Reuse of effluent water from a municipal wastewater treatment plant in microalgae cultivation for biofuel production Sunja Cho a , Thanh Thao Luong a , Dukhaeng Lee a , You-Kwan Oh b , Taeho Lee a,⇑ a Department of Civil and Environmental Engineering, Pusan National University, Busan 609-735, Republic of Korea b Bioenergy Research Center, Korea Institute of Energy Research, Daejeon 305-343, Republic of Korea article info Article history: Received 9 November 2010 Received in revised form 11 March 2011 Accepted 12 March 2011 Available online 15 March 2011 Keywords: Chlorella sp. Effluent water Lipid productivity Nutrients removal Filtration abstract This study assessed the usability of effluent water discharged from a secondary municipal wastewater treatment plant for mass cultivation of microalgae for biofuel production. It was observed that bacteria and protozoa in the effluent water exerted a negative impact on the growth of Chlorella sp. 227. To reduce the effect, filtration or UV-radiation were applied on the effluent water as pre-treatment methods. Of all the pretreatment options tested, the filtration (by 0.2 lm) resulted in the highest biomass and lipid pro- ductivity. To be comparable with the growth in the autoclaved effluent water, the filtration with a proper pore size filter (less than 0.45 lm) or UV-B radiation of a proper dose (over 1620 mJ cm 2 ) are proposed. These findings led us to conclude that the utilization can be realized only when bacteria and other micro- organisms are greatly reduced or eliminated from the effluent prior to its use. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Fossil fuels generate pollutants and global warming effects, even the energy resources are being exhausted. Therefore, it is essential to develop sustainable and eco-friend (clean) energy sources for supporting modern societies. One of the promising energy sources is bioenergy including biomethane, bioethanol, biobutanol and bio- diesel produced from photosynthetic organisms, which has several advantages comparing with petroleum-originated diesel; it is prin- cipally a renewable, biodegradable, less-toxic energy, and essen- tially a sulfur- and aromatics-free energy (Hill et al., 2009). The growth of microalgae is extremely faster than other photosynthetic plants, which indicates high productivity per area. Microalgae can generally double their biomass within 24 h and oil contents in sev- eral microalgae exceed over 30–80% by weight of dry biomass (Chisti, 2007). These facts have been a driving force in the develop- ment of bioenergy for commercialization. To date, great efforts have been concentrating on reducing the costs of producing biodiesel from microalgae as in the application of over-sensing light mechanism for increase of photosynthesis (Wang et al., 2008), increasing the efficiency of light utilization by better design of photoreactors (Zijiffers et al., 2008), applying new light sources such as LED (Lee and Palsson, 1994), improving extraction technology in lipid extraction (Lee et al., 2010), and combining autotrophic and heterotrophic cultivation (Miao and Wu, 2006; Heredia-Arroyo et al., 2010). However, there are still some obstacles to be solved for com- mercial production of algal-based biodiesels even it has a lot of benefits described on the above, for examples, such as limitation of light penetration for mass-cultivation, high cost harvest of algal biomass, and an enormous amount of water demanded by the pho- tosynthetic organisms of the water-dependant culture (Gerbens- Leenes et al., 2009). Nutrients in wastewater such as nitrogen and phosphorous should be removed before discharging to natural water environ- ments, and they can be removed in photosynthesis of microalgae by uptake as biomass. Therefore, wastewater has already been used for cultivation microalgae, but the main purpose was focused on nutrient removal (Hammouda et al., 1995; Lim et al., 2010; de Godos et al., 2010). Recently, cultivation of microalgae in wastewa- ter is being extended to a process for nutrient removal as well as a solution of water and nutrients demanded in mass-cultivation of microalgae as a feedstock of biodiesel (Yun et al., 1997; Wang et al., 2010; Chinnassamy et al., 2010). To meet huge demands of energy in modern society, bio-energy production based on photosynthesis will require tremendous amounts of water for cultivation of photosynthetic organisms such as microalgae. Fortunately, it is known that microalgae can use water of various sources such as wastewater, sea-water, and fresh-water (NREL report, 1998). However, the reuse-efficiency of wastewater in cultivation of microalgae for biodiesel production would be re-estimated by companying with the biomass and lipid productivities in sorts of wastewater. For an example, wastewater 0960-8524/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2011.03.037 ⇑ Corresponding author. Address: School of Civil and Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea. Tel.: +82 (0)51 510 2465; fax: +82 (0)51 514 9574. E-mail address: leeth55@pusan.ac.kr (T. Lee). Bioresource Technology 102 (2011) 8639–8645 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech