Method and device for treating chemical fertilizer production wastewater

Abstract

The invention provides a chemical fertilizer production wastewater treatment method and device, and the treatment method comprises the following steps: mixing chemical fertilizer production wastewater and part of domestic wastewater, balancing the water quality to obtain balanced wastewater, adjusting the pH value of the balanced wastewater, and pretreating to obtain pretreated wastewater; then carrying out chemical reaction treatment, precipitation treatment and biological treatment on the pretreated wastewater to remove pollutants in the wastewater, so as to obtain treated wastewater; carrying out secondary precipitation on the treated wastewater to remove suspended solids and microbial flocs in the water; finally, water and waste residues generated after secondary precipitation are recycled. According to the treatment method, the treated effluent of the chemical fertilizer production wastewater reaches the discharge standard and meets the recycling requirement.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular to a method and device for treating fertilizer production wastewater. Background Art

[0002] The wastewater generated by fertilizer plants during the production process contains a variety of pollutants, among which ammonia nitrogen, sulfide and total cyanide are important indicators of excessive pollutants. The water quality characteristics of this type of wastewater are high ammonia nitrogen content, toxic total cyanide and sulfide, and relatively poor biodegradability. Ammonia nitrogen is the main pollutant in fertilizer plant wastewater. Once it enters the water body, it will cause eutrophication of the water body and cause serious deterioration of water quality. Therefore, its discharge is strictly restricted.

[0003] The main components of fertilizer wastewater include BOD (organic matter), NH3-N (ammonia nitrogen) and SS (suspended solids). Among them, the content of BOD is generally not high, and the ratio to NH3-N is about 1 to 2:1. In the treatment process, a key step to remove NH3-N is denitrification. For SS, most of SS can be removed by adding agents for precipitation treatment, and the remaining small amount of SS is also easily removed after entering the biochemical pool, so the treatment of SS is usually not a problem.

[0004] Fertilizer wastewater mainly comes from high-concentration ammonia nitrogen wastewater produced by synthetic ammonia and urea workshops. The ammonia nitrogen in this part of wastewater mainly exists in the form of inorganic ammonia nitrogen. Therefore, ammonia nitrogen is undoubtedly the main pollutant in fertilizer wastewater, and its effective treatment is of great significance for improving water quality and protecting the environment. However, due to the complex water quality of fertilizer wastewater and the presence of toxic substances, traditional treatment methods often fail to achieve ideal treatment effects, so it is necessary to seek more efficient and environmentally friendly treatment technologies.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first object of the present invention is to provide a method for treating fertilizer production wastewater, which reduces subsequent oxide treatment by adjusting the pH value using alkaline substances and oxidants and oxidizing cyanide, and removes complex cyanide from the water body through chemical reaction treatment of a decyanant, thereby reducing the subsequent treatment load and reducing the inhibitory and toxic effects of cyanide on microorganisms.

[0007] The second purpose of the present invention is to provide a treatment device for fertilizer production wastewater, which uses the treatment device to treat the fertilizer wastewater and the discharged clean water meets the requirements of the "Comprehensive Sewage Discharge Standard" and the "Phosphate Fertilizer Industry Water Pollutant Discharge Standard".

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: A method for treating fertilizer production wastewater comprises the following steps: First, fertilizer production wastewater and part of domestic wastewater are mixed and then the water quality is balanced to obtain balanced wastewater, and then the pH value of the balanced wastewater is adjusted and pretreated to obtain pretreated wastewater; then the pretreated wastewater is subjected to chemical reaction treatment, precipitation treatment, and biological treatment to remove pollutants in the wastewater to obtain treated wastewater; the treated wastewater is subjected to secondary precipitation to remove suspended matter and microbial flocs in the water; finally, the water body and waste residue generated after the secondary precipitation are recycled.

[0009] Preferably, the pH value is adjusted using one or more alkaline substances selected from sodium hydroxide and calcium hydroxide.

[0010] Preferably, the pretreatment is to oxidize the wastewater using an oxidant, and the oxidant is one or more of sodium hypochlorite, chlorine, hydrogen peroxide, and ozone.

[0011] Preferably, the chemical reaction treatment is to use a decyanation agent to further remove organic matter and pollutants in the wastewater.

[0012] Preferably, the biological treatment is to subject the wastewater to denitrification and desulfurization reactions, degradation reactions and nitrification reactions to remove pollutants in the wastewater.

[0013] First, the water quality is balanced by mixing fertilizer production wastewater and part of domestic wastewater, making the water quality more stable in the subsequent treatment process; using alkaline substances such as sodium hydroxide and calcium hydroxide to adjust the pH value of the balanced wastewater, the wastewater can reach the optimal range suitable for subsequent chemical reactions and biological treatments. At the same time, some pollutants in the balanced wastewater can be preliminarily removed through pretreatment, reducing the burden for subsequent treatment. In order to deeply remove pollutants, decyanation agents are first used to further remove organic matter and pollutants in the pretreated wastewater to improve the degree of wastewater purification; then, precipitation treatment can be used to remove suspended matter and some soluble pollutants in the decyanation treated wastewater, so that the water quality can be further improved; the denitrification desulfurization reaction, degradation reaction and nitrification reaction of microorganisms can be used to effectively remove pollutants such as nitrogen and sulfur and organic matter in the wastewater, and finally achieve deep purification. The separation of mud and water through secondary precipitation can further remove suspended matter and microbial flocs in the water, improve the transparency of water quality, and reduce environmental problems during subsequent treatment or discharge. The water and waste residues generated after secondary precipitation are recycled, which can not only save water resources, but also realize the resource utilization of waste and reduce environmental pollution.

[0014] The present invention also provides a fertilizer production wastewater treatment device for implementing the above treatment method, comprising: Along the direction of fertilizer production wastewater inflow, there are regulating tanks, reaction tanks, sedimentation tanks, biological treatment equipment, secondary sedimentation tanks, and recycling equipment; The regulating pool is used to collect fertilizer production wastewater and part of domestic wastewater, and the wastewater is subjected to pH adjustment and preliminary oxidation treatment in the regulating pool; The reaction tank is used to carry out decyanation reaction on the wastewater treated in the regulating tank to reduce the inhibitory and toxic effects of cyanide on microorganisms; The sedimentation tank is used to remove part of the suspended solids and cyanide in the wastewater discharged from the reaction tank; The biological treatment equipment is used to carry out denitrification, desulfurization, degradation and digestion reactions on the wastewater discharged from the sedimentation tank; The secondary sedimentation tank is used to separate mud and water from the wastewater discharged from the biological treatment equipment, making the mixed wastewater clear; The recycling equipment is used to recycle and utilize the clean water discharged from the secondary sedimentation tank.

[0015] Preferably, the biological treatment equipment contains an anoxic tank and an aerobic tank; The anoxic tank performs a denitrification and desulfurization reaction to reduce NO3-N in the fertilizer wastewater to N2 which enters the air; In the aerobic pool, microorganisms carry out nitrification and organic matter degradation under aerobic conditions on the wastewater discharged from the anoxic pool.

[0016] Preferably, the recycling equipment contains a water storage tank for collecting the clean water discharged from the secondary sedimentation tank and entering the industrial reuse water through the lifting action of a pump.

[0017] Preferably, the fertilizer production wastewater treatment device further comprises a sludge storage tank, and the sludge storage tank is used to temporarily store the sludge produced in the sedimentation tank and the secondary sedimentation tank.

[0018] The device of the present invention realizes efficient treatment and deep purification of fertilizer production wastewater through a continuous treatment process of a regulating tank, a reaction tank, a sedimentation tank, a biological treatment device (including anoxic tank and aerobic tank) and a secondary sedimentation tank; each treatment link removes specific pollutants to ensure the stability and optimization of the final effluent water quality. The water volume of the mixed wastewater is balanced by the regulating tank, and the water quality is preliminarily adjusted. Alkaline substances and oxidants are added to the regulating tank to adjust the pH value of the wastewater in the regulating tank to a suitable range, creating a suitable biological treatment environment, and oxidizing the cyanide in the wastewater in the regulating tank to preliminarily reduce the concentration of cyanide in the wastewater. In particular, in the reaction tank, the concentration of cyanide in the wastewater is effectively further reduced by the decyanation reaction, reducing its inhibitory and toxic effects on subsequent biological treatment. At the same time, in the biological treatment equipment, the synergistic effect of the anoxic tank and the aerobic tank realizes the effective removal of pollutants such as nitrogen and sulfur and the degradation of organic matter, further improving the water quality of the wastewater.

[0019] The setting of the water storage tank in the recycling equipment in the device of the present invention enables the clean water discharged from the secondary sedimentation tank to be collected and enter the industrial return water through the lifting action of the pump, thereby realizing the effective recycling and reuse of water resources; this not only saves water resources, but also reduces the cost of water use. The setting of the sludge storage tank enables the sludge generated in the sedimentation tank and the secondary sedimentation tank to be temporarily stored, which is convenient for the subsequent sludge treatment and disposal. This helps to reduce the pollution of the environment by the sludge and realizes the resource utilization or safe disposal of the sludge.

[0020] The device has a reasonable structure design, smooth connection between each processing link, and is easy to operate. At the same time, the maintenance of the device is relatively convenient, which is conducive to reducing operating costs and improving processing efficiency.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention effectively adjusts the pH value of the wastewater by adding alkaline substances such as sodium hydroxide and calcium hydroxide and oxidants in the regulating tank, and performs preliminary oxidation treatment on cyanide; this step not only provides a suitable acid-base environment for subsequent treatment, but also significantly reduces the toxicity of cyanide, reduces its inhibitory effect on subsequent treatment processes, and thus reduces the overall treatment difficulty. A reaction tank is added after the regulating tank, which is specifically used for dehydrogenation reaction. By adding a decyanant in the reaction tank, specific ions in the decyanant react with free cyanide ions in the wastewater to form a water-insoluble complex and precipitate, thereby separating cyanide from the water body, reducing the concentration of cyanide in the wastewater, reducing the load in the subsequent biological treatment link, and reducing the inhibitory and toxic effects of cyanide on microorganisms, thereby improving the efficiency of the entire wastewater treatment process. Combined with the subsequent precipitation treatment biological treatment, pollutants such as organic matter, nitrides, and sulfides in the wastewater are more thoroughly removed.

[0022] The present invention not only focuses on the treatment effect of fertilizer production wastewater, but also pays attention to the recycling of resources. The clean water discharged from the secondary sedimentation tank is recycled and treated by recycling equipment to achieve the reuse of water resources and reduce production costs. The sludge storage tank is added to temporarily store the sludge generated in the sedimentation tank and the secondary sedimentation tank, which helps to achieve standardized treatment of the sludge, which can not only avoid secondary pollution of the environment by the sludge, but also provide convenience for the subsequent resource utilization of the sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By describing the embodiments of the present application in more detail in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present application will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings, the same reference numerals generally represent the same components or steps. Figure 1 A schematic diagram of the overall process of an application of a method for treating chemical production wastewater provided in this application. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0025] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with the implementation methods.

[0026] The present invention provides a method for treating fertilizer production wastewater. Figure 1As shown. Specifically, fertilizer production wastewater and part of domestic wastewater are first mixed and then sent to the regulating tank. The regulating tank is a tank with a storage function, and the regulating tank is equipped with a reagent dosing component. By using the reagent dosing component to add alkaline substances, the pH value of the mixed wastewater is adjusted, and then any oxidant is added to the regulating tank for cyanide in the mixed wastewater. In this way, the water volume balance and water quality stability of the mixed wastewater are ensured in the regulating tank, and the pH of the mixed wastewater is balanced, and favorable conditions are created for subsequent treatment. At the same time, the oxidant performs preliminary oxidation treatment on the cyanide in the mixed wastewater to reduce the concentration of cyanide. The wastewater after adjustment and pretreatment enters the reaction tank. By adding a decyanating agent, the cyanide in the mixed wastewater can be efficiently complexed to form a water-insoluble complex and precipitate, thereby separating it from the mixed wastewater, further reducing the content of cyanide, reducing the load of subsequent treatment links, and effectively avoiding the inhibition and toxicity of cyanide on microorganisms. Then the mixed wastewater treated by chemical reaction enters the sedimentation tank, where part of the suspended solids and most of the complexes are removed by sedimentation. The wastewater discharged from the sedimentation tank enters the anoxic tank in the biological treatment equipment. The anoxic tank is an oxygen-free pool containing denitrifying bacteria. The denitrifying bacteria use the organic matter in the wastewater as a carbon source to reduce NO3-N (nitrate nitrogen) in the water to N2 (nitrogen gas) and release it into the air, removing nitrogen compounds in the wastewater and providing the necessary organic matter and microbial environment for the subsequent aerobic treatment process. Then the wastewater enters the aerobic tank from the anoxic tank. The aerobic tank is an aerobic environment containing a large number of aerobic microorganisms. These microorganisms can efficiently perform degradation and nitrification reactions under sufficient oxygen supply. In the degradation reaction, aerobic microorganisms use organic matter in wastewater as energy and carbon source, decomposing it into harmless substances such as carbon dioxide and water. This process helps to remove BOD (organic matter) in wastewater and reduce the degree of organic pollution in wastewater. At the same time, in the nitrification reaction, aerobic microorganisms oxidize NH3-N (ammonia nitrogen) in wastewater to NO3-N (nitrate nitrogen). This step is an important link in removing nitrogen compounds in wastewater, which helps to prevent eutrophication of water bodies and protect the ecological environment. In order to achieve the smooth progress of nitrification, a high dissolved oxygen concentration and a suitable microbial environment need to be maintained in the aerobic pool; in addition, the sludge in the aerobic pool needs to be regularly returned to the anoxic pool to maintain the number and activity of microorganisms in the anoxic pool. Finally, the wastewater treated in the aerobic pool enters the secondary sedimentation tank for mud and water separation. The suspended matter and microbial flocs in the wastewater are precipitated to form sludge, and the clear water produced after precipitation enters the water storage tank to meet the standards for discharge or reuse. The sludge produced in the sedimentation tank and the secondary sedimentation tank enters the sludge storage tank, where the concentrated sludge is dried and dehydrated to reduce the water content of the sludge, making it easier for subsequent sludge transportation and treatment.Through the steps in the fertilizer wastewater treatment system of the present invention, efficient treatment and reuse of fertilizer production wastewater and domestic sewage are achieved.

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0028] Example The practical application of the process of fertilizer production wastewater of the present invention is shown in Figure 1 As shown, the practical application of the fertilizer production wastewater treatment device of the present invention includes the following process: First, the wastewater from fertilizer production and domestic sewage are mixed through pipes and then enter the equalization tank. The stirring device in the equalization tank makes the wastewater fully and evenly mixed in the equalization tank. Then, sodium hydroxide is added to the equalization tank to adjust the pH value of the wastewater to about 7, creating an environment suitable for biological treatment. Then, sodium hypochlorite oxidant is added to carry out preliminary oxidation treatment of cyanide in the wastewater. Part of the cyanide in the water is oxidized, reducing its toxicity.

[0029] The wastewater treated in the regulating tank enters the reaction tank through a pipeline, and a decyanating agent is added to the reaction tank. The decyanating agent can react with the cyanide in the wastewater to form a stable complex and precipitate that is insoluble in water, thereby separating the cyanide from the water body; reducing the concentration of cyanide in the wastewater, and also reducing the inhibitory and toxic effects of cyanide on microorganisms, creating favorable conditions for the subsequent biological treatment stage. The wastewater after decyanation treatment enters the sedimentation tank, and through the action of gravity, the suspended matter and most of the cyanide in the wastewater are precipitated, and the suspended matter and most of the cyanide in the wastewater are removed, further purifying the water quality, and providing cleaner water for subsequent biological treatment; at the same time, a sludge discharge device is provided at the bottom of the sedimentation tank to discharge the precipitate into the sludge storage tank regularly.

[0030] After sedimentation in the sedimentation tank, the wastewater enters the anoxic tank for denitrification and desulfurization. Under anoxic conditions, denitrifying bacteria reduce NO3-N to N2 and release it into the air, while removing some sulfides. Subsequently, the wastewater enters the aerobic tank for degradation and nitrification. Under aerobic conditions, microorganisms degrade BOD and convert NH3-N into NO3-N. Through the combined use of anoxic and aerobic treatments, nitrogen, sulfur and organic matter in the wastewater are removed. The denitrification reaction reduces the concentration of nitrates and reduces the risk of eutrophication of the water body. Aerobic degradation and nitrification reactions further purify the water quality and improve the biodegradability of the wastewater.

[0031] The wastewater after aerobic treatment enters the secondary sedimentation tank for mud-water separation to produce clarified water and sludge. A sludge return component is provided at the bottom of the secondary sedimentation tank to return part of the sludge to the anoxic tank to maintain the number and activity of microorganisms in the anoxic tank for denitrification and desulfurization reactions; clarified water flows into the water storage tank through the pipeline for use in subsequent production processes, while the remaining sludge is discharged into the sludge storage tank for sludge concentration and drying treatment to facilitate subsequent external transportation.

[0032] It can be seen that the present invention achieves effective removal of various pollutants such as nitrogen, sulfur, and organic matter in wastewater through the steps of mixing, adjusting, decyanation, precipitation, anoxic and aerobic treatment, and improves the treatment efficiency and water quality standard of wastewater. The recycling and reuse of water resources not only saves water resources, but also reduces the production cost of enterprises and improves the utilization efficiency of water resources; the reduction, stabilization and harmless treatment of sludge reduces the pollution of sludge to the environment and protects the ecological environment. At the same time, the resource utilization of dried sludge also has certain economic and social benefits.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating fertilizer production wastewater, characterized in that: The steps include: First, fertilizer production wastewater and part of domestic wastewater are mixed and then the water quality is balanced to obtain balanced wastewater, and then the pH value of the balanced wastewater is adjusted and pretreated to obtain pretreated wastewater; then the pretreated wastewater is subjected to chemical reaction treatment, precipitation treatment, and biological treatment to remove pollutants in the wastewater to obtain treated wastewater; the treated wastewater is subjected to secondary precipitation to remove suspended matter and microbial flocs in the water; finally, the water body and waste residue generated after the secondary precipitation are recycled.

2. The method for treating fertilizer production wastewater according to claim 1, characterized in that: The pH value is adjusted by using one or more alkaline substances selected from sodium hydroxide and calcium hydroxide.

3. The method for treating fertilizer production wastewater according to claim 1, characterized in that: The pretreatment is to oxidize the wastewater using an oxidant, wherein the oxidant is one or more of sodium hypochlorite, chlorine, hydrogen peroxide, and ozone.

4. The method for treating fertilizer production wastewater according to claim 1, characterized in that: The chemical reaction treatment is to use a decyanation agent to further remove organic matter and pollutants in the wastewater.

5. The method for treating fertilizer production wastewater according to claim 1, characterized in that: The biological treatment is to carry out denitrification and desulfurization reaction, degradation reaction and nitrification reaction on the wastewater to remove pollutants in the wastewater.

6. A fertilizer production wastewater treatment device as claimed in any one of claims 1 to 5, characterized in that: include: Along the direction of fertilizer production wastewater inflow, there are regulating tanks, reaction tanks, sedimentation tanks, biological treatment equipment, secondary sedimentation tanks, and recycling equipment; The regulating pool is used to collect fertilizer production wastewater and part of domestic wastewater, and the wastewater is subjected to pH adjustment and preliminary oxidation treatment in the regulating pool; The reaction tank is used to carry out dehydrogenation reaction on the wastewater treated in the regulating tank to reduce the inhibitory and toxic effects of cyanide on microorganisms; The sedimentation tank is used to remove part of the suspended solids and cyanide in the wastewater discharged from the reaction tank; The biological treatment equipment is used to carry out denitrification, desulfurization, degradation and digestion reactions on the wastewater discharged from the sedimentation tank; The secondary sedimentation tank is used to separate mud and water from the wastewater discharged from the biological treatment equipment, making the mixed wastewater clear; The recycling equipment is used to recycle and utilize the clean water discharged from the secondary sedimentation tank.

7. The fertilizer production wastewater treatment device according to claim 6, characterized in that: The biological treatment equipment contains an anoxic tank and an aerobic tank; The anoxic tank performs a denitrification and desulfurization reaction to reduce NO3-N in the fertilizer wastewater to N2 which enters the air; In the aerobic pool, microorganisms carry out nitrification and organic matter degradation under aerobic conditions on the wastewater discharged from the anoxic pool.

8. The fertilizer production wastewater treatment device according to claim 6, characterized in that: The recycling equipment comprises a water storage tank, which is used to collect the clean water discharged from the secondary sedimentation tank and enter the industrial reuse water through the lifting effect of the pump.

9. The fertilizer production wastewater treatment device according to claim 6, characterized in that: The fertilizer production wastewater treatment device also contains a sludge storage tank, which is used to temporarily store the sludge produced in the sedimentation tank and the secondary sedimentation tank.

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