Microalgae As Tertiary Wastewater Treatment: Energy Production, Carbon Neutrality, and High-Value Products

In general, wastewater treatment plants (WWTPs) use basic effluent treatment (primary and secondary). However, including a tertiary treatment may enhance the quality of the treated effluent, making it reusable for different purposes. Several tertiary treatment techniques are available in the literature (e.g., coagulation, flocculation, filtration, and oxidation), but they are mainly focused on nutrients and contaminants remove (e.g., trace metals). However, when microalgae cultivation is applied as tertiary treatment, other possibilities could be explored. During the growth, microalgae incorporate nutrients present in the effluent in their biomass that could generate further high-value products such as biofuel, biochar, and carotenoids. In addition, during photosynthesis process they can fixed high CO2 rates, playing an important role in global climate mitigation under a carbon neutrality perspective. In this sense, we identified the potential of microalgae cultivation as a tertiary treatment, emphasizing its capacity of removal nutrients and also their potential reduce the WWTP's carbon footprint; while generating other high-value products.