The　feasibility　of　attached　culture　Chlorella　vulgaris　in　a　porous　substratum　biofilm　reactor　(PSBR)　for　simultaneous　wastewater　treatment　and　biofuel　production　was　investigated.　The　characteristics,　including　algal　biofilm　growth,　lipid　yield,　nutrient　removal,　and　energy　efficiency　of　the　outdoor　cultures,　were　investigated　under　the　influence　of　both　inoculum　densities　and　the　percent　submerged　area.　A　maximum　biofilm　productivity　of　57.87 g m−2 d−1　with　81.9 %　adhesion　was　achieved　under　optimal　conditions　(inoculum　density　of　18 g m−2　and　the　percent　submerged　area　of　5.7 %).　The　lipid　content　and　lipid　yield　were　38.56 %　and　27.25 g m−2 d−1,　respectively.　Meanwhile,　the　algae　removed　99.95 %　ammonia,　96.05 %　total　nitrogen　(TN),　and　99.83 %　total　phosphorus　(TP).　Further,　the　energy　life　cycle　for　the　PSBR　was　analyzed.　The　biomass　productivity　per　unit　irradiance　was　up　to　4.6 g MJ−1　(photosynthetic　efficiency　of　10.65 %).　The　PSBR　was　considered　to　be　economically　feasible　due　to　the　net　energy　ratio　of　1.3　(>1).　©　2016,　Springer　Science+Business　Media　Dordrecht.