RESEARCH ARTICLE Enhanced nutrient removal from municipal wastewater assisted by mixotrophic microalgal cultivation using glycerol Prabuddha L. Gupta 1 & Hee Jeong Choi 1 & Seung-Mok Lee 1 Received: 16 June 2015 /Accepted: 1 February 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract In a present study, nutrient removal from municipal wastewater by Chlorella vulgaris and Nannochloropsis oculata was investigated by using mixotrophic cultivation with glycerol (0 to 5 g/L). Performance parameters were assessed by estimating the removal of total nitrogen, total phosphorus, chemical oxygen demand (COD), biomass growth, chlorophyll content, lipid yield, and fatty acids. With the addition of 2 g/L glycerol, a maximum biomass productivity of 56 mg/L/day was achieved in the mixotrophic culture of C. vulgaris within 12 days. The mixotrophic culture showed a 30-fold increase in biomass productivity compared to the wastewater without any glycerol. However, the highest total nitrogen removal (80.62 %), total phosphate removal (60.72 %), and COD removal (96.3 %) was observed in the N. oculata culture supplemented with 3, 5, and 1 g/L glycerol, respectively. These results suggest that mixotrophic cultiva- tion using glycerol offers great potential in the production of renewable biomass, waste water treatment, and consequent production of high-value microalgal oil. Keywords Microalgae . Wastewater treatment . Mixotrophy . Biomass . Lipids Introduction In recent years, microalgae have gained a lot of attention due to their photosynthetic ability which can be exploited to gen- erate fuel sources, CO 2 capture, biomass production, and value-added co-products (Singh et al. 2015). Commercial ap- plications of microalgae have been used for a wide array of applications including pharmaceutical, health sector, nutra- ceutical, cosmetics, agriculture (biofertilizers), and for various processes and services (Bhatnagar et al. 2011; Spolaore et al. 2006). Although microalgal biomass has been significantly exploited for numerous biotechnological applications, the pro- duction of biofuels is handicapped by an inability to find a reliable and cost-effective method of producing and harvest- ing large quantities of algae feedstock (Acién et al. 2012). Majority of algal production systems use natural photoau- totrophic conditions for microalgae biomass production; how- ever, photoautotrophic cultivation of microalgae is limited due to low growth rate, low light penetration, and photoinhibition (Li et al. 2013). Microalgae can accumulate lipids under pho- toautotrophic mode, but their current photosynthetic efficien- cies are not viable for commercial scale production (Kruse et al. 2005). Lower biomass production in photoautotrophic cultures has directed the researchers towards mixotrophy with different carbon sources which results in better biomass pro- duction (Bhatnagar et al. 2011; Perez-Garcia et al. 2011). Mixotrophic cultures have several advantages such as reduced photoinhibition, improved growth rates, and independence from photosynthesis for its carbon requirements (Heredia- Arroyo et al. 2011). Among various carbon sources, glucose is the preferred choice since it is highly beneficial in enhanc- ing the biomass as well as lipid productivities of microalgae (Liang et al. 2009; Heredia-Arroyo et al. 2011). However, the drawback with using glucose lies in the fact that the cost of glucose adds up to 80 % of the total medium cost and makes Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (doi:10.1007/s11356-016-6224-1) contains supplementary material, which is available to authorized users. * Seung-Mok Lee leesm@cku.ac.kr 1 Department of Energy and Environment Convergence, Catholic Kwandong University, Gangneung 210701, South Korea Environ Sci Pollut Res DOI 10.1007/s11356-016-6224-1