Influence of suspended solids and back diffusion on organic contaminant uptake by semi-permeable membranes (SPMDs)

The organic contaminant uptake efficiency by a semi-permeable membrane device (SPMD) was assessed by carrying out simple equilibration tests under variable natural suspended solids concentrations. 14C — radiolabelled methylnaphthalene was used to trace total contaminant partitioning between dissolved, solids-sorbed and SPMD dialysate phases. At suspended solids loads typical of most natural waters (<100 mg l−1) there was no effect on SPMD uptake efficiency, however, at high solids concentrations such as may occur at interfaces between water column and bed sediments or during high river flow or tidal resuspension, reduced SPMD uptake occurred. Over an extended SPMD exposure period back diffusion of contaminants from SPMD dialysate will occur following a decline in ambient concentrations.