Harvesting of algae biomass in Hanoi eutrophicated lakes by flotation

Abstract

This study examined water samples from three lakes in Hanoi with varying levels of eutrophication in order to recover microalgae biomass using distributed air flotation technology. The results show that the efficiency of dispersion air flotation ranged from 28,5% to 77,3%, inversely proportional to the bubble size in the range of 0.1 – 1 mm, proportional to the water column depth in the range of 5 – 20 cm, and gives the maximum efficiency at 1.0 liter per minute. Flotation technology is appropriate for filamentous cyanobacteria (Lyngbya and Oscillatoria), colony cyanobacteria, and green algae, but not for other algae phyla such as diatoms. The recovered biomass has an organic content of 49 – 82%, primarily protein and carbohydrates, with a C: N ratio of 15 – 20. The research opens the orientation of applying flotation technology to harvest algae biomass, reducing the risk of aquatic eutrophication and using algae biomass as fertilizer, biogas, and biofuel or adsorbent material.