A non-filtration pre-separation device and method for the removal of algae using the same, comprising a system having a hydrodynamic separator including at least one curved structure for the removal of bio-organisms from seawater, such structure having an inlet in operative connection with a source of raw seawater and a bifurcated outlet operative for passing pre-treated effluent fluid to a downstream filtration system and the removal of waste fluid. Various fluidic structures, implementations and selected fabrication techniques to realize such a device, whether singular or in stacked and/or packed parallel configuration are also provided.