Don Weiss was born in the Melbourne suburb of St Kilda on 4 October 1924 and died in Melbourne on 30 July 2008. He was educated in South Australia, at Scotch College, the South Australian School of Mines and Industry, and the University of Adelaide. He joined the Council for Scientific and Industrial Research (CSIR) in 1948 and worked for CSIR and its successor organization, CSIRO, until his retirement in 1984. He was the Chief of the CSIRO Division of Chemical Technology from 1974 to 1979 and Director of CSIRO's Planning and Evaluation Advisory Unit from 1979 to 1984. He was a highly imaginative and creative scientist whose work was always driven by his clear understanding of its application. He made important contributions to separation science but is best known for his contributions to technology for water and waste water treatment. His enduring legacy is the more than twenty MIEX plants that have been installed around the world.