The recovery of phosphorus from sewage and sludge treatment systems is particularly important because it is a limited resource and a large proportion of the phosphorus currently used in Japan must be imported. We have been experimentally evaluating recovery methods with sulphide. In this study, we focussed on the extraction of phosphate from the sludge, and sought to achieve a greater extraction efficiency and to validate the extraction mechanism. We conducted three experiments, i.e. a sludge-type experiment, a coagulant ratio of pre-coagulated sludge experiment, and a concentration of pre-coagulated sludge experiment. Phosphate was extracted not with normal sewage sludge but with pre-coagulated sludge and FePO4 reagent at S/Fe=1.0–2.0. A coagulant ratio of 23 mg Fe L−1 was required in the pre-coagulation process to effectively extract phosphate. A high concentration of pre-coagulated sludge was required for the phosphate extraction. The mass balance was calculated, and 44.0% of phosphorus was extracted to supernatant, and 98.5% of iron and 98.3% of sulphur (44.1% of sulphur was sulphide). Thus, phosphate can be selectively separated from iron by the phosphate extraction method with NaHS, and phosphorus and iron can be recovered and reused at sewage treatment plants using ferric chloride as a coagulant.
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Research Article|
September 01 2006
Extraction efficiency of phosphate from pre-coagulated sludge with NaHS
F. Kato;
F. Kato
1Department of Urban and Environment Engineering, Graduate School of Engineering, Kyoto University, Yoshida honmachi, Sakyo-ku, Kyoto, Japan
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H. Kitakoji;
H. Kitakoji
1Department of Urban and Environment Engineering, Graduate School of Engineering, Kyoto University, Yoshida honmachi, Sakyo-ku, Kyoto, Japan
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K. Oshita;
1Department of Urban and Environment Engineering, Graduate School of Engineering, Kyoto University, Yoshida honmachi, Sakyo-ku, Kyoto, Japan
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M. Takaoka;
M. Takaoka
1Department of Urban and Environment Engineering, Graduate School of Engineering, Kyoto University, Yoshida honmachi, Sakyo-ku, Kyoto, Japan
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N. Takeda;
N. Takeda
1Department of Urban and Environment Engineering, Graduate School of Engineering, Kyoto University, Yoshida honmachi, Sakyo-ku, Kyoto, Japan
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T. Matsumoto
T. Matsumoto
1Department of Urban and Environment Engineering, Graduate School of Engineering, Kyoto University, Yoshida honmachi, Sakyo-ku, Kyoto, Japan
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Water Sci Technol (2006) 54 (5): 119–129.
Citation
F. Kato, H. Kitakoji, K. Oshita, M. Takaoka, N. Takeda, T. Matsumoto; Extraction efficiency of phosphate from pre-coagulated sludge with NaHS. Water Sci Technol 1 September 2006; 54 (5): 119–129. doi: https://doi.org/10.2166/wst.2006.554
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