A 3-way microalgal system was proposed for both the removal of nitrogen and phosphorus from wastewater and the production of a valuable carotenoid, astaxanthin using CO2 fixation. The system consists of sequential photoautorophic cultivation and induction processes using the green alga Haematococcus pluvialis. The Haematococcus process was applied to primary-treated sewage (PTS) and piggery wastewater (PTP). H. pluvialis grew well on PTS and PTP. resulting in the successful removal of nitrogen and phosphorus from both wastewaters. Following the cultivation stage, N-deprived vegetative cells were transformed to red aplanospores with substantial astaxanthin contents under photoautotrophic induction by continuous feeding of both CO2-mixed gas and intense light. The astaxanthin productivities were 2.1 and 4.4 mg/L.day and the CO2 conversion rates to astaxanthin were 6.1 and 12.8 mg/L.day for the PTS and PTP cultures, respectively. These results indicate the potential of the proposed Haematococcus process as a productive wastewater treatment technology with the capability of biosynthesizing the high-value antioxidant astaxanthin using CO2.