CN101811793B - Pretreatment process of chromium-containing wastewater - Google Patents
Pretreatment process of chromium-containing wastewater Download PDFInfo
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- CN101811793B CN101811793B CN2009100465826A CN200910046582A CN101811793B CN 101811793 B CN101811793 B CN 101811793B CN 2009100465826 A CN2009100465826 A CN 2009100465826A CN 200910046582 A CN200910046582 A CN 200910046582A CN 101811793 B CN101811793 B CN 101811793B
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Abstract
The invention relates to a pretreatment process of chromium-containing wastewater, which comprises the following steps that: 1) scrap iron filter tank is established, iron-containing spare is mixed with carbon-containing particles and porous filler to form a scrap iron filter tank after being washed by alkali so as to remove the oil and being washed by acid to remove the rust and to be activated; 2) chromium-containing wastewater is introduced into the scrap iron filter tank to be undertaken the micro electrolysis reaction after being aerated by an adjusting tank, and pH value and the oxidation reduction potential level ORP value are adjusted by acid liquid, so major hexavalent chrome is reduced to trivalent chromium; 3) the water which is discharged from the filter tank is guided to a reaction tank, neutralizing agent is added, heavy metal complex-precipitation happens, and discharged water is guided into a sedimentation tank; 4) after the majority of heavy metal pollutant inside the sedimentation tank is removed, the upper clean liquid is undertaken the advanced treatment and is discharged after reaching the standard. The pretreatment process not only realizes the resource utilization of waste scrap iron and waste acid liquid, but also greatly reduces the cost of the medicine, reduces the quantity of the following mud, and is easier to realize the resource utilization of the produced mud.
Description
Technical field
The present invention relates to the technical field of heavy metal containing wastewater treatment, particularly a kind of pretreatment technology of chromate waste water.
Background technology
In industry such as iron and steel, semi-conductor, wiring board, plating, nonferrous metallurgy, often use dichromate as electroplate liquid, so inevitably can discharge the multichannel heavy metal wastewater thereby, wherein especially with the harm of chromate waste water for very, its classical group becomes: Cr
6+, 200～900mg/L; T.Cr, 300～1200mg/L; Ni
2+, 200～400mg/L; T.Fe, 300～600mg/L; Cu
2+, 50～200mg/L; Zn
2+, 50～200mg/L; Pb
2+, 20～100mg/L; F
-, 400～5000mg/L; SO
4 2-, 1000～10000mg/L; PH value, 1.5～2.5; SS, 1000～5000mg/L or the like.After sexavalent chrome enters human body, will lodge in liver, kidney, lung, the incretory gland, the human body vitals are caused damage, therefore, chromate waste water must be handled and can discharge after up to standard.
At present, the improvement technology of chromate waste water mainly contains: chemical reduction method, ferrite process, sulfurous gas method, the barium salt precipitator method, ion exchange method, electrolytic process, evaporation concentration method, biochemical process, membrane separation process.Consider that for factors such as technology maturation, running maintenance convenience the main methods of Iron And Steel Industry chromate waste water is that (reductive agent adopts NaHSO more in chemical reduction both at home and abroad
3, Na
2SO
3, FeSO
4)-(neutralizing agent is Ca (OH) to precipitation
2) method handles, up to standard for guaranteeing water outlet, often need to add the overdose of medicine agent, like this, cost for wastewater treatment height, the requirement that chromium-bearing sludge output is big, complicated component, especially contents of heavy metal elements both be difficult to reach comprehensive utilization, and its leaching toxicity has surpassed national standard, so regarded as Hazardous wastes by country, needing to entrust has the unit of qualification to carry out safe disposal.As the pickling waste waters amount is 100m
3The tame stainless steel plant of/h bypasses expensive costs such as medicament, energy consumption, manpower, and only the output of chromium-bearing sludge promptly surpasses 1.5 ten thousand t/a, and these mud can't utilize in the factory, and the expense that annual outer committee handles is up to millions of units.
In recent years, carried out the research of iron-carbon micro-electrolysis art breading chromate waste water both at home and abroad, as Chinese patent CN1382649A, CN1240768A, CN1040016A, CN1792843A, CN1597556A.The flocculation, iron filings that it is based on redox, the cell reaction product of electrochemical reaction is to many-sided comprehensive actions such as the absorption of the electric attached collection of flco, newborn flco and bed filtrations, the novel method that electroplating wastewater is purified claims internal electrolysis, iron dust filtration method etc. again.
Because the employed iron filings of iron-carbon micro-electrolysis technology mostly are iron-containing waste, the wide price of originating is low, the meaning that have the treatment of wastes with processes of wastes against one another, economizes on resources, and have the advantage of methods such as absorption method, neutralization precipitation method, electrolytic process concurrently, can remove contents of many kinds of heavy metal ion simultaneously, shortcomings such as the conventional waste water disposal system investment is big from having changed to a certain degree, working cost height, therefore, application during this technology is administered at heavy metal wastewater thereby, particularly chromate waste water is handled has been subjected to paying close attention to widely, is a kind of new technology that good development prospect is arranged.
But many little electrolyzers phenomenons such as iron filings caking, filtrate channel often occur after the operation of for some time, greatly reduce treatment effect, and when little electrolysis bed was higher, bottom iron filings compacting was overstocked, when waste strength is higher, the treatment effect instability needs frequent recoil and regeneration simultaneously.This be because, little electrolyzer actual motion after for some time the configuration of surface of iron variation has taken place, the flocs unit, the settling parcel that are produced by little electrolysis cover, and have reduced the speed of galvanic deposit, cohesion and redox reaction, thereby have had influence on the effect and the ability of wastewater treatment; Though and fluidized-bed has solved agglomeration problems, for guaranteeing fluidization, waste water needs constantly circulation, thereby power consumption is big, and the loss of iron carbon occurs.
On the other hand, at iron and steel, semi-conductor, wiring board, electroplate, in the industry such as nonferrous metallurgy, not only produce a large amount of acid regeneration iron powders every day, turbid circulating water mud, the ball blast iron powder, iron content spares such as scale oxide, also produce a large amount of spent acid solutions and pickling waste waters, if can make full use of wherein iron content spare, refuses such as spent acid solution, develop a kind of novel iron filings filter tank pretreatment technology, chromate waste water is carried out little electrolytics pre-treatment earlier, import advanced treatment unit again, but the not only treatment of wastes with processes of wastes against one another, save the reagent cost of follow-up advanced treatment unit greatly and handle load, also can make the easier recycling of follow-up mud.
Summary of the invention
In traditional chromate waste water chemical treatment technology, reductive agent and precipitation agent be excessive to add, the processing cost height, sludge yield is big and complicated component is difficult to utilize, and as the outer reality of entrusting and handling of Hazardous wastes high price, the objective of the invention is to propose a kind of pretreatment technology of chromate waste water, adopt the iron filings filter tank that chromate waste water is carried out little electrolysis pretreatment, both realized the recycling of waste iron filing and spent acid solution, significantly reduce reagent cost again, reduced the generating capacity of follow-up mud, and the easier recycling of mud that produces.
For achieving the above object, the present invention is achieved in that
A kind of pretreatment technology of chromate waste water, it comprises the steps:
1) the iron filings filter tank makes up, and the iron content spare after alkali cleaning oil removing, acid pickling and rust removing activation treatment, is mixed with carbon containing pellet, protruded packing, forms the iron filings filter tank;
2) chromate waste water is introduced the iron filings filter tank micro-electrolysis reaction is taken place behind the equalizing tank aeration, and pH value and redox potential ORP value with in the acid solution equalizing tank make most of sexavalent chrome be reduced to trivalent chromium therein;
3) the filter tank water outlet causes reaction tank, adds neutralizing agent, and heavy metal complex-precipitation effect takes place, and settling tank is introduced in water outlet;
4) in settling tank, most of heavy metal contaminants complexing removed after, supernatant liquor carries out advanced treatment, back up to standard discharging.
Further, the structure in iron filings filter tank is selected the iron content spare from industry such as iron and steel, semi-conductor, wiring board, plating, nonferrous metallurgies for use, after activation treatment operations such as alkali cleaning oil removing, acid pickling and rust removing, mix by a certain percentage with coke, protruded packing etc., make up the iron filings filter tank.
Described iron content spare is higher than the ion dust mud contaning of 40wt% for all iron contents such as the acid regeneration iron powder that produces from each operation of industry such as iron and steel, semi-conductor, wiring board, plating, nonferrous metallurgy, turbid circulating water mud, ball blast iron powder, scale oxides.
Described activation treatment operation comprises dipping by lye (the concentration mass percent is 5～20%) 10～30min oil removing, wash be neutrality to pH value after, use acid solution (the concentration mass percent is 1～5%) to soak 10～30min rust cleaning again; For shortening soak time, can and be incubated the little fire heating of iron filings at 60～80 ℃; Filtrate long-play usefulness repeats its activation treatment operation after reducing after can taking out.
The using and the reserved are taked in described iron filings filter tank, or a usefulness is equipped with more; Bottom water inlet, the dynamic upper reaches filter type of top water outlet are taked in each filter tank; Iron powder is contained in the built on stilts layer by layer tray structures that pile up, and tray has 2～20 layers, and the filtrate laying depth of trying to get to the heart of a matter is 10～100mm, and tray can dynamically add or shift out.
Described iron filings filter tank, the granularity of iron filings and carbon containing pellet is respectively 0.05～15mm and 1～10mm in the filter tank, and the weight ratio of iron filings and carbon containing pellet is: iron filings: carbon containing pellet=1: 0.001～0.2; Protruded packing is the inactive ceramic medium, and accounting for the filtrate volume ratio is 30～70%; The carbon containing pellet is a kind of of coke, gac, cinder, flue dust, hard coal etc. and combination thereof.
The iron filings filter tank is a kind of comprehensive utilization redoxomorphism, the attached collection of electrochemistry, coagulating sedimentation, absorption and electrical effect, the pretreatment unit that chromate waste water is purified.After adding the carbon containing pellet in the iron filings, under acidic conditions, iron filings contact with carbon granules and further form big iron-carbon galvanic cell, and (pure iron is anode, Fe being subjected to little galvanic cell to make iron filings
3C is a negative electrode) on the corrosive basis, be subjected to the corrosion of big galvanic cell again, thereby accelerated the carrying out of electrochemical reaction, porous inert filler in the filter tank can be kept the certain voidage in filter tank again simultaneously, prevent that the iron filings caking from hardening, keep hydraulics preferably, prolong the regeneration period.
Anodic product Fe in the micro-electrolysis reaction process
2+Chemically reactive is very high, can be rapidly with the Cr in the waste water
6+Be reduced into Cr
3+, can also generate Fe (OH) with the dissolved oxygen reaction in the waste water simultaneously
3, but under acidic conditions, Fe (OH)
3With very fast dissolving.
Main chemical reactions in the iron filings filter tank:
Fe+2H
+→Fe
2++H
2↑
Fe+2Fe
3+→3Fe
2+
Fe(OH)
3+3H
+→Fe
3++3H
2O
6Fe
2++Cr
2O
7 2-+14H
+→6Fe
3++2Cr
3++7H
2O
2Fe+Cr
2O
7 2-+14H
+→2Fe
2++2Cr
3++7H
2O
2, chromate waste water is introduced the iron filings filter tank micro-electrolysis reaction is taken place behind the equalizing tank aeration
1) described equalizing tank, the bottom is provided with little aerating apparatus, guarantees that aeration is even, and aeration intensity is: 0.1～0.5m
3(air)/m
3(waste water) h, dissolved oxygen content is 3.0～6.0mg/L in the equalizing tank water outlet.
2) described iron filings filter tank, iron filings are 1: 50～1: 1000 with the ratio of pending wastewater flow rate, and the residence time of waste water is 15min～50min, and after handled in the iron filings filter tank, pH value was 3.0～5.0 in the filter tank, and the ORP value is 300～360mv.
3) described iron filings filter tank is by adding pH value and ORP value in the acid solution equalizing tank.
In equalizing tank,, increased the dissolved oxygen in the chromate waste water by aeration, can quicken dissolving, the effect of reinforcement microbattery of iron filings in the follow-up filter tank, can promote the eliminating of iron filings surface mass again, improve fe and be converted into ferrous efficient, thus can be rapidly with the Cr in the waste water
6+Be reduced into Cr
3+By the pH value and the redox potential ORP value of control filter tank waste water, can be with the Cr more than 50～80%
6+Be reduced into Cr
3+
3, the water outlet of iron filings filter tank causes reaction tank, adds neutralizing agent and flocculation agent generation heavy metal complex-precipitation effect
1) described neutralizing agent is NaOH or KOH, and concentration is 1.0～10.0wt%; Also can add flocculation agent in this process, flocculation agent is an aluminium salt, preferred polymeric aluminum chloride PAC, and concentration is 0.001～2.0wt%.
2) described reaction tank is provided with whipping appts in the pond, waste water is 20～40min in the residence time of reaction tank, and going out water ph value is 9.0～10.5.
In reaction tank, along with waste water alkalescence strengthens Fe
2+Change into Fe
3+, under the effect of alkaline neutraliser and flocculation agent, be 9.0～10.5 o'clock at pH value, will form the complex-precipitation of various heavy metal hydroxides.
Main chemical reactions:
Cr
3++3OH
-→Cr(OH)
3↓
Ni
2++2OH
-→Ni(OH)
2↓
Fe
3++3OH-→Fe(OH)
3↓
Pb
2++2OH
-→Pb(OH)
2↓
Zn
2++2OH
-→Zn(OH)
2↓
Mn
2++2OH-→Mn(OH)
2↓
Cu
2++2OH
-→Cu(OH)
2↓
4, most of pollutent obtains removing in settling tank, and supernatant liquor carries out advanced treatment, back up to standard discharging
1) described settling tank is the ramp type settling tank, and the residence time of waste water is 30～90min.
2) described pollutent is mainly the complex-precipitation of heavy metal hydroxide, recycles behind the sludge concentration desiccation, and preferably utilizing mode is raw materials for metallurgy as ferrochrome, chromium nickel, chrome copper.
3) described supernatant liquor advanced treatment is a kind of of conventional depth treatment process such as chemical reduction-precipitation, ion-exchange, charcoal absorption, electrolysis, reverse osmosis, membrane sepn, artificial swamp and combination thereof, preferred chemical reduction-depth of precipitation treatment process.
In settling tank, Fe (OH)
3PAC etc. have suitable complexing absorption, the coprecipitated ability of flocculating, can remove multiple pollutent and dispersion impurity in the waste water, sexavalent chrome more than 50～80% will be removed, according to the emission standard that character, flow and the needs of processing chromate waste water reach, can select follow-up advanced treatment process.For example, increase one-level chemical reduction precipitation operation, use milk of lime as precipitation agent; Also can enter the artificial swamp bed, adopt remaining pollutent in the biological means advanced treatment waste water, can also take materialization modes such as membrane sepn, reverse osmosis, but processing cost be higher.
Beneficial effect of the present invention:
The conventional processes of chromate waste water is: reduce with sulphite earlier, add excessive milk of lime then and precipitate, outer committee handled after discharged wastewater met the national standard, mud concentrated press filtration.Its shortcoming is:
1. for adapting to the variation of chromate waste water character, guarantee that water outlet is up to standard, the dosage of milk of lime is more than 2 times of theoretical requirement often, raised processing cost (dosing is big, equipment energy consumption is high, plant area is big etc.) thus, and increased the mixing sludge generating capacity greatly;
2. reductive agent adopts sulphite, is being the chromic while with hexavalent chrome reduction, HSO in the reductive agent
3 -, SO
3 2-Plasma has also formed a large amount of CaSO with the milk of lime effect
4Precipitation is sneaked in the mud, has increased the output of follow-up mud;
3. contain heavy metal hydroxide mud and calcium salt mud in the mixing sludge simultaneously, the comprehensive utilization difficulty is big, and the risk of secondary pollution is arranged;
4. mixing sludge needs to have the producer's special disposal or the disposal of qualification, will spend high outer committee handling for this reason, has caused the loss of valuable resource simultaneously.
Shortcoming at traditional mode, the present invention utilizes the pretreatment unit of iron filings filter tank as chromate waste water, can effectively realize the source decrement of mixing sludge and the enriching and recovering of heavy metal sewage sludge, and can reduce the reagent cost of the follow-up advanced treatment of chromate waste water and handle load, achieve many things at one stroke.Specify as follows:
1. preposition iron filings filter tank is as pretreatment unit, have and reduce follow-up conventional reduction agent consumption, promote the heavy metal hydroxide precipitation process, improve heavy metal sewage sludge iron grade and reduce four kinds of effects such as follow-up vitriol mud generating capacity: in the iron filings filter tank, control waste water ORP value 300～360mv, PH value 3.0～5.0 make that Fe is with Fe, Fe in the iron filings
2+Form is main; By little electrolytic action, 50～80% hexavalent chrome reduction can be become trivalent chromium at iron filings filter tank pretreatment stage, simultaneously the Fe that rolls up in the waste water
2+, Fe
3+Also will promote the precipitation process of heavy metal hydroxide mud as the flocculation agent of post precipitation process.Practice shows that preposition iron filings filter tank can make the degree of full iron in the heavy metal sewage sludge increase by 15～30wt% as pretreatment unit, is easier to follow-up comprehensive utilization; And owing to taked the preliminary reductive action in iron filings filter tanks, saved the consumption of traditional reductive agent sulphite of 20～50wt%, the content of vitriol mud also can reduce by 15～40wt% in the post precipitation process thus, thereby greatly reduces sludge treatment and disposal costs.
2. it is the superfluous lime breast of 10wt% that traditional chromate waste water treatment process, neutralization precipitation medicament are generally selected concentration for use, though the adding of calcium hydroxide has good heavy metal ion (Cr
3+, Ni
2+, Zn
2+, Fe
3+Deng) precipitation flocculating effect, but can with the F in the waste water
-, SO
4 2-, PO
4 3-Deng the negatively charged ion effect, generate calcium precipitations such as Calcium Fluoride (Fluorspan), calcium sulfate, calcium phosphate respectively, and flocculate with heavy metal sewage sludge sweep along, complex-precipitation gets off, big and the complicated component of this mixing sludge output, especially contents of heavy metal elements both had been difficult to reach the requirement of comprehensive utilization, and its leaching toxicity has surpassed national standard, so regarded as Hazardous wastes by country, needing to entrust have the unit of qualification to carry out safe disposal.In the present invention, use the abbreviated system of " iron filings filter tank+reaction tank+settling tank ", use solubility highly basic (NaOH or KOH) and polymerize aluminum chloride PAC, both guaranteed the sedimentation effect of heavy metal ion, having stopped calcium precipitation again to a great extent sneaks in the heavy metal sewage sludge, make that settling tank mud is easier to utilize, after concentrating, drying, promptly can be used as alloy materials such as smelting ferrochrome, chromium nickel, chromium-copper.
3. the present invention makes full use of the constructed little electrolysis iron filings filter tank of discarded iron filings from industry such as iron and steel, semi-conductor, wiring board, plating, nonferrous metallurgies, replace traditional hexavalent chrome reduction pond, characteristics with treatment of wastes with processes of wastes against one another, the iron filings filter tank is strong to the shock absorption of waste water, reducible sexavalent chrome over half has increased Fe in the waste water simultaneously
2+Content, can play the effect of reductive agent and flocculation agent simultaneously, reduced the reagent cost of subsequent technique and hexavalent chromium-treatments load.
4. in the present invention, the iron filings filter tank adopts movably built on stilts stack multilayer tray structure and " iron filings+carbon containing pellet+protruded packing " three-in-one filtrate to form, porosity is big, and long service life can alleviate greatly that easily harden in traditional iron filings filter tank, the easy phenomenon of channel; Filtrate long-play usefulness can be changed and be regenerated after reducing at any time.
5. the characteristics of technologies such as little electrolytic reduction, chemical reduction, complexing absorption, neutralization precipitation have been merged in the present invention, can remove contents of many kinds of heavy metal ion simultaneously, as the pretreatment technology of heavy metal wastewater thereby, especially chromate waste water, have applied widely, technology is simple, initial cost is few, treatment effect is good, with low cost and advantage such as easy to operate.
Description of drawings
Fig. 1 is the schematic flow sheet of chromate waste water pretreatment technology of the present invention.
Embodiment
The implementation process right below in conjunction with accompanying drawing specifies:
Referring to Fig. 1, the pretreatment technology of a kind of chromate waste water of the present invention, it comprises the steps:
1) the iron filings filter tank makes up, and iron content spare 101 after alkali cleaning oil removing, acid pickling and rust removing activation treatment 102, is mixed with carbon containing pellet, protruded packing, forms iron filings filter tank 1;
2) chromate waste water is introduced iron filings filter tank 1 micro-electrolysis reaction is taken place behind equalizing tank 2 aerations, and pH value and redox potential ORP value with in the acid solution equalizing tank make most of sexavalent chrome be reduced to trivalent chromium therein;
3) the filter tank water outlet causes reaction tank 3, adds neutralizing agent, and heavy metal complex-precipitation effect takes place, and settling tank 4 is introduced in water outlet;
4) in settling tank 4, most of heavy metal contaminants complexing removed after, supernatant liquor carries out advanced treatment 5, back up to standard discharging.
Wherein, the iron filings activation back reuse 6 after the processing in the iron filings filter tank 1; Most of pollutent is removed in settling tank 4, to be recycledly behind the sludge concentration desiccation utilizes 7;
Embodiment 1
(granularity is 0.05～1.5mm) to select ball blast iron powder from stainless-steel cold-rolling enterprise for use, after the NaOH of 10wt% concentration dipping by lye 30min oil removing, wash be neutrality to pH value after, HCl acid soak 30min rust cleaning with 3%, after the activated processing, (granularity is 1～5mm) according to 1: 0.1 mixed, adds 50% porous ceramics medium, constitutes the filtrate in iron filings filter tank with coke granule; The iron filings filter tank takes a usefulness two to be equipped with, and bottom water inlet, the dynamic upper reaches filter type of top water outlet are taked in each filter tank; Iron powder is contained in the tray structures of stacked in multi-layers, and tray has 20 layers, and the filtrate laying depth of trying to get to the heart of a matter is 100mm, and tray can dynamically add or shift out;
The aeration intensity of equalizing tank is 0.5m
3(air)/m
3(waste water) h, dissolved oxygen content is 8.0mg/L in the equalizing tank water outlet; With 10m
3(principal pollutant are the stainless steel cold-rolling pickling wastewater of/h: Cr
3+, Ni
2+, Fe
2+, F
-, SO
4 2-Deng, also contain a spot of Fe
3+, Pb
2+, Zn
2+, Mn
2+, Cu
2+, Mg
2+, Al
3+Etc. heavy metal ion) through equalizing tank, introduce the iron filings filter tank micro-electrolysis reaction takes place, iron filings are 1: 100 with the ratio of pending wastewater flow rate, the residence time of waste water is 30min, after handle in the iron filings filter tank, pH value is 3.0～3.3 in the filter tank, and the ORP value is 300～330mv, passes through to add pH value and ORP value in the acid solution equalizing tank in the whole process;
The water outlet of iron filings filter tank causes reaction tank, and the concentration of neutralizing agent NaOH is 5wt%, and the concentration of flocculation agent PAC is 0.5wt%, and waste water is 20min in the residence time of reaction tank, and going out water ph value is 10.0～10.5;
The reaction tank water outlet is introduced into inclined-plate clarifying basin, and the residence time of waste water is 60min, and most of pollutent is removed in settling tank, utilization to be recycled behind the sludge concentration desiccation; The pH value of supernatant liquor is adjusted to 2.5～3.0 with acid solution, enters chemical reduction-sedimentary degree of depth technology and continues to handle.
After aforesaid technology, the pretreating effect of chromate waste water is as shown in table 1, by table 1 as seen, after iron filings filter tank, reaction tank and settling tank, except that the clearance of T.Fe is lower slightly, Cr
6 +, T.Cr, Ni
2+, Zn
2+, Pb
2+Etc. the clearance of heavy metal ion all above 80%, but F
-, SO
4 2Anionic clearance is only about 10%, this explanation heavy metal ion has obtained basic removal, the content of inorganic salt is lower in the heavy metal sewage sludge simultaneously, the heavy metal sewage sludge that produces of settling tank by analysis, the total content of Fe, Cr, Ni three heavy metal species elements surpasses 40wt% in its butt, and impurity content is low, can be directly after the drying roasting as the raw materials for metallurgy of Inconel(nickel alloys).
The removal effect of principal pollutant in table 1 chromate waste water
| Index (mg/L) | TFe | Cr 6+ | T.Cr | Ni 2+ | Zn 2+ | Pb 2+ | SO 4 2- | F - |
| Before the wastewater treatment | 350 | 800 | 1050 | 300 | 8.5 | 4.5 | 5000 | 1200 |
| After the wastewater treatment | 120 | 105 | 125 | 15 | 1.1 | 0.8 | 4450 | 1105 |
| Clearance (%) | 65.7 | 86.9 | 88.1 | 95 | 87.1 | 82.2 | 11.0 | 7.9 |
(granularity is 0.02～1.0mm) to select acid regeneration iron powder from semi-conductor industry for use, after the NaOH of 15% concentration dipping by lye 20min oil removing, wash be neutrality to pH value after, HCl acid soak 15min rust cleaning with 5%, after the activated processing, (granularity is 1～10mm) according to 1: 0.05 mixed, adds 40% porous ceramics medium, constitutes the filtrate in iron filings filter tank with activated carbon granule; The using and the reserved are taked in the iron filings filter tank, and bottom water inlet, the dynamic upper reaches filter type of top water outlet are taked in each filter tank; Iron powder is contained in the tray structures of stacked in multi-layers, and tray has 10 layers, and the filtrate laying depth of trying to get to the heart of a matter is 20mm, and tray can dynamically add or shift out;
The aeration intensity of equalizing tank is 0.1m
3(air)/m
3(waste water) h, dissolved oxygen content is 6.0mg/L in the equalizing tank water outlet; With 15m
3(principal pollutant are/h semi-conductor industry pickling waste waters: Cr
3+, Ni
2+, Fe
2+, Cu
2+, Zn
2+, F
-Deng, also contain a little P b
2+, Mn
2+, Mg
2+, Al
3+Etc. heavy metal ion) through equalizing tank, introduce the iron filings filter tank micro-electrolysis reaction takes place, iron filings are 1: 500 with the ratio of pending wastewater flow rate, the residence time of waste water is 50min, after handle in the iron filings filter tank, pH value is 3.2～3.5 in the filter tank, and the ORP value is 330～360mv, passes through to add pH value and ORP value in the acid solution equalizing tank in the whole process;
The water outlet of iron filings filter tank causes reaction tank, and the concentration of neutralizing agent NaOH is 10wt%, and waste water is 30min in the residence time of reaction tank, and going out water ph value is 9.0～10.0;
The reaction tank water outlet is introduced into inclined-plate clarifying basin, and the residence time of waste water is 50min, and most of pollutent is removed in settling tank, utilization to be recycled behind the sludge concentration desiccation; The pH value of supernatant liquor is adjusted to about 7.0 with acid solution, enters artificial swamp, the pollutent in the degree of depth chromate waste water.
After aforesaid technology, the pretreating effect of chromate waste water is as shown in table 2, by table 2 as seen, after iron filings filter tank, reaction tank and settling tank, except that the clearance of T.Fe is lower slightly, Cr
6 +, T.Cr, Ni
2+, Zn
2+, Cu
2+, Fe
2+Etc. the clearance of heavy metal ion all above 80%, but F
-Clearance only be 20%, this explanation heavy metal ion has obtained basic removal, the content of inorganic salt is lower in the heavy metal sewage sludge simultaneously, the heavy metal sewage sludge that produces of settling tank by analysis, the total content of five heavy metal species elements such as Fe, Cr, Ni, Cu, Zn surpasses 50wt% in its butt, and impurity content is low, can be directly after the drying roasting as the raw materials for metallurgy of chrome copper.
The removal effect of principal pollutant in table 2 chromate waste water
| Index (mg/L) | T.Fe | Fe 2+ | Cr 6+ | T.Cr | Ni 2+ | Zn 2+ | Cu 2+ | F - |
| Before the processing | 550 | 430 | 90 | 110 | 55 | 60 | 105 | 85 |
| After the processing | 130 | 82 | 8.5 | 12.5 | 2.5 | 8.5 | 10.2 | 68 |
| Clearance (%) | 76.3 | 80.9 | 90.6 | 88.6 | 95.4 | 85.8 | 90.2 | 20.0 |
Select that (granularity is 0.02～10mm) from the acid regeneration iron powder of electroplating industry and two kinds of mixtures of ball blast iron powder for use, after the NaOH of 10% concentration dipping by lye 30min oil removing, wash be neutrality to pH value after, HCl acid soak 20min rust cleaning with 3%, after the activated processing, (granularity is 1～10mm) according to 1: 0.1 mixed, adds 50% porous ceramics medium, constitutes the filtrate in iron filings filter tank with the hard coal particle; The iron filings filter tank takes a usefulness three to be equipped with, and bottom water inlet, the dynamic upper reaches filter type of top water outlet are taked in each filter tank; Iron powder is contained in the tray structures of stacked in multi-layers, and tray has 8 layers, and the filtrate laying depth of trying to get to the heart of a matter is 50mm, and tray can dynamically add or shift out;
The aeration intensity of equalizing tank is 0.4m
3(air)/m
3(waste water) h, dissolved oxygen content is 7.5mg/L in the equalizing tank water outlet; With 20m
3(principal pollutant are/h electroplating wastewater: Cr
3+, Ni
2+, Zn
2+, F
-Deng, also contain a little P b
2+, Cu
2+, Mn
2+, Mg
2+, Al
3+Etc. heavy metal ion) through equalizing tank, introduce the iron filings filter tank micro-electrolysis reaction takes place, iron filings are 1: 1000 with the ratio of pending wastewater flow rate, the residence time of waste water is 15min, after handle in the iron filings filter tank, pH value is 3.1～3.5 in the filter tank, and the ORP value is 315～360mv, passes through to add pH value and ORP value in the acid solution equalizing tank in the whole process;
The water outlet of iron filings filter tank causes reaction tank, and the concentration of neutralizing agent KOH is 1.0wt%, and the concentration of flocculation agent PAC is 2.0wt%, and waste water is 40min in the residence time of reaction tank, and going out water ph value is 10.0～10.5;
The reaction tank water outlet is introduced into inclined-plate clarifying basin, and the residence time of waste water is 90min, and most of pollutent is removed in settling tank, utilization to be recycled behind the sludge concentration desiccation; The pH value of supernatant liquor is adjusted to 3.0～4.0 with acid solution, enters two-stage chemical reduction-sedimentary technology and carries out advanced treatment.
After aforesaid technology, the pretreating effect of chromate waste water is as shown in table 3, by table 2 as seen, behind iron filings filter tank, reaction tank and settling tank, except that the clearance of T.Fe is lower slightly, Cr
6+, T.Cr, Ni
2+, Zn
2+Etc. the clearance of heavy metal ion all above 80%, but F
-And SO
4 2-Clearance only be 10～20%, this explanation heavy metal ion has obtained basic removal, the content of inorganic salt is lower in the heavy metal sewage sludge simultaneously, the heavy metal sewage sludge that produces of settling tank by analysis, the total content of four heavy metal species elements such as Fe, Cr, Ni, Zn surpasses 40wt% in its butt, and impurity content is low, can be directly after the drying roasting as the raw materials for metallurgy of ferrochrome.
The removal effect of principal pollutant in table 3 chromate waste water
| Index (mg/L) | T.Fe | Cr 6+ | T.Cr | Ni 2+ | Zn 2+ | Pb 2+ | SO 4 2- | F - |
| Before the processing | 420 | 750 | 900 | 515 | 94.5 | 7.8 | 240 | 720 |
| After the processing | 280 | 78 | 125 | 102 | 11.5 | 1.4 | 190 | 645 |
| Clearance (%) | 33.3 | 89.6 | 86.1 | 80.2 | 87.8 | 82.1 | 20.8 | 10.4 |
Claims (13)
1. the pretreatment technology of a chromate waste water, it comprises the steps:
1) the iron filings filter tank makes up, and the iron content spare after alkali cleaning oil removing, acid pickling and rust removing activation treatment, is mixed with carbon containing pellet, protruded packing, forms the iron filings filter tank; Described activation treatment operation comprises dipping by lye 10～30min oil removing, and concentration of lye is 5～20%, by percentage to the quality; Wash be neutrality to the pH value after, with acid soak 10～30min rust cleaning, acid strength is 1～5%, by percentage to the quality again; Filtrate long-play usefulness repeats its activation treatment operation after reducing after the taking-up;
2) chromate waste water is introduced the iron filings filter tank micro-electrolysis reaction is taken place behind the equalizing tank aeration, and pH value and ORP value with in the acid solution equalizing tank make most of sexavalent chrome be reduced to trivalent chromium therein;
3) the filter tank water outlet causes reaction tank, adds neutralizing agent, and heavy metal complex-precipitation effect takes place, and settling tank is introduced in water outlet;
4) in settling tank, most of heavy metal contaminants complexing removed after, supernatant liquor carries out advanced treatment, back up to standard discharging.
2. the pretreatment technology of chromate waste water according to claim 1, it is characterized in that, described iron content spare is that wherein all iron content is higher than 40wt% from the ion dust mud contaning of the acid regeneration iron powder of iron and steel, semi-conductor, wiring board, plating, each operation generation of colored metallurgical industrial, turbid circulating water mud, ball blast iron powder, scale oxide.
3. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, described equalizing tank, and the bottom is provided with little aerating apparatus, and aeration intensity is: 0.1～0.5m
3Air/m
3Waste water h, dissolved oxygen content is 3.0～6.0mg/L in the equalizing tank water outlet.
4. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, the using and the reserved are taked in described iron filings filter tank, or a usefulness is equipped with more; Bottom water inlet, the dynamic upper reaches filter type of top water outlet are taked in each filter tank; Iron powder is contained in the built on stilts layer by layer tray structures that pile up, and tray has 2～20 layers, and the filtrate laying depth of trying to get to the heart of a matter is 10～100mm, and tray dynamically adds or shifts out.
5. according to the pretreatment technology of claim 1 or 4 described chromate waste waters, it is characterized in that, described iron filings filter tank, the granularity of iron filings and carbon containing pellet is respectively 0.05～15mm and 1～10mm in the filter tank, and the ratio of weight and number of iron filings and carbon containing pellet is: iron filings: carbon containing pellet=1: 0.001～0.2; Protruded packing is the inactive ceramic medium, and accounting for the filtrate volume ratio is 30～70%; The carbon containing pellet is a kind of or its combination in coke, gac, cinder, flue dust, the hard coal.
6. the pretreatment technology of chromate waste water according to claim 1, it is characterized in that, described iron filings filter tank, iron filings are 1: 50～1: 1000 with the ratio of pending wastewater flow rate, the residence time of waste water is 15min～50min, after handled in the iron filings filter tank, the pH value was 3.0～5.0 in the filter tank, and redox potential ORP value is 300～360mv.
7. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, described iron filings filter tank is by adding pH value and redox potential ORP value in the acid solution equalizing tank.
8. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, described neutralizing agent is NaOH or KOH, and concentration is 1.0～10.0wt%;
9. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, adds in the neutralizing agent process and also adds flocculation agent, and flocculation agent is an aluminium salt, and concentration is 0.001～2.0wt%.
10. the pretreatment technology of chromate waste water according to claim 9 is characterized in that, described flocculation agent is polymerize aluminum chloride PAC.
11. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, described reaction tank is provided with whipping appts in the pond, and waste water is 20～40min in the residence time of reaction tank, and water outlet pH value is 9.0～10.5.
12. the pretreatment technology of chromate waste water according to claim 1 is characterized in that, described settling tank, be the ramp type settling tank, the residence time of waste water is 30～90min, and most of heavy metal contaminants complexing is recycled behind sludge concentration desiccation after removing.
13. the pretreatment technology of chromate waste water according to claim 1, it is characterized in that, described supernatant liquor advanced treatment is a kind of or its combination of chemical reduction-precipitation, ion-exchange, charcoal absorption, electrolysis, reverse osmosis, membrane sepn, artificial swamp advanced treatment process.
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