What is fine bubble?
History and definition of fine bubbles
Traditionally, bubbles had not been clearly distinguished by their size. Because many of the various important properties contributed by bubbles are greater influenced by the material in and/or surrounding the bubbles than the bubble size. In addition, there were no simple equipment or commercially available generators that can artificially and easily reduce the size of bubbles.
Before 2000, however, a first microbubble generator was developed in Japan, the results of promoting the growth of oysters by diffusing very small bubbles in oyster cultivation in Hiroshima, Japan, were reported in the newspaper, in which “very small bubbles” were called “microbubbles” that name has become established in Japanese society. Microbubbles have also been applied to aquaculture, agriculture, clinical medicine, food industry, chemical industry and so on. The production method of microbubbles was developed and improved year by year. In addition, the microbubble research has advanced academically, and the results of numerous fundamental research and applied research have been distributed.
Furthermore, the decomposition of harmful substances by “nanobubbles” which are further refined microbubble was attracted on a newspaper in 2007. After that, the results of waste water treatment, fishery, agriculture, plant cultivation etc. were also reported. Here, “micro-” and “nano-” which are used as the prefix of bubble are not meaning “one part of one million” or “one billionth part” respectively but “fine” and “ extremely fine” degree of designation, frequently the definition and interpretation have differed by the user or researcher.
Because of these circumstances, it is necessary to promptly internationalize these names and definitions, as well as the spread and expansion of products and technologies that use "microbubble" and "nanobubble" in the Japanese market, and in June 2013 the International Organization for Standardization (ISO), Technical Committee for Fine Bubble Technology was established and definitions and standardization of “fine bubbles” are being discussed. By consultation by delegates from all over the world here, bubbles with a sphere equivalent diameter of 100 micrometers or less are called “fine bubbles” and are distinguished from other usual bubbles.
Moreover, it was decided to call bubbles with a diameter of 1 to 100 micrometers as "microbubbles” and the smaller bubbles that are invisible with a diameter of 1 micrometer or less called "ultrafine bubbles." The Union of Fine Bubble Scientists and Engineers was established on April 1, 2015. The fine bubble technology is attracting attention as an innovative technology that can be applied to a wide range of fields from not only Japan but also the world.