About Fine Bubble
Fine bubbles are microscopic bubbles. The International Organization for Standardization (ISO) defines a microscopic bubble with a diameter of less than 100-μm as a Fine Bubble. Depending on the size, fine bubbles are classified into ‘micro bubbles’ and an ‘Uultra-fine bubbles.’ Fine Bubble technology is utilized in various fields, such as environment, agriculture, fishery, cleaning, medical, and food. Further utilization of Fine Bubble technology is expected worldwide in the future.
Characteristics of Fine Bubble
Fine bubbles possess various characteristics that are different from those of normal bubbles as fine bubbles are small. Fine bubbles are now utilized for various purposes that take advantage of their characteristics, and further utilization is expected in the future. We introduce some of the common characteristics possessed by fine bubbles and their advantages.
Low buoyancy, remain in water for long periods and over a wide area
In proportion to the volume of gas, the buoyancy of fine bubbles in gas decreases as the diameter of bubbles gets smaller. Since fine bubbles with low buoyancy can remain in water for long periods, more efficient and continuous treatment can be performed. Furthermore, since bubbles can be dispersed by putting them in a stream, continuous treatment can be performed in a wider area. Fine bubbles also demonstrate effectiveness in dispersing agents into water body.
Large contact area with liquid significantly increases reactivity
Supplying fine bubbles significantly increases the contact area between a gas and a liquid per unit volume compared with large diameter bubbles. This produces various effects, including enhanced reactivity of vapor-liquid, shortened reaction time, reduced reaction tank, and required gas volume. Supplying fine bubbles enables more efficient treatment, specifically ‘activation of microorganisms’ and ‘reduction of usage of agents’, etc.
Promote floatation separation and prevent sludge accumulation at tank bottom
As bubbles attach to suspended matter floating in liquid in the process of floating, the bubbles encourage the suspended matter to float to the surface of the liquid. Since the size and form of suspended matter are not uniform, it is often seen that large bubbles have difficulty in attaching, which makes it hard for the suspended matter to float to the surface. On the other hand, fine bubbles enter into crevices in the components, and the ability of matter to float to the surface is therefore improved by covering the entire components with fine bubbles. Various advantages are gained as a result, including promotion of separation, such as ‘solid-liquid separation’ and ‘oil-water separation,’ and shortening of the separation time.
The surface tension of a liquid is proportional to the density of the liquid. The apparent density of a liquid decreases and the seepage force increases by supplying fine bubbles into the liquid. In addition, as bubbles absorb and separate dirt such as oil content that becomes attached to walls by the effects of the electrostatic property and hydrophobicity of fine bubbles. Fine bubbles deliver enhancement of detergencye, enabling shorter washing times.