曝气增氧系统频繁应用于污水处理、水产养殖、水生态治理等场景中。那么曝气增氧系统都有什么设备组成呢？今天，我们一起来探讨一下！

       一、曝气原理

　　1.曝气及其作用

　　曝气是采用相应的设备和技术措施，使空气中的氧转移到混合液中而被微生物利用的过程。曝气的主要作用除供氧外，还起搅拌混合作用，使曝气池内的活性污泥保持悬浮状态，与污水充分接触混合，从而提高传质效率，保证曝气池的处理效果。

　　2.氧转移原理

　　空气中的氧通过曝气传递到混合液中，氧由气相向液相中转移，**被微生物所利用。这种转移通常以双膜理论为理论基础。双膜理论认为，在气-水界面上存在着气膜和液膜，当气液两相做相对运动时，气膜和液膜间属层流状态，而在其外的两相体系中均为紊流，氧的转移是通过气、液膜间进行的分子扩散和在膜外进行的对流扩散完成的。对于难溶于水的氧来说，分子扩散的阻力大于对流扩散，传递的阻力主要集中在液膜上。因此，采用曝气搅拌是快速变换气-水界面克服液膜阻力的*有效方法。

　　二、曝气装置

　　曝气装置，又名空气扩散装置，是活性污泥系统的重要设备，按曝气方式可将其分为鼓风曝气和机械曝气两大类。

　　衡量曝气装置的主要技术性能指标有动力效率(EP)，氧的利用效率(EA)和氧的转移效率(EL)。动力效率是每消耗1kW电能转移到混合液中的氧量(kg/kWh);氧的利用效率是通过鼓风曝气转移到混合液中的氧量，占总供氧量的百分比(%);氧的转移效率也称充氧能力，是通过机械曝气装置，在单位时间内转移到混合液中的氧量(kg/ h)。

　　1.鼓风曝气装置

　　鼓风曝气系统由鼓风机、曝气装置和空气输送管道组成。鼓风机将空气通过一系列管道输送到安装于曝气池底部的曝气装置，经过曝气装置，将空气中的氧转移到混合液中去。

　　鼓风曝气系统的曝气装置主要分为微气泡、中气泡、水力剪切、水力冲击等类型。

　　(1)微气泡曝气器

　　也称多孔性空气扩散装置，采用多孔材料如陶粒、粗瓷等掺以适当的如酚醛树脂一类的粘合剂，在高温下烧结成为扩散板、扩散管和扩散罩的形式。

　　这一类扩散装置的特点是产生微小气泡，气、液接触面积大，氧利用率高;缺点是气压损失大，易堵塞，送入的空气应预先通过过滤处理。

　　1)固定式平板型微孔曝气器

　　平板型微孔曝气器主要组成包括扩散板、布气底盘、通气螺栓、配气管、三通短管、橡胶密封圈、压盖和连接池底的配件等。

　　常见的平板型微孔曝气器有钛板微孔曝气器、微孔陶板、青刚玉和绿刚玉为骨料烧结成的曝气板。其主要技术参数：平均孔径100～200μm;服务面积0.3～0.75m2/个;动力效率4～6kgO2/kWh;氧利用率20%～25%。

　　2)固定式钟罩型微孔曝气器

　　有微孔陶瓷钟罩型盘、青刚玉骨料烧结成的钟罩型盘。技术参数与平板型微孔曝气器基本相同。

　　3)膜片式微孔曝气器

　　该曝气器的底部为聚丙烯制作的底座，底座上覆盖着合成橡胶制成的微孔膜片，膜片被金属丝箍固定在底座上。在膜片上开有按同心圆形式布置的孔眼。鼓风时，空气通过底座上的通气孔进入膜片和底座之间，使膜片微微鼓起，孔眼张开，空气从孔眼逸出，达到布气扩散的目的。供气停止，压力消失，在膜片的弹性作用下，孔眼自动闭合，由于水压的作用膜片压实在底座之上。曝气池内的混合液不能倒流，因此，不会堵塞膜片孔眼。这种曝气器可扩散出直径为1.5～3.0mm的气泡，即使空气中含有少量尘埃，也可以通过孔眼，不会堵塞，也不需设除尘设备。

　　(2)中气泡曝气器

　　这种装置产生的气泡直径2～6mm，在过去主要是穿孔管。穿孔管由钢管或塑料管制成，直径25～50mm，在管壁两侧下部开直径3～5mm的孔眼，间距50～100mm。穿孔管不易堵塞，构造简单，阻力小;但氧的利用率低，动力效率低。因此，目前在活性污泥曝气池中较少采用。

　　网状膜曝气器是近年来开发出的具有代表性的中气泡曝气器。其特点是不易堵塞，布气均匀，构造简单，便于维护管理，氧的利用率较高。

　　该曝气器由主体、螺盖、网状膜、分配器和密封圈所组成;空气由曝气器底部进入，经分配器**次切割并均匀分配到气室，然后通过网状膜进行二次切割，形成微小气泡扩散到混合液中。

　　每个网状膜曝气器的服务面积为0.5 m2，动力效率2.7～3.7kgO2/kWh，氧利用率12%～15%。

　　(3)水力剪切式空气曝气器

　　1)倒伞式曝气器

　　倒伞式曝气器由伞形塑料壳体、橡胶板、塑料螺杆和压盖等组成。空气从上部进气管进入，由伞形壳体和橡胶板间的缝隙向周边喷出，在水力剪切的作用下，空气泡被剪切成小气泡。停止供气，借助橡胶板的回弹力，使缝隙自行封口，防止混合液倒灌。

　　该曝气器的服务面积为6×2m2;动力效率1.75～2.88kgO2/kWh，氧利用率6.5%～8.5%。

　　2)固定螺旋曝气器

　　该曝气器由直径300或400mm、高1500mm的圆形外壳和固定在壳体内部的螺旋叶片组成，每个螺旋叶片扭曲180º，两个相邻叶片的螺旋方向相反。空气由布气管从底部的布气孔进入装置内，向上流动，由于壳体内外混合液的密度差，产生**作用，使混合液在壳体内外不断循环流动。空气泡在上升过程中，被螺旋叶片反复切割，形成小气泡。

　　该曝气器有固定单螺旋、固定双螺旋和固定三螺旋三种形式。

　　(4)水力冲击式曝气器

　　该种曝气器以射流式空气扩散装置为主，利用水泵打入的泥、水混合液的高速水流的动能，吸入大量空气，泥、水、气混合液在喉管中强烈混合搅动，将气泡粉碎为雾状，使氧迅速转移至混合液中，氧的转移率可高达20%，但动力效率不高。近年来，由于泵的防水性能的改进，已实现动力装置和扩散装置的一体化。

　　2.机械曝气装置

　　机械曝气装置安装在曝气池水面上、下，在动力的驱动下进行转动，通过下述3方面的作用使空气中的氧转移到污水中去：曝气装置转动时，表面的混合液不断地从曝气装置周边抛向四周，形成水跃，液面剧烈搅动，卷入空气;曝气装置转动，具有**液体的作用，使池内混合液连续上下循环流动，气液接触界面不断更新，不断地使空气中的氧向液体内转移;曝气装置转动，在其后侧形成负压区，吸入空气。

　　按转动轴的安装方向，机械曝气装置可分为竖轴式和卧轴式两类。

　　(1)竖轴式曝气装置

　　又称竖轴叶轮曝气机，常用的曝气叶轮有泵型叶轮、倒伞型叶轮、平板型叶轮等，见图6-8。

　　曝气叶轮的充氧能力和**能力与叶轮直径、叶轮旋转速度和浸液深度等因素有关。叶轮直径一定，叶轮旋转的线速度大，充氧能力也强，但线速度过大时，会打碎活性污泥颗粒，影响沉淀效率。一般叶轮周边线速度以2～5m/s为宜。叶轮浸液深度适当时，充氧效率高，浸液深度过大，没有水跃产生，叶轮只起搅拌作用，充氧量极小，甚至没有空气吸入，浸液深度过小，则提水和输水作用减小，池内水流缓慢，甚至存在死区，造成表面水充氧好，而底层充氧不足。因此，常将叶轮旋转的线速度和浸液深度设计成可调的，以便运行中随时调整。一般竖轴叶轮曝气机的氧转移率为15%～25%，动力效率为2.5～3.5kgO2/kWh。

　　(2)卧轴式曝气装置

　　卧轴式曝气装置主要是转刷曝气器。由水平转轴和固定在轴上的叶片所组成，转轴带动叶片转动，搅动水面溅成水花，空气中的氧通过气液界面转移到水中。

　　转刷曝气器主要用于氧化沟，它具有负荷调节方便、维护管理容易、动力效率高等优点。

　　三、曝气池池型

　　活性污泥法处理污水的主要构筑物是曝气池。按混合液在曝气池中的流态可分为推流式、完全混合式和循环混合式三种池型;按平面几何形状可分为长方形、廊道形、圆形、方形和环形跑道形四种;按所采用的曝气方法可分为鼓风曝气池、机械曝气池和两种方法联合使用的机械-鼓风曝气池;按曝气池和二次沉淀池的关系可分为曝气-沉淀合建式和分建式两种。

　　1.推流式曝气池

　　推流式曝气池多为长方廊道形，常采用鼓风曝气。传统的作法是将空气扩散装置安装在曝气池廊道底部的一侧，这样布置可使水流在池中呈螺旋状流动，提高气泡和混合液的接触时间。如果曝气池的宽度较大，则应考虑将空气扩散装置安装在曝气池廊道底部的两侧。也可按一定的形式，如互相垂直的正交形式或呈梅花形交错式均衡地布置在整个曝气池池底。

　　曝气池的数目随污水处理厂的规模而定，一般在结构上分成若干单元，每个单元包括一座或几座曝气池，每座曝气池常由1个或2～5个廊道组成。当廊道数为单数时，污水的进、出口在曝气池的两端;而廊道数为双数时，则位于廊道的同一端。

　　曝气池廊道的长度可达100m，一般以50～70m为宜。为了防止短流，廊道的长度和宽度之比应大于5，甚至大于10。曝气池的宽深比常在1.5～2之间。池深与造价和动力费用密切相关。池深大，有利于氧的利用，但造价和动力费用将有所提高。反之，造价和动力费用降低，但氧的利用率也将降低。

　　此外，还应考虑土建结构和曝气池的功能要求、允许占用的土地面积，能够购置到的鼓风机所具有的压力等因素。目前我国对推流式曝气池采用的深度多为3～5m。

　　为了使混合液在曝气池内的旋转流动能够减少阻力，并避免形成死区，将廊道横剖面池壁两墙的墙顶和墙脚作成45°斜面。为了节约空气管道，相邻廊道的空气扩散装置常沿公共隔墙布置。

　　曝气池的进水口和进泥口均设于水面以下，采用淹没出流方式，以免形成短流，并设闸门以调节流量;出水一般采用溢流堰的方式，处理水流过堰顶，溢流入排水渠道。

　　在曝气池底部设直径为80～100mm放空管，用于维修或池子清洗时放空。考虑到在活性污泥培养、驯化周期排放上清液的要求，根据具体情况，在距池底一定距离处设2～3根排水管，直径也是80～100mm。

　　2.完全混合曝气池

　　完全混合曝气池常采用表面机械曝气装置供氧，其表面多呈圆形、方形或多边形。使用较多的是合建式完全混合曝气沉淀池，简称曝气沉淀池，由曝气区、导流区和沉淀区3部分组成。

　　1)曝气区

　　曝气装置设于池顶部中央，并深入水下某一深度。污水从池底部进入，并立即与池内原有混合液完全混合，并与从沉淀区回流缝回流的活性污泥充分混合、接触。经过曝气反应后的污水从位于顶部四周的回流窗流出并导入导流区。回流窗设有活门，可以通过调节窗孔大小，控制回流污泥量。

　　2)导流区

　　位于曝气区和沉淀区之间，宽度一般在0.6m左右，高约1.5m。内设竖向挡流板，起缓冲水流作用，并在此释放混合液中挟带的气泡，使水流平稳进入沉淀区，为固液分离创造良好条件。

　　3)沉淀区

　　位于导流区和曝气区的外侧，其作用是泥水分离，上部为澄清区，下部为污泥区。澄清区的深度不宜小于1.5m，污泥区的容积应不小于2h的存泥量。澄清的处理水沿设于池四周的出流堰进入排水槽，出流堰常采用锯齿状的三角堰。

　　污泥通过回流缝回流曝气区，回流缝一般宽0.15～0.20m，在回流缝上侧设池裙，以避免死角。在污泥区的一定深度设排泥管，以排出剩余污泥。

　　在生产实践中还有与沉淀池分建的完全混合曝气池。污水和回流污泥沿曝气池池长均匀引入，并均匀地排出混合液，进入二次沉淀池。

      简单来说，常见的污水处理、水产养殖、水生态治理场景中的曝气增氧系统分别由鼓风机、曝气盘、管道、阀门等设备组成！

　　Aeration system is frequently used in sewage treatment, aquaculture, water ecological treatment and other scenarios. What are the components of the aeration and oxygenation system? Today, let's discuss it together!

　　1、 Aeration principle

　　1. aeration and its function

　　Aeration is a process in which the oxygen in the air is transferred to the mixed liquid and utilized by microorganisms by using corresponding equipment and technical measures. The main function of aeration is not only to supply oxygen, but also to stir and mix, so as to keep the activated sludge in the aeration tank suspended and fully contact and mix with the sewage, so as to improve the mass transfer efficiency and ensure the treatment effect of the aeration tank.

　　2. oxygen transfer principle

　　The oxygen in the air is transferred to the mixed liquid through aeration. The oxygen is transferred from the gas phase to the liquid phase and finally used by microorganisms. This kind of transfer is usually based on the double membrane theory. According to the double film theory, there are gas film and liquid film on the gas-water interface. When the gas-liquid two phases move relative to each other, the gas film and liquid film are in a laminar state, while the outer two-phase system is turbulent. The transfer of oxygen is completed through the molecular diffusion between the gas and liquid films and the convective diffusion outside the film. For water-insoluble oxygen, the resistance of molecular diffusion is greater than that of convective diffusion, and the transfer resistance is mainly concentrated on the liquid membrane. Therefore, aeration agitation is the most effective method to quickly change the air-water interface to overcome the liquid film resistance.

　　The aeration and oxygenation system is composed of a fan, an aeration device and an air delivery pipe

　　2、 Aerator

　　Aeration device, also known as air diffusion device, is an important equipment of activated sludge system. According to aeration mode, it can be divided into blast aeration and mechanical aeration.

　　The main technical performance indicators of the aerator are power efficiency (EP), oxygen utilization efficiency (EA) and oxygen transfer efficiency (EL). Power efficiency is the amount of oxygen (kg/kwh) transferred to the mixture for every 1kW of electric energy consumed; The utilization efficiency of oxygen is the percentage (%) of the oxygen transferred to the mixed liquid through blast aeration; The oxygen transfer efficiency, also known as the oxygen charging capacity, is the amount of oxygen (kg/ h) transferred to the mixed liquid in unit time through the mechanical aeration device.

　　1. blast aeration device

　　The blast aeration system consists of a blower, an aeration device and an air transmission pipeline. The blower transmits the air to the aeration device installed at the bottom of the aeration tank through a series of pipes, and the oxygen in the air is transferred to the mixed liquid through the aeration device.

　　The aeration devices of the blast aeration system are mainly divided into micro bubble, medium bubble, hydraulic shear, hydraulic impact and other types.

　　(1) Microbubble aerator

　　It is also called porous air diffusion device. Porous materials such as ceramsite and coarse porcelain are mixed with appropriate adhesives such as phenolic resin, and sintered into the form of diffusion plate, diffusion tube and diffusion cover at high temperature.

　　This kind of diffusion device is characterized by producing tiny bubbles, large gas-liquid contact area and high oxygen utilization rate; The disadvantage is that the air pressure loss is large and it is easy to be blocked. The incoming air should be filtered in advance.

　　1) Fixed plate type microporous aerator

　　The plate type microporous aerator is mainly composed of a diffuser, an air distribution chassis, a vent bolt, a gas distribution pipe, a tee short pipe, a rubber sealing ring, a gland and accessories connecting the bottom of the tank.

　　Common plate type microporous aerators include titanium plate microporous aerators, microporous ceramic plates, and aerated plates made of green corundum and green corundum. Its main technical parameters: average aperture 100 ~ 200 μ m; Service area: 0.3 ~ 0.75m2/ unit; Power efficiency 4 ～ 6kgo2/kwh; The oxygen utilization rate is 20% ~ 25%.

　　2) Fixed bell jar type microporous aerator

　　There are microporous ceramic bell shaped disc and green corundum aggregate sintered bell shaped disc. The technical parameters are basically the same as those of the plate type microporous aerator.

　　3) Diaphragm microporous aerator

　　The bottom of the aerator is a base made of polypropylene, which is covered with a microporous membrane made of synthetic rubber, and the membrane is fixed on the base by a metal wire hoop. The diaphragm is provided with holes arranged in the form of concentric circles. During air blowing, the air enters between the diaphragm and the base through the vent hole on the base, so that the diaphragm is slightly inflated, the eyelet is opened, and the air escapes from the eyelet to achieve the purpose of air distribution and diffusion. The air supply stops and the pressure disappears. Under the elastic action of the diaphragm, the eyelet closes automatically. Due to the action of water pressure, the diaphragm is compacted on the base. The mixed liquid in the aeration tank cannot flow back, so it will not block the diaphragm holes. The aerator can diffuse bubbles with a diameter of 1.5 ~ 3.0mm. Even if there is a small amount of dust in the air, it can pass through the eyelet without blocking, and no dust removal equipment is required.

　　(2) Medium bubble aerator

　　The diameter of bubbles produced by this device is 2 ~ 6mm. In the past, they were mainly perforated tubes. The perforated pipe is made of steel pipe or plastic pipe with a diameter of 25 ~ 50mm. Holes with a diameter of 3 ~ 5mm are opened at the lower part of both sides of the pipe wall with a spacing of 50 ~ 100mm. The perforated pipe is not easy to be blocked, with simple structure and small resistance; However, the utilization rate of oxygen is low and the power efficiency is low. Therefore, it is seldom used in the activated sludge aeration tank at present.

　　Reticulated membrane aerator is a representative medium bubble aerator developed in recent years. The utility model is characterized by not easy blockage, uniform gas distribution, simple structure, easy maintenance and management, and high oxygen utilization rate.

　　The aerator is composed of a main body, a screw cap, a mesh membrane, a distributor and a sealing ring; The air enters from the bottom of the aerator, is cut by the distributor for the first time and evenly distributed to the air chamber, and then is cut through the mesh membrane for the second time to form tiny bubbles and diffuse into the mixed liquid.

　　The service area of each reticular membrane aerator is 0.5 m2, the dynamic efficiency is 2.7 ~ 3.7kgo2/kwh, and the oxygen utilization rate is 12% ~ 15%.

　　(3) Hydraulic shear air aerator

　　1) Inverted umbrella aerator

　　The inverted umbrella aerator is composed of an umbrella shaped plastic shell, a rubber plate, a plastic screw and a gland. The air enters from the upper air inlet pipe and is ejected from the gap between the umbrella shell and the rubber plate to the periphery. Under the action of hydraulic shear, the air bubble is sheared into small bubbles. Stop the gas supply and seal the gap by itself with the help of the resilience of the rubber plate to prevent the backflow of the mixed liquid.

　　The service area of the aerator is 6 × 2m2; The power efficiency is 1.75 ~ 2.88kgo2/kwh, and the oxygen utilization rate is 6.5% ~ 8.5%.

　　2) Fixed spiral aerator

　　The aerator is composed of a circular shell with a diameter of 300 or 400mm and a height of 1500mm and spiral blades fixed inside the shell. Each spiral blade is twisted 180 º, and the spiral directions of two adjacent blades are opposite. The air enters the device from the air distribution hole at the bottom through the air distribution pipe and flows upward. Due to the density difference of the mixed liquid inside and outside the shell, the lifting effect is generated, making the mixed liquid circulate continuously inside and outside the shell. During the rising process, the air bubble is repeatedly cut by the spiral blade to form small bubbles.

　　The aerator has three forms: fixed single screw, fixed double screw and fixed triple screw.

　　(4) Hydraulic impact aerator

　　This kind of aerator is mainly a jet type air diffusion device. It uses the kinetic energy of the high-speed water flow of the mud water mixture pumped by the water pump to suck in a large amount of air. The mud water air mixture is strongly mixed and stirred in the throat, crushing the bubbles into mist, so that oxygen can be quickly transferred to the mixture. The oxygen transfer rate can be as high as 20%, but the power efficiency is not high. In recent years, due to the improvement of the waterproof performance of the pump, the integration of the power device and the diffusion device has been realized.

　　2. mechanical aeration device

　　The mechanical aeration device is installed above and below the water surface of the aeration tank and rotates under the driving of power to transfer the oxygen in the air to the sewage through the following three aspects: when the aeration device rotates, the mixed liquid on the surface is constantly thrown from the periphery of the aeration device to form a hydraulic jump, and the liquid level is violently agitated and drawn into the air; The rotation of the aeration device has the function of lifting the liquid, making the mixed liquid in the pool circulate up and down continuously, and the gas-liquid contact interface is constantly updated, constantly transferring the oxygen in the air to the liquid; The aeration device rotates to form a negative pressure zone at its rear side to inhale air.

　　According to the installation direction of rotating shaft, mechanical aerators can be divided into vertical shaft type and horizontal shaft type.

　　(1) Vertical shaft aerator

　　Also known as vertical shaft impeller aerator, commonly used aeration impellers include pump impeller, inverted umbrella impeller, flat plate impeller, etc., as shown in Figure 6-8.

　　The oxygen charging capacity and lifting capacity of aeration impeller are related to impeller diameter, impeller rotation speed and immersion depth. With a certain impeller diameter, the impeller rotates at a large linear speed and has a strong oxygenation capacity. However, if the linear speed is too large, the activated sludge particles will be broken and the sedimentation efficiency will be affected. Generally, the peripheral linear speed of the impeller should be 2 ~ 5m/s. When the immersion depth of the impeller is appropriate, the oxygen charging efficiency is high. If the immersion depth is too large, there is no hydraulic jump. The impeller only plays the role of stirring, and the oxygen charging is very small, or even no air is sucked in. If the immersion depth is too small, the water lifting and water transmission will be reduced. The water flow in the pool is slow, even there is a dead zone, resulting in good oxygen charging of the surface water and insufficient oxygen charging of the bottom layer. Therefore, the linear speed of impeller rotation and immersion depth are often designed to be adjustable so that they can be adjusted at any time during operation. Generally, the oxygen transfer rate of vertical shaft impeller aerator is 15% ~ 25%, and the power efficiency is 2.5 ~ 3.5kgo2/kwh.

　　(2) Horizontal shaft aerator

　　Horizontal axis aerator is mainly rotary brush aerator. It is composed of a horizontal rotating shaft and blades fixed on the shaft. The rotating shaft drives the blades to rotate, stirs the water surface and splashes, and the oxygen in the air is transferred to the water through the gas-liquid interface.

　　Rotary brush aerator is mainly used in oxidation ditch. It has the advantages of convenient load adjustment, easy maintenance and management, and high power efficiency.

　　3、 Aeration tank type

　　The main structure of sewage treatment by activated sludge process is aeration tank. According to the flow pattern of the mixed liquid in the aeration tank, it can be divided into three types: push flow type, complete mixing type and circulating mixing type; According to the plane geometry, it can be divided into rectangle, corridor, circle, square and circular runway; According to the adopted aeration methods, it can be divided into blast aeration tank, mechanical aeration tank and mechanical blast aeration tank combined with the two methods; According to the relationship between aeration tank and secondary sedimentation tank, it can be divided into Aeration Sedimentation combined construction and separate construction.

　　1. push flow aeration tank

　　The push flow aeration tank is usually in the shape of rectangular Gallery, and blast aeration is often used. The traditional method is to install the air diffusion device on one side of the bottom of the aeration tank gallery. This arrangement can make the water flow in the tank spiral and improve the contact time between bubbles and mixed liquid. If the width of the aeration tank is large, the air diffusion device should be installed on both sides of the bottom of the aeration tank gallery. It can also be evenly arranged at the bottom of the whole aeration tank in a certain form, such as mutually perpendicular orthogonal form or quincunx staggered form.

　　The number of aeration tanks depends on the scale of the sewage treatment plant. Generally, the structure is divided into several units. Each unit includes one or several aeration tanks. Each aeration tank is usually composed of one or two to five galleries. When the number of galleries is singular, the sewage inlet and outlet are at both ends of the aeration tank; When the number of corridors is even, it is located at the same end of the corridor.

　　The length of aeration tank gallery can reach 100m, generally 50 ~ 70m. In order to prevent short flow, the ratio of length to width of the gallery should be greater than 5, or even greater than 10. The width depth ratio of the aeration tank is usually between 1.5 and 2. The pool depth is closely related to the cost and power cost. The deep pool is conducive to the utilization of oxygen, but the cost and power cost will be increased. On the contrary, the cost and power cost will be reduced, but the utilization rate of oxygen will also be reduced.

　　In addition, the functional requirements of the civil structure and aeration tank, the allowable occupied land area, the pressure of the blower that can be purchased and other factors shall be considered. At present, the depth of push flow aeration tank is mostly 3 ~ 5m in China.

　　In order to reduce the resistance and avoid the formation of dead zone for the rotating flow of mixed liquid in the aeration tank, the top and foot of the two walls of the tank wall in the cross section of the gallery are made into a 45 ° slope. In order to save air ducts, air diffusers in adjacent corridors are often arranged along public partitions.

　　The water inlet and sludge inlet of the aeration tank are set below the water surface, and the submerged outflow method is adopted to avoid short flow, and a gate is set to regulate the flow; Generally, the overflow weir is used for the outlet water. The treated water flows through the weir crest and overflows into the drainage channel.

　　A vent pipe with a diameter of 80 ~ 100mm is set at the bottom of the aeration tank for venting during maintenance or tank cleaning. Considering the requirements for discharging supernatant during the cultivation and acclimation cycle of activated sludge, according to the specific conditions, 2 ~ 3 drainage pipes with a diameter of 80 ~ 100mm are set at a certain distance from the bottom of the tank.

　　2. fully mixed aeration tank

　　Fully mixed aeration tanks often use surface mechanical aeration devices for oxygen supply, and their surfaces are mostly circular, square or polygonal. The combined fully mixed aeration sedimentation tank, called aeration sedimentation tank for short, is widely used. It consists of aeration area, diversion area and sedimentation area.

　　1) Aeration zone

　　The aeration device is set in the center of the tank top and goes deep into a certain depth underwater. The sewage enters from the bottom of the tank, and is immediately fully mixed with the original mixed liquid in the tank, and fully mixed and contacted with the activated sludge returned from the reflux joint of the sedimentation area. The sewage after aeration reaction flows out of the reflux window around the top and is led into the diversion area. The return window is equipped with a valve, which can control the amount of returned sludge by adjusting the size of the window hole.

　　2) Diversion area

　　It is located between the aeration area and the sedimentation area, with a width of about 0.6m and a height of about 1.5m. A vertical baffle is set inside to buffer the water flow, release the bubbles carried in the mixed liquid, make the water flow smoothly into the sedimentation zone, and create good conditions for solid-liquid separation.

　　3) Sedimentation zone

　　It is located outside the diversion area and aeration area. Its function is to separate mud and water. The upper part is the clarification area and the lower part is the sludge area. The depth of the clarification area should not be less than 1.5m, and the volume of the sludge area should not be less than 2h of sludge storage. The clarified treated water enters the drainage channel along the outlet weir around the pool, and the outlet weir often adopts a serrated triangular weir.

　　The sludge flows back to the aeration area through the return joint, which is generally 0.15 ~ 0.20m wide. A tank skirt is set on the side of the return joint to avoid dead corners. A sludge discharge pipe shall be set at a certain depth in the sludge area to discharge the excess sludge.

　　In production practice, there is also a fully mixed aeration tank separately built with the sedimentation tank. Sewage and return sludge are evenly introduced along the length of the aeration tank, and the mixed liquid is evenly discharged into the secondary sedimentation tank.

　　Simply put, the aeration and oxygenation system in common sewage treatment, aquaculture and water ecological treatment scenarios is composed of blowers, aeration discs, pipelines, valves and other equipment!