PURPOSE: To lyse and kill microorganisms adhering to solid surfaces in carrying out heat recovery or exchange utilizing seawater by adding an adequate amount of bacterial parasitic bacteria or administering a sponge containing the bacterial parasitic bacteria cultured and impregnated therein into intake seawater.

CONSTITUTION: Fouling microorganisms adhering to solid surfaces in carrying out heat exchange, etc., utilizing seawater, such as various apparatuses in ocean thermal difference power generation systems, littoral electric power stations or combinates, and driving units in ships are prevented and eliminated. In the process, bacterial parasitic bacteria (derovibrio) are added into intake seawater and the above-mentioned microorganisms are subjected to lytic treatment. The treated seawater is subsequently brought into contact with the solid surfaces to lyse newly adhered fouling microorganisms and then partially circulated for use. Alternatively, sponge balls prepared by separately culturing and impregnating the derovibrio thereinto are administered into seawater to lyse the microorganisms. The resultant sponge balls are simultaneously brought into contact with the solid surfaces to also carry out mechanical washing. The derovibrio is readily handled due to high survival ratio and vigorous fecundity thereof.