Effectiveness of pig slurry treatment by activated sludge with regard to some heavy metals

Abstract

The aim of our study was to investigate the levels of some metals of interest in different stages of treatment of pig slurry by activated sludge (influent, effluent and solid fraction) in relation to their release to the environment and its possible contamination. The presence and levels of heavy metals in pig excrements are a subject of concern as they may be discharged into the recipient (effluent), applied to the soil (solid fraction) and pollute the environment. The metals can penetrate the food chain of animals and humans. Our results showed that the effectiveness of removal of metals by the activated sludge system was high. Although limits for the presence of Pb, Hg, Cu, and Zn in surface water were exceeded in the effluent on some samplings no serious risk to surface water quality is envisaged with regard to its further considerable dilution in the recipient. The levels of dangerous heavy metals (Cd, Pb, Hg) in the separated solid fraction were far below the limits required for composted biosolids intended for application to agricultural land.