Population and industrial growth lead to an increase in the production of urban and industrial effluents, requiring ecological and effective solutions to avoid risks to human health and negative environmental impacts. Bioremediation, an approach that uses organisms to remove contaminants, is a candidate for this demand. In this sense, microalgae, photosynthetic organisms, are able to be remediating agents due to their ability to metabolize pollutants through adsorption, bioaccumulation and biodegradation. They can be cultivated in open or closed systems, in different operating modes, with semi-continuous and continuous being the most efficient, but they require favourable environmental and nutritional conditions for the microalgal metabolism, which is a definitive factor in the process efficiency. Thus, in order to make this technology increasingly viable for application in real processes, studies involving genetic engineering have been developed to expand the remediation potential of microalgae, making them more resistant to environmental stresses imposed by liquid wastes. Furthermore, microalgae can be used in consortium with other microorganisms that have a synergistic relationship, such as bacteria and filamentous fungi, enhancing microbial growth and, consequently, the treatment efficiency. Co-cultivation allows complex compounds that cannot be removed by microalgae alone to be degraded and also provides more economical biomass recovery and the possibility to have byproducts with added value. In this sense, this chapter aimed to discuss the aspects involving the treatment of effluents using microalgae as a remediator, addressing everything from the factors that influence the efficiency of the process to the main modes of operation. In addition, the consortium of microalgae with other microorganisms is also presented, showing the treatment mechanism and recent studies in ​​remediation of wastewaters.