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(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 mm. 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.