Potential of electrolytic flocculation for recovery of micro-algae

Cost-effective harvesting of micro-algae has always been a major bottle-neck not only in the exploitation of pure mass algal cultures but also in waste stabilization ponds, high rate algal ponds, and reservoirs for drinking water production. Most existing algal separation processes have several disadvantages such as intolerable costs, undesirable low dry mass percentages after harvest or algal slurries contaminated with toxic flocculants which can make the algal product unsuitable for further uses as food and feed. The algal separation experiments described in this paper deal with a rather new technique, namely electrolytic flocculation. This technique involves no flocculants and needs only relatively little electricity to flocculate the micro-algae from a suspension and subsequently float the algal flocs. Efficiencies of 95% elimination or more are easily obtained with different taxonomic groups of algae tested while the consumption of current only amounted to about 0.3 kWh/m(3). Copyright (C) 1997 Elsevier Science B.V.