PHOSPHATE RECOVERY BY THE CRYSTALLISATION PROCESS: EXPERIENCE AND DEVELOPMENTS

An advanced alternative for phosphate removal by conventional precipitation is to apply crystallisation. DHV, a multi-national group of consulting engineers and general contractors with headquarters in The Netherlands, has developed and patented a fluid-bed type of crystallizer in which phosphate is removed and recovered from the wastewater while phosphate pellets with a typical diameter of 1 mm are produced. The major advantage of the crystallisation technology, the so-called Crystalactor®1, is that in the compact installation high-purity phosphate pellets are produced which have proven to be reusable. Phosphate has been successfully recovered in the form of calcium phosphate, magnesium phosphate and magnesium ammonium phosphate. Up to now Crystalactor ® plants were constructed for the removal/recovery of heavy metals, phosphate, fluoride and the softening of drinking and process water. 1 CONVENTIONAL PHOSPHATE REMOVAL In municipal water applications and many industrial unit operations phosphate-polluted wastewater is generated. In general, conventional phosphate removal techniques are applied for th