Influence of the Coagulated Sludge Characteristics with Ferric Chloride on the Phosphate and Coagulant Recovery Process

OSHITA Kazuyuki, KITAKOJI Hiroyuki, KATO Fumitaka, TAKAOKA Masaki, TAKEDA Nobuo, MATSUMOTO Tadao, HIMONO Ryoichi

doi:10.11532/proes1992.43.399

Removal of phosphate in wastewater is very important because it causes the eutrophication of the lake or pond. On the other hand, phosphate recovery from sewage and sludge treatment systems is particularly important because it is a limited resource and a large proportion of the phosphate currently used in Japan must be imported. Therefore, we have been experimentally evaluating phosphate and coagulant recovery methods from pre-coagulated sludge with NaHS.<BR>In this study, we experimentally investigated the influence of the coagulated sludge characteristics with ferric chloride on its phosphate and coagulant recovery process. The phosphate extraction and recovery from pre-coagulated sludge with various amount of FeCl₃, the iron dissolution using HCl and the oxidation with H₂O₂ experiments were conducted.<BR>As the result of phosphorus extraction experiment, we found that the increase of FeCl₃ dose led to high phosphorus extraction ratio because of the increase of FePO₄ in sludge and not extracted phosphorus could exist with Al, Ca and organic matter. In phosphorus recovery experiment, we could obtain good recovered materials which contained 15% of phosphorus and little heavy metals. And as the result of coagulant recovery experiment, recovered coagulant is as effective as commercial FeCl₃.

Influence of the Coagulated Sludge Characteristics with Ferric Chloride on the Phosphate and Coagulant Recovery Process

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