Microalgae membrane photobioreactor for further removal of nitrogen and phosphorus from secondary sewage effluent

For further removal of nitrogen and phosphorus from secondary sewage effluent, two strains of microalgae, Chlorella sp. ADE4 and Chlorella vulgaris, were selected for cultivation in the membrane photobioreactor. The Chlorella sp. ADE4, isolated from wastewater illustrated higher removal efficiency of T-N and T-P, and faster algal growth than the Chlorella vulgaris in a batch experiment using treated sewage effluent. The T-N and T-P removal efficiency was 66.5% and 94.5%, respectively, within HRT of two days when the photobioreactor of Chlorella sp. ADE4 was operated in continuous mode. The effluent water quality was 6.3 mg/L and 0.044 mg/L for T-N and T-P. It was estimated that the algal biomass productivity was 55 mg/L·d with T-N and T-P uptake rates of 6.25 and 0.483 mg/L·d, respectively, in the system. Operational flux below 58 LMH was found to be effective for separation of algal cell from effluent in membrane system.