CN107381932A

CN107381932A - A kind of chromium containing waste water treatment method, processing system and application

Info

Publication number: CN107381932A
Application number: CN201710446977.XA
Authority: CN
Inventors: 韩全; 张恒
Original assignee: Guangdong Yeanovo Environmental Protection Co Ltd
Current assignee: Guangdong Shangchen Environmental Technology Co ltd
Priority date: 2017-06-14
Filing date: 2017-06-14
Publication date: 2017-11-24
Anticipated expiration: 2037-06-14
Also published as: CN107381932B

Abstract

The present invention provides a kind of chromium containing waste water treatment method, it is characterised in that the processing method sequentially includes：(1) chromate waste water is pre-processed, obtains pretreated water；(2) pretreated water for obtaining step (1) carries out biochemical treatment, obtains biochemical treatment water；(3) the biochemical treatment water for obtaining step (2) carries out concentration, obtains concentration high salt concentrated water and recycle-water；(4) the concentration high salt concentrated water that step (3) obtains is evaporated crystallization treatment, obtains recycle-water and crystal；Wherein recycle water standard is：PH 68, electrical conductivity≤50, COD≤30, turbidity≤1；This method is simple to operate, stable, cost is cheap, treatment effeciency is high, so as to reach the zero-emission or low emission of plating production chromate waste water, while the recovery of higher degree is realized to each metal ion in waste water.

Description

A kind of chromium containing waste water treatment method, processing system and application

Technical field

The present invention relates to a kind of processing method of waste water and processing system, and in particular to a kind of electroplating industry chromate waste water Processing method, the system handled using this method electroplating industry chromate waste water, and this method or the system are existed For handling the application in electroplating industry chromate waste water.

Background technology

The method that chromate waste water processing often uses in waste water treatment process is chemical precipitation method, electrolysis and conventional ion Exchange process etc..Above-mentioned processing method and system have some limitations and can not accomplish the zero-emission of chromate waste water.Its In, chemical precipitation method is widely used in processing waste water containing chrome, due to needing to add substantial amounts of soda acid and sulphur in process of production Sour ferrous, aluminium polychloride, so as to add the saliferous rate of discharge of wastewater, and the chromium ion remained in waste water is difficult to reach discharge Standard.Because controlled substance content is extremely low as defined in wastewater discharge standard, then reaching discharge standard just needs to put into the chemistry of excess Medicine, its cost is high and waste water can not be used as process water recovery to use.Meanwhile chemical precipitation method can not to the chromium in waste water from Son is directly reclaimed, while can produce substantial amounts of sludge, and a large amount of chromium ions are contained in sludge, therefore sludge need to be handled again, Cause secondary pollution；The technical maturity of Electrolytic Theatment of Chrome Containing Wastewater, it is stable, but due to as defined in wastewater discharge standard Controlled substance content is extremely low, so larger using power consumption during Electrolytic Theatment of Chrome Containing Wastewater, processing cost is high, and has been also easy to produce Poisonous gas, so as to be difficult to qualified discharge；And conventional ion commutation rule is effectively gone using organic backbone ion exchange resin Except the various harmful ions in chromate waste water, while the waste water after processing can be with reuse, but is set in its wastewater treatment process The consumption of fat is big, and the processing of its regenerated liquid is difficult, will also consume substantial amounts of soda acid, and processing cost is high.Meanwhile organic backbone ion Exchanger resin will also cause a large amount of ruptures of resin in regenerative process, and economy is not high.

As can be seen that problems be present currently for the various processing methods of chromate waste water, even if to each Electroplate Factory Existing equipment make full use of the largely or entirely reuse for being still unable to reach waste water, and to the valuable gold in waste water Category can not be effectively separated and reclaim.

The content of the invention

It is an object of the invention to overcome produced problem in the prior art and defect, there is provided a kind of simple to operate, operation The stable, chromium containing waste water treatment method that cost is cheap, treatment effeciency is high and corresponding processing system, contain so as to reach plating production The zero-emission or low emission of chrome waste water, while the recovery of higher degree is realized to each metal ion in waste water, save electroplating industry Industrial water amount, pollution of the electroplating industry to environment is substantially reduced, reduce the usage amount of soda acid, effectively save resource reduces production Cost and the recovery for realizing equipment investment, promote and promote cleanly production and the sustainable development of electroplating industry.

The purpose of the present invention is achieved through the following technical solutions：

The present invention provides a kind of chromium containing waste water treatment method, it is characterised in that the processing method sequentially includes：

(1) chromate waste water is pre-processed, obtains pretreated water；

(2) pretreated water for obtaining step (1) carries out biochemical treatment, obtains biochemical treatment water；

(3) the biochemical treatment water for obtaining step (2) carries out concentration, obtains concentration high salt concentrated water and reuse Water；

(4) the concentration high salt concentrated water that step (3) obtains is evaporated crystallization treatment, obtains recycle-water and crystallization Thing；

Wherein recycle water standard is：PH 6-8, electrical conductivity≤50, COD≤30, turbidity≤1.

Preferably, in the step (1), the chromate waste water pH 4-6, it includes Cr VI, trivalent chromium, sulfuric acid, nitre The pollutants such as acid, oxide, COD；

Preferably, the step of pretreatment is：

Chromate waste water is introduced broken chromium pond by (1-1), and it is 2-3 that sulfuric acid is added in broken chromium pond to pH, adds sodium sulfite afterwards It is 230-270mv to ORP value, carries out brokenly chromium reaction；

Waste water after step (1-1) processing is introduced pH regulating reservoirs by (1-2), and addition sodium hydroxide to pH is 8-9；

Waste water after step (1-2) processing is introduced chemical reaction pond by (1-3), is added coagulant, is added flocculant afterwards, stir Mix 20-30min；

Waste water after step (1-3) processing is introduced accurate control High-rate sedimentation system by (1-4)；

Preferably, in the step (1-1), add the sulfuric acid solution that concentration is 10% and adjust pH；Preferably, concentration is added ORP value is adjusted for 10% sodium sulfite solution；

Preferably, the broken chromium reaction time of the step (1-1) is 20-30min；

Preferably, in the step (1-2), add the sodium hydroxide solution that concentration is 10% and adjust pH；

Preferably, in the step (1-3), the coagulant is inorganic coagulant, more preferably PAC；Preferably, it is described Flocculant is organic flocculant, more preferably PAM；Preferably, the time interval between the addition coagulant and flocculant is 20-40min；

Preferably, the wastewater pH handled through step (1-3) is 8-9；

Preferably, the waste water ORP value handled through step (1-3) is 230-270mv；

Preferably, in the step (1-4), the accurate control High-rate sedimentation system by water distribution system, precipitation process pond, Inclined tube, effluent weir, sludge bucket are sequentially connected composition；Preferably, the waste water after step (1-3) processing is introduced into the water distribution successively System, precipitation process pond, inclined tube；Supernatant after above-mentioned processing obtains pretreated water into effluent weir, and obtained sludge sinks Enter sludge bucket；Preferably, the pressure in the precipitation process pond is 2-3Mpa.

Preferably, in the step (2), the biochemical treatment step is：The pretreated water that step (1) obtains is entered successively Enter anaerobic pond, Aerobic Pond, membrane bioreactor；

Preferably, anaerobic bacteria is included in the anaerobic pond；Preferably, the anaerobic bacteria is selected from saccharomycete, nitrate bacterium, shuttle One or more in bacillus or bacteroid；

Preferably, the saccharomycete, nitrate bacterium, Fusobacterium or bacteroid make it have salt tolerance through domestication；

Preferably, aerobic microbiological is included in the Aerobic Pond；

Preferably, one or more of the oxygen animalcule in bacillus, rhizobium, nitrifier or mould；

Preferably, the bacillus, rhizobium, nitrifier or mould make it have salt tolerance through domestication；

Preferably, the membrane bioreactor is made up of hollow fiber film assembly and membrane cisterna；Preferably, the doughnut Membrane module is located in the membrane cisterna；

Preferably, the doughnut membrane aperture is 0.01-0.1 μm；

Preferably, pH is 6-8 after the biochemical treatment.

Preferably, in the step (3), the concentration step is：The biochemical treatment water that step (2) is obtained is successively By one-level nanofiltration system, first-stage reverse osmosis system, two-stage reverse osmosis system；

Preferably, the one-level nanofiltration system is sequentially connected and formed by accurate filter and one-level NF membrane；

Preferably, the filter core of the accurate filter is fusion-jet type PP cottons；

Preferably, the filter core aperture of the precise microfiltration device is 5 μm；

Preferably, the one-level NF membrane is technical grade equipment with high desalinization NF membrane；

Preferably, the aperture of the one-level NF membrane is 1-2nm；

Preferably, the one-level NF membrane is 50-70% to the rejection of sodium ion；Preferably, the one-level NF membrane The rejection ＞ 97% of heavy metal ion and salinity；

Preferably, the film pressure of entering of the one-level nanofiltration system is 1.0-1.5Mpa；

Preferably, the relative molecular mass retention scope of the one-level nanofiltration system is 150-300 dalton；

Preferably, the pH of the water into one-level nanofiltration system is 6-8；

Preferably, the permeate of the one-level nanofiltration system can use as recycle-water；

Preferably, the concentrate of the one-level nanofiltration system enters first-stage reverse osmosis system.

Preferably, in the step (3), the first-stage reverse osmosis system by accurate filter and first-stage reverse osmosis film successively Connection composition；

Preferably, the first-stage reverse osmosis film is bitter reverse osmosis membrane；

Preferably, the rejection ＞ 98% of the first-stage reverse osmosis film heavy metal ion and salinity；

Preferably, the aperture of the first-stage reverse osmosis film is 0.1-1nm；

Preferably, the film pressure of entering of the first-stage reverse osmosis system is 1.8Mpa；

Preferably, the pH of the water into first-stage reverse osmosis system is 5-6；

Preferably, pH is adjusted by adding hydrochloric acid in the first-stage reverse osmosis system；

Preferably, the salt acid for adjusting pH that concentration is 0.2-0.5% is added；

Preferably, the permeate of the first-stage reverse osmosis system returns to one-level nanofiltration system；

Preferably, the concentrate of the first-stage reverse osmosis system enters two-stage reverse osmosis system.

Preferably, in the step (3), the two-stage reverse osmosis system by accurate filter and two-pass reverse osmosis film successively Connection composition；

Preferably, the two-pass reverse osmosis film is seawater reverse osmosis membrane；

Preferably, the rejection ＞ 99.5% of the two-pass reverse osmosis film heavy metal ion and salinity；

Preferably, the aperture of the two-pass reverse osmosis film is 0.1-1nm；

Preferably, the film pressure of entering of the two-stage reverse osmosis system is 4-5Mpa；

Preferably, the pH of the water into two-stage reverse osmosis system is 6-8；

Preferably, pH is adjusted by adding hydrochloric acid in the two-stage reverse osmosis system；

Preferably, the concentration of the hydrochloric acid is 0.2-0.5%；

Preferably, the permeate of the two-stage reverse osmosis system returns to one-level nanofiltration system；

Preferably, the concentrate of the two-stage reverse osmosis system is the high salt concentrated water.

Preferably, in the step (4), the evaporative crystallization processing step is：By the high salt concentrated water that step (3) obtains according to It is secondary to pass through heat exchanger, concentration evaporator, crystallizing evaporator；

Preferably, the operation temperature of the heat exchanger is 80-100 DEG C；

Preferably, the operating pressure of the heat exchanger is 0.05-0.1MPa；

Preferably, the concentration evaporator is sequentially connected group by heating chamber, separation chamber, circular chamber, liquid distributor, demister Into；

Preferably, the crystallizing evaporator is sequentially connected and formed by separation chamber, salt leg, thickener, crystallization kettle；

Preferably, condensed water of the high salt concentrated water after concentration evaporator returns to the two-stage reverse osmosis system；

Preferably, the high salt concentrated water obtains concentrating high salt concentrated water after concentration evaporator；

Preferably, the salt content of the concentration high salt concentrated water is 30-35%；

Preferably, the concentration high salt concentrated water obtains crystal and condensed water after crystallizing evaporator；Preferably, it is described Crystal is sodium sulphate and/or sodium chloride；Preferably, the condensed water uses as recycle-water.

The present invention also provides a kind of processing system of chromium containing waste water treatment method, and the system includes the pre- place being sequentially communicated Manage unit, biochemical treatment unit, concentration unit and evaporative crystallization processing unit.

Preferably, the pretreatment unit includes being sequentially communicated broken chromium pond, pH regulating reservoirs, chemical reaction pond, accurate control High-rate sedimentation system processed；Preferably, the accurate control High-rate sedimentation system is by water distribution system, precipitation process pond, inclined tube, water outlet Weir, sludge bucket are sequentially connected composition.

Preferably, the biochemical treatment unit includes anaerobic pond, Aerobic Pond, the membrane bioreactor being sequentially communicated；

Preferably, the membrane bioreactor is made up of hollow fiber film assembly and membrane cisterna；

Preferably, the hollow fiber film assembly is located in the membrane cisterna；

Preferably, the doughnut membrane aperture is 0.01-0.1 μm.

Preferably, the concentration unit includes one-level nanofiltration system, first-stage reverse osmosis system, the two level being sequentially communicated Counter-infiltration system.

Preferably, the filter core aperture of the accurate filter is 5 μm；

The one-level NF membrane is technical grade equipment with high desalinization NF membrane；

Preferably, the aperture of the one-level NF membrane is 1-2nm；

Preferably, the pH of the water into one-level nanofiltration system is 6-8.

Preferably, the first-stage reverse osmosis system is sequentially connected and formed by accurate filter and first-stage reverse osmosis film；

Preferably, the filter core aperture of the accurate filter is 5 μm；

Preferably, the aperture of the first-stage reverse osmosis film is 0.1-1nm；

Preferably, the concentration of the hydrochloric acid is 0.2-0.5%.

Preferably, the two-stage reverse osmosis system is sequentially connected and formed by accurate filter and two-pass reverse osmosis film；

Preferably, the filter core aperture of the accurate filter is 5 μm；

Preferably, the aperture of the two-pass reverse osmosis film is 0.1-1nm；

Preferably, the pH of the water into two-stage reverse osmosis system is 6-8；

Preferably, the concentration of the hydrochloric acid is 0.2-0.5%.

Preferably, the evaporative crystallization unit includes heat exchanger, concentration evaporator, the crystallizing evaporator being sequentially communicated；

Preferably, the operation temperature of the heat exchanger is 80-100 DEG C；

Preferably, the operating pressure of the heat exchanger is 0.05-0.1MPa；

Preferably, the crystallizing evaporator is sequentially connected and formed by separation chamber, salt leg, thickener, crystallization kettle.

Chromium containing waste water treatment method of the present invention or system for processing chrome-containing wastewater of the present invention are in processing waste water containing chrome In application.

The present invention is to overcome defect present in chromate waste water processing in the prior art, there is provided the new processing side of chromate waste water Method, including：

Chromate waste water pollutant sources analysis of the present invention：Chromate waste water of the present invention is mainly after chrome-plated process Plating piece cleaning, pole plate cleaning, the plating piece passivation such as zinc, stainless steel electrolytic polishing, alumilite process, the process such as plating piece processing produced Raw waste water, its pH are 2-4, mainly contain the pollutants such as Cr VI, trivalent chromium, sulfuric acid, nitric acid, oxide, COD.

Chromium containing waste water treatment method of the present invention and processing system by " effluent segregation, classification processing, waste water recycling, The technology path of resource reclaim ", concentrated using heavy metal high accuracy removal technology, high salinity wastewater biochemical technology, special membrane The fully recovering after processing in production, realizes waste water by electroplated heavy metals chromate waste water for technology and mechanical negative pressure evaporation crystallization technique Zero-emission, wastewater recycle rate is brought up to 99.67%, realizes recycling for water resource to greatest extent, by waste water Pollutant is converted into solid recycling, thoroughly realizes the zero-emission of waste water.

Chromate waste water pretreating process of the present invention：1st, chromate waste water is introduced into broken chromium pond, sulphur is added in broken chromium pond Acid is 2-3 to pH, and rear sodium sulfite to the ORP value that adds is 230-270mv, and it is trivalent chromium to make hexavalent chrome reduction, and the reaction time is suitable Control is in 20-30min；Waste water is introduced into pH regulating reservoirs afterwards, it is 8-9 to add sodium hydroxide to pH, trivalent chromium is formed hydroxide Chromium precipitates, and forms the principle of hydroxide precipitation in alkalescence condition using chromium metal ion, removes harmful metal impurity in waste water； 2nd, waste water is introduced into chemical reaction pond again, in order to accelerate coagulating, adds coagulant, add flocculant afterwards, stir 20- 30min, it is allowed to form larger alumen ustum (0.6-1.0mm), so as to accelerate to precipitate, realizes to add at times in flocculation process and mix Solidifying agent and flocculant, both are made to be in the optimal reaction time, flocculation reaction system uses mechanical agitation, and reaction speed is fast, effect Fruit is good, less developer, there is higher removal effect to phosphorus, fluorine, COD while removing heavy metals are removed；3rd, it is rear to introduce accurate control High-rate sedimentation system processed；Preferably, the accurate control High-rate sedimentation system is by water distribution system, precipitation process pond, inclined tube, water outlet Weir, sludge bucket are sequentially connected composition；Waste water after processing is introduced into the water distribution system, sedimentation basin processing pond, inclined tube successively；Through Supernatant after above-mentioned processing obtains pretreated water into effluent weir, and sludge sinks to sludge bucket；Above-mentioned accurate control High-rate sedimentation System shortens the sedimentation time, improves deposition efficiency, pass through the accurate waterpower for controlling High-rate sedimentation system to increase desilting area Water distribution, high-efficiency sedimentation etc. act on, efficient to precipitate flco and SS, while in setting the inclined tube in pond, make jetsam not by The interference that current stabilization influences, reaches rapid precipitation effect, and the disposal ability of the accurate control High-rate sedimentation system is sunk than in general Shallow lake pond is big 3-7 times, and the sludge of bottom of pond is discharged into sludge-tank by the static pressure mud discharging device of setting and further concentrated, and is then pumped into sludge Filter press press filtration, mud cake are reprocessed according to property, can remove about 80% suspension, 40-70% oils, and make delivery turbidity <30NTU, COD decline 40-60% etc.；Wherein, the reaction mainly occurred is as follows：

4CrO₇ ^2-+3S₂O₃ ^2-+26H⁺→8Cr³⁺+6SO₄ ^2-+13H₂O

Or Cr₂O₇ ^2-+3HSO₃ ^2-+5H⁺→2Cr³⁺+3SO₄ ^2-+4H₂O

Cr³⁺+3OH^-=Cr (OH)₃

Chromate waste water biochemical processing process of the present invention：Pretreated water is sequentially entered into anaerobic pond, Aerobic Pond, film biology Reactor；By A/O/MBR biodegradation, the material such as most COD, ammonia nitrogen and SS in waste water is removed；The present invention The anaerobic technique, using the effect of anaerobic bacteria, makes organic matter that hydrolysis, acid occur under without dissolved oxygen conditions or under anoxia condition Change, remove the organic matter in waste water, improve the biodegradability of sewage, be advantageous to follow-up aerobic treatment process；It is of the present invention Aerobic process is organic matter oxidation Decomposition in the presence of aerobic microbiological under aerobic conditions, and organic concentration declines, micro- life Object amount increases, and the organic matter in sewage, is attracted to activated sludge and biofilm surface first, and connect with microbial cell surface Touch, the organic matter of small molecule can be directed through cell membrane and enter in microbial body, and larger molecular organicses then must be in cell It is hydrolyzed in the presence of exoenzyme-hydrolase after small molecule again by microorganism intake cell body.Organic matter is finally broken down into CO₂And H₂O；Membrane bioreactor of the present invention is made up of hollow fiber film assembly and membrane cisterna；Preferably, the doughnut Membrane module is located in the membrane cisterna；Membrane module is positioned in membrane cisterna, is aerated in pond, because hollow-fibre membrane is less than 0.1 Zoogloea and free bacteria, all can be retained in membrane cisterna by the aperture of micron, so as to reach mud-water separation, various suspensions Grain, bacterium, algae, turbidity and organic matter are effectively removed, and ensure that out excellent water outlet water of the aqueous suspension close to zero Matter.The efficient crown_interception of membrane bioreactor, nitration reaction can be smoothed out with effectively catching nitrifier, effectively removed Ammonia nitrogen；The larger molecular organicses for being difficult to degrade can be retained simultaneously, extends its residence time in biochemical reaction tank, is allowed to Decomposition to the limit.

Chromate waste water concentration technique of the present invention：By biochemical treatment water successively by one-level nanofiltration system, one-level Counter-infiltration system, two-stage reverse osmosis system；The present invention is to realize the zero-emission of chromate waste water, is set in biochemical treatment system rear end Concentrating and treating system, for handling strong brine caused by biochemical treatment system；Concentrating and treating system of the present invention is multistage dense The technique that contracting, nanofiltration/reverse osmosis concentration combine, by the concentration step by step of film, makes the water of high content of salt waste water gradually reduce (institute The high salt concentrated water salt content of acquisition is 40-60g/L) so as to reducing the investment of subsequent evaporation crystal system and operating cost；Should Concentration technique to need strong brine to be processed in follow-up evaporation and crystallization system, than the concentrating and treating system reduction of routine 80%, make the cost of investment of whole Waste Water Treatment reduce 20-30%, the operating cost of wastewater treatment reduces 30- 40%, improve the automaticity of system.

Chromate waste water evaporative crystallization handling process of the present invention：The high salt concentrated water that concentration obtains through successively and being changed Hot device, concentration evaporator, crystallizing evaporator；Fully recovering after wastewater treatment to evaporative crystallization stage is accomplished to contain chromium by the present invention The zero-emission of waste water；Waste water is introduced into the heat exchanger in the evaporation and crystallization system, by heat exchange, removes the O in waste water₂ And CO₂Gas, the waste water after heat exchange, which enters in concentration evaporator, is evaporated concentration, when waste water salt concentration is to 30-35% I.e. before sodium sulphate and sodium chloride crystallization is produced, the waste water is delivered into crystallizing evaporator, obtains crystal and condensed water, condensed Water uses as recycle-water.Evaporation and crystallization system of the present invention causes the negative of waste water evaporation section using mechanical temperature raising device Pressure, the energy can be saved, and the waste steam through overcompression heats supercharging and entered outside the pipe of concentration evaporator, and latent heat is passed to Pipe, itself condense into condensed water, while the brine waste evaporation in pipe.The characteristics of evaporation and crystallization system of the present invention is Small volume, take up an area less, energy consumption is low, and the thermal efficiency is high, and the power consumption of general one ton of waste water is 16-20kwh, and its thermal efficiency is that single-action is dodged 27 times of steaming system, it is 7 times of quadruple effect flash system, is current state-of-the-art evaporation concentration system, its caused crystal Can be through handling or sending relevant departments' purification to utilize, its main component is sodium sulphate and sodium chloride.

The advantages of above-mentioned evaporation and crystallization system, is as follows：(1) system makes identical water tonnage device of making using mixed journey feedwater Ton water power consumes more external technique and reduces 40-50%；(2) it is dense by the high salt of concentrating and treating system because the system mixes journey feedwater Water sequentially enters low temperature effect from the high temperature effect of evaporation and crystallization system, and concentration gradually rises, and temperature gradually reduces.Avoid external work In skill, imitated to caused by high temperature effect make-up cooling water from low temperature and raised in high temperature effect feed water concentration, be effectively reduced the knot of high temperature effect Dirt and corrosion condition；(3) it is evenly distributed by the high salt concentrated water of concentrating and treating system on concentration evaporator, avoids existing steaming Send out the uneven susceptible to plugging shortcoming of spray nozzle type feedwater in crystal system；(4) vacuum system uses differential pressure air extractor, accurate between each effect Really form design pressure difference so that the system run all right is reliable.

The processing system of chromium containing waste water treatment method of the present invention, using programmable logic controller (PLC), while realize electricity Gas and instrument automatic control and monitoring, using industrial computer, the operation process state and operational factor of system are monitored.This Outside, the membranous system in the system periodically uses permeate to rinse to rinse the pollutant of film surface, diaphragm；And establish online Chemical cleaning system, it is ensured that system is long-term, stably, Effec-tive Function.

At present, the Technology development in the prior art on chromate waste water has chemical precipitation technology, biologic treating technique And membrane separation technique, routine techniques have the following disadvantages essentially according to the highway route design of " qualified discharge " compared with the present invention：

(1) routine techniques system wastewater recycle rate is 60%, wherein, water resource does not recycle fully, after wastewater treatment Discharge adds the load of surrounding enviroment；

(2) microorganism is generally 3000mg/L to the poor resistance of salinity, sludge concentration in routine biochemistry treatment technology, this The sludge concentration of inventive technique mesophytization system is 7000-8000mg/L.

(3) heavy metal ion not yet 100% removes, and environmental pollution is still present；

(4) concentrated water need to be handled again caused by film concentration systems, otherwise can cause two layers of pollution；

(5) routine techniques reuse water conductivity is 200-300 μ S/cm, the μ S/ of the technology of the present invention reuse water conductivity≤50 cm。

Chromium containing waste water treatment method of the present invention, the beneficial effect of processing system：

(1) condition that chromate waste water pretreating process of the present invention reacts according to various heavy metal ion is different, uses The on-line monitoring instruments such as pH, ORP, measuring pump quantitative dosing is automatically controlled, add medicament and fully reacted with waste water, and pass through precision High-rate sedimentation system is controlled to carry out separation of solid and liquid processing, removal of heavy metal ions rate is up to 99.99%.

(2) chromate waste water biochemical process of the present invention uses A/O/MBR techniques, and system is by biochemistry pool, membrane module and film Pond forms, and can all be retained in activated sludge in membrane cisterna, the various pollutants such as various suspended particulates, bacterium, organic matter are stopped Stay the time to grow, so as to be sufficiently removed, ensure that effluent quality is excellent, SS is almost nil.This process volume load is high, to water quality Water adaptive faculty is strong, is gone using through taming waste water of the extraordinary microorganism with salt tolerant to salt content height and containing difficult degradation COD Except efficiency high, denitrification effect are good.

(3) chromate waste water concentration technology of the present invention uses special membrane concentration technique by the salinity in waste water according to desalination The technology that concentration and smart desalination and concentration combine by more than 30 times of Waste water concentrating, the production water of advanced treatment system can direct reuse in life Production.Special membrane concentration technique is under with high flow rate still with efficient salt rejection rate, with higher mechanical strength and service life, energy The characteristics of to wave function, chemical stability good, cost-effective is being issued compared with low operating pressure.

(4) chromate waste water evaporative crystallization of the present invention is using the extraordinary both vapor compression technology of Germany, by distillation hydrothermal exchange Device, concentration evaporator, crystallizer and centrifuge etc. form, and when evaporator handles waste water, the heat energy needed for evaporating waste water steams again Release heat energy is provided when vapour condenses and condenses water cooling, in the process of running, without the loss of latent heat, waste water is realized low temperature Negative pressure evaporation.In compressor compresses, pressure and temperature is lifted, and high enthalpy steam can fully reclaim distilled water as thermal source again With dope heat, energy consumption is saved.Evaporated during evaporation using pipe is outer, not only never incrustation in efficiency high and pipe.

Brief description of the drawings

Hereinafter, embodiment of the present invention is described in detail with reference to accompanying drawing, wherein：

Fig. 1 is system for processing chrome-containing wastewater schematic diagram of the present invention.

Embodiment

Illustrate the present invention referring to specific embodiment.It will be appreciated by those skilled in the art that these embodiments are only For illustrating the present invention, its scope not limiting the invention in any way.

Experimental method in following embodiments, it is conventional method unless otherwise specified.Original used in following embodiments Material, reagent material etc., unless otherwise specified, it is commercially available products.

First, chromate waste water pollutant sources analysis of the present invention：Chromate waste water of the present invention is mainly in chromium plating work The processes such as the plating piece passivation such as plating piece cleaning, pole plate cleaning, zinc after skill, stainless steel electrolytic polishing, alumilite process, plating piece processing Caused waste water, its pH are 2-4, mainly contain the pollutants such as Cr VI, trivalent chromium, sulfuric acid, nitric acid, oxide, COD；

2nd, chromate waste water pretreating process of the present invention：1st, chromate waste water is introduced into broken chromium pond, added in broken chromium pond The sulfuric acid solution regulation pH that concentration is 10% is 2-3, and sodium sulfite solution to the ORP value of rear addition 10% is 230-270mv, is made Hexavalent chrome reduction is trivalent chromium, and the reaction time is preferably controlled in 20-30min；Waste water is introduced into pH regulating reservoirs afterwards, adds sodium hydroxide It is 8-9 to pH, trivalent chromium is formed chromium hydroxide precipitation, hydroxide precipitation is formed in alkalescence condition using chromium metal ion Principle, remove harmful metal impurity in waste water；2nd, waste water is introduced into chemical reaction pond again, in order to accelerate coagulating, added PAC, PAM is added afterwards, stir 20-30min, be allowed to form larger alumen ustum (0.6-1.0mm), so as to accelerate to precipitate, flocculating During realize at times addition PAC and PAM, both is in the optimal reaction time, flocculation reaction system is stirred using machinery Mix, reaction speed is fast, effect is good, less developer, there is higher removal effect to phosphorus, fluorine, COD while removing heavy metals are removed Fruit；3rd, it is rear to introduce accurate control High-rate sedimentation system；The accurate control High-rate sedimentation system is by water distribution system, precipitation process Pond, inclined tube, effluent weir, sludge bucket are sequentially connected composition；Waste water after processing is introduced into the water distribution system, precipitation process successively Pond, inclined tube；Supernatant after above-mentioned processing obtains pretreated water into effluent weir, and sludge sinks to sludge bucket；Above-mentioned accurate control High-rate sedimentation system processed shortens the sedimentation time, improves deposition efficiency to increase desilting area.

The accurate settling system shortens the sedimentation time, improves deposition efficiency, controlled by precision to increase desilting area The effect such as the waterpower water distribution of High-rate sedimentation system processed, high-efficiency sedimentation, it is efficient to precipitate flco and SS, while in setting current stabilization in pond Interference unit, the interference for making jetsam not influenceed by current stabilization, reach rapid precipitation effect, the accurate control High-rate sedimentation system Disposal ability it is bigger than in general sedimentation basin 3-7 times, the sludge of bottom of pond is discharged into sludge-tank by the static pressure mud discharging device of setting and entered One step is concentrated, and is then pumped into sludge filter press press filtration, and mud cake is reprocessed according to property, can remove about 80% suspension, 40- 70% oils, and make delivery turbidity<30NTU, COD decline 40-60% etc.；

3rd, chromate waste water biochemical processing process of the present invention：Pretreated water is sequentially entered into anaerobic pond, Aerobic Pond, film Bioreactor；By A/O/MBR biodegradation, the material such as most COD, ammonia nitrogen and SS in waste water is removed；This The anaerobic technique is invented under without dissolved oxygen conditions or under anoxia condition, using the effect of anaerobic bacteria, makes organic matter that water occur Solution, acidifying, remove the organic matter in waste water, improve the biodegradability of sewage, be advantageous to follow-up aerobic treatment process；The present invention The aerobic process is organic matter oxidation Decomposition in the presence of aerobic microbiological under aerobic conditions, and organic concentration declines, Microbial biomass increase, the organic matter in sewage are attracted to activated sludge and biofilm surface first, and with microbial cell table Face contacts, and the organic matter of small molecule can be directed through cell membrane into microbial body, and larger molecular organicses then must be It is hydrolyzed in the presence of exoenzyme-hydrolase after small molecule again by microorganism intake cell body.Organic matter is finally divided Solution is into CO₂And H₂O；Membrane bioreactor of the present invention is made up of hollow fiber film assembly and membrane cisterna, and membrane module is positioned over membrane cisterna In, it is aerated in pond, can be whole by zoogloea and free bacteria because hollow-fibre membrane is less than 0.1 micron of aperture It is retained in membrane cisterna, so as to reach mud-water separation, various suspended particulates, bacterium, algae, turbidity and organic matter obtain effectively Remove, ensure that out excellent effluent quality of the aqueous suspension close to zero.The efficient crown_interception of membrane bioreactor, can be effective Nitrifier is retained, nitration reaction is smoothed out, effectively removes ammonia nitrogen；It is organic that the macromolecular for being difficult to degrade can be retained simultaneously Thing, extend its residence time in biochemical reaction tank, be allowed to be decomposed to greatest extent.

4th, chromate waste water concentration technique of the present invention：By biochemical treatment water successively by one-level nanofiltration system, one Level counter-infiltration system, two-stage reverse osmosis system；The present invention is to realize the zero-emission of chromate waste water, is set in biochemical treatment system rear end Concentrating and treating system is put, for handling strong brine caused by biochemical treatment system；Concentrating and treating system of the present invention is multistage The technique that concentration, nanofiltration/reverse osmosis concentration combine, by the concentration step by step of film, makes the water of high content of salt waste water gradually reduce (the high salt concentrated water salt content obtained is 40-60g/L) is so as to reducing the investment of subsequent evaporation crystal system and operating cost； The concentration technique to need strong brine to be processed in follow-up evaporation and crystallization system, subtracted than conventional concentrating and treating system Lack 80%, made the cost of investment of whole Waste Water Treatment reduce 20-30%, the operating cost of wastewater treatment reduces 30-40%, improve the automaticity of system.

Above-mentioned chromate waste water concentration technique, pre-concentration is carried out through one-level nanofiltration system, by one-level nanofiltration system Permeate can use as recycle-water after ion exchange, and the concentrate of the one-level nanofiltration system enters first-stage reverse osmosis system System；The permeate of the first-stage reverse osmosis system returns to one-level nanofiltration system, and the concentrate of the first-stage reverse osmosis system enters Two-stage reverse osmosis system；The permeate of the two-stage reverse osmosis system returns to one-level nanofiltration system, the two-stage reverse osmosis system Concentrate be the high salt concentrated water.

5th, chromate waste water evaporative crystallization handling process of the present invention：By the high salt concentrated water that concentration technique obtains according to Secondary to pass through heat exchanger, concentration evaporator, crystallizing evaporator, the concentration evaporator is by heating chamber, separation chamber, circular chamber, cloth liquid Device, demister are sequentially connected composition, and the crystallizing evaporator is sequentially connected and formed by separation chamber, salt leg, thickener, crystallization kettle； The concentration high salt concentrated water obtains crystal and condensed water after crystallizing evaporator, and the crystal is sodium sulphate and/or chlorine Change sodium, the condensed water uses as recycle-water.

The technological process of following examples of the present invention, its basic handling flow are：Waste electroplating liquor containing chromium → pretreating process → biochemical processing process → enter anaerobic pond → enter Aerobic Pond → membrane bioreactor → supercharging → one-level nanofiltration UF membrane → Supercharging → first-stage reverse osmosis UF membrane → supercharging → two-pass reverse osmosis UF membrane, high salt concentrated water enters evaporative crystallization system after separation System；In evaporation and crystallization system, high salt concentrated water can meet workshop recycle-water by condensed water caused by concentration evaporator processing Water quality requirement.

Embodiment 1

(1) chromate waste water is pre-processed, and obtains pretreated water

Chromate waste water is taken first, and the chromate waste water is mainly the plating pieces such as plating piece cleaning after chrome-plated process, pole plate cleaning, zinc Waste water caused by process, its pH such as passivation, stainless steel electrolytic polishing, alumilite process, plating piece processing are 2-3, are mainly contained The pollutants such as Cr VI, trivalent chromium, sulfuric acid, nitric acid, oxide, COD；Chromate waste water is pumped into brokenly chromium pond, thrown in broken chromium pond The sulfuric acid of 10% concentration is added to pH to be 2-3, while sodium sulfite solution to the ORP value for adding 10% concentration is 230-270mv, is made Hexavalent chromium in waste water is reduced to trivalent chromic ion, and its reaction time is 20min；Waste water is introduced into pH regulating reservoirs afterwards, added Enter the sodium hydroxide solution of 10% concentration, regulation pH is 8-9, the trivalent chromic ion in waste water is formed chromium hydroxide precipitation；Will Waste water is re-introduced into chemical reaction pond, adds coagulant PAC and flocculant PAM, stirs 25min.Waste water is introduced into accurate control again High-rate sedimentation system.

(2) pretreated water is subjected to biochemical treatment, obtains biochemical treatment water

The pretreated water is sequentially entered into anaerobic pond, Aerobic Pond, membrane bioreactor；Wherein, include and detest in anaerobic pond Aerobic microbiological is included in oxygen bacterium, wherein Aerobic Pond；Enter membrane bioreactor afterwards, the membrane bioreactor is by doughnut Film (aperture of hollow-fibre membrane is 0.01-0.1 μm) component and membrane cisterna composition；Membrane module is positioned in membrane cisterna, is carried out in pond Aeration, pH is 6-8 after the biochemical treatment, can remove the material such as most COD, ammonia nitrogen and SS in waste water；It is of the present invention Anaerobic technique, using the effect of anaerobic bacteria, makes organic matter that hydrolysis, acidifying occur under without dissolved oxygen conditions or under anoxia condition, The organic matter in waste water is removed, the biodegradability of sewage is improved, is advantageous to follow-up aerobic treatment process；It is of the present invention aerobic Technique is organic matter oxidation Decomposition in the presence of aerobic microbiological under aerobic conditions, and organic concentration declines, microbial biomass Increase, the organic matter in sewage, be attracted to activated sludge and biofilm surface first, and contacted with microbial cell surface, The organic matter of small molecule can be directed through cell membrane and enter in microbial body, and larger molecular organicses then must be extracellular It is hydrolyzed in the presence of enzyme-hydrolase after small molecule again by microorganism intake cell body.Organic matter is finally broken down into CO₂ And H₂O；Membrane bioreactor of the present invention is made up of hollow fiber film assembly and membrane cisterna, and membrane module is positioned in membrane cisterna, in It is aerated in pond, because hollow-fibre membrane is less than 0.1 micron of aperture, zoogloea and free bacteria can be all retained in In membrane cisterna, so as to reach mud-water separation, various suspended particulates, bacterium, algae, turbidity and organic matter are effectively removed, It ensure that out excellent effluent quality of the aqueous suspension close to zero.The efficient crown_interception of membrane bioreactor, can be with effectively catching Nitrifier, nitration reaction is smoothed out, effectively removes ammonia nitrogen；The larger molecular organicses for being difficult to degrade can be retained simultaneously, are prolonged Its long residence time in biochemical reaction tank, it is allowed to be decomposed to greatest extent.

(3) the biochemical treatment water is subjected to concentration, obtains high salt concentrated water and recycle-water

By biochemical treatment water successively by one-level nanofiltration system, first-stage reverse osmosis system, two-stage reverse osmosis system；Described one Level nanofiltration system is sequentially connected and formed by accurate filter and one-level NF membrane, and wherein the filter core of accurate filter is fusion-jet type PP Cotton, the aperture of precise microfiltration device is 5 μm；The aperture of the one-level NF membrane is 1nm, and pending water passes through one-level NF membrane When, the rejection to sodium ion is 50%, and the rejection of heavy metal ion and salinity is 98%；Afterwards by one-level nanofiltration system System, pH 6-8, it is 1.5Mpa to enter film pressure；The relative molecular mass retention scope of the one-level nanofiltration system is 300 dalton； The permeate of the one-level nanofiltration system can be continuing with through ion exchange as recycle-water；

Concentrate of the above-mentioned processing water Jing Guo one-level nanofiltration system enters first-stage reverse osmosis system, the first-stage reverse osmosis system System is sequentially connected composition by accurate filter and first-stage reverse osmosis film (bitter reverse osmosis membrane, aperture 0.1-1nm), and one-level is anti- The film pressure of entering of osmosis system is 1.8Mpa, and it is 5-6 to adjust pH by 0.2% hydrochloric acid, by the first-stage reverse osmosis film, counterweight The rejection of metal ion and salinity is 99%；Permeate of the above-mentioned processing water Jing Guo first-stage reverse osmosis system returns to one-level nanofiltration System, its concentrate enter two-stage reverse osmosis system.The two-stage reverse osmosis system is by accurate filter and two-pass reverse osmosis film (seawater reverse osmosis membrane, aperture 0.1-1nm) is sequentially connected composition；The film pressure of entering of two-stage reverse osmosis system is 5Mpa, is passed through 0.2% hydrochloric acid adjustment pH is 6-8, and by the two-pass reverse osmosis film, the rejection of heavy metal ion and salinity is 99.9%； Above-mentioned processing water returns to one-level nanofiltration system by the permeate of two-stage reverse osmosis system, and its concentrate is high salt concentrated water, high salt The salt content of concentrated water is 40g/L, and the two-stage reverse osmosis system also includes cartridge filter in addition, and aperture is 5 μm, and its filter core is molten Spray formula PP cottons.

The present invention is to realize the zero-emission of chromate waste water, sets concentrating and treating system in biochemical treatment system rear end, is used for Handle strong brine caused by biochemical treatment system；Concentrating and treating system of the present invention is multistage concentration, nanofiltration/reverse osmosis concentration With reference to technique, by the concentration step by step of film, make the water of high content of salt waste water gradually reduce (the high salt concentrated water saliferous obtained Measure as 40g/L) so as to reducing the investment of subsequent evaporation crystal system and operating cost；The concentration technique causes follow-up Strong brine to be processed is needed in evaporation and crystallization system, the concentrating and treating system than routine reduces 80%, makes whole wastewater treatment The cost of investment of system reduces 30%, and the operating cost of wastewater treatment reduces 40%, improves the automaticity of system. Above-mentioned chromate waste water concentration technique, pre-concentration is carried out through accurate filter and one-level nanofiltration system, by one-level nanofiltration system The permeate of system can use as recycle-water after ion exchange, and the concentrate of the one-level nanofiltration system enters first-stage reverse osmosis System；The permeate of the first-stage reverse osmosis system returns to one-level nanofiltration system, and the concentrate of the first-stage reverse osmosis system enters Enter two-stage reverse osmosis system；The permeate of the two-stage reverse osmosis system returns to one-level nanofiltration system, the two-pass reverse osmosis system The concentrate of system is the high salt concentrated water.

(4) the high salt concentrated water is evaporated crystallization treatment, obtains recycle-water and crystal

By above-mentioned high salt concentrated water successively by heat exchanger, concentration evaporator, crystallizing evaporator；The operation temperature of the heat exchanger Spend for 80-100 DEG C；The operating pressure of the heat exchanger is 0.05-0.1MPa；The concentration evaporator by heating chamber, separation chamber, Circular chamber, liquid distributor, demister are sequentially connected composition；The crystallizing evaporator by separation chamber, salt leg, thickener, crystallization kettle according to Secondary connection composition；Condensed water of the above-mentioned high salt concentrated water after concentration evaporator returns to above-mentioned two-stage reverse osmosis system；High salt is dense The concentrate that water obtains after concentration evaporator is to concentrate high salt concentrated water, salt content 40-60g/L；The concentration high salt concentrated water Crystal and condensed water are obtained after crystallizing evaporator；Obtained crystal is sodium sulphate and/or sodium chloride；And condensed water is made Workshop is returned to for recycle-water to be continuing with.

Wherein, the concentration evaporator is made up of the multiple evaporators being serially connected, and (90 DEG C or so) heating of low temperature are steamed Vapour is introduced into the first effect, heats feed liquid therein, feed liquid is produced the almost equivalent evaporation lower than vapor (steam) temperature.Caused steam The second effect is introduced into as heating steam, makes the feed liquid of the second effect with than the first effect lower temperature evaporation.This process is always Repeat to last effect.First effect condensate is returned at thermal source, and other each effect condensates export after collecting as desalination water, a steaming Vapour is put into, and can be evaporated more times of water and be come out.Meanwhile feed liquid is passed through by the concentration successively of the first effect to most end effect, in most end Effect reaches supersaturation and crystallizes and separate out.It is achieved in the separation of solid and liquid of feed liquid.

The technical parameter of the evaporation and crystallization system processing concentrated water is as follows：

(1) desalination water salt content (TDS) is less than 10ppm

(2) ton desalination water steam consumption quantity=(1/ effect number)/90%t/t

(3) 2~4kwh/t of ton desalination water power consumption

A kind of chromium containing waste water treatment method of the present invention not only brings up to wastewater recycle rate relative to prior art 99.67%, while the metal ion recycling that can be greatly reduced in processing cost, reduction solid waste yield and waste water, it is thoroughly real The zero-emission of existing waste water.

Comparative example 1

(1) chromate waste water is taken first, and the chromate waste water is mainly plating piece cleaning after chrome-plated process, pole plate cleaning, zinc etc. Waste water caused by process, its pH such as plating piece passivation, stainless steel electrolytic polishing, alumilite process, plating piece processing are 2-3, mainly Contain the pollutants such as Cr VI, trivalent chromium, sulfuric acid, nitric acid, oxide, COD；Chromate waste water is pumped into brokenly chromium pond, in broken chromium pond In add 10% sulfuric acid and 10% sodium sulfite, the hexavalent chromium in waste water is reduced to trivalent chromic ion, its react Time is 20-25min；Waste water is introduced into chemical reaction pond afterwards, adds coagulant PAC and flocculant PAM, stirs 25min.Again will Waste water introduces settling system and carries out mud-water separation, and sludge enters sludge treating system, and supernatant enters biochemical system.

(2) pretreated water is sequentially entered into anaerobic pond, Aerobic Pond, biochemical sedimentation basin；Wherein, include and detest in anaerobic pond Aerobic microbiological is included in oxygen bacterium, wherein Aerobic Pond；Enter biochemical sedimentation basin afterwards, the biochemical sedimentation basin is by water distributing area, sludge Area, Disengagement zone and effluent weir composition；Biochemical sedimentation basin water outlet SS is 30mg/L, COD 50mg/L, and biochemistry pool water outlet 40% is up to standard Discharge, 60% enters film concentration systems.

(3) by water outlet after biochemistry successively by accurate filter, reverse osmosis membrane apparatus；The filter core of wherein accurate filter is PP cottons, the aperture of precise microfiltration device is 5 μm；The film pressure of entering of counter-infiltration system is 1.2-1.6Mpa, is adjusted by hydrochloric acid PH is 5-6, and by the reverse osmosis membrane, the rejection of heavy metal ion and salinity is 99%；The concentrate of reverse osmosis membrane returns Pretreatment system is handled again, reverse osmosis membrane permeate electrical conductivity 200-300 μ S/cm, accounts for the 60% of total waste water, permeate As reuse Water circulation to production line.

In a word, specific description of embodiments of the present invention is not intended to limit the present invention for the above, and those skilled in the art can be with It is variously modified or is deformed according to the present invention, without departing from the spirit of the present invention, all should belong to right appended by the present invention will The scope asked.

Claims

1. a kind of chromium containing waste water treatment method, it is characterised in that the processing method sequentially includes：

(1) chromate waste water is pre-processed, obtains pretreated water；

(3) the biochemical treatment water for obtaining step (2) carries out concentration, obtains concentration high salt concentrated water and recycle-water；

(4) the concentration high salt concentrated water that step (3) obtains is evaporated crystallization treatment, obtains recycle-water and crystal；

2. processing method according to claim 1, it is characterised in that in the step (1),

The chromate waste water pH 4-6, it includes the pollutants such as Cr VI, trivalent chromium, sulfuric acid, nitric acid, oxide, COD；

Preferably, the step of pretreatment is：

Chromate waste water is introduced broken chromium pond by (1-1), and it is 2-3 that sulfuric acid is added in broken chromium pond to pH, and the rear sodium sulfite that adds is to ORP It is worth for 230-270mv, carries out brokenly chromium reaction；

Waste water after step (1-2) processing is introduced chemical reaction pond by (1-3), is added coagulant, is added flocculant afterwards, is stirred 20-30min；

Preferably, in the step (1-1), add the sulfuric acid solution that concentration is 10% and adjust pH；Preferably, adding concentration is 10% sodium sulfite solution regulation ORP value；

Preferably, the broken chromium reaction time of the step (1-1) is 20-30min；

Preferably, in the step (1-3), the coagulant is inorganic coagulant, more preferably PAC；Preferably, the flocculation Agent is organic flocculant, more preferably PAM；Preferably, the time interval added between coagulant and flocculant is 20- 40min；

Preferably, the wastewater pH handled through step (1-3) is 8-9；

Preferably, in the step (1-4), the accurate control High-rate sedimentation system is by water distribution system, precipitation process pond, tiltedly Pipe, effluent weir, sludge bucket are sequentially connected composition；Preferably, the waste water after step (1-3) is handled matches somebody with somebody water system described in introducing successively System, precipitation process pond, inclined tube；Supernatant after above-mentioned processing obtains pretreated water into effluent weir, and obtained sludge is sunk to Sludge bucket；Preferably, the pressure in the precipitation process pond is 2-3Mpa.

3. processing method according to claim 1 or 2, it is characterised in that in the step (2), the biochemical treatment step Suddenly it is：The pretreated water that step (1) obtains is sequentially entered into anaerobic pond, Aerobic Pond, membrane bioreactor；

Preferably, anaerobic bacteria is included in the anaerobic pond；Preferably, the anaerobic bacteria is selected from saccharomycete, nitrate bacterium, Fusobacterium Or the one or more in bacteroid；

Preferably, aerobic microbiological is included in the Aerobic Pond；

Preferably, the membrane bioreactor is made up of hollow fiber film assembly and membrane cisterna；Preferably, the hollow-fibre membrane group Part is located in the membrane cisterna；

Preferably, the doughnut membrane aperture is 0.01-0.1 μm；

Preferably, pH is 6-8 after the biochemical treatment.

4. processing method according to any one of claim 1 to 3, it is characterised in that described dense in the step (3) Contracting processing step is：The biochemical treatment water that step (2) is obtained is successively by one-level nanofiltration system, first-stage reverse osmosis system, two Level counter-infiltration system；

Preferably, the aperture of the one-level NF membrane is 1-2nm；

Preferably, the one-level NF membrane is 50-70% to the rejection of sodium ion；Preferably, the one-level NF membrane counterweight The rejection ＞ 97% of metal ion and salinity；

Preferably, the pH of the water into one-level nanofiltration system is 6-8；

5. processing method according to any one of claim 1 to 4, it is characterised in that in the step (3), described one Level counter-infiltration system is sequentially connected and formed by accurate filter and first-stage reverse osmosis film；

Preferably, the aperture of the first-stage reverse osmosis film is 0.1-1nm；

6. processing method according to any one of claim 1 to 5, it is characterised in that in the step (3), described two Level counter-infiltration system is sequentially connected and formed by accurate filter and two-pass reverse osmosis film；

Preferably, the aperture of the two-pass reverse osmosis film is 0.1-1nm；

Preferably, the pH of the water into two-stage reverse osmosis system is 6-8；

Preferably, the concentration of the hydrochloric acid is 0.2-0.5%；

7. processing method according to any one of claim 1 to 6, it is characterised in that in the step (4), the steaming Sending out crystallization treatment step is：The high salt concentrated water that step (3) is obtained is successively by heat exchanger, concentration evaporator, crystallizing evaporator；

Preferably, the operation temperature of the heat exchanger is 80-100 DEG C；

Preferably, the operating pressure of the heat exchanger is 0.05-0.1MPa；

Preferably, the concentration evaporator is sequentially connected by heating chamber, separation chamber, circular chamber, liquid distributor, demister and formed；

Preferably, the concentration high salt concentrated water obtains crystal and condensed water after crystallizing evaporator；Preferably, the crystallization Thing is sodium sulphate and/or sodium chloride；Preferably, the condensed water uses as recycle-water.

8. the processing system of chromium containing waste water treatment method as any one of claim 1 to 7, it is characterised in that the system System includes pretreatment unit, biochemical treatment unit, concentration unit and the evaporative crystallization processing unit being sequentially communicated.

9. processing system according to claim 8, it is characterised in that the pretreatment unit includes the broken chromium being sequentially communicated Pond, pH regulating reservoirs, chemical reaction pond, accurate control High-rate sedimentation system；Preferably, the accurate control High-rate sedimentation system by Water distribution system, precipitation process pond, inclined tube, effluent weir, sludge bucket are sequentially connected composition.

10. processing system according to claim 8 or claim 9, it is characterised in that the biochemical treatment unit includes being sequentially communicated Anaerobic pond, Aerobic Pond, membrane bioreactor；

Preferably, the doughnut membrane aperture is 0.01-0.1 μm.

11. the processing system according to any one of claim 8 to 10, it is characterised in that the concentration unit bag Include the one-level nanofiltration system being sequentially communicated, first-stage reverse osmosis system, two-stage reverse osmosis system.

12. the processing system according to any one of claim 8 to 11, it is characterised in that the one-level nanofiltration system by Accurate filter and one-level NF membrane are sequentially connected composition；

Preferably, the filter core aperture of the accurate filter is 5 μm；

Preferably, the aperture of the one-level NF membrane is 1-2nm；

Preferably, the pH of the water into one-level nanofiltration system is 6-8.

13. the processing system according to any one of claim 8 to 12, it is characterised in that the first-stage reverse osmosis system It is sequentially connected and is formed by accurate filter and first-stage reverse osmosis film；

Preferably, the filter core aperture of the accurate filter is 5 μm；

Preferably, the aperture of the first-stage reverse osmosis film is 0.1-1nm；

Preferably, the concentration of the hydrochloric acid is 0.2-0.5%.

14. the processing system according to any one of claim 8 to 13, it is characterised in that the two-stage reverse osmosis system It is sequentially connected and is formed by accurate filter and two-pass reverse osmosis film；

Preferably, the filter core aperture of the accurate filter is 5 μm；

Preferably, the aperture of the two-pass reverse osmosis film is 0.1-1nm；

Preferably, the pH of the water into two-stage reverse osmosis system is 6-8；

Preferably, the concentration of the hydrochloric acid is 0.2-0.5%.

15. the processing system according to any one of claim 8 to 14, it is characterised in that the evaporative crystallization unit bag Include the heat exchanger being sequentially communicated, concentration evaporator, crystallizing evaporator；

Preferably, the operation temperature of the heat exchanger is 80-100 DEG C；

Preferably, the operating pressure of the heat exchanger is 0.05-0.1MPa；

16. the processing any one of processing method or claim 8 to 15 as any one of claim 1 to 7 Application of the system in processing waste water containing chrome.