Sewage sludge contains significant amounts of phosphorus, and in order to establish the phosphorus recovery, an investigation of phosphorus recovery from carbonized sewage sludge was investigated. Carbonized sewage sludge was mixed with a potassium hydroxide aqueous solution and treated in hydrothermal conditions for 2 hours. After this treatment, hot-water was added to the treated mixture and phosphorus containing extract was recovered. Phosphorus was recovered as a form of potassium phosphate

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... from phosphorus containing extract. Optimal recovery conditions were investigated in treatment temperature, and recovered phosphorus was confirmed as potassium phosphate by X-ray analysis, and its recovery rate was estimated to be about 76-77%.