Most surface water treatment plants use floc-filtration as the most important treatment step in drinking water production. This paper presents a new technological development which allows floc-filtration to be carried out in pressure filters. Experiments in pilot and full scale show its high efficiency. The technological development allows us to treat algal-rich and high turbid matter containing raw water efficiently at high filtration rates. Floc formation can be realised by means of a special reaction tank in front of the filter inlet. Efficient removal of particles and turbidity is achieved if filtration with filter inlet flow controller is used.