The invention relates to a microbial control system for treating influent water and sump water for control of microbial material in machines which process water such as ice making machines, humidifiers such as cool mist humidifiers and cooling towers. The microbial control system includes antimicrobial treatment media housed in a containment vessel. The treatment media can include any one or more of transition metals and transition metal oxides. The transition metal may be any of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs, Mt, Uun, Uuu and Uub.
