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
combined use of the two agents is attributed to differences in their
mechanisms, that 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
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.
Following the use of coagulant and the flocculating agentsbased on different polymers, the study looked at combined applicationof coagulants and flocculants. Thus, over 5 min of sedimentationthe flocculation efficiency was, for combined use of ferricchloride with Superfloc C-492 and ferric chloride withSibfloc-718, equal to 60% and 87%, respectively (Fig. 3b). Theseindicate that flocculation efficiency of mixtures is much higherthan for these flocculants used individually. Note also, that theflocculation efficiency with mixture exceeded 80% in less than5 min, which is much faster than with pure flocculants. Thus, onecan conclude, that the mixed use of ferric chloride and polymericcationic flocculant can significantly add to the flocculation efficiencyof C. vulgaris. The increased flocculation efficiency withcombined use of the two agents is attributed to differences in theirmechanisms, that ferric chloride is to destabilize the system, somaking the cells stick between each other; while polymer (PAAor PEO) is to help the resulting flocs become larger, allowing theiraggregation with each other. Once the ferric chloride concentrationwas taken equal to 100 mg/l, the biomass harvested has a less concentrationof 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 coagulantand flocculant it was interesting reduce the dosage for lower costs.Fig. 3c shows the dependence of the flocculation efficiency fromthe mixing ratio of the coagulant and flocculant. It found that thereduction of iron concentration to 50 mg/l and flocculant to7.5 mg/l does not affect on flocculation efficiency (approximately90% within 5 min of sedimentation), while further diminishing ofconcentrations reduce flocculation efficiency of C. vulgaris.
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