CN113200626A - Method for treating chromium-free coating wastewater of iron and steel enterprises - Google Patents
Method for treating chromium-free coating wastewater of iron and steel enterprises Download PDFInfo
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- 239000002351 wastewater Substances 0.000 title claims abstract description 65
- 239000011248 coating agent Substances 0.000 title claims abstract description 63
- 238000000576 coating method Methods 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 37
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 34
- 239000010959 steel Substances 0.000 title claims abstract description 34
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims description 39
- 229910052742 iron Inorganic materials 0.000 title claims description 19
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 38
- 238000002156 mixing Methods 0.000 claims abstract description 38
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000005273 aeration Methods 0.000 claims abstract description 22
- 238000004062 sedimentation Methods 0.000 claims abstract description 16
- 239000010802 sludge Substances 0.000 claims abstract description 15
- 230000001105 regulatory effect Effects 0.000 claims abstract description 9
- 238000005188 flotation Methods 0.000 claims abstract description 7
- 238000000605 extraction Methods 0.000 claims abstract description 6
- 239000006228 supernatant Substances 0.000 claims abstract description 6
- 238000005189 flocculation Methods 0.000 claims description 27
- 230000016615 flocculation Effects 0.000 claims description 27
- 238000006243 chemical reaction Methods 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- 239000003814 drug Substances 0.000 claims description 11
- 238000006386 neutralization reaction Methods 0.000 claims description 10
- 239000004519 grease Substances 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 8
- RGPUVZXXZFNFBF-UHFFFAOYSA-K diphosphonooxyalumanyl dihydrogen phosphate Chemical compound [Al+3].OP(O)([O-])=O.OP(O)([O-])=O.OP(O)([O-])=O RGPUVZXXZFNFBF-UHFFFAOYSA-K 0.000 claims description 7
- 230000001276 controlling effect Effects 0.000 claims description 6
- 238000007599 discharging Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 239000000725 suspension Substances 0.000 claims description 6
- 238000007667 floating Methods 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 3
- 239000006260 foam Substances 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 230000001376 precipitating effect Effects 0.000 claims description 3
- 238000007790 scraping Methods 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 239000003403 water pollutant Substances 0.000 claims description 3
- 229920002401 polyacrylamide Polymers 0.000 abstract description 22
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 8
- 229910052804 chromium Inorganic materials 0.000 abstract description 8
- 239000011651 chromium Substances 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000003795 chemical substances by application Substances 0.000 abstract description 5
- 239000008394 flocculating agent Substances 0.000 abstract description 3
- 230000003472 neutralizing effect Effects 0.000 abstract description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 abstract 2
- 229910001385 heavy metal Inorganic materials 0.000 abstract 1
- 238000005086 pumping Methods 0.000 abstract 1
- 238000004065 wastewater treatment Methods 0.000 description 14
- 239000003921 oil Substances 0.000 description 7
- 239000004912 1,5-cyclooctadiene Substances 0.000 description 6
- 239000003344 environmental pollutant Substances 0.000 description 5
- 231100000719 pollutant Toxicity 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical group [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 1
- VQWFNAGFNGABOH-UHFFFAOYSA-K chromium(iii) hydroxide Chemical compound [OH-].[OH-].[OH-].[Cr+3] VQWFNAGFNGABOH-UHFFFAOYSA-K 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/20—Treatment of water, waste water, or sewage by degassing, i.e. liberation of dissolved gases
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
- C02F1/56—Macromolecular compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F2001/007—Processes including a sedimentation step
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/105—Phosphorus compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/203—Iron or iron compound
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
Abstract
The invention discloses a method for treating chromium-free coating wastewater of steel enterprises, which comprises the steps of enabling the chromium-free coating wastewater to enter an aeration regulating reservoir, pumping the chromium-free coating wastewater into a four-stage mixing reactor by a pump, and adding sodium hydroxide, a demulsifier, PAC (polyaluminium chloride) and PAM (polyacrylamide) agents into the four-stage mixing reactor; and the effluent of the fourth-stage mixing reactor enters a high-efficiency air flotation device and then enters a third-stage mixing reactor, sulfuric acid, PAC (polyaluminium chloride) and PAM (polyacrylamide) agents are added into the third-stage mixing reactor 4, and the effluent enters a chromium inclined plate sedimentation tank. After passing through the inclined plate sedimentation tank, the supernatant meets the requirement of entering a biochemical standard extraction system, and the bottom sludge is transported outwards. The method can greatly reduce the consumption of the neutralizing agent and the flocculating agent, greatly reduce the finally produced sludge, and obviously improve the content of heavy metal elements in the sludge, thereby facilitating the centralized treatment of the sludge, and having simple production process and low production cost.
Description
Technical Field
The invention belongs to the technical field of sewage treatment, and particularly relates to a pretreatment process of chromium-free coating wastewater, which ensures that the treated chromium-free coating wastewater meets the requirements of the emission standard of pollutants for water in the steel industry (GB13456-2012), and is particularly suitable for being applied to the field of pretreatment of chromium-free coating wastewater generated in the steel industry.
Background
The wastewater without the chromium coating is wastewater generated in the production process of the metallurgical industry, contains high-concentration oil and pollutants such as grease, iron, phosphorus, COD and the like, is a great problem in the field of wastewater treatment of the steel industry at home and abroad, and often needs to adopt an advanced treatment technology.
The chromium-free coating waste water treatment technology has various types and various advantages and disadvantages. Through years of research, the treatment of the chromium-free coating wastewater at home and abroad mainly adopts a chemical method. The precipitation method is one of chemical methods, and is used for treating chromium-free coating wastewater, mainly enabling pollutants and hydroxyl in the wastewater to form precipitates for removal, and the precipitated chromium-containing sludge has a very high recycling value due to extremely high chromium concentration. The choice of reducing agent is therefore a crucial issue, oftenThe reducing agent is ferrous sulfate-lime method, and 5% -10% FeSO is added into a reaction tank under the condition of pH 2-4 while stirring4Reducing hexavalent chromium in the wastewater into trivalent chromium; then adding Ca (OH)2The insoluble chromium hydroxide precipitate is formed by adjusting the pH to 8-9. The treatment effect is good, the medicament source is easy, but the occupied area is large, the sludge volume is large, the effluent chroma is high, the treatment method is suitable for small plants, and the treatment method has limitation.
In order to solve the technical problem of the chromium-free coating wastewater treatment in the steel industry, a proper method is required, and the reasonable arrangement of the chromium-free coating wastewater treatment process is also very important. Through investigating, researching and analyzing chromium-free coating wastewater treatment systems in a plurality of steel enterprise factories, the current steel industry chromium-free coating wastewater treatment generally has the problems of overhigh wastewater source water quality concentration and large fluctuation coefficient, serious sedimentation of a regulating reservoir for leading the chromium-free coating wastewater to enter, disordered dosing systems, serious long-term corrosion, insufficient stirring and mixing of the chromium-free coating wastewater and medicaments and the like, the problem of the existing steel enterprise chromium-free coating wastewater treatment process needs to be solved urgently, the process flow of the chromium-free coating wastewater treatment system is optimized, the impact load capacity of wastewater treatment is improved to the maximum extent, and the aim of efficiently and stably treating the chromium-free coating wastewater is fulfilled.
Disclosure of Invention
The invention provides a method for treating the chromium-free coating wastewater of the steel enterprises, which can obviously reduce the use amount of a medicament, reduce the wastewater treatment cost and has high treatment efficiency, aiming at solving the technical problems of large medicament consumption, large sludge production amount, complex treatment process, high treatment cost and the like in the chromium-free coating wastewater treatment of the existing steel enterprises, thereby opening up a new way for reaching the standard of the chromium-free coating wastewater treatment.
In order to realize the aim, the method for treating the chromium-free coating wastewater of the steel enterprises adopts the following steps:
1) blast aeration oxidation treatment: feeding the chromium-free coating wastewater of the iron and steel enterprises into an aeration adjusting tank for blast aeration oxidation treatment for 30-50 min; an aeration system in the aeration adjusting tank adopts a ceramic microporous aeration head, so that bubbles are tiny and aeration is uniform; the water quality of the wastewater of the chromium-free coating is as follows: 50-350mg/L of oil and grease, 5-25mg/L of iron, 150-500mg/L of aluminum dihydrogen phosphate, 100-500mg/L of suspended matters, 200-1000mg/L of COD and 3-5 of pH value.
In most cases, the water quality of the wastewater of the chromium-free coating is as follows: oil and grease 100-200mg/L, iron 15-25mg/L, aluminum dihydrogen phosphate 250-450mg/L, suspended matter 200-500mg/L, COD200-600 mg/L.
2) Neutralization and flocculation reaction regulation: feeding the chromium-free coating wastewater treated in the step 1) into a neutralization and flocculation reaction adjusting device, wherein the neutralization and flocculation reaction adjusting device adopts a four-stage mixing reactor, a sodium hydroxide feeding device is adopted to feed sodium hydroxide into the four-stage mixing reactor, the adding amount is 10-50mg/L, and the adding amount is controlled by a metering pump, so that the pH value of the chromium-free coating wastewater in the four-stage mixing reactor is kept between 6 and 8, the acidic chromium-free coating wastewater is subjected to neutralization reaction, and meanwhile, trivalent chromium in water and hydroxide radicals form precipitates; then, adding a demulsifier, a PAC and a PAM into the four-stage mixing reactor through a demulsifier dosing device, a PAC dosing device and a PAM dosing device respectively, and carrying out flocculation reaction on other refractory substances in the chromium-free coating wastewater to form a flocculation complex; the addition amounts of the demulsifier, PAC and PAM are respectively 50-180mg/L, 30-150mg/L and 5-20mg/L, and the addition amounts are also controlled by a metering pump.
In this step, the addition amount of sodium hydroxide is preferably 20 to 30 mg/L; the addition amounts of the demulsifier, PAC and PAM are preferably in the ranges of 80-150mg/L, 60-120mg/L and 5-15mg/L respectively, wherein the addition amount of the demulsifier is preferably in the range of 100-120 mg/L.
3) High-efficiency air flotation: feeding the chromium-free coating wastewater treated in the step 2) into a dissolved air tank of the high-efficiency air floatation device, adhering suspended matters in the wastewater to the micro bubbles under the action of surface tension of a large number of micro bubbles in the dissolved air tank to form a micro bubble suspension with the integral specific gravity less than 1, realizing solid-liquid separation, scraping and discharging the micro bubble suspension into a sludge tank through a foam scraper on the upper part of the high-efficiency air floatation device, and discharging clear water at the bottom.
4) And (3) flocculation reaction adjustment: feeding the bottom clear water discharged in the step 3) into a flocculation reaction regulating device, wherein the flocculation reaction regulating device adopts a three-stage mixing reactor, adding sulfuric acid, PAC and PAM respectively by controlling a sulfuric acid dosing device, a PAC dosing device and a PAM dosing device, wherein the adding amount is 15-25mg/L, 30-150mg/L and 5-20mg/L, and controlling the PH value in the three-stage mixing reactor to be 4-6 so as to enable other difficultly degraded substances in the wastewater to generate flocculation reaction; the dosage is controlled by a metering pump.
In this step, the addition amounts of sulfuric acid, PAC and PAM are preferably 15-25mg/L, 80-100mg/L and 8-12mg/L, respectively.
5) Standing and precipitating: clear water at the upper part in the third-stage mixing reactor is fed into an inclined plate sedimentation tank for standing and sedimentation, and supernatant liquid discharged from the inclined plate sedimentation tank enters a biochemical standard extraction system for treatment until the effluent requirement of the steel industry water pollutant discharge standard (GB13456-2012) is met.
The above-mentioned amount is the amount of wastewater fed to the treatment process.
The indexes that the effluent in the supernatant discharged from the inclined plate sedimentation tank meets the requirements of entering a biochemical standard extraction system are shown in table 1.
TABLE 1 iron and steel industry wastewater entry into Biochemical upgrading System for Each pollutant requirement
The principle of the method for treating the chromium-free coating wastewater of the iron and steel enterprises is as follows: as a large amount of indexes such as phosphorus, nitrogen, COD, oil and the like which are difficult to degrade are generated in the production process of the steel industry, medicaments such as acid and alkali, PAC, PAM and the like with proper concentration are added into the chromium-free coating wastewater to form hydroxide precipitates which are extremely difficult to dissolve in water and insoluble complexes thereof, so that the requirement that the chromium-free coating wastewater enters a biochemical system is met, and the load capacity of the biochemical system for degrading various pollutants is improved.
The method for treating the chromium-free coating wastewater of the iron and steel enterprises has the following positive effects after adopting the technical scheme:
(1) the consumption of neutralizing agents and flocculating agents is greatly reduced, and compared with the conventional process, the consumption of the flocculating agents is reduced by more than 40%;
(2) the finally generated sludge amount is greatly reduced and is less than 1/3 of the sludge amount processed by the conventional process, and the content of chromium in the sludge is obviously improved, thereby facilitating the centralized processing of the sludge;
(3) the production process is simple, the production cost is low, and the treatment cost is reduced by more than 30% compared with the conventional process.
Drawings
FIG. 1 is a process flow diagram of a method for treating chromium-free coating wastewater of steel enterprises according to the present invention;
FIG. 2 is a system structure relationship diagram of a method for treating chromium-free coating wastewater of iron and steel enterprises according to the invention.
Reference numerals: 1-aeration adjusting tank; 2-a four-stage mixing reactor; 3-high-efficiency air flotation device; 4-three-stage mixing reactor; 5-a chromium-free inclined tube sedimentation tank; 6-sodium hydroxide dosing device; 7-demulsifier dosing device; 8-sulfuric acid dosing device; 9-PAC dosing device; 10-PAM dosing device. PAC-polyaluminium oxide: PAM-polyacrylamide.
Detailed Description
In order to better describe the invention, the method for treating the wastewater of the chrome-free coating of the steel enterprise is further described in detail by combining the attached drawings.
The system structure connection diagram of the method for treating the chromium-free coating wastewater of the steel enterprise shown in the figure 2 is combined with the figure 1, so that the method for treating the chromium-free coating wastewater of the steel enterprise firstly enters the aeration regulating tank 1, then is pumped into the four-stage mixing reactor 2 by the pump, and sodium hydroxide, a demulsifier, PAC and PAM agents are added into the four-stage mixing reactor 2. The effluent of the four-stage mixing reactor 2 enters a high-efficiency air flotation device 3, then enters a three-stage mixing reactor 4, sulfuric acid, PAC and PAM reagents are added into the three-stage mixing reactor 4, and the effluent enters a chromium inclined plate sedimentation tank 5. After passing through the inclined plate sedimentation tank 5, the supernatant meets the requirement of entering a biochemical standard extraction system, and the bottom sludge is transported outside. Taking the chromium-free coating wastewater treatment of a certain steel enterprise as an example, the following procedures are specifically adopted:
1) blast aeration oxidation treatment: feeding the chromium-free coating wastewater of the iron and steel enterprises into an aeration adjusting tank 1 for blast aeration oxidation treatment for 30-50 min; the aeration system in the aeration adjusting tank 1 adopts a ceramic microporous aeration head; the water quality of the wastewater of the chromium-free coating is as follows: 150 +/-10 mg/L of oil and grease, 18 +/-2 mg/L of iron, 370 +/-15 mg/L of aluminum dihydrogen phosphate, 360 +/-15 mg/L of suspended matters, 410 +/-20 mg/L of COD and 3-5 of pH value.
2) Neutralization and flocculation reaction regulation: feeding the chromium-free coating wastewater treated in the step 1) into a neutralization and flocculation reaction adjusting device, wherein the neutralization and flocculation reaction adjusting device adopts a four-stage mixing reactor 2, and a sodium hydroxide dosing device 6 is adopted to dose sodium hydroxide into the four-stage mixing reactor 2, and the addition amount is 20-30mg/L, so that the pH value of the chromium-free coating wastewater in the four-stage mixing reactor 2 is kept between 6 and 8; then, respectively adding a demulsifier, a PAC and a PAM into the four-stage mixing reactor 2 through a demulsifier medicine adding device 7, a PAC medicine adding device 9 and a PAM medicine adding device 10, and carrying out flocculation reaction on other refractory substances in the chromium-free coating wastewater to form a flocculation complex; the addition amounts of the demulsifier, PAC and PAM are respectively 100-120mg/L, 80-100mg/L and 8-12 mg/L.
An online PH meter is installed in the four-stage mixing reactor 2, the adding amount of a dosing device is adjusted in time by monitoring the pH value in the four-stage mixing reactor 2, if the display numerical value of the online PH meter is larger than 9, a sulfuric acid dosing device 8 is started, and if the display numerical value of the online PH meter is smaller than 7, a sodium hydroxide dosing device 6 is required to be controlled.
3) High-efficiency air flotation: feeding the chromium-free coating wastewater treated in the step 2) into a dissolved air tank of the high-efficiency air floating device 3, adhering suspended matters in the wastewater to the tiny air bubbles under the action of surface tension of a large number of tiny air bubbles in the dissolved air tank to form tiny air bubble suspension with the integral specific gravity less than 1, realizing solid-liquid separation, scraping and discharging the tiny air bubble suspension into a sludge tank through a foam scraper at the upper part of the high-efficiency air floating device 3, and discharging clear water at the bottom;
4) and (3) flocculation reaction adjustment: feeding the bottom clear water discharged in the step 3) into a flocculation reaction regulating device, wherein the flocculation reaction regulating device adopts a three-stage mixing reactor 4, adding sulfuric acid, PAC and PAM respectively by controlling a sulfuric acid dosing device 8, a PAC dosing device 9 and a PAM dosing device 10, wherein the adding amount is 15-25mg/L, 80-100mg/L and 8-12mg/L respectively, and controlling the PH value in the three-stage mixing reactor 4 to be 4-6 so as to enable other refractory substances in the wastewater to generate flocculation reaction;
an online PH meter is arranged in the third-stage mixing reactor 4, the adding amount of a dosing device is adjusted in time by monitoring the pH value in the third-stage mixing reactor 4, and if the value displayed by the online PH meter is less than 7, a sodium hydroxide dosing device 6 is started; if the on-line PH meter shows that the value is more than 9, only the PAC dosing device 9 and the PAM dosing device 10 need to be controlled.
5) Standing and precipitating: clear water at the upper part in the third-stage mixing reactor 4 is fed into the inclined plate sedimentation tank 5 for standing and sedimentation, and supernatant liquid discharged from the inclined plate sedimentation tank 5 enters a biochemical standard extraction system for treatment until the effluent requirement of the steel industry water pollutant discharge standard (GB13456-2012) is met.
The practical application shows that compared with the conventional process, after the chromium-free coating wastewater passes through a four-stage mixer and a high-efficiency air flotation device, the effluent index of oil and grease is about 15mg/l, the removal rate is about 90%, the effluent index of iron is about 3.6mg/l, the removal rate is about 80%, the effluent index of aluminum dihydrogen phosphate is about 18.5mg/l, the removal rate is about 95%, the effluent index of suspended matters is about 36mg/l, the removal rate is about 90%, the effluent index of COD is about 266.5mg/l, and the removal rate is about 35%; after the wastewater effluent of the chromium-free coating passes through a three-stage reaction mixer and inclined plate precipitation, the effluent index of oil and grease is about 9.75mg/l, the removal rate is about 94%, the effluent index of iron is about 2.52mg/l, the removal rate is about 86%, the effluent index of aluminum dihydrogen phosphate is about 9.25mg/l, the removal rate is about 98%, the effluent index of suspended matters is about 7.2mg/l, the removal rate is about 98%, the effluent index of COD is about 213.2mg/l, and the removal rate is about 48%; the dosage of the flocculant is reduced by 42.8 percent, the obvious effect of reducing the pesticide is achieved, the cost of wastewater treatment is greatly reduced, and unexpected technical and economic effects are achieved.
Claims (5)
1. A method for treating chromium-free coating wastewater of steel enterprises is characterized by comprising the following steps:
1) blast aeration oxidation treatment: feeding the chromium-free coating wastewater of the iron and steel enterprises into an aeration adjusting tank (1) for blast aeration oxidation treatment for 30-50 min; an aeration system in the aeration adjusting tank (1) adopts a ceramic microporous aeration head; the water quality of the wastewater of the chromium-free coating is as follows: 50-350mg/L of oil and grease, 5-25mg/L of ferrum, 150-500mg/L of aluminum dihydrogen phosphate, 100-500mg/L of suspended matters, 1000-1000 mg/L of COD200 and 3-5 of pH value;
2) neutralization and flocculation reaction regulation: feeding the chromium-free coating wastewater treated in the step 1) into a neutralization and flocculation reaction adjusting device, wherein the neutralization and flocculation reaction adjusting device adopts a four-stage mixing reactor (2), and a sodium hydroxide dosing device (6) is adopted to dose sodium hydroxide into the four-stage mixing reactor (2), and the addition amount is 10-50mg/L, so that the pH value of the chromium-free coating wastewater in the four-stage mixing reactor (2) is kept between 6 and 8; then, adding a demulsifier, PAC and PAM into the four-stage mixing reactor (2) through a demulsifier medicine adding device (7), a PAC medicine adding device (9) and a PAM medicine adding device (10) respectively, and carrying out flocculation reaction on other substances which are difficult to degrade in the chromium-free coating wastewater to form a flocculation complex; the addition amounts of the demulsifier, the PAC and the PAM are respectively 50-180mg/L, 30-150mg/L and 5-20 mg/L;
3) high-efficiency air flotation: feeding the chromium-free coating wastewater treated in the step 2) into a dissolved air tank of a high-efficiency air floating device (3), adhering suspended matters in the wastewater to the tiny bubbles under the action of surface tension of a large number of tiny bubbles in the dissolved air tank to form tiny bubble suspension with the integral specific gravity less than 1, realizing solid-liquid separation, scraping and discharging the tiny bubble suspension into a sludge tank through a foam scraper at the upper part of the high-efficiency air floating device (3), and discharging clear water at the bottom;
4) and (3) flocculation reaction adjustment: feeding the bottom clear water discharged in the step 3) into a flocculation reaction regulating device, wherein the flocculation reaction regulating device adopts a three-stage mixing reactor (4), adding sulfuric acid, PAC and PAM respectively by controlling a sulfuric acid dosing device (8), a PAC dosing device (9) and a PAM dosing device (10), wherein the adding amounts are 15-25mg/L, 30-150mg/L and 5-20mg/L respectively, and controlling the PH value in the three-stage mixing reactor (4) to be between 4 and 6 so as to enable other refractory substances in the wastewater to generate flocculation reaction;
5) standing and precipitating: clear water at the upper part in the third-stage mixing reactor (4) is fed into an inclined plate sedimentation tank (5) for standing and sedimentation, and supernatant liquid discharged from the inclined plate sedimentation tank (5) enters a biochemical standard extraction system for treatment until the effluent requirement of the steel industry water pollutant discharge standard (GB13456-2012) is met.
2. The method for treating chromium-free coating wastewater of steel enterprises according to claim 1, wherein the quality of the chromium-free coating wastewater in the step 1) is as follows: oil and grease 100-200mg/L, iron 15-25mg/L, aluminum dihydrogen phosphate 250-450mg/L, suspended matter 200-500mg/L, COD200-600 mg/L.
3. The method for treating chromium-free coating wastewater of iron and steel enterprises according to claim 2, wherein in step 2): the addition amount of the sodium hydroxide is 20-30 mg/L; the addition amounts of the demulsifier, PAC and PAM are respectively 80-150mg/L, 60-120mg/L and 5-15 mg/L.
4. The method for treating chromium-free coating wastewater of iron and steel enterprises according to claim 3, wherein in step 2): the addition amount of the demulsifier is 100-120 mg/L.
5. The method for treating wastewater of chrome-free coating in iron and steel enterprises as claimed in claim 1, 2, 3 or 4, wherein in step 4): the addition amounts of the sulfuric acid, the PAC and the PAM are respectively 15-25mg/L, 80-100mg/L and 8-12 mg/L.
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