Chlorella vulgaris was used to study algal lipid production with wastewater treatment. Artificial wastewater was used to cultivate C. vulgaris in a column aeration photobioreactor (CAP) under batch and semi-continuous cultivation with various daily culture replacements (0.51-1.51 per 21 reactor). The cell density was decreased from 0.89 g/l with the daily replacement of 0.51 to 0.28 g/l with 1.51 replacement. However, C. vulgaris culture achieved the highest lipid content (42%, average value of the phase) and the lipid productivity (147 mg/l d(-1)) with daily replacement of 1.01. And then the nutrient removal efficiency were 86% (COD), 97% (NH4+) and 96% (TP), respectively. Analyses of energy efficiency showed that the net energy ratio (NER) for lipid production with daily replacement of 1.01(1.25) was higher than the other volume replacement protocols. And cost analyses showed that the algal biomass can be competitive with petroleum at US$ 63.97 per barrel with the potential credit for wastewater treatment. According to the above results, it is concluded that the present research will lead to an economical technology of algal lipid production. (C) 2010 Elsevier Ltd. All rights reserved.