CN113816518B - Zinc smelting wastewater treatment method - Google Patents

Abstract

The invention belongs to the field of wastewater harmless and resource utilization, and particularly relates to a method for treating zinc smelting wastewater, which comprises the following steps: step one, adding lime milk into the wastewater for reaction, and then precipitating; step two, extracting supernatant fluid precipitated in the step one, adding a COD degradation agent, a quick flocculant, a high-efficiency coagulant and lime milk for reaction, and then precipitating; step three, extracting the supernatant fluid precipitated in the step two, adding a water purifying agent and a flocculating agent for reaction, and then carrying out precipitation; step four, introducing the supernatant liquid precipitated in the step three into a high-efficiency filtering system for filtering, and simultaneously adding a flocculating agent; and fifthly, adding sulfuric acid into the liquid filtered in the step four for adjustment, and then discharging. The treatment method of the flying zinc smelting wastewater has the advantages that the treatment flow is simpler and more efficient, and pollutants in the zinc smelting wastewater can be effectively removed, so that harmless treatment and recycling of liquid wastewater are realized, and the treatment cost is reduced.

Description

Zinc smelting wastewater treatment method

Technical Field

The invention belongs to the field of wastewater harmless and resource utilization, and particularly relates to a method for treating zinc smelting wastewater.

Background

With the continued development and advancement of science and technology, the production and consumption of zinc has increased rapidly. Such as power plants and their transportation networks, airports, bridges, roads, etc., require the use of large quantities of galvanised material. A large amount of zinc smelting wastewater can be generated in the zinc material production process, the zinc-containing wastewater has serious harm to human bodies and industrial and agricultural production, has strong durability and strong toxicity, is difficult to biodegrade once entering a circulatory system, and mostly participates in food chain circulation, and finally accumulates in organisms to destroy normal physiological metabolism activities of the zinc-containing wastewater and damage animal and plant health.

The prior art generally discloses methods for treating zinc-containing wastewater, such as electrolytic methods, sulfide precipitation methods and the like. Although the electrolytic method can effectively remove zinc ions, the method can not reduce the concentration of zinc ions to be very low, consumes electric energy, has huge water resources, and has high investment cost and low water yield. However, the sulfide precipitation method is low in cost, the use amount of sulfide is difficult to control, secondary pollution is easy to reduce, and excessive sulfur and certain heavy metal ions can form complex ions dissolved in water, so that the treatment effect is reduced.

Disclosure of Invention

In order to solve at least one of the technical problems, the invention provides a zinc smelting wastewater treatment method.

A zinc smelting wastewater treatment method comprises the following steps:

introducing zinc smelting wastewater to be treated into a first regulating tank, adding lime milk at the same time to control the PH value of the wastewater in the first regulating tank to be between 4.0 and 7.0, so that heavy metal ions in the wastewater generate hydroxide which is difficult to dissolve, and finally carrying out precipitation treatment;

introducing the supernatant obtained after the precipitation treatment in the first step into a first-stage reaction tank, simultaneously adding a COD degradation agent, a quick flocculant, a high-efficiency coagulant and lime milk for reaction, and carrying out precipitation treatment after the reaction is finished, wherein the lime milk is used for regulating the pH value of liquid in the first-stage reaction tank to be 10.5-11.5, and the COD degradation agent, the high-efficiency coagulant and the quick flocculant are used for separating and converting COD and residual heavy metals in the liquid into a suspension state and accelerating the sedimentation speed;

introducing the supernatant obtained after the precipitation treatment in the step two into a second-stage reaction tank, adding a water purifying agent and a flocculating agent to react, and carrying out precipitation treatment after the reaction is finished, wherein the PH value of liquid in the second-stage reaction tank is between 10.5 and 11.5, and the water purifying agent and the flocculating agent are used for separating and converting residual heavy metal ions in the liquid into a suspension state and accelerating the sedimentation speed;

introducing the supernatant obtained after the precipitation treatment in the step three into a high-efficiency filtering system composed of inorganic matters with different particles, and simultaneously adding a flocculating agent to flocculate and precipitate suspended matters in the liquid and filtering the suspended matters;

and fifthly, introducing the filtered liquid in the step four into a second regulating tank, adding sulfuric acid with a preset concentration to regulate the PH value to be between 6.0 and 9.0, and discharging supernatant after precipitation treatment.

Preferably, in the first step, the ratio of the amount of lime milk to the total amount of liquid introduced into the first regulating tank is 20%; and

in the second step, the ratio of the dosage of the COD degrading agent, the quick flocculant, the high-efficiency coagulant and the lime milk to the total amount of the liquid introduced into the first-stage reaction tank is respectively as follows: 0.1% -0.4%, 0.6% -2.4%, 0.8% -1.0% and 0.8-4%; and

in the third step, the ratio of the amount of the water purifying agent and the flocculating agent to the total amount of the liquid introduced into the second-stage reaction tank is respectively as follows: 0.18% -0.23% and 0.6% -0.91%; and

in the fifth step, the predetermined concentration of sulfuric acid is 10% -15%.

The formula of the COD degrading agent, the quick flocculant, the high-efficiency coagulant and the water purifying agent suitable for the purpose of the invention requires a wide pH application range, has strong adaptability to the change of raw water temperature, turbidity, alkalinity and organic matter content, and provides a specific formula of the COD degrading agent, the quick flocculant, the high-efficiency coagulant and the water purifying agent for better solving the technical problem of the invention:

the COD degrading agent contains 50-60% FeSO by mass percent ₄ ·7H ₂ O,5-10% ZrOCl ₂ ·8H ₂ O,10-15% Ca (ClO) ₂ And 5-10% NaH ₂ PO ₄ ·2H ₂ O, the balance being water; wherein Ca (ClO) ₂ The effective chlorine content is more than or equal to 65 percent for industrial grade;

the efficient coagulant comprises, by mass, 40% of polymeric ferric sulfate, 30% of polymeric aluminum sulfate, 10-15% of sodium citrate, 15% of dimethylamine and the balance of water;

the rapid flocculant comprises 8-10% of potassium ferrate, 25% of polyaluminium calcium chloride, 35% of aluminum sulfate, 20% of ferric chloride, 10% of polyacrylamide and the balance of water in percentage by mass;

the water purifying agent comprises, by mass, 8-10% of sodium bicarbonate, 15-18% of hydrogen peroxide, 10-12% of sodium dichloroisocyanurate, 25-30% of sodium hypochlorite, 1-3% of potassium permanganate, 5% of sodium silicate, 10% of sodium chloride and 2-5% of boron nitride, and the balance of water.

Preferably, in the first step, the heavy metal ions in the wastewater include at least one of the following heavy metal ions: zn (zinc) ²⁺ 、Cu ²⁺ 、Cd ²⁺ 、Pb ²⁺ 、Fe ³⁺ 。

Preferably, in the third step, before the supernatant obtained after the precipitation treatment in the first-stage reaction tank is introduced into the second-stage reaction tank, the method further comprises the steps of:

introducing the supernatant obtained after the precipitation treatment in the first-stage reaction tank into a first-stage thickening tank for further precipitation treatment, and introducing the supernatant obtained after the precipitation treatment into the second-stage reaction tank.

Preferably, in the fourth step, before introducing the supernatant obtained after the precipitation treatment in the second-stage reaction tank into the high-efficiency filtration system, the method further comprises the following steps:

introducing the supernatant obtained after the precipitation treatment in the second-stage reaction tank into a second-stage thickening tank for further precipitation treatment; and

and introducing the supernatant obtained after the precipitation treatment into an intermediate water tank for sand-lime separation treatment, and finally introducing discharged liquid after the sand-lime separation treatment into the efficient filtering system.

Preferably, the zinc smelting wastewater treatment method further comprises the following steps:

and conveying the sediment obtained after the sedimentation treatment of the regulating tank, the first-stage reaction tank and the first-stage thickening tank to a 6-meter thickening tank, and conveying the sediment in the 6-meter thickening tank to a slag filtering workshop for filter pressing treatment.

Preferably, the zinc smelting wastewater treatment method further comprises the following steps:

and conveying the sediment obtained after the precipitation treatment in the second-stage reaction tank and the second-stage thickening tank to an 8-meter thickening tank, and conveying the sediment in the 8-meter thickening tank to a slag filtering workshop for filter pressing treatment.

Preferably, the zinc smelting wastewater treatment method further comprises the following steps:

and (3) returning the suspension filtered in the step (IV) to the second-stage thickening tank, mixing the suspension with the supernatant obtained after the sedimentation treatment before the second-stage thickening tank, and carrying out sedimentation treatment.

Preferably, the zinc smelting wastewater treatment method further comprises the following steps:

and (3) introducing the supernatant obtained after the precipitation treatment of the second regulating tank in the step five into a total discharge tank to perform discharge.

Preferably, the zinc smelting wastewater treatment method further comprises the following steps:

if the water quality in the total drainage pool can not reach the standard, pumping the water in the total drainage pool to an accident pool, pumping the water into a first regulating pool for subsequent treatment, and discharging until the water quality in the total drainage pool is qualified.

Compared with the prior art, the invention has the following advantages:

according to the zinc smelting wastewater treatment method, lime milk is added, so that main heavy metal ions in wastewater can generate indissolvable hydroxide so as to remove heavy metal ions by precipitation; then, adding COD degradation agent, high-efficiency coagulant, quick flocculant, water purifying agent and other agents into the clear solution obtained by precipitation for multiple separation and precipitation treatment so as to further remove residual heavy metal ions and other organic pollutants; and further, filtering the clear liquid obtained by the final precipitation through a high-efficiency filtering system, so as to entrap the suspended matters remained in the clear liquid to the maximum extent and ensure the water outlet effect.

Drawings

FIG. 1 is a process flow diagram of the zinc smelting wastewater treatment method of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention become more apparent, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. . All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The reagents used in the present invention, unless otherwise specified, refer to conventional reagents that are commercially available.

Wherein the flocculant may be aluminum sulfate or alum, or other conventional commercially available conventional organic or inorganic flocculant products.

The zinc smelting wastewater treatment method of the present invention will be further described with reference to the accompanying drawings and examples.

Example 1

Taking the smelting wastewater treatment of a certain zinc smelting factory as an example, detecting that the content of Zn, cd, hg, ammonia nitrogen and COD in the interior of the zinc smelting wastewater is 274mg/L, 0.5mg/L, 0.11mg/L, 35mg/L and 400mg/L respectively when the zinc smelting wastewater is discharged, and the pH value is 2; the zinc smelting wastewater is treated by the zinc smelting wastewater treatment method of the invention, and the treatment steps are shown in fig. 1, and specifically include:

step one, conveying wastewater to a first regulating tank from a collecting box, and neutralizing the wastewater by adding lime milk, wherein the lime milk is prepared by regulating block or powdery lime with Cao of more than or equal to 60%, and the concentration of the lime milk is 20%; the PH value of the solution in the regulating tank is controlled to be 6-7 after the neutralization treatment, and at the moment, zn in the wastewater is controlled to be ²⁺ 、Cd ²⁺ The equivalent heavy metal ions and the like are combined with hydroxide to generate hydroxide which is difficult to dissolve in water, and finally, sediment (sediment) of the bottom layer and clear liquid positioned on the upper layer are obtained through sediment treatment.

The following specific chemical reaction formulas for combining heavy metal ions and hydroxyl ions mainly contained in the zinc smelting wastewater at present are as follows:

Zn ²⁺ +2OH-＝Zn(OH)2；

Cd ²⁺ +2OH-＝Cd(OH)2；

Cu ²⁺ +2OH-＝Cu(OH)2；

Fe ³⁺ +3OH-＝Fe(OH)3；

Pb ²⁺ +2OH-＝Pb(OH)2。

step two, conveying supernatant obtained after precipitation in the first regulating tank to a first-stage reaction tank, simultaneously introducing COD degradation agents accounting for 0.2% of the total amount of liquid in the first-stage reaction tank for reaction, sequentially introducing 1.2% of a quick flocculant, 0.8% of a high-efficiency coagulant and 3% of lime milk for reaction according to 2-minute interval time after reaction for 25 minutes, and carrying out precipitation treatment after reaction for 30 minutes; the purpose of the lime milk is to adjust the pH value of the liquid in the first-stage reaction tank to 10.5-11.5, and the COD degradation agent, the high-efficiency coagulant and the quick flocculant are used for separating COD and residual heavy metals in the liquid and converting the COD and residual heavy metals into a suspension state, and simultaneously accelerating the sedimentation speed.

Step three, introducing the supernatant obtained after the precipitation treatment in the first-stage reaction tank into a first-stage thickening tank for further precipitation treatment, and introducing the obtained supernatant into a second-stage reaction tank after the precipitation treatment; meanwhile, adding a water purifying agent accounting for 0.2 percent and a flocculating agent accounting for 0.9 percent of the total liquid into the two-stage reaction tank to react, and carrying out precipitation treatment after reacting for 30 minutes; the PH value of the liquid in the second-stage reaction tank is basically the same as that of the liquid in the first-stage reaction tank and is 10.5-11.5, and the water purifying agent and the flocculating agent are used for separating and converting residual heavy metal ions in the liquid into a suspension state and accelerating the sedimentation speed.

And step four, conveying supernatant obtained after the second-stage reaction tank is precipitated to a second-stage thickening tank for further precipitation treatment, introducing the obtained supernatant into an intermediate water tank for sand-lime separation treatment after the precipitation is finished, introducing discharged liquid after the sand-lime separation treatment into an efficient filtration system (FBL filter), and simultaneously adding 0.8% flocculant to flocculate and precipitate suspended matters in the liquid and filtering the suspended matters.

Further, if sediment (sediment) is generated during filtration, the sediment is conveyed back to the second-stage thickening tank, mixed with supernatant after the sedimentation treatment in the second-stage thickening tank, subjected to the sedimentation treatment, and finally conveyed to the high-efficiency filtration system together with the filtered supernatant.

And step five, introducing the filtered liquid in the step four into a second regulating tank, diluting 98% industrial sulfuric acid to 10% and adding the diluted industrial sulfuric acid into the second regulating tank, controlling the PH value in the second regulating tank to be 6.5-8.5, carrying out final precipitation treatment, and conveying the obtained supernatant to a total discharge tank for external discharge after the precipitation is finished.

The formulation reagents used in this example were as follows:

the COD degrading agent contains 55% FeSO by mass percent ₄ ·7H ₂ O,5% ZrOCl ₂ ·8H ₂ O,12% Ca (ClO) ₂ And 12% NaH ₂ PO ₄ ·2H ₂ O, the balance being water; wherein Ca (ClO) ₂ The effective chlorine content is more than or equal to 65 percent for industrial grade;

the efficient coagulant comprises, by mass, 40% of polymeric ferric sulfate, 30% of polymeric aluminum sulfate, 10% of sodium citrate, 15% of dimethylamine and the balance of water;

the rapid flocculant comprises, by mass, 8% of potassium ferrate, 25% of polyaluminium calcium chloride, 35% of aluminum sulfate, 20% of ferric chloride, 10% of polyacrylamide and the balance of water;

the water purifying agent comprises, by mass, 8% of sodium bicarbonate, 18% of hydrogen peroxide, 12% of sodium dichloroisocyanurate, 30% of sodium hypochlorite, 1% of potassium permanganate, 5% of sodium silicate, 10% of sodium chloride and 2% of boron nitride, and the balance of water. In the embodiment, the water obtained in the final total drainage pool is detected, wherein the contents of Zn, cd, hg, ammonia nitrogen and COD are respectively 0.27mg/L, 0.01mg/L, 0.003mg/L, 3.7mg/L and 35mg/L, the pH value is 7.65, and the detection result shows that the water in the total drainage pool meets the emission standard of emission standards of industrial pollutants of lead and zinc (GB 25466-2010), so that the water can be directly discharged.

It should be noted that if the water quality in the total drainage pool cannot reach the above-mentioned drainage standard, the water in the total drainage pool may be pumped to the accident pool, and then pumped to the first adjusting pool for subsequent treatment (i.e. circulation steps one to five), and the water is not drained until the water quality in the total drainage pool is qualified.

It will be appreciated that in the above steps one to four, each reaction stage produces a precipitate (sediment), and for this reason, in this embodiment, the sediment obtained after the precipitation treatment in the adjusting tank, the first reaction tank and the first thickening tank is conveyed to the 6 m thickening tank, the sediment in the 6 m thickening tank is conveyed to the slag filtering plant for press filtration treatment, the sediment obtained after the precipitation treatment in the second reaction tank and the second thickening tank is conveyed to the 8 m thickening tank, and the sediment in the 8 m thickening tank is conveyed to the slag filtering plant for press filtration treatment, so as to recover heavy metals therein, thereby realizing recycling of resources.

Example 2

Taking the smelting wastewater treatment of a zinc smelting factory as an example, as the treated water sample is the smelting wastewater of the factory, when the production fluctuates, the chemical composition also changes to a certain extent, and the water quality analysis of the wastewater (namely raw water) before the treatment is as shown in the following table 1:

TABLE 1 Water quality analysis Table before treatment

The zinc smelting wastewater is treated by the zinc smelting wastewater treatment method, and the treatment steps specifically comprise:

step one, conveying wastewater to a first regulating tank from a collecting box, and neutralizing the wastewater by adding lime milk, wherein the lime milk is prepared by regulating block or powdery lime with Cao of more than or equal to 60%, and the concentration of the lime milk is 20%; the PH value of the solution in the regulating tank is controlled to be 6-7 after the neutralization treatment, and at the moment, zn in the wastewater is controlled to be ²⁺ 、Cd ²⁺ 、Hg ²⁺ The equivalent heavy metal ions and the like are combined with hydroxide to generate hydroxide which is difficult to dissolve in water, and finally, sediment (sediment) of the bottom layer and clear liquid positioned on the upper layer are obtained through sediment treatment.

Step two, conveying supernatant obtained after precipitation in the first regulating tank to a first-stage reaction tank, simultaneously introducing COD degradation agents accounting for 0.3% of the total amount of liquid in the first-stage reaction tank for reaction, sequentially introducing 1.6% of a quick flocculant, 1.0% of a high-efficiency coagulant and 2% of lime milk for reaction according to 2-minute interval time after reaction for 25 minutes, and carrying out precipitation treatment after reaction for 30 minutes; wherein the purpose of the lime cream is to adjust the pH value of the liquid in the first-stage reaction tank to 10.5-11.5.

Step three, introducing the supernatant obtained after the precipitation treatment in the first-stage reaction tank into a first-stage thickening tank for further precipitation treatment, and introducing the obtained supernatant into a second-stage reaction tank after the precipitation treatment; meanwhile, adding a water purifying agent accounting for 0.2 percent and a flocculating agent accounting for 0.9 percent of the total liquid into the two-stage reaction tank to react, and carrying out precipitation treatment after reacting for 30 minutes; wherein the PH value of the liquid in the second-stage reaction tank is basically the same as that of the liquid in the first-stage reaction tank, and is 10.5-11.5.

And step four, conveying supernatant obtained after the second-stage reaction tank is precipitated to a second-stage thickening tank for further precipitation treatment, introducing the obtained supernatant into an intermediate water tank for sand-lime separation treatment after the precipitation is finished, introducing discharged liquid after the sand-lime separation treatment into an efficient filtration system (FBL filter), and simultaneously adding 0.8% flocculant to flocculate and precipitate suspended matters in the liquid and filtering the suspended matters.

Similarly, if sediment (sediment) is generated during filtration, the sediment is conveyed back to the second-stage thickening tank, mixed with supernatant after the sedimentation treatment in the second-stage thickening tank, subjected to the sedimentation treatment, and finally conveyed to the high-efficiency filtration system together with the filtered supernatant.

And step five, introducing the filtered liquid in the step four into a second regulating tank, diluting 98% industrial sulfuric acid to 10% and adding the diluted industrial sulfuric acid into the second regulating tank, controlling the PH value in the second regulating tank to be 6.5-8.5, carrying out final precipitation treatment, and conveying the obtained supernatant to a total discharge tank for external discharge after the precipitation is finished.

The formulation reagents used in this example were as follows:

the COD degrading agent contains FeSO 60% in mass percent ₄ ·7H ₂ O,8% ZrOCl ₂ ·8H ₂ O,15% Ca (ClO) ₂ And 10% NaH ₂ PO ₄ ·2H ₂ O, the balance being water; wherein Ca (ClO) ₂ The effective chlorine content is more than or equal to 65 percent for industrial grade;

the efficient coagulant comprises, by mass, 40% of polymeric ferric sulfate, 30% of polymeric aluminum sulfate, 12% of sodium citrate, 15% of dimethylamine and the balance of water;

the quick flocculant comprises, by mass, 9% of potassium ferrate, 25% of polyaluminium calcium chloride, 35% of aluminum sulfate, 20% of ferric chloride, 10% of polyacrylamide and the balance of water;

the water purifying agent comprises, by mass, 9% of sodium bicarbonate, 17% of hydrogen peroxide, 11% of sodium dichloroisocyanurate, 25% of sodium hypochlorite, 3% of potassium permanganate, 5% of sodium silicate, 10% of sodium chloride and 5% of boron nitride, and the balance of water.

In this example, the water obtained in the last total pool is detected, as shown in table 2 below:

TABLE 2 post-treatment Water quality analysis Table

Detecting items

Pb

Zn

Cd

Hg

COD

pH

NH 3 -N

After treatment

0.07-0.09

0.6-0.8

0.01-0.02

＜0.001

20-30

7-8

3-5

From the above test results, it can be seen that the water in the total drainage pool after treatment meets the emission standard of lead and zinc industrial pollutants (GB 25466-2010), so that the water can be directly discharged.

Likewise, if the water quality in the total drainage pool cannot reach the above-mentioned drainage standard, the water in the total drainage pool can be pumped to the accident pool, and then pumped to the first regulating pool for subsequent treatment steps (i.e. circulating step one to step five), and the water is not drained until the water quality in the total drainage pool is qualified. In addition, the sediment obtained after the sedimentation treatment of the regulating tank, the first-stage reaction tank and the first-stage thickening tank is conveyed to a 6-meter thickening tank, the sediment in the 6-meter thickening tank is conveyed to a slag filtering workshop for filter pressing treatment, the sediment obtained after the sedimentation treatment of the second-stage reaction tank and the second-stage thickening tank is conveyed to an 8-meter thickening tank, and the sediment in the 8-meter thickening tank is conveyed to the slag filtering workshop for filter pressing treatment.

Example 3

Taking the smelting wastewater treatment of a zinc smelting factory as an example, as the treated water sample is the smelting wastewater of the factory, when the production fluctuates, the chemical composition also changes to a certain extent, and the water quality analysis of the wastewater (namely raw water) before the untreated water sample is shown in the following table 3:

TABLE 3 analysis of Pre-treatment Water quality

Detecting items	Pb	Zn	Cd	Hg	COD	Cu	pH
								Raw water (mg/L, except pH)	11.89	104	0.16	0.07	196	0.26	2.6

The zinc smelting wastewater is treated by the zinc smelting wastewater treatment method, and the treatment steps specifically comprise:

step one, conveying wastewater to a first regulating tank from a collecting box, and neutralizing the wastewater by adding lime milk, wherein the lime milk is prepared by regulating block or powdery lime with Cao of more than or equal to 60%, and the concentration of the lime milk is 20%; the PH value of the solution in the regulating tank is controlled to be 6-7 after the neutralization treatment, and at the moment, zn in the wastewater is controlled to be ²⁺ 、Cd ²⁺ 、Hg ²⁺ The equivalent heavy metal ions are combined with hydroxide to generate hydroxide which is difficult to dissolve in water, and finally the precipitation treatment is carried out to obtain the sediment (sediment) of the bottom layer and the sediment positioned in the bottom layerSupernatant of the upper layer.

Step two, conveying supernatant obtained after precipitation in the first regulating tank to a first-stage reaction tank, simultaneously introducing COD degradation agents accounting for 0.1% of the total amount of liquid in the first-stage reaction tank for reaction, sequentially introducing 2.1% of a quick flocculant, 1% of a high-efficiency coagulant and 2.5% of lime milk for reaction according to 2-minute interval time after reaction for 25 minutes, and carrying out precipitation treatment after reaction for 30 minutes; wherein the purpose of the lime cream is to adjust the pH value of the liquid in the first-stage reaction tank to 10.5-11.5.

Step three, introducing the supernatant obtained after the precipitation treatment in the first-stage reaction tank into a first-stage thickening tank for further precipitation treatment, and introducing the obtained supernatant into a second-stage reaction tank after the precipitation treatment; meanwhile, adding a water purifying agent accounting for 0.2 percent and a flocculating agent accounting for 0.9 percent of the total liquid into the two-stage reaction tank to react, and carrying out precipitation treatment after reacting for 30 minutes; wherein the PH value of the liquid in the second-stage reaction tank is basically the same as that of the liquid in the first-stage reaction tank, and is 10.5-11.5.

And step four, conveying supernatant obtained after the second-stage reaction tank is precipitated to a second-stage thickening tank for further precipitation treatment, introducing the obtained supernatant into an intermediate water tank for sand-lime separation treatment after the precipitation is finished, introducing discharged liquid after the sand-lime separation treatment into an efficient filtration system (FBL filter), and simultaneously adding 0.8% flocculant to flocculate and precipitate suspended matters in the liquid and filtering the suspended matters.

Similarly, if sediment (sediment) is generated during filtration, the sediment is conveyed back to the second-stage thickening tank, mixed with supernatant after the sedimentation treatment in the second-stage thickening tank, subjected to the sedimentation treatment, and finally conveyed to the high-efficiency filtration system together with the filtered supernatant.

And step five, introducing the filtered liquid in the step four into a second regulating tank, diluting 98% industrial sulfuric acid to 10% and adding the diluted industrial sulfuric acid into the second regulating tank, controlling the PH value in the second regulating tank to be 6.5-8.5, carrying out final precipitation treatment, and conveying the obtained supernatant to a total discharge tank for external discharge after the precipitation is finished.

The formulation reagents used in this example were as follows:

the COD degrading agent contains 50% FeSO by mass percent ₄ ·7H ₂ O,10% ZrOCl ₂ ·8H ₂ O,10% Ca (ClO) ₂ And 5% NaH ₂ PO ₄ ·2H ₂ O, the balance being water; wherein Ca (ClO) ₂ The effective chlorine content is more than or equal to 65 percent for industrial grade;

the efficient coagulant comprises, by mass, 40% of polymeric ferric sulfate, 30% of polymeric aluminum sulfate, 15% of sodium citrate, 15% of dimethylamine and the balance of water;

the rapid flocculant comprises, by mass, 10% of potassium ferrate, 25% of polyaluminium calcium chloride, 35% of aluminum sulfate, 20% of ferric chloride, 10% of polyacrylamide and the balance of water;

the water purifying agent comprises, by mass, 10% of sodium bicarbonate, 15% of hydrogen peroxide, 10% of sodium dichloroisocyanurate, 28% of sodium hypochlorite, 2% of potassium permanganate, 5% of sodium silicate, 10% of sodium chloride and 4% of boron nitride, and the balance of water.

In this example, the water obtained in the last total pool is detected, as shown in table 4 below:

TABLE 4 post-treatment Water quality analysis Table

Detecting items

Pb

Zn

Cd

Hg

COD

Cu

pH

After treatment

＜0.02

0.03

0.008

0.004

19

0.03

7.5

From the above test results, it can be seen that the water in the total drainage pool after treatment meets the emission standard of lead and zinc industrial pollutants (GB 25466-2010), so that the water can be directly discharged.

Likewise, if the water quality in the total drainage pool cannot reach the above-mentioned drainage standard, the water in the total drainage pool can be pumped to the accident pool, and then pumped to the first regulating pool for subsequent treatment steps (i.e. circulating step one to step five), and the water is not drained until the water quality in the total drainage pool is qualified. In addition, the sediment obtained after the sedimentation treatment of the regulating tank, the first-stage reaction tank and the first-stage thickening tank is conveyed to a 6-meter thickening tank, the sediment in the 6-meter thickening tank is conveyed to a slag filtering workshop for filter pressing treatment, the sediment obtained after the sedimentation treatment of the second-stage reaction tank and the second-stage thickening tank is conveyed to an 8-meter thickening tank, and the sediment in the 8-meter thickening tank is conveyed to the slag filtering workshop for filter pressing treatment.

In conclusion, after the treatment of the flying zinc smelting wastewater treatment method, the detection of the heavy metal leaching toxicity of the wastewater meets the requirements; meanwhile, the method can remove heavy metal elements in sewage to a great extent, improves the water yield, and the sediment can be used as an extract for secondary utilization.

The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily conceivable by those skilled in the art within the technical scope of the present application should be covered in the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (9)

1. The zinc smelting wastewater treatment method is characterized by comprising the following steps of;

introducing zinc smelting wastewater to be treated into a first regulating tank, and simultaneously adding lime milk to control the PH value of the wastewater in the first regulating tank to be between 4.0 and 7.0, so that heavy metal ions in the wastewater generate indissolvable hydroxides, and finally, carrying out precipitation treatment, wherein the heavy metal ions in the wastewater comprise at least one of the following heavy metal ions: zn (zinc) ²⁺ 、Cu ²⁺ 、Cd ²⁺ 、Pb ²⁺ 、Fe ³⁺ ；

Introducing the supernatant obtained after the precipitation treatment in the first step into a first-stage reaction tank, simultaneously adding a COD degradation agent, a quick flocculant, a high-efficiency coagulant and lime milk for reaction, and carrying out precipitation treatment after the reaction is finished, wherein the lime milk is used for regulating the pH value of liquid in the first-stage reaction tank to be 10.5-11.5, and the COD degradation agent, the high-efficiency coagulant and the quick flocculant are used for separating and converting COD and residual heavy metals in the liquid into a suspension state and accelerating the sedimentation speed;

the efficient coagulant comprises, by mass, 40% of polymeric ferric sulfate, 30% of polymeric aluminum sulfate, 10-15% of sodium citrate, 15% of dimethylamine and the balance of water;

the rapid flocculant comprises 8-10% of potassium ferrate, 25% of polyaluminium calcium chloride, 35% of aluminum sulfate, 20% of ferric chloride, 10% of polyacrylamide and the balance of water in percentage by mass;

introducing the supernatant obtained after the precipitation treatment in the step two into a second-stage reaction tank, adding a water purifying agent and a flocculating agent to react, and carrying out precipitation treatment after the reaction is finished, wherein the PH value of liquid in the second-stage reaction tank is between 10.5 and 11.5, and the water purifying agent and the flocculating agent are used for separating and converting residual heavy metal ions in the liquid into a suspension state and accelerating the sedimentation speed;

the water purifying agent comprises, by mass, 8-10% of sodium bicarbonate, 15-18% of hydrogen peroxide, 10-12% of sodium dichloroisocyanurate, 25-30% of sodium hypochlorite, 1-3% of potassium permanganate, 5% of sodium silicate, 10% of sodium chloride and 2-5% of boron nitride, and the balance of water;

introducing the supernatant obtained after the precipitation treatment in the step three into a high-efficiency filtering system composed of inorganic matters with different particles, and simultaneously adding a flocculating agent to flocculate and precipitate suspended matters in the liquid and filter out, wherein the high-efficiency filtering system is an FBL filter;

and fifthly, introducing the filtered liquid in the step four into a second regulating tank, adding sulfuric acid with a preset concentration to regulate the PH value to be between 6.0 and 9.0, and discharging supernatant after precipitation treatment.

2. The method for treating zinc smelting wastewater according to claim 1, wherein: in the first step, the concentration of lime milk is 20 percent, and

in the second step, the ratio of the dosage of the COD degrading agent, the quick flocculant, the high-efficiency coagulant and the lime milk to the total amount of the liquid introduced into the first-stage reaction tank is respectively as follows: 0.1% -0.4%, 0.6% -2.4%, 0.8% -1.0% and 0.8-4%; and

in the third step, the ratio of the amount of the water purifying agent and the flocculating agent to the total amount of the liquid introduced into the second-stage reaction tank is respectively as follows: 0.18% -0.23% and 0.6% -0.91%

In the fifth step, the predetermined concentration of sulfuric acid is 10% -15%;

the COD degrading agent contains 50-60% FeSO by mass percent ₄ ·7H ₂ O,5-10% ZrOCl ₂ ·8H ₂ O,10-15% Ca (ClO) ₂ And 5-10% NaH ₂ PO ₄ ·2H ₂ O, the balance being water; wherein Ca (ClO) ₂ The effective chlorine content is more than or equal to 65 percent for industrial grade.

3. The method for treating zinc smelting wastewater according to claim 1, wherein: in the third step, before the supernatant obtained after the precipitation treatment in the first-stage reaction tank is introduced into the second-stage reaction tank, the method further comprises the following steps:

introducing the supernatant obtained after the precipitation treatment in the first-stage reaction tank into a first-stage thickening tank for further precipitation treatment, and introducing the supernatant obtained after the precipitation treatment into the second-stage reaction tank.

4. A method for treating zinc smelting wastewater according to claim 3, wherein: in the fourth step, before the supernatant obtained after the precipitation treatment in the second-stage reaction tank is introduced into the high-efficiency filtration system, the method further comprises the following steps:

introducing the supernatant obtained after the precipitation treatment in the second-stage reaction tank into a second-stage thickening tank for further precipitation treatment; and

and introducing the supernatant obtained after the precipitation treatment into an intermediate water tank for sand-lime separation treatment, and finally introducing discharged liquid after the sand-lime separation treatment into the efficient filtering system.

5. The method for treating zinc smelting wastewater according to claim 4, wherein: the method also comprises the following steps:

and conveying the sediment obtained after the sedimentation treatment of the regulating tank, the first-stage reaction tank and the first-stage thickening tank to a 6-meter thickening tank, and conveying the sediment in the 6-meter thickening tank to a slag filtering workshop for filter pressing treatment.

6. The method for treating zinc smelting wastewater according to claim 5, wherein: the method also comprises the following steps:

and conveying the sediment obtained after the precipitation treatment in the second-stage reaction tank and the second-stage thickening tank to an 8-meter thickening tank, and conveying the sediment in the 8-meter thickening tank to a slag filtering workshop for filter pressing treatment.

7. The method for treating zinc smelting wastewater according to claim 4, wherein: the method also comprises the following steps:

and (3) returning the suspension filtered in the step (IV) to the second-stage thickening tank, mixing the suspension with the supernatant obtained after the sedimentation treatment before the second-stage thickening tank, and carrying out sedimentation treatment.

8. The method for treating zinc smelting wastewater according to claim 4, wherein: the method also comprises the following steps:

and (3) introducing the supernatant obtained after the precipitation treatment of the second regulating tank in the step five into a total discharge tank to perform discharge.

9. The method for treating zinc smelting wastewater according to claim 8, wherein: the method also comprises the following steps:

if the water quality in the total drainage pool can not reach the standard, pumping the water in the total drainage pool to an accident pool, pumping the water into a first regulating pool for subsequent treatment, and discharging until the water quality in the total drainage pool is qualified.

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