This study compares the performance of two different systems (i) immobilized microalgae and suspended activated sludge (System A) and (ii) suspended co-culture (System B) in simultaneous treatment and biofuel production from domestic wastewater at different HRTs. The System A showed higher lipid content and carbon, nitrogen and phosphorous removal (40, 88, 91, and 93%) than System B (16, 87, 58, and 80%). C18:0 and C18:1n9t are dominant fatty acids observed in System A and C16:0 and C18:1n9t in System B. The immobilization of microalgae exhibited more benefits than suspended co-culture in terms of treatment and biofuel production. © 2018 The Korean Society of Industrial and Engineering Chemistry