Phosphate recycling in the phosphorus industry.

The feasibility of phosphate recycling in the white phosphorus production process is discussed. Several types of materials may be recycled, provided they are dry inorganic materials, low in iron, copper and zinc Sewage sludge ash may be used if no iron is used for phosphate precipitation in the treatment plant; using Ca or Al, or bio-P-removal, increases the recycling potential of the ash, but Cu and Zn are still present in problematic concentrations. Side stream P recovery as Ca- or Al-phosphates is a more attractive option and is discussed in detail. Manure ash also has too high levels of Cu and Zn. Recycling phosphates from industrial sources is possible in many cases, depending on the source.