Shell sand is a natural carbonatic material mainly produced by shells, snails and coral alga(Lithotaminion sp.). At some shallow coastal sites shell sand deposits are 5–10 m deep. One million tons of shell sand are harvested annually from Norway's coastline, mainly used as a liming product. Preliminary investigations indicate that shell sand has chemical and physical properties suitable for filter material in constructed wetlands and wastewater filters. Investigation of filtration properties show that shell sand has a high phosphorus sorption capacity, a variable hydraulic conductivity (60–2000 m/day), a high porosity (30–50%) and a relatively low bulk density (0.7 to 1 g/cm3). Column experiments with wastewater showed that shell sand removed phosphorus and organic matter (TOC) efficiently. Complete nitrification was achieved at high hydraulic loading (10 cm/day).