Microbial sewage treatment device

Abstract

The invention discloses a microbial sewage treatment device, and belongs to the technical field of microbial sewage treatment, the microbial sewage treatment device comprises a container, a microbial film and a biological wax supply member are arranged in the container, and a water inlet mechanism extends into the container; the air inlet mechanism extends into the container; one side of the drainage mechanism is positioned on the upper side of the bottom wall of the container, and the other side is positioned on the outer side of the container; wherein the water inlet mechanism comprises a supply pipe, a main pipe and a plurality of branch pipes, the supply pipe is arranged on the outer side of the container, one end of the main pipe is communicated with the supply pipe through a U-shaped communication structure, the main pipe is horizontally arranged on the upper side of the interior of the container, one end of each branch pipe is communicated with the main pipe, and the other end of each branch pipe is communicated with the main pipe. And the other end of the branch pipe extends to the lower side in the container. Through the unique design of the water inlet mechanism, the gas inlet mechanism, the microbial film, the biological wax supply mechanism and the like, the sewage treatment effect is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial sewage treatment, and in particular relates to a microbial sewage treatment device. Background Art

[0002] In the field of sewage treatment, microbial treatment technology is widely used due to its advantages of high efficiency and environmental protection. However, the existing microbial sewage treatment technology has many shortcomings.

[0003] In traditional sewage treatment methods, sewage is usually injected directly into the top of the container through the water inlet pipe at the bottom of the container. This method has obvious disadvantages. On the one hand, the sewage needs to pass through floating impurities on the liquid surface during injection, which can easily cause impurities to mix into the sewage and cause secondary pollution. On the other hand, it is difficult for the newly injected sewage to fully contact with microorganisms, so that the pollutants in the sewage cannot be efficiently decomposed and transformed by microorganisms, which greatly reduces the efficiency and quality of sewage treatment. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a microbial sewage treatment device, which effectively avoids the defects of traditional technology and significantly improves the sewage treatment effect through unique designs of water inlet mechanism, air inlet mechanism, microbial membrane and bio-wax supply mechanism.

[0005] The present invention is implemented in this way: a microbial sewage treatment device comprises:

[0006] A container, wherein a microbial film and a biowax supply member are provided inside the container,

[0007] A water inlet mechanism extending into the container;

[0008] An air intake mechanism extending into the container;

[0009] A drainage mechanism, one side of which is located on the upper side of the bottom wall of the container and the other side of which is located outside the container;

[0010] Wherein, the water inlet mechanism comprises:

[0011] A supply pipe, a main pipe and a branch pipe, wherein the supply pipe is arranged outside the container, one end of the main pipe is connected to the supply pipe through a U-shaped connecting structure, the main pipe is horizontally arranged on the upper side of the container, there are a plurality of branch pipes, and one end of each branch pipe is connected to the main pipe, and the other end of the branch pipe extends to the lower side of the container.

[0012] As a preferred embodiment of the present invention, the discharge end of the water inlet mechanism is located below 20% of the height of the inner cavity of the container, and the discharge end of the air inlet mechanism is located below 20% of the height of the inner cavity of the container.

[0013] As a preferred embodiment of the present invention, a water inlet solenoid valve is provided on the supply pipe; the air distribution mechanism includes an air pump and an air inlet pipe, and the air inlet pipe is arranged inside the container.

[0014] As a preferred embodiment of the present invention, the water outlet mechanism includes: a water outlet pipe, a flow rate sensor, and a water outlet solenoid valve; the water outlet pipe runs through the container, the inlet end of the water outlet pipe is located inside the container, and the outlet end of the water outlet pipe is located outside the container; the flow rate sensor and the water outlet solenoid valve are both arranged on the water outlet pipe; the flow rate sensor signal is connected to a controller, and the controller signal is connected to the water inlet solenoid valve and the air pump; the inlet end of the water outlet pipe is connected to a drain pan, the upper wall of the drain pan is a filter pan, and the filter pan is horizontally arranged in the container.

[0015] As a preferred embodiment of the present invention, the diameter of the filter disc is 5-20 times the inner diameter of the outlet pipe. The outlet end of the air inlet pipe is connected to the drain disc.

[0016] As a preferred embodiment of the present invention, the controller includes a water outlet speed input module, a calculation module, a water inlet speed control module and an air inlet speed control module; the water outlet speed input module signal is connected to the flow rate sensor; the calculation module is used to calculate the water inlet speed and the air inlet speed according to the data of the flow rate sensor; the water inlet speed control module signal is connected to the water inlet solenoid valve; the air inlet speed control module signal is connected to the air pump; wherein, assuming the water inlet speed is V in , the air intake speed is V air The water outlet speed is V out , set a proportional coefficient k to control the change degree of the air intake speed when the water outlet speed changes; set the initial air intake speed to V air0 ;

[0017] The calculation formula of the calculation module is:

[0018]

[0019] As a preferred embodiment of the present invention, during sewage treatment, the sewage liquid level in the container is not less than 90% of the height of the inner cavity of the container.

[0020] As a preferred embodiment of the present invention, a debris discharge door is provided on the container via an elastic member; an air bag is connected above the debris discharge door via a connecting line, and the air bag is located at the sewage liquid surface.

[0021] As a preferred embodiment of the present invention, the filter disc is rotatably connected to the water outlet pipe via a rotary joint, and the filter disc is connected to a rotating driving member; a toggle plate is fixedly connected to the lower side of the filter disc, and the lower side of the toggle plate is attached to the upper surface of the bottom wall of the container; a roller is fixedly connected to the lower side of the filter disc, and the rolling end of the roller is attached to the bottom upper surface of the container.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. Compared with the traditional method of injecting sewage directly from the water inlet pipe on the lower side of the container to the top of the container, the water inlet mechanism of this device injects sewage from the bottom of the container through the main pipe on the upper side of the container and the branch pipe extending to the lower side, avoiding the problem of impurities floating on the surface of the sewage and reducing the secondary pollution of impurities to the sewage. This method of injecting sewage from the bottom is conducive to a more even distribution of sewage in the container, so that the sewage is fully in contact with the microbial membrane, providing better conditions for microbial treatment of sewage and improving the efficiency of sewage treatment.

[0024] 2. The microbial membrane provides a place for microorganisms to attach, allowing them to gather in large numbers and form a stable microbial community, which can continuously and efficiently treat sewage. The biowax supply mechanism provides nutrients for microorganisms, ensuring their growth and activity, helping to maintain the efficiency of microbial sewage treatment and extending their service life.

[0025] 3. The buoyancy provided by the air intake mechanism can float the floating impurities on the water surface, making the impurities easier to collect and process, and avoiding the impurities from floating around in the sewage and affecting the effect of sewage treatment.

[0026] 4. The air intake mechanism provides the required oxygen for microorganisms, ensuring the aerobic metabolism of microorganisms, which is beneficial to the decomposition and transformation of pollutants by microorganisms and improves the quality and speed of sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of a microbial sewage treatment device provided in Example 1 of the present invention from a first perspective;

[0028] Figure 2 is a signal connection diagram of the controller provided in Example 1 of the present invention;

[0029] Figure 3 is a schematic structural diagram of the microbial sewage treatment device provided in Example 1 of the present invention from a second viewing angle;

[0030] Figure 4 is a schematic diagram of the top view of the microbial sewage treatment device provided in Example 2 of the present invention;

[0031] Figure 5 Embodiment 2 of the present invention provides Figure 4 A schematic diagram of a cross-sectional three-dimensional structure of the AA portion of the middle part omitting the airbag;

[0032] Figure 6 It is a schematic diagram of the internal structure of the microbial sewage treatment device provided in Example 2 of the present invention.

[0033] In the figure: 1. container; 2. microbial membrane; 3. biowax supply part; 4. supply pipe; 5. main pipe; 6. branch pipe; 7. U-shaped connecting structure; 8. air pump; 9. air inlet pipe; 10. water outlet pipe; 11. flow rate sensor; 12. water outlet solenoid valve; 13. controller; 14. drain pan; 15. filter pan; 16. water outlet speed input module; 17. calculation module; 18. water inlet speed control module; 19. air inlet speed control module; 20. impurity discharge door; 21. air bag; 22. toggle plate; 23. roller; 24. water inlet solenoid valve. DETAILED DESCRIPTION

[0034] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings.

[0035] The structure of the present invention is described in detail below in conjunction with the accompanying drawings.

[0036] Example 1

[0037] like Figures 1 to 3 As shown, a microbial sewage treatment device provided by an embodiment of the present invention comprises:

[0038] A container 1, wherein a microbial film 2 and a biowax supply member 3 are provided inside the container 1,

[0039] A water inlet mechanism extending into the container 1;

[0040] An air intake mechanism extending into the container 1;

[0041] A drainage mechanism, one side of which is located on the upper side of the bottom wall of the container 1, and the other side of which is located on the outer side of the container 1;

[0042] Wherein, the water inlet mechanism comprises:

[0043] A supply pipe 4, a main pipe 5 and a branch pipe 6, wherein the supply pipe 4 is arranged outside the container 1, one end of the main pipe 5 is connected to the supply pipe 4 through a U-shaped connecting structure 7, the main pipe 5 is horizontally arranged on the upper side of the container 1, there are several branch pipes 6, and one end of each branch pipe 6 is connected to the main pipe 5, and the other end of the branch pipe 6 extends to the lower side of the container 1.

[0044] With this arrangement, when in use, sewage first enters the supply pipe 4, and then flows into the main pipe 5 through the U-shaped connecting structure. The main pipe 5 is horizontally arranged on the upper side of the container 1, and one end of the plurality of branch pipes 6 is connected to the main pipe 5, and the other end extends to the lower side of the container 1. This design allows sewage to be guided from the upper side of the container 1 through the main pipe 5 and the branch pipes 6, and finally injected from the lower side of the container 1.

[0045] The air intake mechanism extends into the container 1 and has two main functions. On the one hand, it can provide the microorganisms in the container 1 with oxygen required for their metabolism, promote the growth and reproduction of the microorganisms, and enable them to better decompose and transform the pollutants in the sewage. On the other hand, the gas generated by the air intake mechanism can provide buoyancy for floating impurities on the liquid surface, helping the impurities to float on the water surface, facilitating subsequent separation and treatment.

[0046] A microbial membrane 2 is arranged inside the container 1, which is one of the core components for treating sewage. A large number of microorganisms are attached to the microbial membrane 2. When sewage is injected from the bottom, it will flow through the microbial membrane 2. The microorganisms on the microbial membrane 2 will biodegrade organic pollutants and harmful substances in the sewage and convert them into harmless substances or carbon dioxide and water.

[0047] At the same time, a biowax supply mechanism is also provided in the container 1, and the biowax can provide a certain growth environment and nutrients for the microorganisms, promote the growth and activity of the microorganisms, and improve the efficiency of sewage treatment.

[0048] One side of the drainage mechanism is located on the upper side of the bottom wall of the container 1, and the other side is located on the outside of the container 1. The treated sewage is discharged from the container 1 through the drainage mechanism, while the impurities or incompletely treated substances settled at the bottom of the container 1 will be retained in the container 1 and will not be discharged.

[0049] Preferably, the discharge end of the water inlet mechanism is located below 20% of the height of the inner cavity of the container 1 , and the discharge end of the air inlet mechanism is located below 20% of the height of the inner cavity of the container 1 .

[0050] Furthermore, the supply pipe 4 is provided with a water inlet solenoid valve 24 ; the air distribution mechanism includes an air pump 8 and an air inlet pipe 9 , and the air inlet pipe 9 is arranged inside the container 1 .

[0051] Further, the water outlet mechanism includes: a water outlet pipe 10, a flow rate sensor 11, and a water outlet solenoid valve 12; the water outlet pipe 10 runs through the container 1, the inlet end of the water outlet pipe 10 is located inside the container 1, and the outlet end of the water outlet pipe 10 is located outside the container 1; the flow rate sensor 11 and the water outlet solenoid valve 12 are both arranged on the water outlet pipe 10; the flow rate sensor 11 is connected to the controller 13, and the controller 13 is connected to the water inlet solenoid valve 24 and the air pump 8; the inlet end of the water outlet pipe 10 is connected to the drain pan 14, the upper wall of the drain pan 14 is a filter pan 15, and the filter pan 15 is horizontally arranged in the container 1. The water in the container 1 enters the water outlet pipe 10 through the filter pan 15, and the filter pan 15 can be used to filter impurities to ensure the water quality of the drainage in the drain pipe. When the flow rate sensor 11 detects that the drainage flow rate of the water outlet pipe 10 is reduced, the water inlet solenoid valve 24 can be controlled accordingly to reduce the water inlet speed, and the air pump 8 can also be controlled accordingly to increase the air supply speed of the air pump 8.

[0052] Further, the diameter of the filter plate 15 is 5-20 times the inner diameter of the outlet pipe 10. The outlet end of the air inlet pipe 9 is connected to the drain plate 14.

[0053] Through this arrangement, on the one hand, after the gas enters the filter disc 15, it can pass through the filter disc 15 from bottom to top under the action of buoyancy, and the gas is divided into small bubbles, and then enters the container 1, which can improve the effect of gas distribution and the lifting force for floating impurities. On the other hand, since water passes through the filter disc 15 from outside to inside during drainage, impurities will adhere to the outside of the filter disc 15, and bubbles pass through the filter disc 15 from inside to outside, thereby clearing the blocked impurities. At the same time, pressure is also provided to the water in the drain pipe, which can clear the impurities in the drain pipe to a certain extent.

[0054] Furthermore, since the diameter of the filter disc 15 is larger than the diameter of the water outlet pipe 10, the water flow rate at the filter disc 15 is relatively small, so the water flow there can be prevented from flushing the gas into the water outlet pipe 10. Of course, in general, the water outlet solenoid valve 12 can be closed before supplying gas, because the purpose of supplying gas is to improve the effect of microbial treatment, and no water is discharged at this time. However, this is not limited here, and gas supply and drainage can also be carried out simultaneously.

[0055] Specifically, the controller 13 includes a water outlet speed input module 16, a calculation module 17, a water inlet speed control module 18 and an air intake speed control module 19; the water outlet speed input module 16 signal is connected to the flow rate sensor 11; the calculation module 17 is used to calculate the water inlet speed and the air intake speed according to the data of the flow rate sensor 11; the water inlet speed control module 18 signal is connected to the water inlet solenoid valve 24; the air intake speed control module 19 signal is connected to the air pump 8.

[0056] Where, assuming the water inlet velocity is V in Unit: volume / time, such as m 3 / h, intake air velocity is V air Unit: volume / time, such as m 3 / h, water outlet speed is V out Unit: volume / time, such as m 3 / h, a dimensionless proportionality coefficient k is set to control the degree of change of the air intake speed when the water outlet speed changes; the initial air intake speed is set to V air0 Unit: volume / time, such as m 3 / h;

[0057] The calculation formula of the calculation module 17 is:

[0058]

[0059] In the above formula, the following functions are available:

[0060] First, in a stable state, make the water inlet velocity and the water outlet velocity equal, that is, V in =V out .

[0061] Second, control the air intake speed according to the water outlet speed:

[0062] When the water outlet speed is detected to be reduced, the air intake speed is automatically controlled to increase. The air intake speed V can be expressed by the following formula air With water outlet speed V out Relationship: V air =V air0 +k×(V out0 -V out ), where V out0 is the initial setting value of the water outlet speed. out <V out0 When (V out0 -V out ) is a positive value, the intake air velocity V air At the initial intake velocity V air0 Increase on the basis of; when V out =V out0 When the air intake velocity remains at the initial value V air0 The proportional coefficient k needs to be debugged and determined according to the actual water treatment system, so as to achieve the purpose of both reasonably adjusting the air intake speed when the water outlet speed changes and ensuring the stable operation of the entire system.

[0063] Through this setting, the water outlet speed is used to control the water inlet speed and air inlet speed:

[0064] In this device, when the water outlet solenoid valve 12 is normally opened, if the water outlet speed becomes low, it means that the sewage treatment effect is not good (for example, the water inlet speed is too fast, or the oxygen content is too low, which affects the dissolved oxygen content in the water, the microbial metabolic environment, etc., and thus affects the sewage treatment effect), which in turn causes the filter disc 15 to be blocked by impurities.

[0065] At this time, the water inlet speed is automatically controlled to decrease and the air inlet speed is increased through the formula. On the one hand, the oxygen content in the water can be increased, thereby improving the sewage treatment effect; on the other hand, since the air inlet speed is increased, the filter disc 15 can be reversely flushed by the airflow, thereby cleaning the impurities in the filter disc 15. The water inlet speed is correspondingly reduced, and the impurities entering the container 1 are also reduced accordingly, and the excessive sewage can be prevented from overflowing the container 1.

[0066] Furthermore, during sewage treatment, the sewage level in the container 1 is not less than 90% of the inner cavity height of the container 1. Under this condition, according to the above formula, when the water outlet speed is reduced to a certain extent, the air intake speed increases, and the volume of water expands (normally it can increase by 20%-40%), at which time the floating objects can be discharged faster, and the gas can push the floating objects to fall from the upper edge of the container 1.

[0067] Example 2

[0068] The difference from Implementation 1 is that the following settings are added on the basis of Implementation 1:

[0069] See also Figure 1-Figure 6 The container 1 is provided with a waste discharge door 20 through an elastic member (such as a spring); an air bag 21 is connected to the top of the waste discharge door 20 through a connecting line, and the air bag 21 is located at the sewage liquid surface.

[0070] When the water level is normal, the pulling force of the airbag 21 on the impurity discharge door 20 is small and close to 0; when the water level rises, the pulling force of the airbag 21 on the impurity discharge door 20 increases, which can overcome the elastic force of the elastic member and open the impurity discharge door, thereby automatically discharging impurities at the bottom of the container 1. Through this setting, by increasing the air supply speed, floating impurities and bottom precipitated impurities can be discharged at the same time.

[0071] Furthermore, the filter disc 15 is rotatably connected to the water outlet pipe 10 via a rotary joint, and the filter disc 15 is connected to a rotating driving member; a toggle plate 22 is fixedly connected to the lower side of the filter disc 15, and the lower side of the toggle plate 22 is attached to the upper surface of the bottom wall of the container 1; a roller 23 is fixedly connected to the lower side of the filter disc 15, and the rolling end of the roller 23 is attached to the bottom upper surface of the container 1.

[0072] Exemplarily, the rotating drive member includes an outer gear ring fixedly connected to the outer peripheral surface of the filter disc 15, and the motor drives the outer gear ring to rotate through the gear. Through this arrangement, the filter disc 15 can be reciprocated, so that the impurities contained at the bottom are moved to the impurity discharge door 20, thereby facilitating the improvement of impurity discharge efficiency. And the sewage can be rotated slightly, so that the sewage can be distributed more evenly and the sewage can be fully contacted with the vertically arranged microbial membrane 2. For example, the microbial membrane 2 is installed on the vertical part of the branch pipe 6.

[0073] Working principle of the present invention:

[0074] When in use, sewage first enters the supply pipe 4, and then flows into the main pipe 5 through the U-shaped connecting structure. The main pipe 5 is horizontally arranged on the upper side of the container 1, and one end of the multiple branch pipes 6 is connected to the main pipe 5, and the other end extends to the lower side of the container 1. This design allows sewage to be guided from the upper side of the container 1 through the main pipe 5 and the branch pipe 6, and finally injected from the lower side of the container 1. After the gas enters the filter disc 15, it can pass through the filter disc 15 from bottom to top under the action of buoyancy, and the gas is divided into fine bubbles, and then enters the container 1, which can improve the effect of gas distribution and the lifting force of floating impurities. The bubbles pass through the filter disc 15 from the inside to the outside, so that the blocked impurities can be cleaned.

[0075] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0076] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A microbial sewage treatment device, characterized in that: include: A container (1), wherein a microbial membrane (2) and a biowax supply member (3) are provided inside the container (1), A water inlet mechanism extending into the interior of the container (1); An air intake mechanism extending into the interior of the container (1); a drainage mechanism, one side of which is located on the upper side of the bottom wall of the container (1) and the other side of which is located on the outer side of the container (1); Wherein, the water inlet mechanism comprises: A supply pipe (4), a main pipe (5) and a branch pipe (6), wherein the supply pipe (4) is arranged outside the container (1), one end of the main pipe (5) is connected to the supply pipe (4) through a U-shaped connecting structure (7), the main pipe (5) is arranged horizontally on the upper side of the container (1), there are a plurality of branch pipes (6), one end of each of the branch pipes (6) is connected to the main pipe (5), and the other end of each of the branch pipes (6) extends to the lower side of the container (1).

2. A microbial sewage treatment device as claimed in claim 1, characterized in that: The discharge end of the water inlet mechanism is located below 20% of the height of the inner cavity of the container (1), and the discharge end of the air inlet mechanism is located below 20% of the height of the inner cavity of the container (1).

3. A microbial sewage treatment device as claimed in claim 1, characterized in that: The supply pipe (4) is provided with a water inlet solenoid valve (24); The air distribution mechanism comprises an air pump (8) and an air intake pipe (9), and the air intake pipe (9) is arranged inside the container (1).

4. A microbial sewage treatment device as claimed in claim 3, characterized in that: The water outlet mechanism comprises: a water outlet pipe (10), a flow rate sensor (11), and a water outlet solenoid valve (12); The water outlet pipe (10) passes through the container (1), the inlet end of the water outlet pipe (10) is located inside the container (1), and the outlet end of the water outlet pipe (10) is located outside the container (1); The flow rate sensor (11) and the water outlet solenoid valve (12) are both arranged on the water outlet pipe (10); The flow rate sensor (11) is signal-connected to a controller (13), and the controller (13) is signal-connected to the water inlet solenoid valve (24) and the air pump (8); The inlet end of the water outlet pipe (10) is connected to a drain pan (14), the upper wall of the drain pan (14) is a filter pan (15), and the filter pan (15) is horizontally arranged in the container (1).

5. A microbial sewage treatment device as claimed in claim 4, characterized in that: The diameter of the filter disc (15) is 5-20 times the inner diameter of the water outlet pipe (10); The air outlet end of the air inlet pipe (9) is connected to the drain pan (14).

6. A microbial sewage treatment device as claimed in claim 5, characterized in that: The controller (13) comprises a water outlet speed input module (16), a calculation module (17), a water inlet speed control module (18) and an air inlet speed control module (19); The water outlet speed input module (16) is connected to the flow rate sensor (11) by signal; The calculation module (17) is used to calculate the water intake speed and the air intake speed according to the data of the flow rate sensor (11); The water inlet speed control module (18) is signal-connected to the water inlet solenoid valve (24); The air intake speed control module (19) is signal-connected to the air pump (8); Where, assuming the water inlet velocity is V in , the air intake speed is V air The water outlet speed is V out , set a proportional coefficient k to control the change degree of the air intake speed when the water outlet speed changes; set the initial air intake speed to V air0 ; The calculation formula of the calculation module (17) is:

7. A microbial sewage treatment device as claimed in claim 6, characterized in that: During sewage treatment, the sewage liquid level in the container (1) is not less than 90% of the inner cavity height of the container (1).

8. A microbial sewage treatment device as claimed in claim 7, characterized in that: The container (1) is provided with a waste discharge door (20) via an elastic member; an air bag (21) is connected above the waste discharge door (20) via a connecting line, and the air bag (21) is located at the sewage liquid surface.

9. A microbial sewage treatment device as claimed in claim 8, characterized in that: The filter disc (15) is rotatably connected to the water outlet pipe (10) via a rotary joint, and the filter disc (15) is connected to a rotating drive member; A toggle plate (22) is fixedly connected to the lower side of the filter disc (15), and the lower side of the toggle plate (22) is in contact with the upper surface of the bottom wall of the container (1). A roller (23) is fixedly connected to the lower side of the filter disc (15), and the rolling end of the roller (23) is in contact with the upper surface of the bottom of the container (1).

Images