| 摘要 |
PURPOSE:To remove the dissolved phosphorus, and to recover effectively the unreacted iron salt by adding sulfuric acid to the sludge contg. iron salts which is generated from the backwashing of a filter layer consisting of a carbonaceous contact filter medium to regulate the pH to <=1.5, and returning the sludge to th charged original water and mixing. CONSTITUTION:The ferrous sulfate soln. in a vessel 3 is injected in Fe/P=2.0, and 10-20% air based on the flow rate of th original water is injected at 8.3m/ H LV and 5-6l/H SV by a compressor 4 to saturate the water with dissolved oxygen, and the remainer is discharged from an air discharge pipe 5. Dephosphorization is carried out at about 7pH by passing the secondary treated water. When the loss of head becomes about 3m, the filter layer is back-washed, and the waste backwashing water is treated. The waste backwashing water is stored in a waste backwashing water tank 6. The sludge is concentrated in a concentration vessel 7, and the concd. sludge is allowed to react with sulfuric acid from a vessel 9 in a dissolving tank 8 and reutilized.
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