Interference of model wastewater components with flocculation of Chlorella sorokiniana induced by calcium phosphate precipitates.

Amongst harvesting processes, alkaline flocculation stands out as a technically feasible and low cost method. The interference of model wastewater components with alkaline flocculation of Chlorella sorokiniana (pH 8-12), induced by calcium phosphate (CaP) precipitates, was evaluated. Between the compounds tested, inorganic nitrogen, sodium alginate, salinity and algal organic matter had no effect on flocculation efficiency (FE). The negative effect of humic acids, sodium dodecyl sulphate and alkalinity on FE was partial. Bovine serum albumin and bacterial organic matter (BOM) of Escherichia coli showed the strongest disruption of FE. The impact of BOM can be explained by the high protein content (65% of total organic carbon). Proteins, negatively charged at alkaline pH, interrupt microalgae flocculation by preferentially interacting with positively charged CaP precipitates. The simultaneous effects of multiple substances were tested to simulate real wastewater. The results confirm the need to investigate the composition of wastewater prior to alkaline flocculation.