The　effects　of　exogenous　CO2　on　the　growth　and　lipid　accumulation　of　a　local　screened　facultative　heterotrophic　microalgae　strain　Auxenochlorella　protothecoides　(UMN280)　as　well　as　nutrient　removal　from　concentrated　municipal　wastewater　stream　(centrate)　were　examined　in　this　study.　A　12-day　batch　experiment　was　conducted　with　CO2　aeration　at　three　levels,　namely,　0%,　1%,　and　5%　(v/v)　CO2　mixed　with　air,　under　light　intensity　of　60　mu　mol/(m(2)　@@s).　A　two-stage　growth　pattern　was　observed.　The　first　stage　(first-fifth　day)　was　dominated　by　heterotrophic　growth　in　which　organic　carbon　was　the　main　carbon　source.　The　second　stage　(6th-12th　day)　was　dominated　by　autotrophic　growth　in　which　exogenous　CO2　had　a　positive　effect　on　algal　biomass　accumulation.　The　addition　of　5%　CO2　was　better　than　that　of　1%　CO2　on　the　biomass　and　lipid　production.　The　uptakes　of　nutrients　were　similar　between　injection　and　no　injection　of　CO2,　except　on　phosphorus　removal　which　was　affected　by　the　acidification　of　CO2.