The Western Treatment Plant (formerly the Metropolitan Sewage Farm or, more commonly, the Werribee Sewage Farm) of Melbourne Water, is a 110 km² sewage treatment plant located in Cocoroc, Victoria, Australia, 30 km west of Melbourne’s central business district, on the coast of Port Phillip Bay. The plant's land is bordered by the Werribee River to the east, the Princes Freeway to the north, and Avalon Airport to the west.