| 摘要 |
<p>PROBLEM TO BE SOLVED: To enable processing of sewage at a low cost to remove phosphorus from sewage by disposing an eluting device to elute iron ion in a processing device to biologically process the sewage, supplying the iron ion eluted from the eluting device to a processing passage for the sewage. SOLUTION: Waste water flowing in a sedimentation separation tank 1 is separated from a solid content or foreign matter and then sent to a contact aeration tank 2 where oxygen is supplied. The water circulates in the tank 2 while org. phosphates in the water are decomposed to produce orthophosphoric acid. Then the treated water is sent to a sedimentation tank 4 where a floating material in the water is settled and separated from the upper clear liquid. A part of the clear liquid is supplied to an eluting tank 3 where iron ton is added. The liquid with iron ion is then returned to the contact aerating tank 2. The iron ion supplied to the contact aerating tank 2 is oxidized from bivalent to tervalent state by oxygen, then reacts with the orthophosphoric acid, aggregates and precipitates as an insoluble phosphate compd. Thereby, the dephosphorizing efficiency can be improved.</p> |
