Abstract

Coagulation and precipitation process by using lime(Ca(OH)₂) and calcium carbonate (CaCO₃) were applied to remove heavy metals from groundwater in laboratory scale. From results of batch tests, by the addition of 0.3 wt.% lime, more than 90% of As and Mn were removed and 75-80% of Cd and Zn were removed by using 0.5 wt.% of lime. Removal efficiency of Pb almost reached 100% with only 0.1 wt.% of calcium carbonate and more than 93% of Cd were removed by the addition of 1.0 wt.% of calcium carbonate. Pilot scale column experiments were performed to remove heavy metals in the separation process of precipitated floc to supernatant after the coagulation/precipitation. For lime as a coagulant, more than 99% of As were removed from artificial groundwater and removal
efficiencies of Cd, Mn, and Zn were over 80%. By using calcium carbonate, more than 95% of Cd and Pb were removed in column experiment. Fe and Mn contaminated groundwater taken from a real landfill site, Ulsan was used for the column experiment and more than 99% of Fe and Mn were removed by the addition of 1 wt.% lime in column experiment, suggesting that the coagulation/ precipitation process by using lime and calcium carbonate have a great possibility to remove heavy metals from contaminated groundwater.

Keywords coagulation, heavy metal, groundwater, lime, calcium carbonate