HIGH-QUALITY MAGNESIUM AMMONIUM PHOSPHATE PRODUCED FROM DIGESTED SEWAGE SLUDGE BY ADSORPTION

This study was designed to solve the problems caused by the presence of metal ions during the recovery of phosphorus in the form of magnesium ammonium phosphate from digested sewage sludge. The following experimental steps were conducted to maximize magnesium ammonium phosphate production and ensure its quality. First, the excess sludge was digested in anaerobic conditions to decrease pH. The pH was then adjusted to 3 to dissolve heavy metal ions and obtain water rich in phosphorus and ammonia. The heavy metal ions were removed through adsorption using modified bagasse. Phosphorus and ammonia as magnesium ammonium phosphate was then recovered. The product was characterized by scanning electron microscopy, energy disperse spectroscopy and X-ray diffraction. The recovered magnesium ammonium phosphate fulfilled all the ecological indices for fertilizers used in China; thus, it can be used as a high-quality fertilizer in the country.