Invention relates to a water treatment technology, especially to the disinfection of water from gram-positive and a gram-negative bacteria using a formulation comprising CaFeO, preferably Ca2Fe2O5. Invention is a formulation comprising CaFeO, preferably Ca2Fe2O5, and can be used in a method for water disinfection, wherein the method consists of the following steps: a) providing a formulation comprising CaFeO, preferably Ca2Fe2O5; applying said formulation to water to disinfect it, and this step is performed without the presence of light.