Biomass production and nitrogen and phosphorus removal by the green alga Neochloris oleoabundans in simulated wastewater and secondary municipal wastewater effluent Bei Wang, Christopher Q. Lan ⇑ Department of Chemical and Biological Engineering, The University of Ottawa, 161 Louis Pasteur St., Ottawa, ON, Canada K1N 6N5 article info Article history: Received 24 March 2010 Received in revised form 9 February 2011 Accepted 11 February 2011 Available online 17 February 2011 Keywords: Secondary wastewater effluent N/P removal Biomass production Microalgae CO 2 sequestration abstract Biomass productivity of 350 mg DCW L 1 day 1 with a final biomass concentration of 3.15 g DCW L 1 was obtained with Neochloris oleoabundans grown in artificial wastewater at sodium nitrate and phos- phate concentrations of 140 and 47 mg L 1 , respectively, with undetectable levels of residual N and P in effluents. In secondary municipal wastewater effluents enriched with 70 mg N L 1 , the alga achieved a final biomass concentration of 2.1 g DCW L 1 and a biomass productivity of 233.3 mg DCW L 1 day 1 . While N removal was very sensitive to N:P ratio, P removal was independent of N:P ratio in the tested range. These results indicate that N. oleoabundans could potentially be employed for combined biofuel production and wastewater treatment. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Microalgae are promising candidates for large scale global bio- fuel production because of their high photosynthetic efficiency. Whereas a land plant such as switchgrass has a photosynthetic efficiency of less than 0.5% (Lewis and Nocera, 2006), that of mic- roalgae can reach 20% or higher (Richmond, 2000; Huntley and Redalje, 2007). Nevertheless, the fundamental challenge in micro- algal biofuel production remains its relatively high costs of produc- tion. Different strategies have been proposed to improve the cost-effectiveness of microalgal biofuel production (Li et al., 2008a), which include: cultivation using secondary wastewater effluents, farming using seawater (Huntley and Redalje, 2007), farming on land unsuitable for land-based agriculture, integration of microalgal biofuel production with flue gas CO 2 sequestration, production of high-value novel bioproducts, design of advanced photobioreactors (Lehr and Posten, 2009), and use of optimized media (Wang and Lan, 2011) and costeffective downstream pro- cessing technologies. Cultivating microalgae for tertiary wastewa- ter treatment to generate low nitrogen (N) low phosphorus (P) effluents, could reduce nutrient costs for microalgal cultivation and preserving precious freshwater resources. Neochloris oleoabun- dans, a fast growing tri-glyceride-producing microalgal species (Tornabene et al., 1983) that can accumulate up to 40% lipid on a dry biomass basis at a lipid productivity of 0.133 kg m 3 day 1 (Li et al., 2008b; Pruvost et al., 2009), has been shown to be a prom- ising candidate for biofuel production. It is therefore of interest to investigate the potential of this species for integrated wastewater treatment and biofuel production. In this study, we first measured the effects of temperature on cell growth of N. oleoabundans and then investigated the cell growth and N/P removal in artificial and secondary municipal wastewater effluents containing different levels of sodium nitrate and phosphate. The study thus provides valuable guidelines for industrial designs aiming at combined microalgal biofuel production and wastewater treatment using N. oleoabundans and other microalgal species. 2. Methods 2.1. Microalga strain, media and algal cultivation N. oleoabundans OU2 was purchased from the UTEX Culture Col- lection of Algae, Texas (UTEX #1185) and grown in artificial waste- water containing (mg L 1 ): MgSO 4 (37), FeCl 3 (3), CaCl 2 2H 2 O (25), NaCl (0.025), NaNO 3 (850), KH 2 PO 4 (75), K 2 HPO 4 (175), EDTA-Fe (1.642), H 3 BO 3 (2.860), MnCl 2 4H 2 O (1.810), ZnSO 4 7H 2 O (0.220), CuSO 4 5H 2 O (0.079), and (NH 4 ) 6 MO 7 O 24 4H 2 O (0.039). To study the effect of nitrate concentration on cell growth and N removal, artificial wastewater containing NaNO 3 at concentrations of 45, 70, 140, 218 mg N-NO  3 L 1 , which corresponded to the N:P ratios of 0.42, 0.65, 1.33, and 2.02, respectively, were used. A relatively 0960-8524/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2011.02.054 ⇑ Corresponding author. Tel.: +1 613 562 5800x2050. E-mail address: Christopher.Lan@uottawa.ca (C.Q. Lan). Bioresource Technology 102 (2011) 5639–5644 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech