2. Materials and methods
2.1. Activated sludge samples
Activated sludge samples were taken at 15 WWTP from different origins (Flanders, Belgium), i.e., domestic wastewater (samples A), carbohydrate rich wastewater from paper and starch related industries (samples B), protein and fat rich wastewater from food and meat related industries (samples C) and wastewater from textile industry (samples D). A list of the samples together with some operational parameters (SVI=sludge volume index; SRT=sludge retention time; Bx=sludge loading rate) is given in Table 1. The respective companies reported the operational parameters. All samples were collected from the aerated mixed liquid and 50 ml of sample was frozen at 320³C until use. Upon thawing, the total community DNA was extracted and purified as described previously [16].