Following the use of coagulant and the flocculating agents based on different polymers, the study looked at combined application of coagulants and flocculants. Thus, over 5 min of sedimentation the flocculation efficiency was, for combined use of ferric chloride with Superfloc C-492 and ferric chloride with Sibfloc-718, equal to 60% and 87%, respectively (Fig. 3b). These indicate that flocculation efficiency of mixtures is much higher than for these flocculants used individually. Note also, that the flocculation efficiency with mixture exceeded 80% in less than 5 min, which is much faster than with pure flocculants. Thus, one can conclude, that the mixed use of ferric chloride and polymeric cationic flocculant can significantly add to the flocculation efficiency of C. vulgaris. The increased flocculation efficiency with ferric chloride is to destabilize the system, so making the cells stick between each other; while polymer (PAA or PEO) is to help the resulting flocs become larger, allowing their combined use of the two agents is attributed to differences in their mechanisms, that aggregation with each other. Once the ferric chloride concentration was taken equal to 100 mg/l, the biomass harvested has a less concentration of Fe than in the case where FeCl3, was solely used, whose maximum of efficiency was achieved at 500 mg/l concentration. By the reason of such effective action mixture of coagulant and flocculant it was interesting reduce the dosage for lower costs.Fig. 3c shows the dependence of the flocculation efficiency from the mixing ratio of the coagulant and flocculant. It found that the reduction of iron concentration to 50 mg/l and flocculant to 7.5 mg/l does not affect on flocculation efficiency (approximately 90% within 5 min of sedimentation), while further diminishing of concentrations reduce flocculation efficiency of C. vulgaris. From Figs. 2c,d and 3b, efficiency of mixture of 15 mg/l Sibfloc-718 and 25 mg/l Superfloc C-492, 25 mg/l Superfloc C-492 and 15 mg/l Sibfloc-718 equal to 25%, 40% and 50% respectively. This means that combined use of the two cationic flocculants did not show any benefits as compared with them used individually. Since the two flocculants offer similar mechanisms, an effect was obtained in this case, which was similar to what was observed with their concentrations increased to 45 mg/l, when used separately (Fig. 2c and d). Thus, the experimental results show the use of two flocculants similar in mechanism is not effective for efficient sedimentation of C. vulgaris.