Growth of Microalgae for Simultaneous Treatment of Industrial Wastewater and Biodiesel Production

The treatment of industrial wastewater contaminated with phenols is among the main challenges in the chemical, and particularly the petrochemical industry. Phenols, which present in considerable amounts in industrial wastewater, are toxic even at low concentrations. Therefore, it is essential to reduce their concentrations in water to harmless levels before being discharged. On the other hand, the dependence on the conventional fossil sources of energy, which is non-renewable, is not sustainable and can cause harmful environmental impacts. Therefore, in this work, the dual utilization of microalgae as a cheap and efficient means to remove phenolic compounds commonly found in refinery wastewater and as a sustainable source for oils for biodiesel production has been proposed. Most conventional bacteria used in the treatment of phenolics are pathogenic and the collected biomass after treatment is considered a secondary waste that does not have an evident commercial value. Microalgae, however, are promising, sustainable and renewable sources of oils that can be used for biodiesel production. In addition, they contain important compounds, such as proteins and pigments, which have large applications in the food and pharmaceutical industries. Combining the production of these valuable products with wastewater treatment renders the cultivation of microalgae very attractive and economically feasible. In this work, two freshwater microalgae stains, namely Chorella sp. and Tetraselmis sp., were used to remove several phenolic compounds commonly found in refinery wastewater (phenol, 4-nitrophenol and 2,4- dinitrophenol). These compounds were selected since they are very toxic and may cause serious threats for the ecosystem. In addition, the removal of 4-nitrophenol and 2, 4-dinitrophenol is challenging, and there is no previous study conducted their removal using microalgae. The effect of initial concentrations of the phenols on the biomass growth and pheno