Exploring water cleaning system in Sala Silvermine: comparative study of three water treatment processes, with Falun mine as comparison site

Sammanfattning

The Sala Silver Mine, one of Sweden's oldest and most significant mining sites, operated continuously from the 15th century until 1908. Located 60 km west of Uppsala in the Bergslagen mining district, the mine produced approximately 450 tons of silver, 35,000 tons of lead, and an undisclosed quantity of zinc from an estimated 5 million tons of ore (Jansson, 2016).In recent years, efforts have focused on environmental sustainability and remediation at this historic site, addressing issues related to water quality. Groundwater and surface water samples from the area show elevated levels of Ca, Cd, Fe, Mg, Mn, Pb, and Zn that exceed the national threshold values, making an advanced water cleaning system a necessity. The aim of this project is to evaluate the water samples and propose which method is more suitable to be implemented for the water cleaning system.Three water treatment methods, the HDS (High Density Sludge) process, its variant called Heath Steele process and the Geco process, are proposed, each with successful records in past applications. Two pilot tests are described in detail, in order to determine which process is the most suitable one for this case. The pilot tests were performed in Canada and Romania. The most cost effective process is the Heath Steele process, because it excludes the use of the Rapid Mix Tank and the Floc Tank whatsoever.