| 摘要 |
<p>PROBLEM TO BE SOLVED: To concentrate sludge surely by a method in which excess sludge generated by biological treatment, after being added with a polymer flocculant for flocculation treatment, is separated into flocculated sludge and filtrate, the filtrate is separated into a membrane-treated water and concentrated sludge by an immersion type membrane separator, and the concentrated sludge is again subjected to flocculation treatment. SOLUTION: Raw sewage, suspended substances are precipitated/separated in an initial precipitation basin, treated water is supplied to an aerator and the precipitates are supplied to an activated sludge storage tank. In the aerator. the treated water is subjected to biological treatment, and a sludge flock is precipitated/separated in a final precipitation basin. Precipitated sludge is returned to the aerator through a return line 30, and part of it is sent to a gravity type concentration tank to be gravity concentrated. Next, the concentrated sludge is added with a cationic polymer flocculant in order to form a sludge flock, which is treated by a scrape-type screen to be separated into flocculated sludge and filtrate. The filtrate is separated into membrane-treated water and concentrated sludge by an immersion type membrane separator, and the concentrated sludge is returned to the gravity type concentration tank through a return line 31 and flocculated again.</p> |
