Abstract: A method and apparatus is described that uses a device that presents a surface of a dielectric material to a flowing or circulating fluid that results in charge being created at a boundary layer of the dielectric where it contacts the fluid by ion exchange and charging of compounds, for example insoluble dielectric particles such as colloids, and using at least one control impedance to control an impressed current in the fluid caused by the fluid flowing through the device and to cause suspended particles in the fluid to be charged, whereby the charge of the suspended particles is then neutralised causing coagulation of the particles as suspended insoluble particles.