Comparison of Activated Plants Fitted with Different numbers of Selector Units, 1999 Environmental Conference Proceedings

Timo Järvinen and Matti Jauhiainen, UPM-Kymmene plc, Kaipola Mill and Pertti Hynninen,, Helsinki

University of Technology, Department of Forest Products Technology

Almost all activated sludge plants built in Finland by forest industry since the late 1980s have been equipped with aerobic selectors. Waste waters from the printing paper mill are treated in an activated sludge plant with three lines. Line 3 is fitted with a 6-chamber aerobic selector, while lines 1 and 2 each have a 2-chamber selector. Lines 1 and 2 also have slightly different bottom aerators (Frings) than line 3 (OKI). Lines 1and 2 also operate in a different way to line 3: sorption on line 3 is more effective. Analyses performed on the three lines have revealed the following:

· sorption and also treatment results with line 3 are better under most running conditions

· there are clear differences in metal contents between sludges from the different lines

· sludge bulking occurs less often on line 3 than on the other two lines

· there are no major differences in foam formation in the aeration basins (microbiological and/or chemical)