Biomass production and urban centrate nutrient removal using native microalgae tolerant to high nitrogen concentration and temperature

This paper focuses on the evaluation of the biomass production of a novel native microalgal strain Chlorella sorokiniana using centrate from municipal wastewater as the sole source of nutrients and six different temperatures. The experiments were performed in semi-continuous cultures using Bold’s Basal Medium and centrate separately, modifying the temperature (25–50 °C). The study aimed to elucidate whether a thermotolerant strain can be used for both the production of biomass and the removal of nutrients from wastewater. It was observed that C. sorokiniana biomass can be produced using centrate as the sole nutrient source. The highest biomass yield, for both culture media, was achieved at 35 °C showing maximum values for centrate (1.0 gbiomass·L−1, 0.20 gbiomass·L−1·day−1 dry weight), surpassing the productivity obtained when using Bold’s Basal Medium (BBM) (0.60 gbiomass·L−1; 0.13 gbiomass·L−1·day−1 dry weight). Variable chlorophyll fluorescence confirmed that the excess of ammonium (601 mgNH4·L−1) did not inhibit the growth of C. sorokiniana, and thus, the biomass productivity was not affected. The maximum nutrient removals reached for BBM and centrate were 96% and 61.5% for nitrogen, 53.2% and 61% for phosphorus, and 93% and 0.18% for total carbon, respectively. Fatty acids accumulating in the microalgal biomass were mainly composed of arachidonic, oleic, and eicosatetraenoic acids. Consequently, it is demonstrated that microalgae native to desertic areas can be used to produce microalgal biomass using centrate from wastewater treatment plants as the exclusive nutrient source, reaching high productivities.