Evaluation of electrocoagulation, flocculation, and sedimentation harvesting methods on microalgae consortium grown in anaerobically digested abattoir effluent

Microalgae dewatering is a major bottleneck for biomass production in a large-scale microalgal production system which accounts for 20-60% of production cost. In this study, three dewatering systems of electrocoagulation, flocculation, and pH-induced flocculation were evaluated for microalgal consortium grown in anaerobically digested abattoir effluent at pH 6.5 and 9.5. At the shortest time (15 min) and the highest current density (0.08 A cm(-2)), the highest microalgae recoveries of 78 and 84% were obtained with the corresponding power consumptions of 1.25 and 1.07 kWh kg(-1) for cultures at pH 6.5 and 9.5. For microalgae suspension at pH 6.5, the highest biomass recovery of 77% was obtained when 100 mg L-1 of FeCl3 center dot 6H(2)O (after 15 min) or 100 mg L-1 of Al-2(SO4)(3)center dot 18H(2)O (after 30 min) was added. However, microalgal recoveries significantly increased when FeCl3 center dot 6H(2)O or Al-2(SO4)(3)center dot 18H(2)O was used with the culture at pH 9.5. pH-Induced experiments showed that cultures adjusted at pH 10.5 had 36% higher biomass recovery compared to that in cultures at pH 8.5 after 2 h. The results of this study showed that cultures at higher pH (9.5) had a better microalgae recovery in all dewatering systems than cultures at lower pH (6.5).

Automated summary

The study found that cultures at higher pH (9.5) had better microalgae recovery in all dewatering systems compared to cultures at lower pH (6.5).