Illumination wavelengths effect on Arthrospira platensis production and its process applications in River Yamuna water treatment

Illumination triggers the metabolic activities in microalgae. Wavelength governs the energy fluxes and activates the photosystem I and II. Treating the river water is the prime project in India due to disposal of effluent discharge. Lack of well-defined illumination wavelength for microalgae cultivation aimed this study to find optimum wavelength for promoting growth of Arthrospira platensis and hence, treatment of Yamuna water enriched with effluent discharge. Seven experimental set-up each comprising of an Erlynmeyer flask containing Zarrouk's medium supplied with sterile air and kept under different wavelengths, were used. Effects of different energy fluxes were investigated on the production of A. platensis. Optimum illumination wavelength selection was based on the comparison of maximum specific growth rate (μmax). Sunlight exhibited μmax of 0.45 day−1 and maximum biomass productivity of 16.77 mg/L/h, i.e. highest among others. Energy flux per unit power for the corresponding source of illumination was 6.05 × 10−21 s/m2. Optimum wavelength was further used for microalgae cultivation in Yamuna water. Culture was acclimatized to Yamuna water using sequential increased levels to maintain the μmax. Biomass productivity of 10 mg/L/h and removal efficiencies of 99.76% for nitrate, 99.22% for lead, 100% for nickel, 90.80% for cadmium and 68.57% for copper, were achieved. Biomass productivity was 40.3% lesser than that of Zarrouk's medium but lipid content of cells increased by 16.45%. Maximum productivity of value added by-products chlorophyll and phycocyanin was 2.93 and 7.34 mg/g cells/day respectively. A. platensis has great potential for wastewater treatment and production of valuable by-products.