Principles of ozone, deodorization, decolorization, and COD reduction



Ozone (O3) wastewater treatment technology was applied to water treatment in 1905. With the advancement of related technologies and the reduction of the cost of ozonation, it is widely regarded as a promising water treatment method. Due to its technological and economic advantages, it has been widely applied and has achieved some research and engineering application results. Below, we will introduce the principle of ozone in the process of sewage treatment, including deodorization, decolorization, and COD reduction.

1
Ozone reduction of residual sludge
The activated sludge process improves the daily sewage treatment capacity and has been widely used as a common sewage treatment technology both domestically and internationally. However, the excess sludge generated during the sewage treatment process has become a problem, and the cost of sludge treatment accounts for a large proportion of the entire sewage treatment cost. In the technology of reducing excess sludge, the reduction technology of using ozone for pre-treatment of sludge has become relatively mature.

After ozone treatment, the sludge enters the aeration tank together with the target wastewater as a part of the sewage, and is utilized and digested by microorganisms. Part of it is converted into carbon dioxide. Through this ozone pre-treatment process on the sludge, the remaining sludge is significantly reduced. Ozone residual sludge reduction technology requires an ozone generator on site, which consumes a large amount of energy. The development of high-efficiency ozone generators and the utilization rate of ozone play a significant role in reducing sewage costs.

In recent years, Japan has been committed to the development of high-efficiency ozone generators. In research to improve ozone utilization efficiency, it has changed the continuous concentration ozone treatment of sludge to intermittent concentration ozone treatment of sludge. Using actual wastewater as a control experiment, it was found that the improved ozone sludge treatment requires about a quarter of the ozone amount of the raw material. Simultaneously treating water quality is superior to continuous low concentration ozone treatment, providing a possible way to reduce the cost of wastewater treatment technology for reducing ozone sludge.

2
Ozone for removing odors from water bodies
The substances that produce odors during the sewage treatment process are mainly composed of carbon, nitrogen, and sulfur elements.

Only a few substances that produce odors are inorganic compounds, such as ammonia, phosphorus, and hydrogen sulfide; Most odor producing substances are organic compounds, such as low molecular weight fatty acids, amines, aldehydes, ketones, ethers, etc. Based on the inflow situation of the sewage treatment plant where I am located, 80% of the inflow is domestic sewage, which has a high content of organic matter and relatively low content of inorganic compounds.

The substances that produce odors are mostly organic compounds, such as low molecular weight fatty acids, amines, aldehydes, ketones, ethers, etc. These substances all carry active groups and are prone to chemical reactions, especially oxidation. By utilizing the strong oxidizing property of ozone, the active groups are oxidized, and the odor disappears, thus achieving the principle of deodorization.

In addition to removing odors, ozone can also prevent the recurrence of odors. This is because the gas produced by the ozone generator contains a large amount of oxygen or air, and substances that produce odors are prone to odor in oxygen deficient environments. Ozone treatment is used to oxidize and deodorize while creating an oxygen rich environment, which can prevent the recurrence of odors. The improvement effect on the sewage treatment environment of urban domestic sewage plants is still relatively significant.

3
Ozone decolorization of water bodies
With the increasing attention to the environment of tap water sources and the reuse of secondary treated water in sewers, the color removal of secondary treated water has received attention.

As for the color and taste caused by humus, the average chromaticity of water quality is 10 degrees. Up to 20 degrees. Such chromaticity cannot meet the water quality standards for sufficient removal through general coagulation precipitation and sand filtration processes, and may even exceed the worst-case standards. After ozone treatment, the chromaticity can be reduced to below 1 degree. Generally, the reason for coloring tap water is due to excessive iron and manganese content. If these metals are in a free state, conventional methods can fully remove them. If the raw water contains humus, it can sometimes form chromium salts, which are quite difficult to treat with conventional methods. Therefore, color removal is also an important factor in introducing ozone treatment.

4
Principle of Ozone Action
The decolorization mechanism of ozone: With the vigorous development of molecular biology, microbiology has extended ecology to the molecular level.

In fact, both proteins and nucleic acid molecules are organic compounds composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus or sulfur (C, N, O, N, P, or S). At the same time, the toxic shell is composed of many protein subunits, namely shell particles. Each shell particle is connected by non covalent bonds and symmetrically wrapped together, proteins are composed of multiple chains, and nucleic acids are composed of nucleotide chains connected together.



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