What is an oxidizing biocide?
Oxidative bactericidal algicide is a biocide with strong oxidizing properties, usually a strong oxidant, which has a strong killing effect on microorganisms in the water. Oxidizing biocides can oxidize other reducing substances in the water. When organic matter, hydrogen sulfide, and ferrous ions are present in the water, some of the oxidizing biocides will be consumed, reducing their biocidal effect. Commonly used oxidizing biocides in circulating cooling water systems are compounds with oxidizing properties such as chlorine-containing compounds, peroxides, and bromine-containing compounds. These compounds generally have the advantages of fast bactericidal and algae killing speed, high broad-spectrum killing effect, low treatment cost, relatively small impact on environmental pollution, and microorganisms that are not easy to develop drug resistance. The disadvantage is that it is greatly affected by the organic matter and reducing substances in the water, the medicament time is short, and the pH value in the water is also greatly affected. At the same time, the dispersion, penetration and peeling effect is poor. The halogen elements chlorine, bromine and iodine are all oxidizing biocides with good performance. Chlorine has a wide range of sources, low price, convenient use, and good sterilization effect. It can be used with many water treatment chemicals without interference or little interference. It has little environmental pollution. It is widely used as a microbial fungicide for industrial and civil water. Large-scale circulating cooling water systems mostly use liquid chlorine, while cooling water systems with a small amount often use sodium hypochlorite or bleaching powder.
The bactericidal effect of chlorine is that chlorine generates molecular hypochlorous acid in water. Hypochlorous acid molecules can penetrate the cell membrane of microorganisms and produce stable N-CL bonds with proteins, which weaken or inactivate the reductase necessary for respiration. At high concentrations, it will destroy the cell wall. The higher the proportion of chlorine added to the water in the form of hypochlorous acid, the better the sterilization effect.
The effect of chlorine treatment is very fast, and the protozoa (such as paramecium and ciliates) and rotifers in the water are quickly killed after the chlorine is applied. Algae are more likely to be killed by chlorine than bacteria. Adding chlorine to a concentration of 1mg/L can kill most of the algae. The lethal chlorine concentrations of cyanobacteria and diatoms are 0.5-1.01mg/L and 0.1-1.01mg/L, respectively.
