Removal of Nitrogen and Phosphorous from Synthetic Wastewater by Oscillatoria sp. Cultivated in Vertical Tubular Photobioreactor under Natural Environmental Conditions

Abstract

A newly isolated cyanobacterium Oscillatoria sp. from the Sub-Himalayan region of India was assessed for nutrient removal efficiencies. It was cultivated in synthetic wastewater under uncontrolled natural environmental conditions. The filaments of cyanobacterium formed entangled mats which easily floated on the surface of the medium. This characteristic feature was exploited for easy harvesting of the biomass that is hitherto a bottleneck for the industrial scale oil production from microalgae. The cultures of Oscillatoria sp. grown in synthetic wastewater removed 93.02% of 76 mg/L nitrate and 94.11% of 51 mg/L phosphate. The fatty acid profiling of 10-day-old cultures showed the dominance of saturated and monounsaturated fatty acids. The percentages of predominant fatty acids found in Oscillatoria sp. were 25.25% myristoleic acid (14:1w5c), 23.3% myristic acid (14:0), 16.81% palmitoleic acid (16:1w7c), 14.88% palmitic acid (16:0) and 4.765% hexadecanoic acid (16:1 w5c). The biomass productivities of 0.065 g/L/day and 0.05 g/L/day were attained by the cultures grown in synthetic wastewater and control BG-11 growth media respectively. This mesocosm study was conducted under the influence of natural sunlight, uncontrolled temperatures and the presence of biological contaminants namely, bacteria and small ciliates. The main objective of the study was to mimic the outdoor conditions, which is the way forward for achieving economic and environmental sustainability in microalgae biomass production.