A method for regulating the moisture content of activated sludge plate and frame dewatering filter cake

Abstract

This invention provides a method for controlling the moisture content of activated sludge plate and frame filter cake, belonging to the field of environmental protection technology. The invention involves concentrating activated sludge to obtain concentrated sludge; mixing the concentrated sludge with an organic dewatering agent and a dewatering aid, and conditioning it to obtain conditioned sludge; the dewatering aid is clay; and then dewatering the conditioned sludge in a plate and frame filter press to obtain a filter cake. This method is based on the principle of physical cell wall disruption for plate and frame filter press dewatering of activated sludge. During the dewatering process, the dewatering aid particles and the cell walls of microorganisms in the sludge are mutually compressed, resulting in penetration-filling cell wall disruption. After cell wall disruption, the dewatering aid remains and fills the cell cavities, releasing intracellular water and squeezing out adsorbed water. This achieves the purpose of cell wall disruption and volume reduction in the activated sludge, thereby reducing the sludge moisture content. The dewatering effect is good, and the cost per ton of sludge is low, making it economical and practical.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, and in particular to a method for regulating the moisture content of activated sludge plate and frame dewatering filter cake. Background Technology

[0002] Currently, sludge dewatering and volume reduction technology using plate and frame filter presses is widely used in various industries, especially for inorganic sludge. For the disposal of excess activated sludge from wastewater treatment plants, the national standard GB / T23485-2009, "Sludge Quality for Mixed Landfill Disposal of Sludge from Urban Wastewater Treatment Plants," requires a filter cake moisture content of <60 wt%. Some wastewater treatment plants currently use inorganic agents (such as ferric chloride and lime) in conjunction with polyacrylamide (PAM) flocculants, and then utilize dewatering technology to reduce the volume of excess activated sludge. This method can reduce the sludge moisture content to 50-56 wt%, but the cost of these agents is high, approximately 400 yuan per ton of sludge, which hinders large-scale application.

[0003] To reduce treatment costs, some wastewater treatment plants are currently using plate and frame filter press dewatering technology in addition to adding organic dewatering agents (mainly polyquaternary ammonium salt compounds). The cost of the agents used in this method is relatively low. However, when treating excess activated sludge using the above method, the moisture content of the filter cake obtained after filter press dewatering is still relatively high, generally between 60 and 70 wt%. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the moisture content of activated sludge plate and frame dewatering filter cake. Using this method to treat activated sludge results in good dewatering effect and low cost per ton of sludge.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for controlling the moisture content of activated sludge plate and frame dewatering filter cake, comprising the following steps:

[0007] The activated sludge is concentrated to obtain concentrated sludge;

[0008] The concentrated sludge is mixed with an organic dewatering agent and a dewatering aid, and then conditioned to obtain conditioned sludge; the dewatering aid is clay.

[0009] The conditioned sludge is dewatered by plate and frame filter press to obtain filter cake;

[0010] The dosage of the dehydrating agent is calculated according to the equation shown in Formula I:

[0011] [M×(1-f)+X)] / [M+X-(X / ρ1)×ρ2]=1-F Formula I;

[0012] In Formula I, M is the wet weight of the filter cake obtained under the same conditions without the addition of dehydration aids, in tons.

[0013] f represents the moisture content of the filter cake obtained under the same conditions without the addition of dehydration aids, expressed in wt%, with a value ranging from 60 to 70 wt%.

[0014] X represents the dry weight of the dehydrating agent, in tons (t).

[0015] F represents the target moisture content, expressed in wt%, with a range of 20–59 wt%.

[0016] ρ1 is the dry density of the dehydrating agent, in t / m³. 3 ;

[0017] ρ² is the density of water, with units of t / m³. 3 .

[0018] Preferably, the activated sludge includes residual activated sludge from domestic wastewater treatment plants and / or residual activated sludge from industrial wastewater treatment plants; the activated sludge has a water content of 99~99.3wt%.

[0019] Preferably, the concentration is gravity concentration, and the concentration time is 26-30 hours; the moisture content of the concentrated sludge is 96-98 wt%.

[0020] Preferably, the organic dehydrating agent comprises a polyquaternary ammonium salt compound, wherein the average molecular weight of the polyquaternary ammonium salt compound is 400,000 to 2,000,000.

[0021] Preferably, the organic dehydrating agent is used in the form of an aqueous solution of the organic dehydrating agent, and the mass concentration of the aqueous solution of the organic dehydrating agent is 18~22%; based on the mass of the concentrated sludge, the amount of the aqueous solution of the organic dehydrating agent added is 1.25~1.45 kg / t.

[0022] Preferably, the particle size of the dehydration aid is 0.018~2µm.

[0023] Preferably, the conditioning process is carried out under stirring conditions, and the conditioning process takes 34 to 51 seconds.

[0024] Preferably, the pressure for filter dehydration is 1.6 MPa, and the pressure holding time is 2000~2800 s.

[0025] Preferably, the sludge feed pressure is 1.0~1.2MPa during the process of the conditioning sludge entering the plate and frame filter press.

[0026] Preferably, it includes the following steps:

[0027] The activated sludge is transported to the sludge thickening tank via the activated sludge pump well for thickening to obtain concentrated sludge;

[0028] The concentrated sludge is transported to a sludge conditioning tank, and dewatering aids and organic dewatering agents are added to the sludge conditioning tank for conditioning treatment to obtain conditioned sludge.

[0029] The conditioned sludge is pumped to a plate and frame filter press for dewatering via a sludge pump to obtain filter cake and filtrate. The filter cake is then loaded into a sludge storage hopper via a screw conveyor.

[0030] Beneficial Effects: The method for regulating the moisture content of activated sludge plate and frame filter cake provided by this invention includes the following steps: concentrating activated sludge to obtain concentrated sludge; mixing the concentrated sludge with an organic dewatering agent and a dewatering aid, and conditioning it to obtain conditioned sludge; the dewatering aid is clay; and dewatering the conditioned sludge in a plate and frame filter press to obtain filter cake. This invention is a method for dewatering activated sludge based on the principle of physical cell wall disruption. Specifically, by adding a dewatering aid, during the filtration process, the dewatering aid particles and the cell walls of microorganisms in the sludge are mutually compressed, resulting in penetration-filling cell wall disruption. After cell wall disruption, the dewatering aid remains and fills the cell cavities, releasing intracellular water and squeezing out adsorbed water, thus achieving the purpose of breaking down and reducing the volume of microbial cells in the activated sludge, thereby reducing the moisture content of the sludge. This invention uses a combination of organic dewatering agent and dewatering aid. Compared with the combination of inorganic agents and polyacrylamide flocculant, organic dewatering agent is cheaper. At the same time, the dosage of dewatering aid can be accurately determined according to the target moisture content of the filter cake. Compared with using only organic dewatering agent, it can effectively reduce the moisture content of sludge without significantly increasing the cost of agents per ton of sludge, making it economical and practical. Detailed Implementation

[0031] This invention provides a method for controlling the moisture content of activated sludge plate and frame dewatering filter cake, comprising the following steps:

[0032] The activated sludge is concentrated to obtain concentrated sludge;

[0033] The concentrated sludge is mixed with an organic dewatering agent and a dewatering aid, and then conditioned to obtain conditioned sludge; the dewatering aid is clay.

[0034] The conditioned sludge is dewatered by plate and frame filter press to obtain filter cake;

[0035] The dosage of the dehydrating agent is calculated according to the equation shown in Formula I:

[0036] [M×(1-f)+X)] / [M+X-(X / ρ1)×ρ2]=1-F Formula I;

[0037] In Formula I, M is the wet weight of the filter cake obtained under the same conditions without the addition of dehydration aids, in tons.

[0038] f represents the moisture content of the filter cake obtained under the same conditions without the addition of dehydrating agents, expressed in wt%, with a value ranging from 60 to 70 wt%.

[0039] X represents the dry weight of the dehydrating agent, in tons (t).

[0040] F represents the target moisture content, expressed in wt%, with a range of 20–59 wt%.

[0041] ρ1 is the dry density of the dehydrating agent, in t / m³. 3 ;

[0042] ρ² is the density of water, with units of t / m³. 3 .

[0043] To reduce treatment costs, related technologies for dewatering and reducing the volume of activated sludge employ organic dewatering agents in conjunction with plate and frame filter presses. The applicant conducted a trial run following the procedure of concentrating activated sludge, adding organic dewatering agents for conditioning, and then using a plate and frame filter press for dewatering. However, during the trial, the applicant found that under the designed operating pressure of 1.6 MPa, regardless of extending the filtration time, the moisture content of the filter cake remained at approximately 65 wt% after dewatering. Further research revealed that the root cause of this problem was that during the dewatering process of the concentrated sludge in the plate and frame filter press, 90% of the water was squeezed out as filtrate, while 10% of the intracellular water and adsorbed water remained in the sludge without being broken down by the pressure, resulting in a filter cake moisture content of approximately 65 wt% after dewatering. This invention reduces the water content of activated sludge by adding a dewatering aid to break down the cell walls of microorganisms. The specific principle of cell wall breaking is as follows: after conditioning the concentrated sludge with a dewatering aid (e.g., with a particle size of 0.018~2µm) and an organic dewatering agent (e.g., a polyquaternary ammonium salt compound), the sludge is then dewatered by pressing in a plate and frame filter press. During this process, the dewatering aid particles and the cell walls of the microorganisms in the sludge are squeezed together, resulting in a penetration-filling cell wall breaking. After the dewatering aid breaks down the cell walls, it remains and fills the cell cavities. Secondary penetration-filling cell wall breaking usually does not occur (if a single dewatering aid particle can break down the cell walls multiple times, the intracellular water of the activated microorganisms will be broken down by a smaller amount of dewatering aid). Therefore, in practical applications, a unit volume of dewatering aid is usually used to break down the cell walls and release a unit volume of intracellular water and adsorbed water. Therefore, the method of this invention can effectively reduce the moisture content of sludge, and the reagents used are inexpensive, with a low cost per ton of sludge (i.e., the reagent required to obtain one ton of filter cake). It is economical and practical, and helps to maximize the sludge removal efficiency of wastewater treatment plants. The method of this invention will be described in detail below.

[0044] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0045] This invention concentrates activated sludge to obtain concentrated sludge. In one embodiment, the activated sludge may include residual activated sludge from domestic wastewater treatment plants and / or residual activated sludge from industrial wastewater treatment plants. Specifically, it can be residual activated sludge from either domestic or industrial wastewater treatment plants. The active microorganisms in this activated sludge require cell disruption and dewatering, which presents technical challenges. In contrast, ordinary inorganic sludge, such as drilling mud, can be dewatered using general flocculants. In one embodiment, the activated sludge has a moisture content of 99-99.3 wt%. In another embodiment, the concentration can be gravity concentration, specifically continuous gravity concentration; the concentration time can be 26-30 hours, specifically 28 hours; and the concentrated sludge has a moisture content of 96-98 wt%, specifically 97 wt%. In this embodiment, by concentrating under the above conditions, the volume of the concentrated sludge can be reduced to 22-28% of the activated sludge volume, specifically 25%.

[0046] After obtaining concentrated sludge, the present invention mixes the concentrated sludge with an organic dewatering agent and a dewatering aid, and performs conditioning treatment to obtain conditioned sludge. As an embodiment of the present invention, the organic dewatering agent may include polyquaternary ammonium salt compounds, the average molecular weight of which may be 400,000 to 2,000,000. In this embodiment, the organic dewatering agent may specifically be a commercial agent such as Jielin brand plate and frame dewatering agent, PENGFA4880, or Feifuluo 3770DY. As an embodiment of the present invention, the organic dewatering agent is used in the form of an aqueous solution, the mass concentration of which may be 18% to 22%, specifically 20%. Based on the mass of the concentrated sludge, the amount of the organic dewatering agent aqueous solution added may be 1.25 to 1.45 kg / t, specifically 1.35 kg / t. This invention involves conditioning the sludge in the presence of an organic dehydrating agent, which causes the concentrated sludge to form flocculation and sedimentation, facilitating subsequent filter press dewatering. Without the addition of an organic dehydrating agent, the concentrated sludge will not form flocculation and sedimentation during the conditioning process, making subsequent filter press dewatering impossible.

[0047] The dehydrating agent described in this invention is clay; in specific embodiments of this invention, clay is used as the dehydrating agent to verify the feasibility of the method. As one embodiment of this invention, the particle size of the dehydrating agent can be 0.018~2µm; using a dehydrating agent with the above-mentioned particle size in this embodiment of the invention is beneficial for achieving a better penetration-filling cell disruption effect, thereby improving the dehydration effect.

[0048] In this invention, the amount of the dehydration aid is calculated according to the equation shown in Formula I:

[0049] [M×(1-f)+X)] / [M+X-(X / ρ1)×ρ2]=1-F Formula I;

[0050] In Formula I, M is the wet weight of the filter cake obtained under the same conditions without the addition of dehydration aids, in tons.

[0051] f represents the moisture content of the filter cake obtained under the same conditions without the addition of dehydrating agents, expressed in wt%, with a value ranging from 60 to 70 wt%.

[0052] X represents the dry weight of the dehydrating agent, in tons (t).

[0053] F represents the target moisture content, expressed in wt%, with a range of 20–59 wt%.

[0054] ρ1 is the dry density of the dehydrating agent, in t / m³. 3 ;

[0055] ρ² is the density of water, with units of t / m³. 3 .

[0056] In one embodiment of the present invention, f is the moisture content of the filter cake obtained under the same conditions without adding a dewatering aid. Specifically, it refers to the moisture content of the filter cake obtained by dewatering the activated sludge according to the above-described technical solution of the present invention without adding a dewatering aid (i.e., only adding an organic dewatering agent). M is the wet weight of the filter cake obtained under the same conditions without adding a dewatering aid, that is, M is the mass of the filter cake with a moisture content of f. X is the mass of the natural and pollution-free dry dewatering aid. F is the target moisture content, specifically referring to the moisture content obtained when both an organic dewatering agent (with a constant dosage) and a dewatering aid are added simultaneously. In this case, the activated sludge is dewatered according to the above-mentioned technical solution of the present invention. The target moisture content of the resulting filter cake can be determined by setting the predetermined target moisture content, thereby achieving the control of the filter cake moisture content. The value of F ranges from 20 to 59 wt%, further from 39 to 59 wt%, further from 50 to 59 wt%, and further from 55 to 59 wt%. In the embodiments, it can specifically be 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 59 wt%. As an embodiment of the present invention, the dewatering aid is clay, and the dry density (ρ1) of the clay is specifically 1.4 t / m³. 3 In this calculation, X / ρ1 specifically represents the volume of the dehydration aid added, which is the volume of intracellular water and adsorbed water expelled during cell wall disruption, based on the density of water (ρ2) being 1 t / m³. 3 The formula (X / ρ1)×ρ2 represents the mass (t) of intracellular water and adsorbed water that are expelled after cell wall disruption.

[0057] As an embodiment of the present invention, if the activated sludge to be treated in a wastewater treatment plant is concentrated to obtain concentrated sludge, and only an aqueous solution of an organic dewatering agent is added without adding clay, and the other steps are carried out according to the above-described technical solution of the present invention to dewater the activated sludge, the resulting filter cake has a moisture content f of 65wt% and a wet weight of 1t (i.e., M=1t); if the same amount of activated sludge is treated, and an equal amount of aqueous solution of organic dewatering agent and an appropriate amount of clay are added according to the aforementioned scheme, in order to reduce the moisture content of the filter cake (i.e., the predetermined target moisture content) to F of 55wt%, based on the dry density (ρ1) of clay of 1.4t / m³, 3 Substituting the data into Equation I above, the dry weight X of the clay is calculated to be 0.115t. Equation I of this invention is simple and practical, accurately determining the dosage of dewatering aid. Compared to using only organic dewatering agents, it effectively reduces the moisture content of sludge without significantly increasing the cost per ton of sludge, demonstrating strong economic practicality.

[0058] In one embodiment of the present invention, the conditioning treatment can be carried out under stirring conditions; the conditioning treatment time can be 34~51s, specifically 42s. The present invention utilizes the colloidal and inorganic insoluble solid properties of the dewatering aid to achieve uniform mixing of concentrated sludge and organic dewatering agent without precipitation that could clog pipes. In this embodiment of the present invention, the conditioning treatment under the above conditions is beneficial for achieving better dewatering results.

[0059] After obtaining the conditioned sludge, the present invention dewaters the conditioned sludge in a plate and frame filter press to obtain a filter cake. In one embodiment of the present invention, the pressure for dewatering can be 1.6 MPa; the holding time can be 2000~2800 s, specifically 2600 s; the dewatering process is the process of cell wall breaking dewatering with a dewatering aid. In another embodiment of the present invention, the dewatering can be carried out in a plate and frame filter press. During the process of the conditioned sludge entering the plate and frame filter press, the final inlet pressure is 1.0~1.2 MPa. In this embodiment of the present invention, when the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and then the pressure is gradually increased until it reaches 1.2 MPa after 7000 s, at which point the inlet pressure ends, and the sludge is dewatered in the plate and frame filter press. In another embodiment of the present invention, the conditioned sludge is specifically transported to the plate and frame filter press by an inlet pump, and the inlet pressure refers to the working pressure of the inlet pump.

[0060] As an embodiment of the present invention, the pressure filtration and dewatering also yields a filtrate, which is neutral, non-corrosive, and will not affect the pH value of the influent to the wastewater treatment plant.

[0061] The sludge dewatering system applicable to the activated sludge dewatering method in this invention is not particularly limited. As one embodiment of this invention, the sludge dewatering system may include, for example, an activated sludge pump well, a sludge thickening tank, a sludge conditioning tank, a sludge inlet pump, a plate and frame filter press, a screw conveyor, a sludge storage hopper, valves, and pipelines, and is also equipped with a dewatering aid conveying device. The remaining sludge pump well, sludge thickening tank, sludge conditioning tank, sludge inlet pump, plate and frame filter press, screw conveyor, and sludge storage hopper are sequentially connected. The outlet of the dewatering aid conveying device is connected to the sludge conditioning tank. The dewatering aid conveying device can be a belt conveyor or a U-shaped scraper conveyor, as long as it can convey the dewatering aid. As one embodiment of this invention, a sludge thickener is installed in the sludge thickening tank to facilitate continuous gravity thickening. In one embodiment of the present invention, the sludge conditioning tank is provided with four small square tanks of equal size connected in series, each of which is equipped with a stirrer. The first small square tank is equipped with a sludge thickening pipe and a chemical dosing pipe. The first small square tank is connected to a sludge thickening tank through the sludge thickening pipe. The chemical dosing pipe is used to add dewatering aids and organic dewatering agents. The function of the sludge conditioning tank is to fully mix the thickened sludge with the dewatering aids and organic dewatering agents, so that the resulting mixed sludge is destabilized and stacked after neutralizing static electricity, achieving a flocculation and sedimentation effect. If the sludge is not conditioned in the sludge conditioning tank, the dewatering aids will not be able to fully break down the cell walls after the sludge is pumped into the plate and frame filter press, resulting in the sludge not being able to be pressed, filtered, and dewatered. At the same time, the sludge conditioning tank also has the function of regulating the amount of sludge stored.

[0062] As one embodiment of the present invention, activated sludge can be transported to a sludge thickening tank via an activated sludge pump well for thickening to obtain concentrated sludge; the concentrated sludge can be transported to a sludge conditioning tank, and dewatering aids and organic dewatering agents can be added to the sludge conditioning tank for conditioning treatment to obtain conditioned sludge; the conditioned sludge can be pumped to a plate and frame filter press via a sludge inlet pump for dewatering and filtration to obtain filter cake and filtrate, respectively; the filter cake can be loaded into a sludge storage hopper via a screw conveyor.

[0063] Currently, when treating activated sludge using only organic dewatering agents and filter press dewatering technology, the cost per ton of sludge is approximately 160 yuan. This invention adds a dewatering aid as an auxiliary conditioner to the dewatering agent, precisely controlling its dosage. This effectively reduces the sludge moisture content without significantly increasing the cost per ton of sludge, resulting in significant economic benefits. Furthermore, the dewatering aid used in this invention is a natural substance with no chemical pollution and requires no additional chemical agents. The filtrate obtained after filter press dewatering is neutral, non-corrosive, and has no impact on the biological treatment system of wastewater treatment plants. Simultaneously, the method of this invention is simple and easy to implement, with low operational difficulty, making it suitable for large-scale promotion and application.

[0064] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0065] The residual activated sludge used in the following examples and comparative examples came from a domestic wastewater treatment plant, with a moisture content of 99.3 wt%; the organic dewatering agent used was a polyquaternary ammonium salt compound (purchased from Changzhi Huanyi Environmental Technology Co., Ltd., model Huanyi Environmental HY-606 plate and frame desludge dewatering agent); the clay used had a particle size of 0.018~2µm and a dry density (ρ1) of 1.4 t / m³. 3 The density of water (ρ2) is 1 t / m³. 3 .

[0066] Comparative Example 1

[0067] 50t of excess activated sludge was continuously concentrated by gravity for 28h to obtain 11.67t of concentrated sludge with a water content of 97wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge).

[0068] According to the calculation of adding 1.35 kg of 20% organic dehydrating agent aqueous solution per ton of concentrated sludge, the organic dehydrating agent aqueous solution was added to the concentrated sludge, and the conditioning treatment was carried out for 34 seconds at a rotation speed of 20 rpm to obtain conditioned sludge.

[0069] The conditioned sludge is transported to a plate and frame filter press via a sludge pump. When the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and then the pressure is gradually increased. The sludge feeding ends when the pressure reaches 1.2 MPa after 7000 s. The sludge is then dewatered in the plate and frame filter press at a pressure of 1.6 MPa for 2600 s. After the dewatering is completed, filter cake and filtrate are obtained. The filter cake has a moisture content of 65 wt% and a wet weight of 1 t.

[0070] Example 1

[0071] This embodiment adds clay to Comparative Example 1, and it is expected that the moisture content of the filter cake will be reduced to 59 wt% (i.e., F = 59 wt%). Based on this, according to Formula I (M = 1t, f = 65 wt%, ρ1 = 1.4t / m³), 3 ρ2=1t / m 3 The calculated clay dosage is 0.068t; other steps are performed in accordance with Comparative Example 1, as follows:

[0072] 50t of excess activated sludge was continuously concentrated by gravity for 28h to obtain 11.67t of concentrated sludge with a water content of 97wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge). 1.35kg of 20% organic dewatering agent aqueous solution and 0.068t of clay were added, and the mixture was conditioned for 34s at a rotation speed of 20rpm to obtain conditioned sludge.

[0073] The conditioned sludge is transported to a plate and frame filter press for dewatering via a sludge pump. When the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and the pressure is gradually increased. The sludge feeding ends when the pressure reaches 1.2 MPa after 7000 seconds. The sludge is then dewatered in the plate and frame filter press at a pressure of 1.6 MPa for 2600 seconds. After the dewatering is completed, filter cake and filtrate are obtained. The filter cake has a moisture content of 59 wt% and a wet weight of 1.020 t.

[0074] Example 2

[0075] This embodiment adds clay to Comparative Example 1, and it is expected that the moisture content of the filter cake will be reduced to 55 wt% (i.e., F = 55 wt%). Based on this, according to Formula I (M = 1 t, f = 65 wt%, ρ1 = 1.4 t / m³), the filter cake is then filtered. 3 ρ2=1t / m 3 The calculated clay dosage was 0.115t, an increase of 0.047t compared to Example 1, consistent with the increasing trend of physical cell wall disruption; other steps were performed in accordance with Comparative Example 1, as follows:

[0076] 50t of excess activated sludge was continuously concentrated by gravity for 28h to obtain 11.67t of concentrated sludge with a water content of 97wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge). 1.35kg of 20% organic dewatering agent aqueous solution and 0.115t of clay were added, and the mixture was conditioned for 34s at a rotation speed of 20rpm to obtain conditioned sludge.

[0077] The conditioned sludge is transported to a plate and frame filter press for dewatering via a sludge pump. The initial pressure of the conditioned sludge entering the filter press is 0 MPa, which is then gradually increased until it reaches 1.2 MPa after 7000 seconds. Dewatering is then performed in the filter press at a pressure of 1.6 MPa for 2600 seconds. After dewatering, filter cake and filtrate are obtained. The filter cake has a moisture content of 55 wt% and a wet weight of 1.033 t.

[0078] Example 3

[0079] This embodiment adds clay to Comparative Example 1, and it is expected that the moisture content of the filter cake will be reduced to 50 wt% (i.e., F = 50 wt%). Based on this, according to Formula I (M = 1t, f = 65 wt%, ρ1 = 1.4t / m³), 3 ρ2=1t / m 3 The calculated clay dosage was 0.175t, an increase of 0.060t compared to Example 2, consistent with the increasing trend of physical cell wall disruption; other steps were performed as in Comparative Example 1, as follows:

[0080] 50t of excess activated sludge was continuously concentrated by gravity for 28h to obtain 11.67t of concentrated sludge with a water content of 97wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge). 1.35kg of 20% organic dewatering agent aqueous solution and 0.175t of clay were added, and the mixture was conditioned for 34s at a rotation speed of 20rpm to obtain conditioned sludge.

[0081] The conditioned sludge is transported to a plate and frame filter press for dewatering via a sludge pump. When the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and the pressure is gradually increased. The sludge feeding ends when the pressure reaches 1.2 MPa after 7000 seconds. The sludge is then dewatered in the plate and frame filter press at a pressure of 1.6 MPa for 2600 seconds. After the dewatering is completed, filter cake and filtrate are obtained. The filter cake has a moisture content of 50 wt% and a wet weight of 1.050 t.

[0082] Examples 4-9

[0083] Under the same operating conditions as in Example 1, when the target moisture content F of the filter cake is successively taken as: 45wt%, 40wt%, 35wt%, 30wt%, 25wt%, 20wt%, according to Equation I (M=1t, f=65wt%, ρ1=1.4t / m) 3 ρ2=1t / m 3 The clay dosage X was calculated to be 0.237t, 0.302t, 0.369t, 0.438t, 0.569t, and 0.583t, respectively, and the wet weight of the filter cake was 1.068t, 1.086t, 1.105t, 1.125t, 1.145t, and 1.167t, respectively, all consistent with the increasing trend of physical cell wall disruption. This indicates that the method of releasing intracellular water and reducing volume by squeezing out adsorbed water based on Formula I for disrupting the cell walls of activated sludge microorganisms has a wide range of applications.

[0084] Generally, from an economic and practical standpoint, when using a plate and frame filter press to dewater activated sludge, the moisture content of the resulting filter cake is controlled within the core control range of 55-59 wt%. A moisture content of less than 60 wt% is considered acceptable. Looking to the future, if national regulations require a moisture content of less than 40 wt% for filter cakes from plate and frame filter presses used in wastewater treatment plants, the method of this invention will also be applicable.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating the moisture content of activated sludge plate and frame dewatering filter cake, characterized in that, Includes the following steps: Concentrate the activated sludge to obtain concentrated sludge, wherein the activated sludge includes residual activated sludge generated from domestic wastewater treatment plants and / or residual activated sludge generated from industrial wastewater treatment plants. The concentrated sludge is mixed with an organic dewatering agent and a dewatering aid, and then conditioned to obtain conditioned sludge. The organic dewatering agent includes polyquaternary ammonium salt compounds with an average molecular weight of 400,000 to 2,000,000. The dewatering aid is clay with a particle size of 0.018 to 2 µm. The conditioned sludge is dewatered by plate and frame filter press to obtain filter cake; The dosage of the dehydrating agent is calculated according to the equation shown in Formula I: [M×(1-f)+X)] / [M+X-(X / ρ1)×ρ2]=1-F Formula I; In Formula I, M is the wet weight of the filter cake obtained under the same conditions without the addition of dehydration aids, in tons. f represents the moisture content of the filter cake obtained under the same conditions without the addition of dehydration aids, expressed in wt%, with a value ranging from 60 to 70 wt%. X represents the dry weight of the dehydrating agent, in tons (t). F represents the target moisture content, expressed in wt%, with a range of 20–59 wt%. ρ1 is the dry density of the dehydrating agent, in t / m³. 3 ; ρ² is the density of water, with units of t / m³. 3 .

2. The method according to claim 1, characterized in that, The activated sludge has a water content of 99~99.3 wt%.

3. The method according to claim 1 or 2, characterized in that, The concentration is gravity concentration, and the concentration time is 26-30 hours; the moisture content of the concentrated sludge is 96-98 wt%.

4. The method according to claim 1, characterized in that, The organic dehydrating agent is used in the form of an aqueous solution of the organic dehydrating agent, and the mass concentration of the aqueous solution of the organic dehydrating agent is 18~22%; based on the mass of the concentrated sludge, the amount of the aqueous solution of the organic dehydrating agent added is 1.25~1.45 kg / t.

5. The method according to claim 1, characterized in that, The conditioning process is carried out under stirring conditions, and the conditioning process takes 34 to 51 seconds.

6. The method according to claim 1 or 5, characterized in that, The pressure for filter press dehydration is 1.6 MPa, and the pressure holding time is 2000~2800 s.

7. The method according to claim 6, characterized in that, During the process of the conditioning sludge entering the plate and frame filter press, the sludge inlet pressure is terminated at 1.0~1.2MPa.

8. The method according to claim 1, characterized in that, Includes the following steps: The activated sludge is transported to the sludge thickening tank via the activated sludge pump well for thickening to obtain concentrated sludge; The concentrated sludge is transported to a sludge conditioning tank, and dewatering aids and organic dewatering agents are added to the sludge conditioning tank for conditioning treatment to obtain conditioned sludge. The conditioned sludge is pumped to a plate and frame filter press for dewatering via a sludge pump to obtain filter cake and filtrate. The filter cake is then loaded into a sludge storage hopper via a screw conveyor.