A sewage treatment system and a method of sewage treatment

Abstract

The present disclosure relates to a sewage treatment system and a sewage treatment method, the sewage treatment system comprising an aeration tank and a solid-liquid separator; the aeration tank comprises an aeration tank body, the body of the aeration tank has an octagonal sidewall, the octagonal sidewall comprises, in a horizontal direction, a first straight face wall, a second straight face wall, a third straight face wall, a fourth straight face wall, a fifth straight face wall, a sixth straight face wall, a seventh straight face wall and an eighth straight face wall connected in sequence; the first straight face wall is provided with a first water inlet and a first water outlet, and the fifth straight face wall is provided with a second water inlet and a second water outlet; the third straight face wall is provided with a sludge-water outlet; and the sludge-water outlet is in fluid communication with a water inlet of the solid-liquid separator. The sewage treatment system of the present disclosure has good denitrification effect when used for treating sewage, low suspended solids in effluent, and low energy consumption and cost.

Description

TECHNICAL FIELD

[0001] The present application relates to a sewage treatment system and a sewage treatment method. BACKGROUND

[0002] Worsening water quality not only causes water quality shortage in many areas, increases the cost of obtaining water resources, and more seriously, endangers people's health, so it is necessary to treat wastewater containing pollutants so that it can be discharged up to standard. Biochemical treatment technology has become the mainstream technology for sewage treatment because of its good treatment effect, low treatment cost and other advantages.

[0003] Biological treatment of sewage is divided into biofilm method and activated sludge method according to whether there is a carrier. The treatment efficiency of biofilm method is usually higher than that of activated sludge method. In order to improve the treatment effect of biochemical reaction, a biofilm reactor filled with solid carriers inside is developed, such as moving bed biofilm reactor (MBBR). Microorganisms grow on the surface of the carrier in the reactor to form a micro biofilm. Pollutants are degraded and converted through biochemical reaction of microorganisms in the biofilm and adsorption and interception of the carrier layer. The moving bed reactor filled with carriers has high amount of microorganisms, strong impact load resistance, can effectively separate hydraulic retention time (HRT) and sludge retention time (SRT), and has low operation and maintenance cost. It is an ideal reactor form. Therefore, it has been widely studied.

[0004] For example, CN108191048B provides a sludge internal circulation MBBR sewage treatment device and its application. The device includes a pool body and a partition. The pool body is divided into three sections by two outer partitions. The middle section is a settling zone, and the two ends are aerobic MBBR reaction zones. The lower part of the outer partition is inclinedly arranged along the settling zone. The bottom of the outer partition forms a sludge backflow port, which is higher than the bottom of the pool, so as to connect the bottom of the settling zone and the aerobic MBBR reaction zone. The upper part of the outer partition is provided with a water inlet. The settling zone is provided with a group of inner partitions, which are arranged in parallel with the upper part of the outer partition. A communication trench is arranged between the inner partition and the outer partition. The aerobic MBBR reaction zone, the water inlet, the communication trench, the settling zone and the sludge backflow port form a sludge internal circulation. The hydraulic retention time and the sludge age of the device are independent of each other. The sludge discharge period and discharge amount are easy to control. The device has the characteristics of compact structure, good denitrification effect for rural sewage with low C / N ratio, high resistance to COD impact load, and less residual sludge.

[0005] Although the above-mentioned moving bed biofilm method has advantages over the conventional activated sludge method, the conventional moving bed biofilm method still has problems such as large area occupied by sludge settling zone, need for sludge backflow, high energy consumption, and high suspended solids content in effluent. Therefore, it is necessary to develop a reactor with good treatment effect, small area occupied, low energy consumption, and low suspended solids content in effluent. SUMMARY

[0006] The purpose of the present disclosure is to provide a sewage treatment system and a sewage treatment method, the sewage treatment system of the present disclosure has good denitrification effect when treating sewage, low suspended solids in effluent, and low energy consumption and cost.

[0007] To achieve the above-mentioned purpose, the present disclosure provides a sewage treatment system, which comprises an aeration tank and a solid-liquid separator.

[0008] The aeration tank comprises an aeration tank body, the aeration tank body has an octagonal sidewall, the octagonal sidewall comprises, in a horizontal direction, a first straight wall, a second straight wall, a third straight wall, a fourth straight wall, a fifth straight wall, a sixth straight wall, a seventh straight wall and an eighth straight wall connected in sequence.

[0009] The first straight wall is provided with a first water inlet and a first water outlet, and the fifth straight wall is provided with a second water inlet and a second water outlet; the third straight wall is provided with a sludge-water outlet; the sludge-water outlet is in fluid communication with a water inlet of the solid-liquid separator.

[0010] Optionally, the width of the third straight wall is denoted as L1, the end point of the first straight wall and the second straight wall is denoted as a, the end point of the fourth straight wall and the fifth straight wall is denoted as b, the length of the line segment ab is denoted as L2, and the ratio of L2 to L1 is (1.5-20):1, preferably (2-10):1.

[0011] The width of the seventh straight wall is denoted as L3, the end point of the fifth straight wall and the sixth straight wall is denoted as c, the end point of the eighth straight wall and the first straight wall is denoted as d, the length of the line segment cd is denoted as L4, and the ratio of L4 to L3 is (1.5-20):1, preferably (2-10):1.

[0012] The height between the line segment ab and the line segment cd is denoted as H, and the ratio of L2, L4 and H is (2.0-10.0):(2.0-10.0):1, preferably (3.0-5.0):(3.0-5.0):1.

[0013] Optionally, the line segment ab is parallel to the top edge of the first straight wall, the line segment cd is parallel to the top edge of the seventh straight wall, and the end point a, the end point b, the end point c and the end point d form a rectangle.

[0014] Optionally, the first water inlet and the second water outlet are diagonally arranged, and the second water inlet and the first water outlet are diagonally arranged.

[0015] Optionally, the bottom surface of the aeration tank is provided with an aeration device, which is selected from one or more of a microporous aerator, a hose aerator and a disc-type flat plate aerator.

[0016] Optionally, the aeration tank is further provided with a filler, and the total volume of the filler accounts for 30-40% of the volume of the tank.

[0017] The filler is one or more of a plastic filler, a sponge filler and a polyurethane filler, and is preferably a plastic filler.

[0018] The shape of the filler is one or more of a sphere, a cylinder and a cube, and is preferably a sphere with a diameter of 5-20 mm.

[0019] Optionally, the solid-liquid separator has a separation chamber, which includes a straight cylinder section and a reverse cone section below the straight cylinder section, and the straight cylinder section and the reverse cone section are in fluid communication.

[0020] The reverse cone section is provided with a sludge discharge port at the tip of the cone, and the sidewall of the straight cylinder section is provided with a supernatant outlet in fluid communication with the first water inlet and / or the second water inlet; the straight cylinder section is provided with a water inlet pipe, and the upper end of the water inlet pipe is opened to form a water inlet of the solid-liquid separator.

[0021] The second aspect of the present disclosure provides a method for treating sewage by using the sewage treatment system provided in the first aspect of the present disclosure, and the method comprises:

[0022] S1, first introduce the sewage to be treated into the aeration tank through the first water inlet for treatment, then discharge clean water through the second water outlet, and then introduce the sludge-water mixture out of the sludge-water outlet and into the solid-liquid separator;

[0023] S2, switch the water inlet, introduce the sewage to be treated into the aeration tank through the second water inlet for treatment, then discharge clean water through the first water outlet, and then introduce the sludge-water mixture out of the sludge-water outlet and into the solid-liquid separator;

[0024] S3, alternately perform steps S1 and S2.

[0025] Optionally, the concentration of dissolved oxygen in the aeration tank is 2-4 mg / L, the hydraulic retention time of the sewage to be treated in the aeration tank is 2-80 h, and the treatment temperature is 25-35℃; and the retention time of the sludge-water mixture in the solid-liquid separator is 0.5-16 h.

[0026] Optionally, the COD of the sewage to be treated is 200-800 mg / L, and the sludge concentration is 2500-3500 mg / L.

[0027] By the technical scheme, the system of the present disclosure has an octahedral aeration tank capable of dividing an anoxic zone and an aerobic zone in the same tank, and further capable of re-distributing the fillers by combining the alternating water inlet and water outlet, thereby minimizing the nitrogen in the effluent and removing the suspended solids in the water, and reducing the energy consumption and cost.

[0028] Other features and advantages of the present disclosure will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation of the present disclosure. In the drawings:

[0030] Figure 1 is a structural schematic view of one embodiment of the aeration tank of the sewage treatment system of the present disclosure.

[0031] Figure 2 is a structural schematic view of one embodiment of the solid-liquid separator of the sewage treatment system of the present disclosure.

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] 1, first water inlet 2, first water outlet 3, second water inlet

[0034] 4, second water outlet 5, sludge-water outlet 6, water inlet

[0035] 7, aeration device 8, sludge discharge port 9, supernatant outlet

[0036] 10, filler DETAILED DESCRIPTION

[0037] The detailed description of the specific embodiments of the present disclosure is described in detail below in conjunction with the drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0038] In the present disclosure, the orientation words such as "inner" and "outer" are used without the opposite description, which means the inner and outer of the system of the present disclosure can be normally used.

[0039] As Figure 1As shown, the first aspect of the present disclosure provides a sewage treatment system, which comprises an aeration tank and a solid-liquid separator; the aeration tank comprises an aeration tank body, the body of the aeration tank has an octagonal sidewall, which comprises, in the horizontal direction, a first straight wall, a second straight wall, a third straight wall, a fourth straight wall, a fifth straight wall, a sixth straight wall, a seventh straight wall and an eighth straight wall connected in sequence; the first straight wall is provided with a first water inlet 1 and a first water outlet 2, and the fifth straight wall is provided with a second water inlet 3 and a second water outlet 4; the third straight wall is provided with a sludge-water outlet 5; the sludge-water outlet 5 is in fluid communication with a water inlet 6 of the solid-liquid separator.

[0040] The sewage treatment system of the present disclosure has an aeration tank body with an octahedral structure, two water inlets and two water outlets that can realize alternate water inlet, and the above-mentioned octagonal body is wider in the middle and narrower at both ends. With the advancement of water flow, the suspended filler in the aeration tank gradually accumulates downstream of the water flow, i.e., the end of the body, where the end of the body downstream of the water flow is narrower, the accumulated filler is more, the microbial concentration is high, the oxygen consumption rate is faster, and a lower concentration of dissolved oxygen zone is formed; while the filler in the middle of the body in the middle of the water flow is less, the dissolved oxygen concentration is high, and a higher concentration of dissolved oxygen zone is formed. The above-mentioned octahedral structure of the reaction tank can realize the division of anoxic zone and aerobic zone in the same reaction tank, can realize the denitrification process of nitrification and denitrification, the phosphorus removal process of releasing phosphorus and accumulating phosphorus, and can improve the pollutant removal capacity of the system. At the same time, the redistribution of the filler in the aeration tank is realized by combining the alternate water inlet, which effectively reduces the dead zone, so that the system of the present disclosure can maximize the removal of nitrogen and suspended solids in the sewage when applied to the sewage treatment process, and the system of the present disclosure does not need backwashing and sludge return, has the advantages of low treatment cost and energy saving.

[0041] In a specific embodiment of the present disclosure, the width of the third straight wall is denoted as L1, the end point of the top end of the first straight wall and the second straight wall is denoted as a, the end point of the top end of the fourth straight wall and the fifth straight wall is denoted as b, the length of the line segment ab is denoted as L2, and the ratio of L2 to L1 is (1.5-20):1, preferably (2-10):1. According to the present disclosure, the width L1 of the third straight wall can vary within a larger range, for example, it can be 0.5-5m, preferably 1.0-2.0m.

[0042] In one embodiment of the present disclosure, the width of the seventh straight wall is denoted as L3, the end point of the fifth straight wall and the sixth straight wall is denoted as c, the end point of the eighth straight wall and the first straight wall is denoted as d, the length of the line segment cd is denoted as L4, and the ratio of L4 to L3 is (1.5-20):1, preferably (2-10):1. According to the present disclosure, the width L3 of the seventh straight wall can vary in a large range, for example, it can be 0.5-5m, preferably 1.0-2.0m.

[0043] In one embodiment of the present disclosure, the height between the line segment ab and the line segment cd is denoted as H, and the ratio of L2, L4 and H is (2.0-10.0):(2.0-10.0):1, preferably (3.0-5.0):(3.0-5.0):1. In the above embodiment, the structure of the aeration tank is more reasonable, which can improve the treatment effect of the sewage, thereby further effectively removing nitrogen in the sewage and reducing the content of suspended solids in the water.

[0044] In one embodiment of the present disclosure, the line segment ab is parallel to the top edge of the first straight wall, the line segment cd is parallel to the top edge of the seventh straight wall, and the end point a, the end point b, the end point c and the end point d form a rectangle. More preferably, L1 is equal to L3, and the width of the second straight wall, the width of the fourth straight wall, the width of the sixth straight wall and the width of the eighth straight wall are the same. In the above embodiment, the tank body of the aeration tank has a symmetrical octagonal structure, which can further improve the effect of the system of the present disclosure on removing nitrogen and suspended solids in the sewage.

[0045] According to the present disclosure, the height of each straight wall of the octagonal tank body is not specifically limited, and can be selected according to actual needs. In one embodiment, the heights of the first straight wall, the second straight wall, the third straight wall, the fourth straight wall, the fifth straight wall, the sixth straight wall, the seventh straight wall and the eighth straight wall are the same or different, preferably the same, and the height of each straight wall can be independently 0.2-1.0, preferably 0.5-0.7.

[0046] In one preferred embodiment of the present disclosure, the first water inlet 1 and the second water outlet 4 are diagonally arranged, and the second water inlet 3 and the first water outlet 2 are diagonally arranged. The present disclosure does not limit the specific positions of the first water inlet and the first water outlet on the first straight wall, and the positions of the second water outlet 4 and the second water inlet 3 on the fifth straight wall, which can be selected according to actual needs.

[0047] In a preferred embodiment of the present disclosure, the bottom surface of the aeration tank is provided with an aeration device 7. The aeration device is well known to those skilled in the art, for example, the aeration device can be selected from one or more of a microporous aerator, a hose aerator and a disc flat plate aerator.

[0048] In an embodiment of the present disclosure, the aeration tank is further provided with a filler 10, and the total volume of the filler accounts for 30-40% of the volume of the tank, preferably 32-36%. According to the present disclosure, the volume of the tank can vary within a large range, for example, it can be 0.4-180m 3 , preferably 4.0-20m 3 .

[0049] According to the present disclosure, the type of filler in the aeration tank can be routinely used by those skilled in the art. In an embodiment, the filler is one or more of a plastic filler, a sponge filler and a polyurethane filler, preferably a plastic filler. The present disclosure does not specifically limit the form of the filler, and the shape of the filler can be one or more of a sphere, a cylinder and a cube, preferably a sphere, and the diameter of the sphere can vary within a large range, for example, it can be 5-20mm, preferably 8-12mm.

[0050] As shown in Figure 2 , in an embodiment of the present disclosure, the solid-liquid separator has a separation chamber, the separation chamber includes a straight cylinder segment and a reverse cone segment at the lower part of the straight cylinder segment, and the straight cylinder segment and the reverse cone segment are in fluid communication; the tip of the reverse cone segment is provided with a sludge discharge port 8, the sidewall of the straight cylinder segment is provided with a supernatant outlet 9, the supernatant outlet 9 is in fluid communication with the first water inlet 1 and / or the second water inlet 3; the straight cylinder segment is provided with a water inlet pipe, and the upper end of the water inlet pipe is opened to form a water inlet 6 of the solid-liquid separator. The solid-liquid separator in the system of the present disclosure can realize mud and water separation, and the separated water is returned to the aeration tank for further treatment, without the need for backwashing and sludge backflow, and has the advantages of low treatment cost and energy saving.

[0051] The second aspect of the present disclosure provides a method for treating wastewater by using the wastewater treatment system provided by the first aspect of the present disclosure, the method comprising: S1, first introducing the wastewater to be treated into the aeration tank through the first water inlet 1 for treatment, then discharging clean water through the second water outlet 4, and discharging mud and water through the mud and water outlet 5 and then sending it into the solid-liquid separator; S2, switching the water inlet, introducing the wastewater to be treated into the aeration tank through the second water inlet 3 for treatment, then discharging clean water through the first water outlet 2, and discharging mud and water through the mud and water outlet 5 and then sending it into the solid-liquid separator; S3, alternately performing steps S1 and S2.

[0052] According to the present disclosure, the time for water feeding in step S1 and step S2 is not specifically limited, in an embodiment, the water feeding time in step S1 is 60-2400 min, preferably 120-720 min, and the water feeding time in step S2 is 60-2400 min, preferably 120-720 min.

[0053] The method of the present disclosure uses the way of alternating water feeding to treat the wastewater to be treated in the wastewater treatment system, which can remove the nitrogen and suspended substances in the wastewater to be treated to the maximum extent, has small land occupation area and low energy consumption.

[0054] In an embodiment of the present disclosure, the dissolved oxygen concentration in the aeration tank is 2-4 mg / L, preferably 2.5-3.5 mg / L, the treatment temperature is 25-35℃, preferably 28-32℃, the hydraulic retention time of the wastewater to be treated in the aeration tank is 2-80 h, preferably 4-12 h, and the retention time of the sludge and water in the solid-liquid separator is 0.5-16 h, preferably 1-3 h. Under the above conditions, the nitrogen in the wastewater can be effectively further removed and the suspended substances can be removed.

[0055] In an embodiment of the present disclosure, the COD of the wastewater to be treated is 200-800 mg / L, and the sludge concentration is 2500-3500 mg / L.

[0056] The present disclosure will be further illustrated by examples, but the present disclosure is not limited in any way by the examples.

[0057] Example 1

[0058] As shown in Figure 1 and Figure 2 The wastewater treatment system used in the present embodiment includes an aeration tank and a solid-liquid separator. The aeration tank includes an aeration tank body, the aeration tank body has an octagonal side wall, and the effective volume is 1.5 L. The octagonal side wall includes first, second, third, fourth, fifth, sixth, seventh and eighth straight face walls which are sequentially connected in head-tail direction and have the same height. The first straight face wall is provided with a first water inlet 1 and a first water outlet 2, and the fifth straight face wall is provided with a second water inlet 3 and a second water outlet 4. The third straight face wall is provided with a sludge and water outlet 5. The sludge and water outlet 5 is in fluid communication with a water inlet 6 of the solid-liquid separator. The bottom surface in the aeration tank body is provided with a microporous aerator and plastic spherical fillers with a diameter of 10.0 mm, and the total volume of the fillers accounts for 35% of the volume of the tank body.

[0059] The width of the third straight wall is L1, the end point of the first straight wall and the second straight wall is a, the end point of the fourth straight wall and the fifth straight wall is b, the length of the line segment ab is L2, the ratio of L2 and L1 is 2.0:1, the width of the seventh straight wall is L3, the end point of the fifth straight wall and the sixth straight wall is c, the end point of the eighth straight wall and the first straight wall is d, the length of the line segment cd is L4, the ratio of L4 and L3 is 2.0:1, the height between the line segment ab and the line segment cd is H, the ratio of L2, L4 and H is 3.0:3.0:1. The line segment ab is parallel to the top edge of the first straight wall, the line segment cd is parallel to the top edge of the seventh straight wall, and the end point a, the end point b, the end point c and the end point d form a rectangle.

[0060] The solid-liquid separator has a separation chamber, the separation chamber includes a straight cylinder section and a reverse cone section below the straight cylinder section, the straight cylinder section and the reverse cone section are in fluid communication; a sludge discharge port 8 is arranged at the tip of the reverse cone section, a supernatant outlet 9 is arranged on the side wall of the straight cylinder section, the supernatant outlet 9 is in fluid communication with the first water inlet 1 and / or the second water inlet 3; a water inlet pipe is arranged in the straight cylinder section, and the upper end of the water inlet pipe is opened to form a water inlet 6 of the solid-liquid separator.

[0061] The method for treating sewage by using the above system is as follows:

[0062] S1, first, the sewage to be treated is introduced into the aeration tank from the first water inlet for treatment, then the clean water is discharged from the second water outlet, the sludge water is introduced into the solid-liquid separator from the sludge water outlet for sludge water separation, the residence time of the sludge water in the solid-liquid separator is 2h, the separated supernatant is introduced into the first water inlet for circulation, and the sludge is discharged from the sludge discharge port; the water inlet time of this step is 8 hours;

[0063] S2, switch the water inlet, introduce the sewage to be treated into the aeration tank from the second water inlet for treatment, then discharge the clean water from the first water outlet, introduce the sludge water into the solid-liquid separator from the sludge water outlet for sludge water separation, the residence time of the sludge water in the solid-liquid separator is 2h, the separated supernatant is introduced into the second water inlet for circulation, and the sludge is discharged from the sludge discharge port; the water inlet time of this step is 8 hours;

[0064] S3, steps S1 and S2 are alternately performed, wherein the hydraulic retention time of the sewage in the aeration tank is 24h, the sludge concentration is 3320mg / L, the temperature is 30±1℃, and the dissolved oxygen is controlled at 2.5mg / L.

[0065] The wastewater to be treated in the method is 50% diluted coal gasification grey water, the pH of the grey water is 8.25, the ammonia nitrogen content is 525 mg / L, the COD is 205 mg / L, and the initial influent ratio is 40% by volume of coal gasification grey water + 60% by volume of water (only to supplement part of alkalinity, to adjust the pH to 8.3, to facilitate the process start-up), and then the influent ratio is gradually increased. Specifically, in the first 40 days of continuous operation, the influent is 40% by volume of grey water, the ammonia nitrogen content of the influent is 220-230 mg / L, the ammonia nitrogen content of the effluent is gradually reduced from 112.6 mg / L to below 20 mg / L through acclimation and adjustment of operating conditions, the denitrification load is 0.17 kgN / m 3 / d; starting from the 15th day, the proportion of grey water in the influent is increased to 50% by volume, the effluent slightly fluctuates, the ammonia nitrogen content of the effluent is increased to 56 mg / L, and then slowly decreased to 20 mg / L, and the denitrification load is increased to 0.20 kgN / m 3 / d; on the 25th day, the proportion of grey water in the influent is further increased to 60% by volume, the ammonia nitrogen content of the influent is 300-320 mg / L, the ammonia nitrogen content of the effluent is increased to 68 mg / L in the early stage, and through adjustment of aeration, there is no obvious accumulation of nitrite nitrogen, the ammonia nitrogen content of the effluent is decreased to a minimum of 13.8 mg / L, the total nitrogen content of the effluent is 53.5 mg / L, the removal rate of ammonia nitrogen reaches 95.4%, and the removal rate of total nitrogen reaches 82.3%.

[0066] Example 2

[0067] The device and method in Example 1 are used to treat wastewater, except that the wastewater is the effluent of a certain type of anaerobic ammonia oxidation reactor in the laboratory after treating nitrogen-containing petrochemical wastewater, the ammonia nitrogen content of the wastewater is 10-20 mg / L, the nitrate nitrogen concentration is 30-40 mg / L, and the COD is 110-150 mg / L.

[0068] On the basis of Example 1, the denitrifying bacteria are inoculated, the sludge concentration is controlled at 3000-4000 mg / L, sodium acetate is added as a carbon source to increase the influent COD to about 250 mg / L, the dissolved oxygen is controlled at 0.5-1.0 mg / L by reducing aeration, and the simultaneous nitrification and denitrification process is gradually started.

[0069] After 10 days of continuous operation, the ammonia nitrogen content of the effluent is reduced to below 1.0 mg / L, the nitrate nitrogen content is reduced to below 10 mg / L, there is no nitrite nitrogen accumulation, the COD of the effluent is 80-120 mg / L, the total nitrogen content of the effluent is as low as 5.6 mg / L, and the denitrification rate is 88.6%.

[0070] Example 3

[0071] The sewage is treated in the system of embodiment 1 by using the same method as that of embodiment 1, with the only difference being that the structure parameters of the aeration tank are different from those of embodiment 1, the ratio of L2 to L1 is 1.2:1, the ratio of L4 to L3 is 1.2:1, the height between the line segment ab and the line segment cd is H, the ratio of L2, L4 to H is 4.0:4.0:1, and the effective volume of the aeration tank is 560 L.

[0072] The ammonia nitrogen content of the effluent is reduced to a minimum of 12.2 mg / L, the total nitrogen content of the effluent is 77 mg / L, the removal rate of ammonia nitrogen is 95.9%, and the removal rate of total nitrogen is 74.3%.

[0073] Embodiment 4

[0074] The sewage is treated in the system of embodiment 1 by using the same method as that of embodiment 1, with the only difference being that the total volume of the filler in the aeration tank accounts for 25% of the volume of the tank body, the dissolved oxygen concentration in the aeration tank is 1.5 mg / L, the hydraulic retention time of the sewage to be treated in the aeration tank is 8 h, and the treatment temperature is 20℃.

[0075] The ammonia nitrogen content of the effluent is reduced to a minimum of 89.9 mg / L, the total nitrogen content of the effluent is 102.4 mg / L, the removal rate of ammonia nitrogen is 70.3%, and the removal rate of total nitrogen is 65.6%.

[0076] As can be seen from the above, the system of the present disclosure can effectively remove nitrogen-containing compounds in sewage.

[0077] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0078] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present disclosure will not further describe various possible combination manners.

[0079] In addition, various different embodiments of the present disclosure can also be combined in any manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed by the present disclosure.

Claims

1. A sewage treatment system comprising an aeration tank and a solid-liquid separator; the aeration tank comprises an aeration tank body, the aeration tank body has an octagonal sidewall comprising, in a horizontal direction, a first straight wall, a second straight wall, a third straight wall, a fourth straight wall, a fifth straight wall, a sixth straight wall, a seventh straight wall and an eighth straight wall connected in sequence; a first water inlet (1) and a first water outlet (2) are arranged on the first straight wall, a second water inlet (3) and a second water outlet (4) are arranged on the fifth straight wall; a sludge-water outlet (5) is arranged on the third straight wall; the sludge-water outlet (5) is in fluid communication with a water inlet (6) of the solid-liquid separator; the width of the third straight wall is denoted as L1, the end point of the top end of the first straight wall and the second straight wall is denoted as a, the end point of the top end of the fourth straight wall and the fifth straight wall is denoted as b, the length of the line segment ab is denoted as L2, the ratio of L2 to L1 is (1.5-20):1; the width of the seventh straight wall is denoted as L3, the end point of the top end of the fifth straight wall and the sixth straight wall is denoted as c, the end point of the top end of the eighth straight wall and the first straight wall is denoted as d, the length of the line segment cd is denoted as L4, the ratio of L4 to L3 is (1.5-20):1; the height between the line segment ab and the line segment cd is denoted as H, the ratio of L2, L4 to H is (2.0-10.0):(2.0-10.0):

1.

2. The system of claim 1, wherein, the width of the third straight wall is denoted as L1, the end point of the top end of the first straight wall and the second straight wall is denoted as a, the end point of the top end of the fourth straight wall and the fifth straight wall is denoted as b, the length of the line segment ab is denoted as L2, the ratio of L2 to L1 is (2-10):1; the width of the seventh straight wall is denoted as L3, the end point of the top end of the fifth straight wall and the sixth straight wall is denoted as c, the end point of the top end of the eighth straight wall and the first straight wall is denoted as d, the length of the line segment cd is denoted as L4, the ratio of L4 to L3 is (2-10):1; the height between the line segment ab and the line segment cd is denoted as H, the ratio of L2, L4 to H is (3.0-5.0):(3.0-5.0):

1.

3. The system of claim 2, wherein, the line segment ab is parallel to the top edge of the first straight wall, the line segment cd is parallel to the top edge of the seventh straight wall, and a rectangle is formed between the end point a, the end point b, the end point c and the end point d.

4. The system of claim 1, wherein, the first water inlet (1) and the second water outlet (4) are diagonally arranged, and the second water inlet (3) and the first water outlet (2) are diagonally arranged.

5. The system of claim 1, wherein, an aeration device (7) is arranged on the bottom surface in the aeration tank body, the aeration device is selected from one or more of a microporous aerator, a hose aerator and a disc flat plate aerator.

6. The system of claim 1, wherein, a filler (10) is also arranged in the aeration tank body, the total volume of the filler accounts for 30-40% of the volume of the tank body; the filler is one or more of a plastic filler, a sponge filler and a polyurethane filler; the shape of the filler is one or more of a sphere, a cylinder and a cube.

7. The system of claim 6, wherein, The filler is a plastic filler; The shape of the filler is spherical, and the diameter of the spherical shape is 5-20 mm.

8. The system of claim 1, wherein, The solid-liquid separator has a separation cavity, which comprises a straight cylinder section and a rounded cone section below the straight cylinder section, and the straight cylinder section and the rounded cone section are in fluid communication; A sludge discharge port (8) is arranged at the tip of the rounded cone section, and a supernatant outlet (9) is arranged on the sidewall of the straight cylinder section, which is in fluid communication with the first water inlet (1) and / or the second water inlet (3); a water inlet pipe is arranged in the straight cylinder section, and the upper end of the water inlet pipe is opened to form a water inlet (6) of the solid-liquid separator.

9. A method for treating sewage by using the sewage treatment system according to any one of claims 1-8, which comprises: S1, first introducing the sewage to be treated into the aeration tank through the first water inlet (1) for treatment, then discharging clean water through the second water outlet (4), and discharging sludge through the sludge outlet (5) and then into the solid-liquid separator; S2, switching the water inlet, introducing the sewage to be treated into the aeration tank through the second water inlet (3) for treatment, then discharging clean water through the first water outlet (2), and discharging sludge through the sludge outlet (5) and then into the solid-liquid separator; S3, alternately performing steps S1 and S2.

10. The method of claim 9, wherein, The concentration of dissolved oxygen in the aeration tank is 2-4 mg / L, the hydraulic retention time of the sewage to be treated in the aeration tank is 2-80 h, and the treatment temperature is 25-35℃; the retention time of the sludge in the solid-liquid separator is 0.5-16 h.

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