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

ABSTRACT

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.

KEYWORDS:

• Wastewater
• Spirulina platensis
• biogas
• open raceway pond and biomass pre-treatments
• FAMEs

Acknowledgements

The authors would like to thank the Birla Institute of Technology and Sciences (BITS) Pilani, Centre for Research Excellence – Wastewater and Energy, for providing funds to carry out this research. The authors also thank Ms. Jyoti Singh (IIT, Roorkee) for helping with the FAME analysis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the BITS Pilani, Pilani, Rajasthan-India through Center of Research Excellence (CORE) under the theme Wastewater and Energy (WWE) [grant number 111205].