Industrial and social development has increased the use of plastics, generating waste that, broken down by erosion, becomes microplastics (MPs). Wastewater treatment plants (WWTPs) are key in the management of these wastes, capturing them but also emitting them. WWTP technologies are not designed to remove MPs, which accumulate in the sludge resulting from water treatment. This sludge, rich in organic matter, is used as compost to fertilize soils, but it contains MPs that can damage ecosystems. Researchers from INPROQUIMA group are conducting research to develop sustainable methods to separate MPs from sludge prior to its use in compost, using physical, economically and environmentally sustainable techniques. This research, still in its initial stage, is being carried out with sludge supplied by WWTPs, doped with different types of microplastics, with densities higher and lower than that of water. Aeration combined with surfactants and sludge moisture reduction is generating very promising results in this objective.