Sludge conditioning and dewatering production process for sewage plant

Abstract

The invention relates to the technical field of sludge conditioning, concentrating and dewatering, in particular to a sludge conditioning and dewatering production process for a sewage plant, which comprises the following steps of: 1, adding ferric salt or aluminum salt: before sludge enters a concentration tank or a sludge storage tank, adding ferric salt or aluminum salt, uniformly stirring to fully disperse inorganic salt, and uniformly stirring according to the sludge concentration and the sludge amount to obtain a sludge concentration tank or a sludge storage tank; matching the dosage concentration, dosage, stirring speed and stirring time of the ferric salt or the aluminum salt; according to the invention, by reasonably distributing tasks of each dehydration process section, more than 50% of dehydration tasks are completed in the mud-water separation and concentration process section, the burden of mechanical dehydration is reduced, the overall dehydration efficiency is improved, the viscosity and elasticity of the sludge are reduced by introducing ferric salt or aluminum salt for conditioning, and the flocculation stability is improved by optimizing a polyacrylamide flocculation process; and a flocculation concentration process section is added to enhance the structural stability of the sludge, so that the mechanical dehydration and deep dehydration effects are improved, and the process reduces the mechanical dehydration difficulty.

Description

Technical Field

[0001] The invention relates to the technical field of sludge conditioning, concentration and dehydration in sewage treatment plants, and in particular to a production process for sludge conditioning and dehydration in sewage treatment plants. Background Art

[0002] More than a decade ago, the state introduced a new sludge disposal standard (sewage treatment plant dewatering sludge moisture content ≤ 80%, deep dewatering mixed landfill sludge moisture content ≤ 60%), the water treatment industry, a high-pressure mechanical filter press dewatering process or thermal drying dewatering process and other deep dewatering processes, but the current sewage treatment plant sludge conditioning dewatering production process, has not made any changes, still using the old method, the current sludge conditioning dewatering production process, the distribution of dewatering tasks in each section is unreasonable, it is difficult to meet the standards, the production cost is high; the current process does not follow the mechanical dewatering machine The dewatering principle requirements of the dewatering device (low sludge viscosity and elasticity, less intermittent water and capillary water, less use of polyacrylamide, and the presence of a pressure skeleton and hydrophobic channels) make it difficult to produce sludge that meets the standards, and the production cost is high, especially for high-organic matter sludge (organic matter content ≥ 65%). At the same time, the new process developed later also puts forward the same principle requirements for the sludge conditioning and dewatering production process of sewage treatment plants (low sludge viscosity and elasticity, less intermittent water and capillary water, less use of polyacrylamide, and the presence of a pressure skeleton and hydrophobic channels).

[0003] The current sludge conditioning and dehydration production process is as follows: the thin sludge after biochemical treatment in the sewage treatment plant flows into the sludge storage tank or the concentration tank. After being concentrated into thick sludge, polyacrylamide is added in the pipeline, mixed, and stirred in a mixing barrel before entering a belt filter press or a stacked screw dehydrator for mechanical dehydration to produce semi-solid sludge. At this point, the sludge conditioning and dehydration production process of the sewage plant is completed. Then, after a deep dehydration process such as mechanical filter pressing or thermal drying, it is produced into solid sludge, which is then landfilled, incinerated, or recycled. This is the entire sludge disposal process.

[0004] In the current sludge conditioning and dewatering production process, the dehydration tasks are unreasonably allocated in the sludge-water separation and concentration section, the polyacrylamide flocculation section, and the mechanical dewatering (belt machine gravity dewatering, wedge dewatering, and medium-high pressure dewatering) and other dewatering process sections. In the sludge-water separation and concentration process section of sludge, dehydration is the easiest and the cost is extremely low. It should complete more than 50% of the dehydration tasks of the whole process. However, in the concentration and dewatering production process of most sewage treatment plants, only less than 20% of the dehydration tasks of the whole process are completed. Some even do not dehydrate, leaving more than 50% of the dehydration tasks of the process to the limited mechanical dewatering to complete. The task is too heavy and the mechanical dewatering cannot be achieved, resulting in difficulties in meeting the sludge dehydration standards in sewage treatment plants. In addition, mechanical dewatering machines are very difficult to handle sludge with too much intermittent water and capillary water, and are also difficult to handle sludge with too much elasticity and viscosity. Mechanical dewatering requires a pressure skeleton and a hydrophobic channel. Therefore, the principle of the sludge conditioning and dewatering production process is: gradually decreasing and segmental dehydration, each section tries its best to dehydrate, and the dehydration in the previous section should create favorable conditions for the dehydration in the subsequent section, reduce the intermittent water and capillary water of the sludge, and reduce the viscosity and elasticity of the sludge to create a sufficient pressure skeleton and hydrophobic channel for mechanical dewatering; the dissolved oxygen in the sludge is one of the reasons for the large amount of intermittent water and capillary water. Therefore, during the sludge conditioning process, the water pressure and time should be used to release the dissolved oxygen, and at the same time, the sludge density should be increased and the microscopic intermittence of the sludge mass should be reduced. However, in the current sludge conditioning, polyacrylamide is directly used for flocculation, and the microscopic intermittence of the sludge mass is too large, which is another reason for the excessive intermittent water and capillary water in the sludge; moreover, when directly using polyacrylamide to condition the sludge, the dosage of polyacrylamide will be very large, which will increase the elasticity and viscosity of the sludge and damage the pressure skeleton and hydrophobic channel. Therefore, in view of the above problems, a sewage treatment plant sludge conditioning and dewatering production process is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a sewage treatment plant sludge conditioning and dewatering production process to solve the problem that in the dehydration process sections such as the sludge-water separation and concentration section, the polyacrylamide flocculation section, and the mechanical dewatering (belt machine gravity dewatering, wedge dewatering, and medium-high pressure dewatering), the dehydration task allocation is unreasonable. In the sludge-water separation and concentration process section, dehydration is the easiest and the cost is extremely low. More than 50% of the dehydration task of the whole process should be completed. However, in the concentration and dewatering production process of most sewage treatment plants, only less than 20% of the dehydration task of the whole process is completed, and some even do not dehydrate, leaving more than 50% of the task of the process to the limited mechanical dewatering to complete. The task is too heavy and the mechanical dewatering cannot be achieved, resulting in difficulties in meeting the sewage treatment plant sludge dewatering standard. In addition, it is very difficult for mechanical dewatering machines to handle sludge with too high content of intermittent water and capillary water, and it is also difficult to handle sludge with too high elasticity and viscosity. Mechanical dewatering requires a pressure skeleton and a hydrophobic channel. Therefore, the principle of the sludge conditioning and dewatering production process is: gradually decreasing and segmental dehydration, each section tries its best to dehydrate, and the dehydration in the previous section should create favorable conditions for the dehydration in the subsequent section, reduce the intermittent water and capillary water of the sludge, and reduce the viscosity and elasticity of the sludge to create a sufficient pressure skeleton and hydrophobic channel for mechanical dewatering; the dissolved oxygen in the sludge is one of the reasons for the large amount of intermittent water and capillary water; during the sludge conditioning process, the water pressure and time should be used to release the dissolved oxygen, and at the same time, the sludge density should be increased and the microscopic intermittence of the sludge mass should be reduced. However, in the current sludge conditioning, polyacrylamide is directly used for flocculation, and the microscopic intermittence of the sludge mass is too large, which is another reason for the too large intermittent water and capillary water of the sludge; and directly using polyacrylamide to condition the sludge will result in a large amount of polyacrylamide, which will increase the elasticity and viscosity of the sludge and damage the pressure skeleton and hydrophobic channel. In order to reduce the intermittent water and capillary water of the conditioned sludge, and also to reduce the elasticity and viscosity of the conditioned sludge, and at the same time increase the pressure skeleton and hydrophobic channel, it is necessary to reduce the addition amount of polyacrylamide and add a certain amount of iron salt or aluminum salt first; and use the pool depth pressure and time to release the dissolved oxygen to further reduce the intermittent water and capillary water; in order to further reduce polyacrylamide, control the conditioned sludge concentration within the range suitable for polyacrylamide to exert its effect, and ensure the reaction time and the best conditions; in order to further reduce the mechanical dewatering task, add a flocculation and concentration process section.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A sewage treatment plant sludge conditioning and dewatering production process, comprising the following steps:

[0008] Step 1: Ferric salt or aluminum salt addition process section: Before the sludge enters the thickening tank or the sludge storage tank, ferric salt or aluminum salt is added. Through uniform stirring, the inorganic salts are fully dispersed, and according to the sludge concentration and sludge volume, the dosing concentration, dosing amount, stirring speed, and stirring time of ferric salt or aluminum salt are matched to reduce the viscosity and elasticity of the sludge. At the same time, it provides a microscopic pressure skeleton and a hydrophobic channel for the subsequent mechanical dewatering process, and also provides a microscopic hydrophobic channel for the deep dehydration and heat drying process, and can reduce the interstitial water and capillary water of the conditioned sludge;

[0009] Among them, the addition of ferric salt or aluminum salt is achieved through an inorganic salt dosing pump in cooperation with a pipeline mixer; the uniform mixing of ferric salt or aluminum salt and the sludge is achieved through a stirring tank;

[0010] Step 2: Sludge-water separation and thickening process section: In the thickening tank or the sludge storage tank, the sludge added with ferric salt or aluminum salt is subjected to intermittent slow stirring to create conditioning conditions through slow stirring, so that the sludge particles fully aggregate, and the supernatant is concentrated and discharged to reduce the subsequent dewatering task. After concentration, the sludge concentration is controlled within a certain range to create necessary conditions for using less polyacrylamide;

[0011] And the pool depth pressure is used to increase the microscopic density of the sludge. At the same time, the residence time is used to release the dissolved oxygen in the sludge to further increase the sludge density, reduce the capillary water and interstitial water, and reduce the sludge elasticity;

[0012] Step 3: Polyacrylamide addition process section: Using the device for adding polyacrylamide in the original process, according to the sludge concentration and sludge volume, the dosing concentration, dosing amount, and stirring speed of polyacrylamide are matched to achieve the use of less polyacrylamide;

[0013] Step 4: Flocculation and thickening process section: In the newly added thickening tank, the sludge residence time is increased to ensure that the polyacrylamide fully unfolds, improve the flocculation stability of the sludge, and form stable conditioned sludge to achieve the use of less polyacrylamide. At the same time, the water pressure is used to further compress the microscopic gaps of the sludge to reduce the capillary water and interstitial water, as well as reduce the sludge elasticity. At the same time, the supernatant is concentrated and discharged to reduce the mechanical dewatering task;

[0014] Step 5: Mechanical dewatering process section: The sludge is dewatered by a belt filter press or a spiral press. During the dewatering process, the gravity and pressure dewatering time are optimized and lengthened, and the pressure is adjusted to maintain the pressure difference between the upper and lower belts for dewatering.

[0015] For the sludge conditioned by the present invention, in the belt gravity dewatering process section, the dewatering effect is slightly inferior to that of the sludge in the traditional conditioning process, and the gravity dewatering time needs to be longer than the current process; while in the belt pressure section, the dewatering effect is significantly better than that of the sludge in the traditional conditioning process, and the greater the pressure, the more obvious it is. Under the possible production conditions, the gravity dewatering and pressure dewatering time should be extended as much as possible.

[0016] As a further optimized content of the present invention, wherein: in the process section of adding ferric salt or aluminum salt in Step 1, the ferric salt is polyferric sulfate or ferric chloride, and the aluminum salt is polyaluminum chloride;

[0017] The polyferric sulfate is applicable to the sludge conditioning with an organic matter content ≥ 65%, the dosing concentration is 4% - 15%, the amount of pure dry powder polyferric sulfate added per ton of absolute dry sludge is 3 kg - 20 kg, the length of the pipeline mixer is 60 - 120 cm, the volume of the stirring tank (acid-resistant and corrosion-resistant) meets the stirring time of 180 seconds - 600 seconds, the stirring speed is 30 revolutions per minute - 150 revolutions per minute. In the thickening tank or sludge storage tank, stirring is carried out, the stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, at intervals of 30 minutes - 180 minutes, and stirring is repeated once;

[0018] The ferric chloride is applicable to the sludge conditioning with an organic matter content ≤ 65%, the dosing concentration is 2% - 10%, the amount of pure dry powder ferric chloride added per ton of absolute dry sludge is 4 kg - 25 kg, the length of the pipeline mixer is 60 - 120 cm, the volume of the stirring tank (acid-resistant and corrosion-resistant) meets the stirring time of 180 seconds - 600 seconds, the stirring speed is 30 revolutions per minute - 150 revolutions per minute. In the thickening tank or sludge storage tank, stirring is carried out, the stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, at intervals of 30 minutes - 180 minutes, and stirring is repeated once;

[0019] The polyaluminum chloride is applicable to the sludge conditioning with an organic matter content ≤ 60%, the dosing concentration is 2% - 10%, the amount of pure dry powder polyaluminum chloride added per ton of absolute dry sludge is 5 - 30 kg, the length of the pipeline mixer is 60 - 120 cm, the volume of the stirring tank (acid-resistant and corrosion-resistant) meets the stirring time of 180 seconds - 600 seconds, the stirring speed is 30 revolutions per minute - 150 revolutions per minute. In the thickening tank or sludge storage tank, stirring is carried out, the stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, at intervals of 30 minutes - 180 minutes, and stirring is repeated once.

[0020] As a further optimized content of the present invention, wherein: in the process section of sludge-water separation and thickening in Step 2, the residence time in the thickening tank or sludge storage tank is 1 - 10 hours, and the microscopic gaps of the sludge are compressed by the pressure of the tank depth. The fluctuation range of the sludge concentration of the thickened sludge discharged is not more than 2000 mg / L, the sludge concentration of the thickened sludge discharged is 10000 mg / L - 18000 mg / L, and the depth of the thickening tank or sludge storage tank is 2 - 6 m.

[0021] As a further optimized content of the present invention, wherein: in the process section of adding polyacrylamide in step three, polyacrylamide is added through a pipeline mixer. The length of the polyacrylamide pipeline mixer is 50 - 100 cm. The solution ratio concentration of the polyacrylamide is 0.4‰ - 1.5‰. The configured service life of the polyacrylamide is 15 hours. The addition amount of the polyacrylamide is 0.5 kg - 2 kg per ton of absolute dry sludge. The stirring is carried out using a stirring tank. The volume of the stirring tank satisfies a stirring time of 120 seconds - 480 seconds, and the stirring speed is 30 - 120 revolutions per minute.

[0022] As a further technical solution for the further implementation of this scheme, wherein, in the flocculation and concentration process section of step four, the volume of the concentration device satisfies a sludge static settling time of 20 minutes - 360 minutes. The water pressure of the flocculation and concentration device is 2 - 6 meters. The sludge concentration after concentration is ≥ 35000 mg / L, and the fluctuation range of the concentrated concentration is not greater than 5000 mg / L.

[0023] As a further optimized content of the present invention, wherein: in the mechanical dewatering process section, a belt filter press or a spiral press filter is used. The gravity dewatering time of the belt filter press is 60 seconds - 120 seconds, the pressure dewatering time is 60 seconds - 180 seconds, the belt pressure is 0.4 MP - 0.5 MP, and the pressure difference between the upper and lower belts is 0.05 MP.

[0024] As a further optimized content of the present invention, wherein: the deep dewatering process adopts mechanical pressure filtration or thermal drying methods.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. In the present invention, by reasonably allocating the tasks of each dewatering process section, in the mud - water separation and concentration process section, more than 50% of the dewatering tasks are completed, reducing the burden of mechanical dewatering and improving the overall dewatering efficiency. By lengthening the residence time and water pressure, dissolved oxygen is released and the sludge density is increased. By introducing ferric salts or aluminum salts for conditioning, the sludge viscosity and elasticity are reduced, the pressure skeleton and hydrophobic channels of the sludge are increased, and the interstitial water and capillary water of the sludge are reduced. The polyacrylamide addition process is optimized to use less polyacrylamide, reduce the elasticity and viscosity of the sludge, and less damage the pressure skeleton and hydrophobic channels of the sludge. A new flocculation and concentration process section is added to increase the sludge static settling time, enhance the structural stability of the sludge, utilize the water pressure to concentrate the sludge, and further reduce the mechanical dewatering tasks, thereby improving the mechanical dewatering and deep dewatering effects. Therefore, the process of the present invention reduces the difficulty of mechanical dewatering, reduces the moisture content of the produced sludge by at least 5 percentage points compared with the original process, reduces the water content of the sludge produced by the sewage treatment plant by more than 25% compared with the original process, and also reduces the production process cost of the subsequent sludge deep dewatering.

[0027] 2. In the present invention, the chemical dosing cost of the production process of the present invention is 47.9% of that of the original production process. The production process of the present invention reduces the use of polyacrylamide by 67% compared with the original production process. Since polyacrylamide is very difficult to degrade and will cause pollution to water and soil, therefore, a large reduction in the use of polyacrylamide can not only facilitate mechanical pressure filtration dehydration, but also reduce the degree of harm to the environment and increase the economic value of sludge resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a process flow block diagram of a sewage treatment plant sludge conditioning and dewatering production process of the present invention;

[0029] Figure 2 is a process flow diagram of a sewage treatment plant sludge conditioning and dewatering production process of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Please refer to Figure 1-2 , the present invention provides a technical solution:

[0031] A sewage treatment plant sludge conditioning and dewatering production process, comprising the following steps:

[0032] Step 1: Ferric salt or aluminum salt addition process section: Before the sludge enters the thickening tank or sludge storage tank, ferric salt or aluminum salt is added, and through uniform stirring, the inorganic salts are fully dispersed, and the dosing concentration, dosing amount, stirring speed and stirring time of ferric salt or aluminum salt are matched according to the sludge concentration and sludge volume, so as to reduce the viscosity and elasticity of the sludge, and at the same time provide a microscopic pressure skeleton and a hydrophobic channel for the subsequent mechanical dewatering process, and also provide a microscopic hydrophobic channel for the deep dehydration and heat drying process, and can reduce the interstitial water and capillary water of the conditioned sludge;

[0033] Among them, the addition of ferric salt or aluminum salt is realized by an inorganic salt dosing pump in cooperation with a pipeline mixer; the uniform mixing of ferric salt or aluminum salt and sludge is realized by a stirring tank;

[0034] Step 2: Sludge-water separation and thickening process section: In the thickening tank or sludge storage tank, the sludge added with ferric salt or aluminum salt is slowly stirred intermittently, so as to create conditioning conditions through slow stirring, make the sludge particles fully aggregate, and thicken and discharge the supernatant liquid, reduce the subsequent dewatering task, and after thickening, control the sludge concentration within a certain range to create necessary conditions for using less polyacrylamide;

[0035] And utilize the pressure of the tank depth to increase the microscopic density of the sludge. At the same time, utilize the residence time to release the dissolved oxygen in the sludge, further increase the sludge density, reduce the capillary water and interstitial water, and reduce the sludge elasticity;

[0036] Step 3: Polyacrylamide addition process section: Using the device for adding polyacrylamide in the original process, according to the sludge concentration and sludge volume, match the dosing concentration, dosing amount and stirring speed of polyacrylamide to achieve less use of polyacrylamide;

[0037] Step 4: Flocculation and concentration process section: In the newly added concentration tank, increase the sludge retention time to ensure that polyacrylamide fully unfolds, improve the flocculation stability of sludge, form stable conditioned sludge, and achieve less use of polyacrylamide. At the same time, use water pressure to further compress the microscopic gaps of sludge to reduce capillary water and interstitial water, and reduce the elasticity of sludge. Meanwhile, concentrate and discharge the supernatant to reduce the mechanical dewatering task;

[0038] Step 5: Mechanical dewatering process section: The sludge is dehydrated by a belt filter press or a spiral press. During the dewatering process, optimize and extend the gravity and pressure dewatering time, adjust the pressure, and maintain the pressure difference between the upper and lower belts for dewatering.

[0039] For the sludge conditioned by the present invention, in the gravity dewatering process section of the belt machine, the dewatering effect is slightly inferior to that of the sludge in the traditional conditioning process, and the gravity dewatering time needs to be extended compared with the existing process; while in the pressure section of the belt machine, the dewatering effect is significantly better than that of the sludge in the traditional conditioning process, and the greater the pressure, the more obvious it is. Under the possible conditions of production, extend the gravity dewatering and pressure dewatering time as much as possible;

[0040] As a further technical solution of this scheme, in the step of adding ferric salt or aluminum salt process section, the ferric salt is polyferric sulfate or ferric trichloride, and the aluminum salt is polyaluminum chloride;

[0041] The polyferric sulfate is applicable to the conditioning of sludge with an organic matter content ≥ 65%. The dosing concentration is 4% - 15%. The amount of pure dry powder polyferric sulfate added per ton of dry sludge is 3 kg - 20 kg. The length of the pipeline mixer is 60 - 120 cm. The volume of the stirring tank (acid and corrosion resistant) meets the stirring time of 180 seconds - 600 seconds, and the stirring speed is 30 revolutions per minute - 150 revolutions per minute. In the thickening tank or sludge storage tank, add stirring. The stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, and the interval is 30 minutes - 180 minutes, and repeat the stirring once;

[0042] The ferric trichloride is applicable to the conditioning of sludge with an organic matter content ≤ 65%. The dosing concentration is 2% - 10%. The amount of pure dry powder ferric trichloride added per ton of dry sludge is 4 kg - 25 kg. The length of the pipeline mixer is 60 - 120 cm. The volume of the stirring tank (acid and corrosion resistant) meets the stirring time of 180 seconds - 600 seconds, and the stirring speed is 30 revolutions per minute - 150 revolutions per minute. In the thickening tank or sludge storage tank, add stirring. The stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, and the interval is 30 minutes - 180 minutes, and repeat the stirring once;

[0043] The polyaluminum chloride is applicable to the sludge conditioning with an organic matter content of ≤60%, the dosing concentration is 2%-10%, 5-30 kg of pure dry powder polyaluminum chloride is added per ton of absolute dry sludge, the length of the pipeline mixer is 60-120 cm, the volume of the stirring tank (acid-resistant corrosion) meets the stirring time of 180 seconds - 600 seconds, the stirring speed is 30 revolutions per minute - 150 revolutions per minute. In the thickening tank or sludge storage tank, stirring is carried out, the stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, and stirring is repeated every 30 minutes - 180 minutes.

[0044] By optimizing the dosing parameters of iron salts or aluminum salts, the viscosity and elasticity of the sludge are significantly reduced, the dewaterability of the sludge is improved, and a more stable sludge structure is provided for the subsequent thickening and mechanical dewatering processes;

[0045] As a further technical solution of this scheme, in the step two mud-water separation and thickening process section, the residence time in the thickening tank or sludge storage tank is 1 - 10 hours, and the microscopic gaps of the sludge are compressed by the pressure of the tank depth. The fluctuation range of the sludge concentration of the thickened sludge is not more than 2000 mg / L, the sludge concentration of the thickened sludge is 10000 mg / L - 18000 mg / L, and the tank depth of the thickening tank or sludge storage tank is 2 - 6 m.

[0046] By optimizing the sludge residence time and the tank depth pressure, the dissolved oxygen of the sludge is released, the intermittent water and capillary water are reduced, the stability of the sludge is improved, and the sludge concentration fluctuation is reduced, which helps to improve the economy, consistency and operability of the dewatering process;

[0047] As a further technical solution of this scheme, in the step three polyacrylamide dosing process section, polyacrylamide is added through a pipeline mixer. The length of the polyacrylamide pipeline mixer is 50 - 100 cm, the solution ratio concentration of the polyacrylamide is 0.4‰ - 1.5‰, the configured service life of the polyacrylamide is 15 hours, the addition amount of the polyacrylamide is 0.5 kg - 2 kg per ton of absolute dry sludge, and the stirring is carried out using a stirring tank. The volume of the stirring tank meets the stirring time of 120 seconds - 480 seconds, and the stirring speed is 30 - 120 revolutions per minute.

[0048] By controlling the type selection and dosing parameters of polyacrylamide, the flocculation effect of the sludge is improved, the usage amount of polyacrylamide is reduced, thereby reducing the elasticity and viscosity of the sludge, reducing the process treatment cost, and reducing the environmental pollution;

[0049] As a further technical solution of this scheme, in the step four flocculation and thickening process section, the volume of the thickening device meets the sludge static settling time of 20 minutes - 360 minutes, the water pressure of the flocculation and thickening device is 2 - 6 m, the sludge thickening concentration ≥35000 mg / L, and the fluctuation range of the thickening concentration is not more than 5000 mg / L.

[0050] By extending the static settling time and concentrating, it promotes the stabilization of the sludge structure, reduces the task of mechanical dewatering, and improves the efficiency of subsequent mechanical dewatering;

[0051] As a further technical solution of this scheme, in the mechanical dewatering process section of step five, a belt filter press or a spiral screw dehydrator is adopted. The gravity dewatering time of the belt filter press is 60 seconds - 120 seconds, the pressure dewatering time of the belt is 60 seconds - 180 seconds, the belt pressure of the belt is 0.4MP - 0.5MP, and the pressure difference between the upper and lower belts of the belt is 0.05MP.

[0052] As a further technical solution of this scheme, the deep dewatering process adopts mechanical pressure filtration or thermal drying methods to improve the efficiency of the deep dewatering process, reduce the process cost at the same time, make the moisture content of the treated sludge easier to meet the standards for landfill, incineration or resource utilization, and improve the economy and environmental protection of sludge disposal.

[0053] Process flow:

[0054] Iron salt or aluminum salt addition process section: Before the sludge enters the thickening tank or the sludge storage tank, iron salt or aluminum salt is added, and preliminary mixing is carried out through an inorganic salt dosing pump and a pipeline mixer. The iron salt or aluminum salt is evenly mixed with the sludge, and this is achieved through re - mixing in a stirring tank to fully disperse the inorganic salt;

[0055] According to the sludge concentration and sludge volume, match the dosing concentration, dosing amount, stirring speed and stirring time of the iron salt or aluminum salt to reduce the viscosity and elasticity of the sludge and improve the dewaterability of the sludge;

[0056] Sludge - water separation and thickening process section: Adopt an intermittent slow - stirring process to make the sludge particles fully aggregate to form stable conditioned sludge; by discharging the supernatant, complete the preliminary thickening task and control the thickened sludge concentration within a set range;

[0057] Utilize the pool depth pressure and residence time to increase the microscopic density of the sludge mass, reduce the sludge elasticity, provide sludge with a more stable structure for subsequent processes, and at the same time, also reduce the interstitial water and capillary water of the conditioned sludge, reducing the dewatering task of the subsequent process;

[0058] Polyacrylamide flocculation addition process section: According to the sludge concentration and sludge volume, match the dosing concentration, dosing amount and stirring speed of polyacrylamide, especially optimize the stirring speed to prevent excessive fragmentation of the sludge flocs, resulting in over - use of polyacrylamide and increasing the difficulty of mechanical sludge dewatering;

[0059] Flocculation and thickening process section: Increase the sludge retention time, utilize the effects of water pressure and standing time to compress the microscopic gaps of the sludge, reduce the interstitial water and capillary water of the conditioned sludge; meanwhile, concentrate and discharge the supernatant liquid, reduce the dehydration task of the subsequent process, achieve reducing the sludge elasticity and improving the dewaterability of the sludge; the water pressure of the flocculation and thickening device is (2 - 6 meters).

[0060] Mechanical dehydration process section: Use a belt filter press or a spiral screw press for dehydration. The gravity dehydration time of the belt filter press is 60 seconds - 120 seconds, the pressure dehydration time is 60 seconds - 180 seconds, the belt pressure is 0.4MP - 0.5MP, and the pressure difference between the upper and lower belts is 0.05MP.

[0061] The sludge conditioned by the process of the present invention is more in line with the principles of mechanical dehydration and thermal drying dehydration, and can achieve that the moisture content of the sludge produced by the sewage treatment plant is reduced by at least 5 percentage points compared with the original process. Equivalently, the water content of the sludge produced by the sewage treatment plant is reduced by more than 25% compared with the original process. It can achieve reducing the dehydration task of the subsequent sludge deep dehydration production process, reducing the investment in deep dehydration equipment, reducing the process cost, being more conducive to the deep dehydration process, and economically reducing the moisture content of the sludge to ≤60%, meeting the requirements of landfill, incineration or resource utilization.

[0062] The production process of the present invention can achieve that the chemical dosing cost of the production process of the present invention is 47.9% of the original production process. The production process of the present invention reduces the use of polyacrylamide by 67% compared with the original production process. Since polyacrylamide is difficult to degrade and will cause pollution to water and soil, therefore, a large reduction in the use of polyacrylamide can reduce the degree of harm to the environment and increase the economic value of sludge resource utilization.

[0063] The comparative verification test is as follows:

[0064] Qualitative table of the comparative sludge

[0065] (In the present invention, the pilot-scale sludge and the original production sludge use the sludge from the same biochemical treatment process pipeline, with a time difference of 10 minutes before and after, to ensure the value of the comparative test)

[0066]

[0067] Specific comparison table of the sludge conditioning and dehydration process and effect between the present invention and the original production process:

[0068]

[0069] Specific comparison table of the effects of the new and old production processes for sludge conditioning and dehydration:

[0070]

[0071] The sludge conditioning and dewatering production process of the present invention reduces the output sludge by 28% compared with the original process, and the moisture content of the output sludge is also at least 5 percentage points lower than that of the original process. For subsequent mechanical high-pressure deep dewatering, or thermal drying deep dewatering, or sludge incineration and other treatment processes, the dewatering task is reduced by 28% compared with the original, which not only reduces the dewatering difficulty, but also can reduce the investment in expensive disposal equipment.

[0072] In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that due to the limited nature of written expression and the objectively infinite specific structures, for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements, embellishments or changes can be made, and the above technical features can also be combined in an appropriate manner; these improvements, embellishments, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, should all be regarded as the protection scope of the present invention.

Claims

1. A sewage treatment plant sludge conditioning and dewatering production process, characterized in that, It includes the following steps: Step 1: Iron salt or aluminum salt addition process section: Before the sludge enters the thickening tank or sludge storage tank, iron salt or aluminum salt is added. Through uniform stirring, the inorganic salts are fully dispersed. According to the sludge concentration and sludge volume, the dosing concentration, dosing amount, stirring speed, and stirring time of iron salt or aluminum salt are matched to reduce the viscosity and elasticity of the sludge. At the same time, it provides a microscopic pressure skeleton and hydrophobic channels for the subsequent mechanical dewatering process, and also provides microscopic hydrophobic channels for the deep dewatering and heat drying process, and can reduce the interstitial water and capillary water in the conditioned sludge; Among them, the addition of iron salt or aluminum salt is achieved through an inorganic salt dosing pump in cooperation with a pipeline mixer; the uniform mixing of iron salt or aluminum salt and sludge is achieved through a stirring tank; Step 2: Sludge-water separation and thickening process section: In the thickening tank or sludge storage tank, the sludge added with iron salt or aluminum salt is slowly stirred intermittently to create conditioning conditions through slow stirring, so that the sludge particles are fully aggregated, and the supernatant is concentrated and removed, reducing the subsequent dewatering task. After thickening, the sludge concentration is controlled within a certain range to create necessary conditions for reducing the use of polyacrylamide; And the pool depth pressure is used to increase the microscopic density of the sludge. At the same time, the residence time is used to release the dissolved oxygen in the sludge, further increasing the sludge density, reducing capillary water and interstitial water, and reducing the sludge elasticity; Step 3: Polyacrylamide addition process section: Using the device for adding polyacrylamide in the original process, according to the sludge concentration and sludge volume, the dosing concentration, dosing amount, and stirring speed of polyacrylamide are matched to achieve less use of polyacrylamide; Step 4: Flocculation and thickening process section: In the newly added thickening tank, the sludge residence time is increased to ensure that the polyacrylamide is fully stretched, improve the flocculation stability of the sludge, form stable conditioned sludge, and achieve less use of polyacrylamide. At the same time, the water pressure is used to further compress the microscopic gaps of the sludge to reduce capillary water and interstitial water, and reduce the sludge elasticity. At the same time, the supernatant is concentrated and removed to reduce the mechanical dewatering task; Step 5: Mechanical dewatering process section: The sludge is dewatered by a belt filter press or a spiral press. During the dewatering process, the gravity and pressure dewatering time are optimized and lengthened, the pressure is adjusted, and the pressure difference between the upper and lower belts is maintained for dewatering.

2. The sewage treatment plant sludge conditioning and dewatering production process according to claim 1, wherein: In the step 1 iron salt or aluminum salt addition process section, the iron salt is polyferric sulfate or ferric trichloride, and the aluminum salt is polyaluminum chloride; The polyferric sulfate is suitable for the conditioning of sludge with an organic matter content ≥ 65%. The dosing concentration is 4% - 15%. The amount of pure dry powder polyferric sulfate added per ton of absolute dry sludge is 3 kg - 20 kg. The length of the pipeline mixer is 60 - 120 cm. The volume of the stirring tank (acid-resistant and corrosion-resistant) meets the stirring time of 180 s - 600 s, the stirring speed is 30 r / min - 150 r / min. In the thickening tank or sludge storage tank, stirring is carried out, the stirring time is 30 - 600 s, the stirring speed is 1 - 30 r / min, and stirring is repeated once every 30 minutes - 180 minutes; The ferric chloride is applicable to the sludge conditioning with the organic matter content ≤ 65%. The dosing concentration is 2% - 10%. The amount of pure dry powder ferric chloride added per ton of dry sludge is 4 kg - 25 kg. The length of the pipeline mixer is 60 - 120 cm. The volume of the stirring tank (acid-resistant and corrosion-resistant) meets the stirring time of 180 seconds - 600 seconds, and the stirring speed is 30 - 150 revolutions per minute. In the thickening tank or sludge storage tank, stirring is carried out. The stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, and the interval is 30 minutes - 180 minutes. Stirring is repeated once. The polyaluminum chloride is applicable to the sludge conditioning with the organic matter content ≤ 60%. The dosing concentration is 2% - 10%. The amount of pure dry powder polyaluminum chloride added per ton of dry sludge is 5 - 30 kg. The length of the pipeline mixer is 60 - 120 cm. The volume of the stirring tank (acid-resistant and corrosion-resistant) meets the stirring time of 180 seconds - 600 seconds, and the stirring speed is 30 - 150 revolutions per minute. In the thickening tank or sludge storage tank, stirring is carried out. The stirring time is 30 - 600 seconds, the stirring speed is 1 - 30 revolutions per minute, and the interval is 30 minutes - 180 minutes. Stirring is repeated once.

3. A sewage treatment plant sludge conditioning and dewatering production process according to claim 1, characterized in that: In the sludge-water separation and thickening process section of step two, control the residence time of the sludge in the thickening tank or sludge storage tank for 1 - 10 hours, and use the pressure of the tank depth to compress the microscopic gaps of the sludge. The fluctuation range of the sludge concentration of the thickened sludge is not more than 2000 mg / L, and the sludge concentration of the thickened sludge is 10000 mg / L - 18000 mg / L. The depth of the thickening tank or sludge storage tank is 2 - 6 m.

4. A sewage treatment plant sludge conditioning and dewatering production process according to claim 1, characterized in that: In the process section of adding polyacrylamide in step three, add polyacrylamide through the pipeline mixer. The length of the polyacrylamide pipeline mixer is 50 - 100 cm. The solution ratio concentration of the polyacrylamide is 0.4‰ - 1.5‰. The configured service life of the polyacrylamide is 15 hours. The addition amount of the polyacrylamide is 0.5 kg - 2 kg per ton of dry sludge. Stirring is carried out using a stirring tank. The volume of the stirring tank meets the stirring time of 120 seconds - 480 seconds, and the stirring speed is 30 - 120 revolutions per minute.

5. A sewage plant sludge conditioning and dewatering production process according to claim 1, characterized in that: In the flocculation and thickening process section of step four, the volume of the thickening device meets the sludge static time of 20 minutes - 360 minutes. The water pressure of the flocculation and thickening device is 2 - 6 m. The sludge thickening concentration ≥ 35000 mg / L, and the fluctuation range of the thickening concentration is not more than 5000 mg / L.

6. The sewage treatment plant sludge conditioning and dewatering production process according to claim 1, characterized in that: In the mechanical dewatering process section of step five, a belt filter press or a spiral press is used. The gravity dewatering time of the belt filter press is 60 seconds - 120 seconds, the pressure dewatering time is 60 seconds - 180 seconds, the belt pressure is 0.4 MP - 0.5 MP, and the pressure difference between the upper and lower belts is 0.05 MP.

7. A sewage treatment plant sludge conditioning and dewatering production process according to claim 1, characterized in that: The deep dewatering process adopts mechanical pressure filtration or heat drying.

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