Cultivating and harvesting of marine alga Nannochloropsis oculata in local municipal wastewater for biodiesel

The feasibility of using the mixture of seawater and municipal wastewater; (1) the wastewater before activated sludge tank, just after primary settling (BAS) and (2) the wastewater after activated sludge tank, just before addition of polymer flocculants (AAS); as culture medium for the cultivation of marine microalgae Nannochloropsis oculata was investigated.10% BAS, 20% BAS and 10% AAS, 20% AAS, 50% AAS, 70% AAS, 100% AAS effluent loadings were well adapted to used wastewater. Sufficient dry weights obtained (345-406mgL^-1) with growth rates 0.37-0.45 for aerated cultures. High TN and TP removals (~74-90%) were achieved. Harvesting technique for grown cultures was also studied with natural sedimentation and pH induced flocculation. By alkalinity induced flocculation, at pH values of 10.50, high recovery of the cells (~80%) achieved with high sedimentation rates in 10min. The flocculation efficiencies decreased, sedimentation rates increased with the increase of the cell concentration.