Method for regulating and controlling water content of activated sludge plate frame dehydration filter cake

Abstract

The invention provides a method for regulating and controlling the water content of an activated sludge plate frame dehydration filter cake, and belongs to the technical field of environmental protection. The method comprises the following steps: concentrating activated sludge to obtain concentrated sludge; mixing the concentrated sludge with an organic dehydrating agent and a dehydrating auxiliary agent, and carrying out conditioning treatment to obtain conditioned sludge; the dehydration auxiliary agent is clay; and carrying out filter pressing dehydration on the conditioned sludge in a plate-and-frame filter press to obtain a filter cake. The method disclosed by the invention is a method for carrying out plate-frame pressure filtration dehydration on the activated sludge based on a physical wall breaking principle, and in the pressure filtration dehydration process, dehydration auxiliary agent particles and microbial cell walls in the sludge are mutually extruded to generate penetration-filling type wall breaking; after wall breaking, the dehydration auxiliary stays and fills the cell cavities, releases water in the cells and extrudes adsorbed water, so that wall breaking and volume reduction of microbial cells in the activated sludge are realized, the purpose of reducing the water content of the sludge is achieved, the dehydration effect is good, the cost of the agent for per ton of sludge is low, and the economic practicability is high.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a method for regulating the moisture content of activated sludge plate-frame dehydration filter cakes. Background Art

[0002] At present, the plate and frame filter press dewatering technology is widely used in various related industries to achieve sludge dehydration and volume reduction, especially in the dehydration and volume reduction of inorganic sludge. For the disposal of excess activated sludge generated by sewage treatment plants, the national standard "Mud for mixed landfill of sludge disposal in urban sewage treatment plants"-GB / T23485-2009 requires that the moisture content of the filter cake be less than 60wt%. At present, some sewage treatment plants use inorganic agents (such as ferric chloride and lime) and use polyacrylamide (PAM) flocculants in combination. On this basis, dehydration technology is used to achieve dehydration and volume reduction of excess activated sludge. This method can reduce the moisture content of sludge to 50~56wt%, but the cost of the agent using this method is relatively high, and the cost of the agent per ton of sludge is about 400 yuan, which is not conducive to large-scale promotion and use.

[0003] In order to reduce treatment costs, some sewage treatment plants currently use plate and frame filter press dehydration technology based on the addition of organic dehydrating agents (mainly polyquaternary ammonium compounds). The cost of reagents used in this method is relatively low, but when the above method is used to treat residual activated sludge, the moisture content of the filter cake obtained after filter press dehydration is still relatively high, generally between 60 and 70wt%. Summary of the invention

[0004] The purpose of the present invention is to provide a method for regulating the moisture content of activated sludge plate-frame dewatering filter cake. The method of the present invention is used to treat activated sludge, and the dewatering effect is good and the cost of reagents per ton of sludge is low.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for regulating the moisture content of activated sludge plate-frame dewatering filter cake, comprising the following steps: Concentrating the activated sludge to obtain concentrated sludge; The concentrated sludge is mixed with an organic dehydrating agent and a dehydrating aid, and conditioned to obtain conditioned sludge; the dehydrating aid is clay; The conditioned sludge is filtered and dehydrated in a plate and frame filter press to obtain a filter cake; The amount of the dehydration aid 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 adding a dehydration aid, in units of t; f is the moisture content of the filter cake obtained under the same conditions without adding dehydration aid, the unit is wt%, and the value range is 60~70wt%; X is the dry weight of the dehydration aid, in t; F is the target moisture content, in wt%, ranging from 20 to 59wt%; ρ1 is the dry density of the dehydration aid, in t / m 3 ; ρ2 is the density of water, in t / m 3 .

[0006] Preferably, the activated sludge includes excess activated sludge produced by a domestic sewage treatment plant and / or excess activated sludge produced by an industrial sewage treatment plant; the water content of the activated sludge is 99-99.3wt%.

[0007] Preferably, the concentration is gravity concentration, and the concentration time is 26-30 hours; the moisture content of the concentrated sludge is 96-98wt%.

[0008] Preferably, the organic dehydrating agent comprises a polyquaternary ammonium salt compound, and the average molecular weight of the polyquaternary ammonium salt compound is 400,000 to 2,000,000.

[0009] Preferably, the organic dehydrating agent is used in the form of an organic dehydrating agent aqueous solution, and the mass concentration of the organic dehydrating agent aqueous solution is 18-22%; based on the mass of the concentrated sludge, the addition amount of the organic dehydrating agent aqueous solution is 1.25-1.45 kg / t.

[0010] Preferably, the particle size of the dehydration aid is 0.018~2µm.

[0011] Preferably, the conditioning treatment is carried out under stirring conditions, and the conditioning treatment time is 34 to 51 seconds.

[0012] Preferably, the pressure of the filter press dehydration is 1.6 MPa, and the pressure holding time is 2000-2800 s.

[0013] Preferably, during the process of the conditioned sludge entering the plate and frame filter press, the termination sludge inlet pressure is 1.0-1.2 MPa.

[0014] Preferably, the method comprises the following steps: The activated sludge is transported to the sludge thickening tank through the activated sludge pump well for thickening to obtain concentrated sludge; The concentrated sludge is transported to a sludge conditioning tank, a dehydration aid and an organic dehydrating agent are added to the sludge conditioning tank for conditioning to obtain conditioned sludge; The conditioned sludge is pumped into a plate and frame filter press by a sludge inlet pump for filtration and dehydration to obtain filter cake and filtrate respectively, and the filter cake is loaded into a sludge storage hopper by a screw conveyor.

[0015] Beneficial effects: The method for regulating the moisture content of activated sludge plate and frame dewatering filter cake provided by the present invention comprises the following steps: concentrating the activated sludge to obtain concentrated sludge; mixing the concentrated sludge with an organic dehydrating agent and a dehydrating aid, and conditioning the concentrated sludge to obtain conditioned sludge; the dehydrating aid is clay; and subjecting the conditioned sludge to filter pressing and dehydration in a plate and frame filter press to obtain a filter cake. The method of the present invention is a method for dehydrating activated sludge based on the principle of physical wall breaking, specifically, by adding a dehydrating aid, during the filter pressing and dehydration process, the dehydrating aid particles and the microbial cell walls in the sludge are squeezed against each other to cause penetration-filling wall breaking, and after the dehydrating aid breaks the wall, it stays and fills in the cell cavity and releases the intracellular water and squeezes out the adsorbed water, that is, achieving the purpose of breaking the wall and reducing the volume of the microbial cells in the activated sludge, thereby reducing the moisture content of the sludge. The present invention adopts the compound use of organic dehydrating agent and dehydrating auxiliary agent. Compared with the compound use of inorganic agent and polyacrylamide flocculant, the organic dehydrating agent is inexpensive, and the dosage of the dehydrating auxiliary agent can be accurately determined according to the target moisture content of the filter cake. Compared with the use of only organic dehydrating agent, the moisture content of sludge can be effectively reduced without significantly increasing the cost of the agent per ton of sludge, and the economy and practicality are strong. DETAILED DESCRIPTION

[0016] The present invention provides a method for regulating the moisture content of activated sludge plate-frame dewatering filter cake, comprising the following steps: Concentrating the activated sludge to obtain concentrated sludge; The concentrated sludge is mixed with an organic dehydrating agent and a dehydrating aid, and conditioned to obtain conditioned sludge; the dehydrating aid is clay; The conditioned sludge is filtered and dehydrated in a plate and frame filter press to obtain a filter cake; The amount of the dehydration aid 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 adding a dehydration aid, in units of t; f is the moisture content of the filter cake obtained under the same conditions without adding dehydration aids, in wt%, ranging from 60 to 70wt%; X is the dry weight of the dehydration aid, in t; F is the target moisture content, in wt%, ranging from 20 to 59wt%; ρ1 is the dry density of the dehydration aid, in t / m 3 ; ρ2 is the density of water, in t / m 3 .

[0017] For the dehydration and volume reduction treatment of activated sludge, in order to reduce the treatment cost, the relevant technology uses an organic dehydrating agent and a plate-frame filter press for filter pressing and dehydration. The applicant debugs the process of concentrating the activated sludge, adding an organic dehydrating agent for conditioning, and then using a plate-frame filter press for filter pressing and dehydration. However, during the debugging process, the applicant found that under the working condition of the plate-frame filter press with a designed working pressure of 1.6MPa, no matter how the filter pressing time is extended, the moisture content of the filter cake after filter pressing and dehydration remains at about 65wt%. The applicant further found that the fundamental reason for this problem is that during the process of filter pressing and dehydration of the concentrated sludge obtained after concentration in the plate-frame filter press, 90% of the water is squeezed out as filtrate, and 10% of the intracellular water and adsorbed water remain in the sludge under the pressure without being broken, so that the moisture content of the filter cake obtained after filter pressing and dehydration remains at about 65wt%. The present invention achieves cell wall breaking of microorganisms in activated sludge by adding a dehydrating agent, thereby reducing the water content of the sludge. The specific cell wall breaking principle is: the concentrated sludge is mixed with a dehydrating agent (such as a particle size of 0.018-2µm) and an organic dehydrating agent (such as a polyquaternary ammonium salt compound) for conditioning treatment, and then filtered and dehydrated in a plate and frame filter press. In this process, the dehydrating agent particles and the cell walls of microorganisms in the sludge are squeezed against each other to cause penetration-filling cell wall breaking; after the dehydrating agent breaks the cell wall, it stays and fills in the cell cavity, and usually no secondary penetration-filling cell wall breaking occurs (if a single dehydrating agent particle can break the cell wall multiple times, the intracellular water of the active microorganism will be broken by a smaller amount of dehydrating agent). Therefore, in actual application, a unit volume of dehydrating agent is usually used to break the cell wall to release a unit volume of intracellular water and adsorbed water. Therefore, the method of the present invention can effectively reduce the moisture content of sludge, and the reagents used are cheap, the cost of reagents per ton of sludge (i.e., the reagents required to obtain each ton of filter cake) is low, and the economical and practical performance is strong, which is conducive to maximizing the desludge benefits of sewage treatment plants. The method of the present invention is described in detail below.

[0018] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art or are prepared by methods well known to those skilled in the art.

[0019] The present invention concentrates the activated sludge to obtain concentrated sludge. As an embodiment of the present invention, the activated sludge may include excess activated sludge produced by a domestic sewage treatment plant and / or excess activated sludge produced by an industrial sewage treatment plant, specifically excess activated sludge produced by a domestic sewage treatment plant, or excess activated sludge produced by an industrial sewage treatment plant; the active microorganisms of the activated sludge need to be broken and dehydrated, which is technically difficult, while ordinary inorganic sludge such as drilling mud dehydration can be dehydrated by using a general flocculant. As an embodiment of the present invention, the water content of the activated sludge may be 99-99.3wt%. As an embodiment of the present invention, the concentration may be gravity concentration, specifically continuous gravity concentration; the concentration time may be 26-30h, specifically 28h; the water content of the concentrated sludge may be 96-98wt%, specifically 97wt%. In the embodiment of the present invention, by concentrating under the above conditions, the volume of the concentrated sludge can be reduced to 22-28% of the volume of the activated sludge, specifically 25%.

[0020] After obtaining the concentrated sludge, the present invention mixes the concentrated sludge with an organic dehydrating agent and a dehydrating aid, performs conditioning treatment, and obtains conditioned sludge. As an embodiment of the present invention, the organic dehydrating agent may include a polyquaternary ammonium salt compound, and the average molecular weight of the polyquaternary ammonium salt compound may be 400,000 to 2,000,000; in the embodiment of the present invention, the organic dehydrating agent may specifically adopt commercial agents such as Jielin brand plate frame dehydrating agent, PENGFA4880 or Feifuluo 3770DY. As an embodiment of the present invention, the organic dehydrating agent is used in the form of an organic dehydrating agent aqueous solution, and the mass concentration of the organic dehydrating agent aqueous solution may be 18 to 22%, specifically 20%; based on the mass of the concentrated sludge, the addition amount of the organic dehydrating agent aqueous solution may be 1.25 to 1.45 kg / t, specifically 1.35 kg / t. The present invention performs conditioning treatment in the presence of an organic dehydrating agent, and the concentrated sludge will form flocculation precipitation, which is beneficial to the subsequent filter pressing and dehydration sequence; if the organic dehydrating agent is not added, the concentrated sludge will not form flocculation precipitation during the conditioning treatment process, and subsequent filter pressing and dehydration cannot be performed.

[0021] The dehydration aid of the present invention is clay; in the embodiment of the present invention, clay is specifically used as the dehydration aid to verify the feasibility of the method of the present invention. As an embodiment of the present invention, the particle size of the dehydration aid can be 0.018~2µm; in the embodiment of the present invention, the use of the dehydration aid of the above particle size is conducive to better achieving the penetration-filling wall breaking effect, thereby improving the dehydration effect.

[0022] In the present invention, the amount of the dehydration aid 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 adding a dehydration aid, in units of t; f is the moisture content of the filter cake obtained under the same conditions without adding dehydration aids, in wt%, ranging from 60 to 70wt%; X is the dry weight of the dehydration aid, in t; F is the target moisture content, in wt%, ranging from 20 to 59wt%; ρ1 is the dry density of the dehydration aid, in t / m 3 ; ρ2 is the density of water, in t / m 3 .

[0023] As an embodiment of the present invention, f is the moisture content of the filter cake obtained under the same conditions without adding a dehydrating agent, specifically, when no dehydrating agent is added (i.e., only an organic dehydrating agent is added), the activated sludge is dehydrated in other steps according to the above technical scheme of the present invention, and the moisture content of the obtained filter cake; M is the wet weight of the filter cake obtained under the same conditions without adding a dehydrating agent, that is, M is the mass of the filter cake with a moisture content of f; X is the mass of the natural non-polluting dry dehydrating agent; F is the target moisture content, specifically, when the organic dehydrating agent (the dosage remains unchanged) and the dehydrating agent are added at the same time. Under the condition, the activated sludge is dehydrated according to the above technical scheme of the present invention, and the target moisture content of the obtained filter cake, that is, the amount of dehydration aid can be determined according to the predetermined target moisture content, so as to achieve the regulation of the moisture content of the filter cake, and the value range of F is 20~59wt%, further can be 39~59wt%, further can be 50~59wt%, and further can be 55~59wt%; in the embodiment, it can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt% or 59wt%. As an embodiment of the present invention, the dehydration aid takes clay as an example, and the dry density (ρ1) of the clay is specifically 1.4t / m 3 X / ρ1 is the volume of dehydration aid added, which means the volume of intracellular water and adsorbed water discharged after cell wall breaking. According to the density of water (ρ2) of 1t / m 3 Where (X / ρ1)×ρ2 represents the mass (t) of the intracellular water discharged after cell wall breaking and the adsorbed water.

[0024] As an embodiment of the present invention, if the activated sludge to be treated in a sewage treatment plant is concentrated to obtain concentrated sludge, without adding clay but only adding an organic dehydrating agent aqueous solution, the activated sludge is dehydrated in other steps according to the above technical scheme of the present invention, and the moisture content f of the obtained filter cake is 65wt%, and the wet weight is 1t (i.e., M=1t); if the same amount of activated sludge is treated, and an equal amount of organic dehydrating agent aqueous solution and an appropriate amount of clay are added according to the above scheme, the moisture content of the filter cake (i.e., the predetermined target moisture content) is reduced to F of 55wt%, according to the dry density (ρ1) of clay of 1.4t / m 3 The above formula I of the present invention is simple and practical, and can accurately know the dosage of the dehydrating agent. Compared with only using an organic dehydrating agent, it can effectively reduce the moisture content of the sludge without significantly increasing the cost of the agent per ton of sludge, and has strong economic and practicality.

[0025] As an embodiment of the present invention, the conditioning treatment can be carried out under stirring conditions; the conditioning treatment time can be 34 to 51 seconds, specifically 42 seconds. The present invention utilizes the colloid and inorganic insoluble solid properties of the dehydration aid to achieve uniform mixing of concentrated sludge and organic dehydrating agent without precipitation causing pipeline clogging. In the embodiment of the present invention, conditioning treatment is carried out under the above conditions, which is conducive to achieving a better dehydration effect.

[0026] After obtaining the conditioned sludge, the present invention performs filter pressing and dehydration on the conditioned sludge in a plate and frame filter press to obtain a filter cake. As an embodiment of the present invention, the pressure of the filter pressing and dehydration can be 1.6MPa; the pressure holding time can be 2000~2800s, specifically 2600s; the process of the filter pressing and dehydration is the process of dehydration by breaking the wall of the dehydration aid. As an embodiment of the present invention, the filter pressing and dehydration can be carried out in a plate and frame filter press, and the terminating mud inlet pressure is 1.0~1.2MPa during the process of the conditioned sludge entering the plate and frame filter press; in an embodiment of the present invention, when the conditioned sludge enters the plate and frame filter press, the initial pressure is 0MPa, and then gradually pressurized, and the mud inlet is terminated when the pressure is increased to 1.2MPa after 7000s, and the filter pressing and dehydration is carried out in the plate and frame filter press. As an embodiment of the present invention, the conditioned sludge is specifically transported to the plate and frame filter press by a mud inlet pump, and the mud inlet pressure refers to the working pressure of the mud inlet pump.

[0027] As an embodiment of the present invention, the filter pressing and dehydration further obtains a filtrate, which is neutral and non-corrosive and will not affect the pH value of the influent water of the sewage treatment plant.

[0028] The sludge dewatering system applicable to the dewatering method of activated sludge in the present invention is not particularly limited. As one embodiment of the present invention, the sludge dewatering system may include, for example, an activated sludge pump well, a sludge thickening tank, a sludge conditioning tank, a sludge feed pump, a plate-frame filter press, a screw conveyor, a sludge storage hopper, valves, and pipelines, and is also equipped with a dewatering agent delivery device; wherein the residual sludge pump well, the sludge thickening tank, the sludge conditioning tank, the sludge feed pump, the plate-frame filter press, the screw conveyor and the sludge storage hopper are sequentially connected, and the outlet of the dewatering agent delivery device is connected to the sludge conditioning tank, and the dewatering agent delivery device may be a belt conveyor or a U-shaped scraper conveyor, which can realize the delivery of the dewatering agent. As one embodiment of the present invention, a sludge thickener is installed in the sludge thickening tank to facilitate continuous gravity thickening. As an embodiment of the present invention, the sludge conditioning tank is provided with four small square tanks of equal size and connected in series, and each small square tank is installed with an agitator; the first small square tank is provided with a concentrated sludge pipe and a chemical dispensing pipe, and the first small square tank is connected to the sludge thickening tank through the concentrated sludge pipe, and the chemical dispensing pipe is used for adding dehydration aids and organic dehydration agents; the function of the sludge conditioning tank is to fully and evenly mix the concentrated sludge with the dehydration aid and the organic dehydration agent, so that the obtained mixed sludge can be neutralized with static electricity and then stacked unstably to achieve flocculation and sedimentation effect; if the sludge is not conditioned in the sludge conditioning tank, after the sludge is pumped into the plate and frame filter press, the dehydration aid cannot fully break the wall, thereby causing the sludge to be unable to be squeezed, filtered and dehydrated; at the same time, the sludge conditioning tank also has the function of regulating the amount of stored sludge.

[0029] As an embodiment of the present invention, the activated sludge can be transported to a sludge thickening tank through an activated sludge pump well for concentration to obtain concentrated sludge; the concentrated sludge is transported to a sludge conditioning tank, a dehydration aid and an organic dehydrating agent are added to the sludge conditioning tank for conditioning to obtain conditioned sludge; the conditioned sludge is pumped to a plate and frame filter press through a mud feed pump for filtration and dehydration to obtain filter cake and filtrate, respectively, and the filter cake is loaded into a sludge storage hopper through a screw conveyor.

[0030] At present, when only organic dehydrating agents are added and filter press dehydration technology is used to treat activated sludge in the relevant technology, the cost of a ton of sludge is about 160 yuan. On this basis, the present invention adds a dehydrating aid, uses the dehydrating aid as a dehydrating agent auxiliary conditioning agent, and accurately controls its addition amount. It can effectively reduce the sludge moisture content without significantly increasing the cost of a ton of sludge. The economic benefit is significant. In addition, the present invention uses a dehydrating aid as a dehydrating agent auxiliary conditioning agent, which is a natural substance without chemical pollution, and no other chemical agents are added. The filtrate obtained after filter press dehydration is neutral and non-corrosive, and has no effect on the biological treatment system of the sewage treatment plant. At the same time, the method of the present invention is simple and easy to operate, has low control difficulty, and is suitable for large-scale promotion and use.

[0031] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The residual activated sludge used in the following examples and comparative examples comes from a domestic sewage treatment plant, with a water content of 99.3wt%; the organic dehydrating agent used is a polyquaternary ammonium salt compound (purchased from Changzhi Huanyi Environmental Technology Co., Ltd., model: plate and frame desludging agent Huanyi Environmental HY-606); the particle size of the clay used is 0.018~2µm, and the dry density (ρ1) is 1.4t / m 3 ; The density of water (ρ2) is 1t / m 3 .

[0033] Comparative Example 1 50 tons of excess activated sludge were continuously concentrated by gravity for 28 hours to obtain 11.67 tons of concentrated sludge with a moisture content of 97 wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge); According to the addition of 1.35 kg of an organic dehydrating agent aqueous solution with a mass concentration of 20% per ton of concentrated sludge, the organic dehydrating agent aqueous solution is added to the concentrated sludge, and conditioning treatment is performed for 34 seconds at a rotation speed of 20 rpm to obtain conditioned sludge; The conditioned sludge is transported to a plate and frame filter press by a mud feed pump, wherein when the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and then the pressure is gradually increased. When the pressure is increased to 1.2 MPa after 7000 seconds, the mud feeding is stopped, and pressure filtration and dehydration are carried out in the plate and frame filter press. The pressure of the pressure filtration and dehydration is 1.6 MPa, and the pressure holding time is 2600 seconds. After the pressure filtration and dehydration are completed, filter cake and filtrate are respectively obtained; the moisture content of the filter cake is 65wt%, and the wet weight is 1t.

[0034] Example 1 In this embodiment, clay is added on the basis of Comparative Example 1, and it is expected that the moisture content of the filter cake will be reduced to 59wt% (i.e., F=59wt%). On this basis, according to Formula I (M=1t, f=65wt%, ρ1=1.4t / m 3 ,ρ2=1t / m 3 ) The clay dosage is calculated to be 0.068t; the other steps refer to Comparative Example 1, which are as follows: 50 tons of excess activated sludge were continuously concentrated by gravity for 28 hours to obtain 11.67 tons of concentrated sludge with a moisture content of 97 wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge), 1.35 kg of an organic dehydrating agent aqueous solution with a mass concentration of 20% and 0.068 tons of clay were added, and conditioning treatment was carried out at a rotation speed of 20 rpm for 34 seconds to obtain conditioned sludge; The conditioned sludge is transported to a plate and frame filter press by a mud feed pump for filtration and dehydration. When the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and then the pressure is gradually increased. When the pressure is increased to 1.2 MPa after 7000 seconds, the sludge feeding is stopped, and filtration and dehydration are carried out in the plate and frame filter press. The pressure of filtration and dehydration is 1.6 MPa, and the pressure holding time is 2600 seconds. After the filtration and dehydration is completed, filter cake and filtrate are respectively obtained. The moisture content of the filter cake is 59wt%, and the wet weight is 1.020t.

[0035] Example 2 In this embodiment, clay is added on the basis of Comparative Example 1, and it is expected that the moisture content of the filter cake will be reduced to 55wt% (i.e., F=55wt%). On this basis, according to Formula I (M=1t, f=65wt%, ρ1=1.4t / m 3 ,ρ2=1t / m 3 ) The clay dosage is calculated to be 0.115 t, which is 0.047 t more than that in Example 1, which is consistent with the trend of increasing physical wall breaking; the other steps are operated with reference to Comparative Example 1, as follows: 50 tons of excess activated sludge were continuously concentrated by gravity for 28 hours to obtain 11.67 tons of concentrated sludge with a moisture content of 97 wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge), 1.35 kg of an organic dehydrating agent aqueous solution with a mass concentration of 20% and 0.115 tons of clay were added, and the mixture was conditioned for 34 seconds at a rotation speed of 20 rpm to obtain conditioned sludge; The conditioned sludge is transported to a plate and frame filter press by a mud feed pump for filtration and dehydration. When the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and then the pressure is gradually increased. When the pressure is increased to 1.2 MPa after 7000 seconds, the sludge feeding is stopped, and filtration and dehydration are carried out in the plate and frame filter press. The pressure of filtration and dehydration is 1.6 MPa, and the pressure holding time is 2600 seconds. After the filtration and dehydration is completed, filter cake and filtrate are respectively obtained. The moisture content of the filter cake is 55wt%, and the wet weight is 1.033t.

[0036] Example 3 In this embodiment, clay is added on the basis of Comparative Example 1, and it is expected that the moisture content of the filter cake will be reduced to 50wt% (i.e., F = 50wt%). On this basis, according to Formula I (M = 1t, f = 65wt%, ρ1 = 1.4t / m 3,ρ2=1t / m 3 ) The clay dosage is calculated to be 0.175 t, which is 0.060 t more than that in Example 2, which is consistent with the trend of increasing physical wall breaking; the other steps are operated with reference to Comparative Example 1, as follows: 50 tons of excess activated sludge were continuously concentrated by gravity for 28 hours to obtain 11.67 tons of concentrated sludge with a moisture content of 97 wt% (the volume of the concentrated sludge was reduced to 25% of the volume of the excess activated sludge), 1.35 kg of an organic dehydrating agent aqueous solution with a mass concentration of 20% and 0.175 tons of clay were added, and conditioning treatment was carried out at a rotation speed of 20 rpm for 34 seconds to obtain conditioned sludge; The conditioned sludge is transported to a plate and frame filter press by a mud feed pump for filtration and dehydration. When the conditioned sludge enters the plate and frame filter press, the initial pressure is 0 MPa, and then the pressure is gradually increased. When the pressure is increased to 1.2 MPa after 7000 seconds, the sludge feeding is stopped, and filtration and dehydration are carried out in the plate and frame filter press. The pressure of filtration and dehydration is 1.6 MPa, and the pressure holding time is 2600 seconds. After the filtration and dehydration is completed, filter cake and filtrate are respectively obtained. The moisture content of the filter cake is 50wt%, and the wet weight is 1.050t.

[0037] Embodiments 4 to 9 In Example 1, when the operating conditions remain unchanged, when the target moisture content F of the filter cake is 45wt%, 40wt%, 35wt%, 30wt%, 25wt%, and 20wt%, according to Formula I (M=1t, f=65wt%, ρ1=1.4t / m 3 ,ρ2=1t / m 3 ) obtained: clay dosage X is 0.237t, 0.302t, 0.369t, 0.438t, 0.569t, 0.583t, and filter cake wet weight is 1.068t, 1.086t, 1.105t, 1.125t, 1.145t, 1.167t, all in line with the trend of physical cell wall breaking increase. This shows that the method of breaking the cell wall of activated sludge microorganisms to release intracellular water and squeeze out adsorbed water according to formula I has a wide range of application.

[0038] Generally speaking, from the perspective of economic and practical effects, when using a plate and frame filter press to filter and dehydrate activated sludge, the moisture content of the obtained filter cake is controlled by selecting the target moisture content from the core control range of 55-59wt%, and the filter cake is qualified as long as the moisture content is less than 60wt%. Looking to the future, if the country requires the moisture content of the plate and frame dehydration filter cake of the sewage treatment plant to be less than 40wt%, the method of the present invention is also applicable.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as 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: The following steps are involved: Concentrating the activated sludge to obtain concentrated sludge; The concentrated sludge is mixed with an organic dehydrating agent and a dehydrating aid, and conditioned to obtain conditioned sludge; The dehydration aid is clay; The conditioned sludge is filtered and dehydrated in a plate and frame filter press to obtain a filter cake; The amount of the dehydration aid 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 adding a dehydration aid, in units of t; f is the moisture content of the filter cake obtained under the same conditions without adding dehydration aid, the unit is wt%, and the value range is 60~70wt%; X is the dry weight of the dehydration aid, in t; F is the target moisture content, in wt%, ranging from 20 to 59wt%; ρ1 is the dry density of the dehydration aid, in t / m 3 ; ρ2 is the density of water, in t / m 3 .

2. The method according to claim 1, characterized in that The activated sludge includes excess activated sludge produced by a domestic sewage treatment plant and / or excess activated sludge produced by an industrial sewage treatment plant; the water content of the activated sludge is 99-99.3wt%.

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 water content of the concentrated sludge is 96-98wt%.

4. The method according to claim 1, characterized in that: The organic dehydrating agent comprises a polyquaternary ammonium salt compound, and the average molecular weight of the polyquaternary ammonium salt compound is 400,000 to 2,000,000.

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

6. The method according to claim 1, characterized in that The particle size of the dehydration aid is 0.018-2 μm.

7. The method according to claim 1, characterized in that The conditioning treatment is carried out under stirring conditions, and the conditioning treatment time is 34 to 51 seconds.

8. The method according to claim 1 or 7, characterized in that: The pressure of the filter press dehydration is 1.6 MPa, and the pressure holding time is 2000-2800 s.

9. The method according to claim 8, characterized in that During the process of the conditioned sludge entering the plate and frame filter press, the final sludge inlet pressure is 1.0-1.2 MPa.

10. The method according to claim 1, characterized in that The following steps are involved: The activated sludge is transported to the sludge thickening tank through the activated sludge pump well for thickening to obtain concentrated sludge; The concentrated sludge is transported to a sludge conditioning tank, a dehydration aid and an organic dehydrating agent are added to the sludge conditioning tank for conditioning to obtain conditioned sludge; The conditioned sludge is pumped into a plate and frame filter press by a sludge inlet pump for filtration and dehydration to obtain filter cake and filtrate respectively, and the filter cake is loaded into a sludge storage hopper by a screw conveyor.