[Study on the removal of nitrogen and phosphorus from wastewater by Chlamydomonas reinhardtii]

Chlamydomonas reinhardtii was employed to remove nitrogen and phosphorus from wastewater. The effects of initial NH4(+) -N and TP concentrations, N/P ratios, Light/Darkness ratios, pH and immobilization on the removal of NH4(+) -N and TP were evaluated. The results showed that C. reinhardtii could almost 100% remove NH4(+) -N and TP as initial concentrations of NH4(+) -N and TP were no more than 55 mg x L(-1) and 7 mg x L(-1), respectively, whereas the removal ratio of NH4(+) -N decreased drastically to 50% with initial NH4(+) -N concentration coming up to 75 mg x L(-1). Under N/P ratios of 5:1 and 10:1, C. reinhardtii could completely remove NH4(+) -N within 3d, while 6 d was needed with N/P ratio being 25: 1. Different from NH4(+) -N removal, the removal ratio of TP could reach almost 100% within 4 d under 3 N/P ratios. With L/D ratios of 24 h: 0 h and 12 h: 12 h, 100% removal of NH4(+) -N and TP could be achieved by C. reinhardtii, but the removal rate under L/D ratio of 24 h: 0 h was relatively faster. The optimal pH range for C. reinhardtii to remove NH4(+) -N and TP was 6-7. After immobilization, the ability of C. reinhardtii to remove NH4(+) -N was significantly enhanced as the removal ratio of NH4(+) -N came up to 100% with initial NH4(+) -N concentration being 75 mg x L(-1). The ability of immobilized C. reinhardtii to remove TP kept stable, whereas the removal rate was slowed slightly.