Hydrodynamic sloshing of microalgae in membrane type photobioreactor

Abstract

The tropical climate, wide diversity of microalgae species, long coastline, abundant sources of agriculture effluent, and active phycology research are key factors that drives Malaysia to be highly competitive in the global microalgae market. Microalgae are vital in a variety of applications such as: biofuel, health foods, agricultural feeds and chemical extractions. However, mass cultivation of microalgae is still not cost effective in Malaysia due to huge energy consumption Therefore, cultivation of microalgae that utilizes wide ocean space and wave energy for mixing has gained interest since it has considerably lower production cost. Nonetheless, the effects of ocean wave-induced sloshing in terms of its efficiency of mixing have not been fully researched. Thus, this study has been conducted to investigate the effects of sloshing hydrodynamics in microalgae cultivation by studying the interactions of sloshing hydrodynamics and mixing efficiency inside a floating photobioreactor. A membrane type photobioreactor has been used to slosh microalgae culture on its free surface. The result of mixing efficiency for suspended solid particles in liquid is the main concern. Experiments in unidirectional excitation proven that mixing rate of solid-liquid medium is dependent on the excitation amplitude, excitation frequency and filling ratio, where mixing rate is highest at 30% filling ratio with increasing excitation amplitude and excitation frequency. With deeper comprehension on the interaction effects of sloshing hydrodynamics and mixing efficiency, upscaling of novel microalgae cultivation method in industrial size can be expected.