Concentration of heavy metals on surface of filter materials and in backwash water

Filtration is the main technological process realized at Water Treatment Plant (WTP) in Poland. Main target of rapid filters is elimination of iron and manganese from groundwater. In this paper, rapid filter exploitation at three WTP in Poznan agglomeration was analyzed. Incoming water, except iron and manganese, contained also small concentration of other metals. These metals were eliminated from water with different effectiveness by the filtration process, mainly by adsorption on iron hydroxide flocks. To prove, that metals eliminated from water by filtration process are durable built in covering of filter material grains, the covering layer were analyzed to find a iron, manganese, chromium, nickel, copper, arsenic, selenium and lead in it. Samples of filter media (sand) were taken from selected filter of each WTP. Additionally, the backwash water samples were taken directly during filter backwashing and concentration of heavy metals was determined. The concentration of heavy metal was analyzed by ICP-MS methods. Results show different heavy metals concentration at the filter material covering and backwash water. Concentration of iron and manganese were dominating both, on surface of filter material and in backwash water.