Phosphate removal by high-gradient magnetic filtration using permanent magnets

On the basis of rare-earth permanent magnets, a second prototype of a carousel magnetic filter has been constructed for a ´third-stage´ phosphate elimination from municipal sewage. As compared to the first prototype presented on the MT-15, the filter throughput has been increased by more than 500% to about 3-4 m/sup 3//h with the dimensions and the magnet system used remaining the same. At an inlet concentration of 2 mg/L P, separation efficiencies of approximately 80% can be achieved by continuous operation at filtration rates of 100 m/h. The resulting outlet concentrations are below the limit values specified in Germany or Europe. Furthermore it is evident from cost calculations that the system represents a real alternative to the well-established solid-liquid separation methods for phosphate elimination, e.g, sand filters or microsieves.