A fully mixed hydrolysis acidification tank with automatic dissolved oxygen control and its treatment method

Abstract

This invention provides a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control and its treatment method. The fully mixed hydrolysis acidification tank with automatic dissolved oxygen control includes a hydrolysis acidification tank, an exhaust gas circulation system, and an automatic dissolved oxygen control system. The hydrolysis acidification tank includes a covered pool, which sequentially comprises a rapid mixing zone, a hydrolysis acidification reaction zone, a sludge-water separation zone, and a sludge lifting zone. The blower outlet of the exhaust gas circulation system is divided into three paths: one path connects to the air lift pump in the sludge lifting zone via an air lift flow meter; another path connects to the first aerator in the rapid mixing zone via a first aeration flow meter; and the third path connects to the second aerator in the hydrolysis acidification reaction zone via a second aeration flow meter. The blower inlet is open to the atmosphere. This invention solves the problem in the prior art of how to automatically control the dissolved oxygen in the hydrolysis acidification tank to a micro-aerobic state while ensuring uniform mixing intensity within the tank.

Description

Technical Field

[0001] This invention relates to the technical field of environmental wastewater treatment, and in particular to a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control and its treatment method. Background Technology

[0002] In the biological treatment of organic wastewater, during the hydrolysis and acidification stages, suspended solid organic matter and recalcitrant macromolecules in the wastewater are decomposed into volatile fatty acids and COD. Cr The removal rate can reach 10% to 50%, and it greatly improves the biodegradability of wastewater (and the B / C ratio). For high-concentration or recalcitrant wastewater, hydrolysis acidification pretreatment can greatly improve the reaction rate and organic matter removal rate of subsequent aerobic biological treatment systems, reduce land occupation, lower energy consumption, and save investment.

[0003] Hydrolysis acidification treatment equipment includes upflow hydrolysis acidification reactors, composite hydrolysis acidification reactors, and fully mixed hydrolysis acidification reactors (pools). Fully mixed hydrolysis acidification pools have the advantages of simple structure, low investment, and large processing capacity, and are the most commonly used hydrolysis acidification treatment facilities.

[0004] However, traditional fully mixed hydrolysis acidification tanks have some shortcomings: First, the mixing intensity of the agitator is uneven. The mixing intensity at the near end is very high, making sludge particles easily broken and reducing settling performance; while the mixing intensity at the far end is too weak, resulting in uneven mixing of sludge and water, creating dead zones, causing the sludge to turn black and smelly, thus reducing the effectiveness of hydrolysis acidification. Second, a separate sedimentation tank is required for sludge-water separation, making the process more complex and requiring a larger area. Third, the maintenance of the underwater agitator is relatively difficult.

[0005] To address the shortcomings of mixing devices, some fully mixed hydrolysis acidification tanks use air aerators instead of mixers. However, this introduces another problem. Hydrolysis acidification bacteria consist of various facultative and obligate anaerobic bacteria, and good hydrolysis acidification results can only be achieved when dissolved oxygen in the hydrolysis acidification tank is controlled at a microaerobic state (0.1 < DO < 0.5 mg / L). On the one hand, excessively high dissolved oxygen concentrations (> 0.5 mg / L) inhibit the growth of hydrolysis acidification bacteria, thus reducing the efficiency of organic matter hydrolysis acidification. On the other hand, as the first stage of biological treatment, the hydrolysis acidification tank, due to its high load and rapid sludge growth, consumes some oxygen. If the dissolved oxygen concentration is too low (< 0.1 mg / L), the sludge will exhibit blackening, disintegration, and floating under completely anoxic (anaerobic) conditions. Therefore, when an air aerator is used instead of a mixer in the hydrolysis acidification tank to achieve complete mixing of sludge and water, if the air volume is large and continuous aeration is used, the dissolved oxygen will not be sufficient to meet the anoxic environment (DO < 0.5 mg / L). If the air volume is reduced to meet the anoxic environment, the mixing intensity will be insufficient, the activated sludge will not be in full contact with the wastewater, and the activated sludge may even settle at the bottom of the tank. If a large air volume is used for intermittent aeration to prevent long-term sedimentation of activated sludge, the dissolved oxygen in the mixed liquor will fluctuate, which is not conducive to the growth and reproduction of obligate anaerobic bacteria and facultative bacteria, and will inevitably reduce the hydrolysis acidification effect or even lead to system failure.

[0006] Traditional hydrolysis acidification tanks are open-top designs, relying on agitation equipment to introduce trace amounts of air. Although some existing hydrolysis acidification tanks are equipped with dissolved oxygen (DO) meters, there are no effective measures to control dissolved oxygen. With environmental regulations requiring all wastewater treatment tanks to be sealed, hydrolysis acidification tanks often operate in an anaerobic state, resulting in poorer hydrolysis acidification efficiency, reduced COD removal rate, and the generation of malodorous gases such as hydrogen sulfide and methane.

[0007] Therefore, although hydrolysis acidification technology has many advantages as mentioned above, its application is limited by the aforementioned problems in existing hydrolysis acidification tanks. How to ensure thorough and uniform mixing of activated sludge and wastewater in a fully mixed hydrolysis acidification tank, and how to automatically control dissolved oxygen in a microaerobic state, are urgent problems that environmental technicians need to solve. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing fully mixed hydrolysis acidification tanks, such as uneven mixing intensity of the stirring device, difficulty in maintaining the underwater stirring device, large footprint, and inability to control dissolved oxygen. This invention provides a fully mixed hydrolysis acidification tank and its treatment method with automatic dissolved oxygen control, which enables thorough and uniform mixing of wastewater and sludge, improving treatment efficiency; it can automatically control dissolved oxygen in a micro-oxygen state (DO 0.1~0.5 mg / L) to achieve optimal hydrolysis acidification effect; it also eliminates the need for a separate sedimentation tank, saving space; and it has no mechanical parts, requiring no daily maintenance.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is: a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control, characterized in that: the fully mixed hydrolysis acidification tank includes a hydrolysis acidification tank, a waste gas circulation system and a dissolved oxygen automatic control system, the hydrolysis acidification tank includes a covered water tank, and the water tank sequentially includes a rapid mixing zone, a hydrolysis acidification reaction zone, a sludge-water separation zone and a sludge lifting zone;

[0010] The waste gas recirculation system includes a blower, a first aerator located in the rapid mixing zone, a second aerator located in the hydrolysis acidification reaction zone, and an air lift pump located in the sludge lifting zone.

[0011] The dissolved oxygen automatic control system includes a blower frequency converter, a dissolved oxygen meter (DO) for measuring the dissolved oxygen content in the liquid in the hydrolysis acidification reaction zone, an exhaust gas regulating valve, an air regulating valve, an exhaust gas flow meter, an air flow meter, an air lift flow meter, a first aeration flow meter, a second aeration flow meter, and a controller.

[0012] The rapid mixing zone is connected to the hydrolysis and acidification reaction zone, the hydrolysis and acidification reaction zone is connected to the sludge-water separation zone, the sludge-water separation zone is connected to the sludge lifting zone, and the sludge lifting zone is connected to the rapid mixing zone.

[0013] The waste gas in the hydrolysis acidification reaction zone enters the inlet of the blower through the waste gas regulating valve and waste gas flow meter. The inlet of the blower also connects to the atmosphere after passing through the air flow meter and air regulating valve.

[0014] The blower outlet is divided into three paths: one path goes through the air lift flow meter and connects to the air lift pump; another path goes through the first aeration flow meter and connects to the first aerator; and the third path goes through the second aeration flow meter and connects to the second aerator.

[0015] The dissolved oxygen meter (DO), exhaust gas flow meter, air flow meter, first aeration flow meter, second aeration flow meter, air lift flow meter, exhaust gas regulating valve, and air regulating valve feed back information to the controller.

[0016] The controller controls the operation of the blower through the blower frequency converter;

[0017] The dissolved oxygen meter (DO) controls the operation of the air conditioning valve and the exhaust gas conditioning valve through a controller interlock.

[0018] Furthermore, the exhaust gas recirculation system also includes a gas collection hood, through which the exhaust gas in the hydrolysis acidification reaction zone enters the inlet of the blower via the gas collection hood, exhaust gas regulating valve and exhaust gas flow meter;

[0019] Furthermore, the rapid mixing zone and the hydrolysis acidification reaction zone are separated by a first partition wall, the hydrolysis acidification reaction zone and the sludge-water separation zone are separated by a second partition wall, the second partition wall is equipped with a flow stabilizing plate, and the sludge-water separation zone and the sludge lifting zone are separated by a third partition wall.

[0020] The gas phase spaces of the rapid mixing zone, hydrolysis acidification reaction zone, sludge-water separation zone, and sludge lifting zone are interconnected;

[0021] The and / or rapid mixing zone is equipped with a water distribution tank, which is connected to a water distribution pipe;

[0022] And / or the mud-water separation zone is equipped with an outlet weir, and the bottom of the mud-water separation zone is equipped with a cone-shaped hopper;

[0023] The inlet of the blower is also connected to an air duct, on which an air flow meter and an air regulating valve are installed. The end of the air duct is connected to the atmosphere via an air filter.

[0024] The sludge lifting area is equipped with a sludge trough, which is connected to the water distribution trough.

[0025] Furthermore, the cover plate of the hydrolysis acidification tank is equipped with an exhaust pipe. One end of the exhaust pipe is connected to the gas phase space inside the hydrolysis acidification tank, and the other end of the exhaust pipe is inserted below the liquid surface of the water seal tank. The tail gas C of the hydrolysis acidification tank is discharged from the water seal tank and enters the subsequent waste gas treatment system.

[0026] Furthermore, the first aerator is a perforated pipe, and several first aerators are evenly arranged at intervals on the bottom of the rapid mixing zone; the second aerator is a perforated pipe, and several second aerators are evenly arranged at intervals on the bottom of the hydrolysis acidification reaction zone; several small holes with a diameter of 5-10 mm are staggered at 45° on both sides below the perforated pipe.

[0027] Furthermore, the gas collection hood includes a flared opening, a demisting filter, and a connecting flange. The flared opening faces downwards, the demisting filter is positioned above the flared opening, and the connecting flange installs the gas collection hood onto the cover plate and the exhaust gas pipe. The exhaust gas pipe is connected to the exhaust gas regulating valve.

[0028] Furthermore, several flow holes with a diameter of 15-25mm are evenly distributed on the flow stabilizer plate;

[0029] And / or the controller is a programmable logic controller (PLC) or a distributed control system (DCS);

[0030] And / or the other end of the exhaust pipe is inserted 100-1000 mm below the liquid surface of the water seal pool.

[0031] A treatment method for a fully mixed hydrolysis acidification tank with automatically controlled dissolved oxygen, employing the aforementioned fully mixed hydrolysis acidification tank with automatically controlled dissolved oxygen, is characterized by comprising the following steps:

[0032] S1. Wastewater A to be treated enters the rapid mixing zone and is completely mixed with the sludge returned by the air lift pump under the stirring of the first aerator. The suspended solid organic matter and dissolved macromolecular organic matter in the wastewater are quickly intercepted and adsorbed by the activated sludge flocs.

[0033] S2. The mud-water mixture from the rapid mixing zone flows into the hydrolysis and acidification reaction zone. Under the stirring of the second aerator, the activated sludge remains in a suspended state. The adsorbed suspended solid organic matter and dissolved macromolecular organic matter are slowly decomposed by the obligate anaerobic bacteria and facultative acidifying bacteria in the activated sludge into easily biodegradable small molecules and volatile fatty acids, thus completing the hydrolysis and acidification process.

[0034] S3. The mixed liquor at the end of the hydrolysis acidification reaction zone enters the sludge-water separation zone. The supernatant after gravity separation is discharged as the effluent B from the hydrolysis acidification tank and enters the subsequent aerobic biological treatment facility; the sludge settles into the sludge lifting zone.

[0035] Meanwhile, the waste gas in the hydrolysis acidification tank enters the inlet of the blower; the inlet of the blower is also connected to an air duct, which is equipped with an air flow meter and an air regulating valve, and the end of the air duct is connected to the atmosphere; after the blower absorbs the waste gas and air, the blower outlet is divided into three paths: one path enters the air lift pump for lifting sludge; one path enters the first aerator for rapid mixing of wastewater and sludge; and the other path enters the second aerator for continuous mixing of wastewater and sludge and supplementation of oxygen.

[0036] S4. The air lift pump in the sludge lifting zone uses the gas from the blower outlet to lift the activated sludge to the rapid mixing zone. The lifted activated sludge and wastewater A enter the rapid mixing zone together.

[0037] In the above process, the blower frequency converter automatically adjusts the blower outlet air volume to be equal to the sum of the air lift flow meter, the first aeration flow meter, and the second aeration flow meter; the dissolved oxygen meter DO interlock controls the opening of the air regulating valve to keep the dissolved oxygen meter DO reading in a micro-oxygen state (0.1~0.5mg / L); the air flow meter continuously displays the air duct flow, and the controller adjusts the opening of the exhaust gas regulating valve to make the sum of the exhaust gas flow meter and the air flow meter equal to the blower outlet air volume.

[0038] A treatment method for a fully mixed hydrolysis acidification tank with automatically controlled dissolved oxygen, employing the aforementioned fully mixed hydrolysis acidification tank with automatically controlled dissolved oxygen, is characterized by comprising the following steps:

[0039] S1. Wastewater A to be treated enters the rapid mixing zone through the distribution tank and distribution pipe. Under the stirring of the first aerator, it is completely mixed with the sludge returned by the air lift pump. The suspended solid organic matter and dissolved macromolecular organic matter in the wastewater are quickly intercepted and adsorbed by the activated sludge flocs.

[0040] S2. The sludge-water mixture in the rapid mixing zone flows into the hydrolysis and acidification reaction zone from the upper part of the first partition wall. Under the stirring of the second aerator, the activated sludge is always in a suspended state. The adsorbed suspended solid organic matter and dissolved macromolecular organic matter are slowly decomposed by the obligate anaerobic bacteria and facultative acidifying bacteria in the activated sludge into easily biodegradable small molecules and volatile fatty acids, thus completing the hydrolysis and acidification process.

[0041] S3. The mixed liquid at the end of the hydrolysis acidification reaction zone enters the sludge-water separation zone through the flow stabilizer plate on the second partition wall. The supernatant after gravity separation is the effluent B from the hydrolysis acidification tank, which is discharged from the effluent weir and enters the subsequent aerobic biological treatment facility. The sludge settles into the cone bucket and enters the sludge lifting zone from the lower part of the third partition wall. At the same time, the exhaust gas in the hydrolysis acidification tank is collected by the gas collection hood and water mist is removed before entering the inlet of the blower. After the blower absorbs the exhaust gas and air, the blower outlet is divided into three paths: one path enters the air lift pump for lifting sludge; one path enters the first aerator for rapid mixing of sewage and sludge; and the other path enters the second aerator for continuous mixing of sewage and sludge and supplementation of oxygen.

[0042] S4. The air lift pump in the sludge lifting zone uses the gas from the blower outlet to lift the activated sludge to the sludge tank. The sludge tank is connected to the water distribution tank. The lifted activated sludge and wastewater A enter the rapid mixing zone together.

[0043] During the above process, the controller automatically adjusts the air volume at the blower outlet to be equal to the sum of the air lift flow meter, the first aeration flow meter, and the second aeration flow meter via the blower frequency converter; the opening of the air regulating valve is controlled by the dissolved oxygen meter DO interlock to keep the dissolved oxygen meter DO reading in a micro-oxygen state (0.1~0.5mg / L); the air flow meter continuously displays the flow rate of the air duct, and adjusts the opening of the exhaust gas regulating valve via the controller to make the sum of the exhaust gas flow meter and the air flow meter equal to the air volume at the blower outlet.

[0044] Furthermore, in step S1, the hydraulic retention time of wastewater in the rapid mixing zone is 10-60 min, and the aeration intensity provided by the aerator in the rapid mixing zone is 6-10 m³ / min. 3 / m 2 .h;

[0045] In step S2, the dissolved oxygen (DO) meter is installed in the hydrolysis acidification reaction zone; the second aerator provides an aeration intensity of 3-6 m³ / h. 3 / m 2 .h;

[0046] In step S4, the number of air-lift pumps can be one or more, and the ratio of the amount of returned sludge to the amount of wastewater is 0.5-10.

[0047] The number of holes in the first aerator and the number of holes in the second aerator are determined by calculation based on an orifice flow velocity of not less than 10 m / s.

[0048] The area and number of flow holes on the flow stabilizer plate are calculated based on a flow velocity of 0.15-0.2 m / s at the orifice.

[0049] In view of the above technical features, the present invention has the following advantages:

[0050] 1. This invention discloses an automatically controlled dissolved oxygen fully mixed hydrolysis acidification tank. It utilizes perforated aeration pipes (i.e., the first aerator and the second aerator) evenly arranged at the bottom of the tank to ensure uniform mixing intensity of wastewater and sludge within the tank. The perforated aeration pipe design of this invention replaces the existing fully mixed hydrolysis acidification tank's use of a stirring device for mixing wastewater and sludge. This overcomes the problems of uneven mixing intensity in existing stirring devices, where the near-end mixing intensity is very high, leading to easily broken sludge particles and reduced settling performance; while the far-end mixing intensity is too weak, resulting in uneven mud-water mixing, localized dead zones, blackened and foul-smelling sludge, and ultimately, poor hydrolysis acidification effect. Furthermore, because this invention does not include a stirring device, maintenance of the stirring device is unnecessary, overcoming the difficulty of maintaining underwater stirring devices.

[0051] 2. This invention discloses a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control. The hydrolysis acidification tank is a closed design. The exhaust gas from the hydrolysis acidification tank is pressurized by a blower and used as the gas source for mixing wastewater and sludge. When the exhaust gas is recycled, the oxygen content in the exhaust gas is low. Large-volume continuous aeration can ensure that the activated sludge is always in a suspended state without disrupting the anoxic environment of the hydrolysis acidification tank (DO < 0.5 mg / L). Therefore, it overcomes the problems of existing technologies that, when using air aeration for mixing, cannot achieve an anoxic environment if the air volume is large and continuous; if the air volume is reduced to meet the anoxic environment, the mixing intensity is insufficient, the activated sludge cannot fully contact the wastewater, and may even cause the activated sludge to settle at the bottom of the tank; if a large-volume intermittent aeration is used to prevent long-term deposition of activated sludge, the dissolved oxygen in the mixed liquid will fluctuate, which is not conducive to the growth and reproduction of hydrolysis acidification bacteria (obligatory anaerobic bacteria and facultative bacteria), which will inevitably reduce the hydrolysis acidification effect and even lead to system paralysis. Similarly, using recycled waste gas as the air source for the airlift pump, even when a large proportion of wastewater needs to be recirculated to reduce its toxicity, will not cause the phenomenon of excessive oxygen being introduced during airlift, thus avoiding damage to the hypoxic environment.

[0052] 3. This invention provides an automatically controlled dissolved oxygen fully mixed hydrolysis acidification tank. An air duct is connected to the blower inlet, and the amount of air drawn in by the blower is automatically controlled through an interlock between the dissolved oxygen meter and the air regulating valve on the air duct (i.e., the dissolved oxygen meter feeds back information to the controller, which then controls the opening of the air regulating valve). This method can flexibly adjust the air volume according to changes in the wastewater flow rate, water quality, and environment entering the hydrolysis acidification tank, maintaining dissolved oxygen in a microaerobic state (DO 0.1~0.5 mg / L). This prevents the tank from becoming an anaerobic environment, which can lead to sludge blackening, foul odor, disintegration, and floating. Furthermore, it increases the abundance and activity of the microbial community, thereby improving the hydrolysis acidification efficiency. When the wastewater volume or concentration increases, and organic matter is easily degraded, sludge grows rapidly. The hydrolysis and acidification process requires a certain amount of oxygen, so the airflow is automatically increased to prevent sludge from turning black, smelling foul, disintegrating, or floating due to long-term oxygen deficiency in the hydrolysis and acidification tank. Conversely, when the wastewater volume or concentration decreases, or when organic matter is difficult to degrade, the airflow needs to be automatically reduced to maintain the hydrolysis and acidification tank in a micro-aerobic state. Therefore, this overcomes the shortcomings of existing technologies that lack or cannot effectively control dissolved oxygen in a micro-aerobic state.

[0053] 4. This invention provides an automatically controlled dissolved oxygen fully mixed hydrolysis acidification tank with an added rapid mixing zone. Wastewater entering the hydrolysis acidification tank mixes rapidly with the returned high-concentration activated sludge in a small but highly aerated space. This allows particulate and colloidal organic matter and dissolved macromolecular organic matter in the wastewater to be quickly trapped and adsorbed by the activated sludge flocs. Then, in the hydrolysis acidification reaction zone, they are slowly decomposed and metabolized into easily biodegradable small molecules. Because the rapid mixing zone accelerates the adsorption of organic matter by the sludge, it shortens the hydraulic retention time required for the hydrolysis acidification tank, reduces its volume, and saves floor space.

[0054] 5. The present invention provides a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control. The hydrolysis acidification tank is divided into four areas: a rapid mixing zone, a hydrolysis acidification reaction zone, a sludge-water separation zone, and a sludge lifting zone. The hydrolysis acidification tank has a simple structure and occupies a small area. It does not require a separate sedimentation tank to complete the sludge-water separation, thus achieving the goal of eliminating the need for a separate sedimentation tank and saving space.

[0055] In summary, the fully mixed hydrolysis acidification tank and its treatment method with automatic dissolved oxygen control of the present invention represent a disruptive innovation over existing hydrolysis acidification tanks. This will greatly promote the application of hydrolysis acidification technology, thereby significantly reducing energy consumption, land occupation, and investment in wastewater treatment plants. Attached Figure Description

[0056] Figure 1This is a schematic diagram of the structure of a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control and a flowchart of its treatment method in Specific Embodiment 1.

[0057] Figure 2 This is a plan view of the hydrolysis acidification tank in Specific Embodiment 1.

[0058] Figure 3 yes Figure 2 Section I-I.

[0059] Figure 4 This is a schematic diagram of the gas collection hood in specific embodiment 1.

[0060] Figure 5 This is a schematic diagram of the perforated tube (i.e., the first aerator and the second aerator) in specific embodiment 1.

[0061] Figure 6 yes Figure 5 A cross-sectional view of a perforated pipe.

[0062] In the diagram: 1. Rapid mixing zone; 1-1. Water distribution tank; 1-2. Water distribution pipe; 1-3. Partition wall 1; 2. Hydrolysis acidification reaction zone; 2-1. Partition wall 2; 2-2. Flow stabilizer plate; 3. Sludge-water separation zone; 3-1. Effluent weir; 3-2. Conical hopper; 3-3. Partition wall 3; 4. Sludge lifting zone; 4-1. Sludge tank; 5. Gas collection hood; 5-1. Trumpet mouth; 5-2. Demisting filter; 5-3. Connecting flange; 6. Blower; 6-1. Blower frequency converter; 7-1. First aerator (corresponding to rapid mixing zone) 7-2. Second aerator (corresponding to the hydrolysis acidification reaction zone); 7-3. Small orifice; 8. Air lift pump; 9. Dissolved oxygen meter; 10-1. Exhaust gas regulating valve; 10-2. Air regulating valve; 11-1. Exhaust gas flow meter; 11-2. Air flow meter; 11-3. Air lift flow meter; 11-4. First aeration flow meter (corresponding to the rapid mixing zone); 11-5. Second aeration flow meter (corresponding to the hydrolysis acidification zone); 12. Controller; 13. Air filter; 14. Exhaust pipe; 15. Water seal tank; 16. Cover plate;

[0063] A. Wastewater to be treated; B. Effluent from the hydrolysis acidification tank; C. Exhaust gas emissions. Detailed Implementation

[0064] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0065] See Figures 1 to 6Specific embodiment 1, this embodiment 1 provides a fully mixed hydrolysis acidification tank with automatic control of dissolved oxygen. The fully mixed hydrolysis acidification tank includes a hydrolysis acidification tank, an exhaust gas circulation system and a dissolved oxygen automatic control system. The hydrolysis acidification tank includes a water tank with a cover plate 16. The water tank includes a rapid mixing zone 1, a hydrolysis acidification reaction zone 2, a sludge-water separation zone 3 and a sludge lifting zone 4 in sequence.

[0066] Preferably, the rapid mixing zone 1 is provided with a water distribution tank 1-1, which is connected to a water distribution pipe 1-2; the mud-water separation zone 3 is provided with an outlet weir 3-1, and the bottom of the mud-water separation zone 3 is provided with a cone hopper 3-2, which is conducive to sludge sedimentation; the sludge lifting zone 4 is provided with a sludge trough 4-1, which is connected to the water distribution tank 1-1.

[0067] The exhaust gas recirculation system includes a blower 6, a first aerator 7-1 located in the rapid mixing zone 1, a second aerator 7-2 located in the hydrolysis acidification reaction zone 2, and an air lift pump 8 located in the sludge lifting zone 4. The air lift pump 8 is used to lift sludge.

[0068] Preferably, the first aerator 7-1 is a perforated pipe, and several first aerators 7-1 are evenly spaced at the bottom of the rapid mixing zone 1 for rapid mixing of sewage and sludge; the second aerator 7-2 is a perforated pipe, and several second aerators 7-2 are evenly spaced at the bottom of the hydrolysis acidification reaction zone 2 for continuous mixing of sewage and sludge and oxygen replenishment; several small holes 7-3 with a diameter of 5-10 mm are staggered at 45° on both sides below the perforated pipe. The evenly spaced first aerators 7-1 and second aerators 7-2 make the mixing intensity of sewage and sludge more uniform, the sludge-water mixing effect better, and avoid the formation of local dead zones, preventing sludge from turning black and smelly, and improving the hydrolysis acidification effect. The first aerator 7-1 provides a high-intensity airflow to the rapid mixing zone 1, which can remove the aging layer on the surface of activated sludge particles, that is, it plays a role in activating activated sludge flocs and improving the hydrolysis acidification efficiency. However, gas agitation will not break sludge particles like a mixer. The fully mixed hydrolysis acidification tank with automatic dissolved oxygen control has no risk of clogging in the first aerator 7-1, the second aerator 7-2, and the air lift pump 8, and requires no maintenance.

[0069] Preferably, the exhaust gas recirculation system also includes a gas collection hood 5, through which the exhaust gas in the hydrolysis acidification reaction zone 2 enters the inlet of the blower 6 via the gas collection hood 5, the exhaust gas regulating valve 10-1 and the exhaust gas flow meter 11-1.

[0070] Preferably, the gas collection hood 5 includes a flared mouth 5-1, a demisting filter 5-2, and a connecting flange 5-3. The connecting flange 5-3 installs the gas collection hood 5 on the cover plate 16 and the exhaust gas pipe. The exhaust gas pipe is connected to the exhaust gas regulating valve 10-1. The flared mouth 5-1 of the gas collection hood 5 faces downward. The exhaust gas in the hydrolysis acidification tank (i.e., the hydrolysis acidification reaction zone 2) is collected by the flared mouth 5-1, and the water mist is removed by the demisting filter 5-2 above the flared mouth 5-1, so that it can enter the inlet of the blower 5 later.

[0071] The dissolved oxygen automatic control system includes a blower frequency converter 6-1, a dissolved oxygen meter DO9 for measuring the dissolved oxygen content in the liquid in the hydrolysis acidification reaction zone 2, an exhaust gas regulating valve 10-1, an air regulating valve 10-2, an exhaust gas flow meter 11-1, an air flow meter 11-2, an air lift flow meter 11-3, a first aeration flow meter 11-4, a second aeration flow meter 11-5, and a controller 12, which is a programmable logic controller (PLC) or a distributed control system (DCS).

[0072] Preferably, the dissolved oxygen meter DO9 reading can be in any range between 0.1-0.5 mg / L, depending on the nature of the different wastewater.

[0073] Rapid mixing zone 1 is connected to hydrolysis acidification reaction zone 2, hydrolysis acidification reaction zone 2 is connected to sludge-water separation zone 3, sludge-water separation zone 3 is connected to sludge lifting zone 4, and sludge lifting zone 4 is connected to rapid mixing zone 1.

[0074] Preferably, the rapid mixing zone 1 and the hydrolysis acidification reaction zone 2 are separated by a first partition wall 1-3, the hydrolysis acidification reaction zone 2 and the sludge-water separation zone 3 are separated by a second partition wall 2-1, and a flow stabilizing plate 2-2 is provided on the second partition wall. The sludge-water separation zone 3 and the sludge lifting zone 4 are separated by a third partition wall 3-3. The fully mixed hydrolysis acidification tank with automatic dissolved oxygen control in this embodiment 1 is a rectangular tank that, through reasonable layout and structural design, is divided into four zones: the rapid mixing zone 1, the hydrolysis acidification reaction zone 2, the sludge-water separation zone 3, and the sludge lifting zone 4. This completes the entire process of mixing wastewater and activated sludge, hydrolysis acidification of organic matter, sedimentation separation of activated sludge, and lifting and recirculation. It has the advantages of simple structure and small footprint. It overcomes the disadvantages of existing fully mixed hydrolysis acidification tanks that require a separate sedimentation tank for sludge-water separation, resulting in a more complex process and larger footprint.

[0075] In addition, a rapid mixing zone 1 was added. Wastewater entering the hydrolysis acidification tank is rapidly mixed with the returned high-concentration activated sludge in a small space with high aeration intensity. This allows particulate and colloidal organic matter and dissolved macromolecular organic matter in the wastewater to be quickly trapped and adsorbed by the activated sludge flocs. Then, in the hydrolysis acidification reaction zone, they are slowly decomposed and metabolized into easily biodegradable small molecules. Because the rapid mixing zone 1 accelerates the adsorption of organic matter by the sludge, the hydraulic retention time required in the hydrolysis acidification tank is shortened, reducing the tank's volume and saving floor space.

[0076] Preferably, the flow stabilizer plate 2-2 has several flow holes with a diameter of 15-25mm evenly distributed on it.

[0077] Preferably, the gas phase spaces of the rapid mixing zone 1, the hydrolysis acidification reaction zone 2, the sludge-water separation zone 3, and the sludge lifting zone 4 are interconnected.

[0078] The waste gas in the hydrolysis acidification reaction zone 2 enters the inlet of the blower 6 through the waste gas regulating valve 10-1 and the waste gas flow meter 11-1. The inlet of the blower 6 also connects to the atmosphere after passing through the air flow meter 11-2 and the air regulating valve 10-2.

[0079] Preferably, the inlet of the blower 6 is also connected to an air duct, on which an air flow meter 11-2 and an air regulating valve 10-2 are installed. The end of the air duct is connected to the atmosphere via an air filter 13. The air filter 13 is used to filter the air entering the air duct to prevent debris (including small animals) from entering the blower 6.

[0080] The outlet of blower 6 is divided into three paths: one path is connected to air lift pump 8 via air lift flow meter 11-3, another path is connected to first aerator 7-1 via first aeration flow meter 11-4, and the third path is connected to second aerator 7-2 via second aeration flow meter 11-5.

[0081] Preferably, corresponding regulating valves can be added between the outlet of blower 6 and air lift flow meter 11-3, between the outlet of blower 6 and first aeration flow meter 11-4, and between the outlet of blower 6 and second aeration flow meter 11-5. The corresponding regulating valves are controlled by controller 12. The air output of the three outlets of blower 6 can be controlled simultaneously or individually through the corresponding regulating valves, which also helps to improve the accuracy of the statistical data of air lift flow meter 11-3, first aeration flow meter 11-4 and second aeration flow meter 11-5.

[0082] Dissolved oxygen meter DO9, waste gas flow meter 11-1, air flow meter 11-2, first aeration flow meter 11-4, second aeration flow meter 11-5 and air lift flow meter 11-3 feed back information to controller 12;

[0083] The controller 12 controls the operation of the blower 6 through the blower frequency converter 6-1;

[0084] The controller 12 controls the operation of the exhaust gas regulating valve 10-1, the air regulating valve 10-2, and the air lift pump 8;

[0085] The dissolved oxygen meter DO9 controls the operation of the air regulating valve 10-2 and the exhaust gas regulating valve 10-1 through the controller 12.

[0086] Preferably, the cover plate 16 of the hydrolysis acidification tank is provided with an exhaust pipe 14. One end of the exhaust pipe 14 is connected to the gas phase space inside the hydrolysis acidification tank, and the other end of the exhaust pipe 14 is inserted below the liquid surface of the water seal tank 15. The tail gas C of the hydrolysis acidification tank is discharged from the water seal tank 15 and enters the subsequent waste gas treatment system to prevent overpressure in the hydrolysis acidification tank. For example, the other end of the exhaust pipe 14 is inserted 100-1000 mm below the liquid surface of the water seal tank 15, so that a slight positive pressure is formed in the hydrolysis acidification tank, and the gas phase space of the hydrolysis acidification tank is isolated from the atmosphere, which has the advantage of no waste gas pollution.

[0087] A treatment method for a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control includes the following steps:

[0088] S1. Wastewater A to be treated enters the rapid mixing zone 1 through the distribution tank 1-1 and distribution pipe 1-2. Under the stirring of the first aerator 7-1, it is completely mixed with the sludge returned by the air lift pump 8. Suspended solid organic matter and dissolved macromolecular organic matter in the wastewater are rapidly intercepted and adsorbed by the activated sludge flocs. The hydraulic retention time of the wastewater in the rapid mixing zone 1 is 10-60 minutes. In order to achieve the effect of rapid mixing, the aeration intensity provided by the aerator 7-1 in the rapid mixing zone is 6-10 m³ / min, depending on the retention time. 3 / m 2 The number of small holes 7-3 in the first aerator 7-1 is determined by calculating that the flow velocity at the orifice is not less than 10m / s.

[0089] S2. The sludge-water mixture in the rapid mixing zone 1 flows into the hydrolysis-acidification reaction zone 2 from the upper part of the first partition wall 1-3. Under the stirring of the second aerator 7-2, the activated sludge remains in a suspended state. The adsorbed suspended solid organic matter and dissolved macromolecular organic matter are slowly decomposed by the obligate anaerobic bacteria and facultative acidifying bacteria in the activated sludge into easily biodegradable small molecules and volatile fatty acids, completing the hydrolysis-acidification process. The dissolved oxygen meter DO9 is installed in the hydrolysis-acidification reaction zone 2. The aeration intensity of the equalization tank is 1.5-3.0 m. 3 / m 2Because the sludge concentration in the hydrolysis acidification tank is as high as 4-8 g / L, a relatively high aeration intensity is required to maintain the activated sludge in a suspended state. The aeration intensity provided by the second aerator 7-2 is 3-6 m³ / h, depending on the sludge concentration. 3 / m 2 The number of small holes 7-3 in the second aerator 7-2 is determined by calculation based on an orifice flow velocity of not less than 10m / s.

[0090] S3. The mixed liquid at the end of the hydrolysis acidification reaction zone 2 enters the sludge-water separation zone 3 through the flow stabilizer plate 2-2 on the second partition wall 2-1. The supernatant after gravity separation is the effluent B of the hydrolysis acidification tank, which is discharged from the effluent weir 3-1 and enters the subsequent aerobic biological treatment facility. The sludge settles into the cone hopper 3-2 and enters the sludge lifting zone 4 from the lower part of the third partition wall 3-3. At the same time, the exhaust gas in the hydrolysis acidification tank is collected by the gas collection hood 5 and the water mist is removed before entering the inlet of the blower 6. After absorbing waste gas and air, the outlet of blower 6 is divided into three paths: one path enters the air lift pump 8 for lifting sludge; one path enters the first aerator 7-1 for rapid mixing of sewage and sludge; and the other path enters the second aerator 7-2 for continuous mixing of sewage and sludge and supplementation of oxygen. The area and number of flow holes on the flow stabilizer plate 2-2 are determined according to the flow velocity at the orifice is 0.15-0.2m / s, and the diameter of the flow holes on the flow stabilizer plate 2-2 is 15-25mm.

[0091] The fully mixed hydrolysis acidification tank with automatic dissolved oxygen control in Example 1 is a closed structure. The exhaust gas from the hydrolysis acidification tank, pressurized by a blower, serves as the gas source for mixing wastewater and sludge. During exhaust gas recycling, the oxygen content in the exhaust gas is extremely low. Continuous aeration keeps the activated sludge in suspension without disrupting the anoxic environment of the hydrolysis acidification tank. Furthermore, the amount of air drawn in by the blower is automatically controlled via an interlock between the dissolved oxygen meter DO9 and the air regulating valve 10-2, maintaining the dissolved oxygen in the hydrolysis acidification tank at a micro-oxygen level. The collected exhaust gas returns to the bottom of the tank. This prevents the emission of malodorous gases and environmental pollution. During the waste gas recycling process, most of the malodorous substances, such as volatile organic compounds, hydrogen sulfide, and ammonia, are re-dissolved in the wastewater and repeatedly adsorbed, degraded, oxidized, or reduced by the activated sludge, significantly reducing the load on the exhaust gas treatment facilities.

[0092] S4. The air lift pump 8 in the sludge lifting zone 4 uses the outlet gas of the blower 6 to lift the activated sludge to the sludge tank 4-1. The sludge tank 4-1 is connected to the water distribution tank 1-1. The lifted activated sludge and sewage A enter the rapid mixing zone 1 together. The number of air lift pumps 8 can be one or more, and the ratio of the amount of returned sludge to the amount of sewage is 0.5-10.

[0093] During the above process, the controller 12 automatically adjusts the air volume at the outlet of the blower 6 to be equal to the sum of the air lift flow meter 11-3, the first aeration flow meter 11-4, and the second aeration flow meter 11-5 through the blower frequency converter 6-1; the opening of the air regulating valve 10-2 is controlled by the dissolved oxygen meter DO9 (i.e., the amount of air drawn in by the blower is automatically controlled), so that the reading of the dissolved oxygen meter DO9 is controlled in a micro-oxygen state of 0.1 to 0.5 mg / L; the air flow meter 11-2 continuously displays the flow rate of the air duct, and adjusts the opening of the exhaust gas regulating valve 10-1 through the controller 12, so that the sum of the exhaust gas flow meter 11-1 and the air flow meter 11-2 is equal to the air volume at the outlet of the blower 6.

[0094] An air duct is connected to the inlet of blower 5, and the amount of air drawn into the blower is automatically controlled through the interlock between dissolved oxygen meter DO9 and air regulating valve 10-2. This allows for flexible adjustment of the air volume based on changes in wastewater flow rate, water quality, and environment entering the hydrolysis acidification tank, maintaining dissolved oxygen in a micro-oxygen state, increasing the abundance and activity of the microbial community, and thus improving the hydrolysis acidification efficiency. When the wastewater concentration is high and organic matter is easily degraded, sludge growth is rapid, and the hydrolysis acidification process requires a certain amount of oxygen. In this case, the air flow rate is automatically increased to prevent sludge from turning black, smelling foul, disintegrating, or floating due to long-term oxygen deficiency in the hydrolysis acidification tank. Conversely, when the wastewater concentration is low or organic matter is difficult to degrade, the air flow rate is automatically reduced to maintain the hydrolysis acidification tank in a micro-oxygen state.

[0095] Example 1: Influent (i.e., wastewater A to be treated) Taking the wastewater from a certain aniline / nitrobenzene combined unit as an example, the wastewater flow rate Q = 150 m³ / h 3 / h, COD Cr The wastewater contains nitrogen-containing organic compounds such as aniline, nitrobenzene, and nitrophenol, which are stable nitrogenous compounds with benzene rings. Nitrophenol and nitrobenzene are highly toxic to microorganisms, and the B / C ratio is only 0.19, classifying it as difficult to biodegrade. The above wastewater was treated using a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control and the treatment method described in Example 1. Specific parameters and calculation procedures are as follows:

[0096] 1. Determination of parameters for hydrolysis acidification tank

[0097] 1) Rapid mixing zone 1

[0098] Stay duration: 20 min

[0099] Effective water depth: 5m

[0100] Area: 10m² 2

[0101] Effective volume: 50m³ 3

[0102] 2) Hydrolysis and acidification reaction zone 2

[0103] Duration of stay: 8 hours

[0104] Effective water depth: 5m

[0105] Area: 240m² 2

[0106] Effective volume: 1200m³ 3

[0107] sludge concentration: 6 g / L

[0108] 3) Slurry-water separation zone 3

[0109] Duration of stay: 2 hours

[0110] Effective volume: 300m³ 3

[0111] 4) Sludge Enhancement Zone 4

[0112] Stay duration: 10 min

[0113] Effective volume: 25m³ 3

[0114] 2. Blower air volume calculation

[0115] Calculation of the output air volume of blower 6:

[0116] Q 风 =Q1+Q2+Q3…………(1)

[0117] In the formula:

[0118] Q 风 —Rated air volume of the blower, m 3 / h;

[0119] Q1—Required aeration volume for rapid mixing zone 1, m³ 3 / h;

[0120] Q2—Required aeration volume (m³) for hydrolysis acidification reaction zone 2 3 / h;

[0121] Q3—Required airlift volume for airlift pump 8, m 3 / h;

[0122] 1) Required aeration air volume for rapid mixing zone 1

[0123] Q1=q1×S1…………(2)

[0124] In the formula:

[0125] q1—Aeration intensity provided by the rapid mixing zone aerator 7-1, taken as 8 m 3 / m 2 .h;

[0126] S1—The bottom area of ​​the rapid mixing zone 1, in m² 2 ;

[0127] Therefore, Q1 = 8 × 10 = 80 m 3 / h

[0128] 2) Required aeration air volume for hydrolysis acidification reaction zone 2

[0129] Q2=q2×S2…………(3)

[0130] In the formula:

[0131] q2—Aeration intensity provided by aerator 7-2 in the hydrolysis acidification reaction zone, taken as 4.5 m. 3 / m 2 .h;

[0132] S2—The bottom area of ​​hydrolysis and acidification reaction zone 2, in m² 2 ;

[0133] Therefore, Q2 = 4.5 × 240 = 1080 m 3 / h

[0134] 3) Air volume required for airlift pump 8

[0135] According to the air consumption calculation formula for pneumatic lifting sludge return in Volume 5 of the "Water Supply and Drainage Design Manual":

[0136] …………(4)

[0137] In the formula:

[0138] K—Safety factor, taken as 1.1-1.2;

[0139] H—The intended lifting height of the mixture, taken as 0.3 m;

[0140] h—Immersion depth at the gas outlet of the air lift pump 8, taken as 2.0 m;

[0141] η—efficiency coefficient, typically 0.35-0.45;

[0142] Q w —Sludge return flow rate, Q w =w×Q,m 3 / h;

[0143] Q—Wastewater flow rate, 150 m³ / h 3 / h;

[0144] w—the ratio of the amount of returned sludge to the amount of wastewater, taken as 4;

[0145] Substituting the above parameters into equation (4), we get Q3 = 296.5 m. 3 / h

[0146] Then, the air volume Q of the blower 风 =80 + 1080 + 296.5 = 1456.5 m 3 / h, of which the aeration air volume (Q1 + Q2) is 1160m³ / h. 3 / h.

[0147] 3. Calculation of the actual air volume required for the hydrolysis acidification tank

[0148] The aeration volume mentioned above can be functionally divided into three parts: (i) the air volume required for facultative bacterial respiration (G1), which depends on the nature of the wastewater, site conditions, and the characteristics of the microorganisms in the tank, and is a variable in actual operation. In this example, it is assumed that this air volume accounts for 20% of the total aeration volume; (ii) the air volume required to maintain the microaerobic state in the tank (G S (iii) The gas volume used only for mud-water mixing, i.e., the circulating waste gas volume (G2), serves as a supplement when the first two air volumes cannot meet the aeration intensity requirements. For existing technologies, G2=0, the aeration air volume is all air. Under continuous aeration with this air volume, the dissolved oxygen in the tank can reach 4.97 mg / L (second column on the left of Table 1), which obviously cannot meet the conditions for hydrolysis acidification. When using this invention (first column on the left of Table 1), when G S 20 m 3 / h, meaning the total air supply is 232 + 20 = 252m³. 3 / h, the circulating waste gas volume is 908 m³ 3 At a rate of / h, the dissolved oxygen in the tank can be maintained between 0.2-0.3 mg / L, which meets the conditions for micro-aerobic hydrolysis acidification.

[0149] Table 1

[0150]

[0151] It should be noted that the effectiveness of biological treatment is affected by factors such as wastewater volume, water quality, temperature, air pressure, and operational management. Any calculations are only estimates, and the air supply needs to be adjusted accordingly based on changes in actual conditions. Therefore, it is essential to use an automatic dissolved oxygen control air regulating valve 10-2 installed inside the hydrolysis acidification reactor 2 to regulate the opening.

[0152] The other end of the exhaust pipe 14 is inserted 300 mm below the liquid surface of the water seal pool 15;

[0153] The diameter of the small holes 7-3 on the perforated pipe is 8 mm; the flow velocity at the orifice is 10.5 m / s.

[0154] The diameter of the flow passage on the flow stabilizer plate 2-2 is 20mm; the flow velocity at the orifice is 0.15m / s.

[0155] After treatment in the hydrolysis acidification tank using the above method, the COD of the effluent (i.e., effluent B from the hydrolysis acidification tank) is... Cr The concentration of BOD5 was 854 mg / L, with a removal rate of 29%. Due to the hydrolysis of recalcitrant large organic molecules into smaller ones, the biodegradability of the wastewater was significantly improved, with the B / C ratio increasing to 0.29. The effluent BOD5 was approximately 250.6 mg / L, slightly higher than the initial value. This BOD5 was easily removed in the subsequent aerobic biological treatment tank – precisely the purpose of the hydrolysis acidification tank. During the hydrolysis acidification process, ammonia nitrogen and total nitrogen also decreased slightly, mainly due to their use in microbial cell synthesis. The effluent NH3-N was 51.7 mg / L, TN was 83 mg / L, and SS was less than 100 mg / L. Excellent results were achieved.

[0156] The statistics of influent and effluent water quality and treatment effect are as follows:

[0157]

[0158] Example of scenario two: The influent (i.e., wastewater A to be treated) is wastewater from an oil refinery, with a designed wastewater flow rate Q = 350 m³ / s. 3 / h, COD Cr The wastewater has the following concentrations: 800 mg / L, BOD5: 200 mg / L, SS: 150 mg / L, NH3-N: 20 mg / L, TN: 70 mg / L. While the B / C ratio is acceptable, the wastewater contains recalcitrant organic matter such as benzene compounds and phenols. Hydrolysis acidification is used as a pretreatment for aerobic biological treatment to save energy. The above wastewater is treated using the "Automatically Controlled Dissolved Oxygen Completely Mixed Hydrolysis Acidification Tank and Treatment Method" described in Example 1, with the following specific parameters:

[0159] 1. Determination of parameters for hydrolysis acidification tank

[0160] 1) Rapid mixing zone 1

[0161] Stay duration: 10 min

[0162] Effective water depth: 5m

[0163] Area: 11.7m² 2

[0164] Effective volume: 58m³ 3

[0165] 2) Hydrolysis and acidification reaction zone 2

[0166] Duration of stay: 6 hours

[0167] Effective water depth: 5m

[0168] Area: 420m² 2

[0169] Effective volume: 2100m³ 3

[0170] sludge concentration: 4 g / L

[0171] 3) Slurry-water separation zone 3

[0172] Duration of stay: 2 hours

[0173] Effective volume: 700m³ 3

[0174] 4) Sludge Enhancement Zone 4

[0175] Stay duration: 10 min

[0176] Effective volume: 58m³ 3

[0177] 2. Blower air volume calculation

[0178] Parameter values:

[0179] The rapid mixing zone aerator 7-1 provides an aeration intensity of 6 m³ / s. 3 / m 2 .h;

[0180] The aeration intensity provided by aerator 7-2 in the hydrolysis acidification reaction zone is 3 m³ / s. 3 / m 2 .h;

[0181] The ratio of returned sludge volume to wastewater volume is 2;

[0182] Using the same formula as in Example 1, Q1, Q2, and Q3 are calculated to be 70, 1260, and 346m respectively. 3 / h, the air volume Q of the blower 风 =70+1260+346=1676 m 3 / h, of which the aeration air volume (Q1 + Q2) is 1330 m³ / h. 3 / h.

[0183] 3. Calculation of the actual air volume required for the hydrolysis acidification tank

[0184] Assuming that the air volume required for facultative bacteria respiration (G1) accounts for 15% of the total aeration air volume, using the same method as illustrating case one, it can be concluded that when G... S 50 m 3 / h, meaning the total air supply is 200 + 50 = 250m³. 3 / h, circulating waste gas volume is 1080m³ 3 At a rate of / h, the dissolved oxygen in the tank can be maintained between 0.3-0.4 mg / L, which meets the conditions for micro-aerobic hydrolysis acidification, as detailed in Table 2.

[0185] Table 2

[0186]

[0187] After treatment in the hydrolysis acidification tank using the above method, the COD of the effluent (i.e., effluent B from the hydrolysis acidification tank) is... Cr The concentration was 551.5 mg / L, with a removal rate of 31%; the B / C ratio increased from 0.25 to 0.35, achieving a very good hydrolysis and acidification effect.

[0188] The statistics of influent and effluent water quality and treatment effect are as follows:

[0189]

[0190] Example of scenario three: The influent (i.e., wastewater A to be treated) is wastewater from a new material production unit, with a designed wastewater flow rate Q = 10 m³ / s. 3 / h, COD Cr The wastewater contains highly biotoxic organic compounds such as tetrahydrofuran, making it very difficult to treat. The wastewater was treated using the "Automatically Controlled Dissolved Oxygen Completely Mixed Hydrolysis Acidification Tank and Treatment Method Thereof" described in Example 1 of this paper, with the following specific parameters: 2000 mg / L BOD5, 250 mg / L SS, 100 mg / L NH3-N, 50 mg / L TN, 300 mg / L.

[0191] 1. Determination of parameters for the hydrolysis acidification tank

[0192] 1) Rapid mixing zone 1

[0193] Stay duration: 60 min

[0194] Effective water depth: 5m

[0195] Area: 2m 2

[0196] Effective volume: 10m³ 3

[0197] 2) Hydrolysis and acidification reaction zone 2

[0198] Duration of stay: 15 hours

[0199] Effective water depth: 5m

[0200] Area: 30m² 2

[0201] Effective volume: 150m³ 3

[0202] sludge concentration: 8g / L

[0203] 3) Slurry-water separation zone 3

[0204] Duration of stay: 3 hours

[0205] Effective volume: 30m³ 3

[0206] 4) Sludge Enhancement Zone 4

[0207] Stay duration: 30 min

[0208] Effective volume: 5m³ 3

[0209] 2. Blower air volume calculation

[0210] Parameter values:

[0211] The rapid mixing zone aerator 7-1 provides an aeration intensity of 10 m³ / s. 3 / m 2 .h;

[0212] The aeration intensity provided by aerator 7-2 in the hydrolysis acidification reaction zone is 6 m³ / s. 3 / m 2 .h;

[0213] The ratio of returned sludge to wastewater is 10.

[0214] Using the same formula as in Example 1, Q1, Q2, and Q3 are calculated to be 20, 180, and 49m respectively. 3 / h, the air volume Q of the blower 风 =20+180+49=249 m 3 / h, of which the aeration air volume (Q1 + Q2) is 200 m³ / h. 3 / h.

[0215] 3. Calculation of the actual air volume required for the hydrolysis acidification tank

[0216] Assuming that the air volume required for respiration by facultative bacteria (G1) accounts for 30% of the total aeration air volume, using the same method as illustrating case one, it can be concluded that when G... S 25 m 3 / h, meaning the total air supply is 60 + 25 = 85m³.3 / h, circulating waste gas volume is 115m³ 3 At a rate of / h, the dissolved oxygen in the tank can be maintained between 0.1-0.2 mg / L, which meets the conditions for micro-aerobic hydrolysis acidification, as detailed in Table 3.

[0217] Table 3

[0218]

[0219] After treatment in the hydrolysis acidification tank using the above method, the COD of the effluent (i.e., effluent B from the hydrolysis acidification tank) is... Cr The concentration was 1297.5 mg / L, with a removal rate of 35%; the B / C ratio increased from 0.125 to 0.26, an increase of 108%, achieving a better hydrolysis and acidification effect and greatly reducing the difficulty of subsequent biochemical treatment.

[0220] The statistics of influent and effluent water quality and treatment effect are as follows:

[0221]

[0222] The fully mixed hydrolysis acidification tank and its treatment method with automatic dissolved oxygen control in Embodiment 1 are applicable to the biological pretreatment of various organic wastewaters, especially suitable for wastewater with large flow rates and high content of suspended solids and recalcitrant organic matter, which can greatly improve the B / C ratio. Embodiment 2 provides a fully mixed hydrolysis acidification tank with automatic dissolved oxygen control. This fully mixed hydrolysis acidification tank includes a hydrolysis acidification tank, a waste gas circulation system, and a dissolved oxygen automatic control system. The hydrolysis acidification tank includes a water tank with a cover plate 16, which sequentially includes a rapid mixing zone 1, a hydrolysis acidification reaction zone 2, a sludge-water separation zone 3, and a sludge lifting zone 4.

[0223] The exhaust gas recirculation system includes a blower 6, a first aerator 7-1 located in the rapid mixing zone 1, a second aerator 7-2 located in the hydrolysis acidification reaction zone 2, and an air lift pump 8 located in the sludge lifting zone 4.

[0224] The dissolved oxygen automatic control system includes a blower frequency converter 6-1, a dissolved oxygen meter DO9 for measuring the dissolved oxygen content in the liquid in the hydrolysis acidification reaction zone 2, an exhaust gas regulating valve 10-1, an air regulating valve 10-2, an exhaust gas flow meter 11-1, an air flow meter 11-2, an air lift flow meter 11-3, a first aeration flow meter 11-4, a second aeration flow meter 11-5, and a controller 12;

[0225] Rapid mixing zone 1 is connected to hydrolysis acidification reaction zone 2, hydrolysis acidification reaction zone 2 is connected to sludge-water separation zone 3, sludge-water separation zone 3 is connected to sludge lifting zone 4, and sludge lifting zone 4 is connected to rapid mixing zone 1.

[0226] The waste gas in the hydrolysis acidification reaction zone 2 enters the inlet of the blower 6 through the waste gas regulating valve 10-1 and the waste gas flow meter 11-1. The inlet of the blower 6 also connects to the atmosphere after passing through the air flow meter 11-2 and the air regulating valve 10-2.

[0227] The outlet of blower 6 is divided into three paths: one path is connected to air lift pump 8 via air lift flow meter 11-3, another path is connected to first aerator 7-1 via first aeration flow meter 11-4, and the third path is connected to second aerator 7-2 via second aeration flow meter 11-5.

[0228] Dissolved oxygen meter DO9, waste gas flow meter 11-1, air flow meter 11-2, first aeration flow meter 11-4, second aeration flow meter 11-5 and air lift flow meter 11-3 feed back information to controller 12;

[0229] The controller 12 controls the operation of the blower 6 through the blower frequency converter 6-1;

[0230] The controller 12 controls the operation of the exhaust gas regulating valve 10-1, the air regulating valve 10-2, and the air lift pump 8;

[0231] The treatment method of the fully mixed hydrolysis acidification tank with automatic dissolved oxygen control in this embodiment 2, using the above-mentioned fully mixed hydrolysis acidification tank with automatic dissolved oxygen control, is characterized by including the following steps:

[0232] S1. Wastewater A to be treated enters the rapid mixing zone 1. Under the stirring of the first aerator 7-1, it is completely mixed with the sludge returned by the air lift pump 8. The suspended solid organic matter and dissolved macromolecular organic matter in the wastewater are quickly intercepted and adsorbed by the activated sludge flocs.

[0233] S2. The sludge-water mixture from the rapid mixing zone 1 flows into the hydrolysis and acidification reaction zone 2. Under the stirring of the second aerator 7-2, the activated sludge is always in a suspended state. The adsorbed suspended solid organic matter and dissolved macromolecular organic matter are slowly decomposed by the obligate anaerobic bacteria and facultative acidifying bacteria in the activated sludge into easily biodegradable small molecules and volatile fatty acids, thus completing the hydrolysis and acidification process.

[0234] S3. The mixed liquid at the end of the hydrolysis acidification reaction zone 2 enters the sludge-water separation zone 3. The supernatant after gravity separation is discharged as the effluent B of the hydrolysis acidification tank and enters the subsequent aerobic biological treatment facility; the sludge settles into the sludge lifting zone 4.

[0235] Meanwhile, the waste gas in the hydrolysis acidification tank enters the inlet of blower 6; the inlet of blower 6 is also connected to an air duct, on which an air flow meter 11-2 and an air regulating valve 10-2 are installed, and the end of the air duct is connected to the atmosphere; after blower 6 absorbs waste gas and air, the outlet of blower 6 is divided into three paths: one path enters the air lift pump 8 for lifting sludge; one path enters the first aerator 7-1 for rapid mixing of sewage and sludge; and the other path enters the second aerator 7-2 for continuous mixing of sewage and sludge and supplementation of oxygen;

[0236] S4, the air lift pump 8 in the sludge lifting zone 4 uses the gas outlet of the blower 6 to lift the activated sludge to the rapid mixing zone 1. The lifted activated sludge and wastewater A enter the rapid mixing zone 1 together.

[0237] During the above process, the blower frequency converter 6-1 automatically adjusts the air volume at the outlet of blower 6 to be equal to the sum of the air lift flow meter 11-3, the first aeration flow meter 11-4, and the second aeration flow meter 11-5; the controller 12 controls the opening of the air regulating valve 10-2 to keep the dissolved oxygen meter DO9 reading in a micro-oxygen state of 0.1-0.5 mg / L; the air flow meter 11-2 continuously displays the flow rate of the air duct, and the controller 12 adjusts the opening of the exhaust gas regulating valve 10-1 to make the sum of the exhaust gas flow meter 11-1 and the air flow meter 11-2 equal to the air volume at the outlet of blower 6.

[0238] The fully mixed hydrolysis acidification tank and its treatment method with automatic dissolved oxygen control in this embodiment 2 can achieve the same technical effect as in embodiment 1. The first aerator 7-1 ensures uniform mixing intensity of sewage and sludge in the rapid mixing zone 1, and the second aerator 7-2 ensures uniform mixing intensity of sewage and sludge in the hydrolysis acidification reaction zone 2 without dead zones. Since no stirring device is required, the maintenance difficulties of the stirring device are avoided. The dissolved oxygen in the fully mixed hydrolysis acidification tank can also be automatically controlled to be in a micro-oxygen state. That is to say, it can simultaneously satisfy the complete mixing of mud and water and the micro-oxygen state of the mixed liquid, resulting in good mud-water mixing effect and good hydrolysis acidification effect.

[0239] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0240] Furthermore, the terms "first" and "second" are used 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 as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0241] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A completely mixed hydrolysis-acidification tank for automatically controlling dissolved oxygen, characterized by: The complete mixing hydrolysis acidification tank comprises a hydrolysis acidification tank, a waste gas circulation system and a dissolved oxygen automatic control system, the hydrolysis acidification tank comprises a tank with a cover plate (16), and the tank comprises a rapid mixing zone (1), a hydrolysis acidification reaction zone (2), a sludge-water separation zone (3) and a sludge lifting zone (4) in sequence; The waste gas circulation system comprises a blower (6), a first aerator (7-1) arranged in the rapid mixing zone (1), a second aerator (7-2) arranged in the hydrolysis acidification reaction zone (2) and a gas stripping pump (8) arranged in the sludge lifting zone (4); The dissolved oxygen automatic control system comprises a blower frequency converter (6-1), a dissolved oxygen meter DO (9) for measuring the dissolved oxygen content of liquid in the hydrolysis acidification reaction zone (2), a waste gas adjusting valve (10-1), an air adjusting valve (10-2), a waste gas flow meter (11-1), an air flow meter (11-2), a gas stripping flow meter (11-3), a first aeration flow meter (11-4), a second aeration flow meter (11-5) and a controller (12); The rapid mixing zone (1) is communicated with the hydrolysis acidification reaction zone (2), the hydrolysis acidification reaction zone (2) is communicated with the sludge-water separation zone (3), the sludge-water separation zone (3) is communicated with the sludge lifting zone (4), and the sludge lifting zone (4) is communicated with the rapid mixing zone (1); The waste gas in the hydrolysis acidification reaction zone (2) enters the inlet of the blower (6) through the waste gas adjusting valve (10-1) and the waste gas flow meter (11-1), and the inlet of the blower (6) is also communicated with the atmosphere after passing through the air flow meter (11-2) and the air adjusting valve (10-2); The outlet of the blower (6) is divided into three paths, one path is connected with the gas stripping pump (8) through the gas stripping flow meter (11-3), one path is connected with the first aerator (7-1) through the first aeration flow meter (11-4), and the other path is connected with the second aerator (7-2) through the second aeration flow meter (11-5); The dissolved oxygen meter DO (9), the waste gas flow meter (11-1), the air flow meter (11-2), the first aeration flow meter (11-4), the second aeration flow meter (11-5), the gas stripping flow meter (11-3), the waste gas adjusting valve (10-1) and the air adjusting valve (10-2) feed back information to the controller (12); The controller (12) controls the operation of the blower (6) through the blower frequency converter (6-1); The dissolved oxygen meter DO (9) controls the operation of the air adjusting valve (10-2) and the waste gas adjusting valve (10-1) through the controller (12).

2. The completely mixed hydrolysis-acidification tank for automatically controlling dissolved oxygen according to claim 1, wherein: The waste gas circulation system further comprises a gas collecting hood (5), and the waste gas in the hydrolysis acidification reaction zone (2) enters the inlet of the blower (6) through the gas collecting hood (5), the waste gas adjusting valve (10-1) and the waste gas flow meter (11-1).

3. The completely mixed hydrolysis-acidification tank for automatically controlling dissolved oxygen according to claim 2, wherein: The rapid mixing zone (1) and the hydrolysis acidification reaction zone (2) are separated by a first partition wall (1-3), the hydrolysis acidification reaction zone (2) and the sludge-water separation zone (3) are separated by a second partition wall (2-1), the second partition wall is provided with a flow stabilizing plate (2-2), and the sludge-water separation zone (3) and the sludge lifting zone (4) are separated by a third partition wall (3-3); And / or the gas phase space of the rapid mixing zone (1), the hydrolysis acidification reaction zone (2), the sludge-water separation zone (3) and the sludge lifting zone (4) are communicated with each other; And / or the rapid mixing zone (1) is provided with a water distribution tank (1-1), and the water distribution tank (1-1) is communicated with a water distribution pipe (1-2); And / or the sludge-water separation zone (3) is provided with a water outlet weir (3-1), and the bottom of the sludge-water separation zone (3) is provided with a conical hopper (3-2); And / or the inlet of the air blower (6) is further connected with an air pipeline, the air pipeline is provided with an air flow meter (11-2) and an air adjusting valve (10-2), and the end of the air pipeline is communicated with the atmosphere through an air filter (13); And / or the sludge lifting zone (4) is provided with a sludge tank (4-1), and the sludge tank (4-1) is communicated with the water distribution tank (1-1).

4. The completely mixed hydrolysis-acidification tank for automatically controlling dissolved oxygen according to claim 3, wherein: The cover plate (16) of the hydrolysis acidification tank is provided with an exhaust pipe (14), one end of the exhaust pipe (14) is communicated with the gas phase space in the hydrolysis acidification tank, the other end of the exhaust pipe (14) is inserted below the liquid surface of a water seal tank (15), the tail gas C of the hydrolysis acidification tank is discharged from the water seal tank (15) and enters a subsequent waste gas treatment system.

5. The automatic control of dissolved oxygen completely mixed hydrolysis acidification tank according to claim 1 or 2 or 3 or 4, characterized in that: The first aerator (7-1) is a perforated pipe, and a plurality of first aerators (7-1) are uniformly arranged at the bottom of the rapid mixing zone (1); the second aerator (7-2) is a perforated pipe, and a plurality of second aerators (7-2) are uniformly arranged at the bottom of the hydrolysis acidification reaction zone (2); a plurality of small holes (7-3) with a hole diameter of 5-10 mm are staggered in the 45° direction on both sides below the perforated pipe.

6. The completely mixed hydrolysis-acidification tank for automatically controlling dissolved oxygen according to claim 5, wherein: The gas collecting hood (5) comprises a horn mouth (5-1), a demisting filter screen (5-2) and a connecting flange (5-3), the horn mouth (5-1) opens downward, the demisting filter screen (5-2) is arranged above the horn mouth (5-1), and the connecting flange (5-3) is used for mounting the gas collecting hood (5) on the cover plate (16) and a waste gas pipeline, and the waste gas pipeline is communicated with a waste gas adjusting valve (10-1).

7. The completely mixed hydrolysis-acidification tank for automatically controlling dissolved oxygen according to claim 5, wherein: A plurality of flow holes with a diameter of 15-25 mm are uniformly distributed on the surface of the flow stabilizing plate (2-2); And / or the controller (12) is a programmable logic controller (PLC) or a distributed control system (DCS); And / or the other end of the exhaust pipe (14) is inserted into the water seal tank (15) below the liquid surface by 100-1000 mm.

8. A process for the automatic control of the dissolved oxygen in a completely mixed hydrolysis-acidification tank, using an automatic control of the dissolved oxygen in a completely mixed hydrolysis-acidification tank according to claim 1, characterized in that, The method comprises the following steps: S1, the sewage A to be treated enters the rapid mixing zone (1), is fully mixed with the sludge returned by the air-lift pump (8) under the stirring of the first aerator (7-1), and the suspended solid organic matter and the dissolved macromolecular organic matter in the sewage are rapidly intercepted and adsorbed by the activated sludge floc; S2, the sludge-water mixture in the rapid mixing zone (1) flows into the hydrolysis acidification reaction zone (2), under the stirring of the second aerator (7-2), the activated sludge is always in a suspended state, the suspended solid organic matter and the dissolved macromolecular organic matter adsorbed are slowly decomposed into small molecular substances and volatile fatty acids by specific anaerobic bacteria and facultative acidification bacteria in the activated sludge, and the hydrolysis acidification process is completed; S3, the mixed liquid at the end of the hydrolysis acidification reaction zone (2) enters the sludge-water separation zone (3), and the supernatant after gravity separation is the hydrolysis acidification tank effluent B which is discharged and enters the subsequent aerobic biological treatment facility; The sludge sinks into the sludge lifting zone (4); Meanwhile, the waste gas in the hydrolysis acidification tank enters the inlet of the air blower (6); the inlet of the air blower (6) is also connected with an air pipeline, the air pipeline is provided with an air flow meter (11-2) and an air adjusting valve (10-2), and the end of the air pipeline is communicated with the atmosphere; after the air blower (6) absorbs the waste gas and air, the outlet of the air blower (6) is divided into three routes: one route enters the air-lifting pump (8) and is used for lifting the sludge; one route enters the first aerator (7-1) and is used for rapid mixing of the sewage and the sludge; the other route enters the second aerator (7-2) and is used for continuous mixing of the sewage and the sludge and supplement of oxygen; S4, the air-lifting pump (8) in the sludge lifting zone (4) uses the gas at the outlet of the air blower (6) to lift the activated sludge to the rapid mixing zone (1), and the lifted activated sludge and the sewage A enter the rapid mixing zone (1) together; In the above process, the air flow at the outlet of the air blower (6) is automatically adjusted by the air blower frequency converter (6-1) and is equal to the sum of the air-lifting flow meter (11-3), the first aeration flow meter (11-4) and the second aeration flow meter (11-5); the opening degree of the air adjusting valve (10-2) is controlled by the dissolved oxygen meter DO (9) interlocking, so that the reading of the dissolved oxygen meter DO (9) is controlled in the micro-aerobic state, and the reading of the micro-aerobic state is 0.1-0.5 mg / L; the air flow meter (11-2) continuously displays the flow of the air pipeline, and the opening degree of the waste gas adjusting valve (10-1) is adjusted by the controller (12), so that the sum of the waste gas flow meter (11-1) and the air flow meter (11-2) is equal to the air flow at the outlet of the air blower (6).

9. A process for the automatic control of the dissolved oxygen in a completely mixed hydrolysis-acidification tank, using an automatic control of the dissolved oxygen in a completely mixed hydrolysis-acidification tank according to claim 3, characterized in that, The method comprises the following steps: S1, the sewage A to be treated enters the rapid mixing zone (1) through the water distribution tank (1-1) and the water distribution pipe (1-2), is completely mixed with the sludge returned through the air-lifting pump (8) under the stirring of the first aerator (7-1), and the suspended solid organic matter and the dissolved macromolecular organic matter in the sewage are quickly intercepted and adsorbed by the activated sludge floc; S2, the sludge-water mixture in the rapid mixing zone (1) flows into the hydrolysis acidification reaction zone (2) from the upper part of the first partition wall (1-3), under the stirring of the second aerator (7-2), the activated sludge is always in a suspended state, the suspended solid organic matter and the dissolved macromolecular organic matter adsorbed are slowly decomposed into small molecular substances and volatile fatty acids which are easy to be biodegraded by specific anaerobic bacteria and facultative acidification bacteria in the activated sludge, and the hydrolysis acidification process is completed; S3, the mixed liquid at the end of the hydrolysis acidification reaction zone (2) enters the sludge-water separation zone (3) through the flow stabilizing plate (2-2) on the second partition wall (2-1), and the supernatant after gravity separation is the hydrolysis acidification tank effluent B which is discharged from the effluent weir (3-1) and enters the subsequent aerobic biological treatment facility; Sludge sinks to the hopper (3-2), from the third partition wall (3-3) lower into the sludge lifting area (4); while the waste gas in the hydrolysis acidification tank is collected by the gas hood (5) and removed after the water mist, into the inlet of the air blower (6); after the air blower (6) absorbs the waste gas and air, the air blower (6) outlet is divided into three ways: one way into the air stripping pump (8), used for lifting sludge; one way into the first aerator (7-1), used for rapid mixing of sewage and sludge; the other way into the second aerator (7-2), used for continuous mixing of sewage and sludge and supplementing oxygen; S4, the air stripping pump (8) in the sludge lifting area (4) uses the gas from the air blower (6) outlet to lift the activated sludge to the sludge tank (4-1), which is in communication with the water distribution tank (1-1), and the activated sludge lifted together with sewage A enters the rapid mixing area (1); In the above process, the controller (12) automatically adjusts the air volume of the air blower (6) outlet through the air blower frequency converter (6-1) to equal the sum of the air stripping flow meter (11-3), the first aeration flow meter (11-4) and the second aeration flow meter (11-5); the opening of the air regulating valve (10-2) is interlocked controlled by the dissolved oxygen meter DO (9), so that the reading of the dissolved oxygen meter DO (9) is controlled in the micro-oxygen state, and the reading of the micro-oxygen state is 0.1-0.5mg / L; the air flow meter (11-2) continuously displays the flow of the air pipeline, and the opening of the waste gas regulating valve (10-1) is adjusted by the controller (12), so that the sum of the waste gas flow meter (11-1) and the air flow meter (11-2) is equal to the air volume of the air blower (6) outlet.

10. The treatment method of the completely mixed hydrolysis acidification tank with automatic control of dissolved oxygen according to claim 9, characterized in that: In the step S1, the hydraulic residence time of the sewage in the rapid mixing zone (1) is 10-60 min, the aeration intensity provided by the first aerator (7-1) of the rapid mixing zone is 6-10 m 3 / m 2 .h; In the S2 step, the dissolved oxygen meter DO (9) is installed in the hydrolysis acidification reaction zone (2); the second aerator (7-2) provides an aeration intensity of 3-6 m 3 / m 2 .h; In the S4 step, the number of air stripping pumps (8) can be one or more, and the ratio of the amount of backflow sludge to the amount of sewage is 0.5-10; The number of small holes (7-3) of the first aerator (7-1) and the number of small holes (7-3) of the second aerator (7-2) are determined according to the orifice flow velocity not less than 10m / s; The area and number of overflow holes on the steady flow plate (2-2) are determined according to the orifice flow velocity of 0.15-0.2m / s.

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