Effects of pH, Salinity, Biomass Concentration, and Algal Organic Matter on Flocculant Efficiency of Synthetic Versus Natural Polymers for Harvesting Microalgae Biomass

© 2016, Springer Science+Business Media New York. This study investigated the effects of pH, salinity, biomass concentration, and algal organic matter (AOM) on the efficiency of four commercial cationic flocculants. The tannin-based biopolymers Tanfloc SG and SL and the polyacrylamide polymers Flopam FO 4800 SH and FO 4990 SH were tested for flocculation of two microalgae models, the freshwater Chlorella vulgaris and the marine Nannochloropsis oculata. Both biomass concentration and AOM presence affected all polymers evaluated, whereas salinity and pH affected only Flopam and Tanfloc, respectively. A restabilization effect due to overdosing was only observed for Flopam polymers and increasing Tanfloc dose resulted in improved efficiency. Flopam polymers showed a significant decrease in the maximum quantum yield of photosystem II as function of polymer dose for Chlorella, which supported the need for toxicological studies to assess the potential toxicity of Flopam. In overall, Tanfloc was not affected by salinity nor presented potential toxicity therefore being recommended for the flocculation of both freshwater and marine species.status: publishe

Screening of commercial natural and synthetic cationic polymers for flocculation of freshwater and marine microalgae and effects of molecular weight and charge density

Twenty-five natural and synthetic cationic polymers of differentmolecular weightsand charge densitieswere evaluated for microalgae flocculation. Tanfloc is a naturallow molecular weight tanninpolymer whereas Zetag and Flopam are both synthetichigh!molecular weight polyacrylamide polymers. Five exponential concentrations (0.55,1.66, 5, 15 and 45 mg L-1) were tested for freshwater Chlorella vulgarisand marine Nannochloropsis oculata. All polymers were efficient (>90%at ≥ 1.66 mg L-1) for C. vulgaris. However,forN. oculata,only Tanfloc was effective. Charge density positively influenced flocculationdecreasing the required polymer dosage. Restabilisationwas observed only for synthetic polymers when overdosed. Natural polymers performed similarly for both species.In overall, Tanfloc SL and FlopamFO 4990 SH were the most efficientpolymers for microalgae flocculationthough Tanfloc is amore economic option (US$37 ton-1of biomass) and environmentally friendly than Flopam (US$ 171 ton-1of biomass)