Environment Technology

The lifting microporous aerator is mainly composed of microporous aerator, movable rocker arm and hoist. The microporous aerator consists of microporous tube, front cover, back cover and connecting bolt. The movable rocker arm is a liftable piping. The microporous aerator is mounted on the bronchus and is grid-shaped. The base is fixed on the wall of the pool, the movable riser is extended into the pool, and the branch pipe falls on the bottom of the pool and supports it. Supported at the bottom of the pool; (3) Aerator hoist, which is a movable electric hoist, the hoisting trolley can move at will and lift the rocker arm.

Its working principle is that air enters the aeration pipe from the air vent of the back cover of the micro-bubble aeration pipe, and many tiny holes are densely distributed on the pipe wall of the aeration pipe. Under the action of pressure difference, air in the pipe diffuses from the holes in the pipe wall, forms many tiny bubbles in the sewage, and causes turbulence of water, thus achieving the purpose of dissolving oxygen in the air into water.

There are many forms of micro-porous aeration pipe. At present, there are two kinds of commonly used aeration pipe: one is a common aeration pipe sintered from coarse ceramics or corundum. This kind of pipe wall produces many tiny pores in the sintering process. Its main characteristics are that it can produce tiny bubbles with a diameter of about 0.1-0.2 mm, large gas-liquid contact area, high oxygen utilization rate, generally up to 20-25%; The point is that the air pressure loss is large and easily blocked. The incoming air needs to be filtered and damaged. Once damaged, the oxygen utilization rate begins to decline rapidly. The other is tubular diaphragm microporous aeration pipe. This kind of aeration pipe is basically the same as the former one, but its own structure is quite different. It is made of a pipe made of ABS or UPVC as a distribution pipe. There are ventilation holes on the wall of the pipe. The diaphragm made of synthetic rubber is covered around the distribution pipe, and the diaphragm is fixed on the pipe by metal clips. Laser is used to drill uniformly distributed holes on synthetic rubber diaphragm. During aeration, air enters between the diaphragm and the pipe wall through the air vent on the pipe wall. Under the action of compressed air, the diaphragm bulges slightly, and the hole opens to achieve the purpose of air distribution and diffusion. When the gas supply is stopped and the pressure disappears, the diaphragm itself will automatically close the hole under the action of elasticity. Because of the effect of water pressure, the diaphragm will be pressed on the wall of the pipe. Therefore, the sewage will not backflow and plug the hole. However, the diameter of the opening of the diaphragm directly affects the utilization of oxygen, so the diameter of the opening should be appropriate. If the diameter of the hole is too large, the utilization rate of oxygen is low, and the diameter of the hole is too small, the utilization rate of oxygen is high, but the resistance increases. Rubber diaphragm should be aged-resistant, high-strength gum, in order to avoid tearing diaphragm, causing damage to the aerator.

Dynamic aerator:
Dynamic aerator is a new type of aerator, which belongs to fixed micro-bubble aerator. It consists of a dome, a rotary mixing cylinder, a rotary mixing ring, a sleeve joint hoop and a distribution pipe.

The dynamic aerator adopts the technology of "large-hole exhaust bubble air distribution". The air introduced into the aerator is diverted in positive and reverse directions, clockwise and counterclockwise. Under the action of two different directions of swirling flow, a gas-liquid enhanced swirling mixing zone with instantaneous continuous local reaction is formed in the sleeve swirling mixer. A large number of bubbles produced by the action of swirling mixing and swirling flow are blocked by a circular cover, and bubbles are produced upward uniformly and densely. Generally speaking, dynamic aerator is composed of macroporous bi-directional rotary mixing, sleeve enhanced rotary mixing and dome blocking diffusion, which makes gas phase collide, shear and split in liquid phase, thus forming mixed diffusion. Because the dynamic aerator uses large-hole exhaust, even after the air stops and the pressure stops, the sewage will flow back into the aerator and the distribution pipe, which will not cause the blockage of the exhaust hole, thus fundamentally solving the blockage problem of the aerator, and can keep the oxygen utilization rate unchanged for a long time. Oxygen utilization rate is lower than that of microporous aerator due to the larger diameter of bubbles, generally between 15% and 19%. The structure and performance of the dynamic aerator are similar to that of the rotary mixing aerator.

Contrast between Rocker-arm Microporous Aerator and Dynamic Aerator:
In addition to the differences in bubble diameter, oxygen utilization rate and blockage, the two have the following differences:

Installation mode:
Rocker arm micro-porous aerator can be installed movably. When the aerator needs to be replaced or repaired, it can be used to lift the aerator out of the water and carry out construction and maintenance on the surface of the pond. It does not affect the work of other aerators in the same pond. It does not need to stop the pond for water purification. The cost of maintenance is low and the workload is low.

Dynamic aerator is fixed installation, once installed, it can not be moved. If an aeration tank needs to be repaired, it must stop the operation of the tank, and after the sewage and silt and other debris in the tank are removed, construction can be carried out. The cost of maintenance is high.

Durability:
The main failure modes of rocker-arm microporous aerator are as follows: firstly, iron oxide and impurities in sewage and air caused by rusting of steel cloth pipe will cause blockage of aeration pipe, uneven distribution of airflow in aeration pipe, which makes aeration pipe flutter and causes fatigue damage; secondly, aeration pipe is installed on pipe joint, which is easy to follow under the dual effects of aeration pipe flutter and sewage corrosion. When the roots are broken, the corrosion of the sewage will also result in the thinning and perforation of the distribution pipe wall. Third, the movable joints of the underwater rocker arm may be immersed in the water for a long time, which may be unable to rotate due to rust and other reasons, so that the aerator can not be lifted to the water surface normally. The three failure modes mentioned above have been greatly improved by the application of new technologies in recent years, so that the service life of the aerator can reach about 5 years.

The failure modes of dynamic aerator are as follows: due to fatigue or corrosion, the connecting parts of aerator head components (such as dome, rotary mixing cylinder, rotary mixing ring, etc.) are broken or loosened, which results in the disintegration or fall off of aerator head; the distribution pipe is broken; the distribution pipe is generally made of non-metallic pipe materials such as UPVC, and the pipe and pipe are mostly bonded with glue, once the bonding is not firm, it is easy to stick from the pipe. Jointly falling off and leaking. These three failure modes can be avoided by reasonable selection, correct selection of materials and strict quality control. Therefore, the service life of the aerator is longer, reaching 8 to 10 years.

Practical application:
Rocker-arm microporous aerator is widely used in the primary biochemical system with heavy production load and poor sewage quality because of its high oxygen utilization rate and convenient maintenance. Fixed dynamic aerator is generally used in the secondary biochemical system with lower production load and better sewage quality because of its low oxygen utilization rate but long-term maintenance, difficult maintenance and long service life. 。

There are many kinds of aerators. After continuous renewal and development, the structure and performance of aerators are changing with each passing day. The introduction is only a few of them, and the discussion is only based on the situation of a limited number of sewage treatment plants in the region. Some views have great one-sidedness and limitations. In fact, the selection basis of aerator has different emphasis, mainly considering the following factors:

(1) The air diffusion device should have higher oxygen utilization efficiency and power efficiency, and better energy-saving effect;

(2) It is not easy to plug, troubleshoot and maintain.

(3) The structure is simple and easy to install. The cost of the project and the cost of the device itself are low.

In addition, the water quality of sewage, regional conditions, aeration tank type and water depth should also be considered.