Particles in water play an important role in all kinds of water quality and treatment issues. Since the early beginnings of centralised water production and treatment, the main goal of water purification was primarily the removal of water turbidity in order to produce clear water free from visible particles. The Handbook on Particle Separation Processes provides knowledge and expertise from a selected group of international experts with a wealth of experience in the field of particles and particle separation in water and wastewater treatment. The Handbook on Particle Separation Processes includes an edited selection of presentations and workshops held at the academic summer school Particle Separation in Water and Wastewater Treatment, organised under the supervision of the IWA Specialist Group Particle Separation.