Influence of Elevated CO2 and Municipal Wastewater Feed on the Productivity, Morphology, and Chemical Composition of Arthrospira (Spirulina) platensis

Abstract

In this work, a marine strain of Arthrospira (Spirulina) platensis (CCMP1925) was submitted to high concentrations of municipal wastewater (WW) and carbon dioxide (CO2). Under standard conditions (Zarrouk medium and optimal light), production reached 2.79 g/kg of culture after 8 days. Adding wastewater to the mixture led to an increased cell density reaching 3.29 g/kg below 40% wastewater, while above 40%, wastewater was shown to inhibit productivity. At an elevated CO2 concentration fed to the mixture, production reached 3.55 g/kg, although increasing the concentration of CO2 above 2% (v/v) was shown to inhibit the production of biomass. High concentrations of combined wastewater and CO2 were generally shown to be detrimental for the production of algal biomass. However, some synergetic effects were observed for the optimal cell density that was obtained after 5 days for a mixture involving 40% wastewater and 8% CO2, while after 8 days, the best results were obtained with a 40% WW mixture and 0% CO2. A combination of elevated CO2 and WW concentration (8% and 80%, respectively) led to poor cell growth, although the concentration in proteins, carbohydrates, and chlorophyll was generally higher when compared to the control cultures.