Method, system and device for reducing microbial concentration and/or biofilm formation

A device for reducing microbial concentration in a hydrocarbon or for reducing biofilms formed in a hydrocarbon, on the surface of the hydrocarbon, or on the surface of equipment involved in the storage, transport or processing of the hydrocarbon, comprising:

• a hydrocarbon container;
• an oxidizing agent introducing component for introducing a liquid composition oxidizing agent compound to hydrocarbon to be treated, and
• at least one radiation emitting component for creating radiation of certain wavelengths arranged inside the hydrocarbon container, the at least one radiation emitting component being one of (i) a floating mat having a density to enable flotation at an interface between hydrocarbon content and water accumulated in the hydrocarbon container, (ii) a mat that rests on the bottom of the hydrocarbon container, or (iii) a lining layer on a wall of the hydrocarbon container,
• wherein the liquid composition comprising the oxidizing agent compound functions together with the radiation of certain wavelengths to lead to a synergistic reaction.