METHOD FOR PRODUCING PHOSPHOROUS FERTILIZER

[PROBLEM] To recover phosphorous from sewage water at low cost and obtain a high-quality phosphate fertilizer. [SOLUTION] A method for producing a phosphate fertilizer, which comprises bringing phosphorous in a sewage S1 in a sewage-treatment plant into contact with a calcium-containing recovery material A1 to recover the phosphorous and burning the phosphorus recovered material AP, a sludge S9 generated in the sewage-treatment plant and a calcium source that serves as composition-adjusting agent A2. The burning of the phosphorus recovered material AP and others may be carried out at a burning temperature of 1150 to 1350°C inclusive. The calcium oxide content in the phosphate fertilizer may be 30 to 55 mass% inclusive. It becomes possible to produce a high-quality phosphate fertilizer having a ratio of citric acid-soluble phosphate of 60% or more and/or a ratio of hydrochloric acid-soluble silicate of 40% or more. Besides the calcium source, a magnesium source and/or a silica source may be added as the composition-adjusting agent. The resultant burnt product B1 may be pulverized and then granulated together with a granulation aid A3 using a granulating/molding machine 17.