Rotary decanter

Author:hngoob           Renew time:2020-02-22

The decanter is the most commonly used key equipment used in sewage treatment such as SBRCASSICEAS. In the wastewater treatment of beer, food, beverage, pharmacy and other industries and municipal wastewater, SBR process has been widely used. It has the characteristics of small volume, good decanting effect, low energy consumption, no noise, high degree of automation, convenient centralized control, convenient maintenance, etc.

Performance parameters:

Model  Quantity of treated water Width of outlet weir Driving power Depth of skimming Water flow Drainage pipe diameter
BPS-2000 0-200 2000 0.55 1-3MAccording to the design requirements ≤30 DN250
BPS-I-3000 200-300 3000
BPS-I-4000 300-400 4000 0.75 DN300
BPS-I-5000 400-500 5000
BPS-I-6000 500-600 6000 1.1 DN350
BPS-I-7000 600-700 7000
BPS-I-8000 700-800 8000
BPS-I-9000 800-900 9000 1.5     DN400
BPS-I-10000 900-1000 10000 1.5    

Product introduction
Equipment used by decanter in SBR process to regularly remove clarified water has the function of decanting clarified water from the static pool surface without stirring and settling to ensure the effluent quality. The SBR process adopts intermittent reaction, and the water inlet, reaction, precipitation and drainage are completed in the same tank without secondary sedimentation tank and sludge reflux equipment, thus having the advantages of less occupied land, small investment, high efficiency, good effluent quality, etc. At the same time, connecting a plurality of SBR tanks can also have the continuity of the traditional sludge process (continuous water inflow) and the intermittence of the typical SBR process, and is suitable for the needs of large changes in water quality, water quantity and so is widely applied at home and abroad. In order to ensure safe operation and enhance operation effect, operation procedures should be strictly observed during daily use.

1. Regularly check whether the inflation and deflation pipelines and the inflation and deflation solenoid valves of the water collecting device of the decanter are in good condition. If any problems such as pipeline cracking, blockage or solenoid valve damage are found, they shall be cleaned or replaced in time.

2. Regularly check the sealing condition and operation condition of rotary joint, telescopic sleeve and deformed bellows. If there is any problem that cannot be recovered after fracture or abnormal deformation, it shall be replaced in time. According to the use requirements of the product, these parts shall be collectively updated when they reach the service life. 3. Pay attention to the shape and movement of the guide rod, traction lead screw or wire rope of the floating water collecting device during patrol inspection. Repair or replace it in time when deformation, blocking and other phenomena are found. For decanter guide rods that have not been used for a long time, grease should be added to protect them or they should be moved regularly to prevent them from sticking due to corrosion. 4. A special section of deformable pipeline is required below the weir opening of the decanter. The float type uses rubber hose, corrugated pipe, etc. to realize deformation. The sleeve type uses telescopic sliding between the thick and thin sections of pipelines to adapt to the lifting of the weir opening, while the rotary type uses rotary sealing joints to connect the two sections of pipelines to move the weir opening. When the water decanter is used, the gravity of the combined water decanter at each moving position must be balanced with the buoyancy of the water by controlling the moving speed of the water outlet and other methods, so that the buoyancy of the water can be utilized and the random control of the water decanter can be realized.

Regular maintenance is also important to prolong its service life. 1, regularly to drive device and lifting mechanism oil. According to its instructions. 2. Apply lithium grease to the hinge position to check for additional wear. 3. Flush the trough of the water outlet weir and do not allow scum to harden on its surface. 4. If the underwater bearing is found to have leakage (which can be judged according to the water quality of the outlet water), the "O" sealing ring shall be replaced in time. To replace the "O" seal ring: 1) returning the water outlet weir to the initial position; 2) Remove the bearing frame at one end of the drain pipe and remove the upper bearing clamping plate; 3) Loosen the connecting bolts of the flanges at both ends, lift out the rotating shaft sleeve, place it on the platform, gently pull out the rotating inner sleeve, remove the old sealing ring and replace it with a new one. Grease the new sealing ring. 4), after installation in sequence. 5. It is forbidden to disassemble the limit switch during the operation and use of the equipment.

use Rotary decanters are widely used in the treatment of municipal wastewater and various industrial wastewater such as papermaking, beer, leather making, pharmacy, etc. They are used to decant the treated supernatant from the surface in the drainage stage and are the key equipment of SBR process. Structure and working principle The equipment adopts a rotary type and an electric push rod type and is installed in a reaction tank or a sedimentation tank. During operation, the drive device drives the push rod, so that the water decanter gradually descends to the water surface at a certain speed (within a specified stroke range), the weir gate is immersed under the water surface, supernatant fluid flows in from the weir gate, is collected into a main pipe through a water collection branch pipe and is discharged, and when the equipment is stopped, the water decanter is also lifted by the push rod, so that the weir gate is lifted above the water surface, thus completing a water decanting process. main features 1. The equipment has compact structure, stable operation, convenient installation of the overall structure and low operation cost; 2. It has strong adaptability to changes in water quality and quantity, and the decanting depth can reach 3.0m;; 3. if the treatment capacity q is less than 1000m3/h, a single push rod is adopted; if Q≥1000m3/h, a double push rod is adopted; 4. A scum baffle is arranged outside the outlet of the decanting weir to ensure that the liquid level on the weir does not fluctuate and the effluent quality reaches the standard when the equipment is running. 5. Equipment frequency conversion speed regulation and PLC automatic and remote control are convenient for operation and management.

Buoy decanter The float type decanter consists of float, water guide, slide bar frame, water outlet hose, water outlet bamboo joint and other components, and does not need power. During the water inlet and precipitation stages, the decanter floats on the water surface and is in standby state. The clear water accumulated in the hose at its outer opening forms a water seal to prevent dirty water from entering. The decanting starts, the drain valve is opened, and the supernatant fluid in the pool is discharged. As the water level drops, the float slowly slides downward in the guide rod of the bracket. When the water level drops to the water level, the drain valve is closed, and the drain is finished. Siphon decanter The decanter is mainly divided into three parts: a short drain pipe, a U-shaped pipe part and a main drain pipe. (1) short drain pipes: siphon decanter is composed of a series of short drain pipes, with its lower opening below the decanting liquid level and its upper end connected to a horizontal weir arm. The number of short drainage pipes should be sufficient and evenly distributed on the plane of SBR reaction tank to reduce the inlet flow rate, make the drainage uniform and prevent the sludge from stirring and settling. (2) U-shaped pipe part: the U-shaped pipe is partially filled with water to form a water seal. One side of the U-shaped pipe is connected with the horizontal weir arm, and the other side is connected with the water outlet pipe. The connection part of the U-shaped pipe and the water outlet pipe is provided with an overflow pipe, the side connected with the horizontal weir arm is provided with an air discharge pipe, the air discharge pipe is provided with a valve, and the opening and closing of the valve are used for forming or destroying a siphon state. (3) Drainage main pipe: connected with U-shaped pipe in horizontal direction, which can be placed inside or outside the pool. The main pipe is generally 10 cm below the water level. Siphon decanter automatically drains supernatant from SBR reaction tank in a siphon way. When drainage is needed, the electromagnetic valve is opened, air accumulated on the upper part of the pipe is discharged, the electromagnetic valve is closed to form siphonage, and automatic drainage is carried out until the vacuum is destroyed, then drainage is stopped, waiting for the next cycle. Supplementary knowledge point: Siphon principle is a fluid mechanics phenomenon, which can pump liquid without the aid of a pump. The liquid at the higher position opens at the lower position after filling an inverted U-shaped tubular structure (called siphon). Under this structure, the liquid pressure difference between the two ends of the pipe can push the liquid across the point and discharge to the other end. The siphon action is mainly caused by universal gravitation. Knowledge supplement: SBR process   SBR process is also called sequencing batch activated sludge process, which is a professional term for environmental engineering. It refers to an activated sludge sewage treatment method that consists of five basic processes of water inflow, aeration, sedimentation, drainage and standby in chronological order in the same reaction tank (reactor). Water intake stage: There is high concentration activated sludge mixed solution in the reaction tank, which has the function of regulating tank. Reaction stage: When the waste water reaches a predetermined volume, aeration or stirring reaction is carried out to remove organic matters, nitration, nitrogen removal and phosphorus removal. Precipitation stage: Stopping aeration and stirring is equivalent to a secondary sedimentation tank of traditional activated sludge, and the sludge realizes solid-liquid separation through gravity sedimentation. Decanting stage: After precipitation, a mud-water separation layer is formed, and the supernatant is discharged out of the pool through a decanter. Idle stage. In order to maintain the activity of activated sludge, necessary agitation and aeration will be carried out. If phosphorus removal in an energy-saving or anaerobic state is considered, agitation or aeration may not be carried out. This stage is also the beginning of the next cycle.   SBR process features: (1) The ideal push-flow process increases the driving force of biochemical reaction and improves the efficiency. Anaerobic and aerobic conditions in the tank are in an alternating state and the purification effect is good. (2) The operation effect is stable, the sewage is precipitated in an ideal static state, which requires short time, high efficiency and good effluent quality. (3) Impact load resistance. There is retained treated water in the tank, which can dilute and buffer the sewage and effectively resist the impact of water volume and organic pollutants. (4) Each process in the process can be adjusted according to the water quality and quantity, and the operation is flexible. (5) less processing equipment, simple structure and convenient operation, maintenance and management. (6) the concentration gradients of DO and BOD5 exist in the reaction tank to effectively control the expansion of activated sludge. (7) SBR system itself is also suitable for combined construction method, which is beneficial to the expansion and reconstruction of wastewater treatment plant. (8) Nitrogen and phosphorus removal, proper control of operation mode, realization of aerobic, anoxic and anaerobic state alternation, has good nitrogen and phosphorus removal effect. Description of type selection As siphon decanters are used less now and the treatment volume range of float decanters is smaller, we mainly take rotary decanters, the mainstream equipment in the market, as an example to simply interact and communicate with everyone. Working principle, working process In the aeration and sedimentation stages, the decanter is located above the water level (initial position). At the beginning of the decanting stage, the driving mechanism drives the screw rod of the lifting mechanism to move linearly downward to drive the hinged four-bar linkage to swing, so that the outlet weir rotates around the center of the main shaft and quickly approaches the water surface. At this time, the buoy first enters the water surface and floats from the water surface due to the buoyancy force while pushing away scum around the weir. In addition, under the action of slag blocking plates on both sides of the buoy, a scum-free water outlet area is formed. The distance between the buoy and the weir can be automatically adjusted when floating on the water surface. When the water outlet weir reaches the water surface, the supernatant slowly enters the weir from under the buoy. When drainage starts, the liquid level control unit reaching the water level sends out a signal, and the frequency converter automatically adjusts the speed to change the descending speed to a given speed. The water flow is stable and enters the weir in a laminar flow state, and the water yield remains unchanged without disturbing the supernatant fluid. When the water outlet weir reaches the set water level, the limit switch acts and the decanter automatically and quickly returns to the initial position. working process The working process of   SBR is as follows: sewage is added into the reactor in a short period of time, aeration is started after the reactor is filled with water, organic matters in the sewage reach the troubleshooting requirement through biodegradation, aeration is stopped, and supernatant is discharged after settling for a certain period of time. The above-mentioned process can be summarized as follows: short-term water intake-aeration reaction-precipitation-short-term drainage-entering the next working cycle. It can also be called five stages: water intake stage-adding substrate, reaction stage-substrate degradation, precipitation stage-solid-liquid separation, drainage stage-supernatant drainage and standby stage-activity recovery.

Water intake stage The water intake stage refers to the period of time from the start of water intake into the reactor to the time of reaching the reactor volume. The time used in the water intake stage shall be determined according to the actual drainage conditions and equipment conditions. In the intake stage, the aeration tank plays a role in balancing the water quality and quantity of sewage to a certain extent. Therefore, Yang R has certain adaptability to the fluctuation of water quality and quantity. This period can be divided into three situations: aeration (aerobic reaction), stirring (anaerobic reaction) and standing. In the case of aeration, the organic matter has already begun to be oxidized in a large amount in the water inflow process, while in the case of stirring, the aerobic reaction is inhibited. The corresponding three ways are unrestricted aeration, semi-restricted aeration and restricted aeration. During operation, unrestricted aeration, semi-restricted aeration and restricted aeration can be adopted according to the growth characteristics of different microorganisms, the characteristics of wastewater and the treatment targets to be achieved. By controlling the environment in the influent stage, various treatment functions can be completed without changing the reactor. However, it is difficult to change the reaction time and reaction conditions in continuous flow due to the size and specification of each structure and water pump. Reaction stage It is the main stage of SBR personnel, in which pollutants are removed by microbial degradation. According to the different requirements of sewage treatment, such as only removing organic carbon or simultaneously removing chlorine and phosphorus, the corresponding technical parameters can be adjusted, and the reaction stage time and whether continuous aeration is adopted can be determined according to the specific conditions of raw water quality and emission standards. Precipitation stage The purpose of sedimentation is solid-liquid separation, which is equivalent to the secondary sedimentation of traditional activated sludge method. Stop aeration and stirring, so that the mixed liquid is in a static state, mud-water separation is completed, and the static precipitation effect is good. The supernatant separated after precipitation can be discharged. The purpose of precipitation is solid-liquid separation and separation of sludge floc and supernatant. Since the reactor is completely stationary during precipitation, this process is more efficient in SBR system than in medium.

The precipitation process is generally controlled by time, and the precipitation time is between 0.5 and 1 hour, and may even reach 2 hours, so as to facilitate the next drainage process. The sludge layer shall be kept under the drainage equipment and shall not rise beyond the drainage equipment until the drainage is completed. With the development of measuring instruments, the sludge level can be automatically monitored, so the settling time can be changed according to the sludge settling array performance. A value can be set in advance on the automatic control system, and the sedimentation process can be finished once the sludge interface high skin monitored by the sludge interface meter reaches the value. Drainage phase The purpose of the drainage stage is to recover the clarified liquid from the sludge discharged from the reactor to the water level at the beginning of the cycle, which is still at a certain protection level from the sludge layer. Most of the sludge settled at the bottom of the reactor will be used as reflux sludge in the next cycle. Excess sludge can be removed in the drainage stage or in the standby stage.   SBR drainage generally uses decanters. The decanting time is determined by the decanting capacity and will not affect the sludge layer below. Now it is also possible to start draining water at the same time of sedimentation. Of course, the decanting speed should be controlled so as not to affect sedimentation. In this way, the two stages of sedimentation and decanting are merged together. Standby phase The period after precipitation to the beginning of the next cycle is called standby process. Stirring or aeration can be carried out as required. In a multi-tank system, the purpose of standby is to provide time for a reactor to complete its entire cycle before switching to another unit. Standby is not a necessary step and can be removed. According to the process and processing purpose during standby; Aeration, mixing and removal of excess sludge can be carried out. The length of standby period is determined by the amount of treated water. Removal of excess sludge is another important step in sBR operation. It is not one of the five basic processes because the time for removal of excess sludge is uncertain. Like the traditional continuous system, the amount and frequency of excess sludge removal are determined by the operation requirements. Basic Performance and Operating Mode Effectively prevent sludge bulking The large gradient of substrate concentration is an important factor to control expansion. There is basically no concentration gradient in the fully mixed reactor. Filament content is high and it is easy to expand. SBR system belonging to plug flow reactor has large concentration gradient, low filamentous content and is not easy to expand. The alternation of anoxic (anaerobic) and aerobic states in the influent stage and the reaction stage of   SBR system can inhibit the excessive reproduction of obligate aerobic filamentous bacteria and control the expansion. Removal of   BOD An important advantage of   SBR system is that the operator can maintain the selectivity of microorganisms by controlling relevant conditions. In a complete treatment cycle, the microbial selection pressures vary greatly. These selection pressures include the availability of oxygen and matrix. Although some of these selection pressures may occur in some traditional continuous systems, SBR systems have good selection and expansion capabilities, allowing microorganisms to grow in superior environments. Removal and stabilization of suspended solids One of the advantages of   SBR during sedimentation is that it stops the inflow and outflow of water, and also stops the aeration and mixing. It makes full use of the static sedimentation principle, thus obtaining faster separation and settling more solids. The sedimentation unit of the traditional continuous system cannot stop the inflow and outflow of water, so the sedimentation is carried out under dynamic conditions. Another advantage of   SBR system is its flexibility, which can change the time of precipitation process. When the flow rate is large, the settling time can be reduced to the hour required for solid separation, so as to shorten the time of the whole cycle and handle the larger flow rate. If necessary, decanting can be started at the time of settling. Traditional systems do not have this flexibility. Nitrification and Denitrification Nitrogen in sewage enters the system in the form of organic ammonia and ammonia nitrogen, and is removed from the system in the form of nitrogen. The process of ammonia nitrogen conversion into nitrogen is divided into nitrification and denitrification. Nitrification takes place under the condition of sufficient dissolved oxygen, while denitrification takes place under the condition of lack of oxygen. In order to remove nitrogen from SBR system, only simple adjustment (adjustment period and aeration time) should be made to the operation of the treatment plant without major modification to the structure of the treatment plant. Biological phosphorus removal Biological phosphorus removal first requires an anaerobic phase (no dissolved oxygen and oxidized nitrogen), and at the same time, there are easily degradable organic matters. In the aerobic phase (high dissolved oxygen concentration), excess phosphorus uptake by sludge is promoted. A certain amount of excess sludge is removed from the reactor before the start of the next anaerobic period. The flexibility of   SBR shows that these conditions can be met by changing the operation mode. The operating procedures for phosphorus removal in an SBR system are as follows: water intake, aeration, sedimentation and sludge discharge, and drainage. Characteristics of   SBR Process Basic operation mode of classic SBR. Its operation consists of five basic processes: fill, react, settle, draw and idle. From the beginning of sewage inflow to the end of standby time is counted as a cycle. All processes are carried out in sequence in a reactor provided with aeration or stirring devices in a cycle, and equipment such as a sedimentation tank, a reflux sludge pump and the like which are necessary in the continuous activated sludge method are not required. Continuous activated sludge process is to set up different facilities in space to carry out fixed continuous operation. On the contrary, classical SBR is a single reactor to carry out different operations for various purposes in time. Compared with the period of wastewater production in many industries, its intermittent operation mode can fully take advantage of the technical characteristics of SBR, so it is widely used in industrial wastewater treatment. In the treatment of some refractory wastewater, classical SBR is still often used. Due to the small floor area and compact layout of SBR process, there are many examples of successful application of SBR process in sewage treatment of small towns. Working principle The operation of SBR is different from the traditional activated sludge process, which generally adopts the mode of parallel batch operation of multiple SBR reactors. For a single SBR reactor, each operation cycle includes five stages: water intake period, reaction period, precipitation period, drainage and sludge discharge period and idle period. Limited aeration or non-limited aeration can be adopted in the intake stage, and sewage continuously enters the SBR reactor, at which time activated sludge adsorbs and removes organic pollutants. When the concentration of organic pollutants reaches the value, when the sewage reaches the preset water level, stop the inflow to start aeration, and the reaction period starts immediately. In this stage, the organic pollutants are fully removed by the activated sludge, and the BOD and COD values are continuously reduced. When the concentration of organic pollutants is reduced to the appropriate value, stop aeration, and then enter the sedimentation stage. In this stage, the activated sludge in the mixed liquid is continuously settled by gravity, thus achieving an efficient mud-water separation effect. After entering the drainage sludge discharging period, the supernatant is discharged through a decanter, and the surplus sludge is also discharged through a sludge discharging system. When entering the idle period, the activated sludge is in a nutrient starvation state, and the activated sludge per unit weight has a large adsorption surface area. When entering the water intake period of the next operation period, the activated sludge can give full play to the initial adsorption and removal effect.
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