Harvesting microalgae, Chlorella sp. by bio-flocculation of Moringa oleifera seed derivatives from aquaculture wastewater phytoremediation

• Eight derivatives of Moringa oleifera (MO) were extracted for flocculation test.
• Aluminum Sulfate (Alum) was used as the benchmark of conventional coagulant.
• MO derivatives and Aluminum Sulfate were tested at various dosage and mixing rate.
• Parameters of zeta potential, biomass recovery and removal efficiency were studied.
• MO seed powder and seed protein were significantly more effective than Alum.

Moringa oleifera (MO) seed has been widely used for water treatment purposes due to their good flocculation, low cost and non-toxic characteristics. However, these advantages had not yet been utilized for the microalgae harvesting technology. Until today, the harvesting of microalgae biomass still depend on sophisticated and complex approaches such as hollow fiber filtration, chemical flocculants and Alfa Laval decanter technology. Thus, in this study the potential of natural plant-based coagulant was investigated. MO seed derivatives were determined for the harvesting of suspended freshwater microalgae, Chlorella sp.. Flocculation characteristics with various dosages were optimized. The output of this study proved that primary and tertiary MO derivatives yield excellent flocculation efficiency of more than 95% at 20 min sedimentation. In fact, MO derivatives even supersede chemical flocculants, Aluminum Sulfate in terms of flocculation efficiency and biomass recovery at a low dosage of 10 mg L−1 and normal pH (6.9–7.5). Seed powder had the highest removal efficiency whereas seed protein had the highest biomass recovery. Utilization of M. oleifera derivatives as bio-coagulant provides several advantages such as lower impact on the environment, lower cost for microalgae harvesting, allow rapid microalgae culture expansion and as chemical-free green technology.