Performance evaluation of different cationic flocculants through pH modulation for efficient harvesting of Chlorella sp. HS2 and their impact on water reusability

Abstract

Flocculation is an effective technique for harvesting microalgae due to low energy input and being scalable up to industrial algaculture. In this study, four different flocculants at various concentration, and pH levels were employed for the harvesting of Chlorella sp. HS2. Among the tested flocculants, chitosan showed the highest flocculation efficiency of 99.6% +/- 0.25 at 10 mg L-1 dosage, pH 8.0 and 30 min of sedimentation. It turned out that the choice of flocculants had minimum impact on the fatty acids methyl ester (FAME) yield and composition. When the reusability of the spent medium for each flocculant was investigated, the culture supernatant obtained from chitosan-based harvesting method had lower growth inhibitory effects in comparison to those harvested using the other flocculants. The cost analysis also favored chitosan-based flocculation, because it returned the highest flocculant efficiency while the flocculant dosage was the lowest. Due to its high harvest efficiency and low impact on the water footprint, it was concluded that the chitosan offer promising advantages over other flocculants. (C) 2019 Elsevier Ltd. All rights reserved.