Raw municipal sewage treated in a pilot plant were analyzed for COD fractions to collect data necessary for an application of activated sludge model. In particular, the non-biodegradable non-soluble fraction and vol. fatty acids from fermn. were detd. The results were compared with those published by J. Makinia, 2006 (Gdansk, Gdynia), and D. Baetens, 2000 (Belgium). A good agreement was obsd. except for volatile fatty acids produced in the studied sewage with a high yield.