Biofilm= a slime layer which naturally develops when bacteria attach to an inert support that is made of a material such as stone, metal, or wood. In nature, nonfilament-forming microorganisms will stick to the biofilm surface, locating within an area of the biofilm that provides an optimal growth environment. Bacteria preferentially attach to a variety of surfaces, and bacterial communities exhibit properties, behaviors and survival strategies that far exceed their capabilities as individual bacteria. Many studies have shown that the multicellular construction of biofilms affords protection for cells. Moreover, the bacteria in the biofilms react in the different way to the chemical treatment, such as chlorination. The methods that are found to be effective against the biofilms are disinfection by the trace metals, chlorination with the UV light, heat disinfection, combination of ultrasound with the antibiotics, disinfection by ozone, and use of various chemicals. The chemical methods for treatment and preventing the biofilms are described in this work.