a process for the chemical treatment of organic waste materials contaminated with a pathogenic microorganism , such as raw sewage , sewage sludge and other organic waste products , and to the treated organic waste material so obtained , which process comprises : prereacting the organic waste material with a water - soluble methylol compound subject to condensation , such as a methylolurea compound , under alkaline ph conditions ; and , thereafter , condensing the methylol compound by establishing an acid ph condition to form a solid waste product comprising a condensation polymer containing methylene bridges and a sterile solid waste material .