Evaluation of a thermo-tolerant acidophilic alga, Galdieria sulphuraria, for nutrient removal from urban wastewaters

Nutrient removal from primary wastewater effluent was tested using Galdieria sulphuraria, an acidophilic and moderately thermophilic alga. Biomass yield recorded in this study (27.42 g biomass per g nitrogen removed) is higher than the average reported in the literature (25.75 g g−1) while, the theoretical yield estimated from the empirical molecular formula of algal biomass is 15.8 g g−1. Seven-day removal efficiencies were 88.3% for ammoniacal-nitrogen and 95.5% for phosphates; corresponding removal rates were 4.85 and 1.21 mg L−1 d−1. Although these rates are lower than the average literature values for other strains (6.36 and 1.34 mg L−1 d−1, respectively), potential advantages of G. sulphuraria for accomplishing energy-positive nutrient removal are highlighted. Feasibility of growing G. sulphuraria outdoors at densities higher than in high-rate oxidation ponds is also demonstrated.