THE POTENTIAL OF TROPICAL MICROALGAE AS FLOCCULANT IN HARVESTING PROCESS

Abstract

This environmental biotechnology research aims to obtain a diversity of freshwater tropical microalgae which has the ability to form a floc naturally to be utilized as bioflocculants in the process of harvesting other tropical microalgae biomass that does not have such ability. The microalgae Chlorella vulgaris, Chlorella sorokiniana, Chlorococcum sp., Closterium sp., Oscilatoria sp., Monorapidhium sp, Ankistrodesmus sp. and Scenedesmus obliquus are cultivated in batch culture and their environmental condition is controlled at 25°C, fed with 5% pure CO₂with a flow rate of 5 L/min. To determine the ability of microalgae strain as microalgae flocculant or not, it is necessary to calculate recovery efficiency. The addition of Scenedesmus obliquus and Ankistrodesmus sp. as flocculant microalgae followed by slow mixing allows better interaction between flocculant microalgae and non-flocculant microalgae, so the floc size increases. Scenedesmus obliquus and Ankistrodesmus sp. can be used as flocculant species because the value of settling for both types of microalgae is more than 50% for 60 minutes while other microalgae species can be categorized as non-flocculant microalgae since within 60 minutes settles less than 50%. The study also proved that no greenhouse gas was formed during the bioflocculation process. Thus the method of bioflocculation with Scenedesmus obliquus and Ankistrodesmus sp. is feasible to be applied to harvest microalgae biomass on an industrial scale.