Phosphorus removal in microalgal growth and harvesting using natural flocculant: Influence of microalgal characteristics and phosphorus forms.

Phosphorus-induced harmful algae blooms elicited attention, and both microalgae harvesting and phosphorus removal are essential, especially preventing secondary pollution. In this study, starved Chlorella vulgaris removed 68.73 % of dissolved inorganic phosphorus (DIP) compared to 37.47 % of dissolved organic phosphorus (DOP). Microalgae growth promoted the increase of extracellular organic matter, which had little effect on phosphorus removal. As incubation time increased, the phosphorus rebound was even higher than the original, which was not consistent with the continued growth of the microalgae cells, indicating that phosphorus uptake by microalgae alone could not inhibit algal blooms. A starch-based flocculant fed after the phycoremediation process exhibited effective microalgae harvesting, reducing DIP and DOP by 72.06 % and 48.31 %, respectively. Only 1/3 flocculant dose was needed to treat suspensions supplemented with DIP compared with DOP. The study offers an eco-friendly technology for simultaneous phosphorus removal and microalgae harvesting by combining Chlorella vulgaris with natural flocculants.