CN103708679B - Treatment process for fluorine chemical wastewater - Google Patents

Abstract

The invention discloses a process for treating fluorine chemical waste water. The process comprises: first adjustment of fluorine chemical waste water, iron-carbon reaction pretreatment, iron-carbon precipitation, first calcium salt reaction, first calcium salt precipitation, second adjustment, biological Effluent discharge after electrocatalysis, aerobic contact oxidation, secondary calcium salt reaction and secondary precipitation. The process of the invention is used to treat waste water in the fluorine chemical industry, and the waste water treated by the process of the invention can not only meet the first-level standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996), but also has lower operating costs for waste water treatment.

Description

A treatment process for fluorine chemical wastewater

technical field

The invention relates to a process for treating chemical waste water, in particular to a process for treating fluorine chemical waste water.

Background technique

As a special material, organic fluoride has excellent properties and has been widely used in the preparation process of surfactants, flame retardants, refrigerants, pesticides, adhesives, medicines, etc. in recent years, which directly promotes the development of organic fluorine. With the rapid development of the industry, the discharge of fluorine chemical wastewater continues to increase. Inorganic fluoride ions in fluorine chemical wastewater enter the human body and can cause harm to multiple tissues such as human liver and kidney through cell transport;

The organic fluorine pollutants in fluorine chemical wastewater have teratogenic, carcinogenic and mutagenic properties, and some fluorinated aromatic hydrocarbons have been proposed as new POPs, so fluorine chemical wastewater must be properly treated. Generally speaking, the current fluorine chemical wastewater mainly has the characteristics of high salinity, strong biological toxicity and poor biochemical properties. The focus of fluorine chemical wastewater treatment is inorganic fluoride ion and organic fluoride. Among them, organic fluorine pollutants are very stable in nature and poor in biodegradability. This is mainly due to the strong polarity and maximum bond energy (bond energy of about 460kJ/mol) of the C-F bond in organic fluorides. The treatment efficiency of fluoride wastewater is low, and some advanced oxidation processes developed in recent years have high treatment costs.

At present, there is no mature and unified treatment process for fluorine chemical wastewater in the industry. Most fluorine chemical wastewater treatment processes use calcium salt precipitation to treat inorganic fluoride ions, and anaerobic acid hydrolysis plus aerobic treatment to treat organic fluorides. , but for these processes, there are mainly the following main problems:

(1) For the inorganic fluoride ion treatment technology dominated by calcium salt precipitation, since the calcium fluoride precipitation nucleus produced during the treatment process is extremely small, especially for wastewater with high inorganic fluoride ions, it is easy to form latex-like precipitates. The precipitation speed is extremely slow, which affects the efficiency of the entire treatment process.

(2) For inorganic fluoride ions to meet the standard, the current process often uses a large amount of excess calcium salt to precipitate and remove fluoride ions from wastewater, and the dosage is rarely quantified according to the actual fluoride ion content of wastewater. The waste of calcium salt reagents is poor in economy. In addition, the more important thing is that the excess calcium salt dosage greatly increases the salinity of wastewater, which makes the biochemical treatment of fluorine chemical wastewater with relatively high salinity more difficult.

(3) Since the crystal nuclei of calcium fluoride precipitation are very small, for wastewater with low concentration of inorganic fluoride ions, the amount of calcium fluoride precipitation produced when calcium salt is initially added is very small, and the crystal nuclei and flocs are extremely small. The current treatment process In the middle, it is mainly through adding a large amount of calcium salt, and the dosage can even reach hundreds or thousands of times the theoretical dosage to make the wastewater inorganic fluoride ion reach the standard, which also brings about the economical problem of waste of chemicals and the increase of wastewater salinity The problem.

(4) The main reason why organic fluorine in fluorine chemical wastewater is difficult to biodegrade is because C-F in organic matter is very stable, and current research has shown that it is difficult to interrupt C-F in a simple anaerobic treatment system, so the hydrolysis and acidification process is harmful to organic matter. Fluorine does not have a good pretreatment effect, which directly leads to the fact that it is still difficult to meet the COD standard of fluorine chemical wastewater after the current biochemical treatment process.

Contents of the invention

The invention provides a process for treating waste water of fluorine chemical industry. The waste water of fluorine chemical industry can not only meet the first-level standard of "Comprehensive Wastewater Discharge Standard" (GB8978-1996) after being treated by the process, but also the operating cost of waste water treatment is lower.

A treatment process for fluorine chemical waste water, comprising the steps of:

(1) The fluorine chemical wastewater enters the primary adjustment pool, in which the salinity of the fluorine chemical wastewater is adjusted to below 2%, the COD is adjusted to below 10000mg/L, and the pH value is adjusted to 3.5-4.5; The low-concentration fluorine chemical wastewater from different sources is used to regulate the fluorine chemical wastewater to be treated in the level regulation pool;

(2) The effluent from the primary regulating tank enters the iron-carbon reaction tank, and the pH value of the wastewater is adjusted to 3.5-4.5 for iron-carbon pretreatment, and compressed air is used for stirring during the iron-carbon reaction process;

(3) The effluent from the iron-carbon reaction tank flows to the iron-carbon sedimentation tank by itself, and the pH value is adjusted to 8.5-9.5 for flocculation and sedimentation;

(4) After the precipitation, the supernatant overflows into the first calcium salt reaction tank, adds calcium salt and polyacrylamide and adjusts the pH value to 7.5-8.5, stirs and reacts, and enters the first calcium salt precipitation tank to statically after the reaction is completed. Precipitation; through this process section, the concentration of inorganic fluoride ions in fluorine chemical wastewater is reduced to below 10mg/L, so as to avoid the poisonous effect of fluoride ions on microorganisms in the subsequent biochemical treatment system;

(5) The supernatant after precipitation in the first calcium salt sedimentation tank continues to overflow to the secondary adjustment tank to use domestic sewage to adjust the salinity of the wastewater to below 1.5%, and adjust the COD to below 5000mg/L;

(6) The effluent from the secondary regulating pool is injected into the bioelectrocatalytic cell for electrocatalytic reaction; bioelectrocatalysis strengthens the defluorination of organic fluorine pollutants to improve the biochemical properties of wastewater;

(7) The effluent from the bioelectrocatalytic cell is injected into the aerobic contact oxidation tank for advanced treatment to remove organic matter in the wastewater and make the COD reach the standard;

(8) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank, where calcium salt and polyacrylamide are added, and the reaction is stirred. After the reaction is completed, it enters the second calcium salt sedimentation tank for precipitation, and the effluent is discharged after the precipitation is completed.

In the present invention, the treatment of fluorine chemical wastewater is mainly divided into two parts, inorganic fluorine and organic fluorine, and the fluorine chemical wastewater in the fluorine chemical wastewater is treated up to the standard through the direct precipitation technology of high-concentration inorganic fluorine ion wastewater and the calcium salt precipitation and reflux technology of low-concentration inorganic fluorine wastewater. Inorganic fluoride ions; organic fluorine pollutants in fluorine chemical wastewater are finally made to meet the COD standard of wastewater under the synergistic coupling of iron-carbon process, bio-electrocatalytic process and aerobic contact oxidation process. The whole process is realized by conventional treatment equipment , low processing cost.

In the present invention, the combination of iron-carbon pretreatment process and bio-electrocatalytic oxidation process is used to reduce the toxicity of wastewater and improve the biochemical properties of wastewater, so that the organic matter in wastewater can be mineralized to the greatest extent in the aerobic contact oxidation tank to make the COD of wastewater It can finally reach the discharge standard, and the various process steps cooperate with each other to enhance the treatment effect of wastewater.

As a preference, the iron-carbon filler is laid in the iron-carbon reaction tank in step (2), and the Fe/C of the iron-carbon filler is 0.8～1.2:1; the liquid-solid volume ratio of the iron-carbon filler and waste water is 9.5～10.5:1, more Preferably, the Fe/C of the iron-carbon filler is 1:1; the liquid-solid volume ratio of the iron-carbon filler to wastewater is 10:1. Preferably, the calcium salt in step (3) is slaked lime, and the dosage is 150%-200% of the theoretical dosage; the dosage of the polyacrylamide is 2.5-3.0mg per liter of waste water.

Preferably, when the fluoride ion concentration in the wastewater entering the first calcium salt reaction tank is below 1000 mg/L, the sludge in the first calcium salt precipitation tank is returned to the first calcium salt reaction tank.

Further preferably, when the fluoride ion concentration in the wastewater entering the first calcium salt reaction tank is within 100mg/L, the sludge reflux ratio is controlled to be 70-80%; when the fluoride ion concentration of the wastewater entering the first calcium salt reaction tank When the concentration is 100-1000mg/L, the reflux ratio of the control sludge is 20-30%.

When the fluoride ion concentration in the wastewater is lower than 1000mg/L, it is difficult to form calcium fluoride crystal nucleus after adding calcium salt, and it is difficult to precipitate. At this time, it is necessary to add a large amount of calcium salt to form crystal nucleus and promote the growth of crystal nucleus , which not only causes the waste of precipitant but also increases the difficulty and cost of subsequent treatment steps because the salinity of wastewater will increase. The present invention adds a reflux process in this step. When the fluoride ion concentration of wastewater entering the calcium salt reaction tank is lower than When the concentration is 1000mg/L, the sludge in the calcium salt sedimentation tank is returned to the calcium salt reaction tank to accelerate the growth of calcium fluoride crystal nuclei in the calcium salt reaction tank, speed up the reaction speed, reduce the use of precipitant, and save treatment Cost, and at the same time more conducive to the subsequent steps.

Preferably, the current density in the bioelectrocatalytic cell in step (6) is 9.5-10.5 A/m ³ .

Preferably, when the fluoride ion concentration in the wastewater entering the second calcium salt reaction tank is below 1000 mg/L, the sludge in the second calcium salt precipitation tank is returned to the second calcium salt reaction tank.

Further preferably, when the fluoride ion concentration in the waste water entering the second calcium salt reaction tank is within 100mg/L, the control sludge reflux ratio is 75%; when entering the second calcium salt reaction tank, the fluoride ion concentration in the waste water is When the concentration is 100-1000mg/L, the reflux ratio of the control sludge is 25%.

Preferably, the hydraulic retention time of the iron-carbon reaction tank is 4 to 6 hours, the precipitation time of the iron-carbon sedimentation tank is 1 to 2 hours; the reaction time of the first calcium salt reaction tank is 0.5 to 1 h, and the The precipitation time of the first calcium salt sedimentation tank is 2～4h; the hydraulic retention time in the bioelectrocatalytic tank is 8～12h; the hydraulic retention time in the aerobic contact oxidation tank is 6～8h; the second calcium salt The reaction time of the salt reaction tank is 0.5-1 hour, and the precipitation time of the second calcium salt precipitation tank is 2-4 hours.

Preferably, the dissolved oxygen in the aerobic contact oxidation tank is controlled at 2-3 mg/L. .

The dosing type, dosage and dosing method of the precipitant in the second calcium salt reaction tank are the same as those in the first calcium salt reaction tank.

A more preferred technical solution, the treatment process of fluorine chemical wastewater, comprises the following steps:

(1) The fluorine chemical wastewater enters the primary adjustment pool, in which the salinity of the fluorine chemical wastewater is adjusted to below 2%, the COD is adjusted to below 10000mg/L, and the pH value is adjusted to 3.5-4.5;

(2) The effluent from the primary regulating tank enters the iron-carbon reaction tank, and the pH value of the wastewater is adjusted to 3.5-4.5 for iron-carbon pretreatment. During the iron-carbon reaction process, compressed air is used for stirring; iron-carbon filler is laid in the iron-carbon reaction tank, and iron-carbon The Fe/C of the filler is 1:1; the liquid-solid volume ratio between the iron-carbon filler and the wastewater is 10:1; the calcium salt is slaked lime, and the dosage is 150% to 200% of the theoretical dosage; the polyacrylamide The dosage is 2.5~3.0mg per liter of wastewater; the hydraulic retention time of the iron-carbon reaction tank is 4~6h;

(3) The effluent from the iron-carbon reaction tank flows automatically to the iron-carbon sedimentation tank, and the pH value is adjusted to 8.5-9.5 for flocculation and sedimentation; the sedimentation time of the iron-carbon sedimentation tank is 1-2 hours;

(4) After the precipitation, the supernatant overflows into the first calcium salt reaction tank, adds calcium salt and polyacrylamide and adjusts the pH value to 7.5-8.5, stirs and reacts, and enters the first calcium salt precipitation tank to statically after the reaction is completed. Precipitation; the reaction time of the first calcium salt reaction tank is 0.5～1h, and the precipitation time of the first calcium salt precipitation tank is 2～4h;

In this step: when the fluorine ion concentration of the wastewater entering the first calcium salt reaction tank is within 100 mg/L, return the sludge from the first calcium salt sedimentation tank to the first calcium salt reaction tank to control the sludge return ratio is 70-80%; when the fluoride ion concentration of the wastewater entering the first calcium salt reaction tank is 100-1000mg/L, the sludge in the first calcium salt sedimentation tank is returned to the first calcium salt reaction tank to control The reflux ratio of sludge is 20-30%;

(5) The supernatant after precipitation in the first calcium salt sedimentation tank continues to overflow to the secondary adjustment tank to adjust the salinity of the wastewater to below 1.5%, and adjust the COD to below 5000mg/L;

(6) The effluent from the secondary adjustment pool is injected into the bio-electrocatalytic cell for electro-catalytic reaction to further improve the biochemical properties of the wastewater; the current density in the bio-electro-catalytic cell is 9.5-10.5A/m ³ ; the hydraulic retention time in the bio-electro-catalytic cell is 8 ~12h;

(7) The effluent from the bioelectrocatalytic tank is injected into the aerobic contact oxidation tank for advanced treatment to remove organic matter in the wastewater and make the COD reach the standard; the dissolved oxygen concentration in the aerobic contact oxidation tank is controlled at 2-3mg/L; the hydraulic pressure in the aerobic contact oxidation tank The residence time is 6~8h;

(8) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank, where calcium salt and polyacrylamide are added, and the reaction is stirred. After the reaction is completed, it enters the second calcium salt sedimentation tank for precipitation, and the effluent is discharged after the precipitation is completed; the second The reaction time of the calcium salt reaction tank is 0.5 to 1 hour, and the precipitation time of the second calcium salt precipitation tank is 2 to 4 hours;

In this step:

When the fluorine ion concentration of the wastewater entering the second calcium salt reaction tank is within 100mg/L, return the sludge from the second calcium salt sedimentation tank to the second calcium salt reaction tank, and control the sludge return ratio to 70-80 %; When the fluoride ion concentration of the wastewater entering the second calcium salt reaction tank is 100-1000 mg/L, return the sludge from the second calcium salt sedimentation tank to the second calcium salt reaction tank to control the return of the sludge The ratio is 20-30%.

The present invention has following beneficial effects:

(1) Due to the use of polyacrylamide as a coagulant, the formed calcium fluoride crystal nuclei can grow rapidly and gather into large flocs, which greatly shortens the precipitation time in the calcium salt sedimentation tank without adding any equipment In the case of increased wastewater treatment capacity.

(2) The dosage of calcium salt is quantitatively added according to the concentration of fluoride ions in the actual wastewater. For the treatment of fluoride ions in low-concentration inorganic fluoride ion wastewater, the fluorine chemical sludge reflux technology is used, which not only saves the cost of chemical addition, but also avoids The problem of further increase in the salinity of wastewater caused by excessive dosage of chemicals has been solved.

(3) For organic fluorine pollutants in wastewater, the combination of iron-carbon pretreatment process and bio-electrocatalytic oxidation process is used to reduce the toxicity of wastewater and improve the biochemical properties of wastewater, so that the organic matter in wastewater can be absorbed in the aerobic contact oxidation pool Maximize the mineralization so that the COD of the wastewater can finally meet the standard discharge.

Description of drawings

Fig. 1 is the flow chart of the embodiment of wastewater treatment process of the present invention

Detailed ways

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is the flowchart of the waste water treatment process embodiment of the present invention, the waste water treatment process of the present embodiment mainly comprises the following steps:

(1) The wastewater from the fluorine chemical industry enters the primary adjustment pool for pH adjustment. For wastewater with high concentration (salinity above 20mg/L and COD above 10000mg/L), low-concentration fluorine chemical wastewater is used for dilution adjustment of a certain number of times. , while adjusting, adjust the pH value of wastewater by adding acid or alkali;

(2) The adjusted wastewater is pumped to the iron-carbon reaction tank, stirred with compressed air in the iron-carbon tank, and industrial waste acid or alkali is added through the online pH control dosing pump to maintain the pH value of the reaction in the tank;

(3) After the reaction, the wastewater flows to the iron-carbon radial flow sedimentation tank by itself, and the pH value of the wastewater is adjusted to carry out flocculation and sedimentation, and the precipitated sludge enters the sludge concentration tank to concentrate and then press filter to remove water;

(4) The supernatant of the precipitated waste water in the iron-carbon sedimentation tank overflows to the first calcium salt reaction tank, and is added with milk of lime calcium salt and polyacrylamide to adjust the pH value, and enters the first calcium salt after stirring and reacting Sedimentation tank, static precipitation; in this step, select whether to carry out sludge return according to the fluoride ion concentration in the wastewater entering the first calcium salt reaction tank;

(5) The supernatant after the calcium salt precipitation continues to overflow to the secondary adjustment tank, and the domestic sewage is used as the adjustment liquid to control the salinity of the subsequent biochemical system to be lower than 20g/L, and the COD concentration of the influent to be lower than 5000mg/L , and regulate the biochemical properties of wastewater to a certain extent;

(6) The effluent from the secondary adjustment is pumped to the bio-electrocatalytic cell, and the wastewater reaches a biochemical level after bio-electrocatalysis;

(7) The bioelectrocatalytic effluent is sent to the aerobic contact oxidation tank by pump pressure, and compressed air is blown in to control the dissolved oxygen concentration in the aerobic contact oxidation tank to oxidize and decompose the organic matter in the wastewater;

(8) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank after sedimentation in the secondary sedimentation tank, and calcium salt and polyacrylamide are added (the dosage of both is the same as that of the first calcium salt reaction tank) , stirring the reaction, after the reaction is completed, enter the second calcium salt precipitation tank for precipitation, and discharge the effluent after the precipitation is completed. In this step, it is selected whether to carry out sludge reflux according to the concentration of fluoride ions in the wastewater entering the first calcium salt reaction tank; after the wastewater is treated by this treatment process, it can meet the first-level standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996).

In the following examples, three types of fluorine chemical wastewater of a certain chemical enterprise with different water qualities were treated with the above-mentioned wastewater treatment process.

Example 1

(1) The wastewater is pumped to the iron-carbon reaction tank, stirred with compressed air in the iron-carbon tank, and industrial waste acid or waste alkali is added through the online pH control dosing pump to maintain the pH value of the reaction in the tank; the iron-carbon reaction tank is laid Iron-carbon filler, the Fe/C of iron-carbon filler is 1:1; the liquid-solid volume ratio of iron-carbon filler to wastewater is 10:1; the hydraulic retention time of iron-carbon reaction tank is 4h;

(2) After the reaction, the wastewater flows to the iron-carbon sedimentation tank by itself, and the pH value of the wastewater is adjusted for flocculation and sedimentation. The precipitated sludge enters the sludge thickening tank to concentrate and then is filtered to remove water; the sedimentation time of the iron-carbon sedimentation tank is 1h;

(3) The supernatant of the precipitated wastewater in the iron-carbon sedimentation tank overflows to the first calcium salt reaction tank, and the milk of lime calcium salt and polyacrylamide are added (the dosage of calcium salt is completely equal to the fluoride ion content in the wastewater. Add 200% of the theoretical calcium salt required for precipitation, and the dosage of polyacrylamide is 2.5mg per liter of wastewater), and adjust the pH value, stir and react, enter the first calcium salt sedimentation tank, and let it settle; In this step, select whether to carry out sludge reflux according to the fluoride ion concentration in the waste water entering the first calcium salt reaction tank; the reaction time of the first calcium salt reaction tank is 0.5h, and the precipitation time of the first calcium salt sedimentation tank is 2h; In the step, the sludge in the first calcium salt sedimentation tank is returned to the first calcium salt reaction tank, and the reflux ratio is 25%;

(4) The effluent from the first calcium salt sedimentation tank is pumped to the bio-electrocatalytic pool, and the wastewater reaches a biochemical level after bio-electro-catalysis; the current density in the bio-electro-catalytic oxidation pool is 10A/m ³ ; the bio-electro-catalytic The hydraulic retention time in the oxidation tank is 12h;

(5) The bio-electrocatalytic effluent is sent to the aerobic contact oxidation tank by pump pressure, and compressed air is blown in to control the dissolved oxygen concentration in the aerobic contact oxidation tank to 3 mg/L to oxidize and decompose the organic matter in the wastewater; the hydraulic retention time is 6h;

(6) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank after being precipitated by the secondary sedimentation tank, and calcium salt and polyacrylamide are added (the dosage of both is the same as that of the first calcium salt reaction tank) , stirring reaction, after the reaction is completed, enter the second calcium salt sedimentation tank for precipitation, in this step, the sludge in the second calcium salt sedimentation tank is returned to the second calcium salt reaction tank, the reflux ratio is 75%; after the precipitation, the water is discharged emission.

After the entire process treatment, the fluoride ion and COD in the fluorine chemical wastewater can reach the first-level standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996). The results of the effluent quality after each treatment process are shown in Table 1:

Table 1

Note: "/" indicates that the wastewater has not undergone this process step, "—" indicates that the index has not been measured, the same below.

Example 2

(1) The wastewater from the fluorine chemical industry enters the first-level adjustment pool for pH adjustment, and the low-concentration fluorine chemical wastewater in Table 2 is used for adjustment. The raw water and the low-concentration fluorine chemical wastewater are diluted and adjusted at a volume ratio of 1:4, and the pH of the wastewater is adjusted. value;

(2) The adjusted wastewater is pumped to the iron-carbon reaction tank, stirred with compressed air in the iron-carbon tank, and industrial waste acid or alkali is added through the online pH control dosing pump to maintain the pH value of the reaction in the tank; The iron-carbon filler is laid in the carbon reaction tank, and the Fe/C of the iron-carbon filler is 1:1; the liquid-solid volume ratio of the iron-carbon filler to the waste water is 10:1; the hydraulic retention time of the iron-carbon reaction tank is 5h; (3) Reaction Finally, the wastewater flows to the iron-carbon radial flow sedimentation tank by itself, and the pH value of the wastewater is adjusted for flocculation and sedimentation. The sedimented sludge enters the sludge thickening tank to concentrate and then undergoes pressure filtration to remove water; the sedimentation time of the iron-carbon sedimentation tank is 1.5h;

(4) The supernatant of the precipitated wastewater in the iron-carbon sedimentation tank overflows to the first calcium salt reaction tank, and the milk of lime calcium salt and polyacrylamide are added (the dosage of calcium salt is completely equal to the fluoride ion content in the wastewater. Add 200% of the theoretical calcium salt required for precipitation, and the dosage of polyacrylamide is 2.5mg per liter of wastewater), and adjust the pH value, stir and react, enter the first calcium salt sedimentation tank, and let it settle; The reaction time of the first calcium salt reaction tank is 0.75h, and the sedimentation time of the first calcium salt sedimentation tank is 3h; sludge reflux is not carried out in this step;

(5) The supernatant after the calcium salt precipitation continues to overflow to the secondary adjustment tank, and the domestic sewage is used as the adjustment liquid to control the salinity of the subsequent biochemical system to be lower than 20g/L, and the COD concentration of the influent to be lower than 5000mg/L , and regulate the biochemical properties of wastewater to a certain extent;

(6) The effluent from the secondary adjustment is pumped to the bio-electrocatalytic cell, and the wastewater reaches a biochemical level after bio-electro-catalysis; the current density in the bio-electro-catalytic oxidation cell is 10.5A/m ³ ; the bio-electro-catalytic oxidation cell The hydraulic retention time is 10h;

(7) The bio-electrocatalytic effluent is sent to the aerobic contact oxidation tank by pump pressure, and compressed air is blown in to control the dissolved oxygen concentration in the aerobic contact oxidation tank to 3 mg/L to oxidize and decompose the organic matter in the wastewater; the hydraulic retention time is 7h;

(8) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank after sedimentation in the secondary sedimentation tank, and calcium salt and polyacrylamide are added (the dosage of both is the same as that of the first calcium salt reaction tank) , stirring reaction, enter the second calcium salt sedimentation tank to precipitate after the reaction is completed, the reaction time of the first calcium salt reaction tank is 0.75h, and the precipitation time of the first calcium salt precipitation tank is 3h; In this step, the second calcium salt The sludge in the sedimentation tank is returned to the second calcium salt reaction tank with a reflux ratio of 75%; after the sedimentation is completed, the effluent is discharged.

After the whole process treatment, the fluoride ions and COD in the fluorine chemical wastewater can reach the first-level standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996), and the treatment results are shown in Table 3.

Table 2

table 3

Example 3

(1) The wastewater enters the first-level adjustment tank for pH adjustment, and the low-concentration fluorine chemical wastewater in Table 2 is used for adjustment, and the raw water and the low-concentration fluorine chemical wastewater are diluted and adjusted at a volume ratio of 1:9, and the pH value of the wastewater is adjusted;

(2) The adjusted wastewater is pumped to the iron-carbon reaction tank, stirred with compressed air in the iron-carbon tank, and industrial waste acid or waste alkali is added through the online pH control dosing pump to maintain the pH value of the reaction in the tank; The iron-carbon filler is laid in the reaction tank, and the Fe/C of the iron-carbon filler is 1:1; the liquid-solid volume ratio of the iron-carbon filler to the waste water is 10:1; the hydraulic retention time of the iron-carbon reaction tank is 6h;

(3) After the reaction, the wastewater flows to the iron-carbon radial flow sedimentation tank by itself, and the pH value of the wastewater is adjusted for flocculation and sedimentation. The precipitated sludge enters the sludge thickening tank to concentrate and then is filtered to remove water; the sedimentation time of the iron-carbon sedimentation tank is 2h ;

(4) The supernatant of the precipitated wastewater in the iron-carbon sedimentation tank overflows to the first calcium salt reaction tank, and the milk of lime calcium salt and polyacrylamide are added (the dosage of calcium salt is completely equal to the fluoride ion content in the wastewater. Add 200% of the theoretical calcium salt required for precipitation, and the dosage of polyacrylamide is 2.5mg per liter of wastewater), and adjust the pH value, stir and react, enter the first calcium salt sedimentation tank, and let it settle; Sludge reflux is not carried out in this step; the reaction time of the first calcium salt reaction tank is 1h, and the precipitation time of the first calcium salt sedimentation tank is 4h;

(5) The supernatant after the calcium salt precipitation continues to overflow to the secondary adjustment tank, and the domestic sewage is used as the adjustment liquid to control the salinity of the subsequent biochemical system to be lower than 20g/L, and the COD concentration of the influent to be lower than 5000mg/L , and regulate the biochemical properties of wastewater to a certain extent;

(6) The effluent from the secondary adjustment is pumped to the bio-electrocatalytic cell, and the wastewater reaches a biochemical level after bio-electro-catalysis; the current density in the bio-electro-catalytic oxidation cell is 9.5A/m ³ ; the bio-electro-catalytic oxidation cell The hydraulic retention time is 12h;

(7) The bio-electrocatalytic effluent is sent to the aerobic contact oxidation tank by pump pressure, and compressed air is blown in to control the dissolved oxygen concentration in the aerobic contact oxidation tank to 3.0mg/L, so as to oxidize and decompose the organic matter in the wastewater; hydraulic retention time for 8h;

(8) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank after sedimentation in the secondary sedimentation tank, and calcium salt and polyacrylamide are added (the dosage of both is the same as that of the first calcium salt reaction tank) , stirring reaction, after the reaction is completed, enter the second calcium salt sedimentation tank for precipitation, in this step, the sludge in the second calcium salt sedimentation tank is returned to the second calcium salt reaction tank, and the reflux ratio is 75%; the first calcium salt The reaction time of the reaction tank is 1 hour, and the precipitation time of the first calcium salt precipitation tank is 4 hours; after the precipitation is completed, the effluent is discharged. The results are shown in Table 4:

Table 4

From the results of the above examples, it can be seen that after the whole process treatment, the fluoride ions and COD in the fluorine chemical wastewater can reach the first-level standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996).

Claims (6)

1. a process for the treatment of fluorine chemical waste water, is characterized in that, comprises the steps: (1) The fluorine chemical industry wastewater enters the primary regulation pool, in which the salinity of the fluorine chemical industry wastewater is adjusted to be below 2%, the COD is adjusted to be below 10000mg/L, and the pH value is adjusted to 3.5-4.5; (2) The effluent from the primary adjustment pool enters the iron-carbon reaction tank, and the pH value of the wastewater is controlled to be 3.5 to 4.5 for iron-carbon pretreatment, and compressed air is used for stirring during the iron-carbon reaction process; (3) The effluent from the iron-carbon reaction tank flows to the iron-carbon sedimentation tank by itself, and the pH value is adjusted to 8.5-9.5 for flocculation and precipitation; (4) After the precipitation, the supernatant overflows into the first calcium salt reaction tank, adds calcium salt and polyacrylamide and adjusts the pH value to 7.5-8.5, stirs and reacts, and enters the first calcium salt precipitation tank to statically after the reaction is completed. settling; (5) The supernatant after precipitation in the first calcium salt sedimentation tank continues to overflow to the secondary adjustment tank to adjust the salinity of the wastewater to below 1.5% with domestic sewage, and the COD is below 5000mg/L; (6) The effluent from the secondary regulating pool is injected into the bio-electrocatalytic cell for electrocatalytic reaction; (7) The effluent from the bioelectrocatalytic cell is injected into the aerobic contact oxidation tank for advanced treatment to remove organic matter in the wastewater and make the COD reach the standard; (8) The effluent from the aerobic contact oxidation tank enters the second calcium salt reaction tank, add calcium salt and polyacrylamide and adjust the pH value to 7.5-8.5, stir and react, and enter the second calcium salt precipitation tank for precipitation after the reaction is completed. After the precipitation is completed, the effluent is discharged; When the fluoride ion concentration in the wastewater entering the first calcium salt reaction tank is below 1000mg/L, the sludge in the first calcium salt precipitation tank is returned to the first calcium salt reaction tank; When the fluoride ion concentration in the wastewater entering the first calcium salt reaction tank is within 100 mg/L, the sludge reflux ratio is controlled to be 70-80%; when the fluoride ion concentration of the wastewater entering the first calcium salt reaction tank is 100 -1000mg/L, control the reflux ratio of sludge to 20-30%; When the fluoride ion concentration in the wastewater entering the second calcium salt reaction tank is below 1000mg/L, the sludge in the second calcium salt precipitation tank is returned to the second calcium salt reaction tank; When the fluoride ion concentration in the wastewater entering the second calcium salt reaction tank is within 100mg/L, the sludge reflux ratio is controlled to be 70-80%; when the fluoride ion concentration of the wastewater entering the second calcium salt reaction tank is 100 -1000mg/L, control the reflux ratio of sludge to 20-30%. 2. according to the treatment process of the described fluorine chemical waste water of claim 1, it is characterized in that, in the iron-carbon reaction tank in the step (2), iron-carbon filler is laid, and the Fe/C of iron-carbon filler is 0.8～1.2:1; The liquid-solid volume ratio of filler to waste water is 9.5-10.5:1. 3. The process for treating fluorine chemical wastewater according to claim 1, wherein the calcium salt in step (3) is slaked lime, and the dosage is 150% to 200% of the theoretical dosage; the polypropylene The dosage of amide is 2.5-3.0mg per liter of waste water. 4. The process for treating fluorine chemical wastewater according to claim 1, characterized in that the current density in the bio-electrocatalytic cell in step (6) is 9.5-10.5 A/m ³ . 5. The treatment process of fluorine chemical industry wastewater according to claim 1, characterized in that, the hydraulic retention time of the iron-carbon reaction tank is 4 to 6 hours, and the settling time of the iron-carbon sedimentation tank is 1 to 2 hours; The reaction time of the first calcium salt reaction tank is 0.5～1h, the precipitation time of the first calcium salt precipitation tank is 2～4h; the hydraulic retention time in the bioelectrocatalytic tank is 8～12h; the aerobic contact The hydraulic retention time in the oxidation tank is 6-8 hours; the reaction time of the second calcium salt reaction tank is 0.5-1 hour, and the precipitation time of the second calcium salt precipitation tank is 2-4 hours. 6. The treatment process of fluorine chemical wastewater according to claim 1, characterized in that the dissolved oxygen in the aerobic contact oxidation tank is controlled at 2-3mg/L.