Autoflocculation of Scenedesmus Quadricauda: Effects of Aeration Rate, Aeration Gas CO2 Concentration and Medium Nitrogen Concentration

Abstract

After microalgal cultivation step, a recent method to harvest microalgae is adding flocculant into microalgal liquid culture to cause flocculation.  Flocculated cells are easy to concentrate since their sedimentation time and successive filtering time are expected to be shorter. In this sense, autoflocculation of microalgae may be a beneficial phenomenon for easing the harvesting process of microalgae. In this study, autoflocculation was investigated for the growth of Scenedesmus quadricauda, a type of fresh water microalgae, at 25 ºC in a 5-L column photobioreactor. The BG11 medium was used. The effects of aeration rate, CO2 concentration in aeration gas and nitrogen concentration in culture medium on auto flocculating behavior were investigated. Higher aeration rate, higher CO2 concentration and higher nitrogen concentration caused more flocculation. In other words, autoflocculation  became prominent at the condition range where the final cell biomass concentration was lower, in general.