Phosphorus uptake kinetics of immobilized Chlorella in batch and continuous-flow culture

Abstract

Study has been made of the uptake of orthophosphate phosphorus (PO 4-P) by Chlorella emersonii (CCAP 211/8a) entrapped in 4-mm diameter Ca-alginate beads. In batch culture studies, 100 beads, each stocked with 10 7 cells, removed all PO 4-P from 100 ml synthetic growth medium (i.e. about 10 μmol) in under 24 h. Uptake followed exponential kinetics with medium PO 4-P concentration falling by 50% every 2.0 h, when external concentrations were above 6 μM. A stocking density of 10 7 cell/bead (the highest tested) was found to be suitable for rapid phosphorus removal, though this was not necessarily optimal with respect to cellular efficiency. Small-scale packed-bed reactors containing 10 ml gel were able to remove up to 240 μmol PO 4-P from 4–5 / medium over 10–12 day experimental periods. Uptake efficiencies ranged from 29 to 97%, and averaged 66% and 44% with synthetic growth medium and secondary treated effluent, respectively. Uptake kinetics are analyzed and results discussed with respect to process optimization.