Biochemical Engineering Journal 103 (2015) 177–184 Contents lists available at ScienceDirect Biochemical Engineering Journal jo ur nal home page: www.elsevier.com/locate/bej Regular article Simultaneous nutrient removal and lipid production with Chlorella vulgaris on sterilized and non-sterilized anaerobically pretreated piggery wastewater Jatta M. Marjakangas a,b,∗ , Chun-Yen Chen c , Aino-Maija Lakaniemi a , Jaakko A. Puhakka a , Liang-Ming Whang d , Jo-Shu Chang b,e a Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere 33101, Finland b Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan c Center of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan d Department of Environmental Engineering, National Cheng Kung University, Tainan 701, Taiwan e Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan a r t i c l e i n f o Article history: Received 21 April 2015 Received in revised form 10 July 2015 Accepted 14 July 2015 Available online 23 July 2015 Keywords: Aerobic process Lipid production Microalgae Piggery wastewater Sterilization Wastewater treatment a b s t r a c t Piggery wastewater is a potent nutrient source for microalgal lipid production. Wastewater has been usually sterilized when used for microalgal cultivation. This is uneconomical in large-scale applica- tions. Therefore, lipid productivity of Chlorella vulgaris CY5 using sterilized and non-sterilized diluted anaerobically pretreated piggery wastewater was studied in batch reactors. The maximum average lipid productivity was obtained after 12 days of incubation and it was higher with the sterilized wastewa- ter than with the non-sterilized one (117 g/L/d vs. 91.3 g/L/d), due to the higher biomass concentration. Because of the unexpected increase of dissolved organic carbon (DOC) in the cultures, second exper- iment was conducted to characterize the composition of produced DOC in non-sterilized wastewater. Carbohydrate content increased in the liquid phase but decreased in the biomass after nitrogen had been exhausted. After 12 days of incubation, soluble chemical oxygen demand (COD s ) was 414 ± 56 mg/L, biomass production was 2.8 ± 0.15 g/L, and lipid content was 30.3 ± 1.2 wt%. Average lipid productiv- ity from day zero to day 12 was 70.5 ± 1.1 g/L/d. C. vulgaris removed nutrients from the non-sterilized wastewater and produced oleaginous biomass, although the lipid productivity was higher with sterilized wastewater. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The demand for more eco-efficient society is enormous. Indus- trial, agricultural and municipal systems require modifications, such as reusing wastewaters and flue gases in energy generation to become more sustainable. Production of lipid-rich biomass to generate biofuels is one example [1–4]. Lipid-rich biomass can be produced with various microorganisms, such as bacteria, yeasts, fungi, and microalgae, but only photosynthetic organisms can be used to simultaneously fix CO 2 from the flue gas and remove nutri- ents from the wastewater [4]. Several factors, such as various microalgal species, cultivation strategies, reactor designs and harvesting technologies, have been ∗ Corresponding author at: Department of Chemistry and Bioengineering, Tam- pere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland. E-mail address: jatta.marjakangas@tut.fi (J.M. Marjakangas). used to produce third-generation biofuels with microalgae [5]. Chlorella vulgaris is one the most studied microalga due to its abil- ity to grow in relatively harsh conditions and in the presence of culture invaders [6]. Biomass composition of C. vulgaris is highly dependent on cultivation conditions and medium composition [7]. In stressful growth conditions, such as nitrogen starvation, C. vul- garis accumulates lipids mainly in the cytoplasm and chloroplasts [8], but it may also produce starch granules inside the chloroplasts [6]. C. vulgaris accumulated high concentrations of lipids, especially in mixotrophic conditions, where both light, CO 2 , and organic car- bon were provided simultaneously [6]. In mixotrophic conditions algae can grow both using light as energy source and CO 2 as carbon source (autotrophic growth), and using organic carbon as energy and carbon source (heterotrophic growth) [4]. Integration of nutrient removal and biodiesel production with Chlorella spp. and piggery wastewater has been reported [3,9–11]. Microalgal lipid studies on piggery wastewater have been mainly conducted with sterilized wastewater. In addition to autoclaving, http://dx.doi.org/10.1016/j.bej.2015.07.011 1369-703X/© 2015 Elsevier B.V. All rights reserved.