Fractionation of trace metals in surface water with screen filters

Abstract Size fractionation of solid particulate phases serving as carriers of trace elements (e.g. Al, Cd, Cu, Fe, Mn and Zn) in surface waters was conducted by pressure filtration using screen filters with defined pore sizes in the range 5-0.015 μm. The particle size distribution in solution was determined by Photon Correlation Spectroscopy. The accumulation of solids on the filter surface was demonstrated, leading to a successive reduction of the efficient pore size (‘clogging’). Thus, filters with a defined pore size of 0.40 μm and a diameter of 47 mm had an apparent separation efficiency corresponding to a pore size of 0.015 μm after filtration of 100 ml containing approximately 100 mg/l of suspended solids. Aluminium and iron were almost exclusively present in the particle size range 5-0.20 μm. Copper and manganese were retained to 45% and zinc and cadmium to 30% by the 0.015-μm pore size filter.