Evaluation of Biomass Production and Wastewater Nutrient Removal Using Microalgae: Sustainable Strategy to CO2 Bio-Fixation and Bioenergy Production Approach

Abstract

Nowadays, the replacement of renewable energies such as biofuels is one of the main priorities in environmental programming and investments. This study is based on sustainable strategy towards integrating algal biomass generation as a green feedstock with wastewater treatment, CO₂ bio-fixation, and bioenergy production. Therefore, the performance of <em>Trichormus variabilis</em> in biomass production together with ammonium and phosphate removal from an actual effluent obtained from a mixed wastewater streams has been investigated using two mixing methods under aeration and agitation conditions. Dilutions of 10 %, 20 %, 40 %, 60 %, 90 % and 100 % (v/v) were used for growth evaluation. The results showed that the bubbled air effectively enhances the biomass productivity. However, the agitation system was suggested to cultivate the algae in the wastewater due to the elimination of possible mechanical stimulation stress on cells. Moreover, high pH levels (pH>8) indicated a negative inhibitory effect on growth. Thus, unexpected inhibitory impacts were removed through providing the wastewater dilutions mixed with BG₁₁ culture medium, which contains essential required nutrients, to support the algal growth in the wastewater, adjust pH and remove the mechanical stress induced by bubbling compressed air. The results with respect to investigating the effect of the inoculums and wastewater concentrations on the biomass production suggested that the highest biomass generates with 30 mg.mL^-1 inoculum in 40 % mixed wastewater diluted by the BG₁₁ medium having the highest potential in CO₂ bio-fixation of 9.19±0.64 g.L^-1. The results of the wastewater analysis demonstrated the removal potential of ~43 % and ~75 % for NH₄⁺ and PO₄³⁻, respectively. The generated biomass after phycoremediation and CO₂ bio-fixation can be effectively utilized in different types of biofuel production.