CN110981074A - Treatment method for treating organic silicon production wastewater - Google Patents

Abstract

The invention discloses a method for treating organic silicon production wastewater, which comprises the following steps: introducing the organic silicon wastewater into an air flotation process to remove floating oil in the wastewater, collecting the floating oil, returning the collected floating oil to a production recovery process for treatment, introducing air flotation effluent into a pH adjusting tank, adjusting the pH value to 3-4, introducing the effluent into a Fenton oxidation tank, and adding a ferrous sulfate solution and hydrogen peroxide to perform a Fenton oxidation reaction; introducing the wastewater after Fenton oxidation into a multi-effect evaporation system, evaporating to remove salt, pumping an evaporation condensate into a biochemical system, and biologically degrading organic matters in the wastewater by using an activated sludge method and adopting a treatment process combining aerobic hydrolysis and continuous aerobic treatment; carrying out the outward transportation treatment of the residual sludge, carrying out sludge-water separation on biochemical aerobic effluent, and carrying out hydrogen peroxide-ozone coupling oxidation on supernatant fluid to finally realize that COD is less than or equal to 60 mg/L.

Description

Treatment method for treating organic silicon production wastewater

Technical Field

The invention belongs to the field of sewage treatment, and particularly relates to a method for treating organic silicon wastewater.

Background

The organic silicon waste water mainly contains methanol, chloromethane, organic halogen silane, high polymer silicone oil, silicone resin, silicone rubber, silicon intermediate and other substances, and the water contains a large amount of chloride ions and has poor biodegradability. The main process principle of organic silicon production in the prior art is as follows: synthesis of methane chloride, synthesis of dimethyldichlorosilane monomer, hydrolysis of dimethyldichlorosilane monomer, and cracking and rectification of siloxane. From the whole production process, the production of the organic silicon takes methanol, hydrogen chloride and silicon powder as raw materials, and zinc, copper and the like as catalysts. However, the finished product does not contain chlorine components, and except that a small part of high-concentration hydrogen chloride can be recycled, most of the hydrogen chloride is mixed into production wastewater. Methanol and hydrogen chloride which are not completely reacted exist in the production process, and impurities such as dichloromethane, trichloromethane, carbon tetrachloride and the like generated in the synthesis process.

The difficulty of the wastewater treatment mainly lies in that adsorbable organic halides such as 1, organochlorosilane, chloralkane and the like have inhibition on microorganisms. 2. The waste water is strongly acidic, the chloride ion content is high, the salt content is high after neutralization, and the TDS concentration of 30000-. 3. The organic pollutants have obvious characteristic pollutant properties and contain silicon elements, wherein silicon-oxygen bond energy is large, biodegradation and chain scission are difficult, the organic pollutants are always in a water body and cannot be completely degraded, and if the silicon elements in the organic silicon are not completely degraded, a higher COD value can be embodied in wastewater, so that effluent is difficult to reach COD (chemical oxygen demand) less than or equal to 60 mg/L.

At present, the conventional treatment method adopts multi-effect evaporation, and separates salt and partial characteristic pollutants from kettle residue in a separation mode, at the moment, the evaporation condensate enters subsequent biochemical treatment, and because the evaporation condensate still contains a small amount of siloxane and organosilicon, the components cannot be completely mineralized by microorganisms, and the COD of the effluent can not reach 60mg/L

Li Jian, Gao Zhang Feng et al, modified with ozone, biochemically with high salt, and then oxidized with ozone. Because the concentration of the organosilicon which is difficult to biodegrade in the original wastewater is relatively high, the siloxane is more stable than other organic structures, the siloxane is difficult to break, the ozone dosage of the first section is difficult to crack the siloxane, the ozone oxidation of the second section is possible to annihilate ozone free radicals due to high chlorine in the water, the siloxane in the wastewater is always in the water body, a larger amount of ozone is consumed, and the COD is difficult to stably reach less than or equal to 60mg/L based on the factors.

The above shows that the organic silicon wastewater treatment process needs to preferentially evaporate and separate the salt and the characteristic pollutants of the organic silicon wastewater, and needs a chemical strong oxidation process capable of breaking silicon-oxygen bonds in the organic silicon and oxidizing silicon elements in the organic silicon into the highest valence state so as to make the organic silicon wastewater treatment process inorganic.

Disclosure of Invention

Aiming at the problems in the prior art, the invention discloses a method for effectively treating organic silicon wastewater with stable operation, and the method can be used for finally treating wastewater with high efficiency by utilizing the treatment processes of air floatation-Fenton oxidation combination, multi-effect evaporation and the like, so that the COD (chemical oxygen demand) is less than or equal to 60 mg/L.

The invention is realized by the following steps:

the treatment method for treating the organic silicon production wastewater comprises the following steps:

pumping organic silicon wastewater into a pH adjusting tank, and adding an alkaline reagent to adjust the pH to 3-4;

step two, introducing the wastewater pretreated in the step one into an air floatation tank, removing floating oil in the wastewater through an air floatation process, and separately collecting the floating oil to a workshop for recycling a pretreatment process;

step three, adding 2-8% ferrous sulfate solution and 27.5% hydrogen peroxide into the air flotation effluent according to the proportion, introducing the mixture into a Fenton oxidation tank, adding 1-10kg hydrogen peroxide into each ton of wastewater, reacting for 2-4 h,

performing Fenton oxidation reaction;

step four, introducing the wastewater obtained in the step three and sludge into a sedimentation tank together, adding a coagulant, realizing sludge-water separation under the action of gravity, discharging the sludge into a sludge concentration tank, and discharging clear liquid;

step five, introducing the supernatant obtained in the step four into an evaporation water inlet pool; adding an acidic reagent to adjust the pH value to 6-9;

step six, introducing the wastewater obtained in the step five into a multi-effect evaporator, evaporating and desalting, introducing an evaporation condensate into a biochemical water inlet tank, and after an evaporation process, forming evaporation kettle residues by a mixture of salts and high-boiling-point organic matters in the wastewater, and carrying out external transportation on the evaporation kettle residues; the evaporation kettle residue refers to salt, high-boiling point organic matters and a very small amount of water which are separated in the evaporation process.

Introducing the evaporation condensate into a facultative hydrolysis pool, controlling the water temperature to be 20-35 ℃, carrying out facultative hydrolysis for 12-48 hours in a water body through a biochemical reaction form, destroying the structure of organic matters in the wastewater through the biochemical reaction, degrading partial organic matters, and improving the biodegradability of the wastewater;

step eight, continuously introducing the water into an aerobic reaction tank, adjusting the pH to 7-9, controlling the water temperature to be 20-35 ℃ for biochemical reaction, performing primary aerobic reaction for 12-48 hours, and controlling the dissolved oxygen in the aerobic tank to be 2-4 mg/L; .

Step nine, introducing the wastewater obtained in the step eight and the sludge mixed liquor into a secondary sedimentation tank, adding a coagulant, realizing sludge-water separation under the action of gravity, discharging supernatant, and transporting sludge;

step ten, introducing the supernatant obtained in the step nine into an ozone-hydrogen peroxide coupling oxidation reactor, and adding hydrogen peroxide and ozone; and blowing wastewater into the reactor by using the venturi ejector, wherein the reactor forms micro-positive pressure, and the reaction time is 5-30 min.

Further, the acidic reagent is hydrochloric acid or sulfuric acid, and the alkaline reagent is one of sodium hydroxide/potassium hydroxide/calcium hydroxide; the coagulant is one of polyacrylamide, polyaluminium chloride and ferrous sulfate.

Further, the mass ratio of the ferrous sulfate solution to the hydrogen peroxide in the third step is 1.5-10: 1.

Further, the biochemical reaction forms in the seventh step and the eighth step comprise an activated sludge method, a biofilm method and a membrane biological method, and organic matters are degraded through biochemical reactions of the activated sludge method, the biofilm method and the membrane biological method. The activated sludge can be sludge of a municipal sewage treatment plant and can also be a compound microbial community screened by engineering application.

Further, in the step ten, the adding amount of ozone is 3-5: 1 of the mass ratio of the total COD of the wastewater; the addition of the hydrogen peroxide is 0.5-5 per mill of the mass of the wastewater; the micro-positive pressure is micro 0.01-0.05 MPa.

Compared with the prior art, the invention has the beneficial effects that:

1. the air flotation-Fenton oxidation pretreatment process comprises the steps of removing floating oil in wastewater by air flotation, recycling the wastewater after recovery treatment and reusing the wastewater in the production process, and modifying the wastewater by the Fenton oxidation process to remove heavy metals in the wastewater, improve the viscosity of the water quality of the wastewater and reduce the foaming and scaling phenomena in the subsequent multi-effect evaporation process.

2. The separation of salinity and most organosilicon characteristic pollutants in the wastewater is realized by a multi-effect evaporation process, the salinity of the evaporation condensate is less than 1000mg/L, the total silicon is less than 100mg/L, the organosilicon is less than 80mg/L, and the removal of the salinity is easy for biological degradation and the negative influence of high chlorine of a terminal ozone process. The reduction of organic silicon and total silicon reduces the influence of the toxicity of the wastewater on subsequent biochemistry, and simultaneously reduces the ozone dosage of terminal ozone oxidation.

3. The biochemical process of activated sludge A-O includes hydrolyzing and acidifying by facultative bacteria, dechlorinating chloromethane organic matter to produce methane and alcohol matter and breaking chain with small amount of organosilicon under anoxic condition. In the aerobic section, under the action of the metabolism of aerobic bacteria, the biochemical substances in the wastewater are degraded, the COD value is greatly reduced, and organic matters such as organosilicon and siloxane which are difficult to degrade are remained. Thereby reducing the investment cost and the operation cost of the rear-end ozone oxidation; the process of the invention is an integrated invention aiming at the process of treating the organic silicon wastewater, and has the requirements of specific sequences of the process.

4. The ozone-coupled hydrogen peroxide oxidation process can oxidize organic silicon characteristic pollutants such as siloxane and the like by using hydrogen peroxide and ozone together, and has the COD removal rate as high as 70 percent and the organic silicon removal rate as high as 80 percent. Compared with single oxidant ozone, the oxidation removal rate is improved by 50%; the whole process is effective, COD degradation is obvious, and the COD stability aiming at the organic silicon wastewater can reach less than 60 mg/L.

Drawings

FIG. 1 is a process flow diagram of the treatment method for treating wastewater from organosilicon production.

Detailed Description

In order to make the objects, technical solutions and effects of the present invention more clear, the present invention is further described in detail by the following examples. It should be noted that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The process flow diagram of the treatment method for treating the organic silicon production wastewater is shown in figure 1, the organic silicon production wastewater is introduced into an air floatation tank, after floating oil in the wastewater is removed, sodium hydroxide is added to adjust the pH value to 3, 14g of 2% ferrous sulfate solution and 5g of 27.5% hydrogen peroxide are added into each liter of air floatation water, Fenton oxidation reaction is carried out, and the reaction time is 2 hours; adjusting the pH value of the obtained wastewater to be more than 7 by adding sodium hydroxide, adding a coagulant, adding 5mg of coagulant into every 1L of wastewater, introducing the wastewater into a coagulating sedimentation tank, discharging supernatant, carrying out additional external treatment on sludge, introducing the supernatant into triple effect evaporation, evaporating to remove salt, using residual liquid in an evaporation kettle as dangerous solid waste, and conveying the dangerous solid waste to a dangerous waste treatment center. Introducing the evaporation condensate into a biochemical water inlet tank, controlling the water temperature to be 25 ℃, adding activated sludge into the water body, performing primary facultative hydrolysis biochemical reaction for 24 hours, destroying the structure of organic matters in the wastewater, and degrading partial organic matters; continuously introducing the water into an aerobic reaction tank, controlling the water temperature to be 25 ℃, adding activated sludge, carrying out aerobic reaction for 12 hours, and controlling the dissolved oxygen in the aerobic tank to be 2 mg/L; introducing the obtained wastewater and sludge mixed liquor into a secondary sedimentation tank, discharging supernatant, carrying out sludge outward, introducing the obtained supernatant into an ozone oxidation reactor, and adding 0.5ml of 27.5% hydrogen peroxide into every 1L of the supernatant, wherein the addition of ozone is 3 times of COD; the inside of the ozone reactor forms positive pressure of 0.02 MPa. COD of the ozone effluent is less than or equal to 60mg/L, and the specific parameters are shown in the following table 1;

TABLE 1

Index (I)	Raw water	air-float-Fenton	Evaporation of	A-O biochemistry	Ozone oxidation
						COD	1800	1253	796	188	48
Inorganic silicon	18	6	4	4	68
						Silicone	200	162	72	70	6
Total silicon	220	180	80	75	75

Example 2

Introducing the organic silicon production wastewater into an air floatation tank, removing floating oil in the wastewater, adding sodium hydroxide to adjust the pH to 4, adding 10g of 8% ferrous sulfate solution and 8g of 27.5% hydrogen peroxide into each liter of air floatation water, and performing Fenton oxidation reaction for 4 hours; adjusting the pH value of the obtained wastewater to be more than 7 by adding sodium hydroxide, adding a coagulant, adding 5mg of coagulant into every 1L of wastewater, introducing the wastewater into a coagulating sedimentation tank, discharging supernate, carrying out additional outward treatment on sludge, introducing the supernate into double-effect evaporation, evaporating to remove salt, using residual liquid in an evaporation kettle as dangerous solid waste, and conveying the dangerous solid waste to a dangerous waste treatment center. Introducing the evaporation condensate into a biochemical water inlet tank, controlling the water temperature to be 25 ℃, adding activated sludge into the water body, performing primary facultative hydrolysis biochemical reaction for 24 hours, destroying the structure of organic matters in the wastewater, and degrading partial organic matters; continuously introducing the water into an aerobic reaction tank, controlling the water temperature to be 25 ℃, adding activated sludge, carrying out aerobic reaction for 24 hours, and controlling the dissolved oxygen in the aerobic tank to be 3 mg/L; introducing the obtained wastewater and sludge mixed liquor into a secondary sedimentation tank, discharging supernatant, carrying out sludge outward, introducing the obtained supernatant into an ozone oxidation reactor, and adding 2ml of 27.5% hydrogen peroxide into every 1L of the supernatant, wherein the addition of ozone is 5 times of COD; the inside of the ozone reactor forms positive pressure of 0.05 MPa. COD of the ozone effluent is less than or equal to 60mg/L, and the specific parameters are shown in the following table 2;

TABLE 2

Index (I)	Raw water	air-float-Fenton	Evaporation of	A-O biochemistry	Ozone oxidation
						COD	2500	2170	1268	286	55
Inorganic silicon	18	8	5	5	89
						Silicone	230	172	88	88	5
Total silicon	250	200	96	96	96

Example 3

The process steps of this example 3 are substantially the same as those of example 2, except that in this example 3, no fenton or evaporation pretreatment is used, and the specific result data is shown in table 3:

TABLE 3

Index (I)	Raw water	Air-float	A-O biochemistry	Ozone oxidation
					COD	2500	2250	450	250
Inorganic silicon	18	18	28	108
					Silicone	230	215	200	120
Total silicon	250	230	230	230

By combining the table 2 and the table 3, the air flotation-Fenton oxidation pretreatment process of the invention can degrade biochemical substances in the wastewater, greatly reduce the COD value, and leave organic matters such as organosilicon and siloxane which are difficult to degrade. Wherein the air flotation removes the floating oil in the wastewater, the wastewater is recycled after recovery treatment and reused in the production process, the Fenton oxidation process modifies the wastewater, removes the heavy metals in the wastewater, improves the viscosity of the wastewater quality, and reduces the foaming and scaling phenomena in the subsequent multi-effect evaporation process

The above is only a preferred embodiment of the present invention, and the embodiment of the present invention can also be used in other data proportion ranges, for example, adding 2 to 8 mass percent ferrous sulfate solution and 27.5 mass percent hydrogen peroxide solution into the air flotation effluent to be fed into the fenton oxidation tank in proportion, adding 1 to 10kg hydrogen peroxide solution into each ton of wastewater, and performing the fenton oxidation reaction for 2 to 4 hours. It should be noted that modifications can be made by those skilled in the art without departing from the principle of the present invention, and these modifications should also be construed as the scope of the present invention.

Claims (5)

1. A treatment method for treating wastewater generated in organosilicon production is characterized by comprising the following steps:

pumping organic silicon wastewater into a pH adjusting tank, and adding an alkaline reagent to adjust the pH to 3-4;

step two, introducing the wastewater pretreated in the step one into an air floatation tank, removing floating oil in the wastewater through an air floatation process, and separately collecting the floating oil to a workshop for recycling a pretreatment process;

step three, feeding the air flotation effluent, 2-8% by mass of ferrous sulfate solution and 27.5% by mass of hydrogen peroxide into a Fenton oxidation tank in proportion, adding 1-10kg of hydrogen peroxide into each ton of wastewater, and reacting for 2-4 hours to perform Fenton oxidation reaction;

step four, introducing the wastewater obtained in the step three and sludge into a sedimentation tank together, adding a coagulant, realizing sludge-water separation under the action of gravity, discharging the sludge into a sludge concentration tank, and discharging clear liquid;

step five, introducing the supernatant obtained in the step four into an evaporation water inlet pool; adding an acidic reagent to adjust the pH value to 6-9;

step six, introducing the wastewater obtained in the step five into a multi-effect evaporator for evaporation and desalination, introducing an evaporation condensate into a biochemical water inlet tank, and separately transporting and disposing the evaporation kettle residue;

introducing the evaporation condensate into a facultative hydrolysis pool, controlling the water temperature to be 20-35 ℃, and carrying out facultative hydrolysis on the evaporation condensate in a water body through a biochemical reaction form for 12-48 hours; the structure of organic matters in the wastewater is destroyed, partial organic matters are degraded, and the biodegradability of the wastewater is improved;

step eight, continuously introducing the water into an aerobic reaction tank, adjusting the pH to 7-9, controlling the water temperature to be 20-35 ℃ for biochemical reaction, performing primary aerobic reaction for 12-48 hours, and controlling the dissolved oxygen in the aerobic tank to be 2-4 mg/L;

step nine, introducing the wastewater obtained in the step eight and the sludge mixed liquor into a secondary sedimentation tank, adding a coagulant, realizing sludge-water separation under the action of gravity, discharging supernatant, and transporting sludge;

step ten, introducing the supernatant obtained in the step nine into an ozone-hydrogen peroxide coupling oxidation reactor, and adding hydrogen peroxide and ozone; and blowing wastewater into the reactor by using the venturi ejector, wherein the reactor forms micro-positive pressure, and the reaction time is 5-30 min.

2. The method for treating wastewater from organosilicon production according to claim 1, wherein the acidic reagent is hydrochloric acid or sulfuric acid, and the alkaline reagent is one of sodium hydroxide/potassium hydroxide/calcium hydroxide; the coagulant is one of polyacrylamide, polyaluminium chloride and ferrous sulfate.

3. The treatment method for treating wastewater from organosilicon production according to claim 1, wherein the mass ratio of the ferrous sulfate solution to hydrogen peroxide in step three is 1.5-10: 1.

4. The method as claimed in claim 1, wherein the biochemical reaction forms in the seventh step and the eighth step include activated sludge process, biofilm process and membrane biological process, and the organic matter is degraded by the biochemical reaction of the activated sludge process, the biofilm process and the membrane biological process.

5. The treatment method for treating wastewater from organosilicon production according to claim 1, wherein the amount of ozone added in the tenth step is 3-5: 1 by mass of the total amount of COD in the wastewater; the addition of the hydrogen peroxide is 0.5-5 per mill of the mass of the wastewater; the micro-positive pressure is micro 0.01-0.05 MPa.

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