Current progress and challenges of municipal wastewater phycoremediation and microalgae-based biorefinery

Abstract

A review of the literature on the municipal wastewater (MW) composition was performed, with a focus on the treatment technologies and comparing countries with different income levels. The risks associated with the persistence of the severe acute respiratory syndrome coronavirus 2 in MW, and the opportunities posed by MW to accomplish the virus surveillance, are discussed. The current progress and challenges related to MW recycling and nutrient recovery, phycoremediation, and biorefinery, focusing on microalgal biomass cultivated in wastewaters to produce metabolites—lipids, carbohydrates, and proteins—of biotechnological interest are also presented. Based on this background, we commented on the bioprocesses using the microalgae Chlorella spp. and other species for enhancing biomass harvesting and the recovery of value-added products. Within the new paradigm of wastewater resource recovery, MW is presented as a source of valuable raw resources with social, environmental, and economic advantages. Finally, it is suggested that microalgae should be included in municipal effluent treatments, aiming to reuse the water to obtain zero discharge process. Within this complex scenario, the coronavirus 2019 pandemic raises new questions about the apparent controversy between the possibility of reusing MW for different purposes and the need to deepen studies on the virus transmission before programming MW for further uses.