Weighing sediment samples from a sand filter core after drying and crushing

Weighing sediment samples from a sand filter core after drying and crushing. The molecular biomarkers and organic pollutants that these samples contain will be extracted by chromatography. The sand filter is a water purification device located under the Quai de la Madeleine in Orléans. The device filters some 7 million cubic metres of wastewater and rainwater from the north of the city each year. The water is then channelled to treatment plants downstream. The conical basin is 17 m deep and is entirely buried underground. The sediment accumulated since the construction of the basin in 1942 will help researchers reconstitute more than 70 years of local history. The renovation of the sand filter was the perfect opportunity to take core samples of the sediment and examine its content.