Dissolved air flotation (DAF) is an increasingly applied technology for particle removal in water and wastewater treatment. In DAF tiny air bubbles attach to the particles, which float to the surface, forming flocs which can be periodically removed to a sludge channel. The technique originated in the early 1900s, but has steadily widened its application across municipal and industrial water and wastewater treatment, earning a reputation for reliability, controllability and effectiveness. The aim of the Helsinki conference was to provide an opportunity for researchers and practitioners to examine and discuss current developments and applications of DAF technology in water and wastewater treatment. From the 58 oral and poster presentations, 26 papers have been selected for these proceedings. The papers have been divided into four themes: drinking water treatment, wastewater treatment, industrial and trade applications, theory and modelling.