Abstract: A magnetic separation apparatus is described, which is primarily intended for separating magnetic particles contained in a fluid. Such apparatus is primarily used in the process of sewage purification by binding magnetic particles to the substance to be removed, and by applying a magnetic filter. The invention resides in the fact that the channel for supplying the liquid to be treated has such a shape that part of the substance to be separated already precipitates before reaching the actual magnetic filter. This avoid the quick filling of the magnetic filter thus extending periods between rinsing the filter. By applying a relatively weak field in the area in which precipitation takes place, precipitation is enhanced.