METHOD FOR TREATMENT OF PHOSPHATE-CONTAINING SLUDGE

PURPOSE:To recover phosphates and inorganic salts efficiently by a method wherein a phosphate-containing sludge formed by flocculation is dissolved in a mineral acid and then it is contacted to a specified chelating ion exchange resin. CONSTITUTION:The phosphate-containing sludge is treated with a mineral acid to dissolve the phosphates and inorganic salts contained in the sludge. The sludge thus dissolved is then passed through a column packed with a chelating ion exchange resin on which are adsorbed metallic ions capable of forming a complex with phosphate ions. When the adsorption of the phosphate ions is saturated, the passing of the sludge through the column is stopped, and phosphoric acid can be completely recovered by using an aqueous alkali solution as an eluate. Then, the capability of the exchange resin to adsorb phosphate ions is easily regenerated by treating the resin with a diluted acid. On the other hand, the sludge solution deprived of the phosphates contains the inorganic salts, which can be reused as a flocculant. The sludge residue becomes a harmless sludge consisting mainly of organic materials.