil separation by an oil separation tank and then sequentially enters a comprehensive adjusting tank, a pH adjusting tank, a concentration tank, a tubular ultrafiltration membrane system, a pH adjusting tank and an RO membrane system to finally obtain recycled water, the wastewater containing heavy metals is treated by adopting a physical filtration and pH adjustment mode, a large amount of pH adjusting agents are still required in the treatment process, and the metals, TSS and COD removed by the DF membrane filtration are remained on the DF membrane, when the DF membrane bears a certain pollution amount, the DF membrane must be backwashed or directly discarded, heavy metal wastewater can still be formed during backwashing, and the cost is quite high when the DF membrane is directly discarded, in addition, the method does not treat the residual waste liquid which can not pass through the RO system, the residual waste liquid is still harmful substances which pollute the environment, therefore, the method cannot completely treat the wastewater comprehensively, and a large amount of waste liquid remains after treatment for treatment.
Disclosure of Invention
The applicant provides a wastewater treatment method and a wastewater treatment system aiming at the defects that the treatment method used in the existing production cannot thoroughly treat heavy metal pollution, the pollution still exists and the like, the wastewater treatment system adopts a physical treatment method, all substances insoluble in water are removed firstly, and then high-purity recyclable heavy metal substances are refined through evaporation and baking steps, so that the production cost is reduced, the pollution possibility is reduced, pipe blockage of an evaporator is avoided, the energy consumption is low, and the batch production is ensured.
The technical scheme adopted by the invention is as follows:
a method of wastewater treatment comprising the steps of:
(I) primary filtration: removing large-particle substances in the wastewater;
(II) sand filtration: removing organic matters and gravels in the wastewater;
(III) microfiltration: removing oil substances and micro particles with the particle size of more than 0.5-5 um in water;
(IV) ultrafiltration: filtering to remove micro particles above 0.01 um;
(V) RO membrane concentration: filtering to obtain clean recovered water;
(VI) evaporating: the concentrated solution in the step V enters an evaporator tank body, a heating device heats the tank body, the heating is stopped when the temperature in the tank body is 50-90 ℃, and the interior of the tank body is vacuumized; repeatedly adding new liquid for a plurality of times after a period of time after evaporation, continuously heating the heating sleeve until the temperature in the tank body is 50-95 ℃, and vacuumizing the tank body again;
(VII) baking dry powder: and (5) baking at 250-320 ℃ to obtain a solid substance.
As a further improvement of the above technical solution:
and in the step V, the concentrated solution obtained by each stage of membrane system flows back to the relay tank in front of the previous stage of system for secondary filtration again, the obtained clear solution enters the next stage of membrane system, and the clear solution obtained by the last stage of membrane system is discharged from a reuse water outlet.
In step V, the conductivity of the recovered water is 200s/m or less.
And VI, the solid content of the concentrated solution is 30-40%.
A wastewater treatment system used in the wastewater treatment method comprises a raw water collecting tank, a sand filtering system, a precision filtering system, an ultrafiltration system, an RO membrane system, an evaporation system and a baking powder system which are sequentially connected, wherein a recycling oil outlet is formed in the precision filtering system, and a solid waste outlet is formed in the baking powder system.
As a further improvement of the above technical solution:
still be provided with the ultrafiltration relay jar between ultrafiltration system and the RO membrane system, the RO membrane system is including a plurality of grades of membrane systems that set gradually, and the ultrafiltration relay jar is connected with one-level membrane system, and the concentrate export of one-level membrane system is connected with vaporization system, and the clear solution export of one-level membrane system connects gradually first clear solution relay jar, next stage membrane system, and the concentrate export of later each grade membrane system all is connected with the relay jar in last one-level membrane system the place ahead, and the clear solution export then is connected with clear solution relay jar, and the clear solution exit linkage reuse water export of last one-level membrane system.
A sand filtration relay tank is further arranged between the sand filtration system and the precise filtration system, the backwashing system is connected with backwashing water inlets of the sand filtration system, the precise filtration system, the ultrafiltration system and the RO membrane system, backwashing water outlets of the sand filtration system, the precise filtration system, the ultrafiltration system and the RO membrane system are connected with the filter system, and a clear water outlet of the filter system is connected with the sand filtration relay tank.
The heating system is respectively connected with the evaporation system and the dry powder baking system, and the heating system is supplied with heat by a gas system.
The cooling system is connected with the RO membrane system; the cooling system and the evaporation system are respectively connected with the condensation system, and a condensed water outlet of the condensation system is connected with the first clear liquid relay tank.
A raw water relay tank is also arranged between the raw water collecting tank and the sand filtering system, a precise filtering relay tank is also arranged between the precise filtering system and the ultrafiltration system, and a first concentrated solution relay tank is also arranged between the RO membrane system and the evaporation system; and a reuse water outlet is arranged on the RO membrane system.
The invention has the following beneficial effects:
under the condition that heavy metal substances are dissolved in water, the wastewater treatment system does not adopt the traditional chemical method to add chemical substances to precipitate and separate out, but adopts a physical treatment method in the whole process, firstly removes all the substances which are insoluble in water in the water, and then extracts the heavy metal substances through the steps of evaporation and baking, and the finally obtained solid waste of the baking powder system is a compound containing chromium salt, nickel salt or other metal salts with high purity, and the substances can be directly recycled without landfill or discarding treatment, so that extra environmental pollution is not generated; the invention adopts a physical treatment mode, does not carry out chemical treatment, saves the step of chemical treatment, can save the use of a large amount of chemical reagents and obviously reduces the production cost; the secondary pollution of chemical reagents in the production process is reduced, and the method is more environment-friendly; heavy metals can be directly recycled, and the economic value is high.
The wastewater treatment system does not carry out chemical treatment on chromium oxide, chromic acid glycoside and the like in wastewater in the whole process, and the substances are dissolved in water in a stable compound form, so that the stability is good, and an evaporator cannot be corroded; in addition, the crystallization temperature of the compound is far higher than that of a salt substance, so that the compound is not easy to crystallize per se and has certain crystallization resistance, and a pipeline is not easy to block in the evaporation process.
The evaporation operation method adopts the modes of batch feeding and repeated evaporation, new liquid and evaporated concentrated solution are respectively added in the subsequent steps to be evaporated together, different temperature and negative pressure conditions are set at different stages, the temperature and the pressure are sequentially increased, the concentrated solution is evaporated in the tank body without stopping flowing, and the energy consumption required by evaporation can be saved to the greatest extent.
The evaporation system provided by the invention uses the thermometer at the thermometer port and the pressure gauge at the first pressure gauge port to monitor the temperature and the pressure of the liquid in the evaporator tank body in real time, so that the metal compound is prevented from being separated out when the crystallization condition of the metal compound is reached in the evaporation tank body, the pipeline is prevented from being blocked, and solid substances cannot be separated out in the whole process.
According to the invention, the external heat exchanger is not adopted to circularly heat the liquid in the tank body, but the heating sleeve is arranged outside the horizontal tank body to directly heat the tank body, so that the liquid in the tank body is indirectly heated, the temperature control is more accurate, and the risk of blockage of a pipeline through which the liquid passes and the risk of blockage possibly occurring when the liquid passes through the pipeline are reduced, therefore, the crystallization blockage of the liquid in the evaporator is effectively avoided, and the problem of pipe blockage is avoided.
The precise filtering system is arranged in front of the RO membrane filtering system, and because the particles dispersed in the sewage by the oil are very small, even smaller than the water particles, the oil is not easy to float from the sewage, if the oil is not removed in advance in the subsequent RO membrane filtering system, the oil substances are easy to block the RO membrane, and the oil substances in the wastewater in the surface treatment industry can be removed by the preposed precise filtering system, so that the oil substances are prevented from blocking the RO membrane.
According to the invention, large particles, organic matters and oil substances, micro particles above 0.5-5 um and micro particles above 0.01um in the wastewater are sequentially removed through primary filtration, sand filtration, precise filtration and ultrafiltration, so that water-insoluble substances in the wastewater are basically removed completely, and subsequent RO membrane filtration is smoothly carried out.
According to the invention, multi-stage concentrate backflow is arranged in the RO membrane filtration systems of a plurality of stages, concentrate generated by filtration from the second-stage membrane system does not directly enter the next-stage evaporation system, but flows back to the relay tank in front of the previous-stage membrane system 9 for filtration of the previous stage again, and circular filtration enables all the concentrate to be intercepted from the first-stage membrane system and then discharged into the next-stage evaporation system, so that the concentration of the concentrate entering the evaporation system is ensured to be higher, and the energy consumption required by the overall evaporation of the evaporation system is reduced.
The backwashing system can automatically complete the backwashing work of the filter elements of the sand filtration system, the precise filtration system, the ultrafiltration system and the RO membrane system according to the respective needs of each system, and on the other hand, clear water obtained by the filtration of the filter system is introduced into the sand filtration relay tank of the system again, and clear water obtained by the filtration of the filter system is not discharged independently and enters the system for treatment in a unified way, so that the water outlets of the system are reduced, and the overall structure of the system is simplified.
The cooling system is used for cooling the RO membrane system and the condensing system, damage caused by overhigh temperature of the RO membrane system is prevented, when the evaporation effect of the condensing system is poor, the negative pressure system can possibly not work normally, the cooling system can enhance the evaporation and condensation effect of the condensing system, and the normal work of the negative pressure system is ensured. The cooling system and the evaporation system are respectively connected with the condensation system, a condensed water outlet of the condensation system is connected with the first clear liquid relay tank, and condensed water enters the first clear liquid relay tank for filtration and recovery.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Fig. 2 is an evaporator tank of the evaporation system of the present invention.
Fig. 3 is a left side view of fig. 2 (showing the internal structure).
In the figure: 1. a raw water collecting tank; 2. a raw water relay tank; 3. a sand filtration system; 4. a sand filtration relay tank; 5. a precision filtration system; 6. a precision filtration relay tank; 7. an ultrafiltration system; 8. an ultrafiltration relay tank; 9. a first stage membrane system; 10. a first concentrate relay tank; 11. a first clear liquid relay tank; 12. a secondary membrane system; 13. a second clear liquid relay tank; 14. a tertiary membrane system; 15. a reuse water system; 16. an evaporation system; 17. a baking powder system; 18. a backwashing system; 19. an air compressor; 20. a filter system; 21. a filter element solid waste disposal device; 22. a gas system; 23. a cooling system; 24. a condensing system; 25. a negative pressure system; 26. a recycled oil outlet; 27. a solid waste outlet; 28. an exhaust gas treatment device; 29. a vacuum port; 30. a thermometer port; 31. a second pressure gauge port; 32. a first pressure gauge port; 33. an inspection opening; 34. a feed inlet; 35. a heating medium outlet; 36. a level gauge port; 37. a heating medium inlet; 38. a discharge port; 39. a sewage draining outlet; 40. a tank body; 41. and (4) heating the sleeve.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
As shown in fig. 1, the wastewater treatment system of the present invention includes a raw water collection tank 1, a raw water relay tank 2, a sand filtration system 3, a sand filtration relay tank 4, a precision filtration system 5, a precision filtration relay tank 6, an ultrafiltration system 7, an ultrafiltration relay tank 8, an RO membrane system, a first concentrated solution relay tank 10, an evaporation system 16, and a baking powder system 17, which are connected in sequence, wherein the precision filtration system 5 is provided with a recycled oil outlet 26, the RO membrane system is connected with a recycled water system 15, and the baking powder system 17 is provided with a solid waste outlet 27. The precise filtering system 5 is arranged in front of the RO membrane filtering system, because the particles dispersed in the sewage by the oil are very small, even smaller than the water particles, the oil is not easy to float from the sewage, if the oil is not removed in advance in the subsequent RO membrane filtering system, the oil substances are easy to block the RO membrane, and the oil substances in the wastewater in the surface treatment industry can be removed by the preposed precise filtering system 5, so that the oil substances are prevented from blocking the RO membrane.
The RO membrane system is including a plurality of grades of membrane systems that set gradually, the common tertiary membrane system of this embodiment, ultrafiltration relay jar 8 is connected with one-level membrane system 9, the concentrate export of one-level membrane system 9 is connected with first concentrate relay jar 10, the clear solution export of one-level membrane system 9 has connected gradually first clear solution relay jar 11, second grade membrane system 12, the concentrate export of second grade membrane system 12 is connected with ultrafiltration relay jar 8, the clear solution export of second grade membrane system 12 has connected gradually second clear solution relay jar 13, tertiary membrane system 14, the clear solution exit linkage reuse water system 15 of tertiary membrane system 14, tertiary membrane system 14's concentrate export is connected with first clear solution relay jar 11.
According to the invention, multi-stage concentrate backflow is arranged in the RO membrane filtration systems of a plurality of stages, the concentrate generated by filtration from the second-stage membrane system 12 does not directly enter the evaporation system 16 of the next stage, but flows back to the relay tank in front of the previous-stage membrane system for filtration of the previous stage again, and the circulating filtration enables all the concentrate to be intercepted only from the first-stage membrane system 9 and then discharged into the evaporation system 16 of the next stage, so that the concentration of the concentrate entering the evaporation system 16 is ensured to be higher, and the energy consumption required by the overall evaporation of the evaporation system 16 is reduced.
The invention is also provided with a backwashing system 18, the backwashing system 18 is connected with the backwashing water inlets of the sand filtration system 3, the precise filtration system 5, the ultrafiltration system 7 and the RO membrane system, the backwashing water outlets of the sand filtration system 3, the precise filtration system 5, the ultrafiltration system 7 and the RO membrane system are connected with a filter system 20, the clear water outlet of the filter system 20 is connected with the sand filtration relay tank 4, and the washing water outlet of the filter system 20 is connected with the filter element solid waste disposal device 21.
The sand filtering system 3 automatically carries out back washing operation respectively according to the value measured by the internal pressure controller, the precision filtering system 5 according to the value measured by the pressure controller and the water yield, the ultrafiltration system 7 and the RO membrane system according to the water yield and the conductivity, when in back washing, the air compressor 19 inputs water into the sand filtering system 3, the precise filtering system 5 or the ultrafiltration system 7, water flow backflushs filter elements of the sand washing filtering system 3, the precise filtering system 5 or the ultrafiltration system 7, the washing water enters the filter system 20 for filtering, impurities obtained by filtering of the filter system 20 enter the filter element solid waste disposal device 21 for disposal, the backflushing system 18 is connected with the RO membrane system at the same time, the washing water discharged by the RO membrane system also enters the filter system 20 for filtering, clear water obtained by filtering of the filter system 20 enters the sand filtering relay tank 4 and then enters a subsequent water disposal link. On one hand, the backwashing system 18 can automatically complete the backwashing work of the sand filtration system 3, the precise filtration system 5, the ultrafiltration system 7 and the filter element of the RO membrane system according to the respective needs of each system, on the other hand, the clear water filtered by the filter system 20 is introduced into the sand filtration relay tank 4 of the system again, the clear water filtered by the filter system 20 is not discharged independently and enters the system of the invention for treatment in a unified way, the water outlets of the system are reduced, and the overall structure of the system is simplified.
The invention is also provided with a heating system 21, the heating system 21 is respectively connected with the evaporation system 16 and the dry powder baking system 17, the heating system 21 is supplied with heat by a gas system 22, and simultaneously supplies heat to the evaporation system 16 and the dry powder baking system 17. The dry powder baking system 17 is connected with the exhaust gas treatment device 28, and exhaust gas generated in the drying process is treated by the exhaust gas treatment device 28 and then discharged.
The RO membrane system is further provided with a cooling system 23, the cooling system 23 is connected with a primary membrane system 9, a secondary membrane system 12 and a tertiary membrane system 14 of the RO membrane system, the cooling system 23 cools the RO membrane system, the cooling system 23 and an evaporation system 16 are respectively connected with a condensation system 24, a condensed water outlet of the condensation system 24 is connected with a first clear liquid relay tank 11, moisture in the cooling system 23 and the evaporation system 16 is pumped into the condensation system 24 through a negative pressure system 25, and the condensed water flows into the first clear liquid relay tank 11 and is discharged through the secondary membrane system 12 and the tertiary membrane system 14. The water generated by the condensing system 24 is collected and filtered by using the water filtering system in the system, so that the water generated in the whole system is discharged from the same water outlet after being concentrated and filtered, the drainage outlet of the system can be reduced, and the pure water collection work is simplified.
The evaporation system 16 comprises a plurality of evaporator tank bodies 40 connected in parallel, as shown in fig. 2 and 3, one end of each horizontal evaporator tank body 40 is closed, the other end of each horizontal evaporator tank body is provided with a liquid level meter port 36, a vacuum port 29, a temperature meter port 30, a second pressure meter port 31, a first pressure meter port 32 and a feed port 34 are sequentially arranged above the tank body 40 from left to right near the closed end, a temperature meter of the temperature meter port 30 and a pressure meter of the first pressure meter port 32 monitor the temperature and the pressure of liquid in the tank body 40, and a pressure meter of the second pressure meter port 31 monitors the pressure of a heating medium. The heating jacket 41 is sleeved outside the lower half part in the tank body close to the tank body 40, the heating medium inlet 37 and the heating medium outlet 35 are respectively arranged at the bottom and the upper part of the heating jacket 41, the heating medium can be hot kerosene, steam, water and the like, heating can be more uniform by adopting hot kerosene heating, other heating modes of electrical heating arranged on the periphery of the tank body 40 can be selected, and the heating jacket 41 can be sleeved on the whole tank body 40. An inspection opening 33 is arranged at the junction of the upper part of the heating jacket 41 and the tank 40 and is used for inspecting the evaporation operation in the tank 40. The bottom of the tank 40 is provided with a cylindrical sewage discharge pipeline, the bottom of the sewage discharge pipeline is provided with a sewage discharge outlet 39, and the side surface of the sewage discharge pipeline is provided with a discharge port 38.
The evaporation step of the evaporation system 16 of the invention sets 4 to 8 evaporation times, determines the temperature and negative pressure conditions of each stage according to different waste liquid types, and is realized by the following implementation modes:
(i) the interior of the tank 40 is not vacuumized, concentrated solution with the solid content of about 5% enters the evaporator tank 40, the heating sleeve 41 heats the tank 40, heating is stopped when the temperature in the tank 40 is 50-90 ℃, the tank 40 starts to be vacuumized, and the vacuum degree is-0.093 to-0.095 MPa;
(ii) at the moment, the water in the liquid in the tank is quickly evaporated under the conditions of high temperature and low pressure, new concentrated liquid is added after the evaporation is carried out for 2 to 7min, the heating sleeve 41 is continuously heated until the temperature in the tank 40 is 50 to 95 ℃, the interior of the tank 40 is vacuumized again, and the vacuum degree is minus 0.095 to minus 0.097 MPa;
(iii) and (3) repeating the step (2) for 2-6 times, wherein the heating temperature of the heating sleeve 41 is increased by 1-5 ℃ each time, and the vacuum degree of the vacuumizing is increased by 0.001 MPa each time when the step is 1-4. In the last 1-2 steps, no new liquid is added, evaporation is completed after the determined concentration is reached, and the solid content of the concentrated solution finally discharged from the evaporation system 16 is 30-40%.
The amount of liquid added in each step of adding new liquid is 10-35% of the amount of liquid added in the first step, and 1/3 of liquid is preferably constantly added in each step.
First embodiment of evaporation operation:
1. when the treated wastewater is chromium-containing wastewater, about 5% of solid content in the filtrate after the RO membrane step enters the first concentrated solution relay tank 10, 150 kg of concentrated solution in the first concentrated solution relay tank 10 enters the evaporator tank 40, at this time, no vacuum pumping is performed in the tank 40, hot oil enters the heating sleeve 41 from the heating medium inlet 37 and leaves from the heating medium outlet 35, the tank 40 is heated by the hot oil in a circulating manner, when the temperature in the tank 40 is monitored by the thermometer at the thermometer port 30 to be 60 ℃, the heating is stopped, the tank 40 starts to be vacuumized, the vacuum degree is-0.094 MPa until the water starts to boil, and after 2-3min, about 65 kg of water is evaporated.
2. And then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, in the liquid adding process, a part of vacuum degree and pressure are lost inside the tank body 40, the temperature is reduced, the liquid is heated to 62 ℃ by the heating sleeve 41, the tank body 40 is vacuumized again, the vacuum degree is-0.095 MPa, and after 5-6min, the moisture is evaporated to about 50 kg.
3. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 64 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.095 MPa, and after 5-6min, the water is evaporated to about 50 kg.
4. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 66 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.095 MPa, and after 5-6min, the water is evaporated to about 40 kg.
5. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 68 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.095 MPa, and after 5-6min, the water content is evaporated to about 35 kg.
6. Then no more concentrated solution is added, the heating sleeve 41 heats the liquid to 69 ℃, the tank 40 is vacuumized again, the vacuum degree is-0.096 MPa, and the moisture is evaporated for about 30 kg after 6-7 min.
7. Then no more concentrated solution is added, the heating sleeve 41 heats the liquid to 70 ℃, the tank 40 is vacuumized again, the vacuum degree is-0.097 MPa, moisture is evaporated for about 25 kg after 6-7min, and finally the solid content of the liquid from the evaporation system 16 is 31.8%.
Example two of the evaporation operation:
1. when the treated wastewater is nickel-containing wastewater, the solid content in the filtrate after the RO membrane step is about 5%, the wastewater enters a first concentrated solution relay tank 10, 150 kg of concentrated solution in the first concentrated solution relay tank 10 enters an evaporator tank 40, at the moment, the interior of the tank 40 is not vacuumized, hot oil enters a heating sleeve 41 from a heating medium inlet 37 and leaves from a heating medium outlet 35, the hot oil circularly heats the tank 40, when a thermometer at a thermometer port 30 monitors that the temperature in the tank 40 is 55 ℃, the heating is stopped, the tank 40 starts to be vacuumized, the vacuum degree is-0.094 MPa until water starts to boil, and after 6-7min, the water is evaporated to about 70 kg.
2. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 58 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.095 MPa, and after 5-6min, the water is evaporated to about 50 kg.
3. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 61 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.095 MPa, and after 5-6min, the water is evaporated to about 50 kg.
4. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 63 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.096 MPa, and after 5-6min, the water content is evaporated to about 45 kg.
5. Then 50 kg of concentrated solution is added from the first concentrated solution relay tank 10, the heating sleeve 41 heats the solution to 65 ℃, the tank body 40 is vacuumized again, the vacuum degree is-0.096 MPa, and after 5-6min, the water content is evaporated to about 45 kg.
6. Then no more concentrated solution is added, the heating sleeve 41 heats the liquid to 70 ℃, the tank 40 is vacuumized again, the vacuum degree is-0.097 MPa, moisture is evaporated for about 35 kg after 6-7min, and finally the solid content of the concentrated solution from the evaporation system 16 is 31.8%.
The concentrated solution from the evaporation system 16 is sprayed and dried in the baking powder system 17, and all water is baked out, and finally solid substances are formed.
The wastewater treatment method comprises the following steps:
(I) primary filtration: the method comprises the following steps that wastewater enters a raw water collecting tank 1 for pretreatment, different treatment methods are set according to different wastewater types, large granular substances, suspended particles and organic matters in the wastewater are preliminarily filtered, and the wastewater enters a raw water relay tank 2;
(II) sand filtration: the wastewater enters a sand filtering system 3, organic matters in the wastewater are filtered and removed, the COD value (chemical oxygen demand) in the water is further reduced, gravel is further removed at the same time, and the filtrate enters a sand filtering relay tank 4;
(III) microfiltration: the filtrate enters a precise filtering system 5, oil substances and micro particles above 0.5-5 um in the water are filtered and removed, the filtered oil is discharged from a recycled oil outlet 26, and the filtrate enters a precise filtering relay tank 6;
(IV) ultrafiltration: the filtrate enters an ultrafiltration system 7, and is filtered to remove micro particles above 0.01um, all microorganisms such as bacteria in the water can be removed basically in the step, and the filtrate enters an ultrafiltration relay tank 8;
(V) RO membrane concentration: the filtrate enters a plurality of stages of RO membrane systems, the filter residue which can not pass through the primary membrane system 9 is the heavy metal-containing concentrated solution, the concentrated solution directly enters the first concentrated solution relay tank 10, the clear solution enters the first clear solution relay tank 11, then the clear solution enters the secondary membrane system 12 for secondary membrane filtration, the concentrated solution obtained by the secondary membrane filtration flows back to the ultrafiltration relay tank 8 for the primary membrane system 9 filtration again, the clear solution obtained by the secondary membrane filtration enters the second clear solution relay tank 13, then the clear solution enters the tertiary membrane system 14 for the tertiary membrane filtration, the concentrated solution obtained by the tertiary membrane filtration flows back to the first clear solution relay tank 11 for the secondary membrane filtration again, the clear solution obtained by the secondary membrane filtration, namely the clean recovered water finally obtained, directly enters the reuse water system 15, and the conductivity of the recovered water is below 200 s/m.
(VI) evaporating: the heavy metal-containing concentrated solution in the first concentrated solution relay tank 10 enters an evaporation system 16 and is evaporated by adopting the evaporation method;
(VII) baking dry powder: the evaporated concentrated solution enters a baking powder system 17, a high-purity compound containing chromium salt, nickel salt or other metal salt is obtained by spraying and drying at 250-320 ℃, and is discharged from a solid waste outlet 27, and waste gas generated in the baking process is discharged from a waste gas treatment device 28.
The invention adopts a physical treatment mode without chemical treatment, the solid waste finally obtained by the baking powder system 17 is a compound containing chromium salt, nickel salt or other metal salt with high purity, and the substances can be directly recycled without landfill or disposal treatment, so that no additional environmental pollution is generated and the economic value is obvious; the method saves the chemical treatment step, also can save a large amount of chemical reagents, avoids secondary pollution of the chemical reagents and obviously reduces the production cost.
The foregoing description is illustrative of the present invention and is not to be construed as limiting thereof, as the invention may be modified in any manner without departing from the spirit thereof.
Claims (10)
1. A method for treating wastewater, which is characterized in that: the method comprises the following steps:
(I) primary filtration: removing large-particle substances in the wastewater;
(II) sand filtration: removing organic matters and gravels in the wastewater;
(III) microfiltration: removing oil substances and micro particles with the particle size of more than 0.5-5 um in water;
(IV) ultrafiltration: filtering to remove micro particles above 0.01 um;
(V) RO membrane concentration: filtering to obtain clean recovered water;
(VI) evaporating: the concentrated solution in the step V enters an evaporator tank body (40), a heating device heats the tank body (40), when the temperature in the tank body (40) is 50-90 ℃, the heating is stopped, and the interior of the tank body (40) starts to be vacuumized; repeatedly adding new liquid for a plurality of times after a period of time after evaporation, continuously heating the heating sleeve (41) until the temperature in the tank body (40) is 50-95 ℃, and vacuumizing the tank body (40) again;
(VII) baking dry powder: and (5) baking at 250-320 ℃ to obtain a solid substance.
2. The wastewater treatment method according to claim 1, characterized in that: and in the step V, the concentrated solution obtained by each stage of membrane system flows back to the relay tank in front of the previous stage of system for secondary filtration again, the obtained clear solution enters the next stage of membrane system, and the clear solution obtained by the last stage of membrane system is discharged from a reuse water outlet.
3. The method for treating waste water according to claim 1, wherein: in step V, the conductivity of the recovered water is 200s/m or less.
4. The method for treating waste water according to claim 1, wherein: and VI, the solid content of the concentrated solution is 30-40%.
5. A wastewater treatment system for use in the wastewater treatment process of claim 1, wherein: the device comprises a raw water collecting tank (1), a sand filtering system (3), a precise filtering system (5), an ultrafiltration system (7), an RO membrane system, an evaporation system (16) and a baking powder system (17) which are sequentially connected, wherein a recycling oil outlet (26) is formed in the precise filtering system (5), and a solid waste outlet (27) is formed in the baking powder system (17).
6. The wastewater treatment system according to claim 5, characterized in that: still be provided with ultrafiltration relay jar (8) between ultrafiltration system (7) and the RO membrane system, the RO membrane system is including a plurality of levels of membrane systems that set gradually, ultrafiltration relay jar (8) are connected with one-level membrane system (9), the concentrate export of one-level membrane system (9) is connected with vaporization system (16), the clear solution export of one-level membrane system (9) connects gradually first clear solution relay jar (11), next stage membrane system, the concentrate export of later each level of membrane system all is connected with the relay jar in last one-level membrane system the place ahead, the clear solution export then is connected with clear solution relay jar, the clear solution exit linkage reuse water export of last one-level membrane system.
7. The wastewater treatment system according to claim 5, characterized in that: still be provided with sand between sand filtration system (3) and precise filtration system (5) and filter relay jar (4), backwash system (18) is connected with sand filtration system (3), precise filtration system (5), ultrafiltration system (7) and the back flush water inlet of RO membrane system, and the back flush delivery port of sand filtration system (3), precise filtration system (5), ultrafiltration system (7) and RO membrane system is connected with filter system (20), and the clear water export of filter system (20) is connected with sand filtration relay jar (4).
8. The wastewater treatment system according to claim 5, characterized in that: the heating system (21) is respectively connected with the evaporation system (16) and the dry powder baking system (17), and the heating system (21) is supplied with heat by the gas system (22).
9. The wastewater treatment system according to claim 5, characterized in that: the cooling system (23) is connected with the RO membrane system; the cooling system (23) and the evaporation system (16) are respectively connected with the condensing system (24), and a condensed water outlet of the condensing system (24) is connected with the first clear liquid relay tank (11).
10. The wastewater treatment system according to claim 5, characterized in that: a raw water relay tank (2) is also arranged between the raw water collecting tank (1) and the sand filtering system (3), a precise filtering relay tank (6) is also arranged between the precise filtering system (5) and the ultrafiltration system (7), and a first concentrated solution relay tank (10) is also arranged between the RO membrane system and the evaporation system (16); and a reuse water outlet is arranged on the RO membrane system.
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