Comparison of different harvesting methods of microalgae: Assessment of efficiency and energy

Microalgae is a promising feedstock for various applications and it has gained appreciation in recent years. The high costs related with microalgal biomass isolation hinder its large-scale applications. The application of an efficient and less costly harvesting method is fundamental for achieving a viable process. For this reason, a comparison of different microalgae harvesting technique's efficiencies was performed and energy costs were investigated in this thesis. In this work, harvesting efficiencies of Synechocystis sp., Chlorella Vulgaris sp. and Scenedesmus Quadricauda sp. were compared by electrocoagulation and chemical coagulation with initial pH and adjusted values of 4, 7 and 12. The chemicals FeSO4 and Al2(SO4)3.18H2O were analyzed as coagulant whilst Fe and Al electrodes were tested in the electrocoagulation. The energy consumption and operating cost were calculated for EC and CC experiments. Al2(SO4)3.18H2O achieved higher efficiency than FeSO4 and the Al electrodes in EC experiment also was more efficient in harvesting than Fe ones. The harvesting efficiency was increased by increasing the applied electric current in electrocoagulation and with an increased dosage of the coagulant in chemical coagulation experiment. The obtained results showed that the adjusted pH values with Al electrodes presented high efficiency. The power and energy consumption rose with an increase of the applied current thereby increasing the operating costs. The electrocoagulation and chemical coagulation techniques achieved high efficiency values and appear to be suitable harvesting methods.