In this study, use of microalgae for secondary and tertiary wastewater treatment was evaluated. First phase of the study investigated the ability of microalgae to remove nutrients, organic carbon and indicator bacteria from secondary effluents and centrate. For secondary wastewater and centrate, the reductions in soluble concentrations of total nitrogen, phosphorus, and COD were 27, 51.7, 29.5% and 49.4, 78.6. 32.8%, respectively. Total coliform reduction was greater than 99.5%. The second phase investigated the use of microalgae in combination with activated sludge system. Soluble COD
removal improved from 1.5% for sample A (activated sludge) to 65.6 and 77.8% for samples B (activated sludge and microalgae) and C (microalgae). Ammonia was removed by 99.9% for B and C, while the removal was 46.4% for A. Total dissolved phosphorus was removed by 81.3 and 73.2% for B and C, but there was no reduction in dissolved phosphorus for A.