Tertiary treatment of domestic wastewater by Spirulina platensis integrated with microalgal biorefinery

The present study aims at reclamation of secondarily treated water using the microalga Spirulina platensis. The objective is to consider wastewater pollutants as nutrients for microalgae cultivation. The process led to production of microalgal biomass that can be used for extraction of value-added products with the potential to be commercialized. An open raceway pond was used as a cultivation system. It can remove 2.86 g Chemical Oxygen Dmand (COD)/day, 0.12 g PO4-P/day, 0.82 g NH4-N/day, 0.13 g NO3-N/day and 0.88 g total nitrogen/day. The harvested microalgal biomass was used to produce biomethane at 0.1-L and 5-L capacities. The biomass was found to contain 26.65% (dry weight) of lipids with C:16 and C18:1 fatty acids. The residual biomass can produce 165.0 +/- 5.39 mL of biogas per g Volatile Solids (VS) with an average methane content of 62.38 +/- 2.12%. Different biomass pre-treatments methods were also studied to increase the biogas production. This study demonstrates the commercial potential of S. platensis cultivation using wastewater streams wherein it can reduce the cost of wastewater treatment and earn revenue from value-added products.