Microalgae have long been known to remove pollutants from the aquatic environment efficiently due to the large surface/volume ratio of their small cells and their formidable capabilities for bioaccumulation. Separation of the microalgae from the aqueous suspension, however, remained a major obstacle for successful applications. Our laboratory uses microalgae immobilized on Twin-Layers to readdress this problem. We have shown the efficiency of the novel technology to remove nitrate, ammonium and phosphate from municipal and aquaculture secondary wastewater, and zinc from low-grade ores. Scale-up of the Twin-Layer system for wastewater purification in rural settings and for aquaculture recirculation systems is currently being developed.