A process for treating caffeine production wastewater

Abstract

The present invention relates to the field of wastewater treatment technology, and in particular to a process for treating caffeine production wastewater, comprising: collecting and treating high-salt wastewater and equipment and ground washing wastewater to obtain a first supernatant and sludge, and discharging the first supernatant into a transfer tank; discharging domestic wastewater and drainage from a pure water purification device into a second water collection tank, and pumping the drainage to the transfer tank via a third water pump to mix with the first supernatant to obtain a second mixed wastewater; subjecting the second mixed wastewater to secondary precipitation in the transfer tank to obtain a second supernatant, and discharging the second mixed wastewater into a regulating tank; discharging the dehydrated sludge into a sludge low-temperature drying device for sludge strip cutting and low-temperature heating, and discharging the resulting supernatant, filtrate, and condensate into the transfer tank for secondary precipitation. By discharging the intermediate wastewater obtained from the wastewater treatment into the transfer tank for secondary precipitation, the present invention improves precipitation efficiency and water utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, in particular to a process for treating caffeine production wastewater. Background Art

[0002] Caffeine is produced through artificial synthesis (i.e., chemical synthesis). The raw materials used primarily include acetic acid, sulfuric acid, nitric acid, sodium sulfate, sodium acetate, sodium nitrate, purpuric acid, and dimethyl 4AU. These ingredients also contain small amounts of heavy metals such as nickel and manganese, as well as smaller amounts of toxic substances such as furans. Furthermore, the production process generates a large volume of wastewater with complex composition, high levels of organic pollutants and inorganic salts, and high biological toxicity. Direct discharge of this wastewater is not only harmful to humans but also poses significant environmental risks. Therefore, it is crucial to treat the wastewater generated during caffeine production before discharge.

[0003] Caffeine production wastewater contains high concentrations of organic nitrogen, high concentrations of salt, and sludge. Existing technologies primarily use physical and chemical treatment methods to treat wastewater, removing total nitrogen and organic matter from the wastewater, separating and transporting the salt, and discharging the resulting sludge into a sludge storage tank. During the treatment process, intermediate wastewater and sludge sediment are generated. Furthermore, some of the sediment in the intermediate wastewater is not completely removed. At the same time, the sludge sediment contains a large amount of water, remaining a mud-water mixture. Direct discharge results in low water utilization. Furthermore, if the intermediate wastewater and sludge sediment are not completely treated, the water in the intermediate wastewater tank is disturbed by the pumping action during the discharge of the intermediate wastewater, causing the water to become turbid again, resulting in low sedimentation efficiency.

[0004] In order to solve the problem of low sedimentation efficiency of intermediate wastewater in the above-mentioned caffeine production wastewater treatment, this patent proposes a process method for treating caffeine production wastewater in the whole process. Summary of the Invention

[0005] To this end, the present invention provides a process for treating caffeine production wastewater in a full process, by discharging the intermediate wastewater obtained by treating the wastewater into a transfer tank for secondary precipitation, so as to solve the problem of low precipitation efficiency of intermediate wastewater in the prior art.

[0006] To achieve the above object, the present invention provides a process for treating caffeine production wastewater in a full process, the process comprising:

[0007] S01, collecting and treating high-salt wastewater to obtain evaporated wastewater and separated salt, and collecting the evaporated wastewater into a first water collection tank;

[0008] S02, discharging the equipment and ground flushing wastewater into the first water collection tank and mixing it with the evaporated wastewater to form first mixed wastewater;

[0009] S03, performing oxidation treatment on the first mixed wastewater to obtain pretreated wastewater, separating the pretreated wastewater to obtain a first supernatant and sludge, and discharging the first supernatant into a transfer tank;

[0010] S04, draining the domestic wastewater and the pure water purification device into a second water collection tank and pumping them to the transfer tank through a third water pump to mix with the first supernatant to obtain second mixed wastewater;

[0011] S05, performing secondary sedimentation on the second mixed wastewater in the transfer tank to obtain a second supernatant and discharging the second supernatant into a regulating tank;

[0012] S06, adjusting the pH value of the second supernatant and stirring it evenly to obtain adjusted wastewater, and sending the adjusted wastewater into a dynamic hydrolysis acidification tank through a fourth water pump for hydrolysis to obtain hydrolyzed wastewater;

[0013] S07, the hydrolysis wastewater flows into the two-stage A / O tank by gravity, and ammonia nitrogen, total nitrogen and organic matter in the hydrolysis wastewater are removed, and then flows into the sedimentation tank by gravity for mud-water separation to obtain sedimentation tank effluent;

[0014] S08, the effluent from the sedimentation tank enters the intermediate water tank and is sent to the magnetic coagulation device through the fifth water pump for treatment to obtain sludge and magnetic coagulation effluent;

[0015] S09, the magnetic coagulation effluent flows by gravity into the ozone reaction tank for decolorization and disinfection to produce treated water, which then flows by gravity into the Parshall cell; when it is determined that the pollutant content in the treated water meets the standard, the treated water is discharged;

[0016] S10, treating the sludge in the sludge storage tank to produce sludge treatment supernatant, filtrate, condensate and dehydrated dry sludge, wherein the sludge treatment supernatant, the filtrate and the condensate are discharged into the transfer tank for further treatment, and the dehydrated sludge is discharged into the sludge low-temperature drying equipment for sludge strip cutting and low-temperature heating.

[0017] Furthermore, step S03 includes:

[0018] S031, sending the first mixed wastewater into the Fenton oxidation system through a second water pump;

[0019] S032, the Fenton oxidation system decomposes nitrogen-containing macromolecular organic matter in the first mixed wastewater into small molecular organic matter and decomposes organic nitrogen into ammonia nitrogen or small molecular organic nitrogen to obtain pretreated wastewater;

[0020] S033, separating the muddy water in the pretreated wastewater into a first supernatant and sludge through a coagulation sedimentation tank, discharging the supernatant into a transfer tank and discharging the sludge into a sludge storage tank.

[0021] Furthermore, the water inlet of the transfer tank is respectively connected to the outlet pipe of the coagulation sedimentation tank, the outlet pipe of the second water collection tank and the outlet pipe of the sludge storage tank, so as to collect the first supernatant, the outlet water of the second water collection tank and the sludge supernatant, the filtrate and the condensate. The water inlet of the transfer tank is arranged at the top of the transfer tank; the first outlet of the transfer tank is connected to the water inlet of the regulating tank to discharge the second supernatant to the regulating tank. The first outlet is arranged on the side wall of the transfer tank and is at a first height away from the bottom of the transfer tank. The second outlet is arranged on the side wall of the transfer tank and is at a second height away from the bottom of the transfer tank. The second outlet is connected to the coagulation sedimentation tank, and a first reflux pump is arranged at the second outlet to pump the sediment at the bottom of the transfer tank back to the coagulation sedimentation tank for mud-water separation; a bottom plate is arranged at the bottom of the transfer tank, and a pressure sensor is arranged under the bottom plate to obtain the bottom pressure of the transfer tank; a liquid level gauge is arranged on the side wall of the transfer tank to obtain the liquid level height in the transfer tank, and the liquid level height includes the second supernatant liquid level height and the sediment liquid level height.

[0022] Furthermore, step S05 includes:

[0023] S051, the second mixed wastewater enters the transfer tank and is allowed to stand for mud-water separation to obtain a second supernatant and a precipitate;

[0024] S052, the pressure sensor obtains real-time bottom pressure at standard time intervals. When the real-time bottom pressure exceeds the standard bottom pressure, it is determined that the amount of bottom sediment is large, and the second supernatant is discharged;

[0025] S053, obtain the second supernatant liquid level height. When the second supernatant liquid level height is lower than the preset standard second supernatant liquid level height, it is determined that the discharge of the second supernatant is completed and the first reflux pump is started to pump the sediment back to the coagulation sedimentation tank for mud-water separation, and the first supernatant is obtained and discharged into the transfer tank again for sedimentation.

[0026] Furthermore, the standard bottom pressure is determined according to the sediment liquid level height coefficient and the sedimentation time coefficient, and the standard bottom pressure is set to Kb, Kb=K0×α1×β1, where K0 is the preset standard pressure, α1 is the positive correlation coefficient between the sediment liquid level height and the standard bottom pressure, and β1 is the negative correlation coefficient between the sedimentation time and the standard bottom pressure.

[0027] Furthermore, the sediment level height coefficient is set to α1, α1=Hc / H0+αk, where Hc is the obtained sediment level height, H0 is the preset standard level height, and αk is the basic height coefficient value;

[0028] αk is related to the density of the second mixed wastewater in the transfer tank. The first density is set to ρ1, the second density is set to ρ2, and the density of the second mixed wastewater is ρ.

[0029] When 0<ρ<ρ1, αk=αk1;

[0030] When ρ1≤ρ≤ρ2, αk=αk2;

[0031] When ρ>ρ2, αk=αk3.

[0032] Furthermore, the precipitation time coefficient is β1, β1=T0 / Tc+βk, where Tc is the total precipitation time, T0 is the standard time interval, and βk is the basic time coefficient.

[0033] Furthermore, chemical agents are added to the sludge in the sludge storage tank to condition the sludge and separate the sludge from the water to obtain sludge treatment supernatant and sludge, the sludge is pumped into the high-pressure plate and frame filter press equipment by a second high-pressure pump for filtration to obtain filter press sludge and filtrate, and the filter press sludge is treated again by the sludge low-temperature drying equipment to produce the condensed water and dry sludge; the chemical agents include lime, ferric chloride and PAM.

[0034] Furthermore, the two-stage A / O pool includes a primary A / O pool and a secondary A / O pool, the primary A / O pool includes a primary A pool and a primary O pool, and the secondary A / O pool includes a secondary A pool and a secondary O pool, wherein the ammonia nitrogen in the hydrolyzed wastewater is converted into nitrate nitrogen or nitrite nitrogen through nitrification in the primary O pool and the secondary O pool, the nitrified liquid is returned from the primary O pool to the primary A pool, the nitrified liquid of the secondary O pool is returned to the primary A pool and the secondary A pool respectively, and the effluent of the secondary O pool flows into the sedimentation tank by gravity;

[0035] The effluent from the secondary O tank is separated into mud and water in the sedimentation tank, and the small-particle sludge is returned to the front-end primary A tank and secondary A tank respectively through the second reflux pump, and the precipitated large-particle sludge is discharged into the sludge storage tank.

[0036] Furthermore, the magnetic coagulation device is used to remove suspended matter in the effluent from the sedimentation tank to produce sludge and magnetic coagulation effluent, wherein the sludge is discharged into the sludge storage tank, and the magnetic coagulation effluent flows into the ozone reaction tank by gravity.

[0037] Compared with the prior art, the beneficial effects of the present invention are that the salt in coffee production wastewater can be separated by treating high-salt wastewater, and evaporated wastewater can be obtained during the treatment process, which is helpful for further treatment; by discharging equipment and ground washing wastewater into the first collecting tank and mixing it with the evaporated wastewater to form a first mixed wastewater, it is helpful to simultaneously treat the evaporated wastewater of high-salt wastewater in caffeine wastewater and the equipment and ground washing wastewater, thereby improving the wastewater treatment efficiency; by pre-treating the first mixed wastewater to obtain a first supernatant and sludge, oxidation treatment of caffeine production wastewater and sludge precipitation are achieved; by discharging the first supernatant into the transfer tank, it is helpful for the transfer tank to perform secondary precipitation treatment on the first supernatant, thereby improving the precipitation efficiency of the precipitate in the first supernatant; by discharging domestic wastewater and pure water purification device drainage into the second collecting tank and sending it to the transfer tank through the third water pump and mixing it with the first supernatant to obtain a second mixed wastewater, it is helpful to simultaneously treat domestic waste The water and pure water purification device drains water, thereby improving the wastewater treatment efficiency; the second mixed wastewater is subjected to secondary precipitation in the transfer tank to obtain a second supernatant, thereby improving the precipitation efficiency of the precipitate in the mixed wastewater; the pH value of the second supernatant is adjusted to obtain adjusted wastewater, and then hydrolyzed in a dynamic hydrolysis acidification tank to obtain hydrolyzed wastewater, which helps to improve the wastewater treatment efficiency; ammonia nitrogen, total nitrogen and organic matter in the hydrolyzed wastewater are removed through two-stage A / O tanks, thereby improving the removal rate of ammonia nitrogen, total nitrogen and organic matter; the effluent from the sedimentation tank enters the intermediate water tank and is sent to the magnetic coagulation device through the fifth water pump for treatment to obtain sludge and magnetic coagulation effluent, thereby achieving the treatment of suspended matter in the caffeine production wastewater; decolorization and disinfection are carried out in the ozone reaction tank to obtain treated water, thereby improving the wastewater treatment efficiency; the sludge in the sludge storage tank is further treated, and the resulting supernatant, filtrate and condensate are discharged into the transfer tank for secondary precipitation, thereby improving the precipitation efficiency of the intermediate wastewater and improving the utilization rate of the water in the sludge outlet tank.

[0038] In particular, the wastewater is pretreated through the Fenton oxidation system to effectively remove nitrogen-containing macromolecular organic matter in the wastewater; the muddy water in the pretreated wastewater is separated into the first supernatant and sludge through the coagulation sedimentation tank, thereby realizing the first precipitation of the sludge in the wastewater.

[0039] In particular, the first supernatant, the effluent from the second collecting tank, and the sludge supernatant, filtrate, and condensate are collected through the transfer tank, thereby realizing secondary treatment of the intermediate wastewater of caffeine production wastewater by the transfer tank; by arranging a first reflux pump at the second outlet of the transfer tank, the sediment at the bottom of the transfer tank can be pumped back to the coagulation sedimentation tank for mud-water separation, thereby improving the sedimentation efficiency of the sediment in the mud and water; by arranging a pressure sensor under the bottom plate, the bottom pressure can be obtained in real time, and the amount of sediment in the transfer tank can be monitored in real time; by arranging a liquid level gauge on the side wall of the transfer tank, the liquid level height in the transfer tank can be monitored in real time.

[0040] In particular, by allowing the second mixed wastewater to enter the transfer tank and stand for mud-water separation to obtain a second supernatant and sediment, sedimentation is achieved in the wastewater in the transfer tank; by obtaining real-time bottom pressure, the amount of sediment in the tank is determined in real time, and the supernatant is discharged in a timely manner; by starting the first reflux pump to reversely pump the sediment back to the coagulation sedimentation tank for mud-water separation, the first supernatant is obtained and again discharged into the transfer tank for sedimentation, achieving secondary sedimentation of the sediment and improving sedimentation efficiency. The sediment level height coefficient and the sedimentation time coefficient are combined to determine the amount of sediment in the tank, making the judgment result more scientific and reliable.

[0041] In particular, by further treating the sludge in the sludge storage tank, the generated supernatant, filtrate and condensate are discharged into the transfer tank for secondary sedimentation, thereby improving the sedimentation efficiency of the intermediate wastewater and improving the utilization rate of the water in the sludge outflow tank.

[0042] In particular, wastewater is treated through two-stage A / O tanks and the sludge is discharged into the sludge storage tank, thereby improving the wastewater treatment efficiency; a magnetic coagulation device is used to remove suspended matter in the effluent of the sedimentation tank to generate sludge and magnetic coagulation effluent and discharge the sludge into the sludge storage tank, thereby improving the wastewater treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A flow chart of a process for treating caffeine production wastewater provided by an embodiment of the present invention;

[0044] Figure 2 This is a process flow chart of step S03 in the process for treating caffeine production wastewater provided by an embodiment of the present invention;

[0045] Figure 3 This is a process flow chart of step S05 in the process for treating caffeine production wastewater provided by an embodiment of the present invention;

[0046] Figure 4 This is a process flow chart of step S01 in the process for treating caffeine production wastewater provided by an embodiment of the present invention;

[0047] Figure 5 A schematic diagram of the structure of the transfer tank in the process for treating caffeine production wastewater provided by an embodiment of the present invention;

[0048] Figure 6 A schematic diagram of the system structure for treating caffeine production wastewater provided by an embodiment of the present invention;

[0049] Figure numerals: 1. Mother liquor collection tank; 2. Wet oxidation equipment; 3. Intermediate water tank; 4. MVR evaporation equipment; 5. First water collection tank; 6. Fenton oxidation system; 7. Coagulation sedimentation tank; 8. Equalization tank; 9. Second water collection tank; 10. Dynamic hydrolysis acidification tank; 11. Primary AO tank; 12. Secondary A / O tank; 13. Sedimentation tank; 14. Intermediate water tank; 15. Magnetic coagulation device; 16. Ozone reaction tank; 17. Clear water tank; 18. Ozone generator; 19. Sludge storage tank; 20. High-pressure plate and frame filter press; 21. Sludge low-temperature drying equipment; 22. Aeration fan; 100. Transfer tank; 101. First outlet; 102. Second outlet; 103. Water inlet; 104. Bottom plate; 105. Pressure sensor; 106. Liquid level gauge. DETAILED DESCRIPTION

[0050] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0052] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0053] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0054] A process for treating caffeine production wastewater, see Figure 1-6 As shown, it can be implemented as follows:

[0055] like Figure 1 As shown, the method includes:

[0056] S01, collecting and treating high-salt wastewater to obtain evaporated wastewater and separated salt, and collecting the evaporated wastewater into a first water collection tank;

[0057] S02, discharging the equipment and ground flushing wastewater into the first water collection tank and mixing it with the evaporated wastewater to form first mixed wastewater;

[0058] S03, performing oxidation treatment on the first mixed wastewater to obtain pretreated wastewater, separating the pretreated wastewater to obtain a first supernatant and sludge, and discharging the first supernatant into a transfer tank;

[0059] S04, draining the domestic wastewater and the pure water purification device into a second water collection tank and pumping them to the transfer tank through a third water pump to mix with the first supernatant to obtain second mixed wastewater;

[0060] S05, performing secondary sedimentation on the second mixed wastewater in the transfer tank to obtain a second supernatant and discharging the second supernatant into a regulating tank;

[0061] S06, adjusting the pH value of the second supernatant and stirring it evenly to obtain adjusted wastewater, and sending the adjusted wastewater into a dynamic hydrolysis acidification tank through a fourth water pump for hydrolysis to obtain hydrolyzed wastewater;

[0062] S07, the hydrolysis wastewater flows into the two-stage A / O tank by gravity, and ammonia nitrogen, total nitrogen and organic matter in the hydrolysis wastewater are removed, and then flows into the sedimentation tank by gravity for mud-water separation to obtain sedimentation tank effluent;

[0063] S08, the effluent from the sedimentation tank enters the intermediate water tank and is sent to the magnetic coagulation device through the fifth water pump for treatment to obtain sludge and magnetic coagulation effluent;

[0064] S09, the magnetic coagulation effluent flows by gravity into the ozone reaction tank for decolorization and disinfection to produce treated water, which then flows by gravity into the Parshall cell; when it is determined that the pollutant content in the treated water meets the standard, the treated water is discharged;

[0065] S10, treating the sludge in the sludge storage tank to produce sludge treatment supernatant, filtrate, condensate and dehydrated dry sludge, wherein the sludge treatment supernatant, the filtrate and the condensate are discharged into the transfer tank for further treatment, and the dehydrated sludge is discharged into the sludge low-temperature drying equipment for sludge strip cutting and low-temperature heating.

[0066] By treating high-salt wastewater, the salt in coffee production wastewater can be separated, and evaporated wastewater can be obtained during the treatment process, which is helpful for further treatment; by discharging equipment and ground washing wastewater into the first collecting tank and mixing it with the evaporated wastewater to form a first mixed wastewater, it is helpful to simultaneously treat the evaporated wastewater of high-salt wastewater in caffeine wastewater and the equipment and ground washing wastewater, thereby improving wastewater treatment efficiency; by pre-treating the first mixed wastewater to obtain a first supernatant and sludge, oxidation treatment of caffeine production wastewater and sludge precipitation are achieved; by discharging the first supernatant into the transfer tank, it is helpful for the transfer tank to perform secondary precipitation treatment on the first supernatant, thereby improving the precipitation efficiency of the precipitate in the first supernatant; by discharging domestic wastewater and pure water purification device drainage into the second collecting tank and sending it to the transfer tank through the third water pump and mixing it with the first supernatant to obtain a second mixed wastewater, it is helpful to simultaneously treat domestic wastewater and pure water purification device drainage. water, improving wastewater treatment efficiency; by performing secondary precipitation on the second mixed wastewater in the transfer tank to obtain a second supernatant, the precipitation efficiency of the precipitate in the mixed wastewater is improved; by adjusting the pH value of the second supernatant to obtain adjusted wastewater and hydrolyzing it in a dynamic hydrolysis acidification tank to obtain hydrolyzed wastewater, which helps to improve wastewater treatment efficiency; by passing through two-stage A / O tanks and removing ammonia nitrogen, total nitrogen and organic matter in the hydrolyzed wastewater, the removal rate of ammonia nitrogen, total nitrogen and organic matter is improved; the effluent from the sedimentation tank enters the intermediate water tank and is sent to the magnetic coagulation device through the fifth water pump for treatment to obtain sludge and magnetic coagulation effluent, thereby realizing the treatment of suspended matter in the caffeine production wastewater; by decolorization and disinfection treatment in the ozone reaction tank to obtain treated water, the wastewater treatment efficiency is improved; by further treating the sludge in the sludge storage tank, the generated supernatant, filtrate and condensate are discharged into the transfer tank for secondary precipitation, which improves the precipitation efficiency of the intermediate wastewater and improves the utilization rate of the water in the sludge outflow tank.

[0067] like Figure 2 As shown, step S03 includes:

[0068] S031, sending the first mixed wastewater into the Fenton oxidation system through a second water pump;

[0069] S032, the Fenton oxidation system decomposes nitrogen-containing macromolecular organic matter in the first mixed wastewater into small molecular organic matter and decomposes organic nitrogen into ammonia nitrogen or small molecular organic nitrogen to obtain pretreated wastewater;

[0070] S033, separating the muddy water in the pretreated wastewater into a first supernatant and sludge through a coagulation sedimentation tank, discharging the supernatant into a transfer tank and discharging the sludge into a sludge storage tank.

[0071] The wastewater is pretreated by the Fenton oxidation system to effectively remove nitrogen-containing macromolecular organic matter in the wastewater; the muddy water in the pretreated wastewater is separated into the first supernatant and sludge through the coagulation sedimentation tank, thereby realizing the first precipitation of the sludge in the wastewater.

[0072] Specifically, if Figure 5 As shown, the water inlet 103 of the transfer tank 100 is respectively connected to the outlet pipe of the coagulation sedimentation tank, the outlet pipe of the second collecting tank and the outlet pipe of the sludge storage tank, so as to collect the first supernatant, the outlet water of the second collecting tank and the sludge supernatant, the filtrate and the condensate. The water inlet of the transfer tank is arranged at the top of the transfer tank; the first outlet 101 of the transfer tank is connected to the water inlet of the regulating tank to discharge the second supernatant to the regulating tank. The first outlet is arranged on the side wall of the transfer tank and is at a first height from the bottom of the transfer tank. The second outlet of the transfer tank is arranged at a first height from the bottom of the transfer tank. The outlet 102 is arranged on the side wall of the transfer tank and is at a second height away from the bottom of the transfer tank. The second outlet is connected to the coagulation sedimentation tank, and a first reflux pump H1 is arranged at the second outlet to pump the sediment at the bottom of the transfer tank back to the coagulation sedimentation tank for mud-water separation; a bottom plate 104 is arranged at the bottom of the transfer tank, and a pressure sensor 105 is arranged under the bottom plate to obtain the bottom pressure of the transfer tank; a liquid level gauge 106 is arranged on the side wall of the transfer tank to obtain the liquid level height in the transfer tank, and the liquid level height includes the second supernatant liquid level height and the sediment liquid level height.

[0073] The first supernatant, the effluent from the second collecting tank, and the sludge supernatant, filtrate, and condensate are collected through the transfer tank to realize secondary treatment of the intermediate wastewater of caffeine production wastewater; a first reflux pump is provided at the second outlet of the transfer tank to enable the sediment at the bottom of the transfer tank to be pumped back to the coagulation sedimentation tank for mud-water separation, thereby improving the sedimentation efficiency of the sediment in the mud and water; a pressure sensor is provided under the bottom plate to obtain the bottom pressure in real time and monitor the amount of sediment in the transfer tank in real time; a liquid level gauge is provided on the side wall of the transfer tank to monitor the liquid level in real time.

[0074] Specifically, if Figure 3 As shown, step S05 includes:

[0075] S051, the second mixed wastewater enters the transfer tank and is allowed to stand for mud-water separation to obtain a second supernatant and sediment;

[0076] S052, the pressure sensor obtains the real-time bottom pressure at a standard time interval. When the real-time bottom pressure is greater than or equal to the standard bottom pressure, it is determined that the amount of bottom sediment is large, and the second supernatant is discharged;

[0077] S053, obtain the second supernatant liquid level height. When the second supernatant liquid level height is less than the preset standard second supernatant liquid level height, it is determined that the second supernatant discharge is completed and the first reflux pump is started to pump the sediment back to the coagulation sedimentation tank for mud-water separation to obtain the first supernatant and discharge it into the transfer tank again.

[0078] Specifically, the standard bottom pressure is determined according to the sediment liquid level height coefficient and the sedimentation time coefficient, and the standard bottom pressure is set to Kb, Kb = K0×α1×β1, where K0 is the preset standard pressure, α1 is the positive correlation coefficient between the sediment liquid level height and the standard bottom pressure, and β1 is the negative correlation coefficient between the sedimentation time and the standard bottom pressure.

[0079] Specifically, the sediment level height coefficient is set to α1, α1=Hc / H0+αk, where Hc is the obtained sediment level height, H0 is the preset standard level height, and αk is the basic height coefficient value;

[0080] αk is related to the density of the second mixed wastewater in the transfer tank. The first density is set to ρ1, the second density is set to ρ2, and the density of the second mixed wastewater is ρ.

[0081] When 0<ρ<ρ1, αk=αk1;

[0082] When ρ1≤ρ≤ρ2, αk=αk2;

[0083] When ρ>ρ2, αk=αk3.

[0084] Specifically, the precipitation time coefficient is β1, β1=T0 / Tc+βk, where Tc is the total precipitation time, T0 is the standard time interval, and βk is the basic time coefficient.

[0085] The second mixed wastewater enters the transfer tank and is allowed to stand for mud-water separation to obtain a second supernatant and sediment, thereby achieving sedimentation in the wastewater in the transfer tank; by obtaining real-time bottom pressure, the amount of sediment in the tank is judged in real time, and the supernatant is discharged in a timely manner; by starting the first reflux pump to reversely pump the sediment back to the coagulation sedimentation tank for mud-water separation, the first supernatant is obtained and again discharged into the transfer tank for sedimentation, achieving secondary sedimentation of the sediment and improving sedimentation efficiency. The sediment level height coefficient and the sedimentation time coefficient are combined to determine the amount of sediment in the tank, making the judgment result more scientific and reliable.

[0086] Specifically, chemical agents are added to the sludge in the sludge storage tank to condition the sludge and separate the mud and water to obtain sludge treatment supernatant and sludge, the sludge is pumped into the high-pressure plate and frame filter press equipment by a second high-pressure pump for filtration to treat the sludge to obtain filter press sludge and filtrate, and the filter press sludge is further treated by the sludge low-temperature drying equipment to produce the condensed water and dry sludge; the chemical agents include lime, ferric chloride and PAM.

[0087] By further treating the sludge in the sludge storage tank, the generated supernatant, filtrate and condensate are discharged into the transfer tank for secondary sedimentation, thereby improving the sedimentation efficiency of the intermediate wastewater and the utilization rate of the water in the sludge outflow tank.

[0088] Specifically, if Figure 4 As shown, step S01 includes:

[0089] S011, collecting the high-salt wastewater into a mother liquor collection tank and sending the high-salt wastewater into a wet oxidation device through a first high-pressure pump;

[0090] S012, oxidizing the high-salt wastewater in the wet oxidation equipment to remove some organic matter in the high-salt wastewater to obtain intermediate wastewater, and the intermediate wastewater enters the intermediate water tank and is sent to the MVR evaporation equipment through the first water pump;

[0091] S013, evaporating and separating the intermediate wastewater through the MVR evaporation equipment to obtain evaporated wastewater and separated salts, wherein the evaporated wastewater is collected and enters the first water collection tank, and the separated salts are converted into solid matter and transported out for treatment.

[0092] Specifically, the two-stage A / O pool includes a primary A / O pool and a secondary A / O pool, the primary A / O pool includes a primary A pool and a primary O pool, and the secondary A / O pool includes a secondary A pool and a secondary O pool, wherein the ammonia nitrogen in the hydrolyzed wastewater is converted into nitrate nitrogen or nitrite nitrogen through nitrification in the primary O pool and the secondary O pool, the nitrified liquid is returned from the primary O pool to the primary A pool, the nitrified liquid of the secondary O pool is returned to the primary A pool and the secondary A pool respectively, and the effluent of the secondary O pool flows into the sedimentation tank by gravity;

[0093] The effluent from the secondary O tank is separated into mud and water in the sedimentation tank, and the small-particle sludge is returned to the front-end primary A tank and secondary A tank respectively through the second reflux pump, and the precipitated large-particle sludge is discharged into the sludge storage tank.

[0094] Specifically, the magnetic coagulation device is used to remove suspended matter in the effluent from the sedimentation tank to produce sludge and magnetic coagulation effluent, wherein the sludge is discharged into the sludge storage tank, and the magnetic coagulation effluent flows into the ozone reaction tank by gravity.

[0095] The high-salt wastewater is oxidized in a wet oxidation device and the intermediate wastewater is evaporated and separated by an MVR evaporation device to obtain evaporated wastewater and separated salt, thereby improving the wastewater treatment efficiency; the wastewater is treated in a two-stage A / O tank to improve the wastewater treatment efficiency; and the magnetic coagulation device is used to remove suspended matter in the effluent of the sedimentation tank to generate sludge and magnetic coagulation effluent, thereby improving the wastewater treatment efficiency.

[0096] Example 1, as Figure 6 As shown, the system for treating caffeine wastewater includes:

[0097] The mother liquor collection tank 1 collects high-salt wastewater for temporary storage. A high-pressure pump sends the high-salt wastewater in the mother liquor collection tank to the wet oxidation equipment 2. In the wet oxidation equipment, a strong oxidizing air oxidation process is carried out under high temperature and high pressure conditions to treat a large amount of organic matter in the wastewater to obtain intermediate wastewater. The intermediate wastewater enters the intermediate water tank 3 and is sent to the MVR evaporation equipment through a water pump. Specifically, the high temperature and high pressure conditions are between 200°C and 300°C and between 3MPa and 15MPa. The removal rate of organic matter in this stage is 50% to 60%.

[0098] The MVR evaporation equipment 4 evaporates and separates the intermediate wastewater, collects the evaporated wastewater and enters the first water collection tank 5, and the separated salts are converted into solid sulfates and transported for treatment. Specifically, the working conditions of the MVR evaporation equipment are: evaporation material temperature of 90°C-98°C, secondary steam temperature of 85°C-88°C, condensate outlet temperature of 60°C-70°C, and evaporation pressure of -30kPa-50kPa. Under the above working conditions, the wastewater is evaporated, and the salt in the water is separated to form solid substances (mainly sulfates), which are finally transported for treatment. Since a large amount of organic matter is still present in the evaporated wastewater, it cannot meet the discharge standards and therefore needs to enter the first water collection tank again.

[0099] Equipment and ground washing wastewater is discharged into the first water collection tank through the plant drainage system and mixed with the evaporated wastewater to form the first mixed wastewater, which then enters the Fenton pretreatment system;

[0100] The Fenton pretreatment system includes a Fenton oxidation system 6. The pH value of the reactants in the Fenton oxidation system is 3-5, and the temperature is 10°C-30°C. Hydrogen peroxide and ferrous sulfate are added to the Fenton oxidation system. The first mixed wastewater is oxidized under the oxidation capacity of the Fenton oxidation system to obtain pretreated wastewater. Specifically, the Fenton oxidation system decomposes nitrogen-containing macromolecular organic matter in the first mixed wastewater into small molecular organic matter and decomposes organic nitrogen into ammonia nitrogen or small molecular organic nitrogen. In this embodiment, the mass ratio of the hydrogen peroxide added to the Fenton oxidation system to the mass ratio of the organic matter in the pretreated first mixed wastewater is 1:1, and the mass ratio of the hydrogen peroxide added to the ferrous sulfate is 1:1.

[0101] Since the Fenton pretreatment system generates a large amount of sludge, a coagulation sedimentation tank 7 is provided to separate the muddy water in the pretreated wastewater into a first supernatant and sludge. The first supernatant is discharged into a transfer tank, where it undergoes secondary sedimentation to obtain a second supernatant. The second supernatant is sent to a regulating tank 8 and the sludge is discharged into a sludge storage tank. The supernatant contains decomposed small molecular organic matter, ammonia nitrogen or small molecular organic nitrogen.

[0102] Domestic wastewater and pure water purification device drainage are discharged into the second water collection tank 9 and pumped to the transfer tank 100 to be mixed with the first supernatant to obtain a second mixed wastewater for sedimentation treatment to obtain a second supernatant;

[0103] Adjusting the pH value of the second mixed wastewater and stirring it evenly to obtain adjusted wastewater; providing a pH adjustment device and a stirring system in the regulating tank, wherein the pH adjustment device is used to adjust the pH value of the second mixed wastewater to obtain adjusted wastewater, and the stirring system is used to stir the adjusted wastewater evenly to a homogeneous and uniform amount, wherein the pH value of the adjusted wastewater after homogenization and uniform amount is 7-9 and the temperature is 10°C-35°C; specifically, the residual difficult-to-biodegrade macromolecular substances are converted into easily biodegradable small molecular substances through biochemical reactions, and the B / C value is increased, thereby improving the biodegradability of the wastewater and providing a good water quality environment for subsequent biochemical treatment;

[0104] The water pump sends the regulated wastewater into the dynamic hydrolysis acidification tank 10 for hydrolysis to obtain hydrolyzed wastewater. The dynamic hydrolysis acidification tank is used to use hydrolytic bacteria and acidifying bacteria to hydrolyze insoluble organic matter in the water into soluble organic matter, and convert the remaining macromolecular substances into small molecular substances through biochemical reactions;

[0105] The wastewater after hydrolysis flows by gravity into the two-stage AO system, and after ammonia nitrogen, total nitrogen and organic matter in the wastewater after hydrolysis are removed, it flows by gravity into the sedimentation tank; the two-stage AO system includes a primary AO tank 11 and a secondary AO tank 12, the primary AO tank includes a primary A tank and a primary O tank, and the secondary AO tank includes a secondary A tank and a secondary O tank, wherein the nitrification liquid of the primary O tank is returned to the primary A tank, and the nitrification liquid of the secondary O tank is returned to the primary A tank and the secondary A tank respectively, and the effluent of the secondary O tank enters the sedimentation tank 13;

[0106] Specifically, the effluent from the secondary O tank is separated into mud and water in the sedimentation tank, and the small-particle sludge is returned to the front-end primary A tank and secondary A tank respectively through the second reflux pump H2, and the precipitated large-particle sludge is discharged into the sludge storage tank;

[0107] The effluent from the sedimentation tank enters the intermediate water tank 14 and enters the magnetic coagulation device 15 through a pump. The magnetic coagulation device is used to remove suspended matter in the effluent from the sedimentation tank and produce sludge and magnetic coagulation effluent. The sludge produced by the magnetic coagulation device is discharged into the sludge storage tank, and the magnetic coagulation effluent flows into the ozone reaction tank by gravity. Specifically, the coagulation chamber HRT of the magnetic coagulation device is 30s-90s, and a paddle mixer is used for sufficient stirring; the hydraulic retention time of the magnetic medium coagulation chamber is 90s-180s, and a paddle mixer is used. Stir thoroughly; the hydraulic retention time in the flocculation reaction chamber is 2 to 5 minutes, and a paddle stirrer is used for thorough stirring; the magnetic medium sludge return rate is generally 3%-8% of the designed water volume; the PAC concentration is 8%-12%, the dosage is 10-30 mg / L, and the PAM concentration is 0.1%-0.3%, the dosage is 0.5 mg / L; the surface load is 15-20 m3 / m2·h), to remove suspended matter in the water and reduce SS to below 10 mg / L;

[0108] The magnetic coagulation effluent is decolorized and disinfected by the oxidation of ozone in the ozone reaction tank 16 to produce treated water, which flows by gravity into the clean water tank 17. Specifically, in this embodiment, the ratio of ozone dosage to COD removal is (2-5):1. When the pollutant content in the treated water meets the standard, it is discharged. Specifically, in this embodiment, ozone is supplemented by an ozone generator 18. The clean water tank used in this embodiment is a Parshall tank.

[0109] Chemical agents are added to the sludge in the sludge storage tank 19 for conditioning, and then mud and water separation is performed to obtain sludge treatment supernatant and sludge, which are pumped into the high-pressure plate and frame filter press 20 through a high-pressure pump to produce filtrate and dehydrated sludge. The dehydrated sludge is discharged into the sludge low-temperature drying equipment 21 for sludge strip cutting and low-temperature heating to obtain condensed water and sludge dry strips; specifically, the chemical agents added in this embodiment are lime, ferric chloride, PAM and other chemical agents; the generated sludge treatment supernatant, filtrate and condensed water are sent to the transfer tank for re-precipitation.

[0110] Example 2

[0111] The caffeine production wastewater generated during the production process in the caffeine workshop of a caffeine production enterprise is required to be treated on-site to meet the standards. The designed water treatment capacity is 3000m3 / d. The influent COD is 5000-6000mg / L, the total nitrogen is 600-800mg / L, and the ammonia nitrogen is 300mg / L. The effluent complies with the "Chemical Synthesis Pharmaceutical Industry Water Pollutant Discharge Standard" and the industrial park discharge standards, requiring COD 200mg / L, ammonia nitrogen 25mg / L, and total nitrogen 40mg / L. The specific implementation method is as follows:

[0112] The generated production wastewater is pumped through the workshop to a mother liquor collection tank, which is 8 meters high and equipped with a lift pump, pH meter, and ultrasonic level gauge. The lift pump automatically operates in conjunction with the ultrasonic level gauge, activating one pump when the liquid level reaches 7.5 meters and stopping when the low level falls below 1.5 meters. Above 7.5 meters, the host computer triggers an alarm, notifying the workshop and halting drainage. The two pumps rotate in operation, and if one fails, the other automatically starts. The water discharged by the lift pump is then sent to the wet oxidation equipment.

[0113] The wet oxidation equipment and MVR equipment are equipped with on-site power distribution boxes, which are linked to the lifting pump during automatic operation. When the lifting pump is turned on, the equipment is turned on; when the water collection well lifting pump is turned off, the equipment stops running.

[0114] Wet oxidation equipment reaction conditions: 250-300°C; MVR equipment reaction conditions: evaporation material temperature (90-98°C), secondary steam temperature (85-88°C), condensate outlet temperature (60-70°C), evaporation pressure (-30kPa to -50kPa). The effluent flows into the first water collection tank by gravity, which also collects equipment and ground flushing wastewater. The first water collection tank is 6 meters deep and is equipped with a lift pump, a first acid dosing pump, a first alkali dosing pump, a pH meter, an electromagnetic flow meter, and an ultrasonic level meter.

[0115] The effluent from the first collection tank is pumped to the Fenton oxidation and coagulation sedimentation tank. This system houses six chemical storage tanks: sulfuric acid, hydrogen peroxide, liquid caustic soda, ferrous sulfate, PAM, and PAC. Within the Fenton system, sulfuric acid is first used to adjust the wastewater pH to approximately 3-4. Hydrogen peroxide (H2O2:COD mass ratio = 1:1) and ferrous sulfate (H2O2:Fe2+ = 1:1) are then added to initiate the Fenton reaction. Liquid caustic soda is then added again to adjust the pH to neutral (pH: 7-8), followed by coagulation and sedimentation for sludge-water separation. The supernatant then enters a transfer tank for secondary sedimentation, which is then discharged into the regulating tank. The precipitated sludge is then discharged into the sludge storage tank for dewatering.

[0116] Domestic sewage and pure water preparation device drainage enter the second collection tank for temporary storage.

[0117] A liquid level meter and a lifting pump are installed in the second water collection tank to lift the wastewater to the transfer tank for sedimentation, and the supernatant after sedimentation is discharged into the regulating tank.

[0118] The regulating tank is designed to be 6m deep and is equipped with a regulating tank lift pump, a submersible mixer, a first acid metering pump, a first alkali metering pump, a pH meter, an electromagnetic flow meter, and an ultrasonic level meter. The submersible mixer can be linked to the ultrasonic level meter of the regulating tank. When the liquid level is lower than 1m, the submersible mixer will automatically stop running.

[0119] The regulating tank lifting pump can be linked with the electromagnetic flowmeter. The electromagnetic flowmeter sets the operating flow rate to 125m3 / h. The operating frequency of the regulating tank lifting pump is automatically adjusted according to this flow rate. When operating automatically or manually, the regulating tank lifting pump is linked with the ultrasonic liquid level meter. It will automatically stop running when it is lower than 1.5m and automatically start when it is higher than 2m. When it is higher than 5.5m, the host computer will alarm.

[0120] The first acid and alkali metering pumps, when in automatic operation, are linked to the pH meter in the regulating tank to automatically adjust the dosing rate. When the pH is below 5, the first alkali metering pump automatically adds chemicals, and stops adding chemicals when the pH is above 8 (the value can be set by the host computer). When the pH is above 9, the first acid metering pump automatically adds chemicals, and stops adding chemicals when the pH is below 6. The final pH value after water quality adjustment is controlled between 7.5 and 9.

[0121] The effluent from the regulating tank flows through the regulating tank lifting pump into the dynamic hydrolysis tank (sludge concentration 6000-10000 mg / L, temperature 15-35°C). The dynamic hydrolysis tank is equipped with a circulating water pump to control the rising flow rate of the dynamic hydrolysis tank. The effluent from the dynamic hydrolysis tank flows by gravity into the dynamic denitrification tank, which is equipped with a submersible mixer and flows by gravity into the two-stage A / O tank.

[0122] Tank A is equipped with a submersible mixer, while Tank O is equipped with an aeration fan, dissolved oxygen meter, and air stripping and reflux device. The sludge concentration is controlled at 6,000-8,000 mg / L. The dissolved oxygen meter is linked to the aeration fan. The dissolved oxygen in Tank O is set at 2-3 mg / L, and the aeration fan frequency is automatically adjusted. The air stripping and reflux device returns the nitrification solution to the front end of Tank A, eliminating the need for a nitrification solution reflux pump.

[0123] The effluent from the two-stage A / O tank flows into the sedimentation tank by gravity, and mud and water are separated in the secondary sedimentation tank, which is equipped with a mud pump and a mud scraper.

[0124] The sludge from the secondary sedimentation tank can be returned to tank A to replenish the activated sludge. The effluent from the secondary sedimentation tank flows by gravity into the magnetic coagulation device, which has its own on-site control box and the signal can be fed back to the host computer.

[0125] The wastewater from the magnetic coagulation unit flows by gravity into the ozone reaction tank (the ozone generator dosage is 15-20kg / h). In the ozone reaction tank, it undergoes decolorization and disinfection through strong oxidation. The wastewater then meets the discharge standards.

[0126] All electrical equipment can display operating status and fault alarms on the host computer. Operation can be performed manually on the power distribution cabinet or the host computer. The host computer can switch between manual and automatic operation, and in automatic mode, it will operate according to the set time or program. Instruments such as flow meters, dissolved oxygen meters, and pH meters can display readings on the host computer, and related setting parameters can be set and adjusted on the host computer.

[0127] After actual operation test, the effluent COD is less than 200mg / L, total nitrogen is less than 25mg / L, and ammonia nitrogen is less than 40mg / L, which can achieve continuous and stable emission standards and is easy to operate and maintain.

[0128] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0129] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A process for treating caffeine production wastewater, characterized in that: include: S01, collecting and treating high-salt wastewater to obtain evaporated wastewater and separated salt, and collecting the evaporated wastewater into a first water collection tank; S02, discharging the equipment and ground flushing wastewater into the first water collection tank and mixing it with the evaporated wastewater to form first mixed wastewater; S03, performing oxidation treatment on the first mixed wastewater to obtain pretreated wastewater, separating the pretreated wastewater to obtain a first supernatant and sludge, and discharging the first supernatant into a transfer tank; Step S03 includes: S031, sending the first mixed wastewater into the Fenton oxidation system through a second water pump; S032, the Fenton oxidation system decomposes the organic nitrogen in the first mixed wastewater into ammonia nitrogen or small molecular organic nitrogen to obtain pretreated wastewater; S033, separating the muddy water in the pretreated wastewater into a first supernatant and sludge in a coagulation sedimentation tank, discharging the supernatant into a transfer tank and discharging the sludge into a sludge storage tank; S04, draining the domestic wastewater and the pure water purification device into a second water collection tank and pumping them to the transfer tank through a third water pump to mix with the first supernatant to obtain second mixed wastewater; S05, performing secondary sedimentation on the second mixed wastewater in the transfer tank to obtain a second supernatant and discharging the second supernatant into a regulating tank; S06, adjusting the pH value of the second supernatant and stirring it evenly to obtain adjusted wastewater, and sending the adjusted wastewater into a dynamic hydrolysis acidification tank through a fourth water pump for hydrolysis to obtain hydrolyzed wastewater; S07, the hydrolysis wastewater flows into the two-stage A / O tank by gravity, and ammonia nitrogen, total nitrogen and organic matter in the hydrolysis wastewater are removed, and then flows into the sedimentation tank by gravity for mud-water separation to obtain sedimentation tank effluent; S08, the effluent from the sedimentation tank enters the intermediate water tank and is sent to the magnetic coagulation device through the fifth water pump for treatment to obtain sludge and magnetic coagulation effluent; S09, the magnetic coagulation effluent flows by gravity into the ozone reaction tank for decolorization and disinfection to produce treated water, which then flows by gravity into the Parshall cell; when it is determined that the pollutant content in the treated water meets the standard, the treated water is discharged; S10, treating the sludge in the sludge storage tank to produce sludge treatment supernatant, filtrate, condensate and dehydrated dry sludge, wherein the sludge treatment supernatant, the filtrate and the condensate are discharged into the transfer tank for further treatment, and the dehydrated sludge is discharged into the sludge low-temperature drying equipment for sludge strip cutting and low-temperature heating.

2. The process for treating caffeine production wastewater according to claim 1, wherein: The water inlet of the transfer tank is respectively connected to the outlet pipe of the coagulation sedimentation tank, the outlet pipe of the second water collecting tank and the outlet pipe of the sludge storage tank, so as to collect the first supernatant, the outlet water of the second water collecting tank and the sludge supernatant, the filtrate and the condensate. The water inlet of the transfer tank is arranged at the top of the transfer tank; the first outlet of the transfer tank is connected to the water inlet of the regulating tank, so as to discharge the second supernatant to the regulating tank. The first outlet is arranged on the side wall of the transfer tank and is at a first height away from the bottom of the transfer tank. The second outlet of the transfer tank is arranged on the side wall of the transfer tank and is at a second height away from the bottom of the transfer tank. The second outlet is connected to the coagulation sedimentation tank, and a first reflux pump is arranged at the second outlet to pump the sediment at the bottom of the transfer tank back to the coagulation sedimentation tank for mud-water separation. A bottom plate is provided at the bottom of the transfer tank, and a pressure sensor is provided below the bottom plate to obtain the bottom pressure of the transfer tank; a liquid level gauge is provided on the side wall of the transfer tank to obtain the liquid level height in the transfer tank, and the liquid level height includes the second supernatant liquid level height and the sediment liquid level height.

3. The process for treating caffeine production wastewater according to claim 2, wherein: Step S05 includes: S051, the second mixed wastewater enters the transfer tank and is allowed to stand for mud-water separation to obtain a second supernatant and a precipitate; S052, the pressure sensor obtains real-time bottom pressure at standard time intervals. When the real-time bottom pressure exceeds the standard bottom pressure, it is determined that the amount of bottom sediment is large, and the second supernatant is discharged; S053, obtain the second supernatant liquid level height. When the second supernatant liquid level height is lower than the preset standard second supernatant liquid level height, it is determined that the discharge of the second supernatant is completed and the first reflux pump is started to pump the sediment back to the coagulation sedimentation tank for mud-water separation, and the first supernatant is obtained and discharged into the transfer tank again for sedimentation.

4. The process for treating caffeine production wastewater according to claim 3, wherein: Chemical agents are added to the sludge in the sludge storage tank for conditioning and mud-water separation to obtain sludge treatment supernatant and sludge, the sludge is pumped into the high-pressure plate and frame filter press equipment by a second high-pressure pump for filtration to obtain filter press sludge and filtrate, and the filter press sludge is further treated by the sludge low-temperature drying equipment to produce condensed water and dry sludge; the chemical agents include lime, ferric chloride and PAM.

5. The process for treating caffeine production wastewater according to claim 4, wherein: The two-stage A / O pool includes a primary A / O pool and a secondary A / O pool, the primary A / O pool includes a primary A pool and a primary O pool, and the secondary A / O pool includes a secondary A pool and a secondary O pool, wherein the ammonia nitrogen in the hydrolyzed wastewater is converted into nitrate nitrogen or nitrite nitrogen through nitrification in the primary O pool and the secondary O pool, the nitrified liquid is returned from the primary O pool to the primary A pool, the nitrified liquid of the secondary O pool is returned to the primary A pool and the secondary A pool respectively, and the effluent of the secondary O pool flows into the sedimentation tank by gravity; The effluent from the secondary O tank is separated into mud and water in the sedimentation tank, and the small-particle sludge is returned to the front-end primary A tank and secondary A tank respectively through the second reflux pump, and the precipitated large-particle sludge is discharged into the sludge storage tank.

6. The process for treating caffeine production wastewater according to claim 5, characterized in that: The magnetic coagulation device is used to remove suspended matter in the effluent from the sedimentation tank to produce sludge and magnetic coagulation effluent, wherein the sludge is discharged into the sludge storage tank, and the magnetic coagulation effluent flows into the ozone reaction tank by gravity.

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