Bucaramanga, with a population of about one million, is the capital of the Department of Santander (Colombia), and has the Río Suratá as its main source of drinking water.In the upper reaches of the river, small-scale gold mining has been going on for many centuries (Vetas-California mining district).Geologically, the Vetas-California mining district is part of the Santander Massif, which is composed of pre-Devonian metamorphic rocks and Mesozoic igneous rocks.The mineralisation is restricted to structurally controlled veins and is often associated with hydrothermal alteration.There is also disseminated mineralisation, but presently only the vein-type is mined.The processing residues are discharged into the nearby watercourses, contaminating the waters of the Suratá river basin.As part of a joint Colombian-German technical cooperation project, with the purpose of controlling the negative environmental effects of gold mining pollution, an integrated distillation system for the recovery of mercury has been designed and tested.