Abstract
In ferromagnetic powder supplemented activated sludge method, a procedure for recycling ferromagnetic powder was examined for saving costs and reducing residual ash of sludge incineration. In a “wet recovery method”, ferromagnetic powder supplemented to activated sludge was recovered from waste sludge with an apparatus using plastic magnet. Ninety six % of ferromagnetic powder (magnetite) was able to recycle by this procedure. The ratio of return sludge to waste sludge was 86/14. In a “dry recovery method”, waste sludge was incinerated to obtain residual ash containing ferromagnetic powder for reuse. Ferromagnetism was not lost by sludge incineration at 600-650°C for magnetite and at less than 700°C for Sr-ferrite. No change, practically, was observed on the values of settling volume after 1 or 30 min and COD removal when ferromagnetic powder incinerated was resupplemented into activated sludge.
