1. Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zurich, CH-8092 Zurich, Switzerland, Department of Civil Engineering, Dhaka University of Engineering and Technology, Gazipur-1700, Bangladesh, and Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh