Two species of green algae, Micractinium nov. and Chlorella sp., were cultivated in primary effluent and the mixture of sludge centrate and primary effluent (SC1) to evaluate nutrient removal and their anaerobic digestibility under mesophilic condition. Results showed that cultivation of both species of algae reduced 95 % of phosphorous and the finial concentration of phosphorus was reduced to 0.17 mg/L. Over 94% of nitrogen was removed from primary effluent. The nitrogen in SC1was reduced from about 200 to 100 mg/L. Anaerobic digestion of algae grown in SC1 showed that the CH4 yield of Chlorella and Micratinium were 296 and 248 mL g-1 volatile solids fed (VSfed), respectively. It was presumed that different growth characteristics of two types of algae affected their anaerobic digestibility differently. Co-digestion of algae with waste activated sludge (WAS) improved the volatile solids reduction efficiency as well as the biogas yield of both algae species.