Method for designing sludge hopper of sedimentation tank based on brachistochrone, sludge hopper, sedimentation tank and application of sludge hopper and sedimentation tank

Abstract

The invention provides a method for designing a sludge hopper of a sedimentation tank based on a brachistochrone, the sludge hopper, the sedimentation tank and application of the sludge hopper and the sedimentation tank, and relates to the technical field of water treatment. The method for designing the sludge hopper of the sedimentation tank based on the brachistochrone is simple, and the sludge hopper with the brachistochrone curved surface as the side face can be obtained through accurate design according to the brachistochrone expression. According to the sludge bucket, on one hand, sludge flocs falling onto the sludge bucket can slide to the bottom of a sludge tank more quickly, the sludge flocs can be effectively prevented from being adhered to the sludge bucket, and denitrification bubbles are reduced, so that the concentration of effluent suspended matters is reduced; on the other hand, sludge flocs at the middle and upper parts and the middle and lower parts of the sludge hopper can reach the bottom of the tank body at the same time, so that the sludge at the upper, middle and lower parts can be discharged at the same time when the sludge is discharged out of the system, and the discharge efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for designing a sludge hopper of a sedimentation tank based on a brachistoline, a sludge hopper, a sedimentation tank and applications thereof. Background Art

[0002] Mud hoppers are required in the concentration area of ​​sedimentation tanks. The function of the mud hoppers is to compress the activated sludge and increase its concentration, thereby reducing the amount of sludge return and saving energy. Figure 1 As shown, the traditional sludge hopper generally adopts an inclined straight line type, but in the process of practical application, it is found that due to the slow descent speed of sludge on the inclined surface, the activated sludge flocs will stick to the inclined hopper to form sludge balls. After a period of denitrification reaction, many small denitrification bubbles will be generated around the sludge balls. The small bubbles will eventually drive the sludge balls out of the hopper, float to the surface of the upper clear water, and flow away with the effluent, increasing the SS content of the effluent suspended matter and worsening the effluent water quality.

[0003] During the sludge discharge stage of the sedimentation tank, the sludge in the middle and upper part of the sludge hopper has a long distance to slide to the bottom and takes a long time, while the sludge in the middle and lower part has a short distance to slide to the bottom and takes a short time. Therefore, the sludge at the bottom will be discharged from the system first, and the sludge in the middle and upper part will remain in the sedimentation tank because it has not reached the bottom of the tank. The ideal state of the sludge discharge process is that the sludge in the middle and upper part and the sludge in the middle and lower part can reach the bottom of the tank at the same time and be discharged out of the system at the same time.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first object of the present invention is to provide a method for designing a sedimentation tank sludge hopper based on the brachistoline. The sludge hopper designed by this method can be used to replace the traditional inclined linear sludge hopper to solve the many shortcomings of the traditional sludge hopper.

[0006] A second object of the present invention is to provide a sludge hopper.

[0007] The third object of the present invention is to provide a sedimentation tank.

[0008] The fourth object of the present invention is to provide application of the above-mentioned sedimentation tank in activated sludge sedimentation.

[0009] In order to achieve the above objectives, the following technical solutions are adopted:

[0010] In a first aspect, the present invention provides a method for designing a sludge hopper of a sedimentation tank based on a brachistocentre line, comprising:

[0011] Assume: the sludge hopper of the sedimentation tank is placed in the first quadrant of the rectangular coordinate system; the bottom of the sludge hopper is on the x-axis; the side wall of the sludge hopper is designed as the brachistodes surface. When any point on the top of the sludge hopper side wall is on the y-axis, it is recorded as point A (0, b). From point A, along the brachistodes on the side wall of the sludge hopper, it intersects with the x-axis at point B (a, 0);

[0012] Then the expression of the fastest descent line from point A to point B on the side wall of the sludge hopper is:

[0013]

[0014] Among them, r is the radius of the rolling circle, which is an intermediate variable; θ is the arc rolled by a particle on the circle; b is the height of the mud bucket of the sedimentation tank;

[0015] The side wall of the sludge hopper is designed according to the brachistodes curve expression.

[0016] As a further technical solution, the steps for solving the parameter r in the brachistodes curve expression include: firstly determining the coordinates of points A (0, b) and B (a, 0) according to the required depth and size of the sludge hopper, and then respectively substituting the coordinates of points A and B into the brachistodes curve expression, and obtaining r by assigning θ.

[0017] As a further technical solution, the processing method of the sludge hopper includes 3D printing or casting.

[0018] In a second aspect, the present invention provides a sludge hopper, wherein the side wall of the sludge hopper is a brachistodes curve surface;

[0019] The brachistodes curve surface is designed by the above method.

[0020] As a further technical solution, the top of the sludge hopper is open, and the shape of the opening includes circular and polygonal.

[0021] As a further technical solution, the bottom of the sludge hopper is open, and the bottom opening is connected to a sludge discharge pipeline.

[0022] In a third aspect, the present invention provides a sedimentation tank, which includes the above-mentioned sludge hopper.

[0023] In a fourth aspect, the present invention provides application of the above-mentioned sedimentation tank in activated sludge sedimentation.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The method for designing a sedimentation tank sludge hopper based on the brachistoline provided by the present invention is simple, and a sludge hopper with a side surface that is a brachistoline curved surface can be accurately designed according to the brachistoline expression. On the one hand, the sludge hopper can make the sludge flocs that fall on the sludge hopper slide to the bottom of the sludge pool more quickly, which can effectively prevent the sludge flocs from adhering to the sludge hopper, reduce the generation of denitrification bubbles, and thus reduce the concentration of suspended solids in the effluent; on the other hand, the sludge flocs in the middle and upper parts and the middle and lower parts of the sludge hopper can reach the bottom of the tank body at the same time, so that the sludge in the upper, middle and lower parts can be discharged from the sludge discharge system at the same time, thereby improving the discharge efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is the form of traditional sludge hopper and the schematic diagram of sludge settling;

[0028] Figure 2 This is a design drawing of the sludge hopper according to Example 1 of the present invention.

[0029] Icons: 1- side wall of sludge hopper; 2- sedimentation tank; 3- sludge flocs; 4- sludge discharge pipe. DETAILED DESCRIPTION

[0030] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but it will be appreciated by those skilled in the art that the following embodiments and examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified, proceed according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0031] The term "bristichiometric curve" is also called a cycloid, which is the trajectory of any point on a circle when it rolls along a straight line (without sliding). The brachistocentric curve has isochronism, that is, no matter where the object starts to slide down the brachistocentric curve, the time to reach the end point is the same and the time is the shortest.

[0032] In a first aspect, the present invention provides a method for designing a sludge hopper of a sedimentation tank based on a brachistocentre line, comprising:

[0033] like Figure 2 As shown, it is assumed that: the sludge hopper of the sedimentation tank 2 is placed in the first quadrant of the rectangular coordinate system; the bottom of the sludge hopper is located on the x-axis; the side wall 1 of the sludge hopper is designed as a brachistodes surface, when any point on the top of the sludge hopper side wall 1 is located on the y-axis, it is recorded as point A (0, b), and the brachistodes on the side wall 1 of the sludge hopper intersects with the x-axis at point B (a, 0);

[0034] Then the expression of the fastest descent line from point A to point B on the side wall 1 of the sludge hopper is:

[0035]

[0036] Among them, r is the radius of the rolling circle, which is an intermediate variable; θ is the arc rolled by a particle on the circle; b is the height of the sludge hopper in the sedimentation tank;

[0037] The sludge hopper side wall 1 is designed according to the brachistodes curve expression.

[0038] The method for designing a sedimentation tank sludge hopper based on the brachistoline provided by the present invention is simple, and a sludge hopper with a side surface that is a brachistoline curved surface can be accurately designed according to the brachistoline expression. On the one hand, the sludge hopper can make the sludge flocs 3 that fall on the sludge hopper slide to the bottom of the sludge pool more quickly, which can effectively prevent the sludge flocs 3 from adhering to the sludge hopper, reduce the generation of denitrification bubbles, and thus reduce the concentration of suspended solids in the effluent; on the other hand, the sludge flocs 3 in the middle and upper parts and the middle and lower parts of the sludge hopper can be made to reach the bottom of the tank body at the same time, so that the sludge in the upper, middle and lower parts can be discharged from the sludge discharge system at the same time, thereby improving the discharge efficiency.

[0039] In some optional embodiments, the step of solving the parameter r in the brachistodes curve expression includes: first determining the coordinates of points A (0, b) and B (a, 0) according to the required depth and size of the sludge hopper, and then respectively substituting the coordinates of points A and B into the brachistodes curve expression, and obtaining r by assigning θ.

[0040] In a specific implementation, the steps for solving the parameter r in the brachistodes curve expression are as follows:

[0041] 1. Based on the coordinate point A(0, b), substitute into the formula y=r(cosθ-1)+b=0, and then get

[0042]

[0043] 2. According to the coordinate point B(a,0), Substituting into the expression x = r (θ - sinθ) = a, we get Wherein, a is the horizontal distance between the wall of sedimentation tank 2 and the bottom of the sludge hopper;

[0044] 3. Use the assignment method to calculate θ, making both sides of the above formula equal, and obtain the value θ1;

[0045] 4. Substitute θ1 into In the formula, the value r1 is calculated;

[0046] In some optional embodiments, the processing method of the sludge hopper includes 3D printing or casting.

[0047] For example, the brachistocentre curve of cast-in-place or precast concrete can be plotted with different values ​​of [(x n ,y n )n=1,2……n] values, and then use smooth curves to connect different points to form curves, and then connect multiple curves to form a surface (if the top opening of the sludge hopper is circular, then the sludge hopper is horizontally formed by concentric circles passing through each point), and finally the brachistocentric descent line surface is formed by grinding or secondary casting, at this time θ∈[0,θ1];

[0048] If it is a machining equipment, the above expression can be input into a computer program, and the brachistocentric descent line surface can be produced using 3D printing technology. In this case, θ∈[0, θ1] is also used.

[0049] In a second aspect, the present invention provides a sludge hopper, wherein the side wall 1 of the sludge hopper is a brachistodes curve surface;

[0050] The brachistodes curve surface is designed by the above method.

[0051] The sludge hopper provided by the present invention is a new type of sludge hopper used in the concentration area of ​​the sedimentation tank. The application of this type of sludge hopper can shorten the time for the sludge dropped on the sludge hopper to slide to the bottom of the concentration area, increase the sludge settling speed, reduce the suspended matter content in the effluent, and solve the problem of inconsistent time for the sludge in the upper, middle and lower parts of the sludge hopper to slide to the bottom, so that the sludge entering the sedimentation tank can be discharged at the same time.

[0052] The present invention does not impose any specific limitation on the shape of the top opening of the sludge hopper. In some optional embodiments, the top opening of the sludge hopper has a shape including but not limited to a circle and a polygon.

[0053] In some optional embodiments, the bottom of the sludge hopper is open, and the bottom opening is connected to a sludge discharge pipe 4 for discharging sludge.

[0054] In a third aspect, the present invention provides a sedimentation tank, which includes the above-mentioned sludge hopper.

[0055] The sedimentation tank can effectively reduce the concentration of suspended solids in the effluent and improve the discharge efficiency of sludge.

[0056] In a fourth aspect, the present invention provides application of the above-mentioned sedimentation tank in activated sludge sedimentation.

[0057] The sedimentation tank provided by the present invention is used for sedimentation of activated sludge, can effectively prevent sludge flocs from adhering to the sludge hopper, reduces the generation of denitrification bubbles, thereby reducing the concentration of suspended matter in effluent and improving the sludge discharge efficiency.

[0058] The present invention is further described below by means of specific examples and comparative examples. However, it should be understood that these examples are only used for more detailed description and should not be construed as limiting the present invention in any form.

[0059] Example 1

[0060] A method for designing a sludge hopper of a sedimentation tank based on a brachistocentre line, comprising:

[0061] like Figure 2 As shown, it is assumed that: the sludge hopper of the sedimentation tank 2 is placed in the first quadrant of the rectangular coordinate system; the bottom of the sludge hopper is located on the x-axis; the side wall 1 of the sludge hopper is designed as a brachistodes surface, when any point on the top of the sludge hopper side wall 1 is located on the y-axis, it is recorded as point A (0, b), and the brachistodes on the side wall 1 of the sludge hopper intersects with the x-axis at point B (a, 0);

[0062] Then the expression of the fastest descent line from point A to point B on the side wall 1 of the sludge hopper is:

[0063]

[0064] Among them, r is the radius of the rolling circle, which is an intermediate variable; θ is the arc rolled by a particle on the circle; b is the height of the sludge hopper in the sedimentation tank;

[0065] The sludge hopper side wall 1 is designed according to the brachistodes curve expression.

[0066] The steps for solving the parameter r in the expression of the brachistodes curve include:

[0067] 1. Based on the coordinate point A(0, b), substitute into the formula y=r(cosθ-1)+b=0, and then get

[0068]

[0069] 2. According to the coordinate point B(a,0), Substituting into the expression x = r (θ - sinθ) = a, we get Wherein, a is the horizontal distance between the wall of sedimentation tank 2 and the bottom of the sludge hopper;

[0070] 3. Use the assignment method to calculate θ, making both sides of the above formula equal, and obtain the value θ1;

[0071] 4. Substitute θ1 into In the formula, the value r1 is calculated.

[0072] Example 2

[0073] A sludge hopper is provided, the top and bottom of which are open. The side wall 1 of the sludge hopper is designed by the method of Example 1, and the bottom opening is connected to a sludge discharge pipe 4.

[0074] Comparative Example 1

[0075] A sludge hopper, which is different from Example 2 in that it is a traditional inclined linear sludge hopper.

[0076] Test Example 1: Sedimentation velocity test

[0077] 1. Sedimentation velocity experiment: The bottoms of two 2000mL (500mm in height) acrylic cylinders were respectively changed into inclined linear traditional sludge buckets (Comparative Example 1) and the steepest descending line sludge buckets (Example 2). The size of the sludge buckets matched the acrylic cylinders. The angle between the line connecting points A and B and the horizontal line was 45°. A sludge-water mixture with good sedimentation performance and MLSS of about 3000mg / L was added to the two measuring cylinders at the same time. A static sedimentation experiment was carried out. The scale positions of the mud-water interface of the sedimentation tank corresponding to the two different sludge buckets at 5min, 10min, 15min, 20min, 30min, 40min, 50min, and 60min were recorded respectively. The sedimentation velocity of the sludge was judged by the position of the mud-water interface. The lower the mud-water interface, the faster the sedimentation velocity. The experimental data are shown in Table 1:

[0078] Table 1

[0079]

[0080] Note: Settlement distance refers to the distance the mud-water interface drops, and settlement velocity refers to the average speed at which the mud-water interface drops.

[0081] It can be seen from the table that the sludge hopper sedimentation tank with the steepest descent line can quickly achieve the sedimentation effect that the traditional inclined linear sludge hopper can only achieve in about 50 minutes in the first 30 minutes. Its sedimentation rate in the first 30 minutes is 3.41% to 15.32% faster than that of the linear sludge hopper, and is 7.4% faster on average. This shows that the steepest descent line can indeed speed up the sedimentation rate, or in other words, the sedimentation tank with the steepest descent line sludge hopper requires less time to achieve the same sludge concentration.

[0082] Test Example 2: Sludge Discharge Experiment

[0083] Sludge discharge experiment: after the first precipitate of the test example is no longer precipitated (the sludge interface scale lines of the two measuring cylinders are both at about 380 mL), a hole is opened at the bottom of the above-mentioned sedimentation tank, and a hose for discharging sludge is set, and a valve is set on the hose. At the same time, the valve of the sludge discharge hose is opened. After the sludge at the bottom is basically emptied, the sludge discharge situation of the sludge bucket wall is observed, and it is found that the sludge at the top of the traditional inclined straight line sludge bucket is not completely discharged, and only the sludge in a small area near the discharge pipe is discharged. Part of the sludge in the upper part of the sludge bucket has not yet slid to the bottom, resulting in insufficient sludge discharge; while the discharge of the steepest descent line sludge bucket is relatively sufficient, and the sludge in the middle and upper parts of the sludge bucket is also completely discharged. There is a clear sludge interface during the sludge discharge process, indicating that the steepest descent line sludge bucket can discharge the sludge at the top, middle and bottom at the same time during sludge discharge, ensuring the balance of sludge discharge, and proving that the steepest descent line sludge bucket has "isochronism".

[0084] Test Example 3: Effluent Water Quality Test

[0085] The factory processed and manufactured two sets of circular sedimentation tanks with a diameter of 2m. The sludge hoppers used the traditional inclined linear sludge hopper (Comparative Example 1) and the fastest descending linear sludge hopper (Comparative Example 2). The height and width of the two sludge hoppers were both 0.7m, and the size matched the circular sedimentation tank. The mud-water separation experiments were carried out respectively. The experimental parameters were as follows: the inlet flow rate of the mud-water mixture was 2.5m 3 / h, the MLSS content of the mud-water mixture is about 4000mg / L, and the mud discharge interval is 1.5min every 100min;

[0086] Experimental process: The suspended solids in the water were sampled every 2 hours for testing. The effluent conditions for 48 hours are shown in Table 2:

[0087] Table 2

[0088]

[0089] It can be seen from the table that after 8 hours, the effluent suspended solids concentration of the steepest descent line type (average 10.76 mg / L) is lower than the effluent suspended solids concentration of the traditional linear type (12.54 mg / L). The reason is that the sludge in the steepest descent line hopper falls quickly, which can effectively avoid the generation of denitrification bubbles and reduce the concentration of effluent suspended solids.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing a sedimentation tank sludge hopper based on the brachistocentre curve, characterized in that: include: Assume: the sludge hopper of the sedimentation tank is placed in the first quadrant of the rectangular coordinate system; the bottom of the sludge hopper is on the x-axis; the side wall of the sludge hopper is designed as the brachistodes surface. When any point on the top of the sludge hopper side wall is on the y-axis, it is recorded as point A (0, b). From point A, along the brachistodes on the side wall of the sludge hopper, it intersects with the x-axis at point B (a, 0); Then the expression of the fastest descent line from point A to point B on the side wall of the sludge hopper is: Among them, r is the radius of the rolling circle, which is an intermediate variable; θ is the arc rolled by a particle on the circle; b is the height of the mud bucket of the sedimentation tank; The side wall of the sludge hopper is designed according to the brachistodes curve expression.

2. The method according to claim 1, characterized in that The steps for solving the parameter r in the brachistocentre expression include: firstly determining the coordinates of points A (0, b) and B (a, 0) according to the required depth and size of the sludge hopper, and then respectively bringing the coordinates of points A and B into the brachistocentre expression, and obtaining r by assigning θ.

3. The method according to claim 1, characterized in that: The processing method of the sludge hopper includes 3D printing or casting.

4. A sludge hopper, characterized in that: The side wall of the sludge hopper is a brachistocentric curved surface; The brachistodes curve surface is designed by the method described in any one of claims 1 to 3.

5. The sludge hopper according to claim 4, characterized in that: The top of the sludge hopper is open, and the shape of the opening includes a circle and a polygon.

6. The sludge hopper according to claim 4, characterized in that: The bottom of the sludge hopper is open, and the bottom opening is connected to a sludge discharge pipeline.

7. A sedimentation tank, characterized in that: The sedimentation tank comprises the sludge hopper described in any one of claims 4-6.

8. Use of the sedimentation tank described in claim 7 in activated sludge sedimentation.

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