Growth of microalgae Botryococcus sp. in domestic wastewater and application of statistical analysis for the optimization of flocculation using alum and chitosan.

Microalga biomass has been recognized as a sustainable bio-product to replace terrestrial biomass in biofuel production. The microalga industry has high operating costs, specifically on harvesting and biomass recovery. Therefore, the development of an efficient harvesting method is crucial to the minimization of production cost. A statistical analysis through response surface methodology was used to investigate the optimization of harvesting efficiency using alum and chitosan as a coagulant. Growth rate and biomass productivity were also determined. This research revealed that the harvesting efficiency using alum was 99.3%, with optimum dosage and pH of 177.74 mg L-1 and 8.24, respectively. Chitosan achieved 94.2% biomass recovery at an optimal dosage of 169.95 mg L-1 at pH of 12. Moreover, Botryococcus sp. achieved the maximum growth of 0.7551 µmax d-1, with an average total biomass productivity of 9.81 mg L-1 d-1 in domestic wastewater. Overall, this study shows that both alum and chitosan coagulants have great potential for efficient microalgal biomass recovery. It suggests that domestic wastewater as a potential growth medium for the large-scale production of microalga biomass.