The cause of the odor is "trimethylamine", which is produced by decomposing dimethylamine derived from fish. Test introduction of a device that injects "chlorine dioxide water", which is an effective disinfectant, while generating it locally. In addition, a pH control device for circulating water in the scrubber tower was installed and evaluated for 8 months. [Evaluation points] ・ Even in the summer, when problems tend to occur, the odor in the factory is reduced to a value that does not cause problems. ・ 35% reduction in chemical cost compared to the disinfectant [sodium hypochlorite] used before ・ The adhesion _of minerals _and biofilm [propagation of germs] that had been seen before have been eliminated, _and maintenance costs have been reduced. ≪Advantages of chlorine dioxide≫ -It works as a powerful oxidizing agent _and efficiently decomposes odorous components "sulfide" _and "trimethylamine". The bactericidal effect lasts, so the inside of the tower is kept clean. ・ The effect does not decrease depending on the pH value. ・ No generation of trihalomethane