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Effect of foam production on sewage treatment system

2019-11-12 Classify:技术支持

Effect of foam production on sewage treatment system

Activated sludge process is widely used in the world today. Foam treatment is a common phenomenon when sewage treatment plants treat sewage with activated sludge process. A major problem in the implementation of activated sludge process and the normal operation of the system is the formation of foam on the surface of the aeration tank. Relevant information shows that this phenomenon is widespread all over the world.

1. Effect of foam production on sewage system

The influence of foam generation on the normal operation of sewage treatment system is manifested in:

(1) in the initial commissioning process, the sludge after inoculation will be taken away by a large amount of foam, which not only increases the commissioning time, increases the investment cost, but also increases the difficulty of debugging, and seriously affects the debugging results in the low temperature area.

(2) because of the viscosity of the foam, the aeration efficiency of the aeration tank is greatly reduced. This is because, under the action of its viscosity, a lot of solids will fall into the floating foam layer, and the floating layer will turn over.

(3) the activated sludge system adopts pure oxygen seal, and a large number of foam enters into the oxygen compressor may cause fire.

(4) in the process of flowing into the sedimentation tank, the existence of baffles results in the increase of suspended solids and further deterioration of water quality.

(5) the accumulation of foam is one of the important causes of corruption. At the same time, it is easy to freeze in cold winter, which affects the normal operation of the system.

(6) in the remaining sludge, there will be some foam in the process of anaerobic nitrification, which will cause bubbles and damage the anaerobic sludge treatment process.

Two. Analysis of the causes of bubbles

1, the emergence of chemical foam.

The active substances contained in detergents or industrial products in the waste water will form chemical foam when they are agitated or aerated. Under the action of the active agent produced by the microorganism itself or brought by the water, the surface tension of the liquid is greatly reduced. With the decrease of the surface tension of the liquid, the bubble will have certain elasticity, light weight and milky white. With the increasing amount of activated sludge, microorganisms can effectively decompose surface substances and detergents, and gradually dissolve the foam.

2. Denitrification foam production

In the normal operation of the system, digestion reaction may take place in the biochemical tank, while denitrification will take place in the place where there is insufficient gas burst and sedimentation, and the generation of bubbles such as nitrogen in the reaction will drive the local sludge to float up. Denitrification foam was produced.

3. Generation of biological foam

In the activated sludge, abnormal growth of microbes often occurs. During the aeration process, bubbles will selectively combine with microorganism and produce biological foam.

Three. Measures to eliminate bubbles

1. Physical methods to eliminate bubbles

High speed spraying of water or water droplets can break the surface of the water, thus effectively reducing the amount of foam. But this can not eliminate this phenomenon fundamentally. It is a commonly used physical method that the settling performance of the dispersed sludge can be partially restored. Another way is to increase the sludge concentration. The consumption of active agents is increased and the foam is fundamentally eliminated.

2. Chemical methods to eliminate bubbles

A large amount of defoamer is added. The use of defoamers includes the use of strong oxidizing chemicals such as ozone, bactericide and peroxide. In addition, the use of polyethylene glycol, ferric chloride and copper acid pickling fluid can reduce the growth rate of foam, but the formation of foam can not be prevented.

3. Biological methods to eliminate bubbles

Addition of special microorganisms. Relevant research data show that cultivating a special strain can effectively eliminate the vitality of the strain. Among them, special species include protozoa such as nephromorpha. At the same time, it can also play a control role in the resistance and predatory microorganisms.

Four, summary

This paper systematically analyzes the influence of foam generation on the normal operation of sewage treatment system, the causes of bubbles and the elimination measures of bubbles. It shows that a major problem in the implementation of activated sludge process and the normal operation of the system is the emergence of foam on the surface of the aeration tank. The methods of eliminating bubbles by physical method, chemical method and biological method are put forward.