DIGESTION OF WWTP SLUDGE IN FLANDERS (BELGIUM): EXPERIENCES WITH MIXED SLUDGE VERSUS PROSPECTS FOR BIOLOGICAL SLUDGE.
Marjoleine Weemaes, Johan Cauwenberghs, Chris Thoeye, Greet De Gueldre
Aquafin, Belgium
(Free)
Municipal wastewater treatment in Flanders generates ± 80.000 tds of sewage sludge/year. Approximately 1/3 of this sludge is anaerobically digested, thereby decreasing the amount of sludge to be disposed by 10%. Until recently, digestion was mainly confined to mixed (primary and biological) sludges. However, the increased application of lowloaded oxidation ditches without primary settling resulted in more biological sludges.
To assess the impact of the altered sludge characteristics, we carried out a two-year pilot trial on digestion with biological sludges from different WWTPs. This paper discusses the findings of the pilot tests and illustrates the first results of full scale digesters with changed sludge characteristics as a result of renovation.
KEY WORDS Anaerobic digestion, Biological sludge, Digestibility, Mixed sludge