3. Results and discussion
3.1. Effect of different types and dosages of flocculants on flocculation efficiency of C. vulgaris
In early stage of the study, different flocculants were tested individually. It was the goal of that stage to pick out the more efficient flocculants for further experimentation using coagulant and flocculant mixtures, and with flocculated biomass used as ballast agent. From the experiments, it was found for non-ionic Superfloc N-300 (Fig. 2a) and anionic Superfloc A-100 (Fig. 2b) flocculants used, that the flocculation efficiency both was of them close to the control experiment. Our study has shown that the PEO-based cationic flocculant Sibfloc-718 has similar efficiency to that of the PAA cationic flocculant Superfloc C-492. Thus, sedimentation efficiency of about 80% was achieved in 120 min for both flocculants. However, note that the efficiency, over 5 min of sedimentation, for Sibfloc-718 of 15 mg/l concentration (Fig. 2d) was 50%, whereas in Superfloc C-492 case at 25 mg/l concentration (Fig. 2c) it was 40%.