The effects of exogenous CO 2 on the growth and lipid accumulation of a local screened facultative heterotrophic microalgae strain Auxenochlorella protothecoides (UMN280) as well as nutrient removal from concentrated municipal wastewater stream (centrate) were examined in this study. A 12-day batch experiment was conducted with CO 2 aeration at three levels, namely, 0%, 1%, and 5% (v/v) CO 2 mixed with air, under light intensity of 60 μmol/(m 2 @@s). A two-stage growth pattern was observed. The first stage (first-fifth day) was dominated by heterotrophic growth in which organic carbon was the main carbon source. The second stage (6th-12th day) was dominated by autotrophic growth in which exogenous CO 2 had a positive effect on algal biomass accumulation. The addition of 5% CO 2 was better than that of 1% CO 2 on the biomass and lipid production. The uptakes of nutrients were similar between injection and no injection of CO 2, except on phosphorus removal which was affected by the acidification of CO 2.
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Acknowledgement The study was supported by grants from the University of Minnesota Initiative for Renewable Energy and the Environment (IREE) and Metropolitan Council Environmental Services (MCES), as well as the Legislative-Citizen Commission on Minnesota Resource (LCCMR). The authors are also grateful to Robert C. Polta and Adam Sealock of Saint Paul MCES Wastewater Treatment Plant for helping with the sample collection.
Copyright 2012 Elsevier B.V., All rights reserved.
- Concentrated municipal wastewater
- Mixotrophic growth
- Nutrient removal