A simple method to release polyphosphate from activated sludge for phosphorus reuse and recycling

In enhanced biological phosphorus removal processes, activated sludge microorganisms accumulate large quantities of polyphosphate (polyP). It was discovered that nearly all of the polyP could be released from activated sludge simply by heating it at 70 degrees C for about 1 h. The chain length of released polyP ranged from 100 to 200 phosphate (P(i)) residues. The addition of CaCl(2) precipitated approximately 75% of the total phosphorus without pH adjustment. The formed precipitate contained more P and less Ca than typical natural phosphorite deposits. Hence, in combination with enhanced biological phosphorus removal, the present method has potential for the development of a simple process for recovering phosphorus in a reusable form from wastewater.