1. Hamburg University of Technology, Institute of Wastewater Management and Water Protection, Eissendorfer Str. 42, 21073 Hamburg, Germany and Before March 2011, RWTH Aachen University, Institute of Environmental Engineering (ISA), Mies-van-der-Rohe-Str. 1, 52074 Aachen, Germany
2. RWTH Aachen University, Institute of Environmental Engineering (ISA), Mies-van-der-Rohe-Str. 1, 52074 Aachen, Germany
3. Pöyry GKW GmbH, Kruppstr. 82, 45145 Essen, Germany