ABSTRACT
Sedimentation and dissolved air flotation (DAF) were studied for particle removal, in particular of the single cells form of the cyanobacterium Microcystis aeruginosa. This cyanobacterium species is considered a suitable representative of algae and particles of the problematic size range (3-10 µm) in the assessment of removal efficiency. The agglomeration (coagulation/flocculation) phase was proven to determine the down-stream process efficiency. Relevant process parameters were studied on a bench-scale (using model water) and pilot plant scale (using reservoir water), including the influence of coagulant dose (FeCl3), coagulation pH, flocculation time, energy input (G value), single stage versus tapered flocculation, and application of cationic polyelectrolyte as coagulant aid. The process efficiency was interpreted in function of the preceding agglomeration (coagulation/flocculation) phase and the obtained particle (floc) size distributions. The particle (floc) size - density relationship was addressed.
