Culturing of Autoflocculating Microalgal Consortium in Continuous Raceway Pond Reactor

Abstract

The goal of this study was to develop a self-settling microalgal consortium in raceway pond reac-tor (RPR). Experiments were carried out with cultures that developed without additional seeding, but naturally promoted by process conditions in a raceway pond reactor. The changes in microal-gal communities and total biomass under nitrogen and phosphorous limitations were studied in both batch and continuous systems. At the steady state batch had the population of 46% Euglena sp., 16% Closterium sp., 14% Chlorella sp., 14% Scenedesmus sp. and 10% Ankistrodesmus sp. with a maximum biomass of 900 mg/L. In order to get self-settling microalgal consortium, the opera-tion was changed to continuous continuous mode with the aid of a specially designed settler for daily harvest and recycling of the biomass. Grazing fauna could be controlled by managing re-duced liquid and solid retention time. At steady-state condition, an autofloculating and self-set-tling consortium was developed which had mainly Fragilaria sp., Scenedesmus sp., and filamentous Ulothrix sp. The maximum biomass concentration obtained was 140 mg/L. The presence of neutral lipid droplets in the consortium was identified by staining with Nile Red. Development of the lipid rich consortium could be a suitable method for producing biofuel.