The biogeochemical activity of microorganisms from sulphide biogeocoenosis in the zones of sulphide copper ores deposits in East Serbia has been studied by us since 1975. All deposits of copper mineralization were dominantly sulphides and arsenic sulphides with the constant presence of pyrite. The obtained results proved that the biochemical and chemical activity of thionic bacteria have an influence on the global pollution of waters. All the waters were characterized by a low pH value and by high Eh values, mineralization (over 7 gL-1) and in total iron (even more than 4 gL-1) dominantly as Fe3+ ions. These waters were characterized by toxic concentrations of copper ions, within the limits from about 2 to almost 200 mgL-1 and arsenic, up to more than 4 mgL-1. These waters partly arrive in an aquifer and the major part flows into surface water¬ courses gravitating towards the Danube River, which empties into the Black Sea. In a hypothetical case, if maximum concentrations of copper and arsenic and maximum capacity of the springs are considered, under the assumption that the pollutants do not precipitate on the way to the main recipient, the striking information is obtained that the Danube River receives about 31 t of copper and more than 0.6 t of arsenic per annum from one place alone, which undoubtedly points to the contribution of thionic bacteria as "biological agents" to global pollution of surface and ground waters.