CN112960866A

CN112960866A - Treatment process of complex pesticide comprehensive wastewater

Info

Publication number: CN112960866A
Application number: CN202110248522.3A
Authority: CN
Inventors: 王洪; 王鑫; 侯永侠; 陈红亮
Original assignee: Shenyang University
Current assignee: Shenyang University
Priority date: 2021-03-08
Filing date: 2021-03-08
Publication date: 2021-06-15

Abstract

The invention discloses a treatment method of complex pesticide comprehensive wastewater, which is characterized in that the pesticide wastewater is divided into degradable wastewater and refractory high-salt wastewater according to the source and property; the nondegradable high-salt wastewater is pretreated by a Fenton reagent or iron-carbon micro-electrolysis to improve the biodegradability of the wastewater, then is mixed and regulated with the degradable wastewater in a comprehensive regulating tank to form comprehensive wastewater, and the comprehensive wastewater is subjected to anaerobic-anoxic-two-stage aerobic biological strengthening treatment and then is subjected to advanced treatment or discharged into a sewage treatment plant, so that the complex high-salt high-pollution load sewage is purified. The treatment method provided by the invention classifies and treats the sewage, reduces the salinity and the toxicity of organic matters through pretreatment, improves the biochemical property of the wastewater, reduces the subsequent treatment difficulty, adopts longer retention time for two-stage anaerobic and anoxic treatment to reduce the load, improves the treatment efficiency, and ensures the integral removal capacity and effect of the process on pollutants.

Description

Treatment process of complex pesticide comprehensive wastewater

Technical Field

The invention belongs to the field of pesticide wastewater treatment processes, and particularly relates to a treatment process of complex pesticide comprehensive wastewater.

Background

With the improvement of environmental protection policies, regulations and law enforcement in China and the improvement of sewage management and treatment technologies, point-source pollution of industrial enterprises is controlled vigorously, but sewage in some industries is still the key point and difficult point for treatment. The production and use amount of pesticides in China are large, and due to the fact that pesticides are various, the wastewater quality is complex, the pesticides are difficult to degrade, the toxic component content is high, the COD is high, the salinity is high, the pesticides are difficult to biodegrade, and the treatment is relatively difficult and complex; if the wastewater is directly discharged to a sewage treatment plant, great impact is caused to the treatment process, especially a biochemical treatment system, and even the system is broken down.

In order to improve the biodegradability of the pesticide wastewater and enable the pesticide wastewater to undergo conventional biological treatment, a pretreatment method is first used. CN 104150567A discloses a method for electrochemically pretreating imidacloprid pesticide wastewater, titanium-based tin, antimony, cerium and iridium dioxide are used for electrically pretreating imidacloprid pesticide wastewater, the electrode has strong catalytic oxidation capability and can enable wastewater BOD₅The COD is increased from below 0.1 to above 0.3, and the biodegradability is greatly improved. CN104803507A discloses a method for comprehensively treating high-efficiency cypermethrin wastewater, which adopts the technical steps of sodium chlorate oxidation, chlorine dioxide oxidation, ozone oxidation and the like to improve the biodegradability of the wastewater and the BOD of the wastewater₅The COD was increased from 0.06 to 0.38. CN107739084A adopts an electric Fenton-ozone oxidation combined technology to remove COD and decolor the pesticide wastewater which is difficult to degrade.

Although the pretreatment can improve partial biodegradability of the wastewater, the subsequent biochemical treatment of the wastewater is still difficult due to the complexity of the pollutants in the wastewater. CN 101979346A invents a method for treating high-concentration pesticide wastewater by adopting two or three integrated methods of membrane biochemical reaction, three-phase fluidized reaction or aerobic biological treatment on the basis of pretreatment, thereby realizing standard discharge.

In summary, how to develop a complex pesticide production wastewater treatment process for treatment and discharge of production wastewater is an urgent problem to be solved by those skilled in the art.

Disclosure of Invention

The invention provides a treatment process of complex pesticide comprehensive wastewater for making up the defects of the existing pesticide production wastewater treatment technology, and the problem of discharge of pesticide production wastewater is efficiently solved by combining a pretreatment technology and a multi-section anaerobic-aerobic process.

Drawings

FIG. 1 is a schematic diagram of a treatment process of complex pesticide comprehensive wastewater.

As shown in figure 1, the treatment process of the complex pesticide comprehensive wastewater divides the pesticide comprehensive wastewater treatment into a pretreatment unit, a biological enhanced treatment unit and a deep treatment unit. According to the source of pesticide wastewater, the comprehensive wastewater is divided into degradable wastewater І and refractory high-salt wastewater II; the refractory high-salt wastewater II is subjected to pretreatment and mixed adjustment with the degradable wastewater І in the comprehensive adjusting tank to form comprehensive wastewater III, and the comprehensive wastewater III is subjected to anaerobic-anoxic-two-stage aerobic biological enhanced treatment and then is subjected to advanced treatment or discharged into a sewage treatment plant, so that the complex high-salt high-pollution load sewage is purified.

The invention is described in detail below by means of specific implementation steps, without limiting the scope of protection of the invention. The specific technical scheme is as follows:

(1) pretreatment: according to the source and the characteristic of pesticide production sewage of pesticide factory, divide into degradable waste water І and difficult degradation high salt waste water II with the waste water, difficult degradation high salt waste water II needs to carry out the preliminary treatment, and pesticide production sewage organic matter concentration and inorganic salt concentration are high, and the preliminary treatment section of waste water is at first considered getting rid of difficult degradation organic pollutant and reducing the salinity, adopts iron carbon electrolysis technique or fenton oxidation technique improvement waste water biodegradability. The refractory high-salt wastewater II is firstly fed into an iron-carbon electrolysis reactor, the iron-carbon porosity is 55-65%, the designed reaction time is 1.5-2.5 h, aeration is continuously carried out in the reaction process, and the gas-water ratio is 3-5: 1; the Fenton oxidation technology can also be adopted, the pH value is 3-5, the reaction time is 1.5-2.5 h, the pretreated effluent is uniformly mixed after the pH value is adjusted and precipitation is carried out, the concentration of refractory high-salt wastewater II organic matters after pretreatment is reduced, the salinity is reduced, the biodegradability is improved, the pretreated effluent is mixed with degradable wastewater І to form comprehensive wastewater III, and the COD is kept to be less than 4000mg/L, the pH value is 6.5-8, and the salinity is less than 0.7%;

(2) introducing the effluent comprehensive wastewater III in the step (1) into a biochemical treatment system for enhanced biological treatment, and adopting a two-stage anaerobic-aerobic process AAOO. The sewage firstly enters an anaerobic reactor І (namely a hydrolysis acidification pool: 1030), the hydrolysis fermentation stage and the acid and acetic acid production stage in the anaerobic reaction process are utilized, and the methane production stage which requires complicated equipment and has slow reaction speed is discarded; anaerobic reactor І maintaining dissolved oxygen concentration at DO<0.3mg/L, 6-8g/L of sludge concentration, 24-48 h of sewage hydraulic retention time control, 0.3-0.6 kgCOD/(m) of COD organic load³D) action of extracellular enzymes in anaerobic bacteriaOrganic matters which are difficult to degrade are hydrolyzed and acidified to be simpler organic matters, and organic matters with certain biological toxicity are degraded to be less toxic under the action of a long time, so that the biodegradability of sewage is improved;

as the pesticide sewage is complex in water quality, difficult to degrade and high in toxic component content, the effluent enters an anoxic reactor II, the hydrolysis acidification process is continuously carried out, the reflux water of the aerobic unit is subjected to a denitrification process, and organic matters are further degraded into soluble micromolecules and ammonia nitrogen is removed. In-reactor DO<0.5mg/L, 24-48 h of sewage hydraulic retention time and 0.6-0.9 kgCOD/(m) of COD organic load³d)；

(3) And (3) enabling effluent from the anoxic biochemical reactor II to enter a two-section oxidation reactor, and carrying out aerobic biochemical treatment on the sewage to further reduce COD. An alkali adding system is arranged in front of the aerobic biochemical reactor І to make up the acidity generated in the anoxic hydrolysis acidification stage, so that the pH value of the sewage entering the aerobic biochemical reactor is maintained at 6-8. The aerobic biochemical reactor І adopts a biological contact oxidation process, high-efficiency biological fillers are distributed inside the reactor, and aerobic activated sludge exists on the surface of the biological fillers in a biological film form and is suspended inside the reactor. The biological contact oxidation process has strong water quality and water quantity impact resistance. DO in the aerobic biochemical reactor І is 2-3 mg/L, the sewage stays for 18-36 h, and microporous aeration is adopted, wherein the ratio of gas to water is (20-30): 1, organic load of 0.8 to 1.2 kgBOD/(m)³d)；

The effluent of the aerobic biochemical reactor І enters an aerobic biochemical reactor II and a secondary contact oxidation tank to further remove pollutants in the sewage, DO in the reactor is 2-4 mg/L, the sewage stays for 24-36 h, and the gas-water ratio is (20-30): 1, organic load of 1.0 to 1.5 kgBOD/(m)³d)；

Aerobic biochemical effluent enters a next treatment unit after being precipitated by a secondary sedimentation tank, the other part of the aerobic biochemical effluent flows back to an anaerobic reactor І and an anoxic biochemical reactor II to be subjected to denitrification treatment, backflow sewage contains a large amount of nitrates, denitrification process is carried out in the anaerobic/anoxic reactor, the sewage backflow ratio is 200-400%, and the treatment process is as follows, 3: the 2-proportion is respectively returned to the anaerobic reactor І and the anoxic reactor II. Partial II sludge of the aerobic biochemical reactor is precipitated by a secondary sedimentation tank and discharged as excess sludge, and partial II sludge flows back to the anaerobic biochemical reactor І to supplement the sludge amount of the system;

(4) and a depth processing unit. Because the organic matter components contained in the pesticide wastewater are complex, if the effluent water after the two-stage anaerobic-aerobic process AAOO enhanced biological treatment still cannot meet the discharge requirement, advanced treatment is required. The active carbon adsorption process or the ozone oxidation and aerobic treatment process can be adopted, organic matters which are not degraded before are oxidized into degradable organic matters in the ozone oxidation process, and then the aerobic treatment is carried out to ensure that the sewage reaches the standard and is discharged.

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

according to the characteristic of many sources of sewage in the pesticide factory, the sewage is classified and treated, and the salinity and the toxicity of organic matters are effectively reduced and the biochemical property of the wastewater is improved by utilizing the pretreatment technologies such as Fenton oxidation/iron-carbon micro-electrolysis and the like; the two anaerobic and anoxic stages adopt a hydrolysis acidification process with longer residence time to gradually convert refractory organic matters in the pesticide wastewater into organic matters capable of being utilized by microorganisms, and simultaneously can reduce the treatment load of a subsequent aerobic tank and reduce the aeration energy consumption and the excess sludge yield in the aerobic treatment stage, thereby greatly reducing the cost of the whole wastewater treatment process. The invention also fully considers the further deep purification of the sewage, and the treated wastewater can be further treated by ozone oxidation and aerobic treatment to remove pollutants. The integral removing capability and effect of the process on the pollutants are ensured.

Detailed Description

Application example 1

A chemical company in a chemical industry park is mainly used for producing cyclohexenone series herbicides, and the production wastewater needs to reach the discharge standard COD of the industrial park<300mg/L，NH₄-N<30 mg/L. Fenton oxidation pretreatment, two-stage anaerobic and two-stage aerobic multi-stage biochemical combined technology and ozone oxidation-aerobic biochemical process advanced treatment are selected. The discharged wastewater is divided into two types according to the process and the property, namely degradable wastewater І and refractory high-salt wastewater II. Feeding refractory high-salt wastewater II into a Fenton oxidation reactor, adjusting the pH value of the wastewater II to 3-5, reacting for 1.5-2.5 h, adjusting the pH value of pretreated effluent, and flocculating and precipitating the pretreated effluent by using a flocculating agent to obtain supernatantThe solution and the degradable wastewater І are mixed to form the comprehensive wastewater III, the COD is 3132mg/L, and the NH is₄175 mg/L of-N and 6-8 of pH.

The comprehensive wastewater III enters a two-stage anaerobic-aerobic process AAOO system of the biochemical treatment system. The anaerobic reactor І is kept stirring slowly, and the dissolved oxygen concentration is kept DO<0.3mg/L, sludge concentration of 6-8g/L, hydraulic retention time of 48h, COD organic load of 0.5 kgCOD/(m)³D); the effluent enters an anoxic reactor II or an anoxic reactor II and DO in the reactor II<0.5mg/L, 24h of sewage hydraulic retention time, 5-6g/L of sludge concentration and 0.8 kgCOD/(m) of COD organic load³D). Adjusting the stirring speed to control the anaerobic state in the hydrolysis acidification stage.

The effluent COD of the anoxic biochemical reactor II is 2565mg/L, the total removal rate of two-stage anaerobism is 18.1 percent, the effluent enters an aerobic biochemical reactor І, and an alkali adding system is arranged in front of the reactor to maintain the pH of the sewage entering the aerobic biochemical reactor to be about 7. DO is 2.5-3 mg/L, the sewage stays for 24 hours, the micropore aeration is carried out, and the gas-water ratio is 20: 1, organic load 1.0 kgBOD/(m)³D). DO in the aerobic biochemical II reactor is 4-5 mg/L, the sewage retention time is 18h, and the gas-water ratio is 30: 1, organic load 1.45 kgBOD/(m)³D). And (3) enabling the effluent to enter a secondary sedimentation tank, and refluxing partial sewage after mud-water separation, wherein the reflux ratio is 200-400%, and the ratio is 3: the 2-proportion is respectively returned to the anaerobic reactor І and the anoxic reactor II. Part of sludge flows back to anaerobic biochemical І, and the reflux ratio is 50-100%. The COD of the effluent of the biochemical system is 632mg/L, which does not reach the water inlet standard of a sewage treatment plant in a park, and advanced treatment is needed to further reduce the concentration of pollutants. Advanced treatment ozone oxidation and aerobic treatment process, wherein the COD of the final effluent of ozone oxidation is 276mg/L, and NH₄175 mg/L of-N and 91-93 percent of total COD removal rate.

Application example 2

A certain chemical company is mainly used for producing carbamate pesticides, and the treated wastewater needs to meet the pipe connection standard COD of a sewage treatment plant in a park of less than 500 mg/L. The deep treatment is carried out by adopting a multistage biochemical combination technology of iron-carbon micro-electrolysis, two-stage anaerobic treatment and two-stage aerobic treatment. The waste water is divided into refractory waste water II and degradable waste water І according to the process and properties. Feeding the refractory high-salt wastewater II into an iron-carbon electrolysis reactor, wherein the iron-carbon porosity is 60-65%, the designed reaction time is 2-2.5 h, and the aeration is continuously carried out in the reaction process, wherein the gas-water ratio is 4: 1; the treated effluent is mixed with degradable wastewater І after the pH value is adjusted and the treated effluent is precipitated to form comprehensive wastewater III, the COD is 3687mg/L, and the pH is 7-8.

The comprehensive wastewater III enters a two-stage anaerobic-aerobic process AAOO system of the biochemical treatment system. Anaerobic reactor І maintaining dissolved oxygen concentration at DO<0.3mg/L, hydraulic retention time of 36h, COD organic load of 0.55 kgCOD/(m)³D); the effluent enters an anoxic reactor II or an anoxic reactor II and DO in the reactor II<0.5mg/L, 48h of sewage hydraulic retention time and 1.0 kgCOD/(m) of COD organic load³•d)。

The COD of the effluent of the anoxic biochemical reactor II is 2890 mg/L, the total removal rate of the two-stage anaerobism is 21.6 percent, the effluent enters a two-stage oxidation reactor, and an alkali adding system is arranged in front of an aerobic biochemical reactor І, so that the pH of the sewage entering the aerobic biochemical reactor is maintained at about 7. DO is 2-3 mg/L, the sewage retention time is 36h, the micropore aeration is carried out, and the gas-water ratio is 20: 1, organic load 1.0 kgBOD/(m)³D). The DO in the aerobic biochemical reactor І entering the aerobic biochemical reactor is 3-4 mg/L, the sewage stays for 36h, and the gas-water ratio is 25: 1, organic load 1.65 kgBOD/(m)³D). And (3) enabling the effluent to enter a secondary sedimentation tank, and refluxing partial sewage after mud-water separation, wherein the reflux ratio is 200-500%, and the ratio is 3: the 2-proportion is respectively returned to the anaerobic reactor І and the anoxic reactor II. And part of sludge flows back to anaerobic biochemical І, the reflux ratio is 50-100%, the sludge amount of the system is supplemented, and other residual sludge is discharged. The COD of the effluent is 415mg/L, and the effluent index reaches the standard COD of the pipe connecting standard of the sewage treatment plant in the garden<500mg/L, and further reduction of the pollutant concentration is not needed by advanced treatment.

Claims

1. The treatment process of the complex pesticide comprehensive wastewater is characterized by comprising the following steps of:

the method comprises the following steps: according to the source and the characteristics of the pesticide production sewage of the pesticide factory, the wastewater is divided into degradable wastewater and refractory high-salt wastewater, the refractory high-salt wastewater needs to be pretreated, and the pretreated wastewater is mixed with the degradable wastewater to form pesticide comprehensive wastewater;

step two: introducing the effluent comprehensive wastewater obtained in the step I into a biochemical treatment system for enhanced biological treatment, and adopting a two-stage anaerobic-aerobic process AAOO;

step three: the effluent from the second step enters two sections of oxidation reactors in sequence, and aerobic biochemical treatment is carried out on the sewage, so that the COD is further reduced;

step four: if the effluent water after the two-stage anaerobic-aerobic process AAOO enhanced biological treatment still can not meet the discharge requirement, advanced treatment is required to be carried out, so that the sewage can reach the discharge standard.

2. The treatment method according to claim 1, wherein the pretreatment stage of the wastewater first considers the removal of refractory organic pollutants and the reduction of salinity, and the iron-carbon electrolysis technology or the Fenton oxidation technology is adopted to improve the biodegradability of the wastewater;

preferably, in the iron-carbon electrolysis reactor, the iron-carbon porosity is 55-65%, the designed reaction time is 1.5-2.5 h, aeration is continuously carried out in the reaction process, and the gas-water ratio is 3-5: 1;

preferably, a Fenton oxidation technology is adopted, the pH value is kept to be 3-5, and the reaction time is 1.5-2.5 h;

preferably, the COD of the comprehensive pesticide wastewater is less than 4000mg/L, the pH value is 6.5-8, and the salinity is less than 0.7%.

3. The treatment method as claimed in claim 1, wherein two stages of anaerobic reactions are carried out, and the reactions are controlled in a hydrolysis fermentation stage and an acid-producing and acetic acid-producing stage;

preferably, the dissolved oxygen concentration of the anaerobic reactor І is maintained at DO<0.3mg/L, 6-8g/L of sludge concentration, 24-48 h of hydraulic retention time control, 0.3-0.6 kgCOD/(m) of COD organic load³•d) ；

Preferably, in order to further degrade the organic matters into soluble small molecules and remove ammonia nitrogen, the anaerobic reactor II-type DO<0.5mg/L, 24-48 h of sewage hydraulic retention time and 0.6-0.9 kgCOD/(m) of COD organic load³d)。

4. The treatment method according to claim 1, wherein the two sections of aerobic biochemical reactors respectively adopt a biological contact oxidation process, and high-efficiency biological fillers are distributed inside the two sections of aerobic biochemical reactors;

preferably, an alkali adding system is arranged in front of the oxygen biochemical reactor to make up acidity generated in an anoxic hydrolysis acidification stage, so that the pH value of sewage entering the aerobic biochemical reactor is maintained at 6-8;

preferably, DO in the aerobic biochemical reactor І is 2-3 mg/L, the sewage stays for 18-36 h, microporous aeration is adopted, and the ratio of gas to water is (20-30): 1, organic load of 0.8 to 1.2 kgBOD/(m)³d) ；

Preferably, the aerobic biochemical reactor II DO is 2-4 mg/L, the sewage retention time is 24-36 h, and the gas-water ratio is (20-30): 1, organic load of 1.0 to 1.5 kgBOD/(m)³d) ；

Preferably, one part of aerobic biochemical effluent enters a next treatment unit after being precipitated by a secondary sedimentation tank, the other part of the aerobic biochemical effluent flows back to the anaerobic reactor І and the anoxic biochemical reactor II for denitrification treatment, the sewage reflux ratio is 200-400%, and the treatment is carried out according to the proportion of 3: the 2-proportion is respectively returned to the anaerobic reactor І and the anoxic reactor II.

5. The treatment method as claimed in claim 1, wherein the advanced treatment comprises activated carbon adsorption and ozone oxidation + aerobic treatment.