a contaminated water disinfectant and method including a quantity of substantially dry soluble alkali metal ferrate particles . a porous sealed packet contains the particles in a quantity sufficient to disinfect a predetermined quantity of contaminated water by oxygenation . a quantity of substantially dry insoluble inert particles are also contained within said packet and are of sufficient weight to cause the packet to at least partially sink into the contaminated water . the packet is formed of a porous sheet material capable of passing oxygen and water therethrough while preventing undissolved ferrate and inert particles from passing from the packet and entering the water .