To provide a means of biological treatment of org. substances which is a more natural, safe, sure and low-cost treatment for the water quality control in the chemical treatment of cooling water in a cooling tower.

A steric vacant structure of wires is formed by irregularly bending fused wires on the surface of a cooling liquid and welding points of wire surfaces adjacent to one another to form a cylindrical, planer or boxlike structure. The obtd. product is used as a contact material for a gas flow and used as a contact material or a noise-reductive or deodorizing material which generates electrostatic charges by friction on the wire surfaces to adsorb and trap floating dust. Or, the wire structure is assembled as a contacting material for an industrial water, cooling water, circulating water or the like to oxidize and decompose floating org. substances. Thus, a biological treatment which can be easily controlled is realized instead of chemical treatment.