Wastewater treatment system and method

Abstract

The application relates to a sewage treatment system and method. The sewage treatment system comprises a sewage bin, a heater, a sewage treatment device and a heat exchange assembly. The heater is connected downstream of the sewage bin and is used for heating sewage. The sewage treatment device is connected downstream of the heater. The sewage treatment device performs sewage treatment on the sewage. The sewage treatment device is provided with a water outlet. One end of the heat exchange assembly is connected to the water outlet. High-temperature treatment water exchanges heat with the heat exchange assembly. The heat exchange assembly collects heat of the high-temperature treatment water and discharges low-temperature treatment water. The other end of the heat exchange assembly is connected between the sewage bin and the heater. The heat exchange assembly preheats sewage discharged from the sewage bin through heat. The heat exchange assembly collects heat of the high-temperature treatment water and preheats the sewage in the sewage bin, reduces the dependence on the heater, reduces the heating power of the heater, reduces the waste of heat, makes the treatment water discharged from the sewage treatment system be low-temperature treatment water, and reduces the temperature influence on the surrounding environment.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to wastewater treatment systems and methods. Background Technology

[0002] Centrifugal wastewater treatment units are widely used in FLNG projects. A centrifugal wastewater treatment unit is a highly efficient, continuous wastewater treatment device that uses centrifugation to separate and purify wastewater. The optimal separation temperature is typically around 40 degrees Celsius. Temperatures that are too high or too low are detrimental to the separation process, reducing equipment efficiency or increasing operational risks and costs.

[0003] Traditional technologies typically employ heating devices to raise the temperature of low-temperature wastewater to the optimal separation level of 35-40°C before oil-water separation. However, direct heating typically requires high power, placing significant demands on the electrical load. Furthermore, the treated water reaches temperatures close to 40°C when discharged into the ocean, impacting the surrounding environment and potentially altering the ecological balance. Therefore, current designs suffer from high heating power consumption and heat waste. Summary of the Invention

[0004] Based on this, a wastewater treatment system and method are provided to solve the problems of high heating power and heat waste.

[0005] An embodiment of the first aspect of this application provides a wastewater treatment system, comprising:

[0006] Wastewater tank, used for storing wastewater;

[0007] A heater, connected downstream of the wastewater tank, is used to heat the wastewater;

[0008] A wastewater processor is connected downstream of the heater. The wastewater processor treats the wastewater and has an outlet for discharging high-temperature treated water.

[0009] A heat exchange component is provided, with one end connected to the water outlet, where the high-temperature treated water exchanges heat with the heat exchange component, which collects the heat from the high-temperature treated water and discharges the low-temperature treated water; the other end of the heat exchange component is connected between the wastewater tank and the heater, where the heat is used to preheat the wastewater discharged from the wastewater tank.

[0010] In one embodiment, the heat exchange assembly includes two heat exchangers connected in parallel, each of which is provided with a start / stop valve for controlling start and stop.

[0011] In one embodiment, the wastewater treatment system further includes a first oil content detector, which is used to detect the oil content of the high-temperature treated water and record it as the first oil content.

[0012] In one embodiment, the first oil separator is installed at the water outlet to extract the high-temperature treated water discharged from the water outlet and perform oil separation detection.

[0013] A first return pipe is connected between the first oil separator and the wastewater tank, and the first return pipe returns the extracted high-temperature treated water to the wastewater tank.

[0014] In one embodiment, the wastewater treatment system further includes a second oil content detector, which is used to detect the oil content of the low-temperature treated water and record it as the second oil content.

[0015] In one embodiment, the heat exchange assembly is connected to a drain pipe for discharging the low-temperature treated water, and a second return pipe is connected between the drain pipe and the wastewater tank. A three-way valve is provided at the connection between the drain pipe and the second return pipe.

[0016] The second oil separator is installed on the drain pipe to extract the low-temperature treated water in the drain pipe for oil separation detection; a third return pipe is connected between the second oil separator and the second return pipe, and the third return pipe returns the extracted low-temperature treated water to the wastewater tank.

[0017] When the second oil content is not lower than the preset oil content, the low-temperature treated water is returned to the wastewater tank through the second return pipe.

[0018] In one embodiment, the heat exchanger includes a water passage configured as a sacrificial tube.

[0019] In one embodiment, a pre-pump filter and a sewage pump are sequentially arranged downstream of the sewage pump, and the downstream of the sewage pump is connected to the heat exchange assembly.

[0020] An embodiment of the second aspect of this application provides a wastewater treatment method, including providing a wastewater treatment system as described in any of the foregoing embodiments, wherein the heat exchange component collects heat from the high-temperature treated water and preheats the wastewater using the collected heat.

[0021] In one embodiment, the heat exchange assembly includes two heat exchangers connected in parallel, each heat exchanger being provided with a start / stop valve for controlling start and stop, and the wastewater treatment unit uses only one of the heat exchangers when it is in operation;

[0022] The wastewater treatment system further includes a first oil content detector, which is used to detect the oil content of the high-temperature treated water and record it as the first oil content; the wastewater treatment system further includes a second oil content detector, which is used to detect the oil content of the low-temperature treated water and record it as the second oil content.

[0023] Wherein, when the second oil content is not lower than the preset oil content and the first oil content is not lower than the preset oil content, the wastewater treatment device shall be repaired;

[0024] When the second oil content is not lower than the preset oil content and the first oil content is lower than the preset oil content, the heat exchanger is switched, the original working heat exchange component is shut down and repaired, and the other heat exchanger continues to work to maintain the continuous operation of the sewage treatment system.

[0025] In the aforementioned wastewater treatment system and method, the heater can heat the wastewater in the wastewater tank to reach the optimal treatment temperature for the wastewater processor. The wastewater processor treats the wastewater and discharges high-temperature treated water. The heat exchange component collects the heat from the high-temperature treated water and preheats the wastewater in the wastewater tank, reducing dependence on the heater, thereby reducing the heater's heating power and heat waste. This results in the treated water discharged from the wastewater treatment system being low-temperature treated water, reducing the temperature impact on the surrounding environment and protecting the ecological environment. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a wastewater treatment system according to an embodiment of this application.

[0027] Figure 2 This is a schematic diagram of a wastewater treatment system according to an embodiment of the present application, including a first oil separator and a second oil separator.

[0028] Figure 3 This is a schematic diagram of a wastewater treatment system according to an embodiment of this application, which includes a second return pipe and a third return pipe.

[0029] Figure label:

[0030] 1. Sewage tank;

[0031] 2. Heater;

[0032] 3. Wastewater treatment unit; 31. Water outlet;

[0033] 4. Heat exchange assembly; 41. Heat exchanger; 411. Sacrificial tube;

[0034] 5. First oil separator detector; 51. First reflux pipe;

[0035] 6. Second oil separator detector; 61. Third reflux pipe;

[0036] 7. Drain pipe; 71. Second return pipe; 72. Three-way valve;

[0037] 8. Pre-pump filter;

[0038] 9. Sewage pump. Detailed Implementation

[0039] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0040] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0041] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0043] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0045] See Figure 1 , Figure 1 A schematic diagram of a wastewater treatment system according to an embodiment of this application is shown. At least one embodiment of this application proposes a wastewater treatment system including a wastewater tank 1, a heater 2, a wastewater processor 3, and a heat exchange assembly 4. The wastewater tank 1 stores wastewater. The heater 2 is connected downstream of the wastewater tank 1 and heats the wastewater. The wastewater processor 3 is connected downstream of the heater 2 and treats the wastewater. The wastewater processor 3 is provided with an outlet 31 for discharging high-temperature treated water. One end of the heat exchange assembly 4 is connected to the outlet 31, where the high-temperature treated water exchanges heat with the heat exchange assembly 4. The heat exchange assembly 4 collects the heat from the high-temperature treated water and discharges low-temperature treated water. The other end of the heat exchange assembly 4 is connected between the wastewater tank 1 and the heater 2, preheating the wastewater discharged from the wastewater tank 1 using heat.

[0046] According to the wastewater treatment system of this application embodiment, the heater 2 can heat the wastewater in the wastewater tank 1 to reach the optimal treatment temperature of the wastewater processor 3. The wastewater processor 3 treats the wastewater and discharges high-temperature treated water. The heat exchange component 4 collects the heat of the high-temperature treated water and preheats the wastewater in the wastewater tank 1, reducing the dependence on the heater 2, thereby reducing the heating power of the heater 2 and reducing heat waste. This makes the treated water discharged from the wastewater treatment system low-temperature treated water, reducing the temperature impact on the surrounding environment and protecting the ecological environment.

[0047] In some embodiments, the wastewater treatment system can be applied to a floating liquefaction unit, and the wastewater processor 3 can be configured as a centrifugal wastewater treatment unit. This type of processor has certain temperature requirements for the treated water. The optimal separation temperature is typically around 40 degrees Celsius. Temperatures that are too high or too low are detrimental to the separation process, reducing equipment operating efficiency or increasing operational risks and costs. Water temperature varies with the seasons. Even in tropical regions, water temperatures can drop below 20 degrees Celsius, resulting in very low efficiency for the centrifugal wastewater processor 3. In non-tropical regions, wastewater temperatures may be even lower in winter. The heater 2 needs to heat the low-temperature wastewater to the optimal separation temperature of 35-40 degrees Celsius before it is delivered to the wastewater processor 3 for oil-water separation. By employing the wastewater treatment system of this application, the heat from the high-temperature treated water discharged from the wastewater processor 3 can be recovered, and this recovered heat can be used to preheat the low-temperature wastewater, reducing the heating power of the heater 2.

[0048] Specifically, when the wastewater processor 3 is configured as a centrifugal wastewater treatment device, its processing capacity is 10 m³ / h, its design pressure is 10 bar, its processing temperature is 35℃, and its power is 22 kW. It has an automatic slag discharge function and can operate continuously for 8000 hours. The oil content after separation is below 15 ppm, and the power supply is 400V, 3-phase, 50Hz.

[0049] In some embodiments, the heat exchange assembly 4 includes two parallel heat exchangers 41, each equipped with a start / stop valve (not shown) for controlling their operation. Specifically, the two parallel heat exchangers 41 can be selected to operate by controlling the start / stop valve, while the other heat exchanger 41 is shut down and on standby. When the operating heat exchanger 41 fails, the other standby heat exchanger 41 can be switched to operate by controlling the start / stop valve. This configuration effectively improves the overall operational stability of the wastewater treatment system and ensures continuous operation of the equipment. When the heat exchange efficiency of the two heat exchangers 41 decreases, the two parallel heat exchangers 41 can also be used synchronously to improve heat exchange efficiency.

[0050] It is understandable that, depending on different wastewater treatment needs and different usage environments, the heat exchange assembly 4 can be equipped with a greater number of heat exchangers 41 connected in parallel, and is not limited to two. In some embodiments of this application, the heat exchange assembly 4 includes two heat exchangers 41 connected in parallel. Under the condition of ensuring the continuous operation of the equipment, selecting the minimum number of heat exchangers 41 can reduce the cost of the equipment, while making the wastewater treatment system compact and not occupying too much space.

[0051] In some embodiments, specifically, the heat exchanger 41 is designed with a pressure of 10 bar, a flow rate of 10 m³ / h, and a power of 69 kW. The heater 2 can be configured as an electric heater 2 with a power of 150 kW, a design pressure of 10 bar, a throughput of 10 m³ / h, an inlet temperature of 22°C, an outlet temperature of 35°C, and is made of 316L stainless steel. The device is a shell-and-tube type and operates on a voltage of 400V, 3-phase, 50Hz.

[0052] In some embodiments, the heat exchanger 41 includes a water supply line configured as a sacrificial pipe 411. When the wastewater treatment system is applied in a floating liquefaction plant, the wastewater being treated contains seawater. The arrangement of the sacrificial pipe 411 can mitigate the corrosion of critical equipment and instruments in the heat exchanger 41 by the wastewater, effectively improving the continuous operation capability of the equipment.

[0053] See Figure 2 , Figure 2 A schematic diagram of a wastewater treatment system according to an embodiment of this application, including a first oil content detector 5 and a second oil content detector 6, is shown. In some embodiments, the wastewater treatment system further includes a first oil content detector 5, which is used to detect the oil content of the high-temperature treated water and record it as the first oil content. The first oil content detector 5 obtains the oil content value of the high-temperature treated water by detecting it, and uses it as the first oil content of the high-temperature treated water to determine whether the treatment effect of the high-temperature treated water after treatment by the wastewater processor 3 meets the standards.

[0054] In some embodiments, the first oil separator 5 is installed at the outlet 31 to extract the high-temperature treated water discharged from the outlet 31 and perform oil content detection. A first return pipe 51 connects the first oil separator 5 to the wastewater tank 1, and the first return pipe 51 returns the extracted high-temperature treated water to the wastewater tank 1. The first oil separator 5 extracts high-temperature treated water from the outlet 31 and performs oil content detection, resulting in relatively accurate results. The extracted high-temperature treated water directly returns to the wastewater tank 1 through the first return pipe 51, eliminating the need for additional drainage devices for the first oil separator 5, thus forming a complete closed loop in the wastewater treatment system, resulting in a clever and compact structure.

[0055] In some embodiments, the wastewater treatment system further includes a second oil content detector 6, which is used to detect the oil content of the low-temperature treated water and record it as the second oil content. The second oil content detector 6 obtains the oil content value of the low-temperature treated water by detecting it, and uses it as the second oil content of the low-temperature treated water to determine whether the treatment effect of the low-temperature treated water after exchanging heat through the heat exchanger 41 meets the standard.

[0056] See Figure 3 , Figure 3This diagram illustrates a wastewater treatment system according to an embodiment of the present application, which includes a second return pipe 71 and a third return pipe 61. In some embodiments, the heat exchange assembly 4 is connected to a drain pipe 7, which discharges low-temperature treated water. A second return pipe 71 connects the drain pipe 7 to the wastewater tank 1, and a three-way valve 72 is provided at the connection between the drain pipe 7 and the second return pipe 71. A second oil content detector 6 is installed on the drain pipe 7 to extract the low-temperature treated water from the drain pipe 7 for oil content detection. A third return pipe 61 connects the second oil content detector 6 to the second return pipe 71, and the third return pipe 61 returns the extracted low-temperature treated water to the wastewater tank 1. Specifically, when the second oil content is not lower than a preset oil content, the low-temperature treated water returns to the wastewater tank 1 through the second return pipe 71.

[0057] With the above setup, firstly, the second oil content detector 6 draws high-temperature treated water through the drain pipe 7 and performs oil content detection, with relatively accurate results. Secondly, the three-way valve 72 controls the drainage of the wastewater treatment system. Specifically, when the second oil content detected by the second oil content detector 6 is not lower than the preset oil content, the low-temperature treated water is considered substandard. By controlling the three-way valve 72, the low-temperature treated water flows back to the wastewater tank 1 through the drain pipe 7 and the second return pipe 71 for further wastewater treatment. This process continues until the second oil content detected by the second oil content detector 6 reaches the preset oil content. Only then is the three-way valve 72 controlled, allowing the low-temperature treated water to be directly discharged through the drain pipe 7. When the wastewater treatment system is applied to a centrifugal wastewater treatment unit within a floating liquefaction plant, the preset oil content must meet the relevant regulatory requirements of the classification society for wastewater treatment unit discharge standards, such as 15 ppm. The low-temperature treated water extracted by the second oil separator 6 flows back to the sewage tank 1 through the third return pipe 61 and the second return pipe 71. There is no need to equip the second oil separator 6 with other drainage devices, so that the sewage treatment system forms a complete closed loop. The structure is ingenious and compact.

[0058] In some embodiments, specifically, the first oil separator 5 and the second oil separator 6 have a measurement range of 0-100ppm, a design temperature of 65 degrees Celsius, and a design pressure of 10 barg. Specifically, the three-way valve 72 is made of SS316 stainless steel, has a design pressure of 10 barg, and is pneumatically controlled.

[0059] In some embodiments, a pre-pump filter 8 and a sewage pump 9 are sequentially arranged downstream of the sewage pump 9, and the downstream of the sewage pump 9 is connected to a heat exchange assembly 4.

[0060] Specifically, the pre-pump filter 8 can be configured as a Y-type filter with a maximum capacity of 10 m³ / h and a filtration accuracy of 0.3 mm to prevent solid particles from damaging the equipment. The Y-type filter uses a corrosion-resistant stainless steel shell made of SS316. A sewage pump 9 is installed after the pre-pump filter 8, with a design pressure of 10 bar, a flow rate of 10 m³ / h, a head of 50 m, made of nickel-aluminum bronze, a power of 7.5 kW, a voltage of 400V, 3-phase, 50 Hz, 2900 rpm, F / IP-55 / IE3, and a mechanical seal.

[0061] At least one embodiment of this application proposes a wastewater treatment method, including providing a wastewater treatment system as described in any of the above embodiments, wherein a heat exchange component 4 collects heat from high-temperature treated water and preheats the wastewater using the collected heat.

[0062] In the above-mentioned wastewater treatment method, the heater 2 can heat the wastewater in the wastewater tank 1 to reach the optimal treatment temperature of the wastewater processor 3. The wastewater processor 3 treats the wastewater and discharges high-temperature treated water. The heat exchange component 4 collects the heat from the high-temperature treated water and preheats the wastewater in the wastewater tank 1, reducing the dependence on the heater 2, thereby reducing the heating power of the heater 2 and reducing heat waste. This ensures that the treated water discharged from the wastewater treatment system is low-temperature treated water, reducing the temperature impact on the surrounding environment and protecting the ecological environment.

[0063] In some embodiments, the heat exchange assembly 4 includes two heat exchangers 41 connected in parallel, each heat exchanger 41 being equipped with a start / stop valve for controlling start and stop. The wastewater treatment system 3 operates using only one heat exchanger 41. The wastewater treatment system also includes a first oil content detector 5, used to detect the oil content in the high-temperature treated water and record it as the first oil content; and a second oil content detector 6, used to detect the oil content in the low-temperature treated water and record it as the second oil content. Wherein, when the second oil content is not lower than a preset oil content and the first oil content is not lower than a preset oil content, the wastewater treatment system 3 is repaired; when the second oil content is not lower than a preset oil content and the first oil content is lower than a preset oil content, the heat exchanger 41 is switched, the previously operating heat exchange assembly 4 is shut down and repaired, and the other heat exchanger 41 continues to operate to maintain the continuous operation of the wastewater treatment system.

[0064] Wastewater is drawn into wastewater tank 1 by wastewater pump 9, which then pumps it to the cold side of heat exchanger 41. After preheating in heat exchanger 41, the wastewater enters heater 2, which further raises the temperature to the optimal treatment temperature. The wastewater then enters wastewater processor 3, where it undergoes centrifugal treatment to separate oil and water. The separated high-temperature treated water passes through first oil detector 5 and enters the hot side of heat exchanger 41, transferring its temperature to the wastewater to be treated on the cold side of heat exchanger 41. After cooling, the high-temperature treated water becomes low-temperature treated water. This low-temperature treated water is then tested for oil content by second oil-water detector. If the oil content is below the preset oil content of 15 ppm, it will flow into the sea through three-way valve 72. If the oil content is 15 ppm or higher, an alarm connected to the second oil-water detector will sound, and the three-way valve 72 will automatically return the substandard low-temperature treated water back to wastewater tank 1. By comparison, it can be found that the wastewater treatment system and method of this application can reduce operating energy costs by approximately 70 kW. This calculation result is based on design parameters for tropical regions. The lower the ambient temperature, the more pronounced the power-saving effect will be.

[0065] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A sewage treatment system characterised in that, The sewage treatment system comprises: a sewage bin for storing sewage; a heater connected downstream of the sewage bin for heating the sewage; a sewage processor connected downstream of the heater, the sewage processor performing sewage treatment on the sewage, the sewage processor being provided with a water outlet for discharging high-temperature treated water; a heat exchange assembly, one end of the heat exchange assembly being connected to the water outlet, the high-temperature treated water exchanging heat with the heat exchange assembly, the heat exchange assembly collecting heat of the high-temperature treated water and discharging low-temperature treated water, the other end of the heat exchange assembly being connected between the sewage bin and the heater, the sewage discharged from the sewage bin being preheated by the heat; the heat exchange assembly being connected with a drain pipe for discharging the low-temperature treated water, a second reflux pipe being connected between the drain pipe and the sewage bin; the heat exchange assembly comprising two parallel heat exchangers; the sewage treatment system further comprises a first oil content detector for detecting oil content of the high-temperature treated water, the oil content being recorded as a first oil content; 2. The sewage treatment system of claim 1, wherein, a second oil content detector for detecting oil content of the low-temperature treated water, the oil content being recorded as a second oil content, the second oil content detector being arranged on the drain pipe to extract the low-temperature treated water in the drain pipe for oil content detection, a third reflux pipe being connected between the second oil content detector and the second reflux pipe, the third reflux pipe returning the extracted low-temperature treated water to the sewage bin; 3. The sewage treatment system of claim 1, wherein, when the second oil content is not lower than a preset oil content, the low-temperature treated water is returned to the sewage bin through the second reflux pipe; 4. The sewage treatment system of claim 1, wherein, when the second oil content is not lower than the preset oil content and the first oil content is not lower than the preset oil content, the sewage processor needs to be repaired; when the second oil content is not lower than the preset oil content and the first oil content is lower than the preset oil content, the heat exchangers are switched, the original working heat exchange assembly is stopped and repaired, and the other heat exchanger continues to work.

5. The sewage treatment system of claim 4, wherein, Each of the heat exchangers is provided with a start-stop valve for controlling start and stop.

6. The sewage treatment system of claim 1, wherein, The sewage processor is configured as a centrifugal sewage treatment device.

7. The sewage treatment system of claim 2, wherein, The first oil content detector is arranged at the water outlet to extract the high-temperature treated water discharged from the water outlet for oil content detection.

8. The sewage treatment system of claim 1, wherein, A first reflux pipe is connected between the first oil content detector and the sewage bin, the first reflux pipe returning the extracted high-temperature treated water to the sewage bin.

9. A method of sewage treatment, characterised in that, A three-way valve is arranged at a connection between the drain pipe and the second reflux pipe. The heat exchanger comprises a water pipeline, the water pipeline being configured as a sacrificial pipe. The heater is configured as an electric heater. The sewage treatment system is provided, the heat exchange assembly collecting heat of the high-temperature treated water and preheating sewage by the collected heat. When the second oil content is not lower than the preset oil content and the first oil content is not lower than the preset oil content, the sewage treater needs to be repaired; when the second oil content is not lower than the preset oil content and the first oil content is lower than the preset oil content, the heat exchange assembly needs to be repaired.

10. The method of sewage treatment according to claim 9, characterized in that, The heat exchange assembly comprises two parallel heat exchangers, each of which is provided with a start-stop valve for controlling start and stop, and only one of the heat exchangers is used when the sewage treater is working; When the second oil content is not lower than the preset oil content and the first oil content is lower than the preset oil content, the heat exchanger is switched, the original working heat exchange assembly is stopped and repaired, and the other heat exchanger continues to work to maintain the continuous work of the sewage treatment system.

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