BACKGROUNDFive microalgal strains characterized by high biogas tolerance and rapid growth were cultured in biogas slurry to identify strains capable of simultaneous nutrient removal and biogas upgrading. The potential contribution of these algae to these processes was evaluated for different photoperiods. RESULTSThe growth rates of the microalgae were inversely related to their initial concentrations. The growth rates of Scenedesmus obliquus (FACHB-31), Chlorella vulgaris (FACHB-416), and Nitzschia palea (FACHB-211) were higher than those of Selenastrum capricornutum (FACHB-271) and Anabaena spiroides (FACHB-498) under a moderate photoperiod (14h light: 10h dark). Under this condition and an initial CH4 concentration of 61.38% (v/v), the final concentrations in crude biogas were 84.28%, 84.21%, and 83.46% for S. obliquus, C. vulgaris, and N. palea, respectively. Biogas slurry nutrients were optimally reduced under the moderate photoperiod. CONCLUSIONAppropriate selection of microalgal strains for the treatment of biogas slurry and crude biogas is crucial to achieve optimal nutrient removal and biogas upgrading. (c) 2015 Society of Chemical Industry