Selection of a separation method used for harvesting of microalgae from aqueous solutions

Abstract

Harvesting of microalgae from aqueous solutions is still a bottleneck for biotechnologies using microalgae as a source of metabolites. The aim of the article is to provide an overview of four microalgae separation methods and highlight their core advantages, disadvantages, efficiencies and energy and economy requirements for various concentrations of microalgae suspensions and different microalgae strains. These four separation methods are centrifugation, coagulation/flocculation, flotation and membrane technologies. Possible optimizations of the separation methods inducing more effective harvesting are proposed as well. Based on the data included in the article, final conclusions are presented and the separation methods are compared. Flotation harvesting efficiency is more than 75 % when chemicals enhancing the process are applied. Harvesting efficiency of coagulation and flocculation achieves more than 80 %. Harvesting efficiency of membrane technologies and centrifugation is more than 90 %. The energy requirements are in the range of 0.07 to 11.1 kWh m-3 of the permeate or microalgal suspension volume and 0.09 to 9.5 kWh kg-1 of the dry weight of harvested biomass, depending on the separation method.