This　paper　explores　the　feasibility　of　using　potassium　manganate　(K2MnO4)　in　water　treatment.　Manganate　(Mn(VI)),　like　ferrate　(Fe(VI)),　can　act　as　both　an　oxidant　and　a　coagulant/adsorbent　arising　from　the　formation　of　insoluble　manganese　dioxide　(Mn(IV))　from　the　chemical　reduction　of　MnO42.　In　this　paper　the　basic　properties　of　K2MnO4　are　described,　including　the　standard　electrode　potential　which　exceeds　several　oxidizing　agents　commonly　used　as　water　treatment　chemicals.　The　methods　of　preparing　K2MnO4　are　outlined,　and　the　main　reaction　products,　which　are　potassium　permanganate　(KMnO4)　and　manganese　dioxide　(MnO2),　and　their　use　in　water　treatment　are　summarized.　Some　preliminary　results　of　water　treatment　tests　in　China　and　at　Imperial　College　London　are　presented,　and　alternative　ways　of　applying　K2MnO4　in　water　treatment　are　proposed.　Finally,　the　paper　provides　a　preliminary　evaluation　of　the　economic　feasibility　of　using　K2MnO4　in　comparison　with　alternative　chemicals,　such　as　KMnO4.　Overall,　it　is　believed　that　K2MnO4　may　be　a　useful　water　treatment　chemical　in　the　future.