Assessment of the environmental impact of discharges of suspended solids in Frierfjord

Summary

This report assesses the dispersion of a planned discharge of suspended particles from diamond cutting of super-pure silicon. The particles are stated to be <3 μm large and discharged at 24 m depth at in the Frierfjord. The dispersion was modeled for a discharge of 550 kg/day of particles of 2 μm. In this report we quantified how the spill will affect three key parameters: 1. Concentration of suspended solids in the water column in the Frierfjord. 2. Sedimentation at the bottom in the Frierfjord. 3. Flux of particles out of the Frierfjord. The calculations showed that, of these, about 10 kg sediment in Frierfjord within Brevik, ca. 200 kg/day will be transported out of the Frierfjord in the fresh water layer, while the remaining particles will accumulate in deeper water masses of the fjord.