Lipid-rich microalgal biomass production and nutrient removal by Haematococcus pluvialis in domestic secondary effluent

The coupled system of wastewater treatment and microalgal biofuel production based on microalgal cultivation is a promising process. Screening of suitable microalgal species for this coupled system is necessary to achieve the dual purpose of the single system. In this study, biomass production, nutrient removal, and lipid accumulation in domestic secondary effluent by Haematococcus pluvialis were investigated. The maximal algal dry weight, maximal population growth rate, and maximal algal biomass productivity achieved by H. pluvialis in a typical domestic secondary effluent were 207 mg L−1, 1.16 × 104 cells mL−1 d−1, and 27.8 mg L−1 d−1, respectively. Although the nitrogen/phosphorus ratio was as high as 15:1 in the secondary effluent used in this study, both nitrogen (93.8%) and phosphorus (97.8%) were removed efficiently by H. pluvialis when the stationary growth stage was reached. Furthermore, the lipid content of H. pluvialis increased from 25% to 43% due to nutrient depletion on the 10th day of cultivation. The maximal lipid accumulation rate obtained was 12.0 mg L−1 d−1. Compared with most microalgal species reported in the literature, H. pluvialis showed significant advantages in biomass production, nutrient removal, and lipid accumulation in domestic secondary effluent.