A new generation of USF Memcor's microfiltration (CMF) process has been developed. The design utilizes submerged membranes in an open tank rather than multiple pressure vessels, as in the existing CMF technology. The technology is known as CMF-S (submerged). It is the result of several years of R&D and represents a natural progression of the CMF technology into very large-scale filtration applications. The simplification of the process and system makes it cost effective even at capacities greater than 100 ML/day, using unit multiples of approximately 20 ML/day. This paper briefly reviews the history of CMF development and describes the first commercial project using the new CMF-S at Marulan in Australia. Although only a small scale system, the concepts are applicable to very large plants. Design concepts for large scale systems are also outlined.