Detecting waterborne pathogens is a challenging task because of their low concentration in water and their wide diversity. In order to ease this detection process, the potential of microfluidics is investigated in this paper. Spiral channels are designed for separating particles, in a single device and without any external forces or additional buffer, depending on their size at high flowrates. This paper focuses first on the impact of the channel length, flowrate, particle concentration and size on the separation efficiency of polystyrene beads of relevant sizes (4-7 mu m). The system is then tested with viable and non-viable pathogens (Cryptosporidium parvum) with an average size around 4-5 mu m. (C) 2015 The Authors. Published by Elsevier Ltd.