Improving refinery wastewater for microalgal biomass production and CO2 biofixation: Predictive modeling and simulation

The objective of this research was to evaluate the use of refinery wastewater in microalgae cultivation for CO2 biofixation and biomass production. Two strategies were considered in making the use of wastewater viable for supporting biomass growth: (i) dilution of wastewater in synthetic BGN medium and (ii) supplementation of wastewater with salts from synthetic medium. Five mathematical growth models (logistic, Gompertz, modified Gompertz, Baranyi, and Morgan) were used to estimate the biomass productivity in continuous processes and to predict the following parameters of cell growth: lag phase duration, maximum specific growth rate and maximum cell concentration. The results demonstrated that the addition of 25% of the salts (w/v) in the BGN medium to wastewater favors microalgae growth. Using statistical and physiological significance criteria, the modified Gompertz model was considered the most appropriate for quantifying biomass growth. The model prediction analysis shows the possibility to obtain 1.41 kgbiomass/Lreactor in 1000 h of continuous processing with a consequent biofixation of 2.61 kgCO2/Lreactor.