The use of carbonate-silica rock (opoka) to remove iron, manganese and indicator bacteria from groundwater

The study investigated the efficiency of removal of iron, manganese and indicator bacteria from potable groundwater by using carbonate-silica rock (opoka). The tests were performed in a laboratory in three filter columns supplied with water containing increased concentrations of iron and manganese. Two of the columns were filled with carbonate-silica rock with particle sizes of 2-5 mm; retention time for water in the columns was set at 1 h and 2 h. A third column was filled with 1-2 mm rock particles, with hydraulic retention time set at 1 h. High removal efficiencies were determined for iron, manganese and coliform bacteria and low removal efficiencies for psychro- and mesophilic bacteria. An increase in the alkalinity of the investigated water was also observed.