The removal of bacteria from rearing water and washing water in aquaculture systems, aquariums
and fishing port facilities is the most important means of diminishing the risk of fish diseases,
improving public health and ensuring high food quality. However, there are few methods of
bacterial elimination, e.g., disinfection. Thus, it is necessary to develop a technology for bacterial
removal from coastal seawater. In this study, the removal efficiency for several groups of bacteria
by foam separation using dispersed bubbles and surface-active substances was determined using
both batch equipment and a continuous-flow unit. By batch processing with only 1mg/l milk casein
added as a surface-active substance and by supplying bubbles, viable bacteria, enterococci, Vibrio,
and Salmonella-like bacteria were removed effectively at removal efficiencies of 80% or greater.
In addition, suspended solids were also removed from coastal seawater. However, fecal coliforms
were difficult to remove by foam separation. The removal efficiency for viable bacteria was greater
than 70% using a continuous system. Bacteria were concentrated in a very small amount of generated
foam and removed from the water. The foam separation using dispersed bubbles and surface-
active substances is a feasible convenient technology for seawater purification as a treatment
prior to membrane filtration or ultraviolet irradiation.