CN111704321A

CN111704321A - Pesticide wastewater treatment process

Info

Publication number: CN111704321A
Application number: CN202010625349.XA
Authority: CN
Inventors: 戴军; 郭家; 冯文钦; 王超; 曹江行; 张璇玑; 洪波
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2020-09-25

Abstract

The invention discloses a pesticide wastewater treatment process in the technical field of wastewater treatment, which comprises the following specific steps: the pesticide wastewater is divided into high-salt high-halogen wastewater and other comprehensive wastewater, the high-salt high-halogen wastewater is firstly evaporated, and the condensate is mixed with the comprehensive wastewater for treatment. After the treatment units such as a comprehensive adjusting tank, a reaction tank, a primary sedimentation tank, a circulating water tank, an anaerobic tank, a multi-section AO tank, a secondary sedimentation tank, a reaction final sedimentation tank, an intermediate water tank, a sand filter tank, a catalytic oxidation tower and the like are processed, COD, ammonia nitrogen, total phosphorus and the like in the pesticide wastewater can be greatly reduced, and the method has the advantages of stable effect, low comprehensive cost and the like. The process is suitable for treating high-salt, high-COD and high-halogen pesticide wastewater.

Description

Pesticide wastewater treatment process

Technical Field

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

Background

As a large country for grain production in China, most grains can use pesticides such as insecticides in the growth process: lufenuron, propargite, and the like, herbicides: buthiuron, flumetsulam, a plant growth regulator: flumetralin. These pesticides produce large amounts of waste water during the production process, including process waste water, ground and equipment cleaning waste water, tank field spray waste water, waste gas treatment waste water, domestic sewage, and the like.

The pesticide wastewater has large water quantity and complex water quality, and is difficult to treat. The following features are generally provided: (1) high salt content. The control of the pH during the production of the product is rather critical and often additional acid, base and salt additions are made, which lead to an increase in the salt content of the waste water. The organic salt is often a byproduct of the synthesis reaction and remains in the mother liquor. A large amount of salt substances exist in the wastewater, so that the biochemical treatment of wastewater treatment is difficult to perform. (2) High organic matter concentration. In the production process, a large amount of organic substances are used as raw and auxiliary materials, the residues of the raw and auxiliary materials after reaction, intermediate products, products and byproducts are organic chemical substances and mainly contain substances such as nitrobenzene, aniline, p-aminophenol, alcohols, esters, petroleum, organic solvents and the like, the content of organic matters in the wastewater generated by the production process is high, and the COD can reach hundreds of thousands. (3) The waste water containing halogen organic matters is difficult to biodegrade. A large amount of toluene, xylene, halogenated hydrocarbon and heterocyclic substances contained in the wastewater are all substances which are difficult to be biochemically degraded or nonbiodegradable. The BOD/COD of the wastewater is 0.05-0.1, the biodegradability is poor, and the defects of overhigh organic load, incapability of degrading certain refractory components in the wastewater and the like exist in the direct biochemical treatment. (4) It is toxic. Some of the starting materials or products are biologically toxic or are difficult to biodegrade. In addition, the wastewater contains substances that inhibit the growth of microorganisms, such as microbial metabolic intermediates (MEPs) and residual antibiotics. (5) The wastewater discharge is periodic discharge, the water quantity and the water quality are unstable, the fluctuation of organic matters and salinity is large, serious over-interference is caused to a biochemical treatment system, microorganisms are difficult to adapt, and even irreversible fatal poison is caused. Because the pesticide wastewater has the characteristics, if the pesticide wastewater is directly discharged to the natural environment without being treated, the natural environment is inevitably polluted greatly, and finally the pesticide wastewater enters a human body through a food chain and seriously harms the health of people. Therefore, the treatment of pesticide wastewater is a problem which is urgently needed to be solved at present.

Disclosure of Invention

The invention provides a pesticide wastewater treatment process aiming at wastewater generated in the pesticide production process, which can be suitable for high-salt, high-COD and high-halogen (chloride ion) pesticide wastewater, can greatly reduce COD, ammonia nitrogen, total phosphorus and the like in the pesticide wastewater, and has the advantages of stable effect, low comprehensive cost and the like.

In order to solve the technical problems and achieve the purposes, the technical scheme adopted by the invention is as follows: a pesticide wastewater treatment process comprises the following key steps:

(1) firstly, the wastewater is divided into high-salt high-halogen (mainly salt containing halogen elements such as NaCl) production wastewater and comprehensive wastewater with low salt content, and the high-salt high-halogen production wastewater and the comprehensive wastewater are respectively treated. The waste water with high salt content and high halogen content is pretreated by evaporation and crystallization, and the crystallized substances can be used as by-products of production. And discharging the evaporated condensate to a high-salt high-halogen buffer tank of the wastewater station, and then mixing the condensate with the comprehensive wastewater for treatment.

(2) Other comprehensive waste water and the high-salt and high-halogen waste water evaporation condensate are converged into a comprehensive regulating tank together for regulating the water quality and the water quantity.

(3) And the regulated wastewater enters a reaction tank. Adding a coagulant into the reaction tank, pretreating by the residual adsorption capacity of the returned sludge to condense colloid and fine suspended matters in the wastewater into floccules, separating and removing the floccules, and separating sludge and water from the wastewater after the coagulation reaction in a primary sedimentation tank.

(4) And supernatant liquid after mud-water separation enters a circulating water tank, and sludge enters a sludge tank through a sludge pump.

(5) The circulating water tank is provided with a sewage pump to supply water for the anaerobic tank, anaerobic microorganisms convert refractory organic matters in wastewater into substances such as methane, carbon dioxide and the like through digestion under the anaerobic condition, the biodegradability of the wastewater is improved, COD (chemical oxygen demand) and BOD (biochemical oxygen demand) in the wastewater are removed through the activated sludge adsorption capacity and the capacity of degrading the organic matters of the anaerobic tank, and redundant sludge in the anaerobic tank is discharged into the sludge tank.

(6) Then the wastewater enters a multi-section A/O pool to remove COD, BOD and ammonia nitrogen in the wastewater. The A/O tank biological denitrification process consists of an anoxic tank and an aerobic tank. In the anoxic tank, organic matters in the wastewater are used as a carbon source to carry out denitrification, nitrate nitrogen is converted into nitrogen, and when the content of the organic matters is insufficient, the carbon source needs to be artificially added; in the aerobic tank, the ammonia nitrogen is converted into nitrate nitrogen through nitrification, and the nitrate nitrogen enters the anoxic tank through the backflow of the mixed liquid.

(7) The treated waste water enters a secondary sedimentation tank for mud-water separation, and the supernatant enters a reaction final sedimentation tank. Adding a flocculating agent into the reaction tank, and entering the sedimentation tank after reaction. And the sludge at the bottom of the tank respectively flows back to the reaction tank, the anaerobic tank and the A/O tank, and the residual sludge is conveyed to the sludge tank.

(8) And carrying out mud-water separation in the reaction final sedimentation tank, and filtering out larger particles from the supernatant through sand filtration to prevent the catalytic oxidation tower from being blocked.

(9) In order to ensure that the wastewater can stably reach the standard, a catalytic oxidation tower preservation process is arranged, so that COD is further reduced, and the color is basically faded out.

(10) The waste water after catalytic oxidation enters a clean water tank and is discharged after reaching the standard through a metering channel.

Preferably, in the step (1), the process wastewater with the salt content of more than 80000mg/L is classified as high-salt wastewater, and the process wastewater, equipment and ground cleaning water, waste gas treatment wastewater, domestic sewage and other wastewater with the salt content of less than 80000mg/L is classified as comprehensive wastewater.

Furthermore, before the high-salinity wastewater enters the evaporation system, the water quantity and the water quality of the high-salinity wastewater are adjusted in the adjusting tank and then enter the sedimentation tank for sedimentation, so that the wastewater enters the evaporation system under the optimal process condition.

Preferably, in the step (2), the comprehensive adjusting tank can adjust both the water quantity and the water quality. The water quantity regulation adopts in-line regulation, the water quality regulation adopts external power to force regulation, and the aeration pipe is arranged at the bottom of the tank, so that the wastewater entering the tank at different times can be mixed under the action of air stirring.

Preferably, in the step (3), the coagulant is polyaluminium chloride (PAC), and the reaction tank is provided with an automatic medicine feeding device. The dosing mode adopts a wet method, namely, the medicament is firstly prepared into solution with certain concentration and then is put into the reaction tank. The return sludge is sludge in a secondary sedimentation tank and a reaction final sedimentation tank.

In the step (6), the carbon source is sodium carbonate.

In the step (7), the secondary sedimentation tank and the reaction final sedimentation tank are provided with sludge pumps. And returning a part of sludge to the reaction tank, the anaerobic tank and the A/O tank, and conveying the rest sludge to the sludge tank.

In the step (9), the oxidant is hydrogen peroxide, and the catalyst is a compound metal compound.

In the step (10), the clean water tank is provided with an online monitoring system, so that various indexes of the discharged water can be monitored in real time.

Preferably, the residual sludge entering the sludge tank passes through a conditioning tank, Polyacrylamide (PAM) with anions is added, and then the dehydration treatment is carried out through a plate-and-frame filter press. Therefore, the filter pressing efficiency can be improved, and the filter pressing time can be shortened.

The invention has the beneficial effects that: the pretreated high-salinity wastewater and other comprehensive wastewater sequentially pass through treatment units such as a regulating tank, a reaction tank, an initial precipitation tank, a circulating water tank, an anaerobic tank, a multi-section AO tank, a secondary precipitation tank, a reaction final precipitation tank, an intermediate water tank, a sand filter tank, a catalytic oxidation tower, a clean water tank and the like, so that the contents of pollutants such as COD (chemical oxygen demand), total nitrogen, ammonia nitrogen, total phosphorus, SS (suspended solid) and the like in the pesticide wastewater can be reduced, the effluent can be discharged up to the standard, the use amount of medicaments is small, and the comprehensive use cost is low.

Drawings

FIG. 1 is a process flow diagram of the present invention

Detailed Description

The invention will be further illustrated with reference to process flow diagrams and examples.

Example (b):

the amount and quality of the wastewater from a certain agricultural chemical plant are shown in Table 1

The specific implementation mode comprises the following steps:

(1) firstly, high-salt high-halogen production wastewater and comprehensive wastewater with low salt content are respectively treated. Because the wastewater with high salt content and high halogen has high toxicity to the biochemical operation of the wastewater station, if the wastewater is not controlled, the biochemical system of the wastewater station is difficult to operate. The high-salt high-halogen wastewater is firstly subjected to water quality and water quantity regulation, and then subjected to primary precipitation, and the supernatant enters an evaporation system. And discharging the evaporated condensate to a high-salt high-halogen buffer pool of a waste water station, crystallizing and dehydrating the evaporated residual liquid, wherein the crystal can be used as a by-product of production, and the residual waste water enters a water collecting pool and enters an evaporation system again.

(2) Other comprehensive waste water and the high-salt and high-halogen waste water evaporation condensate are converged into a comprehensive regulating tank together for regulating the water quality and the water quantity. The water quantity adjusting mode adopts in-line adjustment, and the highest water level in the pool does not exceed the designed water level of the water inlet pipe. The water quality regulation adopts forced regulation by external power, and the aeration pipe is arranged at the bottom of the tank, so that the wastewater entering the tank at different times can be mixed under the action of air stirring.

(3) And the regulated wastewater enters a reaction tank. The residual adsorption capacity of the returned sludge in the secondary sedimentation tank and the final reaction sedimentation tank is pretreated, PAC is quantitatively fed through an automatic dosing device, under the action of a coagulant, colloid and fine suspended matters in the wastewater are coagulated into floccules and then separated and removed, and the wastewater after the flocculation reaction enters the primary sedimentation tank for sludge-water separation.

(6) Then the wastewater enters a multi-section A/O tank, and a high-efficiency adsorbent is added to remove COD, BOD and ammonia nitrogen in the wastewater. The A/O tank biological denitrification process consists of an anoxic tank and an aerobic tank. In the anoxic tank, organic matters in the wastewater are used as carbon sources for denitrification, nitrate nitrogen is converted into nitrogen, and when the content of the organic matters is insufficient, carbon sources such as sodium carbonate and the like need to be artificially added; in the aerobic tank, the ammonia nitrogen is converted into nitrate nitrogen through nitrification, and the nitrate nitrogen enters the anoxic tank through the backflow of the mixed liquid.

(7) And the treated wastewater enters a secondary sedimentation tank for sludge-water separation, the supernatant enters a reaction final sedimentation tank, sludge respectively returns to the reaction tank, the anaerobic tank and the A/O tank through a sludge pump, and the residual sludge is conveyed to the sludge tank.

(8) And adding a flocculating agent into the reaction final sedimentation tank for sedimentation, performing sludge-water separation, filtering the supernatant through sand to filter out larger particles and prevent the catalytic oxidation tower from being blocked. And the sludge respectively flows back to the reaction tank, the anaerobic tank and the A/O tank through a sludge pump, and the residual sludge is conveyed to the sludge tank.

(9) In order to ensure that the wastewater can stably reach the standard, a catalytic oxidation tower preservation process is arranged, the catalytic oxidation process mainly aims at catalyzing a chain reaction for generating hydroxyl free radicals, and because the hydroxyl free radicals are strong oxidants next to fluorine, the catalytic oxidation process can carry out nonselective oxidation on organic matters in a wide range, and organic pollutants can be mineralized into carbon dioxide and water under necessary conditions. The oxidant is selected from hydrogen peroxide, and the catalyst is a compound noble metal compound. After removing solid impurities from the wastewater, the wastewater enters a catalytic oxidation tower, organic pollutants in the wastewater are decomposed by an oxidant after organic matters and oxidant molecules in the wastewater are subjected to adsorption, catalytic oxidation reaction, product desorption and other steps on the surface of a catalyst in the reaction, benzene rings and heterocyclic organic matters are subjected to ring opening and chain scission, macromolecules are changed into micromolecules, and the micromolecules are further oxidized into carbon dioxide and water, so that the COD value in the wastewater is greatly reduced, and the color and luster are basically faded out.

(10) The wastewater after catalytic oxidation enters a clean water tank, and the clean water tank is provided with an online monitoring system, so that various indexes of the effluent can be monitored in real time. Finally, the waste water is discharged after reaching the standard through a metering channel.

The water quality table of inlet and outlet water in each stage is shown in table 2:

as can be seen, after the pesticide wastewater is treated by the process, COD, total nitrogen, ammonia nitrogen, total phosphorus and the like in the wastewater are greatly reduced, the COD is reduced from 100000mg/L to 300mg/L, the total nitrogen is reduced from 1000mg/L to 60mg/L, the ammonia nitrogen is reduced from 500mg/L to 30mg/L, and the total phosphorus is reduced from 50mg/L to 6.5 mg/L. Meets the pipe connection standard of a certain municipal sewage treatment plant.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are included in the scope of the present invention.

Claims

1. A pesticide wastewater treatment process is characterized by comprising the following steps:

(3) And the regulated wastewater enters a reaction tank. Adding a coagulant into the reaction tank, pretreating by the residual adsorption capacity of the returned sludge to condense colloid and fine suspended matters in the wastewater into floccules, separating and removing the floccules, and separating sludge and water in the wastewater after the flocculation reaction in a primary sedimentation tank.

(6) Then the wastewater enters a multi-section A/O tank, and a high-efficiency adsorbent is added to remove COD, BOD and ammonia nitrogen in the wastewater. The A/O tank biological denitrification process consists of an anoxic tank and an aerobic tank. In the anoxic tank, organic matters in the wastewater are used as a carbon source to carry out denitrification, nitrate nitrogen is converted into nitrogen, and when the content of the organic matters is insufficient, the carbon source needs to be artificially added; in the aerobic tank, the ammonia nitrogen is converted into nitrate nitrogen through nitrification, and the nitrate nitrogen enters the anoxic tank through the backflow of the mixed liquid.

(7) And (3) the treated wastewater enters a secondary sedimentation tank for mud-water separation, the supernatant enters a flocculation reaction tank, a flocculating agent is added for reaction, the reaction tank enters a final reaction sedimentation tank, sludge respectively flows back to the reaction tank, the anaerobic tank and the A/O tank, and the residual sludge is conveyed to a sludge tank.

2. The pesticide wastewater treatment process as set forth in claim 1, characterized in that: in the step (1), the process wastewater with the salt content of more than 80000mg/L is classified as high-salt wastewater, and the process wastewater, equipment and ground cleaning water, waste gas treatment wastewater, domestic sewage and other wastewater with the salt content of less than 80000mg/L are classified as comprehensive wastewater.

3. The pesticide wastewater treatment process as set forth in claim 1, characterized in that: in the step (2), the water quantity adjusting mode adopts in-line adjustment, and the highest water level in the pool does not exceed the designed water level of the water inlet pipe. The water quality regulation adopts forced regulation by external power, and the aeration pipe is arranged at the bottom of the tank, so that the wastewater entering the tank at different times can be mixed under the action of air stirring.

4. The pesticide wastewater treatment process as set forth in claim 1, characterized in that: in the step (6), the carbon source is sodium carbonate.

5. The pesticide wastewater treatment process as set forth in claim 1, characterized in that: in the step (9), the oxidant is hydrogen peroxide, and the catalyst is a compound metal compound.