DATE2019-01-08 12:44:24
AUTHORSDirenis Cayli (1)|Tuba Hande Ergüder (2)|Baris Kaymak (2)|Göksel N. Demirer (2)|Sibel Uludag Demirer (3)
  1. Middle East Technical University, Ankara, Turkey
  2. Middle East Technical University, Ankara, Turkey
  3. Middle East Technical University, Ankara, Turkey
  4. Middle East Technical University, Ankara, Turkey
  5. Karabük University, Karabük, Turkey
ABSTRACTVarious CO2 mitigation strategies have been investigated, which can be classified into two categories: (1) chemical reaction-based approaches, and (2) biological CO2 mitigation. Chemical reaction-based methods for capturing CO2 are relatively costly and energy-consuming. However, biological CO2 mitigation is seen as an alternative strategy because it leads to the production of biomass energy in the process of CO2 fixation through photosynthesis. The microalgae-for- CO2-mitigation strategy offers numerous advantages especially when it is combined with other processes like wastewater treatment and biofuel production. Our team has been working on an integrated process configuration which consists of both microalgal and anaerobic bio-reactors. The aim is to provide parallel nutrient (nitrogen and phosphorus) removal from domesic and industrial wastewaters, CO2 mitigation from industrial flue gas, and bio-fuel (biogas and biohydrogen) and fertilizer production. This study was designed to investigate the growth of microalgae in municipal wastewater in photobioreactors operating at batch mode. Inorganic carbon is supplied by CO2. The batch reactors (V=500 mL) were illuminated continuously (approximately 200 µmol/m2.s) and kept in a shaker to increase the contact between nutrients (total ammonium nitrogen (TAN) and ortho-phosphate (ortho-PO4). The microalgae was collected from Araç Creek (Karabük) and cultivated in bold’s basal medium (3N-BBM+V). Wastewater was collected from Ankara Tatlar Municipal Wastewater Treatment Plant and used as the nutrient supply. The headspace of the reactors was purged by air and CO2 mixture to provide high levels of CO2 (10-30%) to understand (i) the tolerance of high CO2 levels by microalgae, (ii) removal of nutrients from wastewater, (iii) the amount of CO2 biotransformed by microalgae, and (iv) performance of microalgae cultivation reactors fed by flue gas. To this purpose, the CO2 composition of the headspace in the reactors was monitored regularly by GC. In addition, the nutrient concentrations and microalgal biomass (total volatile solids) increase were measured. The results from this study can be used to propose the employment of photobioreactors in which microalgal growth is promoted for concomitant cleaning up of flue gas and wastewater while producing biomass with a potential to be used as raw material for producing biofuels. Keywords: biofuel, CO2 sequestration, microalgae, nutrient removal, photobioreactor